by Ronald G. Worl - pubs.usgs.gov · by Ronald G. Worl ABSTRACT ... countries to the north. The...

U. S. GEOLOGICAL SURVEY

SAUDI ARABIAN PROJECT REPORT 233

MINERAL EXPLORATION: MAHD ADH DHAHAB DISTRICT

KINGDOM OF SAUDI ARABIA

by

Ronald G. Worl

U.S. Geological Survey Jiddah, Saudi Arabia

1978

CONTENTS

Page

ABSTRACT................................................... 1

INTRODUCTION. I ............................................. 2

Location and description.............................. 2

Previous investigations............................... 4

Present investigations................................ 6

Acknowledgements...................................... 7

GEOLOGIC SETTING........................................... 8

Regional geology...................................... 8

Lithologies and alteration............................ 9

Structure............................................. 14

Mineralization........................................ 17

GEOCHEMISTRY............................................... 20

Sampling plan......................................... 20

Discussion of results................................. 22

EXPLORATION PROGRAM........................................ 28

Introduction.......................................... 28

Drill targets......................................... 34

Southern mineralized zone........................ 34

The SAMS mine area............................... 42

Geophysical target............................... 59

CONCLUSIONS AND RECOMMENDATIONS............................ 59

REFERENCES................................................. 65

APPENDIX A Analytical results............................. 66a

APPENDIX B Core logs...................................... 79

ILLUSTRATIONS

Paqe

Plate 1. Generalized geologic map of the Mahd adhDhahab area.............................. Back pocket

2. Geology of the main metalized quartz vein zone, Mahd adh Dhahab area, Kingdom of Saudi Arabia, showing sample locations in southern mineralized zone............. Back pocket

3. Geology of the 300' level ^ the Mahd adhDhahab mine............... =.............« Back pocket

Figure 1~. Index map showing the location of theMahd adh Dhahab district...................... 3

2. Geologic cross section along line A-A 1 .......... 18

3. Histograms and computer and visually derived smooth curves for Si02 distribution in the upper, middle, and lower units of the lower agglomerate............................. 26

4. Geologic cross section through diamond drillhole MD-1..................................... 35


6. Geologic cross section through diamond drillholes MD-3 and 8.............................. 37



9. Geologic cross section along SAMS minecoordinate 8000 north......................... 44

10. Geologic cross section through diamond drillhole SAMS-1................................... 45

11. Geologic cross section through diamond drillhole SAMS-13 - <,....««. ......................... 46

12. Geologic cross section through diamond drillhole SAMS-12 ...........o...................... 47


ii

Paqe

Figure 14. Geologic cross section through diamond drillholes SAMS-10, 7, 2, and 8.................. 49

15. Geologic cross section through diamond drillholes SAMS-9 and 11......................... 50

16. Geologic cross section through diamond drillholes SAMS-3................................ 51

17. Geologic cross section through diamond drillhole MD-6................................... 52

18. Geologic cross section through diamond drillhole MD-5................................... 57

19. Geologic cross section through diamond drillhole MD-10.................................. 60

TABLES Table 1. Summary of analytical results and specific

gravity determinations of 128 character core samples from diamond drill holes MD-1, 2, 3, and 4. ........................................ 23

2. High, medium, and low population mode values determined by visual inspection of bimodal and trimodal distribution curves.............. 27

3. Zones of metalization in core from diamonddrill holes MD-1 through 10................... 30

4. Length, azimuth, inclination and location ofdiamond drill holes MD-1 through 10........... 33

5. Potential resource grades and tonnages (metric)of the southern mineralized zone.............. 43

111

MINERAL EXPLORATION: MAHD ADH DHAHAB DISTRICT KINGDOM OF SAUDI ARABIA

by

Ronald G. Worl

ABSTRACT

Mahd adh Dhahab is the largest of numerous ancient gold

mines scattered through the Precambrian shield of Saudi Arabia

and the only one with recent production. During the period

1939-54, 765,768 fine ounces of gold and 1,002,029 ounces of

silver were produced from the mines by the Saudi Arabian Mining

Syndicate.

Ore minerals at Mahd adh Dhahab include free gold and

silver, tellurides, sphalerite, and chalcopyrite in and

associated with a system of north-trending quartz veins and quartz

veinlet stockworks. Pyrite is a common sulfide gangue mineral.

Country rocks are a north dipping sequence of pyroclastic and

transported pyroclastic rocks of the Hulayfah Group that are

locally highly silicified and potassium-feldspathized.

The prime target for this exploration program was a north-

trending zone of quartz veins and breccias, faults, alteration,

and metalization approximately 400 m wide and 1000 m long. The

ancient and recent mine workings are located in the northern

part of this zone. Although the quartz veins and alteration

cut all lithologies, the major metalization is confined to

the intersection of veins and agglomerate. Ten holes were

diamond drilled to explore geochemical, geological, and geo

physical targets in the area.

1

A significant new zone of metalization was discovered

700 m south of the ancient and recent mine workings and within

the same major zone of quartz veins, alteration, and faults.

Metalization in this southern mineralized zone is at the inter

section of the quartz veins and a distinctive and highly altered

agglomerate. The total zone of vein and agglomerate intercept

is potentially metalized and comprises a block of ground 40 m

thick and 400 m wide along the strike of the agglomerate and

projected downdip 250 m. Tonnage of this block is 17.2 million

tons. The explored zone, approximately 25 percent of the

potentially metalized rock, has a potential resource of 1.1

million tons containing 27 g/t gold and 73 g/t silver.

INTRODUCTION

Location and description

Mahd adh Dhahab, situated 250 km north of At Ta'if and

170 km southeast of Al Madinah at lat 23°30'N.; and long

40°53 I E. (fig.1), is an ancient and recent gold mining site.

Access to the area is by unimproved tracks across playas and

low rolling rocky hills north from the At Ta'if-Riyad surfaced

highway and south from the Al Madinah-Suwaydurah highway.

During the later part of 1975 construction of a new road from

Mahd adh Dhahab to Al Madinah was initiated.

The village of Mahd adh Dhahab, a local trade center, lies

just north of Jabal Mahd adh Dhahab and the ancient and recent

mining site situated along the eastern flank of the Jabal.

The Mahd adh Dhahab area has been a center of mining activity

throughout the recorded history of Arabia. Besides gold mining,

2

36

16

Figure 1. * Index map showing the location of the Mahd adh Dhahab district.

3

which may date back to 950 B.C. (Luce and others, 197Jf, p. 2) ,

the area was a central point along trade routes and the inland

pilgrim routes between Mecca, Al Madinah, and the Moslem

countries to the north. The caravan and pilgrim trails followed

a natural route along easily-traveled terrain between wells and

springs situated along the eastern front of the Harrat Rahat

(Tertiary plateau basalts). The ease of access and abundance

of nearby water was probably an important factor in making this

a major mining center in ancient times.

Previous investigations

Ancient mining activity in the area is indicated by

numerous narrow workings that extend to a depth of 85 m along

major veins, several thousand tons of slag left from crude

smelting .operations, and a largely destroyed tell with

attendant ruins and artifacts. These operations occurred during

two periods, possibly about 950 B.C. and during the Abbasiad

Caliphate about 800 A.D. (Luce and others, 1976, p. 1). These

dates are based upon C^ dating of charcoal found in slag and

from scanty mention in historical journals. No evidence of

mining activity between about 1000 A.D. and the twentieth

century has been found. In recent times (1931) the Mahd adh

Dhahab mine was recognized as part of a major mining district

by geologists and engineers retained by the Saudi Arabian

government. A concession for development of the Mahd adh

Dhahab mine was granted the Saudi Arabian Mining Syndicate

(SAMS) in 1936, and production of gold began in 1939. SAMS

will be used throughout to designate the Saudi Arabian Mining

4

Syndicate mining operations at Mahd adh Dhahab. During the

period 1939-54, 765,768 fine ounces gold and 1,002,029 ounces

of silver were produced from the mine by SAMS. Ancient gold

production probably equaled recent production. During the

SAMS operation of the general mine area, all mine workings and

diamond drill core were mapped and studied in detail. The

geologic maps and sections from this period are largely the

work of Dirom (1947) with modifications and additions by

succeeding mine geologists.

Geologists of the U.S. Geological Survey (USGS) mission

and the Saudi Arabian Directorate General of Mineral Resources

(DGMR) covered the general region in the early to middle 1960s

doing 1:500,000 scale mapping of the Precambrian shield

(Brown and others, 1963) and by more detailed (1:50,000)

regional studies in the Mahd adh Dhahab area (Goldsmith and

Kouther, 1971). During this period the USGS drilled two

exploration holes in an altered zone that contains anomalous

molybdenum values, at the western edge of Jabal Mahd adh Dhahab

approximately 1 km southwest of the SAMS mine shaft (Theobald

and others, 1977) .

Geologists of the French Bureau de Recherches Geologiques

et Minieres (BRGM) mapped and studied at a scale of 1:100,000

the Jabal Sayid quadrangle (Aguttes and Duhamel, 1971) and

the Sufaynah quadrangle (Lefevre, 1969, and Dottin, 1974).

Mahd adh Dhahab lies close to the boundary line between these

two quadrangles. BRGM geologists have undertaken extensive

studies in the vicinity of Jabal Sayid, a major copper

5

occurrence, 40 km to the north. The regional geology was being

analyzed and synthesized as part of a 1:250,000 scale mapping

program by BRGM geologists in 1976.

Present investigations

The United States Geological Survey, in accordance with a

work agreement with the Ministry of Petroleum and Mineral

Resources, Kingdom of Saudi Arabia, has been studying and

evaluating mineral deposits in the Mahd adh Dhahab district

(23°30'N.; 40°53'E.). The first phases of the study included

geologic mapping at a scale of 1:2,500 (Luce and others, 1976),

geochemical investigations (Roberts and others, 1978) , and

placer gold investigations (Bagdady and others, H75 ) The

second phase of the study, reported here, included extensive

diamond drilling/ detailed mapping at a scale of 1:1000, limited

surface geochemical investigations, and synthesis and evaluation

of SAMS geological data.

U.S. Geological Survey drill holes are designated throughout

this report by the symbol MD- and the drill hole number; i.e.

MD-5. Saudi Arabian Mining Syndicate drill holes are designated

by SAMS- and the drill hole number; i.e. SAMS-5.

Plates 1 and 3 and figures 9 through 16 and the northern

portion of plate 2 are modified and simplified after Dirom

(.1947). Modifications to Dirom 1 s maps and sections were minor

and involved only lithologic reinterpretations based upon

fieldwork and examination by the author of representative core

samples from the SAMS drilling program. Samples (5 cm split

core chips) from the 13 SAMS diamond drill holes were discovered

6

late in the spring of 1975, beneath a pile of rubble within

the village of Mahd adh Dhahab. Unfortunately the bulk of the

SAMS drill core was unusable as it had been dumped into one

rubble pile some time after mining operations ceased. Many

representative lithologic core samples however, could be

accurately positioned with respect to hole number and depth and

afford a direct connection between surface rocks, USGS drill

core, SAMS drill core, and subsurface mine mapping and also

provided fresh samples for petrologic and petrographic studies.

Incomplete drill logs and assay data are available for the

SAMS drill holes, but were not in suitable shape to use in this

report. The 1" to 40' scale maps and cross sections of Dirom

(1947) contain a wealth of data that could not be transferred

to the author's 1:1000 scale working maps.

Three horizontal controls are included on plates 1, 2 and

3; the SAMS mine grid, in feet; latitude and longitude; and

a 50-meter square grid set by the USGS and used for 1:1000

scale mapping and sampling and geophysical studies. The SAMS

mine grid is included for correlation. Several of the maps

and sections used were poor paper copies that have not held

scale, thus correlations between some plates is not exact.

Transfer of data from one control system to another was based

on distance from the southwest corner of the main shaft.

Acknowledgements

Acknowledgement is due the Minister of Petroleum and

Mineral Resources of the Kingdom of Saudi Arabia and the

Directorate General of Mineral Resources for providing the

support that made the study possible.

The guidance and discussion concerning this study by

T.H. Kiilsgaard, Project Chief, and R.J. Roberts of the USGS

are gratefully acknowledged. Abdulaziz Bagdady contributed

to the synthesis of the SAMS data and general geologic knowledge

of the area. Ziad Al Kolak logged core from drill hole MD-9

and is responsible for geologic interpretation of that core.

Roy Nixon and Charles Robins laid out the 50-meter square grid

that served as base for detailed mapping and for geophysical

work. Geologists too numerous to mention, from the USGS, DGMR,

BRGM, and private industry have contributed by discussion of

the area.

GEOLOGIC SETTING

Regional geology

The Mahd adh Dhahab district is underlain by a complex of

Precambrian pyroclastic, volcanic, and clastic rocks overlying

a large body of diorite to granodiorite (Goldsmith and Kouther,

1971, pi. 1). Regional correlations of this largely pyroclastic

sequence, the Mahd adh Dhahab series, is not in agreement among

previous investigators. The rocks have been assigned to the

Hulayfah Group (Halaban Group) (Aquttes and Duhamel, 1971;

Delfour, 1975), the Halaban Group and Fatima Formation (Brown

and others, 1963), an intraformational agglomerate above the

Halaban (Lefevre, 1969), the Fatima and Murdama Formations

(Goldsmith and Kouther, 1971) and to the Murdama Group (Luce

and others, 1976; Dottin, 1975). The author concurs with

assignment to the Hulayfah Group. This sequence rests upon

granitic rocks .of the type that intrude pre-Hulayfah Group

8

rocks elsewhere in the region and in turn is overlain by

relatively nonmetamorphosed volcanic flow rocks and breccia of

the Murdama Group (Brown and others, 1963). The Mahd adh

Dhahab series in the vicinity of the Mahd adh Dhahab mine is

described by Aguttes and Duhamel (1971, p. 17) as predominantly

"rhyolitic pyroclastites" with interstratified andesite,

fine-grained sedimentary rocks, "ignimbrite", and silicic tuff,

none of which has regional extent except the "ignimbrite".

They consider the Mahd adh Dhahab series in the mine area as a

succession of lenses several meters to 40 m thick and limited

in areal extent by numerous facies changes. Towards the west

the Mahd adh Dhahab series grades by intertonguing and facies

changes to a predominantly tuff and dolomite sequence (Aguttes

and Duhamel, 1971, p. 18). Alkalic granite and rhyolite cut

the sequence north of Mahd adh Dhahab and andesite dikes and

sills cut it throughout its exposures.

