Unravelling the high-altitude Nansen blue ice field meteorite trap (East Antarctica) and implications for regional palaeo-conditions

Zekollari, Harry; Goderis, Steven; Debaille, Vinciane; Ginneken, Matthias Van; Gattacceca, J.; Jull, A. J. T.; Lenaerts, Jan T. M.; Yamaguchi, A.; Huybrechts, Philippe; Claeys, Philippe

doi:10.1016/j.gca.2018.12.035

Cited by 21 publications

(14 citation statements)

References 107 publications

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“…By assuming conservation of glacial mass (see the Supplemental Material 1 ), we find the effective surface area to be 2.58× larger than the actual area, on average. This implies that the areas of the upstream catchments are significantly smaller than previously assumed (Sinisalo and Moore, 2010), but consistent with a recent study (Zekollari et al, 2019). In addition, by considering the ice surface velocity for each MSZ (see the Supplemental Material), we find that meteorites have a mean surface residency time scale of ∼7.2 k.y.…”

Section: Methods and Resultssupporting

confidence: 90%

The spatial flux of Earth’s meteorite falls found via Antarctic data

Evatt

Smedley

Joy

et al. 2020

Geology

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Contemporary calculations for the flux of extraterrestrial material falling to the Earth’s surface (each event referred to as a “fall”) rely upon either short-duration fireball monitoring networks or spatially limited ground-based meteorite searches. To date, making accurate fall flux estimates from the much-documented meteorite stranding zones of Antarctica has been prohibited due to complicating glacial ice dynamics and difficulties in pairing together distinct meteorite samples originating from the same fall. Through glaciological analysis and use of meteorite collection data, we demonstrate how to overcome these barriers to making flux estimates. Furthermore, by showing that a clear latitudinal variation in fall frequencies exists and then modeling its mathematical form, we are able to expand our Antarctic result to a global setting. In this way, we hereby provide the most accurate contemporary fall flux estimates for anywhere on Earth. Inverting the methodology provides a valuable tool for planning new meteorite collection missions to unvisited regions of Antarctica. Our modeling also enables a reassessment of the risk to Earth from larger meteoroid impacts—now 12% higher at the equator and 27% lower at the poles than if the flux were globally uniform.

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Section: Methods and Resultssupporting

confidence: 90%

The spatial flux of Earth’s meteorite falls found via Antarctic data

Evatt

Smedley

Joy

et al. 2020

Geology

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“…The rinds have been explained assuming that weathering occurred once meteorites were exposed at the ice surface, because of the interaction with acidic atmospheric species and tiny amounts of liquid water during summer 18 . Meteorites from blue ice can have remained into the ice for periods up to tens of thousands of years, reaching deep portions of the Antarctic ice sheet before surfacing 19 , 53 , 54 . The interface between deep ice and meteorites could promote the occurrence of acidic aqueous brines because of the crystallographic misfits between ice and mineral structures.…”

Section: Resultsmentioning

confidence: 99%

Jarosite formation in deep Antarctic ice provides a window into acidic, water-limited weathering on Mars

et al. 2021

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Many interpretations have been proposed to explain the presence of jarosite within Martian surficial sediments, including the possibility that it precipitated within paleo-ice deposits owing to englacial weathering of dust. However, until now a similar geochemical process was not observed on Earth nor in other planetary settings. We report a multi-analytical indication of jarosite formation within deep ice. Below 1000 m depth, jarosite crystals adhering on residual silica-rich particles have been identified in the Talos Dome ice core (East Antarctica) and interpreted as products of weathering involving aeolian dust and acidic atmospheric aerosols. The progressive increase of ice metamorphism and re-crystallization with depth, favours the relocation and concentration of dust and the formation of acidic brines in isolated environments, allowing chemical reactions and mineral neo-formation to occur. This is the first described englacial diagenetic mechanism occurring in deep Antarctic ice and supports the ice-weathering model for jarosite formation on Mars, highlighting the geologic importance of paleo ice-related processes on this planet. Additional implications concern the preservation of dust-related signals in deep ice cores with respect to paleoclimatic reconstructions and the englacial history of meteorites from Antarctic blue ice fields.

