| In the process of industrialization of China, there are a series of ecological environment problems due to the use of traditional energy. Geothermal energy is a significant strategic resource, which plays an important role to alleviate the environmental problems. C hangbai Mountain area is a famous modern volcanic region in our country, where is rich in geothermal water resources. The geothermal water is misdistribution and various types, and the formation mechanism of geothermal water is complex due to special geothermal geological conditions. There is no systematic understanding for concealed geothermal water resources. Therefore, to find the characteristics, causes and genetic models of the geothermal water resources, and then reasonable, effective and scientific development and utilization of the geothermal water resources are particularly important theoretical and practical significance. Meanwhile, there is extremely important promoting for clean energy supply and establish multivariate supply system of energy security strategy.This article is supported by the geological prospecting fund project of Jilin Province which is ―Geothermal resources survey of C hangbai mountain basalt area of Jilin Province(No. 2014-13)‖. The formation mechanism of geothermal water resources of C hangbai Mountain basalt area was studied by data collection and analysis, geothermal field hydrogeological investigation, sampling test, remote sensing, mathematical calculation, geophysical prospecting, geothermal well drilling, pumping test, water-rock experiment and comprehensive technical methods under instruction of geology, hydrology, geology, geophysical exploration, remote sensing, numerical simulation and other multi-disciplinary theory. This article showed the following results:(1) The geothermal geological condition, types and distribution characteristics of the geothermal water resource were determined. The geothermal water resources can be summed up as three types including volcanic lava type, sedimentary basin type and fracture structure type. The potential areas of geothermal water resources in the study area can be divided into four regions including around the Tian C hi volcano areas which belong to volcanic lava type; Songjianghe- Fusong county areas and Erdaobaihe- Songjiang town areas which belong to sedimentary basin type; Changbai County- Shisidaogou areas which belong to fracture structure type, and Xianrenqiao county areas which also belong to fracture structure type.(2) The hydrochemical characteristics of geothermal water were studied. The hydrochemical types of the hot springs were mainly HCO3-Na, while there were large differences in the geothermal wells samples. The spring water was fresh water, while the geothermal well water was brackish water. The trace elements of the geothermal water were mainly metasilicate, lithium, strontium, aluminum and borate, with the metasilicate was the highest. The depths of reservoir of hot springs were ranged 2.94 to 4.30 km, the circulation depths of hot springs samples were ranged 3.05 to 4.68 km, and the reservoir temperatures of hot spring samples were ranged 72.27 to 161.96 ℃; While the depth reservoir of geothermal wells samp les were ranged 3.11 to 3.88 km, the circulation depths of geothermal wells samples were ranged 3.16 to 3.97 km and the reservoir temperatures of geothermal wells samples were ranged 61.84 to 114.46 ℃.(3) The causes of the geothermal water resources were studied from geological structure and geothermal water supply mechanism and age, water chemical composition cause. The distribution of geothermal water was controlled by NNE, EW, and NW faults. The recharge source of geothermal water was atmospheric precipitation and the tritium isotope ages of geothermal water were higher than 62 years. The chemical compositions of geothermal water were mainly composed by hydrolysis of feldspar minerals(calcium feldspar, sodium feldspar and potassium feldspar) and pyroxene, and also influenced by cation exchange and the release mechanisms of the chemical compositions were followed Stanford first-order kinetic equation.(4) The forming elements of the geothermal water were determined by the comprehensive analysis of geothermal geological conditions. The heat sources were composed by volcanic magma heat source, conduction heat of upper mantle, radioactive decay heat in crustal rocks and degradation heat by organic matters. The cap rocks were basalt of Junjianshan formation, andesite of Guosong formation, Changbai formation and Linzitou formation; the thermal reservoirs were limestone Ordovician and Cambrian, and marble of Zhenzhumen formation.(5) The genetic models of geothermal water were come up including volcanic magma type, sedimentary basin type and fracture structure type.(1) The genetic model for volcanic magma type geothermal water resources, the heat source was magma body below the north of C hangbai Mountain Tianchi crater with the distance of 7-8 km. And the heat was migrated in the form of thermal conduction manner. The cap rocks were composed by trachyte of Baitoushan formation, basalt of Junjianshan formation, andesite of Changbai formation with the thickness was about 1912 m. The thermal reservoirs were mainly composed by fault zone of volcanic rocks and marble of Liao he group with the thickness was higher than 780 m. Geothermal water of volcanic magma type was mainly supplied by precipitation, and exposed on the surface along the fault zone along deep circulation with the distance of 4.00-4.56 km and mixing of hot and cold water in shal ow.(2) The genetic model for sedimentary basin type geothermal water resources was: The heat source was conduction heat of upper mantle. The cap rocks were composed by basalt of Junjianshan formation, andesite of Guo song formation and Changbai formation with the thickness of 2400 m. The thermal reservoirs were mainly composed by limestone Ordovician and Cambrian with the thickness higher than 1200 m. The geothermal water was mainly supplied by precipitation and a small amount of connate water. The geothermal water was exposed on the surface along the fault zone and heated by geothermal conduction heat along deep circulation with the distance of 3.10-3.30 km. Among the deep circulation process, geothermal water has caused chemical reaction with rocks and mixed with cold water in shal ow.(3) The genetic model for fracture structure type geothermal water resources was: The heat source was radioactive decay heat in granite of Mesozoicera Jurassic; The cap rocks were composed by basalt of Junjianshan formation and andesite of Guosong formation with the thickness was about 1067m; The thermal reservoirs were mainly composed by sandstone of Sinian and limestone Ordovician and Cambrian with the thickness was about 1500m; The geothermal water was exposed on the surface along the fault zone or contact plane of permeable rocks and impermeable rocks, and heated by radioactive decay heat in granite along deep circulation with the distance of 3.00-3.50 km. Among the deep circulation process, geothermal water has also caused chemical reaction with rocks and mixed with cold water in shal ow. |
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