MANTLE EVOLUTION FROM ARCHAEN TO PALEOPROTEROZOIC: SYNTHESIS OF TRACE ELEMENT AND Nd ISOTOPIC DATA ON MAFIC ASSOCIATIONS FROM SOUTH-WESTERN SIBERIAN CRATON

Abstract

Based on trace element and Nd isotopic data on Early Precambrian mafic rocks, we traced the evolution of the mantle of the SW Siberian craton from the Archean to Paleoproterozoic. The sources of the Archean mafic rocks varied from weakly depleted to primitive mantle, i.e. the Archean mantle was less differentiated than modern one. From 2.8-2.7 Ga, it is assumed an existence of a metasomatically altered lithospheric mantle. The trace element and isotopic parameters of Paleoproterozoic mafic rocks reflect an increase in mantle heterogeneity and the formation of long-lived enriched sources. From the Archean to the Paleoproterozoic, the mantle differentiated in terms of trace element and Nd isotopic composition, due to separation and local metasomatism of the subcontinental lithospheric mantle.