To clarify the main enrichment-controlling factors and accumulation mechanisms of shale gas in the Permian Dalong Formation within the Western Hubei-Eastern Chongqing complex structural zone,this study systematically ...To clarify the main enrichment-controlling factors and accumulation mechanisms of shale gas in the Permian Dalong Formation within the Western Hubei-Eastern Chongqing complex structural zone,this study systematically reveals the enrichment patterns and accumulation model through analysis of typical drilling data,geochemical testing,scanning electron microscopy(SEM),methane isothermal adsorption experiments,numerical simulations,and research on tectonic evolution and preservation condition.The results are obtained in two aspects.First,the enrichment of shale gas in the Dalong Formation is synergistically controlled by four factors,i.e.rift troughs controlling shale development,provenance controlling reservoir heterogeneity,temperature and pressure controlling gas occurrence,and structure controlling differential enrichment.The geometry and scale of rift troughs(Chengkou-Western Hubei,and Kaijiang-Liangping)determine the development of organic-rich shale(average TOC>6%,thickness of 15-50 m).Multi-source materials lead to strong heterogeneity of the reservoir,with endogenous minerals as the main component(accounting for 74.31%),and the pores mainly organic matter pores(micropores and mesopores accounting for 93.4%).The formation temperature and pressure control the occurrence state of shale gas,with adsorbed gas(higher than 50%)dominantly in 500-2750 m depth,while free gas(higher than 50%)prevailing at depth deeper than 2750 m depth.The uplift,erosion,and fault systems associated with the Yanshanian tectonic activity result in differential enrichment of shale gas,with three structural styles—broad gentle anticlines,residual synclines,and low gentle slopes—exhibiting relatively high shale gas enrichment.Second,the self-sealing mechanism of medium-shallow shale gas in the Western Hubei-Eastern Chongqing complex structural zone is revealed.Specifically,the Dalong Formation shale aquifer forms a lateral seal for shale gas in the downdip direction via water films and capillary forces,and it combines with the overlying Daye Formation limestone and underlying Xiayao Formation tight layers to establish a synclinal/monoclinal self-sealing accumulation model.The geological insights,such as“four-factor synergistic control”and self-sealing accumulation model,provide a dynamic coupling evaluation framework for shale gas in complex structural zones,promoting the transition of shale gas exploration and evaluation from static descriptions to integrated reservoir-tectonic-fluid analysis.展开更多
To rapidly generate a reentry trajectory for hypersonic vehicle satisfying waypoint and no-fly zone constraints, a novel optimization method, which combines the improved particle swarm optimization （PSO） algorithm w...To rapidly generate a reentry trajectory for hypersonic vehicle satisfying waypoint and no-fly zone constraints, a novel optimization method, which combines the improved particle swarm optimization （PSO） algorithm with the improved Gauss pseudospectral method （GPM）, is proposed. The improved PSO algorithm is used to generate a good initial value in a short time, and the mission of the improved GPM is to find the final solution with a high precision. In the improved PSO algorithm, by controlling the entropy of the swarm in each dimension, the typical PSO algorithm＇s weakness of being easy to fall into a local optimum can be overcome. In the improved GPM, two kinds of breaks are introduced to divide the trajectory into multiple segments, and the distribution of the Legendre-Gauss （LG） nodes can be altered, so that all the constraints can be satisfied strictly. Thereby the advan- tages of both the intelligent optimization algorithm and the direct method are combined. Simulation results demonstrate that the proposed method is insensitive to initial values, and it has more rapid convergence and higher precision than traditional ones.展开更多
