3. CHINA
Meghalaya
Domiasiat
INDIA Wahkyn
BANGLADESH
MYANMAR
4. GEOLOGICAL CUM TECTONIC MAP OF MEGHALAYA, INDIA
90° 91° 92° 93° 94°
F
F
F BARPUNG
KO
t & R.
UTRA Faul
BRAHMAP
PIL
IF
JAMUNA F
GUWAHATI SAMCHAMPI
F E
ON
26° 26°
KULSI F
RZ
DUDHNOI F
EA T.
SH
A NI GA
AP NA
R JASRA
BA
SHILLONG
F
T
DAP US
SI T. SUNG VALLEY F T HR
COMPLEX NG
F DISA
F 0 50Km
F F
25° DAUKI F F 25°
F 90° F 91° F 92° 93° 94°
ALLUVIUM JAINTIA GROUP CARBONATITE COMPLEX. INTRUSIVE GRANITE SHILLONG GROUP
GARO GROUP & EQ. KHASI GROUP SYLHET TRAP KHASI GREENSTONE BASEMENT GNEISSIC COMPLEX
(AFTER NANDY, D.R., 2001)
5. STRATIGRAPHIC SUCCESSION OF THE MEGHALAYA PLATEAU, INDIA
(Modified after GSI, 1974)
Geological age Group Formation Lithology
Miocene Chengapara (700 m) Sandstone, siltstone, clay and marl.
Oligocene Garo Baghmara (530 m) Feldspathic sandstone, conglomerate and
clay.
Kopili-Rewak(500) m Shale, sandstone and marl.
Eocene Shella (600 m) Alternations of sandstone and limestone.
Paleocene Jaintia
Langpar (50-100 m) Calc shale, sandstone and impure limestone.
Unconformity
Upper: Coarse, arkosic sandstone and shale,
250m
characteristic purple colour
Mahadek
Lower: Grey, coarse to fine grained
Upper Cretaceous Khasi feldspathic sandstone, arkose.
70m
Sandstone-conglomerate alternations.
Jadukata (235 m)
Unconformity Basalt, alkali-basalt, and acid tuff. Alkaline
Late Jurassic
to Early Cretaceous Sylhet Trap and rocks of carbonatite complexes.
Tectonic Coarse, porphyritic granite, pegmatite, aplite
Intrusive
Late Proterozoic granites 479 -690 Ma and quartz vein. Epidiorite and dolerite.
Lower -Middle Intrusive Quartzite with basal conglomerate.
Proterozoic Shillong Barapani Meta phyllite sequences.
Tyrsad
Archaean Unconformity Granite gneiss, migmatite, mica schist,
sillimanite-quartz schist, granulite.
6. MAHADEK BASIN OF MEGHALAYA, INDIA
1800 sq km
28% area covered
20,000 tonnes of uranium oxide
12% of Indian reserves
12. PALAEO- CHANNEL MAHADEK BASIN
Cross bedded Lower Mahadek sandstone
PHOTOMOSAIC OF THE SECTION
Palaeo-flow direction perpendicular to the photograph
15. MEMBER LITHOLOG LITHO FACIES INTEPRETATION
Proximal fan environment by
braided river channel in
Fluvial regime
Sm, Sh, Sp, Fm rare
Gmm; Top part of LM
is relatively finer, rich
in matrix. Fluvial braided
channel systems
Several small fining
upward cycles
Bottom part of LM Mineralisation
dominated by Gmm, associated with the
Sm and Sp; More of basal part of the
coarser components cycles close to the
basement.
