Extraterrestrial chromite in the resurge deposits of the early Late Ordovician Lockne Crater, central Sweden

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doi: 10.1016/j.epsl.2006.10.034
Authors:Alwmark, Carl; Schmitz, Birger
Author Affiliations:Primary:
University of Lund, Department of Geology, Lund, Sweden
Volume Title:Earth and Planetary Science Letters
Source:Earth and Planetary Science Letters, 253(1-2), p.291-303. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X
Publication Date:2007
Note:In English. Supplemental information/data is available in the online version of this article. 56 refs.; illus., incl. anals., 2 tables, geol. sketch map
Summary:The distribution of extraterrestrial chromite grains (> 63 µm) has been studied in the resurge deposit of the early Late Ordovician (458 Ma) Lockne impact structure in central Sweden. A 1-kg-sample of resurge sediment from the rim of the crater is extremely rich in extraterrestrial chromite. In total the sample contains > 125 chromium spinel grains kg-1, most grains being chromite. Due to post-depositional alterations, the origin of several of the grains is dubious, although it is clear that the major part of the chromites is of extraterrestrial origin (> 75 grains kg-1), most likely derived from the impactor. The alterations are primarily due to the hydrothermal system induced by the impactor, with zinc enrichment in the chromites as the most common characteristic. The element chemistry of the least altered chromite grains indicates that the impactor was an ordinary L chondrite. This concurs with a suggested increase in the flux of L chondritic asteroids to Earth, following the disruption of the L chondrite parent body at ca. 470 Ma. More than 170 impact craters are known from around the Earth, but only few of the impactors have been identified, mainly due to the low survival rate of projectile material. Further studies of impact craters will reveal if survival of extraterrestrial chromite is unique for the Lockne structure. Abstract Copyright (2007) Elsevier, B.V.
Sections:Meteorites and tektites; Mineral data
Subsections:Non-silicates
Subjects:Accessory minerals; Chemical composition; Chondrites; Chromite; Diagenesis; Hydrothermal alteration; Impact craters; Impact features; Iridium; L chondrites; Metals; Metasomatism; Meteorites; Ordinary chondrites; Ordovician; Oxides; Paleozoic; Parent bodies; Platinum group; Resurgence; Spinel; Stony meteorites; Upper Ordovician; Weathering; Zinc; Europe; Lockne Crater; Scandinavia; Sweden; Western Europe
Coordinates:N630000 N630000 E1450000 E1450000
Abstract Numbers:07M/886
Record ID:2007051083
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands
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