Geological Study of Active Cold Seeps in the Syn-Collision Accretionary Prism Kaoping Slope off SW Taiwan
Geological Study of Active Cold Seeps in the Syn-Collision Accretionary Prism Kaoping Slope off SW Taiwan
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DOI：
10.3319/tao.2006.17.4.679(gh
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发表时间：
2006-12
影响因子：
0.8
通讯作者：
Chi‐Yue Huang;C. Chien;Meifang Zhao;Hong-chun Li;Y. Iizuka
中科院分区：
文献类型：
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作者：
Chi‐Yue Huang;C. Chien;Meifang Zhao;Hong-chun Li;Y. Iizuka
利用Pogonophoran管蠕虫、细长的黄铁矿管和自生碳酸盐结核来评价台湾西南部同碰撞吸积棱柱高坪斜坡潜在冷渗的发生。在表层和岩心沉积物中至少发现了两种棘足类管虫。黄铁矿以三种不同的形式存在：有孔虫腔体内的填充物、钙质微化石之间的胶结物和细长的管子。台湾西南部的底层水是好氧的，但在几个地点的表层沉积物中发现了自生黄铁矿，这表明当地存在有利于黄铁矿形成的还原环境。这些环境很可能是由活跃的冷渗漏造成的，其中甲烷会被排出。在5个以上的地点发现了具有高度贫化碳同位素值(-54至-43‰)的自生碳酸盐，这与甲烷来源的碳源一致。综合这些地质和生物研究结果，本研究表明，在前缘同碰撞增积棱柱高坪斜坡水深800~1500m的逆冲断裂以东的几个背斜枢纽带，存在活跃的冷渗漏和甲烷排出现象。明显的似海底反射体(BSR)、浅的硫酸盐-甲烷界面和底水中高浓度的溶解甲烷也支持了这些高势活动冷渗点的存在。
Pogonophoran tube worms, elongated pyrite tubes and authigenic carbonate nodules are used to evaluate the occurrence of potential cold seeps in the syn-collision accretionary prism Kaoping Slope off SW Taiwan. At least two species of pogonophoran tubeworms were found in surface and core sediments. Pyrites occur in three different forms: fillings inside foraminiferal chambers, cements between calcareous microfossils, and elongated tubes. The bottom water off SW Taiwan is aerobic, but authigenic pyrites are found in the surface sediments at several sites, suggesting the existence of local reducing environments enabling the formation of pyrites. These environments are most likely caused by the occurrence of active cold seeps where methane expulses. Authigenic carbonates with highly depleted carbon isotope values (-54 to -43‰) were found at more than 5 locations, in agreement with a methane-derived source for the carbon. Integrating these geological and biological results, this study demonstrates that there are active cold seeps with methane expulsions in several anticline hinge zones east of the associated thrust faults in water depths of 800-1500 m of the frontal syn-collision accretionary prism Kaoping Slope. The existence of these high potential active cold seep sites is also supported by the occurrences of distinct bottom simulating reflectors (BSRs), shallow sulfate-methane interface and high concentrations of dissolved methane in bottom water.