The Late Archean Fuping Group of the Xiaojiao area in Pingshan County, HebeiProvince consists mainly of three metamorphic rock types of supracrustal affinity, i. e., K-feldspar leucoleptite, biotite leptite-gneiss and...The Late Archean Fuping Group of the Xiaojiao area in Pingshan County, HebeiProvince consists mainly of three metamorphic rock types of supracrustal affinity, i. e., K-feldspar leucoleptite, biotite leptite-gneiss and hornblendic rocks. Their anatectic derivativesformed in the initial stage of anatexis are petrochemically of K-feldspar granitic, trondhjemiticand granodioritic compositions respectively, and in general have inherited the main petrochemi-cal features from their parent rock types. Probably due to the fact that they contain less REE-rich accessory minerals as compared with their parent rocks, the anatectic derivatives are ingeneral lower in ∑REE content. But both the derivatives and their parent rocks have similarREE patterns, which serves as an additional indication of the genetic relationship betweenthem.展开更多
Parametamorphic rocks from Arong County in southeastern Inner Mongolia- Daxinganling district are regarded as Proterozoic in age, belonging to the Wolegen Group and composed of volcanoclastic and sand- stone in origin...Parametamorphic rocks from Arong County in southeastern Inner Mongolia- Daxinganling district are regarded as Proterozoic in age, belonging to the Wolegen Group and composed of volcanoclastic and sand- stone in origin, and have been disputed in tectonic setting. Because of the stability in metamorphism, the rare earth elements indicate the features of their protoliths. The authors integrated the petrologic methods with the geochemical parameters which include ЕREE, ЕLREE/NHREE, δCe, δEu, La/Yb, Sm/Nd, Th/Sc and the standard values of chondrite. The results show that the protoliths of Wolengen Group may be a group of volcanoclastic and continental margin clastic rocks, and their tectonic setting is the continent island arc.展开更多
Detailed REE geochemical studies of the Xingzi Group metasedimentary rocks at Lushan and rock-forming minerals such as garnet have been conducted and the results show that the REEs are partly present in the rock-formi...Detailed REE geochemical studies of the Xingzi Group metasedimentary rocks at Lushan and rock-forming minerals such as garnet have been conducted and the results show that the REEs are partly present in the rock-forming minerals and are dominantly contained in the lattice of accessory minerals. In the process of metamorphism the REEs reached partition equilibrium between garnet porphyroblast and rock and the partitioning of REEs between garnet and host rock is obviously controlled by the chemical composition of the system. The REE compositions of metamorphic veins and their minerals display remarked lanthanide tetrad effects and the element pairs Zr-Hf, U-Th and Y-Ho have also experienced remarkable fractionation with respect to the metamorphic rocks and they can be used as discriminating indicators for the occurrence of fluid processes in the process of metamorphism of the Xingzi Group.展开更多
Samples were systematically collected from metamorphic basic volcanic rocks in the Jiehekou and Xiyupi areas on both sides of the Lüliang Mountains, Shanxi Province and analyzed for their major elements, trace el...Samples were systematically collected from metamorphic basic volcanic rocks in the Jiehekou and Xiyupi areas on both sides of the Lüliang Mountains, Shanxi Province and analyzed for their major elements, trace elements and rare earth elements (REE). The geochemical characteristics of their major, trace and rare-earth elements indicated that the metamorphic basic volcanic rocks in this area were emplaced in the tectonic environment like a modern continental rift. Sm-Nd and Rb-Sr isotope chronological studies demonstrated that the Jiehekou Group metamorphic basic volcanic rocks were formed during the 2600-Ma crust/mantle differentiation event, and were transformed by granulite facies metamorphism during the late Neo-Archaean period (2500 Ma ±), making the Sm-Nd systematics of the rocks reset. During the late Paleoproterozoic period (1800 Ma ±) the Rb-Sr systematics of the rocks were disturbed again in response to the Lüliang movement. Since the extent of disturbance was so weak that the Sm-Nd systematics was not affected, the age of 1600 Ma ± obtained from this area seems to be related to local magmatic activities within the craton. Research results lend no support to the idea that the Lüliang Group was formed during the Archaean. Instead, it should be formed during the Proterozoic.展开更多
