| Hadamengou Gold Mine area is located about 30 km northwest of Baotou City,Inner Mongolia.It is a large gold mine discovered by the Armed Police Gold Force in the middle and late 1980 s.In the mining area,magmatic activity is strong and there are a lot of vein rocks,among which pegmatite vein and diabase vein are the most developed.Vein rocks are generally produced in the context of regional lithospheric extension.The study of vein rocks can reveal the tectonic change and dynamic background,and some of them are closely related to mineralization in the region.On the basis of detailed field geological investigation and indoor research,this paper systematically discusses and studies the geological and geochemical characteristics of vein rocks and the relationship between vein rocks and gold mineralization in Hadamengou Gold Mine Area by means of petrography,petrochemistry,zircon U-Pb dating and other contents and methods.The fault structure is developed in the mining area,and a large number of vein rocks are controlled by faults,showing the characteristics of near east-west,north-east and North-South distribution in space.The North-South diabase vein was formed earlier than other vein rocks,cut by later vein rocks,and the nearly East-West pegmatite vein was formed earlier than the north-east pegmatite vein.Therefore,the occurrence of vein rocks in Hadamengou Gold Mine area is obviously controlled by the regional tectonic activity,and the vein rock activity shows the characteristics of multi-stage and multi-stage.On the other hand,there is also a close spatial relationship between the vein rock and the gold vein.The place where the vein rock is concentrated is also the place where the gold vein occurs.The gold vein is close to the vein rock or cuts off the vein rock,which indicates that the vein rock should be formed earlier than the gold vein,and the ore-forming fluid is likely to follow the channel of the early vein rock in the process of upward migration,which leads to the occurrence of the gold vein and the vein rock Close spatial relationship between them.Zircon U-Pb dating of the vein rocks exposed in the gold area shows that the formation ages of the pegmatite vein are 2.43 Ga and 2.45Ga;the diabase vein is mainly divided into two stages,the U-Pb zircon age of the North-South diabase vein is 2.52 Ga,and the age of the north-east diabase vein is 2.45 Ga.The geochemical characteristics of pegmatite vein are high silicon,high aluminum and high potassium,belonging to peraluminous strong peraluminous granite;the geochemical characteristics of the North-South diabase vein are low silicon,high iron and high magnesium,which are produced in island arc environment,accompanied by the metasomatism of subduction fluid;the tectonic environment of the north-east diabase vein shows the intraplate extension environment.In this study,it is believed that the vein rocks formed in the late Neoproterozoic to early Paleoproterozoic stage,which are related to the amalgamation of micro continental blocks within the North China Craton,plate subduction collision and regional extension mechanism after craton. |
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