| Abstract:The present paper deals with geological-geochemical characteristics of the ore-hosting strata of molybdenum and tungsten deposits in the nonferrous metallogenic belt of eastern Qinling. On the basis of a wealth of quantitative data obtained front the systematic sampling along seven measured geological-geochemical sections of ore-hosting strata, lithological characters, variation in contents of molybdenum and tungsten, distribution of trace elements, and multivariate regression analysis for correlation between molybdenum and trace metallogenic elements (copper, manganese, lead, zinc, tungsten), it is evident that the major ore-hosting strata for molybdenum and tungsten deposits are Baishugou Formation, SanchUan Formation, Nannihu Formation, Meiyaogou Formation of Luanchuan Group and Longjiayuan Formation of Quandaokou Groupithese strata, therefore, are host rocks for large-size molybdenum and tungsten deposits: the Shangfang molybdenum deposit occurs in Meiyaogou Formation, the Nannihu molybdenum deposits present in Nannihu Formation, the Sandaozhuang molybdenum and tungsten deposits exist in Sanchuan Formation and Baishugou Formation, and the Yechangping molybdenum deposit is seen in Longjiayuan Formation and Xunjiansi Formation. The richer molybdenum and tungsten in ore-hosting strata might be attributed to inheriting these elements from erosional source rocks of Taihua Group and Xionger Group. This is a regional geochemical characteristic of the eastern Qinling metallogenic belt. Although different stratigraphic formations, members or lithologic units have remarkably different average contents of molybdenum and tungsten, they are all characterized strikingly by very high contents of these elements, i.e., from several to tens of times higher than their abundances in the earths crust (molybdenum l.3 ppm, tungsten l.1 ppm). The preliminary concentration of the metallogenic elements in these strata, which served both as wall rocks and as ore source beds, laid the material foundation for the formation of large-size molybdenum and tungsten deposits in eastern Qinling. |
