Isoprenoidal glycerol dialkyl glycerol tetraethers （iGDGTs） from the Gulu hot springs （23--83.6 ℃, pH 〉 7） and Yangbajing hot springs （80-128 ℃, pH 〉 7） were analyzed in order to investigate the distribution...Isoprenoidal glycerol dialkyl glycerol tetraethers （iGDGTs） from the Gulu hot springs （23--83.6 ℃, pH 〉 7） and Yangbajing hot springs （80-128 ℃, pH 〉 7） were analyzed in order to investigate the distribution of archaeal lipids among different hot springs in Tibet. A soil sample from Gulu was incubated at different temperatures and analyzed for changes in iGDGTs to help evaluate whether surrounding soil may contribute to the iGDGTs in hot springs. The sources of bacterial GDGTs （bGDGTs） in these hot springs were also investigated. The results revealed different profiles ofiGDGTs between Gulu and Yangbajing hot springs. Core iGDGTs and polar iGDGTs also presented different patterns in each hot spring. The PCA analysis showed that the structure of polar iGDGTs can be explained by three factors and suggested multiple sources of these compounds. Bivariate correlation analysis showed significant positive correlations between polar and core bGDGTs, suggesting the in situ production of bGDGTs in the hot springs. Furthermore, in the soil incubation experiment, temperature had the most significant influence on concentration of bGDGTs rather than iGDGTs, and polar bGDGTs had greater variability than core bGDGTs with changing temperature. Our results indicated that soil input had little influence on the composition of GDGTs in Tibetan hot springs.展开更多
The early aged ophiolites have attracted attention of many geologists in recent decades, because the early aged ophiolites can provide the information about the ancient oceanic processes relevant to the evolution of p...The early aged ophiolites have attracted attention of many geologists in recent decades, because the early aged ophiolites can provide the information about the ancient oceanic processes relevant to the evolution of plate tectonics in the early period of the earth, and also concern such problems as whether there existed a ＂Proto-Tethys＂ and the break-up and convergence of the Rodinian Supercontinent. This paper reveals a definite complete ophiolite of Neoproterozoic-Early Paleozoic, named Kuda ophiolite in the western Kunlun Mrs., NW Tibetan Plateau, and reports the recent reasonable SHRIMP zircon U-Pb ages of 510±4 Ma, and 502±13 Ma for the cumulates of the Kuda ophiolite, using the most powerful dating tool, the SHRIMP-Ⅱ. The geochemical and geochronology data integrating with the geological setting suggest that the Kuda ophiolite might have formed in an archipelago oceanic basin, not in a vast ocean, the so-called ＂Proto-Tethys＂, and was tectonically emplaced during the Early Paleozoic.展开更多
LA-ICPMS zircon U-Pb dating has been greatly advanced and widely applied in the past decade because it is a cheap and fast technique.The internal error of LA-ICPMS zircon U-Pb dating can be better than 1%,but reproduc...LA-ICPMS zircon U-Pb dating has been greatly advanced and widely applied in the past decade because it is a cheap and fast technique.The internal error of LA-ICPMS zircon U-Pb dating can be better than 1%,but reproducibility(accuracy)is relatively poor.In order to quantitatively assess the accuracy of this technique,zircons from two dioritic rocks,a Mesozoic dioritic microgranular enclave(FS06)and a Neoproterozoic diorite(WC09-32),were dated independently in eight laboratories using SIMS and LA-ICPMS.Results of three SIMS analyses on FS06 and WC09-2 are indistinguishable within error and give a best estimate of the crystallization age of 132.2 and 760.5 Ma(reproducibility is^1%,2RSD),respectively.Zircon U-Pb ages determined by LA-ICPMS in six laboratories vary from 128.3±1.0 to 135.0±0.9 Ma(2SE)for FS06 and from 742.9±3.1 to777.8±4.7 Ma(2SE)for WC09-32,suggesting a reproducibility of^4%(2RSD).Uncertainty produced during LA-ICPMS zircon U-Pb analyses comes from multiple sources,including uncertainty in the isotopic ratio measurements,uncertainty in the fractionation factor calculation using an external standard,uncertainty in the age determination as a result of common lead correction,age uncertainty of the external standards and uncertainty in the data reduction.Result of our study suggests that the uncertainty of LA-ICPMS zircon U-Pb dating is approximately 4%(2RSD).The uncertainty in age determination must be considered in order to interpret LA-ICPMS zircon U-Pb data rationally.展开更多
