LA-ICP-MS Zircon U-Pb dating of Early Jurassic granite basement in Chagan Area of the Northest Guangdong and its geological implications

Jinhui Tang,Feng Lou

doi:10.15446/esrj.v24n2.87364

Abstract

Rencha basin is one of the typical Mesozoic-Cenozoic volcanic fault basins in northeastern Guangdong. The borehole data indicate that the basement is mainly composed of Paleozoic metamorphic rocks and Wenxiang granite. At present, the basement granite has been lacking in precise years. In order to discuss its formation age and improve the understanding of the geological evolution of the area, LA-ICP-MS zircon U-Pb isotopic dating of Wenxiang granite cores from two boreholes in the Chagan area of the basin is carried out, and the two harmonic ages are 179+1 Ma and 186 Ma, respectively. The results show that the basement Wenxiang granite in Rencha Basin was formed in late Early Jurassic, which is the product of the first volcanic activity of Yanshan. This age not only deepens the understanding of the formation and evolution of Rencha Basin, but also provides new chronological data for the lack of magmatic activity in the Early Jurassic in northeastern Guangdong, China.

Highlights

The Renzi Basin is located at the intersection of the eastern end of the east-west Nanling polymetallic metallogenic belt and the northwestern Wuyi polymetallic metallogenic belt (Fig. 1-b)
The early Yanshanian in southeastern China is generally considered to be a critical period for the transition from the Paleo-Tethys tectonic domain to the Pacific tectonic domain (Shu & Zhou, 2002; Chen et al, 2002)
Before the Middle Jurassic was affected by the Tethys tectonic domain and the Indosinian collision, the Late Jurassic has been mainly constrained by the combination of Pacific tectonic and intracontinental deep structures

Summary

Introduction

The Renzi Basin is located at the intersection of the eastern end of the east-west Nanling polymetallic metallogenic belt and the northwestern Wuyi polymetallic metallogenic belt (Fig. 1-b). The results of LA-ICP-MS zircon U-Pb isotope dating parameters of fine grained Wenxiang granite in Rencha Basin are shown in Tables 1 to 10, respectively. A small part of zircon oscillating zoning or fan-shaped zoning of fine-grained Wenxiang granite in the two samples is not obvious, considering the Th/U ratio of zircon, the zircon selected in this test has typical magmatic zircon characteristics, and the U-Pb age of the main group zircon can represent the age of magmatic crystallization. The weighted average value of the remaining 27 206Pb/238U ages obtained by Isoplot software is 179+1Ma (MSWD=0.18), which represents the crystallization age of fine grained granite from B-2 samples. The above LA-ICP-MS zircon U-Pb dating data show that the MSWD values of the basement fine-grained hieroglyphic granites in Renchao Basin are small and reliable. 0.0003 0.0003 0.0002 0.0003 0.0002 0.0003 223.95 423.93 184.78 230.07 189.16 204.8 δ 206Pb/ 238U Age(Ma)

Discussion

Conclusion