Geochemical characteristics of Recent sediments of channel bar of the Ganges (Padma) River, Bangladesh

Abstract

 The present research deals with the geochemical characteristics of Recent sediments of channel bar of the Ganges (Padma) River, Bangladesh. The main objectives of the study are to delineate source area weathering, sorting and sediment recycling, provenance and tectonic setting of the Ganges sediments. The geochemical characteristics of the sediments display relatively a wide variation in accordance with lithosequences in their major element contents (e.g. SiO2: 59.24-73.44, Al2O3: 10.39-15.25 in wt.%), reflecting the distinctive provenance and in part an unstable period in terms of tectonic activity. Oxides of some major elements (viz., K 2O, TiO2, and MgO) and trace elements (viz., Rb and Ni) exhibit comprehensive correlations with Al 2O3 confirming their possible hydraulic fractionation. The geochemical composition reveals that the studied sands are arkose and litharenite in type. The values of SiO2/Al2O3, CIA (Chemical Index of Alteration), ICV (Index of Compositional Variability) and PIA (Plagioclase Index of Alteration) derived from the geochemical analyses of the studied sediments show low degree of maturity indicating poor chemical weathering in source areas. The entire rock geochemistry data reveals that the sediments were derived from mostly felsic to intermediate igneous rock provenance. These kinds of source rocks are present in a vast region of the Himalayan belt and catchment areas of Ganges. The tectonic setting discrimination plots (K2O/ Na 2O vs. SiO2 and SiO2/Al2O3 vs. K2O/Na2O) shows the sediments in the source area belong to Passive Margin (PM) to Active Continental Margin (ACM).