To better understand the Pan-African-early Paleozoic tectonothermal events of the Nyainrong microcontinent and the con- straints on its tectonic evolution, here we report the results of zircon LA-ICP-MS U-Pb dating an...To better understand the Pan-African-early Paleozoic tectonothermal events of the Nyainrong microcontinent and the con- straints on its tectonic evolution, here we report the results of zircon LA-ICP-MS U-Pb dating and geochemical features of Amdo gneiss in the Nyainrong microcontinent. The outcrops of Amdo gneiss is about 30 km south of Amdo County in north- ern Tibet. The field occurrence, mineral composition, textural characteristics, and whole-rock geochemical features of the four gneiss samples indicate the protolith of the gneisses is intermediate-acid intrusive rock. Gneiss zircon trace element tracing and genetic analysis shows that zircon has typical characteristics of magmatic zircon. The 2~6pbF38U concordant age of zircon is 505-517 Ma, corresponding to the Middle-Late Cambrian, which is the formation age of the protolith. The samples have char- acteristics of high silicon, alkali-rich, alkalic rate AR =1.73-3.7, the differentiation index DI = 70.78-90.28; rock aluminum saturation index ranges from 1.02 to 1.05, FeO / MgO ranges from 2.63 to 4.50, 10000 x Ga/AI ranges from 2.12 to 2.41, and P205 and A1203 content decreased with SiO2 increasing. Th and Y contents have a good positive correlation with Rb content; the genetic type of protolith of the gneiss is the differentiation of subalkaline over aluminum I-type granite. Combined with re- gional data, the tectonic setting of the Amdo gneiss protolith is closely related to the collision orogenic process. The prelimi- nary view is that the Middle-Late Cambrian magmatic events developed on the microcontinent could be the result of Andean- type orogeny along the Gondwana super-continental margin after the end of the Pan-African orogeny.展开更多
The Songshugou dunite body,which occupies an area of about 20 km2,is the largest ultramafic massif in the eastern Qinling orogenic belt,Central China.The major compo-nent of this body is dunitic rocks including myloni...The Songshugou dunite body,which occupies an area of about 20 km2,is the largest ultramafic massif in the eastern Qinling orogenic belt,Central China.The major compo-nent of this body is dunitic rocks including mylonitic dunite and coarse-grained dunite;they oc-cupy about 95 vol%of the total body.Petrography,mineral composition,major and trace ele-ments and primitive melt inclusions have been investigated in this paper;all revealed that this dunite body is the product of melt-rock interaction by porous percolation flow.In comparison with dunite sills or veins in harzburgite from the basal part of Oman ophiolite,this dunite body is characterized by lower contents of Al2O3,CaO and HREE but higher content of highly incom-patible elements and Zr and Hf.The LREE enriched patterns and primitive mantle normalized spidergrams of trace elements are also different from the Oman dunite.Combining with melt in-clusions observed in olivines,we conclude that this dunite body is the product of large-scale porous percolation flow of high-MgO melts within depleted mantle peridotites.The high-MgO magma,in essence,was most probably produced at the hot head of an upwelling mantle plume.The occurrence of the Songshugou dunite body is closely associated with the activity of mantle super-plume in Neo-Proterozoic era in the Yangtze Craton.展开更多
