Hydrothermal petroleum in the sediments of the Andaman Backarc Basin,Indian Ocean |
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| Institution: | 1. Virginia Institute of Marine Science, Gloucester Point, VA, USA;2. North Carolina State University, Raleigh, NC, USA;3. University of Yangon, Yangon, Myanmar;4. Mawlamyine University, Mawlamyine, Myanmar;1. Hubei Key Laboratory of Marine Geological Resource, China University of Geosciences,, Wuhan 430074, China;2. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Wuhan), Wuhan 430074, China;3. Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China;4. Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China;5. Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China |
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| Abstract: | Recent sediments of the Andaman Backarc Basin, Indian Ocean, between the Andaman Nicobar islands and the Malay Peninsula have been analyzed for biomarker lipids. Three cores were selected: one each from the fault zone in a deep basin (a graben between two fault systems), another from a location adjacent to the fault, and the third from the topographic high in the rift valley. The molecular composition of the lipid classes (n-alkanes, isoprenoids, alkylbenzenes, alkylcyclohexanes, hopanoids, polycyclic aromatic hydrocarbons, steranes, alcohols, sterols and fatty acids) was examined by gas chromatography (GC) and GC/mass spectrometry to understand the nature and source of the hydrocarbons present and the processes of maturation of organic matter. The data show that the hydrocarbons are of hydrothermal origin, derived from thermal alteration of sedimentary organic matter, consisting of a mixture predominantly of marine-derived components with some terrestrial inputs. Normal alcohols and fatty acids also corroborate the distribution of n-alkanes. The distribution profiles and various parameters computed from the concentration of the target compounds suggest that oxidative reactions and microbial degradation in this environment are insignificant. Triterpane and PAH compositions indicate that the thermal maturity of the bitumen in the samples is comparable to or lower than that found at other hydrothermal regions such as the Northern Juan de Fuca Ridge, Guaymas Basin and Escanaba Trough. |
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