Zhu Y.-D.,Southwest Petroleum University |
Zhang D.-H.,China University of Geosciences |
Wang L.-L.,China University of Geosciences |
Dai Y.-P.,Chengdu Center |
Xi A.-H.,Southwest Petroleum University
International Geology Review | Year: 2017
The northwest Zhejiang Province is a key domain for providing deep insight into the crust–mantle interaction and tectonic evolution of the South China block. In this paper, we collect geochemical, geochronological, and isotopic data of the Jurassic porphyries in this region, and investigated the Huangbaikeng ore-bearing porphyry in the Tongcun Mo–Cu deposit, using it as an example to uncover the porphyry petrogenesis and evaluate their metallogenic potential. Two varieties of the Huangbaikeng porphyry were distinguished: the medium- to coarse-grained type and medium- to fine-grained type. Zircon Sensitive High-Resolution Ion Microprobe U–Pb dating indicates that they were emplaced at 161.8 ± 2.8 and 162.7 ± 3.5 Ma, respectively, which are consistent with the molybdenite Re–Os ages of 163.9–161.8 Ma. The inherited zircons age spectrum significantly recorded a series of geological events, for example, assembly and breakup of the Columbia and Rodinia supercontinent, and the Triassic collision of Yangtze and North China blocks. Whole rock Sr–Nd and Jurassic zircon Hf isotopic data yield mostly negative εHf(t) values (0.5 to −8.4) and εNd(t) values (−0.79 to −4.82). Besides the Huangbaikeng porphyry, all the Jurassic porphyries in the northwest Zhejiang Province have a wide range of SiO2 contents (76.78–60.91 wt.%). They do not contain typical aluminous minerals (e.g. cordierite and garnet), and are mainly metaluminous to weakly peraluminous with high Na2O, low FeOT/MgO, and Zr + Nb + Ce + Y concentrations in composition. They thus fit the I-type granite definition. Some major and trace elements show strong correlations with SiO2, possibly indicating extensive fractional crystallization during their magma evolution. Tectonic discriminations imply that these plutons were likely formed in a volcanic arc regime possibly related to subduction of the Palaeo-Pacific plate. Sr–Nd–Hf isotopic data suggest a mixed source of the Mesoproterozoic crust and 30–50% mantle components. Compared with the adjacent Dexing Cu-bearing porphyies, which have more positive εHf(t) and εNd(t) values with more significant mantle components (55–70%), the Jurassic porphyries in the northwest Zhejiang Province probably lack metallogenic potential to form a giant porphyry copper deposit as Dexing. © 2016 Informa UK Limited, trading as Taylor & Francis Group.
Zhu Y.,Southwest Petroleum University |
Zhang D.,China University of Geosciences |
Wang L.,China University of Geosciences |
Dai Y.,Chengdu Center |
Xi A.,Southwest Petroleum University
Journal of Geochemical Exploration | Year: 2017
The Tongcun ore-bearing porphyry is located in the Tongcun porphyry Mo[sbnd]Cu deposit of NW Zhejiang Province, which is a key domain for providing deep insight into crust–mantle interaction and tectonic evolution of the South China block. SHRIMP zircon U[sbnd]Pb geochronology indicates an emplacement age of 168.7 ± 2.8 Ma. Its inherited zircon age spectrum recorded the assembly and breakup of the Rodinia supercontinent, and the Triassic collision of the Yangtze and North China blocks. This porphyry does not contain peraluminous minerals (e.g. muscovite, cordierite and garnet), and has high SiO2 (73.52–64.68 wt.%) and low FeOT/MgO and Zr + Nb + Ce + Y contents. It thus fits the I-type granite definition. Some major and trace elements show strong correlations with SiO2, indicating extensive fractional crystallization during magma evolution. Tectonic discrimination diagrams suggest a volcanic arc setting probably related to the subduction of the paleo-Pacific plate. Hf isotope of zircons with Jurassic age and bulk-rock Sr[sbnd]Nd isotopic data yield mostly negative εHf(t) values (2.5 to − 4.5) and εNd(t) values (− 3.55 to − 5.83), together with high Mg# ratios (average 46.1), suggesting a mixed source of ancient crust and 30–50% juvenile components. Compared with the Dexing Cu-bearing porphyies, which have relatively higher Mg# ratios, more positive εHf(t) and εNd(t) values, the Jurassic porphyries in NW Zhejiang Province probably lack metallogenic potential to form a giant porphyry Cu deposit. © 2016 Elsevier B.V.
