• Baswani S R

      Articles written in Journal of Earth System Science

    • Petrography and geochemistry of the Proterozoic sandstones of Somanpalli Group from Pomburna area, Eastern Belt of Pranhita–Godavari Valley, central India: Implications for provenance, weathering and tectonic setting

      Rao N K Dora M L Baswani S R Malpe D B Deshmukh M S

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      In this paper, we, for the first time, report geochemistry of sandstone from Somanpalli Group from Pomburna area in the Eastern Belt of Pranhita–Godavari (PG) Valley, central India and studied to infer their provenance, intensity of paleo-weathering and depositional tectonic setting. Petrographic study of sandstones show QFL modal composition of arenite. Chemical results show high $\rm{SiO_{2}}$ and CIA but lower $\rm{Al_{2}O_{3}}$, $\rm{TiO_{2}}$, Rb, Sr, $\rm{K_{2}O}$ indicating mixed sources. Major elements chemistry parameters such as, $\rm{K_{2}O/Al_{2}O_{3}}$ ratio and positive correlation of Rb with $\rm{K_{2}O}$, reflects a warm and humid climate for study area. The tectonic discrimination plots $\rm{(SiO_{2}/20–K_{2}O+Na_{2}O–TiO_{2}+Fe_{2}O_{3}+MgO}$; $\rm{K_{2}O/Na_{2}O}$ vs. $\rm{SiO_{2}}$; Th–Sc–Zr/20) indicate dominantly passive margin and slight active tectonic setting. Concentrations of Zr, Nb, Y, and Th are higher compared to the UCC values and the trends in Th/Cr, Th/Co, La/Sc and Cr/Zr ratios support a felsic and mafic source for these sandstones and deposition in passive margin basin. Chondrite normalized REE pattern reflects LREE depletion, negative Eu anomaly and flat HREE similar to UCC, felsic components. ICV value (0.95) also supports tectonically quiescent passive margin settings. CIA values (74) indicate high degree of chemical weathering and warm and humid paleoclimatic condition.

    • A new find of calc-alkaline lamprophyres in Thanewasna area, Western Bastar Craton, India

      Meshram R R Dora M L Naik R Shareef M Gopalakrishna G Meshram T Baswani S R Randive K R

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      Lamprophyre dykes within the granitoid and charnockite are reported for the first time from the Western Bastar Craton, Chandrapur district, Maharashtra. It shows porphyritic–panidiomorphic texture under a microscope, characterised by the predominance of biotite phenocrysts with less abundance of amphibole and clinopyroxene microphenocryst. The groundmass is composed more of K-feldspars over plagioclase, amphiboles, clinopyroxene, biotite, chlorite, apatite, sphene and magnetite. The mineral chemistry of biotite and magnesio-hornblende is indicative of minette variety of calc-alkaline lamprophyre (CAL), which is further supported by preliminary major oxides and trace element geochemistry. This unique association of CAL with granitoid provides an opportunity to study the spatio-temporal evolution of the lamprophyric magma in relation to the geodynamic perspective of the Bastar Craton.

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