The Mahd adh Dhahab area is in a zone of strong regional

northeast-trending faults and folds (Goldsmith, 1971, p. 36).

Within the study area (pi. 2), however, north-trending structures

dominate with subordinate northeast and northwest-trending

structures. The southwestern edge of the northwest-trending

Najd fault system is only a few kilometers northeast.

Lithologies and alteration

Rocks of the Mahd adh Dhahab series exposed in the study

area (pi. 2) are composed of an intimate mixture of pyroclastic

and transported pyroclastic and clastic detrital material.

Volcanic flow rocks, welded tuff, and breccia are subordinate.

Grain size and related parameters of sorting, grading, and

9

bedding vary much more than lithic, pyroclastic, and mineral

composition, which is relatively consistent through most units

mapped. Most of the medium- to fine-grained rocks are bedded,

and commonly graded. The rocks exposed range from coarse

agglomerate to very fine-grained tuff. Lithic and pyroclastic

fragments in order of decreasing abundance are andesite to

rhyodacite volcanic rock, silicic tuff, and chert, with locally

abundant broken feldspar grains, diorite, pumice, and glass

shards. The common minerals are chlorite, plagioclase, potassium-

feldspar, and quartz, with locally abundant epidote and minor

amphibole. The rocks are not regionally metamorphosed, but are

hydrothermally altered. The original mafic minerals have

altered to chlorite and magnetite. Much of the plagioclase

has been altered to either masses of sericite and quartz or

to saussurite aggregates.

Two types of post-depositional alteration have affected

these rocks: 1) hydrothermal alteration, mainly silicification,

pyritization, and propylitization centered on the quartz vein

zone and 2) more widespread and pervasive potassium-feldspathiza-

tion. The relationship between the two is not documented, but

the potassium-feldspathization seems to be in part contempor

aneous with early quartz veining. Three types of potassium-

feldspar are found: disseminated crystals, as a replacement of

plagioclase, and as a minor vein mineral. All three types are

similar optically and X-ray diffraction patterns suggest they

are compositionally similar, nearly maximum microcline.

10

Randomly disseminated potassium-feldspar crystals occur in all

map units indiscriminately throughout the groundmass and in

lithic and pyroclastic fragments of all types. The subhedral

potassium-feldspar crystals commonly cut grain boundaries of

metamorphic minerals. Fragmental plagioclase in crystal-lithic

tuff of the upper and lower agglomerates are partially to

totally replaced by potassium-feldspar; plagioclase cores with

potassium-feldspar rims are common. Potassium-feldspar occurs

as an early vein mineral in banded veins and as monomineralogic

veinlets, mostly in the mine area.

The lithologic sequence of Luce and others (1976) , in

decreasing age of lower agglomerate, lower tuff, upper agglo

merate and upper tuff, with further breakdown of the units is

retained in this report. The lower agglomerate has been

subdivided by the author into lower, middle, and upper units

on the basis of drill core information. The subdivision is

recognizable at the surface, but is not readily discernible on

the scree-covered outcrops. The lower unit is mainly andesite

tuff and lapilli tuff and is distinctive from the middle and

upper units. The middle and upper units, both mafic-lapilli

tuff to agglomerate, appear similar but the upper unit has a

mostly siliceous gray groundmass while the middle unit has a

chlorite and epidote-rich groundmass. In addition, the middle

unit has locally abundant chert and siliceous tuff fragments

not present in the upper unit. The three units also differ

geochemically as discussed in this report under the section

on geochemistry. The contact of the lower agglomerate and

11

lower tuff is gradational across a wide zone of intercalated

lapilli tuff, agglomerate, and massive tuff. The upper

contact of the lower tuff with the upper agglomerate is sharp

with no gradation or intercalation of the two lithologies.

Rocks considered by previous investigators to be rhyolite

(Dirom, 1947; Luce and others, 1976) are considered by the

author to be potassium-feldspathized tuff, wacke, and sandstone

and are probably raetasomatized equivalents of part of the lower

tuff. Rocks of the two units are similar in texture, composi

tion, and mineralogy, with the exception of the locally abundant

potassium-feldspar crystals and zones of sericitization(?) in

the metasomatized rock. The gradation from unaltered to altered

rock can be observed in core from drill holes MD-6, 9, and 10

and SAMS-1, 4, 5, and 13.

The upper agglomerate is here divided into two units,

crystal-lithic tuff to agglomerate and gray agglomerate. The

crystal-lithic tuff conformably overlies the lower tuff. The

lower few meters are primarily a mafic pyroclastic rock and

contains an abundance of flattened lapilli and possible shards.

The remainder of the crystal-lithic tuff and agglomerate is

generally bedded and commonly graded. The gray agglomerate seems

to be unconformable to the crystal-lithic tuff and agglomerate, as

its outcrop pattern transects layering in the underlying crystal-

lithic tuff and agglomerate and in some areas it directly

overlies potassium-feldspathized tuff and sediments. The gray

agglomerate is characterized by subrounded chert, tuff, and

12

volcanic rock fragments set in a siliceous gray groundmass.

Layering is not common but is present in a few finer-grained

zones.

The upper tuff is largely agglomerate-conglomerate with

a relatively thin unit of argillite and carbonate-bearing tuff

at the base. It is in unconformable contact with the underlying

upper agglomerate. Where penetrated by drill or mine workings

the contact is a bedding plane fault, parallel to bedding in

the upper tuff. The nature of this contact is important as the

quartz veins terminate upward against it. If the contact is

a fault plane with major offset, the vein system may continue

northward from the faulted offset whereas if it is primarily an

unconformity it may represent the northward terminus of the vein

system. The vein system may predate the unconformity and be

truncated by that structure, or the veins may have terminated

upwards against the unconformity because of the overlying

incompetent tuff. Whereas the more competent underlying

agglomerate would fracture and subsequently fill with vein

forming material the less competent tuff would absorb the

fracturing stress and open fractures would not develop. The

argillite and carbonate-bearing tuff of the upper tuff are

finely bedded, waterlain and differ distinctly from the lower

tuff. The overlying agglomerate-conglomerate portion is

characterized by an abundance of pale-green dacite fragments

and well-rounded red chert fragments, and local fragmental

quartz.

13

Structure

The Mahd adh Dhahab series, aside from the upper tuff, is

highly fractured and cut by numerous faults, joints, and quartz

veins, but the rocks are not highly sheared and primary textures,

bedding, and lithologic layering may be seen in most outcrops.

Schistosity or other metamorphic penetrative surfaces are not

well developed. Deformation of the rocks other than the upper

tuff was brittle rather than plastic, and more typical of near

surface fracturing than deep-seated thermal dynamic metamorphism.

The most obvious structural feature within the study area

(pi. 2) is the zone of north to N45°E trending quartz veins,

andesite dikes, and faults. There is also an important, but

less obvious because of lack of contained quartz veining, fault

system that trends N45°W to west. Several periods of faulting

and quartz vein and andesite dike emplacement along the north

to northeast trending systems and to a lesser extent the north

west to west system are evident (Luce and others, 1976). The

latest faulting was along the northwest to west trending system,

although lateral offset in the map area (pi. 2) is minor. The

low angle thrust faults in the northern part of the area (pi. 2)

are nearly parallel to layering in the crystal-lithic tuff-

agglomerate unit of the upper agglomerate. These are local

features related to folding, and are not of regional significance.

A major northeast-trending right lateral fault system

bounds the map area on the southeast (Goldsmith and Kouther,

1971, pi. 1; also pi. 1 of this report). Although not exposed,

the individual zones of alteration associated with this fault

14

system are well delineated by SP and EM geophysical anomalies

in the alluvial covered valley just to the east of the study

area (Mark Gettings, personal communication, 1975). The

anomalies associated with these faults are offset and truncated

by northwest to west trending faults. A segment of a major

northeast-trending fault was penetrated by drill hole MD-10.

This was the only fault zone penetrated in the USGS diamond

drilling characterized by an abundance of clay-rich gouge, vugs,

and complete water loss during drilling. The other intersected

fault zones were characterized by minor sericite mylonitic

shears, or thin seams of gouge and granulated rock.

A nearly horizontal joint system cuts all rock types and

in some places minor offset of quartz veins along this system

can be seen. In drill core these joints are generally open

and often lined with fine drusy quartz and are nearly penetrative

surfaces in some sections of core. The significance of this

system is unknown.

Structure of the Mahd adh Dhahab Series is defined by

primary sedimentary or volcanic bedding and lithologic layering

in most units. Only the agglomerates lack measurable bedding

or other primary layering features. Foliation and other meta-

morphic penetrative planar structures are not well developed,

and where present are generally parallel to bedding or to an

adjacent major shear zone. Minor fold axes and other measurable

linear penetrative structures are lacking. Folds in the Mahd

adh Dhahab series are broad, open flexural types; shear folds

and flow folds common in higher metamorphic grade rocks of the

Arabian Precambrian shield were not seen.

15

Main strike direction of bedding and layering is east-west

with north dips. Structural analysis of measured attitudes

available from all sources (unpublished SAMS data; Dirom, 1947;

Goldsmith and Kouther, 1971; Luce and others, 1976; this report)

defined areas of broad open folds (pi. 1). Poles to bedding

attitudes were plotted on the lower hemisphere of a Schmidt

equal-area net to define structurally homogeneous subareas I

through VI (pi. 1). Fold models shown by curvilinear strike and

dip symbols within each subarea are based upon the distribution

of poles to bedding on the corresponding stereonet. Structure

in most of the map area, and in subareas I and V (pi. 1), is a

slightly folded homocline. In structural subareas II, III, and

IV, structure is open flexural folding around a north-plunging

axis, while in the subarea VI the folding is around an east-

plunging axis. Relationship of folding in subareas II, III,

and IV to regional structure is unknown, but these folds are

probably subsidiary folds on the flanks of large regional-scale

features. Variation in attitude of axis of folding between

subareas, and variation of poles to bedding away from the

best-fit great circle within subareas is the result of post-

folding block faulting. Note that most subarea boundaries are

along major faults. The structures defined in subarea VI are

probably the result of drag folding along the major northeast-

trending fault system just to the east and are not of regional

significance. There is no evidence in any of the subareas for

multiple episodes of folding.

16

Special mention must be made of structural subarea III as

the structure defined in this subarea is the basis for the

structural interpretation in cross-section A-A 1 (fig. 2), which

shows that metasomatized tuff is continuous with and is an

altered portion of the lower tuff. Data in this subarea

includes attitudes noted as flow-banding in rhyolite on the

SAMS 300' level geologic map (Dirom, 1947). The poles to bedding

have relatively wide scatter around the defined great circle, but

there is little question that this area is structurally homo

geneous. This supports the premise that the lower tuff is

continuous into the metasomatized rock.

Mineral!zation

Mineralization at Mahd adh Dhahab consists of gold, silver,

copper, and zinc metalization in or associated with quartz veins.

Although quartz veins occur throughout Jabal Mahd Dhahab they

are most abundant in a north-trending zone 400 m wide and

approximately 1000 m in length along the eastern edge of the

jabal. This zone of faulting, veining, and metalization is the

prime exploration target of this study and contains the SAMS

mine and most ancient workings.

The quartz veins range in width from 1 mm to as much as 5 m

for some composite veins, but most individual veins are 10 to

50 cm in width. Vein material is generally space filling of

fractures, open breccias, and fissures and commonly earlier vein

material is brecciated and healed by later quartz. The larger

veins are invariably brecciated composite veins composed of

quartz-healed breccias of previous vein material and wall rock

, /f

fragments and sheeted veins in the 10 to 50 cm width range.

Veins 10 to 50 cm wide are typified by banding, crystal-lined

vugs, cockade structure, and comb structure of inwardly

terminated zoned quartz crystals. The veins are mostly quartz

with subordinate bands of pyrite, sphalerite, chalcopyrite, and

chlorite. Chalcendonic quartz and carbonate are late consti

tuents in some veins. In a few sections of core dark-gray

quartz-sulfide veinlets cut all other quartz. Potassium feldspar

is locally abundant, especially in the SAMS mine area, as bands

in the veins and as veinlets in altered wall rock. Metalization

is highest where quartz veining is most intense, but all such

zones are not metalized.

Luce and others (1976) recognized four types of quartz veins.

Their breakdown was not readily apparent in drill core, although

two or three distinct generations of quartz deposition was

evident and mm veinlets of drusy quartz and carbonate lining a

nearly horizontal joint system are common throughout. Post-

mineral (.quartz vein) shears and faults occur within and along

the edge of most of the major veins.

Sulfides present in the veins are pyrite, chalcopyrite, at

least two generations of sphalerite, minor galena, tetrahedrite,

and argentite. Native gold and silver accompany the major

sulfides. Preliminary petrologic and mineralogic studies of the

USGS drill core indicate that much of the gold, and presumably

also the silver, in the southern mineralized zone as outlined

by drill holes MD-3, 7, and 8, is in the form of tellurides.

BRGM geologists have recognized hessite, empressite, and rare

19

altaite and pezite in ore samples from Mahd adh Dhahab (Delfour,

1975, p. 24). An occasional gold grain or wire can be found in

quartz from the dumps or outwash plain. Visible gold was seen

in only one core sample, from drill hole MD-6. According to

studies by Luce and others (1976) "Silver is distributed

throughout the specimen (study sample) in galena and tetra-

hedrite, but gold is mainly in selvage zones".

The degree of wall rock alteration is variable. Most of

the core is pyritized and propylitized(?) while some zones are

intensely silicified and other zones are potassium-feldspathized,

as shown by veinlets of potassium-feldspar and pyroclastic

fragments and plagioclase replaced by potassium-feldspar.

Highly fractured rock with a pervasive stockwork of 1 cm sized

veinlets is the most strongly altered. Alteration at the contact

of the larger veins sometimes consists of a thin zone of dark-

green chlorite, although there is generally no contact alteration.

GEOCHEMISTRY

Sampling plan

Three types of samples were collected for geochemical

analysis; split core, character core, and surface samples. The

split core was analyzed to test for metalization while the

character core was used to determine the geochemistry of the

host rocks. Surface samples were taken to check the distribution

of metals in and along quartz veins through rocks of different

lithologies. All analyses were performed by the DGMR-USGS

laboratory in Jiddah. Analytical results are stored in the RASS

system. Split core samples have sample (RASS) numbers 97,000-

97,499, 97,628-97,749, 97,900-97,999, 105,100-105,999, and

20

110,100-110,356; character core samples have sample (RASS)

numbers 97,500-97,628; and surface character samples have

numbers (RASS) 105,700-105,999.