Shallow gas reservoirs are distributed widely in Chinese heavy oil-bearing basins.At present,shallow gas resources have opened up giant potentials.The previous researches indicate the intimate genetic relationship bet...Shallow gas reservoirs are distributed widely in Chinese heavy oil-bearing basins.At present,shallow gas resources have opened up giant potentials.The previous researches indicate the intimate genetic relationship between shallow gas and heavy oil.Shallow gas resources are generated from crude oil degraded by anaerobic microscopic organism,it belongs to biogenic gas family of secondary genesis,namely heavy oil degraded gas.Shallow gas resources are usually distributed in the upward position or the vicinity of heavy oil reservoirs.They are mainly of dry gas,which are composed of methane and only tiny C2+heavy hydrocarbon and relatively higher contents of nitrogen gas.Generally,methane isotopes are light,whose values are between biogenic gas and thermal cracking gas.Ethane isotopes are heavy,which mixed possibly with thermogenic gas.Carbon dioxide bear the characteristics of very heavy carbon isotope,so carbon isotopic fractionation effects are very obvious on the process of microscopic organism degradation crude oil.The heavy oil degraded gas formation,a very complex geological,geochemical and microbiological geochemical process,is the result of a series of reactions of organic matter-microbes and water-hydrocarbon,which is controlled by many factors.展开更多
Using SHRIMP zircon U-Pb dating methods and cathodoluminescence (CL) technique, we have pre- cisely dated ore samples from tungsten ore deposit, ore-bearing volcanic-sedimentary strata and granite in the Yushan region...Using SHRIMP zircon U-Pb dating methods and cathodoluminescence (CL) technique, we have pre- cisely dated ore samples from tungsten ore deposit, ore-bearing volcanic-sedimentary strata and granite in the Yushan region within the east Tianshan-Beishan W-bearing zone. This study reveals Yu- shan tungsten ore deposit zone formed in 250 ± 9 Ma, and it is closely associated with the Permian granites and felsic volcanic rocks. This new type of tungsten ore deposit in the east Tianshan-Beishang multiple-metallogenetic province may probably be associated with the regionally right-literal shearing after the main Carboniferous collisional orogeny, and the formation of pull-apart basin and the felsic magmatism.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.40972211)the US National Science Foundation(Grant Nos.ETBC-1024614 and OISE- 0968421 )
文摘Isoprenoidal glycerol dialkyl glycerol tetraethers （iGDGTs） from the Gulu hot springs （23--83.6 ℃, pH 〉 7） and Yangbajing hot springs （80-128 ℃, pH 〉 7） were analyzed in order to investigate the distribution of archaeal lipids among different hot springs in Tibet. A soil sample from Gulu was incubated at different temperatures and analyzed for changes in iGDGTs to help evaluate whether surrounding soil may contribute to the iGDGTs in hot springs. The sources of bacterial GDGTs （bGDGTs） in these hot springs were also investigated. The results revealed different profiles ofiGDGTs between Gulu and Yangbajing hot springs. Core iGDGTs and polar iGDGTs also presented different patterns in each hot spring. The PCA analysis showed that the structure of polar iGDGTs can be explained by three factors and suggested multiple sources of these compounds. Bivariate correlation analysis showed significant positive correlations between polar and core bGDGTs, suggesting the in situ production of bGDGTs in the hot springs. Furthermore, in the soil incubation experiment, temperature had the most significant influence on concentration of bGDGTs rather than iGDGTs, and polar bGDGTs had greater variability than core bGDGTs with changing temperature. Our results indicated that soil input had little influence on the composition of GDGTs in Tibetan hot springs.
基金This research is financially supported by China Geological Survey(Project No.2003 13000059)the Department of International Cooperation and Science and Technology,Ministry of Land and Resources(Project No.2001010205)the key project of the Ministry of Science and Technology(MOST)(Project No.2001CB711001).
