Petrogenesis and geodynamic implications of the intrusions related to the Pusangguo skarn Cu‐dominated polymetallic deposit in Tibet: Constraints from geochronology, geochemistry, and Sr–Nd–Pb–Hf isotopes. (17th June 2020)

• Record Type: Journal Article
• Authors: Li, Zhuang; Lang, Xinghai; Zhang, Qizhi; Liu, Xinkai; Yang, Xin
• Is Part Of: Geological journal. Volume 55:Number 12(2020)
• Page Start: 7659
• Page End: 7686
• Publication Date: 2020-06-17
• Subjects: adakitic rocks -- geodynamic implication -- petrogenesis -- Pusangguo deposit -- Tibet; Geology -- Periodicals; 551
• DOI: 10.1002/gj.3902
• Languages: English
• ISSNs: 0072-1050

Abstract

Abstract : Pusangguo is a high‐grade skarn‐type Cu‐dominated polymetallic deposit and the only large‐sized Cu‐Pb‐Zn‐(Co‐Ni) deposit in the Gangdese metallogenic belt (GMB); the magmatic rocks associated with this deposit are poorly documented, and their petrogenesis and geodynamic setting are unclear. To explore these issues, we present zircon U–Pb ages along with Hf isotopic, whole‐rock geochemical, and Sr–Nd–Pb isotopic data for Pusangguo biotite granodiorite (PBG) and Pusangguo diorite porphyrite (PDP) in this deposit. Zircon U–Pb dating for these rocks indicates that they were emplaced during the Miocene (13.6–14.6 Ma). Geochemically, both PBG and PDP show characteristics of adakites, with intermediate SiO2 (65.55–67.30 wt% and 60.56–58.27 wt%, respectively), relatively high Al2 O3 (15.28–15.85 wt% and 17.71–16.71 wt%, respectively) and Sr (599–723 ppm and 687–1, 616 ppm, respectively) and low Y and Yb. In addition, they show relatively low ratios of ( 87 Sr/ 86 Sr) i and ( 206 Pb/ 204 Pb) i, ( 207 Pb/ 204 Pb) i and ( 208 Pb/ 204 Pb) i and relatively low values of ε Nd ( t ) and ε Hf ( t ). The Sr‐Nd‐Pb‐Hf isotopes of PBG and PDP are similar to those of the Miocene adakitic rocks associated with the porphyry–skarn deposits in the GMB, indicating that they were predominantly generated by partial melting of the thickened juvenile Lhasa Terrane lower crust and the PDP were likely to be generated through mixing between the magma parental to the PBG and a mafic end‐member. By combining our results with the previously reported results, we suggest that the model of delamination of the overthickened mantle lithosphere of Lhasa Terrane and convective upwelling of mantle asthenosphere which may involve Indian continental lithosphere.