Publication Date:
2017-04-04
Description:
Igneous garnets have the potential to
strongly fractionate rare earth elements (REE). Yet
informations on partition coefficients are very scant,
and criteria for distinguishing between hydrothermal
and magmatic garnets are ambiguous. To fill this gap,
we present trace element and isotopic data for two
types of Ca-rich garnets from phonolites (Mt. Somma-
Vesuvius). Both Ca-garnet populations are different in
their style and dynamics of fractionation: one population
is progressively strongly depleted in HREE from
core to rim, reflecting REE fractionation in the host
phonolite via earlier-crystallized garnets. Such examples
for extreme changes in HREE in garnets are only
known for hydrothermal grandites by REE-bearingfluids. The second garnet population is homogeneous
and formed in a closed system. Near-flat patterns between
Sm and Lu confirm experimental data indicating
lower D(Sm)/D(Lu) for Ca-rich garnets than for e.g.
pyrope-rich garnets. It follows: DGrt/PhMelt for La = 0.5,
Sm = 48 and Yb = 110.
Description:
Published
Description:
55-74
Description:
2.3. TTC - Laboratori di chimica e fisica delle rocce
Description:
3.5. Geologia e storia dei sistemi vulcanici
Description:
JCR Journal
Description:
reserved
Keywords:
Grandite
;
Ca-rich garnets
;
Andradite
;
Rare earth elements
;
Fractionation
;
Partition coefficient
;
04. Solid Earth::04.04. Geology::04.04.07. Rock geochemistry
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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