Crystallization of titaniferous chromite, magnesian ilmenite and armalcolite in tholeiitic suites in the Karoo Igneous Province
Article Abstract:
The base of the differentiated tholeiitic Mount Ayliff Intrusion in the Karoo Province of southern Africa contains titaniferous chromite and magnesian ilmenite, which shows the presence of titanium oxide (TiO2) in the original magma. It is quite uncommon for tholeiitic rocks to contain armalcolite and for chromite and ilmenite to exist together as in the case of Karoo Province and in Hawaii. A large amount of magnesium oxide is found in ilmenite and armalcolite, and chronium contains a large quantity of TiO2. The effect of TiO2 on the crystallization, composition of ilmenite, chromite, and the effect of armalcolite on atmospheric pressure are studied. The results show that the TiO2 content of the spinel is increased in the picritic magmas affecting Al2O3, while Cr2O3 remains unaffected.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1993
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Models for incompatible trace-element abundances in cumulus minerals and their application to plagioclase and pyroxenes in the Bushveld Complex
Article Abstract:
A mathematical model predicts the outcome of trapped liquids in causing variations in incompatible trace-element distribution in cumulus minerals. Variations occur with different modes in mineral composition. Concentrations of incompatible elements present in low abundance in the rock exhibit extreme enrichment compared to that in the original cumulus mineral. The application of different models on Bushveld Complex shows that plagioclase have Rb contents of 1-5 ppm. The rare earth elements in clinopyroxenes may be twice as much contained in parent liquid.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1996
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Evidence for the trapped liquid shift effect in the Mount Ayliff Intrusion, South Africa
Article Abstract:
An analysis of the trapped liquid shift effect is presented. The analysis considers post-cumulus trapped liquid shift in layered complexes which generate cumulat materials exhibiting more fractionated compositions than initial primary phases. The Mount Ayliff Intrusion shows this effect in olivine compositions forming its base. The occurrence of the shift effect rocks close to intrusion basal contact shows that it is a rapid process.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1992
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