Evolution history of north Anarak, Central Iran ophiolitic olistoliths using petrographical and mineral chemistry studies

Abstract

The Anarak ophiolite is formed along with the tectonic evolution of the Paleo-Tethys Ocean and Paleozoic, in which consists of meta-peridtites of mantle and crust, cumulate rocks, massive gabbros, pillow lava, basic and ultrabasic dikes, rodaingite and listwanite that all covered by schist and marble units. The olistolithic patches of the Anarak ophiolite have commonly exposed in Sebarz schist, within the sole of Chah-Gorbeh complex. Olistoliths composed of listwanite, meta-mafic, serpentinite and meta-peridotite olistoliths that vary from centimeter to several hundred meters, in size. Results of electron microprobe analyses shows that the fundamental rock-forming minerals of the listwanitized olistoliths are composed of chromian spinel and pyroxene, secondary minerals include calcite, garnet, tremolite, cholorite, magnetite and opaque minerals. Meta-mafic olistoliths composed of chromian spinel, sphene, epidote, chlorite and opaque minerals; Serpentinity olistoliths composed of chromian spinel, magnetite, tremolite, talc and chlorite. It also shows that the meta-peridotite olistoliths composed of chromian spinel, chrom-bearing magnetite, chlorite, calcite, garnet and antigorite. Based on the geochemical analyses, Cr# in the listwanite patches, meta-mafic, serpentinite and meta-peridotite olistoliths are 87.40-97.92, 49.38-51.89, 49.22-60.05 and 29.76-55.97 respectively with very low amount of TiO2. The very chemical composition of minerals in the North Anarak complex shows different petrogenesis for ophiolitic olistoliths suggests characteristic of the MORB and/or supra-subduction zone.