CHINA Meghalaya DomiasiatINDIA Wahkyn BANGLADESH MYANMAR
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 ON26° 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 F25° 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)
STRATIGRAPHIC SUCCESSION OF THE MEGHALAYA PLATEAU, INDIA (Modified after GSI, 1974)Geological age Group Formation LithologyMiocene 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 grainedUpper Cretaceous Khasi feldspathic sandstone, arkose. 70m Sandstone-conglomerate alternations. Jadukata (235 m) Unconformity Basalt, alkali-basalt, and acid tuff. AlkalineLate Jurassicto Early Cretaceous Sylhet Trap and rocks of carbonatite complexes. Tectonic Coarse, porphyritic granite, pegmatite, aplite IntrusiveLate Proterozoic granites 479 -690 Ma and quartz vein. Epidiorite and dolerite.Lower -Middle Intrusive Quartzite with basal conglomerate.Proterozoic Shillong Barapani Meta phyllite sequences. TyrsadArchaean Unconformity Granite gneiss, migmatite, mica schist, sillimanite-quartz schist, granulite.
MAHADEK BASIN OF MEGHALAYA, INDIA1800 sq km28% area covered20,000 tonnes of uranium oxide12% of Indian reserves
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
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 basementUMTHONGKUT 73.00
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 cycleUMTHONGKUT
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 crossbedded 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 insupported gravel Gmm the most active part of a fluvial channel sedimentation by rapid flowing clast Massive, Clastsupported gravel Gcm rich sediments deposited in a fluvial proximal fan setting
COMPARISON OF CHARACTERS OF DOMIASIAT AND UMTHONGKUT DEPOSITSl. Characteristics Domiasiat UmthongkutNo.1 Facies Gm, Gmm, Gt, PS, Sh, St, Fl & C Sm, Sh, St, Fm, Fl & Gmm Channel (CH), Sedimentary Gravity Channel (CH), Sandy bed form2 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 system3 to Fan environment environment Hosted by immature, poorly sorted, Hosted by feldspathic wacke, Sm grey arkosic to sub- arkosic pebbly facies4 Radioactivity quartz arenite and pebbly feldspathic wacke of PS facies Av. thickness of 40-50m 30-35m5 Lower Mahadek Basement Irregular, with highs and lows Irregular, with highs and lows6 topography Pitchblende and minor uranyl Pitchblende, Coffinite urano7 U - Minerology minerals organic complex and secondary uranyl minerals8 Ore body 10-15 above the basement 25-35m above the basement Depth of ore 25m, max up to 45m Min-15.45m & Max - 194.85m9 body
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 SmRongcheng (750m) U Sh Domiasiat Sm Gmm (750m) Umtryngai River (500m) Umthongkut (450m)
SIMPLIFIED FACIES MODELS VIS-À-VIS A URANIUM DEPOSITS DOMIASIAT an n Fa dF al & Mi xi m WAHKYNPro B l ma rgina e rin Ma GOMAGHAT
BASEMENT CONTOUR MAP OF WAHKUT PALAEO CHANNEL COURSE
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.
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 T5600 15 C -1 7 11 C -2 1 17 0 200 400 600 m C -2 25400 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 35200 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 345000 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 54800 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
ISOPACH CONTOUR MAP OF LOWER MAHADEK, UMTHONGKUT Av. thickness of Lower Mahadek is 35m The thickness increases towards South