Late Ordovician high-Mg adakitic andesite in the western South China block: evidence of oceanic subduction. Issue 9 (4th July 2018)

• Record Type: Journal Article
• Authors: Hu, Pei-yuan; Zhai, Qing-guo; Ren, Guang-ming; Wang, Jun; Tang, Yue
• Is Part Of: International geology review. Volume 60:Issue 9(2018)
• Page Start: 1140
• Page End: 1154
• Publication Date: 2018-07-04
• Subjects: South China -- Early Palaeozoic -- zircon U–Pb age -- geochemistry and isotope -- petrogenesis; Geology -- Periodicals; Electronic journals; 551.05
• DOI: 10.1080/00206814.2017.1370617
• Languages: English
• ISSNs: 0020-6814

Abstract

ABSTRACT: The Early Palaeozoic was an important period in the geologic evolution of the South China block (SCB), marking the intracontinental orogen in the Wuyi-Yunkai region. One salient feature of the western SCB is the absence of Early Palaeozoic oceanic subduction-related magmatism. Here, we report the first known occurrence of Late Ordovician andesites from the Shimian area, western SCB. Zircon SHRIMP U–Pb dating reveals that the andesites formed at ca. 451 Ma. They have geochemical features of high-Mg adakitic andesite (HMAA) and are characterized by low K2 O (1.09–2.24 wt.%) and Th (2.50–5.65 ppm) and high MgO (4.02–6.91 wt.%) and Mg# (56–71). Furthermore, their zircon grains display positive ε Hf ( t ) (+11.4 to +19.6) and low δ 18 O (4.72–6.20‰) values. The andesites are interpreted to have been derived from partial melting of a peridotitic mantle wedge in an oceanic subduction setting and subsequent fractional crystallization. Integrating previous studies of the Qinling-Dabie orogenic belt with the data presented in this contribution, we suggest that the SCB was probably involved in the Early Palaeozoic Andean-type orogeny along the Gondwanan proto-Tethyan margin. Graphical Abstract: