The Identification Of Biotite To The Granite Gold Metallogenic Relationship

The North China Craton,as the most important gold mineralization province in China,experienced intense magmatic activity and massive gold mineralization in the late Mesozoic,forming many large-and ultra-large gold deposits,but there are obvious differences in the distribution of these gold deposits.The Jiaodong gold mining area has the largest number of deposits and the largest scale,followed by the Xiaoqinling area,and relatively fewer in the Taihangshan area.This paper attempts to reveal the relationship between granite diagenesis and gold mineralization by studying the genetic mineralogy of biotite in granites in the North China Craton gold deposit concentration area.The composition characteristics of biotite in granite can effectively indicate the intensity of gold mineralization.The biotites in the granites such as Guojialing in the Jiaodong area,Mapeng in the west of Hebei,and Wenyu in Xiaoqinling,which are in the same period as the gold mineralization(early Cretaceous)and near in space,are magnesium-rich biotite with high magnesium content and medium iron content index;The biotite in the Huashan granite,which is in the same period as the gold mine but far away in space,is mafic biotite,with a relatively low magnesia rate,a relatively high iron content index,and a lower gold-forming potential;it is different from the gold mine(late Jurassic),the biotite in the Linglong granite of Jiaodong is iron-rich biotite,with low magnesium content and high iron content index,indicating that it has little to do with the gold mineralization in the area.The pictorial area of biotite Al/Si-Fe /Mg in the granite of Guojialing,Mapeng and Wenyu is lower,the pictorial area of Al/Si-Fe/Mg of biotite in Linglong granite is higher,and the biotite Al/Si-Fe/Mg of Huashangranite,the illustrated area is located between the two,which also indicates the difference in the contribution of rock masses to gold mineralization in the area.The involvement of mantle-derived materials is related to the regional distribution of gold deposits in the east and west of North China.The eastern craton is severely damaged,the mantle-derived components are added more,the rock body has a shallow diagenetic depth,and the gold mineralization is good.In terms of granite types,I-type granites such as Guojialing,Mapeng,and Wenyu are closely related to gold deposits,I-S transitional Huashan granite is weakly associated with gold deposits,and S-type Linglong granite is not related to gold mineralization.Trace elements(V,Cr,Co,Ni)have a certain tracing effect on the gold mineralization properties in North China.The higher V,Cr,Co,Ni content of biotite in granite can be used as a sign that the rock mass is beneficial to gold mineralization.