The entire diamond drill core obtained, with the exception

of sections of drill holes MD-5, MD-6, and MD-7, was split,

with one-half being retained and stored, the other half being

submitted for analyses. Sampled intervals were generally 1 or

2 m lengths of core. The split core samples were analyzed for

gold, silver, copper, and zinc by atomic absorption methods.

The results are part of the permanent core record on file with

the USGS project, Jiddah. Only the logs and analyses for holes

MD-7, 8, and 3 are included with this report (Appendix B).

Every tenth sample from part of the drill core was further

analyzed by semiquantitative spectrographic methods. The

results of the spectrographic analyses are listed in Appendix A.

One hundred twenty-eight lithologic character samples from

diamond drill holes MD-1, -2, -3, and -4 were taken according

to a nested hierarchical sampling plan. The purpose was to test

element concentration variation within and between lithologic

units. These 20-30 gram samples were taken before the core was

split by sawing out a 1 to 2 cm disk. Since this size is the

equivalent of a chemical split, no variation in analytical

results was introduced by sample splitting or sample preparation.

The total sample was used in the analysis. An attempt was made

to include only wall rock in the sample disk, but in some sample

zones the wall rock contained a pervasive network of mm-sized

quartz veinlets that could not be avoided.

21

Analyses performed on the lithologic character samples

included gold, silver, copper, lead, zinc, bismuth, cadmium,

cobalt, manganese, sodium, potassium, SiO2 , aluminium, and

calcium by atomic absorption methods and molybdenum, tungsten,

arsenic, and antimony by colorimetric methods. Values for

molybdenum, tungsten, arsenic, antimony, and bismuth were

generally low, at or below detection levels. Values for copper,

lead, and zinc were erratic and generally corresponded to values

obtained from the split core samples. Mean, variance, and

standard deviation of each element grouped as to lithologic

unit within the lower agglomerate are given in table 1.

A suite of surface geochemical samples were taken to test

metal distribution within and along veins in several lithologies.

Sample locations are shown on plate 2, and sample description

and anlytical results are listed in Appendix A. Gold, silver,

copper, and zinc were determined by atomic absorption methods.

Each sample was composed of numerous 1 to 3 cm sized chips

taken from outcrop along the length of the sample zone which

varied with each sample (Appendix A). The total weight of sample

varied with sample length; aim sample contained approximately

2 kg of rock chips.

Discussion of results

Metal values in split core samples from drill holes MD-3,

-7, and -8 indicate a major body of metalization within the

lower agglomerate in the southern part of the zone of quartz

veins, alteration, and faults. Surface expression of this

mineralized zone is shown by anomalous gold geochemical values

22

Table 1. Summary of analytical results and specific gravity determinations of 128 character core samples from diamond drill holes MD-1, 2, 3, and 4.

I Upper unit of lower agglomerate - 32 samples

Element Mean Standard deviation Range in values

KSi02NaAlCaMgMn

Sp GrAg

Au(-)AuCuZn

0.3675.690.663.720.492.53.11

2.7013.100.141.250.090.38

0.4213.701.132.420.511.79.08

0.1243.70.105.190.130.41

0.02-1.50 50.38-94.16 0.01-3.40 0.50-9.40 0.05-2.22 0.16-5.98 0.01-0.25 2.41-3.13 1.00-245.00 0.04-0.40 0.04-29.44 0.002-.58 0.03-1.65

II Middle unit of lower agglomerate - 80 samples

KSiO2 NaAlCaMg Mn

Sp GrAg

Au(-)AuCuZn

2.9070.25 0.844.220.432.35.15

2.681.98 0.080.200.05.17

1.689.931.402.100.361.43.07.08

5.500.080.620.15.21

0.04-5.81 45.70-93.02 0.01-8.00 0.30-7.60 0.01-1.18 0.58-5.80 0.03-.34 2.28-2.89 0.10-47.10 0.02-0.50 0.02-4.80 0.001-.95 0.008-1.12

III Lower zone of lower agglomerate - 16 samples

KSiO2 NaAlCaMg Mn

Sp Gr Ag AuCuZn

1.7263.38 2.306.071.562.48 0.162.77 1.57 0.060.020.22

1.320.872.173.581.161.300.080.080.920.050.0080.52

0.30-3.45 42.06-95.78 0.06-5.90 0.30-9.80 0.06-3.00 0.24-4.16 0.04-0.25 2.65-2.86 0.60-4.70 0.02-0.16 0.003-0.03 0.009-2.14

23

(pi. 2, and Roberts and others, 1978, pi. 1). High metal

values in the core are in altered and quartz veinlet zones

next to major veins, or within major quartz veinlet stockworks.

More importantly all of the high gold and silver values and

most of the high copper and zinc values are restricted to a

distinct stratigraphic horizon; the upper unit of the lower

agglomerate. The high values from surface samples also occur

within this unit. The distinction of units within the lower

agglomerate was made first by examination of the drill core, but

later was recognized on the surface. Although similar in hand

specimen lithology, units 1 and 2 of the lower agglomerate differ

markedly geochemically (see for example table 1). Unit 1 is

distinctly lower in K and possibly lower in SiC>2 and Al than

unit 2. Metal values are higher in unit 1, even when the few

anomalously high values are removed from consideration.

The variance of element concentration values within each

unit is high for most elements (table 1); too high to allow

direct comparison of element concentration between units.

Assuming that any one element within a lithologic unit has a

single and evenly distributed origin the analytical determina

tions for that element will be from a single population, and will

have a normal or lognormal distribution. Something other than

normal or lognormal distribution and especially distributions

with more than one mode (high), suggests that more than one

population was being sampled. In this case it suggests that the

element being analyzed had either more than one origin, or that

it was not evenly distributed at the time of formation of the

24

unit being sampled. Of the elements listed in table 1, only

the values for specific gravity and background metals have

normal or lognormal distribution; the others are mostly bimodal

or trimodal. The lack of normal distributions, reflected in

the high variance values (table 1), makes comparison of chemistry

between the units difficult. Only the differences in K values

between the upper unit and the other two units has statistical

significance. The mode of individual populations within the

obviously bimodal or trimodal distribution curves can be approxi

mated. For example, using SiO2 values from the upper unit three

populations with approximate mode values of 48 percent, 67

percent, and 90 percent can be differentiated (fig. 3). This was

done by visually fitting curves to a histogram of the SiO2

values. The 90 percent SiO2 population is slightly greater in

abundance than the 67; the 50 percent is relatively minor. Using

SiO2 values from the lower unit (fig. 3), the same three popula

tions can be recognized, only here the 45 percent SiO2 population

is dominant and the 68 percent and 92 percent SiO2 populations

are less, but still significant. Only two populations can be

seen in the SiO2 histogram for the middle unit; a very dominant

67 percent Si02 population and a minor 90 percent SiO2 population

(fig. 1). The modes for all significant elements were determined

in this manner and are listed in table 2.

The trimodal nature of element value distribution reflects

the genetic history of the lower agglomerate. Using the modes

listed in table 2 and petrography as a guideline it can be

inferred that the source of elements for the lower agglomerate

25

N =

ME

\N

=

ST

D.

DE

V .

= SK

EX

YN

ESS

=

KL

RT

OS

IS =

X

MIN

-

XM

AX

=

RA

NG

E =

16 63. 38

20.8747

0. 3072

1.28

9542.0600

95. 78

0053

,720

0

DO05

PERCENT

N =

ME

AN

=

ST

D.

DE

V,

=S

KE

WN

ES

S =

KU

RT

OS

IS =

XM

IN =

XM

AX

=R

AN

GE

=

80 70, 9. 0. ?,

45,

93.

47.

2534

9328

3050

8646

7000

0200

3200

o

N

=M

EA

N =

ST

D.

DE

V.

= S

KE

W N

ES

S =

K

UR

TO

SIS

=

XM

IN =

X

MA

X =

R

AN

GE

=

PE

RC

EN

T S

i02

LO

WE

R

t'NIT

PE

RC

EN

T S

iO2

MID

DL

E U

NIT

PE

RC

EN

T S

i02

UP

PE

R U

NIT

Figu

re 3

. - H

isto

gram

s an

d co

mpu

ter

deri

ved

( o 0

o 0 )

and

vis

ually

der

ived

( )

smoo

th

curv

es f

or S

iO2

dist

ribu

tion

in t

he u

pper

, mid

dle,

and

low

er u

nits

of t

he l

ower

agg

lom

erat

e.

Table 2. High, medium, and low population mode values determined by visual inspection of bimodal and trimodal distribution curves. Value representing dominant population is underlined

Element Upper unit Middle unit Lower unit

hK m % 1

h Si02 m % 1

hNa m % 1

hAl m% 1

hCa m % 1

hMg m% 1

h Mn m ppm 1

h Au m ppm 1

.50

90 67 48

3.8 1.5 .50

9.05.51.25

2.1.9

5.7 3.2

2400 1400 400

.35

.1,

4.001.75 .50

87 6J7

2.2 .25

7.004.751.00

.9 JL!

5.5 3.81.2

3200

800

.02

3.502.00 .25

92 68 £5

4.5 2.2 .50

9.504.251.25

2.8.9 .3

3.5.75

2400 1800 700

.02

27

was in part andesite volcanic rock and in part diorite to

granodiorite plutonic rock and dacite to rhyodacite volcanic

rock. This is consistent with the geologic history of the

region. Imposed upon the agglomerate were later metamorphic and

hydrothermal alterations reflected by the high K, high SiC^ /

high Na, low Al, high Mg(?), and high metal modes. The modes

(table 2) suggest that the upper unit is more highly altered

than either the middle or lower unit. If the upper unit was

originally composed largely of andesitic component, similar to

the lower unit, alteration involved the introduction of SiO2 and

metals and removal or dilution of Ca, Mn, Al, and Mg. If the

upper unit was originally composed largely of diorite-dacite

component, similar to the middle unit, alteration involved the

introduction of SiO2 and metals and removal or dilution of K,

and possibly Al, and Mg. In conclusion, the chemical differences

including the higher metal content of the upper unit were

introduced by post-depositional alteration rather than being a

primary feature.

EXPLORATION PROGRAM

Introduction

The USGS exploration project at Mahd adh Dhahab was

initiated in 1972. The area of Jabal Mahd adh Dhahab was mapped

at a scale of 1:2500 and the petrology and genesis of the gold

deposits studied (Luce and others, 1976) . An extensive traverse

and grid geochemical sampling program in parts of Jabal Mahd adh

Dhahab outlined several areas containing anomalous metals and

also provided information on the genetic relationships of the

28

metals present (Roberts and others, 1978). The placer potential

of the gravels surrounding the mine area was also investigated

(Bagdady and others, /97V ) Tne diamond drilling program

was based upon results of work by Luce, Roberts, and Bagdady.

An extensive geophysical survey was done under contract to ARGAS

during July and August of 1975.

Three target areas were tested: the southern mineralized

zone, the SAMS mine area, and a geophysical anomaly between the

mine area and the southern mineralized zone. The main objective

of the diamond drilling program was to prove existence of

metalization, not to outline size, shape, and tonnage of ore

bodies. The drill holes were located in a manner to obtain the

maximum geologic information in addition to testing potential

metalized zones. Targets were picked on the basis of geology,

geochemistry, and undergound maps and data of the SAMS operation

Geophysical data were utilized in the placement of drill hole 10

Diamond drilling was by the Arabian Drilling Company during

the period November 11, 1973 to June 28, 1975. A total of 10

holes with an aggregate length of 3720 m were drilled into the

selected targets. Core logs containing drilling information,

core recovery, structure, lithology and mineralization of core

sample, and sample interval and anlytical results are on

permanent file with the USGS project, Jiddah. Appendix B

contains complete logs for drill holes MD-3, 7, and 8, and

summary logs of the other drill holes. Metalized zones are

listed in table 3 and drill-hole information in table 4.

29

Table 3.--Zones of metalization in core from diamond drill holes MD-1 through 10

Coreinterval (m)

MD-1

292-303.6

MD-2

nothing

MD-3

16-1862-74

106-120124-140148-158166-190

(includes)174-190174-182176-182178-182

214-230

MD-4

40-4664-86

118-122156-168194-198

MD-5

351-379

Length (m)

11.6

21214161024

16864

16

6124

124

28

Aug/ton

17.132.842.460.9

3.8

.20

Agg/ton

84.9164.0207.0200.5

30.1

.30

Cu%

.25

.12

.25

.42

.30

.23

.50

.45

.20

.32

.62

.51

.23

.30

Zn%

.81

.271.19

.40

Au/Ag

.52

.85

.42

.20

.20

.20

.30

.13

.67

Cu/Zn

.75

30

Table 3.--Zones of metalization in core from diamond drill holes MD-1 through 10 (cont'd.)

Coreinterval

MD-6

218.02-219.10247.00-250. 00303.05-304.70332.40-335.25353.00-355.00366.35-368.45403.40-404.45

MD-7

121.00-125.50129.50-139.50

(includes)133.50-135-50

149.90-151.20174.50-175.65185.90-186.70198.80-200.63248.25-256.00262.00-267.00271.00-276.00289.30-289.80299.15-299.30

MD-8

72-7878-8181-8787-9090-9494-9797-112

112-122122-123123-130130-132132-133133-135135-148

Length

1.023.001.652.852.002.101.05

4.5010.00

2.001. 301.15.80

1.837.755.05.0.50.15

636343

151017212

13

Aug/ton

.96

.18

.04

.04

.04

.0816.40

4.15.7

15.020.84.37.21 .401.48

.14

.14

1281.412.897.33.2

31 .85.0.21

10.2.30

9.2190.010.0

.33

Ag ;g/ton ;

19.59.58.14.89.4

65.0.3

26. 728.6

64.0140.079.527.010.020.194.25.05

13.703.40

1216956.2

24920.4

17031.74.431.06.53

3024019.02.68

Cu%

.631.351.56.91.92

2.80

.24

.26

.472.151.92

. 78

. 701.571.45.87

4.058.65

.40

.70

.60

.60

.401.201.20.20-

.20

.20

.45

.20

.16

Zn%

5.00.51.93.17.70

2.00

.901.40

3.4512.504.972.10.22

4.10

1 .022.90.07

.701.401.504.30.50

3.002.90.97-

.90

.302.30.70.30

1

Au/Ag

.05

.02

.004

.01

.004

.001

.55

.15

.15

.23

.15

.05

.27

.14

.07

.03

.01

1.48.23.39.16.19.16.05.10.05.31.79.53.12

Cu/Zn

.132.651.685.361.311.40

.27

.18

.14

.17

.39

.373.18.38

.871.40

123.6

31

Table 3.--Zones of metalization in core from diamond drill holes MD-1 through 10 (cont'd.)

