Halogen behaviour in subduction zones: eclogite facies rocks from the Western and Central AlpsCitation formats

  • External authors:
  • Lewis Hughes
  • Deborah Chavrit
  • Alison Pawley
  • Giles Droop
  • Christopher Ballentine

Standard

Halogen behaviour in subduction zones: eclogite facies rocks from the Western and Central Alps. / Hughes, Lewis; Burgess, Raymond; Chavrit, Deborah; Pawley, Alison; Tartese, Romain; Droop, Giles; Ballentine, Christopher; Lyon, Ian.

In: Geochimica et Cosmochimica Acta, Vol. 243, 15.12.2018, p. 1-23.

Research output: Contribution to journalArticle

Harvard

Hughes, L, Burgess, R, Chavrit, D, Pawley, A, Tartese, R, Droop, G, Ballentine, C & Lyon, I 2018, 'Halogen behaviour in subduction zones: eclogite facies rocks from the Western and Central Alps', Geochimica et Cosmochimica Acta, vol. 243, pp. 1-23. https://doi.org/10.1016/j.gca.2018.09.024

APA

Vancouver

Author

Hughes, Lewis ; Burgess, Raymond ; Chavrit, Deborah ; Pawley, Alison ; Tartese, Romain ; Droop, Giles ; Ballentine, Christopher ; Lyon, Ian. / Halogen behaviour in subduction zones: eclogite facies rocks from the Western and Central Alps. In: Geochimica et Cosmochimica Acta. 2018 ; Vol. 243. pp. 1-23.

Bibtex

@article{0c2b0a8620cd47ab84215a4244b0794d,
title = "Halogen behaviour in subduction zones: eclogite facies rocks from the Western and Central Alps",
abstract = "We examined F, Cl, Br and I concentrations and distributions in eclogite facies rocks and minerals from the Western and Central Alpine ophiolitic zone to determine halogen behaviour in subduction zones, and to identify potential host phases that may be able to transport halogens to the deeper mantle. Analysis was carried out on a range of ophiolitic lithologies — peridotites, serpentinites, metagabbros, metabasalts and metasediments — to assess the distribution of halogens within deeply subducted oceanic crust. Halogen abundances in individual mineral phases range from below detection (∼100 ppm) to ∼1900 ppm for F, ∼1 to ∼3000 ppm for Cl, ∼1 to ∼11,000 ppb for Br and from <1 to ∼1300 ppb for I. Bulk rock estimates of Cl, Br and I abundances are variable, but are generally more than one order of magnitude lower than those in altered oceanic crust (AOC), suggesting major halogen loss prior to or during eclogite facies metamorphism. Fluorine, however, can be enriched within metabasalts and metasediments, relative to the heavy halogens, suggesting F can be retained at eclogite facies conditions within the upper layers of the subducting slab. Bulk rock estimates suggest that upon reaching eclogite facies, the subducting slab has lost over 90{\%} Cl, Br and I. Bromine and iodine concentrations show positive correlation, suggesting that they exhibit similar behaviour at high pressure. A lack of any other correlations suggest that F and Cl behave differently to Br and I during subduction. Elevated F/Cl, Br/Cl and I/Cl ratios, relative to AOC, suggest the preferential loss of Cl during shallower depths of subduction. In situ analyses and chemical mapping using electron probe micro-analysis and time of flight secondary ion mass spectrometry indicate that measured halogen abundances are primarily hosted within the mineral structure. Overall, our dataset provides new constraints on the available inventory of halogens that can be transferred to the deeper mantle via the subduction of oceanic crust.",
author = "Lewis Hughes and Raymond Burgess and Deborah Chavrit and Alison Pawley and Romain Tartese and Giles Droop and Christopher Ballentine and Ian Lyon",
year = "2018",
month = "12",
day = "15",
doi = "10.1016/j.gca.2018.09.024",
language = "English",
volume = "243",
pages = "1--23",
journal = "Geochimica et Cosmochimica Acta",
issn = "0016-7037",
publisher = "Elsevier BV",

}

RIS

TY - JOUR

T1 - Halogen behaviour in subduction zones: eclogite facies rocks from the Western and Central Alps

