The Tayuan(Cu-Mo)-Pb-Zn deposit is located in the northern part of Daxinganling,NE China.Lenticular ore body occurs in the skarn zone.The skarn minerals mainly include garnet,pyroxene,epidote and wollastonite.Electron...The Tayuan(Cu-Mo)-Pb-Zn deposit is located in the northern part of Daxinganling,NE China.Lenticular ore body occurs in the skarn zone.The skarn minerals mainly include garnet,pyroxene,epidote and wollastonite.Electron microprobe analysis shows that the end member of garnet is mainly andradite(Ad_(62-97)Gr_(11-45),the pyroxene is mainly diopside,and epidote is mainly clinozoisite.These characteristics indicate that the Tayuan polymetallic skarn deposit is mainly calcareous skarn.Sometimes the content zonation can be observed in garnets.With one garnet crystal,content is shifty from the core to the rim.In general,the iron content in the core is higher than in the edge.The content in the garnet shows that the garnet in the Tayuan deposit formed from weak oxidation in alkaline environment with the oxygen fugacity increasing,suggesting that the hydrothermal fluid evolved from an acidic to a slight alkaline state.In the Tayuan polymetallic deposit,the ratio of Mn/Fe in pyroxene is about 1.3,and of Mg/Fe,it is about 2.The components of garnet in the Tayuan deposit plot in the field of the typical skarn Zn,Cu,Mo deposits in the world.展开更多
Detrital zircons in five sedimentary samples, MC1 to MC5, from the bottom of the Chuanlinggou Formation in the Ming Tombs District, Beijing, were dated with the LA-ICP-MS and SHRIMP U-Pb methods. Age spectra of the fi...Detrital zircons in five sedimentary samples, MC1 to MC5, from the bottom of the Chuanlinggou Formation in the Ming Tombs District, Beijing, were dated with the LA-ICP-MS and SHRIMP U-Pb methods. Age spectra of the five samples show a major peak at 2500 Ma and a secondary peak at 2000 Ma, suggesting their provenances were mainly from the crystalline basement of the North China Craton and the Trans-North China Orogen. The youngest zircon has an age of 1673 d： 44 Ma, indicating that the Chuanlinggou Formation was deposited after this age. From sample MC4 to MC5, lithology changed from a clastic rock （fine-grained sandstone） to a carbonate rock （fine-grained dolomite）, suggesting that the depositional basin became progressively deeper. The age spectrum of sample MC5 shows a major peak at 2500 Ma and a secondary peak at 2000 Ma. Sample MC4, which is stratigraphically lower than sample MC5, only had one peak at 2500 Ma. We conclude that there was a transgressive event when sediments represented by MC5 was deposited, and seawater carried ca. 2000 Ma clastic materials to the basin where the Chuanlinggou Formation was deposited, leading to the addition of ca. 2000 Ma detritus. Our research indicates that the source area for the sediments became more extensive with time. We conclude that the Chuanlinggou Formation in the Ming Tombs District was deposited in a low-energy mud fiat sedimentary environment in the inter-supra tidal zone because it is mainly composed of silty mudstone and fine-grained sandstone with relatively simple sedimentary structures.展开更多
Mangrove sediments were sampled form 14 main mangrove reserves of China. Concentrations of Cu, Pb, Zn, Cr and Cd were analyzed with a PE ICP-MS, and physical and physicochemical factors such as particle size distribut...Mangrove sediments were sampled form 14 main mangrove reserves of China. Concentrations of Cu, Pb, Zn, Cr and Cd were analyzed with a PE ICP-MS, and physical and physicochemical factors such as particle size distribution, pH, salinity and Total Organic Matter （TOM） were also determined. In the mangrove sediments of China, the average contents of heavy metals decreased in the order ofZn 〉 Pb 〉 Cu 〉 