Cenozoic exhumation in the Tianshan is controlled by a complex interaction between tectonics and climate. However, the timing and magnitude of exhumation of the Tianshan and its contribution to ...climate change in Central Asia remains debated. In this study, we report new apatite fission track and (U‐Th)/He ages for granite samples from the roof of the South Tianshan that are significantly younger than those published for other parts of the South Tianshan. Inverse and forward modeling reveals two phases of accelerated cooling at 10∼6 Ma and since ∼3 Ma, which can be linked to (1) the reactivation of strike‐slip faults and hot asthenospheric upwelling during India‐Eurasia convergence and (2) the interplay between tectonics and glaciation, respectively. The 10∼6 Ma exhumation phase further corresponds to the timing of climate change, suggesting that this exhumation phase significantly contributed to the enhanced aridification of the Tarim Basin.
Plain Language Summary
The tectonic uplift of the Mountains is closely related to climate change in nearby areas, e.g. the uplifting of the Tibetan Plateau plays an important on the aridification of the Tarim Basin since the Cenozoic. This study reported a new set of low‐temperature thermochronological data from the high‐elevation area of the Tianshan. They revealed the rapid exhumation of the central Chinese South Tianshan during 10.0‐6.0 Ma, simultaneous with the enhanced aridification of the Tarim Basin. Therefore, we speculated that the uplift of the central South Tianshan have effectively blocked the humid westerlies from the Atlantic and Indian Oceans to enter the Tarim Basin and enhanced the aridification in the Tarim Basin during the late Miocene.
Key Points
We present a new set of AFT and AHe data for the Central South Tianshan, Central Asia.
The Central South Tianshan experienced two phases of accelerated cooling occurred during 10∼6 Ma and since ∼3 Ma
Rapid exhumation of the South Tianshan significantly contributed to the enhanced aridification of Tarim Basin during Late Miocene.
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 800–1400km 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 76mW/m2 to 51mW/m2. Thermal history modeling results show that an abnormal high paleo-heat flow of 90–110mW/m2 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 ~1600–1800km. Our research provides new insights into the geodynamics of the Emeishan mantle plume through study of heat flow.
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•The regional heat flow is examined to trace the after effects of the Emeishan mantle plume.•Paleogeothermal indicators were used to constrain the thermal effect of the Emeishan large igneous province.•New geothermal evidence for the pre-volcanism uplift and implications for the lateral extent of the Emeishan mantle plume
•The temperature and pressure evolution of the Precambrian reservoirs in South China was first reconstructed by comprehensive method including paleo-thermal indicators, inclusions PVT simulation and ...basin modeling.•The thermal history of the Gaoshiti-Moxi area experienced stable normal heat flow before Late Paleozoic, short-term high heat flow during Middle-Late Permian and back to normal thermal background now.•The pore pressure evolution of the Sinian reservoirs (574–541 Ma) in Gaoshiti-Moxi area could be divided into four stages, especially the overpressure reached maximum at the end of early Cretaceous.
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/m2). During the Early Paleozoic, the heat flow increased rapidly to the peak value (75–100 mW/m2). From Mesozoic to present, the thermal subsidence occurred in the basin with the heat flow decreasing to the present value (60–70 mW/m2). 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.
The Tianshan in western China is rich in ore resources, but its tectonic uplift and exhumation history closely related to the resource exploration is still controversial. This study provides a new ...strategy to uncover the tectonic uplift processes in southern Tianshan by combining the morphological characteristics and thermochronological ages of detrital zircons in the Tarim Basin. The morphology of the Meso-Cenozoic detrital zircons in the Kuqa Foreland Basin, a secondary tectonic unit of the Tarim Basin, is dominated by three types of P, S, and G, and their average alkaline and temperature indexes are 668.0−677.2 and 347.6−413.5, respectively. Moreover, the U-Pb ages of these detrital zircons are primarily divided into two groups of 270−330 and 380−470 Ma. These features indicate that the Early Carboniferous-Early Permian and Middle Ordovician-Middle Devonian alkaline granites distributed in the South Tianshan and southern Central Tianshan were the main sources of the detrital zircons in the Kuqa Foreland Basin. The decomposition of the detrital zircon fission track ages further reveals that the provenances of the Kuqa Foreland Basin primarily consisted of the southern Central Tianshan, the eastern South Tianshan, and the central South Tianshan during Meso-Cenozoic. Among them, the eastern South Tianshan played a dominant role in the material supply. The synthesis of the decomposed zircon fission track (ZFT) ages and the lag-time evolution pattern indicated that the South Tianshan and the southern Central Tianshan mainly experienced five stages of tectonic uplifting that occurred in the Devonian, the Permian, the Middle Triassic-Middle Jurassic, the Cretaceous, and since the Miocene, respectively. They were related to the subduction of the South Tianshan Ocean northward to the bottom of the Central Tianshan, the compression and accretion after the closure of the South Tianshan Ocean, and a series of collisions between the Qiangtang-Lassa-India plates and the southern margin of the Eurasia plate in the Meso-Cenozoic, respectively. This study provides a new provenance analysis method, which was successfully applied in the Tianshan, and also develops a new way to study Central Asia’s tectonic evolution.
