| Gonghe Basin is located in the northeast of Hainan Tibetan Autonomous Prefecture,Qinghai Province.It was formed in the Mesozoic and belongs to a faulted basin.There are a large number of deep and large faults around the basin.There are thick Quaternary,Neogene and Paleogene strata in the basin.The basin basement is a large-scale Indosinian-Yanshanian granite basement.There are many hot springs in and around the Gonghe Basin.There are abundant geothermal water,high heat flow value and obvious thermal anomaly in the basin.Since 2011,the national and Qinghai provincial governments have carried out many geothermal resource exploration work in Gonghe County in the north of the Gonghe Basin and Guide County in the east of the Gonghe Basin.The results show that the geothermal gradient in most areas of the Gonghe Basin is above 5 C/100 m,the highest is 11.5 C/100 m,and the temperature of rock mass in the depth of 2200 m is up to 150 C,so the geothermal gradient in the Gonghe Basin is higher than 5 C/100 m.The resource reserves are considerable and the economic potential is enormous,which has high research value.In September 2017,the magnetotelluric sounding research group of China University of Geosciences(Beijing)carried out the data acquisition of magnetotelluric sounding(MT)in Guinan area of Gonghe Basin,Qinghai Province.I used the measured MT and AMT data to study the underground electrical structure characteristics of the area.Combining with the existing regional geological,tectonic and geophysical and geochemical data in Gonghe Basin,the conductivity structure and thermal structure of the crust and mantle in southern Guizhou are studied in depth,and the prospect of geothermal resources in the area is preliminarily discussed.Through the research,the following conclusions and understandings have been obtained:(1)The electrical structure of shallow underground in Guinan area shows obvious stratification.Within 2Km depth,it can be divided into five layers,and the sounding curve is QHA type.Comparing with borehole data,the results show that there are welldeveloped layered strata in this area,and the strata with good permeability and waterresistivity develop alternately,thus forming two sets of favorable underground hot water storage structures.The upper part is Neogene-Pliocene thermal reservoir,and the lower part is Paleogene thermal reservoir with larger thickness.(2)MT inversion model shows that there are two obvious low-resistivity anomalous zones at depths of 5Km-10 Km and 25Km-60 Km in the south of Gonghe basin,which are consistent with the results of natural seismic exploration.In addition,the borehole data of the basin show that the underground temperature increases linearly with the depth as a whole.These results show that the heat source of Gonghe basin is closely related to the deep heat transfer and conduction.(3)In this paper,the occurrence of geothermal resources in the Gonghe Basin is studied comprehensively from the aspects of geological structure,fluid migration,distribution of thermal reservoirs and mechanism of heat sources.A reliable genetic model of geothermal resources in the area is established,and the prospect of geothermal resources is briefly discussed. |
PDF Full Text Request