According to an analysis of biotite from Guojialing granudiorite in such aspects as its common characteristics, shape, composition, genetic diagram ard Mossbauer spectra, It iS shown That this mineral，rich in Fe, Fe3+，F- and Mg and deficient in OH-，was formed under an unstable. ard oxidized condition. The projections of its chemical composition fall into the diorite recrion, granite regior, as well as rear the granodiorito and adamellite ragion, sugge- stingy that a part of this mineral is primary biotite in granodiorite, and the other part is local remelting relic hiotite in biotite leptynite of Archean Jiaodong Group whos0e gold content is the highest(28.23 x 10-).After its formation, biotite underwent tectonic activity and alteration, forming chlorite and pyrite. All this shows that the formation condition and compositional characteristics of biutite are favorable for gold metallogenesis, i.e.，Guojialing granodioritc is favorable for the formation of gold deposits. Before 1986， people had all thought that the Guojialing granodiorite was unfavorable for gold metallization, and hence drilling and mining were always stopped whe- rever the work reached the Guojialing granodiorite. Nevertheless, our research has shown that this granodioritte body could form ore deposits, even rich ones, as is substantiated by the discovery of the Jiehe gold deposit in this body.