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Underplating of basaltic magmas and crustal growth in a continental arc: Evidence from Late Mesozoic intermediate–felsic intrusive rocks in southern Qiangtang, central Tibet

Authors :
Zi-Qi Jiang
Quan Ou
Wei Dan
Qiang Wang
Fu-Yuan Wu
Jin-Hui Yang
Xiao Ping Long
Derek A. Wyman
Jie Li
Lu Lu Hao
Source :
Lithos. 245:223-242
Publication Year :
2016
Publisher :
Elsevier BV, 2016.

Abstract

Phanerozoic growth of continental crust has widely been considered as an important geological phenomenon and mainly occurs in an arc setting. However, the crustal growth models (mantle-derived basalt underplating or accretion of island or intra-oceanic arc complexes or oceanic plateau) have been disputed. Here we present new zircon LA–ICPMS U–Pb age, whole-rock major and trace element, Sr–Nd and zircon Hf isotopic data for Late Mesozoic intermediate–felsic intrusive rocks in the Rena Co area in southern Qiangtang, central Tibet. LA–ICP–MS zircon U–Pb dating for two granodiorite and three diorite samples and one granodiorite porphyry sample gives ages of ca. 150 Ma, ca. 112 Ma, respectively, indicating they were generated in the Late Jurassic–Early Cretaceous. All rocks are sub-alkaline in composition and belong to the high-K cal-alkaline series. The ~ 150 Ma diorites (SiO2 = 57.9–61.2 wt.%) exhibit relatively high MgO (3.13–3.88 wt.%) and Cr (52.4–282 ppm) contents and Mg# (47–51) values, similar to magnesian diorites. They are geochemically characterized by uniformly low eNd(t) (− 5.5 to − 5.2), high (87Sr/86Sr)i (0.7071 to 0.7078) and Th/La (0.22–0.32), and variable zircon eHf(t) (− 8.7 to + 4.8) values. They were probably generated by melting of oceanic sediment diapirs, followed by interaction with the surrounding mantle during the northward subduction of Bangong–Nujiang Oceanic lithosphere. The ~ 150 Ma granodiorites and ~ 112 Ma granodiorite porphyries are characterized by low MgO ( 15% wt.%) and Sr (> 400 ppm) and low Y (

Details

ISSN :
00244937
Volume :
245
Database :
OpenAIRE
Journal :
Lithos
Accession number :
edsair.doi...........768da3a5bb66a2b928cf3b51b8ea5550
Full Text :
https://doi.org/10.1016/j.lithos.2015.09.015