HR: 11:50h
AN: V22C-07    [Abstracts]
TI: Mineralogy And Geochemistry Of Mud From Andaman Mud Volcanoes And Its Potential As A Hydrocarbon Source
AU: * Datta, S
EM: saugata.datta@gcsu.edu
AF: Georgia College and State University, Department of Biological and Environmental Sciences, Campus Box 081, Milledgeville, GA 31061, United States
AU: Bhattacharyya, C R
EM: crbcgeology@yahoo.com
AF: University of Calcutta, Department of Geology, 35 Ballygunj Circular Road, Kolkata, WB 700019, India
AB: Mud volcanoes are a common feature, reported by several workers, in the Baratang Island of Middle Andamans, India. The association of methane gas and adsorbed hydrocarbons in the mud has been cited well by scientists working in Andamans and also by others working on other eruption areas around the world. Our intended work centres around delineating the nature of such mud volcanoes in the above terrain, their chemical composition with special reference to the clay minerals formed under this sedimentary volcanism environment and exploiting such volcanic deposits towards potential hydrocarbon reserves (if any). The analysis so far suggests that, at any instant of time, gas vents at variable rates in different gas channels at the same site, and that the compositional differences in these vent gases are nearly as large as can be produced by hydrate crystallization. Our hypothesis is compatible with geologic generalizations that venting evolves from fast (mud volcano), to intermediate (hydrate crystallization), to slow (carbonate precipitation) if venting organized into more discrete vents with time. The most realistic agent that explains the observed effects is a rapid local emission of mud and/or water. 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. In addition, micro- XRD of sample cores in situ provide mineral identification as well as textural information such as grain size and distribution (e.g. fine-grained polycrystalline versus larger crystals) as well as preferred orientation (e.g. due to flow layering or strain). Stable isotopes of the separated clay minerals (smectite- and illite-rich extruded mud) from the mud volcanoes will be utilized towards the knowledge of nature of volcanism in the Andaman areas. The most likely mechanism believed is re-hydration of shales by both hydrocarbons and a geochemically mature fluid from greater depth within the wedge. Trace element and REE studies of the muds will be conducted to attest to the above hypothesis. The overall results attest 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.
DE: 8413 Subduction zone processes (1031, 3060, 3613, 8170)
DE: 8425 Effusive volcanism
DE: 8426 Mud volcanism
DE: 8428 Explosive volcanism
DE: 8439 Physics and chemistry of magma bodies
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting