Geophysical Characterization of Uranium-REE · PDF fileDharmapuri Shear Zone, in the Northern...
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Transcript of Geophysical Characterization of Uranium-REE · PDF fileDharmapuri Shear Zone, in the Northern...
A.K.Chaturvedi and P.S.Parihar
Geophysical Characterization of Uranium-REE Mineralization
associated with Alkaline-Carbonatite Complex along North
Singhbhum Shear Zone, Singhbhum Craton, Jharkhand and
West Bengal, India.
Department of Atomic Energy
Atomic Minerals Directorate for Exploration & Research
Government of India
Technical Meeting on Uranium from Unconventional Resources 4-7 November 2014
International Atomic Energy Agency (IAEA), Vienna, Austria
Introduction on Alkaline-Carbonatite Complexes
(ACC) of India.
ACC areas under exploration
1. Dharmapuri Shear Zone (DSZ), and
2. North Singhbhum Shear Zone (NSSZ)
Geophysical Characterization of NSSZ
1. Using High Resolution Heliborne Survey
2. Interpretation and modeling of Heliborne TEM,
Magnetic, Radiometric data.
3. Integrated interpretation of Geophysical,
geological and drilling data for further
subsurface exploration.
Scheme of Presentation
Alkaline-Carbonatite Complex (ACC) of India holds considerable
potential and few of them are being explored to establish low-grade
polymetallic U-REE deposits.
Important Alkaline Complex of India :
Ambadongar related to late stage Deccan alkaline magmatism,
Gujarat.
Newania within Archaean basement granite, Rajasthan
Beldih and Kutni along North Singhbhum Shear Zone (NSSZ),
West Bengal.
Sevattur and Rasimallai along Dharmpuri Shear Zone, Tamil
Nadu.
Sung Valley along Um Ngot lineament, Meghalaya and
Samchampi along Kalyani lineament, Assam.
Alkaline-Carbonatite Complex (ACC) of India
75°E
22°N
Ambadonagar Village
(Map modified after Deans et al., 1972)
•The sub-volcanic alkaline ring
complex of Amba Dongar (~ 65 m.y.)
consists of carbonatites,
nephelinites and phonolites, and is
well known for hosting the largest
fluorite deposits (av. 30% CaF2) of
India.
•It is a part of the Chotta-Udaipur
alkaline province and is located at
the northern periphery of the Deccan
flood basalts besetting the western
edge of the Narmada Rift Zone.
•Fluorite, Apatite, Magnetite/Hematite
Pyrochlore, Barite, Monazite and
thorogummite are common minerals
recovered from Ambadongar
Carbonatite Complex.
•The Newania carbonatite , located
about 40 km east of Udaipur town,
Rajasthan and is situated within the
structurally highly deformed Aravalli
Mountain Range.
•The Newania carbonatite consists
mainly of dolomite (rauhaugite, ~ 2.27
Ga, Pb-Pb age) and younger,
differentiated ankerite carbonatite
(~1.55 Ga, Pb-Pb age), and dykelets of
calcite carbonatite (sovite).
• Apatite is the main economic
mineral mined from Newania
Carbonatite Complex. Associated by-
products are magnetite, pyrochlore
and traces U-REE bearing minerals.
25°N
24°N
74°E
0 50Km
GEOLOGICAL MAP OF MEGHALAYA PLATEAU AND THE MIKIR HILLS
ALLUVIUM
GARO GROUP & EQ.
JAINTIA GROUP
KHASI GROUP
CARBONATITE COMP.
SYLHET TRAP KHASI GREENStonne
INTRUSIVE GRANITE SHILLONG GROUP
BASEMENT GNEISSIC COMP.
90° 91° 92° 93° 94°
90° 91° 92° 93° 94°
25°
26°
25°
26°
F
F F
F
F
F F F
F
F
F
F
F
JA
MU
NA
F
GUWAHATI
DAUKI F
SUNG VALLEY
COMPLEX
SHILLONG
(AFTER NANDY, D.R., 2001)
F
SAMCHAMPI
COMPLEX
Barpung
Jasra
Sankri, Nongcharam
• The Sung Valley ultramafic-alkaline–carbonatite complex
(~115 Ma) is an oval shaped body covering an area of about 26
Sq. Km and is emplaced within the Shillong Plateau, an
uplifted horst-like feature in Meghalaya state.
• Sung Valley complex consists of pyroxenite, serpentinized
peridotite, ijolite, nepheline syenite and carbonatite.
