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

M. J. Genge, J. Larsen, M. van Ginneken and M. D. Suttle
An urban collection of modern-day large micrometeorites; evidence for variations in the extraterrestrial dust flux through the Quaternary
Geology (Boulder) (December 2016) 45 (2): 119-122

Abstract

We report the discovery of significant numbers (500) of large micrometeorites (>100 mu m) 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 approximately 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.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 45
Serial Issue: 2
Title: An urban collection of modern-day large micrometeorites; evidence for variations in the extraterrestrial dust flux through the Quaternary
Affiliation: Imperial College London, Department of Earth Sciences and Engineering, London, United Kingdom
Pages: 119-122
Published: 20161205
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 32
Accession Number: 2017-004900
Categories: Petrology of meteorites and tektitesExtraterrestrial geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Secondary Affiliation: Project Stardust, NOR, NorwayUniversite Libre de Bruxelles, BEL, Belgium
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201704
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