Element partitioning between carbonates and high-pressure phases in mafic and ultramafic C-O-H bearing systems
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Data di Pubblicazione:
2012
Citazione:
Element partitioning between carbonates
and high-pressure phases in mafic and
ultramafic C-O-H bearing systems / C. Tiraboschi, S. Tumiati, P. Fumagalli, J.F. Molina, E. Franzolin, S. Poli. ((Intervento presentato al 14. convegno International Conference on Experimental Mineralogy Petrology Geochemistry tenutosi a Kiel nel 2012.
Abstract:
Element partitioning between carbonates and coexisting
high pressure phases plays a critical role in
unravelling petrogenetic processes of eclogitic rocks,
peridotites, diamond-bearing rock suites, and carbonatitic
magmas. Experiments were carried out
on MORB and lherzolitic bulk compositions, from
gel starting materials, using piston-cylinder and
multianvil machines at P from 1 to 6 GPa and T
from 650 C to 1050 C, in the presence of C-O-H fluids
generated from starting mixtures of oxalic acid
dihydrate and silver oxalate. fH2 was buffered at
NNO, OH (X, COH) and hematite-magnetite HM,
OH (X, COH) buffers using a double capsule technique
(notation after [1]). Although element partitioning
is examined in synthesis experiments and
reversals are hindered by low-reactivity of starting
materials composed of crystalline mixtures, excellent
T-P correlation of Mg/Fe partitioning between
garnet and pyroxenes reveals approach to equilibrium
conditions in both mafic and ultramafic systems.
New results were integrated with a dataset from
other high-pressure synthesis experiments recently
published on carbonate-bearing mafic and ultramafic
systems. A significant temperature dependence
of Ca-Mg exchange reactions and the negative
correlation of lnKFeMg vs. 1/T between
Ca-carbonate and garnet allow formulating thermometric
expressions suitable for the estimation
of equilibrium crystallization temperatures in a variety
of bulk compositions. Differences between
mafic and ultramafic systems will be highlighted.
Comparison with element partitioning predicted by
thermodynamic calculations will also be shown.
[1] Eugster & Skippen, 1967, Res. Geochem. 2, 492–526.
Tipologia IRIS:
14 - Intervento a convegno non pubblicato
Elenco autori:
C. Tiraboschi, S. Tumiati, P. Fumagalli, J.F. Molina, E. Franzolin, S. Poli
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