Compositional variations and heterogeneity in fertile lithospheric mantle: peridotite xenoliths in basalts from Tariat,Mongolia |
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| Authors: | Dmitri A Ionov |
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| Institution: | (1) LTL, UMR-CNRS 6524, Département de Géologie, Université J. Monnet, 23 rue P. Michelon, 42023 Saint-Etienne Cedex 2, France;(2) Max-Planck-Institut für Chemie, Postfach 3060, 55020 Mainz, Germany;(3) School of Earth Sciences, Macquarie University, Sydney, Australia |
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| Abstract: | Clinopyroxene-rich, poorly metasomatised spinel lherzolites are rare worldwide but predominate among xenoliths in five Quaternary
basaltic eruption centres in Tariat, central Mongolia. High-precision analyses of the most fertile Tariat lherzolites are
used to evaluate estimates of primitive mantle compositions; they indicate Mg#PM = 0.890 while lower Mg# in the mantle are likely related to metasomatic enrichments in iron. Within a 10 × 20 km area, and
between ~45 and ≥60 km depth, the sampled xenoliths suggest that the Tariat mantle does not show km-scale chemical heterogeneities
and mainly consists of residues after low-degree melt extraction at 1–3 GPa. However, accessory (<1%) amphibole and phlogopite
are unevenly distributed beneath the eruption centres. Ca abundances in olivine are controlled by temperature whereas Al and
Cr abundances also depend on Cr/Al in coexisting spinel. Comparisons of conventional and high-precision analyses obtained
for 30 xenoliths show that high-quality data, in particular for whole-rocks and olivines, are essential to constrain the origin
of mantle peridotites.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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| Keywords: | Peridotite xenolith Spinel lherzolite Major elements Mantle heterogeneities Primitive mantle |
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