Tectonic evolution of the Dabieshan orogen: In the view from polyphase deformation of the Beihuaiyang metamorphic zone

2005 ◽  
Vol 48 (7) ◽  
pp. 886 ◽  
Author(s):  
Wei LIN
Keyword(s):  
Tectonic Evolution ◽  
Polyphase Deformation ◽  
Metamorphic Zone ◽  
Dabieshan Orogen

Tectonic evolution of the Chinese Tianshan Orogen from subduction to arc-continent collision: Insight from polyphase deformation along the Gangou section, Central Asia

2020 ◽  
Vol 132 (11-12) ◽  
pp. 2529-2552
Author(s):  
Pengfei Li ◽  
Min Sun ◽  
Gideon Rosenbaum ◽  
Keda Cai ◽  
Chao Yuan ◽  
...  
Keyword(s):  
Tectonic Evolution ◽  
Shear Zones ◽  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Plate Boundaries ◽  
Polyphase Deformation ◽  
Central Asian ◽  
Chinese Tianshan ◽  
Southern Central ◽  
Parallel Extension

Abstract The Central Asian Orogenic Belt, as the largest accretionary orogen on Earth, is an ideal candidate to study the geodynamics of convergent plate boundaries through a prolonged period. The evolution of this orogen has been explained by different tectonic models, which incorporated one, or a combination, of the following mechanisms: lateral stacking of arc systems along major shear zones, arc amalgamation, oroclinal bending, and trench migration. Here we elucidate major mechanisms responsible for the tectonic evolution of the Central Asian Orogenic Belt, focusing on the Chinese Tianshan Orogen in the southern Central Asian Orogenic Belt. Structural observations from the ∼50-km-long Gangou section show evidence of polyphase deformation. The earliest episode of orogen-parallel sinistral shearing, constrained to the Early Devonian (ca. 399 Ma) by syn-deformational intrusions, was possibly controlled by oblique subduction. This was followed by an episode of ∼NE–SW contractional deformation, dated at ca. 356 Ma (40Ar/39Ar age of syn-deformational hornblende), and likely associated with an episode of trench advance. The third stages of deformation during the latest Carboniferous and Permian involved ∼NE-SW contraction, orogen-parallel extension, and dextral transpression. Our new geochronological data constrain the timing of orogen-parallel extension to ca. 303–293 Ma, and confirm that dextral activation along shear zones occurred during the Permian. The results highlight the role of trench migration, oblique tectonics, and syn-collisional orogen-parallel extension in the build-up of the Central Asian Orogenic Belt, and contribute to the pre-collisional reconstruction of this orogenic system.

Polyphase deformation of the Dorsale Calcaire Complex and the Maghrebian Flysch Basin Units in the Jebha area (Central Rif, Morocco): New insights into the Miocene tectonic evolution of the Central Rif belt

2015 ◽  
Vol 90 ◽  
pp. 14-31 ◽  
Author(s):  
Stefano Vitale ◽  
Mohamed Najib Zaghloul ◽  
Bilal El Ouaragli ◽  
Francesco D’Assisi Tramparulo ◽  
Sabatino Ciarcia
Keyword(s):  
Tectonic Evolution ◽  
Polyphase Deformation ◽  
Rif Belt

Direct Observation of Crystalline Ordering In Naturally Graphitized Carbon Produced by Low Grade Metamorphism

1977 ◽  
Vol 35 ◽  
pp. 162-163
Author(s):  
Thomas R. McKee ◽  
Peter R. Buseck
Keyword(s):  
Crystallite Size ◽  
Sedimentary Rocks ◽  
Carbonaceous Material ◽  
Low Grade ◽  
X Ray ◽  
Graphitized Carbon ◽  
Transmission Electron ◽  
Heat Treated ◽  
Commercial Carbon ◽  
Metamorphic Zone

Sediments commonly contain organic material which appears as refractory carbonaceous material in metamorphosed sedimentary rocks. Grew and others have shown that relative carbon content, crystallite size, X-ray crystallinity and development of well-ordered graphite crystal structure of the carbonaceous material increases with increasing metamorphic grade. The graphitization process is irreversible and appears to be continous from the amorphous to the completely graphitized stage. The most dramatic chemical and crystallographic changes take place within the chlorite metamorphic zone.The detailed X-ray investigation of crystallite size and crystalline ordering is complex and can best be investigated by other means such as high resolution transmission electron microscopy (HRTEM). The natural graphitization series is similar to that for heat-treated commercial carbon blacks, which have been successfully studied by HRTEM (Ban and others).

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