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An urban collection of modern-day large micrometeorites: Evidence for variations in the extraterrestrial dust flux through the Quaternary

Genge, M.J., Larsen, J., van Ginneken, M., Suttle, M.D. (2017) An urban collection of modern-day large micrometeorites: Evidence for variations in the extraterrestrial dust flux through the Quaternary. Geology, 45 (2). pp. 119-122. ISSN 0091-7613. E-ISSN 1943-2682. (doi:10.1130/G38352.1) (KAR id:88137)

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Official URL:
https://doi.org/10.1130/G38352.1

Abstract

We report the discovery of significant numbers (500) of large micrometeorites (>100 μm) from rooftops in urban areas. The identification of particles as micrometeorites is achieved on the basis of their compositions, mineralogies, and textures. All particles are silicate-dominated (S type) cosmic spherules with subspherical shapes that form by melting during atmospheric entry and consist of quench crystals of magnesian olivine, relict crystals of forsterite, and iron-bearing olivine within glass. Four particles also contain Ni-rich metal-sulfide beads. Bulk compositions are chondritic apart from depletions in the volatile, moderately volatile, and siderophile elements, as observed in micrometeorites from other sources. The reported particles are likely to have fallen on Earth in the past 6 yr and thus represent the youngest large micrometeorites collected to date. The relative abundance ratio of barred olivine to cryptocrystalline spherule types in the urban particles of 1.45 is shown to be higher than a Quaternary average of ∼0.9, suggesting variations in the extraterrestrial dust flux over the past 800 k.y. Changes in the entry velocities of dust caused by quasi-periodic gravitational perturbation during transport to Earth are suggested to be responsible. Variations in cosmic spherule abundance within the geologic column are thus unavoidable and can be a consequence of dust transport as well as major dust production events.

Item Type: Article
DOI/Identification number: 10.1130/G38352.1
Subjects: Q Science > QE Geology > QE515 Geochemistry
Divisions: Divisions > Division of Natural Sciences > Physics and Astronomy
Depositing User: Matthias van Ginneken
Date Deposited: 14 May 2021 13:23 UTC
Last Modified: 25 Jan 2022 22:24 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/88137 (The current URI for this page, for reference purposes)
van Ginneken, M.: https://orcid.org/0000-0002-2508-7021
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