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Early to mid-Paleozoic magmatic and sedimentary records in the Bainaimiao Arc: An advancing subduction-induced terrane accretion along the northern margin of the North China Craton.

Authors :
Chen, Yan
Zhang, Zhicheng
Qian, Xiaoyan
Li, Jianfeng
Ji, Zejia
Wu, Tairan
Source :
Gondwana Research; Mar2020, Vol. 79, p263-282, 20p
Publication Year :
2020

Abstract

The early to mid-Paleozoic subduction-induced terrane accretion along the northern margin of the North China Craton is not well understood. To address this issue, we investigate the magmatic and sedimentary records, including both new and previously published geochemical, Sr–Nd isotopic, and zircon U–Pb–Hf isotopic data from the Bainaimiao Arc. The collected gabbro–diorites and granitoids have been dated to 431–453 Ma. The gabbro–diorites have high Mg/(Mg + Fe) molar ratios (44.41–73.39); depleted Nb, Ta and Ti; and negative ε Nd (t) values (-9.43–-6.80). They were derived from a mantle wedge metasomatized by subduction-derived fluids with crustal contamination. The granitoids are characterized by high silica, low to high K, low Fe and Mg contents, strong fractionation of rare earth elements, and positive ε Hf (t) values (+1.42–+8.19). They were derived from crustal melts with juvenile additions. The clastic rocks from the Baoerhantu Group and Xibiehe Formation are dominated by early Paleozoic zircons, whereas those from the Bainaimiao Group are dominated by early Paleozoic and Precambrian zircons. Detrital zircon geochronology and field geology confirm their deposition in early to mid-Paleozoic. The U–Pb ages and petrographic and geochemical analyses indicate that the clastic rocks were deposited in arc-related basins with felsic sources from the Bainaimiao Arc. The xenocrystic and detrital zircons in the magmatic and clastic rocks, respectively, imply a Precambrian basement for the Bainaimiao Arc. The early Paleozoic magmatic rocks of the Bainaimiao Arc show secular changes with decreasing age: increasing K 2 O contents and Sr/Y ratios and decreasing Fe 2 O 3 <superscript>T</superscript> + MgO contents and ε Hf (t) and ε Nd (t) values. This is likely in response to advancing subduction and related crustal thickening. Accordingly, the following tectono-paleogeographic model was proposed for the Bainaimiao Arc: (a) ∼500–455 Ma initial subduction and juvenile arc development, (b) ∼455–415 Ma continuous subduction with mature arc development, and (c) ∼415–400 Ma accretion to the North China Craton. Image 1 • A Precambrian basement has been identified for the Bainaimiao Arc. • An advancing subduction model with crustal thickening has been proposed. • A three-stage subduction-accretion process has been reconstructed. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
1342937X
Volume :
79
Database :
Supplemental Index
Journal :
Gondwana Research
Publication Type :
Academic Journal
Accession number :
141563720
Full Text :
https://doi.org/10.1016/j.gr.2019.08.012