Basalts (Traps)

Deccan Traps Basalt

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.