文摘The early aged ophiolites have attracted attention of many geologists in recent decades, because the early aged ophiolites can provide the information about the ancient oceanic processes relevant to the evolution of plate tectonics in the early period of the earth, and also concern such problems as whether there existed a ＂Proto-Tethys＂ and the break-up and convergence of the Rodinian Supercontinent. This paper reveals a definite complete ophiolite of Neoproterozoic-Early Paleozoic, named Kuda ophiolite in the western Kunlun Mrs., NW Tibetan Plateau, and reports the recent reasonable SHRIMP zircon U-Pb ages of 510±4 Ma, and 502±13 Ma for the cumulates of the Kuda ophiolite, using the most powerful dating tool, the SHRIMP-Ⅱ. The geochemical and geochronology data integrating with the geological setting suggest that the Kuda ophiolite might have formed in an archipelago oceanic basin, not in a vast ocean, the so-called ＂Proto-Tethys＂, and was tectonically emplaced during the Early Paleozoic.
基金supported by the State Key Laboratory of Lithospheric EvolutionThe analyses at the University of Newcastle were financially supported by the Analytical&Biomolecular Research Facility(ABRF)unitsupported by the National Basic Research Program of China(Grant Nos.2012CB416702)
文摘LA-ICPMS zircon U-Pb dating has been greatly advanced and widely applied in the past decade because it is a cheap and fast technique.The internal error of LA-ICPMS zircon U-Pb dating can be better than 1%,but reproducibility(accuracy)is relatively poor.In order to quantitatively assess the accuracy of this technique,zircons from two dioritic rocks,a Mesozoic dioritic microgranular enclave(FS06)and a Neoproterozoic diorite(WC09-32),were dated independently in eight laboratories using SIMS and LA-ICPMS.Results of three SIMS analyses on FS06 and WC09-2 are indistinguishable within error and give a best estimate of the crystallization age of 132.2 and 760.5 Ma(reproducibility is^1%,2RSD),respectively.Zircon U-Pb ages determined by LA-ICPMS in six laboratories vary from 128.3±1.0 to 135.0±0.9 Ma(2SE)for FS06 and from 742.9±3.1 to777.8±4.7 Ma(2SE)for WC09-32,suggesting a reproducibility of^4%(2RSD).Uncertainty produced during LA-ICPMS zircon U-Pb analyses comes from multiple sources,including uncertainty in the isotopic ratio measurements,uncertainty in the fractionation factor calculation using an external standard,uncertainty in the age determination as a result of common lead correction,age uncertainty of the external standards and uncertainty in the data reduction.Result of our study suggests that the uncertainty of LA-ICPMS zircon U-Pb dating is approximately 4%(2RSD).The uncertainty in age determination must be considered in order to interpret LA-ICPMS zircon U-Pb data rationally.
基金supported by National Natural Science Foundation of China(Grant Nos.41072166 and 41272240)Program of China Geological Survey(Grant Nos.1212011121248,1212011221093)
文摘To better understand the Pan-African-early Paleozoic tectonothermal events of the Nyainrong microcontinent and the con- straints on its tectonic evolution, here we report the results of zircon LA-ICP-MS U-Pb dating and geochemical features of Amdo gneiss in the Nyainrong microcontinent. The outcrops of Amdo gneiss is about 30 km south of Amdo County in north- ern Tibet. The field occurrence, mineral composition, textural characteristics, and whole-rock geochemical features of the four gneiss samples indicate the protolith of the gneisses is intermediate-acid intrusive rock. Gneiss zircon trace element tracing and genetic analysis shows that zircon has typical characteristics of magmatic zircon. The 2~6pbF38U concordant age of zircon is 505-517 Ma, corresponding to the Middle-Late Cambrian, which is the formation age of the protolith. The samples have char- acteristics of high silicon, alkali-rich, alkalic rate AR =1.73-3.7, the differentiation index DI = 70.78-90.28; rock aluminum saturation index ranges from 1.02 to 1.05, FeO / MgO ranges from 2.63 to 4.50, 10000 x Ga/AI ranges from 2.12 to 2.41, and P205 and A1203 content decreased with SiO2 increasing. Th and Y contents have a good positive correlation with Rb content; the genetic type of protolith of the gneiss is the differentiation of subalkaline over aluminum I-type granite. Combined with re- gional data, the tectonic setting of the Amdo gneiss protolith is closely related to the collision orogenic process. The prelimi- nary view is that the Middle-Late Cambrian magmatic events developed on the microcontinent could be the result of Andean- type orogeny along the Gondwana super-continental margin after the end of the Pan-African orogeny.
