| Guide Basin was located in the North-Eastern section of Tibet Plateau, which rich in the geothermal resources in Qinghai Province. Various geothermal manifestations and types were distributed in the study area, there are rich in middle and low geothermal resources in Guide Basin. In this paper, we choose Zhacang hot spring and Sanhe plain geothermal field as the object of the research respectively. On the basis of the previous research data, researched in the geothermal-geological settings, the thermal reservoirs features, the characteristics of the temperature field and hydrogeochemical features five aspects, then make a conclusion on the formation conditions and genetic model of the geothermal resources. According to the research, the main results were as follow:In the study area, it was obviously that the geological structure and the faults controlled geothermal activity. Zhacang hot spring and Sanhe plain geothermal field were belonged to banding-like and layer-like respectively. The thermal reservoirs of Zhacang hot spring was lied in the fault broken zone, while Sanhe plain geothermal field was in Cenozoic sedimentary layer. Sanhe plain geothermal field including two thermal reservoirs, which were Neogene thermal reservoirs and Paleogene thermal reservoirs. The two geothermal zones had the higher geothermal background, their heat flow were 73.492 m W/m2 and 88 m W/m2 respectively.As the analysis hydrochemistry of geothermal water, it showed that the Na+、SO42-、Cl- was dominant while the Mg2+、HCO3- was poor in Zhaceng hot spring, the water chemical type was SO4·Cl-Na; Sanhe plain geothermal field had different water chemical types, there were SO4·Cl-Na、Cl·SO4-Na、SO4-Na、SO4·HCO3-Na、HCO3·SO4-Na、HCO3·SO4·Cl-Na、Cl·HCO3·SO4-Na and SO4·Cl·HCO3-Na types, it can be mixed with cold water from near source. Compared with Sanhe plain geothermal field geothermal water, the concentration of F、Li、Sr、H3Si O3 and HBO2 in Zhacang hot spring water were much higher. Na-K-Mg equilibrium diagram is used to judge the water-rock interaction levels of Zhacang hot spring and Sanhe plain geothermal field geothermal water, both of them were under no equilibrium state. Temperature of geothermal reservoir in Zhacang hot spring was calculated with Si O2 geothermometer, the geothermal reservoir temperature was 147.75℃, and the hot spring water was estimated to circulate at depth of 2017.86 m.From the hydrogen and oxygen stable isotopes data, hot spring and the ground thermal water showed mainly meteoric recharge, the hot spring presence slight “Oxygen-18 drift”, showed its water-rock interaction was relatively high. The hot spring was from rainfall infiltration after a long distance heating, which from the southwestern mountains above 3463.9m high and the surrounding mountains, while he geothermal water was from rainfall infiltration after a long distance heating, which from the south, west and north mountains above 3605 m high and the surrounding mountains. Analysis carbon and sulfur stable isotopic characteristics of thermal water, revealed carbon and sulfur sources in thermal water mainly from leaching of the deposited layer, atmospheric source increased with cold water mixed.Finally, combined with the geophysical results, the regional geological data and the analyze results of geothermal water, obtained the genetic model of different types’ geothermal systems, For the latter depth research and development and utilization provided and important scientific basis. |
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