Size Statistics of Plagioclase Phenocrysts in Mineralized and Barren Porphyries in Shaxi Porphyry Copper Gold Deposit, Anhui Province and Its Significance for Studying Magma Crystallization Kinetics and Ore Forming Process
安徽沙溪含和不含铜(金)矿斑岩斜长石斑晶粒度统计及其岩浆结晶动力学和成矿意义

Through size statistics of plagioclase phenocrysts in mineralized and barren porphyries in Shaxi porphyry copper gold deposit, the three parameters, i.e. average grain size ( S ),grain density ( D ) and homogeneity of distribution ( H ), have been calculated. On the basis of the crystal size distribution (CSD) theory, the growth rates, nucleation density and nucleation rates of plagioclase have been worked out. Comparing these parameters of mineralized porphyries with those of barren ones, we find that nucleation rates and nucleation density of mineralized porphyries are higher than those of barren ones, but crystal growth rates of mineralized porphyries are slower. This study shows that a slight difference of the characteristics of magma crystallization kinetics among the porphyries having similar petrochemical and geochemical composition, may result in obviously distinctive ore bearing potentiality.