宁夏固原凹陷岩盐矿床后生改造成矿作用—来自矿物学的证据  

Epigenetic Reforming Mineralization of the Guyuan Rock Salt Deposit in Ningxia:Evidence from Mineralogy

作　　者：刘芳 田景雄 何伟 褚小东 宋新华 LIU Fang;TIAN Jingxiong;HE Wei;CHU Xiaodong;SONG Xinhua(School of the Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083;Geological Bureau of Ningxia Hui Autonomous Region,Yinchuan,Ningxia 750021;Ningxia Institute of Basic Geological Survey,Yinchuan,Ningxia 750021;Coal Geology Bureau of Ningxia Hui Autonomous Region,Yinchuan,Ningxia 750000;Natural Resources Survey of Ningxia Hui Autonomous Region,Yinchuan,Ningxia 750000)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]宁夏回族自治区地质局,宁夏银川750021 [3]宁夏回族自治区基础地质调查院,宁夏银川750021 [4]宁夏回族自治区煤炭地质局,宁夏银川750000 [5]宁夏回族自治区自然资源勘测调查院,宁夏银川750000

出　　处：《地质与勘探》2023年第1期27-42,共16页Geology and Exploration

基　　金：宁夏自然科学基金项目“固原岩盐矿沉积旋回特征与成因分析”(编号:2021AAC03440)资助。

摘　　要：为深入理解岩盐矿床复合成矿作用,研究宁夏固原凹陷岩盐矿成矿规律和成矿模式,在野外地质调查的基础上,通过镜下观察、扫描电镜分析、电子探针能谱分析、X射线粉晶衍射分析,结合岩石学和矿物学研究,对该矿床矿石结构构造特征和矿物特征进行对比研究,并对其岩盐矿成矿期次进行了划分。结果表明,固原凹陷岩盐矿矿石具有原生沉积和后生改造结构构造。矿石结构中自形细晶结构为原生沉积结构,自形粗晶、港湾和蠕虫交代结构为后生改造结构。矿石构造中纹层、条带、团块状构造为原生沉积构造,块状、角砾状和网脉状构造为后生改造构造。岩盐矿床矿物组合主要有石盐、钙芒硝、硬石膏、无水芒硝以及粘土矿物、钠长石、白云石,具有原生沉积和后生改造的矿物组合特征,盐类矿物均可见原生沉积型和后生改造型矿物。岩相学和矿物学研究证实,固原凹陷岩盐矿床是一个典型的原生沉积-后生改造型矿床。钙芒硝和硬石膏矿主要由早期沉积作用形成矿化体,经历了后期微弱的改造作用;而石盐矿主要由早期沉积作用形成矿体,在后期盆地构造变化中发生塑性流动、溶解-重结晶或构造变形而充填于围岩的裂隙或构造活动形成的有利空间中成矿,表明矿床经历了原生沉积成矿期和后生改造成矿期两个成矿期次。In order to better understand the composite mineralization of rock salt deposits,this work conducted field investigations,microscopic observations,SEM analysis,energy spectra analysis,X-ray powder diffraction analysis of the Guyuan rock salt deposits in Ningxia Province to reveal the metallogenic rules and model.Combined with petrology and mineralogy,the ore textures and structures were studied,and the mineralization period was divided.Results show that the Guyuan rock salt ores are featured by primary sedimentation and epigenetic reformation.The euhedral fine crystalline texture is primary sedimentary texture,and the euhedral coarse crystalline,embayed and wormy metasomatic textures are typical of epigenetic reformation.The layered,stripped and lumpy structures are primary sedimentary structures,while massive,brecciated and net-veined structures are epigenetic reforming structures.Mineral assemblages of rock salt deposits mainly include halite,glauberite,anhydrite,anhydrate glauberite,clay minerals,albite and dolomite,characterized by primary sedimentation and epigenetic reformation.Primary sedimentary type and epigenetic reforming type minerals can be observed in salt minerals.Petrographic and mineralogical studies have confirmed the Guyuan rock salt deposits to be typical of primary sedimentary-metamorphic reformation.The mineralization of glauberite and anhydrite was mainly formed by early sedimentation and experienced weak reformation in the later stage,while the rock salt deposit was mainly formed by early sedimentation.In the later period,plastic flow,dissolution-recrystallization or tectonic deformation occurred and filled in the favorable space formed by the fracture or tectonic activity of the surrounding rock.The deposits have experienced two metallogenic periods,i.e.,primary sedimentary mineralization and epigenetic reforming mineralization.

关 键 词：岩盐矿床 后生改造 矿物学 成矿期次 固原凹陷 宁夏 

分 类 号：P588.12[天文地球—岩石学]