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Université de Neuchâtel

Aluminous websterite and granulite xenoliths from the Chyulu Hills volcanic field, Kenya: gabbro–troctolitic cumulates subjected to lithospheric foundering

Ulianov, Alexey ; Kalt, Angelika ; Pettke, Thomas

In: Contributions to Mineralogy and Petrology, 2006, vol. 152, no. 4, p. 459-483

Whole rock major and trace element abundances in aluminous garnet–spinel websterite, sapphirine-bearing Mg–Al granulite and hibonite-bearing Ca–Al granulite xenoliths from the Chyulu Hills volcanic field, Kenya, suggest that the samples represent a meta-igneous suite linked by fractionation. The incompatible major element contents increase from the websterites to the Mg–Al granulites and...

Université de Neuchâtel

Detrital, metamorphic and metasomatic tourmaline in high-pressure metasediments from Syros (Greece): intra-grain boron isotope patterns determined by secondary-ion mass spectrometry

Marschall, Horst R. ; Altherr, Rainer ; Kalt, Angelika ; Ludwig, Thomas

In: Contributions to Mineralogy and Petrology, 2008, vol. 155, no. 6, p. 703-717

The boron isotopic composition of zoned tourmaline in two metasediments from the island of Syros, determined by secondary-ion mass spectrometry (SIMS), reflects the sedimentary and metamorphic record of the rocks. Tourmaline from a silicate-bearing marble contains small (≤20 μm) detrital cores with highly variable δ11B values (−10.7 to +3.6‰), pointing to a heterogeneous...

Université de Neuchâtel

Pyroxenite xenoliths from Marsabit (Northern Kenya): evidence for different magmatic events in the lithospheric mantle and interaction between peridotite and pyroxenite

Kaeser, Benjamin ; Olker, Bettina ; Kalt, Angelika ; Altherr, Rainer ; Pettke, Thomas

In: Contributions to Mineralogy and Petrology, 2009, vol. 157, no. 4, p. 453-472

Garnet-bearing and garnet-free pyroxenite xenoliths from Quaternary basanites of Marsabit, northern Kenya, were analysed for microstructures and mineral compositions (major and trace elements) to constrain the thermal and compositional evolution of the lithospheric mantle in this region. Garnet-bearing rocks are amphibole-bearing websterite with ~5–10 vol% orthopyroxene. Clinopyroxene is...

Université de Neuchâtel

Li, B and Be Contents of Harzburgites from the Dramala Complex (Pindos Ophiolite, Greece): Evidence for a MOR-type Mantle in a Supra-subduction Zone Environment

Pelletier, Laure ; Vils, Flurin ; Kalt, Angelika ; Gméling, Katalin

In: Journal of Petrology, 2009, vol. 49, no. 11, p. 2043-2080

The Pindos ophiolite represents oceanic lithosphere obducted during the Jurassic. The Dramala mantle section mainly consists of highly depleted spinel harzburgite and minor plagioclase-bearing harzburgite. Textural observations and major element compositions of minerals indicate that the harzburgites experienced impregnation by a mafic, depleted melt and subsequent high-temperature (high-T)...

Université de Neuchâtel

Boron, lithium and strontium isotopes as tracers of seawater–serpentinite interaction at Mid-Atlantic ridge, ODP Leg 209

Vils, Flurin ; Tonarini, Sonia ; Kalt, Angelika ; Seitz, Hans-Michael

In: Earth and Planetary Science Letters, 2009, vol. 386, no. 3-4, p. 414-425

Spinel harzburgites from ODP Leg 209 (Sites 1272A, 1274A) drilled at the Mid-Atlantic ridge between 14°N and 16°N are highly serpentinized (50–100%), but still preserve relics of primary phases (olivine ≥ orthopyroxene >> clinopyroxene). We determined whole-rock B and Li isotope compositions in order to constrain the effect of serpentinization on δ11B and δ7Li. Our...