Coreinterval

MD-8 (cont'd.)

148-156277-280295-296353-355358-359

72-9097-112

112-130130-135135-156

72-112 72-156

MD-9

nothing

MD-10

84-8888-9090-9292-9797-99

119-121122-123133-139

171.43-171.70

Lengthm

83121

2515185

21

40 84

42252

213

.27

Auppm

.88

.09

.20

325.8

46.5

22 14

.15

.15

.10

.15

.10

2.44-.23

-

Agppm

7.182.01.633.12

16

90325

685

68 39

2.785.802.653.521.50

42.002 .068.00

7.00

Cu%

.72

.53

.881.98

.601.20.20.30.37

.30

.55

.10

.80

.18

.25

Zn%

1.35.84.55.13.80

1.632.90.92.90.70

.90 1.43

. 302.25.20

1.21j .39

Au/Ag

.01

.06

.01

.36

.16

.16

.68

.10

. 32

.36

1.052.031.042.041

i.64 1.06

Cu/Zn

.37

.41

.22

.33

.53

.33

.38

. 33

. 36

.90

.21

.50 2.70 2 ; .19

.57

2.88

.41 1.03 1.39i j

12i

32

Table 4. Length, azimuth, inclination and location of diamond drill holes MD-1 through 10

MapHole #

uses

MD-1

MD-2

MD-3

MD-4

MD-5

MD-6

MD-7

MD-8

MD-9

MD-10

Length

303.60

321.45

251.85

223.60

601.80

450.05

300.30

445.65

582.45

249.70

Azimuth

265°

305°

300°

115°

100°

157°

300°

300°

112°

90°

Inclination

30°

40°

35°

50°

45°

50°

35°

50°

70°

50°

Coordinates

346S 116W

346S 116W

286S 12E

344S 114W

662N 298W

608N 91E

244S 36E

303S 38E

444N 251W

OOON 207E

33

Drill targets

Southern mineralized zone

The southern mineralized zone occurs at the intersection

of the north-trending zone of faults, alteration, and quartz

veins and the east-striking, north-dipping, upper unit of the

lower agglomerate (pi. 2). Metalization is mainly gold and

silver, but copper and zinc are also important constituents.

Although metals are most abundant next to the major quartz

veins, anomalous gold and silver occur throughout the intervein

areas penetrated by drilling. The entire zone of quartz

vein~upper unit intersection can be considered as potentially

metalized. As surface exposures are poor the outcrop pattern

of the metalized zone is not exactly defined (pi. 2). The

surface expression is best shown by the distribution of samples

containing anomalous gold (pi. 2).

Diamond drill holes MD-1, 2, 3, 4, 7, and 8 (figs. 4-8)

explored the southern mineralized zone. Several major veins

cut the agglomerate and the rock is sufficiently fractured and

filled with quartz veins and veinlets to constitute a stockwork

in many areas. Large areas of rock near and around the veins

are highly silicified. Ancient people mined along many of these

veins and faults by means of shallow pits and trenches. Most

importantly, surface rock samples indicate a large area with

anomalous concentrations of gold, silver, copper, lead, and

zinc (Roberts and others, 1978, and pi. 2) that coincides with

the major vein systems. All drill holes in this zone were

designed to intersect numerous veins and still remain within the

lower agglomerate.

34

Elevation in Meters

1150 r

1100 -

1050 -

1000

950

MD 1

975m elevation

303.60

50 100 Meters

MOT

EXPLANATIONLOWER AGGLOMERATE

Upper UnitMiddle UnitLower Unit

CONTACT

FAULT ZONE

MAJOR AND SIGNIFICANT QUARTZ VEINS

NUMEROUS TO ABUNDANT QUARTZ VEINS

ANDESITE DIKE

DIAMOND DRILL HOLE TRACE

Figure 4. Geologic cross section through diamond drill hole MD 1

35

1050 -

1000 -

950 -

900 L

EXPLANATION

LOWER TUFF Tuff and sediment

LOWER AGGLOMERATEUpper UnitMiddle Unit

CONTACT

FAULT ZONEMAJOR AND SIGNIFICANT QUARTZ VEINS


ANDESITE DIKE



36

EXPLANATION


LOWER AGGLOMERATEUpper UnitMiddle UnitLower Unit

CONTACT FAULT ZONE

BEDDING ATTITUDE Approximate


850 -

800 -

750 L


ANDESITE DIKE


CROSS SECTION OF BLOCK OF METALIZEDGROUND USED TO CALCULATE POTENTIALRESOURCES TONNAGES

50 100 Meters

Figure 6. Geologic cross section through diamond drill holes MD 3 and 8

37

1050 -

1000 -

950 L

50 100 Meters

EXPLANATIONLOWER AGGLOMERATE

Middle UnitLower Unit

CONTACT FAITLT ZONE


////// NUMEROUS TO ABUNDANT QUARTZ VEINS

ANDESITE DIKE

\ DIAMOND DRILL HOLE TRACE


38

950 -

900 L

50 100 Maters

MD 7

EXPLANATION


LOWER AGGLOMERATEUpper Unit Middle Unit

CONTACT

FAULT ZONE

BEDDING ATTITUDE Approximate



ANDESITE DIKE

H DIAMOND DRILL HOLE TRACE

CROSS SECTION OF BLOCK OF METAL1ZED GROUND USED TO CALCULATE POTENTIAL RESOURCES TONNAGES


39

Drill holes MD-1, 2, and 4 (figs. 4, 5, and 7) penetrated

mainly the lower and middle units of the lower agglomerate.

Core from these drill holes was generally barren of metals.

Drill holes MD-3, 8, and 7 (figs. 6 and 8) penetrated mainly

the upper unit of the lower agglomerate. Core from these three

holes contain extensive lengths of anomalous to very high-grade

metalized rock. This zone of metalization, is thought to be a

major orebody and worthy of more extensive exploratory investi

gations.

Tonnages and grades given in this report are not reserve

calculations, but are estimates of potential resources. Only

geologic presence and perspective of metalization is given in

this report. Determination of size, distribution, and grade of

ore bodies must await development work. The following assump

tions are placed upon the estimates of potential resources:

a. Metalization is confined to a 40-m thick section of

the upper unit of the lower agglomerate,

b. Metalization is parallel to the major quartz veins,

c. The size, shape, and grade of any one metalized block is

consistent and continuous from surface to a point 50 m

downdip from deepest drill penetration. This point is

250 m downdip and 160 m vertically below surface,

d. Core interval, totaling 254 m, from MD-3, 7, and 8 is

representative of that zone of vein-upper unit

intersection,

e. Specific gravity averages 2.7.

40

f. No assumption is made about metallurgical properties

or recoverability of the metals.

The potentially metalized rock includes all of the upper

unit of the lower agglomerate within the zone of faults,

alteration, and quartz veins. The exposed width of the vein

zone is approximately 300 m f but an additional 100 m of width

under wadi fill to the east of the exposures can be inferred by

southward projection of veins from the mine areas (pi. 2). The

potentially metalized rock can be visualized as a north-dipping

tabular sheet 40 m thick, 250 m wide (downdip of upper unit) ,

and 400 m long (along strike of upper unit). North, northwest,

and west-trending faults break this block into wedges that are

slightly offset from one another. This block contains 17,210,000

tons of potentially metalized rock.

Drill holes MD-3, 8, and 7 (figs. 6 and 8) tested approxi

mately 150 m of the possible 400 m length of vein-upper unit

intersection. The block of ground tested by drilling, a north-

dipping tabular sheet 40 m thick, 250 m wide (downdip), and

150 m long (along strike), contains 4,050,000 metric tons.

Average grade of this block, as determined from analyses of all

split core from the upper unit of the lower agglomerate, is

6 g/t gold and 22 g/t silver.

Five blocks of higher-grade metalization can be defined

within the zone tested by drilling. Cross-sections of the

higher-grade blocks are noted on figures 6 and 8. Each block is

40 m thick, 250 m wide (downdip) and of the length (along strike)

shown on the cross-sections. The size and grade of each of the

41

five blocks is given in table 5. Various combinations of the

high-grade blocks are used to calculate estimated potential

resources, also given in table 5. The potential resources

compare favorably in grade to the grade determined from production

figures of the SAMS operation. Approximately 585,000 metric tons

of underground ore containing an average of 37 g/t gold and

58 g/t silver were produced during the SAMS operation. The

southern mineralized zone has a potential resource of 783,000

metric tons of 31 g/t gold and 68 g/t silver ore or 1,107,000

metric tons of 27 g/t gold and 73 g/t silver ore. Because only

150 m of the possible 400 m width of vein-upper unit intersection

has been explored, it is tempting to increase all potential

resource figures 2.7 times. However, the geologic perspective

does not warrant this; much of the untested zone is not exposed

and is inferred to begin with, and metalization along the untested

veins is unproved.

The SAMS mine area

The SAMS mine area was the center of most ancient mining

and all recent mining. Ancient mining was from surface pits and

narrow stopes and shafts as much as 50 m deep. The SAMS operation

was from a quarry and from 150', 300', 450*, and 600' levels of

the mine (figs. 9-17). Most ore came from four major vein

systems, numbers 1, 4, 8, and 14. Approximately 600,000 tons of

ore averaging 1 oz of gold were taken from underground workings

during the SAMS operation.

The number 1 vein system (pis. 2 and 3), the easternmost

of the productive veins, is a north-trending system that was

mined from surface to the 450' level. It was most productive

42

Table 5.--Potential resource grades and tonnages (metric) of the southern mineralized zone

Block

Total potential metalized rock

Total metalizedrock tested by drilling program

I/ A

B

C

D

E(includes A,B, and intervening rock)

Size (meters)

40x250x400

40x250x150

40x250x40

40x250x04

40x250x12

40x250x07

40x250x50

Tonnage (metric)

17,210,000

4,050,000

675,000

108,000

324,000

189,000

1,350,000

Grade Gold g/ton Silver g/ton

6 22

28 68

47 68

17 84

11 57

13 38

Potential Resources

C, D, and E

A and B

A, B, and C

1,863,000

783,000

1,107,000

13.5

31

27

48

68

73

Outline of blocks A-E shown on figures 5 and 6.

43

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1

1000 -

950 -

900 u

50 100 Meters

SAMS 6

EXPLANATIONUPPER TUFF

Tuff

UPPER AGGLOMERATEAgglomerateTuff

K-FELDSPATHIZED TUFF AND SEDIMENT

CONTACT

FAULT ZONE



ANDESITE DIKE


MINE WORKINGS

Figure 11. Geologic cross section through diamond drill holes SAMS 6 and 13

46

950 -

900 -

850 L

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Figure 12. G

eologic cross section through diamond drill hole SA

MS

12

47

975m elevation 300 ft Level

EXPLANATIONUPPER AGGLOMERATE

Agglomerate

K-FELDSPATHIZED TUFF AND SEDIMENT

CONTACTFAULT ZONE

. BEDDING ATTITUDE Approximate


////// NUMEROUS TO ABUNDANT QUARTZ VEINS

« t ANDESITE DIKE

600 -

5OO LMD 9

©

H DIAMOND DRILL HOLE TRACE

DIAMOND DRILL HOLE INTERCEPT


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1000 -

950 h

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975m elevation

uaa

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SAMS3

EXPLANATION

UPPER TUFFAgglomerateTuff

UPPER AGGLOMERATEAgglomerate

CONTACT FAULT ZONE


ANDESITE DIKE

50 100 Maters

-I DIAMOND DRILL HOLE TRACE

~ DIAMOND DRILL HOLE INTERCEPT

Figure 16. Geologic cross section through diamond drill holes SAMS 3

51

800 -

750 -

700 I-

® MO 5

50 100 Meters


AgglomerateTuff


K-FELDSPATHIZED TUFF AND SEDIMENT CONTACT FAULT ZONE


ANDESITE DIKE



MINE WORKINGS

Figure 17. Geologic cross section through diamond drill holes MD 6 and SAMS 14.

52

on and above the 300' level where 250 m of vein length in 3 ore

shoots was stoped. Only 107 m of vein length in one ore shoot

was stoped on the 450' level and there was no mining attempted

on the 600' level because only narrow widths of low-grade ore

were indicated by exploratory diamond drilling.

The number 4 is a northeast-trending vein system that was

the early major producer for the SAMS operation. Towards the

southwest the number 4 system turns southward and joins the

north-trending number 8 vein system (pi. 2). Excellent ore

was mined above the 300' level from one ore shoot 165 m long;

the same ore shoot on the 450' level was 130 m long, but was of

very low grade. Only minor ore was taken from the number 4 vein

on the 600' level. The south-trending portion of the number 4

vein system, before it joins the number 8 system, was a major

producer at the surface but yielded no ore below the 150' level.

The number 8 vein system was the focus of extensive ancient

near-surface mining. That portion of the number 8 system north

of the intersection with the number 4 vein was also a major SAMS

producer. Above the 300' level one ore shoot approximately 100 m

long was stoped to the surface. On the 450' level this ore shoot

was only 30 m long and it did not extend to the 600' level.

South of the intersection with the number 4 vein the number 8

system splits into a multitude of minor mineralized fractures.

One stope in this zone mined from 300' to 150' level produced

ore of very erratic grade and low average gold content.

The number 14 vein system consists of two major veins, the

14 footwall (14 FW) and the 14 hanging wall (14 HW) veins (pis. 2

53

and 3). Only the number 14 footwall vein has produced ore.

The number 14 hanging wall is a post-ore barren quartz vein.

The nature of the number 14 footwall vein is not well documented.

Based on some mine reports and maps the vein seems to steepen

abruptly in dip at the 300' level from 45° above to 90° below.

Other mine reports and maps suggest that there are actually two

veins, a 45° dipping vein that is cut off by a later nearly

vertical vein. Surface indications support this concept, as

throughout the study area (pi. 2) earlier shallow dipping veins

are cut by later nearly vertical veins, faults, and dikes.

According to mining records several stopes along the number 14

footwall vein stopped abruptly against faults, mafic dikes, or

barren quartz veins of north-trend and nearly vertical attitude.

