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Lin G.-C.,Changan University | Lin G.-C.,Key Laboratory of Western Chinas Mineral Resources and Geological Engineering
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | Year: 2010

Neoproterozoic magmatic rocks are widespread in western margin of the Yangtze block, and their genesis and tectonic setting have been an issue in hot debate at the present time. SHRIMP U-Pb zircon age, petrology, geochemical and Nd isotopic data are reported for the Neoproterozoic Shimian granite in the Kangdian rift of western Sichuan. This pluton is of metaluminous high-K calc-alkalic I-type granite and emplaced at 818±7 Ma. Petrology, geochemical and Nd isotopic characters suggest that the pluton was generated by partial melting of pre-existing, young (Late Mesoproterozoic to Early Neoproterozoic) island arc crust, with contamination of old crust materials during magma ascending and emplacement. The Shimian granite is the product of the tectonic transition from compression to introplate extension in western margin of the Yangtze block. Their arc-like geochemical features (such as Nb-Ta depletion) should have been inherited from the protoliths, rather than reflection of their tectonic setting when the pluton formed. Source


Zhang Y.,Changan University | Zhang Y.,Key Laboratory of Western Chinas Mineral Resources and Geological Engineering | Gu Q.,Sinopec
Journal of Earth Science | Year: 2011

Petroleum system theory has been used to study characteristics of the Fula depression in the Central African fault zone. In this system, deep lacustrine facies mudstone in the Abu Gabra Formation of the Lower Cretaceous is a very good source rock, thick deltaic facies sandstone of the Abu Gabra Formation and fluvial facies sandstone of the Bentiu Formation are good reservoir beds, and the mudstone in the Upper Cretaceous Darfur Group is the regional cap rock. The oil search mode and fault block trap seal-off conditions are considered here for passive rift basins. Particularly with respect to oil source rock distribution, successive development of reverse fault block and faulted anticlinal traps on low relief structures could have accumulated hydrocarbons because of lateral sealing by downthrown mudstone along the up-dipping reservoir beds. At present, discoveries in this system are all large-duty oil fields. In 2009, proved reserves exceeded 2×108 t, and about 3×106 t annual throughput of crude oil was obtained. Risk exploration of the Fula depression is of short cycle and high benefit, which will be of great help for exploration in the Muglad basin. © 2011 China University of Geosciences and Springer-Verlag Berlin Heidelberg. Source


Bai C.-Y.,Changan University | Bai C.-Y.,Key Laboratory of Western Chinas Mineral Resources and Geological Engineering | Huang G.-J.,Changan University | Zhao R.,Changan University | Zhao R.,China Earthquake Administration
Geophysical Journal International | Year: 2010

The purpose of this study is to introduce a multistage irregular shortest-path method (ISPM) for tracking multiple seismic arrivals including any combinations of transmissions, reflections (or refractions) and mode conversions in complex 2-D/3-D layered media, incorporating irregular interfaces (or subsurface in 3-D) and velocity discontinuities. The basic principle is to first divide the model into several different layers (using irregular cells near each interface, discontinuity and the Earth's undulating surface topography) and then to apply the multistage technique to trace the multiple arrivals. It is possible to realize the multiple arrival tracking with the multistage scheme because the multiple arrivals are just different combinations or conjugations of the simple incident, transmitted, reflected (or refracted) and mode converted waves via the velocity discontinuities and the interfaces. Benchmark tests against the popular multistage fast marching method (FMM) and the multistage MSPM (modified shortest path method) are undertaken to assess the solution accuracy and the computational efficiency. The results show that the multistage ISPM is advantageous over both the multistage FMM and the multistage MSPM in both solution accuracy and CPU time. Several examples (including the Marmousi model) are used to demonstrate the viability and versatility of the multistage ISPM in heterogeneous media, even in the presence of high-velocity contrasts involving interfaces of relatively high curvature. Applications to the seismological problems, such as traveltime tomography and earthquake location, indicate that it is possible to improve the spatial resolution in traveltime tomography and solution accuracy in earthquake location if later arrival information is combined with the first arrivals. © 2010 The Authors Geophysical Journal International © 2010 RAS. Source


Zhao R.,Changan University | Bai C.,Changan University | Bai C.,Key Laboratory of Western Chinas Mineral Resources and Geological Engineering
Acta Seismologica Sinica | Year: 2010

This study introduces the multistage scheme incorporating with an irregular shortest path method (ISPM) for tracking multiple arrivals composed of any kind of combinations of transmissions, conversions and reflections in complex 2D/3D layered media. The principle is first to divide the layered model into several different computational domains using irregular cells at the interface and the Earth's undulated surface, and then to apply the multistage technique to trace the multiple arrivals. It is possible to realize the multiple arrival tracking with the multistage technique, because the multiple arrivals are different combinations or conjugations of the simple incident, transmitted and reflected waves via the velocity discontinuities. Benchmark tests against the multistage fast marching method (FMM) are undertaken to assess the solution accuracy and the computational efficiency. The results show that the multistage ISPM method is advantageous over FMM method in both solution accuracy and CPU times. Source


Zhao C.,Changan University | Zhao C.,Key Laboratory of Western Chinas Mineral Resources and Geological Engineering | Lu Z.,U.S. Geological Survey | Zhang Q.,Changan University | Zhang Q.,Key Laboratory of Western Chinas Mineral Resources and Geological Engineering
Remote Sensing Letters | Year: 2013

Underground mining can induce large vertical displacements that often lead to the loss of coherence in repeat-pass interferometric synthetic aperture radar (SAR) images. Using SAR intensity images, this paper employs the image offset tracking method to map SAR slant range changes due to ground deformation over areas of mining. The rationale of slant range offset measurement with respect to the vertical deformation is analysed and the prerequisite of applying the slant range offset method to monitor vertical deformation is discussed. Results from the slant range offset method are used to produce time-series of cumulative ground displacements via least square estimate. We use six Advanced Land Observation Satellite (ALOS)-Phased Array L-band SAR (PALSAR) images over two coalfields in Inner Mogolia, China, to illustrate the proposed method and its effectiveness.We achieve deformation measurements with a precision of ∼0.2 m, with the maximum vertical displacement over the mining sites reaching ∼4.5 m. Finally, we use time-series results to outline common features identified in mining-induced deformation. Our results are supported by in situ investigations. © 2012 Taylor & Francis. Source

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