Mineral Prospecting & Depositsin India - An OverviewAKHIL PRABHAKAR3rdYear, Intg. M.TechGeophysical Technology09411004
INTRODUCTION• A scrutiny of research work onmineral prospecting in Indiaduring the period from January2004 to January 2007 revealsthat study of base-metalsreceived maximum attention.• This was followed by gold-diamond-bearing rocks(kimberlite and lamproite), andatomic minerals.• Besides, prospecting of iron ore,manganese, bauxite andchromite received significantattention.• Increasing demand in the powersector has witnessed a thrust onprospecting for coal and lignite.• Besides geological prospecting,geophysical prospectingemploying differentmethodologies have alsoreceived attention.
1. BASE METALS• A few old workings besides profuse malachiteencrustation, bornite, covellite and chalcopyrite are themain surface manifestations of mineralisation inRAJASTHAN.• Mainly metasoda rhyolite, garnet mica schist andmetavolcanics host mineralisation in Bhagal block.• The copper mineralisation is, by and large, controlled bythe structural elements.• Chalcopyrite is main copper ore mineral in the area. Theother ore minerals are pyrrhotite, pyrite and magnetitein the decreasing order of abundance.• Ilmenite, Haematite, Graphite and Sphene are present asminor minerals whereas Limonite/goethite, Sphalerite,Pentlandite, Machinawite and Tennantite occur asaccessory minerals.• Mineralisation occurs as veins, veinlets, stringers, fracturefillings, patches and disseminations.
…LEAD-ZINC DEPOSITS• Most of these deposits are Carbonatehosted Lead-Zinc Ore deposits.• Source: host carbonate sequencewhere diagenetic recrystallisationoccurs• The trapped deposits are formed byreplacement processes in thepresence of trapped hydrocarbons.• Sulfide minerals such as Galena,Sphalerite, Marcasite and Pyrite thusform.• Often the prospectivity of particularcarbonate formations for lead-zincdeposits of this nature is firstidentified by core drilling by oilexplorers.
2. GOLD•Greenstone belts•Geology, structure & mineralization comparableto SA•Preferentially concentrated in vein quartz, oftenassociated with sulphides• These gold prospects represent typical Archeanhydrothermal lode gold mineralisation.• Some deposits are hosted within sulphic bandediron formation. Ex.: Mallapokanda deposits (SouthKolar)•Mineralisation is hosted by hornblende schist inthe western part of the schist belt•Whereas in the eastern part mineralisation occursin the felsic volcanic of the Champion Gneiss.•Mineralisation is controlled by shear zonesGold mines of Chittoorare closed as they arenot economicallyviable•Recently, there has been a gold rush inEastern Singhbhum.•Gold deposits here, occur along the shearzone with Uranium and copper deposits.
3. DIAMOND•Thrust for diamond prospecting was noticedin Andhra Pradesh, Chhattisgarh, MadhyaPradesh, Karnataka andOrissa.•New kimberlite/lamproite fields have beenlocated in Andhra Pradesh and Karnataka. Afew lamproite bodies have also been reportedfrom Orissa.•Investigations forkimberlite/lamproite wascarried out in the Krishna River Basin.•Discovery of three kimberlite pipes from theBasin in Gadwal area, Mahboobnagar district,Andhra Pradesh came into light in 2004.
…IRON ORE DEPOSITSThe iron ore deposits of India can be broadlydivided in to the following six groups on thebasis of mode of occurrence and origin:1. Banded Iron Formations (BIF) of Pre-CambrianAge2. Sedimentary Iron Ore Deposits of Siderite andLimonitic Composition3. Lateritic Ores derived from the Sub-AerialAlternations4. Apatite-Magnetite Rocks of SinghbhumCopper belt (Very rare – Pathargora)5. Titanifereous and Vanadiferous Magnetites6. Fault and Fissure Filling DepositsLocations:1.Rich Iron Ore group: Noamundi (W.Singhbhum) – Singhbhum, Keonjhar2.Western Dharwar Craton (along withsome Mn) – Bellary & Goa
…MANGANESE• Important Manganese deposits are found in Bonai-Kendujhar belt and Eastern Ghat,Granulite belt in Orissa.• In the Eastern Ghat Granulite belt, discontinuous manganese mineralization was associatedwith khondalite group of rocks.• Manganiferous horizon with syn-genetic manganese ore from the granulite belt was alsoreported.• The manganese ore occurrences of Eastern Ghat are of syn-genetic type.• These were later remobilized in different phases of structural deformation by meteoric wateralong the weak planes of associated host rocks to form the secondary minerals.• In Bonai- Kendujhar belt, the mineralization is associated with a low grade volcanicsedimentary sequence, belonging to the Koira Group of Iron Ore Supergroup.• A formational status was proposed to the manganiferous horizon in Bonai-Kendujhar belt.
5. URANIUMMajority of these resources occur in following 3 uraniumprovinces.(i) Singhbhum uranium province, located in the Eastern Region.All the deposits, presently being exploited, such as Jaduguda,Narwapahar, Turamdih, and Bagjata occur in this province. Theother deposits in this belt are Mohuldih, Nandup, Rajgaon,andGaradih . All these occurrences are of vein type.(ii) Mahadek uranium province, located in theNortheastern Region. The Cretaceous Mahadek Formation inMeghalaya contains the largest and richest sandstone-hosteduranium deposit of the country at Domiasiat (KPM deposit) inWest Khasi Hills district. Another deposit of similar nature isat Wahkyn where exploration activities are in progress.Indias identified conventional uranium resources (RAR and Inferred) are estimated to amount to 105 900 tUand are hosted by the following type of deposits
URANIUM…iii) Cuddapah uraniumprovince, located in theSouthern and South CentralRegions. It contains theProterozoic unconformityrelated uranium depositat Lambapur-Peddagattu inNalgonda district, AndhraPradesh. The Cuddapahbasin also hosts a uniquestratabound uranium depositassociated with siliceousdolostone at Tummalapalle inCuddapah district, AndhraPradesh.
6. MOLYBDENUM & TUNGSTEN• The tungsten mineralization occurs atBalda, Rajasthan.• The Balda granite is spatially associatedwith mineralization that owes its genesisto the associated magmatichydrothermal system.• The wolframite mineralization isconfined to quartz veins and greisenizedpegmatites located along the shear zonesin Balda granite.
7. COAL1. The chief source of commercial energyin the country.2. Economically exploitable Indian coalsare broadly3. restricted to two geological times —Permian Gondwanas and Tertiaries.4. More than 99% of the known geologicalresources are contained in theGondwanas of well-defined5. belts of Damodar-Koel, Son-Mahanadi,Narmada (Satpura), Pranhita-Godavarivalleys and Rajmahal basin.6. Economic deposits of Tertiary coaloccur mainly in the northeastern Indiaand a few small deposits along Jammufoothills.7. The spread of Gondwanas has also beenreported from beneath the BengalBasin, eastern India and the DeccanTraps in central India.
SUMMARY• Trends of Mineral Prospecting in INDIA• Mineral Deposits• …their Locations and Geological settings• …and Processes by which they form