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Abstract

A variety of xenoliths from the lower crust to mantle transition occur in Quaternary mafic intraplate lavas of the Bayuda volcanic field of northern Sudan. The lower-crust xenoliths include plagioclase- and garnet-bearing mafic granulite. Ultra-mafic garnet-bearing pyroxenite, websterite, hornblendite, and distinct peridotite xenoliths are from the upper lithospheric mantle. Sr, Nd, and Pb isotope signatures distinguish between ultramafic and granulite xenoliths. The latter show a strong compositional affinity to juvenile Neoproterozoic crust. The Pb isotope composition of the ultramafic xenoliths resembles the distinct high-μ signature (206Pb/204Pb >19.5) of their host basanite. These xenoliths may represent cumulates of late Mesozoic to Quaternary mafic intraplate magmatism. The felsic upper crust in a schematic lithospheric profile of the Bayuda area includes predominantly granitoids, migmatites, and metasedimentary rocks that represent reworked old cratonic or juvenile Neoproterozoic rocks. The deep lower crust is represented by mafic granulite, likely cumulate rocks from Neoproterozoic juvenile magmatism. The crust-mantle transition is characterized by ultramafic cumulate rocks possibly from the late Mesozoic to Quaternary magmatism. The peridotites of the same xenolith suites represent typical lithospheric mantle with variable degrees of depletion by melt extraction.