The ca. 126e120 Ma Au deposits of the Jiaodong Peninsula, eastern China, define the country＇s largest gold province with an overall endowment estimated as＆gt;3000 t Au. The vein and disseminated ores are hosted by N...The ca. 126e120 Ma Au deposits of the Jiaodong Peninsula, eastern China, define the country＇s largest gold province with an overall endowment estimated as＆gt;3000 t Au. The vein and disseminated ores are hosted by NE-to NNE-trending brittle normal faults that parallel the margins of ca. 165e150 Ma, deeply emplaced, lower crustal melt granites. The deposits are sited along the faults for many tens of kilometers and the larger orebodies are associated with dilatational jogs. Country rocks to the granites are Pre-cambrian high-grade metamorphic rocks located on both sides of a Triassic suture between the North and South China blocks. During early Mesozoic convergent deformation, the ore-hosting structures developed as ductile thrust faults that were subsequently reactivated during Early Cretaceous ＂Yan-shanian＂intracontinental extensional deformation and associated gold formation. 〈br〉 Classification of the gold deposits remains problematic. Many features resemble those typical of orogenic Au including the linear structural distribution of the deposits, mineralization style, ore and alteration assemblages, and ore fluid chemistry. However, Phanerozoic orogenic Au deposits are formed by prograde metamorphism of accreted oceanic rocks in Cordilleran-style orogens. The Jiaodong de-posits, in contrast, formed within two Precambrian blocks approximately 2 billion years after devolati-lization of the country rocks, and thus require a model that involves alternative fluid and metal sources for the ores. A widespread suite of ca. 130e123 Ma granodiorites overlaps temporally with the ores, but shows a poor spatial association with the deposits. Furthermore, the deposit distribution and mineral-ization style is atypical of ores formed from nearby magmas. The ore concentration requires fluid focusing during some type of sub-crustal thermal event, which could be broadly related to a combination of coeval lithospheric thinning, asthenospheric upwelling, paleo-Pacific plate subduction, and seismicity along the continental-scale Tan-Lu fault. Possible ore genesis scenarios include those where ore fluids were produced directly by the metamorphism of oceanic lithosphere and overlying sediment on the subducting paleo-Pacific slab, or by devolatilization of an enriched mantle wedge above the slab. Both the sulfur and gold could be sourced from either the oceanic sediments or the serpentinized mantle. A better understanding of the architecture of the paleo-Pacific slab during Early Cretaceous below the eastern margin of China is essential to determination of the validity of possible models.展开更多
A glasshouse experiment using a rhizobox technique was conducted to examine salt dynamics in the rhizosphere of a salt-tolerant grass, Puccinellia ciliata Bor. ’Irwin Hunter’, grown in a loamy soil, and to study the...A glasshouse experiment using a rhizobox technique was conducted to examine salt dynamics in the rhizosphere of a salt-tolerant grass, Puccinellia ciliata Bor. ’Irwin Hunter’, grown in a loamy soil, and to study the effect of rainfall flush on salt accumulation in the rhizosphere. The rhizobox (10 × 5.5 × 50 cm) had a nylon mesh (1 μm) positioned vertically in the middle to create two compartments filled with soil amended with 1 g NaCl kg-1. The plants were grown in one compartment only. Flushed treatments received 275 mL of deionized water two days before harvest. In the plant-growing compartment, soils were sectioned vertically at 5 cm intervals. Significant differences in soil electrical conductivity (EC) (P < 0.05) and pH (P < 0.05) were observed for depths, but not between flushed and non-flushed treatments. In the no-plant compartment (rhizosphere), soil cores were taken horizontally at depths of 5, 20 and 40 cm and sliced at 1, 2, 3, 4, 5, 7, 10, 15 and 20 mm away from the roots. Soil EC and Cl- concentration at the 5 and 20 cm depths, and Na+ concentration at the 5 cm depth significantly decreased (P < 0.05) with the distance away from the root, but no significant differences were observed in soil pH and concentrations of the K+ and Ca2+. The flush treatment only had significant influence on soil EC, pH, and Cl- concentration at the 20 cm depth. Thus, salt accumulation could occur in the rhizosphere of salt-tolerant species on saline soils, and the periodic low rainfall might not have a strong influence on salt distribution in the rhizosphere and/or root zone.展开更多