Cr 〉 Cd. The average contents of heavy metals were： Cu = 22.8 4- 16.46 mg/kg, Pb = 76.1 4- 52.33 mg/kg, Zn = 86.3 4- 42.65 mg/kg, Cr = 18.4 4- 5.83 mg/kg and Cd = 0.21 4- 0.25 mg/kg. Compared with previous studies, levels of heavy metals increased greatly. Contents of Cd, Cu, Pb and Zn were higher than the Background Values （BV）. However, the contents of Cr was under the BV. The results revealed that levels of heavy metals changes significantly with anthropogenic input, physical and physicochemical factors. Significant correlations were found between concentrations of Cu, Ph and pH, TOM.展开更多
The Chengjiang Formation is the earliest continental clastic deposit after the Jinning Orogeny in central Yunnan Province,and therefore its accurate depositional age is significant for understanding the formation and ...The Chengjiang Formation is the earliest continental clastic deposit after the Jinning Orogeny in central Yunnan Province,and therefore its accurate depositional age is significant for understanding the formation and evolution of the Neoproterozoic rift basins in southern China.However,hampered by accuracy of the dating technique,the existing age data for the Chengjiang Formation are not very reliable.A large number of magmatic zircons were obtained from the tuff interbed in the lower part of the Chengjiang Formation in Jinyang area and the bottom part of the Chengjiang Formation in Dongchuan area,central Yunnan Province,and high-precision SHRIMP U-Pb dating was carried out on these zircons.The results show that the weighted mean 206 Pb/238 U ages are 797.8±8.2 and 803.1±8.7 Ma respectively.In combination with related geological evidence,it has been demonstrated that the bottom boundary age of the Chengjiang Formation should be 800±5 Ma,whereas the top boundary age could be ca 725 Ma.By synthetically analyzing the latest age data for the relevant strata,it has been confirmed that the Chengjiang Formation should be correlated with the Suxiong Formation and the Kaijianqiao Formation in western Sichuan Province,the Liantuo Formation in the middle and lower Yangtze,the Hongchicun Formation and the Shangshu Formation in northern Zhejiang Province,the Puling Formation in southern Anhui Province,the Luokedong Formation and the Majianqiao Formation in northwestern Jiangxi Province,the Wuqiangxi Formation in northwestern Hunan Province,the Fanzhao Formation and the Qingshuijiang Formation in southeastern Guizhou Province,and the Sanmenjie Formation and the Gongdong Formation in northern Guangxi Province.Sedimentary cycle analysis shows that the sedimentary filling sequence of the Neoproterozoic rift basins in southern China can be divided into four cycles.Among them,Cycle II began at ca.800 Ma,accompanied by intensive tectonic-thermal events.The zircon U-Pb ages from the bottom of the Chengjiang Formation reported in this paper indicate that the Neoproterozoic Kangdian rift subbasin probably started to develop at ca.800 Ma and therefore missed Cycle I of the Neoproterozoic sedimentary filling sequence in southern China.展开更多
U-Pb ages of Devonian detrital zircons from Tabei Uplift have been determined through LA-ICP-MS test technology.The results revealed that most zircon ages concentrate on 460-414 Ma,especially around 436-423 Ma,indicat...U-Pb ages of Devonian detrital zircons from Tabei Uplift have been determined through LA-ICP-MS test technology.The results revealed that most zircon ages concentrate on 460-414 Ma,especially around 436-423 Ma,indicating possible occurrences of strong tectonic events at the northern margin of Tarim Basin during that period.Combined with previous researches on the basin marginal orogenic belts,intense tectonic activities developed at the northeast margin of Tarim Basin and its obvious