Mineral chemistry and geothermobarometry of xenoliths within Peliocene volcanic rocks from the Ghikhlar area (Northwest of Marand, NW Iran)

The study area is located at the Mishow mountain ranges in NW Marand town. The main outcropping rocks are Pliocene volcanic and volcaniclastic rocks. Lamprophyre, mica pyroxenite, amphibolite and carbonate rocks occure as xenoliths within andesites. The main rock forming minerals for lamprophyre xenolith are coarse grained biotite, clinopyroxene and rare plagioclase within a matrix composed of the same crystals with porphyric and hyaloporphyric textures. These can be classified as kersantite. Mica pyroxenite xenolith is composed of clinopyroxene, biotite, plagioclase, (±) hornblende and opaque phases. Plagioclase, clinopyroxene as well as rare amphibole and biotite are seen as scattered magmatic crystals within carbonate matrix in the carbonate xenolith. On the basis of mineral chemistry of clinopyroxene, magma nature for the lamprophyre and mica pyroxenite xenoliths has been detremined as calc-alkaline. Clinopyroxene composition indicates high fugacity of oxygen for lamprophyre and mica pyroxenite xenoliths. The estimated temperatures are 1100C-1200C, 1080C-800C for mica pyroxenite and lamprophyre respectively at pressures of 5-10 kbar. The pressure and temperature of amphibolite xenolith have been estimated based on amphibole geothermobarometer as 750-800 (±12oC) and 6.2±0.6 kbar, respectively.