AMPHIBOLE-PHLOGOPITE XENOLITHS FROM KIMBERLITES AS EVIDENCE OF METASOMATIC PROCESSES IN THE LITHOSPHERIC MANTLE BENEATH KUOIKA FIELD

This paper devoted to the mantle xenoliths with evidence of modal metasomatic alteration from the Obnazhennaya kimberlite pipe (Kuoika kimberlite field). The first data presents for trace elements content in minerals from such rocks, and they are compared with xenoliths from this pipe having no evidence of modal metasomatism. Based on the trace elements content in clinopyroxene and amphibole, as well as 40Ar/39Ar dating of phlogopite, it was concluded that enriched in Nb+Ta and REE melt-fluids were formed beneath the Kuoika field in the Lower Proterozoic, which lead to the phlogopite-amphibole formation from pyroxene.