Metasomatised lower crustal and upper mantle xenoliths from north Queensland: Chemical and isotopic evidence bearing on the composition and source of the fluid phase

Journal Article · Wed Mar 01 00:00:00 EST 1989 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(89)90008-2· OSTI ID:5098028

Stolz, A J; Davies, G R ^[1]

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1. Univ. of Tasmania (Australia)

A diverse range of ultramafic and mafic granulite xenoliths from cone No. 32, north Queensland display mineralogical and chemical evidence for enhanced fluid activities in the lowermost crust and uppermost mantle. Metasomatism of spinel lherzolite, garnet and spinel websterite and garnet granulite produced variable amounts of amphibole {plus minus} mica, locally resulting in development of hornblendite as the end-product of reaction between spinel websterite and C-O-H fluids. In contrast, associated felsic and 2-pyroxene granulite xenoliths have remained relatively unaffected. The garnet granulites and spinel websterites are interpreted as products of underplating of the lower crust by Cenozoic magmatic activity, whereas Nd-Sr isotope systematics for the 2-pyroxene and felsic granulite xenoliths suggest that they may be of Proterozoic age. The chemical and isotopic data suggest that the metasomatism is a relatively young feature caused by oxidized fluids exsolved from alkaline magmas similar to the host as they ascended through the lithosphere. This style of metasomatism is considered a relatively localized phenomenon which is unlikely to provide an important contribution to the source regions of alkali basaltic magmas.

• OSTI ID: 5098028
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Vol. 53:3; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
BASALT
CHEMICAL COMPOSITION
HYDROTHERMAL STAGE
INCLUSIONS
PETROGENESIS
HYDROTHERMAL ALTERATION
MINERALOGY
QUEENSLAND
AMPHIBOLE
GARNETS
GEOCHEMISTRY
GEOTHERMAL FLUIDS
ISOTOPE RATIO
MAGMA
MAGMATISM
METAMORPHISM
MICA
NEODYMIUM ISOTOPES
PYROXENES
STRONTIUM ISOTOPES
ALKALINE EARTH ISOTOPES
AUSTRALASIA
AUSTRALIA
CHEMISTRY
FLUIDS
IGNEOUS ROCKS
ISOTOPES
MINERALS
OXYGEN COMPOUNDS
ROCKS
SILICATES
SILICON COMPOUNDS
VOLCANIC ROCKS
580000* - Geosciences