Geochemical characteristics and depositional environment of Kalpakkam, southeast coast of India

摘要

Sediments from Kalpakkam, southeast coast of India were geochemically analyzed to document the provenance, tectonic setting, and role of chemical weath­ering. The sediments are dominated by quartz (Si), and the higher concentration of Si suggests the presence of quartz (±feldspar) dominated terrigenous sands. The study dem­onstrates that the sediments are derived from the granitic to gneissic or from a sedimentary source. Beach sediments are deposited in a passive continental margin setting and sea­bed sediments are deposited in active continental margin. In the A-CN-K diagram, most of the samples fall in the lower part, i.e., below the plagioclase feldspar joint which indicates a low degree of alteration. Only S6 falls just above the plagioclase feldspar joint, close to the AK boundary suggesting a slightly advanced weathering of sediment and source. Beach and seabed sediments lie close to CNK and FM region suggesting the presence of ferro-magnesian minerals (likely to be pyroxene) except S6 which falls in the inner triangle of the minerals feldspar, garnet, and biotite in A-CNK-FM diagram. Both CIA and CIW values depict the unweathered nature of the sediments under humid to semi-humid climatic conditions.