The Susong complex zone is a relatively low-grade metamorphic unit located in the southern part of the Dabie orogen and preserves a variety of metasedimentary rocks,mostly with epidote-amphibolite facies.However,their...The Susong complex zone is a relatively low-grade metamorphic unit located in the southern part of the Dabie orogen and preserves a variety of metasedimentary rocks,mostly with epidote-amphibolite facies.However,their depositional age,provenance and tectonic setting of sedimentary protolith remain controversial due to the lack of fossils,precise dating and integrated geochemical investigation.This study has conducted whole-rock elemental,and zircon U-Pb SHRIMP dating and Lu-Hf isotope analyses on three types of representative metasedimentary rocks including garnetbearing mica-quartz schist,graphite-muscovite-quartz schist and dolomitic marble from the Susong complex zone.The UPb SHRIMP dating data indicate that the sedimentary protolith of these rocks have the maximum depositional ages of less than 840-750 Ma and have various sedimentary provenances.In combination with zircon Lu-Hf isotope compositions,the provenance of the metasedimentary rocks in the region is for the first time documented to be mainly derived from four groups of magmatic rocks formed at~2.5 Ga,~2.0 Ga,~1.4 Ga and~0.8 Ga in response to four episodes of igneous activity in the northeastern margin of the Yangtze Block.The conventional geothermobarometry combined with rare metamorphic zircon ages indicate that the studied rocks underwent the Late Triassic continental subduction-related metamorphism with peak epidote-amphibolite facies conditions at P=0.34-0.91 GPa and T=427-532°C.In addition,results of the elemental contents(i.e.,La,Ce,Th andΣREE)and ratios(i.e.,Eu/Eu^(*)and La_(N)/Yb_(N))suggest that the protoliths of the metasedimentary rocks were mainly shales,wackes and limestones,most probably related to the Rodinia supercontinent rifting along the northern margin of the Yangtze Block during the Neoproterozoic.展开更多
Objective The Susong complex zone（SCZ）is a relatively lowgrade metamorphic unit mostly with an epidoteamphibolite facies,located in the southernmost part of the Dabie orogen.However,its rock compositions,ages,
The quantitatively/semi-quantitatively formation conditions of vertical dominant hydrocarbon migration pathways were analyzed based on the big data analysis of petroleum geological parameters of complex fault Zone zon...The quantitatively/semi-quantitatively formation conditions of vertical dominant hydrocarbon migration pathways were analyzed based on the big data analysis of petroleum geological parameters of complex fault Zone zone in the central-south Bohai Bay. According to this condition, the vertical dominant migration pathway and its charge points/segments are searched through structural modeling assistant analysis in the East Sag of Huanghekou. Under the constraints of charge points/segments, numerical simulation of hydrocarbon charge and migration is carried out to successfully predict hydrocarbon migration pathways and hydrocarbon enrichment blocks in shallow layers of complex fault zone. The main results are as follows:(1) The hydrocarbon charge in shallow layers of the active fault zone is differential, the charge points/sections of vertical dominant migration pathways are the starting points of shallow hydrocarbon migration and are very important for the hydrocarbon migration and accumulation in the shallow layers.(2) Among the shallow faults, those cutting the deep transfer bins or deep major migration pathways, with fault throw of more than 80 m in the accumulation period and the juxtaposition thickness between fault and caprock of the deep layers of less than 400 m are likely to be vertical dominant migration pathways in the sag area.(3) By controlling the vertical dominant migration pathways and charging points/segments in carrier layer, Neo-tectonic movement caused the differential hydrocarbon accumulation in the complex fault zone. The research results are of great significance for the fine exploration of the complex fault zone.展开更多
The Jitang metamorphic complex is key to studying the tectonic evolution of the Northern Lancangjiang zone.Through structural-lithological mapping,structural analysis and laboratory testing,the composition of the Jita...The Jitang metamorphic complex is key to studying the tectonic evolution of the Northern Lancangjiang zone.Through structural-lithological mapping,structural analysis and laboratory testing,the composition of the Jitang metamorphic complex was determined.The macro-and microstructural analyses of the ductile detachment shear zone(Guoxuepu ductile shear zone,2–4 km wide)between the metamorphic complex and the overlying sedimentary cap show that the shear sense of the ductile shear zones is top-to-the-southeast.The presence of various deformation features and quartz C-axis electron backscatter diffraction(EBSD)fabric analysis suggests multiple deformation events occurring at different temperatures.The average stress is 25.68 MPa,with the strain rates(έ)ranging from 9.77×10^(−14)s^(−1)to 6.52×10^(−16)s^(−1).The finite strain of the Guoxuepu ductile shear zone indicates an elongated strain pattern.The average kinematic vorticity of the Guoxuepu ductile shear zone is 0.88,implying that the shear zone is dominated by simple shear.The muscovite selected from the protomylonite samples in the Guoxuepu ductile shear zone yields a 40Ar-39Ar age of 60.09±0.38 Ma.It is suggested that,coeval with the initial Indo–Eurasian collision,the development of strike-slip faults led to a weak and unstable crust,upwelling of lower crust magma,then induced the detachment of the Jitang metamorphic complex in the Eocene.展开更多
