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| Characteristics of mantle degassing and deep-seated geological structures in different typical fault zones of China | |
| 作者姓名： | TAO Mingxin XU Yongchang SHI Baoguang JIANG Zhongti SHEN Ping LI Xiaobin & SUN Mingliang . Key Laboratory of Gas Geochemistry Lanzhou Institute of Geology Chinese Academy of Sciences Lanzhou China . Beijing Normal University Beijing China . The Practical Geologic Data Center State Land Resource |
| 作者单位： | TAO Mingxin1，2，XU Yongchang1，SHI Baoguang1，JIANG Zhongti3，SHEN Ping1，LI Xiaobin1 & SUN Mingliang1 1. Key Laboratory of Gas Geochemistry，Lanzhou Institute of Geology，Chinese Academy of Sciences，Lanzhou 730000，China; 2. Beijing Normal University，Beijing 100875，China; 3. The Practical Geologic Data Center，State Land Resource Department，Sanhe 065201，China |
| 基金项目： | 国家重点基础研究发展计划(973计划)，国家自然科学基金 |
| 摘 要： | Large-scale fault zones play an important role in controlling and adjusting all kinds of geological proc-esses,such as deposition,magmatism,metamorphism,metallogenesis,tectonic stress field,tectonic deforma-tion,even the movement of geological massifs,earth-quakes,and they also are the key to solving geological problems concerned,especially regional and even global structures.Due to their special geological tec-tonic significance,they are one of the main research fields of tectonic geology and … |
Characteristics of mantle degassing and deep-seated geological structures in different typical fault zones of China |
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| TAO Mingxin,,XU Yongchang,SHI Baoguang,JIANG Zhongti,SHEN Ping,LI Xiaobin & SUN Mingliang . Key Laboratory of Gas Geochemistry,Lanzhou Institute of Geology,Chinese Academy of Sciences,Lanzhou ,China, . Beijing Normal University,Beijing ,China, . The Practical Geologic Data Center,State Land Resource.Characteristics of mantle degassing and deep-seated geological structures in different typical fault zones of China[J].Science in China(Earth Sciences),2005,48(7). | |
| Authors: | TAO Mingxin XU Yongchang SHI Baoguang JIANG Zhongti SHEN Ping Li Xiaobin Sun Mingliang |
| Institution: | 1. Key Laboratory of Gas Geochemistry, Lanzhou Institute of Geology, Chinese Academy of Sciences, Lanzhou 730000, China;Beijing Normal University, Beijing 100875, China 2. Key Laboratory of Gas Geochemistry, Lanzhou Institute of Geology, Chinese Academy of Sciences, Lanzhou 730000, China 3. The Practical Geologic Data Center, State Land Resource Department, Sanhe 065201, China |
| Abstract: | In this paper a comprehensive tracing study is conducted on mantle degassing and deep-seated geological structures in different types of fault zones in the continent of China based on the helium isotope data, coupled with some indices such as CO2/3He, CH4/3He and 40Ar/36Ar,and geological tectonics data. There are four representative types of fault zones: (1) Lithospheric fault zones in the extensional tectonic environment are characterized by a small Earth's crust thickness, a lower CH4/3He-high R and lower CO2/3He-high R system, the strongest mantle degassing, and the dominance of mantle fluid, as is represented by the Tancheng-Lujiang fault zone.(2) The lithospheric fault zones or the subduction zone in the strongly compresso-tectonic environment, for instance, the Bangonghu-Nujiang fault zone, are characterized by a huge thick Earth's crust, with the R/Ra values within the range of 0.43-1.13, and weak mantle degassing with mantle-source helium accounting for 5%-14% of the total. (3) The deep-seated fault zones at the basinal margins of an orogenic belt are characterized by R values being on order of magnitude of 10-7, and the CH4/3He values, 109-1010, CO2/3He values, 106-108; as well as much weak mantle degassing. (4) The crustal fault zones in the orogenic belt, such as the Yaojie fault zone (F19), possess a high CH4/3He-low R (10-8) and high CO2/3He-low R system, with no obvious sign of mantle degassing. Studies have shown that the deep-seated huge fault zones are the major channel ways for mantle degassing, the main factors controlling the intensity of mantle degassing are fault depth, tectonic environment and crust thickness; the intensity of mantle degassing can reflect the depth and the status of deep-seated tectonic environment of fault, while the geochemical tracing studies of gases can open up a new research approach; upwelling activity of hydrothermal fluids from the deep interior of the Earth may be one of the driving forces for the formation and evolution of the huge deep fault zones. Piedmont fault zones are the locations where deep-seated tectonic activity and crust/mantle structure are transformed, which are of great significance in understanding the mechanisms of formation of orogenic belts and basins. |
| Keywords: | fault zone mantle degassing deep-seated structure 3He/4He CO2/3He CH4/3He |
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