ORE DEPOSIT GEOLOGY

CONTENTS : WEEK 2

a) ORE STRUCTURES / TEXTURES

Ore Textures (megascopic)

Ore Textures (megascopic)

Replacement textures

Exolution textures

Void-filling textures

Others

b) ORE FORMING MELTS / SOLUTIONS

Magma and Magmatic fluids

Occurences related to crystallisation of magma

Hydrothermal fluids

ORE DEPOSIT GEOLOGY

LEARNING OUTCOMES

(What You will have obtained after the class hour)

You will be able to

• recognise and identify different types of textures , and relate them to ore minerals

• infer types of mineral deposits and mineral paragenesis based on textures

ORE TEXTURES

• Megascopic and three dimentional appearance of ore and gangue minerals making up an ore

• Definiton of megascopic view of an ore. i.e. How it looks, howw we describe the sample

ORE TEXTURES

1) Massive texture

Ores in which samples have rather homogene character & fearure, and usually made up of one ore few minerals

Characteristic of mineral deposits formed usually at high temperatures

Sample:

a) Cr, Fe, Ni-Cu deposits

b) Skarn-type deposits

c) VMS deposits Sudbury Ni-Cu deposit

ORE TEXTURES

Sudbury Ni-Cu yatağı

1) Massive texture

Ores in which samples have rather homogene character & fearure, and usually made up of one ore few minerals

Characteristic of mineral deposits formed usually at high temperatures

Sample:

a) Cr, Fe, Ni-Cu deposits

b) Skarn-type deposits

c) VMS deposits

ORE TEXTURES

Pyrotite; Dereli skarn deposit

1) Massive texture

Ores in which samples have rather homogene character & fearure, and usually made up of one ore few minerals

Characteristic of mineral deposits formed usually at high temperatures

Sample:

a) Cr, Fe, Ni-Cu deposits

b) Skarn-type deposits

c) VMS deposits

ORE TEXTURES

Çayeli VMS deposit

1) Massive texture

Ores in which samples have rather homogene character & fearure, and usually made up of one ore few minerals

Characteristic of mineral deposits formed usually at high temperatures

Sample:

a) Cr, Fe, Ni-Cu deposits

b) Skarn-type deposits

c) VMS deposits

2) Disseminated texture

Textures in which disseminations of minerals accumulate throughout the sample, giving the rock usually homogenous view

Characteristic in podiform cromite deposits

ORE TEXTURES

chromite; Kop podiform chromite deposit

ORE TEXTURES

Chromite; Kop podiform chromite deposit

2) Disseminated texture

Textures in which disseminations of minerals accumulate throughout the sample, giving the rock usually homogenous view

Characteristic in podiform cromite deposits

3) Ring texture

Ore samples in which ore minerals are in the form of rings, bracelets, etc.

Characteristic for podiform type chromite deposits, as well as deposits formed by weathering (bauxite deposits

Chromite; Kop podiform chromite deposit Rings are chromite

Slayt-10

ORE TEXTURES

Slayt-11

ORE TEXTURES

Bauxite: Al ore

3) Ring texture

Ore samples in which ore minerals are in the form of rings, bracelets, etc.

Characteristic for podiform type chromite deposits, as well as deposits formed by weathering (bauxite deposits

4) Banded or laminated texture

Ores in which ore minerals or disseminations of ore minerals accumulate as bands of mm to cm in thickness.

Characteristic in podiform chromite deposits

Slayt-12

ORE TEXTURES

Chromite bands in harzburgite

Slayt-13

ORE TEXTURES

4) Banded or laminated texture

Ores in which ore minerals or disseminations of ore minerals accumulate as bands of mm to cm in thickness.

Characteristic in podiform chromite deposits

Chromite bands in harzburgite

Slayt-14

ORE TEXTURES

Carbonate nodules

5) Nodular texture

Ores in which minerals are formed at the surface and have the kidney-like shape

When nodules are in cm scale, it is called oolitic texture, when in mm scale, then pisolitic texture.

Sedimentary Fe-Mn deposits, travertine depoits

Slayt-15

ORE TEXTURES

Oolitik yumrular

5) Nodular texture

Ores in which minerals are formed at the surface and have the kidney-like shape

When nodules are in cm scale, it is called oolitic texture, when in mm scale, then pisolitic texture.

Sedimentary Fe-Mn deposits, travertine depoits

6) Stockwork texture

Ore minerals are along veinlets cross-cutting each other

ağsal kuvars ve pirit

ORE TEXTURES

7) Brecciated texture

Ores which have undergone deformation following its formation, giving rise to brecciation of rock as well as minerals.

Brecciation takes place after the mineralisation.

Çayeli (Rize) bakır madeninde breşleşmiş cevher kütlesi (pirit, kalkopirit, sfalerit ve gang mineralleri)

ORE TEXTURES

8) Breccia-fill texture

The ores in which ore minerals fill in the gaps formed due to brecciation of rock

i.e. The brecciation is before the mineral occurrence

Found usually in htrothermal deposits

breşleşmiş damar içerisindeki boşlukların galen tarafından doldurulması.

