We have investigated 78 core samples of basaltic trap and Neoarchean basement in the laboratory from a 981 m deep scientific borehole KBH-05, in the Koyna−Warna seismic zone, in order to characterize their thermal and physical properties and present a probable crustal thermal model. The Koyna−Warna, located in the Deccan Volcanic Province (DVP), is globally one of the most prominent Reservoir Triggered Seismicity (RTS) regions. Thermal conductivity, density, and porosity vary widely (1.0-1.7 Wm -1 K -1 , 2400-3000 kg m -3 , 0.2-10%) for the basalt due to their lithological heterogeneities, i.e., massive/amygdaloidal/vesicular. In comparison, the basement, which dominantly consists of gneiss/migmatite gneiss (granodiorite to tonalite to quartz monzodiorite in composition) and amphibolite, have shown a wider range in thermal conductivity (2.2-3.4 Wm -1 K -1 ) but constricted range in density and porosity (2600-2800 kg m -3 , 0.01-0.15%).Based on gamma and sonic logs, as well as radioelements (Th, U, K), the 499 m thick basaltic trap can be divided into two thick layers (325, 174 m) and five sub-layers, which can be correlated with different basaltic formations. Similarly, the underlying basement can also be divided into two layers (93, 384 m). The upper basement layer has two times higher concentrations of Th and U than the lower layer, with heat production of 2.0, 0.8 μWm -3 . Further, the study provides a robust temperature estimate of 165-250 o C at 10 km depth, considerably higher than reported earlier for the DVP, and reveals that in addition to thermal parameters, RTS also plays an important role in the seismogenesis of the region.

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An occurrence of Palaeoarchaean ferropicrite cumulates and ferrobasalts is being reported from the Jojohatu area of the Iron Ore Group (IOG) greenstone belt, which is situated in the northern part of the Singhbhum Craton (eastern India). The ferropicrite cumulates contain serpentine and clinopyroxene as major constituents and spinel, magnetite, and ilmenite as accessories. Their bulk rock chemistry exhibits an extremely high amount of FeOT (19.0–20.8 wt%) and MgO (22.0–23.9 wt%) and quite low Al2O3 (4.5–5.2 wt%) and Na2O + K2O (<1.0 wt%), thus making them as one of the most Fe‐rich ferropicrite cumulates in the world. They are also characterized by high contents of compatible trace elements (Ni: 986–1,470 ppm; Cr: 990–1,256 ppm) and moderate TiO2 (1.5–1.7 wt%), Nb (15–18 ppm), and Zr (82–90 ppm). These cumulates are possibly formed due to accumulation of olivine from the ferrobasaltic melts. In comparison, ferrobasalts consisting of plagioclase, pyroxene, and opaques are alkaline in nature. Some of the plagioclase and pyroxene grains have shown a signature of metasomatic alteration, which resulted into formation of secondary minerals such as epidote, chlorite, and hornblende. They exhibit relatively low contents of FeOT (14.6–18.4 wt%), MgO (8.4–10.8 wt%), Ni (32–122 ppm), and Cr (41–131 ppm) than the ferropicrite cumulates, while TiO2 (2.9–4.1 wt%), Nb (42–61 ppm), and Zr (216–318 ppm) contents are higher. Incompatible elemental patterns and their ratios, as well as Zr/Y versus Nb/Y plot, indicate their ocean island basalts (OIB) affinity and genesis from a hot mantle plume, having mantle potential temperature of about 1,600°C and pressure of 3.5–5 GPa. Considerably low CaO (3.00–7.16 wt%) and FeO/MgO and CaO/MgO systematics indicate that the primary source of the basaltic melt could be pyroxenite. These volcanic occurrences possibly represent remnants of the OIB formed during the Palaeoarchean in the eastern part of the Indian shield.

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