Email this article High-alumina pyroxenite xenoliths from Quaternary basalts of NW Spitsbergen - evidence of continental crust delamination
- Authors: Koreshkova M.Y.1, Marin Y.B.2, Nikitina L.P.3, Downes H.4, A. Tokusheva A.5, Goncharov A.G.5
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Affiliations:
- Institute of Еarth Science of Saint-Petersburg State University
- Saint-Petersburg Mining University
- Institute of Precambrian Geology and Geochronology of the Russian Academy of Sciences
- Birkbeck University of London
- Institute of Еarth Science of Saint Petersburg State University
- Issue: Vol 485, No 5 (2019)
- Pages: 604-608
- Section: Geochemistry
- URL: https://journals.eco-vector.com/0869-5652/article/view/14307
- DOI: https://doi.org/10.31857/S0869-56524855604-608
- ID: 14307
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Abstract
The origin of spinel-garnet pyroxenite from xenoliths in Quaternary basaltoids of Spitsbergen Island (Svalbard Archipelago) is discussed. The rocks have a high concentration of Al2O3 and MgO and low Cr. The primary magmatic association Spl-Opx-Cpx and the high Al content in pyroxenes provide evidence for the formation of these rocks as cumulates of hydrous basaltic melts in the lower crust at a pressure of ~1.2 GPa. Transformation of the texture from the magmatic hypidiomorphic to the metamorphic granoblastic and growth of garnet at the expense of spinel and high-alumina pyroxenes indicate transport of rocks to a depth below the spinel/garnet phase transition boundary in the Cr2O3-free CaO-MgO-Al2O3-SiO2 system. The parameters of the Grt-Opx equilibrium range within 1060-1120 °C and 2.2-2.6 GPa. Thus, magmatic pyroxenite was transported to a great depth into the mantle, which provides evidence for delamination in the region of the lower continental crust containing ultramafic cumulates.
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About the authors
M. Yu. Koreshkova
Institute of Еarth Science of Saint-Petersburg State University
Author for correspondence.
Email: m.koreshkova@spbu.ru
Russian Federation, 33-35, 10 th line, Vasilevsky Ostrov, Saint-Petersburg, 199178
Yu. B. Marin
Saint-Petersburg Mining University
Email: m.koreshkova@spbu.ru
Corresponding Member of the Russian Academy of Sciences
Russian Federation, 2, 21st line, Vasilevsky Ostrov, Saint-Petersburg, 199106L. P. Nikitina
Institute of Precambrian Geology and Geochronology of the Russian Academy of Sciences
Email: m.koreshkova@spbu.ru
Russian Federation, 2, Makarova embankment, St.Petersburg, 199034
H. Downes
Birkbeck University of London
Email: m.koreshkova@spbu.ru
United Kingdom, WC1E 7HX, Malet Street, Bloomsbury, London
A. A. Tokusheva
Institute of Еarth Science of Saint Petersburg State University
Email: m.koreshkova@spbu.ru
Russian Federation, 33-35, 10 th line, Vasilevsky Ostrov, Saint-Petersburg, 199178
A. G. Goncharov
Institute of Еarth Science of Saint Petersburg State University
Email: m.koreshkova@spbu.ru
Russian Federation, 33-35, 10 th line, Vasilevsky Ostrov, Saint-Petersburg, 199178
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