The number 14 hanging wall vein is within and along a major shear

zone that extends the length of the map area (pi. 2), and the

number 14 footwall vein is broken and offset as it approaches

this zone. Two major ore shoots were mined along the number 14

footwall vein; a southern ore shoot approximately 100 m in

length was stoped from the surface' to the 300' level and a

northern ore shoot approximately 100 m in length was stoped

from the 300' level to the 600' level.

The ore shoots mined by the SAMS operation are all within

200 m of the contact of the upper agglomerate and the overlying

upper tuff and occur only in the upper agglomerate. Fracturing

and subsequent vein filling was post folding; the veins are not

folded. The number 4 vein system and the number 14 footwall

vein probably represent vein filling of fractures developed

54

along the contact of the metasomatized tuffs and sediments and

the overlying upper agglomerate at the time of folding.

Although much of the mine data suggests that metalization

does not extend below the 450' level of the mine there is

evidence to the contrary. Most of the ore shoots mined quit

with depth; but this seems to be more a function of distance

from the overlying upper tuff contact than from actual depth.

The southern ore shoots along the number 8 and north-trending

portion of number 4 veins were productive only near the surface.

The bulk of these ore shoots were probably removed by erosion

with only the lower tail left. The north ore shoot along the

number 8 vein was productive from the surface, or the contact

with the overlying upper tuff to the 450' level. The southern

ore shoot along the number 14 footwall vein was productive from

the surface to the 300' level while the northern ore shoot was

productive from the upper tuff contact to the 600' level. Also

a blind ore body that extends to depth in the number 10 vein,

was discovered in the northwesternmost workings of the 600'

level, shortly before mining operations ceased.

In summary, there were three controlling factors in ore

formation: the distance below the overlying upper tuff, the

presence of upper agglomerate wallrock, and the metal-bearing

quartz veins. Any zone, no matter the depth, where all three

criteria are met- short distance below the upper tuff, upper

agglomerate wallrock, and metal-bearing quartz-veins is a prime

target area. Three such targets were explored by diamond drill

holes MD-5, 6, and 9 (figs. 18, 17, and 13).

55

Diamond drill hole MD-5 (fig. 18) was designed to test the

extensions of vein systems 8 and 14 and 10 northward from the

mine area. Metalization in the mine area is confined to a zone

directly below the tuff, that rakes approximately 50° north

more or less parallel to the northward dip of the upper tuff.

MD-5 intersected veins thought to be extensions of vein systems

14 and 8 just below the overlying tuff in the down rake extension

of the mined ore bodies. The intersections were in the projected

target area. The drill penetrated 60 m of silicified agglomerate

containing abundant quartz veins and stockworks of veinlets, but

the core contains only trace amounts of gold f .08 to 1.6 g/t,

throughout. The best zone of metalization, 28 cm of core length,

contains an average .20 g/t gold, .30 g/t silver, .30 percent

copper, and .40 percent zinc (table 3).

Although quartz veining does continue northward from the

mine under the overlying tuff cover, the low metal values detected

in the split drill core do not justify further investigations.

Diamond drill hole MD-6 (fig. 17) was designed to test vein

system number 4 below the 600' level of the SAMS mine and to

test for possible parallel vein systems to the north. SAMS data

and maps indicate that the number 4 vein system was a major

producer from all mine levels, except the 600' level, and that

ore on the 600' level was confined to that section of vein within

agglomerate. Drill hole MD-6 intersected several veins of the

number 4 system within agglomerate and one vein within fine

grained rocks (fig. 8). Most contain anomalous concentrations

of copper, zinc, or silver, but only one has significant gold

56

Ele

vatio

n in

M

eter

s

MD

5

1050

1000

950

90

0

T-

850

800

750

700

650

L

SAM

S 14

55

m N

orth

of

sect

ion

Geo

logy

pro

ject

ed t

o se

ctio

n

EX

PLA

NA

TIO

NU

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ER

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FF

A

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f

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CO

NT

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ON

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KW

OR

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INL

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S

//////

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AM

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(table 3 and fig. 17). Although not encouraging, the results

of drill hole MD-6 indicate that the number 4 vein system and

some metalization does extend to depth and that most of the

veins remain within agglomerate at depth.

Diamond drill hole MD-9 (fig. 13) was designed as a test

of vein system 16, a possible westward extension of the flat

dipping number 14 footwall vein and also to test the interior

of what was presumed to be an altered and possibly mineralized

rhyolite stock. This drill hole was completed before the

abandoned SAMS drill core samples were discovered. Instead of

rhyolite, the drill intersected fine-grained tuff and meta-

sediment, locally potassium-feldspathized. Following examination

of the SAMS drill core samples it was determined that the rock

intersected in drill hole MD-9 was the relatively unaltered

equivalent of the rock mapped at the surface as rhyolite.

Rather than rhyolite the rock is considered to be potassium-

feldspathized tuff and metasediment. The drill penetrated only

minor veins and vein systems (fig. 13) that may be the extensions

of veins 14 and 16. Faults paralleling vein systems 8, 14, and

16 are major structures, and it is possible that the drill

intersected a zone where the vein systems had been faulted out.

The results of MD-9 indicate little potential for metaliza

tion at depth immediately below the 600' level; the veins

diminish in size, the grade of mineralized material decreases,

and the country rock is crytal-lithic tuff, a poor host for

metalization.

58

Geophysical target

Ground IP and SP geophysical surveys outlined several

geophysical anomalies east of the main zone of shearing,

veining and alteration in an area of alluvial cover (Habib M.

Merghelani, personal commun., 1975). One northeast-trending

zone of coincident IP and SP anomalies occurs just east and

south of the abandoned SAMS mill. Diamond drill hole MD-10

(fig. 19) was designed to test the highest of these anomalies.

The anomalies undoubtedly outline alteration associated with

major faults; but the purpose of the drilling was to ascertain

the presence of metalized veins within or parallel the fault.

The drill penetrated several quartz veins and quartz veinlet

stockworks and a major fault system. Several intervals of core

contained anomalous but not high metal values (table 3). The

metalization potential below the trace of drill hole MD-10 is

not considered favorable as the veins pass into fine-grained

tuffs and metasediments with depth. However, this is a newly

recognized gold-bearing quartz vein and by tracing this vein

northward or southward to areas of favorable agglomerate host

rock significant ore bodies may be found.

CONCLUSIONS AND RECOMMENDATIONS

The main target investigated at Mahd adh Dhahab is a north-

trending zone of quartz veins, faults, alteration, and related

metalization that is exposed in an area approximately 400 m wide

and 1000 m long. The eastern and southern boundaries of the

quartz vein zone are covered by alluvium. The quartz vein zone

cuts a sequence of volcanic, volcanic-sedimentary, and sedimentary

59

Oi o

950 -

900

L

-«

»-

K-F

EL

DSP

AT

HIZ

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FF

AN

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and

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0 M

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10

rocks of the Mahd adh Dhahab Series, which may be correlated

regionally to the Hulayfah Group. Most of the rock types

exposed at Mahd adh Dhahab, from coarse-grained agglomerate to

very fine-grained tuff, are of mixed clastic, pyroclastic, and

transported pyroclastic origin. Low-grade metamorphism has not

obliterated original textures of the rock, nor has alteration,

shearing, and large scale brecciation within the vein zone.

Host rocks within the quartz vein zone are generally propylitized

and locally silicified. A more widespread potassium-

feldspathization has affected all rock types, but is most

intense in the vicinity of the SAMS mine.

Anomalous metal values occur within or next to quartz veins

throughout the length of their exposure within all rock types.

Significant concentrations of gold and silver, however, occur

only where the quartz vein zone intersects agglomerate. The

SAMS mine ore bodies occur along the quartz vein zone-upper

agglomerate intersection, and the southern metalized zone occurs

along the quartz vein zone-lower agglomerate intersection. In

both metalized zones the agglomerate is propylitized, highly

silicified, and locally highly pyritized, with fragments in the

agglomerate replaced by pyrite. Quartz veins through the

agglomerates are larger and have extensive stockworks of veinlets

extending out from them that are not present where the veins

cut finer-grained rocks.

The southern metalized zone at the intersection of quartz

vein zone and the upper unit of the lower agglomerate contains

approximately 4 million metric tons of potentially metalized

61

rock. Size of this block is 40 m thick, 250 m downdip, and

150 m along strike of the lower agglomerate. Average grade of

the block explored by three diamond drill holes is 6 g/t gold

and 22 g/t silver. Unexplored portions of the zone of quartz

vein-upper unit intersection contain an additional 13 million

metric tons of potentially metalized rock. Three higher grade

blocks within the explored block contain 1.1 million metric tons

containing an average 27 g/t gold and 73 g/t silver.

The potential for additional ore in the SAMS mine area lies

in zones directly below the upper tuff where metal-bearing

quartz veins cut agglomerate. Several of these zones were

tested by diamond drilling with little success. The down-rake

extension of vein systems 8, 10, and 14 below the upper tuff

were tested by drill hole MD-5. ,The possibility of metal-

bearing veins north of and parallel to the number 4 vein system

and the extension of the number 4 vein system to depth was

tested by drill hole MD-6. The number 16 vein system and the

possibility of a westward extension of the shallow dipping

number 14 footwall vein were tested by drill hole MD-9.

Two targets remain untested in the SAMS mine area: the

possibility of metalization in the lower agglomerate below

the potassium-feldspathized tuffs and sediments and the north

and northeast extensions of the number 1 and number 4 vein

systems. Thickness of the lower tuff is estimated to be 150

to 200 m. Depth to the contact in the vicinity of the southern

portions of vein systems 8 and 14 should be 250 to 300 m.

However the depth to the contact will increase rapidly north, west,

and south, as the structure is a northwest-plunging antiform.

62

The extensions of the number 4 and number 1 vein systems

to the north and east are thought to have the best potential

for undiscovered metalization. Neither the northward and

down-rake extension of vein system number 1, nor the eastward

and down-rake extension of vein system number 4 have been

adequately tested. Both systems have been traced underground

to their terminations against the overlying upper tuff, but

their extensions under the tuff were not checked. The

favorable host-rock agglomerates extend to depth in this area.

The potential of hidden quartz veins and zones of metal

ization under alluvial cover in the wadi to the east of the

map area (pi. 2) is unknown. A few poor outcrops of veins can

be seen, but the configuration of the favorable agglomerates

is unknown as extensive faulting along north and northeast

trends makes projection from the mapped area difficult. A

series of drill holes in a panel extending eastward in the

plane of drill holes MD-3, 7, and 8 is needed to define the

eastern limit of the vein zone-lower agglomerate intersection.

Planning of other drill holes in this area should be based on

geophysical surveys.

The quartz veins and related metalization occupy north

and northeast-trending fractures that are thought to be tear

faults associated with major northeast-trending right lateral

faulting. The metals were deposited largely in the agglomerates

because the agglomerate was a "chemical" and "physical"

receptive host and in part because poorly developed fractures

63

in the tight lower and upper tuffs restricted fluid movement,

thus trapping metal-bearing fluids in the underlying agglo

merates. The setting of quartz vein emplacement and metaliza-

tion in the geologic history of the region is uncertain.

Quartz veins in the surrounding area are genetically and

physically related to a series of rhyodacite to rhyolite dikes.

Although not exposed in the map area, similar dike rock occurs

on the SAMS mine dump, suggesting that dikes were intersected

underground. These dikes terminate in flow rocks and breccia

of the Murdama Group (Brown and others, 1963) exposed a few

kilometers north of the mine area, and are probably feeder

dikes to that volcanic sequence. All intrusive rocks in the

region including the alkaline granites are cut by the dike

swarms that may be a late phase of alkaline granite igneous

activity. It is thought that both the potassium-feldspathization

and the quartz veining and metalization are related to alkaline

igneous activity, best represented by the intrusive bodies at

Jabal Sayid and Jabal Hadh'b Daheen, north and northeast of

the mine area, and the series of dikes. The potassium-

feldspathization took place during emplacement of the plutonic

bodies, dikeswarms, and volcanic rocks, and the quartz veining

and metalization during late-stage dike and vein formation.

64

REFERENCES

Aguttes, J., and Duhamel, M. , 1971, Geology and mineral explora-?

tion of the Jabal Sayid quadrangle: French Bur. Recherches

Geol. Minieres open-file rept. 71-JED-4, 49 p./97J,

Bagdady, A., Whitlow, Jesse, and Roberts, R.J.,x Placer deposits

at Jabal Mahd adh Dhahab, Kingdom of Saudi Arabia: U.S.

Brown, G.F., Jackson, R.O., Bogue, R.G., and Maclean f W.H.,

1963, Geologic map of the Southern Hijaz quadrangle,

Kingdom of Saudi Arabia: U.S. Geol. Survey Misc. Geol.

Inv. Map I-210A, scale 1:500,000.

Delfour, J. , 1975, Volcanism and mineral deposits of the Arabian-

Nubian Shield: Bur. Recherches Geol. Minieres open-file

rept. 75-JED-33.

Dirom, G.A. , 1947, Mahd adh Dhahab mine and vicinity, surface-

geologic plan and cross-sections : Saudi Arabian Mining

Syndicate, Ltd., unpub. maps in files of Saudi Arabian

Dir. Gen. Mineral Resources, Jiddah.

Dottin, O., 1975, Revised geology of the Sufaynah quadrangle,*

23/40 D: Bur. Recherches Geol. Minieres open-file rept.

75-JED-29.

Goldsmith, Richard, 1971, Mineral resources of th2 So J them

Hijaz quadrai.^xe, Kingdom of Saudi Arabia: Saudi Arabian

Dir. Gen. Mineral Resources bull. 5, 62 p.

Goldsmith, Richard, and Kouther, J.H., 1971, Geology of the

Mahd adh Dhahab-Umm ad Damar area, Kingdom of Saudi Arabia:

Saudi Arabian Dir. Gen. Mineral Resources bull. 6, 20 p. >

65

Lefevre, J.C. , 1969, Mineral resources and geology of the

Safaynah quadrangle (sheet 112): Bur. Recherches Geol.

Minieres open-file rept. 69-JED-8, 51 p., 5 maps, 2 apps.

Luce, R.W., Bagdady, A., and Roberts, R.J., 1974, Geology and

ore deposits of the Mahd adh Dhahab mine, Kingdom of Saudi

Arabia: U.S. Geol. Survey open-file rept. (IR)SA-176.

Roberts, R.J., Bagdady, A., and Luce, R.W., 1978, Geochemical

investigations in the Mahd adh Dhahab district, Kingdom

of Saudi Arabia: U.S. Geol. Survey open-file rept.

