In this paper we report geochemical and Nd-Sr isotopic data for a late Archean gneissic granitic pluton （Hengling pluton）, an early Paleoproterozoic complex （Xipan complex） and a late Paleoproterozoic granitic plu...In this paper we report geochemical and Nd-Sr isotopic data for a late Archean gneissic granitic pluton （Hengling pluton）, an early Paleoproterozoic complex （Xipan complex） and a late Paleoproterozoic granitic pluton （Yunzhongshan granites） from the Liiliang-Wutai terrain, North China, to trace the source of these late Archean-Paleoproterozoic granitoids and, particularly, to understand the nature and mechanism of continental growth at that time. The Hengling granitic gneisses （ca. 2.51 Ga） are characterized by high Na2O and LILEs, TTG-like REE patterns （highly depleted HREE and minor Eu anomalies） and moderately depleted Nd-Sr isotopic compositions （εNd（t） =1.2-2.7, ISr=0.7015-0.7019）, and were considered as being products of arc magmatism that was developed upon the North China craton. The Xipan complex （ca. 2.2 Ga） contain gabbroic diorite and monzonite, mostly being Na2O-rich, highly fractionated REE patterns and isotopically enriched （εNd（t） =-1.5 to -4.1, Isr=0.7038-0.706）. The gabbroic diorites probably originated from melting of an enriched mantle source, but significantly contaminated by lower crustal material, and the monzonites probably represent a product of a mixture between the gabbroic dioritic magma and granitic melts of crustal origin. The Yunzhongshan post-collisional granitoids （ca. 1.8 Ga） are characterized by high-K affinity and highly-enriched and homogeneous Nd isotopic compositions （εNd（t）=-4.9 to -5.7）, although they split into two groups in terms of REE patterns： one group showing elevated HREE （and Sc, Y and Zr） with significant negative Eu anomalies and the other showing highly depleted HREE and, to a lesser extent, mid-REE with negligible Eu anomalies. These granites are genetically related to a process of extensional collapse of a thickened orogen. They formed through magma mixing between mantle-derived basaltic magmas and crust-derived granitic melts, followed by significant fractionation of ferromagnesian phases （like hornblende and Cpx） and feldspar and accessory zircons. Some Yunzhongshan granites show very old Nd model ages （2.9-3.0 Ga）, suggesting the existence of continental crust older than 2.7 Ga, which is supported by our zircon Hf isotopic data for these granites.展开更多
The late Paleoproterozoic Dagushi Formation comprises a fluvial-lacustrine succession and represents the initial fill of the Xiong'er Basin in the southern North China Craton.Employing integrated outcrop surveys a...The late Paleoproterozoic Dagushi Formation comprises a fluvial-lacustrine succession and represents the initial fill of the Xiong'er Basin in the southern North China Craton.Employing integrated outcrop surveys and detrital zircon UPb-Hf dating,this study examines the provenance and depositional setting of the Dagushi Formation.Five major depositional facies,including braided channel,distributary channel,subaqueous stream/mouth bar,pro-delta and shallow lake,were identified,based on lithofacies and associations.They were interpreted as representing a braided river deltalacustrine system.The ages of the last metamorphic event of the basement,covering volcanics and the youngest zircon together constrain a depositional age of ca.1.79 Ga for the Dagushi Formation.Zircon age distributions reveal a provenance change from ca.2.7–2.5 Ga rocks in the lower part,to ca.2.3–1.9 Ga sources in the middle-upper part of the Dagushi Formation.Considering the vertical sedimentology,this provenance change could be induced by the rising water-level caused by a tectonic subsidence.The ca.2.7–2.5 Ga zircons are suggested to be locally sourced from the late Neoarchean–Paleoproterozoic metamorphic basement.The northeast Zhongtiao Mts area(current co-ordinates)is supposed to have appeared as a paleo-uplift and served as a source area for the Paleoproterozoic grains.The Dagushi Formation records an early‘underfilled'stage of the Xiong'er Rift.展开更多
