Crystal chemistry of amphiboles: implications for oxygen fugacity and water activity in lithospheric mantle beneath Victoria Land, Antarctica
Amphibole is the hydrous metasomatic phase in spinel-bearing mantle xenoliths from Baker Rocks, Northern Victoria Land, Antarctica. It occurs in veins or in disseminated form in spinel lherzolites. Both types derive from reaction between metasomatic melts and the pristine paragenesis of the continen...
Published in: | Contributions to Mineralogy and Petrology |
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ftuncamerinoiris:oai:pubblicazioni.unicam.it:11581/309583 2024-04-14T08:04:07+00:00 Crystal chemistry of amphiboles: implications for oxygen fugacity and water activity in lithospheric mantle beneath Victoria Land, Antarctica C. Bonadiman S. Nazzareni M. Coltorti P. Comodi B. Faccini GIULI, Gabriele C., Bonadiman S., Nazzareni M., Coltorti P., Comodi Giuli, Gabriele B., Faccini 2014 STAMPA http://hdl.handle.net/11581/309583 https://doi.org/10.1007/s00410-014-0984-8 eng eng info:eu-repo/semantics/altIdentifier/wos/000332585700007 volume:167 issue:3 firstpage:984_17 lastpage:984_1 numberofpages:1 journal:CONTRIBUTIONS TO MINERALOGY AND PETROLOGY http://hdl.handle.net/11581/309583 doi:10.1007/s00410-014-0984-8 info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-84894621103 info:eu-repo/semantics/article 2014 ftuncamerinoiris https://doi.org/10.1007/s00410-014-0984-8 2024-03-21T20:37:07Z Amphibole is the hydrous metasomatic phase in spinel-bearing mantle xenoliths from Baker Rocks, Northern Victoria Land, Antarctica. It occurs in veins or in disseminated form in spinel lherzolites. Both types derive from reaction between metasomatic melts and the pristine paragenesis of the continental lithospheric mantle beneath Northern Victoria Land. To determine the effective role of water circulation during the metasomatic process and amphibole formation, six amphibole samples were fully characterized. Accurate determination of the site population and the state of dehydrogenation in each of these amphiboles was carried out using single-crystal X-ray diffraction, electron microprobe and secondary ion mass spectroscopy on the same single crystal. The Fe3+/Sigma Fe ratio was determined by X-ray absorption near edge spectroscopy on amphibole powder. The degree of dehydrogenation determined by SIMS is 0.870-0.994 O3(O2-) a.p.f.u., primary and ascribed to the Ti-oxy component of the amphibole, as indicated by atom site populations; postcrystallization H loss is negligible. Estimates of aH(2)O (0.014-0.054) were determined from the dehydration equilibrium among end-member components assuming that amphiboles are in equilibrium with the anhydrous peridotitic phases. A difference up to 58 % in determination of aH2O can be introduced if the chemical formula of the amphiboles is calculated based on 23 O a. p. f. u. without knowing the effective amount of dehydrogenation. The oxygen fugacity of the Baker Rocks amphibole-bearing mantle xenoliths calculated based upon the dissociation constant of water (by oxy-amphibole equilibrium) is between -2.52 and -1.32 log units below the fayalitemagnetite- quartz (FMQ) buffer. These results are systematically lower and in a narrow range of values relative to those obtained from anhydrous olivine-orthopyroxene-spinel equilibria (fO(2) between -1.98 and -0.30 log units). A comparative evaluation of the two methods suggests that when amphibole is present in mantle peridotites, the ... Article in Journal/Newspaper Antarc* Antarctica Victoria Land CAMPUS Pubblicazioni Scientifiche Unicam (Università di Camerino) Victoria Land The Baker ENVELOPE(-54.765,-54.765,49.667,49.667) Baker Rocks ENVELOPE(164.750,164.750,-74.233,-74.233) Contributions to Mineralogy and Petrology 167 3 |
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Open Polar |
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CAMPUS Pubblicazioni Scientifiche Unicam (Università di Camerino) |
op_collection_id |
ftuncamerinoiris |
language |
English |
description |
