南海北部甲烷渗漏的沉积地球化学指标(Sr/Ca和Mg/Ca)识别  

Implication of Methane Seeps from Sedimentary Geochemical Proxies(Sr/Ca & Mg/Ca)in the Northern South China Sea

作　　者：杨克红[1,2] 初凤友[1,2] 叶黎明[1,2] 章伟艳[1,2] 许冬[1,2] 朱继浩[1,2] 杨海丽[1,2] 葛倩[1,2] 

机构地区：[1]国家海洋局海底科学重点实验室,杭州310012 [2]国家海洋局第二海洋研究所,杭州310012

出　　处：《吉林大学学报（地球科学版）》2014年第2期469-479,共11页Journal of Jilin University：Earth Science Edition

基　　金：国家自然科学基金项目(41106047);国家海洋局第二海洋研究所基本科研业务费专项(JG1002);国家海洋局青年海洋科学基金项目(2012303)

摘　　要：自生碳酸盐矿物是揭示甲烷渗漏过程及其周期性变化的重要指标。为了方便、快速地识别出自生碳酸盐矿物,在探讨了前人建立的端元组分模型(文石、高镁方解石、生物成因方解石和碎屑)在我国南海北部适用性的基础上,利用沉积物全样中Sr/Ca和Mg/Ca值计算了南海北部神狐海域两支沉积物柱状样中自生碳酸盐矿物的质量分数,计算结果表明,在不同沉积深度均有含量不等的自生碳酸盐矿物。这一结果被X射线衍射结果和沉积物中存在晶形完好的自生高镁方解石和文石矿物所验证,表明利用前人建立的端元组分模型计算的结果具有可靠性。自生碳酸盐矿物的出现显示该海域深受甲烷渗漏作用影响。利用地球化学指标(Sr/Ca和Mg/Ca)获得的自生碳酸盐矿物含量垂向变化显示该区域甲烷渗漏具有强弱交替的周期变化。运用端元组分模型来获取沉积物柱状样中自生碳酸盐矿物的高分辨率剖面,从而识别甲烷渗漏信息非常方便,在大范围寻找甲烷渗漏和天然气水合物方面具有较大潜力。Authigenic carbonate minerals are important proxies for the methane seepage and its periodical variation.In order to identify carbonate mineral easily and quickly,the authors discuss whether the end-members（which are aragonite,high-Mg calcite,biogenic calcite and detritalindividually）model presented by previous researchers is applicable,and then calculate the authigenic carbonates contents according to the Sr/Ca and Mg/Ca ratios of the bulk sediment of two cores individually in Shenhu area in the northern South China Sea.The results show that there are authigenic carbonate minerals in different depths,which are also proved by the results of XRD and the appearance of authigenic high-Mg calcite and aragonite crystals in the sediments.The appearance of the authigenic carbonate minerals show that the methane seepages has been existing in ancient time and nowadays.The vertical variances based on the sedimentary geochemical proxies implicate that the methane seepages had multi-stages variations.So the end-members model presented by previous researchers can be used in the northern South China Sea.The end-members model is a good method to gain the high-resolution authigenic carbonate minerals profiles,consequently to identify methane seepages recorded in marine sediments,and potential to trace methane seepages and to explore gas hydrate in extent area.

关 键 词：甲烷渗漏 碳酸盐 Sr CA Mg CA 地球化学 南海北部 

分 类 号：P59[天文地球—地球化学] P618.14[天文地球—地质学]