Huang X.,China Earthquake Administration |
Zhang J.,China Earthquake Administration |
Peng P.,CAS Institute of Geology and Geophysics |
Li T.,Ningxia Institute of Geological Survey
Acta Petrologica Sinica | Year: 2013
Ductile deformation shear zones in varied degrees are preserved in the crystalline basement in the northern segment of Helan Mountain. Four stages of ductile shearing are identified by detailed outcrop research and microstructure study from the Paleoproterozoic crystalline basement in the northern segment of Helan Mountain. The earliest one is a kind of layer-paralleled shear zone composed by banded khondalite and granitic gneisses along with lots of parallelling folds, boudinages and sheathe folds, showing north to south extension with deforming characteristics of mid-lower crust level. The second one is mylonitic gneiss shear zone in high amphibolite to granulite facies resulted from a compressional tectonic movement in N-S direction to cause fast uplift of the high temperature and high pressured metamorphosed khondalite from lower crust to middle crust. The third kind of shear zone metamorphosed in low amphibolite to high greenshist facies maybe happened in the late extensional collapse stage in the same orogenic cycle with the khondalite, lifting the crystalline basement more up into the middle crust. They are composed of two sets of molynitic shear zones caused by a NW-SE extension followed another NE-SW extension. The latest kind of ductile shear zones are NE to EW trending greenshist-faced mylonitic shear zones in left-lateral thrusting sense, bring the crystalline basement up into the upper crust through the brittle-ductile transition zone. They could be resulted in another orogeny different from the khondalite because owning an obviously different kinematic character from the extensional shear zones. Similar structural deformation characters and ductile shear zones occurred in the Wula Mountains and Daqing Mountains as the northern segment of Helan Mountain indicate the existence of a EW-trending Paleoproterozoic collision orogenic belt in west part of the north edge of the North China Craton and perhaps followed by another orogeny in late-Paleoproterozoic.
Mi C.,Tianjin University |
Ma A.,Linyi Bureau of Land and Resources |
Zhang X.,Ningxia Institute of Geological Survey |
Jiang L.,Linyi Bureau of Land and Resources
WIT Transactions on Information and Communication Technologies | Year: 2014
PCA is the method based on the relativity of variables, which express multivariable using several factors without losing information as far as possible. In the multispectral images or hyper-spectrum images, there is much redundant information because of relativity of the data in different band. Employing PCA most information of the RS images can be expressed with fewer bands, it not only reduces data size but also eliminates redundant information. PCA method is always used to data preprocessing in order to depress data and enhance image. Article on the PCA in remote sensing image processing examples demonstrate the practical application of applied research. © 2014 WIT Press.
Zheng H.,Jilin University |
Sun X.M.,Jilin University |
Zhu D.F.,Petrochina |
Tian J.X.,Ningxia Institute of Geological Survey |
And 3 more authors.
Science China Earth Sciences | Year: 2015
The Erguna Fault runs along the east bank of the Erguna River in NE China and is a large-scale ductile shear zone comprising granitic mylonites. This paper reports on the geometry, kinematic indicators, and 40Ar/39Ar biotite ages of the granitic mylonites,to constrain the structural characteristics, forming age, and tectonic attribute of the Erguna ductile shear zone. The zone strikes NE and records a top-to-the-NW sense of shear. A mylonitic foliation and stretching lineation are well developed in the mylonites, which are classified as S-L tectonites. Logarithmic flinn parameters (1.18–2.35) indicate elongate strain which approximatesto plane strain. Kinematic vorticity numbers are 0.42–0.92 and 0.48–0.94, based on the polar Mohr diagram and the oblique foliation in quartz ribbons, respectively, suggesting that the ductile shear zone formed under general shear, or a combinationof simple and pure shear. According to finite strain and kinematic vorticity analyses, the Erguna Fault is a lengthening-thinning ductile shear zone that formed by extension. The deformation behavior of minerals in the mylonites indicates that the fault was the site of three stages of deformation: an initial stage of middle- to deep-level, high-temperature shear, a post-stress recovery phase of high-temperature static recrystallization, and a final phase of low-temperature uplift and cooling. The 40Ar/39Ar plateau ages of biotite from the granitic mylonites are 106.16 ± 0.79 and 111.55 ± 0.67 Ma, which constrain the timing of low-temperature uplift and cooling but are younger than the ages of metamorphic core complexes (MCCs) in the Transbaikalia-northeast Mongolia region. Using measured geological sections, microtectonics, estimates of finite strain and kinematic vorticity, and regional correlations and geochronology, we conclude that the Erguna Fault is an Early Cretaceous, NNE-trending, large-scale, sub-horizontal, and extensional ductile shear zone. It shares a similar tectonic background with the MCCs, volcanic fault basins, and large and super-large volcanic-hydrothermal deposits in Transbaikalia-northeast Mongolia and the western Great Khingan Mountains, all of which are the result of overthickened crust that gravitationally collapsed and extended in the Early Cretaceous after plate collision along the present-day Sino-Russia-Mongolia border tract. © 2015, Science China Press and Springer-Verlag Berlin Heidelberg.
