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Thermal lithospheric thickness is an important parameter in studying the tectonic‐thermal evolution of basins and plate dynamics. Based on the measured geothermal data and thermophysical properties of the rocks, the thermal lithospheric thickness of the Sichuan Basin was calculated according to the principles of heat conduction in the crust and lithospheric mantle. The calculation results revealed that the thickness of the thermal lithosphere in the Sichuan Basin is 140–190 km and is unevenly distributed. The thickness of the thermal lithosphere in central Sichuan and southwestern Sichuan is less than 160 km, while that in the western Sichuan depression and eastern Sichuan is larger (∼180 km). The distribution of the thermal lithospheric thickness in the basin has a good correlation with the geological units and the thickness of the sedimentary layers. The thickness of the thermal lithosphere in the depression area, which has thick sedimentary layers and the fault‐fold zone with shallow crustal deformation and thickening, are larger than that in the basement uplifted area, which has thin sedimentary layers. The calculated thermal lithospheric thickness is in good agreement with the geophysical data and reflects the stable conduction temperature field in the Sichuan Basin. The present thermal regime and thermal lithospheric thickness of the Sichuan Basin indicate that flexural thickening of the lithosphere occurred in the eastern Sichuan fault‐fold belt and the Longmen Mountain–Western Sichuan depression foreland basin system, while asthenospheric uplift occurred in the central Sichuan region, which were the result of the expansion of the Xuefeng orogeny from the east and the compression of the Tibetan Plateau from the west. [ABSTRACT FROM AUTHOR]

The lack of effective paleogeothermometers restricts the study of the thermal history of carbonate strata. Carbonate clumped isotope thermometry and in-situ U–Pb dating are appropriate for reconstructing the thermal history of carbonate strata. Herein, this study analyzed clumped isotope compositions and U–Pb ages of calcite fabrics, including micrite matrix and veins, from Permian carbonate strata in the eastern Sichuan Basin. U–Pb dating of the micrite matrix was performed to rule out the influence of recrystallization and determine the diagenetic age of the samples. Clumped isotope temperatures of the four micrite matrix samples ranged from 102 °C to 137 °C. The maximum paleotemperature derived from a solid-state reordering model was between 210 °C and 220 °C. From all four samples, three calcite veins yielded crystallization temperatures corresponding to 160 ± 10 °C, 60 ± 10 °C, and 29 ± 4 °C, as determined by clumped isotope and solid-state reordering model analyses. In-situ U–Pb dating provided corresponding crystallization ages of 159 ± 17 Ma, 256.6 ± 5.5 Ma, and 17.86 ± 0.8 Ma. The crystallization ages and temperatures of the three calcite veins align well with the thermal history of the Permian strata, indicating a high degree of accuracy. This study introduces a new strategy for reconstructing the thermal history of carbonate strata. The thermal history can be quantified using the constraints of the crystallization ages and temperatures from different stages of calcite veins or cements. This approach is suitable for determining the maturation progress of the source rock and conducting oil and gas exploration in petroliferous basins. • Permian strata's maximum paleotemperature simulated by clumped isotope is 210–220 °C. • Solid-state reordering model can get the calcite vein's crystallization temperature. • Calcite veins are essential to reconstructing the thermal history of carbonate strata. [ABSTRACT FROM AUTHOR]

Previous studies proposed thermal simulation experiment to investigate the annealing characteristics of fission tracks in igneous zircon samples. However, basic research about detrital zircon fission track was relatively weak. This study discussed the initial track length, annealing temperature and annealing model of zircon fission track by using the measured track lengths obtained from natural borehole samples in the sedimentary basins with different thermal background. The results show that the initial track length of zircon fission track is 12.97 µm. The total annealing temperature (Ttotal) of zircon fission track derived from the evolutionary curve of the mean track lengths is approximately 400 °C. The temperature ranges of 120–230 °C corresponds to the partial annealing zone (PAZ), and is lower than the range obtained through thermal annealing experiments. The annealing model is modified based on the measured track lengths. In addition, a functional formula about the mean track length, annealing temperature, and geological time is proposed, and the fitted values of track lengths consist with the measured track lengths in this study. By properly understanding the initial track length and annealing behavior of zircon fission track can provide a significant guidance for the study of hydrocarbon accumulation in sedimentary basins. [ABSTRACT FROM AUTHOR]

Zircon fission‐track thermochronometry was used as an effective indicator to investigate the thermal history of sedimentary basins with high temperatures, and fission‐track ages and annealing temperatures were very important parameters. We measured fission‐track ages and discussed the annealing behaviour of zircon fission track from natural borehole samples in the Bohai Bay and Tarim basins. The annealing temperature of the zircon fission track was approximately 220°C in the deep borehole samples of the Bohai Bay Basin with a high thermal background. However, the annealing temperature was approximately 170°C in the deep borehole samples of the Tarim Basin with a low thermal background. In Neogene–Quaternary, the heating rate ranged from 2 to 7°C/Ma in the Sk1 samples, and 4 to 18°C/Ma in the K1 samples. This explained that zircon fission track with different thermal backgrounds existed different annealing temperatures due to the different heating rates. The uranium concentration of the K1 samples mostly ranged from 16 to 1,500 ppm, with a few grains spread from >1,500 to 3,000 ppm, while the Sk1 samples mainly distributed between 4 ppm and 350 ppm. The K1 samples with high uranium contents tended to accumulate much radiation damages and were less resistant to annealing and appeared to have a lower annealing temperature compared to zircons of lower uranium contents in the Sk1 samples. By properly understanding annealing behaviour and annealing temperature, zircon fission‐track thermochronometry could provide a correct explanation for fission‐track ages. [ABSTRACT FROM AUTHOR]

Abtract The Lower Cambrian Qiongzhusi shale and the Upper Ordovician–Lower Silurian Wufeng‐Longmaxi shale are major source rocks and important shale gas exploration targets in the Sichuan Basin. Cutting and core samples from two shale gas wells in south‐western Sichuan Basin have been selected for organic matter (OM) reflectance measurement and Raman spectra analysis with the aim to determine maturity. The results were incorporated for basin modelling to construct the thermal evolution of this area. Graptolite fragments and pyrobitumens are the dominant form of OM in Wufeng‐Longmaxi shale. A limited number of the OM as pyrobitumens and vitrinite‐like particles is presented in Qiongzhusi shale. According to the measured reflectance of OM in conjunction with the maturity calculated using Raman spectra, the equivalent vitrinite reflectance (EqVRo) values based on solid bitumen and graptolite is 2.53–2.81% for the Wufeng‐Longmaxi shale. The EqVRo value is 2.85–3.53% within 300 m depth intervals for the Qiongzhusi shale. A significant difference in oil generation occurred before the Late Permian between Qiongzhusi shale and Wufeng‐Longmaxi shale based on basin modelling and reassessment of previous published data. Compared with the Qiongzhusi shale, the Wufeng‐Longmaxi shale would have lower maturities before Late Permian and less hydrocarbon could be generated/expelled at that time, therefore, this shale remained with a large amount of oil, which could crack into gas. This difference had shown a favourable time relationship for generation and accumulation of shale gas in Wufeng‐Longmaxi shale. [ABSTRACT FROM AUTHOR]

The strike-slip fault-controlled ultra-deep fractured-vuggy carbonate reservoir is an increasingly important exploration target. However, the high heterogeneity of fault-controlled reservoirs and the ineffective methods available for pressure prediction make it difficult to assess the risk of potential overpressure in ultra-deep carbonate reservoirs. Abnormal overpressure is common in the ultra-deep strike-slip fault-controlled carbonate reservoirs in the Shunbei Oilfield of the Tarim Basin. According to measured pressures, petroleum accumulation history, and fault framework, this study investigates the generation mechanisms of overpressure in fault-controlled carbonates and reconstructs the pressure evolution of reservoirs. Finally, the effect of strike-slip faults on current overpressure distribution is discussed. Measured pore pressure data from 90 wells showed that all reservoirs present in the major fault zones are normally pressured, and the reservoirs present far away from the major faults commonly develop overpressures. The distribution patterns of overpressure in the Middle-Lower Ordovician reservoirs coincide with areas with fault reactivation during the Himalayan Period. The results of the comprehensive analysis of petroleum accumulation history, fault activity, and well production suggested that dry gas generation is a primary cause of overpressure in the Middle-Lower Ordovician reservoirs. The relatively low temperature in the reservoir, in addition to the highly compartmentalized nature of overpressure, indicated that these overpressured gas migrate vertically into the Ordovician formation from deep strata along strike-slip faults. The pressure evolution restored by basin modelling and fluid inclusion showed that distinct differences in overpressure magnitude in the different reservoirs were formed at the stage of gas charging but not at the early stages of oil accumulation. The difference in physical properties of the two types of fault-controlled reservoirs resulted in different pressure distributions and oil-bearing levels in the ultra-deep carbonate reservoirs at present. The strike-slip fault zones are the primary pathways by which overpressured fluids migrate from the deeper Cambrian formation into the Ordovician reservoirs and act as barriers to separate the pressure systems in the ultra-deep carbonate reservoirs. These findings are expected to help mitigate the drilling risks with overpressure in deep strike-slip fault-controlled carbonate reservoirs. • Faults act as barrier to separate the carbonate into many isolated pressure systems. • Overpressured gas from deep strata vertically migrate into reservoir via active fault. • The two types of fault-controlled reservoirs have different pressure states. [ABSTRACT FROM AUTHOR]

