Detailed Clay Mineralogy and Pore Water Geochemistry of Mud and Thermal Measurements from the Vents from Baratang Mud Volcanoes from Andamans, India: Linking Tectonics to Mud Chemistry to Extrusion Mechanism

The location of the Andaman mud volcano close to the long magmatic volcanic chain in Indian Ocean results in a high geothermal temperature gradient that triggers mineralogical transformations and geochemical reactions at shallow depth. The formation of the mud volcanoes is predominantly ascribed to release of overpressure from clay and organic-rich sediments, leading to impressive buildup of mud mountains in submarine and subaerial settings. Baratang Islands of Middle Andamans, India have recently (2006) been in news. This study examines the nature and geochemistry of slurry mud that emanates, in terms of new data analyses from Trace element and REE geochemistry, pore water geochemistry, and mineralogical composition of the mud, with particular reference to the specific clay minerals formed by sedimentary volcanism. Powder XRD of bulk mud samples done previously has enabled identification of the complete suite of minerals, in addition to the clay minerals. In situ micro-X-ray diffraction of the clay separates from these mud samples may help to understand the sequence of transformations of the hydrated clays, and the crystallochemical characterization of illite, chlorite or other interlayered clay minerals that can be an indicator of depth of origin of the fluid. In this work we are also targeting a study of the detailed structure and composition of the new phyllosilicates that may provide important information about the nature of the fluids. 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. The overall results will confirm the sedimentary vs thermogenic nature of the clays, origin of the fluids and assessment of high temperature imprint in the fluid signature.