The effect of diffusive re-equilibration time on trace element partitioning between alkali feldspar and trachytic melts

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11310%2F18%3A10382170" target="_blank" >RIV/00216208:11310/18:10382170 - isvavai.cz</a>

Result on the web

<a href="https://doi.org/10.1016/j.chemgeo.2018.07.035" target="_blank" >https://doi.org/10.1016/j.chemgeo.2018.07.035</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.chemgeo.2018.07.035" target="_blank" >10.1016/j.chemgeo.2018.07.035</a>

Result language

angličtina

Original language name

The effect of diffusive re-equilibration time on trace element partitioning between alkali feldspar and trachytic melts

Original language description

We present new experimental data on major and trace element partition coefficients between alkali feldspar and trachytic melt. Experiments were conducted at 500 MPa, 870-890 degrees C to investigate through short disequilibrium and long near-equilibrium experiments the influence of diffusive re-equilibration on trace element partitioning during crystallization. Our data show that Ba and Sr behave compatibly, and their partition coefficients are influenced by re-equilibration time, orthoclase (Or) content, growth rate and cation order-disorder. High field strength elements (HFSE) and rare earth elements (except Eu) are strongly incompatible, but alkali feldspar efficiently fractionates light (LREE) from heavy rare earth elements (HREE). Our crystallization experiments reveal a strong influence of disequilibrium crystal growth on the partitioning of Ba and Sr. In particular, short-duration experiments show that rapid alkali feldspar crystal growth after nucleation, promotes disordered growth and less selectivity in the partitioning of compatible trace elements that easily enter the crystal lattice (e.g., Ba and Sr). This produces partition coefficients of compatible elements higher than those obtained through long-duration experiments, in which growth is slower and more selective. On approach to equilibrium, decreasing growth rate and timescales of diffusive re-equilibration facilitates the incorporation of compatible elements within the crystal lattice (through ordered growth), on the basis of the charge and size of the octahedral site, resulting in lower partition coefficients of Ba and Sr. Therefore, our results indicate that besides crystal-chemical effects, i.e. lattice strain, the substitution mechanisms during growth (with different degrees of ordering) of Ba and Sr in alkali feldspar are strongly influenced by diffusive re-equilibration and crystal growth kinetics. This implies that partition coefficients of Ba and Sr can be used to establish timescales of crystallization processes under pre- and syn-eruptive conditions. The application of our results to alkali feldspar in rocks from Campi Flegrei, constrain the magma residence time at subliquidus conditions in a reservoir to a maximum of 6 days under disequilibrium conditions and to a minimum of 9 days upon approaching near-equilibrium conditions.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10505 - Geology

Project

<a href="/en/project/GA18-01982S" target="_blank" >GA18-01982S: Experimental determination of the effect of oxygen fugacity on mineral/melt partitioning for the Highly Siderophile Elements at mantle conditions</a><br>

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2018

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Chemical Geology

ISSN

0009-2541

e-ISSN

—

Volume of the periodical

495

Issue of the periodical within the volume

SEP 2018

Country of publishing house

NL - THE KINGDOM OF THE NETHERLANDS

Number of pages

17

Pages from-to

50-66

UT code for WoS article

000442381800005

EID of the result in the Scopus database

2-s2.0-85051662785