LA-ICP-MS zircon U-Pb dating of the gold-bearing quartz veins in the Bainaimiao Au deposit of Inner Mongolia and its geological significance

Cathodoluminescence image (CL) and zircon LA-ICP-MS U-Pb dating techniques were used to study the metallogenic age of the Bainaimiao gold deposit．According to the results obtained, all zircons from the gold-bearing quartz veins show clear core-mantle-rim texture, the core-mantles are of magmatic and metamorphic characteristics，the rims of zircons show the features of hydrothermal zircon with clear core-mantle-rim texture, non-luminescent rim, and euhedral and subhedral crystals, Th/U ratios vary in the range of 0.2～0.5，and the results of the rim dating are 421.4～447.6Ma, suggesting that the Bainaimiao gold deposit formed in Silurian. The ages are accordant to ages of granodiorite porphyry, which has similar zircon core-mantle CL features. It is thus held that the gold deposit was closely related to tectonic-magmatism, post-magmatic hydrothermal activities and durative orogenesis resulting from the intense subduction of Early Paleozoic paleo-Asian oceanic plate towards the northern margin of North China craton.