sedimentary responses in basin during the end of Ordovician to Early-Middle Silurian are discussed.These include(1) several unconformities within the Late Ordovician-Silurian,showing truncation,erosion,and onlap characteristics,which reflected the local uplift formed during the surrounding extrusion process;(2) the Silurian fluvial delta system from northeast to southwest in Keping,Yingmaili,Hade,and Caohu areas,which reflected the partial uplift at the northeast margin and provided clastic supply to basin;and(3) as indicated by heavy mineral analysis,the Silurian sediments came mainly from the recycles of orogenic belts provenance,which indicated the compress tectonic setting.In addition,a wide range of red mudstone layer distribution in the upper part of the Silurian may be closely related to the surrounding tectonic uplift and the rapid decline of sea levels.展开更多
Suizhou-Zaoyang area is located in the southern Qinling-Tongbai-Dabie Orogen, China. A combined research on U-Pb ages and Lu-Hf isotopes for detrital zircons from three meta-sedimentary rocks in the Wudang Group is re...Suizhou-Zaoyang area is located in the southern Qinling-Tongbai-Dabie Orogen, China. A combined research on U-Pb ages and Lu-Hf isotopes for detrital zircons from three meta-sedimentary rocks in the Wudang Group is reported. The upper Wudang Group has a major age population of ca. 750 Ma and a sub-major of ca. 860 Ma. But the lower part only yields one age peak at ca. 2.03 Ga. In situ Lu-Hf analyses of the young age group of ca. 750 Ma for zircons from the upper Wudang Group yield an average εHt（t） value of -8.6 and two-stage Hf model ages （TDM2） from 1837 to 2230 Ma, respectively. However, zircons from the lower Wudang Group give an average εHf（t） value of 4.5 and TDM1 of 2220±22 Ma, close to the timing of zircon crystallization. Thus, it is suggested that, in the study area, the continental crust grew during the middle Paleoproterozoic and reworked during the middle Neoproterozoic, which shows the affinity to the Dabie Orogen. In addition, in the lower Wudang Group, two metamorphic zircon ages of 1992±91 and 1999±61 Ma are consistent with that of the middle Paleoproterozoic metamorphism event in the northern Yangtze Block, which may represent the assemblage of the Columbia Supercontinent. On the basis of the U-Pb ages and Hf isotopes, it is proposed that Suizhou-Zaoyang area was involved in the subduction-collision event in the middle Paleoproterozoic and the Yangtze Block was one of the components of the Paleo-Mesoproterozoic supercontinent.展开更多
基金supported by the Natural Science Foundation of China(No.41203039)
文摘The Tayuan(Cu-Mo)-Pb-Zn deposit is located in the northern part of Daxinganling,NE China.Lenticular ore body occurs in the skarn zone.The skarn minerals mainly include garnet,pyroxene,epidote and wollastonite.Electron microprobe analysis shows that the end member of garnet is mainly andradite(Ad_(62-97)Gr_(11-45),the pyroxene is mainly diopside,and epidote is mainly clinozoisite.These characteristics indicate that the Tayuan polymetallic skarn deposit is mainly calcareous skarn.Sometimes the content zonation can be observed in garnets.With one garnet crystal,content is shifty from the core to the rim.In general,the iron content in the core is higher than in the edge.The content in the garnet shows that the garnet in the Tayuan deposit formed from weak oxidation in alkaline environment with the oxygen fugacity increasing,suggesting that the hydrothermal fluid evolved from an acidic to a slight alkaline state.In the Tayuan polymetallic deposit,the ratio of Mn/Fe in pyroxene is about 1.3,and of Mg/Fe,it is about 2.The components of garnet in the Tayuan deposit plot in the field of the typical skarn Zn,Cu,Mo deposits in the world.