The Linqing Sub‐basin is situated in the south‐west of the Bohai Bay Basin (BBB), which is the centre of lithospheric destruction and thinning of the eastern North China Craton (NCC). It is also one of China's premier hydrocarbon‐bearing basins. To better understand the Mesozoic–Cenozoic thermal history of the Linqing Sub‐basin, 178 vitrinite reflectance (Ro) data from nine wells and six apatite fission track (AFT) ages have been used. The effective AFT ages range from 53.5 to 107.7 Ma, with mean track lengths of 10.6 μm, recording the tectonic–thermal events from the Early Cretaceous to the Palaeogene. The thermal modelling results of AFT show that the Linqing Sub‐basin experienced two rapid cooling events during the Late Cretaceous (100–70 Ma) and Middle Eocene–Miocene (40–20 Ma), respectively, which are closely related to the subduction and rollback of the Pacific Plate. The thermal modelling results of Ro indicate that the Linqing Sub‐basin has experienced two heat flow peaks during the Early Cretaceous and the Palaeocene–Late Eocene, with the heat flow values of 80 and 86 mW/m2, respectively. These heat flow values were consistent with the destruction peak of the North China Craton and the extension peak of the Bohai Bay Basin. The Carboniferous source rocks experienced a large‐scale hydrocarbon generation stage from the early Mesozoic to the Late Cretaceous and the Shahejie 3 Formation source rocks from the Middle Eocene to the Late Oligocene. Our study provides new geothermal evidence for the process of the destruction of the North China Craton. [ABSTRACT FROM AUTHOR]

Paleo-pressure reconstruction in sedimentary basins is one of the most important aspects of hydrocarbon accumulation research. In view of the advantages and disadvantages of the current methods for paleo-pressure research, a new method to reconstruct the paleo-pressure is presented in this paper. According to the geological background, quantitative analyses of the factors that might control overpressure were first conducted to clarify the contributions of each mechanism during different geological periods. Pressure evolution was reconstructed by fluid-compaction modelling with constraints imposed by the paleo-pressures obtained from fluid inclusions or differential stress methods. Determining the mechanisms responsible for overpressures during geological history is the basic prerequisite for paleo-pressure research. Thus, quantitative studies were conducted of the contributions of disequilibrium compaction, gas charging, oil cracking, temperature reduction, and tectonic uplift and subsidence to overpressures. Three case studies of paleo-pressure reconstruction were performed for the Sinian strata in the Sichuan Basin, Ordovician strata in the north uplift in the Tarim Basin and the Permian strata in the Sulige Gas Field in the Ordos Basin, where these three study sites are normally pressured, weakly over-pressured and abnormally low pressured at present, respectively. The new method developed in this paper is very important for the practical reconstruction of the paleo-pressure in marine strata and ancient strata in deep basins. [ABSTRACT FROM AUTHOR]

Zircon (U-Th)/He thermochronometry was used as an effective indicator to study the thermal history of deep sedimentary basins with high temperatures. Zircon He ages and closure temperatures are very important parameters. In this paper, detrital zircon He closure temperature was studied by establishing the evolutionary pattern between zircon He ages and burial depth of borehole samples obtained from the Cenozoic strata in the Bohai Bay and Tarim basins, which have different thermal settings. The results show that the zircon He closure temperature of natural evolution samples is 200°C, which is higher than the temperature obtained from thermal simulation experiments (183°C). The temperature range of 140–200°C corresponds to the zircon helium partial retention zone. By properly understanding zircon He closure temperatures, zircon (U-Th)/He thermochronometry can provide a correct explanation of the He ages, and significant guidance in the study of the evolution of source rocks and the process of hydrocarbon accumulation in deep sedimentary basins. [ABSTRACT FROM AUTHOR]

Abstract The Wufeng-Longmaxi marine shale of the Upper Ordovician (O 3 w)-Lower Silurian (S 1 l) is the main source rock and target for shale gas exploration in Sichuan Basin, China. Maturity assessment is very important for shale gas evaluation, and such assessment is difficult because of the absent of vitrinite, which is the main objective for vitrinite reflectance analysis. Graptolite fragments and solid bitumens are the dominant forms of organic matter in the shales. In this article, optical reflectance analysis of solid bitumen and graptolite and Raman spectroscopy characterization of graptolite were investigated to reduce the levels of uncertainty in thermal maturity assessment. The aims were to (1) build the correlation between graptolite reflectance and solid bitumen reflectance, to (2) establish the relationship between graptolite reflectance and Raman spectroscopy, and (3) to re-build the maturity distribution of such gas shale in Sichuan Basin. 32 core samples and 22 outcrop samples have been collected for the optical reflectance analysis, and the mean graptolite random reflectance in Sichuan Basin ranges from 1.21% to 4.91%. The random reflectance of graptolite (GRo) is higher than that of solid bitumen (BRo), and graptolite random reflectance can effectively be used as a maturity indicator. Compared with graptolite maximum reflectance (GRomax), graptolite random reflectance is more precise owing to smaller standard deviation. A natural evolution of maturity series of graptolites have been chosen for Raman spectroscopy analysis. Based on the previous studies of the relationship between Raman spectroscopy and vitrinite reflectance, the correlations between the graptolite random reflectance and vitrinite reflectance (VRo) for over maturity stage were obtained through characteristic of the Raman spectroscopy. The results indicate relationship between GRo and VRo is not a single linear relationship. Through the calculation, the maturities of this gas shale interval range from 1.16% to 3.63%, which provides the basic important information for shale gas evaluation in Sichuan Basin. Highlights • The graptolite reflectance of gas shales in Sichuan Basin has been systematically analyzed. • Graptolite reflectance related to Raman spectral parameters has been summarized. • The relationship between graptolite reflectance and vitrinite reflectance has been built. • The maturity distribution of gas shales in Sichuan Basin has been systematically analyzed. [ABSTRACT FROM AUTHOR]

The temperature history of samples and maximum palaeogeothermal profiles of boreholes were reconstructed based on low‐temperature thermochronology and vitrinite reflectance data, and the results provide limits for the timescale and amount of uplift–denudation of the eastern Sichuan Basin. The thermal history showed that the uplifting and cooling of eastern Sichuan Basin began around the Late Cretaceous (approximately 100–80 Ma). The region had experienced a continuous cooling process from the Late Cretaceous until the present, with the geothermal gradient decreasing from 32–36 °C/km to 20–23 °C/km. The amount of denudation at the Puguang region in north‐eastern Sichuan was approximately 2.3 km, whereas that at south‐eastern Sichuan was 1.9 km, and the erosion thickness in the eastern Sichuan fold belt that was revealed via the field samples is 2.3 ± 0.3–2.6 ± 0.3 km. The north‐eastern Sichuan experienced sustained cooling with inconspicuous fluctuations, whereas the thrust belt and the south‐eastern Sichuan Basin presented 2–4 stages with different cooling rates. It may indicate that the eastern Sichuan fold belt experienced a complex structural evolution, characterized by episodic upliftings and deformations since Late Cretaceous, while a different and gentle deformation took place in the northeastern Sichuan Basin. [ABSTRACT FROM AUTHOR]

Reconstructing the evolution of paleofluid pressure in carbonate reservoirs is a challenging problem, particularly when no oil-bearing fluid inclusions are available to provide barometric constraints on the fluid system. To recover the paleofluid pressure in the Sinian Dengying Formation (Z 2 dn) and the Cambrian Longwangmiao Formation (Є 1 l) of the central paleo-uplift of the Sichuan Basin, we conducted a comprehensive analysis combining the inclusion pressure-volume-temperature simulation, inclusions in situ Raman shifts, and basin modeling. The results showed that the evolution of the pore pressure could be divided into four stages. Prior to the end of the late Triassic, the whole central paleo-uplift was in a normal pressure state. During the Jurassic, a moderate overpressure prevailed in the dolomitic reservoirs of the Gaoshiti-Moxi area and decreased in the adjacent units. At the end of the early Cretaceous, the overpressure reached a maximum in the whole region and was strongest in the Longnüsi area, decreasing to the west. From the late Cretaceous to the present day, the central area of the basin has uplifted rapidly with the overpressure significantly decreasing. Z 2 dn has been restored to normal pressure during the Neogene, while Є 1 l remains moderately overpressurized. Based on an analysis of the structural background and preservation conditions, the types of sedimentary facies, the preservation condition of the traps, and the differential weathering process are the primary reasons for the different pressure states in Z 2 dn and Є 1 l during the last stages. [ABSTRACT FROM AUTHOR]

The Sichuan Basin is among the basins with the most abundant oil and gas resources in China. The Sinian and Cambrian strata are the most important source rocks. Previous studies of the thermal history of the central Sichuan Basin have focused on the Late Paleozoic and studies of the Early Paleozoic thermal history are not available in literature and the thermal evolution of the Sinian and Cambrian source rocks are yet to be examined. A new thermal history was reconstructed using integrated thermal indicators, including apatite and zircon (U-Th)/He, zircon fission tracks, and equivalent vitrinite reflectance. The modeled results indicated that the heat flow was relatively low (<65 mW/m 2 ) from the Sinian to Early Permian. During the Middle-Late Permian, the heat flow reached a maximum value (75–100 mW/m 2 ) which may have been controlled by the heating effect of the Emeishan mantle plume and crustal extension. Following the Triassic, the heat flow gradually decreased to its present value of 60–70 mW/m 2 . The maturity histories of the source rocks, modeled based on the new thermal histories, indicate that the Sinian and Cambrian source rocks were slowly maturing during the Early Paleozoic, underwent rapid maturation during the Mesozoic, and reached the dry-gas stage during the Late Cretaceous. These new data on the thermal history and source rock maturity histories of the central Sichuan Basin provide new insights to guide oil and gas exploration of the basin. [ABSTRACT FROM AUTHOR]

Recently, trillions of cubic meters gas resources have been found in Sinian reservoirs of Gaoshiti-Moxi region in the central uplift of Sichuan Basin, which is the first commercial discovery of primary gas field in Precambrian anywhere in the world. To obtain a great breakthrough in Precambrian hydrocarbon exploration, it is necessary to find out the evolution process of temperature and pressure. Reconstructing the thermal history and pore pressure evolution in carbonate reservoirs are challenging problems, especially in deep-old layers without available samples and methods. To study the temperature and pressure system, we conducted a comprehensive analysis combining the paleo-thermal indicators and inclusions Pressure-Volume-Temperature (PVT) simulation with basin modeling. The results showed that the thermal history of the Gaoshiti-Moxi area could be divided into three stages. From the Late Sinian to Late Paleozoic, the thermal regime was stable with low heat flow value (<65 mW/m 2 ). During the Early Paleozoic, the heat flow increased rapidly to the peak value (75–100 mW/m 2 ). From Mesozoic to present, the thermal subsidence occurred in the basin with the heat flow decreasing to the present value (60–70 mW/m 2 ). With the boundary condition of above thermal history, the simulated pressure of Dengying Formation in Gaoshiti-Moxi area could be divided into four stages. The excess pressure began to form during the Triassic. From the end of Triassic to Middle Jurassic, the excess pressure increased steadily and slowly. From Middle Jurassic to the end of Early Cretaceous, the strata subsided rapidly while the excess pressure increased significantly. Since the Late Cretaceous, the Dengying Formation suffered from rapid uplifting and gas lateral migrating with the excess pressure decreasing, until the Late Neogene, the excess pressure in reservoirs declined to zero. [ABSTRACT FROM AUTHOR]