(IR)SA-231.

Theobald, P.K., Jr., 1977, Geologic status report, April 1965,

Mahd adh Dhahab area,Saudi Arabia: U.S. Geol. Survey

open-file rept. (IR)SA-15, 11 p.

APPENDIX A

Analytical results

The list that follows contains sample descriptions and

analytical values for geochemical surface samples and semi-

quantitative spectrographic analysis results of split core

samples. Locations of the geochemical surface samples are

given on plate 2.

66a

Appendix A-l.

Geoc

hemi

cal

surface

sample descriptions and

analytical values

Mapi-

Location

033N

038N

032N

031N

015N

001S

002S

002S

012N

004S

019S

019S

003S

023S

02 3S

024S

024S

024S

031S

043S

034S

030S

027S

007S

02 5S

032S

051S

051S

051S

051S

027E

027E

020E

02 2E

030E

028E

030E

025E

008E

001E

002W

002W

02 4W

02 3W

024W

025W

026W

02 7W

044W

090W

085W

080W

075W

01 OE

003E

006W

024W

02 3W

022W

01 5W

Au

Ag

ppm

ppm .75

.95

3.30

1.50

.18

2.80

8.40

6.20

24.00

8.00

20.00

3.00

11.50

.30

.40

6.40

.12

2.00

-1.

30 .40

.80

1.30

2.50

1.60

2.30 .70

.50

.08

1.30 .80

.80

.80

240.5

0

1.00

1.00 .50

.70

Cu

ppm 100

2650 240

2500 240

2500

3050

3000 90

2950

425 85

6250 500

600

700

1700

7750 500

650

3900

1325

3550 310

600

135

1225

1375 325

1025

Zn

ppm 90

2750 175

2000 110

3875

6750

4300

1500 650

350

325 90 - 90

450

700

425

925

1150 750

600 - 325

1000 475

450

150

150

Sample

Au/Ag

number

105700 701

702

703

704

.26

705

.40

706

.26

707

708

709

710

711

712

713

713

714

715

716

.70

717

718

719

720

721

722

723

724

725

726

726

727

728

729

Inte

rval

meters

1.2

2.0 .90

.30

.60

.40

.30

.60

.15

dump

2.4

2.4

2.0

through 717

1.2 .9

1.2 .8

2.9 .20

.50

1.0

1.0 .80

1.0

1.0 .60

through 72

8

.70

.90

1.0

1.0

Description

Country rock

, no

quartz

Quartz breccia on

east ed

ge main zone

Comb

quartz vein on west edge of main

zone

Copper-stained sheared

Cr on ed

ge main vein zo

neQu

artz

breccia from center

main ve

in zo

neQu

artz

breccia from center main vein zone

Sheared and

brecciated Cr on ea

st edge main ve

in zo

neStringy quartz veinlet zo

ne on we

st ed

ge main vein

Comb

quartz ve

in,

west-trend

Quar

tz breccia

Inte

rcal

ated

wall

rock from stringy

quartz veinlet zo

neQu

artz

only from abo

ve zo

neSh

eare

d, granular quartz br

ecci

a, ea

st ed

ge main zone

Continuous sequence from east to

west across zone

Quartz breccia

on east ed

ge main vein zo

neMassive quartz br

ecci

a, minor WR

Massive quartz

Chlorite-rich quartz veinlets in

andesite tuff

Massive

to slightly veined an

desi

te tuff

Comb quartz ve

in,

25°

tren

dStringy co

mb quartz vein

Stringy quartz breccia ve

in,

50%

WR,

copp

er stain

Stringy quartz breccia vein

Comp

osit

e, comb and

breccia ve

in,

loca

l copper stain

Lense of quartz breccia in stringy

comb quartz vein zo

neQu

artz

breccia

on edge of large

comb quartz vein

Massive comb quartz

Continuous sequence from west to

ea

st across zo

ne

Slightly sheared

and

altered purple tuff

Sheared an

d altered

tuff with abundant gr

een

chlo

rite

White quartz breccia vein

Slightly veined and

sheared

breccia

I/ Map coordinates oc

cur

as field

number ca

rd 3

in RAS.S

syst

em:

columns

1-5

mete

rs north or south; column 6-letter N

or S; co

lumn

7-

blan

k;

~~

colu

ms 8-

12 meters east or west;

colu

mn 13,

letter E

or W.

Appendix A-2.

Geoc

hemi

cal

surf

ace

samp

le descriptions and

analytical v

alues

(cont'd.)

0> 00

Map

Location

Au

ppm

Ag

ppm

Cu

ppm

Zn

ppm

Sample

Au/Ag

number

Interval

meters

730 through 73

2

052S

052S

052S

016S

0188

030S

037S

050S

0253

022S

022S

002N

040N

031S

034S

056S

0808

074S

053S

068S

107S

120S

1248

118S

109S

09 3S

101S

104S

0868

098E

01 2W

011W

010W

01 8E

026E

02 5E

030E

035E

050E

065E

065E

090E

130E

130E

112E

132E

14 OE

139E

090E

02 6E

146E

148E

14 3E

132E

12 5E

101E

097E

07 OE

060E

050E

.05

- - .20

- - - - - .65

2.00

2.10

.16

6.20

.16

.14

.35

.06

.06

.06

.44

1.10

- - - .40

.24

.08

.34

.34

2.30

.70

.80

1.80

- - - - .70

.70

1.50

7.00

2.30

15.00

4.00

1.30

.50

1.50

.70

- .50

.80

.40

.80

.40

.80

.60

.40

.40

.40

7500

600

340

875

235 80

80

350

350

1700

1250

1000

6375

1845

1500

1325

975

825

110

360

750

18000

150

360

300

1225

1125

260

525

175

225 90

150

125

150

110

100

100

1000

250

1875

2375

1075

3500

2375

475

700

55060 50

375

45090 90

150

300

650

250

150

150

105731

732

734

735

736

737

738

739

740

1.33

741

.30

742

.41

743

744

745

746

747

748

749

750

751

1.4

752

753

754

755

756

757

758

759

760

.80

1.0

1.0 .60

1.2 .50

1.0 .30

.50

.40

.40

2.0

Dump

1.2

1.3 .80

.60

1.0

1.0 .60

.90

.90

.90

1.20

.50

.30

1.0 .90

Dump

.80

Desc

ript

ion

Contin

uous

se

quen

ce from wes

t to

ea

st

Quartz breccia on

west ed

ge ve

in,

copper st

aine

dMa

inly

massive quartz

Massive qu

artz

Comb quartz v

ein,

so

me copper-stain

Quartz an

d Cr breccia

Comb

quartz,

30%

CrStringy quartz breccia

Banded comb quartz

Silicified zo

ne al

ong

edge of fault

Stri

ngy

comb

qu

artz

vein,

low west dip

Granular quartz br

ecci

a, ea

st ed

ge ve

inStringy co

mb qua

rtz

veins

Quartz breccia, copper-stained

Banded st

ring

y ve

ins

Diffuse

stri

ngy

vein

Quartz br

ecci

a, along

low we

st di

ppin

gQuartz breccia, lo

w we

st dip, Mn

an

d Fe

Altered

Cr b

reccia.

Fe ox

ides

Sili

cifi

ed bre

ccia

zo

neComb quartz ve

in

, Cu st

aine

d

litho

contact

oxides

Veined an

d al

tere

d zone,

low west di

p, Cu

st

aine

dVeined an

d altered

zone al

ong

post-altered fault

Altered breccia in

Wadi

Comb qu

artz

vein

Brec

ciat

ed co

mb qu

artz

Comb

quartz

Brec

cia,

co

mb qu

artz

with 40

% Cr

Stringy

comb

quartz

vein

s, 50%

Quartz br

ecci

aStringy

comb q

uartz

Appendix A-3.

Geochemical surface sample descriptions and analytical values (c

ont'

d.)

Map

Location

100S

100S

100S

100S

100S

100S

101S

095S

092S

094S

CO

094S

094S

095S

095S

091S

071S

061S

097S

103S

103S

104S

134S

134S

133S

137S

137S

148S

148S

154S

150S

020W

21W

22W

23W

25W

26W

33W

SOW

52W

81W

82W

83W

89W

90W

104W

83W

76W

02W

HE

12E

02 8E

12 1W

128W

105W

098W

09 3W

092W

08 3W

076W

06 OW

Au

ppm .12

- .06

.12

.12

.14

.24

4.00

.32

.08

.04

1.10

.28

- - .12

.12

- .14

- .12

- - .04

.14

.72

.12

.18

3.00

.14

Ag

ppm .50

.50

1.30

.80

1.00

1.00

1.00

4.50

1.00

1.00

1.60

2.10

3.20

1.00

1.00

3.30

2.80

.40

2.10

1.00

.50

.50

.80

.70

1.00

1.90

1.60

1.60

5.30

1.10

Cu

ppm

3925

700

1750

750

425

600

1700

3250

3125

750

900

875

1225

425

260

300

750

300

1800

875

2025 975

100

260

1075

1700

600

2825

24500

1500

Zn

ppm

Au/Ag

350

175

500

210

175

210

2500

2750

.93000

425

510

700

.52

2250

1475

950

1100

700

225

950

1225

520

400

925

600

975

925

1200

650

2175

.57

750

Sample

number

761

105761

762

763

764

765

766

767

768

769

770

770

771

772

773

774

775

776

111

778

779

780

781

782

783

784

785

786

787

788

789

790

Interval

meters

through 766

1.0

1.1

1.0

1.8

1.5 .60

.65

.90

.70

through 772

.90

1.2 .80

.90

.80

.60

.40

.30

.20

.50

.30

.60

1.3

1.0 .40

.35

1.1 .20

.35

.50

.80

Description

Continuous sequence from east to west across zone

Comb quartz

Granular quartz breccia

Same

Same

Massive

to co

mb quartz

Gran

ular

quartz breccia

Quar

tz br

ecci

a, Mn

ox

ides

Stringy banded ve

in,

abundant ch

lori

te,

Cu stained

Same

Continuous sequence from ea

st to

west across zo

ne

String quartz breccia

Granulated breccia

of quartz and

CrStringy quartz breccia

Brecciated co

mb quartz

Veined and

altered

zone on

west ed

ge ve

in.

Cu stained

Stringy co

mb quartz

Faul

t breccia, mixed quartz and

CrBrecciated co

mb quartz

Comb

quartz

Brecciated co

mb quartz

Chlorite-rich breccia on

ed

ge of

vein

Stringy comb quartz

Brecciated co

mb quartz

Granulated fa

ult

breccia

Brecciated comb quartz

Stringy co

mb quartz,

east

trend

Vuggy br

ecci

a, 60

% Cr

Stringy quartz breccia

Same

Granulated quartz br

ecci

a, Cu

stain

Altered an

d shear

Cr an

d qu

artz

al

ong

fault

Appendix A-4.Geochemical surface sample descriptions and analytical values (c

ont'

d.)

Map

Location

147S

142S

142S

142S

142S

142S

144S

144S

144S

144S

^

143S

O

154S

150S

146S

147S

156S

156S

156S

156S

156S

156S

125S

118S

129S

157S

200S

196S

152S

160S

175S

051W

037W

034W

033W

032W

031W

02 3W

022W

021W

020W

014W

019W

001W

021W

024W

041E

042E

04 3E

044E

04 5E

04 6E

080E

083E

044E

066E

07 OE

069E

100W

Q95W

70W

Au

ppm .88

.40

- .18

- - .08

.08

.08

.08

1.24

- - - .84

1.98

.08

.20

.22

.60

- - .32

.14

.05

.08

- 3.10

4.90

.27

Ag

ppm

1 1 2 1 3 3 2 2 3 2 0 1 2 7 4

.50

.70

.50

.00

.10

.80

.10

.80

.10

.80

.70

.50

.20

.80

.90

.50

.20

.60

.20

.70

.90

.80

.10

.60

.50

.50

.50

.00

.20

.20

Cu

ppm 600

2125 700

700

575

1635 825

575

1425

1500

500

270

370

1600

825

2575 285

825

2250

1800

190

2400

33000

500

380

575

575

825

3075

38000

Zn

ppm

Au/Ag

575

425

600

425

225

520

350

300

175

175

200

.34

50

300

825 50

250

.57

7512

5450

325 75

400

1150 75 70

225

550

1875

1.55

460

.68

9259

Sample

numb

er

105791 792

792

793

794

795

796

797

797

798

799

800

801

802

803

804

805

806

806

807

808

809

810

811

812

813

814

815

816

817

818

819

820

Interval

meters

through 1 1 1 2

through 1 1 1 1

through 1 1

.40

.75 796

.5 .0 .4 .0 800

.60

.0 .0 .9 .75

.55

.65

.3 .0 811

.7 .6 .7 .9 .2 .3 .60

.25

Dump

.60

.35

.90

.70

.45

.40

Description


Stringy comb quartz

Continuous sequence from west to east across zone

Fine-grained tuffaceous sandstone

Fault breccia, knots of quartz

Same

Slightly sheared and altered country rock

Continuous sequence from west to east across zone

Stringy veinlet zone on west edge main vein


Granulated quartz breccia, Fe oxides

Same ,

Cu stained

Comb quartz

Brecciated zone on east edge vein

Comb quartz ,

combined with minor Cr

Granulated quartz and Cr breccia

Same

Continuous se

quen

ce fr

om west

to ea

st across zo

ne


ecci

a, Fe

oxides

Comb quartz

Stringy co

mb quartz


ecci

a, abundant chlorite

Same

Comb

quartz


Altered

fault

zone,

copper-stained

Quartz br

ecci

a, Fe oxides

Slightly brecciated comb quartz

Quartz br

ecci

a, Fe

oxides

Coarse br

ecci

a, mostly comb quartz

Stringy

quartz breccia

Band

ed ch

lorite quartz ve

in,

Cu stained

Granulated quartz breccia

in bedding pla

ne fault

Appendix A-5.Geochemical surface sample descriptions and analytical values (c

ont'

d.)