Amphibole is the hydrous metasomatic phase in spinel-bearing mantle xenoliths from Baker Rocks, Northern Victoria Land, Antarctica. It occurs in veins or in disseminated form in spinel lherzolites. Both types derive from reaction between metasomatic melts and the pristine paragenesis of the continental lithospheric mantle beneath Northern Victoria Land. To determine the effective role of water circulation during the metasomatic process and amphibole formation, six amphibole samples were fully characterized. Accurate determination of the site population and the state of dehydrogenation in each of these amphiboles was carried out using single-crystal X-ray diffraction, electron microprobe and secondary ion mass spectroscopy on the same single crystal. The Fe3+/Sigma Fe ratio was determined by X-ray absorption near edge spectroscopy on amphibole powder. The degree of dehydrogenation determined by SIMS is 0.870-0.994 O3(O2-) a.p.f.u., primary and ascribed to the Ti-oxy component of the amphibole, as indicated by atom site populations; postcrystallization H loss is negligible. Estimates of aH(2)O (0.014-0.054) were determined from the dehydration equilibrium among end-member components assuming that amphiboles are in equilibrium with the anhydrous peridotitic phases. A difference up to 58 % in determination of aH2O can be introduced if the chemical formula of the amphiboles is calculated based on 23 O a. p. f. u. without knowing the effective amount of dehydrogenation. The oxygen fugacity of the Baker Rocks amphibole-bearing mantle xenoliths calculated based upon the dissociation constant of water (by oxy-amphibole equilibrium) is between -2.52 and -1.32 log units below the fayalitemagnetite- quartz (FMQ) buffer. These results are systematically lower and in a narrow range of values relative to those obtained from anhydrous olivine-orthopyroxene-spinel equilibria (fO(2) between -1.98 and -0.30 log units). A comparative evaluation of the two methods suggests that when amphibole is present in mantle peridotites, the ... |
author2 |
C., Bonadiman S., Nazzareni M., Coltorti P., Comodi Giuli, Gabriele B., Faccini |
format |
Article in Journal/Newspaper |
author |
C. Bonadiman S. Nazzareni M. Coltorti P. Comodi B. Faccini GIULI, Gabriele |
spellingShingle |
C. Bonadiman S. Nazzareni M. Coltorti P. Comodi B. Faccini GIULI, Gabriele Crystal chemistry of amphiboles: implications for oxygen fugacity and water activity in lithospheric mantle beneath Victoria Land, Antarctica |
author_facet |
C. Bonadiman S. Nazzareni M. Coltorti P. Comodi B. Faccini GIULI, Gabriele |
author_sort |
C. Bonadiman |
title |
Crystal chemistry of amphiboles: implications for oxygen fugacity and water activity in lithospheric mantle beneath Victoria Land, Antarctica |
title_short |
Crystal chemistry of amphiboles: implications for oxygen fugacity and water activity in lithospheric mantle beneath Victoria Land, Antarctica |
title_full |
Crystal chemistry of amphiboles: implications for oxygen fugacity and water activity in lithospheric mantle beneath Victoria Land, Antarctica |
title_fullStr |
Crystal chemistry of amphiboles: implications for oxygen fugacity and water activity in lithospheric mantle beneath Victoria Land, Antarctica |
title_full_unstemmed |
Crystal chemistry of amphiboles: implications for oxygen fugacity and water activity in lithospheric mantle beneath Victoria Land, Antarctica |
title_sort |
crystal chemistry of amphiboles: implications for oxygen fugacity and water activity in lithospheric mantle beneath victoria land, antarctica |
publishDate |
2014 |
url |
http://hdl.handle.net/11581/309583 https://doi.org/10.1007/s00410-014-0984-8 |
long_lat |
ENVELOPE(-54.765,-54.765,49.667,49.667) ENVELOPE(164.750,164.750,-74.233,-74.233) |
geographic |
Victoria Land The Baker Baker Rocks |
geographic_facet |
Victoria Land The Baker Baker Rocks |
genre |
Antarc* Antarctica Victoria Land |
genre_facet |
Antarc* Antarctica Victoria Land |
op_relation |
info:eu-repo/semantics/altIdentifier/wos/000332585700007 volume:167 issue:3 firstpage:984_17 lastpage:984_1 numberofpages:1 journal:CONTRIBUTIONS TO MINERALOGY AND PETROLOGY http://hdl.handle.net/11581/309583 doi:10.1007/s00410-014-0984-8 info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-84894621103 |
op_doi |
https://doi.org/10.1007/s00410-014-0984-8 |
container_title |
Contributions to Mineralogy and Petrology |
container_volume |
167 |
container_issue |
3 |
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1796300490197172224 |