• A more realistic structural model derived from geomechanics-based structural restoration. • Significant structural dependencies of the thermal history and hydrocarbon charge. • Various sources of hydrocarbons are recognised and potential prospects are analysed. The eastern Kuqa Depression is part of a tectonically active foreland basin and hosts structure-related petroleum systems with Jurassic coals and Triassic lacustrine mudstones acting as source rocks. However, the relationship between the recent structural evolution and the development of petroleum systems is poorly understood. In this study, the paleo-geometries are restored by structural reconstruction based on a regional 2D seismic section. The geological evolution of the petroleum systems was modelled integrating structural restoration with basin and petroleum system model. Results show significant structural dependencies of the thermal history and hydrocarbon charge. Source rock thermal maturity in the Yangxia Sag and Dina Fold Belt in the south increased continuously since the onset of tectonic compression, whereas the maturity of the Yiqikelike Anticline in the north remained unchanged due to structural uplift. Hydrocarbon accumulations are modelled across different structural units, emphasising the control of tectonics on petroleum systems' development. Hydrocarbon accumulations occur mainly in structural traps located in the Dina Fold Belt and Dibei Slope. The present-day accumulations are characterised by multiple stages of hydrocarbon filling, during which the proportion of gas components was increasing. Finally, the different sources of hydrocarbons in various reservoirs are recognised and prospects are predicted. The fold- and fault-related traps and tight sand reservoirs in the Dina Fold Belt and Dibei Slope should be treated as prospective targets in the area. This study highlights the importance of integrating structural restoration and petroleum system modelling, which is particularly important for tectonically active basins. [ABSTRACT FROM AUTHOR]

Abundant gas condensates have been proven in the Ordovician carbonate reservoirs in the Tazhong area, the centre of the Tarim Basin, where complicated geological evolution and multiple hydrocarbon accumulations have occurred. Property, geochemistry, and stable carbon isotopes of the Ordovician condensate are characterized to identify the oil and gas origins in the Tazhong area. Fluid inclusion data, combined with numerical modelling methods was used to determine petroleum accumulation processes. Our results suggest that oils are characterized by mixed sources, with 64% of contributions from the Middle‐Upper Ordovician (O2+3) source rocks and 36% of contributions from the Lower‐Middle Cambrian (Є1+2) source rocks. Gases are primarily generated from the thermal cracking of pre‐existing oils in the underlying strata, with a small amount derived from kerogen cracking accompanied with oil generation. Three petroleum filling stages are determined, including the filling of the Є1+2‐derived oils during the Late Hercynian period, filling of the O2+3‐derived oils during the Yanshan period and oil‐cracking‐gas charge during the Himalayan period. The accumulation processes and relative contribution ratios of the two source rocks vary among the reservoirs and are mainly related to the transport system. Due to the lack of faults in the regions away from the No. 1 Fault Belt, the Є1+2‐derived oils are difficult to fill into the Ordovician reservoirs through the gypsolyte, and thus the accumulated oils are mainly from the O2+3 source rocks. The percentage of the O2+3‐derived oils is high in the southeast and northwest segments of the No. 1 Fault Belt, but relatively low in the middle segment and the vicinity of the No. 10 Structure Belt. Likewise, the late gas charge intensity is controlled by regionally varying conduit systems. Gas condensate formed in reservoirs with high gas/oil ratios. Otherwise, light oil retains with respect to low gas/oil ratios. [ABSTRACT FROM AUTHOR]

Studies on the tectono-thermal evolution of the western Bohai Bay Basin (WBBB), including the Jizhong Sub-basin and Cangxian Uplift, are important for further petroleum exploration and exploitation. This study aims to reconstruct the tectono-thermal history of the WBBB based on a combination of 125 vitrinite reflectance (Ro) data and seven apatite fission track (AFT) and nine apatite (U-Th)/He (AHe) ages. The effective AFT ages range from 60.3 to 97.0 Ma, with mean track lengths of 10.86–12.64 μm. The variable single-grain AFT ages are explained to be due to the parameter D par . The effective AHe ages range from 21.1 Ma to 75.0 Ma. Two rapid cooling events revealed by the thermal modeling results occurred during the Early-Late Cretaceous (130–90 Ma) and Late Eocene-Early Miocene (40–18 Ma), respectively. The Fuping Complex, which is located in the western margin of the WBBB and mainly composed of the Paleo-proterozoic high-grade gneisses, experienced the intensive extension-detachment during the Early-Late Cretaceous along with the subduction of the Izanagi Plate, that was probably responsible for the first cooling event. The second cooling event was caused by the subduction of the Pacific Plate during the Middle Eocene-Early Miocene (43–23 Ma), as well as the collision of the Indian and Eurasian Plates and the rollback of the subducting Pacific Plate during the Early Miocene (23–18 Ma). The WBBB experienced two heat flow peaks of ∼75 and ∼80 mW/m 2 during the Early Cretaceous and the Late Eocene, respectively. During the Late Eocene-Early Miocene, rapid subsidence in the Baxian Depression (one secondary tectonic unit of the Jizhong Sub-basin) coupled with the rapid uplift in the Cangxian Uplift caused the Shahejie Formation of the middle-upper Eocene to generate gas during the Early Miocene. Meanwhile, tectonic movement during the Early Miocene also caused faults to become migration paths, as revealed by the homogenization temperature of the fluid inclusion. This study provides new insights regarding the tectonic and hydrocarbon evolution of the WBBB. [ABSTRACT FROM AUTHOR]

The Emeishan large igneous province (ELIP) is widely considered to be a consequence of a mantle plume. The supporting evidence includes rapid emplacement, voluminous flood basalt eruptions, and high mantle potential temperature estimates. Several studies have suggested that there was surface uplift prior to the eruption of the Emeishan flood basalts. Additionally, the plume's lateral extent is hard to constrain and has been variously estimated to be 800–1400 km in diameter. In this study, we analyzed present-day heat flow data and reconstructed the Permian paleo-heat flow using vitrinite reflectance and zircon (U-Th)/He thermochronology data in the ELIP region and discussed implications for the geodynamics of the Emeishan mantle plume. The present-day heat flow is higher in the inner and intermediate zones than in the outer zone, with a decrease of average heat flow from 76 mW/m 2 to 51 mW/m 2 . Thermal history modeling results show that an abnormal high paleo-heat flow of 90–110 mW/m 2 was caused by the Emeishan mantle plume activity. Based on the present-day heat flow data, we can calculate that there is lithospheric thinning in the central ELIP region, which may be due to the destruction of the lithosphere by mantle plume upwelling and magmatic underplating. The Permian paleo-heat flow anomaly implies that there was a temperature anomaly in the mantle. The ascending high-temperature mantle plume and the thinned lithosphere may have induced the large-scale uplift in the ELIP region. According to the range of the surface heat flow anomaly, it can be estimated that the diameter of the flattened head of the Emeishan mantle plume could have reached ~ 1600–1800 km. Our research provides new insights into the geodynamics of the Emeishan mantle plume through study of heat flow. [ABSTRACT FROM AUTHOR]

The Meso-Cenozoic lithospheric thermal-rheological structure and lithospheric strength evolution of the Jiyang sub-basin were modeled using thermal history, crustal structure, and rheological parameter data. Results indicate that the thermal-rheological structure of the Jiyang sub-basin has exhibited obvious rheological stratification and changes over time. During the Early Mesozoic, the uppermost portion of the upper crust, middle crust, and the top part of the upper mantle had a thick brittle layer. During the early Early Cretaceous, the top of the middle crust's brittle layer thinned because of lithosphere thinning and temperature increase, and the uppermost portion of the upper mantle was almost occupied by a ductile layer. During the late Early Cretaceous, the brittle layer of the middle crust and the upper mantle changed to a ductile one. Then, the uppermost portion of the middle crust changed to a thin brittle layer in the late Cretaceous. During the early Paleogene, the thin brittle layer of the middle crust became even thinner and shallower under the condition of crustal extension. Currently, with the decrease in lithospheric temperature, the top of the upper crust, middle crust, and the uppermost portion of the upper mantle are of a brittle layer. The total lithospheric strength and the effective elastic thickness ( T ) in Meso-Cenozoic indicate that the Jiyang sub-basin experienced two weakened stages: during the late Early Cretaceous and the early Paleogene. The total lithospheric strength (approximately 4-5 × 10 N m) and T (approximately 50-60 km) during the Early Mesozoic was larger than that after the Late Jurassic (2-7 × 10 N m and 19-39 km, respectively). The results also reflect the subduction, and rollback of Pacific plate is the geodynamic mechanism of the destruction of the eastern North China Craton. [ABSTRACT FROM AUTHOR]

