0016-7622/2008-72-5-691/$ 1.00 © GEOL. SOC. INDIA JOURNAL GEOLOGICAL SOCIETY OF INDIA Vol.72, November 2008, pp.691-702 Exploration for PGE and Base Metal Mineralization in the Archaean Ultramafic-Mafic Rocks of the Holenarasipur Greenstone Belt, Western Dharwar Craton (Southern India): A Preliminary Report T.C. DEVARAJU 1 , R.H. SAWKAR 2 , R.P. VILJOEN 3 , T.L SUDHAKARA 2 , M.G. OMKESH MURTHY 2 , S. VIJAYA KUMAR 2 and R.G. VIJAYA VIKRAM 2 1 ‘Rajamangala’, Saptapur, Haliyal Road, Dharwad - 580 001 2 Ramgad Minerals and Mining Pvt. Ltd., Baldota Enclave, Hospet - 583 203 3 School of Geosciences, University of Witwatersrand, Johannesburg, South Africa Email: tcdevaraju@dataone.in Abstract: The ultramafic-mafic rocks of the Archaean Holenarasipur greenstone belts of the western Dharwar craton in southern India has been explored for PGE and base metal mineralization. This initiative was prompted by the overall favourable geological setting and the presence of anomalies of Pt (10-27 ppb) and Pd (8-21 ppb) in several of the stream sediment samples collected from different parts of the belt. The exploration programme consisted of field examination and analysis of over 276 samples collected from a range of mafic-ultramafic rocks in four main exploration blocks of the belt viz. Yedegondanahalli, Bantaratalalu, Yenneholeranganabetta and Bettadasatenahalli. The investigation has revealed weak mineralization with 10 to 111 ppb Pt, 16 to 166 ppb Pd and 40 to 277 ppb of (Pt+Pd). Anomalies were located in serpentinite, amphibolite and sill/dyke-like bodies of hornblendite. Two small patches of sulphide mineralisation located in the belt, in the Yedegondanahalli and Yenneholeranganabetta blocks, are Cu dominated (> 1.0 wt% Cu) and analyze up to 0.3 wt% Ni, 0.09 wt% Co, 40 ppm Ag and 0.5 ppm Au. Keywords: Ultramafic-mafic rocks, PGE-Base metal exploration, Holenarasipur belt, Dharwar craton. GEOLOGY The contact between the Bababudan and the Sargur Groups of rocks can be seen in the Holenarasipur belt. The northern part of the belt, lying to the north of the Hemavathi River, is classified as Bababudan Group while the southern N-S striking limb, lying to the south of the River, is classified as part of the Sargur Group (Fig.1). The southern N-S striking 20 km long limb of the belt is made up of an association of ultramafic-mafic and meta- sedimentary rocks. The prominent planar fabric of the rocks strikes N-S and dips 45°-70° east. The ultramafic rocks occur as isolated linear to nearly circular patches of variable sizes occupying the centers of the limb. The mafic rocks, which form the outer portions of the complex are comprised of amphibolite to anorthosite. In the very outer portions of the southern limb, a suite of meta- sedimentary rocks occur. The lithostratigraphy of the Holenarasipur belt is INTRODUCTION The Holenarasipur greenstone belt of southern India is well known for a variety of mineral deposits such as chromite, asbestos, magnesite, corundum, kyanite, staurolite, beryl, feldspar, muscovite, quartz, graphite and iron ore. There has been intermittent mining of these deposits, on a small scale, over several decades. The present investigation for assessing PGE and base metal mineralization potential in the belt has been prompted by the favourable geology of the belt. The ultramafic-mafic rocks of the belt with chromite mineralization, probably constituted a portion of a dismembered elongated body, extending over a strike length of 320 km, from Solepur-Sinduvalli-Talur in the south to Anthargange-Shivani-Kallanagavi in the north (Fig.1A). This study highlights the analytical results of 106 stream sediment and 276 bedrock samples collected from that part of the belt occupied by ultramafic-mafic rocks.