A No-Fly Zone (NFZ) is a unique mode of humanitarian intervention that is understudied in international relations. This article focuses on the politics of NFZs in international relations, and investigates their nature...A No-Fly Zone (NFZ) is a unique mode of humanitarian intervention that is understudied in international relations. This article focuses on the politics of NFZs in international relations, and investigates their nature by empirically reviewing all three cases of NFZs to date. NFZs represent a middle ground for international intervention which, both legally and legitimately, may be aimed at either protecting populations or promoting regime change in weak states, depending on the circumstances. There may be efforts by intervening states to highlight humanitarian crises among certain targets in order to secure UN authorization for the NFZs;but the implementation of NFZs is also largely driven by the security interests of the enforcing states. As a result, there is the potential for those states implementing NFZs to transcend legal authorization and to at times use excessive force, with the potential for calamitous results for local people, or, in extreme cases, to accomplish regime change by supporting opposition parties in target states.展开更多
Special economic zones(SEZs)help provide the momentum for China’s economic growth.This paper studies the influence of SEZs on enterprise’s export structures from the perspective of production complexity using data f...Special economic zones(SEZs)help provide the momentum for China’s economic growth.This paper studies the influence of SEZs on enterprise’s export structures from the perspective of production complexity using data from the China Industry Business Performance Database(CIBPD)collected between 2000 and 2007.We found that enterprises in SEZs have a higher export propensity and volume due to more complexity.Also,enterprises with more complexity outside SEZs show a higher export propensity and volume depending on the number of SEZs near them and the radiation effect of the SEZs.Similarly,high and new-tech industrial development zones perform more prominently in this regard.展开更多
A No-Fly Zone(NFZ)is a unique mode of humanitarian intervention which is understudied in international relations.This article focuses on the political dimension of NFZs in international relations and investigates thei...A No-Fly Zone(NFZ)is a unique mode of humanitarian intervention which is understudied in international relations.This article focuses on the political dimension of NFZs in international relations and investigates their implementations by empirically reviewing all three cases of NFZs to date.There may be efforts by intervening states to highlight humanitarian crises among certain targets to secure UN authorization for the NFZs;yet the implementation of NFZs is also driven largely by the security interests of enforcing states.As a result,there is the potential for those states implementing NFZs to transcend legal authorization and sometimes use excessive force,with likely calamitous results for local populations,or in extreme cases,accomplishing regime change by supporting opposition parties in target states.展开更多
The Shangla Complex ophiolite represents a relic of the Neo-Tethyan oceanic lithosphere along the Indus Suture Zone(also known as the Main Mantle Thrust)in northern Pakistan.This section,thrust onto the continental ma...The Shangla Complex ophiolite represents a relic of the Neo-Tethyan oceanic lithosphere along the Indus Suture Zone(also known as the Main Mantle Thrust)in northern Pakistan.This section,thrust onto the continental margin between the Indian and Karakoram(Asian)plates,is predominantly composed of depleted harzburgites,dunites and chromitites.In this study,we conducted a thorough analysis of mineralogy,whole-rock geochemistry(major oxides,trace elements,PGE),and integrated Re-Os isotopic data from mantle-derived peridotites to understand their petrogenesis and melt evolution.These peridotites exhibit a depleted nature,characterized by a low modal composition of clinopyroxene,a wide forsterite content range in olivine(86.5 to 95.2),and a large variation in Cr#values(25.1–91.4).Their diverse whole-rock geochemistry further suggests varying degrees of partial melting.The Cpx-harzburgites show high average Al_(2)O_(3)(1.83 wt.