The hydrocarbon migration and accumulation of the Suqiao deep buried-hill zone, in the Jizhong Subbasin, the Bohai Bay Basin, eastern China, was investigated from the perspective of paleo-fluid evidence by using fluid inclusions, quantitative fluorescence techniques (QGF), total scanning fluorescence method (TSF) and organic geochemical analysis. Results show that the current condensate oil-gas reservoirs in the study area once were paleo-oil reservoirs. In addition, the reservoirs have experienced at least two stages of hydrocarbon charge from different sources and/or maturities. During the deposition of the Oligocene Dongying Formation (Ed), the deep Ordovician reservoirs were first charged by mature oils sourced from the lacustrine shale source rocks in the fourth member of Shahejie and Kongdian Formations (Es 4 +Ek), and then adjusted at the end of Ed period subsequently by virtue of the tectonic movement. Since the deposition of the Neogene Minghuazhen Formation (Nm), the reservoirs were mainly charged by the gas that consisted of moderate to high-maturity condensate and wet gas sourced from the Es 4 +Ek lacustrine shale source rocks and mature coal-derived gas sourced from the Carboniferous-Permian (C-P) coal-bearing source rocks. Meanwhile, the early charged oil was subjected to gas flushing and deasphalting by the late intrusion of gas. The widely distributed hydrocarbon inclusions, the higher QGF Index, and FOI (the frequency of oil inclusions) values in both gas-oil and water zone, are indicative of early oil charge. In addition, combined with the homogenization temperatures of the fluid inclusions (<160 °C) and the existence of solid-bitumen bearing inclusions, significant loss of the n -alkanes with low carbon numbers, enrichments of heavier components in crude oils, and the precipitation of asphaltene in the residual pores suggest that gas flushing may have played an important role in the reservoir formation. [ABSTRACT FROM AUTHOR]

Lower Silurian shale, with a variable gas enrichment, in the Upper Yangtze Block is used to evaluate the response of shale fracturing and gas loss to differential tectonic reworking. The Meso-Cenozoic uplift process was reconstructed by apatite fission track, zircon fission track, apatite (U–Th)/He and zircon (U–Th)/He dating. During the Mesozoic, due to Pacific-Eurasian convergence the Upper Yangtze Block underwent northwestward progressive deformation, with a periodic uplift process characterized by rapid uplift during the Early-Late Cretaceous, followed by subsequent slow uplift. The Cenozoic uplift process was characterized by rapid uplift in the Sichuan Basin as a result of Indian-Asian collision and inherited slow uplift in the Hubei–Hunan–Guizhou fold belt in response to Pacific-Eurasia convergence. The pressure evolution of the Lower Silurian shale was reconstructed using fluid inclusions and variation in shale gas content was quantified. By comparing the differences in pressure reduction, fracturing, and shale gas loss we explore the effect of tectonic reworking on shale fracturing and gas preservation in relation to deformation, uplift and the maximum burial depth. Deformation increases fracture development and reduces the sealing capacity of the shale. Uplift amplitude is a major controlling factor. Large amounts of uplift resulted in clear fracturing and massive gas loss. Triaxial fracture tests show that the maximum burial depth is associated with shear fractures in the shale and thereby affects shale gas preservation during uplift. The differences of slip deformation, tectonic uplift amplitude and the maximum burial depth of shale resulted in the differential enrichment of the Lower Silurian shale gas. • The Meso-Cenozoic uplift process of the Upper Yangtze Block was characterized by two-stage and three-stage. • Differential uplift, depressurization and shale gas loss occurred in the Lower Silurian shale during the Meso-Cenozoic. • The differences of slip deformation, tectonic uplift amplitude and the maximum burial depth of shale resulted in the differential gas enrichment. • The uplift amplitude is the major factor controlling the shale gas preservation. [ABSTRACT FROM AUTHOR]

The Sichuan Basin is overpressured and has experienced a reduction in temperature since the Late Cretaceous due to uplift and denudation. The temperature and pressure of the central Sichuan Basin are investigated utilising borehole data. Pressure positively correlates with temperature in each overpressured system, with a coefficient of 0.851 MPa/°C for the Cambrian pressure system and 1.064 MPa/°C for the Upper Triassic pressure system. Physical simulation experiments carried out with absolute sealing conditions demonstrate that the temperature–pressure relationship in a water-filled system is linear with a gradient of 1.076 MPa/°C, similar to the observed temperature–pressure gradients in the study area. The integration of thermal indicators, including vitrinite reflectance and fluid inclusions, is used to reconstruct the palaeotemperature of the basin. Formation temperatures have decreased since 90 Ma, with a significant decrease since 20 Ma. The amount of cooling varies between hydrocarbon fields as it is dependent on the local extent of exhumation during basin uplift. The Weiyuan field exhibits the greatest amount of cooling, followed by the Moxi field, with the Bajiaochang field experiencing the smallest reduction in temperature. The maximum palaeopressure is calculated to be > 200 MPa in the Cambrian strata and ∼150 MPa in the Upper Triassic strata. The existence of gas within the hydrocarbon fields can change the temperature–pressure relationship, lowering the maximum pressure. However, we propose that temperature reduction is the primary cause of the pressure decrease since 90 Ma and that it controls the present-day overpressure distribution in the basin. [ABSTRACT FROM AUTHOR]

In this study the dynamic aspects of the Cenozoic extension in the Bohai Bay Basin are considered in the context of initial thickness of the crust and lithosphere, tectonic force, strain rate and thermal rheology, which are directly or indirectly estimated from a pure shear extensional model. It is accordingly reasonable to expect that, in the Bohai Bay Basin, the thickness variation could be present prior to the initiation of extension. The extensional deformation is localized by a thickness variation of the crust and lithosphere and the heterogeneity of the initial thickness plays an important role in rifting dynamics. The onset of rifting requires a critical tectonic force (initial tectonic force) to be applied, which then immediately begins to decay gradually. Rifting will only occur when the total effective buoyancy force of the subducting slab reaches a critical level, after a certain amount of subduction taking place. The magnitude of the tectonic force decreases with time in the early phase of rifting, which indicates the weakening due to the increase in geothermal gradient. In order to deform the continental lithosphere within the currently accepted maximum magnitude of the force derived from subducted slab roll-back, the following conditions should be satisfied: (1) the thickness of the continental lithosphere is significantly thin and less than 125 km and (2) the lithosphere has a wet and hot rheology, which provides implications for rheological layering in continental lithosphere. Our results are strongly supported by the “crème brûlée” model, in which the lower crust and mantle are relatively ductile. [ABSTRACT FROM AUTHOR]

Heat has a close relation to cratonic stability. We reconstructed the thermal history of the eastern North China, Wyoming, and Siberian cratons by using xenolith and thermal indicator data, and then the thermal lithospheric thickness in geological time was calculated by combining the crustal structural and thermal parameters. Researches from three cratons demonstrate that heat-flow values of the eastern North China Craton (eNCC) and Wyoming Craton (WC) have increased exceeding 20 mW/m2in the Meso-Cenozoic and the thermal lithospheric thickness has decreased by >100 km because of the cratonic destabilization. However, the thermal history variation of the Siberian Craton (SC) is small, ~5 mW/m2, the lithosphere has remained stable and it has experienced relatively little lithospheric thinning <100 km. The differences of the cratonic thermal regime are related to the breakup of the Pangea supercontinent. Destabilized cratons on active continental margin are directly affected by plate subduction. Stable cratons in the interior of the supercontinents are directly affected by the upwelling of superplumes and that may result in lithospheric thinning. Differences in the thermal evolutions of cratons provide new geothermal evidence for the different thermal regimes associated with the breakup of the Pangea supercontinent. [ABSTRACT FROM AUTHOR]

The Tarim Basin, which is the largest basin in Central Asia, experienced a complicated tectonic evolution along with the development of the South Tianshan, Kunlun Mountains, and the Tibetan Plateau during the Phanerozoic. This article provides a systematic overview of the thermal regime of the Tarim Basin based on new results and previous studies. The present-day average heat flow and geothermal gradient of the Tarim Basin are 42.5 ± 7.7 mW/m2 and 20.7 ± 2.9°C/km, respectively. The palaeo-geothermal gradient in the eastern and central parts of the Tarim Basin during the early Palaeozoic was 35–39°C/km, which is higher than the gradient of 28–34°C/km in the northwestern part of the Basin. The palaeo-geothermal gradient has decreased gradually since the late Palaeozoic. Except for the Southeast Uplift, the thickness of the thermal lithosphere in most of the Tarim Basin ranges from 164 km to 205 km, and the Moho temperature varies from 520°C to 614°C. The thermo-rheological structure of the lithosphere in the Tarim Basin can be approximated by a typical jelly sandwich model with the exception of the Southeast Uplift, which can be represented by a crème brûlée model. Generally, the long-term sedimentation and subduction of the adjacent mountains had an important effect on the spatial differentiation of the thermal regime in the Tarim Basin. This study provides a detailed description of the shallow and deep thermal states of the Tarim Basin, which are important for hydrocarbon exploration in the basin and structural research on Central Asia. [ABSTRACT FROM AUTHOR]

The Sichuan Basin is a prime petroliferous basin in China, and multiple overpressure systems exist vertically in the central portion of the basin. Understanding the mechanisms and evolution of an overpressure system is significant for petroleum migration and accumulation. DSTs and well logs data reveal that the Upper Triassic overpressures start at a depth of about 1300 m, and the pressure coefficient ( r ) is greater in the northwestern part of the study area ( r >1.8) and relatively lower in the south ( r ≈1.3). Sonic transit times of shales in the Upper Triassic Formation are abnormally high, and velocity-density plots deviate from the normal compaction trend, which demonstrate that disequilibrium compaction should be the primary mechanism of overpressures. Evolution history of overpressure was reconstructed based on numerical modeling method. The results from 1D and 2D modeling indicate that the Upper Triassic overpressures began developing at 195 Ma because of rapid sedimentation in this period. The maximum overpressure appeared at 90 Ma, which is 38 MPa in the Bajiaochang field and 50 MPa in the Anyue field, respectively. After that, pore pressure reduced to current value due to uplift and erosion that began in the Late Cretaceous. Overpressures are higher in the greater depth area and relatively lower at the structural crest. Gas generation from the Upper Triassic source rocks occurred during 160–90 Ma which is coincident with disequilibrium compaction. The contribution of gas generation to the Upper Triassic overpressures is not important, because gases just created small volume increase and likely to be expelled out by the high disequilibrium compaction overpressure in the corresponding period. Permeabilities of 10 −22 –10 −23 m 2 are required for barriers to maintain the overpressure in geological timescale. Overpressure systems in the central portion of the Sichuan Basin appear to be explained by static paradigms. For that, temperature has significant impact on the sealed systems. Greater pressures are preserved in the area with less temperature reduction. [ABSTRACT FROM AUTHOR]

