Genetic Mechanism And Prediction Of Ore Prospecting To The Geothermal Field In Shicheng Of Jiangxi Province

The research geothermal field is located in Jiangxi Province and is about 10km to the east of Shicheng.It is classified as the low-medium temperature and deep fault convective geothermal system.This geothermal field has a great development potential because of the active tectonic movement,well developed fracture,frequent activities of metamorphism and magmatic,and the extremely strong modern hydrothermal activities.But limited researches were conducted on the distribution of geothermal resources and the genetic model of the site,which increase the blindness and risk in developing the geothermal resources.To investigate the distribution of geothermal resources and the genetic model at the Shicheng geothermal field,the following works were performed:collecting and sorting the geological background information,field reconnaissance and investigation,and lab data analysis.It is systematically discussed on the meteorological hydrology,topography,regional geology,thermal field geological condition,terrestrial heat flow and geothermal characteristics,fluid chemical characteristics in thermal reservoirs,etc.Finally,the formation mechanism of the thermal field was worked out.Moreover,a concept model was established and the prospecting criteria were proposed.The detailed conclusions are mainly shown as follows:(1)The research geothermal field is classified as a low-medium temperature geothermal resources and the heat supply is at the bottom from the high elevated region.The well-developed fracture structure at the Shicheng geothermal field determines the range of thermal field,and prov ides favorable channels for the migration of geothermal fluids.What's more,the fracture is the thermal reservoir and is the principal controlling factors at the Shicheng geothermal field.(2)The average geothermal gradients of the hot water drills are?3.5?.The geothermal anomaly plane is mainly concentrated to the west of F1(Anyuan-Hhengjiang fracture)and show a zonal distribution along the fracture.As for the vertical axis,two models can be used to fit the borehole temperature curve,one is temperature-increasing type and the other is Raising temperature cooling type;(3)Based on the hydro-chemical analysis,the chemical composition of the groundwater at the Shicheng geothermal field can be classified to three different hydro-chemical types,that is,SO42-?Na+·Ca2+?SO42-·HCO3-?Na+·Ca2+?HCO3-·SO42-?Na+·Ca2+.The various hydro-chemical types suggested that the hot water was mixed with the cold water with different proportions.Moreover,the analysis concluded that the higher content of Ca2+and Mg2+in the groundwater,the more of cold water was mixed:the Isotopes show that the underground hot water mainly comes from atmospheric precipitation;(4)The formation mechanism of the Shicheng geothermal field is as follows:the weathering fissure network water was recharged by precipitation.When the fissure water migrated to the fault zone or secondary fault zone and penetrated to the deep area to participate in the water cycle,the cold water can be heated up by various source of heat.The heat source will be getting much more with the increase of depth.So the temperature of the groundwater was increasing during the processes of the deep area water cycle.Driven by the water contrastand density difference,the heated water raised along the tectonic fissures,met and mixed with cold water.The whole processes contributed to form the Shicheng geothermal field;(5)The proposed ore-prospecting criteria at the Shicheng geothermal field are:?the thermal springs at the surface;?the geophysical anomaly(low resistance);?high F content in groundwater and fluorite mineralization phenomenon;?sinter;? kaolinite,protein fossil hydrothermal alteration phenomenon;?Hydrothermal mineralization phenomenon;?All landowners earth chemistry geothermometer.