Geochemical Split Among the Suspended and Mud Sediments in the Nethravati River: Insights to Compositional Similarity of Peninsular Gneiss and the Deccan Basalt Derived Sediments, and Its Implications on Tracing the Provenance in the Indian Ocean

Abstract

Major, trace, and rare earth element (REE) geochemistry of sediments from a tropical mountain river is investigated to understand the behavior of chemical elements during weathering and transportation in a Peninsular Gneissic terrain. The results from this study are compared with the Deccan Basalt-derived River sediments and the eastern Arabian Sea sediments with an intent to highlight the challenges associated with the provenance determination of sediments along the continental margin of India. The geochemistry of suspended particulate matter (SPM) and mud sediments (<63 μm) of the Nethravati River indicate that sediments are derived from a relatively homogenous lithology, characterized by intermediate rocks of tonalitic (low-Al TTGs) composition. The tectonic origin of the source rocks discriminated using sediment geochemistry suggests an ocean island arc origin. The sediments experience intense chemical weathering in the source region. The elemental composition and their inter-element relationships suggest differential chemical weathering of mineral phases fractionate mafic components and their secondary mineral products in SPM, and mixed sources dominated by felsic components and their secondary mineral products in mud sediments. Intense chemical weathering induces significant geochemical splits among the suspended and mud sediments. The transport of mafic-biased sediments from Peninsular India to Oceans, and the geochemical similarity with Deccan Basalt-derived sediments makes it challenging to track the Peninsular Gneiss-derived sediment provenance along the continental margin of India using conventional elemental geochemistry. The inferences from this study have important implications for determining the sediment provenance along the continental margin of India.