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青海尕科合含铜银砷矿床成矿地质特征及矿床成因浅析 总被引:1,自引:0,他引:1
笔者在系统研究尕科合银砷矿床成矿地质背景和矿床地质特征的基础上,重新厘定了矿区赋矿地层层序,探讨了尕科合石英闪长岩体与矿化的关系。 相似文献
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焉耆盆地活动断层的晚第四纪右行走滑 总被引:4,自引:0,他引:4
本研究对天山东南侧山间盆地——焉耆盆地的晚第四纪右行走滑活动断层的位移和滑动速率进行了测量.详细的卫星图像分析和野外调查表明活动断层(开都河断层带)主要分布在盆地的南缘,具典型的走滑断层特征.发育在晚更新世—全新世冲积扇中的水系记录了3~250 m的右行错断和位移的累积.冲积扇中的断层陡坎高1 m到25 m,沿断层带走向左行雁列状断层崖呈现,向NE和SW倾.基于河道的错断,14C数据和断层岩组构的分析可以得出:①活动断层的平均右行走滑速率为8 mm/a,垂直分量的速率为1 mm/a,(②典型的单次地震断裂事件产生的错断量为3~7 m,③大地震事件(Ms>7)的平均重复间隔约为500年,④开都河断层带最新的地震断裂事件发生在过去2 500 a间.与印度—欧亚板块碰撞相关联的天山是一个逆冲构造占主导地位的造山带,而山间盆地中晚第四纪的走滑断层表明了这种造山机制中具有水平滑动. 相似文献
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Basement-Cover Sequences within the UHP unit of the Dabie Shan 总被引:5,自引:0,他引:5
R. Schmid R. L. Romer L. Franz R. Oberhänsli G. Martinotti 《Journal of Metamorphic Geology》2003,21(6):531-538
Field data define two lithologically distinct basement‐cover sequences within the ultrahigh‐pressure metamorphic (UHPM) unit of the Dabie Shan, eastern China. One of the cover units, the Changpu unit, comprises calc‐arenitic metasediments in stratigraphic contact with a basement consisting of gneisses of the Yangtze craton. The second cover unit, the Ganghe unit, consists of felsic‐intermediate metavolcanics and clastic metasediments. Basement exposure of the Ganghe unit is not known. Fold axes in the Ganghe unit are oblique to those of the Changpu unit, which are parallel to those of the Yangtze gneisses. Preservation of primary textures in some volcanic rocks, and tectonic separation from the Yangtze gneisses by a greenschist facies mylonite, support an interpretation of the Ganghe unit as a low‐strain domain. Protolith associations in the Ganghe and Changpu units are compatible with deposition in a rift setting and along a passive continental margin, respectively. A U–Pb single zircon age of 761 ± 33 Ma for volcanoclastic rocks of the Ganghe unit demonstrates a Neoproterozoic deposition age, concordant with inferred rifting at that time. Eclogite facies parageneses in the gneisses and both cover units, along with P–T data demonstrate regional UHPM in the Dabie Shan. 相似文献
399.
Isabel Abad Gabriel Gutirrez-Alonso Fernando Nieto Igor Gertner Alex Becker Ana Cabero 《Tectonophysics》2003,365(1-4):103
Geological mapping and structural analysis of the Talas Ala Tau (Tien Shan, Kyrgyz Republic) have revealed a complex structure composed of folds with axial-plane cleavage and thrust faults verging towards the NE. The main structures of the range correspond to minor Tertiary and Carboniferous–Permian deformation superimposed on the main deformation event that took place during the Baikalian orogeny. The pervasive axial-plane cleavage diminishes in penetrativity from the hinterland to the foreland in both the Uzunakhmat and Karagoin sheets. The main thrusts developed phyllonitic shear-related rocks on the hangingwall immediately above the thrust planes. A crystal-chemical study of the phyllosilicates growth during the Baikalian deformation event along a cross-section revealed changes in the crystallinity, composition and lattice parameters of them. The phyllosilicates present in the Talas Ala Tau rocks were crystallized in very low-grade metamorphic conditions, that is below 300 °C, as indicated by their Kübler Index (KI), which decreases from SW towards the NE. Detailed TEM study of the phyllosilicates reveals a clear textural difference at the lattice level between samples with higher or lower KI parameters. There is also a clear difference in crystal-chemical parameters (KI and b) and composition between the phyllosilicates growth in relation to the axial-plane cleavage and the ones belonging to the thrust-related phyllonites. The first ones are more affected by the ferrimuscovitic vector than the phyllosilicates of phyllonites, closer to the theoretical phengitic component. Huge ranges of values of phengitic content of micas at sample level are interpreted as the result of a decompression path from at least 8 kbar. We propose a subduction geodynamic environment for the regional deformation and the origin of the phyllosilicates, as they are similar to those obtained in more recent accretionary complexes. 相似文献
400.
Paleozoic northward drift of the North Tien Shan (Central Asia) as revealed by Ordovician and Carboniferous paleomagnetism 总被引:7,自引:0,他引:7
Mikhail L. Bazhenov Adam Q. Collins Kirill E. Degtyarev Natalia M. Levashova Alexander V. Mikolaichuk Vladimir E. Pavlov Rob Van der Voo 《Tectonophysics》2003,366(1-2):113-141
Three new Middle–Late Ordovician and two new Early Carboniferous paleomagnetic poles have been obtained from the North Tien Shan Zone (NTZ) of the Ural–Mongol belt in Kyrgyzstan and Kazakhstan. Paleolatitudes for the Carboniferous are unambiguously northerly and average 15.5°N, whereas the Ordovician paleolatitudes (6°, 9°, and 9°) are inferred to be southerly, given that a very large (180°) rotation of the NTZ would be necessary during the middle Paleozoic if the other polarity option was chosen. Thus, the NTZ drifted northward during much of the Paleozoic; east–west drift cannot be determined, as is well known, from paleomagnetic data. In addition, detailed thermal demagnetization analysis reveals two overprints, one of recent age and the other of Permian age, which is a time of strong deformation in the NTZ. The paleolatitude of the combined Permian overprint is 30.5+2°N. The paleolatitudes collectively track those predicted for the area by extrapolation from Baltica very well, but are different from those of Siberia for Ordovician times. This finding is compatible with Sengör and Natal'in's [Sengör, A.M.C., Natal'in, B.A., 1996. Paleotectonics of Asia: fragments of a synthesis. In: Yin A., Harrison, M. (Eds.), The Tectonic Evolution of Asia. Cambridge Univ. Press, Cambridge, pp. 486–640] model of tectonic evolution of the Ural–Mongol belt and disagrees with the models of other researchers. Declinations of the Ordovician and Early Carboniferous results range from northwesterly to northeasterly, and are clearly affected by local relative rotations, which seem characteristic for the entire NTZ, because the Permian overprint declinations also show such a spread. Apparently, the important latest Paleozoic–Triassic deformation involved shear zone-related rotations as well as folding and significant granitic intrusions. 相似文献