MI2023 - 17 Priyeshu Srivastava: Characterizing high-land laterites of the Deccan Traps
Channel: MagNetZ
Date: 2023-01-17

Magnetic Interactions 2023 conference at the University of Cambridge
Session 4: Environmental Magnetism

Title: Characterizing high-land laterites of the Deccan Traps using environmental magnetism
Author: Priyeshu Srivastava from Universidade de São Paulo, Brazil

The laterites developed on high-land plateaus of the Deccan Traps are often discussed for their origin either as autochthons (in-situ) weathering of Deccan basalts or as an allochthonous enriched ferricrete. The source of iron in latter case has been hypothesized from relief inversion and/or from alteration of aeolian deposits. We analysed geochemical, diffuse reflectance spectroscopy and environmental magnetic properties of a ~46 m thick deeply weathered laterite profile from the Bamnoli Range of the Western Ghats. The sharp distinction between saprolite and laterite (ferricrete) zones could be identified with dominant ferrimagnetic mineral assemblage in the saprolite zone, and high concentration of antiferromagnetic minerals in ferricrete zone. The index of lateritisation (IOL) ranged between 43 and 98, and showed an increasing trends towards the top of profile (30 to 46 m) indicating strong lateritisation. Mass balance of major and trace elements showed 80 to 99% of depletion in mobile elements (e.g., Na2O, K2O, CaO), whereas gains in immobile elements (e.g., TiO2) except in top samples. FeO(T) showed very erratic behaviour with several samples showing minimum loss or gain, whereas anomalous gains (400%) and loss (-86%) were also found in lateritic (ferricrete) zone. The allochthonous source of iron oxides in the laterite (ferricrete) zone was shown by presence of low coercivity ferrimagnetic mineral. The new data on environmental magnetism, geochemistry and diffuse reflectance spectroscopy provides better understanding on in-situ weathering and allochthonous processes during lateritisation in the Deccan Traps.

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00:00 - Intro
00:30 - Presentation
14:49 - Questions