• Carbonatite is the youngest member of the complex as it
intrudes in other rock types as small dykes, veins and oval
shaped bodies.
• Carbonatite from Sung valley indicated moderate uranium
contents (95–165 ppm), low thorium contents (45–284 ppm)
and quite variable Th/U (0.27– 1.96).
Geological map of Alkaline Carbonatite Complex along
Dharmapuri Shear Zone, in the Northern part of Tamil Nadu,
India
The NE-SW trending Dharmapuri Shear Zone (DSZ), located in the northern part of Tamilnadu and
characterized by the presence of a number of Alkaline-Carbonatite Intrusions (~700-900 Ma age)
such as Pakkanadu, Samalpatti, Sevattur, Elagiri, Rasimalai, Paravaimalai and Pallikonda.
Subsurface exploration at Pakkanadu and Rasimalai areas by AMD has indicated significant
polymetallic U-REE mineralisation.
Rasimalai
M R
B Alpha track
O O
O
Sy
Car
Py Py Cpy
G
Mi
Mi Ba
Hy
Cai-Str
Microphotographs of Rasimalai Alkali Syenite (A) with microcline (M) ,
riebeckite (R), hypersthene (H) (B) Betafite (B) with alpha track (C)
Carbonate (Car) injections in syenite with sulphide opaque (O) (D) same as
Fig.C in reflected light containing pyrite (Py) and chalcopyrite (Cpy) (E)
Suplide mineral galena (G) and millerite(Mi) (F) Grain mount of heavy
mineral showing baryte (Ba), hypersthene(Hy), opaque(O) (G) Calcite-
strontianite (cal-Str) in grain mount .
H
O
B A C
D E
F
G
676
m
RASIMALAI
Radio active Pink syeniteNon Radioactive Grey syenite
Element (ppm) Min Max
Cr 11 418
Cu 10 1056
Zn 10 411
Sr 80 23208
Y 10 133
Zr 11 3038
Nb 10 2797
Ba(%) 0.01 17.33
Ce 16 48430
Th 10 1549
U 10 1074
U - n=524 <10 ppm, n=114 10-1000 ppm, n=409 >1000 ppm, n=1
Nb - n=524 <10 ppm , n=48 10-1000 ppm, n=468 >1000 ppm, n=8
Sr - n=524 <0.01%, n=2 0.01-0.1%, n=196 >0.1-1%, n=317 >1%, n=9
Trace Element Concentration in Rasimalai area, Tamilnadu
Inferences
Betafite has been identified as the main radioactive phase at
Rasimalai hill.
Higher concentration of Nb, Pb, Ba and Sr associated with
the radioactive syenite (Galena, Barite, Strontianite).
Uranium mineralisation is syn to epigenetic disseminated in
nature
Sulphide phases are epigenetic in origin.
Radioactive phase is associated with alkali syenite (aegirine,
acmite and riebeckite).
INFERENCES FROM RASIMALAI AREA, TAMILNADU
Geophysical Characterization of U-REE Mineralisation
Associated with Alkaline-Carbonatite Complex along
North Singhbhum Shear Zone
High Resolution Heliborne Geophysical Survey over North Singhbhum
Shear Zone, Jharkhand and West Bengal, Eastern India
VTEM Measure vertical component of time derivative of the
electromagnetic induction (dB/dt) & compute the vertical
component of electromagnetic induction (B-Field) .
Specification : sampling at 0.1 sec, base frequency at 25
Hz, diapole moment : 4,25,000 NIA, 40 time gates; Half
period : 20 ms
MAGNETIC : Measure the total magnetic field.
Specification : sampling at 0.1 sec, Cs-vapour
Magnetometer, operational range : 15,000 – 1,05,000 nT
Gamma Ray Spectrometer : Measure the gamma radiation
from U, Th & K from top 30 cm of ground.
Specification : sampling at 1 sec, NaI crystals,
Data in 1024 channels over 0 to 3 MeV energy
Survey Specifications
Line Spacing: 200 m (North - South)
Tie line Spacing: 4 Km (East – West)
Survey Height: 60 meter (AGL)
TDEM: VTEM System (Geotech Airborne Ltd.)
Magnetic: Cs Vapour Magnetometer (Geometrics)
Gamma Ray Spectrometer: RSX-5 (Radiation Solution
Ltd.)
GPS: Dual Frequency GPS
Helicopter: A350 B3 Squirrel - VT VAD (Global Vectra)
Survey Operations EM, Magnetic and Radiometric Data Acquisition
Magnetic Base Station – to observe the diurnal variation in magnetic data
Ground Radiometric Calibration - pre and post survey using Uranium,
Thorium and Cesium standards to check the spectrometer functioning.
