Mineral Prospecting & Depositsin India - An Overview AKHIL PRABHAKAR 3rd Year, Intg. M.Tech Geophysical Technology 09411004
INTRODUCTION• A scrutiny of research work on mineral prospecting in India during the period from January 2004 to January 2007 reveals that study of base-metals received maximum attention.• This was followed by gold- diamond-bearing rocks (kimberlite and lamproite), and atomic minerals.• Besides, prospecting of iron ore, manganese, bauxite and chromite received significant attention.• Increasing demand in the power sector has witnessed a thrust on prospecting for coal and lignite.• Besides geological prospecting, geophysical prospecting employing different methodologies have also received attention.
1. BASE METALS• A few old workings besides profuse malachite encrustation, bornite, covellite and chalcopyrite are the main surface manifestations of mineralisation in RAJASTHAN.• Mainly metasoda rhyolite, garnet mica schist and metavolcanics host mineralisation in Bhagal block.• The copper mineralisation is, by and large, controlled by the structural elements.• Chalcopyrite is main copper ore mineral in the area. The other ore minerals are pyrrhotite, pyrite and magnetite in the decreasing order of abundance.• Ilmenite, Haematite, Graphite and Sphene are present as minor minerals whereas Limonite/goethite, Sphalerite, Pentlandite, Machinawite and Tennantite occur as accessory minerals.• Mineralisation occurs as veins, veinlets, stringers, fracture fillings, patches and disseminations.
…LEAD-ZINC DEPOSITS • Most of these deposits are Carbonate hosted Lead-Zinc Ore deposits. • Source: host carbonate sequence where diagenetic recrystallisation occurs • The trapped deposits are formed by replacement processes in the presence of trapped hydrocarbons. • Sulfide minerals such as Galena, Sphalerite, Marcasite and Pyrite thus form. • Often the prospectivity of particular carbonate formations for lead-zinc deposits of this nature is first identified by core drilling by oil explorers.
2. GOLD •Recently, there has been a gold rush in Eastern Singhbhum. •Gold deposits here, occur along the shear zone with Uranium and copper deposits. •Greenstone belts •Geology, structure & mineralization comparable to SA •Preferentially concentrated in vein quartz, often associated with sulphides • These gold prospects represent typical Archean hydrothermal lode gold mineralisation. • Some deposits are hosted within sulphic banded iron formation. Ex.: Mallapokanda deposits (South Gold mines of Chittoor Kolar) are closed as they are •Mineralisation is hosted by hornblende schist in not economically the western part of the schist belt viable •Whereas in the eastern part mineralisation occurs in the felsic volcanic of the Champion Gneiss. •Mineralisation is controlled by shear zones
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 Deposits Locations: 2.Rich Iron Ore group: Noamundi (W. Singhbhum) – Singhbhum, Keonjhar 3.Western Dharwar Craton (along with some Mn) – Bellary & Goa
…CHROMITE DEPOSITS 1. Sukinda Formed in 2. Nushai Ultra-basic 3. Jojohatu rocks 4. Kimsiburu Magmatic layering due to segregation
…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 associated with khondalite group of rocks.• Manganiferous horizon with syn-genetic manganese ore from the granulite belt was also reported.• The manganese ore occurrences of Eastern Ghat are of syn-genetic type.• These were later remobilized in different phases of structural deformation by meteoric water along the weak planes of associated host rocks to form the secondary minerals.• In Bonai- Kendujhar belt, the mineralization is associated with a low grade volcanic sedimentary sequence, belonging to the Koira Group of Iron Ore Supergroup.• A formational status was proposed to the manganiferous horizon in Bonai-Kendujhar belt.
5. URANIUM Indias identified conventional uranium resources (RAR and Inferred) are estimated to amount to 105 900 tU and are hosted by the following type of depositsMajority 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.
URANIUM…iii) Cuddapah uraniumprovince, located in theSouthern and South Central Regions. 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 at Balda, Rajasthan.• The Balda granite is spatially associated with mineralization that owes its genesis to the associated magmatic hydrothermal system.• The wolframite mineralization is confined to quartz veins and greisenized pegmatites located along the shear zones in Balda granite.
7. COAL 1. The chief source of commercial energy in the country. 2. Economically exploitable Indian coals are broadly 3. restricted to two geological times — Permian Gondwanas and Tertiaries. 4. More than 99% of the known geological resources are contained in the Gondwanas of well-defined 5. belts of Damodar-Koel, Son-Mahanadi, Narmada (Satpura), Pranhita-Godavari valleys and Rajmahal basin. 6. Economic deposits of Tertiary coal occur mainly in the northeastern India and a few small deposits along Jammu foothills. 7. The spread of Gondwanas has also been reported from beneath the Bengal Basin, eastern India and the Deccan Traps in central India.
SUMMARY• Trends of Mineral Prospecting in INDIA• Mineral Deposits• …their Locations and Geological settings• …and Processes by which they form