Mantle metasomatism vs host magma interaction

the ongoing controversy

Costanza Bonadiman, M. Coltorti, Luigi Beccaluva, Franca Siena

Research output: Contribution to journalMeeting abstract

Abstract

Mantle-derived xenoliths brought up to surface by
intraplate magmatism, are an essential source of information
about the nature and evolution of mantle. Since the Seventies
they are considered from the scientific community precious
material to study the processes affecting the mantle domain
that they represent, particularly mantle metasomatism.
However, on the basis of major element compositions of the
phases, recent studies contrast the efficacy of this approach in
studying the state of the mantle, concluding that most of the
metasomatic textures which include alkali-silicate glasses are
erroneous interpreted as effects of mantle metasomatism. They
are instead interpreted as textures imposed on the xenoliths
during magma transport and/or residence in a magma
chamber. The most common features of metasomatised
mantle-derived xenoliths are the occurrence of spongy texture
of the peridotitic minerals, frequently associated with glassy
patches. Various explanations on their possible origin have
been proposed on the basis of heterogeneous geochemical data
set. They include: i) fluid-induced melting at mantle depths; ii)
reactions induced by the influx of exotic melts into the
lithospheric mantle and iii) interaction with host magma
during the transport. The goal of this contribution is to
reinforce the worth of studying mantle metasomatism
analyzing mantle xenoliths, taking into account that the
interaction between host lavas and mantle xenoliths exists and
sometimes masquerades the processes occurring at mantle
depth. To pursue this, it is important to find geochemical
criteria to discriminate such processes in relation to the mode
of formation of the most common metasomatic textures. In
order to carry out modeling for geochemical discriminates, we
use a selected group of mantle xenoliths from Cape Verde
Island, which clearly show textural and geochemical features
which can be related to metasomatic modifications at mantle
depth. We propose an approach which include not only interand
intra-major element compositions of minerals, but, most
relevant, trace element and isotopic compositions in primary
and “metasomatic” minerals and glasses, which provide a
robust geochemical tool to efficiently investigate the mantle
metasomatism behind the possibly curtain of the host lava
interaction.
Original languageEnglish
Pages (from-to)A95-A95
Number of pages1
JournalGeochimica et Cosmochimica Acta
Volume72
Issue number12, Supplement
DOIs
Publication statusPublished - Jul 2008
Externally publishedYes
EventGoldschmidt Conference (18th : 2008) - Vancouver, Canada
Duration: 13 Jul 200818 Jul 2008

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