Mineral authigenesis in sediments from a cold-seep site at Yung-An ridge, offshore southwestern Taiwan

• Main Authors: Ta-WeiHsu, 徐達偉
• Other Authors: Wei-Teh Jiang
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/09155930312416737115

博士 === 國立成功大學 === 地球科學系 === 103 === Authigenic phases including pyrite, greigite, mackinawite, vivianite, ferric smectite, and carbonate minerals in a sediment core of 2389 cm in length collected at site MD052911 in Yung-An Ridge off southwestern Taiwan were found to have specific distributions and versatile microtextures at different depths as characterized by polarized light microscopy, X-ray diffraction, scanning and transmission electron microscopy, and Raman and Fourier transform infrared spectroscopy. Such dramatic down-core variations in mineral authigensis were inferred to be a temporal and spatial record of non-steady state diagenesis due to time-varying methane flux characteristic of cold-seep sediments. A record of temporal cold-seep activities associated with enhanced anaerobic oxidation of methane was marked by the occurrence of high pyrite concentrations, highly versatile pyrite textures, and abundant ferric smectite pellets in sediments from the upper and lower sections of the core. By contrast, the sediments in the middle section do not contain the aforementioned mineral authigenesis and microtextures due to a lack of intense anaerobic oxidation of methane. The sequence and conditions favorable for the formation of various authigenic minerals were outlined in detail in this study. The result adds to the limited body of direct observation and characterization of authigenic minerals from cold-seep sediments.