Tectonic evolution and paleogeography of the two major continental blocks Fennoscandia and VolgoSarmatia during their docking to form the East European Craton(Baltica)at 1.8–1.7 Ga represent important‘puzzle
Archaea, bacteria and eukaryotes constitute the cellular life on our planet, but all complex life on Earth are eukaryotes with nuclei inside cells. Therefore, the origin and early evolution of eukaryotes is one of the...Archaea, bacteria and eukaryotes constitute the cellular life on our planet, but all complex life on Earth are eukaryotes with nuclei inside cells. Therefore, the origin and early evolution of eukaryotes is one of the most puzzling evolutionary events in the history of life on Earth。展开更多
纳木那尼穹窿位于特提斯喜马拉雅带西段,属变质杂岩体,由黑云母片麻岩、花岗片麻岩、糜棱岩、混合岩、变杂砂岩、角闪岩、大理岩及后期侵位的电气石花岗岩和二云母花岗岩组成。本次研究对穹隆核部出露的混合岩、花岗片麻岩、电气石花岗...纳木那尼穹窿位于特提斯喜马拉雅带西段,属变质杂岩体,由黑云母片麻岩、花岗片麻岩、糜棱岩、混合岩、变杂砂岩、角闪岩、大理岩及后期侵位的电气石花岗岩和二云母花岗岩组成。本次研究对穹隆核部出露的混合岩、花岗片麻岩、电气石花岗岩及边缘出露的二云母花岗岩和黑云母片麻岩进行了岩相学、锆石U-Pb定年及地球化学研究,结果表明:(1)混合岩(T0768-4A-4C)锆石^(206)Pb/^(238)U谐和图上交点年龄为1873±28Ma,^(207)Pb/^(206)Pb加权平均年龄为1877±21Ma。混合岩Sr同位素比值(1.25018~1.44452)和ε_(Nd)(t)值(-28.8^-28.5)指示其具其有低喜马拉雅岩石单元的地球化学属性;(2)花岗片麻岩锆石核部^(206)Pb/^(238)U谐和图上交点年龄为1878±9Ma,下交点年龄为10.9±0.5Ma。个别震荡环带边记录有13.1±0.3Ma的年龄数据,表明古元古代花岗片麻岩可能经历了~10Ma左右的熔融事件;(3)侵位于古元古代混合岩和花岗片麻岩之中的电气石花岗岩(T0768-LG)具有与深熔事件相一致的年龄,其^(206)Pb/^(238)U谐和年龄为9.0±0.2Ma;(4)穹隆核部电气石花岗岩ε_(Nd)(t)值集中在(-18.9^-16.1),显著低于穹隆边缘的二云母花岗岩(ε_(Nd)(t)=-14.4^-10.3),指示电气石花岗岩部分熔融源区有更多成熟地壳物质的加入;(5)个别电气石花岗岩ε_(Nd)(t)值为-12.6,可能是岩浆上升过程中受到变泥质岩的混染所致。本次在纳木那尼穹隆的研究结果支持19~13Ma左右喜马拉雅造山带发生构造转换的模型(Zhang et al.,2012),并表明这种构造转化可能进一步引发了淡色花岗岩部分熔融源区的变化。南北伸展阶段为深度相对较浅的高喜马拉雅变泥质岩和杂砂岩等发生部分熔融,形成穹隆边缘的二云母花岗岩(~16Ma);进入东西向伸展阶段后,深熔作用导致深部主中央逆冲断层(MCT)附近的古元古代岩石单元和变泥质岩混合源区发生部分熔融,岩浆沿着南北向断裂带上升,形成电气石花岗岩体(~9Ma)。展开更多
Migmatite-like rocks transformed from strongly metamorphosed and deformed enclave- bearing felsic plutons usually make people confuse with the true migmatites and mistake in interpreta- tion of their petrogenesis and ...Migmatite-like rocks transformed from strongly metamorphosed and deformed enclave- bearing felsic plutons usually make people confuse with the true migmatites and mistake in interpreta- tion of their petrogenesis and tectonic implications. Here we report a suite of rocks that have long been called as migmatites from the Guandi complex in Zhoukoudian region, southwest of Beijing. The rocks are dominated by felsic gneisses with garnet-free amphibolites. Field occurrence, petrography and geochemistry indicate that the felsic gneisses and amphibolites were metamorphosed from protoliths of intermediate-acid and basic igneous rocks, respectively. New LA-ICP-MS zircon U-Pb dating and geothermobarometry study further reveal that precursor magmas of the two types of rocks were emplaced at 2.54-2.56 Ga and the rocks subsequently underwent medium P/T-type metamorphism with upper amphibolite facies conditions of 0.55-0.90 GPa and 670-730℃ at -2.48-2.50 Ga. Geochemically, precursor magmas of the amphibolites were suggested to be derived from an enriched lithospheric mantle source in continental arc setting, and those of the felsic gneisses are characterized by tonalitic to trondhjemitic magmas that are usually considered to be generated by partial melting of hydrated, thickened metamorphosed mafic crust with garnet as residues, suggesting that the rock associations are not of true migmatites but migmatite-like rocks. Our study reveal that protoliths of the migmatite-like rocks from the Guandi complex, were likely formed via magmatism in a continental arc setting, followed by accretion and collision of the continental arc as well as the intro-oceanic arc terranes to the Eastern Block of the North China Craton in the transition from the Late Neoarchean to Early Paleoprnterozuic.展开更多
基金This study is financially supported by the National Natural Science Foundation of China （No. 40420120135）.
