The characteristics of climatic change and fiver runoff, as well as the response of fiver runoff to climatic change in the northern Xinjiang are analyzed on the basis of the hydrological and meteorological data over t...The characteristics of climatic change and fiver runoff, as well as the response of fiver runoff to climatic change in the northern Xinjiang are analyzed on the basis of the hydrological and meteorological data over the last 50 years by the methods of Mann-Kendall nonparametric test and the nonlinear regression model. The results show that: 1) The temperature and the precipitation increased significantly in the whole northern Xinjiang, but the precipitation displayed no obvious change, or even a decreasing trend in the northern mountainous area of the northern Xinjiang. 2) River runoff varied in different regions in the northern Xinjiang. It significantly increased in the northern slope of the Tianshan Mountains and the north of the northern Xinjiang (p = 0.05), while slightly ificreased in the west of the northern Xinjiang. 3) North Atlantic Oscillation (NAO) affects fiver runoff by influencing temperature and precipitation. The NAO and precipitation had apparent significant correlations with the fiver runoff, but the temperature did not in the northern Xinjiang. Since the mid-1990s fiver runoff increase was mainly caused by the increasing temperature in the northern slope of the Tianshan Mountains and the north of the northern Xinjiang. Increased precipitation resulted in increased fiver runoff in the west of the northern Xinjiang.展开更多
This paper presents a synthetic U-Pb and Hf isotopic study of zircons and a whole-rock geochemical study on diabase swarms that were emplaced into the Proterozoic formations in the Xuzhou-Huaibei area,the southeast ma...This paper presents a synthetic U-Pb and Hf isotopic study of zircons and a whole-rock geochemical study on diabase swarms that were emplaced into the Proterozoic formations in the Xuzhou-Huaibei area,the southeast margin of North China Craton.Zircons from the diabase dykes display weak oscillatory zoning in the cathodoluminescence(CL) images and show high Th/U ratios(0.91-6.90),both of which are typical of a magmatic origin.The SHRIMP and Q-ICP-MS U-Pb zircon dating results indicate that the diabase swarms were emplaced at ca.890 Ma.Hf isotopic analysis on these zircons gives Hf(t) values ranging from 2.26 to 14.74 and Hf model age t DM1 and t DM2 ranging from 843 to 1321 Ma and from 808 to 1779 Ma,respectively.Geochemically,the diabase swarms are characterized by a relative enrichment in LREE and LILE(Rb,Ba and La),a comparative enrichment in Cr and Ni,but a slight depletement in HFSE(Th,Nb,Ta,Zr and Hf).They are plotted in the within-plate tholeiite series on the tectonic discrimination diagrams.Taken together,these geochemical and isotopic data suggest that the primary magmas to form the diabase dykes in the Xuzhou-Huaibei area could have been derived from a transitional mantle in the Mesoproterozoic,and were most probably emplaced under a continental margin extensional setting at ca.890 Ma.The results of this study demonstrate that the Neoproterozoic(800-900 Ma)magmatism was not restricted to the Yangtze Block,but also occurred at the southeast margin of the North China Craton.展开更多
Forty-two Cenozoic (mostly Miocene) basalt samples from Jining, Chifeng, Fansi, Xiyang, and Zuoquan areas of the North China Craton (the NCC basalts hereafter) were analyzed for platinum-group elements (PGE, incl...Forty-two Cenozoic (mostly Miocene) basalt samples from Jining, Chifeng, Fansi, Xiyang, and Zuoquan areas of the North China Craton (the NCC basalts hereafter) were analyzed for platinum-group elements (PGE, including Os, It, Ru, Rh, Pt, and Pd). Most of them are alkaline basalts and tholeiites and all of them display little crustal contamination. The total PGE contents of the NCC basalts vary from 0.1 to 0.9 ppb, much lower than those of the primitive mantle values of 23.5 ppb. Primitive man- tie-normalized PGE patterns of these basalts define positive slopes and Pd/Ir ratios vary from 1.2 to 25. In terms of both PGE contents and Pd/Ir ratios, they are quite similar to the mid-ocean ridge basalts. There are no obvious negative correlations be- tween PGE vs. MgO, Ni, and Cu in the NCC basalts, indicating that fractional crystallization of olivine, pyroxene, and/or