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

Kód výsledku v 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>

Výsledek na webu

<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>

Jazyk výsledku

angličtina

Název v původním jazyce

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

Popis výsledku v původním jazyce

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.

Název v anglickém jazyce

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

Popis výsledku anglicky

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.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10505 - Geology

Projekt

<a href="/cs/project/GA18-01982S" target="_blank" >GA18-01982S: Experimentální určení vlivu fugacity kyslíku na distribuci vysoce siderofilních prvků mezi minerály a taveninu v plášťových podmínkách</a><br>

Návaznosti

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

Rok uplatnění

2018

Kód důvěrnosti údajů

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

Název periodika

Chemical Geology

ISSN

0009-2541

e-ISSN

—

Svazek periodika

495

Číslo periodika v rámci svazku

SEP 2018

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

17

Strana od-do

50-66

Kód UT WoS článku

000442381800005

EID výsledku v databázi Scopus

2-s2.0-85051662785