%),CaO(2.27 wt.%),ΣREE(12.9 ppb),and^(187)Os/^(188)Os values between 0.13095 and 0.12571.On the other hand,the depleted harzburgites and dunites exhibit lower average Al_(2)O_(3)(0.57 wt.%and 0.14 wt.%,respectively),CaO concentration(0.59 wt.%and 0.21 wt.%,respectively),and∑REE concentrations,measured at 12.7 ppb and 8.9 ppb,respectively.The^(187)Os/^(188)Os ratios in the depleted harzburgites and dunites range from 0.12643 to 0.11777,indicating they are less radiogenic compared to the Cpx-harzburgites.The spoon-shaped rare earth elements(REE)patterns suggest that the Cpx-harzburgites underwent low degrees of partial melting(∼10%–15%),whereas the depleted harzburgites and dunites indicate somewhat higher degrees of partial melting(additional melting of the Cpx-harzburgites).The PGE abundances in these depleted harzburgites and dunites are linked to the partial melting of Cpx-harzburgites,resulting in a boninitic-like melt.Their low degree of melting and melt extraction suggests that Cpx-harzburgites initially formed at a mid-ocean ridge(MOR)spreading center or a distal fore-arc basin.In contrast,the depleted harzburgites and dunites were formed during a second phase of melting,followed by refertilization,closely associated with a supra-subduction zone(SSZ)setting.The Re-Os isotopic systematics of the Shangla Complex peridotites reveal model age clusters of ca.250 Ma and ca.450 Ma,potentially corresponding to significant tectonic events in the geodynamic evolution of the Neo-Tethyan,Rheic,and Proto-Tethyan oceans.展开更多
基金Supported by the National Natural Science Foundation of China(42472210)Project of the China Geological Survey(DD20221653,DD20230043).
文摘To clarify the main enrichment-controlling factors and accumulation mechanisms of shale gas in the Permian Dalong Formation within the Western Hubei-Eastern Chongqing complex structural zone,this study systematically reveals the enrichment patterns and accumulation model through analysis of typical drilling data,geochemical testing,scanning electron microscopy(SEM),methane isothermal adsorption experiments,numerical simulations,and research on tectonic evolution and preservation condition.The results are obtained in two aspects.First,the enrichment of shale gas in the Dalong Formation is synergistically controlled by four factors,i.e.rift troughs controlling shale development,provenance controlling reservoir heterogeneity,temperature and pressure controlling gas occurrence,and structure controlling differential enrichment.The geometry and scale of rift troughs(Chengkou-Western Hubei,and Kaijiang-Liangping)determine the development of organic-rich shale(average TOC>6%,thickness of 15-50 m).Multi-source materials lead to strong heterogeneity of the reservoir,with endogenous minerals as the main component(accounting for 74.31%),and the pores mainly organic matter pores(micropores and mesopores accounting for 93.4%).The formation temperature and pressure control the occurrence state of shale gas,with adsorbed gas(higher than 50%)dominantly in 500-2750 m depth,while free gas(higher than 50%)prevailing at depth deeper than 2750 m depth.The uplift,erosion,and fault systems associated with the Yanshanian tectonic activity result in differential enrichment of shale gas,with three structural styles—broad gentle anticlines,residual synclines,and low gentle slopes—exhibiting relatively high shale gas enrichment.Second,the self-sealing mechanism of medium-shallow shale gas in the Western Hubei-Eastern Chongqing complex structural zone is revealed.Specifically,the Dalong Formation shale aquifer forms a lateral seal for shale gas in the downdip direction via water films and capillary forces,and it combines with the overlying Daye Formation limestone and underlying Xiayao Formation tight layers to establish a synclinal/monoclinal self-sealing accumulation model.The geological insights,such as“four-factor synergistic control”and self-sealing accumulation model,provide a dynamic coupling evaluation framework for shale gas in complex structural zones,promoting the transition of shale gas exploration and evaluation from static descriptions to integrated reservoir-tectonic-fluid analysis.
