Atomic Minerals Directorate for Exploration and Research

Southern Region covers the states of Andhra Pradesh (South of 15° N latitude), Karnataka and Maharashtra (South of 17°N latitude), Goa, Kerala, Tamil Nadu and Puducherry. The Region explores Archean basement comprising granulite facies of rocks and the peninsular gneisses /migmatites of Southern Granulite Terrain. The late Archean volcano-sedimentary sequence of Dharwar Supergroup rocks with linear tracts of limestone, manganese and associated iron formations occur mostly in Karnataka and parts of Andhra Pradesh. The Paleoproterozoic Closepet Granites exposed along a narrow north-south trending belt marks a geo-suture separating the eastern and western Dharwarcratons. The intracratonic, Proterozoic basins viz. Cuddapah, Bhima and Kaladgi basins overlie the Archaean basement marked by Eparchaean unconformity. The Cuddapah Basin comprises sedimentary succession of Cuddapah Supergroup and Neoproterozoic Kurnool Group of rocks. The Kaladgi and Bhima basins occur in the northern parts and extend below the Deccan Traps. Younger sedimentary basins of Mesozoic–Tertiary age include Gondwanas of Palar Basin, Cretaceous rocks of Tiruchinapally, Cuddalore Sandstone, Warkala beds, Quilon beds, etc. The beach and inland placers of Tamil Nadu, Kerala and Karnataka represents the Quaternary sediments.

The unique geological set-up provides several target areas for exploration of uranium, rare-metals and rare-earth minerals. Additionally, the long coastal stretch along the western and eastern margin of Southern India contains rich concentration of beach sand minerals including monazite and exploration is continuing for these minerals in various parts of the coastal stretches (see under Beach Sand Mineral Investigations).

Carbonate type, stratabound, phosphatic-siliceous dolostone (Vempalle Formation of Cuddapah Supergroup) hosted uranium deposit at Tummalapalle, YSR Kadapa district, Andhra Pradesh is globally unique and the largest (by tonnage) uranium deposit in the country. Geological and radiometric surveys in the Vempalle Formation, carried in first phase from 1986 to 1993, helped to delineate uranium mineralisation in the phosphatic-siliceous dolostone over a strike length of 160 km from Reddipalle in the north to Maddimadugu in southeast through Tummalapalle – Rachakuntapalle area, Andhra Pradesh. The syn-diagenetic uranium mineralisation occur along the bedding plane in the form of two distinguishable lodes, hangwalllode and footwall lode with a vertical separation of 1m to 3m. The complex nature of uranium mineralisation in the ore viz. absence of discrete mineral phase, ultra-fine dissemination in various minerals, lean tenor and the need for deploying the alkaline leaching route for its extraction warranted exhaustive research investigations for making the process flowsheet techno-economically viable and eco-friendly. Therefore, sub-surface exploration in the Tummalapalle area was discontinued after 1993 with establishing ~15,000t of uranium oxide. Subsequently, Materials Group, BARC came up with an innovative hydrometallurgical process flowsheet comprising of ‘oxidative alkaline pressure leaching–counter-current filtration–direct precipitation–reagent regeneration cum recycle’ for effective recovery of the uranium values. Following this, AMD initiated its second phase of exploratory programme since 2006 to establish the continuity of dolostone hosted uranium mineralisation on either side (i.e. east and west) of Tummalapalle uranium deposit. Systematic sub-surface exploration in Tummalapalle group of deposits, which includes seven exploration blocks (Motnutalapalle, Kanampalle, Tummalapalle-II, Tummalapalle-I, Rachakuntapalle, Rachakuntapalle East and Gidankivaripalle) covering 21 km strike length and ~3km width. It was also established that alongwith uniform persistent uranium mineralisation, the deposits also hold promise for substantial contents of associated critical elements like Cu, Mo and V for further value addition to the deposit. Uniform configuration and continuity of the ore body prompted enhanced exploration inputs for quick assessment and accordingly, the departmental drilling was backed up by introduction of outsourced drilling since year 2007. This resulted in quantum jump in the drilling productivity and consequently substantial uranium resources (>2,50,000 tonne total uranium oxide) could be established from the Tummallapalle group of deposits. UCIL is carrying out underground mining and processing of uranium ore since 2012.

