Increased mantle heat flow with on-going rifting of the West

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TitleIncreased mantle heat flow with on-going rifting of the West Antarctic rift system inferred from characterisation of plagioclase peridotite in the shallow Antarctic mantleAbstractThe lithospheric, and shallow asthenospheric, mantle in Southern Victoria Land are known to record anomalously high heat flow but the cause remains imperfectly understood. To address this issue plagioclase peridotite xenoliths have been collected from Cenozoic alkalic igneous rocks at three localities along a 150. km transect across the western shoulder of the West Antarctic rift system in Southern Victoria Land, Antarctica. There is a geochemical, thermal and chronological progression across this section of the rift shoulder from relatively hot, young and thick lithosphere in the west to cooler, older and thinner lithosphere in the east. Overprinting this progression are relatively more recent mantle refertilising events. Melt depletion and refertilisation was relatively limited in the lithospheric mantle to the west but has been more extensive in the east. Thermometry obtained from orthopyroxene in these plagioclase peridotites indicates that those samples most recently affected by refertilising melts have attained the highest temperatures, above those predicted from idealised dynamic rift or Northern Victoria Land geotherms and higher than those prevailing in the equivalent East Antarctic mantle. Anomalously high heat flow can thus be attributed to entrapment of syn-rift melts in the lithosphere, probably since regional magmatism commenced at least 24. Myr ago. The chemistry and mineralogy of shallow plagioclase peridotite mantle can be explained by up to 8% melt extraction and a series of refertilisation events. These include: (a) up to 8% refertilisation by a N-MORB melt; (b) metasomatism involving up to 1% addition of a subduction-related component; and (c) addition of ~. 1.5% average calcio-carbonatite. A high MgO group of clinopyroxenes can be modelled by the addition of up to 1% alkalic melt. Melt extraction and refertilisation mainly occurred in the spinel stability field prior to decompression and uplift. In this region mantle plagioclase originates by a combination of subsolidus recrystallisation during decompression within the plagioclase stability field and refertilisation by basaltic melt. ©2013 Elsevier B.V.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) scholarship and a University of Otago stipend (Department of Geology). Antarctica New Zealand is thanked for logistic support. Mike Palin is thanked for assistance with trace element analysis. Thank you to J. Gamble and E. Rampone for constructive reviews and A. Kerr for editorial handling.

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1st AuthorMartin, A.AuthorMartin, A.Cooper, A.Price, R.Year2014JournalLithosVolume190-191Pages173-190DOI10.1016/j.lithos.2013.12.012URLhttps://www.scopus.com/inward/recor.....975386b5651dac90329042beaKeywordscarbonatiteCenozoicclinopyroxenegeothermometryheat flowhigh temperaturelithospheric structuremantle structuremetasomatismperidotiteplagioclaserecrystallizationrift zoneriftingsubductionxenolith, AntarcticaEast AntarcticaVictoria LandWest Antarctica, Calluna vulgaris, rank5Author KeywordsAntarctic lithosphereContinental riftingGeothermometryMantle refertilisationMetasomatismPlagioclase peridotite

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TypeArticleCitationMartin, A., Cooper, A. and Price, R. (2014). Increased mantle heat flow with on-going rifting of the West Antarctic rift system inferred from characterisation of plagioclase peridotite in the shallow Antarctic mantle. Lithos, 190-191: 173-190 doi:10.1016/j.lithos.2013.12.012 IdentifierMartin2014aRelevancerank5