Zircon U–Pb dating, geochemistry, and Sr–Nd–Pb–Hf isotopes of the subvolcanic intrusion from Beina Pb–Zn–(Ag) deposit in the southern Lhasa terrane, Tibet: Implications for petrogenesis and mineralization

Abstract

The Beina Pb–Zn–(Ag) deposit is a newly discovered deposit situated in the southern Lhasa terrane, Tibet. LA‐ICP‐MS U–Pb dating for the ore‐bearing rhyolite porphyry indicates that it was emplaced at 64.6 Ma. The Beina rhyolite porphyry displays high SiO2 (74.31–76.52 wt%), K2O + Na2O (6.99–8.05 wt%), and A/CNK (0.97–1.33), similar to the peraluminous S‐type granites related to Pb–Zn–(Ag) mineralization in the central Lhasa terrane. The Beina rhyolite porphyry is strongly depleted in Nb, Ta, Ti, P, Sr, and Ba, enriched in Rb, K, Th, U, and Pb, enriched in light rare earth elements (LREEs), slightly depleted in heavy rare earth elements (HREEs) (LaN/YbN = 6.52–9.28), and has moderate negative Eu anomalies (δEu = 0.38–0.48), showing an arc affinity. It also shows high CaO/Na2O ratios (0.21–0.73), low Rb/Ba (0.30–0.46), and Rb/Sr ratios (1.17–4.01), indicating that it was mainly derived from partial melting of a clay‐poor, plagioclase‐rich metapsammitic source. The samples have relatively high 87Sr/86Sr(i) (0.7084–0.7092) and Pb isotopes (206Pb/204Pb = 18.61–18.74, 207Pb/204Pb = 15.65–15.68, 208Pb/204Pb = 38.99–39.14) and low εNd(t) (−8.6 to −7.2) and εHf(t) (−8.6 to −4.8) values, yielding ancient two‐stage Nd model ages (1,459–1,569 Ma) and two‐stage Hf model ages (1,433–1,684 Ma), respectively. The Beina rhyolite porphyry was formed at relatively high temperatures (average 817°C) according to zircon saturation thermometer. These results reveal that Beina rhyolite porphyry was generated by partial melting of ancient crustal materials (dominated by metapsammite) heated by mantle‐derived magma during rollback of the Neo‐Tethyan oceanic slab. In addition, our research suggests that both I‐ and S‐type granites related to Pb–Zn mineralization are believed to exist in the Lhasa terrane. Similar to the central Lhasa terrane, the middle segment of the southern Lhasa terrane (83°E–87°E) is also an ancient block, large‐scaled silicic volcanic rocks of the Linzizong Group, and coeval plutons are widely exposed and several Pb–Zn deposits have recently been discovered in the Nuocang–Chazi area. All these facts indicate that there is a great potential for prospecting of intrusions‐related Pb–Zn deposits in the middle segment of the southern Lhasa terrane.

Sulphur and lead isotopic compositions of the Pb–Zn polymetallic deposits in the Linzizong volcanic area, Gangdese belt, Tibet: Implications for variation characteristics of ore‐forming material sources and exploration targeting

“…The Linzizong volcanic wall rocks range from 18.598 to 18.658, 15.651 to 15.668, and 38.921 to 38.997. The 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, and 208 Pb/ 204 Pb ratios of 13 sulphides from the Beina deposit vary from 18.630 to 18.733, 15.649 to 15.760, and 38.947 to 39.320, respectively, which are partially consistent with those of the Linzizong volcanic wall rocks (the 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, and 208 Pb/ 204 Pb ratios of 18.640 to 18.740, 15.660 to 15.670, and 38.990 to 39.140, respectively; Liu et al, ).…”

“…The negative ε Hf(t) values of the Nuocang and Beina ore‐related porphyries (−22.0 to −6.0; −15.0 to −5.2; Jiang, ) plotted in area of the Lhasa terrane basement indicate that greater contributions from mature crustal materials are vital for the formation of ore‐related porphyries (Figure b). Similarly, the Sr–Nd isotope compositions of the Nuocang and Beina Linzizong volcanic wall rocks (Figure c; Jiang, ; Liu et al, ) suggest the main source of metals is the Lhasa terrane basement. These evidences support the hypothesis that the main upper crust sources of Lhasa terrane basement are responsible for the Nuocang and Beina Pb–Zn mineralization.…”

“…(c) ε Nd(t) versus 87 Sr/ 86 Sr (i) diagram for the Linzizong volcanic rocks in the Cuoqin Basin, western Gangdese, Nanmulin Basin, central Gangdese, and Linzhou Basin, eastern Gangdese. Sr–Nd isotopic data sources: the Linzizong volcanic rocks in the Cuoqin Basin, western Gangdese (Jiang et al, ; Liu et al, ; Xie, Zhou, Xie, Tian, & Liao, ; Yue, ; Yu et al, ); the Linzizong volcanic rocks in the Nanmulin Basin, central Gangdese (Zhang, ); the Linzizong volcanic rocks in the Linzhou Basin, eastern Gangdese (Dong, ; Dong, Mo, Zhao, Wang, & Zhou, ; He et al, ; Lee et al, , ; Mo et al, , ; Yang, Xiang, Wang, Laba, & Wang, ; Zhou et al, ). Abbreviations: NC: Nuocang; BN: Beina; DX: Dexin; NR: Narusongduo; LQL: Leqingla; XGG: Xingaguo [Colour figure can be viewed at wileyonlinelibrary.com]…”

“…The giant Gangdese metallogenic belt within the Lhasa terrane, one of the famous metallogenic belts in China, is composed of the Gangdese porphyry copper belt to the south and the Gangdese Pb–Zn polymetallic metallogenic belt (Cao, Zhang, Tang, et al, ; Hou, Duan, et al, ; Liu, Zheng, Gao, Jiang, & Cao, ; Sun et al, , ; Xu et al, , b; Xu et al, ; Zhang et al, ; Zheng et al, ; Zheng, Fu, Hou, Yang, & Huang, ). The well‐known Gangdese porphyry belt contains several world‐class porphyry Cu–(Mo) deposits, including the Jiama, Qulong, Bangpu, Lakang'e, Dabu, Tinggong, Gangjiang, Chongjiang, Jiru, and Zhunuo.…”

Spatiotemporal Variation of the Cretaceous‐Eocene Arc Magmatism in Lhasa‐Tengchong Terrane

“…45 Ma and characterized by high-K calc-alkaline felsic rocks with dominantly negative zircon ε Hf (t) values (J. Liu et al, 2019;Zhao et al, 2017;R.-Z. Zhu et al, 2022).…”