Geochemistry of Talkh-rud Sub-volcanic Intrusion, Damavand Volcano

The study subvolcanic intrusion, comprising syenodiorite, monzonite and quartz-monzonite, is cropped out in Talkh-rud valley located in the northeast of Damavand volcano flank. This sub-volcanic intrusion possesses porphyritic texture and consists of plagioclase, alkali feldspar, phelogopite, amphibole, clinopyroxene, apatite and titanomagnetite. Evidences of disequilibrium such as zoning and sieve textures in plagioclase and opacity of phlogopite crystals could be due to variations in water vapor pressure during magma ascent. The intrusion is geochemically metaluminous, alkaline and shoshonitic and tectonically plots in the realm of within plate volcanics. Normalized to the chondrite and primary mantle multi elemental spider diagrams show enrichment of LREE and LILE and depletion of HREE and HFSE such as Ti, Nb. Comparison of these rocks with their extrusive counterparts, i.e., trachy-andesites and trachytes of Damavand shows no significant difference between the geochemistry and mineralogy.