Pervasive, tholeiitic refertilisation and heterogeneous metasomatism in Northern Victoria Land lithospheric mantle (Antarctica)

• Published in: Lithos
• Main Authors: Pelorosso, B., Bonadiman, C., Coltorti, Massimo, Faccini, B., Melchiorre, Massimiliano, Ntaflos, T., Grégoire, Michel
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2016
• Subjects: Garnet signature; Mantle xenoliths; Tholeiitic refertilisation; Antarctic; Baker Rocks; Greene; Greene Point; Victoria Land; Antarc*; Antarctica
• Online Access: http://hdl.handle.net/10261/130169; https://doi.org/10.1016/j.lithos.2016.01.032

The petrology of peridotite xenoliths in the Cenozoic volcanics from Greene Point (Northern Victoria Land, Antarctica) provides new constraints on the characterisation of the lithospheric mantle beneath the West Antarctic Rift.Based on mineral major and trace element models, this mantle domain is proposed to represent a residuum after 10% and 20% partial melting. Moreover, melting models and isotopic results for Sr and Nd systematics highlight the substantial contribution of tholeiitic melts percolating through peridotites. Close correlation with trace element contents in clinopyroxene phenocrysts from Ferrar and Karoo tholeiites allows us to ascribe this refertilisation event to the Jurassic. This asthenospheric melt was also able to transfer a garnet signature to the Northern Victoria Land mantle segment. The rare presence of glass and secondary phases indicate that Greene Point xenoliths were heterogeneously affected by alkaline metasomatism, probably related to the West Antarctic Rift System opening; this has also been widely observed in other Northern Victoria Land localities (i.e., Baker Rocks).Temperature and fO2 were calculated (950 °C; δlog fO2 (QFM), -1.70 to -0.39) at a fixed pressure of 15 kbar, confirming the tendency of the anhydrous Greene Point xenolith population to have higher equilibration temperatures and comparable redox conditions, compared to the nearby amphibole-bearing peridotites from Baker Rocks. This work was funded by PNRA (National Programme Antarctic Research) projects; in particular, samples were collected during the XX Italian expedition in Antarctica. Analyses were possible also thank to the PNRA project 2013–2015 Peer reviewed