Experimental investigation of the reaction between corundum xenocrysts and alkaline basaltic host magma: Constraints on magma residence times of basalt-hosted sapphires

Baldwin, Lisa; Ballhaus, Chris

doi:10.1016/j.lithos.2018.01.020

Cited by 5 publications

(4 citation statements)

References 48 publications

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“…Thus, the relationship between alkali basalts and corundum megacrysts is evident but, at the same time, it indicates disequilibrium of the corundum and the hosting basalt. A similar point of view was expressed earlier [41,42].…”

Section: Discussionsupporting

confidence: 73%

Naryn-Gol Creek Sapphire Placer Deposit, Buryatia, Russia

et al. 2022

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A new gem corundum occurrence has been discovered in the Naryn-Gol Creek placer of the Dzhida volcanic field (Russia). In this placer deposit, sapphire associates with large crystals of garnet, spinel, augite, olivine, enstatite, ilmenite, Ti-magnetite, and alkali feldspar. Such a combination of minerals is typical for the placer deposits associated with alkali basalts widely distributed in Southeastern Asia and Australia. We have also found sapphire crystals in phonotephrites of the nearby Cenozoic alkali-basalt paleovolcano Barun Khobol Pravyi, and in basalt sample and trachybasalt from the valley flood basalts. The chemical composition of sapphire is generally typical for ‘basalt’ corundum: it is rich in Fe, and depleted in Ti and Cr. The δ18O SMOW values of corundum and related megacrysts range from 4.6 to 6.8 ‰, thus corresponding to the isotopic signature of igneous rocks. Etched and corroded surfaces of sapphire and other megacrysts indicate that they are in non-equilibrium with their host alkali basalts. Volatile components, CO2 in particular, played a significant role during sapphire formation as gas inclusions reveal.

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Section: Discussionsupporting

confidence: 73%

Naryn-Gol Creek Sapphire Placer Deposit, Buryatia, Russia

et al. 2022

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“…In another spinel occurrence, sapphires from the Siebengebirge Volcanic Field in Germany are coated with a very thin reaction rim of spinel (Baldwin and Ballhaus, 2018). Interestingly, spinel was not recognized on the surfaces of any of the sapphires from the Rock Creek district, the South Fork of Dry Cottonwood Creek, or the French Bar sill along Hauser Lake.…”

Section: Spokanementioning

confidence: 99%

“…Spinel variety hercynite adheres to some of the sapphires from the Yogo deposits (Clabaugh, 1952) where sapphires are mined from a lamprophyre dike. Also, sapphires from a basalt in the Siebengebirge Volcanic Field in Germany have spinel coronas (Baldwin and Ballhaus, 2018).…”

Section: Features Formed By Partial Resorption In the Magma And Also ...mentioning

confidence: 99%

“…A similar reaction has been recognized for sapphires from the Yogo deposit, some of which are partially coated with spinel (Fe variety hercynite) as a result of reaction of the sapphire with the enclosing lamprophyre(Claubaugh, 1952, p. 18). In another spinel occurrence, sapphires from the Siebengebirge Volcanic Field in Germany are coated with a very thin reaction rim of spinel(Baldwin and Ballhaus, 2018). Interestingly, spinel was not recognized on the surfaces of any of the sapphires from the Rock Creek district, the South Fork of Dry Cottonwood Creek, or the French Bar sill along Hauser Lake.…”

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Morphology of sapphires from secondary deposits, southwestern Montana

Berg

2022

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Petrologically controlled oxygen isotopic classification of cogenetic magmatic and metamorphic sapphire from Quaternary volcanic fields in the Eifel, Germany

Schmidt,

Hertwig,

Cionoiu

et al. 2024

Contrib Mineral Petrol

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Gem sapphire is commonly retrieved from primary and secondary deposits associated with alkali basaltic fields, but its source rocks are rarely preserved. The Eifel (Rhenish Massif, western Germany), although not producing gem sapphire, shares many petrologic and geochemical similarities with such fields worldwide. Due to the young age of volcanic deposits and active quarrying, sapphire-bearing rocks are readily accessible, along with detrital sapphire from modern sediments. Here, oxygen isotope and trace element compositions are reported for 223 sapphire grains, and rutile and zircon inclusions in sapphire were dated indicating crystallization synchronous with Paleogene–Quaternary volcanism. Endmembers in δ18O range are sapphires from syenites representing mantle-derived differentiated melts with minor crustal contamination (~4–6‰) and contact metamorphic mica schists (>10‰) as purely crustal source rocks. Intermediate values between ~6 and 10‰ require variable degrees of mantle-crust hybridization. Lower crustal granulite sources are dismissed based on their oxygen isotopic compositions being lower than most sapphire crystals. Diffusion modelling of sharp oxygen isotopic zonation in compositionally zoned crystals precludes crystal residence at >900 °C over the lifetime of evolved magma reservoirs in the Eifel (c. 50 ka). This argues against direct mantle or lower crustal sapphire origins. Instead, low temperature residence is consistent with sharp δ18O gradients, coexisting andalusite, and fluid inclusion barometry. Hence, Eifel sapphire crystallization is attributed to contact metamorphic aureoles around upper crustal (5–7 km) magma bodies where phonolite, trachyte, and carbonatite melts differentiated from mafic parental magmas, and reacted with metasedimentary wall rocks.

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Experimental investigation of the reaction between corundum xenocrysts and alkaline basaltic host magma: Constraints on magma residence times of basalt-hosted sapphires

Cited by 5 publications

References 48 publications

Naryn-Gol Creek Sapphire Placer Deposit, Buryatia, Russia

Naryn-Gol Creek Sapphire Placer Deposit, Buryatia, Russia

Morphology of sapphires from secondary deposits, southwestern Montana

Petrologically controlled oxygen isotopic classification of cogenetic magmatic and metamorphic sapphire from Quaternary volcanic fields in the Eifel, Germany

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