Thermal Structure Of Lithosphere Research Articles

Terrestrial Heat Flow and Lithospheric Thermal Structure of the Hubao Basin, North Central China

Terrestrial Heat Flow and Lithospheric Thermal Structure of the Hubao Basin, North Central China

The contradiction between lithospheric thermal and seismic structures reveals a nonsteady thermal state – A case study from Northeast China

The nature of the lithosphere, as the outermost layer of the solid Earth, has long been a focus of the Earth sciences. Many methods have been used to study the properties and structure of the lithosphere, including gravity, magnetism, electricity, seismic, and geothermics. Since the 1970 s, a coupled heat-flow heat-production steady-state model has been employed to study the thermal structure of the continental lithosphere and has helped researchers explain many geothermal observations. However, the steady-state model does not work well in some areas. Taking Northeast China as a case study, we systematically calculated the lithospheric thermal structure, compared the result with seismic research, and concluded that the lithospheric thermal state is nonsteady in the southern Songliao Basin, the southern Greater Xing’an Range and the Changbai Volcano. The lithosphere in southern Songliao Basin features a hot top and a cold bottom. The lithosphere in southern Greater Xing’an Range and the Changbai Volcano feature a cold top and a hot bottom. Our numerical simulation has demonstrated that the response of surface heat flow to thermal disturbance at the bottom of the lithosphere often lags by more than 20 Myr, resulting in a significant disparity between the thermal structure calculated based on surface heat flow and the velocity structure of seismic waves. In addition, this study of the thermal structure in Northeast China shows that the temperature of the Moho in Songliao Basin is very high (>600 °C), which may be an important cause of the lack of Cenozoic volcanism in the Songliao Basin.

Differences and Causal Mechanisms in the Lithospheric Thermal Structures in the Cratons in East China: Implications for Their Geothermal Resource Potential

The thermal structure of the lithosphere is key to understanding its thickness, properties, evolution, and geothermal resources. Cratons are known for their low heat flow and deep lithospheric roots. However, present-day cratons in East China have geothermal characteristics that are highly complex, with variable heat flow values, diverging from the typical thermal state of cratons. In this study, we conducted a detailed analysis of the geothermal geological background of the cratons in East China, summarizing the thermal state and tectono-thermal processes of different tectonic units, calculating the temperature at various depths, and discussing differences in temperature and thermal reservoirs at different depths. The observed lithospheric thermal thickness within the North Jiangsu Basin and the Bohai Bay Basin is notably reduced in comparison to that of the Jianghan Basin and the Southern North China Basin. The phenomenon of craton destruction during the Late Mesozoic emerges as a pivotal determinant, enhancing the geothermal resource prospects of both the Bohai Bay Basin and the North Jiangsu Basin. Our findings contribute significantly to the augmentation of theoretical frameworks concerning the origins of heat sources in global cratons. Furthermore, they offer invaluable insights for the methodical exploration, evaluation, advancement, and exploitation of geothermal resources.

Thermophysical properties and geochemical characteristics of granites in the Tengchong area: Indications for resource potential of hot dry rocks

Ascertaining regional radiogeochemical characteristics and lithospheric thermal structure characteristics is paramount for identifying the resource potential of hot dry rocks (HDRs). This study conducted thermal conductivity testing and whole-rock analyses of outcrop granites of different formation epochs from the Tengchong area. Moreover, combined with the previously published whole-rock data and the data related to radioactive heat production rates, this study conducted geological, geophysical, and geothermal analyses. Key findings are as follows: (1) Granites in the Tengchong area exhibit an average radioactive heat generation rate of 5.54 μW/m 3 . Among them, the Late Cretaceous granites have an average radioactive heat generation rate of 8.08 μW/m 3 , suggesting high heat production granites; (2) Granites in the Tengchong area present an average thermal conductivity of 3.135 W/(m·K), relatively akin to the average values of granitic rocks worldwide. Compared to granites of other epochs, the Late Cretaceous granites manifest significantly higher thermal conductivities, with an average of 3.28 W/(m·K); (3) There is a negative correlation between the mica content and the thermal conductivity of the granites in the Tengchong area; (4)The Tengchong area holds potential for HDR exploitation and is inferred to have a lithospheric structure characterized by hot mantle and cold crust.

