Publication Date:
2021-04-07
Description:
Magma generation in the Ross Sea system is related to partial melting of strongly
metasomatised mantle sources where amphibole most probably plays a crucial role. In this
context, metasomatism induced by a mela-nephelinite melt in lithospheric mantle of the Mt.
Melbourne Volcanic Province (northern Victoria Land – NVL, Antarctica) was investigated
experimentally studying the effects of melt interaction with lherzolite at 1.5-2.0 GPa and
T=975-1300°C, and wehrlite at 1.0 GPa and T=1050-1250°C. The experiments were
designed to induce melt infiltration into the ultramafic rocks. The observed modifications in
minerals are compared with those found in mantle xenoliths from NVL. The effects of
metasomatic modifications are evaluated on the basis of run temperature, distance from the
infiltrating melt and on the diffusion rates of chemical components. Both in lherzolite and
wehrlite, clinopyroxene exhibits large compositional variations ranging from primary
diopside to high Mg-Cr-(Na) augitic and omphacitic clinopyroxenes in lherzolite, and to
low Mg and high Ti-Al-Fe-Na augites in wehrlite. Olivine (in wehrlite) and spinel (in
lherzolite) also result compositionally modified, the former shows enrichments in Fe, the
latter displays a higher Cr/(Cr+Al) ratio. The systematic variations in mineral compositions
imply modifications of the chemistry of the infiltrating melt as recorded by the glass
veinlets and patches observed in some charges. In experiments involving wehrlite
paragenesis, the glass composition approaches that of melt patches associated to both
amphibole-free and amphibole-bearing natural samples, and is related to
olivine+clinopyroxene crystallisation coupled with primary clinopyroxene dissolution at the
contact between the metasomatising melt and the solid matrix. Even if amphibole
crystallisation was not attained in the experiments, we were able to explain the occurrence
of amphibole in the natural system considering that in this case a hot metasomatising melt
infiltrates a cooler matrix.
Description:
Published
Description:
279-302
Description:
2.3. TTC - Laboratori di chimica e fisica delle rocce
Description:
N/A or not JCR
Description:
open
Keywords:
Mantle
;
metasomatism
;
lherzolite
;
wehrlite
;
melt-rock reaction experiments
;
04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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