Petrology and mineral chemistry of serpentinized peridotites in the south of Bavanat (Fars Province)

The studied area is located in the high Zagros zone and it is considered a part of the Neyriz ophiolite. In this area, the ophiolitic complex is a small coloured melange including radiolarite cherts and serpentinized peridotite rocks. The peridotite rocks are mostly serpentinized harzburgite. The peridotite rocks are mostly serpentinized harzburgite. These rocks composed mainly of olivine, pyroxene, serpentine and spinel, where olivines have been strongly altered to serpentine and pyroxenes to bastite. So, serpentine group minerals are seen in abundance in these rocks. Also, spinel is found in amorphous and amoebic shape in these rocks. Based on mineral chemistry, serpentines are in the range of stability of all three mineral phases, i.e. lizardite, chrysotile and antigorite, and the range of pseudomorphic serpentinites, which shows they are the result of the regressive replacement of olivine and pyroxene with serpentines. Also, these minerals are mostly located in Ol-mesh and Cpx bastite ranges, which shows they are the result of regressive metamorphism of harzburgite and dunite rocks. The spinels are Cr- spinel and pleonaste type. These Cr spinels are ophiolitic type and have residual nature. The low TiO2 and the enrichment of these spinels from Cr is similar to spinel in fore-arc harzburgites. Also, these spinels, in addition to having the characteristics of alpine peridotites, are placed in the overlapping range between suprasubduction (SSZ) and abyssal peridotites. So, the studied serpentinized peridotites are formed from high degrees of partial melting (25-30%) of a depleted mantle in a suprasubduction (SSZ) - fore-arc setting.