Basalts (Traps)

The Deccan Traps flow basalt (65 Ma) is one of the largest volcanic features on Earth, and crops out over 500,000 sq. km of the west-central Indian subcontinent. The trap complex is predominantly composed of multiple layers of tholeiitic flood basalt. The thickness varies from more than 2000 m in the Western Ghats to over 1000 m in eastern part of the province to less than 100 m in some southeastern regions. The basalts progressively overlap the basement from north to south. Most flows are 10–50 m thick, and dip at < 0.5°.

PGEs have been analyzed from mafic igneous rocks of the Kutch region, Gujarat, supported by association of Cu, Ni, Cr, and S together with Nd and Sr isotopic compositions. The PGE content is compared to the Deccan basalts of the Western Ghats region that indicated mantle-normalized Ni–PGE–Cu plots, PGE–base-metal ratio plots, and Nd–Sr initial-ratio diagrams (Crocket et al., 2007).

Deccan Trap basalts are comparable with the Siberian Trap at Noril’sk as both igneous provinces are widely considered the product of a mantle-plume event with the presence of large crustal contamination. The Noril’sk Ni–Cu–PGE-sulfide deposits are contemporaneous with the Siberian Trap flood-basalt magmatic event (Keays and Lightfoot, 2010). The S saturation to form magmatic Ni–Cu–PGE-sulfide systems is boosted by volumetrically important crustal contamination. The contaminated southern Deccan Trap lavas did not achieve S saturation, imposing constraints on the potential of the Deccan Trap in southern India to host significant magmatic-sulfide deposits.

The mafic–ultramafic rocks within Deccan Trap in parts of the Thane, Raigad, Satara, Sindhudurg, and Kolhapur districts, Maharashtra, were investigated and values up to 6 ppb Pt and 155 ppb of Pd were detected. Two hundred and fifty core samples covering a width of 2.95 m indicated 13–237 ppb Pt, 81–165 ppb Pd, and 0.1–1.3 ppb Ir. Samples were studied under scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX-ray). The investigation continued. A vast area of Deccan Traps may hold potential for precious metals.