scholarly journals Pre-Variscan tectonic setting of the south margin of Armorica: Insights from detrital zircon ages distribution and Hf isotopic composition of the St-Georges-sur-Loire Unit (S. Armorican Massif, France)

2019 ◽  
Vol 766 ◽  
pp. 340-378 ◽  
Author(s):  
Wei Lin ◽  
Michel Faure ◽  
Xian-Hua Li ◽  
Wenbin Ji
2011 ◽  
Vol 149 (4) ◽  
pp. 626-644 ◽  
Author(s):  
JOHN D. BRADSHAW ◽  
ALAN P. M. VAUGHAN ◽  
IAN L. MILLAR ◽  
MICHAEL J. FLOWERDEW ◽  
RUDOLPH A. J. TROUW ◽  
...  

AbstractField observations from the Trinity Peninsula Group at View Point on the Antarctic Peninsula indicate that thick, southward-younging and overturned clastic sedimentary rocks, comprising unusually coarse conglomeratic lenses within a succession of fine-grained sandstone–mudstone couplets, are the deposits of debris and turbidity flows on or at the foot of a submarine slope. Three detrital zircons from the sandstone–mudstone couplets date deposition at 302 ± 3 Ma, at or shortly after the Carboniferous–Permian boundary. Conglomerates predominantly consist of quartzite and granite and contain boulders exceeding 500 mm in diameter. Zircons from granitoid clasts and a silicic volcanic clast yield U–Pb ages of 466 ± 3 Ma, 373 ± 5 Ma and 487 ± 4 Ma, respectively and have corresponding average εHft values between +0.3 and +7.6. A quartzite clast, conglomerate matrix and sandstone interbedded with the conglomerate units have broadly similar detrital zircon age distributions and Hf isotope compositions. The clast and detrital zircon ages match well with sources within Patagonia; however, the age of one granite clast and the εHf characteristics of some detrital zircons point to a lesser South Africa or Ellsworth Mountain-like contribution, and the quartzite and granite-dominated composition of the conglomerates is similar to upper Palaeozoic diamictites in the Ellsworth Mountains. Unlike detrital zircons, large conglomerate clasts limit possible transport distance, and suggest sedimentation took place on or near the edge of continental crust. Comparison with other upper Palaeozoic to Mesozoic sediments in the Antarctic Peninsula and Patagonia, including detrital zircon composition and the style of deformation, suggests deposition of the Trinity Peninsula Group in an upper plate basin on an active margin, rather than a subduction-related accretionary setting, with slow extension and rifting punctuated by short periods of compression.


Geology ◽  
2011 ◽  
Vol 39 (10) ◽  
pp. 955-958 ◽  
Author(s):  
Navot Morag ◽  
Dov Avigad ◽  
Axel Gerdes ◽  
Elena Belousova ◽  
Yehudit Harlavan

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 745
Author(s):  
Wenhua Han ◽  
Haizhou Ma ◽  
Weixuan Fang ◽  
Huaide Cheng ◽  
Yongshou Li ◽  
...  

Qamdo basin is located between the suture zone of Jinsha River (Ailao Mountains) and that of Ban Gong Lake (Nujiang) in the eastern Tethys. Part of the Jingxing Formation is deposited in the southwest of the basin. In this study, two profiles were investigated from the north and south of Qamdo basin. The characteristics of detrital zircon LA-ICP-MS U-Pb age, and the main and trace elements of sandstone were analyzed. The characteristics of major and trace elements showed that the tectonic setting of the study area is mainly composed of a relatively stable active continental margin and a passive continental margin, showing characteristics of a continental island arc. The weathering degree of Jingxing Formation in the Qamdo area is lower than that in the Lanping-Simao area, which may be closer to the origin. The age distribution characteristics of detrital zircon grains indicate that the Qiangtang Block, Youjiang basin, and Yangtze area jointly constitute the provenance of the Qamdo-Lanping-Simao basin. Both basins may be part of a large marine basin with unified water conservancy connection before evaporite deposition. Metamorphic seawater from the Qamdo basin may migrate to the Lanping-Simao basin and even the Khorat basin, where evaporite was deposited.


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