The thermal history and organic matter maturity evolution of the source rocks of boreholes in the Puguang gas field were reconstructed. An integrated approach based on vitrinite reflectance and apatite fission track data was used in the reconstruction. Accordingly, the geothermal conditions of gas accumulation were discussed in terms of the geological features of reservoirs in the northeastern Sichuan Basin. The strata reached their maximum burial depth in the Late Cretaceous era and were then uplifted and denuded continuously to the present day. The geothermal gradient and heat flow in the Late Cretaceous era were approximately 30.0 °C/km and 66 mW/m, respectively, which were both higher than those at present. The tectonothermal evolution from the Late Cretaceous era to the present is characterized by denudation and cooling processes with an erosion thickness of ~2.7 km. In addition to the Triassic era, the Jurassic era represents an important hydrocarbon generation period for both Silurian and Permian source rocks, and the organic matter maturity of these source rocks entered into a dry gas period after oil generation. The thermal conditions are advantageous to the accumulation of conventional and unconventional gas because the hydrocarbon generation process of the source rocks occurs after the formation of an effective reservoir cap. In particular, the high geothermal gradient and increasing temperature before the denudation in the Late Cretaceous era facilitated the generation of hydrocarbons, and the subsequent cooling process favored its storage. [ABSTRACT FROM AUTHOR]

Thermal structure of the lithosphere studies the partition of crustal and mantle heat flow of the continental area and is of significant importance to understand various energy-related geodynamic processes. The study addresses the spatial distribution of the Meso-Cenozoic mantle heat flow and Moho temperatures in the region of the Bohai Bay Basin based on the thermal history of the sedimentary basin, radioactive heat production rate and thickness of crustal layering. The results show that the ratio of the mantle and surface heat flow (qm/qs) experienced two peaks in the late period of the Early Cretaceous (qm/qs ~ 68%) and the Middle to Late Palaeogene (qm/qs ~ 75%), respectively. Based on the qm/qs ratio, the lithosphere of the Bohai Bay Basin transformed its thermal structure during the Meso-Cenozoic, from the 'cold mantle but hot crust' stage in the Triassic-Jurassic to the 'hot mantle but cold crust' stage in the Cretaceous and Cenozoic. The Moho temperatures (Tm) during the Meso-Cenozoic were also calculated by using the equation of one-dimensional heat conduction, and the result shows that there exist three Tm peaks occurring in the late period of the Early Cretaceous (930-1080 °C), the Middle-Late Palaeogene (820-890 °C) and the Early Neogene (770-810 °C). The qm/qs ratio began to exceed 50%, and the Moho temperature started to go over 700 °C from the Cretaceous to the present day, which revealed that the activity of the upper mantle in the eastern North China Craton (NCC) increased significantly accompanied by the strong crustal movement in the Cretaceous. The thermal structure revealed the Cretaceous to be a revolutionary period during the evolution of the Bohai Bay Basin, and this paper may provide some thermal evidence for the studies of the geodynamic evolution during the destruction of the NCC. [ABSTRACT FROM AUTHOR]

The Kuqa Depression is part of a Mesozoic-Cenozoic foreland basin located at the northern margin of the Tarim Basin. High fluid overpressures were reported in the Mesozoic section related to both the complex tectonic evolution and the sealing by the salt-bearing sequence within the Paleogene Kumugeliemu Group. The role of structural evolution and compressional shortening in the generation of overpressures is poorly understood and requires a model-based understanding of the basin structure for different time steps. Structurally restored geometries based on a present-day geological section interpreted from a 2D seismic line, has been used as input for a basin and petroleum system model to simulate pore pressure history through geological time. In this simulation, we demonstrate structural dependencies of pore pressure development, and examine the impact of disequilibrium compaction, tectonic compression, opening and closing of faults over time, as well as folding on overpressure evolution. The poroelastic model is used to quantitatively evaluate the contribution of horizontal shortening due to tectonic compression on overpressure. We found that the pressure increase caused by 12.5% shortening can account for a maximum of more than 60% of overpressure, depending on lithology and deformation strength. We also simulated the effect of salt content within the seal layer on overpressure and found that the increase in salt has promoted the onset time and magnitude of overpressure in the underlying strata, which favors porosity preservation. A heat flow sensitivity analysis was performed, suggesting that the pressure increase caused by extremely high heat flow is rather low. • Integrating structural history and numerical simulation to model overpressure evolution. • Coupling disequilibrium compaction, tectonic compression, salt seal, fault, and fold. • Quantitatively evaluating the contribution of tectonic compression to overpressures. • Examine the effect of salt content in seal layer on the development of overpressures. [ABSTRACT FROM AUTHOR]

Buried-hill reservoirs in the Shulu Depression of the Jizhong Subbasin, Bohai Bay Basin have shown great exploration potential. However, the origins of natural gas and oil resources in buried-hill reservoirs are still uncertain, hindering future exploration. The present study is the first to provide a comprehensive investigation on geochemical characteristics and sources of natural gases and oils from buried-hill reservoirs in the Shulu Depression. The results show that the source rocks in the lower first member of the Paleogene Shahejie Formation (Es 1 L) in the Shulu Depression were deposited under anoxic brackish-water environments containing inputs of immature to low-mature organic matter (OM) derived from algae and planktons. In contrast, the lower third member of the Paleogene Shahejie Formation (Es 3 L) source rocks were deposited under suboxic fresh-brackish water environments with inputs of high-mature OM sourced from a mixture of planktons and land plants. The natural gases only presented in the paleo-uplifts in the East Sag of the Shulu Depression are characterized as shale-sourced gases and primary cracking gases, and mainly generated by the Es 3 L source rocks. Relative to the crude oils in the East Sag, the oils from the West Slope exhibit lower maturity and have experienced various degrees of biodegradation. Such spatial difference is probably due to the various depth and localities of corresponding source rocks. Low mature-mature oils in the shallow buried-hill reservoirs of the West Slope are mainly derived from the Es 3 L source rocks that are shallowly buried at the western edge of the East Sag. By comparison, highly mature oils in the deep buried-hill reservoirs are predominantly derived from the Es 3 L rocks deeply buried in central East Sag. In addition, variations in oil physical properties between the West Slope and the East Sag are probably caused by various maturations of source rocks and biodegradation of oils. Collectively, the results provide insights into the origins of hydrocarbons in the buried-hill reservoirs in the Shulu Depression and better knowledge needed for optimizing future exploration and production. •The paper provides the first comprehensive study on the sources of hydrocarbons in the Shulu Depression. •Natural gases in the Shulu Depression are shale-sourced and primary cracking gases. •Natural gases in the Shulu Depression are mainly sourced from the Es 3 L source rocks. •Oils in buried-hill reservoirs of the Shulu Depression come from the Es 3 L source rock. •Various maturations of source rocks and biodegradation of oils may cause spatial variations in oil physical properties. [ABSTRACT FROM AUTHOR]

Apatite fission track and vitrinite reflectance are integrated for the first time to study the cooling history in the Central Tarim, northwest China. The paleo-temperature profiles from vitrinite reflectance data of the Z1 and Z11 wells showed a linear relationship with depth, suggesting an approximately 24.8 °C/km paleo-geothermal gradient and 2700-3900 m of erosion during the Early Mesozoic. The measured apatite fission track ages from well Z2 in the Central Tarim range from 39 to 159 Ma and effectively record the Meso-Cenozoic cooling events that occurred in Central Tarim. Moreover, two cooling events at 190-140 Ma in the Early Jurassic-Early Cretaceous and 80-45 Ma in the Late Cretaceous-Paleocene revealed by measured AFT data and thermal modeling results are related to the collisions of the Qiangtang-Lhasa terranes and the Greater India Plate with the southern margin of the Eurasian Plate, respectively. This study provides new insights into the tectonic evolution of the Tarim Basin (and more broadly Central Asia) and for hydrocarbon generation and exploration in the Central Tarim. [ABSTRACT FROM AUTHOR]

The formation and evolution of a rift basin is the shallow response of deep geodynamic processes. The Bohai Bay Basin is at the center of lithosphere destruction and thinning in the eastern North China Craton (NCC). In this article, the Meso-Cenozoic thermal lithospheric thickness of the Bohai Bay Basin was calculated by reconstructing the thermal history of the sedimentary basin using apatite fission track and vitrinite reflectance data. The eso-Cenozoic thermal modeling results show that the basin experienced four evolutionary stages with two heat flow peaks in the late Early Cretaceous and in the iddle to Late Paleogene, which had heat flow values of 82-86 and 81-88mW/m², respectively. Accordingly, the thermal lithospheric thicknesses of the basin, calculated from the thermal histories, experienced two thinning stages in the Cretaceous and the Paleogene. The lithosphere began with an initial thickness of 150 km in the Early Mesozoic and was thinned to approximately 51-61 km in the late Early Cretaceous. The thickness then increased to approximately 80-90 km at the end of the Cretaceous. A second thinning phase occurred in the Middle to Late Paleogene, resulting in a thickness of only 43-55 km. The lithosphere thickened thereafter, and the NCC now has a thermal lithosphere of 75-97 km. The lithospheric thinning in the Cenozoic was dominated by extension rather than thermal erosion. At the same time, there existed some differences in the thermal evolution and lithospheric thinning evolution among different sub-basins, but the time of peak heat flow and peak lithosphere thinning in the Cenozoic is consistent with the migration of the depocenter of the basin. Therefore, the thermal history of sedimentary basins may provide continuous temporal and spatial evidence to reveal deep geodynamic processes. Our research provides new geothermal evidence for the lithospheric thinning of the NCC. [ABSTRACT FROM AUTHOR]