Map

Location

184S

184S

175S

***

182S

182S

182S

182S

191S

192S

192S

191S

196S

197S

198S

197S

182S

187S

206S

204S

202S

178S

185S

204S

204S

205S

205S

205S

217S

218S

***

172S

70W

69W

40W

26W

25W

24W

23W

13E

29E

30E

34E

49E

50E

51E

64E

120W

119W

107W

103W

100W

95W

92W

91W

91W

87W

86W

85W

54W

46W

26W

Au

ppm .12

- .05

- - - .08

- .08

- - - - - - .38

.12

.12

.12

.05

.05

.14

- - .46

.17

- -

Ag

ppm

1 1 1 3 1 1 1 1 1 5 2 3 1 2 1 1 1

.30

.40

.70

.90

.80

.80

.80

.40

.90

.50

.80

.80

.80

.60

.80

.84

.40

.70

.60

.60

.40

.00

.10

.50

.50

.30

.40

.10

.70

.40

Cu

ppm

1200

1250

1100

650

575

1200

41000

400

425

150

475

415

850

455

260

3000

335

425

800

375

4000

1650

480 75

700

900

600

1150

265

250

Zn

Sample

ppm

Au/Ag

number

123

145

760

1100

300

138

500

525

325 48

300

225

475

275 40

1800

625

2250

300

550

2250

1625

950

350

1875

850

350

250

103

125

105821

822

823

825

825

826

827

828

829

830

831

832

833

834

835

836

837

838

839

840

841

842

843

844

845

846

846

847

848

849

850

824

Interval

meters

.20

.60

.65

through

838

.50

1.0 .80

.90

.35

.45

.50

.70

.40

.70

.50

.70

.50

.45

.50

.35

.20

1.0 .70

.85

.85

through

848

.50

.50

.50

.70

.20

.30

Description

Bleached and altered tuff on west edge vein

Vuggy, dursy stringy vein

Same

Continuous sequence from west to east

Granular, rounded quartz breccia on edge vein

Quartz breccia, abundant small angular fragments

Vuggy, stringy veins, Fe oxides

Quartz breccia, granulated, Cu stained

Stringy vein, Fe oxides

Comb quartz

Comb quartz

Stringy quartz breccia, rounded to angular

Comb quartz copper-stained

Same

Stringy comb quartz ,

30%

Cr

Comb quartz

Brecciated comb quartz ,

local vugs

Breccia from fault zone

fragments

.Bre

ccia

ted

and altered rock next to fault zone

Banded comb quartz vein

Comb quartz

Coarse breccia, minor quartz cement, Cu stain

Quartz breccia, Fe oxides and Cu stain

Comb quartz with chlorite banding

Country rock from same zone as 844


Quartz and wall rock breccia, locally granulated

Same

Same

Quartz breccia, Fe oxides, minor Cu stain

Banded comb quartz

Comb anartz .

oael- 1-r

-pnr

l i nr

r TToin

Appe

ndix

A-6.

Geochemical

surf

ace

samp

le descriptions an

d analytical values (c

ont'

d.)

to

Map

Location

218S

218S

239S

239S

239S

239S

239S

239S

239S

239S

239S

239S

239S

245S

244S

240S

250S

246S

248S

254S

248S

233S

235S

233S

233S

235S

313S

308S

299S

295S

43W

41W

12 9W

12 8W

127W

126W

12 5W

124W

123W

12 2W

121W

120W

119W

116W

113W

111W

111W

101W

98W

90W

85W

60W

56W

47W

35W

34W

140W

120W

150W

160W

Au

ppm

- -

3.30

1.60

3.80

.18

.28

.35

.72

.58

.17

.17

.15

1.50

.12

.12

.17

.12

.20

.25

.02

.17

.15

.05

.05

.12

6.50

3.50

- .17

Ag

ppm

2.70

1.70

2.80

7.30

25.00

3.60

4.50

4.25

3.25

8.50

1.56

2.75

3.35

3.90

2.21

2.40

1.10

2.10

.75

1.75

1.00

1.20

.75

.51

.75

1.25

32.50

21.20

1.20

1.65

Cu

ppm

365

600

2700

520

2400

1000

1500

1350

625

485

850

950

580

700

1375

750

450

1150

1150

1150

1250

465

1150

520

110

350

21500

1800

900

485

Zn

ppm

Au/Ag

108

135

126

1.18

100

.22

1000

.15

410

145

145

350

300

875

625

550

975

.38

250

750

300

500

130

1375

560

126

350

325 74

350

8000

.20

775

.17

300

970

Sample

number

105851

852

853

853

854

855

856

857

858

859

860

861

862

863

864

865

866

867

868

869

870

871

872

873

874

875

876

877

878

879

880

Interval

meters

2.5 .55

through 86

3

1.0

1.0

1.0

1.0

1.0

1.0 .50

1.0

1.0

1.0

1.0 .55

1.0 .45

.60

.45

.35

.30

.70

.45

.70

.40

.70

1.4

Dump

1.0 .80

.40

Description

Coarse quartz and wall rock breccia

Breccia on east edge vein, mostly Cr with granular quartz


Massive healed quartz breccia

Sheared Cr with numerous 1-2 cm quartz veinlets

Vuggy banded quartz vein

Slightly sheared and vein Cr

Same

Same

wi

th se

vera

l banded ve

inle

tsMajor

fracture zo

ne,

brec

ciat

ed qu

artz

an

d Cr

Lacy b

anded

vein systems

in sh

eare

d Cr

Lacy b

anded

vein and

vein

let

syst

em in

sh

eare

d Cr

Same

Same

Granulat

ed qu

artz

breccia

Stringy

vein

s of

granulated an

d br

ecci

ated

quartz

Banded an

d lo

call

y granulated vein

Stringy

vein

s of

brecciated

quartz

Same

30%

SrQuartz breccia, granulated

Stringy

veins

Horsetail

zone of la

rger

ve

inBa

nded

, vu

ggy

quar

tz carbonate

vein,

Cu st

ain

Same

Granulated qu

artz

br

ecci

a, Fe

ox

ides

Quartz br

ecci

a, an

gula

r fr

agme

nts

Brec

ciat

ed and

silicified WR

on

east

ed

ge vein

Quartz br

ecci

a, Fe

oxides,

Cu st

aine

dQuartz breccia, ch

lori

te-r

ich

Quar

tz br

ecci

a, may

not

be in

place

Stringy

comb

qu

artz

veins

Appendix A-7.

Geochemical surface sample descriptions and analytical values (cont'd.)

Map

Location

287S

273S

270S

268S

265S

265S

264S

262S

27 3S

351S

352S

353S

353S

353S

343S

31 6S

31 6S

316S

316S

316S

316S

320S

322S

320S

322S

323S

325S

32 5S

325S

325S

158W

141W

135W

125W

12 3W

11 3W

115W

108W

73W

174W

169W

160W

159W

158W

148W

75W

74W

73W

72W

71W

64W

63W

61W

59W

46W

42W

36W

35W

34W

33W

Au

ppm .10

.65

.72

.72

.20

.97

.42

.20

.10

2.50

7.80

31.00

1.70

27.50

35.00

.15

.15

2.50

1.80

1.80

.12

.66

2.40

.55

.95

.17

.25

.62

.92

2.20

Ag

ppm

2.75

3.25

10.00

1.85

2.25

2.75

3.00

1.65

.51

18.00

75.00

47.50

17.50

31.50

33.50

8.50

1.85

22.50

56.00

32.50

6.50

13.50

15.00

6.50

38.50

3.80

4.75

15.00

37.50

9.00

Cu

ppm

500

2125

1450

1100

450

950

1200

1125

475

7500

2300

61000

2200

8500

1450

675

1200

1725

2200

975

475

1725

6875

4625

1250

825

250

11500

20000

5625

Zn

ppm

1500

840

1250

1750

190

450

1375

1250

450

7000

650

7800

2500

7800

1625

1700

67000

1150

1575

790

575

2900

3450

2825

465

500

910

450

31000

5400

Au/Ag

.14

.10

.65

.10

.87

1.04

.11

.03

.06

.16

.24

Sample

number

105881

882

883

884

885

886

887

888

889

890

891

892

through

892

893

894

895

896 through

896

897

898

899

900

901

902

903

904

905

906

907

through

907

908

909

910

Interval

meters

.75

.60

1.0 .70

.20

1.5 .70

1.0

1.0

1.0

1.0

894 1.0

1.0

1.0 .40

900 1.0

1.0

1.0

1.0 .80

.75

1.0 .50

.80

1.0 .80

910 1.0

1.0

1.0

. 1.0

Description

Altered WR between vein and andesite dike

Stringy comb quartz veins

Same

Brecciated CR from fault zone

Comb quartz

Quartz breccia, angular to rounded fragments

Quartz and WR breccia along edge of major vein

Brecciated and altered country rock

Stringy veins of brecciated quartz, 50% WR

Stringy comb quartz ,

Cu stain

Coarse breccia of quartz and silifified WR


Sheared, altered veinlet zo

ne,

Cu stained

Vuggy quartz breccia, rounded

fragments

Same

Quartz breccia, with abundant chlorite-rich fragments



Quartz breccia, with post mieral shearing

Same

Stringy breccia zone,

boudins of older quartz

Same

Granulated quartz vein, banding

Same

Comb quartz,

copper -stained

Altered breccia zo

ne on east edge vein

Stringy vein zone,

abun

dant

chlorite


Continuous sequence from west to

east

Quar

tz breccia

Same

Same

, abundant copper stain

Altered Cr on ea

st ed

ge of vein

Appendix A-8

Geochemical surface samples descriptions and analytical values (cont'd.)

Map

Location

326W

326S

297S

266S

264S

265S

285S

345S

345S

345S

347S

348S

35 OS

350S

338S

342S

345S

350S

354S

358S

359S

358S

360S

362S

364S

365S

367S

368S

369S

370S

27W

24W

11W

21W

20W

26W

30W

19W

18W

17W

04W

01W

06W

22E

109W

91W

90W

78W

SOW

76W

75W

66W

63W

62W

60W

56W

54W

52W

SOW

49W

Au

ppm

9.00

1.32

.10

.10

.15

.26

.15

2.20

2.24

24.00

3.60

1.72 .11

3.30

.14

.05

.30

.87

.25

.10

.20

.25

.12

.05

- .22

.22

.60

2.24

.02

Ag

ppm

5.00

2.50

1.10

2.70

4.00

21.20

1.00

38.50

37.50

100.00

24.00

18.50

-

1.10

5.00

2.20

5.00

18.50

5.00

1.77

2.15

3.60

4.60

1.77

3.30

2.10

5.50

3.30

7.50

5.00

Cu

ppm

475

375

625

325

1725

1450

375

325

250

375

2700

1550

675

625

500

675

1500

625

625

675

1700

325

575

1500

1350

875

675

13750

13750

375

Zn

ppm

Au/Ag

279

1.80

225 90 80

700

1550

510

250

.06

60

.06

120

.24

1550

.15

715

.09

75

3.0

7539

0465

6200

2520

585

500

1000

490

465

1700

850

510

365

5100

2900

250

.30

Sample

Interval

number

meters

105911

912

913

914

915

916

917

918 through 920

918

919

920

921

922

923

924

925

926

927

928

929

930

931

932

933

934

935

936

937

938

939

340

.70

1.2 .60

.50

1.0 .50

1.0 .80

.50

.70

.65

1.0 .45

.40

.30

1.10

.55

.50

.85

.45

.50

1.3 .40

.20

.55

1.0 .60

1.0 .60

.60

Description

Quartz WR breccia

Stringy banded veins, Fe

oxides,

post mineral shears

Massive

quartz

Quartz breccia

Altered tuff on east edge of vein

Veined and

altered Cr

, al

ong NW tr

end

Bleached an

d altered zone

Continuous sequence fr

om west

to east

Altered and

sheared

zone,

50% WR


Altered and

veined zone,

30% WR


ecci

a, slight banding

Stringy qu

artz

veins

Massive

comb qu

artz

Band

ed comb quartz

Same

Granulated qu

artz

breccia

with comb quartz along edges

Quar

tz breccia, abundant chlorite

Stringy qu

artz

veins

Stringy qu

artz

veins, 50

% WR

Vuggy quartz br

ecci

a, abundant Fe ox

ide

Altered Cr

on east ed

ge of

vein

Lacy breccia with banded quartz


Bleached and

altered WR on

edge

of vein

Boudin of

older quartz,

brecciated

Altered and

veined WR

, 30

% vein

Vugg

y, open drusy ve

ins

carbonate (?) ,

Cu stained

Granulated qu

artz

breccia

Altered WR,

Fe oxides,

Cu stained

Breccia of

WR a

nd gr

anul

ated

qu

artz

Appendix A-9.

Geochemical surface sample descriptions and analytical values (cont'd.)

Map

Location

365S

366S

365S

359S

372S

370S

374S

363S

369S

380S

372S

374S

370S

376S

375S

384S

396S

398S

396S

406S

397S

398S

4 DOS

437S

438S

425S

432S

441S

440S

432S

430S

41 OS

400S

409S

404S

43W

34W

27W

21W

23W

18W

16W

11W

08W

06W

01E

06E

HEHE

16E

25E

23E

35E

4 IE

40E

48E

61E

80E

36W

38W

30W

36W

48W

SOW

19W

10W

01E

17W

24W

33W

Au

ppm .02

.07

.14

.85

.20

1.28

7.52 .60

7.24

3.60

.30

.06

.20

3.30

.24

.16

.32

1.48

.10

.16

.16

.26

.12

.10

.22

.24

-

23.00

.02

- .35

1.00

.20

.17

-

Ag

ppm

3.30

3.14

3.70

7.00

6.50

5.00

75.00

6.50

11.00

5.00

.85

.50

.95

.65

1.35

1.65

.65

2.40

.80

.65

1.10

1.35

.50

1.20

.85

2.00

.30

6.50

1.10

1.20

1.00

.85

1.35

1.00

.65

Cu

ppm 775

1250

675

775

375

775

1600

675

825

25250

1451

160

675

2525

450

450

1250

9250

500

925

475

500

195

238

625

1250

125

4875

275

325

575

1050

1175

190

185

Zn

ppm 620

860

465

1800

690

3050

850

730

600

9550

245

475

345

790

690

730

675

1875

325

2650

1675

760

175

760

730

140

500

725

190

860

565

2100

650

1950

530

Sample

Au/Ag

number

105941

942

943

944

945

.26

946

.10

947

948

.66

949

.72

950

951

952

953

5.08

954

955

956

957

.62

958

959

960

961

962

963

964

965

966

967

6.54

968

969

970

971

972

973

974

975

Interval

meters

.75

.75

1.6

1.3

1.2

1.1

1.1 .25

.50

.50

.30

1.1 .30

.25

.40

.40

.60

,60

.40

.75

.60

.85

.25

.70

1.4 .60

.65

1.0

1.0 .45

.85

1.0

1.0

1.0 .80

Description

Altered shear zo

ne,

Fe oxides

Same


Quartz br

ecci

a, fr

agme

nts

of older

quar

tzGranulated quartz,

chlorite banding

Same

Quartz br

ecci

a, abundant chlorite an

d older quartz fr

ags

Band

ed comb quartz

Quartz breccia

with later

comb quartz in

center

Same

, Cu stained

Banded comb quartz

Silicified breccia,

tuff

an

d chert

frag

ment

sCo

mb quartz

Comb quartz with Cu stain

Stringy

veins

Band

ed and

crustified vein with granular quartz

Same ,

but

by la

ter

comb

Stringy

band

ed veins, Cu stained

Massive

brown chert

Massive white quartz

Band

ed and

crustified quartz veins

Massive

white quartz ,

minor banding

Milky white quartz with sc

atte

red

clear quartz

Quartz br

ecci

a, fr

agme

nts

of older, cu

t by comb

Vuggy quartz breccia, may crosscut 96

4Stringy ve

ins,

Cu

st

ain

Brec

cia,

quartz and WR fr

agme

nts

Breccia

, rounded

to angular fr

agme

nts

quar

tz an

dSa

me to

we

stQuartz breccia

quartz

WR

Quartz br

ecci

a, so

me ch

lori

te banding, cut

by comb quartz

Quartz breccia with fr

agme

nts

of older, cu

t by comb qu

artz

Granulated qu

artz

breccia

Quartz br

ecci

a, ol

der

quartz frags

set

in milky

Breccia

of WR and

comb qu

artz

fragments

quar

tz matrix

Appe

ndix

A-10.

