Petrogenesis of Cenozoic, alkalic volcanic lineages at Mount

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TitlePetrogenesis of Cenozoic, alkalic volcanic lineages at Mount Morning, West Antarctica and their entrained lithospheric mantle xenoliths: Lithospheric versus asthenospheric mantle sourcesAbstractTwo volcanic lineages are identified at Mount Morning, a Cenozoic to recent, eruptive centre in the Ross Sea, West Antarctica, which is part of the McMurdo Volcanic Group. Both the older (at least 18.7-11.4Ma), mildly alkalic, nepheline- or quartz-normative Mason Spur Lineage, and the younger (at least 6-0.02Ma), nepheline normative, strongly alkalic Riviera Ridge Lineage evolved by fractional crystallization from nominally anhydrous (<0.5wt% H2O) parental magmas. Both lineages are analogous to other, relatively anhydrous lineages in the McMurdo Volcanic Group and distinctly different from those in which kaersutite is present on the liquid line of descent. Sub-continental lithospheric mantle (SCLM) xenoliths entrained in Riviera Ridge lineage rocks show trace element and isotopic Sr-Nd-Pb variation that is consistent with four-component mixing whereby depleted mantle has been refertilised by enriched, HIMU-like and Nb-enriched (carbonatite) components. Refertilization may have occurred c. 530-490Ma ago when fluids derived from subduction associated with Gondwanaland amalgamation infiltrated the SCLM. Similar trace element and isotope variation (Sr-Nd-Pb) in Mount Morning basaltic rocks and entrained xenoliths suggests that the source for the basaltic magmas lies (at least in part) in the lithospheric mantle. It has long been recognized that Cenozoic volcanic rocks in Antarctica (Victoria Land - including Mount Morning - and Marie Byrd Land), Zealandia and eastern Australia share common chemical and isotopic source characteristics and they have been argued to collectively constitute a single diffuse alkaline magmatic province (DAMP). Source characteristic similarities suggest DAMP volcanic rocks inherit at least some of their trace element and isotopic characteristics from the lithospheric mantle. Super-chondritic Nb/Ta values measured in some SCLM xenoliths and volcanic rocks at Mount Morning, and in volcanic rocks across the DAMP, can be explained by addition of ≤5wt% carbonatite to the source. The DAMP SCLM is a significant Nb reservoir that offers an explanation for the Nb paradox. © 2013.AcknowledgementsDamian Walls and Brent Pooley at Otago University are thanked for help in XRF analysis and sample preparation. Adam Martin was supported by an Antarctica New Zealand (New Zealand Post) Antarctic scholarship and a University of Otago award from the Department of Geology. Antarctica New Zealand is thanked for logistic support. Roland Maas is thanked for Sr-Nd-Pb analysis and selected whole rock trace element analyses. Andreas Audétat at Bayerisches Geoinstitut is thanked for assistance with mineral analysis. Candace Martin and Mike Palin are thanked for assistance with trace element analysis. The authors thank Kurt Panter, Andreas Stracke and Carsten Münker for constructive reviews and Steve Shirey for editorial handling and assistance.

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1st AuthorMartin, A.AuthorMartin, A.Cooper, A.Price, R.Year2013JournalGeochimica et Cosmochimica ActaVolume122Pages127-152DOI10.1016/j.gca.2013.08.025URLhttps://www.scopus.com/inward/recor.....739291f1110526b44694fb0a5KeywordsasthenospherebasaltCenozoicfractional crystallizationGondwanaigneous geochemistryisotopic compositionlead isotopelithospheric structuremagmamantle sourceneodymium isotopenephelinepetrogenesisstrontium isotopetrace elementvolcanic rockxenolith, AntarcticaEast AntarcticaMount MorningRoss SeaSouthern OceanWest Antarctica, rank5

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TypeArticleCitationMartin, A., Cooper, A. and Price, R. (2013). Petrogenesis of Cenozoic, alkalic volcanic lineages at Mount Morning, West Antarctica and their entrained lithospheric mantle xenoliths: Lithospheric versus asthenospheric mantle sources. Geochimica et Cosmochimica Acta, 122:127-152 doi:10.1016/j.gca.2013.08.025 IdentifierMartin2013Relevancerank5