SHRIMP U-Pb zircon age, geochemical and Nd isotopic data are reported for the Neoproterozoic Guandaoshan pluton in the Yanbian region, SW Sichuan. This pluton is of typical I-type granite and emplaced at (857±13)...SHRIMP U-Pb zircon age, geochemical and Nd isotopic data are reported for the Neoproterozoic Guandaoshan pluton in the Yanbian region, SW Sichuan. This pluton is of typical I-type granite and emplaced at (857±13) Ma. Geochemical and Nd isotopic characters suggest that the pluton was generated by partial melting of pre-existing, young (late Mesoproterozoic to early Neoproterozoic) low-K tholeiitic protolith within an intraplate anorogenic setting. The Guandaoshan pluton probably records the earliest magmatism induced by the proposed ca. 860-750 Ma mantle superplume beneath the supercontinent Rodinia.展开更多
The end-Permian mass extinction not only severely distressed the Paleozoic ecosystems but also dramatically changed the sedimentary systems, resulting in a peculiar Early Triassic ecosystem and submarine environment d...The end-Permian mass extinction not only severely distressed the Paleozoic ecosystems but also dramatically changed the sedimentary systems, resulting in a peculiar Early Triassic ecosystem and submarine environment during the recovery time following the mass extinction. The Lower Triassic is characteristic of the wide occurrence of various distinctive sediments and related sedimentary structures, such as flatpebble conglomerates, vermicular limestone, subtidal wrinkle structures, microbialite, carbonate seafloor fans, thin-bedded limestone and zebra limestone-mudstone. These sediments were common in the Precambrian to Early Ordovician marine settings, and then they occurred only in some extreme and unusual environments with the expansion of metazoan faunas. However, the Early Triassic witnessed an "anachronistic" reappearance of some distinctive sedimentary records in normal shallow marine settings. The study of these anachronistic facies should be of great importance for the understanding of the unique ecosystem and marine environment through the great Paleozoic-Mesozoic transition. The anachronistic facies characterized by vermicular limestone have been documented in many localities in South China and occur at various horizons of the Lower Triassic. Most types of re- ported distinctive sediments over the world have been observed in the Lower Triassic of South China. This provides an excellent opportunity for understanding the Early Triassic environment and its co- evolution with the biotic recovery. Among the anachronistic facies the vermicular limestone is the most characteristic and common distinctive sediments in the Lower Triassic of South China but has received relatively few investigations. Taking it as a case study, we will detail the variation of vermicular limestone and its stratigraphic distribution in the Three Gorges area, Hubei Province. The investigation on the vermicular limestone and other distinctive sediments from the Lower Triassic of South China further indicates that the appearance of anachronistic facies immediately following the mass extinction and the elimination from normal shallow marine facies with the radiation of Mesozoic marine faunas imply the natural response of the sedimentary systems and ecosystems to the great Paleozoic-Mesozoic transitional events and their induced harsh environments. Therefore, the ups and downs of the anachronistic facies may act as a proxy for the evolution of ecosystems independent of fossil analyses.展开更多
A paleomagnetic study was carried out on the Yangzhuang Formation (~1350 Ma) of the Jixian System in the North China Block (NCB). Detailed stepwise thermal demagnetization isolated two components. The soft compo- nent...A paleomagnetic study was carried out on the Yangzhuang Formation (~1350 Ma) of the Jixian System in the North China Block (NCB). Detailed stepwise thermal demagnetization isolated two components. The soft compo- nent (component A) was interpreted as a remagnetization in the recent geomagnetic field. The hard component (compo- nent B) with higher unblocking-temperatures was carried by hematite. Its site-mean direction is D/I = 77.6°/-24.3° (κ = 5.4, α95 = 18.3°, N = 15 sites) before, and D/I = 72.2°/11.5° (κ = 24.6, α95 = 7.9°) after tilt correction. It passes a fold test (Mesozoic folding) at 99% confidence level and reversal test at 95% confidence level. The corresponding pole locates at 17.3°N, 214.5°E (dp = 4.1°, dm = 8.0°). A best fit of paleo- magnetic poles from the NCB, Baltica, Siberia and the ap- parent polar wander path for Laurentia suggests a long-lived connection between these paleo-continents between ~1800 and 1350 Ma.展开更多
