地球化学温标估算长白山地热系统热储温度

长白山地区地热系统的研究目前还处于初级阶段,热储温度仍然是具有争议的问题。为进一步明确其高温地热成因机理,本文对该区域的4个温泉点与2口地热井进行了离子及气体组分测定与分析,并应用地球化学温标估算了热储温度。Na-K-Mg三角图和部分矿物I_S值指示长白山地区地热水与围岩未达到水岩平衡状态,稀释作用明显,仅石英、玉髓和部分含Ca²⁺矿物达到饱和并发生沉淀。根据本文及前人的研究,研究区同时存在高温喷气孔、高_ρ(Cl^-)水和高_ρ(SO_4^2-)水,这符合White汽-液分离模式提出的地热地表显示组合,因此推断长白山地区下部流体发生汽-液分离作用(沸腾)且地热系统为双相地热系统。由于双相地热系统的存在制约了水化学温标与部分气化学温标在研究区热储温度估算中的应用,因此本文结合研究区气组分特征,选取CO_2/H_2温标作为可靠温标,估算出热储温度在234.5～284.7℃之间。将长白山天池地区地质特征与地热流体特征结合,建立了长白山地区地热成因模式。

Estimation of Thermal Storage Temperature of Geothermal System in Changbai Mountain by Geothermometers

The research of geothermal system in Changbai Mountain is still in its infancy. Thermal storage temperature is still a controversial issue. In order to further clarify its high-temperature geothermal mechanism, we measured the ion and gas components of 4 hot springs and 2 geothermal wells in this area. We used geothermometers to estimate thermal storage temperature. Na-K-Mg ternary plot and I_S values of some minerals indicate that the water-rock equilibrium of hot water and surrounding rocks in Changbai Mountain area has not been reached,and the dilution is serious; only quartz, chalcedony and some other minerals containing Ca²⁺ are saturated and precipitated. According to this study and predecessors', the existence of high temperature fumarole, high ρ(Cl^-) water and high ρ (SO₄^2-) water in the study area conforms to the geothermal surface display combination proposed by White's vapor-liquid separation model. Therefore, it is considered that vapor-liquid separation (boiling) of the fluids in the bottom of Changbai Mountain occurred, and the geothermal system is a Two-Phase geothermal system,limiting the application of hydro-chemical geothermometer and some gas geothermometers in the estimation of reservoir temperature in the study area. Based on the characteristics of gas components in the study area, the CO₂/H₂ geothermometer was selected as a reliable geothermometer, and estimated the temperature of the reservoir of 234.5-284.7℃. Based on the geological characteristics and geothermal fluid characteristics of Tianchi area in Changbai Mountain, a geothermal genesis model of Changbai Mountain is established.