Bell, S.K. orcid.org/0000-0002-4638-2863, Morgan, D.J. orcid.org/0000-0002-7292-2536, Joy, K.H. et al. (2 more authors) (2023) Determining the thermal histories of Apollo 15 mare basalts using diffusion modelling in olivine. Geochimica et Cosmochimica Acta, 357. pp. 77-91. ISSN 0016-7037
Abstract
Mare basalts collected at the Apollo 15 landing site can be classified into two groups. Based on differing whole-rock major element chemistry, these groups are the quartz-normative basalt suite and the olivine-normative basalt suite. In this study we use modelling of Fe-Mg interdiffusion in zoned olivine crystals to investigate the magmatic environments in which the zonation was formed, be that within the lunar crust or during cooling within a surficial lava flow, helping to understand the thermal histories of the two basalt suites. Interdiffusion of Fe-Mg in olivine was modelled in 29 crystals in total, from six olivine-normative basalt thin sections and from three quartz-normative basalt thin sections. We used a dynamic diffusion model that includes terms for both crystal growth and intracrystalline diffusion during magma cooling. Calculated diffusion timescales range from 5 to 24 days for quartz-normative samples, and 6 to 91 days for olivine-normative samples. Similarities in diffusion timescales point to both suites experiencing similar thermal histories and eruptive processes. The diffusion timescales are short (between 5 and 91 days), and compositional zonation is dominated by crystal growth, which indicates that the diffusion most likely took place during cooling and solidification within lava flows at the lunar surface. We used a simple conductive cooling model to link our calculated diffusion timescales with possible lava flow thicknesses, and from this we estimate that Apollo 15 lava flows are a minimum of 3–6 m thick. This calculation is consistent with flow thickness estimates from photographs of lava flows exposed in the walls of Hadley Rille at the Apollo 15 landing site. Our study demonstrates that diffusion modelling is a valuable method of obtaining information about lunar magmatic environments recorded by individual crystals within mare basalt samples.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) |
Keywords: | Diffusion; Olivine; Mare basalt; Lunar magmatism; Apollo 15 |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 22 Aug 2023 14:50 |
Last Modified: | 22 Aug 2023 14:50 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.gca.2023.08.009 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:202382 |