Research on the characteristics and influencing factors of terrestrial heat flow in Guizhou Province

Terrestrial heat flow is an important physical parameter in the study of heat transfer and thermal structure of the earth and it has great significance in the genesis and development and utilization potential of regional geothermal resources.Although several breakthroughs in geothermal exploration have been made in Guizhou Province.The terrestrial heat flow in this area has not been properly measured,restricting the development of geothermal resources in the province.For this reason,the terrestrial heat flow in Guizhou was measured in this study,during which the characteristics of heat flow were determined using borehole thermometry,geothermal monitoring and thermal property testing.Moreover,the influencing factors of the terrestrial heat flow were analyzed.The results show that the thermal conductivity of rocks ranges from 2.0W/(m·K)to 5.0 W/(m·K),with an average of 3.399 W/(m·K);the heat flow varies from 30.27 mW/m^(2) to 157.55 mW/m^(2),with an average of 65.26±20.93 mW/m^(2),which is slightly higher than that of the average heat flow in entire land area in China.The heat flow in Guizhou generally follows a dumbbell-shaped distribution,with high values present in the east and west and low values occurring in the north and south.The terrestrial heat flow is related to the burial depths of the Moho and Curie surface.The basaltic eruptions in the Emeishan led to a thinner lithosphere,thicker crust and lateral emplacement,which dominated the basic pattern of heat flow distribution in Guizhou.In addition,the dichotomous structure of regional active faults and concealed deep faults jointly control the heat transfer channels and thus influence the terrestrial heat flow.

Quantitative Expression of Heat Flow versus Tectonic Deformation in the China Continent: The Effects of Plastic-Flow Network and Stable Block

Based on the heat flow data published in 1990 and 2001, a study of the factors influencing the terrestrial heat flow distribution in the China continent and its quantitative expression is carried out using the ＂Netlike Plastic-Flow＂ continental dynamics model and the methods of statistic analysis and optimum fitting. The result indicates that the factors influencing the heat flow distribution is classified into two groups, i.e. background and tectonic ones, in which the former mainly involves the non- uniform distribution of mantle heat flow, heat production of radioactive dements in the crust, heattransfer media and hydrothermal circulation, while the latter mainly involves plastic-flow networks and relatively-stable blocks. The plastic-flow network is a manifestation of shear localization in the netlike plastic-flow process in the lower lithosphere, which is composed of two sets of plastic-flow belts （PFBs） intersecting each other and, as one of the basic action regimes, controls the intraplate tectonic deformation. Relatively stable blocks （RSBs）, which are the tectonic units with relatively-high viscosities existing in the netlike plastic-flow field, as one of the principal origins, result in the development of large-seale compressional basins. PFB and RSB, as the active and quiet states of tectonic deformation, give rise to the higher and lower heat flow values, respectivdy. The provincial average heat flow in continent can be estimated using the expression qav = q0 ＋ a Pbt-c Pbk, where the three terms of the right side are background heat flow, PFB-positive contribution and RSB-negative contribution, Pbt and Pbk are the PFB- and RSB-coverage ratios, respectively, a is the coefficient of PFB- positive contribution depending mainly on the strain in the lower lithosphere, and c is the coefficient of RSB-negative contribution related mainly to the thickness of the lithosphere, the aseismic-area ratio and the tectonic age. For the major portion of the China continent excluding some of the southeastern region of China, the confidence interval of the provincial average background heat flow is qo=57.25±24.8 mW/m^2 and the PFB-positive- and RSB-negative-contribution coefficients are a=14.8-71.9 mW/m^2 and c=0-25.6 mW/m^2, respectively. The concepts of PFB and RSB effects and the heat flow expression suggested provide a new choice of the approach to the quantitative description of the characteristics of heat flow distribution in continent and their physical mechanisms.

Geothermal anomalies in the Xianshuihe area: Implications for tunnel construction along the Sichuan-Tibet Railway, China

This study presents a comprehensively analysis of geothermal characteristics in the Xianshuihe geothermal area along the Sichuan-Tibet Railway,using temperature logging,temperature monitoring and thermal conductivity measurement,and regional geothermal geological survey data.The research focuses on the geothermal background,geothermal field,and their potential impact on the surrounding tunnels.The investigation reveals that the average heat flow value in the study area is approximately 73.0 mW/m^(2),significantly higher than the average terrestrial heat flow in China's Mainland(62.5 mW/m^(2)).This high terrestrial heat flow signifies a distinct thermal background in the area.In addition,geothermal anomalies in the area are found to be closely associated with the distribution of hot springs along NW faults,indicating a strong control by the Xianshuihe fault zone.The study concludes that the region's favorable conditions for geothermal resources are attributed to the combination of high terrestrial heatflow background and water-conducting faults.However,these conditions also pose a potential threat of heat damage to the tunnels along the Sichuan-Tibet Railway.To evaluate the risk,the research takes into account the terrestrial heat flow,thermal conductivity of the tunnel surrounding rocks,characteristics of the regional constant temperature layer,as well as the distribution of hot springs and faults.The analysis specifically focuses on the thermal damage risk of Kangding 1# tunnel and 2# tunnel passing through the study area.Based on the findings,it is determined that Kangding 1# tunnel and 2# tunnel have relatively low risk of heat damage,as they have avoided most of the high temperature anomaly areas.However,several sections of the tunnels do traverse zones with low to medium temperatures,where surface rock temperatures can reach up to 45℃.Therefore,these regions should not be neglected during the construction and operation of the tunnel project,and mitigation measures may be necessary to address the potential heat-related challenges in the area.

A research on the geothermal structure in Yanqing-Huailai Basin and its neighbouring region

ＡｒｅｓｅａｒｃｈｏｎｔｈｅｇｅｏｔｈｅｒｍａｌｓｔｒｕｃｔｕｒｅｉｎＹａｎｑｉｎｇ┐ＨｕａｉｌａｉＢａｓｉｎａｎｄｉｔｓｎｅｉｇｈｂｏｕｒｉｎｇｒｅｇｉｏｎＪＩＮ－ＨＵＡＺＵ（祖金华）ＱＩＡＮ－ＦＡＮＷＵ（吴乾蕃）ＹＵ－ＦＡＮＧＬＩＡＮ（廉雨方）...

Relationship between crustal magnetic anomalies and strong earthquake activity in the south segment of the China North-South Seismic Belt

The south segment of the China North-South Seismic Belt is located in the southeast margin of the Qinghai Tibet Plateau.This region is characterized by the frequent seismic activity in Chinese mainland.In this paper,the geomagnetic field model NGDC-720 and the data of terrestrial heat flow are used to investigate the distribution of crustal magnetic anomalies,the depth of Curie surface,and the characteristics of the crustal thermal structure in the south segment of the North-South Seismic Belt.The distribution characteristics of the vertical component AZ and the magnetic declination AD in the area with earthquakes over a magnitude of 6 and their aftershocks since 1970 are focused on.The results show that the earthquakes are mainly observed in the area of negative magnetic anomaly or the strong and weak transition zone.It especially shows in the AD.The Curie surface in the study area varies significantly,ranging from 20.8 to 31 km.The uplift area of the Curie surface is consistent with the high-value area of terrestrial heat flow.The high geothermal area corresponds to the strong earthquake activity area.The focal depth of most strong earthquakes is shallower than the depth of the Curie surface.The strong earthquakes mainly occur in the deep-shallow transition zones of the Curie surface.The results can be used as a reference for strong earthquake prediction in this area.