A Preliminary Study on Chemical Weathering and Development of Regolith over Rajmahal Basalt

Kisku, Prem Chand (2013) A Preliminary Study on Chemical Weathering and Development of Regolith over Rajmahal Basalt. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS Dissertation of Prem Chand Kisku) Prem_Chand_Kisku-08Ms14-MSThesis.pdf - Submitted Version Restricted to Repository staff only Download (2MB)

Abstract

Chemical weathering is the process in which, Geochemically mobile elements, alkali and alkaline earth elements are easily leached out from the rocks, leaving the residual elements to combine with components from atmosphere to form new minerals. The primary minerals of basalt, which include olivine, plagioclase, pyroxene all form solid solutions between two or more end-members. Compared to other rock type on earth’s surface, basalts weather faster. Primary minerals dissolved into water, forms secondary minerals and preserves in the regolith such as clay, soil. It is the important geological process that controls the morphology of the earth’s surface, Soil formation, natural CO2 sequestration and elemental flux into the ocean. Rajmahal basalt is ~130Ma old and having a large thickness of basaltic lava flows, it covers ~4000 sq. km area. The gneissic terrain is ~2.1Ga old. Major river Ganga drains the north eastern part of the Rajmahal basalt, some of the small tributaries drains through both the terrain in dendritic pattern. It experience tropical humid climate. Petrological microscope, XRD and XRF is used for the analysis of Mineralogical, mineral facies and bulk chemical composition of whole rock. Chemical index of alteration (CIA) is calculated to understand the elemental behavior in the weathering profile and A-CN-K and A-CNK-FM ternary diagram is plotted to understand the formation of secondary minerals and loss of alkali and alkaline earth elements.

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