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Zhang Y.-C.,Deakin University | Zhang Y.-C.,CAS Nanjing Institute of Geology and Palaeontology | Wang Y.,CAS Nanjing Institute of Geology and Palaeontology | Zhang Y.-J.,Chengdu Center | And 2 more authors.
Palaeoworld | Year: 2012

A fusuline fauna of seven species belonging to six genera from the lower part of the Lugu Formation in the Qiangtang Block, Tibet, is described for the first time. This fauna is assigned to the middle Kungurian based on the dominance of Cancellina primigena (Hayden). Biogeographically, the fauna is characterised by influx of many palaeoequatorial Tethyan taxa by comparison with the underlying Artinskian fauna. The palaeobiogeography of fusuline fauna in the Qiangtang Block from the Artinskian to the middle Kungurian is characterised by a pronounced transition from peri-Gondwanan affinity to a transitional affinity (Tethyan Cimmerian subregion). This transition is considered to have resulted from the combined effects among a northward drift of the Qiangtang Block, contemporaneous global climatic amelioration during the Permian, and the oceanic currents along the new-formed Neotethys Ocean. © 2012 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. Source

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. Source

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. Source

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. Source

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. Source

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