基金financially supported by the Ministry of Land and Natural Resources (Grant No. 201311116)the National Natural Science Foundation of China (Grant No. 41173065)+1 种基金Ministry of Science and Technology (No. 2012FY120100)the Basic Outlay of Scientific Research Work from the Ministry of Science and Technology (Grant No. J1403)
文摘Detrital zircons in five sedimentary samples, MC1 to MC5, from the bottom of the Chuanlinggou Formation in the Ming Tombs District, Beijing, were dated with the LA-ICP-MS and SHRIMP U-Pb methods. Age spectra of the five samples show a major peak at 2500 Ma and a secondary peak at 2000 Ma, suggesting their provenances were mainly from the crystalline basement of the North China Craton and the Trans-North China Orogen. The youngest zircon has an age of 1673 d： 44 Ma, indicating that the Chuanlinggou Formation was deposited after this age. From sample MC4 to MC5, lithology changed from a clastic rock （fine-grained sandstone） to a carbonate rock （fine-grained dolomite）, suggesting that the depositional basin became progressively deeper. The age spectrum of sample MC5 shows a major peak at 2500 Ma and a secondary peak at 2000 Ma. Sample MC4, which is stratigraphically lower than sample MC5, only had one peak at 2500 Ma. We conclude that there was a transgressive event when sediments represented by MC5 was deposited, and seawater carried ca. 2000 Ma clastic materials to the basin where the Chuanlinggou Formation was deposited, leading to the addition of ca. 2000 Ma detritus. Our research indicates that the source area for the sediments became more extensive with time. We conclude that the Chuanlinggou Formation in the Ming Tombs District was deposited in a low-energy mud fiat sedimentary environment in the inter-supra tidal zone because it is mainly composed of silty mudstone and fine-grained sandstone with relatively simple sedimentary structures.
基金This project is supported by National Natural Science Foundation of China （No. 41176090）.
文摘Mangrove sediments were sampled form 14 main mangrove reserves of China. Concentrations of Cu, Pb, Zn, Cr and Cd were analyzed with a PE ICP-MS, and physical and physicochemical factors such as particle size distribution, pH, salinity and Total Organic Matter （TOM） were also determined. In the mangrove sediments of China, the average contents of heavy metals decreased in the order ofZn 〉 Pb 〉 Cu 〉 Cr 〉 Cd. The average contents of heavy metals were： Cu = 22.8 4- 16.46 mg/kg, Pb = 76.1 4- 52.33 mg/kg, Zn = 86.3 4- 42.65 mg/kg, Cr = 18.4 4- 5.83 mg/kg and Cd = 0.21 4- 0.25 mg/kg. Compared with previous studies, levels of heavy metals increased greatly. Contents of Cd, Cu, Pb and Zn were higher than the Background Values （BV）. However, the contents of Cr was under the BV. The results revealed that levels of heavy metals changes significantly with anthropogenic input, physical and physicochemical factors. Significant correlations were found between concentrations of Cu, Ph and pH, TOM.
基金supported by National Natural Science Foundation of China (Grant Nos. 41030315,41072088)the China Geological Survey(Grant No. 1212011121105)
文摘The Chengjiang Formation is the earliest continental clastic deposit after the Jinning Orogeny in central Yunnan Province,and therefore its accurate depositional age is significant for understanding the formation and evolution of the Neoproterozoic rift basins in southern China.However,hampered by accuracy of the dating technique,the existing age data for the Chengjiang Formation are not very reliable.A large number of magmatic zircons were obtained from the tuff interbed in the lower part of the Chengjiang Formation in Jinyang area and the bottom part of the Chengjiang Formation in Dongchuan area,central Yunnan Province,and high-precision SHRIMP U-Pb dating was carried out on these zircons.The results show that the weighted mean 206 Pb/238 U ages are 797.8±8.2 and 803.1±8.7 Ma respectively.In combination with related geological evidence,it has been demonstrated that the bottom boundary age of the Chengjiang Formation should be 800±5 Ma,whereas the top boundary age could be ca 725 Ma.By synthetically analyzing the latest age data for the relevant strata,it has been confirmed that the Chengjiang Formation should be correlated with the Suxiong Formation and the Kaijianqiao Formation in western Sichuan Province,the Liantuo Formation in the middle and lower Yangtze,the Hongchicun Formation and the Shangshu Formation in northern Zhejiang Province,the Puling Formation in southern Anhui Province,the Luokedong Formation and the Majianqiao Formation in northwestern Jiangxi Province,the Wuqiangxi Formation in northwestern Hunan Province,the Fanzhao Formation and the Qingshuijiang Formation in southeastern Guizhou Province,and the Sanmenjie Formation and the Gongdong Formation in northern Guangxi Province.Sedimentary cycle analysis shows that the sedimentary filling sequence of the Neoproterozoic rift basins in southern China can be divided into four cycles.Among them,Cycle II began at ca.800 Ma,accompanied by intensive tectonic-thermal events.The zircon U-Pb ages from the bottom of the Chengjiang Formation reported in this paper indicate that the Neoproterozoic Kangdian rift subbasin probably started to develop at ca.800 Ma and therefore missed Cycle I of the Neoproterozoic sedimentary filling sequence in southern China.