Objective: This study was to assess the influence of interaction of combination of immobilized nitrogen cycling bacteria (INCB) with aquatic macrophytes on nitrogen removal from the eutrophic waterbody, and to get ins...Objective: This study was to assess the influence of interaction of combination of immobilized nitrogen cycling bacteria (INCB) with aquatic macrophytes on nitrogen removal from the eutrophic waterbody, and to get insight into different mechanisms involved in nitrogen removal. Methods: The aquatic macrophytes used include Eichhornia crassipes (sum-mer-autumn floating macrophyte), Elodea nuttallii (winter-growing submerged macrophyte), and nitrogen cycling bacteria in-cluding ammonifying, nitrosating, nitrifying and denitrifying bacteria isolated from Taihu Lake. The immobilization carriers materials were made from hydrophilic monomers 2-hydroxyethyl acrylate (HEA) and hydrophobic 2-hydroxyethyl methylacrylate (HEMA). Two experiments were conducted to evaluate the roles of macrophytes combined with INCB on nitrogen removal from eutrophic water during different seasons. Results: Eichhornia crassipes and Elodea nuttallii had different potentials in purification of eutrophic water. Floating macrophyte+bacteria (INCB) performed best in improving water quality (during the first experiment) and decreased total nitrogen (TN) by 70.2%, nitrite and ammonium by 92.2% and 50.9%, respectively, during the experimental period, when water transparency increased from 0.5 m to 1.8 m. When INCB was inoculated into the floating macrophyte system, the populations of nitrosating, nitrifying, and denitrifying bacteria increased by 1 to 2 orders of magnitude compared to the un-inoculated treatments, but ammonifying bacteria showed no obvious difference between different treatments. Lower values of chlorophyll a, CODMn, and pH were found in the microbial-plant integrated system, as compared to the control. Highest reduction in N was noted during the treatment with submerged macrophyte+INCB, being 26.1% for TN, 85.2% for nitrite, and 85.2% for ammonium at the end of 2nd experiment. And in the treatment, the populations of ammonifying, nitrosating, nitrifying, and de-nitrifying bacteria increased by 1 to 3 orders of magnitude, as compared to the un-inoculated treatments. Similar to the first ex-periment, higher water transparency and lower values of chlorophyll a, CODMn and pH were observed in the plant+ INCB inte-grated system, as compared to other treatments. These results indicated that plant-microbe interaction showed beneficial effects on N removal from the eutrophic waterbody.展开更多
A Late Pleistocene-Holocene pollen, phosphorus, and charcoal record was reconstructed from a peatland in southern Jiangxi Province in southern China. The area today has a mountainous and rolling landscape with village...A Late Pleistocene-Holocene pollen, phosphorus, and charcoal record was reconstructed from a peatland in southern Jiangxi Province in southern China. The area today has a mountainous and rolling landscape with villages, small towns, and agriculture dominated by rice paddies, vegetable, and fruit gardens, as well as areas of secondary forest and pine re-afforestation. The record opens before 14 300 yr BP, with Alnus woodland dominating the wetland areas and with an open Quercus woodland on the surrounding slopes. The forest area becomes more complex from approximately 12 800 yr BP and further from 9 000 yr BP. At approximately 6 000 yr BP, there is evidence of clearing and, by 4 500-4 000 yr BP, a complete collapse in the wetland Alnus and terrestrial forest as the low-lying areas are converted to rice production. For much of the record, the occurrence of fire around the site was low, although there is evidence of regional fires. Fire was used as a tool in clearing and then used in the annual cycles of stubble burning after rice harvest. Nutrient levels, as reflected by total phosphorus in the sediment, seem to be closely related to forest changes and high values in the surface layers probably result from land-management techniques associated with agriculture. Therefore, human impact greatly altered forest cover, fire frequency, and nutrient dynamics; this has been evident for approximately 6 000 yr BP and then intensities towards the present day.展开更多
