scholarly journals Middle Jurassic collision of an exotic microcontinental fragment: Implications for magmatism across the Southeast China continental margin

2016 ◽  
Vol 38 ◽  
pp. 304-312 ◽  
Author(s):  
Roderick J. Sewell ◽  
Andrew Carter ◽  
Martin Rittner
Keyword(s):  
Continental Margin ◽  
Middle Jurassic ◽  
Southeast China

Late Mesozoic Paleo-Pacific Plate “scissors-like” subduction: Insight from the magmatism in the Gan-Hang Belt, Southeast China

2020 ◽  
Author(s):  
Liu Boran ◽  
Zhao Xilin ◽  
Yu Shengyao ◽  
Jiang Yang ◽  
Mao Jianren ◽  
...  
Keyword(s):  
Continental Margin ◽  
Middle Jurassic ◽  
Tectonic Setting ◽  
Pacific Plate ◽  
Geochemical Data ◽  
Asian Continent ◽  
Southeast China ◽  
Late Mesozoic ◽  
Extensional Tectonic ◽  
Roll Back

Though it is widely accepted that the Paleo-Pacific Plate has a subducted beneath the eastern Asian continent, controversy still exists regarding the initial timing and geodynamic model of the subduction. In this contribution, we report new geochronology and geochemical data of granitic plutons within the Gan-Hang Belt in Southeast China. The Damaoshan pluton yields zircon U-Pb ages of 139.60 ± 0.69 Ma and 133.90 ± 1.70 Ma, and the Qianshan and Fenglonggu plutons are dated at 135.70 ± 1.30 Ma and 135.33 ± 0.93 Ma, respectively. The Hecun and Huangtuling plutons yield ages of 157.85 ± 0.77 Ma and 167.10 ± 7.50 Ma, respectively. The Damaoshan pluton has an obvious A-type geochemical signature in terms of major and trace element compositions, such as high K2O+Na2O contents (average 8.46 wt%) and FeOT/MgO ratios (average 10.29). The low CaO/Na2O ratios but high Al2O3/TiO2 (average is 110.05), Rb/Ba (average is 9.14), and Rb/Sr (average is 22.53) ratios indicate a derivation from pelite-derived melt. Meanwhile, we also studied the Mesozoic adakites related to magmatic ore formed during a compressive tectonic setting as well as the later bimodal dikes and A-type granitic plutons formed during the extensional tectonic setting in the Gan-Hang Belt. The multiphase qualitative plutons with geochemical characteristics of the adakitic and island arc types (175−150 Ma) related to the northwestward subduction of the Paleo-Pacific Plate, several bimodal dikes, and A-type granitic plutons (135−123 Ma) related to the subducted slab roll-back are found within the Gan-Hang Belt. All of these plutons show a decreasing trend of isotopic ages from the inland area to the coast, from SW to NE. We propose that the distribution pattern of these plutons in Southeast China was controlled by a scissors-like subduction and slab roll-back of the Paleo-Pacific Plate, which occurred roughly from SW to NE along the continental margin approximately during the Middle Jurassic to the Early Cretaceous.

Geodynamic evolution of the Canadian Cordillera — progress and problems

1979 ◽  
Vol 16 (3) ◽  
pp. 770-791 ◽  
Author(s):  
J. W. H. Monger ◽  
R. A. Price
Keyword(s):  
Continental Margin ◽  
Middle Jurassic ◽  
Rocky Mountain ◽  
Ocean Basin ◽  
Strike Slip ◽  
Granitic Rocks ◽  
Canadian Cordillera ◽  
Thrust Faulting ◽  
Western Cordillera ◽  
Geophysical Surveys

