LA-ICP-MS Zircon U-Pb and Alunite Ar-39/Ar-40 Dating of the Saozhouhe Alunite Deposit: Implications for the Metallogenic Significance of the Xiaotian Basin

As an important part of the northern Huaiyang tectonic belt, the Mesozoic Xiaotian basin hosts a series of gold and alunite deposits. However, the ages of these deposits remain unclear, constraining the further understanding of the genesis of these deposits. In this work, zircon LA-ICP-MS and alunite Ar-39/Ar-40 isotopic dating studies were carried out on the andesitic porphyrite and alunite of the Saozhouhe alunite deposit, respectively. LA-ICP-MS zircon U-Pb dating for the Saozhouhe andesitic porphyrite yields a weighted average age of 122.8 +/- 0.9 Ma (MSWD = 1.8), indicating that these volcanic rocks were formed in the Early Cretaceous period. The alunite 39Ar/40Ar dating yields a plateau age of 121.0 +/- 1.1 Ma (MSWD = 4.4) and an isochron age of 121.2 +/- 1.9 Ma (MSWD = 8.5), indicating that the alunite was also formed in the Early Cretaceous period. Our finding confirms that the formation of the Saozhouhe alunite deposit is genetically related to the Cretaceous volcanic magmatism, which has great significance in the metallogenetic regularity of and further ore prospecting in the Xiaotian basin.