The origin, age and evolution of the Precambrian metamorphic basement of southern China provide useful insights into early crustal development. Here, we present new laser ablation-inductively coupled plasma-mass spect...The origin, age and evolution of the Precambrian metamorphic basement of southern China provide useful insights into early crustal development. Here, we present new laser ablation-inductively coupled plasma-mass spectrometry （LA-ICP-MS） U-Pb age data for detrital zircons from five samples of the Precambrian metamorphic basement of the Xiangshan uranium orefield. Two of these samples, from the northern Xiangshan volcanic basin, yielded a total of 140 U-Pb ages that cluster within the Neoproterozoic （773-963 Ma; 79.3% of data points）, with the rest being scattered through the Paleoproterozoic and Mesoproterozoic, along with a single Archean age. These ages indicate that this basement material is associated with the Cathaysia Block. In comparison, the 172 concordant ages from the other three samples from the southern part of the Xiangshan volcanic basin cluster within the Neoproterozoic （767-944 Ma; 59.8%） as well as the Proterozoic （37.8%） and the Archean （2502-2712 Ma; 14.5%）. These samples are also free of zircons with Grenvillian ages, indicating that these units are associated with the southeastern Yangtze Block. Combining these data with the geochemistry of these units, which suggests that the metamorphosed sedimentary rocks within the northern and southern parts of the Xiangshan basin have a common component from a magmatic island arc that formed during the early Neoproterozoic, we infer that the basin was located along the boundary between the Cathaysian and Yangtze blocks. In addition, the zircons within the samples from the southern and northern parts of the Xiangshan basin show different pre-Neoproterozoic （963 Ma） age populations but similar post- Neoproterozoic zircon populations, indicating that the amalgamation of the Cathaysian and Yangtze blocks occurred after the Neoproterozoic （960 Ma）, with magmatism peaking at 830 Ma and rifting starting at -770 Ma, leading to the subsequent deposition （from bottom to top） of the Shenshan, Kuli, and Shangshi formations.展开更多
The Precambrian basement rocks in the Bengbu and neighboring areas, located at the southeastern margin of the North China Craton, occur as granulite terrains and xenoliths in the Mesozoic dioritic porphyry.
We report zircon U-Pb geochronology,geochemistry and Sr-Nd-Pb isotope data from mafic granulites and garnet amphibolites of the Wuhe Complex in the southeastern margin of the North China Craton (NCC).In combination wi...We report zircon U-Pb geochronology,geochemistry and Sr-Nd-Pb isotope data from mafic granulites and garnet amphibolites of the Wuhe Complex in the southeastern margin of the North China Craton (NCC).In combination with previous data,our results demonstrate that these rocks represent fragments of the ancient lower crust,and have features similar to those of the granulite basement in the northern margin of the NCC.A detailed evaluation of the Pb isotope data shows that Pb isotopes cannot effectively distinguish the role of the Yangtze Craton basement from that of the NCC basement with regard to the source and generation of magmas,at least for southeastern NCC.The age data suggest that the protoliths of the granulites or amphibolites in the Wuhe Complex were most likely generated in Neoarchean and that these rocks were subjected to Paleoproterozoic(1.8-1.9 Ga) high-pressure granulite facies metamorphism. This study also shows that the Precambrian metamorphic basement in the southeastern margin of the NCC might have formed in a tectonic setting characterized by a late Neoarchean active continental margin.展开更多
The late Mesozoic antimony(Sb)mineralization belt in South China hosts a large portion of the world’s Sb reserves.However,the source and mineralization processes of these Sb deposits remain controversial.Here,we meas...The late Mesozoic antimony(Sb)mineralization belt in South China hosts a large portion of the world’s Sb reserves.However,the source and mineralization processes of these Sb deposits remain controversial.Here,we measured mercury(Hg)concentrations and isotopic compositions of stibnite in the Banpo Sb-only and Woxi Sbpolymetallic ore deposits,as well as associated rocks in the Yangtze Block in order to constrain the metal sources and ore formation processes in the South China Sb mineralization belt.Stibnite samples from both deposits exhibit significant enrichment in Hg(4.23–50.6 ppm)and have higher δ^(202)Hg values(−0.47‰to 2.03‰)than the studied Precambrian basement rocks(−1.42‰to 0.59‰),Paleozoic sedimentary rocks(−2.40‰to−0.32‰),and other natural Hg reserves(e.g.,marine and continental systems).This indicates that significant mass-dependent fractionation of Hg isotopes occurred during hydrothermal processes.Negative to slightly positive Δ^(199)Hg values of−0.17‰to 0.02‰were obtained for stibnite from the studied deposits,similar to values for the Precambrian basement rocks,but different from those of the Paleozoic sedimentary rocks and data previously reported for mantle materials.This suggests that Precambrian basement rocks were the source of Hg and associated metals.Our data and the tectonic evolution of South China indicate that late Mesozoic asthenospheric upwelling,in response to the Paleo-Pacific oceanic slab foundering,generated heat that drove the circulation of fluids in the basement and crustal basinal rocks.These fluids leached Sb,Hg,and other metals from the Precambrian basement rocks and formed the world-class Sb mineralization belt in South China.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.41602069 and 41572185)the Fundamental Science on Radioactive Geology and Exploration Technology Laboratory(Grant No.RGET1402)+1 种基金the Natural Science Foundation of Jiangxi Province(Grant No.20171BAB213026)Science and technology research projectfrom the Education Department of Jiangxi Province(Grant No.GJJ150554)
