Zircon U-Pb geochronology, geochemistry, and S-Pb isotopic compositions of the Lietinggang iron polymetallic deposit, Tibet, China

Abstract

The Lietinggang deposit is a representative skarn iron polymetallic deposit in the Nyainqêntanglha skarn polymetallic zone (NSP) in Lhasa Terrane, Tibet. The mineralization is hosted in skarn of the Early and Middle Triassic Chaqupu Formation. Plutons in the deposit include gabbro, diorites (divided into the D1 and D2 diorites), granodiorite, syenogranite and porphyritic granite, and the D2 diorite and syenogranite are the mineralization associated plutons. In this study, we present LA-ICP-MS zircon U-Pb dating, zircon Hf isotopic and whole rock geochemical data of the diorites and porphyritic granite and S-Pb isotopic compositions of the ore sulfides in the Lietinggang deposit. Zircon U-Pb dating results for these intrusions yield Paleocene ages of 62.2–59.0 Ma. All the intermediate and felsic intrusions are I-type, and characterized by arc magma geochemical features, enriched in LREE and LILE, well developed negative Eu anomalies and depletion in HFSE, with most having positive εHf(t) values. These geochemical characteristics are similar with the coeval intrusions of the Gangdese batholith and Linzizong Group volcanic rocks, indicating they share a similar magma source. This magma source is proposed to be partial melting of the young metasomatized asthenospheric mantle wedge-derived basaltic rocks. During the magma evolution the fractionated crystallization has also play an important role. δ34S values for sulfides have features of magma source. The 206Pb/204Pb (18.043–18.711), 207Pb/204Pb (15.520–15.776), and 208Pb/204Pb (38.288–39.215) values of sulfides show that ore-forming metals were derived from mixing sources of mantle with upper crust materials. Geochemical characteristics of the intermediate and felsic intrusions, combined with the dating results, indicate that the Lietinggang magmatism and mineralization were formed within the India-Asia continental-collision tectonic setting.