روابط صحرایی، ژئوشیمی و خاستگاه ژئودینامیکی نهشته‌ی کرومیتی معدن بندان (شرق ایران)

The Bandan chromite mine is the main chromite deposit in Sistan suture zone, eastrn Iran. The chromite deposits are structurally tabular to lens-shaped bodies hosted by dunitic to harzburgitic mantle peridotites. Similar to Alpine type podiform chromites, chromitite pods are enclosed within dunitic envelops. The chromites show mainly massive to disseminated and also brecciated textures. Chemically, the Cr/Fe ratio is higher than 2 and TiO2 content in accordance with ophiolitic chromites is low (< 0.2 wt. %). As a result of low Cr# (Cr#=Cr×100/(Cr+Al)) ranging from 50 to 52 the Bandan chromite deposit is high-Al type. Calculated parental melt chemistry shows MORB (Mid-ocean ridge basalt)-type signature with Al2O3 and FeO/MgO ratio contents of 15-16 and 1.1-1.2, respectively. Although the geodynamic setting of high-Al podiform chromites have been debated but petrographical- geochemical characteristics of ophiolitic mantle-crust sequences may relate chromite genesis to supra subduction zone setting.