The Tarim Block, one of the largest Precambrian cratonic blocks in East Asia, is located in northwestern China. The Precambrian formation and evolution of the Tarim Block, and its tectonic affinity to other major continental blocks in China, specifically the North China Craton (NCC) and the South China Block (SCB), remain poorly understood, in spite of their implications for understanding the ancient tectonic framework of East Asia. To achieve a better understanding of the Precambrian tectonothermal history of the Tarim Block, we have undertaken U–Pb dating and Lu–Hf isotopic analyses of detrital zircons from late Neoproterozoic–early Permian sandstones in the Aksu area of the northwestern Tarim Basin. The morphologies, Th/U ratios, U–Pb ages and Lu–Hf isotopes of these detrital zircons indicate magmatic episodes took place in the late Neoarchaean–early Palaeoproterozoic (ca. 2.6–2.4 Ga, peak at 2.48 Ga), middle Palaeoproterozoic (ca. 2.0–1.8 Ga, peak at 1.87 Ga), latest Mesoproterozoic–early Neoproterozoic (ca. 1.05–0.9 Ga, peak at 0.94 Ga), middle Neoproterozoic (ca. 0.85–0.7 Ga, peak at 0.78 Ga), and early Palaeozoic (ca. 0.45–0.4 Ga, peak at 0.43 Ga). By integrating our results with previous geological observations, we argue that the Tarim Block as a whole was affected by Precambrian tectonothermal events at ca. 2.6–2.4, 2.0–1.8, 1.05–0.9 and 0.85–0.7 Ga. These events are respectively thought to have been associated with a late Neoarchaean–early Palaeoproterozoic global continent-building event, the assembly of the Palaeoproterozoic Columbia supercontinent, the latest Mesoproterozoic–early Neoproterozoic accretion of the Tarim Block to the Rodinia supercontinent, and the middle Neoproterozoic separation of the Tarim Block from Rodinia. Comparisons of detrital zircon U–Pb age spectra, geochronological data for magmatic and metamorphic rocks, in situ zircon Lu–Hf isotopes, and other geological data from among the Tarim Block, the NCC and the SCB point to a close tectonic affinity between the Tarim Block and the SCB in the Neoproterozoic. However, during 2.6–1.8 Ga, the Tarim Block underwent a different tectonic evolution from the SCB, and instead was tectonically linked to the NCC. [ABSTRACT FROM AUTHOR]

[Display omitted] • Except for the areas with magma intrusion, the Emeishan mantle plume has no impact on the Permian source rocks' maturity evolution. • Maturity evolution of Permian source rocks was mainly controlled by Mesozoic sedimentation and uplift. • There are three maturity evolutionary patterns: Middle Permian maturing abrupt jump, Mesozoic continuous heating and Middle-Late Triassic heating cessation. The Permian source rocks in the Sichuan Basin, Southwestern China, are hypothesized to have undergone thermal over-maturation associated with the Emeishan mantle plume. In this study, by comparing the maturity evolution of Permian source rocks, we identified three maturity evolutionary patterns, including (1) Middle Permian maturing abrupt jump in the areas where the Permian magmatic intrusions, (2) Mesozoic continuous heating in the southwestern Sichuan Basin, and (3) Middle-Late Triassic heating cessation common in the Sichuan Basin. Furthermore, we assess the evolution model of the Emeishan large igneous province and investigate the thermal effect of the mantle plume on hydrocarbon maturation of Permian source rocks. During the mid-Guadalupian, the mantle upflow reached the base of the northeastern Sichuan Basin and little eruptions and intrusions formed along the basement faults. As the South China block kept moving northward, the major eruption and crustal magma underplating occurred at the end-Guadalupian near the southwest margin of the Sichuan Basin. The mantle plume caused the Middle-Lower Permian source rocks in the intrusion area to mature rapidly and achieve peak maturity (R equ > 3%) during the Middle Permian. Except for the areas with magma intrusion, the mantle plume had no obvious impact on the maturity evolution of the Permian source rocks and the maturity evolution is controlled by Mesozoic sedimentation and uplift. In addition to providing new insights into the thermal effects of the Emeishan Permian mantle plume, this study has great implications for gas exploration in the Sichuan Basin. [ABSTRACT FROM AUTHOR]

The thermal history of sedimentary basins is a key factor for hydrocarbon accumulation and resource assessment, and is critical in the exploration of lithospheric tectono-thermal evolution. In this paper, the Cenozoic thermal histories of nearly 200 wells and the Mesozoic thermal histories of 15 wells are modeled based on the vitrinite reflectance and apatite fission track data in Bohai Bay Basin, North China. The results show that the basin experienced Early Cretaceous and Paleogene heat flow peaks, which reveals two strong rift tectonic movements that occurred in the Cretaceous and the Paleogene in the basin, respectively. The thermal evolution history in Bohai Bay Basin can be divided into five stages including (1) the low and stable heat flow stage from the Triassic to the Jurassic, with the heat flow of 53 to 58 mW/m; (2) the first heat flow peak from the Early Cretaceous to the middle of the Late Cretaceous, with a maximum heat flow of 81 to 87 mW/m; (3) the first post-rift thermal subsidence stage from the middle of the Late Cretaceous to the Paleocene, with the heat flow of 65 to 74 mW/m at the end of the Cretaceous; (4) the second heat flow peak from the Eocene to the Oligocene, with a maximum heat flow of 81 to 88 mW/m; and (5) the second thermal subsidence stage from the Neogene to present, with an average heat flow of 64 mW/m. [ABSTRACT FROM AUTHOR]

This article discusses the Meso–Cenozoic thermal history, thermal lithospheric thinning, and thermal structure of the lithosphere of the Bohai Bay Basin, North China. The present-day thermal regime of the basin features an average heat flow of 64.5 ± 8.1 mW m–2, a lithospheric thickness of 76–102 km, and a ‘hot mantle but cold crust’-type lithospheric thermal structure. The Meso–Cenozoic thermal history experienced two heat flow peaks in the late Early Cretaceous and in the middle to late Palaeogene, with heat flow values of 82–86 mW m‒2and 81–88 mW m‒2, respectively. Corresponding to these peaks, the thermal lithosphere experienced two thinning stages during the Cretaceous and Palaeogene, reaching a minimum thickness of 43–61 km. The lithospheric thermal structure transformed from the ‘hot crust but cold mantle’ type in the Triassic–Jurassic to the ‘cold crust but hot mantle’ type in the Cretaceous–Cenozoic, according to the ratio of mantle to surface heat flow (qm/qs). The research on the thermal history and lithospheric thermal structure of sedimentary basins can effectively reveal the thermal regime at depth in the sedimentary basins and provide significance for the study of the basin dynamics during the Meso–Cenozoic. [ABSTRACT FROM AUTHOR]

Geochemical fingerprinting of formation waters and hydrocarbons can be utilized to track the migration, accumulation, and preservation of hydrocarbons. The present case study from the Shulu Sag, Bohai Bay Basin, NE-China analyzes the origin of the formation waters and the relationship between water chemistry and hydrocarbon preservation by combining the geochemical characteristics of formation waters and crude oils. There are three geochemical groups of formation waters with different origins, which represent different hydrodynamic environments and hydrocarbon preservation conditions. Group 1 waters are related to meteoric water with the lowest total dissolved solids (TDS), γ(Cl–Na)/γMg and the highest γNa/γCl, representing an open environment with poor hydrocarbon preservation conditions, accompanied by super heavy oils. Group 3 waters are connate water with the highest TDS, γ(Cl–Na)/γMg and the lowest γNa/γCl, representing a closed environment with the best hydrocarbon preservation conditions, accompanied by light oils. Group 2 waters are intermediate between Group 1 and Group 3 waters, representing a semi-open environment with intermediate hydrocarbon preservation conditions, accompanied by light, medium, and heavy oils. The clear corresponding relationship between oil quality and associated water type shows that water chemistry significantly affects the oil quality and accumulation in the Shulu Sag through secondary changes. Biodegradation is the dominant effect in the strata above 2100 m. Water washing is dominant in the depth range of 2100–3400 m, and there are no noticeable secondary changes in the strata below 3400 m. A model for the origin, evolution, and flow of formation waters in the Shulu Sag is established to analyze the hydrocarbon accumulation process. Meteoric waters flow into the buried hills from Ningjin Uplift as a result of gravity flow, resulting in modification of oil composition, destruction of the oil reservoirs, and the formation of Group 1 waters. During the hydrocarbon charging, the centrifugal flow driven by overpressure flows in two directions from the source rocks, one is to the western slope and mixes with meteoric waters to form Group 2 waters and heavy oil reservoirs, and the other is to the paleo-uplift to form Group 2 and Group 3 waters and light oil reservoirs. Water chemistry is sensitive to the hydrodynamic environment change and can be an important reference for oil and gas exploration. Buried hills with Group 3 waters should be the highest priority for further exploration, whose oil reservoirs are dominated by light oil with high commercial value. Although the oil quality is poor, buried hills with Group 2 waters in the slope can be secondary targets. In comparison, the buried hills with Group 1 waters should be avoided for oil and gas exploration. The geochemistry of formation waters helps understand the origin and evolution of formation waters, predict oil quality and distribution, and further aids oil and gas exploration. • Three types of formation water with different characteristics were identified. •A clear relationship between oil quality and associated water type was defined. •The hydrogeological model and its relationship to oil accumulation were established. •The hydrocarbon preservation condition was evaluated from the water chemistry. [ABSTRACT FROM AUTHOR]

This study provides new insight for kinematic restoration in the thrust nappe and the effect of tectonic evolution on shale gas preservation was demonstrated in a case study from the Dingshan area in the southeastern Sichuan Basin, southwest China. The uplift process was reconstructed by sandbox experiment, discrete element method, vitrinite reflectance and thermochronology data, including apatite fission track, apatite (U–Th)/He and zircon (U–Th)/He. Thermo-kinematic analysis indicated that from southeast to northwest, the initial uplift time was getting earlier and the erosion increased, while the horizontal displacement decreased during the Alpine stage (Early Cretaceous-Eocene). During the Himalayan stage (Eocene-present time), it was characterized with rapid uplift as a whole. To study dynamic evaluation of shale gas preservation during tectonic evolution, the temperature and pressure evolution were revealed combining fluid inclusion analysis and basin modeling and variation in shale gas content was quantified. Differential uplift caused obvious differences in the process of cooling, pressure decreasing, fracturing and shale gas losing. With moderate uplift (∼3350–3550 m), a few fractures generated in the shale and roof and few gas (∼0.95–1.72 m3/t) diffused laterally. Enormous uplift (∼5350 m) resulted in obvious fractures and massive gas loss (∼3.22 m3/t) by lateral diffusion and vertical dissipation. • Tectonic evolution of thrust nappe revealed by new thermo-kinematic method. • Firstly proposed the burial-hydrocarbon generation-uplift-gas loss evolution of shale. • Dynamic analysis of shale gas preservation and loss during different uplift process. • Evidence for the effect of tectonism on the shale fracturing at a regional scale. [ABSTRACT FROM AUTHOR]