Mantle Plume‐Lithosphere Interactions Beneath the Emeishan Large Igneous Province

AbstractThe formation of large igneous provinces (LIPs) has been widely believed to be linked to mantle plume activity. However, how the plume modifies the overlying lithosphere, particularly its compositional structure, remains uncertain. Here, we characterize the deep thermochemical structure beneath the Emeishan LIP (ELIP), which is a well‐known Permian plume‐related LIP in China, by taking a multi‐observable probabilistic inversion. Our results find a clear correlation between the lithospheric composition with the ELIP's concentric zones. We infer that the fertile feature of the lithospheric mantle in the ELIP's inner zone was caused by the plume‐derived fertile magmas which infiltrated into and chemically refertilized the ambient depleted lithosphere. This plume‐modified lithospheric compositional structure is likely to be preserved after the plume event, while the present lithospheric thermal structure has been mainly influenced by the subsequent thermal‐tectonic activity. Our results improve our understanding of the physicochemical interactions between the lithosphere and ancient plume.

Heterogeneities of the lithospheric thermal structure and rheology control Cenozoic intracontinental deformation in southeast China

It still remains elusive how the rheology of the lithosphere influences intracontinental deformation. We constructed a thermo-rheological model of the lithosphere in southeast China, a typical intracontinental deformation area, to address this issue. The thermal model was derived from updated heat flow data assuming steady-state heat conduction, using xenoliths and Pn seismic velocity data as constraints. This thermal model was integrated with a compositional and structural model of the lithosphere to estimate the strength distribution. Remarkable heterogeneities in the thermo-rheological structure were obtained. Most of southeast China is characterized by a large mantle heat flow and high temperature, thin and weak lithosphere, except for the western Yangtze Craton where a cold and rigid lithosphere exists. The lithosphere thins southeastward from 200 km in the craton interior to 70 km in the northern South China Sea. Both the ‘jelly sandwich’ and ‘crème brûlée’ rheological profiles for the continental lithosphere exist in southeast China, depending on the geothermal condition. The seismicity in southeast China is restricted to areas cooler than 600 °C, which are rheologically weak and characterized by strength transition zones. The Mesozoic flat-slab subduction of the Paleo-Pacific Ocean and far-field effects of the Cenozoic Indo-Asia collision influence the thermo-rheological pattern in southeast China, and the thermo-rheological heterogeneities control the Cenozoic intracontinental deformation.

Two-Dimensional Geothermal Model of the Peruvian Andes above the Nazca Ridge Subduction

The aseismic Nazca Ridge produces localized flat-slab subduction beneath the South American margin at latitudes 10° to 15° S. The geological evolution and the spatio-temporal pattern of deformation of the upper plate have been strongly influenced by the presence of the flat slab. In this study, we investigated the lithospheric thermal structure of this region by elaborating a 2D geothermal model along a section across the top of the Nazca Ridge, the Peru–Chile trench, the Andean Cordillera, and the Amazonian Basin, for a total length of 1000 km. For the sake of modelling, the crust of the overriding plate was subdivided into two parts, i.e., a sedimentary cover (including the entire lithostratigraphic sequence) and a crystalline basement. Applying an analytical methodology, we calculated geotherms and isotherms by setting (i) thickness, (ii) density, (iii) heat production, and (iv) thermal conductivity for each geological unit and considering (v) heat flux at the Moho, (vi) frictional heating produced by faults, and (vii) plate convergence rate. The resulting model could make a significant advance in our understanding of how flat slab geometry associated with the Nazca Ridge subduction affects the thermal structure and hence the tectonic evolution of the region.

