石油实验地质2016，Vol.38Issue(2)：251-258,265,9.DOI:10.11781/sysydz201602251
四川盆地南江栖霞组白云岩岩石学、地球化学特征及成因
Petrologic and geochemical characteristics and the origin of dolomites in the Qixia Formation in Nanjiang county of the Sichuan Basin
摘要
Abstract
Limestones are locally dolomitized in the 2nd member of the Middle Permian Qixia Formation of Qiaoting section, located in Nanjiang county of the Sichuan Basin. Matrix dolomites primarily consist of non⁃planar xenotopic dolomite crystals, and vugs and fractures are filled with saddle dolomites and crystalline calcites. Dissolution occurs mainly in dolomites. Characteristics and origin of matrix dolomites and saddle dolomites have been determined based on petrographic examinations, integration of carbon and oxygen stable isotopes, trace element content, fluid inclusion data, cathodoluminescence images, burial and thermal maturation history and abnormal thermal events associated with the Emeishan basalt eruption. The research showed that the fluid inclusion homogenization temperatures of matrix dolo⁃mites, saddle dolomites and crystalline calcites range 100~110℃, 130~230℃ and 130~230℃, respectively. Theδ18 O values of the samples which mainly consist of matrix dolomites, saddle dolomites and crystalline calcites range-4.27‰~-6.28‰,-4.87‰~-5.80‰and -5.16‰~-6.50‰, respectively. Saddle dolomites and crystalline calcites have the characteristics of more negative δ18 O values than matrix dolomites. The δ13 C values of the samples which mainly consist of matrix dolomites, saddle dolomites and crystalline calcites range 3.97‰~5.22‰, 4.88‰~5.35‰and 2.73‰~4.29‰, respectively, indicating that the carbon source is generally from the coeval seawater. The δ18 O values of dolomitizing fluids for matrix dolomite and saddle dolomite range +3‰~+6‰( SMOW) and +7‰~+14‰(SMOW), respectively. This is consistent with the formation of matrix and saddle dolomites in fluids with elevated salinity and temperature. Matrix dolomites, saddle dolomites and crystalline calcites were influenced by thermal events caused by Emeishan basalt eruption activity. The kinetic barrier of dolomite precipitation was overcome by high salinity and temperature, and it allowed the transformation of limestones into replacive matrix dolomites and precipitate saddle dolomites in vugs and fractures. Due to lasting high temperature and Mg2+ loss, calcites with high temperature precipitated, which showed that hydrothermal fluids altered the carbonate rocks.关键词
鞍形白云石/基质白云岩/峨眉山玄武岩/碳酸盐岩的热液改造/栖霞组/南江桥亭/四川盆地Key words
saddle dolomite/matrix dolomite/Emeishan basalt/hydrothermal alteration of carbonates rock/Qixia Formation/Qiaoting section in Nanjiang county/Sichuan Basin分类
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李小宁,黄思静,黄树光,黄可可,袁桃,罗文..四川盆地南江栖霞组白云岩岩石学、地球化学特征及成因[J].石油实验地质,2016,38(2):251-258,265,9.基金项目
国家自然科学基金项目（41272130，41172099）和“中央财政支持地方高校发展专项资金”联合资助。 （）
