藏北羌塘中部吉瓦地热田的特征及其资源评价

Characteristics and resource evaluation of the Jiwa geothemal field in central Qiangtang, northern Tibet, China

吉瓦温泉位于西藏尼玛县绒马乡吉瓦村北。温泉出露于一个新生代断陷盆地之中,受江爱藏布活动断裂带的控制。地下热水矿化度为5.54×103～5.58×103mg/L,水化学类型属Na-Cl·HCO3型。温泉水中H2SiO3、Li+、F-等含量较高,这3项指标满足医疗矿水的标准。热水系统的热源来自于地壳中的部分熔融层,热水的补给来源主要为大气降水,伴有深部热液加入。混合模型研究显示,温泉水为地下热水和冷水的混合物,冷水占的比例介于77%～95%之间,混合水的循环年龄约31a,利用SiO2温标法计算出浅部热储温度为120℃,深度为832m。混合前热水温度为215～280℃,对应深部热储深度为1466～1900m。吉瓦热田面积约6km2,天然放热量为7.53×1013J/a,地热资源量为32606×1014J。

The Jiwa hot springs are located north of Jiwa Villiage in Nima Country, Tibet. The occurrence of the hot springs are within a Cenozoic rift basin, controlled by Jiangaizangbu faults. The thermal groundwater has total dissolved solids content of 5.54 × 103-5.58×103 mg/L, and is hydrochemically of Na-Cl·HCO3 type. The thermal groundwater has high content of H2SiO3、Li＋ and F-, and these 3 items meet the requirement of medical use. The fractional melting layers in crust have provided heat energies to the hydrothermal system while the atmospheric precipitation is the major water charging supply, secondly deep area hot fluid. The mixing model study shows that the thermal groundwater is a mixture of hot and cool groundwater, the cool water proportion is between 77% and 95%, and the residence time of mixture is 31a. The temperature of the shallow geothermal reservoir is calculated at 120℃ using SiO2 geothermometer method with a depth of 832 m. The temperature of the hot water before mixing is between 215℃ and 280℃. The corresponding deep geothermal reservoir is estimated at between 1466m and 1900 m. The Jiwa geothemal field has a total area of 6km2. The natural heat discharge amount is more than 7.53×1013 J/a, according to primary evaluation, and the geothermal resource energies in the field is more than 32606×1014 J.