The Beizhan large iron deposit located in the east part of the Awulale metallogenic belt in the western Tianshan Mountains is hosted in the Unit 2 of the Dahalajunshan Formation as lens, veinlets and stratoid, and bot...The Beizhan large iron deposit located in the east part of the Awulale metallogenic belt in the western Tianshan Mountains is hosted in the Unit 2 of the Dahalajunshan Formation as lens, veinlets and stratoid, and both of the hanging wall and footwall are quartz-monzonite; the dip is to the north with thick and high-grade ore bodies downwards. Ore minerals are mainly magnetite with minor sulfides, such as pyrite, pyrrhotite, chalcopyrite and sphalerite. Skarnization is widespread around the ore bodies, and garnet, diopside, wollastonite, actinolite, epidote, uralite, tourmaline sericite and calcite are ubiquitous as gangues. Radiating outwards from the center of the ore body the deposit can be classified into skarn, calcite, serpentinite and marble zones. LA-ICP-MS zircon U-Pb dating of the rhyolite and dacite from the Dahalajunshan Formation indicates that they were formed at 301.3±0.8 Ma and 303.7±0.9 Ma, respectively, which might have been related to the continental arc magmatism during the late stage of subduction in the western Tianshan Mountains. Iron formation is genetically related with volcanic eruption during this interval. The Dahalajunshan Formation and the quartz-monzonite intrusion jointly control the distribution of ore bodies. Both ore textures and wall rock alteration indicate that the Beizhan iron deposit is probably skarn type.展开更多
Marble is associated with ultrahigh pressure eclogite in the Dabie Mountains.East China.U-Pb isotope data for the marble define a 238U-206Pb isochron age of 435±45a with an initial 206Pb/204Pb value of 18.075...Marble is associated with ultrahigh pressure eclogite in the Dabie Mountains.East China.U-Pb isotope data for the marble define a 238U-206Pb isochron age of 435±45a with an initial 206Pb/204Pb value of 18.075±0.006,The age of -435 Ma is interpreted to represent the time of limestone diagensis rather than the time of metarmorphic resetting accompanied by the formation of the ultrahigh pressure eclogites at Triassic.The paleontologic and stratigraphic studies also favor a local excursion in the carbon isotopic composition of the latest ordovician water within a sedimentary basin between the Sino-Korean and Yangtze cratos.Becasuse the latest ordovician limestone was involved in the eclogite formation,the continental collision between the Yangtze and Sino-Korean Plates would postdate ordovican.展开更多
The Shicaogou granite has been identified as a magnesian (Fe-number=0.71-0.76), calcic to calc-alkalic (MALI=3.84-5.76) and peraluminous (ASI=1.06-1.13) granite of the syn-collisional S-type, with high SiO2(>71%), ...The Shicaogou granite has been identified as a magnesian (Fe-number=0.71-0.76), calcic to calc-alkalic (MALI=3.84-5.76) and peraluminous (ASI=1.06-1.13) granite of the syn-collisional S-type, with high SiO2(>71%), A12O3 (>13%) and Na2O+K2O (6.28%-7.33%, equal for NaO2 and K2O). Trace element and REE analyses show that the granite is rich in LILE such as of Rb, Sr, Ba and Th, and poor in HFSE like Yb, Y, Zr and Hf. Its Rb/Sr ratio is greater than 1; the contents of Nb and Ta, and the ratio of Nb/Ta as well as the REE geochemical features (e.g. REE abundance, visible fractionation of LREE and HREE and medium to pronounced negative Eu anomalies) are all similar to those of crust-origin, continent-continent syn-collisional granite. Moreover, the granite exhibits almost the same pattern as that of the typical continent-continent syn-collisional granite on the spider diagram and all samples fall within the syn-collisional granite field.The cathodoluminescence (CL) investigations have revealed that the zircon from the Shicaogou granite represents a typical magmatic product characterized by its colorless, transparent and euhedral crystals, and distinct zoning of oscillatory bands. Residual cores of irregular zircon can be found in a few enhedral grains. Trace element studies of the zircon grains, with high contents of P, Y, Hf, Th, U and REE and high ratios of Th/U, obviously positive Ce anomalies and HREE enrichment compared to LREE, also result in the same conclusion.The LA-ICP-MS U-Pb isotopic data from 24 spots of 21 zircon grains demonstrate that 20 spots in the oscillatory zone yield an average weighted 206Pb/238U age of 925±11 Ma, indicating that the Shicaogou granite was formed in the Neoproterozoic. Combined with other Neoproterozoic syn-collisional granites found in the study area, the present geochronological determination can further reveal that collision-amalgamation events could have occurred among some continental blocks in the Qinling orogenic belt during the Neoproterozoic. This in turn provides an accurate chronological constraint on the Neoproterozoic break-up and convergence in the belt.展开更多
