Genesis mechanisms of medium- and low- temperature convective geothermal fields in Wenquan County, Xinjiang.

Abstract

The area around Wenquan County, Xinjiang, is home to numerous hot springs and abundant geothermal resources, offering significant potential for development and utilization. Currently, systematic research on the formation mechanisms of geothermal fields in this region remains relatively limited, which to some extent constrains the comprehensive development and utilization of Wenquan County's geothermal resources. This study selected the area around Wenquan County as the study area and employed methods such as remote sensing interpretation, ground temperature measurement, geophysical exploration and drilling, geothermal gradient calculations, rock radioelement measurements, hydrochemical analysis, and isotope analysis to elucidate the genesis mechanisms of the geothermal field. The results indicate that: (1) The geothermal anomaly areas in the Wenquan County geothermal field are primarily controlled by fault structures such as F2, F4, F3-1, and F17. The average geothermal gradient reaches 11.53°C/100 m, and the heat flow value of 320 mW/m2 is significantly higher than the average heat flow value at the northwestern margin of the Junggar Basin in Xinjiang, indicating a favorable terrestrial heat flow background. (2) Within the study area, well-developed structural fissures formed at the intersections of F2, F17, and F3-1, coupled with fractured rock masses, provide favorable conditions for groundwater storage and hydrothermal exchange. Based on the silica geothermometer, the average reservoir temperature is estimated at 132.4°C. Analysis indicates that the geothermal reservoir is located within structurally fractured zones, extending in a strip-like pattern on the surface, and belongs to the medium-low temperature belt-type geothermal reservoir. (3) The geothermal water in the study area has a SO4-Na hydrochemical type, originating from the infiltration of atmospheric precipitation in the southern Biezhentao Mountain area. It has undergone intense water-rock interactions, including hydrothermal alteration, sulfide oxidation, and decarbonation, transporting deep-seated heat to the surface through fault fracture zones. This study has essentially clarified the genesis model of the Wenquan County geothermal field, providing a crucial basis for the development and utilization of geothermal resources.