文摘The ca. 126e120 Ma Au deposits of the Jiaodong Peninsula, eastern China, define the country＇s largest gold province with an overall endowment estimated as＆gt;3000 t Au. The vein and disseminated ores are hosted by NE-to NNE-trending brittle normal faults that parallel the margins of ca. 165e150 Ma, deeply emplaced, lower crustal melt granites. The deposits are sited along the faults for many tens of kilometers and the larger orebodies are associated with dilatational jogs. Country rocks to the granites are Pre-cambrian high-grade metamorphic rocks located on both sides of a Triassic suture between the North and South China blocks. During early Mesozoic convergent deformation, the ore-hosting structures developed as ductile thrust faults that were subsequently reactivated during Early Cretaceous ＂Yan-shanian＂intracontinental extensional deformation and associated gold formation. 〈br〉 Classification of the gold deposits remains problematic. Many features resemble those typical of orogenic Au including the linear structural distribution of the deposits, mineralization style, ore and alteration assemblages, and ore fluid chemistry. However, Phanerozoic orogenic Au deposits are formed by prograde metamorphism of accreted oceanic rocks in Cordilleran-style orogens. The Jiaodong de-posits, in contrast, formed within two Precambrian blocks approximately 2 billion years after devolati-lization of the country rocks, and thus require a model that involves alternative fluid and metal sources for the ores. A widespread suite of ca. 130e123 Ma granodiorites overlaps temporally with the ores, but shows a poor spatial association with the deposits. Furthermore, the deposit distribution and mineral-ization style is atypical of ores formed from nearby magmas. The ore concentration requires fluid focusing during some type of sub-crustal thermal event, which could be broadly related to a combination of coeval lithospheric thinning, asthenospheric upwelling, paleo-Pacific plate subduction, and seismicity along the continental-scale Tan-Lu fault. Possible ore genesis scenarios include those where ore fluids were produced directly by the metamorphism of oceanic lithosphere and overlying sediment on the subducting paleo-Pacific slab, or by devolatilization of an enriched mantle wedge above the slab. Both the sulfur and gold could be sourced from either the oceanic sediments or the serpentinized mantle. A better understanding of the architecture of the paleo-Pacific slab during Early Cretaceous below the eastern margin of China is essential to determination of the validity of possible models.
文摘A glasshouse experiment using a rhizobox technique was conducted to examine salt dynamics in the rhizosphere of a salt-tolerant grass, Puccinellia ciliata Bor. ’Irwin Hunter’, grown in a loamy soil, and to study the effect of rainfall flush on salt accumulation in the rhizosphere. The rhizobox (10 × 5.5 × 50 cm) had a nylon mesh (1 μm) positioned vertically in the middle to create two compartments filled with soil amended with 1 g NaCl kg-1. The plants were grown in one compartment only. Flushed treatments received 275 mL of deionized water two days before harvest. In the plant-growing compartment, soils were sectioned vertically at 5 cm intervals. Significant differences in soil electrical conductivity (EC) (P < 0.05) and pH (P < 0.05) were observed for depths, but not between flushed and non-flushed treatments. In the no-plant compartment (rhizosphere), soil cores were taken horizontally at depths of 5, 20 and 40 cm and sliced at 1, 2, 3, 4, 5, 7, 10, 15 and 20 mm away from the roots. Soil EC and Cl- concentration at the 5 and 20 cm depths, and Na+ concentration at the 5 cm depth significantly decreased (P < 0.05) with the distance away from the root, but no significant differences were observed in soil pH and concentrations of the K+ and Ca2+. The flush treatment only had significant influence on soil EC, pH, and Cl- concentration at the 20 cm depth. Thus, salt accumulation could occur in the rhizosphere of salt-tolerant species on saline soils, and the periodic low rainfall might not have a strong influence on salt distribution in the rhizosphere and/or root zone.