ORE TEXTURES

9) Cellular texture

The ore or rock in which ore and gangue minerals leave voids due mainly to escape of gas during cooling of fuids.

Occurs mainly in replacement type deposits.

Characteristic in epithermal Au deposits

Cerattepe (Kafkasör, Artvin) Au deposit

ORE TEXTURES

Emirli (Ödemiş, İzmir) antimony deposit

ORE TEXTURES

9) Cellular texture

The ore or rock in which ore and gangue minerals leave voids due mainly to escape of gas during cooling of fuids.

Occurs mainly in replacement type deposits.

Characteristic in epithermal Au deposits

CEVHER YAPILARI

10) Dendiritic texture

The ore or any rock in which ore and gangue minerals are deposited or crystallised in the form of branching tree.

Occurs under surficial conditions.

Characteristic for Mn occurences

Manganese dendirites (Abdulaliler Mn occurrence, Maçka, Trabzon

CEVHER YAPILARI

11) Sferulitic texture

Any rock or ore specimen in which minerals are crystallised in the form of spherulites

Occurs mainly during low temperature crystallisation under near-surface conditions

Characteristic for zeolite, chlorite occurences

Stibnite sferülites (Emirli Sb deposit, Ödemiş)

CEVHER YAPILARI

12) Colloidal Texture

Any rock that is formed as a result of colloidal (in the form of a gel) transport of particles.

Occurs as concentric layers around a microscopic particle

ORE TEXTURES

13) Void-filling textures

Characteristic in low temperature, silica enriched (epithermal type Au) deposits.

a) Banded texture,

b) Comb texture,

c) Cokard texture

d) colloform texture

1

A geod (piece of rock which has a large void in it)

ORE TEXTURES

2

Sample opened up a little

ORE TEXTURES

3

Sample opened completely.

ORE TEXTURES

Slayt-28

13) Void-filling textures

a) Banded texture,

Minerals are crystallised along certain zones or bands which may or may not repeat symmetrically Usually occurs in epithermal deposits

Direction of crystallisation

Quartz

Carbonate

ORE TEXTURES

ORE TEXTURES

13) Void-filling textures

a) Banded texture,

1) Symmetricly banded texture

Usually a piece of vein in which crystallisation of minerals takes place symmetrically from the wall to the center of the vein, such as a-b-c-b-a

Gümüşköy Ag deposit (Kütahya).

ORE TEXTURES

Murgul (Artvin) Cu deposit (wall rock-quartz- ametist-quartz-chalcopyrite zones)

13) Void-filling textures

a) Banded texture,

1) Asymmetricly banded texture

Usually a piece of vein in which crystallisation of minerals takes place in the form of asymmetrical zones or bands, such as a-b-c

ORE TEXTURES

13) Void-filling textures

b) Comb texture

A piece of vein in which crystallisation of minerals (usually quartz) takes place as single euhedral crystals growing towards the center of the vein. Characteristic in epithermal systems Olucak (Gümüşhane) Au occurrence

ORE TEXTURES

13) Void-filling textures

c) Cocard Texture

A colloidal-like texture in which mineral precipitation takes place around a megascopic particle or piece of rock. Characterisitic in low T systems

ORE TEXTURES

A colloidal-like texture in which mineral precipitation takes place in te form of symmetric or asymmetric circular or elliptical zones around a microscocopic particle. Characterisitic in low T systems

Çataltepe (Tonya) vein type Pb-Zn deposit

13) Void-filling textures

d) Colloform Texture

ORE TEXTURES

A colloidal-like texture in which mineral precipitation takes place in te form of symmetric or asymmetric circular or elliptical zones around a microscocopic particle. Characterisitic in low T systems

13) Void-filling textures

d) Colloform Texture

MICROSCOPIC TEXTURES

Microscopic Texture refers to the physical appearance or character of a rock, such as grain size, shape, arrangement, and pattern microscopic level. This includes the geometric aspects and relations amongst the minerals. Instead of texture, the term microstructure is preferred by some petrographers

How they are formed? – What they tell us ? 1) Features of hyrothermal fluid 2) Physical characteristic of country rock 3) Physical characteristic of country rock 4) Changes in T and P during crystallisation of minerals

MICROSCOPIC TEXTURES

What they tell us? 1) Temporal relations between gangue and ore minerals

• When a mineral was formed and how it was formed? 2) Mineral paragenesis and succession of mineralisation 3) Formational temperatures of ore and gangue minerals 4) Briefly, conditions under which the ore was formed

Types of microscopic ore textures 1) Ornatım dokuları, 2) Eksolüsyon dokuları 3) Boşluk dolgusu dokuları

MICROSCOPIC TEXTURES

Zerbanos Yayla Cu-Pb-Zn vein, Maçka, Trabzon)