METAMORPHIC fluids, an important type of the ore-forming fluids within the Earth’ s crust, are the necessary materials for metamorphic hydrothermal ore formation. Their direct products are varieties of synmetamorphic...METAMORPHIC fluids, an important type of the ore-forming fluids within the Earth’ s crust, are the necessary materials for metamorphic hydrothermal ore formation. Their direct products are varieties of synmetamorphic veins occurring in metamorphic rocks’. Studies on the genesis of these veins can be availablefor investigating the source material and formation processes of metamorphic hydrothermal deposit. Previous studies on metamorphic veins have focused mainly on their mineralogical, major elemental and oxygenisotopic compositions, and two different hypotheses have been advanced to account for metamorphicvein genesis. In this paper, we use rare-earth elemental method, together with field geological andpetrologic studies, to inquire into the origin of synmetamorphic veins occurring in Xingzi Group ofLushan, southeast China.展开更多
A report is presented of SHRIMP zircon U-Pb dating data of meta-igneous and meta-sedimentary rocks of the Xinghuadukou Group(Xinlin-Hanjiayuanzi area,Heilongjiang Province)and meta-volcanic rocks of the Zhalantun Grou...A report is presented of SHRIMP zircon U-Pb dating data of meta-igneous and meta-sedimentary rocks of the Xinghuadukou Group(Xinlin-Hanjiayuanzi area,Heilongjiang Province)and meta-volcanic rocks of the Zhalantun Group(Zhalantun district,Inner Mongolia).The SHRIMP analyses show that the meta-igneous rocks from the Xinghuadukou Group formed at 506±10―547±46 Ma,belonging to Early-Middle Precambrian,whereas the meta-sedimentary rocks yielded detrital zircons,with ages of 1.0―1.2,1.6―1.8 and 2.5―2.6 Ga,indicative of deposition age at least<1.0 Ga. Meta-basic volcanic rocks from the Zhalantun Group have a formation age of 506±3 Ma.These data suggest that both the Xinghuadukou and Zhalantun Groups formed during Cambrian and/or Neoproterozoic time,rather than Paleoproterozoic time as previously thought.Early Precambrian inherited zircons in the meta-igneous rocks and numerous Precambrian detrital zircons in the meta-sedimentary rocks imply that these rocks were formed proximal to older crust.It is inferred that the Xinghuadukou and Zhalantun Groups represent Cambrian and/or Neoproterozoic vol- cano-sedimentary sequences formed in an active continental margin setting.展开更多
文摘The Late Archean Fuping Group of the Xiaojiao area in Pingshan County, HebeiProvince consists mainly of three metamorphic rock types of supracrustal affinity, i. e., K-feldspar leucoleptite, biotite leptite-gneiss and hornblendic rocks. Their anatectic derivativesformed in the initial stage of anatexis are petrochemically of K-feldspar granitic, trondhjemiticand granodioritic compositions respectively, and in general have inherited the main petrochemi-cal features from their parent rock types. Probably due to the fact that they contain less REE-rich accessory minerals as compared with their parent rocks, the anatectic derivatives are ingeneral lower in ∑REE content. But both the derivatives and their parent rocks have similarREE patterns, which serves as an additional indication of the genetic relationship betweenthem.
文摘Parametamorphic rocks from Arong County in southeastern Inner Mongolia- Daxinganling district are regarded as Proterozoic in age, belonging to the Wolegen Group and composed of volcanoclastic and sand- stone in origin, and have been disputed in tectonic setting. Because of the stability in metamorphism, the rare earth elements indicate the features of their protoliths. The authors integrated the petrologic methods with the geochemical parameters which include ЕREE, ЕLREE/NHREE, δCe, δEu, La/Yb, Sm/Nd, Th/Sc and the standard values of chondrite. The results show that the protoliths of Wolengen Group may be a group of volcanoclastic and continental margin clastic rocks, and their tectonic setting is the continent island arc.
基金Project supported jointly by the Outstanding Youth Foundation (Grant No. 49625304)the Ministry of Science and Tech nology of China (Grant No. 95-Pre-39).
