LA-ICP-MS zircon U-Pb age, geochemistry of andesite in Bilihe goldfield, Suniteyouqi, Inner Mongolia and its tectonic significance
内蒙古苏右旗毕力赫金矿区安山岩LA-ICP-MS锆石 U-Pb年龄、元素地球化学特征及其形成的构造环境

The Bilihe large-scale porphyry gold deposit locates in the Early Paleozoic accretionary orogenic belt of the northern margin of North China Craton. The lithology in Bilihe goldfield was the set of volcanic rocks which include andesite, dacite and rhyolite. The andesite belongs to sub-alkaline, high-K calc-alkaline series, with higher content of MgO (2.05%~10.29%), low FeOT/MgO ratio and the content of TiO2 (0.21%~0.85%) and with high content of Cr (44×10-6~473×10-6), Ni (19.3×10-6~249.4×10-6), depleted Nb, Ta, Ti, P, absence or minor of Eu/Eu* anomalies, which collectively indicated the andesite with the characteristics of volcanic rocks of typical Andean-type active continental margin. The weighted average 206Pb/238U ages of andesite and andesitic tuff were 281±4.3Ma and 281±12Ma (the Early Permian), by LA-ICP-MS zircon U-Pb dating respectively, and consistent with the crystallization age (279Ma) of granodiorite porphyry that related to gold mineralization and ore-forming age (272Ma), which indicated that diagenesis-metallogenesis of mining area was associated with collisional orogeny between the North China plate and the Siberian plate in the Late Paleozoic, and suggesting that it had the great potential to find Late Paleozoic epithermal-porphyry type gold (copper) deposits in northern margin of the North China Craton. U-Pb ages of the ancient inherited zircons presents in the volcanic rocks and intrusive rocks associated with mineralization were 1.8Ga, 2.0Ga and 2.4Ga, implying that the mining area was presence of ancient basement of the North China Craton, and as a major factor in generating gold mineralization.