Comparison of the Compositions of Clinopyroxenes, Garnets, and Spinels from Mantle and 'Crustal' Peridotites of Collisional High-Pressure/Ultrahigh-Pressure Zones

摘要

Ultrabasic rocks in collisional belts of high and ultrahigh pressures may provide important petrological information. Among these rocks in Phanerozoic orogenic zones there are peridotites, which may be divided into mantle and "crustal" by the genetic sign [1]. The first ones were intruded as tectonic fragments of restite mantle to the deeply subducted lithosphere. They preserved all geochemical signs of rocks of mantle origin being characterized by high concentrations of MgO, low concentrations of FeO, MnO, and A1_2O_3, and relatively enriched in rare elements such as Cr and Ni and depleted in REE, Zr, Y, and Nb [2].