Geochronology and trace elements of zircon in the Southern Chinese Altay: Implications for tectonic setting

Abstract

Zircon (ZrSiO4) trace elements are commonly used to distinguish the tectonic settings of their host rocks. The Chinese Altay is a key area for deciphering the accretionary history of the Central Asian Orogenic Belt (CAOB), and its tectonic setting during the Devonian is debated. In this study, we describe the systematic investigations of the magmatic and metamorphic rocks from the Qiemuerqieke and Qinghe areas situated to the west and east of Southern Altay, respectively. In doing so, we present the first attempt to elucidate the Devonian tectonic setting of the Southern Altay based on zircon trace elements. Zircon U–Pb geochronological studies on the magmatic and metamorphic rocks in Southern Altay yielded ages of 395–360 Ma, which indicate that these metamorphic rocks formed in the Devonian rather than the Precambrian. Furthermore, most of the zircons from these rocks were concentrated in the arc‐related orogenic setting of the discrimination diagrams of Th/U versus Nb/Hf and Th/Nb versus Hf/Th, and in the continental field of the discrimination diagrams of Yb versus U, Hf versus U/Yb, Y versus U/Yb, and Nb/Yb versus U/Yb. These results are consistent with the geochronology and whole‐rock geochemistry of Devonian granitoids in Southern Altay. Therefore, we propose that the continental arc along the Southern Chinese Altay was triggered by the active continental margin of the Altay‐Mongolian Terrane during the Devonian.