煤田地质与勘探2024，Vol.52Issue(1)：168-176,9.DOI:10.12363/issn.1001-1986.23.10.0639
秦岭山前眉县低温地热水及伴生氦气成因机制
Genetic mechanisms of low-temperature geothermal water and its associated helium gas in Meixian County in the piedmont of Qinling Mountains
摘要
Abstract
Meixian County in the piedmont of the Qinling Mountains boasts abundant geothermal water resources with high-abundance associated helium gas.However,the characteristics and origin of geothermal fluids in the study area are yet to be studied.By analyzing the chemical composition and isotopic geochemistry of geothermal fluids and combining the distributions of regional structures and faults,this study delved into the characteristics and genetic mechanisms of geothermal fluids in the study area.The results show that the geothermal water exhibits salinity ranging from 638.96 to 1 026.83 mg/L and a hydrochemical type of HCO3-Na.The low-degree metamorphism suggests that the geothermal wa-ter is unbalanced water or partially balanced water,with solutes primarily originating from the weathering of silicate rocks.The geothermal water yielded δD and δ18O values ranging from-77.3‰ to-70.8‰ and from-10.9‰ to-9.8‰,respectively,both of which fell near the meteoric water line.Furthermore,the geothermal water features an average re-charge elevation of approximately 1 030 m,recharge water temperatures ranging between 4.9℃ and 7.0℃ ,and a maxim-um circulation depth of about 3 200 m.The geothermal water-associated gas is dominated by nitrogen gas,exhibiting low hydrocarbon gas concentrations and high-abundance helium gas.The methane in the associated gas showed an aver-age δ13C value of-52.8‰ and an average δD value of-247‰.Besides,the associated gas displayed low R/Ra ratios and high 4He/20Ne ratios.As revealed by this study,the meteoric water from the Qinling Mountains infiltrated downward in-to fault fractures and sandstone pores through deep-seated faults and their secondary faults,ultimately forming geo-thermal water via geothermal heating.The low-temperature and high-volume geothermal water in the study area is primarily formed by the close and sufficient water sources,poor sealing,and fast circulation at shallow depths.The heli-um in the associated gas was principally crust-derived and formed by the radioactive decay of uranium and thorium ele-ments in crustal rocks.The results of this study will provide critical geochemical evidence for the exploitation and utiliz-ation of geothermal resources in the study area.关键词
低温地热水/氦气/氢氧同位素/成因机制/秦岭山前Key words
low-temperature geothermal water/helium gas/hydrogen and oxygen isotopes/genetic mechanism/pied-mont of Qinling Mountains分类
天文与地球科学引用本文复制引用
韩元红,吕俊,张育平,罗娜宁,李兵,申小龙..秦岭山前眉县低温地热水及伴生氦气成因机制[J].煤田地质与勘探,2024,52(1):168-176,9.基金项目
国家重点研发计划课题(2022YFC2904301) （2022YFC2904301）
陕西省重点研发计划项目(2021ZDLSF05-12) （2021ZDLSF05-12）
陕西省自然科学基金项目(2021JLM-14,2023-JC-QN-0631) （2021JLM-14,2023-JC-QN-0631）
