high-pressure marbles from the nahavand area in the sanandaj-sirjan metamorphic belt, iran

marbles containing high-pressure mineral assemblage was found from the sanandaj-sirjan metamorphic belt in the nahavand area in western iran.  the high-pressure marbles occur as small bodies or lenses within pelitic schist layers and show compositional banding of carbonate- and silicate- rich bands.  textural analysis revealed two metamorphic stages.  the early stage is testified by relicts of the minerals such as rounded jadeite-bearing diopside, epidote (clinozoisite), amphibole 1 (pargasite-edenite) and titanite 1. the second stage (main stage) documented to have phlogopite, chlorite, amphibole 2 (tremolite) and titanite 2. p-t-xco2 estimates for the early stage of metamorphism give an average pressure, temperature and xco2 of 13.5 kbar, 670 ºc and 0.35, whereas the second stage has been constrained at p=3.8 kbar, t=500 ºc and xco2=0.45.  the high-pressure mineral assemblage documented in the nahavand area, were formed during the subduction stage, while the second metamorphic blastesis were recorded during the exhumation event.