<abstract xml:lang="en" xmlns="http://www.w3.org/1999/xhtml">Clinopyroxenites, phoscorites and carbonatites from the Devonian Seblyavr intrusion (Kola Peninsula, Russia) have petrographic characteristics indicating that they are accumulative in origin. Their geochemical (major and rare earth elements) compositions can be accounted for by mixtures of their major rock-forming minerals and accessory phases, i.e. they reflect the record of mineral accumulation. All of the analysed Seblyavr rocks are strongly LREE-enriched with (La/Yb)N mostly ranging from 38 to 189. However, a dolomite carbonatite with hydrothermal LREE-Sr mineralization has an extreme (La/Yb)N value of 1659. Such late-stage dolomite carbonatites were formed by hydrothermal (rather than magmatic) processes. Whole-rock samples of representative magmatic lithologies from Seblyavr have initial 87Sr/86Sr and εNd that fall in a very narrow range from 0.7031 to 0.7033 and +4.9 to +5.9, respectively. We therefore conclude that clinopyroxenites, phoscorites and carbonatites were formed by differentiation and crystallization of a single batch of melt. The parental melt was derived from a depleted upper mantle source that had been meta-somatised prior to melting.</abstract>

Clinopyroxenites, phoscorites and carbonatites from the Devonian Seblyavr intrusion (Kola Peninsula, Russia) have petrographic characteristics indicating that they are accumulative in origin. Their geochemical (major and rare earth elements) compositions can be accounted for by mixtures of their major rock-forming minerals and accessory phases, i.e. they reflect the record of mineral accumulation. All of the analysed Seblyavr rocks are strongly LREE-enriched with (La/Yb)N mostly ranging from 38 to 189. However, a dolomite carbonatite with hydrothermal LREE-Sr mineralization has an extreme (La/Yb)N value of 1659. Such late-stage dolomite carbonatites were formed by hydrothermal (rather than magmatic) processes. Whole-rock samples of representative magmatic lithologies from Seblyavr have initial 87Sr/86Sr and εNd that fall in a very narrow range from 0.7031 to 0.7033 and +4.9 to +5.9, respectively. We therefore conclude that clinopyroxenites, phoscorites and carbonatites were formed by differentiation and crystallization of a single batch of melt. The parental melt was derived from a depleted upper mantle source that had been meta-somatised prior to melting.

Ree and Sr-Nd Isotope Compositions of Clinopyroxenites, Phoscorites and Carbonatites of the Seblyavr Massif, Kola Peninsula, Russia

Geological Institute, Kola Science Centre, 14 Fersman St., Apatity, Murmansk Region, 184200, Russia

School of Earth Sciences, Birkbeck University of London, Malet St., London WC1E 7HX, UK.

Géochimie Isotopique, CP 160/02, Université Libre de Bruxelles, 50 Av. Roosevelt, 1050 Brussels, Belgium

Mineralogia

Clinopyroxenites, phoscorites and carbonatites from the Devonian Seblyavr intrusion (Kola Peninsula, Russia) have petrographic characteristics indicating that...

Ree and Sr-Nd Isotope Compositions of Clinopyroxenites, Phoscorites and Carbonatites of the Seblyavr Massif, Kola Peninsula, Russia

Pubblicato online: 28 gen 2008

Pagine: 29 - 45

DOI: https://doi.org/10.2478/v10002-007-0017-6

Parole chiave
Seblyavr, clinopyroxenite, carbonatite, phoscorite, Kola Peninsula

This content is open access.

Ree and Sr-Nd Isotope Compositions of Clinopyroxenites, Phoscorites and Carbonatites of the Seblyavr Massif, Kola Peninsula, Russia

Pubblicato online: 28 gen 2008

Pagine: 29 - 45

DOI: https://doi.org/10.2478/v10002-007-0017-6

Parole chiaveSeblyavr, clinopyroxenite, carbonatite, phoscorite, Kola Peninsula

This content is open access.

Parole chiave
Seblyavr, clinopyroxenite, carbonatite, phoscorite, Kola Peninsula