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dc.contributor.authorMutch, Euanen
dc.contributor.authorBlundy, JDen
dc.contributor.authorTattitch, BCen
dc.contributor.authorCooper, FJen
dc.contributor.authorBrooker, RAen
dc.date.accessioned2016-11-17T14:31:18Z
dc.date.available2016-11-17T14:31:18Z
dc.date.issued2016-10en
dc.identifier.issn0010-7999
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/261193
dc.description.abstractWe report new experimental data on the composition of magmatic amphiboles synthesised from a variety of granite (sensu lato) bulk compositions at near-solidus temperatures and pressures of 0.8–10 kbar. The total aluminium content (Al$^\text{tot}$) of the synthetic calcic amphiboles varies systematically with pressure ($\small \textit{P}$), although the relationship is nonlinear at low pressures (<2.5 kbar). At higher pressures, the relationship resembles that of other experimental studies, which suggests of a general relationship between Al$^\text{tot}$ and P that is relatively insensitive to bulk composition. We have developed a new Al-in-hornblende geobarometer that is applicable to granitic rocks with the low-variance mineral assemblage: amphibole + plagioclase (An$_{15–80}$) + biotite + quartz + alkali feldspar + ilmenite/ titanite + magnetite + apatite. Amphibole analyses should be taken from the rims of grains, in contact with plagioclase and in apparent textural equilibrium with the rest of the mineral assemblage at temperatures close to the haplogranite solidus (725 ± 75 °C), as determined from amphibole–plagioclase thermometry. Mean amphibole rim compositions that meet these criteria can then be used to calculate $\small \textit{P}$ (in kbar) from Al$^\text{tot}$ (in atoms per formula unit, apfu) according to the expression: $P$ (kbar) = 0.5 + 0.331(8) × Al$^\text{tot}$ + 0.995(4) × (Al$^\text{tot}$)$^2$ This expression recovers equilibration pressures of our calibrant dataset, comprising both new and published experimental and natural data, to within ±16 % relative uncertainty. An uncertainty of 10 % relative for a typical Al$^\text{tot}$ value of 1.5 apfu translates to an uncertainty in pressure estimate of 0.5 kbar, or 15 % relative. Thus the accuracy of the barometer expression is comparable to the precision with which near-solidus amphibole rim composition can be characterised.
dc.description.sponsorshipBHP Billiton, Royal Society (Wolfson Research Merit Award), California Institute of Technology (Moore Scholarship)
dc.language.isoenen
dc.publisherSpringer
dc.rightsAttribution 4.0 Internationalen
dc.rightsAttribution 4.0 Internationalen
dc.rightsAttribution 4.0 Internationalen
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en
dc.subjectgranitoid geobarometryen
dc.subjectAl-in-hornblendeen
dc.subjectamphibole stabilityen
dc.subjectphase-equilibria experimentsen
dc.titleAn experimental study of amphibole stability in low-pressure granitic magmas and a revised Al-in-hornblende geobarometeren
dc.typeArticle
prism.issueIdentifier10en
prism.number85en
prism.publicationDate2016en
prism.publicationNameContributions to Mineralogy and Petrologyen
prism.volume171en
dc.identifier.doi10.17863/CAM.6362
dcterms.dateAccepted2016-09-07en
rioxxterms.versionofrecord10.1007/s00410-016-1298-9en
rioxxterms.versionVoRen
rioxxterms.licenseref.urihttp://creativecommons.org/licenses/by/4.0/en
rioxxterms.licenseref.startdate2016-10en
dc.contributor.orcidMutch, Euan [0000-0002-0794-4392]
dc.identifier.eissn1432-0967
rioxxterms.typeJournal Article/Reviewen
cam.issuedOnline2016-09-24en
cam.orpheus.successThu Jan 30 12:56:59 GMT 2020 - The item has an open VoR version.*
rioxxterms.freetoread.startdate2100-01-01


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Attribution 4.0 International
Except where otherwise noted, this item's licence is described as Attribution 4.0 International