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Primary magmas and mantle temperatures

Green, David; Falloon, T J; Eggins, Stephen; Yaxley, Gregory

Description

The composition of olivine phenocrysts in Hawaiian tholeiitic picrites and in Mid-Ocean Ridge picrites vary up to Mg91.3# and Mg92.1# respectively. The compositions and liquids temperatures of the magmas crystallizing the most magnesian phenocrysts can be estimated and we find that anhydrous liquids temperatures (at 1 bar pressure) of Hawaiian tholeiitic picrites average 1365°C, for E-MOR picrites average 1355°C, and for N-MOR picrites average 1335°C. Water contents of the magmas decrease in...[Show more]

dc.contributor.authorGreen, David
dc.contributor.authorFalloon, T J
dc.contributor.authorEggins, Stephen
dc.contributor.authorYaxley, Gregory
dc.date.accessioned2015-12-10T23:23:04Z
dc.date.available2015-12-10T23:23:04Z
dc.identifier.issn0935-1221
dc.identifier.urihttp://hdl.handle.net/1885/66788
dc.description.abstractThe composition of olivine phenocrysts in Hawaiian tholeiitic picrites and in Mid-Ocean Ridge picrites vary up to Mg91.3# and Mg92.1# respectively. The compositions and liquids temperatures of the magmas crystallizing the most magnesian phenocrysts can be estimated and we find that anhydrous liquids temperatures (at 1 bar pressure) of Hawaiian tholeiitic picrites average 1365°C, for E-MOR picrites average 1355°C, and for N-MOR picrites average 1335°C. Water contents of the magmas decrease in the order Hawaiian picrites, E-MOR picrites to N-MOR picrites, and considerations of liquids by these water contents leads to the conclusion that magma temperatures for all types were approximately 1325°C at ∼ 1 bar. The data from parental or primary magmas suggests that the temperature contrast between 'Hot-Spot' and MOR magmas is ≤ 20°C. Application of information from partial melting studies of lherzolites and liquidus studies of the Hot-Spot and MOR picrites leads to the conclusion that both 'Hot-Spot' and MOR primary basalts are derived from mantle with potential temperature Tp ∼ 1430°C. Insofar as primitive magmas may be used to infer the potential temperature of their sources, there is no evidence for a temperature contrast of Δ Tp = 100-250°C between Hot-Spot' or 'Deep Mantle Plume' sources and ambient (MOR source) asthenospheric mantle. Although magma temperatures are similar, the residual mantle compositions for Hawaiian picrites are refractory harzburgites, more refractory (including Cr/Cr+Al ratio) than the lherzolite to harzburgite residue from MOR picrite extraction. It is argued that the buoyancy plume and geophysically anomalous mantle beneath the Hawaiian Arch is due to compositional and not temperature contrasts in the upper mantle. The four-component mixing identified in the Hawaiian source is attributed to interaction between old subducted lithospheric slabs, buoyant or suspended in the upper mantle, and surrounding ambient mantle at Tp = 1430°C.
dc.publisherE. Schweizerbartsche Verlagsbuchhandlung
dc.sourceEuropean Journal of Mineralogy
dc.subjectKeywords: magma; mantle; melting; picrite; temperature Mantle melting; Mantle potential temperature; Plumes; Primary magmas
dc.titlePrimary magmas and mantle temperatures
dc.typeJournal article
local.description.notesImported from ARIES
local.description.refereedYes
local.identifier.citationvolume13
dc.date.issued2001
local.identifier.absfor040304 - Igneous and Metamorphic Petrology
local.identifier.ariespublicationMigratedxPub1345
local.type.statusPublished Version
local.contributor.affiliationGreen, David, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationFalloon, T J, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationEggins, Stephen, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationYaxley, Gregory, College of Physical and Mathematical Sciences, ANU
local.bibliographicCitation.startpage437
local.bibliographicCitation.lastpage451
local.identifier.doi10.1127/0935-1221/2001/0013-0437
dc.date.updated2015-12-10T10:36:27Z
local.identifier.scopusID2-s2.0-0034995358
CollectionsANU Research Publications

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