The role of continental lithospheric thermal structure in the evolution of orogenic systems: application to the Himalayan–Tibetan collision zone

Abstract. Continental collision is a crucial process in plate tectonics. However, in terms of the evolution and the controlling parameters of its lateral heterogeneity, our understanding of the tectonic complexities at such a convergent plate boundary remains largely unclear. In this study, we conducted a series of two-dimensional numerical experiments to investigate how continental lithospheric thermal structure influences the development of lateral heterogeneity along the continental collision zone. The following two end-members were achieved. First, continuous subduction mode, which prevails when the model has a cold procontinental Moho temperature (≤450 ∘C). In this case, a narrow collision orogen develops, and the subducting angle steepens with the increasing retrocontinental Moho temperature. Second, continental subduction with a slab break-off, which generates a relative wide collision orogen and dominates when the model has a relatively hot procontinental Moho temperature (≥500 ∘C), especially when the Moho temperature ≥ 550 ∘C. Radioactive heat production is the second-order controlling parameter in varying the continental collision mode, while it prefers to enhance strain localization in the upper part of the continental lithosphere and promote the growth of shear zones there. By comparing the model results with geological observations, we suggest that the discrepant evolutionary paths from the continuous subduction underlying the Hindu Kush to the continental subduction after slab break-off beneath eastern Tibet may originate from the inherited lateral inhomogeneity of the Indian lithospheric thermal structure. Besides, the high content of crustal radioactive elements may be one of the most important factors that controls the formation of large thrust fault zones in the Himalayas.

Sensitivity of gravity anomalies to mantle rheology at mid-ocean ridge – transform fault systems

Marine gravity data can provide information on the distribution of mass anomalies in the oceanic crust and upper mantle. Computing corresponding gravity anomalies, especially so-called ‘residual’ gravity anomalies that directly reflect variations in the crustal structure, relies on gravity corrections of both seafloor relief and lithospheric thermal structure. The lithospheric thermal gravity correction involves either a plate cooling approximation or a mantle flow model with the latter typically done using simplified assumptions on mantle rheology. However, a detailed study of how differing rheological models affect the computed gravity anomalies is still missing. Here, we systematically examine the differences in residual mantle Bouguer anomalies (RMBA) caused by differing assumptions on mantle rheology for 16 mid-ocean ridge – transform fault systems. Our calculations show that isoviscous models tend to underpredict RMBA values within the transform deformation zone and overpredict them in the far field at older plate ages, when compared to plate cooling and nonlinear viscoplastic models. This discrepancy stems from isoviscous models failing to capture plate-like deformation, as well as their inability to resolve brittle failure and the associated strain localization that leads to warm upwelling beneath the transform fault. By exploring a wide parameter range, we find that the importance of mantle rheology scales with plate tectonic parameters at the mid-ocean ridge – transform fault system such as transform age offset, spreading rate, and transform fault length. These findings suggest that gravity thermal corrections at the intrinsically three-dimensional ridge – transform systems should employ mantle flow models that resolve plate-like deformation and brittle failure.

Thermal structure beneath Changbaishan Volcano, northeastern Asia: new insights from temperature logging and numerical modelling

SUMMARY Changbaishan Volcano is considered one of the most hazardous active volcanic fields in northeastern Asia, and it has been the subject of increasing concern due to its unrest from 2002 to 2006. The physical conditions of magma chambers in the crust, particularly temperature and pressure, are crucial factors that determine the tempo and magnitude of volcanic eruptions, which are closely linked to potential hazards. However, the lithospheric thermal structure, which strongly influences rheological behaviour and melting, has been poorly studied. We conducted direct geothermal measurements and numerical forward modelling to address this issue to confirm whether a crustal magma chamber lies beneath the caldera as in earlier geophysical interpretations. We first reported four heat-flow data sets in Changbaishan Volcano. The research findings indicate that the heat flow value near the Tianchi caldera is remarkably high, at 270±16 mW m−2. As the distance from the caldera increases, the heat flow gradually decreases to a normal continental heat flow value of 75 mW m−2. 3-D transient heat simulations with a magma cooling model and a continuous magma supply model demonstrate the thermal effect of the magma chamber. The best-fitting model for the Tianchi magma system is an ellipsoidal magma chamber with a depth of 8–14 km, a 20 km east–west axis and a 70 km north–south axis, supplied with magma from the asthenosphere for 2 Myr. The high surface heat flow and crustal temperatures suggest that magma is active beneath Changbaishan Volcano within the middle-upper crust, and volcanic reactivation could occur. Thus, further research on the lithospheric thermal structure is necessary to understand the potential volcanic hazards associated with Changbaishan Volcano.

