On the Origin of Diamond in Eclogites of the Maksyutov Complex

Abstract

Progressive metamorphism of the Maksyutov eclogite-blueschist (MC) complex (Southern Urals) does not reach the stability range of ultra-high-pressure (UHP) index minerals – diamond and coesite – in its PT parameters. Their origin is associated with the tectonic intrusion of deep mantle-crustal inclusions into the terrigenous-schist strata of mafic rocks of the terrane at the peak of its subduction. Testing and validation of the latest “Subduction Initiation Rule” concept revealed that the age and PT parameters of the complex’s subduction processes and the metamorphism of its rocks do not coincide with the conditions and timing of the ascent of the mantle-crustal plume containing diamond-bearing blocks of deep matrix inclusions. Therefore, the UHP status of the origin of diamond and coesite during prograde metamorphism cannot be considered valid, nor can the UHP status of the Maksyutov Complex be considered valid