Biotite as a recorder of an exsolved Li-rich volatile phase in upper crustal silicic magma reservoirs

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00025798%3A_____%2F22%3A00000031" target="_blank" >RIV/00025798:_____/22:00000031 - isvavai.cz</a>

Výsledek na webu

<a href="https://pubs.geoscienceworld.org/gsa/geology/article/50/4/481/611422/Biotite-as-a-recorder-of-an-exsolved-Li-rich" target="_blank" >https://pubs.geoscienceworld.org/gsa/geology/article/50/4/481/611422/Biotite-as-a-recorder-of-an-exsolved-Li-rich</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1130/G49484.1" target="_blank" >10.1130/G49484.1</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Biotite as a recorder of an exsolved Li-rich volatile phase in upper crustal silicic magma reservoirs

Popis výsledku v původním jazyce

The magmatic-hydrothermal transition is key in controlling the fate of many economically important elements due to the change in partitioning when melt and magmatic fluid co-exist. Despite its increasing economic importance, the behaviour of lithium (Li) in such environments remains poorly known. Here we illustrate how compositionally unusual biotites from the rhyolitic Bishop and Kos Plateau tuffs may contain a magmatic volatile phase trapped between layers of biotite crystals. Despite originating in pristine deposits, and showing the expected XRD spectra, these biotites return low (< 95 wt.percent) analytical totals via electron microprobe (EMP) consistent with the presence of considerable amounts of light elements (non-measurable by EMP). Lithium contents and isotope ratios in these biotites are remarkable with abundances reaching >2,300 ppm and exceptionally light Li isotopic compositions (delta7Li as low as -27.6per mille) and large isotopic fractionation between biotite and corresponding bulk samples (D7Libt–bulk as low as -36.5per mille). Other mineral phases, groundmass glass, and melt inclusions from the same units do not support an extremely Li-rich melt prior to eruption. Biotites from phonolitic systems (Tenerife and Campi Flegrei) do not show such extreme compositional differences with biotite and melt showing roughly equivalent Li contents, underscored by significantly reduced D7Libt–bulk to a maximum of -10.9per mille. We ascribe the difference in behavior to the near liquidus appearance of biotite in alkaline magmatic suites, before widespread exsolution of a magmatic volatile phase in the magma reservoir, while in rhyolitic suites, biotite crystallises at low temperature, trapping the co-existing exsolved fluid phase in the reservoir.

Název v anglickém jazyce

Biotite as a recorder of an exsolved Li-rich volatile phase in upper crustal silicic magma reservoirs

Popis výsledku anglicky

The magmatic-hydrothermal transition is key in controlling the fate of many economically important elements due to the change in partitioning when melt and magmatic fluid co-exist. Despite its increasing economic importance, the behaviour of lithium (Li) in such environments remains poorly known. Here we illustrate how compositionally unusual biotites from the rhyolitic Bishop and Kos Plateau tuffs may contain a magmatic volatile phase trapped between layers of biotite crystals. Despite originating in pristine deposits, and showing the expected XRD spectra, these biotites return low (< 95 wt.percent) analytical totals via electron microprobe (EMP) consistent with the presence of considerable amounts of light elements (non-measurable by EMP). Lithium contents and isotope ratios in these biotites are remarkable with abundances reaching >2,300 ppm and exceptionally light Li isotopic compositions (delta7Li as low as -27.6per mille) and large isotopic fractionation between biotite and corresponding bulk samples (D7Libt–bulk as low as -36.5per mille). Other mineral phases, groundmass glass, and melt inclusions from the same units do not support an extremely Li-rich melt prior to eruption. Biotites from phonolitic systems (Tenerife and Campi Flegrei) do not show such extreme compositional differences with biotite and melt showing roughly equivalent Li contents, underscored by significantly reduced D7Libt–bulk to a maximum of -10.9per mille. We ascribe the difference in behavior to the near liquidus appearance of biotite in alkaline magmatic suites, before widespread exsolution of a magmatic volatile phase in the magma reservoir, while in rhyolitic suites, biotite crystallises at low temperature, trapping the co-existing exsolved fluid phase in the reservoir.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10505 - Geology

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2022

Kód důvěrnosti údajů

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

Název periodika

Geology

ISSN

0091-7613

e-ISSN

—

Svazek periodika

50

Číslo periodika v rámci svazku

4

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

5

Strana od-do

481-485

Kód UT WoS článku

000752199400001

EID výsledku v databázi Scopus

2-s2.0-85127926016