AHA MRE W L
O
Basement:
Precambrian gneissic
complex, Granite,
WAHKUT gneisses/Migmatite
16. MEMBER LITHOLOG LITHO FACIES INTEPRETATION
BH No
UKT/C-5
Sm and minor Sh, Fm Mineralisation
Mahadek
GRAIN SIZE
MUD SAND GRAVEL
Upper
& Gmm. associated with the
30.00 m si vf f m c vc gr
31.30 Sm
basal part of the
Lower Mahadek
Several small fining cycles at the upper
Sh
Cm(<5%)
upward cycles part of LM
Radioactive
Sm
37.00
bands
Fm
Sm
Sm and Gmm at the
basal part of LM
41.00 Gms
Radioactive
Sh
Deposited under
bands
Sm
Cm(<5%)
braided fluvial
47.30 Sm regime by small
Sh
Py, CM (>5%) channels with
Sm
carbonaceous
53.25
matter under
Relatively thicker reducing condition
Py, Cm
fining upward cycles
Lower Mahadek
Sm Proximal fan environment by
AHA MRE W L
O
59.60
braided river channel in
Fluvial regime
Sm
Py, Coaly
matter
65.55
66.45 Gms
Basement, Granite
Basement
gneisses/Migmatite
Migmatitic
basement
UMTHONGKUT
73.00
17. MEMBER LITHOLOG LITHO FACIES INTEPRETATION
Fm, Sm (minor) Deposited
as over bank facies
under oxidizing
condition
Overbank & abandoned channel fill
deposited in Meandering Fluvial Regime
Shallow sandy Sm
Sm braided system
Sm
Sm
Sm
Sm
Sm
Sm
Fm
Sm
Sm
Sm
Sm
Fm
Sm
Sm
Fm
Sm
Fm
Sm
Fm
under oxidizing
condition
Sm, Fm (minor) Shallow sandy
AHA MRE PP U
braided system
19.90m
48.50m
Upper Mahadek
under oxidizing
condition with little
development of
Marker overbank facies at
Horizon the end of the
depositional cycle
UMTHONGKUT
18. MAJOR LITHOFACIES OF MAHADEK BASIN
LITHOFACIES FACIES INTERPRETATION PHOTOGRAPHS
CODE
Massive deposited under sediment gravity
sandstone
Sm flow within a braided fluvial channel
Horizontally deposited on large flood bar in
channel deposits during the waning
laminated Sh stage of flood events (possibly
sandstone seasonal)
deposited during low water level or
Planar cross
bedded sandstone
Sp waning stage of flow under lower
flow regime
deposition from suspension of
Massive Fm overbank sediments in flood plain
mudstones setting
rapid sedimentation from a high
Massive, matrix energy flow, which are common in
supported gravel
Gmm the most active part of a fluvial
channel
sedimentation by rapid flowing clast
Massive, Clast
supported gravel
Gcm rich sediments deposited in a fluvial
proximal fan setting
19. COMPARISON OF CHARACTERS OF DOMIASIAT AND UMTHONGKUT DEPOSIT
Sl. Characteristics Domiasiat Umthongkut
No.
1 Facies Gm, Gmm, Gt, PS, Sh, St, Fl & C Sm, Sh, St, Fm, Fl & Gmm
Channel (CH), Sedimentary Gravity Channel (CH), Sandy bed form
2 Architectural flow (SG), Gravel bar (GB), Sandy (SB) & Down stream accretion (DA)
Elements bed form (SB) & Down stream
accretion (DA)
Depositional By gravel or sandy bed river proximal Sandy bed Braided river system
3 to Fan environment
environment
Hosted by immature, poorly sorted, Hosted by feldspathic wacke, Sm
grey arkosic to sub- arkosic pebbly facies
4 Radioactivity quartz arenite and pebbly feldspathic
wacke of PS facies
Av. thickness of 40-50m 30-35m
5
Lower Mahadek
Basement Irregular, with highs and lows Irregular, with highs and lows
6
topography
Pitchblende and minor uranyl Pitchblende, Coffinite urano
7 U - Minerology minerals organic complex and secondary
uranyl minerals
8 Ore body 10-15 above the basement 25-35m above the basement
Depth of ore 25m, max up to 45m Min-15.45m & Max - 194.85m
9
body
20. GENERALISED LITHOFACIES OF MAHADEK BASIN
8 KM 31.5 KM 45 KM 45.5 KM
E D C B A
Gmm
Fm
Gmm
St
U
Sm
Sm
Sh
Fm St
Gmm
Ps Sh
U Sh
U St St
Sh Ps
Ps Sm Fl Gcm
Sh Sh
PS U Sh
Ps Ps
Gmm St Gcm
Sh Sm Sh
Sh
Sp Sh U Ps Laitduh Gmm
U Sm Gmm Sh
Ps
Gmm Gt Gcm
(1215m) Gcm
U St U Sh
Ps Sm
Rongcheng (750m) U Sh
Domiasiat
Sm
Gmm
(750m) Umtryngai River (500m)
Umthongkut (450m)
21. SIMPLIFIED FACIES MODELS
VIS-À-VIS
A URANIUM DEPOSITS
DOMIASIAT
an
n
Fa
dF
al &
Mi
xi m
WAHKYN
Pro
B
l
ma rgina
e
rin
Ma
GOMAGHAT
23. BASEMENT CONTOUR MAP OF UMTHONGKUT
Basement slope is on av.
7.5˚ towards south
(varies between 5-10˚)
The richer part of ore body is
associated with NNE-SSW,
NE-SW and NW-SE depression
The basement low observed
in the southern part is
favorable for uranium
mineralization.
