Geochronology,Geochemistry,Fluid Inclusion and C,O Isotope Compositions of Calcite Veins in the Paleogene of the Jiangling Basin,South China:Implications for Fluid Evolution and Brine Potash Mineralization  

作　　者：YU Xiaocan WANG Chunlian LIU Chenglin WANG Jiuyi SHEN Lijian 

机构地区：[1]MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China [2]School of Earth Resources,China University of Geosciences,Wuhan 430074,China

出　　处：《Acta Geologica Sinica(English Edition)》2023年第2期513-525,共13页地质学报（英文版）

基　　金：supported by the Central Public Welfare Scientific Research Basic Scientific Research Business Expenses(Grant Nos.KK2005,KY1603);National Natural Science Foundation of China(Grant No.U20A2092);the National Basic Research Program of China(973 Program)(Grant No.2011CB403007);the China Geological Survey(Grant No.DD20190606)。

摘　　要：Deep-seated potassium-rich brines were identified in the Jiangling Basin,South China.Although magmatichydrothermal sources have been proposed,the relationship between brine-type potash mineralization and volcanism remains unclear.In this study,U-Pb geochronology,geochemistry,fluid inclusion and C-O isotopic compositions of hydrothermal vein minerals in the Jiangling Basin are examined.Laser ablation U-Pb dating of calcite veins indicates that the ages are slightly younger than the formation age of the Balingshan basalt.Fluid inclusions in hydrothermal minerals show medium–low homogenization temperatures(160–220℃)and low salinities(0.14 to 4.9 wt%NaCl eqv.)and densities(0.882–0.944 g/cm^(3)).The liquid compositions of fluid inclusions in calcite veins from sedimentary strata have higher contents of potassium,compared with those from basalt.The coupled negativeδ^(13)CPDB(-10.3‰to-8.0‰)and positiveδ^(18)OSMOW(17.4‰to 20.7‰)values imply that calcite precipitation resulted from CO_(2)degassing of the basaltic magmatic fluids,as indicated by the gas composition of these inclusions in hydrothermal minerals.Rare earth element patterns indicate that water-rock interaction between hydrothermal fluids and sedimentary wall rocks contributed to the calcite precipitation in sedimentary strata.It is proposed that high-temperature water-rock interaction between magmatic fluids and sedimentary strata resulted in the potassium enrichment in fluids,interpreted as one of the sources of potassium-rich brines in the Jiangling Basin.

关 键 词：rare earth element patterns calcite U-Pb geochronology C-O isotopes hydrothermal fluids water-rock interactions 

分 类 号：P59[天文地球—地球化学] P619.211[天文地球—地质学]