内蒙古甲乌拉铅锌银矿绢云母40Ar-39Ar年龄及其地质意义

40Ar-39Ar Ages of the Sericite in the Jiawula Pb-Zn-Ag Deposit,Inner Mongolia and Their Geological Significance

内蒙古甲乌拉大型铅锌银矿位于大兴安岭成矿带北段,为一与火山-次火山作用有关的浅成低温热液型矿床。该矿床绢云母的矿物学特征方面研究程度较低,绢云母的年龄还未见报道。本次研究拟从绢云母入手,利用电子探针和40 Ar/39 Ar同位素年龄测定,研究其矿物学特征,测定其年龄,进一步探究该矿区热液事件的发生和地球动力学背景,增进对该矿床成矿机制的理解。甲乌拉矿床绢云母40 Ar/39 Ar坪年龄为133.27±0.66 Ma,等时线年龄为131.88±0.83 Ma。研究认为,甲乌拉矿床绢云母可能代表了发生于矿化后的另外一期热液事件。该热液事件发生于古太平洋板块俯冲方向改变之后,可能与碰撞后的伸展背景有关。

The Jiawula large-scale Pb-Zn-Ag deposit is located in the northern part of the Da Hinggan Mountains metallogenic belt in the eastern section of the Central Asian orogenic belt.It is an epithermal deposit associated with volcanic or sub-volcanic activity.So far the mineralogical characteristics of the sericite in this deposit are less studied,and its age has not been reported.This study intends to study the mineralogical characteristics of the sericite by electron probe micro-analysis(EPMA),determine its 40 Ar/39 Ar isotope age,further explore the occurrence of hydrothermal events and geodynamic background,and improve the understanding of mineralization mechanism of this deposit.The 40 Ar/39 Ar plateau age of the sericite in the Jiawula deposit is 133.27±0.66 Ma,and the isochronal age is 131.88±0.83 Ma.The results argue that the sericite of the Jiawula deposit may represent another hydrothermal event that occurred after mineralization.The hydrothermal event occurred after the subduction direction of the ancient Pacific Plate changed,which may be related to the extension background after collision.