Study On Geothermal Resources And Its Causes In Xiamen

Geothermal resource is a renewable energy stored in the earth's interior,which generally concentrated in the edge of plate tectonics and originated in the earth's molten magma and the decay of radioactive substances.Based on the distribution,field investigation data and previous results of geothermal in Xiamen and using a variety of research methods,this paper analyzes the causes of heat formation from the strata,regional geological structure and the regional hydro-geological conditions.At the same time,the relevant data are summarized,and some suggestions for further exploration of geothermal resources in Xiamen are proposed in this paper.The main conclusions of this paper are as follows:(1)Distribution and characteristics of hot spots in XiamenAccording to the geomorphologic position,the geothermal anomaly area in Xiamen is distributed in the marine accumulation land-form,the downstream area of the stream into the sea,the alluvial plain area,the alluvial area and the lower hilly area.They are mainly distributed in the volcanic strata of Nan Yuan Formation and granite in the Yanshanian,and mostly distributed in the composite parts of NWtrending t and NE-trending.(2)Storage characteristics and dynamic changes of geotherm in XiamenThe main underground hot water storage layers of geothermal resources in Xiamen are the quaternary overburden and surface loose bedrock fissure layers,mixed zone and heat reservoir.The structural faulted zones are the main occurrence and circulation areas of underground hot water.Due to the diffierences of the width,fracture negotiability and hydrogeological conditions,the amount of geothermal energy is also different.(3)Geothermal field characteristics of abnormal areaOn the plane: The abnormal range forms of the platform,alluvial tract and littoral areas are generally irregular oval and round shape,the distribution of the structural fault orientation is generally long and narrow in the low hilly region.In the vertical: The hot zones are isolated island from a regional view,and the central temperature of the island is high,and it is gradually reduced from the center to the outside.The individual lot is connected in a shallow part,and it presents a saddle shape between two abnormal centers.(4)Cause analysisGeothermal anomaly area and its surrounding groundwater infiltrate along the formation pore,the joint of the rock and tectonic fracture,whose process is a constantly absorbing heat(heating,volume expansion,smaller specific gravity)process.When the infiltration depth reaches into a certain position(heat),it forms pressure difference because of the outside high temperature.The pressure difference promotes the geothermal water(along the extensional fractures),release heat,then the surrounding low temperature geothermal water recharge it,resulting a steady stream of geothermal water and forming the hot water circulatory system.