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Early Permian mafic dikes in the Nagqu area, central Tibet, China, associated with embryonic oceanic crust of the Meso‐Tethys Ocean
Author(s) -
Chen ShengSheng,
Shi RenDeng,
Fan WeiMing,
Gong XiaoHan,
Wu Kang
Publication year - 2017
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2016jb013693
Subject(s) - geology , mafic , mantle plume , gondwana , permian , geochemistry , oceanic crust , rift , magmatism , carboniferous , paleontology , continental crust , large igneous province , crust , subduction , lithosphere , tectonics , structural basin
During the latest Carboniferous to Early Permian, a possible mantle plume initiated continental rifting along the northern Gondwana margin, which subsequently developed into the Meso‐Tethys Ocean. However, the nature and timing of the embryonic oceanic crust of the Meso‐Tethys Ocean remain poorly understood. Here we present for the first time a combined analysis of petrological, geochronological, geochemical, and Sr‐Nd isotopic data for mafic rocks from the Nagqu area, central Tibet. Zircons from the mafic rocks yield a concordant age of ~277.8 ± 1.8 Ma, which is slightly younger than the age of mantle plume activity (~300–279 Ma), as represented by the large igneous province (LIP) on the northern Gondwana margin. Geochemical features suggest that the Nagqu mafic rocks, which display normal mid‐ocean ridge basalt affinities, are different from those of the LIP, which display oceanic island basalt‐type affinities. The Nagqu mafic rocks result from a relatively high degree of melting of depleted asthenospheric mantle. Combined with observations from previous studies, we suggest that the late Early Permian Nagqu magmatism fully records processes of early stage rifting and incipient formation of oceanic crust. Moreover, the patterns of magmatism are consistent with patterns of rift‐related sedimentation that records the transition from predominantly continental to marine deposition in the region during the Carboniferous‐Permian. We therefore suggest that rifting of the eastern Cimmerian and northern Gondwana continents started at ~277.8 Ma, and the rifting culminated in the opening of the Meso‐Tethys Ocean.