A high geothermal setting in the Linyi geothermal field: Evidence from the lithospheric thermal structure

The lithospheric thermal structure has a profound indicative significance for the potential evaluation and exploration of geothermal resources. The Linyi geothermal field, located in the southern section of the Yishu fault in Shandong Province, boasts abundant geothermal resources. However, its origin is still unclear. This study analyzed the characteristics of terrestrial heat flow using the temperature logging of geothermal wells and measurements of thermal conductivity and heat production. Combined with the geophysical information of the Xiangshui (Jiangsu Province)-Mandula (Nei Mongol) geoscience transect and the lithology revealed by the geothermal wells, this study built a conceptual model of the lithospheric thermal structure using the one-dimensional steady-state heat conduction equation. Based on this model, the heat flow is 64.9 mW/m2, indicating a high geothermal setting in the study area. Furthermore, the ratio of crustal to mantle heat flow is < 1 (0.67), implying that surface heat flow originates predominantly from the mantle. The Yishu fault probably acts as a pathway for heat transfer from the mantle. The temperature of the Moho boundary in the study area was estimated to be 614.8 °C. The Curie depth was calculated to be 29.5 km (585 °C), which is consistent with the depth estimated using the aeromagnetic data. In sum, the Linyi geothermal field has a high geothermal setting, which contributes to the formation of geothermal resources.

The role of lithospheric thermal structure in the development of lateral heterogeneous of the continental collision system

The role of lithospheric thermal structure in the development of lateral heterogeneous of the continental collision system

Terrestrial heat flow measurement and numerical simulation of lithospheric thermal structure in western Sichuan, China

The western Sichuan in the eastern Qinghai-Tibet plateau has significant geothermal potential. Heat flow is one of the most important parameters in geothermic, its measurement can help obtain a better understanding of the regional lithospheric thermal structure. In this study, we reported 4 heat flow data based on the continuous steady-state temperature logging and rock thermal conductivity test, including two class-A and two class-D data. Furthermore, we calculated the lithospheric thermal structure by a 2D steady-state thermal conduction equation in COMSOL, analyzing the lateral differences of lithospheric thermal structure in the eastern Qinghai-Tibet plateau. Our study has determined that the heat flow values in the western Sichuan range from 94.7 to 116.2 mW/m2, with a corresponding geothermal gradient of 32.1–37.3 °C/km. Moreover, numerical simulation results indicate significant differences in lithospheric thermal structure between western Sichuan and Sichuan Basin, where the Longmen Shan fault zone is a crucial regional tectonic boundary and a significant temperature gradient zone. Specifically, the Moho temperature in the western Sichuan region ranges from 1000 to 1200 °C with an average temperature of 1060 °C, while the Sichuan Basin ranges from 600 to 700 °C. Besides, the thermal lithosphere thickness in the western Sichuan and the Sichuan Basin is 88–97 km and 105–110 km, respectively. These observations suggest that the western Sichuan region is characterized by high thermal anomaly and provide theoretical evidence for the geodynamic and geothermal development in this area. Finally, we suggest that the high thermal anomaly in western Sichuan is the result of a combination of factors, such as thickened crust, high radioactive heat production, and shear frictional heating from deep fault and so on.

Crust-mantle differentiation and thermal accumulation mechanisms in the north China plain

The North China Plain, which is the central part of the lithospheric thinning in the North China Craton, is rich in clean geothermal energy. However, a current lack of understanding about the thermal accumulation mechanisms of the deep geothermal resources in this area is hindering the exploration, exploitation, and utilization of these resources and the achievement of the carbon reduction targets. Based on deep drilling and the tests of thermal property parameters at different depths, this study calculated the terrestrial heat flow and the heat flux at different depths of the lithosphere in the North China Plain and revealed the lithosphere thermal structure characteristics and the thermal accumulation mechanisms in the plain, obtaining the following results. The North China Plain has widely varying terrestrial heat flow of 33.5–92.1 mW/m2 (average: 62.1 ± 17.04 mW/m2). The average mantle heat flow and crustal heat flow in the plain are 42.05 ± 13.90 mW/m2 and 20 mW/m2, respectively, which account for approximately 67% and 33% of the total surface heat flow in the plain, respectively. This plain has a greatly varying Moho depth of 30–40 km and a Moho temperature of 420–920 °C mostly. The thermal lithosphere in the North China Plain has a thickness of 80–100 km and a thermal structure of the cold crust and hot mantle type. It has thinned on a large scale due to the extensional process, and the mantle-derived materials have migrated upward along the weak structural plane (e.g., deep faults) after pressure release and remelting. The resultant high mantle heat flow serves as a stable heat source for the formation of layered medium-low temperature geothermal fields.