The present geodynamic pattern of the Canadian Cordillera, the main features of which were probably established in Miocene time, involves a combination of right-hand strike-slip movements on transform faults along the continental margin, and, in the south and extreme north, convergence in subduction zones in which oceanic lithosphere moves beneath the continent, with consequent magmatism along the continental margin. In the southern Canadian Cordillera, geophysical surveys have outlined the subducting slab and the asthenospheric bulge that occurs beneath and behind the magmatic arc. They also show that there is now no root of thickened Precambrian continental crust beneath the tectonically shortened supracrustal strata in the southern parts of the Omineca Crystalline Belt and Rocky Mountain Belt.The Rocky Mountain, Omineca Crystalline, Intermontane, Coast Plutonic, and Insular Belts, the structural and physiographic provinces that dominate the present configuration of the Canadian Cordillera, were established with the initial uplift and the intrusion of granitic rocks in the Omineca Crystalline Belt in Middle and Late Jurassic time and in the Coast Plutonic Complex in Early Cretaceous time, and they dominated patterns of uplift, erosion and deposition through Cretaceous and Paleogene time. Their development may be due to compression with thrust faulting in the eastern Cordillera, and to magmatism that accompanied subduction and to accretion of an exotic terrane, Wrangellia, in the western Cordillera. Major right-lateral strike-slip faulting, which occurred well east of but sub-parallel with the continental margin during Late Cretaceous and Paleogene time, accompanied major tectonic shortening due to thrusting and folding in the Rocky Mountain Belt as well as the main subduction-related (?) magmatism in the Coast Plutonic Complex.The configuration of the western Cordillera prior to late Middle Jurassic time is enigmatic. Late Paleozoic and early Mesozoic volcanogenic strata form a complex collage of volcanic arcs and subduction complexes that was assembled mainly in the Mesozoic. The change in locus of deposition between Upper Triassic and Lower to Middle Jurassic volcanogenic assemblages, and the thrust faulting in the northern Cordillera may record emplacement of another exotic terrane, the Stikine block, in latest Triassic to Middle Jurassic time.The earliest stage in the evolution of the Cordilleran fold belt involved the protracted (1500 to 380 Ma) development of a northeasterly tapering sedimentary wedge that discordantly overlaps Precambrian structures of the cratonic basement. This miogeoclinal wedge may be a continental margin terrace wedge that was prograded into an ocean basin, but it has features that may be more indicative of progradation into a marginal basin in which there was intermittent volcanic activity, than into a stable expanding ocean basin of the Atlantic type.

scholarly journals Middle Jurassic (Bajocian) planktonic foraminifera from the northwest Australian margin

2020 ◽  
Vol 39 (2) ◽  
pp. 93-115
Author(s):  
Marjorie Apthorpe
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Southern Hemisphere ◽  
Continental Margin ◽  
Middle Jurassic ◽  
Planktonic Foraminifera ◽  
Microscope Images ◽  
Northwestern Australia ◽  
Tethys Ocean ◽  
Scanning Electron

Abstract. The aim of this paper is to document three well-preserved morphotypes of Middle Jurassic (Bajocian) planktonic foraminifera from the continental margin of northwestern Australia. This location is on the southern shelf of the Middle Jurassic Tethys Ocean, and these occurrences of planktonic or meroplanktonic species are the first to be reported from the Jurassic of the Southern Hemisphere. The morphotypes include a new subspecies of Globuligerina bathoniana (Pazdrowa): Globuligerina bathoniana australiana n. ssp. Two other taxa are also described: Globuligerina altissapertura n. sp. and Mermaidogerina loopae n. gen. n. sp. The microstructure of the wall is shown in scanning electron microscope images. The change from chamber to chamber in the formation of the surface ornament by secondary lamination, and its subsequent burial within the wall, is demonstrated in detail.

Eastward tectonic migration and transition of the Jurassic-Cretaceous Andean-type continental margin along Southeast China

2019 ◽  
Vol 196 ◽  
pp. 102884 ◽  
Author(s):  
Yanhui Suo ◽  
Sanzhong Li ◽  
Chong Jin ◽  
Yong Zhang ◽  
Jie Zhou ◽  
...  
Keyword(s):  
Continental Margin ◽  
Southeast China ◽  
Andean Type ◽  
Tectonic Migration
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