Aluminum plate test for current polarity check before the start of survey.
Radiometric Test line (length 7-8 Km) in start of survey and end of survey
to observe the repeatability of radiometric data.
High Altitude Test – pre and post flight; in between flight,if flight is of long
duration or drift in data is not linear , which is useful in VTEM system
noise estimation, current compensation and zero level the data.
Regular Traverse lines on the basis of navigation file (*.pgn file).
First Hand Data Quality Check – at heli-base after each flight by running
Geotech proprietary software GND.
EM (VTEM) data (*.d file, each of maximum 10 minutes) of each flight were converted to
*.xyz file using GND, which was imported to Geosoft and database file was generated.
GPS QC – Checked the profile plots and statistics for longitude latitude, GPS time and
GPS altitude and by plotting on the plan map generated using nav file.
EM QC (Where we recorded the statistics of SR[10], BR[10], SR[33] and BR[33] and
observed profile plots for spikes and other noise.
Current Compensation - Raw dB/dt (SR) and B field (BR) data were compensated for
effect residual current of transmitter loop over receiver loop using the MaxB recorded
data.
Filtering - Compensated dB/dt (SC) and B field (BC) data were filtered (4 fiducial Non-
linear & 0.0001 tolerance and 10-15 fiducial low pass filter) for removal of spikes.
Leveling - To bring the every channels data at same/zero level, the leveling is done
separately for filtered dB/dt (SF) and B field (BF) data by using high altitude correction
records in the start of each flight and end of each flight.
VTEM & Magnetic Data quality Validation and Preliminary Processing
Visualization of Processing Steps on B Field Data in Log-Linear Scale
B Field Raw Data
B Field Compensated Data
B Field Filtered Data
B Field Levelled Data
Magnetic and Power Line
Power line effect on B Field data
VTEM & Magnetic Data quality Validation and Preliminary Processing
VTEM & Magnetic Data quality Validation and Preliminary Processing
Base mag – base mag data (*.txt file) imported to Geosoft and processed
(5 fiducial Non-linear & 0.0001 tolerance and 100 fiducial low pass filter)
for removal of spikes. Finally *.tbl file is created, which will be used for
diurnal correction to raw magnetic data.
Diurnal Correction – Raw Magnetic data (Mag1) was corrected for diurnal
variation by importing the *.tbl file by matching the Gtime.
Flight database is split in to lines.
Grid images generation – by using minimum curvature gridding
technique and cell size of 50m.
Interpretation of Heliborne Geophysical Datasets.
Target delineation & Prioritization on the basis of
integrated interpretation.
Ground checking of selected prioritized target areas.
Integrated study of drilled borehole results with
interpreted results from Heliborne datasets.
Planning of boreholes for Subsurface Exploration.
Evaluation of the proposed Boreholes.
Steps for Information Extraction and
Integration
Uranium anomaly Zones in NSSZ Block
Area Line No. U (ppm) Th (ppm) K% U/Th Rock Type
Beldih
15000-15060
(along 7 line,
Mine dumps)
8.4-54.6 12.5-25.7 1.15-2.11 0.62-2.1
Quartz-
magnetite
apatite rock
Dandudih-
Kutni
16260-16340
(Anomaly extent
is 1.6 km)
6.97-43.42 13.28-20.81 0.92-1.88 0.72-2.56
Ferruginous
