Geothermal Accumulation Constrained by the Tectonic Transformation in the Gonghe Basin, Northeastern Tibetan Plateau

Abstract

Advances in the exploration of the geothermal resources with remarkably high temperatures in the Gonghe Basin, northeastern Tibetan Plateau, provide an enhanced understanding of the origin and emplacement of hot dry rock (HDR). Based on the integrating analysis on the boundary faults distribution and their activity histories, springs and geothermal borehole data, and magnetotelluric data, we propose that the Gonghe Basin formed in a zone of slip dissipation between two major large-scale left-lateral strike-slip faults of the Kunlun fault to the south and the Haiyuan fault to the north during the Neogene time. During the evolution of these two major strike-slip faults, the basin has experienced two-phase developments: the transrotational Gonghe-Qinghai lacustrine basin system during the Miocene and the transpressional Gonghe-Tongde basin system during the Pliocene-Quaternary. In response to the crustal transtension components of the transrotational Gonghe Basin, the partial melting zone at depths of 10–25 km in the thickened crust (~54 km) has been uplifted by ~10 km compared with adjacent regions since the Pliocene. This uplifted partial melting zone may have provided prominent potential heat energy for the HDR in the Triassic granitoid batholith at shallower depths (~3–10 km) by effective enhancement of the geothermal conduction process via deep faulting. With obliquely south-verging thrusting of the Gonghe Nan Shan thrusts in the northern, the Gonghe Basin has transformed from transrotation to transpression-domination during the 6–3 Ma, as well as accompanying with the depocentre migrating to the northwest and in turn the basement elastically uplifting in the southeast. This differential deformation of the basin floor has resulted in a northeastward upward tilting of the Triassic batholith and an isothermal surface. It finally developed the high-temperature and shallow-burial HDR with anomalously temperatures of over 100°C at a depth of 1.5 km in the Qiabuqia and Zhacang geothermal areas in the Gonghe Basin, NE margin of the Tibetan Plateau.

Forms and Sources of Arsenic in the Groundwater of the Northeastern Tectonic Active Zone of the Qinghai-Tibet Plateau

“…The Neogene geothermal reservoir, with water temperatures potentially reaching 40℃ to 85℃, consists of Neogene-era siltstone, ne sandstone, medium sandstone, and pebbly medium-coarse sandstone, buried at depths extending from 800 to 1,150 meters. The principal heat source for this reservoir is the geothermal convective system associated with the tectono-magmatic belt of the Ela and Waligong mountains [22] . Accordingly, this study delineates the two geothermal reservoirs using 40℃ as the threshold and categorizes the thermal environments into high-temperature hot springs (HT) and low-temperature hot springs (LT).…”

Hydrogeochemical Characteristics of Earthquake-Related varied-temperature Springs along the Eastern Kunlun Fault Zone, China

“…The intrusion and uplift of granite to the Earth's surface contribute to an increase in the geothermal gradient to some extent in the study area [33,34]. Recent magmatic activities and geothermal phenomena in the Quaternary, especially the Holocene, suggest ongoing sub-crustal processes [35,36].…”

“…The heat produced by magmatic activities is an essential source for the deep thermal environment. The residual heat from magmatic activities since the Paleozoic era, along with potential ongoing magmatic activities, transfers from the magma to the surrounding rock and then to the groundwater by conduction, affecting the higher temperature ranges of the springs [35,36]. It is important to note that, due to the scarcity of hydrogeological data in this region and the absence of measurements such as flow rate, velocity, temperature variations, and drilling data in our study, we can only roughly estimate the potential heat sources for the overall spring waters in the Eastern Kunlun Fault Zone.…”

The Hydrogeochemistry of and Earthquake-Related Chemical Variations in the Springs along the Eastern Kunlun Fault Zone, China

“…The uplift of granite to the surface has, to some extent, increased the geothermal gradient in the study area [33,34]. Recent magmatic activities and geothermal phenomena in the Quaternary, especially the Holocene, suggest ongoing sub-crustal processes [35,36].…”