THE XILING Sn DEPOSIT, EASTERN GUANGDONG PROVINCE, SOUTHEAST CHINA: A NEW GENETIC MODEL FROM Ar-40/Ar-39 MUSCOVITE AND U-Pb CASSITERITE AND ZIRCON GEOCHRONOLOGY

摘要

The Xiling Sn deposit is hosted in volcanic and subvolcanic rocks and belongs to the Southeastern Coastal metallogenic belt in China. Here we present zircon and cassiterite U-Pb and muscovite Ar-40/Ar-39 ages to constrain the timing of granitic magmatism and the genesis of the Sn mineralization. Laser ablation-inductively coupled plasma-mass spectrometry U-Pb dating of zircon grains from the tuff, tuffaceous lava, rhyolite porphyry, and granodiorite porphyry yielded weighted mean Pb-206/U-238 ages of 166.9 +/- 3.6, 164.8 +/- 3.0, 161.5 +/- 2.6, and 169.5 +/- 0.5 Ma, respectively. Zircon from the biotite granite adjacent to the southeastern part of the mine area yielded a U-Pb age of 145.8 +/- 0.6 Ma. Hydrothermal muscovite coexisting with cassiterite yielded a Ar-40/Ar-39 plateau age of 140.6 +/- 1.0 Ma, whereas cassiterite from two Sn ores yielded weighted mean Pb-206/U-238 ages of 146.4 +/- 1.0 and 147.5 +/- 1.1 Ma. The age data obtained in this study indicate that the volcanic-subvolcanic rocks in the mine area are genetically unrelated with the Xiling Sn mineralization and suggest hidden granitic intrusions at depth. In combination with the data from recent studies, we propose that the 145 to 135 Ma interval represents a newly recognized W-Sn metallogenic period linked with granitic intrusions in the southwestern part of the Southeastern Coastal metallogenic belt. The granitic intrusions formed during this period might therefore be potential candidates for W-Sn and Sn-Pb-Zn exploration in the region.