基金supported by the National Climbing Project(Grant No.95-Y-25)the National Natural Science Foundation of China(Grant Nos.40032010-B and 49725309)the Chinese Academy of Sciences(Grant No.KZCX2-101).
文摘SHRIMP U-Pb zircon age, geochemical and Nd isotopic data are reported for the Neoproterozoic Guandaoshan pluton in the Yanbian region, SW Sichuan. This pluton is of typical I-type granite and emplaced at (857±13) Ma. Geochemical and Nd isotopic characters suggest that the pluton was generated by partial melting of pre-existing, young (late Mesoproterozoic to early Neoproterozoic) low-K tholeiitic protolith within an intraplate anorogenic setting. The Guandaoshan pluton probably records the earliest magmatism induced by the proposed ca. 860-750 Ma mantle superplume beneath the supercontinent Rodinia.
基金NSFC Innovation Research Group Program (Grant No. 40621002)MOE Innovative Research Team Program (Grant No. IRT0546)+1 种基金China Geological Survey Project (Grant No. 1212010610709)"111" Project (Grant No. B08030)
文摘The end-Permian mass extinction not only severely distressed the Paleozoic ecosystems but also dramatically changed the sedimentary systems, resulting in a peculiar Early Triassic ecosystem and submarine environment during the recovery time following the mass extinction. The Lower Triassic is characteristic of the wide occurrence of various distinctive sediments and related sedimentary structures, such as flatpebble conglomerates, vermicular limestone, subtidal wrinkle structures, microbialite, carbonate seafloor fans, thin-bedded limestone and zebra limestone-mudstone. These sediments were common in the Precambrian to Early Ordovician marine settings, and then they occurred only in some extreme and unusual environments with the expansion of metazoan faunas. However, the Early Triassic witnessed an "anachronistic" reappearance of some distinctive sedimentary records in normal shallow marine settings. The study of these anachronistic facies should be of great importance for the understanding of the unique ecosystem and marine environment through the great Paleozoic-Mesozoic transition. The anachronistic facies characterized by vermicular limestone have been documented in many localities in South China and occur at various horizons of the Lower Triassic. Most types of re- ported distinctive sediments over the world have been observed in the Lower Triassic of South China. This provides an excellent opportunity for understanding the Early Triassic environment and its co- evolution with the biotic recovery. Among the anachronistic facies the vermicular limestone is the most characteristic and common distinctive sediments in the Lower Triassic of South China but has received relatively few investigations. Taking it as a case study, we will detail the variation of vermicular limestone and its stratigraphic distribution in the Three Gorges area, Hubei Province. The investigation on the vermicular limestone and other distinctive sediments from the Lower Triassic of South China further indicates that the appearance of anachronistic facies immediately following the mass extinction and the elimination from normal shallow marine facies with the radiation of Mesozoic marine faunas imply the natural response of the sedimentary systems and ecosystems to the great Paleozoic-Mesozoic transitional events and their induced harsh environments. Therefore, the ups and downs of the anachronistic facies may act as a proxy for the evolution of ecosystems independent of fossil analyses.
基金supported by the National Natural Science Foundation of China(Grant No.40032010-B).
文摘A paleomagnetic study was carried out on the Yangzhuang Formation (~1350 Ma) of the Jixian System in the North China Block (NCB). Detailed stepwise thermal demagnetization isolated two components. The soft compo- nent (component A) was interpreted as a remagnetization in the recent geomagnetic field. The hard component (compo- nent B) with higher unblocking-temperatures was carried by hematite. Its site-mean direction is D/I = 77.6°/-24.3° (κ = 5.4, α95 = 18.3°, N = 15 sites) before, and D/I = 72.2°/11.5° (κ = 24.6, α95 = 7.9°) after tilt correction. It passes a fold test (Mesozoic folding) at 99% confidence level and reversal test at 95% confidence level. The corresponding pole locates at 17.3°N, 214.5°E (dp = 4.1°, dm = 8.0°). A best fit of paleo- magnetic poles from the NCB, Baltica, Siberia and the ap- parent polar wander path for Laurentia suggests a long-lived connection between these paleo-continents between ~1800 and 1350 Ma.
