The Yindu deposit,a silver polymetallic deposit of hydrothermal vein-type controlled by faults,is located in the west slope of Great Xing’an Range,Inner Mongolia.The magmatic body is quartz diorite in this mining area,in which the zircons are divided into magmatic ones and hydrothermal one.The magmatic zircons are colourless,transparent,euhedral columnar,with the characteristics of oscillatory zoning,whereas hydrothermal zircons are light brown,translucent-opaque,equiaxed,with its dark hyperplasia edge cutting significantly over the nuclear of magmatic zircons. Hydrothermal zircons are characterized by low values of Th/U and LREE,and high values of Hf and HREE,relative to magmatic zircons.206 Pb/238 U weighted mean age of magmatic zircons is (451.8±7.8)Ma in Yindu District.It belongs to the Caledonian,representing the crystallization age of the Yindu rock.206 Pb/238 U weighted mean age of hydrothermal zircons is (337.0 ± 7.7 ) Ma. It belongs to the Middle Carboniferous,representing the hydrothermal age.It was indicated that there is a strong hydrothermal process in the mining area around 337 Ma. The hydrothermal process may be related to the peakmetamorphism of orogeny in the area.Accoring to the regional geological characteristics and fluid inclusion characteristics,it was shown that the formation of silver ore is likely closely related to this hydrothermal activity in the mining district.%银都矿床位于内蒙古大兴安岭西坡，为受断裂控制的银多金属矿床。该矿床的岩体主要为石英闪长岩。该岩体中的锆石分为岩浆锆石和热液锆石两类：岩浆锆石无色透明，自形长柱状，具有典型的振荡环带特征；而热液锆石呈浅褐色，半透明不透明，等轴状，其暗色增生边明显切过了核部岩浆锆石结构。热液锆石相对岩浆锆石具有低 Th/U 和 LREE，高 Hf 和 HREE 的特征。银都岩体岩浆锆石的206 Pb/238 U加权平均年龄为（451．8±7．8）Ma，属加里东期，为岩体的结晶年龄；热液锆石的206 Pb/238 U 加权平均年龄为（337．0±7．7）Ma，属中石炭世，代表了热液作用的年龄。热液锆石年龄表明，该区在337 Ma 左右经历了一次强烈的热液作用，该期热液作用可能与该区造山峰期的变质作用有关。本区的地质特征和流体包裹体特征表明，本区银矿的形成很可能与这期热液活动密切相关。
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