24. ISOTOPE COMPOSITIONS OF GASES IN SEDIMENTS FROM THE CHILE CONTINENTAL MARGIN1
24. ISOTOPE COMPOSITIONS OF GASES IN SEDIMENTS FROM THE CHILE CONTINENTAL MARGIN1
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24. 智利大陆边缘沉积物中气体的同位素组成1
DOI：
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
B. M. Didyk
中科院分区：
文献类型：
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作者：
A. Waseda;B. M. Didyk
报告了ODP Leg 141站点859、860、861和863处气穴气体的分子和同位素测量结果。甲烷δ’3C值在-86‰~ -61‰之间。甲烷δD值在-249‰~ -163‰之间。所有样品的C]/(C2 + C3)比值均大于300。这些数据表明甲烷主要由细菌活动产生，主要的产甲烷途径是CO2还原。乙烷的δ13C值在-70‰~ -44%c之间。这些值是天然气中乙烷的最轻的碳同位素值之一，表明乙烷的来源也主要是细菌。在860站点海底200 m以下的深层地层中，乙烷的δ13C值在-60‰~ -45‰范围内变重，C]/C3比值随深度的增加而减小。这表明存在少量的产热碳氢化合物。有机质的低成熟程度表明，热生烃组分不是在原位产生的，而是从更成熟的地层中运移而来，可能是由这些地层中活跃的流体流动驱动的。
Molecular and isotope measurements of gases from gas pockets at ODP Leg 141 Sites 859, 860, 861, and 863 are reported. The δ' 3C values of methane range between -86‰ and -61 ‰. The δD values of methane range between -249‰ and -163‰. The C]/(C2 + C3) ratios of all samples are higher than 300. These data indicate methane is mainly produced by bacterial activity, and the primary methanogenic pathway is CO2 reduction. The δ13C values of ethane range between -70‰ and -44%c. These values are among the lightest carbon isotope values reported for ethane in natural gas, indicating the origin of ethane is also predominantly bacterial. In deeper strata below 200 m below seafloor (mbsf) at Site 860, the δ13C values of ethane become heavier from -60‰ to -45‰ and the C]/C3 ratios decrease with increasing depth. This indicates the presence of a small amount of thermogenic hydrocarbons. The low degree of maturation of the organic matter suggest the thermogenic hydrocarbon components are not generated in situ but have migrated from more mature strata, possibly driven by active fluid flow in these strata.