基金Project supported by the Ministry of Science and Technology of China, the Education Ministry of China (No. 20305), Australia Gov-ernment’s Innovation Statement Backing Australia’s Ability (No. [2002]68), and the Science and Technology Bureau of ZhejiangProvince (No. 2005C22020), China
文摘Objective: This study was to assess the influence of interaction of combination of immobilized nitrogen cycling bacteria (INCB) with aquatic macrophytes on nitrogen removal from the eutrophic waterbody, and to get insight into different mechanisms involved in nitrogen removal. Methods: The aquatic macrophytes used include Eichhornia crassipes (sum-mer-autumn floating macrophyte), Elodea nuttallii (winter-growing submerged macrophyte), and nitrogen cycling bacteria in-cluding ammonifying, nitrosating, nitrifying and denitrifying bacteria isolated from Taihu Lake. The immobilization carriers materials were made from hydrophilic monomers 2-hydroxyethyl acrylate (HEA) and hydrophobic 2-hydroxyethyl methylacrylate (HEMA). Two experiments were conducted to evaluate the roles of macrophytes combined with INCB on nitrogen removal from eutrophic water during different seasons. Results: Eichhornia crassipes and Elodea nuttallii had different potentials in purification of eutrophic water. Floating macrophyte+bacteria (INCB) performed best in improving water quality (during the first experiment) and decreased total nitrogen (TN) by 70.2%, nitrite and ammonium by 92.2% and 50.9%, respectively, during the experimental period, when water transparency increased from 0.5 m to 1.8 m. When INCB was inoculated into the floating macrophyte system, the populations of nitrosating, nitrifying, and denitrifying bacteria increased by 1 to 2 orders of magnitude compared to the un-inoculated treatments, but ammonifying bacteria showed no obvious difference between different treatments. Lower values of chlorophyll a, CODMn, and pH were found in the microbial-plant integrated system, as compared to the control. Highest reduction in N was noted during the treatment with submerged macrophyte+INCB, being 26.1% for TN, 85.2% for nitrite, and 85.2% for ammonium at the end of 2nd experiment. And in the treatment, the populations of ammonifying, nitrosating, nitrifying, and de-nitrifying bacteria increased by 1 to 3 orders of magnitude, as compared to the un-inoculated treatments. Similar to the first ex-periment, higher water transparency and lower values of chlorophyll a, CODMn and pH were observed in the plant+ INCB inte-grated system, as compared to other treatments. These results indicated that plant-microbe interaction showed beneficial effects on N removal from the eutrophic waterbody.
基金SuppoSed by funding from the Australia-China Co-operation and the National Natural Science Foundation of China （40372077）. Acknowledgements The authors thank Huabing Xie and Redao Xie for digging the pit from which the samples were taken, Lorraine Wilson for preparing the samples for pollen analysis, and Xue Shang and Xinying Zhou for help with the preparation of the diagrams.
文摘A Late Pleistocene-Holocene pollen, phosphorus, and charcoal record was reconstructed from a peatland in southern Jiangxi Province in southern China. The area today has a mountainous and rolling landscape with villages, small towns, and agriculture dominated by rice paddies, vegetable, and fruit gardens, as well as areas of secondary forest and pine re-afforestation. The record opens before 14 300 yr BP, with Alnus woodland dominating the wetland areas and with an open Quercus woodland on the surrounding slopes. The forest area becomes more complex from approximately 12 800 yr BP and further from 9 000 yr BP. At approximately 6 000 yr BP, there is evidence of clearing and, by 4 500-4 000 yr BP, a complete collapse in the wetland Alnus and terrestrial forest as the low-lying areas are converted to rice production. For much of the record, the occurrence of fire around the site was low, although there is evidence of regional fires. Fire was used as a tool in clearing and then used in the annual cycles of stubble burning after rice harvest. Nutrient levels, as reflected by total phosphorus in the sediment, seem to be closely related to forest changes and high values in the surface layers probably result from land-management techniques associated with agriculture. Therefore, human impact greatly altered forest cover, fire frequency, and nutrient dynamics; this has been evident for approximately 6 000 yr BP and then intensities towards the present day.
