Early Cretaceous magmatism and associated polymetallic mineralization in South China: the Tiantang example

ABSTRACT

The Tiantang Cu–Pb–Zn polymetallic deposit in western Guangdong, South China, is hosted in the contact zone between the monzogranite porphyry and limestone of the Devonian Tianziling Formation. Orebodies occur in the skarn and skarnized marble as bedded, lenses, and irregular shapes. In this study, we performed LA-ICP-MS zircon U–Pb dating, zircon trace elements, and Hf isotopic analyses on the Tiantang monzogranite porphyry closely related to Cu–Pb–Zn mineralization. Twenty-two zircons from the sample yield excellent concordia results with a weighted mean ²⁰⁶Pb/²³⁸U age of 104.5 ± 0.7 Ma, which shows that the emplacement of the monzogranite porphyry in the Tiantang deposit occurred in the Early Cretaceous. The zircon U–Pb age is largely consistent with the sulphide Rb–Sr isochron ages, indicating that both the intrusion and Cu–Pb–Zn mineralization were formed during the Early Cretaceous in South China. The ε_Hf(t) values of three inherited zircons from the monzogranite porphyry are 13.1, 11.9, and 12.9, respectively, and the two-stage Hf model ages are 1096 Ma, 1087 Ma, and 1055 Ma, respectively. Except for the three inherited zircons, all ε_Hf(t) values of zircons are negative and have a range of −7.6 to −3.4, with the two-stage model ages (T_DM2) of 1380–1643 Ma, which indicates the rock-forming materials were mainly derived from the partial melting of Mesoproterozoic to Neoproterozoic crust rocks, and probably included some Neoproterozoic arc-related volcanic-sedimentary materials. In this study, the monzogranite porphyry from the Tiantang deposit has calculated Ce⁴⁺/Ce³⁺ ratios of zircon ranging from 91 to 359, indicative of a more oxidized signature and significant prospecting potential for ore-related magmatism. Based on ore deposit geology, isotope geochemistry, and geochronology of the Tiantang Cu–Pb–Zn deposit and regional geodynamic evolution, the formation of Early Cretaceous magmatism and associated polymetallic mineralization in South China is believed to be related to large-scale continental extension and subsequent upwelling of the asthenosphere.

KEYWORDS:

• LA-ICP-MS zircon U–Pb dating
• isotope geochemistry
• zircon trace elements
• Tiantang Cu–Pb–Zn polymetallic deposit
• The Qin–Hang metallogenic belt
• South China

Acknowledgements

We thank the Geological Survey of Guangdong Province and Geology Bureau for Nonferrous Metals of Guangdong Province for their support during the field geological investigation. We would like to thank Dr Kejun Hou, Dr Chunli Guo, and Qian Wang for their technical analysis for U–Pb and Hf isotope analyses and are grateful to Dr Linhao Zhao for helping with zircon trace-elements analyses. We appreciate Editor-in-Chief, Professor Bob Stern, Guest Editors Professor Weidong Sun and Xiaoyong Yang, and two anonymous reviewers for their constructive comments and excellent suggestions that helped improve the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

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Funding

The work was financially supported by Open Research Project of key laboratory of Metallogeny and Mineral Assessment (Grant No. ZS1503), National Natural Science Foundation of China (Grant No. 41430314, 41203036), and National Nonprofit Institute Research Grants of China (Grant No. K1617).