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Experimental partitioning of fluorine and barium in lamproites

Isra S. Ezad and Stephen F. Foley
Experimental partitioning of fluorine and barium in lamproites
American Mineralogist (November 2022) 107 (11): 2008-2019

Abstract

The dynamic properties and melting behavior of the Earth's mantle are strongly influenced by the presence of volatile species, including water, carbon dioxide, and halogens. The role that halogens play in the mantle has not yet been fully quantified: their presence in only small quantities has dramatic effects on the stability of mantle minerals, melting temperatures, and in generating halogen-rich melts such as lamproites. Lamproites are volumetrically small volcanic deposits but are found on every continent on the planet: they are thought to be melts generated from volatile-rich mantle sources rich in fluorine and water. To clarify the mantle sources of lamproites, we present experimentally determined mineral/melt partition coefficients for fluorine and barium between phlogopite and lamproite melts. Both fluorine and barium are compatible in phlogopite [D (sub F) (super (Phl/Melt)) 0.96 + or - 0.02 - 3.44 + or - 0.33, D (sub Ba) (super (Phl/Melt)) 0.52 + or - 0.05 - 3.68 + or - 0.43] at a range of pressures (5-30 kbar), temperatures (1000-1200 degrees C), and fluid compositions (C-O-H mixtures). Using our partition coefficients, we model the melt compositions produced by potential lamproite sources, including phlogopite garnet lherzolite, phlogopite harzburgite, and hydrous pyroxenite. The results demonstrate that hydrous pyroxenites and phlogopite garnet lherzolite can produce melts with F and Ba contents similar to lamproites, but only hydrous pyroxenites fully reproduce other geochemical characteristics of lamproites including high K (sub 2) O, low CaO contents, and high F/H (sub 2) O ratios.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 107
Serial Issue: 11
Title: Experimental partitioning of fluorine and barium in lamproites
Affiliation: Macquarie University, Department of Earth and Environmental Sciences, Sydney, N.S.W., Australia
Pages: 2008-2019
Published: 202211
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 103
Accession Number: 2022-065322
Categories: Geochemistry of rocks, soils, and sedimentsIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2022
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