The Dongpu sag is located in the south of the Bohai Bay basin, China, and has abundant oil and gas reserves. To date, there has been no systematic documentation of its geothermal fields. This study measured the rock thermal conductivity of 324 cores from 47 wells, and calculated rock thermal conductivity for different formations. The geothermal gradient and terrestrial heat flow were calculated for 192 wells on basis of 892 formation-testing data from 523 wells. The results show that the Dongpu sag is characterized by a medium-temperature geothermal field between stable and active tectonic areas, with an average geothermal gradient of 32.0°C/km and terrestrial heat flow of 65.6 mW/m2. The geothermal fields in the Dongpu sag is significantly controlled by the Changyuan, Yellow River, and Lanliao basement faults. They developed in the Paleogene and the Dongying movement occurred at the Dongying Formation depositional period. The geothermal fields distribution has a similar characteristic to the tectonic framework of the Dongpu sag, namely two subsags, one uplift, one steep slope and one gentle slope. The oil and gas distribution is closely associated with the present geothermal fields. The work may provide constraints for reconstructing the thermal history and modeling source rock maturation evolution in the Dongpu sag. [ABSTRACT FROM AUTHOR]

The Liaohe (辽河) depression is an important part of the Bohai (渤海) Bay Basin, and the Bohai Bay Basin located in the center of lithospheric destruction and thinning in the eastern North China Craton. The North China lithospheric thinning activities have been verified from evidences of structural geology, petrology, geochemistry and geophysics, but there are still some controversies on their timing, mechanism and controlling factors. The sedimentary basin is a thin-bedded geologic unit with a limited distribution in the upper lithosphere, and its formation and evolution represent the shallow response of the deep geodynamic process. Therefore, its thermal evolution is closely related to the deep dynamic conditions. In this article, the Mesozoic-Cenozoic thermal history of the Liaohe depression is reconstructed using the vitrinite reflectance and apatite fission track data. Meanwhile 'thermal' lithospheric thicknesses in the Mesozoic and Cenozoic are calculated using the geothermic method on the basis of the above thermal history results. The results show that the Liaohe depression has under- peaks, 81 and 83 mW/m, respectively, corresponding to two strong rift movements. Accordingly, the depression has experienced two different levels of thinning processes in the Cretaceous and the Paleogene since the Mesozoic, and the 'thermal' lithospheric thicknesses were 60 and 50 km, respectively. This may reveal that the depression has experienced two large-scale destructions. The work may provide valuable geothermal evidence for initial revealing the time, process and stage of the lithospheric thinning in the Liaohe depression. [ABSTRACT FROM AUTHOR]

The emplacement of the Late Permian Emeishan large igneous province (ELIP) in the Upper Yangtze craton, SW China, is considered to be a crucial factor that triggered the end-Guadalupian biodiversity crisis. However, the contribution of ELIP remains debated because of its relatively modest known size. The restricted assessment of its areal extent is, in part, due to the lack of study of the potential volcanic rocks concealed beneath younger strata. Here we present the first geochemical and isotopic variations and detailed spatial distribution of Late Permian basaltic rocks penetrated by deep exploratory boreholes in the Sichuan Basin. The Late Permian basaltic rocks are mainly distributed in the western and northeastern parts of the Sichuan Basin and are positioned at the same stratigraphic level as the Emeishan flood basalts. Petrography, whole-rock trace elements and Sr-Nd-Pb isotopic compositions demonstrate that these rocks are alkaline basalts and have oceanic island basalt - like characteristics, indicating a similar origin as the Emeishan flood basalts. The trace element and isotope ratios suggest that the basaltic magmas in the western Sichuan Basin were derived by low degrees of partial melting of a garnet-bearing source. In contrast, the basalts in the northeastern part of the basin were generated by higher degrees of melting of a shallower mantle source in the spinel-garnet transition zone. Varying amounts of contamination by lower continental crustal melts are suggested by rough correlations between isotope and immobile trace element ratios. The spatial changes in composition and origin of the basaltic rocks in the Sichuan Basin can be interpreted as the result of varying extents of Emeishan mantle plume-lithosphere interaction under different lithospheric stress backgrounds, such that the reactivation of pre-existing basement faults controlled the emplacement of basaltic magma in the periphery of the ELIP. Our work reveals a substantially broader extent of the ELIP in buried sedimentary strata, which might have contributed to the abrupt end-Guadalupian climatic change. [Display omitted] [ABSTRACT FROM AUTHOR]

Thermal regime and thermal history are of significant important in basin dynamics and hydrocarbon generation of source rocks. The sedimentary basins in three typical cratons of China, North China Craton (NCC), Yangtze Craton (YC) and Tarim Craton (TC), underwent completely different tectonic background and dynamic mechanism, which resulted in the differentials of their thermal regimes. In this paper, the thermal regimes of the Bohai Bay Basin in the eastern NCC, Tarim Basin in TC, and Sichuan basin in the Upper YC were studied. There has some lower thermal background in the area of western China than eastern side of the NCC. The mean heat flow value of Tarim basin is 42.5 mW/m2, 53.8 mW/m2 in the Sichuan basin and 66.7 mW/m2 in the eastern NCC. And the temperature at 10000 m ultra-depth in the Tarim Basin also shows lower values than that of Sichuan and Bohai Bay basins. The thermal history, modeled from thermal indicators of vitrinite reflectance (R o), equivalent vitrinite reflectance data (R equ), fission track and (U Th)/He data of apatite and zircon, evolved differently because of the different tectonic history in these basins. The Tarim basin underwent a cooling history with the heat flow of 55–65 mW/m2 in the Cambrian decreasing to the present-day of 40–50 mW/m2. The Meso-Cenozoic thermal history of the Bohai Bay basin experienced four evolutionary stages with two heat flow peaks in the late Early Cretaceous and in the Middle to Late Paleogene, which correspond to the destruction peaks of the eastern NCC and had heat flow values of 82–86 mW/m2 and 81–88 mW/m2, respectively. The Sichuan basin was stable with heat flow value of less than 65 mW/m2 from the Late Sinian to Late Paleozoic, and the heat flow increased rapidly to the peak value (75–100 mW/m2) at the end of Early Permian by thermal effect of the Emeishan mantle plume. From Mesozoic to present, the heat flow decreased to the present value (60–70 mW/m2). In addition, the comparation of thermal characteristics of typical cratons around the world, including heat flow, thermal history, lithospheric thermal structure and thermal lithospheric thickness, also have been caried out. The differential thermal histories of Tarim and Sichuan basins resulted in the different thermal evolution of Cambrian source rocks. This study may provide some new geothermal evidence for hydrocarbon generation and phase distribution of oil and gas in the deep and/or ultra-deep basin. Thermal regime and thermal history of typical sedimentary basins in three typical cratons of China underwent completely different evolution. The Tarim basin underwent a cooling history, the Bohai Bay basin experienced four evolutionary stages with two heat flow peaks, and the Sichuan basin was stable with heat flow but to a peak at the end of Early Permian. Nansheng Qiu, Chang Jian, Zhu Chuanqing, Liu Wen, Zuo Yinhui, Xu Wei, Li Dan. [Display omitted] • Three typical cratons of China show great differences in heat flow and deep-temperature. • Three typical cratons of China show great differences in lithospheric thickness from 76–170 km. • Thermal histories of Bohai Bay, Sichuan and Tarim basins are summarized. • Thermal regime between stable and destabilized cratons are compared. • Three thermal evolution patterns of source rocks are obtained. [ABSTRACT FROM AUTHOR]

The relationship between the tectonic event of the Linqing Sub-basin and the destruction of the North China Craton (NCC) is an important factor to consider when studying geodynamic mechanisms in eastern China. In the current study, we present a low-temperature apatite thermochronological analysis of 14 samples to study the tectonic event of the Linqing Sub-basin. Our data showed that the apatite fission track (AFT) ages were in the range of 53.5–124.4 Ma, and the average track lengths were 8.00–11.24 μm. The grain ages showed that 10 samples had mixed ages and were characterized by discordant distribution. The minimum ages decomposed from AFT ages mainly ranged from 105.3 to 40.8 Ma. We identified a break-in-slope from the depth-minimum age profile, which was related to the Meso-Cenozoic tectonic event. The AFT age data could be decomposed into three age groups, namely, P3 (394.8–215.7 Ma), P2 (124.6–83.4 Ma), and P1 (70.7–40.8 Ma), indicating three significant tectonic events in the NCC. P3 is related to the uplift of the NCC at 445.0–315.0 Ma and deformation and magmatism at 320.0–200.0 Ma. P2 corresponds to the Mesozoic tectonic activities, such as the closure of the Mongol–Okhotsk Ocean, the turning of the Izanagi plate and mantle convection. P1 mainly corresponds to the Izanagi–Pacific ridge, the closure of the Tethys Ocean, and the rotation of the Philippine Sea plate in the Cenozoic. Our study provides evidence for the destruction of the NCC, and has significance for the understanding of the deep mechanism. [ABSTRACT FROM AUTHOR]

