Combined garnet, scheelite and apatite U-Pb dating of mineralizing events in the Qiaomaishan Cu-W skarn deposit, eastern China

Determining the precise timing of mineralization and mineralizing events is crucial to understanding regional mineralizing and other geological events and processes. However, there are a number of miner-alogical and analytical limitations to the approaches developed for the absolute dating of mineralizing systems, such as molybdenite Re-Os and zircon and garnet U-Pb, among others. This means that the pre-cise and accurate dating of mineralizing systems that may not contain minerals suitable for dating using existing approaches requires the development of new (and ideally in situ) approaches to absolute dating. This study outlines a new in situ analytical approach that has the potential to rapidly and accurately eval-uate the timing of ore formation. Our study employs a novel application of in situ scheelite U-Pb dating analysis using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and samples from the Qiaomaishan deposit, a representative example of skarn mineralization within the Xuancheng ore district of eastern China. Our approach to scheelite dating of the deposit is verified by cross-comparison to dating of cogenetic garnet and apatite, proving the effectiveness of this approach. Our new approach to dating of scheelite-bearing geological systems is rapid, cheap, requires little sample preparation, and is undertaken in situ, allowing crucial geological and mineralogical context to be retained during analysis. The approaches outlined here not only allow the determination of the absolute timing of formation of the Qiaomaishan deposit through the U-Pb dating of scheelite [138.6 +/- 3.2 Ma, N = 39, mean square weighted deviation (MSWD) = 1.17], garnet (138.4 +/- 1.0 Ma, N = 40, MSWD = 1.3), and apatite (139.6 +/- 3.3 Ma, N = 35, MSWD = 0.72), but also further supports the theoretical genetic links between this mineralization and the emplacement of a proximal porphyritic granodiorite intrusion (zircon U-Pb age: 139.5 +/- 1.2 Ma, N = 23, MSWD = 0.3). Moreover, our research indicates that the higher the concentrations of U within scheelite, the more suitable that scheelite is for U-Pb dating, with the main factor controlling the U content of scheelite seemingly being variations in oxygen fugacity conditions. This novel approach provides a potentially powerful tool, not just for the dating of skarn sys-tems but also with potential applications in orogenic and intrusion-related gold, porphyry W-Mo, and greisen mineralizing systems as well as other scheelite-bearing geological bodies or geological systems.(c) 2022 China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).