Preservation of Xiuwacu W-Mo deposit and its constraint on the uplifting history of Eastern Tibetan Plateau

Abstract

Thermochronology has become an increasingly effective tool to reveal the post-mineralization uplift and exhumation history of ore deposits. In this paper, we studied the exhumation history and preservation conditions of the Xiuwacu tungsten-molybdenite deposit (resource: 24,000 t Mo and 23,000 t WO3), which is located on the southern Yidun Terrane (SYT), Eastern Tibetan Plateau. At Xiuwacu, both the eastern and western ore zones contain quartz-vein-type orebodies in the K-feldspar, greisen, and silicic alteration zones. The orebodies distributed in a northwestward trend along regional faults, with ore minerals including mainly molybdenite, scheelite, chalcopyrite, and pyrite.The mineralization at Xiuwacu occurred in 86–82 Ma, coeval with the emplacement of the ore-causative Xiuwacu porphyry monzogranite. The deposit likely underwent rapid cooling from 750 − 800 °C (magmatic zircon U-Pb age) to ~ 300 °C during 90–86 Ma (molybdenite Re-Os mineralization age). After that, the temperature slowly and continuously cooled to ~ 180 °C from the Late Cretaceous to 25 Ma, and then rapidly cooled to ~ 125 °C in 25–17 Ma, and eventually to 125–60 °C during 17–5 Ma (apatite fission-track ages; n = 8).The thermochronologic history of the Xiuwacu intrusive complex was reconstructed by inverse modelling based on the apatite fission-track ages and lengths. There was 6426–6915 m (average 6650 m) uplift, while only 1982–2471 m (average 2200 m) exhumation. Considering the depth of current exploration and typical depth of granitoid-related W-Mo mineralization, we infer that there is still great potential to discover concealed W-Mo orebodies beneath the current mining level at Xiuwacu.