PORE WATER GEOCHEMISTRY AND MINERALOGY OF MUD FROM ANDAMAN MUD VOLCANIC PROVINCE, INDIA: LINKING TECTONICS TO MUD EXTRUSION MECHANISM

Baratang Islands of Middle Andamans, India has recently been in news due to mud volcanic eruptions as has been demostrated in Indonesia, Gulf of Cadiz and Azerbaijan among others. The association of methane gas and adsorbed hydrocarbons in the mud has been cited widely by scientists working in the Andamans. This study examines the nature of these mud volcanoes, in terms of their geochemical and mineralogical composition, with particular reference to the clay minerals formed by sedimentary volcanism. Powder XRD of bulk mud samples enable identification of the complete suite of minerals, in addition to the clay minerals. Variability in modal mineralogy is tracked using Rietveld Method of crystal structure refinement. The most likely mechanism is the re-hydration of shales by both hydrocarbons and a geochemically mature fluid from a greater depth within the wedge. Trace element and REE studies of the mud/sediments is being conducted to test the above hypothesis. The overall results attest to an active local flow of geochemically different fluids along deep-seated faults penetrating the wedge, with the waters as well as the gases coming from below.