天然气水合物系统多幕次甲烷渗漏作用的底栖有孔虫同位素响应——以IODP 311航次为例  

CARBON AND OXYGEN STABLE ISOTOPES OF BENTHIC FORAMINIFERA AS POSSIBLE INDICATORS OF EPISODIC METHANE SEEPS IN GAS HYDRATE GEO-SYSTEM——A STUDY FROM IODP EXPEDITION 311

作　　者：李清[1,2] 王家生[3] 蔡峰[1,2] 陈祈[4] 胡高伟[1,2] 

机构地区：[1]国土资源部海洋油气资源与环境地质重点实验室,青岛266071 [2]青岛海洋地质研究所,青岛266071 [3]中国地质大学(武汉)地球科学学院,武汉430074 [4]中石化江汉油田分公司采油工艺研究院,武汉430035

出　　处：《海洋地质前沿》2011年第6期29-36,共8页Marine Geology Frontiers

基　　金：国家自然科学基金项目(40772073)

摘　　要：为了探索底栖有孔虫壳体同位素特征对海洋天然气水合物地质系统中多幕次甲烷渗漏作用的响应,对综合大洋钻探计划(IODP)311航次5个站位(U1325、U1326、U1327、U1328和U1329)沉积物岩心中底栖有孔虫种属Uvigerina peregrina和Bulimi-na mexicana进行了地球化学研究,发现2个种属的壳体碳氧同位素存在较大的变化范围,分别为-3.32‰^-0.22‰(PDB)和3.4‰~4.91‰(PDB),异常负偏的碳同位素和正偏的氧同位素特征指示了水合物分解释放出的甲烷气体在沉积物中发生厌氧氧化作用(AOM)影响生活在其中的底栖有孔虫的壳体同位素特征。5个站位的多个层位中有孔虫壳体异常同位素特征,较好地指示了水合物地质系统的多幕次甲烷渗漏作用,通过与海平面升降对比发现,该多幕次甲烷渗漏作用与10万a尺度的全球海平面升降变化相一致,很好地印证了间冰期、冰期的交替导致的海平面升降变化对于水合物地质系统的稳定性有重要的影响作用。The research of shallow infauna benthic foraminifera species Uvigerina peregrina and Bulimina mexicana collected from all five sites（U1325,U1326,U1327,U1328,and U1329） during the Integrated Ocean Drilling Program（IODP） Leg 311 at the Cascadia margin,northeast Pacific was carried out to reveal the response of carbon isotopic compositions of benthic foraminifera to the episodic methane seeps in gas hydrate geo-system.Both the two species exhibit dramatic negative carbon isotopic excursions and positive oxygen isotopic anomalies（-3.32‰ ^-0.22‰（PDB） and 3.4‰ ~ 4.91‰（PDB）） clearly indicative of gas hydrate dissociation influencing the dissolved inorganic carbon of the pore water via anaerobic oxidation of methane and further influencing the isotopic compositions of benthic foraminifera tests.The negative carbon isotopic excursions and positive oxygen isotopic values of benthic foraminifera tests from the five sites clearly indicate episodic methane seeps in the gas hydrate system.The episodic methane seep stages recognized at the five sites coupled well with the 100 kyr-scale eustatic sea-level fluctuations during the past 1.0 Ma,which demonstrates that glacioeustatic sea-level fluctuations play significant roles in the destabilization of gas hydrate geo-system.

关 键 词：底栖有孔虫 碳同位素负偏 多幕次甲烷渗漏 海平面升降 水合物地质系统 

分 类 号：TE122.113[石油与天然气工程—油气勘探]