文摘In this paper we report geochemical and Nd-Sr isotopic data for a late Archean gneissic granitic pluton （Hengling pluton）, an early Paleoproterozoic complex （Xipan complex） and a late Paleoproterozoic granitic pluton （Yunzhongshan granites） from the Liiliang-Wutai terrain, North China, to trace the source of these late Archean-Paleoproterozoic granitoids and, particularly, to understand the nature and mechanism of continental growth at that time. The Hengling granitic gneisses （ca. 2.51 Ga） are characterized by high Na2O and LILEs, TTG-like REE patterns （highly depleted HREE and minor Eu anomalies） and moderately depleted Nd-Sr isotopic compositions （εNd（t） =1.2-2.7, ISr=0.7015-0.7019）, and were considered as being products of arc magmatism that was developed upon the North China craton. The Xipan complex （ca. 2.2 Ga） contain gabbroic diorite and monzonite, mostly being Na2O-rich, highly fractionated REE patterns and isotopically enriched （εNd（t） =-1.5 to -4.1, Isr=0.7038-0.706）. The gabbroic diorites probably originated from melting of an enriched mantle source, but significantly contaminated by lower crustal material, and the monzonites probably represent a product of a mixture between the gabbroic dioritic magma and granitic melts of crustal origin. The Yunzhongshan post-collisional granitoids （ca. 1.8 Ga） are characterized by high-K affinity and highly-enriched and homogeneous Nd isotopic compositions （εNd（t）=-4.9 to -5.7）, although they split into two groups in terms of REE patterns： one group showing elevated HREE （and Sc, Y and Zr） with significant negative Eu anomalies and the other showing highly depleted HREE and, to a lesser extent, mid-REE with negligible Eu anomalies. These granites are genetically related to a process of extensional collapse of a thickened orogen. They formed through magma mixing between mantle-derived basaltic magmas and crust-derived granitic melts, followed by significant fractionation of ferromagnesian phases （like hornblende and Cpx） and feldspar and accessory zircons. Some Yunzhongshan granites show very old Nd model ages （2.9-3.0 Ga）, suggesting the existence of continental crust older than 2.7 Ga, which is supported by our zircon Hf isotopic data for these granites.
基金financially supported by the National Natural Science Foundation(Grant No.41872238)。
文摘The late Paleoproterozoic Dagushi Formation comprises a fluvial-lacustrine succession and represents the initial fill of the Xiong'er Basin in the southern North China Craton.Employing integrated outcrop surveys and detrital zircon UPb-Hf dating,this study examines the provenance and depositional setting of the Dagushi Formation.Five major depositional facies,including braided channel,distributary channel,subaqueous stream/mouth bar,pro-delta and shallow lake,were identified,based on lithofacies and associations.They were interpreted as representing a braided river deltalacustrine system.The ages of the last metamorphic event of the basement,covering volcanics and the youngest zircon together constrain a depositional age of ca.1.79 Ga for the Dagushi Formation.Zircon age distributions reveal a provenance change from ca.2.7–2.5 Ga rocks in the lower part,to ca.2.3–1.9 Ga sources in the middle-upper part of the Dagushi Formation.Considering the vertical sedimentology,this provenance change could be induced by the rising water-level caused by a tectonic subsidence.The ca.2.7–2.5 Ga zircons are suggested to be locally sourced from the late Neoarchean–Paleoproterozoic metamorphic basement.The northeast Zhongtiao Mts area(current co-ordinates)is supposed to have appeared as a paleo-uplift and served as a source area for the Paleoproterozoic grains.The Dagushi Formation records an early‘underfilled'stage of the Xiong'er Rift.