基金supported by the National Natural Science Foundation of China(61272011)
文摘To rapidly generate a reentry trajectory for hypersonic vehicle satisfying waypoint and no-fly zone constraints, a novel optimization method, which combines the improved particle swarm optimization （PSO） algorithm with the improved Gauss pseudospectral method （GPM）, is proposed. The improved PSO algorithm is used to generate a good initial value in a short time, and the mission of the improved GPM is to find the final solution with a high precision. In the improved PSO algorithm, by controlling the entropy of the swarm in each dimension, the typical PSO algorithm＇s weakness of being easy to fall into a local optimum can be overcome. In the improved GPM, two kinds of breaks are introduced to divide the trajectory into multiple segments, and the distribution of the Legendre-Gauss （LG） nodes can be altered, so that all the constraints can be satisfied strictly. Thereby the advan- tages of both the intelligent optimization algorithm and the direct method are combined. Simulation results demonstrate that the proposed method is insensitive to initial values, and it has more rapid convergence and higher precision than traditional ones.
基金financially supported by the National Natural Science Foundation of China(Grant No.42072059)。
文摘The Susong complex zone is a relatively low-grade metamorphic unit located in the southern part of the Dabie orogen and preserves a variety of metasedimentary rocks,mostly with epidote-amphibolite facies.However,their depositional age,provenance and tectonic setting of sedimentary protolith remain controversial due to the lack of fossils,precise dating and integrated geochemical investigation.This study has conducted whole-rock elemental,and zircon U-Pb SHRIMP dating and Lu-Hf isotope analyses on three types of representative metasedimentary rocks including garnetbearing mica-quartz schist,graphite-muscovite-quartz schist and dolomitic marble from the Susong complex zone.The UPb SHRIMP dating data indicate that the sedimentary protolith of these rocks have the maximum depositional ages of less than 840-750 Ma and have various sedimentary provenances.In combination with zircon Lu-Hf isotope compositions,the provenance of the metasedimentary rocks in the region is for the first time documented to be mainly derived from four groups of magmatic rocks formed at~2.5 Ga,~2.0 Ga,~1.4 Ga and~0.8 Ga in response to four episodes of igneous activity in the northeastern margin of the Yangtze Block.The conventional geothermobarometry combined with rare metamorphic zircon ages indicate that the studied rocks underwent the Late Triassic continental subduction-related metamorphism with peak epidote-amphibolite facies conditions at P=0.34-0.91 GPa and T=427-532°C.In addition,results of the elemental contents(i.e.,La,Ce,Th andΣREE)and ratios(i.e.,Eu/Eu^(*)and La_(N)/Yb_(N))suggest that the protoliths of the metasedimentary rocks were mainly shales,wackes and limestones,most probably related to the Rodinia supercontinent rifting along the northern margin of the Yangtze Block during the Neoproterozoic.
