Late Cretaceous Sn mineralization at Haobadi, southwestern Yunnan province, China: Constraints from cassiterite and zircon U − Pb geochronology

Abstract

The Late Cretaceous marks a significant period for tin mineralization in the Sibumasu block. Although the Baoshan block has been considered as the northern extension of the Sibumasu block, the genetic connection of tin mineralization remains unclear due to a lack of robust age data. To address this issue, we present cassiterite and zircon U–Pb geochronological data in the Haobadi tin deposit in the northern Baoshan block. This deposit is hosted by the Triassic sedimentary rocks intruded by the Triassic Lailitoushan pluton with zircon U–Pb ages ranging from 219.1±1.3 Ma to 215.7±1.4 Ma. Cassiterite U–Pb data indicate that tin mineralization occurred at 75.5±2.7 Ma. Notably, zircons from the Lvyintang pluton yield zircon U–Pb ages of 75.6±0.6 Ma and 77.4±0.5 Ma for the biotite granite and two-mica granite, respectively. Zircon trace element compositions indicate that the two-mica granite is more evolved and has lower magmatic oxygen fugacity than the biotite granite. These data indicate that Haobadi tin mineralization is not linked to the Triassic Lailitoushan pluton but associated with the Late Cretaceous granite such as the Lvyintang two-mica granite. The Late Cretaceous tin mineralization observed in the Baoshan block is attributed to the eastward subduction of the New-Tethys Ocean. Given the paramount importance of the Late Cretaceous episode in tin mineralization within the Baoshan block, more attention in future ore exploration should be paid.