论文部分内容阅读
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1.06~1.2 g/cm3和1.06~1.11 g/cm3,成矿压力分别为150~180 MPa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 the geological background and the rock structure, the fluid inclusions of barite minerals in the lacustrine hydrothermal sedimentary rocks of the Xiagou Formation in the Qingxi Sag, Jiuquan Basin were studied. The results show that there are mainly four types of primary fluid inclusions in the barite cements, such as two phases of rich liquid, three phases of sub-minerals, single liquid phase and single gas phase. The detritus- Liquid inclusions. The microscopic temperature measurement results show that the ore-forming fluid of barite cement and detritus barite is NaCl-H2O system with the temperature of 160 ~ 200 ℃ and 120 ~ 140 ℃ respectively and the salinity (NaCl) of 20 % To 22% and 18% to 20%, respectively. The densities were 1.06-1.2 g / cm3 and 1.06-1.11 g / cm3, respectively. The metallogenetic pressures were 150-180 MPa and 30-45 MPa, respectively. Combined with the analysis of strontium isotopes, it is considered that the ore-forming fluid belongs to medium- and low-temperature, medium-high salinity and medium-density mixed heat brine formed by deep-circulating infiltration water and magmatic water. The ore-forming fluid has undergone the hydrothermal boiling and superposition coupling of mixing to form barite cement in the early stage, and detritus-like barite formed in the late stage by mixed hydrothermal dilution and sedimentation. Both should belong to the same hot fluid at different stages and different ways of chemical precipitation products, barite cement formed in the jet orifice; detrital barite formed in the relatively open jet from the open system, there is more atmospheric water (Lake water) so that its thermal fluid temperature, salinity, density and pressure decreased compared to barite cement. The study on the characteristics and genesis of barite mineral fluid can lay a foundation for the analysis of the thermal fluid characteristics, source and genesis of the hydrothermal sedimentary rocks in the Xiagou Formation of Xiagou Formation.