三塘湖盆地中二叠统芦草沟组白云岩成因  

Origin of Dolostone in Lucaogo Formaion of Middle Permian in Santanghu Basin

作　　者：朱玉双[1] 柳益群[1] 周鼎武[1] 

机构地区：[1]西北大学地质学系、西北大学大陆动力学国家重点实验室,陕西西安710069

出　　处：《西北地质》2009年第2期95-99,共5页Northwestern Geology

基　　金：国家重点基础研究发展计划项目(2003CB214603)资助

摘　　要：三塘湖盆地中二叠统的芦草组碳酸盐岩是盆地内重要的储集岩之一,碳酸盐岩中50%以上为白云岩。有纹层状白云岩和斑块状白云岩两种,前者白云石自形程度较好;后者白云石为含铁白云石交代方解石而成,铁白云石晶体粗大,自形程度差,其形成时间晚于纹层状铁白云石。白云岩的Mg/Ca值均小于1;Sr的含量为31×10-6～527×10-6,平均为217.8mg/kg;方解石和白云石的δ18O差值大多数小于6%;芦草沟组膏岩并未普遍存在,盐度指数Z平均为124.43。通过对上述特征综合研究认为,三塘湖盆地中二叠统的芦草组白云岩为混合水成因,并建立了相应的白云石化模式。Carbonate rock of Lucaogou Formation in Middle Permian is a major reservoir rock in Santanhu Basin and dolostone accounts for more than 50% in composition of the carbonate rock. There are two types of dolostone, one is the bedded dolostone and the other is the patch dolomite. In the bedded dolostone, the mineral dolomite has a good idiomorphism; on the contrary, in the patch dolostone, the idiomorphism of dolomite is not good. The patch dolostone is composed of ankerite with crassitude crystal replacing calcite. The dolostone has a Mg/Ca ratio of 〈1; a Sr content of 31×10^-6- 527×10^-6, averaged by 217.8mg/kg; and a difference in δ^18O between calcite and dolomite being less than 6. In addition, gypsum rock is not widely found in Lugcaogou Formation, with the salinity being 124.43. Based on the aforementioned idexes, we hold that the dolostone in Lucaogou Formation of Middle Permian in Santanghu basin is of the mixed water origin and have built the correspondent dolomitization model.

关 键 词：三塘湖盆地 中二叠统 白云岩成因 白云石化模式 

分 类 号：P588.25[天文地球—岩石学]