Hepworth, LN, Daly, JS, Gertisser, R ORCID: https://orcid.org/0000-0002-9973-2230, Johnson, CG, Emeleus, CH and O’Driscoll, B (2020) Rapid crystallization of precious-metal-mineralized layers in mafic magmatic systems. Nature Geoscience.

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Abstract

The solidified remnants of mafic magmatic systems host the greatest concentrations of platinum-group metals in the Earth’s crust. Our understanding of precious-metal mineralization in these intrusive bodies is underpinned by a traditional view of magma chamber processes and crystal mush solidification. However, considerable uncertainty remains regarding the physical and temporal controls on concentrating these critical metals, despite their importance to modern society. We present high-precision 87Sr/86Sr analyses of plagioclase and clinopyroxene from within centimetre-thick precious-metal-enriched layers in the Palaeogene open-system Rum layered intrusion (northwest Scotland). Isotopic heterogeneity is present between plagioclase crystals, between clinopyroxene and plagioclase and within plagioclase crystals throughout the studied section. On the basis of these observations, we demonstrate that platinum-group element mineralization formed by repeated small-volume reactive melt percolation events. The preservation of strontium isotope heterogeneities at 10–100 µm length scales implies cooling of the melts that formed the precious-metal-rich layers occurred at rates greater than 1 °C per year, and cooling to diffusive closure within tens to hundreds of years. Our data highlight the importance of cyclic dissolution–recrystallization events within the crystal mush and raise the prospect that precious-metal-bearing mafic intrusions may form by repeated self-intrusion during cooling and solidification.

Item Type: Article
Additional Information: The final accepted manuscript and all relevant information can be found at; https://www.nature.com/articles/s41561-020-0568-3
Uncontrolled Keywords: Economic geology; Geochemistry; Scientific community; Solid Earth sciences
Subjects: G Geography. Anthropology. Recreation > G Geography (General)
G Geography. Anthropology. Recreation > GE Environmental Sciences
Divisions: Faculty of Natural Sciences > School of Geography, Geology and the Environment
Depositing User: Symplectic
Date Deposited: 28 Apr 2020 09:02
Last Modified: 28 Apr 2020 09:02
URI: https://eprints.keele.ac.uk/id/eprint/7877

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