The Bohai Bay Basin is at the center of lithosphere destruction and thinning in the eastern North China Craton (NCC). In this paper, the thermal lithospheric thicknesses of the Meso-Cenozoic Jiyang ...sub-basin in the Bohai Bay Basin were calculated by reconstructing the thermal history of the sedimentary basin using apatite fission track and vitrinite reflectance data. The results show that the Jiyang sub-basin experienced two heat flow peaks in the late Early Cretaceous and in the Middle to Late Paleogene, with heat flow values of 84~88mW/m2 and 85~88mW/m2, respectively. The thermal lithosphere thicknesses of the Jiyang sub-basin, calculated from the modeled thermal histories, experienced two thinning stages in the Cretaceous and in the Paleogene. The lithosphere began with an initial thickness of 150km in the Early Mesozoic and reached a thinning peak of 51km in the late Early Cretaceous. The thickness then increased to approximately 80km at the end of the Cretaceous. A second thinning peak occurred in the Middle and Late Paleogene, with a thickness of only 48km, which corresponds to a rift phase in the Bohai Bay Basin. The lithosphere thickened thereafter and is 78km at present. The North China Craton now has a thin lithosphere. Our research provides new geothermal evidence for the lithospheric thinning of the NCC.
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•Jiyang sub-basin experienced two heat flow peaks in the K1 and E2+3.•Lithosphere of the NCC experienced two thinning stages in the Cretaceous and Paleogene.•Thermal history provides new evidence for the lithospheric thinning of the NCC.
Abstract
Kinematic restoration of the eastern Sichuan fold‐and‐thrust belt (ESFTB) in South China is calibrated with a new thermo‐kinematic model combining analog models, discrete element method, and ...thermochronology data. Thermo‐kinematic analysis provides constraints on the onset, rate, and lateral variation of deformation and exhumation. Results show that the ESFTB experienced a northwestward thrusting and periodic exhumation. Its evolution was characterized by five major stages based on the deformation characteristics; (a) Shortening above a basal decollement and formation of large imbricates separated by narrow synclines during 170–130 Ma; (b) Transition stage during 130–100 Ma; (c) Stepping up of deformation to shallow decollement levels and shaping of the thick‐skinned domain during 100–70 Ma; (d) Shaping of the thin‐skinned domain during 70–20 Ma; and (e) Continuous exhumation and structural modification from 20 Ma to present. The changes in the exhumation rate have been tectonic responses to the subduction retreat of the Paleo‐Pacific Plate and the eastward growth of the Tibetan Plateau. The westward subduction of the Paleo‐Pacific Plate resulted in northwestward shortening across South China, progressive deformation of the ESFTB, and rapid exhumation from the Late Jurassic to the Late Cretaceous. The crustal extension associated with the rollback of the Paleo‐Pacific slab accounted for the Mesozoic exhumation rate decrease until the Miocene. The accelerated cooling of the thin‐skinned domain of the ESFTB since the Miocene was a response to the eastward growth of the Tibetan Plateau, while the continuous slow exhumation in the thick‐skinned domain was related to the continuous crustal extension in South China.
Key Points
New thermo‐kinematic method combining analog modeling, discrete element method, balanced reconstruction, and thermochronology data
Eastern Sichuan fold‐and‐thrust belt (ESFTB) experienced northwestward thrusting and periodic exhumation and its evolution can be subdivided into five stages
Exhumation rate changes are responses of ESFTB to subduction retreat of the Paleo‐Pacific Plate and eastward growth of the Tibetan Plateau
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.
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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 (Ro), equivalent vitrinite reflectance data (Requ), fission track and (UTh)/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.
The Kuqa fold-and-thrust belt developed in response to Cenozoic southward shortening between the Chinese Tian Shan and the Tarim Basin. This study aims to constrain the timing of the Late Cenozoic ...deformation by determining the onset time of enhanced rock cooling using apatite (U-Th-Sm)/He thermochronometry. Eight sedimentary samples were collected from Triassic to Cretaceous strata exposed along a 17km N-S transect, cross-cutting the northern Kuqa fold-and-thrust belt. Single-grain AHe ages from these samples mostly cluster around 8–16Ma and are younger than their depositional ages. Older AHe ages show a positive relationship with eU, a proxy for radiation damage. Modelling of the observed age-eU relationships suggest a phase of enhanced cooling and erosion initiated at Mid-Late Miocene time (10–20Ma) in the northern Kuqa fold-and-thrust belt. This result is consistent with a coeval abrupt increase of sedimentation rate in the foreland Kuqa depression, south of the study area, indicating a Mid-Late Miocene phase of shortening in the northern Kuqa fold-and-thrust belt.
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•28 new apatite (U-Th)/He data (3.6–35.8Ma) from the northern Kuqa fold-and-thrust belt•Positive relationship between single-grain AHe ages and eU•Forward modelling revealed a phase of enhanced cooling at 10–20Ma.•Mid-Late Miocene enhanced erosion in response to the crustal shortening.
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