川东北下三叠统飞仙关组白云岩的地球化学特征  

Geochemical Characteristics of Dolomites in Lower Triassic Feixianguan Formation,Northeast Sichuan,China

作　　者：王一[1] 王兴志[1] 王一刚[2] 文应初[2] 强子同[1] 王保全[1] 邓静[3] 

机构地区：[1]西南石油大学资源与环境学院,成都610500 [2]中国石油西南油气田公司勘探开发研究院,成都610051 [3]中国石油长庆油田分公司第五采油厂,西安710018

出　　处：《沉积学报》2009年第6期1043-1049,共7页Acta Sedimentologica Sinica

基　　金：四川省重点建设学科建设项目(SZD0414)资助

摘　　要：四川盆地川东北部下三叠统飞仙关组是我国重要的天然气储集层,白云石化的鲕粒滩为主要的油气储集层,鲕粒滩主要发育在川东北碳酸盐台地的边缘,台地内主要为泥晶碳酸盐岩夹蒸发岩。鲕粒滩在不同程度上发生白云石化并形成鲕粒白云岩,一些研究者把它们看成近地表混合水白云岩,但飞仙关组鲕粒白云岩的微量元素铁和锰、白云石的阴极发光、白云岩的稳定同位素C和O值、87Sr/86Sr比值等特征表明这些白云岩具有埋藏成因的证据。下三叠统飞仙关组白云岩具有暗红色阴极发光,微量元素Fe为600×10-6～1000×10-6,Mn为14×10-6～78×10-6,稳定同位素氧组分为-6.73～-3.65‰(PDB),(平均值为-4.89‰PDB),稳定同位素锶(87Sr/86Sr)为0.707 35～0.708 00。薄片下可以看到白云石沿着裂缝交代,上述的特征表明白云岩在埋藏条件下形成的。The lower Triassic Feixianguan Formation is a shallow marine carbonate sequence with shale and evaporates. The edge of carbonate platform commonly developed some oolitic banks, which are dolomitized. The oolitic bank dolomites are the most important gas reservoir in Sichuan. Some researchers considered them as the origin of marine-fresh water mixing model. However, petrography and chemistry of dolomite are not in consistence with origin of marine-fresh water mixing dolomitization. Feixianguan oolitic dolomites included dull-red cathodoluminescence, trace elements of 14×10^-6-78×10^-6 for Mn and 600×10^-6-1000×10^-6 for Fe, stable isotopic oxygen composition of -6.73‰--3.65‰（PDB）, the average is -4.89‰（PDB）, for matrix and vug-filling saddle dolomite and bright dolomite cement, stable isotopic strontium composition of 0.70735-0.708 00 for ^87Sr/^86Sr. Dolomite replaced host rock along the fractures in section. These data about oolitic bank dolomite suggest that the dolomitization was formed in the buried condition.

关 键 词：混合水白云岩 埋藏白云岩 碳酸盐台地 

分 类 号：P588.245[天文地球—岩石学] P593[天文地球—地质学]