ANDESITE AND CO-MAGMATIC ANDESITE INCLUSIONS IN THE KUHE-LANGAR AREA, SW OF KERMAN, IRAN: CONSTRAINTS ON MINERALOGICAL COMPOSITION FOR MAGMA CHAMBER PROCESSES
The hypocrystalline porphyritic to glomeroporphyritic andesite in parts contains conspicuous, dark grey co-magmatic igneous enclaves that occur both as ribbon and spheroidal to ellipsoidal components Mineralogically, the enclaves consist of phenocrysts and microlites of plagioclase, clinopyroxene, orthopyroxene and magnetite enclosed in a slightly glassy groundmass and the host andesite contains the same mineral assemblage in a glassier groundmass. Compositionally, the mineral phases in the andesite and the inclusions overlap each other. For example, both have a relatively large amount of anorthite content (An43-91). Plagioclase grains show normal, reverse, oscillatory and patchy zoning patterns with sieve textures. The pyroxenes generally show a uniform chemical composition and are identified mainly as hypersthene (En59.67 to En73.30) and augite (Wo40.88-46.00, Fs11.08-17.07, En36.69-47.85). Orthopyroxene phenocrysts exhibit a reverse zoning with iron rich cores and more magnesian rims. The reverse zoning in the inclusions can be attributed to changing oxidation estates during crystallization in andesitic rocks. This and other mineralogical and petrological analyses urge us to believe that the igneous inclusions are cogenetic with the host andesite and we conclude that at the time of mingling, due to the vigorous convection, andesitic inclusions incorporated some of the phenocrysts from the host andesitic magma while other phenocrysts remained in the host magma. Therefore, magma mixing is considered as the main cause for the observed disequilibrium in textures as well as in the composition of mineral phases in the the Kuhe-Langar andesitic rock.