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The effect of H (sub 2) O on F and Cl solubility and solution mechanisms of in aluminosilicate melts at high pressure and high temperature

Celia Dalou and Bjorn O. Mysen
The effect of H (sub 2) O on F and Cl solubility and solution mechanisms of in aluminosilicate melts at high pressure and high temperature
American Mineralogist (2015) 100 (2-3): 633-643

Abstract

Effects of H (sub 2) O on the solution behavior of fluorine and chlorine in peralkaline sodium aluminosilicate glasses quenched from melts at high temperature (1400 degrees C) and pressure (1.5 GPa) were studied by combining solubility measurements and Raman spectroscopy. With increasing H (sub 2) O content from 0 to approximately 10 wt%, the fluorine solubility increases from 3.3 to 4.4 mol% in Al-free glasses and from 6.3 to 9.3 mol% in Al-rich glasses (10 mol% Al (sub 2) O (sub 3) ). In contrast, in the same H (sub 2) O concentration range the chlorine solubility decreases from 5.7 to 3.4 mol% in Al-free glasses and from 3.6 to 1.7 mol% in Al-rich glasses.In Al-free glasses, interaction between H (sub 2) O and the silicate to depolymerize the network is Q (super 4) + H (sub 2) O <--> Q (super 2) (H) and Q (super 3) + H (sub 2) O <--> Q (super 2) (H). The effect of water on silicate melt structure is different in halogen-bearing melts because in hydrous melt systems both F and Cl can act to depolymerize the melt further. For fluorine, this is accomplished via formation of Si-F, Al-F, and Na-F bonding in addition to Si-OH, whereas in chlorine-bearing hydrous melts, there is no interaction between Si (super 4+) and Cl (super -) . The halogen solubility in the magmatic liquid influences mineral/melt partition coefficients of chlorine and fluorine and implies partition coefficients different from unity. Moreover because of the contrasting effects of H (sub 2) O on fluorine and chlorine solubility, the Cl/F ratio in magmas formed in water-rich environments such as subduction zones can be a sensitive indicator of H (sub 2) O content during arc magmas genesis. Transport properties of melts, such as diffusion and viscosity, also vary differently in halogen-bearing hydrous melts compared with halogen-free systems. Moreover, those effects on melt properties are the strongest in F-bearing systems.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 100
Serial Issue: 2-3
Title: The effect of H (sub 2) O on F and Cl solubility and solution mechanisms of in aluminosilicate melts at high pressure and high temperature
Affiliation: Carnegie Institution of Washington, Washington, DC, United States
Pages: 633-643
Published: 2015
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 53
Accession Number: 2015-024174
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201512
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