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“…12). While surface snow samples in Antarctica have revealed highly variable O isotopic compositions, the nearby Nansen blue icefield indicates d 18 O values of À43 ± 3‰ (1 SD; n = 185; Zekollari et al, 2019). Although alteration products of Antarctic CSs vary widely depending on the sample location, exposure age, and textural type of the particles, these will be dominated by Feoxyhydroxides, clay minerals, or palagonite .…”

Section: Constraints From Oxygen Isotope Ratiosmentioning

confidence: 99%

Cosmic spherules from Widerøefjellet, Sør Rondane Mountains (East Antarctica)

Goderis

Soens

Huber

et al. 2020

Geochimica et Cosmochimica Acta

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A newly discovered sedimentary accumulation of micrometeorites in the Sør Rondane Mountains of East Antarctica, close to the Widerøefjellet summit at $2750 m above sea level, is characterized in this work. The focus here lies on 2099 melted cosmic spherules larger than 200 lm, extracted from 3.2 kg of sampled sediment. Although the Widerøefjellet deposit shares similarities to the micrometeorite traps encountered in the Transantarctic Mountains, both subtle and more distinct differences in the physicochemical properties of the retrieved extraterrestrial particles and sedimentary host deposits are discernable (e.g., types of bedrock, degree of wind exposure, abundance of metal-rich particles). Unlike the Frontier Mountain and Miller Butte sedimentary traps, the size fraction below 240 lm indicates some degree of sorting at Widerøefjellet, potentially through the redistribution by wind, preferential alteration of smaller particles, or processing biases. However, the cosmic spherules larger than 300 lm appear largely unbiased following their size distribution, frequency by textural type, and bulk chemical compositions. Based on the available bedrock exposure ages for the Sør Rondane Mountains, extraterrestrial dust is estimated to have accumulated over a time span of $1-3 Ma at Widerøefjellet. Consequently, the Widerøefjellet collection reflects a substantial reservoir to sample the micrometeorite influx over this time interval. Petrographic observations and 3D microscopic CT imaging are combined with chemical and triple-oxygen isotopic analyses of silicate-rich cosmic spherules larger than 325 lm. The major element composition of 49 cosmic spherules confirms their principally chondritic parentage. For 18 glassy, 15 barred olivine, and 11 cryptocrystalline cosmic spherules, trace element concentrations are also reported on.Based on comparison with evaporation experiments reported in literature and accounting for siderophile and chalcophile element losses during high-density phase segregation and ejection, the observed compositional sequence largely reflects progressive heating and evaporation during atmospheric passage accompanied by significant redox shifts, although the influence of (refractory) chondrite mineral constituents and terrestrial alteration cannot be excluded in all cases. Twenty-eight cosmic spherules larger than 325 lm analyzed for triple-oxygen isotope ratios confirm inheritance from mostly carbonaceous chondritic precursor materials ($55% of the particles). Yet, $30% of the measured cosmic spherules and $50% of all glassy cosmic spherules are characterized by oxygen isotope ratios above the terrestrial fractionation line, implying genetic links to ordinary chondrites and parent bodies currently unsampled by meteorites. The structural, textural, chemical, and isotopic characteristics of the cosmic spherules from the Sør Rondane Mountains, and particularly the high proportion of Mg-rich glass particles contained therein, imply a well-preserved and representative new sedimentary micrometeorite collect...

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Unravelling the high-altitude Nansen blue ice field meteorite trap (East Antarctica) and implications for regional palaeo-conditions

Cited by 21 publications

References 107 publications

The spatial flux of Earth’s meteorite falls found via Antarctic data

The spatial flux of Earth’s meteorite falls found via Antarctic data

Jarosite formation in deep Antarctic ice provides a window into acidic, water-limited weathering on Mars

Cosmic spherules from Widerøefjellet, Sør Rondane Mountains (East Antarctica)

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