Abstract: The northwestern edge of the Tarim Basin, which contains the Kalpin Uplift and the north Bachu Uplift, lies between the South Tianshan and Tarim continental block and its tectonic evolution is closely correlated with the Tianshan. The pre-Mesozoic units are widely exposed in the northwestern edge of the Tarim Basin, which allow detailed geological observation and sample collection. In this paper, the apatite (U–Th)/He thermochronology was used to study the tectono-thermal evolution of the northwestern edge of the Tarim Basin. The sandstone samples from the Upper Neoproterozoic, Silurian, Devonian, Carboniferous and Permian units, etc. on the northwestern edge of the Tarim Basin were collected and used to determine apatite (U–Th)/He ages. The apatite He ages in the Kalpin Uplift reveal the tectonic uplift events during the Late Cretaceous (96–70Ma) and the Miocene (22–20Ma). These uplift events are linked to collisions of the Lhasa Block and the India plate with the southern Eurasian continental margin, respectively. However, apatite He ages in the north Bachu Uplift show only the Eocene event at ∼40Ma because the west Kunlun orogenic belt thrust over the southwestern edge of the Tarim Basin during the Eocene. The thermal modeling results reveal four cooling events in the Kalpin Uplift since the Late Neoproterozoic, corresponding to 460–445Ma, 350–320Ma, 220–210Ma and 20–10Ma but only one episode with 220–210Ma in the north Bachu Uplift since the Devonian. Based on the thermal modeling results, the north Bachu Uplift did not experience the cooling events at 460–445Ma, 350–320Ma and 20–10Ma shown in the Kalpin Uplift. This paper provides a new insight into the tectonic evolution of the Tianshan and the northwestern Tarim Basin. [Copyright &y& Elsevier]

The apatite (U-Th)/He thermochronometry has been used to study the tectono-thermal evolution of mountains and sedimentary basins for over ten years. The closure temperature of helium is important for the apatite (U-Th)/He thermochronometry and has been widely studied by thermal simulation experiments. In this paper, the apatite He closure temperature was studied by establishing the evolutionary pattern between apatite He ages and apatite burial depth based on examined apatite He ages of natural samples obtained from drillholes in the Tarim basin, China. The study showed that the apatite He closure temperature of natural samples in the Tarim basin is approximately 88±5°C, higher than the result (∼75°C) obtained from the thermal simulation experiments. The high He closure temperature resulted from high effective uranium concentration, long-term radiation damage accumulation, and sufficient particle radii. This study is a reevaluation of the conventional apatite He closure temperature and has a great significance in studying the uplifting events in the late period of the basin-mountain tectonic evolution, of which the uplifting time and rates can be determined accurately. [ABSTRACT FROM AUTHOR]

Abstract: The timing of the transition of a peripheral foreland basin from underfilled to overfilled provides important insights into the post-orogenic dynamics of its coupled orogenic wedge. Such information is lacking in the Mesozoic foreland basins surrounding the Qinling Orogen, central China, such as the Daba Shan Foreland Basin (DSFB), the northeastern part of the Sichuan Basin. In an effort to constrain the timing of maximum burial and onset of denudation, we report detrital zircon (U–Th)/He (ZHe) data from four deep boreholes in the DSFB. Results show that ZHe ages from the oldest foreland basin formations (Upper Triassic–lower Middle Jurassic) are mostly younger than their depositional age, whereas non-reset ZHe ages characterize younger strata. This suggests that the oldest strata attained maximum temperatures between ~130°C and 200°C (ZHe partial retention zone), which is consistent with previous independent paleotemperatures (organic matter reflectance and illite crystallinity) reported in two of the boreholes and another nearby. The fully reset ages apparently show the youngest peaks at ~80Ma and ~100Ma, which are interpreted as the minimum constraints on the timing of maximum basinal burial and subsequent denudation. Considering that the regional deposition has lasted to Aptian time, it is proposed that the onset of the basin exhumation in the DSFB started at Aptian–Albian time (~100–125Ma), heralding the termination of regional tectonic shortening in the hinterland (Southern Qinling). [Copyright &y& Elsevier]

We identified a Neogene rapid uplift-denudation event of the South Tianshan based on apatite (U-Th)/He and apatite fission track (AFT) ages in Tertiary rocks of the Tarim basin, using borehole samples. The (U-Th)/He thermochronology can be used to reveal the tectono-thermal events with lower temperature than that of AFT thermochronology and has not been used previously to study the uplift of the Tianshan Mountain. Using these data, we show the relationship between the uplift of the South Tianshan and the subsidence/deposition of the northern Tarim basin during the Neogene. The apatite helium ages reveal the migration of uplift, erosion and deposition in the northern Tarim basin. A rapid uplift of the South Tianshan during the Miocene and a corresponding rapid subsidence in the northern Tarim basin occurred. However, in the Pliocene, the Kuqa Depression and South Tianshan uplifted and eroded at the same time and in turn provided the detrital source rocks for the Northern Uplift of the Tarim basin. In contrast to earlier studies, we arrive at the conclusion that the South Tianshan experienced rapid uplift in the Miocene based on (U-Th)/He data of apatite obtained from borehole samples collected in the Tarim basin itself, and not from the bordering mountain chain. Combined apatite (U-Th)/He and fission track thermochronometry enables reconstruction of thermal histories of sedimentary rocks between 40 and 120°C, and this has implications for the generation of liquid hydrocarbon in the 65-120°C range in the basin. Thermal and burial histories of typical samples were also modelled to show the rapid uplift in our study. Our works not only provide a new evidence for the South Tianshan uplift but also indicate that there is a coupling between uplift and subsidence in the South Tianshan and adjacent northern part of the Tarim basin, which controlled hydrocarbon accumulation in the Kuqa Depression and Northern Uplift of the Tarim basin. [ABSTRACT FROM AUTHOR]

Abstract: This study uses a new application of the apatite and zircon (U–Th)/He thermochronometry technique to investigate the thermal history and tectonic uplift of sedimentary basins. Based on measured apatite and zircon (U–Th)/He ages, apatite fission track data and equivalent vitrinite reflectance measurements of borehole core samples, the thermal history of the Bachu Uplift of the Tarim Basin was modeled. Our analysis indicates a complicated thermal history in the Bachu Uplift region during the Paleozoic. The thermal gradient initially increased from 28–30°C/km in the Cambrian period to 30–33°C/km in the Ordovician period and increased up to 33–34°C/km in the Silurian period. The thermal gradient began to decrease during the Devonian period and was estimated to be approximately 30°C/km during the Late Devonian and the Early Carboniferous periods. The low thermal gradient phase was followed by an additional high gradient phase from the Late Carboniferous to the Early Permian when the gradient was approximately 32°C/km. Thermal gradients in the Paleozoic were substantially different than the present-day gradient (21°C/km). Tectonothermal modeling results also revealed uplift events in the Bachu Uplift region that shifted from south to north (e.g., ∼150Ma to ∼100Ma) and from west to east (e.g., ∼250Ma to ∼150Ma). This thermal evolution of the Bachu Uplift is consistent with its tectonic progression. The thermal spike in the Late Carboniferous and Early Permian periods could be related to magmatic activities in the Early Permian period. The Paleozoic thermal history of the Bachu Uplift region of the Tarim Basin could not be reconstructed properly due to a lack of reliable thermal indicators in the Lower Paleozoic successions, and a poor understanding of the thermal evolution of Lower Paleozoic source rocks during the Paleozoic has hindered petroleum exploration in this area. This study provides a new Paleozoic thermal history and shows that the Paleozoic thermal history plays an important role in the maturation process of the Lower Paleozoic source rocks. [Copyright &y& Elsevier]

The Emeishan mantle plume is supposed to play an important role in the Permian thermal regime and source rock hydrocarbon generation evolution in the Sichuan Basin, Southwest China. In this paper, we provide new valuable insights into the spatial thermal effect of the Emeishan mantle plume to the Sichuan basin and maturity evolution of the Paleozoic source rocks. Cambrian core samples from four wells were selected for zircon fission track and zircon (U–Th)/He analysis in order to determine their thermal histories. Then the thermal histories of typical wells throughout the basin were obtained based on the above result and previous studies. According to the peak heat flow value (q), four Permian geothermal units were classified: a stratospheric heat flow unit (q ≥ 90 mW/m2), a high heat flow unit (80 ≤ q < 90 mW/m2), a medium heat flow unit (70 ≤ q < 80 mW/m2), and a normal heat flow unit (q < 70 mW/m2). The interpretation of the abnormal Permian heat flow indicates that the enormous heat flow anomalies with values of >20 mW/m2 occurred in the stratospheric and high heat flow units was mainly caused by the mantle plume, while the weak Permian thermal perturbation with heat flow anomalies of <15 mW/m2 in other two units was more likely associated with crustal thinning. The thermal effect of the Emeishan mantle plume may be contained within the stratospheric and high heat flow units. By comparing the maturation histories of the Paleozoic source rock, we identified the thermal effect on the maturity evolution. The thermal perturbation had no obvious impact on the maturity evolution of the Lower Permian and Lower Silurian Longmaxi Formation. Only the Lower Cambrian Qiongzhusi Formation within high geothermal unit suffered significant thermal effect of the mantle plume and matured rapidly during the end of the Early Permian. • Four Permian geothermal units in the Sichuan basin were first classified. • New insight for the spatial thermal effect of Emeishan mantle plume. • Formation mechanism of Permian heat flow anomalies was identified. • The effect of mantle plume on the maturity evolution of source rocks was characterized. [ABSTRACT FROM AUTHOR]

Abstract: The relationships between free radical concentration (N g) and vitrinite reflectance (%R o) of coal were tested through 36 laboratory anhydrous pyrolysis experiments. The experiments were carried out at isothermal reactor with pyrolysis temperatures ranging from 300 to 550 °C over 30–480 min. The effects of temperature and retention time on the N g were investigated. The concentrations of free radicals in pyrolysis coal samples increase with increasing time and temperature of experiments and reach a maximum value at about 1.75 %R o, and then decrease with further maturation. The Temperature Time Index (TTI) integral equation was applied to establish the relationship between the TTI and N g in this paper. As the free radical concentration in organic matter is strongly maturity dependent, it may prove to be a valuable geothermometer for paleogeotemperature study in sedimentary basins. [Copyright &y& Elsevier]