Petrogenesis of the granitoids related to skarn-type mineralization in the Nyainqentanglha Metallogenic Belt, Tibet

Fu Yangang; Duan Zhuang; Gao Jianweng; Hao Zejiang; Yang Jianzhou; Zhao Keqiang; Wang Zhenliang

doi:10.1016/j.heliyon.2024.e24859

Petrogenesis of the granitoids related to skarn-type mineralization in the Nyainqentanglha Metallogenic Belt, Tibet

Heliyon. 2024 Jan 19;10(3):e24859. doi: 10.1016/j.heliyon.2024.e24859. eCollection 2024 Feb 15.

Authors

Fu Yangang^{1

2}, Duan Zhuang^{1

2}, Gao Jianweng^{1

2}, Hao Zejiang^{1

2}, Yang Jianzhou^{1

2}, Zhao Keqiang^{1

2}, Wang Zhenliang^{1

2}

Affiliations

¹ Institute of Geophysical and Geochemical Exploration, CAGS, Langfang 065000, Hebei, China.
² Key Laboratory for Geochemical Exploration Technology, MNR, Langfang 065000, China.

Abstract

The Nyainqentanglha Metallogenic Belt (NMB) is an economically important lead-zinc ore province located in the Central and Southern Lhasa subterrane, Tibet. The NMB consists mainly of skarn-type lead-zinc polymetallic deposits that form at the contact between Late Cretaceous-Eocene intrusive rocks and carbonatite/volcanic-sedimentary strata. These deposits are generally considered to be related to S-type granites formed by the Indo-Asian continental collision. However, the ε_Hf(t) (ave. -1.6) of zircons from the mineralization-related granitoids indicates that it is crust-mantle mixing products. In addition, the volcanic rocks of the Dianzhong Formation, which have a close spatio-temporal relationship with the skarn-type deposits, typically show mantle-derived features. Therefore, the occurrence of AFC processes in mantle-derived material passing through the thick basement of the Lhasa Terrane may better explain the genesis of the mineralization-related granitoids. In this study, we present results on zircon U-Pb ages, major and trace elements of the granitoids associated with skarn-type mineralization from the Narusongduo district. LA-ICP-MS zircon U-Pb dating shows that the granite formed in the Paleocene (58.6 ± 0.5 Ma). Combined with published regional data, we propose the mineralization age of the skarn-type deposits in the NMB ranges from the Late Cretaceous to Eocene. Detailed petrology and geochemistry of mineralization-related granitoids are evaluated to constrain the magmatic evolution process. The granitoids have high contents of SiO₂ (mean 72.8 %), K₂O (mean 4.0 %), Rb (mean 186.9 ppm), DI (differentiation index) 84.7, A/CNK (mean 1.3), and low contents of MgO, TFe, suggesting that the granitoids have undergone strong differentiation. In addition, the continuous decrease of P₂O₅ with progressive differentiation and the lower average P₂O₅ abundance suggest that the mineralization-related granitoids belong to the I-type granite. The results suggest that the mineralization-related granitoids in the NMB originated from the mantle and is the fractionated I-type granite formed by the process of AFC (Assimilation and Fractional Crystallization). Considering that Pb and Zn often coexist in deposits, we suggest that magmatic differentiation may play an important role in the formation of the granite-related Pb and Zn mineralization.

Keywords: AFC process; I-type granite; Nyainqentanglha metallogenic belt; Skarn deposit.