冲绳海槽中部热液活动与IODP331航次初步成果  

Hydrothermal Activity in Middle Okinawa Trough and Preliminary Results of Integrated Ocean Drilling Program Expedition 331

作　　者：杨守业[1] 王权[1] 

机构地区：[1]同济大学海洋地质国家重点实验室,同济大学海洋与地球科学学院,上海200092

出　　处：《地球科学进展》2011年第12期1282-1289,共8页Advances in Earth Science

基　　金：国家自然科学基金项目“末次盛冰期以来长江入海沉积铁化学相态组成及环境响应”(编号:41076018)资助

摘　　要：伊平屋北部热液区(Iheya North hydrothermal field)位于冲绳海槽中部地区。综合大洋钻探计划(IODP)331航次于2010年9月1日至10月4日在该区钻探了5个站位(C0013～C0017):C0016站位位于North Big Chimney(NBC)地区活跃的热液烟囱和硫化物—硫酸盐丘状体上;在C0013、C0014、C0015、C0016站位发现了异常高热流值;在热液补给区C0017站位,实现最大钻探深度达到海底下151 m。在活跃的丘状热液喷口处的C0016站位,尽管取芯率只有4.7%,但首次在现代海底获得黑矿型(Kuroko-type)、富闪锌矿的黑色矿石样品。其他4个站位岩芯主要为具有不同热液蚀变和矿化程度(沸石相到绿片岩相)的互层状半深海和火山碎屑沉积物,及火山角砾和浮岩砾屑。钻孔中不规则的地温梯度剖面变化揭示出地下流体的横向运移趋势。现场数据表明,岩芯孔隙水和气体组成在垂向和横向上变化较大。海底作用主要包括通过相态分离而形成高盐水和富气体的流体,矿物蚀变释放Ca而吸附Mg和Na,高温下K释放而低温吸收,硬石膏形成,有机质的微生物氧化和甲烷利用硫酸盐的厌氧氧化,微生物作用下甲烷形成等。船上研究未证实研究区存在活跃的深部生物圈,细胞丰度明显低于以前的ODP/IODP在陆架边缘的钻探站位。The Iheya North Hydrothermal Field is located in the middle Okinawa Trough. During the Integrated Ocean Drilling Program （IODP） Expedition 331, the Deep Hot Biosphere Project, five sites （C0013 -C0017） were drilled in the Iheya North Hydrothermal System from September 1 to October 4, 2010 in order to investigate metabolically diverse subseafloor microbial ecosystems and their physical and chemical settings. Site C0016 located in the active hydrothermal vent site and sulfide-sulfate mound at North Big Chimney （NBC） has the recovery rate of only 4.7%, but the core included the first Kuroko-type, sphalerite-rich black ore ever recovered from the modem seafloor. The other four sites yielded interbedded hemipelagic and volcaniclastic sediment and volcanogenic breccias and pumice that are variably hydrothermally altered and mineralized, in the zeolite to greenschist facies. Detailed temperature profiles at Sites C0014 and C0017 display irregularities suggestive of lateral flow. The analysis of interstitial water and headspace gas yielded complex patterns with depth and laterally at most sites over distances of only a few meters. Documented processes include formation of brines and vapor-rich fluids by phase separation and segregation, uptake of Mg and Na by alteration minerals in exchange for Ca, leaching of K at high temperature and uptake at low temperature, anhydrite precipitation, microbial oxidation of organic matter and anaerobic oxidation of methane utilizing sulfate, microbial methanogenesis. Shipboard analysis has not confirmed the presence of an active deep hot biosphere. Cell abundances are much lower than those found in previous Ocean Drilling Program/IODP sites on continental margins, and attempts at culturing were generally unsuccessful.

关 键 词：综合大洋钻探计划IODP 深部生物圈 冲绳海槽 热液活动 

分 类 号：P736.2[天文地球—海洋地质]