Thermal Conductivity and Thermal Diffusivity of Tremolite at High Temperature and Pressure and Implications for the Thermal Structure of the Venusian Lithosphere

AbstractThermal conductivity (κ) and thermal diffusivity (D) of tremolite were measured at up to 2.5 GPa and 1,373 K using the transient plane‐source method in a multi‐anvil apparatus. Thermal conductivity and thermal diffusivity of tremolite decrease monotonically before dehydration (<1,173 K) and increase significantly after dehydration. Tremolite exhibits positive pressure dependence before dehydration. Heat capacity (C) of tremolite calculated fromκandDshows a positive pressure dependence and is controlled by an almost constant thermal expansion coefficient (α) with temperature. Conductive heat transport and radiative heat transport dominate the heat transport process before dehydration, and the significant increase in thermal conductivity after dehydration is attributed to convective heat transport. A compositional model of the Venusian lithosphere composed of a basaltic crust and peridotite mantle with or without tremolite was established. The thickness of the Venusian lithosphere with or without tremolite for Venus was calculated by combining the heat flow (from 20 to 80 mW/m2) at a certain depth (from 5 to 25 km) of crust, ranging from 24.4 to 184.6 km.

High‐Resolution Broadband Lg Attenuation Structure of the Anatolian Crust and Its Implications for Mantle Upwelling and Plateau Uplift

AbstractThe Anatolian Plateau, currently experiencing rapid uplift and westward escape, records both the termination of oceanic subduction and the conversion to continental collision. The crustal response to the transition of the subduction environment from eastern to western Anatolia can be inferred by the seismic velocity and attenuation structures. With this study, we construct a broadband Lg‐wave attenuation model for the Anatolian Plateau and use it to constrain lateral crust heterogeneities linked to this transition. Crustal Lg attenuation links late Cenozoic magmatism with asthenospheric upwelling by characterizing the lithospheric thermal structure. The widely distributed strong attenuation observed in eastern Anatolia may be related to the crustal partial melting due to mantle upwelling after the delamination and subsequent break‐off of the Bitlis slab. Lithospheric dripping in central Anatolia likely facilitates the mantle flows through the window between the Cyprus and Aegean slabs, which results in the piecemeal low anomaly in central Anatolia.

Strong Variability in the Thermal Structure of Tibetan Lithosphere

AbstractWe present a model of thermal lithospheric thickness (the depth where the geotherm reaches a temperature of 1300°C) and surface heat flow in Tibet and adjacent regions based on a new thermal‐isostasy method. The method accounts for crustal density heterogeneity, is free from any assumption of a steady‐state lithosphere thermal regime, and assumes that deviations from crustal Airy‐type isostasy are caused by lithosphere thermal heterogeneity. We observe a highly variable lithospheric thermal structure which we interpret as representing longitudinal variations in the northern extent of the subducting Indian plate, southward subduction of the Asian plate beneath central Tibet, and possible preservation of fragmented Tethyan paleo‐slabs. Cratonic‐type cold and thick lithosphere (200–240 km) with a predicted surface heat flow of 40–50 mW/m2 typifies the Tarim Craton, the northwest Yangtze Craton, and most of the Lhasa Block that is likely refrigerated by underthrusting Indian lithosphere. We identify a “North Tibet anomaly” with thin (<80 km) lithosphere and high surface heat flow (>80–100 mW/m2). We interpret this anomaly as the result of removal of lithospheric mantle and asthenospheric upwelling at the junction of the Indian and Asian slabs with opposite subduction polarities. Other parts of Tibet typically have intermediate lithosphere thickness of 120–160 km and a surface heat flow of 45–60 mW/m2, with patchy anomalies in eastern Tibet. While different uplift mechanisms for Tibet predict different lithospheric thermal regimes, our results in terms of a highly variable thermal structure beneath Tibet suggest that topographic uplift is caused by an interplay of several mechanisms.