基金supported by National Natural Science Foundation of China (Grant No. 41130422)National Natural Science Foundation of China (Grant No.40372056)Fundamental Research Funds for the Central Universities (Grant No. 2010ZD07)
文摘U-Pb ages of Devonian detrital zircons from Tabei Uplift have been determined through LA-ICP-MS test technology.The results revealed that most zircon ages concentrate on 460-414 Ma,especially around 436-423 Ma,indicating possible occurrences of strong tectonic events at the northern margin of Tarim Basin during that period.Combined with previous researches on the basin marginal orogenic belts,intense tectonic activities developed at the northeast margin of Tarim Basin and its obvious sedimentary responses in basin during the end of Ordovician to Early-Middle Silurian are discussed.These include(1) several unconformities within the Late Ordovician-Silurian,showing truncation,erosion,and onlap characteristics,which reflected the local uplift formed during the surrounding extrusion process;(2) the Silurian fluvial delta system from northeast to southwest in Keping,Yingmaili,Hade,and Caohu areas,which reflected the partial uplift at the northeast margin and provided clastic supply to basin;and(3) as indicated by heavy mineral analysis,the Silurian sediments came mainly from the recycles of orogenic belts provenance,which indicated the compress tectonic setting.In addition,a wide range of red mudstone layer distribution in the upper part of the Silurian may be closely related to the surrounding tectonic uplift and the rapid decline of sea levels.
基金supported by the National Natural Sciences Foundation of China(Grants Nos.41172189,40972137,and 41402179)
文摘Suizhou-Zaoyang area is located in the southern Qinling-Tongbai-Dabie Orogen, China. A combined research on U-Pb ages and Lu-Hf isotopes for detrital zircons from three meta-sedimentary rocks in the Wudang Group is reported. The upper Wudang Group has a major age population of ca. 750 Ma and a sub-major of ca. 860 Ma. But the lower part only yields one age peak at ca. 2.03 Ga. In situ Lu-Hf analyses of the young age group of ca. 750 Ma for zircons from the upper Wudang Group yield an average εHt（t） value of -8.6 and two-stage Hf model ages （TDM2） from 1837 to 2230 Ma, respectively. However, zircons from the lower Wudang Group give an average εHf（t） value of 4.5 and TDM1 of 2220±22 Ma, close to the timing of zircon crystallization. Thus, it is suggested that, in the study area, the continental crust grew during the middle Paleoproterozoic and reworked during the middle Neoproterozoic, which shows the affinity to the Dabie Orogen. In addition, in the lower Wudang Group, two metamorphic zircon ages of 1992±91 and 1999±61 Ma are consistent with that of the middle Paleoproterozoic metamorphism event in the northern Yangtze Block, which may represent the assemblage of the Columbia Supercontinent. On the basis of the U-Pb ages and Hf isotopes, it is proposed that Suizhou-Zaoyang area was involved in the subduction-collision event in the middle Paleoproterozoic and the Yangtze Block was one of the components of the Paleo-Mesoproterozoic supercontinent.