The general classification of intermediate-acid intrusive rocks in the metamorphic zone of Gaoligong Mountains as one of the metamorphic terranes of Proterozoic Gaoligong Mountains is problematic regarding the intrusi...The general classification of intermediate-acid intrusive rocks in the metamorphic zone of Gaoligong Mountains as one of the metamorphic terranes of Proterozoic Gaoligong Mountains is problematic regarding the intrusion stage and age, as well as the subsequent metamorphism and deformation. In this study, we investigated granitic gneiss in the metamorphic zone of Gaoligong Mountains based on the 1：50,000 regional geological survey of Qushi Street （2011-2013） and SHRIMP U-Pb zircon geochronology. Results showed that the SHRIMP U-Pb zircon dating of granitic gneiss ranged from 163.5±5.7 Ma to 74.0±2.0 Ma. Thus, the granitic gneiss was grouped into orthometamorphic rocks （metamorphic intrusions）. The dating data of granite rocks associated with intense metamorphism and deformation were divided into three groups, 163.5±5.7 to 162.3±3.1 Ma, 132.2-101.0 Ma and 99.4±3.5-74.0±2.0 Ma, which respectively represented three independent geologic events including an important magma intrusion with superimposed metamorphic effects in the late Middle Jurassic, regional dynamic metamorphism and superimposed reformation of fluid action in the early Cretaceous, and dynamic metamorphism dominated by ductile shear and metamorphism starting from the late Cretaceous.展开更多
The Yushugou terrain of high\|pressure granulite facies in southern Tianshan Mountain is composed mainly of an ophiolite suite. Most selected zircons are round or elliptical in shape, and some are of tetragonal prism ...The Yushugou terrain of high\|pressure granulite facies in southern Tianshan Mountain is composed mainly of an ophiolite suite. Most selected zircons are round or elliptical in shape, and some are of tetragonal prism with round edges. The granulometric analyses show that they are well sorted in sedimentation. ZrO\-2/HfO\-2 ratios in zircons range from 45 to 57. These characters, together with the petrologic and geochemical characters of plagioclase\|garnet\|orthopyroxenite bearing zircons, indicate that the protolith of plagioclase\|garnet\|orthopyroxenite may be derived mainly from volcanic base surge sedimentary debris in oceanic islands and from clays formed by seafloor weathering. Zircons are simply of pyroclastic debris. The ophiolite formation age of (440±18) Ma and the first\|stage metamorphic age (amphibolite or granulite facies) of (364±5) Ma were obtained with a method of multiple grains in different groups and a method of concordia plot. These ages provide important information on the temporal and spatial occurrence of southern Paleozoic Tianshan Ocean, the subduction rate of the oceanic crust and the formation mechanism of ophiolite of granulite facies.展开更多
The Grove Mountains, 400 km south of the Chinese Antarctic Zhongshan Station, are an inland continuation of the Pan-African-aged （i.e., Late Neoproterozoic/Cambrian） Prydz Belt, East Antarctica. In this paper we car...The Grove Mountains, 400 km south of the Chinese Antarctic Zhongshan Station, are an inland continuation of the Pan-African-aged （i.e., Late Neoproterozoic/Cambrian） Prydz Belt, East Antarctica. In this paper we carried out a combined U-Th-Pb monazite and Sm-Nd mineral-whole-rock dating on para- and orthogneisses from bedrock in the Grove Mountains. U-Th-Pb monazite dating of a cordierite-bearing pelitic paragneiss yields ages of 523 ？ 4 Ma for the cores and 508 ？ 6 Ma for the rims. Sm-Nd mineral-whole-rock isotopic analyses yield isochron ages of 536 ？ 3 Ma for a coarse-grained felsic orthogneiss and 507 ？ 30 Ma for a fine-grained quartzofeldspathic paragneiss. Combined with previously published age data in the Grove Mountains and adjacent areas, the older age of ~530 Ma is interpreted as the time of regional medium- to low-pressure granulite-facies metamorphism, and the younger age of ~510 Ma as the cooling age of the granulite terrane. The absence of evidence for a Grenville-aged （i.e., Late Mesoproterozoic/Early Neoproterozoic） metamorphic event indicates that the Grove Mountains have experienced only a single metamorphic cycle, i.e., Pan-African-aged, which distinguishes them from other polymetamorphic terranes in the Prydz Belt. This will provide important constraints on the controversial nature of the Prydz Belt.展开更多
基金supported by Project 2012CB416803 of the State Key Fundamental Programthe National Scientific and Technological Supporting Key Projects (#2011BAB06B02)Geological Survey Project No. 1212011085060
