Relationship Between Gold Mineralization And Acid Dikes Of The Yangshan Gold Deposit In The Western Qinling Belt,Central China

The Yangshan gold belt, with proved gold resources over300tons, is the largestgold deposit in the Western Qinling Belt. The lodes of high gold values have a veryclose spatial relationship with the acid dikes. But the geological feature of the dikes,the correlation between the alterations and mineralizations, and the relationshipbetween the dikes and mineralization are poorly studied and still controversial. Tosolve these problems, systematic deposit geology, petrology, ore microscopy, andgeochemistry have been studied here, and the following results were achieved.1. The mineralization styles in the Yangshan gold belt can be classified into alteredrock type and quartz-vein type. The host rocks are phyllite, limestone, sandstone, andacid dikes, and the richest gold ores are usually found near the contact area of thedikes and the phyllite. The mineralization zoning from the dike to the phyllite is:pyrite±arsenopyrite→stibnite±native gold→pyrite±arsenopyrite→pyrite.Whereas there is no apparent correlation between gold grade and the degree to whichthe host rock have undergone argillization, and have weak correlation between thegold values and the degree to which the host rock have undergone silication, littlecorrelation with the amount of the pyrite.2. The dikes are distributed in three different orientations: NEE, NE, and NW.Most dikes are granite porphyry dikes and granite aplite dike, with a few dikes arequartz porphyry dikes and subvolcanic breccia. The dikes with pyrite and arsenpyritemineralization usually have the highest gold grade, and the REE pattern of themineralized dikes is similar to that of the unmineralized dikes. Isocon plots show thatmineralization involved addition of Au, S, Ag, As, W, and Hg, but loss of Bi, Co, Cr,Cu, Ba, Sn, Pb, and Sn. The sulfur content in oxidized mineralized dikes is lower thandthikate sin a rteh es iumniolaxri.d Tizheed δd3i4kes, but the gold grades of both the oxidized and unoxidizedS values of sulfides in ores vary from-4.7‰to3.7‰,（is15d.3if‰fe^re1n7t.5f‰ro）m, butht ei s δ³⁴whichsimSi lavra tlou etsh eo δf34phyllite （-24.6‰^-29.0‰） and limestone S value of intermediate-acid magmatic dikes（-6‰⁺6‰）.3. The close time relationship of the gold metallogensis （190Ma） and dikestfhoerm daiktieosn, a（1n9d5tMhea R²E1E7Mpaatt）e, rtnhse acnldo steh es pδa3t4ial relationship of the richest gold lodes andS values, indicate that the gold ores and thedikes come from the same source. The dikes and gold mineralization are theproductions of the same tectonic-magmatic activity, which caused the closetime-spatial coexistence of the dikes and gold ores.