quartzite
Rangamatiya
16500 &
16630-16380
Anomaly extent
is 1.0 km
7.34-10.99 3.91-7.67 0.30-0.90 1.05-2.30
Brecciated
ferruginous
quartz breccia
Porapahar 17520, 17530
17600, 17650,
17690
6.06-8.76 7.60-11.79 0.52-1.09 0.65-1.15
Brecciated
ferruginous
quartz breccia
Geological map of Alkaline-Carbonatite Complex around Beldih,
Purulia district, West Bengal, Eastern India
Magnetic
B-Field
dB/dt
-400
-200
0
200
400
600
800
1000
-150 -100 -50 0 50 100 150
dB
z/d
t (u
V/A
)
Station (m)
Beldih_S3
Ch21
Ch22
Ch23
Ch24
Ch25
Ch26
Ch27
Ch28
Ch29
Ch30
Ground TEM Response of Line 14980
3D Iso-surface Map of Magnetic Susceptibility 0.03 SI unit for Beldih Area by using UBC-Mag3D Software
1100m (l) x 280m (b) x 800m (d)
3D-Modeling of Magnetic Data of U-
REE bearing Alkaline-Carbonatite
Complex (ACC) in Beldih Area
Carbonatite Drill Cores, Beldih
0
50
100
150
200
250
0 2000 4000 6000 8000 10000
Dep
th (m
)
Magnetic Susceptibilty (X10--6) SI units
Magnetic Susceptibility Log of BLD12 Magnetic Susceptibility
Measurement of BH No. BLD12
At Depth 217m to 221m
Chalcopyrite-Pyrite and magnetite
abundance
Ch Py Mag
Py
Magnetite Rich Zone± sulphides (mainly pyrite) in
Ultramafic rock with carbonatite veins
Carbonatite rich Zone with clasts of Ultramafic rock
± magnetite and specks of sulphides
Mylonitized alkali granite
with ultramafic and
carbonatite
Magnetite zone, sulphides (mainly pyrite) in
Ultramafic rock with carbonatite
RA Zone
190
195
200
205
210
215
220
1 10 100 1000 10000
De
pth
(m)
Magnetic Susceptibilty (X10-6) SI units
Magnetic Suscepetibility log of BLD-12
190
195
200
205
210
215
220
0 0.01 0.02 0.03 0.04 0.05
De
pth
(m)
%eU3O8
Uranium Mineralisation of BLD12
0.016%eU3O8 x 2.45m(201.36m-203.82m) core assay
0.021%eU3O8 x 0.42mCore assay
0.0165%eU3O8 x 0.90m(211.42m-212.30m) core assay
S
N0 10 20 30 40m
BLD-3RL-242.94m
R.L.
in m.
DATUM
D.D.
299.90m
BLD-5RL-243.12m
240
220
200
180
160
140
120
100
80
60
40
0
20
D.D.
163.55m
0.023 x 6.40m
(0.032 x 3.20m)
(0.018 x 8.40m)
0.023 x 3.20m
(0.025 x 2.80m)
0.019 x 6.20m
(0.022 x 3.60m)
VEIN QUARTZ
A
A
A
A
B
B
B
T.D.
170.00m
BLD-16&25
TRANSVERSE SECTIONS THROUGH BLD-3, 5 & 16 & 25, BELDIH AREA
Conductor
104.00m
145.00m
ULTRAMAFICS ± CARBONATITE
ALKALI GRANITE
I N D E X
OVERBURDEN/MINE DUMP
CARBONATITE ± ULTRAMAFICS
RADIOACTIVE BAND (0.010%eU3O8 cut-off)
KAOLINITE± GOETHITE
APATITE RICH ZONE
RL-243.079m
Fel
dspa
r ri
ch z
one
D.D.
338.40m
0.021 x 8.20m
(0.034 x 2.40m)
0.013 x 3.20m
0.026 x 15.20m
RADIOACTIVE BAND (0.020%eU3O8 cut-off)
(0.034 x 6.00m)
(0.033 x 2.90m)
D.D.
121.00m
VERTICAL LONGITUDINAL SECTION THROUGH BOREHOLE NOS. BLD-11, 14, 7, 8, 13, 6, 5, 9 & 10 BELDIH AREA, PURULIA DIST., WEST BENGAL T.S.No. 73 I/8W E
0 10 20 30 40m
R.L.
in m
240
220
200
180
160
140
120
100
80
60
40
DATUM
20
BLD-5BLD-6BLD-7
D.D.
283.90m
D.D.
169.60m
D.D.
299.90m
0.016 x 1.40m0.013 x 2.10m
0.016 x 1.00m
0.018 X 1.30m
0.023 x 3.20m
(0.025 x 2.80m)*
0.019 x 6.20m
(0.022 x 3.60m)*
*Values at 0.02% eU3O8 (Cut Off)
A
A
A
A
B
B
B
B
B
(Abandoned)
A
A
A
A
AA
B
B
BD.D.
280.70m
0.032 x 14.30m
(0.034 x 12.90m)*
0.014 x 2.30m
BLD-8
D.D.
293.70m
A
A
A
A
B
B
BLD-9
0.028 x 3.40m
(0.031 x 2.80m)*
0.021 x 4.40m
(0.021 x 1.80m &
0.025 x 1.60m)*
0.016 x 9.40m
0.012 x 4.60m
D.D.
289.30m
BLD-13 (P)
0.014 x 2.40m
D.D.
282.70m
A
A
A
BLD-10 (P)
BLD-14
D.D.
