Garnet-bearing basites of the Kuvalorog massif (Kamchatka Peninsula)
E.G. Konnikov a , A.N. Nekrasov a , D.A. Orsoev b , Hongquan Yan c , Xiaoguo Chi c
a Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka, 142432, Russia
b Geological Institute, Siberian Branch of the RAS, 6a ul. Sakh'yanovoi, Ulan Ude, 670047, Russia
c Jilin Univ., 79 Jianshe, 130061 Changchun, Jilin Province, China
Keywords: pyrope-almandine garnet; endocontact leucodiorites; hornfels relics; thermal effect; subsolidus; fluids; thermodynamic regime
Pages: 445-461
Abstract
The petrographic, petrochemical, and mineralogical compositions of the Kuvalorog Ni-bearing cortlandite-norite intrusion and endocontact leucodiorites hosting pyrope-almandine garnet are considered. Lamprophyre dikes with scarce pyrope-almandine garnet, first discovered in the massif, and plagioclase-pyroxene symplectites in garnet porphyroblast areas are studied. Judging from the petrography of rocks and the composition of inclusions rich in incompatible elements in the garnet, the mineral was produced by the reaction of orthopyroxene with the anorthite component of plagioclase at the subsolidus stage of formation of endocontact diorites. This reaction was probably favored by the fluid phase abundant in the parental magma of the Kuvalorog intrusion and, especially, in the zones near its contact with relics of terrigenous rocks, where it was produced as a result of the rock dehydration under the thermal effect of the intrusion.
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