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Immiscible iron- and silica-rich liquids in the Upper Zone of the Bushveld Complex
Citation
Fischer, L and Wang, M and Charlier, B and Namur, O and Roberts, RJ and Veksler, IV and Cawthorn, RG and Holtz, F, Immiscible iron- and silica-rich liquids in the Upper Zone of the Bushveld Complex, Earth and Planetary Science Letters, 443 pp. 108-117. ISSN 0012-821X (2016) [Refereed Article]
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Copyright Statement
© 2016 Elsevier
DOI: doi:10.1016/j.epsl.2016.03.016
Abstract
The Bushveld Complex (South Africa) is the largest layered intrusion on Earth and plays a considerable role in our understanding of magmatic differentiation and ore-forming processes. In this study, we present new geochemical data for apatite-hosted multiphase inclusions in gabbroic cumulates from the Bushveld Upper Zone. Inclusions re-homogenized at high-temperature (1060–1100 °C) display a range of compositions in each rock sample, from iron-rich (35 wt.% FeOtot; 28 wt.% SiO2) to silica-rich (5 wt.% FeOtot; 65 wt.% SiO2). This trend is best explained by an immiscible process and trapping of contrasted melts in apatite crystals during progressive cooling along the binodal of a two-liquid field. The coexistence of both Si-rich and Fe-rich immiscible melts in single apatite grains is used to discuss the ability of immiscible melts to segregate from each other, and the implications for mineral and bulk cumulate compositions. We argue that complete separation of immiscible liquids did not occur, resulting in crystallization of similar phases from both melts but in different proportions. However, partial segregation in a crystal mush and the production of contrasting phase proportions from the Fe-rich melt and the Si-rich melt can be responsible for the cyclic evolution from melanocratic (Fe–Ti–P-rich) to leucocratic (plagioclase-rich) gabbros which is commonly observed in the Upper Zone of the Bushveld Complex where it occurs at a vertical scale of 50 to 200 m.
Item Details
| Item Type: | Refereed Article |
|---|---|
| Keywords: | layered intrusion, melt inclusion, apatite, troctolite, immiscibility, Bushveld |
| Research Division: | Earth Sciences |
| Research Group: | Geology |
| Research Field: | Igneous and metamorphic petrology |
| Objective Division: | Expanding Knowledge |
| Objective Group: | Expanding knowledge |
| Objective Field: | Expanding knowledge in the earth sciences |
| UTAS Author: | Fischer, L (Mr Lennart Fischer) |
| ID Code: | 115049 |
| Year Published: | 2016 |
| Web of Science® Times Cited: | 38 |
| Deposited By: | Earth Sciences |
| Deposited On: | 2017-03-06 |
| Last Modified: | 2017-10-16 |
| Downloads: | 139 View Download Statistics |
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