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Early Jurassic tectonism occurred within the Basu metamorphic complex, eastern central Tibet: Implications for an archipelago-accretion orogenic model.

Authors :
Li, Hua-Qi
Xu, Zhi-Qin
Webb, A. Alexander G.
Li, Tian-Fu
Ma, Shi-Wei
Huang, Xue-Meng
Source :
Tectonophysics. Apr2017, Vol. 702, p29-41. 13p.
Publication Year :
2017

Abstract

The Basu metamorphic complex, surrounded by ophiolitic melanges and intruded by a large volume of undeformed granitoid rocks along the eastern segment of the Bangong-Nujiang suture, holds one of the keys to understanding the pre-Cenozoic tectonic evolution of central Tibet. Zircon U-Pb dating of rocks from the Basu metamorphic complex reveals that meta-igneous rocks yield Early Paleozoic crystallization ages of 500–492 Ma and an Early Jurassic metamorphic age of ~ 173 Ma, and that undeformed granitoid rocks yield crystallization ages of approximately 186–174 Ma. Whole rock geochemical and zircon Lu-Hf isotopic data indicate that the undeformed granitoid rocks originated mainly from partial melting of ancient crustal sources, which may reflect a collisional orogenic setting. 40 Ar/ 39 Ar dating of biotite from a sillimanite-garnet-biotite paragneiss shows cooling to 300 ± 50 °C at ~ 165 Ma. These data indicate significant Early Jurassic tectonism, during which most of the Basu metamorphic complex was formed. Furthermore, the age data resemble those of the Amdo metamorphic complex located approximately 500 km to the west along the Bangong-Nujiang suture. Together, these complexes may represent a “destroyed or unrecognized” block, i.e., the Amdo-Tongka block, which may be the eastern extension of the South Qiangtang terrane. Based on the tectonic outlines of the multiple ophiolitic zones and magmatic belts, we suggest a new archipelago-accretion model that attributes the Early Jurassic tectonism to an arc-continent/micro-continent collision. This model further enables the reconstruction of the eastern Tethyan Ocean and the orogenic processes of central Tibet during the Mesozoic. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00401951
Volume :
702
Database :
Academic Search Index
Journal :
Tectonophysics
Publication Type :
Academic Journal
Accession number :
122037652
Full Text :
https://doi.org/10.1016/j.tecto.2017.02.016