Geochronology and Genesis of Meta-felsic Volcanic Rocks from the Kangbutiebao Formation in Chonghuer Basin on Southern Margin of Altay, Xinjiang

The Chonghuer basin is one of the fault-bounded volcano-sedimentary basins on the southern margin of the Altay orogenic belt, where the Kangbutiebao Formation (Fm.) stratigraphic unithosted many economic deposits outcrops. LA-ICP-MS U-Pb zircon analyses from two meta-rhyolites and one meta-tuff of the Kangbutiebao Fm. in the Chonghuer Basin yield weighted mean 206Pb/238U ages of 385.3±1.2Ma,398.1±1.8Ma and 405.6±2.2Ma, respectively, which can be interpreted as the eruption age of the Kangbutiebao silicic volcanic rocks in the Chonghuer Basin. The meta-rhyolites have similar geochemical features to meta-rhyolites in Kelang Basin and Maizi Basin, which are low-Ti rhyolite with obvious negative anomaly of Ti, P, Sr, Ba, Nb, Ta and Eu (δEu=0.25~0.54), obvious enrichment of Th, U, Pb, Zr, Hf and LREE. These features, together with the regional geological characteristics, indicate that these felsic volcanic rocks were generated by partial melting of lower crust on an active continental margin. These volcano-sedimentary basins are down-faulted Basin formed in compression tectonic environment of Early—Middle Devonian period.