Pt, Rh and chromite solubility in basalt-rhyolite mixtures at 1400°C, 0.1 MPa, FMQ +3.4 and FMQ (fayalite-magnetite-quartz-buffer) is presented. Melt samples were equilibrated on Pt90Rh10 loops and in chromite crucibles for up to 100 hours. Pt/Rh solubility decreased 20 and 7-fold respectively, progressing to rhyolitic compositions. Cr solubility decreased 3-fold (FMQ+3.4) and 4-fold (FMQ) over the same compositional interval. At FMQ+3.4, reduced Cr solubility, compared to FMQ, reflects Cr3+ and Fe3+ exchange, stabilizing Fe3+-rich spinel. As SiO2 increases, decreasing Pt/Rh and Cr solubility is interpreted to result from low abundances of non-bridging oxygens and lack of octahedral sites for Cr3+.Numerically simulated diffusive exchange between basalt and rhyolite predicts rapid alloy saturation at high fO2, but undersaturated mixtures at low fO2. Magma mixing produced Fe3+-rich spinel at high fO2; chromite undersaturation occurs near FMQ. Combined chromite and Pt-rich alloy saturation does not appear to result from magma mixing near FMQ.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/42953 |
| Date | 28 November 2013 |
| Creators | Turchiaro, Francesco |
| Contributors | Brenan, James |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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