Mantle metasomatism beneath western Victoria, Australia. I. Metasomatic processes in Cr-diopside lherzolites
Most Cr-diopside spinel lherzolite xenoliths from Bullenmerri and Gnotuk Maars, western Victoria, show modal metasomatism involving the growth of amphibole +- mica +- apatite at the expense of primary pyroxenes + spinel. The metasomatism is attributed to CO/sub 2/-rich fluids, observed in fluid inclusions. REE patterns of anhydrous lherolites range from LREE-depleted ((LaYb)/sub n/ approx. = 0.3) to LREE-enriched ((LaYb)/sub n/ = 30-60), and show an inverse correlation of NdSm with CaO. Amphibole-rich peridotites are enriched in LREE ((LaYb)/sub n/ = 10-30), Ar and Ta, with high KRb. Mica-rich rocks are enriched in K, Rb, Ba, Ta and Ti, with low KRb. Introduction of apatite leads to high ..sigma..REE (with (LaYb)/sub n/ = 40-100), Sr, U and Th contents. The distribution of trace and minor elements in the ilherzolites is thus controlled by the crystal chemistry of the primary and metasomatic phases. Micaceous xenoliths may be derived from thin selvedges on pyroxenite veins. Abundant amphibole lherzolites may form a matrix enclosing relic volumes of anhydrous lherzolites showing varying degrees of cryptic metasomatism. The overall pattern of trace-element enrichment in the mantle beneath Victoria will depend on the volumetric proportions of these rock types.
- Research Organization:
- Macquarie Univ., Sydney (Australia)
- OSTI ID:
- 5100308
- Journal Information:
- Geochim. Cosmochim. Acta; (United States), Journal Name: Geochim. Cosmochim. Acta; (United States) Vol. 52:2; ISSN GCACA
- Country of Publication:
- United States
- Language:
- English
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Mantle metasomatism
Related Subjects
580400* -- Geochemistry-- (-1989)
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
AMPHIBOLE
APATITES
AUSTRALASIA
AUSTRALIA
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
CHEMISTRY
DIOPSIDE
EARTH MANTLE
GEOCHEMISTRY
HYDROTHERMAL ALTERATION
INCLUSIONS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
METAMORPHISM
MICA
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHOSPHATE MINERALS
PYROXENES
QUANTITATIVE CHEMICAL ANALYSIS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SPINELS
VICTORIA