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The interpretation of 40 Ar/ 39 Ar apparent age spectra produced by mixing: application of the method of asymptotes and limits

Forster, Margaret; Lister, Gordon

Description

A method is presented for the analysis and interpretation of apparent age spectra produced during 40Ar/39Ar step-heating experiments. Application of this method is particularly relevant to complex apparent age spectra produced from minerals taken from exhumed metamorphic tectonites, particularly when these rocks once resided in an ancient Argon Partial Retention Zone. Such rocks may have been subject to localised deformation and/or recrystallisation during orogenesis. Yet microstructures relict...[Show more]

dc.contributor.authorForster, Margaret
dc.contributor.authorLister, Gordon
dc.date.accessioned2015-12-13T22:37:45Z
dc.identifier.issn0191-8141
dc.identifier.urihttp://hdl.handle.net/1885/77236
dc.description.abstractA method is presented for the analysis and interpretation of apparent age spectra produced during 40Ar/39Ar step-heating experiments. Application of this method is particularly relevant to complex apparent age spectra produced from minerals taken from exhumed metamorphic tectonites, particularly when these rocks once resided in an ancient Argon Partial Retention Zone. Such rocks may have been subject to localised deformation and/or recrystallisation during orogenesis. Yet microstructures relict of earlier episodes of deformation and/or metamorphism may retain relatively old apparent ages. As a result complex apparent age spectra can be produced during a conventional step-heating experiment, and these age spectra often cannot be simply interpreted. The recognition (and the interpretation) of a plateau in such spectra is sometimes uncertain, and in any case, the definition of a 'plateau' is then a concept of limited theoretical validity. To avoid these difficulties an alternative strategy is presented, based on a theory of mixing gas from different microstructural/microchemical reservoirs. This method relies on the definition of asymptotes and limits in sequences of apparent ages in apparent age spectra obtained from step-heating experiments. Frequently measured ages (FMAs) in individual datasets can then be recognized using statistical analysis. The significance of FMAs must be independently assessed.
dc.publisherPergamon-Elsevier Ltd
dc.sourceJournal of Structural Geology
dc.subjectKeywords: Orogenesis; Deformation; Heating; Microstructure; Minerals; Rocks; Statistical methods; Argon; argon-argon dating; dating method; deformation; metamorphism; orogeny; recrystallization; tectonite 40Ar/39Ar geochronology; Apparent age spectra; Deformation ages; Diffusion domains; Excess argon; White mica
dc.titleThe interpretation of 40 Ar/ 39 Ar apparent age spectra produced by mixing: application of the method of asymptotes and limits
dc.typeJournal article
local.description.notesImported from ARIES
local.description.refereedYes
local.identifier.citationvolume26
dc.date.issued2004
local.identifier.absfor040303 - Geochronology
local.identifier.absfor040312 - Structural Geology
local.identifier.ariespublicationMigratedxPub6133
local.type.statusPublished Version
local.contributor.affiliationForster, Margaret, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationLister, Gordon, College of Physical and Mathematical Sciences, ANU
local.description.embargo2037-12-31
local.bibliographicCitation.issue2
local.bibliographicCitation.startpage287
local.bibliographicCitation.lastpage305
local.identifier.doi10.1016/j.jsg.2003.10.004
dc.date.updated2015-12-11T09:38:28Z
local.identifier.scopusID2-s2.0-1642457223
CollectionsANU Research Publications

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