返回Google圖書搜尋

Geochemistry of Hydrothermal Vent Fluids from the Northern Juan de Fuca Ridge

出版	Massachusetts Institute of Technology, 2003
URL	http://books.google.com.hk/books?id=MSkeAQAAIAAJ&hl=&source=gbs_api

註釋The presence of aqueous organic compounds derived from sedimentary organic matter has the potential to influence a range of chemical processes in hydrothermal vent environments. For example, hydrothermal alteration experiments indicate that alteration of organic-rich sediments leads to up to an order of magnitude more metals in solution than alteration of organic-poor basalt. This result is in contrast to traditional models for the evolution of vent fluids at sediment-covered mid-ocean ridge axis environments, and indicates the fundamental importance of including the effects of organic compounds in models of crustal alteration processes. However, in order to rigorously constrain their role in crustal alteration processes, quantitative information on the abundances and distributions of organic compounds in hydrothermal vent fluids is required. This thesis was undertaken to provide quantitative information on the distributions and stable carbon isotopic compositions of several low-molecular weight organic compounds (C1-C4 alkanes, C2-C3 alkenes, benzene and toluene) in fluids collected in July, 2000, at three sites on the northern Juan de Fuca Ridge: the Dead Dog and ODP Mound fields, which are located at Middle Valley, and the Main Endeavour Field, located on the Endeavour segment. At Middle Valley, the ridge axis is covered by up to 1.5 km of hemipelagic sediment containing up to 0.5 wt. % organic carbon. The Main Endeavour Field (MEF) is located approximately 70 km south of Middle Valley in a sediment-free ridge-crest environment, but previously measured high concentrations of NH3 and isotopically light CH4 relative to other bare-rock sites suggest that the chemical composition of these fluids is affected by sub-seafloor alteration of sedimentary material (LILLEY et al., 1993).