264.50m
BLD-11
D.D.
244.50m
QUARTZ - MAGNETITE - APATITE ROCK
RADIOACTIVE BAND(S)
I N D E X
OVERBURDEN/MINE DUMP
ULTRAMAFICS ± CARBONATITE
VEIN QUARTZ
CARBONATITE ± ULTRAMAFICS
ULTRAMAFICS WITH ALKALI FELDSPAR
ULTRAMAFICS WITH PODS OF BIOTITE
A
B
ALKALI GRANITE
Carbonatite of Beldih Area
Intruded within Alkali Granite prior to Shearing
Segregated Apatite rich zone (in carbonatite) hosts U mineralization
Calcite, Apatite, Amphibole, Biotite, magnetite, Pyrochlore
Varieties 1. Calciocarbonatite
2. Magnesio carbonatite 3. Carbonatite with ultramafics
Carbonatite Ultramafics (Amphibolite)
Apatite rich zone
Alkali Granite
Elements in
ppm Carbonatite (n=13)
RA Apatite rich rocks
(n=13)
Av. carbonatite
(Woolley & Kempe,
1989)
Ba 27 – 627 ( 125) 66 – 993 (244) 3400
Sr 1930 – 4600 (3584) 1500 – 5800 (4000) 8600
Zr 24 – 187 (58) 45 – 265 (150) 189
Nb 57 – 1808 (777) 2400 – 14000 (6700) 1204
Ta 5 – 112 (28) 69 – 800 (372) 5.0
U 1 – 35 (10) 70 – 1391 (570) 8.7
Th 5 – 27 (09) 5 – 40 (25) 52
Y 10 – 78 (28) 86 – 423 (218) 119
REE (T) 390 – 1973 (797) 1887 – 8757 (4719)# 776
LREE (T) 321 - 1827 (718) 1738 – 8211 (4363) # 3850
Dy 1.5 – 20 (07) 28 – 129 (71)# 34
Trace element data (ICP-AES/MS)
# N=17
Chemical Analysis of Carbonatite and Radioactive
Apatite-Magnetite rich rocks in Beldih
In Parenthesis - Average value is given
Radioactive Phases in Apatite Rich Rocks from Beldih Area
Chl
Ap Qtz
Pcl
BLD 8
BLD 8
Microphotograph of Carbonatite and Apatite bearing Rocks
Beldih area
Ap
Ap rim
Cc
Cal
Apt
Uranium Exploration
in Dandudih-Kutni
Alkaline Carbonatite
Complex, NSSZ
Deformation Stratigraphy Metamorphism/
Metasomatism
Hydrothermal
Alteration
Mineralization
Brittle
Deformation II
Kaolinite /
Ferruginised apatite rocks
(<100m depth)
Metasomatism –III :
K-feldspar
Zeolite, Hematite
Mn minerals
Goethite, vug silica
Adsorbed
Uranium
Brittle
Deformation I
Best developed with in Apatite
rich rocks (> 100m depth)
Vug silica, Chlorite
Pyrite, siderite; 2nd
gen. Apatite
Urano –
Pyrochlore
Closure of rift , ductile deformation (500 – 600
Ma?)
Amphibolite facies metamorphism, Monazite (?)
Extension of
crust and
development of
rift zone
Carbonatite and formation of
apatite-rich rock and
ultramafics
Metasomatism II:
Na metasomatism in alkali granite
Apatite, Monazite
Pyrochlore,
Cb-Ta
Syenite (0.92 Ga)
Alkali granite (1.8 Ga)
Barabazar Granite (1.8 Ga)
Sedimentation
and Early
deformation
Tuff, meta sediments Carbon
Phyllite, quarzite
Early metamophism
Metasomatism-I: Tourmalinization
Minor allanite
Schematic Evolutionary Model for NSMB/NSSZ
U fixation
DISCUSSION & CONCLUSION
• Uranium exploration is multidisciplinary activity which
requires integration of geological, geochemical and
geophysical evidences on common georeferenced GIS
platform.
• Application of high resolution multiparameter geophysical data often providing critical information in support of local or regional framework mapping and mineral exploration modeling.
• India has many promising alkaline-carbonatite complexes which can turn into viable low-grade polymetallic uranium deposits by integration of geophysical, geological, geochemical and drilling data in GIS platform. A few of them like ACC along North Singhbhum Shear Zone and Dharmapuri Shear Zone are under active exploration to prove viable uranium deposits.
Thank you
SHEARED QUARTZITE AT PORAPAHAR