Petrography and geochemistry of terrigenous sedimentary rocks in the neoproterozoic rabanpalli formation, bhima basin, southern India: Implications for paleoweathering conditions, provenance and source rock composition

摘要

Petrographic, major, trace, and rare earth element compositions of quartz arenites, arkoses, and siltstones of Neoproterozoic Rabanpalli Formation of Bhima Basin have been investigated to understand the provenance. The quartz arenites, arkoses, and siltstones have large variations in major element. concentrations. For example, quartz arenites and arkoses contain the higher SiO2 (average with one standard deviation being 97 +/- 1, 73 +/- 2, respectively) and lower Al2O3 (0.95 +/- 0.4, 9.6 +/- 0.9, respectively) concentrations than siltstones (SiO2 = 64 +/- 4, Al2O3 = 14 +/- 1), which is mainly due to the presence of quartz and absence of other Al-bearing minerals in relation with rock types. This is also supported by our petrography, since quartz arenites and arkoses contain significant amount of quartz relative to feldspar and lithic fragments. The observed low CIA values and A-CN-K diagram suggest that the sedimentary rocks of Rabanpalli Formation have undergone K-metasomatism.