基金funded by grant 14-05-00731 from the Russian Foundation of Basic Research
文摘Tectonic evolution and paleogeography of the two major continental blocks Fennoscandia and VolgoSarmatia during their docking to form the East European Craton(Baltica)at 1.8–1.7 Ga represent important‘puzzle
基金supported by the Strategic Priority Research Program(B)of CASthe National Natural Science Foundation of Chinathe Swedish Research Council
文摘Archaea, bacteria and eukaryotes constitute the cellular life on our planet, but all complex life on Earth are eukaryotes with nuclei inside cells. Therefore, the origin and early evolution of eukaryotes is one of the most puzzling evolutionary events in the history of life on Earth。
文摘纳木那尼穹窿位于特提斯喜马拉雅带西段,属变质杂岩体,由黑云母片麻岩、花岗片麻岩、糜棱岩、混合岩、变杂砂岩、角闪岩、大理岩及后期侵位的电气石花岗岩和二云母花岗岩组成。本次研究对穹隆核部出露的混合岩、花岗片麻岩、电气石花岗岩及边缘出露的二云母花岗岩和黑云母片麻岩进行了岩相学、锆石U-Pb定年及地球化学研究,结果表明:(1)混合岩(T0768-4A-4C)锆石^(206)Pb/^(238)U谐和图上交点年龄为1873±28Ma,^(207)Pb/^(206)Pb加权平均年龄为1877±21Ma。混合岩Sr同位素比值(1.25018~1.44452)和ε_(Nd)(t)值(-28.8^-28.5)指示其具其有低喜马拉雅岩石单元的地球化学属性;(2)花岗片麻岩锆石核部^(206)Pb/^(238)U谐和图上交点年龄为1878±9Ma,下交点年龄为10.9±0.5Ma。个别震荡环带边记录有13.1±0.3Ma的年龄数据,表明古元古代花岗片麻岩可能经历了~10Ma左右的熔融事件;(3)侵位于古元古代混合岩和花岗片麻岩之中的电气石花岗岩(T0768-LG)具有与深熔事件相一致的年龄,其^(206)Pb/^(238)U谐和年龄为9.0±0.2Ma;(4)穹隆核部电气石花岗岩ε_(Nd)(t)值集中在(-18.9^-16.1),显著低于穹隆边缘的二云母花岗岩(ε_(Nd)(t)=-14.4^-10.3),指示电气石花岗岩部分熔融源区有更多成熟地壳物质的加入;(5)个别电气石花岗岩ε_(Nd)(t)值为-12.6,可能是岩浆上升过程中受到变泥质岩的混染所致。本次在纳木那尼穹隆的研究结果支持19~13Ma左右喜马拉雅造山带发生构造转换的模型(Zhang et al.,2012),并表明这种构造转化可能进一步引发了淡色花岗岩部分熔融源区的变化。南北伸展阶段为深度相对较浅的高喜马拉雅变泥质岩和杂砂岩等发生部分熔融,形成穹隆边缘的二云母花岗岩(~16Ma);进入东西向伸展阶段后,深熔作用导致深部主中央逆冲断层(MCT)附近的古元古代岩石单元和变泥质岩混合源区发生部分熔融,岩浆沿着南北向断裂带上升,形成电气石花岗岩体(~9Ma)。
基金supported by the National Natural Science Foundation of China (No. 41672060)the Undergraduate Teaching Projects of China University of Geosciences (Nos. ZL201610 and 2018G36)
文摘Migmatite-like rocks transformed from strongly metamorphosed and deformed enclave- bearing felsic plutons usually make people confuse with the true migmatites and mistake in interpreta- tion of their petrogenesis and tectonic implications. Here we report a suite of rocks that have long been called as migmatites from the Guandi complex in Zhoukoudian region, southwest of Beijing. The rocks are dominated by felsic gneisses with garnet-free amphibolites. Field occurrence, petrography and geochemistry indicate that the felsic gneisses and amphibolites were metamorphosed from protoliths of intermediate-acid and basic igneous rocks, respectively. New LA-ICP-MS zircon U-Pb dating and geothermobarometry study further reveal that precursor magmas of the two types of rocks were emplaced at 2.54-2.56 Ga and the rocks subsequently underwent medium P/T-type metamorphism with upper amphibolite facies conditions of 0.55-0.90 GPa and 670-730℃ at -2.48-2.50 Ga. Geochemically, precursor magmas of the amphibolites were suggested to be derived from an enriched lithospheric mantle source in continental arc setting, and those of the felsic gneisses are characterized by tonalitic to trondhjemitic magmas that are usually considered to be generated by partial melting of hydrated, thickened metamorphosed mafic crust with garnet as residues, suggesting that the rock associations are not of true migmatites but migmatite-like rocks. Our study reveal that protoliths of the migmatite-like rocks from the Guandi complex, were likely formed via magmatism in a continental arc setting, followed by accretion and collision of the continental arc as well as the intro-oceanic arc terranes to the Eastern Block of the North China Craton in the transition from the Late Neoarchean to Early Paleoprnterozuic.
