Garnet as indicator of the protolith type of UHP-peridotites from Marun-Keu complex (Polar Urals, Russia)

Mantle and crustal peridotites contain principally different petrogenetic information. The former characterize composition and thermodynamic conditions of mantle restitic material emplaced into the crust, the latter reflect multistage metamorphic evolution of crustal magmatic protoliths. Chemical peculiarities of garnet from garnet peridotites of Marun-Keu UHP-complex from Polar Urals (N. Russia) in comparison with garnet from crustal and mantle peridotites of different collision zones were study. The relic areas of plagioclase-bearing protoliths in garnet peridotite bodies of Marun-Keu Complex are obvious evidence of their crustal low pressure origin. The composition of garnet from Marun-Keu UHP-ultramafics is similar to crustal UHP-peridotites of collision zones of N. Kazakhstan, W. Norway, N.-W. China and E. China. Thermobarometric comparison showed that PT-conditions are not the reason of chemical differences of peak garnets from two genetic types of peridotites. Multiple chemical composition of peak metamorphic garnets as a function of petrochemical composition of peridotites can be used as indicator of crustal/mantle genesis of ultramafics in UHP-collision zones.