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Kanfenggou UHP Metamorphic Fragment in Eastern Qinling Orogen and Its Relationship to Dabie-Sulu UHP and HP Metamorphic Belts, Central China 总被引:3,自引:0,他引:3
SuoShutian ZhongZengqiu ZhouHanwen YouZhendong 《中国地质大学学报(英文版)》2003,14(2):95-102
In the Central Orogenic Belt, China, two UHP metamorphic belts are discriminated mainly based on a detailed structural analysis of the Kanfenggou UHP metamorphic fragment exposed in the eastern Qinling orogen, and together with previous regional structural, petrological and geochronological data at the scale of the orogenic domain. The first one corresponds to the South Altun-North QaidamNorth Qinling UHP metarnorphic belt. The other is the Dabie-Sulu UHP and HP metamorphic belts. The two UHP metamorphic belts are separated by a series of tectonic slices composed by the Qiniing rock group, Danfeng rock group and Liuling or Foziling rock group etc. respectively, and are different in age of the peak UHP metamorphism and geodynamic implications for continental deep subduction and collision. Regional field and petrological relationships suggest that the Kanfenggou UHP metamorphic fragment that contains a large volume of the coesite- and microdiamond-bearing eclogite lenses is compatible with the structures recognized in the South Altun and North Qaidam UHP metamorphic fragments exposed in the western part of China, thereby forming a large UHP metamorphic belt up to 1000 km long along the orogen strike. This UHP metamorphic belt represents an intercontinental deep subduction and collision belt between the Yangtze and Sino-Korean cratons, occurred during the Paleozoic. On the other hand, the well-constrained Dabie-Sulu UHP and HP metamorphic belts occurred mainly during Triassic time (250-220 Ma), and were produced by the intracontinental deep subduction and collision within the Yangtze craton. The Kanfenggou UHP metamorphic fragment does not appear to link with the DabieSulu UHP and HP metamorphic belts along the orogen. There is no reason to assume the two UHP metamorphic belts as a single giant deep subduction and collision zone in the Central Orogenic Belt situated between the Yangtze and Sino-Korean cratons. Therefore, any dynamic model for the orogen must ac-count for the development of UHP metarnorphic rocks belonging to the separate two tectonic belts of different age and tectono-metamorphic history. 相似文献
62.
Sequence of Ductile Shear Zones in UHP Metamorphic Province within Dabie Massif, China 总被引:2,自引:0,他引:2
Suo Shutian 《中国地质大学学报(英文版)》1998,9(3):189-195
INTRODUCTIONOverthelasttwodecadesconsiderableadvanceshavebeenmadetowardsrecognizingandunderstandingthetectonicsignificanceofd... 相似文献
63.
The strongly deformed eclogites are well developed in ultra-high pressure jadeite-quartzite zone of the Dabie Mountains, Eastern
China, and garnets had been deformed strongly. Observations by transmission electron microscopy identified not only structure
of plastic deformation occurring as free dislocation, dislocation loops and dislocation walls, but also clusters of water
molecules present in the deformed garnet. Using infrared spectroscopy, two types of hydrous components are identified as the
hydroxyl and free-water in the garnet. Based on analysis of microstructure mechanism of deformation in garnets, and experimental
data of petrology, the clusters of water molecules were considered to lead strong plastic deformation of garnet by dislocations
because of mechanical weakening. 相似文献
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Fluid-Rock Interaction of Shear Zones in Continental Crust:as Evidenced by Xincheng-Xishui and Hetai Shear Zones 总被引:1,自引:0,他引:1
Zhong Zengqiu You Zhendong Xu QidongFaculty oj Earth Sciences China University of Geosciences Wuhan 《中国地质大学学报(英文版)》1995,(2)
There is a coupling of thermal, mechanical, chemical and fluidal processes in a continental shear zone. Both Xincheng-Xishui and Hetai shear zones are typical continental crust shear zones of greenschist facies environment. The representative mylonite zones of the shear zones are studied with whole rock major and trace element analyses. The chemical compositional variation tendencies in both shear zones are very similar and the gain-loss ratios of various components in the mylonitic rocks are reflected in the mass balance equations. The enrichment of those immobile high-field-strengh elements is considered to he related to the volume loss of the myionitic rocks in a shear zone. Based on the volume loss expression C_s/C_o=1/(1-V),the fractional volume losses (V)are 37.5% and 36.5%-42.3% respectively for mylonites and ultramylonites in the Xincheng-Xishui shear zone and 11% and 28% respectively for mylonites and phyllonites in the Hetai shear zone. The high volume loss and large removal of SiO_2 from 相似文献
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云开隆起低压麻粒岩相变质作用时代的重要发现 总被引:8,自引:0,他引:8
首次报道云开隆起低压麻粒岩950Ma左右的变质作用年龄,结合麻粒岩的岩相学以及区域地质特征,指出晋宁期云开地区处于拉张的构造环境。 相似文献
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Geochemical Characteristics of Pb Isotope of High-Pressure Metamorphic Rocks and Foliated Granites from HP Unit of Tongbai-Dabie Orogenic Belt 总被引:1,自引:0,他引:1
ZhangLi ZhangHongfei ZhongZengqiu ZhangBenren WangLinsen 《中国地质大学学报(英文版)》2003,14(4):321-329
Whole-rock Pb isotopic compositions of the high-pressure (HP) metamorphic rocks, consisting of two-mica albite gneisses and eclogites, and foliated granites from the HP metamorphic unit of the Tongbai-Dabie orogenic belt are firstly reported in this paper. The results show that the tip metamorphic rocks in different parts of this orogenic belt have similar Pb isotopic compositions. The twomica albite gneisses have ^206 pb/^204 Pb=17. 657 -18. 168, ^207pb/^204 Pb=15. 318-15. 573,^ 208Pb/^204ob=38.315-38. 990, and the eclogites have ^206Pb/^204 Pb=17. 599 -18. 310, ^207Pb/^204 Pb=15. 465 -15. 615,^208Pb/^204Pb=37. 968-39. 143. The HP metamorphic rocks are characterized by upper crustal Pb isotopic composition. Although the Pb isotopic composition of the HP metamorphic rocks partly overlaps that of the ultrahigh-pressure (UHP) metamorphic rocks, as a whole, the former is higher than the latter. The high radiogenic Pb isotopic composition for the HP metamorphic rocks confirms that the subducted Yangtze continental crust in the Tongbai-Dabie orogenic belt has the chemical structure of increasing radiogenic Pb isotopic composition from lower crust to upper crust. The foliated granites, intruded in the HP metamorphic rocks post the HP/UHP metamorphism, have ^206Pb/^204 Pb=17. 128- 17. 434,^207Pb/^204pb=15. 313-15. 422 and ^208Pb/^204Pb=37. 631-38. 122, which are obviously different from the Pb isotopic compositions of the HP metamorphic rocks but similar to those of the UHP metamorphic rocks and the foliated garnet-bearing granites in the UHP unit. This shows that the foliated granites from the HP and UHP units have common magma source. Combined with the foliated granites having the geochemical characteristics of A-type granites, it is suggested that the magma for the foliated granites in the UHP and HP unit would be derived from the partial melting of the retrometamorphosed UHP metamorphic rocks exhumed into middle to lower crust, and partial magmas were intruded into the HP unit. 相似文献