Deep faults could provide fluent channels for geothermal water uplift so that it is one of the targets for high-temperature hydrothermal exploration in orogenic geothermal belt. In the eastern edge of the Qinghai Tibet Plateau, significant geothermal potential reflected by hot springs, fumaroles, and sinters, are indeed exposed along a series of lithospheric-scale faults, including the Jinshajiang, the Ganzi-Litang and the Xianshuihe faults. However, as the controlling fault of the eastern edge of the plateau, the Longmenshan Fault has few geothermal manifestations. In order to uncover the role of deep faults in the genesis of high-temperature geothermal systems, a comprehensive chemical and isotopic comparison of geothermal fluid between the Xianshuihe-Anninghe Fault and the Longmenshan-Minjiang Fault was investigated in this paper. According to FixAl modeling and cation geothermometric calculations, the reservoir temperatures of geothermal systems along the Longmenshan Fault are lower than 150 °C with circulation depth of geothermal water less than 4 km while those in the Xianshuihe Fault reaches up to 260 °C with geothermal water circulating as deep as 8 km. Compared to the Xianshuihe Fault, the low reservoir temperatures along the Longmenshan Fault are accompanied by two characteristics of geothermal fluid: (1) no distinctive oxygen shift occurs in stable isotopes of geothermal waters; and (2) little mantle-derived volatiles found in the gaseous components. We propose that, extensional fracture systems are locally formed in the strike-slip movement of the Xianshuihe and Anninghe faults, which not only act as conduits for deep-derived geothermal volatiles, such as metamorphic carbon dioxide and mantle helium, but also enhance the heat convection processes, resulting in the formation of high-temperature geothermal systems. In contrast, in the Longmenshan Thrust Fault, the shallow circulation of geothermal water in closed fracture systems accounts for its lower reservoir temperatures. Therefore, deep extensional fault is a crucial element in forming a high-temperature geothermal system in the eastern edge of the Qinghai Tibet Plateau.

深部断层可为地热水抬升提供流畅通道，是造山带地热带高温热液勘探的目标之一。在青藏高原东缘，由金沙江、甘孜-理塘和鲜水河断裂等一系列岩石圈规模的断裂带，确实暴露了由温泉、喷气孔和烧结矿反射的显着地热潜力。但龙门山断裂作为高原东缘的控制断层，地热表现较少。为揭示深断裂在高温地热系统成因中的作用，本文对鲜水河-安宁河断裂与龙门山-闽江断裂地热流体进行了综合化学和同位素对比研究。根据FixAl模型和阳离子地球测温计算，龙门山断裂沿线地热系统储层温度低于150℃，地热水循环深度不足4km，而鲜水河断裂带地热水循环深度可达260℃循环深达8公里。与鲜水河断裂相比，龙门山断裂沿线的低储层温度伴随着地热流体的两个特征：（1）地热水稳定同位素中没有明显的氧转移；(2) 在气态组分中发现少量地幔衍生挥发物。我们认为，在鲜水河和安宁河断裂的走滑运动中局部形成伸展裂缝系统，不仅作为深部地热挥发物的通道，如变质的二氧化碳和地幔氦，还会增强热对流过程，从而形成高温地热系统。相比之下，在龙门山逆冲断层中，地热水在闭合裂缝系统中的浅层循环导致其储层温度较低。因此，深部伸展断裂是青藏高原东缘高温地热系统形成的关键因素。