Granite related uranium deposits and occurrences have been established through an integrated exploration programme in the Bhima Basin, where a number of surface uranium anomalies and occurrences reported along Kurlegere-Gundahalli (KG), Farhatabad and Wadi fault zones. The most prominent and significant uranium anomalies like those in Malla, Ukinal, Darshanapur, Gogi, Kanchankayi and Halbhavi in Yadgiridirstict, Karnataka. AMD has established epigenetic, Granite related uranium deposit hosted by brecciated Shahabad Limestone and basement granite cataclasite at Gogi, Kanchanakyi and Hulkal along the Kurlegere-Gundahalli fault. Coffinite, pitchblende and uraninite are main uranium minerals and in addition, multi-metal mineralisation (Pb-Ag-Mo) has also been identified in these deposits, which are, by far, the richest grade (0.15 - 0.20% U3O8) of uranium deposit established in India. Exploratory mining at Gogi was commenced in 2007 to study the ore body characteristics and to obtain bulk ore for process studies.

Fracture-controlled uranium occurrences have also been delineated within the basement complex in the south western margin of the Cuddapah Basin in a number of locations between Nagari-Kurvapallearea in the east to Bimunipalle area near Gooty in the west. These fracture zones show varying trends ranging from NNE-SSW (Sanipaya-T.Sundupalle), ENE-WSW (Mulapalle), and NW-SE (Lakshmipuram). Mineralisation is associated with cataclasite and mylonite along fault/shear zones. First phase of exploratory drilling commenced in 1989 which established a mineralised zone over a 500 m strike length at the Sanipaya-T. Sundupalle fracture zone, over 700 m strike length at Mulapalle fracture zone, and 1.3km along strike length at Varikuntapalle fracture zone. Second phase of exploration started during 2015-16 along 15 km long N20°E-S20°W Kamaguttapalle fracture zone where detailed surface investigations were carried out in the 1990s and was established for 320m with vertical depth impact of 250m. Subsequently, Pincha-Sivaramapuram, Varikuntapalleand Reddivaripalle fracture zones were also explored.Presently, 27 km long NE-SW trending BR Palle fracture zone taken up for subsurface exploration, where significant mineralisation zone has been established over a 300m strike length.

Proterozoic Unconformity type uranium occurrences have been delineated in 2005 near Deshnur, which is about 30 km east of Belagavi, Karnataka in unconformity surface below the feldspathic conglomerate and arenite of Badami Group. Subsequent exploration efforts have established uranium occurences proximal to the unconformity contact between quartz arenite of Badami Group and the basement Chitradurga Group of metasediments in Suldhal-Gujanal area. Besides, a systematic multipronged approach resulted in identifying uranium mineralisation in Gujanal-Ankalgi Block. Exploration targeted along NE-SW trending fault zone intercepted correlatable mineralisation over 700 m, hosted by sulphide-bearing feldspathic conglomerate/arenite and basement chlorite schist in fracture zone.

Quartz Pebble Conglomerate (QPC) type uranium deposits and occurrences have been established in Bababudan Group, Chitradurga Group and the Dharwar volcano-sedimentary succession. Out of these occurrences, based on systematic exploratory drilling, one (01) small low tonnage, low grade uranium deposits has been established by AMD at Walkunji – Yellakki in Karnataka.

Intrusive and Metamorphite type uranium occurrences associated with REEs and critical minerals hosted by syenite, quartz-barite veins, carbonatites, pegmatites, and ultrabasic rocks have been delineated since latesixties. Important and significant uranium anomalies among them are at Pakkanadu (ultrabasics, carbonatite, syenite and pegmatite), Sevattur-Samalpatti (carbonatite), Kalarapatti-Andiyappanur (quartz-barite veins),Rasimalai (pink microsyenite and quartz-barite veins) and Narlapalle-Pungurthi (migmatite and quartz-barite veins).The presences of anomalous content of polymetallic elements at Sevattur (U, Th& Nb-Ta), Rasimalai (U, Th, Sr, Bi, Pb& Nb)and Pakkanadu (U, Th, REEs, Y, Sc,V& Nb) areas were taken up for subsurface exploration and significant correlatable mineralised zoneswere established over a strike length of 250m, 900m and 800km, respectively. Subsequently, Kalarapattiand Pudur areas were also explored.

Presently, the uranium exploration in Southern Region is planned and executed in different geological domains ranging from Paleoproterozoic to Tertiary with prime focus on Proterozoic unconformity type, carbonate type and granite-related types. Accordingly, the Kaladgi-Badami and Bhima Basins in Karnataka and the Cuddapah Basin in Andhra Pradesh along with basement complex in the south western margin of the Cuddapah Basin are under active exploration. Besides, exploration activities are also taken up in Southern Granulite Terrain in parts of Tamil Nadu to probe for metamorphite and intrusive type uranium and associated REE mineralisation.