Petrophysical Studies on Metabasics of the Sanko-Kargil Area, Kashmir Himalaya

Petrologically, the metabasites comprise of metavolcanics (metabasalt, spilitic basalt, metadolerite, spilitic diabase and trachybasalt), green schists, amphibolites and meta-greywackes, and of these the meta volcanics are the most predominant. The physical properties of these rocks are: density (2.77-3.00 g·cm^-3), porosity (0.2-1.9%), compressional velocity (5-7 km·sec^-1), shear velocity (3-4km·sec^-1), P-anisotropy (up to 7.6%), compressive strength (700-2800kg cm^-2), tensile strength (70-190 kg cm^-2), Young's modulus (6.5-11.5 × 10^-11 dynes·cm^-2), and Poisson's ratio (0.14-0.29). These variations in the physical parameters are due to (i) Metamorphic effects (low to moderate P and T conditions, green schist-amphibolite facies), (ii) The serpentinization of the phenocryst minerals, (iii) The glassy nature of the groundmass, and (iv) The differences in the groundmass/phenocryst ratios.

In general, the physical parameters of these crustal rocks from the Himalayas are higher than those of Deccan basalts even at ambient conditions. This is due to (i) Differences in their mineralogical characters, and (ii) The mode of their occurrence, the former being associated with highly folded, disturbed and tectonically affected eugeosynclinal zones, whereas the latter are of the fissure eruption type, relatively free from metamorphic effects and large scale tectonic activity.