Geochronology and geochemistry of igneous rocks in the Qinfang belt: Implications for spatio-temporal framework of Paleo-Tethys

Abstract

The formation and evolution of the Paleo-Tethys is well documented in Southeast Asia. The Qinfang tectonic belt in the South China Block contains numerous granitic and volcanic rocks; however, the timing of their formation remains unconstrained. In this study, a spatiotemporal framework for the Paleo-Tethys is proposed based on a comprehensive analysis of zircon UPb geochronological and geochemical data of the Indosinian igneous rocks in the Qinfang tectonic belt. Geochronological results showed that the granitic and volcanic rocks had zircon UPb ages of 252–245 Ma, indicating that contemporaneous granitic and volcanic activities occurred in the belt. The granite samples belonged to the peraluminous high-K calc-alkaline-shoshonitic series of rocks and showed geochemical signatures similar to those of the S-type granite. Their formation is related to the evolution of the Paleo-Tethys with the parental magma of the rocks likely derived by partial melting of crustal materials that differentiation by fractional crystallization. Combined with regional geological data, this suggests that the Indosinian magmatic assemblages, geochemical characteristics, and sedimentary sequences in the Qinfang tectonic belt are consistent with those in the Jinshajiang, Ailaoshan, and Hainan Island regions. This indicates that these regions belong to the Paleo-Tethyan tectonic domain during the Indosinian, and that the Qinfang tectonic belt likely represents a branched ocean basin of the Paleo-Tethys.