Abstract
Terrestrial analogues are often investigated to get insights into the geological processes occurring on other planetary bodies. Due to its thickness and petrological similarities, the pyroxenitic layer of the 120m-thick magmatic pile Theo’s Flow (Archean Abitibi greenstone belt Ontario, Canada), has always been regarded as the terrestrial analogue for Martian nakhlites. However, its origin and cooling history and, as a consequence those of nakhlites, have always been a matter of vigorous debate. Did this lava flow originate from a single magmatic event similar to those supposed to occur on Mars or do the different units derive from multiple eruptions? We demonstrate, by a combination of geothermometric constraints on augite single crystals and numerical simulations, that Theo’s Flow has been formed by multiple magma emplacements that occurred at different times. This discovery supports the idea that the enormous lava flows with similar compositions observed on Mars could be the result of a process where low viscosity lavas are emplaced during multiple eruptions. This has profound implications for understanding the multiscale mechanisms of lava flow emplacement on Earth and other planetary bodies.
Highlights
Terrestrial analogues are often investigated to get insights into the geological processes occurring on other planetary bodies
An ancient lava flow such as Theo’s Flow, due to its thickness and lithology of the stratigraphic layers, represents the perfect candidate that has been used in the past 20 years as a terrestrial analogue for thick lava flows erupted on Mars
Theo’s Flow is a 120 m-thick magmatic pile located in the mafic and ultramafic region of the Archean Abitibi greenstone belt (Munro Township, Ontario)[1] that was affected by metamorphic alteration under greenschist facies conditions (e.g.
Summary
Terrestrial analogues are often investigated to get insights into the geological processes occurring on other planetary bodies. Its origin and cooling history and, as a consequence those of nakhlites, have always been a matter of vigorous debate Did this lava flow originate from a single magmatic event similar to those supposed to occur on Mars or do the different units derive from multiple eruptions? Based on detailed petrological and stratigraphic analyses Lentz et al.[2,5] concluded that the lithologic diversity observed in Theo’s Flow was the result of a differentiation process of a single, thick magma pulse, rather than being generated by the eruption of multiple magmatic batches with distinct composition This conclusion was based on the absence of sharp boundaries between adjacent units and on the progressive compositional changes www.nature.com/scientificreports observed in mineral and bulk-rock compositions. Given the analogy with Martian lava flows, the mechanism and timing of differentiation of Theo’s Flow deserves further investigation to shed light on these geological processes on Mars
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