AU - Hughes, Lewis

AU - Burgess, Raymond

AU - Chavrit, Deborah

AU - Pawley, Alison

AU - Tartese, Romain

AU - Droop, Giles

AU - Ballentine, Christopher

AU - Lyon, Ian

PY - 2018/12/15

Y1 - 2018/12/15

N2 - We examined F, Cl, Br and I concentrations and distributions in eclogite facies rocks and minerals from the Western and Central Alpine ophiolitic zone to determine halogen behaviour in subduction zones, and to identify potential host phases that may be able to transport halogens to the deeper mantle. Analysis was carried out on a range of ophiolitic lithologies — peridotites, serpentinites, metagabbros, metabasalts and metasediments — to assess the distribution of halogens within deeply subducted oceanic crust. Halogen abundances in individual mineral phases range from below detection (∼100 ppm) to ∼1900 ppm for F, ∼1 to ∼3000 ppm for Cl, ∼1 to ∼11,000 ppb for Br and from <1 to ∼1300 ppb for I. Bulk rock estimates of Cl, Br and I abundances are variable, but are generally more than one order of magnitude lower than those in altered oceanic crust (AOC), suggesting major halogen loss prior to or during eclogite facies metamorphism. Fluorine, however, can be enriched within metabasalts and metasediments, relative to the heavy halogens, suggesting F can be retained at eclogite facies conditions within the upper layers of the subducting slab. Bulk rock estimates suggest that upon reaching eclogite facies, the subducting slab has lost over 90% Cl, Br and I. Bromine and iodine concentrations show positive correlation, suggesting that they exhibit similar behaviour at high pressure. A lack of any other correlations suggest that F and Cl behave differently to Br and I during subduction. Elevated F/Cl, Br/Cl and I/Cl ratios, relative to AOC, suggest the preferential loss of Cl during shallower depths of subduction. In situ analyses and chemical mapping using electron probe micro-analysis and time of flight secondary ion mass spectrometry indicate that measured halogen abundances are primarily hosted within the mineral structure. Overall, our dataset provides new constraints on the available inventory of halogens that can be transferred to the deeper mantle via the subduction of oceanic crust.

AB - We examined F, Cl, Br and I concentrations and distributions in eclogite facies rocks and minerals from the Western and Central Alpine ophiolitic zone to determine halogen behaviour in subduction zones, and to identify potential host phases that may be able to transport halogens to the deeper mantle. Analysis was carried out on a range of ophiolitic lithologies — peridotites, serpentinites, metagabbros, metabasalts and metasediments — to assess the distribution of halogens within deeply subducted oceanic crust. Halogen abundances in individual mineral phases range from below detection (∼100 ppm) to ∼1900 ppm for F, ∼1 to ∼3000 ppm for Cl, ∼1 to ∼11,000 ppb for Br and from <1 to ∼1300 ppb for I. Bulk rock estimates of Cl, Br and I abundances are variable, but are generally more than one order of magnitude lower than those in altered oceanic crust (AOC), suggesting major halogen loss prior to or during eclogite facies metamorphism. Fluorine, however, can be enriched within metabasalts and metasediments, relative to the heavy halogens, suggesting F can be retained at eclogite facies conditions within the upper layers of the subducting slab. Bulk rock estimates suggest that upon reaching eclogite facies, the subducting slab has lost over 90% Cl, Br and I. Bromine and iodine concentrations show positive correlation, suggesting that they exhibit similar behaviour at high pressure. A lack of any other correlations suggest that F and Cl behave differently to Br and I during subduction. Elevated F/Cl, Br/Cl and I/Cl ratios, relative to AOC, suggest the preferential loss of Cl during shallower depths of subduction. In situ analyses and chemical mapping using electron probe micro-analysis and time of flight secondary ion mass spectrometry indicate that measured halogen abundances are primarily hosted within the mineral structure. Overall, our dataset provides new constraints on the available inventory of halogens that can be transferred to the deeper mantle via the subduction of oceanic crust.

U2 - 10.1016/j.gca.2018.09.024

DO - 10.1016/j.gca.2018.09.024

M3 - Article

VL - 243

SP - 1

EP - 23

JO - Geochimica et Cosmochimica Acta

JF - Geochimica et Cosmochimica Acta

SN - 0016-7037

ER -