Reservoirs in the dolomites of the Middle Permian Qixia Formation in the Sichuan Basin are currently important oil and gas exploration objects in China. However, the questions concerning the sources of the dolomitized fluids and the control factors of the Qixia hydrothermal dolomites remain unclear. In this study, the original hydrothermal dolomites (the replacement dolomites (RDs) and saddle dolomites (SDs)) from the Qixia Formation in the southwestern Sichuan Basin (the PR1 well and Baoxing section) were mainly examined using novel in situ carbonate U-Pb dating with clumped isotopes (∆₄₇). Our results show that the U-Pb ages of the latest SDs from the PR1 well (located in the middle zone of the Emeishan large igneous province (ELIP) and distanced from the Orogenic Belt of Longmenshan) are 257.9–251.0 Ma, coincident with the period of main activity of the ELIP. Combined with the previous U-Pb dating, we propose that the high-temperature T_∆47 (82.2–108.4 °C and 127.5–205.9 °C) recorded for SDs from the PR1 well and Baoxing section may have responded to ELIP activity and Longmenshan orogeny activity, respectively. In addition, in the entire southwestern Sichuan Basin, the RDs and SDs yield similar δ¹³C and δ¹⁸O values, indicating that the dolomites were formed by hydrothermal fluids of similar sources, with marine hydrothermal fluids being a highly possible source. Finally, this study proposes a new hydrothermal dolomite genesis model for the Qixia Formation, emphasizing that the formation of hydrothermal dolomites mainly depends on the proximity to tectonic thermal events in space and time.

In order to further reveal the tectonic activity of the central and northern North China Craton (NCC) since late Paleozoic, the Datong coal-bearing basin was selected as the research object. The tectono-thermal events and uplifting cooling events of the basin were retrieved through zircon and apatite fission tracks and vitrinite reflectance measurements. The research shows that the Datong coal-bearing basin experienced three tectono-thermal events with ages of 245–207 Ma (middle–late Triassic), 179 ± 9 Ma (early Jurassic), and 140 Ma to 78 ± 11 Ma (middle–late Cretaceous), respectively. That just coincides with the lamprophyre activity, Kouquan fault activity, and Zuoyun basaltic andesite magmatic activity which surround the Datong coalfield. The basin also experienced three uplift events with the peak ages of 202 ± 18 Ma (late Triassic), 157 ± 7 Ma (late Jurassic), and 45 ± 3 Ma or 36 ± 3 Ma (middle Eocene), respectively. The Datong Permo-Carboniferous and Jurassic coal vitrinite reflectance proved that the average metamorphism temperature is 104–108 °C, even reaching 163–367 °C. The fission track results showed that the paleotemperature was even higher than 170–250 °C from 117 to 282 Ma and 80–120 °C from 20 to 68 Ma, in the Datong coal-bearing basin. The results show that the deep tectonic activities of the NCC were still active in the Mesozoic and even Cenozoic Paleogene.

As one of the comprehensive exploration techniques for underground geological resources, surface geochemical methods could play an important role in geothermal exploration, which requires detailed and systematic investigations. In this study, we take the Shiba geothermal basin in Huizhou, China, as the research object and apply surface geochemical testing methods to analyze the intrinsic relationship between the geothermal system and the surface soil. The contents of soil gases and elements are mainly determined, among which hydrogen (H₂) and radon (Rn) show three obvious negative anomalies, corresponding to three positive anomalies of soil elements (Fe, U, Cr, V, Cu, and As) that are easy to migrate. The largest negative and positive anomalies correspond to the surface above the fault, which is related to the dominant channel from underground to the surface and is caused by the gas loss effect and the dissolution and migration of inorganic ions. However, the effects of the surface environment and organisms cannot be ignored. Only when the geothermal system has a significant impact on a certain geochemical parameter could the anomaly be manifested in the surface soil. Otherwise, most of the geothermal information, including thermal conduction, will be covered by surface factors. After surface geochemical anomalies related to the geothermal system have been identified, anomaly patterns (especially the top anomaly pattern) can be preliminarily established, which can be used for geothermal exploration. Furthermore, based on the empirical regional geothermal formula, the temperature and depth of the Shiba geothermal system are evaluated at 170°C and 4500 m, respectively, indicating that surface geochemical methods have a good practical prospect in the prediction of geothermal resources.