News Article | June 30, 2017
Understanding modern biodiversity and extinction threats is important. It is commonly assumed that being large contributes to vulnerability during extinction crises. However, researchers from the University of Bristol and the Chengdu Center of the China Geological Survey, have found that size played no role in the extinction of fish during the largest mass extinction of all time. The study focused on the evolution of bony fishes during the Permian-Triassic mass extinction 252 million years ago. During this crisis, as many as 90 percent of all species on Earth were killed by massive climate change triggered by huge volcanic eruptions in Russia. The erupted gases led to worldwide acid rain and atmospheric warming of as much as 20 degrees centigrade. This killed plants, and soil was stripped by rainfall and washed into the sea. Oceans were also heated and life fled from the tropics. It was expected that a key feature in extinction would have been body size: the large animals would suffer heat and starvation stress first. However, in the new paper, published today in Palaeontology, it is shown that larger fish were no more likely to go extinct than small fish. The study used a detailed summary of all information on fossil fish through a span of over 100 million years, from well before to well after the disaster. Body size information was identified for over 750 of these fishes, and multiple calculations were carried out to allow for variations in the shape of the evolutionary tree and the exact dating of all the species. The result was clear - body size did not provide any advantages or disadvantages to fish during the crisis. Lead researcher Dr Mark Puttick from the Natural History Museum and University of Bristol's School of Earth Sciences, explained: "These results continue the trend of recent studies that suggest body size played no role in determining which species survive or go extinct. This is the opposite result we would expect, but provides increasing support for previous studies that show body size plays no role in extinction selectivity." The team explored the largest dataset used in an analysis of this type and applied a range of computational evolutionary models to understand these patterns in deep time. The models take account of uncertainties in the quality of the fossil data and the reconstructed evolutionary tree, and the result was clear. Professor Michael Benton, also from the University of Bristol, added: "These are exciting results. What is important also is that we were able to deploy new methods in the study that take greater account of uncertainties. "The methods are based around a detailed evolutionary tree so, unlike most previous work in the field, we paid attention to the relationships of all the species under consideration." Professor Shixue Hu, leader of the China Geological Survey: "It's great to see this new analytical work. We were able to include many new fossils from our exceptional biotas in China, and we can see the full impact of the extinction and the subsequent recovery of life during the Triassic."
Liu J.,Chengdu Center |
Liu J.,University of Hong Kong |
Rieppel O.,Field Museum |
Jiang D.-Y.,Peking University |
And 6 more authors.
Journal of Vertebrate Paleontology | Year: 2011
A new genus and species of Pachypleurosauria, Dianopachysaurus dingi, gen. et sp. nov., from a recently discovered Middle Triassic Lagerstatte in the Anisian Guanling Formation of Yunnan Province is described. The monophyly of Pachypleurosauria, including all potential Chinese pachypleurosaurs in this study, is supported by the rigorous cladistic analysis conducted here. Phylogenetic relationships of Chinese pachypleurosaurs are clarified. Wumengosaurus occupies the most basal position within Pachypleurosauria. Keichousaurus and Dianopachysaurus form the monophyletic Keichousauridae that is the sister group of all European pachypleurosaurs. Our cladistic analysis also supports a previously proposed paleobiogeographic hypothesis of an eastern Tethyan origin of pachypleurosaurs and their migration into the western Tethyan faunal province. The existence of a long ghost lineage as required by the paleobiogeographic hypothesis is greatly shortened by the discovery of Dianopachysaurus. © 2011 by the Society of Vertebrate Paleontology.
Wang P.,Peking University |
Wang P.,CAS Guangzhou Institute of Geochemistry |
Wang Y.,Science Press |
Yang Y.-F.,Chengdu Center
Ore Geology Reviews | Year: 2016
The Tangjiaping Mo deposit is located in the Dabie Shan in eastern China. Molybdenum (Mo) mineralization mainly occurs as veinlets in the Tangjiaping granite porphyry, which is featured by the development of potassic-silicic-, phyllic- and propylitic alterations. The Mo-mineralized granite porphyry yields a zircon UPb age of 118.1±0.8Ma (MSWD=1.6, 2σ, n=24), and may have formed under post-collision extensional tectonics after the Yangtze-North China collision. The Tangjiaping granite porphyry is characterized by the enrichments of LILEs and LREEs, depletions of Ba, Nb, Ta, Sr, P, Ti and HREEs, and negative Eu anomaly. Zircons from the granite porphyry yield negative εHf(t) of -15.3 to -9.9, with TDM2(Hf) ages of 1.80 to 2.14Ga. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb of the granite porphyry and its K-feldspar are 16.842-17.342, 15.388-15.439 and 37.706-38.260, respectively, while those of the sulfides are 17.090-17.832, 15.420-15.510, and 37.550-38.026, respectively. The δ34S of these sulfides exhibit a relatively narrow range of 3.2-4.9‰, with an average of 4.0‰. The HfPbS isotopic signatures indicate that the granite porphyry and the ore-forming materials at Tangjiaping were mainly derived from the partial melting of both the Southern Dabie Complex and the Precambrian basement of the North China Craton. © 2016 Elsevier B.V.