24. ISOPACH CONTOUR MAP OF LOWER MAHADEK, WAHKUT
IS O P A C H C O N T O U R M A P O F L O W E R M A H A D E K , W A H K U T
5600
15 C -1 7
11 C -2 1 17 0 200 400 600 m
C -2 2
5400 C -1 4 21 9
18 C -3 3
C -2 4
C -1 0
C -3 6 2 0 C -2 7
14 19
C -2 9 C -6 33 C -2 3
5200 16 C -3 4
C -4 3 23 1 3C -1 8 A
C -3 0 22 C -3 1 32 37 C -3 36
C -2 0 12 C -1 6 A 8
31 C -1 9
C -3 5
10
29 7A C -8 34
5000 6A 5
C -4 4 28 C -3 2 C -1 3 A C -1
24
C -2 6 35
30 3 C -7 38
27 C -2 5 4 2A
C -4 5 C -3 7 26 C -3 9 25 C -2 8 C -1 2 C -2
C -1 1
1 C -1 5
4800 C -4 0 C -4 2 C -3 8 A
C -4 1
39A
C -5 A
C -4 C -9
3600 3800 4000 4200 4400 4600 4800 5000 5200 5400
M IN E R A L IS E D B O R E H O L E S
N O N -M IN E R A L IS E D B O R E H O L E S
Av. thickness of Lower
Mahadek is 52m
25. ISOPACH CONTOUR MAP OF LOWER MAHADEK, UMTHONGKUT
Av. thickness of Lower
Mahadek is 35m
The thickness increases towards
South
28. TECTONIC SETTING IN WAHKYN AND UMTHONGKUT SECTOR
Um
N
Po
th
rjr
on
iL
gk
ine
ut
am
Fa
en
ul
t
t
LOSTOIN
CHIRA FAULT WAHKYN
UMTHONGKUT
Ri
ng WAHKUT
wa
llu
m
fau
lt
Uranium Deposit Uranium Anomaly
40. GEOCHEMICAL CLASSIFICATION
(PETTIJOHN, 1972 WITH BOUNDARIES REDRAWN AFTER HERRON, 1988)
A B D
E
F
C
A Greywacke
B Litharenite
C Arkose
D Subarkose
E Sublitharenite
F Quartz Arenite
41. Discriminant function 1
DISCRIMINATION DIAGRAMS FOR TECTONIC ENVIRONMENT AFTER BHATIA 1983
- 0.0447 SiO2 - 0.972 TiO2 + 0.008 Al2O3 - 0.267 Fe2O3 + 0.208 FeO - 3.082 MnO
+ 0.140 MgO + 0.195 CaO + 0.719 Na2O - 0.032 K2O + 7.510 P2O5 + 0.303
Discriminant function 2
- 0.421 SiO2 + 1.988 TiO2 – 0.526 Al2O3 – 0.551 Fe2O3 – 1.610 FeO + 2.720 MnO
+ 0.881 MgO + 0.907 CaO – 0.177 Na2O – 1.840 K2O + 7.244 P2O5 + 43.57
A B
C
D
A Passive Margin
B Oceanic island-arc
C Continental island-arc
D Active continental margin.
42. DIAGRAM SHOWING VARIATION OF Fe+3/Fe+2 RATIO WITHIN
THE LITHO COLUMN,
MEGHALAYA, INDIA
Fe+3/Fe+2 10.56
UKT/C-5 UKT/C-6 WKT/C-27 WKT/C-29
0.00m 0.00m 0.00m 0.00m
3.10
MAHADEK UPPER MAHADEK MEMBER
UPPER
11.50
3.10 2.65 28.29
DEPTH (m)
1.90 20.65
3.25
31.30 1.66 0.53
1.99
1.15
MAHADEK
Fe+3/Fe+2
1.07
LOWER
10.66 0.59
0.71
2.39 0.48
4.74
Fe+3/Fe+2 0.88 LOWER MAHADEK MEMBER
0.45
0.94 (Non Radioactive zone)
66.45 m 0.45 0.84
0.42
LOWER MAHADEK MEMBER
0.27 (Ore zone)
0.26
98.00 m 98.00 m
INDEX
100.35 m UPPER MAHADEK MEMBER
LOWER MAHADEK MEMBER
Fe+3/Fe+2 0.77
RADIOACTIVE BAND
BASEMENT
Fe+3/Fe+2 RATIO
1.74
43. CHEMICAL INDEX OF ALTERATION (after NESBIT AND YOUNG 1982)
KAOLINITE KAOLINITE
SMECTITE ILLITE
SMECTITE ILLITE
PLAGIOCLASE K-FELDSPAR PLAGIOCLASE K-FELDSPAR
Mol.% Al – K- Ca+Na MINIMUM AND MAXIMUM FOR LOWER (n=26) AND UPPER MAHADEK ( n=13)
Mol.Al2O3 % 0.050 – 0.225 0.036 – 0.113
Mol.K2O% 0.001– 0.045 0.010 – 0.054
Mol. CaO + Na2O 0.001 – 0.013 0.003 – 0.012
