西沙群岛西琛1井碳酸盐岩白云石化特征及成因机制  

Dolomitization Characteristics of Carbonate Rock in Xisha Islands and Its Formation:A Case Study of Well Xichen-1

作　　者：魏喜[1] 贾承造[1] 孟卫工[2] 

机构地区：[1]中国石油勘探开发研究院博士后流动站,北京100083 [2]中国石油辽河油田分公司博士后工作站,辽宁盘锦124010

出　　处：《吉林大学学报（地球科学版）》2008年第2期217-224,共8页Journal of Jilin University：Earth Science Edition

基　　金：国家自然科学基金重点项目(40234048);中国地质大学(北京)优秀博士论文扶持奖励基金([2005]115号)

摘　　要：西沙群岛西琛1井碳酸盐岩地层可分为3个白云岩层和4个石灰岩层。白云岩层白云石矿物体积分数为91.1%-100%,其他矿物小于8.9%,以泥晶为主,分布在岩石的骨架颗粒和孔隙充填物等各种结构组分中。白云岩δ^13C为0.80‰-3.16‰,平均为2.24‰;δ^18O为0.56‰-5.23‰,平均为2.56‰。这些特征反映了白云石化作用发生在准同生超浓缩卤水条件下,古盐度为36.88%,古温度为1.07℃。石灰岩层白云石矿物体积分数多在25%以下,以亮晶为主,在孔隙或裂缝发育部位富集,而坚硬的骨架部位几乎没有白云石。白云石流体包体的均一温度为102.5296℃,平均为156.3℃;盐度为0.55%-6.25%,平均为3.75%;密度为0.950.99 g/cm^3,平均为0.97 g/cm^3;压力为20.6542.65 MPa,平均为33.65 MPa。这些特征反映了白云石化作用可能与成岩期后热水作用相关。Carbonate rock strata in well Xichen 1, Xisha islands consist of 3 layers of dolostone and 4 layers of limestone. In dolostone layers, the micritic dolomite, containing 91. 1%- 100% of dolomite, can distribute in all kinds of contents such as framework grains and inter-grain fillings. Isotopes of the dolomite are as follows,δ^13C varies from 0.80‰ to 3.16‰, averaging 2.24‰; δ^18O varies from 0.56%0 to 5.23‰, averaging 2.56‰. These characteristics reflect that dolomitization occurred in synsedimentary heavy brine environment when paleosalinity is 36.88‰ and paleotemperature is 1.07℃. The limestone layers with dominant calcsparite contain dolomite in general less than 25 %, in which dolomite are concentrated in pore or fissure fillings and absent in framework grains. The fluid inclusion homogenization temperature measured in domolite range 102.5-296℃ with an average of 156.3℃; the salinity is 0.55%- 6.25%, averaging 3.75%; the density is 0.95-0.99 g/cm^3, averaging 0.97 g/cm^3; the pressure is 20.65 42.65 MPa, averaging 33.65 MPa. These characteristics reflect that dolomitization may be in connection with post diagenetic hydrothermal event.

关 键 词：碳酸盐岩 白云石化 成因机制 西沙群岛西琛1井 

分 类 号：P581[天文地球—岩石学] P588.245[天文地球—地质学]