基金the Major State Basic Resesrch Development Projects(Gant No.2001CB409801)the National Natural Science Foundation of China(Grant No.49972075)the Foundation of Continental Dynamic Laboratory of Northwestern Univeristy.
文摘The Songshugou dunite body,which occupies an area of about 20 km2,is the largest ultramafic massif in the eastern Qinling orogenic belt,Central China.The major compo-nent of this body is dunitic rocks including mylonitic dunite and coarse-grained dunite;they oc-cupy about 95 vol%of the total body.Petrography,mineral composition,major and trace ele-ments and primitive melt inclusions have been investigated in this paper;all revealed that this dunite body is the product of melt-rock interaction by porous percolation flow.In comparison with dunite sills or veins in harzburgite from the basal part of Oman ophiolite,this dunite body is characterized by lower contents of Al2O3,CaO and HREE but higher content of highly incom-patible elements and Zr and Hf.The LREE enriched patterns and primitive mantle normalized spidergrams of trace elements are also different from the Oman dunite.Combining with melt in-clusions observed in olivines,we conclude that this dunite body is the product of large-scale porous percolation flow of high-MgO melts within depleted mantle peridotites.The high-MgO magma,in essence,was most probably produced at the hot head of an upwelling mantle plume.The occurrence of the Songshugou dunite body is closely associated with the activity of mantle super-plume in Neo-Proterozoic era in the Yangtze Craton.
文摘Shallow gas reservoirs are distributed widely in Chinese heavy oil-bearing basins.At present,shallow gas resources have opened up giant potentials.The previous researches indicate the intimate genetic relationship between shallow gas and heavy oil.Shallow gas resources are generated from crude oil degraded by anaerobic microscopic organism,it belongs to biogenic gas family of secondary genesis,namely heavy oil degraded gas.Shallow gas resources are usually distributed in the upward position or the vicinity of heavy oil reservoirs.They are mainly of dry gas,which are composed of methane and only tiny C2+heavy hydrocarbon and relatively higher contents of nitrogen gas.Generally,methane isotopes are light,whose values are between biogenic gas and thermal cracking gas.Ethane isotopes are heavy,which mixed possibly with thermogenic gas.Carbon dioxide bear the characteristics of very heavy carbon isotope,so carbon isotopic fractionation effects are very obvious on the process of microscopic organism degradation crude oil.The heavy oil degraded gas formation,a very complex geological,geochemical and microbiological geochemical process,is the result of a series of reactions of organic matter-microbes and water-hydrocarbon,which is controlled by many factors.
基金the National Natural Science Foundation of China (Grant No. 40572045)the State Key Laboratory of Geological Processes and Mineral Re-sources in China University of Geosciences (GPMR0543)the research project ‘The study of metallization of ore deposits in Gansu Province’ in Gansu Geology and Mineral Resources Bureau
文摘Using SHRIMP zircon U-Pb dating methods and cathodoluminescence (CL) technique, we have pre- cisely dated ore samples from tungsten ore deposit, ore-bearing volcanic-sedimentary strata and granite in the Yushan region within the east Tianshan-Beishan W-bearing zone. This study reveals Yu- shan tungsten ore deposit zone formed in 250 ± 9 Ma, and it is closely associated with the Permian granites and felsic volcanic rocks. This new type of tungsten ore deposit in the east Tianshan-Beishang multiple-metallogenetic province may probably be associated with the regionally right-literal shearing after the main Carboniferous collisional orogeny, and the formation of pull-apart basin and the felsic magmatism.