Zhang Y.-C.,Deakin University |
Zhang Y.-C.,CAS Nanjing Institute of Geology and Palaeontology |
Shen S.-Z.,CAS Nanjing Institute of Geology and Palaeontology |
Shi G.R.,Deakin University |
And 3 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2012
The tectonic evolution of the Qiangtang Block in the Qinghai-Tibetan Plateau has been a controversial subject for a long time. In this paper, the discovery of new stratigraphic and fusuline fossil evidence from the Permian sequences (Qudi and Lugu formations) of the Qiangtang Block is reported and the palaeogeographical position and tectonic history of this block during the Late Cisuralian (Late Early Permian) are discussed.The Qudi Formation is typified by thick turbidite deposits and contains Artinskian fusulines such as Pseudofusulina and Chalaroschwagerina. The fusulines were deposited as grains involved in debris flow deposits, suggesting a synchronicity with the depositional time of the turbidites. The subsequent Lugu Formation is dominated by seamount-type carbonates with an irregular basalt base. Fusulines Cancellina, Pseudodoliolina and Parafusulina in the base of the carbonates confirm its age as middle Kungurian. The transition from the turbidite Qudi Formation to the seamount Lugu Formation is here interpreted to be a continuous depositional process recording the Qiangtang Block's separation from the Indian Plate. This separation signaled the opening of the Neotethys Ocean between the Qiangtang Block and the Indian Plate. Palaeogeographically, the Qiangtang Block's separation is comparable with the Baoshan Block's separation in the east and Central Pamir's separation in the west. By contrast, the ultimate opening of the Neotethys Ocean by the separation of India-Pakistan and northern Oman is apparently much later than this event recorded in the Qiangtang Block. Consequently, it is interpreted that the opening of the Neotethys Ocean in the whole northern Gondwanan margin is a diachronous series of events. © 2012 Elsevier B.V.
Yin Y.,China Geological Survey |
Zheng W.,Chengdu Center |
Li X.,China Geological Survey |
Sun P.,Key Laboratory of Neotectonic Movement and Geohazard |
Li B.,Key Laboratory of Neotectonic Movement and Geohazard
Bulletin of Engineering Geology and the Environment | Year: 2011
Numerous earthquake-induced landslides occurred in the Longmenshan tectonic belt associated with the 12th May 2008 Wenchuan earthquake where the vertical acceleration was greater than the horizontal ground motion. Many of these landslides originated in the steep mountain terrain which amplified the effect of the ground shaking. Three typical landslides are discussed: the Niujuangou sturzstrom, the Chengxi rock slide and the 1,100 million m3 Daguangbao rock slide. Having discussed the individual slides and some previously published models, a mechanism to explain both the very fast velocity of the slides and their long run-out distance is proposed, taking into account aerodynamic principles. The model postulates that air trapped in the steep-sided valley by the collapsing rock mass forms a "cushion-effect" on which the debris moves. © 2010 Springer-Verlag.
Zhou H.,Chengdu Center |
Wang C.,Chengdu Center |
Nie D.,Chengdu University of Technology |
Chen Z.,China Southwest Geotechnical Investigation and Design Institute Co.
Advances in Science and Technology of Water Resources | Year: 2016
Based on analysis and measurement of a geostress field at the dam site of the Jiangpinghe Hydropower Station, and comparison of calculated and measured stress at the points for stress fitting, inverse analysis of the initial geostress field at the dam site of the Jiangpinghe Hydropower Station was conducted using a three-dimensional numerical model with different boundary loading conditions. The results show that the initial geostress is low at the dam site of the Jiangpinghe Hydropower Station, the maximum principal stress is 2.5 MPa and its direction is N45°W, and the minimum principal stress is 1.5 MPa with a direction of N45°E. There is agreement between the calculated and measured stress at the points for stress fitting, indicating that the initial geostress field at the dam site obtained by inverse analysis is reasonable and conforms to the historical background of the geological structure. © 2016, Editorial Board of Advances in Science and Technology of Water Resources, Hohai University. All right reserved.
