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Geophysical responses and possible geothermal mechanism in the Gonghe Basin, China
Geomechanics and Geophysics for Geo-Energy and Geo-Resources ( IF 3.9 ) Pub Date : 2020-01-10 , DOI: 10.1007/s40948-020-00141-5
Xueyu Zhao , Zhaofa Zeng , Nan Huai , Kun Wang

In Qinghai Province of China, the Gonghe Basin is characterized as a potential hot dry rock (HDR) area due to the high heat flow rate and high-temperature records from several springs and drillings. However, the regional geothermal mechanism is still disputable and then essential to be discussed for the HDR exploration strategy, even for analysis in other areas. Geophysical methods are useful tools of analysing regional tectonic activities and geological structures, which are related to heat generation and conduction. In this paper, we mainly focus on the geophysical data within different scales. Firstly, we mapped the epicentral distribution along a profile covering Qinghai-Tibetan Plateau and the north part of India. This result shows that the Gonghe Basin was in a relatively stable area where less earthquake happened in deep zones (> 40 km). The geothermic mode should be thereby different from another geothermal field Yangbajain, which has a high frequency of earthquake events in deep zones (> 40 km). Secondly, we focus on the area of the Gonghe Basin and its surrounding area. By using the gravity and magnetic data, we estimated the Moho depth and Curie point depth through the Park-Oldenburg algorithm. The results indicate that the Gonghe Basin was at the gravity gradient zone without noticeable depth gap of Moho interface. The regional aeromagnetic data along with the Curie point depth was in a different trend. The high-value magnetic zone covers the major part of the Triassic igneous rock area. In this case, the heat from the deep zone (> 30 km) might not be the major contributor to the HDR forming here. Referred MT, seismic inversion results, we integrated all geophysical results. Based on this, a conceptual model in the Gonghe basin was then put forward. The low resistivity zones such as the magma capsules or melted granites in the upper-crust might be the significant heat resource for the HDR, although those from lower crust, mantle and the igneous rocks might make some contributions. The heat was conducted through the near-ground fractures and make the Gonghe Basin as a potential geothermal area, also validated by other geochemical evidence.
更新日期:2020-01-10
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