酒泉盆地青西凹陷下沟组湖相热水沉积岩流体包裹体特征  

Characteristics of Fluid Inclusions in the Lacustrine Hydrothermal Sedimentary Rock from the Xiagou Formation,Lower Cretaceous in Qingxi Sag,Jiuquan Basin

作　　者：文华国[1] 郑荣才[1] Hairuo QING 范铭涛 汪满福 

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,沉积地质研究院,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

出　　处：《地质学报》2010年第1期106-116,共11页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号40672073);教育部博士点基金项目(编号20060616014)资助成果

摘　　要：以地质背景和岩石组构分析为基础,系统研究了酒泉盆地青西凹陷下沟组湖相热水沉积岩中的流体包裹体特征。结果表明,热水沉积岩中的原生流体包裹体以气液二相包裹体为主、单一液相和单一气相包裹体较少、偶见含子矿物三相包裹体。成矿流体属NaCl-H2O型热液体系,温度为90～200℃,盐度为8%～22%NaCl,密度为0.99～1.2g/cm3,成矿压力为15～180MPa。结合锶同位素等地球化学资料分析,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。提出以不同产状的重晶石、铁白云石和萤石为代表的热水沉积岩的成矿热流体系统,自主喷流通道、分支喷流通道经喷流口至附近及远端的盆地热卤水沉积区存在温度、盐度、密度和压力等物理化学参数逐渐降低的分带性变化规律。在热流体特征分析基础上,对研究区早白垩世湖底热流体成矿机制和成因模式进行了探讨。Based on the analysis of geologic background and rock textures,fluid inclusions in the lacustrine hydrothermal sedimentary rock from the Xiagou Formation,Lower Cretaceous in the Qingxi sag,Jiuquan basin was studied.The results show that native fluid inclusions in the hydrothermal sedimentary rock are dominated by vapor-liquid types,with minor haploid liquid and haploid vapor inclusions as well as triune inclusions of filial mineral.The mineralizing fluid is NaCl-H2O hydrothermal brine system.The temperature vary between 90℃ and 200℃,salinities between 8% and 22% NaCl eq.,density between 0.99 g/cm3 and 1.2 g/cm3 and mineralization pressure between 15 MPa and 180 MPa.Sr isotope geochemical analysis suggests that mineralizing fluid was the mixed hot brine consisting of deep circulation descending lake water and magmatic fluid,which was characterized by low—mid temperature,mid—high salinity and mid—high density.This study indicates that ore-forming hydrothermal fluid system which formed hydrothermal sedimentary rocks such as various barite,ankerite and fluorite shows zonation changes in terms of temperature,salinity,density and pressure,decreasing from the main exhalative-channel-branch exhalative-channel-exhalative mouth-near exhalative mouth-distal basin.Based on the analysis of the characteristics of hot fluid,the mineralization mechanism and genesis model of the Early Cretaceous sublacustrine hot fluid in the area is discussed.

关 键 词：湖相热水沉积岩 流体包裹体 热流体 成矿机制 下白垩统 青西凹陷 

分 类 号：P611[天文地球—矿床学]