文摘Detailed REE geochemical studies of the Xingzi Group metasedimentary rocks at Lushan and rock-forming minerals such as garnet have been conducted and the results show that the REEs are partly present in the rock-forming minerals and are dominantly contained in the lattice of accessory minerals. In the process of metamorphism the REEs reached partition equilibrium between garnet porphyroblast and rock and the partitioning of REEs between garnet and host rock is obviously controlled by the chemical composition of the system. The REE compositions of metamorphic veins and their minerals display remarked lanthanide tetrad effects and the element pairs Zr-Hf, U-Th and Y-Ho have also experienced remarkable fractionation with respect to the metamorphic rocks and they can be used as discriminating indicators for the occurrence of fluid processes in the process of metamorphism of the Xingzi Group.
基金the Key Project of the Chinese Academy of Sciences(Grant No.KZ951-A1-404) the Key Project(Grant No KZCX1-07)under the Knowledge-Innovation Program of the ChineseAcademy of Sciences.
文摘Samples were systematically collected from metamorphic basic volcanic rocks in the Jiehekou and Xiyupi areas on both sides of the Lüliang Mountains, Shanxi Province and analyzed for their major elements, trace elements and rare earth elements (REE). The geochemical characteristics of their major, trace and rare-earth elements indicated that the metamorphic basic volcanic rocks in this area were emplaced in the tectonic environment like a modern continental rift. Sm-Nd and Rb-Sr isotope chronological studies demonstrated that the Jiehekou Group metamorphic basic volcanic rocks were formed during the 2600-Ma crust/mantle differentiation event, and were transformed by granulite facies metamorphism during the late Neo-Archaean period (2500 Ma ±), making the Sm-Nd systematics of the rocks reset. During the late Paleoproterozoic period (1800 Ma ±) the Rb-Sr systematics of the rocks were disturbed again in response to the Lüliang movement. Since the extent of disturbance was so weak that the Sm-Nd systematics was not affected, the age of 1600 Ma ± obtained from this area seems to be related to local magmatic activities within the craton. Research results lend no support to the idea that the Lüliang Group was formed during the Archaean. Instead, it should be formed during the Proterozoic.
文摘METAMORPHIC fluids, an important type of the ore-forming fluids within the Earth’ s crust, are the necessary materials for metamorphic hydrothermal ore formation. Their direct products are varieties of synmetamorphic veins occurring in metamorphic rocks’. Studies on the genesis of these veins can be availablefor investigating the source material and formation processes of metamorphic hydrothermal deposit. Previous studies on metamorphic veins have focused mainly on their mineralogical, major elemental and oxygenisotopic compositions, and two different hypotheses have been advanced to account for metamorphicvein genesis. In this paper, we use rare-earth elemental method, together with field geological andpetrologic studies, to inquire into the origin of synmetamorphic veins occurring in Xingzi Group ofLushan, southeast China.
基金Supported by the National Natural Science Foundation of China(Grant Nos.40473030 and 40234045)the Chinese Academy of Sciences(Grant No.KZCX2-104)and the Key Laboratory Mineral Resources,Chinese Academy of Sciences
文摘A report is presented of SHRIMP zircon U-Pb dating data of meta-igneous and meta-sedimentary rocks of the Xinghuadukou Group(Xinlin-Hanjiayuanzi area,Heilongjiang Province)and meta-volcanic rocks of the Zhalantun Group(Zhalantun district,Inner Mongolia).The SHRIMP analyses show that the meta-igneous rocks from the Xinghuadukou Group formed at 506±10―547±46 Ma,belonging to Early-Middle Precambrian,whereas the meta-sedimentary rocks yielded detrital zircons,with ages of 1.0―1.2,1.6―1.8 and 2.5―2.6 Ga,indicative of deposition age at least<1.0 Ga. Meta-basic volcanic rocks from the Zhalantun Group have a formation age of 506±3 Ma.These data suggest that both the Xinghuadukou and Zhalantun Groups formed during Cambrian and/or Neoproterozoic time,rather than Paleoproterozoic time as previously thought.Early Precambrian inherited zircons in the meta-igneous rocks and numerous Precambrian detrital zircons in the meta-sedimentary rocks imply that these rocks were formed proximal to older crust.It is inferred that the Xinghuadukou and Zhalantun Groups represent Cambrian and/or Neoproterozoic vol- cano-sedimentary sequences formed in an active continental margin setting.
