European Geosciences Union General Assembly 2015 - Garnet Classification
Conclusions
GEOSCIENCES UN
EUROPEAN OF
General
Assembly
2015
The studying of the geochemical composition of Gar and Cpx form the mantle peridotite
xenoliths suggests evolution of the metasomatic agent from early protokimberlitic melts with
high carbonate contents to later more silicate kimberlitic melts:
1. Early (protokimberlitic) high-T melts:
enriched in LREE and Fe-Ti (HFSE);
high carbonate/silicate ratio within the
evolutionary increasing silicate components to
megacryst equilibrium melt composition;
✰ were existed before the crystallization of the
megacryst assemblage (garnet,
clinopyroxene, olivine, spinel, ilmenite);
probably were formed by melting of
carbonated peridotite mantle source.
crystallisation
of megacrysts..
accumulation
kimberlite melts
forming the first
parts of proto-
kimberlite melt
IV
M
2
2.
Amell percolation
through mantle
column
carbonate
component
decreasing
Later (kimberlitic) low-T melts
depleted in Fe-Ti and low
carbonate/silicate ratio;
✰ were existed after the crystallization of the
megacryst assemblage (garnet,
clinopyroxene, olivine, spinel, ilmenite);
could be metasomatic agent for peridotite
xenoliths of III, IV, V groups where the
different C1-normalized REE patterns
("sinusoidal" and "normal") may be
explained by the model of melt injection
and percolation through a refractory
mantle column.
lithosphere
asthenosphere
carbonate veins in
the lithospheric
mantle
1
melting of
carbonated
peridotite source
ascent of asthenosphere
material
CC
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