Anomalous Seismic Velocity Drop in Iron and Biotite Rich Amphibolite to Granulite Facies Transitional Rocks from Deccan Volcanic Covered 1993 Killari Earthquake Region, Maharashtra (India): a Case Study

摘要: 65 Ma Deccan Volcanic Province of western India forms one the largest flood basaltic eruptions on surface earth. The nature concealed crust below this earthquake prone region, which is marked by several low velocity zones at different depths has hardly been understood. These have invariably interpreted as fluid-filled zones, genetically connected to nucleation. While carrying out detailed geological and petrophysical studies Late Archean basement cores, obtained from a 617 m deep KLR-1 borehole, drilled in epicentral zone 1993 Killari region southern Province, we came across instances where observed remarkable drop measured P-wave number high density cores. We provide petrographic data 11 such anomalous samples belong mid-crustal amphibolite granulite facies transitional rocks. They are associated with mean 6.02 km/s (range 5.82–6.22 km/s) conforming granitic upper crust, but contrast 2.91 g/cm3 2.75–3.08 g/cm3), characterise mid lower crust. This drop, much 15 % some primarily attributed FeOT enrichment (up about 23 wt%) during course mantle-fluid driven retrogressive metasomatic reactions, caused exhumation deep-seated mafic Presence Iron content (mainly magnetite), widely seen opaques thin sections rocks, seems resulted into sharp increase density, well atomic weight. Our study indicates that Vp inversely related weight rock.