文摘The Beizhan large iron deposit located in the east part of the Awulale metallogenic belt in the western Tianshan Mountains is hosted in the Unit 2 of the Dahalajunshan Formation as lens, veinlets and stratoid, and both of the hanging wall and footwall are quartz-monzonite; the dip is to the north with thick and high-grade ore bodies downwards. Ore minerals are mainly magnetite with minor sulfides, such as pyrite, pyrrhotite, chalcopyrite and sphalerite. Skarnization is widespread around the ore bodies, and garnet, diopside, wollastonite, actinolite, epidote, uralite, tourmaline sericite and calcite are ubiquitous as gangues. Radiating outwards from the center of the ore body the deposit can be classified into skarn, calcite, serpentinite and marble zones. LA-ICP-MS zircon U-Pb dating of the rhyolite and dacite from the Dahalajunshan Formation indicates that they were formed at 301.3±0.8 Ma and 303.7±0.9 Ma, respectively, which might have been related to the continental arc magmatism during the late stage of subduction in the western Tianshan Mountains. Iron formation is genetically related with volcanic eruption during this interval. The Dahalajunshan Formation and the quartz-monzonite intrusion jointly control the distribution of ore bodies. Both ore textures and wall rock alteration indicate that the Beizhan iron deposit is probably skarn type.
文摘Marble is associated with ultrahigh pressure eclogite in the Dabie Mountains.East China.U-Pb isotope data for the marble define a 238U-206Pb isochron age of 435±45a with an initial 206Pb/204Pb value of 18.075±0.006,The age of -435 Ma is interpreted to represent the time of limestone diagensis rather than the time of metarmorphic resetting accompanied by the formation of the ultrahigh pressure eclogites at Triassic.The paleontologic and stratigraphic studies also favor a local excursion in the carbon isotopic composition of the latest ordovician water within a sedimentary basin between the Sino-Korean and Yangtze cratos.Becasuse the latest ordovician limestone was involved in the eclogite formation,the continental collision between the Yangtze and Sino-Korean Plates would postdate ordovican.
基金the National NaturalScience Foundation of China(Grant No.140032010-C,49972063)the National Key Basic Research andDevelopment Project of China(Grant No.G1999075508)+3 种基金the Ministry of Education's Teacher Fund(No.40133020)the Natural Science Foundation of Shaanxi Province(2002D03)the Special Foundation of the Department ofEducation of Shaanxi Province(01JK108) the ScienceFoundation of Northwest University.
文摘The Shicaogou granite has been identified as a magnesian (Fe-number=0.71-0.76), calcic to calc-alkalic (MALI=3.84-5.76) and peraluminous (ASI=1.06-1.13) granite of the syn-collisional S-type, with high SiO2(>71%), A12O3 (>13%) and Na2O+K2O (6.28%-7.33%, equal for NaO2 and K2O). Trace element and REE analyses show that the granite is rich in LILE such as of Rb, Sr, Ba and Th, and poor in HFSE like Yb, Y, Zr and Hf. Its Rb/Sr ratio is greater than 1; the contents of Nb and Ta, and the ratio of Nb/Ta as well as the REE geochemical features (e.g. REE abundance, visible fractionation of LREE and HREE and medium to pronounced negative Eu anomalies) are all similar to those of crust-origin, continent-continent syn-collisional granite. Moreover, the granite exhibits almost the same pattern as that of the typical continent-continent syn-collisional granite on the spider diagram and all samples fall within the syn-collisional granite field.The cathodoluminescence (CL) investigations have revealed that the zircon from the Shicaogou granite represents a typical magmatic product characterized by its colorless, transparent and euhedral crystals, and distinct zoning of oscillatory bands. Residual cores of irregular zircon can be found in a few enhedral grains. Trace element studies of the zircon grains, with high contents of P, Y, Hf, Th, U and REE and high ratios of Th/U, obviously positive Ce anomalies and HREE enrichment compared to LREE, also result in the same conclusion.The LA-ICP-MS U-Pb isotopic data from 24 spots of 21 zircon grains demonstrate that 20 spots in the oscillatory zone yield an average weighted 206Pb/238U age of 925±11 Ma, indicating that the Shicaogou granite was formed in the Neoproterozoic. Combined with other Neoproterozoic syn-collisional granites found in the study area, the present geochronological determination can further reveal that collision-amalgamation events could have occurred among some continental blocks in the Qinling orogenic belt during the Neoproterozoic. This in turn provides an accurate chronological constraint on the Neoproterozoic break-up and convergence in the belt.
