No genetic link between Late Cretaceous felsic dikes and Carlin-type Au deposits in the Youjiang basin, Southwest China

Abstract

The Youjiang basin in southwest China is distinguished by preserving a number of Carlin-type gold deposits. Tens of felsic dikes occur in this region, and some are present within the ore fields. A genetic link between these felsic dikes and ore-formation has previously been proposed, but detailed field investigation shows that the dikes crosscut the main ore body, and clearly postdate gold mineralization. Three felsic dikes in the Youjiang basin have been dated, and SIMS zircon U-Pb dating results show that the Liaotun and Xiabaha dikes were emplaced at 97.2±1.1Ma (MSWD=2.9) and 95.4±2.4Ma (MSWD=0.56), respectively, broadly consistent with a LA-ICP-MS zircon U-Pb age for the Bama dike (99.4±0.37Ma, MSWD=1.4). Combined with published dates of the other felsic dikes in this region, it is suggested that the felsic magmatic event in the Youjiang basin occurred between ∼100 and 95Ma. Although a wide range of ages for gold mineralization (275–46Ma) has been reported by a variety of methods, the best available ages suggest a timing between 235 and 193 (Direct Re-Os dating on Fe-sulfides; Chen et al., 2015, Re–Os isochron ages for arsenopyrite from Carlin-like gold deposits in the Yunnan–Guizhou–Guangxi “golden triangle”, southwestern China), significantly older than the emplacement age of the felsic dikes. Taken together, we conclude that there is no genetic link between these Late Cretaceous felsic dikes and Carlin-type Au mineralization in the Youjiang basin.