Geoc

hemi

cal

surf

ace

samp

le descriptions and

analytical values (c

ont'

d.)

Map

Location

Au

ppm

ppm

Cu

ppm

Zn

ppm

Au/Ag

Samp

le

number

Inte

rval

meters

Desc

ript

ion

401S

404S

401S

395S

401S

458S

47

3S

470S

48

0S

39W

52W

65W

104W

12 OW

72W

54W

46W

30W

.10

2.70

.08

.80

.16

.08

1.00

.06

2.0

1.00

.85

1.45

2.50

1.10

.80

2.60

1.10

825

675

475

675

475

7250

1075

1075

1306

220

520

110

1100

875

155

875

230

640

2.70

.38

105976

977

978

979

980

981

982

983

984

..0 .80

.90

.60

.35

.70

.60

.85

.35

Granulated quartz breccia, abundant chlorite

Same with cross-cutting comb quartz veinlets

White massive quartz, Cu stain

Stringy banded vein

Faulted continuation of 979

Stringy comb quartz, Cu stained

Same with 50% altered andesite

Chlorite fragments in quartz breccia

Breccia, quartz and andesite

-3

O5

Appendix A-ll, Semiquantitative spectrographic analyses of 2-meter split core. Other elements analyzed for include: As, B, Be, Bi, Cd, Co, Cr, La, Mo, Nb, Ni, Sb, Sc, Sn, Sr, W. and Y. Their values were generally at or below detection levels.

Sample number

97181971919720197211972219723197241972519726197271972819729197301973119732197331973419735197361973719738197391974019741197421974319744197451974619747197481974919763197641976519766197671

Fe % Mg %

3 .53 23 22 12 .52 .73 1.52 15 1.53 1.53 15 1.53 1.55 23 332 33 15 22 22 23 33 53 33 51 1.52 23 25 35 52 22 25 25 25 22 .53 3

Ca %

.3

.3

.5

.3

.3

.05

.51.52.3.5

2.5.7.3.3.05.05.1.1.7.3.3.7

2.1.1.05.3.2.3.7

3.5.3.2.7

Ti %

.7

.5

.7

.5

.5

.3

.5

.31.7.3.7.3.7.7.7.5.7.7.5.5.5.5.7.7.15.2.2.5.5.2.2.5.5.5.1.7

Mn ppm

300100010001500700

1000100010001500700700

150010001500150015001500

701000500

10001000500050005000700

100010001500200010001000150015001500500

1000

Ba ppm

50003000

G50003000200015003000200015001500500020001500

50200015005002000500070020002000

G500030002000700300500200150

15001000200700

1000500

1000

V ppm

15015070

1507070

150150

100070030070020030070505070

7005070

100150300300505050

1001005050

15070

10030

100

Zr ppm

5030303020503030705030303030

10010010010010050

10010050

1001001501505070

3001001005050

10050

500

78

APPENDIX B

Core logs

The section that follows includes summary geologic logs

for drill holes MD-1, 2, 4, 5, 6, 9, and 10 and photo

reductions of complete drilling and geologic logs for drill

holes MD-3, 7, and 8. The complete logs (similar to those

included here for holes MD-3, 7, and 8) are on permanent file

with the U.S. Geological Survey Mission, Jiddah, Saudi Arabia

79

Appendix B. Summary geologic logs of diamond drill core from MD-1, 2, 4, 5, 6, 9, and 10

B-l

Summary log MD-1

From

0

31.05

34.50

65.00

108.30

118.30

158.38

180.80

214.15

265.20

0

47.10

60.20

66.05

To

31.05

34.50

65.00

108.30

118.30

158.38

180.80

303.60

216.40

266.40

S

47.10

60.20

66.05

67.20

Description

Weathered agglomerate

Quartz vein

Intercalated lithic tuff and agglomerate

Intercalated lithic tuff and agglomerate Several gougy fault zones Several quartz veins Numerous to abundant quartz veinlets

Agglomerate

Intercalated lithic tuff and agglomerate Numerous quartz veinlets

Agglomerate

Andesitic tuff

Fault zone, gouge

Fault zone gouge

ummary log MD-2

Agglomerate

Agglomerate, numerous quartz veinlets and several quartz veins

Agglomerate

Andesite dike

80

SummaryB-2 From

67.20

69.80

111.25

120.30

143.94

167.95

170.30

171.48

179.40

218.33

219.25

244.00

0

39.50

40.75

86.00

96.40

99.80

113.72

log MD-2 (<

To

69.80

111.25

120.30

143.94

167.95

170.30

171.48

179.40

218.33

219.25

244.00

321.45

j

39.50

40.75

86.00

96.40

99.80

113.72

180.00

continued)

Description

Fault, gouge

Intercalated tuff and agglomerate/ numerous quartz veinlets and several quartz veins

An de site tuff

Intercalated agglomerate and lithic tuff, numerous quartz veinlets

Intercalated agglomerate and lithic tuff, numerous quartz veinlets and several quartz veins

Andesite dike

Fault zone

Agglomerate

Agglomerate, numerous quartz veinlets

Andesite dike

Andesitic tuff

Andes! tic tuff to agglomerate, numerous to abundant quartz veinlets, several small faults

Summary log MD-4

Agglomerate

Quartz vein

Intercalated lithic tuff and agglo merate, several fault zones, gouge. Numerous large quartz healed breccias

Agglomerate

Fault zone, gouge

Quartz healed breccia

Agglomerate, numerous quartz veinlets81

Summary log MD-4 (continued) B-3

From

180.00

191.00

196.35

199.60

0

37.70

38.98

71.58

11?. 40

121.45

152.53

200.05

216.36

218.90

230.55

233.85

To Description

191.00

196.35

199.60

223.60

Intercalated agglomerate and andesitic tuff, numerous quartz veinlets

Andesitic tuff

Fault zone, gouge, vein quartz fragments

Andesitic tuff

Summary log MD-5

37.70

38.98

71.58

118.40

121.45

152.53

200.05


Fault zone

Massive tuff

Intercalated lapilli to massive tuff and agglomerate

Fault zone, gouge

Intercalated mafic agglomerate cherty tuff

Mafic agglomerate

216.36 1 Carbonate-bearing tuffj

218.90 i Fault zone

230.55 ' Talc, massive

233.85 Fault zone, gouge

and

332.00 j Intercalated argillite, carbonate and ? talc bearing tuff and volcanic , conglomeratet

332.00 359.90 , Numerous fault zones, gouge

359.90 376.00 Agglomerate gray, silicified, abundantquartz veinlets and stockworks

82

Summary log MD-5 (continued) B-4

From

376.00

542.20

547.07

590.25

To

542.20

547.07

590.25

601.80

Description

Lithic to crystal tuff intercalated with mafic agglomerate

An de site dike

Mafic agglomerate

Massive tuff

Summary log MD-6

0

38.25

88.00

119.40

140.60

146.90

260.45

296.70

298.60

418.20

38.25

88.00

119.40

140.60

146.90

260.45

296.70

298.60

418.20

450.05


Agglomerate, to lithic tuff

Intercalated agglomerate lapilli tuff, lithic tuff and carbonate- bearing tuff

Carbonate-bearing tuff

Fault zone

Agglomerate, gray, several 50 cm quartz veins and abundant quartz veinlets from 218.08 to 253.42

Agglomerate , mafic

Fault zone

Crystal tuff to lapilli tuff, abundant K- feldspar, numerous quartz veinlets 300.30 to 315.30, 331,70 to 339.85, 351.00 to 355.00, 366.35 to 368.45

Tuff, massive to well bedded, numerous auartz veinlets

Summary log MD-9

0 31.85 Weathered agglomerate

31.85 36.80 Andesite dike

36.80 39.10 Fault zone

83

Summary log MD-9 B-5

(continued)

From

39.10

100.00

106.50

192.80

194.30

207.20

211.20

296.80

306.20

322.55

342.40

343.80

355.00

356.30

364.80

365.20

371.60

376.00

431.85

To

100.00

106.50

192.80

194.30

207.20

211.20

296.80

306.20

342.40

322.80

343.80

355.00

356.30

364.80

365.20

371.60

376.00

431.85

580.45

Description

Agglomerate, gray scattered quartz veins

Stockwork of quartz veins

Agglomerate, gray, scattered quartzveins

Fault zone

Lithic to crystal tuff, generally bedded

Quartz vein, minor sulfides

Lithic to crystal tuff, scatteredquartz veins

Stockwork of quartz veins and veinlets

Andes! tic tuff intercalated withagglomerate and lapilli tuff

Shear zone

Stockwork of quartz veins

Agglomerate intercalated with lithic tuff

Stockwork of quartz veinlets

Intercalated agglomerate and lithic tuff

Shear zone

Andes! tic tuff, generally bedded

Stockwork of quartz veins and veinlets

Intercalated andesitic tuff, lapilli tuff and agglomerate

Massive to well bedded andesitic tuff,local mafic lapilli

84

Summary log MD-10B-6

From

0

23.25

23.85

38.95

40.35

85.40

110.00

122.10

125.20

148.30

160.10

165.80

182.15

193.75

198.80

219.50

247.75

To

23.25

23.85

38.95

40.35

85.40

110.00

122.10

125.20

148.30

160.10

165.80

193.75

187.00

198.80

249.70

238.95

249.70

Description


Fault zone

Agglomerate , gray

Andesite dike

Intercalated agglomerate, andesitic tuff, lapilli tuff and crystal tuff, generally layered

Andesitic tuff and tuff breccia, numerous to abundant quartz veins and veinlets

Andesitic tuff

Quartz breccia vein, minor sulfides

Intercalated andesitic tuff toagglomerate, layered, several 20 cm quartz veins and numerous quartz veinlets

Agglomerate

Andesite dike

Intercalated andesitic tuff toagglomerate

Sheared zone

Agglomerate with abundant pyrite and pyrite-rich fragments

Intercalated andesitic tuff, crystal tuff and lithic tuff

Fault zone, gouge and shear planes

Fault zone

85

MINISTRY OF PETROLEUM AND MINERAL RESOURCES DIRECTORATE GENERAL OF MINERAL RESOURCES

KINGDOM OF SAUDI ARABIA SA (IR) 233 PLATE 3

9.000 E 10.000 N

9 000 N -

10000E 11 .ODD E

6.000 N -

Protected from SAMutt

SAMS 10 SAMS.7

EXPLANATION

AGGLOMERATEAgglomerate Crystal-lap'"' tuff

MF.TASOMATIZFD ROCK

ANDESITE DIKE


CONTACT

FAULT

MINE WORKINGS


Major laull zone

project ) from MD 10r

10.000 N

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100

SCALE 1:2500

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200 MtTERS

GEOLOGY OF THE 300 FT LEVEL OF THE MAHD ADH DHAHAB MINE

A'

Major north-trending vein, nearly parallel to section

MO 8 MD 7

300 ft Level SAMS mine


Agglomerate Tuff


K-FELDSPATHlZfcD TUFF AND SEDIMtNT


LOWER AGGLOMERATEUpper UnitMiddle UnitLower Unit

CONTACT

900 -

850 -

800 -

750 >-

ANALYTICAL RESULTS- 48 ppm Au

16-48 ppm Au

FAULT ZONE




CROSS SEC MON OF BLOCK OF METALIZED GROUND USED TO CALCULATE POTENTIAL RESOURCES TONNAGES

Figure 2. Geologic cross section along line A-A'

18

Date started; November 14.1974

Date Completed: January 9^1975

Driller: A DC

KINGDOM OF SAUDI ARABIA Ministry of P*troi«um and Mineral Resources Directorate General of Mineral Resources

U S Geological SurveySurvey Data

Lal Long Z3-49'54" 4l-3l'47"

Mineral Occurrence Collar Coorde

Subsurface

Depth

Collar

Mahd adh DhahabDrill Hole Number:

MD 7Inclination Azimuth

300- 35-

( Troparj)

298- 35'

296 39

SA(IR) 233

APPENDIX B

MINERALIZATION

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KINGDOM OF SAUDI ARABIA Ministry of Petroleum and Mineral Resources Directorate General of Mineral Resources

U S Geological Survey

Mineral Occurrence

Mohd adh OhahabDrill Hal* Number: _

ML) 3

SA(IR) 233

APPENDIX B

COKE

RECOVERY

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Date storied: March 21. 1974

Dote completed: M>y £6,1974

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KINGDOM OF SAUDI ARABIA Ministry of Petroleum and Mineral Resources Directorate General of Mineral Resources

U S Geological Survey

Mineral Occurrence

Drill Hole Number:MD8 Sheet 2

SA(IR) 233

APPENDIX B

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by Ronald G. Worl - pubs.usgs.gov · by Ronald G. Worl ABSTRACT ... countries to the north. The...

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Transcript of by Ronald G. Worl - pubs.usgs.gov · by Ronald G. Worl ABSTRACT ... countries to the north. The...