sul- fides during magmatic process cannot be the controlling factor for the observed PGE variation. The observed Pd/Ir variations of the NCC basalts require involvement of non-chondritic heterogeneous mantle sources. Based on Sr-Nd-Pb-Hf isotopic sys- tematics and incompatible-element signatures, a mixing of partial melts from both asthenospheric peridotites and enclosed mantle eclogites at the top of asthenosphere was proposed for the origin of these NCC basalts. The lenses of eclogites are de- rived from upwelling of recycled continental crust during the westward subduction of the Pacific plate from the -600 km dis- continuity zone. The PGE geochemistry of these basalts provides independent evidence to support this conclusion and the ob- served Pd/Ir variations may reflect variations in proportions of tapped peridotitic and eclogitic melts.展开更多
Here we report the first discovery of a relatively complete skull of Choerolophodon from the late early Miocene Dalanggou quarry of Linxia Basin, Gansu Province in China. The skull is low and elongated, with two ename...Here we report the first discovery of a relatively complete skull of Choerolophodon from the late early Miocene Dalanggou quarry of Linxia Basin, Gansu Province in China. The skull is low and elongated, with two enamel-less and out ward-and-upward curved incisors and the choerolophodont molars. These characters indicate that the new specimen can be as signed to the genus Choerolophodon, as it is quite distinct from other common gomphotheres in northern China such as Gom photherium, Platybelodon, and Sinomastodon. The skull is also primitive in possessing laterally-expanded zygomatic arches, anteriorly-positioned orbits, weakly-developed cheek teeth cement, and retention of a P4. Prior to this discovery, Cho erolophodon was found primarily from the middle-late Miocene of Africa, Eastern Europe, and western and southern Asia. The discovery of this new material expands the known temporal and spatial distributions of this taxon and helps us better un derstand the phylogeny, evolution, and adaptive radiation of gomphotheres in early Miocene of China.展开更多
Zircon U-Pb ages(SHRIMP and LA-ICPMS) and Lu-Hf isotope data(LA-ICPMS) are presented for two granite and two quartzite pebbles from the basal conglomerates of the Sijizhuang Formation in the Hutuo Group from the Wutai...Zircon U-Pb ages(SHRIMP and LA-ICPMS) and Lu-Hf isotope data(LA-ICPMS) are presented for two granite and two quartzite pebbles from the basal conglomerates of the Sijizhuang Formation in the Hutuo Group from the Wutai Mountains area in the North China Craton.These two granite pebbles give zircon 207 Pb/206 Pb ages of 2513±8 Ma and 2527±8 Ma respectively,which are consistent with the emplacement ages of the Wangjiahui grey granite and Guangmingsi or Shifo granite in the Wutai Mountains.Detrital zircons from those two quartzite pebbles are mostly 2550-2490 Ma old with lesser number of 2800-2550 Ma grains,which is similar to the ages of detrital zircons from quartzites in the Gaofan Subgroup of the Neoarchean Wutai Group.Thus,the pebbles in the Hutuo Group basal conglomerates were derived locally from Wutai Mountains Neoarchean sources.Zircons from the Sijizhuang Formation conglomerate granite and quartzite pebbles mostly have positive ε Hf(t) values,a minority with ε Hf(t) values like model depleted mantle(DM) of the same age,but with most showing DM model ages 200-100 Ma.This indicates that most of the source materials were derived from the mantle within the previous 200 million years,whereas some are derived from 2550-2510 Ma juvenile crustal additions.This additional evidence suggests that in the North China Craton there was important initial polycyclic crustal formation and cratonization in the late Neoarchaean,prior to superimposed Palaeoproterozoic orogenic cycles.展开更多
基金Under the auspices of Knowledge Innovation Programs of Chinese Academy of Sciences (No. KZCX2-YW-127, KZCX2-XB2-03-01, KZCX2-Q10-5-4)