基金part of the 1:50000 regional geological surveys of Qushi Sheet, Daqie Street and Dadong Street carried out in 2004 and financially supported by the National Program on Key BasicResearch Project of China (973 Program)(No.2009CB421007)
文摘The general classification of intermediate-acid intrusive rocks in the metamorphic zone of Gaoligong Mountains as one of the metamorphic terranes of Proterozoic Gaoligong Mountains is problematic regarding the intrusion stage and age, as well as the subsequent metamorphism and deformation. In this study, we investigated granitic gneiss in the metamorphic zone of Gaoligong Mountains based on the 1：50,000 regional geological survey of Qushi Street （2011-2013） and SHRIMP U-Pb zircon geochronology. Results showed that the SHRIMP U-Pb zircon dating of granitic gneiss ranged from 163.5±5.7 Ma to 74.0±2.0 Ma. Thus, the granitic gneiss was grouped into orthometamorphic rocks （metamorphic intrusions）. The dating data of granite rocks associated with intense metamorphism and deformation were divided into three groups, 163.5±5.7 to 162.3±3.1 Ma, 132.2-101.0 Ma and 99.4±3.5-74.0±2.0 Ma, which respectively represented three independent geologic events including an important magma intrusion with superimposed metamorphic effects in the late Middle Jurassic, regional dynamic metamorphism and superimposed reformation of fluid action in the early Cretaceous, and dynamic metamorphism dominated by ductile shear and metamorphism starting from the late Cretaceous.
文摘The Yushugou terrain of high\|pressure granulite facies in southern Tianshan Mountain is composed mainly of an ophiolite suite. Most selected zircons are round or elliptical in shape, and some are of tetragonal prism with round edges. The granulometric analyses show that they are well sorted in sedimentation. ZrO\-2/HfO\-2 ratios in zircons range from 45 to 57. These characters, together with the petrologic and geochemical characters of plagioclase\|garnet\|orthopyroxenite bearing zircons, indicate that the protolith of plagioclase\|garnet\|orthopyroxenite may be derived mainly from volcanic base surge sedimentary debris in oceanic islands and from clays formed by seafloor weathering. Zircons are simply of pyroclastic debris. The ophiolite formation age of (440±18) Ma and the first\|stage metamorphic age (amphibolite or granulite facies) of (364±5) Ma were obtained with a method of multiple grains in different groups and a method of concordia plot. These ages provide important information on the temporal and spatial occurrence of southern Paleozoic Tianshan Ocean, the subduction rate of the oceanic crust and the formation mechanism of ophiolite of granulite facies.
基金financial support from the National Natural Science Foundation of China (Grant no.41530209)the Central Public-Interest Scientific Institution Basal Research Fund (Grant no.JYYWF201819)
文摘The Grove Mountains, 400 km south of the Chinese Antarctic Zhongshan Station, are an inland continuation of the Pan-African-aged （i.e., Late Neoproterozoic/Cambrian） Prydz Belt, East Antarctica. In this paper we carried out a combined U-Th-Pb monazite and Sm-Nd mineral-whole-rock dating on para- and orthogneisses from bedrock in the Grove Mountains. U-Th-Pb monazite dating of a cordierite-bearing pelitic paragneiss yields ages of 523 ？ 4 Ma for the cores and 508 ？ 6 Ma for the rims. Sm-Nd mineral-whole-rock isotopic analyses yield isochron ages of 536 ？ 3 Ma for a coarse-grained felsic orthogneiss and 507 ？ 30 Ma for a fine-grained quartzofeldspathic paragneiss. Combined with previously published age data in the Grove Mountains and adjacent areas, the older age of ~530 Ma is interpreted as the time of regional medium- to low-pressure granulite-facies metamorphism, and the younger age of ~510 Ma as the cooling age of the granulite terrane. The absence of evidence for a Grenville-aged （i.e., Late Mesoproterozoic/Early Neoproterozoic） metamorphic event indicates that the Grove Mountains have experienced only a single metamorphic cycle, i.e., Pan-African-aged, which distinguishes them from other polymetamorphic terranes in the Prydz Belt. This will provide important constraints on the controversial nature of the Prydz Belt.
