Кошрабадский массив гранитов рапакиви в Узбекистане и связанные с ним месторождения золота

The Koshrabad pluton is composed of two rock series: (1) mafic rocks and quartz monzonites and (2) granites of the main phase. Porphyritic granitoids of the main phase are characterized by the rapakivi texture and contain ovoids of alkali feldspar, often rimmed by plagioclase. Mafic rocks, locally, occurred in the core of the pluton originated from injections of mafic magma into unconsolidated rocks of the main phase, which produced hybrid rocks and various dike series. All rocks of the pluton are characterized by high Fe/(Fe+ Mg) values and contain fayalite, which indicate reducing conditions of crystallization. The mafic rocks are the products of fractional crystallization of alkali-basaltic mantle melt and granitoids of the main phase show signatures of crustal contamination. The high Fe/(Fe + Mg) values and HFSE contents make the granitoids ofthe Koshrabad pluton similar to A-type granites. Data on geochemical evolution of the pluton confirm a genetic relationship of gold deposits of the pluton with magmatic processes and suggest the accumulation of gold in residual acid melts and rapid formation of ore quartz veins in the same structures that controlled the intrusion of late dikes.