Huang X.-N.,China Earthquake Administration |
Zhang J.-S.,Ningxia Institute of Geological Survey |
Li T.-B.,Ningxia Institute of Geological Survey |
Liu F.,China Earthquake Administration |
Feng J.,National Earthquake Response Support Service
Dizhen Dizhi | Year: 2012
The recent researches of active faults related to the north segment of the eastern boundary of GTSR(the great triangular seismotectonic region of Central Asia), including the north part of the North-South Seismic Belt and central Mongolia, are summarized based on their geological background and seismic activities at present. The north segment of the eastern boundary of the GTSR is composed by a series of terminal structures, lateral structures of large sinistral strike-slip faults, and transtensional graben fault systems between the large sinistral strike-slip faults. From south to north, the fault systems, which compose the north segment of the eastern boundary of GTSR, include: (1)Liupanshan arcuate fault zone, which is the eastern terminal compression structure of the Haiyuan Fault zone and Zhongwei-Tongxin Fault zone; (2)Zhuozishan-Helanshan Fault system, which is a transtensional graben fault systems between the Zhongwei-Tongxin Fault zone and the Yabulaishan-Bayanxiboshan Fault zone; (3)Langshan-Sertengshan piedmont fault system, which is the eastern relaxing structure of the Yabulaishan-Bayanxiboshan Fault zone; (4)Dalandzadgad Fault system, which is the eastern terminal compression structures of the Gobi-Tienshan Fault zone and Gobi-Altay Fault zone; (5)Mogod Faults system, the possible eastern terminal compressional structures of the North Hangay Fault zone; and (6)Hovsgol rift system, which is the extensional lateral structures of the Tunka Fault zone. The nature of the seismic structures of the north segment of the eastern boundary of the GTSR is the re-activation of the pre-existing faults that locate beside or on the terminations of giant strike-slip fault zones in the present regional stress field, controlled by the northward pushing of the Indian-Eurasia collision and local upper mantle material flow or significant anisotropies deep in the upper mantle.
Jiang X.-W.,China University of Geosciences |
Jiang X.-W.,Water Resources University |
Wan L.,China University of Geosciences |
Wan L.,Water Resources University |
And 5 more authors.
Geophysical Research Letters | Year: 2014
Groundwater flow systems and stagnant zones in drainage basins are critical to a series of geologic processes. Unfortunately, the difficulty of mapping flow system boundaries and no field example of detected stagnant zones restrict the application of the concept of nested flow systems. By assuming the variation in bulk resistivity of an aquifer with uniform porosity is mainly caused by groundwater salinity, the magnetotelluric technique is used to obtain the apparent resistivity of a profile across a groundwater-fed river in the Ordos Plateau, China. Based on the variations in apparent resistivity of the Cretaceous sandstone aquifer, the basin-bottom hydraulic trap below the river has been detected for the first time, and its size is found to be large enough for possible deposition of large ore bodies. The boundaries between local and regional flows have also been identified, which would be useful for groundwater exploration and calibration of large-scale groundwater models. Key Points The hydraulic trap with higher TDS has been identified for the first time The continuous boundaries of local and regional flow systems have been mapped The magnetotelluric method is useful for large-scale flow system studies ©2014. American Geophysical Union. All Rights Reserved.