青西凹陷下沟组湖相热水沉积岩中的重晶石流体包裹体特征  

Characteristics of fluid inclusions in the barite of lacustrine hydrothermal sedimentary rock from the Lower Cretaceous Xiagou Formation in Qingxi sag,Jiuquan basin,China

作　　者：文华国[1] 郑荣才[1] Hairuo QING 范铭涛 吴国瑄[4] 夏佩芬[4] 汪满福 桑廷元 廖一[1] 陈浩如[1] 

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,成都610059 [2]Department of Geology, University of Regina, Regina SK Canada S4S OA2 [3]中国石油玉门油田分公司,甘肃酒泉735019 [4]同济大学“海洋地质”国家重点实验室,上海200092

出　　处：《成都理工大学学报（自然科学版）》2008年第3期288-296,共9页Journal of Chengdu University of Technology: Science & Technology Edition

基　　金：国家自然科学基金资助项目(40672073);教育部博士点基金资助项目(20060616014)

摘　　要：以地质背景和岩石组构分析为基础，对酒泉盆地青西凹陷下沟组湖相热水沉积岩中的重晶石矿物进行了流体包裹体研究。结果表明，重晶石胶结物中主要发育富液两相、含子矿物三相、单一液相和单一气相四类原生流体包裹体，碎屑状重晶石主要发育富液两相和少量单一液相包裹体。显微测温结果显示，重晶石胶结物和碎屑状重晶石的成矿流体为NaCl-H2O体系，温度分别为160-200℃和120～140℃，盐度（NaCl）分别为20％～22％和18％～20％，密度分别为1．06～1．2g／cm3和1．06～1．11g／cm3，成矿压力分别为150～180MPa和30～45MPa。结合锶同位素分析，认为成矿流体属于深循环的下渗湖水与岩浆水共同构成的中低温、中高盐度和中偏高密度混合热卤水。成矿流体经历了早期阶段的热液沸腾作用和混合作用的叠加耦合而形成重晶石胶结物，较晚期阶段热液混合稀释沉淀作用则形成碎屑状重晶石。两者应属于同一热流体不同阶段和不同方式的化学沉淀产物，重晶石胶结物形成于喷流口内；碎屑状重晶石形成于相对远离喷流口的开放系统，有更多大气水（湖水）的注入而使得其热流体温度、盐度、密度和压力相比重晶石胶结物均有所下降。重晶石矿物流体特征和成因研究，可为研究区下沟组湖相热水沉积岩热流体性质、来源和成因分析奠定基础。Based on the analysis of geologic background and rock fabric, the authors study the fluid inclusions in the barite of the lacustrine hydrothermal sedimentary rock from the Lower Cretaceous Xiagou Formation in the Qingxi sag of Jiuquan basin. On the basis of optical observations and microthermometric study, four types of fluid inclusion in barite cement are recognized： the aqueous liquid-rich inclusions, the halite bearing multiphase inclusions, the liquid only, the vapor only, and two types of the fluid inclusions in clastic barite are recognized： the aqueous liquid-rich inclusions and liquid only. The mineralizing fluid of the barite cement and clastic barite is NaCl·H2O brine system.The temperature is 160-200℃ and 120-140℃ , the salinity （NaCl） is 20~22% and 18~20%, the density is 1.06~1.2 g/cm3 and 1.06~1. 11 g/cm3 and the mineralization pressure is 150~180MPa and 30~45 MPa. Integrated with Sr isotope analysis, the authors figure that the mineralizing fluid is the mid-low temperature, mid-high salinity and mid-high density mixed hydrothermal brine which consists of the deep circulating lake water and a little magmatic water. The barite cement is formed by the overprinting and coupling of hydrothermal boiling and the intermingling of the mineralizing fluids in the early stage, and the clastic barite is only formed by the hydrothermal intermingling, dilution and precipitation in the late stage. Both of them are the chemical precipitation products in different stages and different ways in the same hydrothermal fluid. The barite cement is formed in the vent, and the clastic barite is formed in the open system where is relatively far away from the vent, with the meteoric water （lake water） injected, the temperature, salinity, density and pressure of the clastic barite are lower than the fomer. The fuild characteristics and origin of the barite minerals can lay the foundation for the fluid properties, genesis and origin analysis of the lacustrine hydrothermal sedimentary rock from Xiagou Formation i

关 键 词：湖相热水沉积岩 重晶石 流体包裹体 成矿流体 下白垩统 青西凹陷 

分 类 号：P578.71[天文地球—矿物学]