文摘The origin, age and evolution of the Precambrian metamorphic basement of southern China provide useful insights into early crustal development. Here, we present new laser ablation-inductively coupled plasma-mass spectrometry （LA-ICP-MS） U-Pb age data for detrital zircons from five samples of the Precambrian metamorphic basement of the Xiangshan uranium orefield. Two of these samples, from the northern Xiangshan volcanic basin, yielded a total of 140 U-Pb ages that cluster within the Neoproterozoic （773-963 Ma; 79.3% of data points）, with the rest being scattered through the Paleoproterozoic and Mesoproterozoic, along with a single Archean age. These ages indicate that this basement material is associated with the Cathaysia Block. In comparison, the 172 concordant ages from the other three samples from the southern part of the Xiangshan volcanic basin cluster within the Neoproterozoic （767-944 Ma; 59.8%） as well as the Proterozoic （37.8%） and the Archean （2502-2712 Ma; 14.5%）. These samples are also free of zircons with Grenvillian ages, indicating that these units are associated with the southeastern Yangtze Block. Combining these data with the geochemistry of these units, which suggests that the metamorphosed sedimentary rocks within the northern and southern parts of the Xiangshan basin have a common component from a magmatic island arc that formed during the early Neoproterozoic, we infer that the basin was located along the boundary between the Cathaysian and Yangtze blocks. In addition, the zircons within the samples from the southern and northern parts of the Xiangshan basin show different pre-Neoproterozoic （963 Ma） age populations but similar post- Neoproterozoic zircon populations, indicating that the amalgamation of the Cathaysian and Yangtze blocks occurred after the Neoproterozoic （960 Ma）, with magmatism peaking at 830 Ma and rifting starting at -770 Ma, leading to the subsequent deposition （from bottom to top） of the Shenshan, Kuli, and Shangshi formations.
基金financially supported by the Ph.D Foundation of the Ministry of Education of China(grant No.20133402130008)the National Basic Research Program of China(grant No.2015CB856104)the National Natural Science Foundation of China(grant No.41273036)
文摘The Precambrian basement rocks in the Bengbu and neighboring areas, located at the southeastern margin of the North China Craton, occur as granulite terrains and xenoliths in the Mesozoic dioritic porphyry.
基金supported by the National Natural Science Foundation of China(Grant Nos.90814008,40634023 and 40973043)the National Basic Research Program of China (Grant No.2009CB825002)
文摘We report zircon U-Pb geochronology,geochemistry and Sr-Nd-Pb isotope data from mafic granulites and garnet amphibolites of the Wuhe Complex in the southeastern margin of the North China Craton (NCC).In combination with previous data,our results demonstrate that these rocks represent fragments of the ancient lower crust,and have features similar to those of the granulite basement in the northern margin of the NCC.A detailed evaluation of the Pb isotope data shows that Pb isotopes cannot effectively distinguish the role of the Yangtze Craton basement from that of the NCC basement with regard to the source and generation of magmas,at least for southeastern NCC.The age data suggest that the protoliths of the granulites or amphibolites in the Wuhe Complex were most likely generated in Neoarchean and that these rocks were subjected to Paleoproterozoic(1.8-1.9 Ga) high-pressure granulite facies metamorphism. This study also shows that the Precambrian metamorphic basement in the southeastern margin of the NCC might have formed in a tectonic setting characterized by a late Neoarchean active continental margin.
基金This research was supported by the National Natural Science Foundation of China(Grant Nos.41873047 and 41603020)Guizhou Scientific and Technology Fund(Grant No.QKHJZ[2015]2081).
文摘The late Mesozoic antimony(Sb)mineralization belt in South China hosts a large portion of the world’s Sb reserves.However,the source and mineralization processes of these Sb deposits remain controversial.Here,we measured mercury(Hg)concentrations and isotopic compositions of stibnite in the Banpo Sb-only and Woxi Sbpolymetallic ore deposits,as well as associated rocks in the Yangtze Block in order to constrain the metal sources and ore formation processes in the South China Sb mineralization belt.Stibnite samples from both deposits exhibit significant enrichment in Hg(4.23–50.6 ppm)and have higher δ^(202)Hg values(−0.47‰to 2.03‰)than the studied Precambrian basement rocks(−1.42‰to 0.59‰),Paleozoic sedimentary rocks(−2.40‰to−0.32‰),and other natural Hg reserves(e.g.,marine and continental systems).This indicates that significant mass-dependent fractionation of Hg isotopes occurred during hydrothermal processes.Negative to slightly positive Δ^(199)Hg values of−0.17‰to 0.02‰were obtained for stibnite from the studied deposits,similar to values for the Precambrian basement rocks,but different from those of the Paleozoic sedimentary rocks and data previously reported for mantle materials.This suggests that Precambrian basement rocks were the source of Hg and associated metals.Our data and the tectonic evolution of South China indicate that late Mesozoic asthenospheric upwelling,in response to the Paleo-Pacific oceanic slab foundering,generated heat that drove the circulation of fluids in the basement and crustal basinal rocks.These fluids leached Sb,Hg,and other metals from the Precambrian basement rocks and formed the world-class Sb mineralization belt in South China.
