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

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 Al2O3 (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 (87Sr/86Sr)i and (206Pb/204Pb)i, (207Pb/204Pb)i and (208Pb/204Pb)i and relatively low values of εNd(t) and εHf(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.

Sphalerite and Pyrite Geochemistry from the Pusangguo Co-Rich Cu–Zn–Pb Skarn Deposit, Tibet: Implications for Element Occurrence and Mineralization

“…There is no evident intrusion relationship among the granodiorite, diorite porphyry, and gabbro. The zircon U-Pb geochronology indicates that the granodiorite and diorite porphyry were formed in the Miocene [8], which is consistent with the timing of the mineralization (13.2 ± 0.7 Ma, [7]).…”

“…The Pusangguo deposit is the first cobalt-rich Cu-Pb-Zn skarn deposit discovered in the GMB, and has metal resources of 1.42 Mt Cu at 1.42%, 0.08 Mt Pb at 1.01%, 0.14 Mt Zn at 1.82%, and 285.8 t Co at 140 g/t Co [4]. Previous studies have mainly focused on the geological characteristics [5,6], diagenetic and metallogenic geochronology [7][8][9], isotopic geochemistry [10], mineralogy and cobalt occurrence [11,12], and ore-forming fluids [13,14]. However, the trace and minor element geochemistry of sphalerite and pyrite in the Pusangguo has not been studied, which may give better insights into the physicochemical conditions of ore mineralization, and improve our understanding of ore formation.…”