内蒙古哈达门沟金矿田金成矿时代厘定

Determination of gold metallogenic age in the Hadamengou Gold Field,Inner Mongolia

为查明哈达门沟金矿田金成矿时代,野外系统观察了该矿田内金矿(化)体特征及其与岩体的穿插接触关系等,结合近30年来成矿时代测年结果,较准确地厘定了哈达门沟金矿田金成矿时代。哈达门沟金矿田金矿(化)体类型主要为石英脉型、钾长石脉型、石英-钾长石脉型和蚀变片麻岩型,其中石英脉型、钾长石脉型具有规律的含金不均一性特征,证实了石英脉和钾长石脉的形成是两期成岩作用,而非成矿过程。此外,区域变质作用、构造变质作用等热事件均在后期形成的金矿(化)体中留下了年龄痕迹,导致已有成矿时代测年结果数据量大且跨度大(132~387)Ma。地表金矿(化)体露头黑色窄条状矿质脉穿插石英细脉与钾长石脉,也成为一期成矿而非多期成矿的有力证据,且成矿发生于较晚期。综合区域成矿特征,认为哈达门沟金矿田金成矿时代为燕山期(132 Ma±2 Ma)。

In order to determine gold metallogenic age in the Hadamengou Gold Field,the characteristics of gold ore(mineralization)ore body and their interpenetrating contact relationship with rock body in the field are observed systematically in field.And with metallogenic age dating results for the last 30 years,the metallogenic age in the Hadamengou Gold Field is determined in a relatively precise way.The gold ore(mineralization)body type in the Hadamengou Gold Field includes potassic feldspar vein type,quartz vein type,quartz-potassic feldspar vein type and altered gneiss type;among them,the quartz vein type and potassic feldspar vein type have regular gold content heterogeneity,confirming that the formation of quartz vein and the formation of potassic feldspar vein are two-stage diagenesis rather than two-stage mineralization process.Besides,thermal events such as regional metamorphism and structural metamorphism all left age footprints in the later formed gold ore(mineralization)bodies,leading that the current data of gold mineralization age are in large volumes and wide span(132-387)Ma.The black narrow strip of mineral materials outcropping from the surface gold ore(mineralization)body intruding quartz veinlets and potassic feldspar veins has also become a strong evidence of one-stage gold mineralization rather than multi-stage gold mineralization,and of the fact that the gold mineralization occurred in the later stage.The regional metallogenic characteristics are comprehensively analyzed,and based on that,it is considered that the gold mineralization age of Hadamengou Gold Field is Yan-shannian period(132 Ma±2 Ma).