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处于大兴安岭中北段额尔古纳地块的莫尔道嘎地区发育大量花岗质岩石,本文报道了该地区与斑岩钼矿有关的花岗斑岩、花岗闪长斑岩的锆石U-Pb年龄、Hf同位素特征。锆石的LA-ICPMSU-Pb年龄测试结果显示,太平川含矿斑岩体的形成年龄分别为183.6、193.7和199.1Ma,表明花岗岩主要形成于早侏罗世,可能代表蒙古-鄂霍茨克洋闭合阶段的岩浆侵入事件。锆石的Hf同位素研究显示,3件含矿斑岩样品锆石εHf(t)分别为-3.2～0.4、-3.1～1.8和-3.7～-1.1,两阶段模式年龄分别为1322、1276和1394Ma,岩浆起源于中新元古代增生的地壳物质。结合额尔古纳地块已有的花岗岩锆石Hf同位素资料,认为额尔古纳地块在中新元古代曾发生过地壳增生,增生的地壳物质于早侏罗世发生熔融,形成花岗质岩浆并成矿。太平川含矿斑岩具有与乌奴格吐山含矿斑岩相似的大地构造背景、岩石地球化学特征和岩石年龄,推测太平川斑岩钼矿的成矿年代大致在195～180Ma。
A large amount of granitic rocks are developed in Moerdaag area in the middle and northern part of the Greater Xing’an Mountains in the Erguna massif. The paper reports the granite porphyry related to porphyry molybdenum and the zircons U-Pb age, Hf isotope characteristics. The results of LA-ICPMSU-Pb dating of zircon show that the age of formation of the Taipingchuan ore-bearing porphyry is 183.6, 193.7 and 199.1 Ma respectively, which indicates that granite mainly formed in the Early Jurassic and may represent the Mongolia-Okhotsk Ocean Magmatic intrusion during the closure phase. The Hf isotope studies of zircons show that the εHf (t) of the zircons from the three ore-bearing porphyries are -3.2 ~ 0.4, -3.1 ~ 1.8 and -3.7 ~ -1.1, respectively. The two-stage model ages are 1322, 1276 and 1394 Ma The magma originated from the crustal material in Mesozoic and Proterozoic. Based on the Hf isotopic data of zircons from the granites in the Erguna block, it is considered that the Erguna block occurred during the Meso-Neoproterozoic and crustal thickening occurred, and the accreted crustal material melted during the Early Jurassic to form granite Magmatic and mineralization. The Taipingchuan ore-bearing porphyry has the similar tectonic setting, rock geochemistry characteristics and rock age as the Ungugutu ore-bearing porphyry. It is speculated that the Taipingchuan porphyry molybdenum deposit is about 195 ~ 180Ma in age.