Origin of Carboniferous intra-oceanic arc granitoids from the eastern Pamir and implications for the Paleo-Tethyan ocean. (December 2020)

• Record Type: Journal Article
• Authors: Tang, Wenkun; Wang, Shifeng; Liu, Yiduo; Yao, Xin; Li, Meng
• Is Part Of: Journal of Asian earth sciences. Volume 204(2021)
• Publication Date: 2020-12
• Subjects: Eastern Pamir -- Jinshajiang Paleo-Tethyan suture -- Granitoid -- Zircon U–Pb age -- Sr–Nd–Hf isotopes -- Oceanic island arc; Earth sciences -- Asia -- Periodicals; Sciences de la terre -- Asie -- Périodiques; Earth sciences; Asia; Periodicals; 555.05
• DOI: 10.1016/j.jseaes.2020.104558
• Languages: English
• ISSNs: 1367-9120

Abstract

Graphical abstract: Highlights: Subduction of the Paleo-Tethys had started by Carboniferous in the eastern Pamir. Waqia granitoids were formed by hydrous partial melting of a juvenile mafic crust within an intra-oceanic arc setting. Closure of the Jinshajiang Paleo-Tethys Ocean is diachronous from west to east, indicating oblique convergence pattern. Abstract: The expanding and diminishing of the Paleo-Tethyan ocean recorded in the Pamir, and relationships between different segments of the Paleo-Tethyan suture from Pamir to Tibet are poorly constrained. Here we present new zircon U–Pb ages and geochemical data of the Waqia granitoid pluton from the eastern Pamir. Both the host granitoids and gabbroic to dioritic enclaves have similar zircon U–Pb ages of 323–318 Ma, being contemporaneous in origin. These rocks are metaluminous, calc-alkaline, tholeiitic series. They exhibit low K2 O, low Sr/Y ratios, low REE contents with depleted to flat LREE patterns, slight enrichment in Rb, Ba, Zr, Hf, and negative Nb, Ta, P, and Ti anomalies. They have similar initial 87 Sr/ 86 Sr ratios of 0.7040 to 0.7045, positive εNd (t) (+4.63 to +5.02) and εHf (t) (+9.9 to +14.7) values. Detailed elemental and isotopic data indicate that these coeval rocks in the Waqia pluton were cognate and formed by hydrous partial melting of a juvenile mafic crust within an intra-oceanic arc setting. This study is the first to report reliable isotopic ages of the early Paleo-Tethyan subduction in the eastern Pamir. Further, the Tanymas-Mazha Paleo-Tethyan suture in the eastern Pamir should be the western extension of the Jinshanjiang Paleo-Tethyan suture in the central to eastern Tibetan plateau. An integration of published results leads us to conclude that closure of the Jinshanjiang Paleo-Tethyan ocean was diachronous along its 3000–4000 km length, with closure times of ca 240 Ma in the Pamir and ca 220 Ma in the Sanjiang region.