基金financially supported by the National Basic Research Program of China(grant No.2015CB856104)the National Natural Science Foundation of China(grant No.41773020)
文摘Objective The Susong complex zone（SCZ）is a relatively lowgrade metamorphic unit mostly with an epidoteamphibolite facies,located in the southernmost part of the Dabie orogen.However,its rock compositions,ages,
基金Supported by the National Science and Technology Major Project(2016ZX05024-003)
文摘The quantitatively/semi-quantitatively formation conditions of vertical dominant hydrocarbon migration pathways were analyzed based on the big data analysis of petroleum geological parameters of complex fault Zone zone in the central-south Bohai Bay. According to this condition, the vertical dominant migration pathway and its charge points/segments are searched through structural modeling assistant analysis in the East Sag of Huanghekou. Under the constraints of charge points/segments, numerical simulation of hydrocarbon charge and migration is carried out to successfully predict hydrocarbon migration pathways and hydrocarbon enrichment blocks in shallow layers of complex fault zone. The main results are as follows:(1) The hydrocarbon charge in shallow layers of the active fault zone is differential, the charge points/sections of vertical dominant migration pathways are the starting points of shallow hydrocarbon migration and are very important for the hydrocarbon migration and accumulation in the shallow layers.(2) Among the shallow faults, those cutting the deep transfer bins or deep major migration pathways, with fault throw of more than 80 m in the accumulation period and the juxtaposition thickness between fault and caprock of the deep layers of less than 400 m are likely to be vertical dominant migration pathways in the sag area.(3) By controlling the vertical dominant migration pathways and charging points/segments in carrier layer, Neo-tectonic movement caused the differential hydrocarbon accumulation in the complex fault zone. The research results are of great significance for the fine exploration of the complex fault zone.
基金financially supported by the China Geological Survey Scientific Research Project(Grant Nos.DD20190167 and DD20190053)the National Natural Science Foundation of China(Grant No.42172259).
文摘The Jitang metamorphic complex is key to studying the tectonic evolution of the Northern Lancangjiang zone.Through structural-lithological mapping,structural analysis and laboratory testing,the composition of the Jitang metamorphic complex was determined.The macro-and microstructural analyses of the ductile detachment shear zone(Guoxuepu ductile shear zone,2–4 km wide)between the metamorphic complex and the overlying sedimentary cap show that the shear sense of the ductile shear zones is top-to-the-southeast.The presence of various deformation features and quartz C-axis electron backscatter diffraction(EBSD)fabric analysis suggests multiple deformation events occurring at different temperatures.The average stress is 25.68 MPa,with the strain rates(έ)ranging from 9.77×10^(−14)s^(−1)to 6.52×10^(−16)s^(−1).The finite strain of the Guoxuepu ductile shear zone indicates an elongated strain pattern.The average kinematic vorticity of the Guoxuepu ductile shear zone is 0.88,implying that the shear zone is dominated by simple shear.The muscovite selected from the protomylonite samples in the Guoxuepu ductile shear zone yields a 40Ar-39Ar age of 60.09±0.38 Ma.It is suggested that,coeval with the initial Indo–Eurasian collision,the development of strike-slip faults led to a weak and unstable crust,upwelling of lower crust magma,then induced the detachment of the Jitang metamorphic complex in the Eocene.
基金sponsored by the Key Research Base Project “The Comparative Study of the States outside the NPT Regime”(project number: 11JZ004)from the Education Department of Shaanxi Provincial Government
文摘A No-Fly Zone (NFZ) is a unique mode of humanitarian intervention that is understudied in international relations. This article focuses on the politics of NFZs in international relations, and investigates their nature by empirically reviewing all three cases of NFZs to date. NFZs represent a middle ground for international intervention which, both legally and legitimately, may be aimed at either protecting populations or promoting regime change in weak states, depending on the circumstances. There may be efforts by intervening states to highlight humanitarian crises among certain targets in order to secure UN authorization for the NFZs;but the implementation of NFZs is also largely driven by the security interests of the enforcing states. As a result, there is the potential for those states implementing NFZs to transcend legal authorization and to at times use excessive force, with the potential for calamitous results for local people, or, in extreme cases, to accomplish regime change by supporting opposition parties in target states.
基金a staged result of “Statistical Monitoring and Evaluation Research on China’s New Economy and Growth Drivers in the Context of Big Data”(Approved under No.18ZDA124),a key program sponsored by the National Social Science Fund of China
文摘Special economic zones(SEZs)help provide the momentum for China’s economic growth.This paper studies the influence of SEZs on enterprise’s export structures from the perspective of production complexity using data from the China Industry Business Performance Database(CIBPD)collected between 2000 and 2007.We found that enterprises in SEZs have a higher export propensity and volume due to more complexity.Also,enterprises with more complexity outside SEZs show a higher export propensity and volume depending on the number of SEZs near them and the radiation effect of the SEZs.Similarly,high and new-tech industrial development zones perform more prominently in this regard.