Tie Y.,Chengdu Center |
Tie Y.,Chengdu University of Technology
Natural Hazards | Year: 2013
Our aim is to determine the run-out distance of the debris flow that is crucial in the assessment, prevention and control of the debris flow hazard. Based on the variation characteristic of debris flow velocity in the alluvial fan, this paper proposes the calculation method of the velocity attenuation coefficient of the debris flow. By defining the velocity attenuation coefficient and deducing its calculating formula, this paper puts forward a new method to determine the run-out distance of the debris flow based on the velocity attenuation coefficient, and Gangou debris flow in Luding County, Sichuan Province is selected as a case for calculation and verification. Having 10 m as its measuring spacing, this paper measured 19 sections at the alluvial fan of the Gangou debris flow (among them, 11 sets of data are valid). And based on the measurement, this paper analyzes the characteristic of the velocity attenuation and calculates its velocity attenuation coefficient after the 2005 debris flow. The study indicates that when the velocity of Gangou debris flow at the alluvial fan is greater than 12 % of the initial velocity (at the mouth of gully), the attenuation is quite remarkable. But when the velocity at the alluvial fan is less than 12 % of the initial velocity, the attenuation is quite slow. Besides, when Gangou debris flow rushes out of the gully mouth (the initial velocity is 10 m/s) and when it attenuates to the 32 time, its velocity is less than 0. 1 m/s, the debris flow is considered to stop flowing, and the run-out distance of Gangou debris flow is calculated to be 320 m. But the present alluvial fan of Gangou debris flow is measured to be 285 m in length, and the calculated run-out distance is 320 m, which is 35 m longer than its present length. This means when the debris flow runs out in 2005, it blocked up the main river (Dadu River) in some extent. And this finding is generally in accordance with that from the field survey. The findings can be of theoretical and practical significance in the debris flow hazard assessment, as well as its prevention and mitigation. © 2012 Springer Science+Business Media Dordrecht.
Wang J.,Chengdu Center |
Deng Q.,Chengdu Center |
Wang Z.-J.,Chengdu Center |
Qiu Y.-S.,Hubei Geological Survey |
And 3 more authors.
Precambrian Research | Year: 2013
Recent field geological investigations and sedimentary facies analysis have disclosed that the "Macaoyuan conglomerates" should be assigned to the dolomitized intraclastic lime grainstones rather than the basal conglomerates as previously reported. The conglomerates display depositionally-erosional conformable contacts with their underlying stratigraphic succession. There is no so-called "angular unconformity" or associated "Shennong movement" between the Macaoyuan Group and Shennongjia Group. The Macaoyuan Group consists primarily of carbonate platform facies association and mixed clastic and carbonate shelf facies association, while the "Macaoyuan conglomerates" are mainly made up of carbonate platform slope-channel gravity flow deposits. The sedimentary structures such as basal scouring structures, slump-convolute structures, imbricate structures, inverse grading bedding and lenticular filling deposits are well developed in the slope-channel gravity flow sedimentary succession, whereas cross bedding, wavy bedding, parallel bedding, ripple bedding, and normal grading bedding are common in the mixed inner shelf and platform-margin shoal sedimentary succession. The SHRIMP and LA-ICP-MS zircon age dating techniques are employed for the synsedimentary tuff sample collected from the upper part and sedimentary detrital zircons from the topmost part of the Baliya Formation in the lower part of the Macaoyuan Group. The synsedimentary tuff sample gives a SHRIMP zircon U-Pb age of 1157. ±. 19. Ma, which agrees well with the maximum depositional age of 1180 Ma for the sedimentary detrital zircons. It follows that the age of deposition of the Macaoyuan Group should be traced back to the Mesoproterozoic rather than the Neoproterozoic. The ages of the detrital zircons are mainly concentrated in two time intervals: 1.16-1.26. Ga and 2.60-2.95. Ga. The ca. 2.60. Ga as a marked peak age may represent an important period for the crustal accretion and evolution of the Yangtze block. © 2013 Elsevier B.V.