Age of the Dahongliutan rare metal pegmatite deposit, West Kunlun, Xinjiang (NW China): Constraints from LA–ICP–MS U–Pb dating of columbite-(Fe) and cassiterite

Abstract

Dahongliutan is a medium-size Li–Be–Ta–Nb rare metal pegmatite deposit in the Tianshuihai terrane, West Kunlun orogenic belt (NW China). In this paper, LA–ICP–MS U–Pb ages of columbite-(Fe) and cassiterite are reported to constrain the metallogenic age. Columbite-(Fe) (with high U and low Th) yielded a Late Triassic weighted mean 206Pb/238U age of 211.9±2.4Ma, whilst cassiterite yielded a 206Pb/238U–207Pb/235U concordia lower intercept age of 218±12Ma and a Tera-Wasserburg lower intercept age of 218±12Ma, which is identical to the columbite-(Fe) U-Pb age and thus represents the emplacement age of the pegmatite dikes. The ore-hosting pegmatite dikes are intimately time-space related to the Dahongliutan S-type granite (ca. 220–217Ma), indicating that they may have been cogenetic. Integrating new and published geological data, we suggest that the Dahongliutan pegmatites may have evolved from the granitic magma represented by the Dahongliutan S-type pluton in a post-collisional tectonic setting. Regionally, the Tianshuihai terrane is the western extension of the Songpan-Ganzi block, and thus the Kunlun Li-mineralization belt may have been connected to the Songpan-Ganzi Li-mineralization belt which contains eleven lithium deposits with about 9.8% of Li2O reserves in China, implying that the Dahongliutan pegmatite deposit may also have favorable ore-forming conditions. The similar columbite-(Fe) and cassiterite ages demonstrate that these minerals can be precisely dated and could provide useful alternatives to accurately constrain the timing and evolution of rare metal mineralization.