The Generation of High-Enthalpy Geothermal in a Nonvolcanic Environment, a Case Study of Yangbajing Geothermal Fields, Qinghai-Tibet Plateau, China

Abstract

Among global high-enthalpy geothermal resources, only geothermal fields within Tibet are located in a non-volcanic environment. Results of the PTt (pressure-temperature-time) trajectory calculation of the Plateau uplifting gave a comparatively satisfactory explanation for the formation and for the depth of burial of high-enthalpy resources-the reason why an volcanic environment is not formed.
The method of PTt trajectory reconstruction used in the study of metamorphic rocks can be adopted for study of thermal evolution of young orogenic belts. For lack of petrographic PT data recording the influence of uplifting in Qinghai-Tibet plateau, we brought such data from the Caledonides orogenic belt of North Europe for the calculation. The results show that any double-layered block can make the earth crust "heating" and originate high-enthalpy geothermal activities near the earth surface, if only it uplifts at a high speed. The calculation of the Qinghai-Tibet plateau uplifting model showed that along with the increase of uplifting speed, the temperature of the earth crust increases and the depth to high-temperature front increases.
A new type of high-enthalpy geothermic-the uplifting -thick crust type-is being put forward.