文摘The characteristics of climatic change and fiver runoff, as well as the response of fiver runoff to climatic change in the northern Xinjiang are analyzed on the basis of the hydrological and meteorological data over the last 50 years by the methods of Mann-Kendall nonparametric test and the nonlinear regression model. The results show that: 1) The temperature and the precipitation increased significantly in the whole northern Xinjiang, but the precipitation displayed no obvious change, or even a decreasing trend in the northern mountainous area of the northern Xinjiang. 2) River runoff varied in different regions in the northern Xinjiang. It significantly increased in the northern slope of the Tianshan Mountains and the north of the northern Xinjiang (p = 0.05), while slightly ificreased in the west of the northern Xinjiang. 3) North Atlantic Oscillation (NAO) affects fiver runoff by influencing temperature and precipitation. The NAO and precipitation had apparent significant correlations with the fiver runoff, but the temperature did not in the northern Xinjiang. Since the mid-1990s fiver runoff increase was mainly caused by the increasing temperature in the northern slope of the Tianshan Mountains and the north of the northern Xinjiang. Increased precipitation resulted in increased fiver runoff in the west of the northern Xinjiang.
基金supported by National Natural Science Foundation of China (Grant Nos. 40772037,90814003)
文摘This paper presents a synthetic U-Pb and Hf isotopic study of zircons and a whole-rock geochemical study on diabase swarms that were emplaced into the Proterozoic formations in the Xuzhou-Huaibei area,the southeast margin of North China Craton.Zircons from the diabase dykes display weak oscillatory zoning in the cathodoluminescence(CL) images and show high Th/U ratios(0.91-6.90),both of which are typical of a magmatic origin.The SHRIMP and Q-ICP-MS U-Pb zircon dating results indicate that the diabase swarms were emplaced at ca.890 Ma.Hf isotopic analysis on these zircons gives Hf(t) values ranging from 2.26 to 14.74 and Hf model age t DM1 and t DM2 ranging from 843 to 1321 Ma and from 808 to 1779 Ma,respectively.Geochemically,the diabase swarms are characterized by a relative enrichment in LREE and LILE(Rb,Ba and La),a comparative enrichment in Cr and Ni,but a slight depletement in HFSE(Th,Nb,Ta,Zr and Hf).They are plotted in the within-plate tholeiite series on the tectonic discrimination diagrams.Taken together,these geochemical and isotopic data suggest that the primary magmas to form the diabase dykes in the Xuzhou-Huaibei area could have been derived from a transitional mantle in the Mesoproterozoic,and were most probably emplaced under a continental margin extensional setting at ca.890 Ma.The results of this study demonstrate that the Neoproterozoic(800-900 Ma)magmatism was not restricted to the Yangtze Block,but also occurred at the southeast margin of the North China Craton.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.41173036,40534022)the Chinese Academy of Sciences(Grant No.KZCX2-YW-103)
文摘Forty-two Cenozoic (mostly Miocene) basalt samples from Jining, Chifeng, Fansi, Xiyang, and Zuoquan areas of the North China Craton (the NCC basalts hereafter) were analyzed for platinum-group elements (PGE, including Os, It, Ru, Rh, Pt, and Pd). Most of them are alkaline basalts and tholeiites and all of them display little crustal contamination. The total PGE contents of the NCC basalts vary from 0.1 to 0.9 ppb, much lower than those of the primitive mantle values of 23.5 ppb. Primitive man- tie-normalized PGE patterns of these basalts define positive slopes and Pd/Ir ratios vary from 1.2 to 25. In terms of both PGE contents and Pd/Ir ratios, they are quite similar to the mid-ocean ridge basalts. There are no obvious negative correlations be- tween PGE vs. MgO, Ni, and Cu in the NCC basalts, indicating that fractional crystallization of olivine, pyroxene, and/or sul- fides during magmatic process cannot be the controlling factor for the observed PGE variation. The observed Pd/Ir variations of the NCC basalts require involvement of non-chondritic heterogeneous mantle sources. Based on Sr-Nd-Pb-Hf isotopic sys- tematics and incompatible-element signatures, a mixing of partial melts from both asthenospheric peridotites and enclosed mantle eclogites at the top of asthenosphere was proposed for the origin of these NCC basalts. The lenses of eclogites are de- rived from upwelling of recycled continental crust during the westward subduction of the Pacific plate from the -600 km dis- continuity zone. The PGE geochemistry of these basalts provides independent evidence to support this conclusion and the ob- served Pd/Ir variations may reflect variations in proportions of tapped peridotitic and eclogitic melts.
