海水胶结作用对碳酸盐岩石组构的影响:以四川盆地东北部三叠系飞仙关组为例  

Influences of marine cementation on carbonate textures: A case of feixianguan carbonates of Triassic, NE Sichuan Basin

作　　者：黄思静[1,2] 李小宁[1,2] 兰叶芳[1,2] 成欣怡[1,2] 

机构地区：[1]成都理工大学油气藏地质及开发工程国家重点实验室,四川成都610059 [2]成都理工大学沉积地质研究院,四川成都610059

出　　处：《中南大学学报（自然科学版）》2013年第12期5007-5018,共12页Journal of Central South University:Science and Technology

基　　金：国家自然科学基金资助项目(40839908;41172099)

摘　　要：在薄片分析、阴极发光分析、全岩化学分析、不同组构电子探针分析和包裹体均-化温度分析的基础上，研究了四川盆地东北部三叠系飞仙关组鲕粒灰岩、在成分上介于灰岩和白云岩之间的亮晶鲕粒白云岩-灰岩（灰质白云岩或白云质灰岩1以及结晶白云岩的结构。研究表明：四川盆地东北部三叠系飞仙关组鲕粒碳酸盐岩的海水胶结作用发育，这些胶结物目前全由方解石组成，具有非常低的锰、铁含量，没有或只有极弱的阴极发光，缺乏可进行温度测量的气-液两相包裹体，显示近地表海水潜流环境的特征；鲕粒碳酸盐岩的海水胶结物具有大范围变化的锶含量，-部分分布在10^-4数量级，另-部分分布在10^-3数量级，说明它们是由不同的先驱CaCO3矿物新生变形而来，低锶含量的方解石是镁方解石新生变形的产物，高锶含量的方解石是文石新生变形的产物；由低锶方解石胶结（先驱矿物是镁方解石）和由高锶方解石胶结（先驱矿物是文石）的鲕粒碳酸盐岩具有不同的胶结物结构和岩石结构，前者有极好的栉壳状胶结物结构，岩石的鲕粒结构保存较好，白云化后白云石晶体较小，不完全白云化时白云石仅分布在鲕粒中，后者缺乏良好的栉壳状胶结物结构，岩石的鲕粒结构保存差，白云化后白云石晶体较大，完全白云化时白云石可分布在鲕粒中，也可分布在胶结物中；原始胶结物为镁方解石的鲕粒碳酸盐岩和原始胶结物为文石的鲕粒碳酸盐岩相比，在相同的白云化环境中，前者因具有内部镁来源而可能使白云石的结晶速度更快，白云石的晶体相对较小，白云石的锰含量更低，阴极发光更弱，白云化作用不-定需要对海水开放的环境以提供镁的来源；后者因缺乏内部镁来源而可能使白云石的结晶速度较慢，白云石的晶体相对较大，白云石的锰含�Based on the thin section observation under microscope and cathodoluminoscope, electron microprobe and whole rock chemical analysis of different fabrics, and inclusion homogenization temperature analysis, the textures ofoolitic limestone, sparry oolitic dolomite-limestone （with the transition composition between limestone and dolomite） and crystalline dolomite were studied. The results show that： Marine cementation is well developed in oolitic carbonates of Triassic Feixianguan Formation in NE Sichuan Basin. All these marine cements are composed of calcite with very low manganese and iron, without cathodoluminescene or dull cathodoluminescene, and are in lack of two-phase inclusions that can be used to measure temperature, representing the characteristics of marine phreatic zone near surface. The strontium content of marine cements in oolitic carbonates varies in a large range, with one distributing in several hundreds of 10-6 and the other in several thousands for 10-6, which indicates that these marine cements are generated by different precursor minerals ＇of CaCO3 through neomorphism, that is, the calcite with low strontium is generated by Mg-calcite and the calcite with high strontium by aragonite through neomorphism. Oolitic carbonates cemented by calcite with low strontium （Mg-calcite as precursor mineral） has excellent pectinate fabric cement, well preserved oolitic texture and small dolomite crystals after dolomitization. In case of incomplete dolomization, the dolomite is constrained in the oolite. On the other hand, oolitic carbonates cemented by calcite with high strontium （aragonite as precursor mineral） is lack of pectinate calcite cement, with oolitic texture poorly preserved. The dolomite crystal is relatively large after dolomitization, and the oolite is frequently cut by dolomite crystals. The oolitic carbonates cemented by original Mg-calcite may have faster dolomitization rate due to the internal source of magnesium, resulting in smaller dolomite crystal size, lower manganese co

关 键 词：四川盆地东北部 三叠系飞仙关组 海水胶结作用 镁方解石-文石 碳酸盐岩的结构 

分 类 号：P588.245[天文地球—岩石学]