Models of corundum origin from alkali basaltic terrains: a reappraisal

Sapphires related to alkali basalts from the Cerová Highlands, Western Carpathians (southern Slovakia): composition and origin

“…Similar models for corundum origin from upper mantle to lower crustal, fractionated syenitic/anorthoclasitic magma are also proposed for other sapphire occurrences (e.g. Coenraads et al 1995;Sutherland et al 1998Sutherland et al , 2009Upton et al 1999Upton et al , 2009Graham et al 2008).…”

“…5a). The Fe/Ti vs. Cr/Ga diagram (Sutherland et al 2009) is the equivalent of the Fe 2 O 3 /TiO 2 vs. Cr 2 O 3 /Ga 2 O 3 diagram proposed by Sutherland et al (1998) for classification of corundum in the alkali basalts domain. The diagram separates efficiently the metamorphic from the magmatic corundum (Sutherland et al 2003), it indicates that the Gortva sapphires differs from the Hajnáčka ones, and they plot obviously in the field of the magmatic sapphires in agreement with their petrological nature (Fig.…”

Petrogenesis of alkaline basalt-hosted sapphire megacrysts. Petrological and geochemical investigations of in situ sapphire occurrences from the Siebengebirge Volcanic Field, Germany

“…Such high concentrations in the HFSE are well known from highly evolved silicate melts and from carbonatitic melts. Most authors (e.g., Sutherland et al 1998b) relate the HFSE enrichment of the sapphires and the presence of Columbite Group, Pyrochlore Group and of Nb-rich rutile mineral inclusions to highly evolved SiO 2 undersaturated silicate melts such as syenites, or nepheline syenites. A further observation leading these authors to favor syenites as parental melts is that repeatedly melt inclusions of syenitic composition were reported from magmatic sapphires (e.g., Pakhomova et al 2006;Zaw et al 2006;Izokh et al 2010).…”

“…(2) Crystallization from alkaline Si-and Al-rich melts formed by partial melting of amphibole-bearing lithospheric mantle (Sutherland 1996;Sutherland et al 1998b). (3) Growth as restitic component during partial melting of Al-rich crustal protoliths such as anorthosites (Palke et al 2016(Palke et al , 2017.…”

Sapphires from Antsiranana Province, Northern Madagascar

“…The origin of these rubies and sapphires has been widely debated among geologists and mineralogists (for a summary, see, e.g., Levinson and Cook, 1994;Sutherland et al, 1998a). The alkali basalts are thought to carry the corundum crystals to the surface from the earth's interior, where they formed.…”