基金supported by the Knowledge Innsovation Program of Chinese Academy of Sciences (Grant Nos. KZCX2-YW-Q09-120, KZCX2-YW-120)National Natural Science Foundation of China (Grant Nos. 40730210, 41002010)+1 种基金Ministry of Science and Technology of China (Grant No. 2006CB806400)Key Laboratory of Evolutionary Systematics of Vertebrates, CAS (Grant No. 2010LESV004)
文摘Here we report the first discovery of a relatively complete skull of Choerolophodon from the late early Miocene Dalanggou quarry of Linxia Basin, Gansu Province in China. The skull is low and elongated, with two enamel-less and out ward-and-upward curved incisors and the choerolophodont molars. These characters indicate that the new specimen can be as signed to the genus Choerolophodon, as it is quite distinct from other common gomphotheres in northern China such as Gom photherium, Platybelodon, and Sinomastodon. The skull is also primitive in possessing laterally-expanded zygomatic arches, anteriorly-positioned orbits, weakly-developed cheek teeth cement, and retention of a P4. Prior to this discovery, Cho erolophodon was found primarily from the middle-late Miocene of Africa, Eastern Europe, and western and southern Asia. The discovery of this new material expands the known temporal and spatial distributions of this taxon and helps us better un derstand the phylogeny, evolution, and adaptive radiation of gomphotheres in early Miocene of China.
基金supported by China Geological Survey (Grant Nos. 1212010611802,1212010711815 and 1212011120152)National Natural Science Foundation of China (Grant No. 41172171)+1 种基金Basic Foundation of Scientific Research Work from Ministry of Science and Technology of China (GrantNos. J0721 and J0907)National Commission on Stratigraphy of China(Grant Nos. 1212010511702-01 and 1212011120142)
文摘Zircon U-Pb ages(SHRIMP and LA-ICPMS) and Lu-Hf isotope data(LA-ICPMS) are presented for two granite and two quartzite pebbles from the basal conglomerates of the Sijizhuang Formation in the Hutuo Group from the Wutai Mountains area in the North China Craton.These two granite pebbles give zircon 207 Pb/206 Pb ages of 2513±8 Ma and 2527±8 Ma respectively,which are consistent with the emplacement ages of the Wangjiahui grey granite and Guangmingsi or Shifo granite in the Wutai Mountains.Detrital zircons from those two quartzite pebbles are mostly 2550-2490 Ma old with lesser number of 2800-2550 Ma grains,which is similar to the ages of detrital zircons from quartzites in the Gaofan Subgroup of the Neoarchean Wutai Group.Thus,the pebbles in the Hutuo Group basal conglomerates were derived locally from Wutai Mountains Neoarchean sources.Zircons from the Sijizhuang Formation conglomerate granite and quartzite pebbles mostly have positive ε Hf(t) values,a minority with ε Hf(t) values like model depleted mantle(DM) of the same age,but with most showing DM model ages 200-100 Ma.This indicates that most of the source materials were derived from the mantle within the previous 200 million years,whereas some are derived from 2550-2510 Ma juvenile crustal additions.This additional evidence suggests that in the North China Craton there was important initial polycyclic crustal formation and cratonization in the late Neoarchaean,prior to superimposed Palaeoproterozoic orogenic cycles.