2013

Migdisova N.A.¹, Sushchevskaya N.M. ¹, Portnyagin M.V. ², Kuzmin D.V.³

¹Institute for geochemistry and analytical chemistry RAS, Moscow, Russian Federation

+74959397017, nat-mig@yandex.ru

²Helmholtz-Zentrum fur Ozeanforschung, Kiel, Germany

³Max-Planck Institute fur Chemie, Mainz, Germany

Olivine leucitites of late Cenozoic age form the Gaussberg extinct volcanic cone on the coast of the Antarctic ice sheet. Samples gathered during 2^nd Soviet Antarctic Expedition (1957-1958) are mostly pillow lavas with a well defined black glassy crust.

New high precision data on selected lamproitic samples from Gaussberg volcano (Antarctica) including rare elements in olivine phenocrysts, clinopyroxene phenocrysts coupled with whole rock and quenched glass rare and main elements patterns show distinct features of continental ultra-potassium alkaline magmatism. Isotope systems (Pb, Sr, Nd) indicate a LOMU type primary mantle. According to isotopic data Gaussberg melting source is ancient Gondwana lithosphere (in East Antarctica).

Olivine (Fo up to 90.7) is a first cotectic phase in Gaussberg magmatic system (Ol ® Ol + Cpx ® Ol + Cpx + Lc). High Ni content (up to 0.6%) in olivine phenocrysts suggests probable olivine free mantle domains such as pyroxenites in the melting source. In Gaussberg olivine phenocrysts parameter X_PXNi proposed by Sobolev [1] to define the amount of pyroxenite component in the mantle source vary from 0.2 to 0.7 detecting a considerable contribution of olivine free lithology in the source. Meanwhile typical volcanic olivine Li contents (<10 ppm) suggest non-contaminated by crustal material character of this pyroxenite [2].

Rare element contents for high TiO₂ and low Al₂O₃ group Cpx phenocrysts and Ol phenocrysts are specifically enriched in LILE. Co, Ni, Zn, V values in olivine phenocrysts are 133-152, 2870-3860, 74-162, 1-2.9, correspondingly.

[1] Sobolev A.V., Hofmann A.W., Sobolev S.V., Nikogosian I.K. An olivine-free mantle source of Hawaiian shield basalts. 2005. Nature, 434, p. 590.

[2] Prelevick D., Jacob D.E., Foley S.F. Recycling plus: A new recipe for the formation of Alpine-Himalayan orogenic mantle lithosphere. 2013. Earth Planet.Sci.Lett., 362, pp. 187-197.