基金This article has been sponsored by the Core Research Base Project“The Comparative Study of the States outside the NPT Regime”(project number:11jz004)from Education Department of Shaanxi Provincial Government and two-class General Financial Grant for the China Postdoctoral Science Foundation(Grant No.:2012M521660).
文摘A No-Fly Zone(NFZ)is a unique mode of humanitarian intervention which is understudied in international relations.This article focuses on the political dimension of NFZs in international relations and investigates their implementations by empirically reviewing all three cases of NFZs to date.There may be efforts by intervening states to highlight humanitarian crises among certain targets to secure UN authorization for the NFZs;yet the implementation of NFZs is also driven largely by the security interests of enforcing states.As a result,there is the potential for those states implementing NFZs to transcend legal authorization and sometimes use excessive force,with likely calamitous results for local populations,or in extreme cases,accomplishing regime change by supporting opposition parties in target states.
基金supported by a grant from the Science and Technology Innovation Program of Hunan Province(Grant No.2021RC4055)Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,during the Postdoctoral research of the first author(Zaheen Ullah,Assistant Professor,University of Swat,Pakistan)at the Central South University,Changsha,China.
文摘The Shangla Complex ophiolite represents a relic of the Neo-Tethyan oceanic lithosphere along the Indus Suture Zone(also known as the Main Mantle Thrust)in northern Pakistan.This section,thrust onto the continental margin between the Indian and Karakoram(Asian)plates,is predominantly composed of depleted harzburgites,dunites and chromitites.In this study,we conducted a thorough analysis of mineralogy,whole-rock geochemistry(major oxides,trace elements,PGE),and integrated Re-Os isotopic data from mantle-derived peridotites to understand their petrogenesis and melt evolution.These peridotites exhibit a depleted nature,characterized by a low modal composition of clinopyroxene,a wide forsterite content range in olivine(86.5 to 95.2),and a large variation in Cr#values(25.1–91.4).Their diverse whole-rock geochemistry further suggests varying degrees of partial melting.The Cpx-harzburgites show high average Al_(2)O_(3)(1.83 wt.%),CaO(2.27 wt.%),ΣREE(12.9 ppb),and^(187)Os/^(188)Os values between 0.13095 and 0.12571.On the other hand,the depleted harzburgites and dunites exhibit lower average Al_(2)O_(3)(0.57 wt.%and 0.14 wt.%,respectively),CaO concentration(0.59 wt.%and 0.21 wt.%,respectively),and∑REE concentrations,measured at 12.7 ppb and 8.9 ppb,respectively.The^(187)Os/^(188)Os ratios in the depleted harzburgites and dunites range from 0.12643 to 0.11777,indicating they are less radiogenic compared to the Cpx-harzburgites.The spoon-shaped rare earth elements(REE)patterns suggest that the Cpx-harzburgites underwent low degrees of partial melting(∼10%–15%),whereas the depleted harzburgites and dunites indicate somewhat higher degrees of partial melting(additional melting of the Cpx-harzburgites).The PGE abundances in these depleted harzburgites and dunites are linked to the partial melting of Cpx-harzburgites,resulting in a boninitic-like melt.Their low degree of melting and melt extraction suggests that Cpx-harzburgites initially formed at a mid-ocean ridge(MOR)spreading center or a distal fore-arc basin.In contrast,the depleted harzburgites and dunites were formed during a second phase of melting,followed by refertilization,closely associated with a supra-subduction zone(SSZ)setting.The Re-Os isotopic systematics of the Shangla Complex peridotites reveal model age clusters of ca.250 Ma and ca.450 Ma,potentially corresponding to significant tectonic events in the geodynamic evolution of the Neo-Tethyan,Rheic,and Proto-Tethyan oceans.
