Petrogenesis of the Early Cretaceous Tiantangshan A-Type Granite, Cathaysia Block, SE China: Implication for the Tin Mineralization

• Main Authors: Ru-Ya Jia, Guo-Chang Wang, Lin Geng, Zhen-Shan Pang, Hong-Xiang Jia, Zhi-Hui Zhang, Hui Chen, Zheng Liu
• Format: Article
• Language: English
• Published: MDPI AG 2019-04-01
• Series: Minerals
• Subjects: A-type granite; tin mineralization; Tiantangshan tin polymetallic deposit; SE China
• Online Access: https://www.mdpi.com/2075-163X/9/5/257

The newly discovered Tiantangshan tin polymetallic deposit is located in the southeast Nanling Range, Cathaysia block, Southeast China. The tin orebodies are mainly hosted in the greisen and the fractured alteration zones of the tufflava and trachydacite. However, the genetic relationship between the hidden alkali-feldspar granite and volcanic rocks and the tin mineralization remains poorly understood. This paper presents SHRIMP zircon U−Pb dating, whole-rock major and trace element analyses, as well as Nd isotopic data of the trachydacite and alkali-feldspar granite. The SHRIMP zircon U−Pb dating of the alkali-feldspar granite and trachydacite yields weight mean ²⁰⁶Pb/²³⁸U ages of 138.4 ± 1.2, and 136.2 ± 1.2 Ma, respectively. These granitic rocks have high levels of SiO₂ (64.2−75.4 wt%, mostly > 68 wt%), alkalis (K₂O + Na₂O > 8.3 wt%), REE (except for Eu), HFSE (Zr + Nb + Ce + Y > 350 ppm) and Ga/Al ratios (10,000 × Ga/Al > 2.6), suggesting that they belong to the A-type granite. According to the high Y/Nb and Yb/Ta ratios, they can be further classified into A₁ subtype. Their ε_Nd (T) range from −3.8 to −6.5. They were likely generated by the assimilation-fractional crystallization (AFC) of the coeval oceanic island basalts -like basaltic magma. This study suggests that the A₁ type granite is also a potential candidate for the exploration of tin deposits.