程俊^1,2,3, 王淑红^1,2, 黄怡^1,2,3, 颜文^1,2,3
1.中国科学院南海海洋研究所, 广东 广州 510301;2.中国科学院边缘海与大洋地质重点实验室, 广东 广州 510301;3.中国科学院大学, 北京 100049

摘要:
综述了天然气水合物赋存区甲烷渗漏活动的地球化学响应指标的研究进展，分析了应用单一指标识别甲烷渗漏活动各自所存在的问题，包括浅表层沉积物孔隙水中CH₄、SO₄^2-、Cl^-等离子浓度随深度的变化；浅层沉积物全岩W_TOC（W表示质量分数，TOC表示总有机碳）和W_TS（TS表示总硫）之间的相关性及比值；自生碳酸盐岩δ¹³C和δ¹⁸O；自生矿物重晶石、黄铁矿、自生石膏的δ³⁴S；有孔虫壳体和生物标志化合物的δ¹³C等。结果表明孔隙水中的CH₄、SO₄^2-浓度及溶解无机碳的碳同位素组成可以用来识别目前正在发生的甲烷渗漏活动；而沉积物中的W_TS、自生矿物的δ³⁴S、钡含量及其异常峰值和生物标志化合物的δ¹³C等指标的联合使用可以更真实准确地反映地质历史时期天然气水合物赋存区的甲烷渗漏活动。因此，在实际研究过程中，可将孔隙水和沉积物两种介质的多种指标相结合。随着非传统稳定同位素（Fe、Ca、Mg等）和沉积物氧化还原敏感元素（Mo、V、U等）等研究的发展，甲烷渗漏活动地球化学响应指标的研究也将得到拓展，而多种地球化学指标的联合使用将为天然气水合物勘探及其形成分解过程识别研究提供重要的科学依据。
关键词:天然气水合物甲烷渗漏地球化学响应特征
DOI：10.11759/hykx20180426001
分类号:P59
基金项目:国家自然科学基金（41576035）

Geochemical response characteristics of methane seepage activities in gas hydrate zones
CHENG Jun^1,2,3, WANG Shu-hong^1,2, HUANG Yi^1,2,3, YAN Wen^1,2,3
1.South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China;2.Key Laboratory of Ocean and Marginal Sea Geology, Chinese Academy of Sciences, Guangzhou 510301, China;3.University of Chinese Academy of Sciences, Beijing 100049, China
Abstract:
This study summarized the research progress of the geochemical response indices of methane seepage in gas hydrate zones and analyzed the respective problems of applying any single indicator, including the concentrations of CH₄, SO₄^2-, and Cl^- in the interstitial water of shallow surface sediment changes with depth; correlation and ratio between the weight percentage of sedimentary total organic carbon (W_TOC) and that of sedimentary total sulfur (W_TS) of total bulk in shallow surface sediment; the carbon and oxygen isotope composition of the authigenic carbonate; the sulfur isotope composition of authigenic barite, pyrite, and gypsum; and the carbon isotope composition of the benthic foraminifera shells and biomarkers. The results show that the carbon isotope composition of the dissolved inorganic carbon and the CH₄ and SO₄^2- concentrations in the interstitial water can be used to identify the current methane leakage; moreover, the combination of W_TS, the sulfur isotope composition of authigenic minerals (barite, pyrite, and gypsum), the barium content variation and barium fronts, and the carbon isotope composition of biomarkers can exactly reflect the occurrence of methane leakage during geological history. Therefore, the multiple geochemical indicators of sediment and interstitial water can be combined in the related research cases. With the advances of non-traditional stable isotopes (e.g., Fe, Ca, and Mg) and sediment redox-sensitive elements (e.g., Mo, V, and U), the new geochemical response indices of methane seepage are expected to be determined. Ultimately, the studies regarding combined geochemical indicators of methane seepage will provide a valuable tool to explore gas hydrate and understand its formation and decomposition processes.
Key words:gas hydratemethane seepagegeochemical response characteristics





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