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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 (10601100 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 (FeTiP-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
Author:Fischer, L (Mr Lennart Fischer)
ID Code:115049
Year Published:2016
Web of Science® Times Cited:3
Deposited By:Earth Sciences
Deposited On:2017-03-06
Last Modified:2017-10-16
Downloads:8 View Download Statistics

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