摘要
Most vein minerals deposited in fractures of the Jialingjiang Formation from Libixia section,Hechan area include a large amount of saddle dolomite and accompanying celestite,calcite and fluorite.This study analyzed the nature,source,evolution of the fluids by plane-light petrography,fluid-inclusion methods,cathodoluminescence images,and stable isotopic compositions.The homogenization temperatures of two-phase aqueous fluid inclusions in dolomite range between100 and 270℃.Combined with theδ^(18)O data,it is suggested that the fluid responsible for the precipitation of fracture fillings haveδ^(18)O values between 10‰and 18‰(relative to SMOW).The saddle dolomite and the accompanying minerals were the result of activity of dense brines at elevated temperatures.Moreover,analysis shows that the fluid was derived from a mixture of marine-derived brine and deeper circulating flow.This fluid was enriched in Sr during diagenesis and formed celestite in fracture and for regional mineralization.Dissolution of saddle dolomite was attributed to the cooling of Mg/Ca-decreased fluids,which may relate to a leaching of gypsum to celestite in surrounding carbonates.
Most vein minerals deposited in fractures of the Jialingjiang Formation from Libixia section, Hechan area include a large amount of saddle dolomite and accompanying celestite, calcite and fluorite. This study analyzed the nature, source, evolution of the fluids by plane-light petrography, fluid-inclusion methods, cathodoluminescence images, and stable isotopic compositions. The homogenization temperatures of two-phase aqueous fluid inclusions in dolomite range between 100 and 270℃. Combined with the jlSO data, it is suggested that the fluid responsible for the precipitation of fracture fillings have δ18O values between 10%o and 18‰ （relative to SMOW）. The saddle dolomite and the accompanying minerals were the result of activity of dense brines at elevated temperatures. Moreover, analysis shows that the fluid was derived from a mixture of marine-derived brine and deeper circulating flow. This fluid was enriched in Sr during diagenesis and formed celestite in fracture and for regional mineralization. Dissolution of saddle dolomite was attributed to the cooling of Mg/Ca-decreased fluids, which may relate to a leaching of gypsum to celestite in surrounding carbonates.
基金
supported by the National Natural Science Foundation of China(grants no.41272130 and 41172099)
support provided by Key Laboratory for Sedimentary Basin and Oil and Gas Resources of MLR(grant no.zdsys2014003)
关键词
嘉陵江组
轴承断裂
白云石
热卤水
充填物
活动记录
鞍形
重庆市
Libixia section, Jialingjiang Formation, saddle dolomite, hot brine, Hechuan area, Chongqing
