Mantle Metasomatism Recorded in Phlogopite: Compositional Indicators from Kimberlites and Inclusions in Diamonds

Abstract Phlogopite is an important hydrous silicate that is the primary indicator of modal mantle metasomatism. The review presents a comprehensive analysis of a dataset of phlogopite compositions from mantle xenoliths in kimberlite and inclusions in natural diamonds. Variations in major- and minor- element contents are examined in relation to mineral parageneses and geodynamic settings, spanning lherzolitic and harzburgitic peridotites, eclogitic assemblages, and phlogopite-bearing metasomatites. Systematic trends in Mg#, Ti, Cr, Al contents record two main pathways: metasomatic overprinting of mantle material and contribution of crust-derived material. Mantle metasomatism tends to diminish compositional differences between micas in peridotitic and eclogitic xenoliths. The compiled dataset demonstrates that the phlogopite composition can be used as a petrogenetic and geodynamic tracer of mantle processes beneath kimberlite provinces. Examples from peridotitic and eclogitic inclusions in diamonds, mantle xenoliths, and phlogopite-bearing metasomatites underscore the diagnostic value of such approach for reconstruction of the evolution of volatile-rich mantle domains and identification of their role in kimberlite and related magmatism.