1) Replacement textures

Forms as a result of the interaction of a fluid while it goes through already-formed minerals due to cooling and exchange of ions between the fluids and the minerals

a) Infilling of a fracture by a mineral

MICROSCOPIC TEXTURES

1) Replacement textures

b) Occurrence of a mineral as island or discrete pieces of mineral within

another minerl

Zerbanos Yayla Cu-Pb-Zn

vein, Maçka, Trabzon)

MICROSCOPIC TEXTURES

1) Replacement textures

c) Occurrence of a mineral as island or discrete pieces of mineral within

another minerl

Zerbanos Yayla Cu-Pb-Zn

vein, Maçka, Trabzon)

MICROSCOPIC TEXTURES

1) Ornatım Dokuları:

c) Intrusion of a mineral through another mineral

Replaement of bornite

by chalcopyrite

MICROSCOPIC TEXTURES

1) Replacement textures:

d) Irregularly surrounding of a mineral around / along another mineral

Tetrahedrite and galena

around chalcopyrite

MICROSCOPIC TEXTURES

1) Replacement textures:

e) Encompassing a mineral

A silver mineral around

another silver mineral from

Gümüşköy, Kütahya

MICROSCOPIC TEXTURES

1) Replacement textures:

f) Irregularly intrusion of a mineral within a mineral

Replacement od sphalerite

by tehtahedrite. Bakacak,

Ordu

MICROSCOPIC TEXTURES

2) Exolution textures:

Katı ergiyik içerisinde bulunan bileşenlerin özellikle sıcaklığın

düşmesine bağlı olarak birbirinden ayrlması ve ergiyik içerisinde az

olarak bulunan fazın ana faz içerisinde ayrı olarak kristalleşmesiyle

oluşan doku türüdür. Bu doku türü oluşum sıcaklığının

belirlenmesinde son derece faydalıdır.

Some Exolution textures

Pirotin içinde pendlantit

Kalkopirit içinde kübanit

Sfalerit içinde kalkopirit: 400oC

Stannit içinde sfalerit: 325 oC

Manyetit içinde ilmenit

İlmenit içinde hematit

Hematit içinde ilmenit

Sfalerit içinde kalkopirit:

MICROSCOPIC TEXTURES

2) Exolution textures:

0102030405060708090100

A SixOy B SixOy

T2

T4

T3

T1X3X2

Sıvı (Ergiyik)

X1T2

T4

T3

T1

Karışabilirlik aralığı

T

Homojen

c

a

Moleküler %

MICROSCOPIC TEXTURES

2) Exolution textures:

a) Inclusions:

Chalcopyrite inclusions

within sphalerite.

Zerbanos Yayla Cu-Pb-

Zn vein, Maçka,

Trabzon)

MICROSCOPIC TEXTURES

2) Exolution textures:

b) Lattice texture :

Chalcopyrite lattice in

bornite

MICROSCOPIC TEXTURES

2) Exolution textures:

a) Lattice texture:

MICROSCOPIC TEXTURES

3) Boşluk Dolgusu Dokuları:

Same as megascopic void-filling textures

MICROSCOPIC TEXTURES

3) Boşluk Dolgusu Dokuları:

1) Microveins of a mineral within another mineral

Tetrahedrite vein within

chalcopyrite

Zerbanos Yayla Cu-Pb-

Zn damarı, Maçka,

Trabzon)

MICROSCOPIC TEXTURES

3) Void-filling texture

2) Veinlets

Tetrahedrite-veinlets in

chalcopyrite

Zerbanos Yayla Cu-Pb-Zn

vein, Maçka, Trabzon)

MICROSCOPIC TEXTURES

3) Boşluk Dolgusu Dokuları:

Breccia-infill texture

CEVHER DOKULARI

3) Void-filling texture

4) Colloform texture

CEVHER DOKULARI

4) Other Textures

a) Needle-like textures

CEVHER DOKULARI

4) Other Textures

b) Kink-banded textures

Stibnite kink-bands (Gümüşler, Niğde).

c) Dissolution textures

Dissolution of pyrite (Gümüşler, Niğde).

Pyrite

Pyrite

lst

lst

lst

Barite

Sphalerite+galena+fahlore

2 cm

Limestone

kçt

kçt

kçt

kçt

kçt

ORE: Mineral Paragenesis - 1

ORE: Mineral Paragenesis - 2

1

2

3

5

1

2 1

5

3

6

4

ORE: Mineral Paragenesis - 3

4 6 1

5 4

2

1

4

1

3 3’

3

3’

6

4

ORE: Mineral Paragenesis - 4

%45,941 Cu, %16,863 Te, % 9, 046 As, % 0,533 Zn, % 0,44 Ag, %0,276 Fe, % 25,58 S

0, 74 at. % Cu+Fe+Zn+Ag, 0,263 at. % Te+As+Sb, 0,768 at. % S

Cu12Te4S13 : Goldfieldit

Mik

rop

rob