SULFIDE MICROINCLUSIONS IN ACID AND INTERMEDIATE VOLCANICS OF THE KURILE-KAMCHATKA ISLAND-ARC

Primary sulfide microinclusions in phenocrysts from Quaternary andesit e-dacite, dacite, and rhyodacite of the Kamchatka Peninsula and Kurile Islands consist of pyrrhotite and a copper-bearing phase. The inclusi ons are sulfide-melt drops trapped in a liquid state or after solidifi cation by growing phenocrysts. The average chemical composition of the inclusions (wt %) is as follows: S = 38.42; Fe = 55.28; Cu = 6.03; Ni = 0.13; and Co = 0.14. Judging by this composition, the acid and inte rmediate magmas contained 50-230 ppm Cu, which is roughly an order of magnitude higher than the Cu concentration in solid volcanic rocks.