Geochemical and mineralogical analysis of ophiolitic and sedimentary formations in middle Andaman

The Middle Andaman region of the Andaman Islands is of considerable geological and ecological significance. This study provides a comprehensive geochemical and mineralogical analysis of major oxides and trace elements in soil and rock samples from ophiolitic and sedimentary formations. A total of 24 samples were collected and analyzed using X-ray fluorescence (XRF), X-ray diffraction (XRD), and thin section analysis to assess their composition and distribution. Dominant major oxides identified include silica (SiO₂), alumina (Al₂O₃), and iron oxide (Fe₂O₃), which are typically associated with felsic volcanic and sedimentary formations. Trace elements are found in the following order of abundance: Cr, Ba, Zr, Zn, V, Ni, Rb, Sr, Pb, Co, Th, and Sc. Mineralogical investigations reveal key minerals such as albite, biotite, garnet, kyanite, chromite, and celestite, indicating volcanic and sedimentary origins, with a complex geological history shaped by a semi-arid to semi-humid climate. Geochemical analysis suggests moderate to intense weathering, reflected in the chemical index of alteration (CIA) values. Dissolution of undersaturated minerals like calcite and gibbsite influences groundwater chemistry, while oversaturated minerals such as halite and manganese oxides precipitate, affecting groundwater flow and aquifer permeability. Trace metals, including iron, manganese, cadmium, and lead, indicate both natural and anthropogenic influences. These findings underscore the need for ongoing geochemical monitoring and integrated management strategies for sustainable groundwater and marine resource management in the region.