Eastern Yunnan Geothermal Occurrence Of The Law And The Genetic Model

Geothermal resources was an important type of new energy sources with the advantages of being large in deposit,producing less pollution and low cost of operation. Yunnan is one of the provinces with the richest geothermal resources in China.The exploitation of geothermal resources has been developing rapidly in recent years,head and shoulder above step of survey,evaluation and research.Finding out accumulation rule, genetic model and available amount of the resources can reduce blindness and risk of the exploitation.In this paper,east of Yunnan(to the east of E102°)was choosed as the study area.On the basis of the integration and summarization to previous data,the geothermo-geological settings concerned with the occurrence and formation of geothermal resources were analysed;the distribution and accumulation rule,hydrogeochemical characteristics and genetic model of geothermal system were investigated.The study may play an important theoretical and practical value in survey,exploitation and utilization of the geothermal resources.The data of 220 hot springs and 163 geothermal drill holes in the area were analyzed. It is found that distribution and accumulation of the thermal water were mainly influenced by many factors including heat flow,geological structure,lithology,landform visage, hydrogeologic condition,nontectonic movement and earthquake,especially controlled by geological structure.Then concrete structural locations of hot springs exposured in study area were summarized.Structure of geothermal reservoirs play an important role in formation of geothermy. In this paper,it could be classified into such two types as layer-like and banding-like.Zbdn, P₁q+m,D₂qj and Pt₂d were considered as four layer-like geothermal reservoirs. Banding-like geothermal reservoirs were divided into three subtypes.Geothermal hosting characteristics vary with structure of geothermal reservoirs.The major hydrochemical types of thermal groundwater in the area are HCO₃—Ca·Mg, HCO₃—Ca and HCO₃—Ca·Na,and the second are HCO₃—Na,HCO₃·SO₄—Na·K. Characteristics in common of most thermal groundwater are low TDS,low Cl and neutral-alkalescent.Temperature of geothermal reservoir in geothermal anomalous area was calculated with SiO₂ geothermometer and K-Mg geothermometer,showing that geothermal resources were medium to low temperature.Combined with geothermic gradient,the thermal groundwater was estimated to circulate at depth of 1200～2700m.Based on the principles of classification of geothermal systems at home and abroad, according to conditions of geothermal geology and accumulation of thermal water, geothermal systems in the area can be classified into two types,such as:fold-fault type and fault-depression basin type,represented by Anning hot spring and Kunming geothermal field respectively,and their geothermo-geological settings,the temperature field,structure of geothermal reservoirs,hydrochemical,dynamic changes of thermal water were discussed systemically,the geological genetic models were summarized.