Mineralogy and Isotopic Composition of Pyrites-Bearing Ejects from a Mud Volcano, Baratang, Andaman Islands

The Jarawa Creek mud volcano on Baratang Island has produced a variety of ejecta including mud containing illite, kaolinite and microfossils, volcanic glass, brine, methane gas and sulfide nodules. The nodules are of pyrite with a δ³⁴S ranging from -3.6 to 25.4‰. Sulfate leached from the mud has δ³⁴S values of -9.3 and -11.37‰. Our study reveals that the sulfate could not have been derived either from the nodules themselves or from the sea water or from connate brine. The nodules are of sedimentary origin and the most likely source of sulfate is sedimentary sulfide implying subsurface oxidation and a supply of oxidant possibly in groundwater.