西藏羊八井—宁中盆地地下水深循环三维模拟及对地热异常分布的限定  

Geothermal distribution and forming mechanism: Insight from 3D numerical simulation on Yangbajing−Ningzhong Basin, Tibet

作　　者：刘畅 苏金宝 LIU Chang;SU Jinbao(College of Oceanography,Hohai University,Nanjing 210098,Jiangsu,China)

机构地区：[1]河海大学海洋学院,江苏南京210098

出　　处：《中国地质》2024年第6期1868-1882,共15页Geology in China

基　　金：国家重点研发计划(2023YFC2907105);国家自然科学基金项目(42272236,41872074)资助。

摘　　要：【研究目的 】高山区大气降水下渗至地下深部,经地下深循环排泄至地表,该过程涉及深部构造和水文地球化学,是形成丰富的地热和矿产资源的流体来源之一。前人使用水化学与同位素和数值模拟等方法研究探讨地下水源区和流动系统等,分析地下水循环深度、地下水循环时间和地下水运移机制,进而评估区域地热和矿产资源分布。【研究方法 】结合西藏羊八井—宁中盆地DEM数据、断层和岩性等资料建立三维有限元几何模型,使用地下水模拟软件求解标准饱和地下水流动方程,探讨研究区典型热泉的循环系统和区域地下水运移规律。【研究结果 】模拟结果表明,地下水在羊八井、拉多岗和曲才热泉的最大循环深度分别为5~7 km、3.5~4 km和3~3.6 km,相应的地下水循环时间为23~80年、5~6年和4~8年。念青唐古拉山地下水入渗深度达10 km,时间达百万年。【结论 】各个热泉的地下水循环深度不同,循环补给时间也差异较大,它们之间的补给源区和循环路径存在较大差异,虽位于同一裂谷,但羊八井、拉多岗和曲才热泉彼此之间没有水力联系,造成物质组成的差异。This paper is the result of hydrogeological survey engineering.Objective Meteoric water in the mountain areas infiltrates deep underground and circulates to the surface.It involves deep structural and hydrogeochemical processes,and it is one of the fluid source of forming rich geothermal and mineral resources.Predecessors focused on the groundwater source,circulation depth and flow system using methods of hydrochemistry isotope and numerical simulation,and further evaluated the distribution of regional geothermal and mineral resources.Methods Based on the data of DEM,fault structure,and lithology of the Yangbajing−Ningzhong basin,we establish 3D geometry finite element model.The standard saturated groundwater flow equation is solved using groundwater simulation software,and we analyse the circulation system of the typical hot springsand regional groundwater migration.Results The simulation results show that the maximum circulation depths of groundwater are respectively 5−7 km,3.5−4 km,and 3−3.6 km at Yangbajing,Laduogang,and Qucai springs,and the corresponding groundwater circulation times are 23−80,5−6 and 4−8 years.The groundwater of Nyainqentanglha Mountain seeps down to 10 km depth,where the time spans million years.Conclusions In general,the circulation depth and the recharge time of hot springs are different due to their different supply sources and circulation paths.Notably,there is no hydraulic connection between the hot springs at Yangbajing,Laduogang,and Qucai,although they are located in the same rift valley.It results in differences in material composition among these springs.

关 键 词：青藏高原 高温热泉 地下水 断层 数值模拟 水文地质调查工程 地热地质调查工程 

分 类 号：P641.6[天文地球—地质矿产勘探]