Cenozoic thermal-rheological evolution of the coastal cathaysia block of East Asia: geodynamic implications

ABSTRACT The thermal-rheological structure of the continental lithosphere is an important indicator of geodynamic processes. Tectonic compression and extension may change thermal-rheological structure of lithosphere. However, the thermal-rheological evolution over geological time may be difficult to determine because of overprints of subsequent geological events. Mantle xenolith temperature and pressure conditions can differentiate the lithospheric thermal structure over geological time and indicate the lithospheric rheological strength. Chronological and temperature-pressure condition data from 11 mantle xenoliths in Cenozoic basalts from the Wuyishan terrane (WYT) and coastal terrane (CT) on both sides of the Zhenghe-Dapu Fault (ZDF) in the Cathaysia Block indicate that these terranes have experienced distinct thermal-rheological evolution since the Eocene. Moreover, the thermal-rheological evolution of the CT and WTY were differently influenced by the West Pacific tectonic domain, respectively, because the ZDF has been relatively active since 23 Ma and thus has partly accommodated and thus reduced the tectonic impact of Eurasia-Pacific convergence. Therefore, we classified the thermal-rheological structural evolution of the Cathaysia Block into three stages (35.5–20 Ma, 20–6.5 Ma, and 6.5–0 Ma) that sequentially recorded the opening and closing dynamics of the northeastern margin of the South China Sea and uplift of Taiwan Island on the eastern margin of Eurasia.

Geothermal Heat Flow and Thermal Structure of the Antarctic Lithosphere

AbstractHigh‐quality maps of Geothermal heat flow (GHF) are crucial when modeling ice dynamics, shape, and mass loss of the Antarctic Ice Sheet, which is one of the largest potential contributors to sea level rise. The determination of GHF remains challenging, as in situ data are sparse and geophysical models exhibit large discrepancies in amplitude and resolution, especially on regional scales. Using a novel approach implementing a joint inversion of gravity and seismic tomography data with various geophysical and mineral physics information, we estimate the 3D thermal lithospheric structure and present a new GHF map. The resulting surface heat flow correlates with the location of subglacial volcanism and can represent a boundary condition for accurate ice dynamics models that can explain observed acceleration in the ongoing ice mass loss. Absolute values are within the range of other seismology‐based methods and are much lower than those obtained using for example, magnetic data. High uncertainties remain in the parametrization of the upper crustal structure and thermal parameters.

Thermal and rheological structure of lithosphere beneath Northeast China

We investigate 3-D thermal and rheological structures of the lithosphere beneath Northeast China using detailed P- and S-wave velocity models following mineral physics as well as geothermal methods. Small-scale temperature changes and thermal lithosphere thickness variations between different tectonic blocks are revealed. Our results show that strong lateral heterogeneities exist in the lithospheric thermal structure and rheological structure on both sides of the North-South Gravity Lineament (NSGL). The Changbai volcanic area and the central part of the Songliao Basin in the eastern side of the NSGL exhibit higher temperatures, thinner thermal lithosphere and lower rheological strength, which are closely associated with the western Pacific plate subduction under the Eurasian continent, resulting in upwelling of wet and hot asthenospheric material above the stagnant Pacific slab in the mantle transition zone. The thermo-chemical erosion of the upwelling asthenospheric material may induce delamination of partial lithosphere under the Songliao Basin. In addition, the western and southern edges of the Songliao Basin are characterized by lower temperature, thicker thermal lithosphere and higher rheological strength, which may indicate a relatively stable lithosphere. The Halaha and Abaga volcanic areas in the western side of the NSGL exhibit higher temperature, thinner thermal lithosphere and lower rheological strength, which could be caused by small-scale upwelling of hot asthenospheric material associated with delamination of partial lithosphere beneath the Songliao Basin.