• 责任者：Guo Kai (State Key Laboratory of Petroleum Resource and Prospecting ; China University of Petroleum ; Beijing 102249 ; China) ; Zeng Jianhui
• 刊名：Journal of China University of Petroleum
• 出版年：2013
• 卷期：37(2)
• 关键词：方解石 ; calcite ; 烃源岩 ; source rocks ; 甘肃 ; Gansu Province
• 页码：p.36-42,49
• 图表：illus., 2 tables, 25 refs.
• 分类号：1003
• issnNo：ISSN1673-5005
• isbnNo：CN37-1441/TE

The origin of calcite veins and their relationship with hydrocarbon fluid flow were studied by analyzing trace element and stable isotope, which occurred extensively in the widely distributed tectonic fractures of Yanchang formation in Longdong area of Ordos Basin. The results show that calcite veins in sandstones and mudstones are all ferrocalcite with relatively high Fe and Mn content and low Mg content, and their δ^13 ranges from -6.6‰ to 2.7‰ （PDB） and δ^18 ranges from -23.0%‰ to -14. 9‰ （PDB）. Combining these data with geological features, it is indicated that the enrichment of Mn in calcite veins is attributed to corrosion of volcanic tuff in Chang 7 member by hydrocarbon fluid, and the formation of these calcite veins is associated with carbon dioxide of rich ^13 C generated by microbial methanogenesis and that of poor ^13 C generated by thermal decarboxylation. The calcite veins mainly formed in the Early Cretaceous during oil generation and expulsion of source rocks in Chang 7 member, and their formation was prior to or coeval with extensive hydrocarbon fluid flow. The tectonic fractures formed in the Late Jurassic are significant fluid flow pathway and play an important role for oil expulsion from source rocks and migration through low permeability sandstones.