Sediment-Dispersed Extraterrestrial Chromite Traces a Major Asteroid Disruption Event

Schmitz, Birger; Häggström, Therese; Tassinari, Mario

doi:10.1126/science.1082182

Cited by 121 publications

(132 citation statements)

References 14 publications

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“…In summary, all inclusions plot within the L-chondritic field, which is in accordance with the previous classifications for the Ö sterplana fossil meteorites and the sediment-dispersed EC grains (Schmitz et al, 2001(Schmitz et al, , 2003Schmitz and Häggströ m, 2006;Bridges et al, 2007;Greenwood et al, 2007) as well as the revised classification of the Brunflo meteorite (Alwmark and Schmitz, 2008). The overall concordance in classification of the fossil meteorites and the sediment-dispersed grains with previous studies implies that the composition of inclusions of olivine and Ca-poor pyroxene in chromite from ordinary equilibrated chondrites can be used in determining meteorite group with no or very little overlap.…”

Section: Classification Of the Fossil Meteorites And The Origin Of Thsupporting

confidence: 67%

“…The Brunflo meteorite has formerly been assigned to the H-chondrite group (Thorslund et al, 1984), but a recent study by Alwmark and Schmitz (2008) shows that it belongs to the L group, founded, for example, on mean chondrule size. The sediment-dispersed EC grains have been interpreted as originating from mainly L-chondritic material; this is based primarily on the chromite element composition (Schmitz et al, 2003;Schmitz and Häggströ m, 2006).…”

Section: Methodsmentioning

confidence: 99%

“…This is the first report on silicate inclusions in chromite from recent chondrites as well as in 470 Ma old fossil meteorites (Schmitz et al, 2001) and coeval sediment-dispersed chondritic chromite grains (Schmitz et al, 2003;Schmitz and Häggströ m, 2006). We demonstrate how these inclusions can be used for assessing the meteorite group from which the host chromite grain originates.…”

Section: Introductionmentioning

confidence: 99%

“…At 470 Ma the disruption of the L-chondrite parent body occurred (Anders, 1964;Korochantseva et al, 2007), and the high abundance of fossil meteoritic material in sediments from this time has been related to this event, based partly on the L-chondritic composition of relict chromite grains (Schmitz et al, 2001(Schmitz et al, , 2003Schmitz and Häggströ m, 2006). Because meteoritic material on the Earth surface is rapidly altered or weathered away, with the exception of chromite (FeCr 2 O 4 ), constituting 0.05-0.5 wt% of recent chondrites (Keil, 1962), the classification of the fossil chondritic material in these studies has been based mainly on elemental and O-isotopic composition of chromite (e.g., Schmitz et al, 2001;Alwmark and Schmitz, 2007;Greenwood et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

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Relict silicate inclusions in extraterrestrial chromite and their use in the classification of fossil chondritic material

Alwmark

Schmitz

2009

Geochimica et Cosmochimica Acta

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Chromite is the only common meteoritic mineral surviving long-term exposure on Earth, however, the present study of relict chromite from numerous Ordovician (470 Ma) fossil meteorites and micrometeorites from Sweden, reveals that when encapsulated in chromite, other minerals can survive for hundreds of millions of years maintaining their primary composition. The most common minerals identified, in the form of small (<1-10 lm) anhedral inclusions, are olivine and pyroxene. In addition, sporadic merrillite and plagioclase were found.Analyses of recent meteorites, holding both inclusions in chromite and corresponding matrix minerals, show that for olivine and pyroxene inclusions, sub-solidus re-equilibration between inclusion and host chromite during entrapment has led to an increase in chromium in the former. In the case of olivine, the re-equilibration has also affected the fayalite (Fa) content, lowering it with an average of 14% in inclusions. For Ca-poor pyroxene the ferrosilite (Fs) content is more or less identical in inclusions and matrix. By these studies an analogue to the commonly applied classification system for ordinary chondritic matrix, based on Fa in olivine and Fs in Ca-poor pyroxene, can be established also for inclusions in chromite. All olivine and Ca-poor pyroxene inclusions (>1.5 lm) in chromite from the Ordovician fossil chondritic material plot within the Lchondrite field, which is in accordance with previous classifications. The concordance in classification together with the fact that inclusions are relatively common makes them an accurate and useful tool in the classification of extraterrestrial material that lacks matrix silicates, such as fossil meteorites and sediment-dispersed chromite grains originating primarily from decomposed micrometeorites but also from larger impacts.

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Section: Classification Of the Fossil Meteorites And The Origin Of Thsupporting

confidence: 67%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Relict silicate inclusions in extraterrestrial chromite and their use in the classification of fossil chondritic material

Alwmark

Schmitz

2009

Geochimica et Cosmochimica Acta

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“…Chromite is the only common mineral in chondrites that survives extensive weathering on the wet Earth surface. In the limestone beds containing common meteorites also abundant chromite grains from decomposed micrometeorites are found [10][11][12] . Cosmic-ray induced 21 Ne in chromite from the fossil meteorites increases upward in the strata, supporting a common origin from an asteroid breakup event 13 .…”

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confidence: 99%

Asteroid breakup linked to the Great Ordovician Biodiversification Event

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Population of Impactors and the Impact Cratering Rate in the Inner Solar System

Michel¹,

Morbidelli²

2012

Impact Cratering

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The investigation of the surface histories of the solid planets and satellites is a major objective of planetary exploration. Most solid bodies in the Solar System display a record of accumulated impact cratering on their surfaces. These craters range in size from a few metres or smaller in diameter to hundreds of thousands of kilometres (e.g. giant basins on the Moon, Mars and Mercury). Assuming a constant impact rate with time, the age of a surface is proportional to the number of impacts it has experienced. Thus, if it is possible to estimate the rate of crater production on a surface, then the total number of craters can allow the estimate of the age of this surface. However, the cratering rate on a planet is related to the population of projectiles, in particular their orbital and size distribution. The determination of cratering rates, therefore, requires a good knowledge of the population of potential impactors, which allows the determination of their impact frequencies on planets. Then, a good understanding of the cratering process itself is required to establish the relationship between the diameters of the crater and the projectile, as a function of the projectile's mass, velocity, impact angle and planetary characteristics.The only absolute chronology of craters up to 3.8 Ga that has been studied in detail so far is the lunar case, which was calibrated by dating of lunar samples brought back by the Apollo missions. The lunar crater-production function is the best investigated among those on terrestrial planet surfaces, as it is based on a large image database at various resolutions. Conversely, we do not yet have any samples of known portions of the Martian surface, and this is the main reason why different models have been developed to estimate the Martian cratering rate, with the goal of establishing a Martian surface chronology. On Earth, the situation is even worse, as the geological activity is high and several mechanisms (e.g. erosion, plate tectonics) erase crater features over time, making the cratering record incomplete (see Chapter 16). Of the terrestrial planets, only the Moon, Mercury and Mars Impact Cratering: Processes and Products, First Edition. Edited by Gordon R. Osinski and Elisabetta Pierazzo. have heavily cratered surfaces, and all these surfaces have complex crater size distributions. For instance, the crater distributions of Mercury and Mars at diameters less than 40 km are steeper than the lunar distribution due to the obliteration of a fraction of small craters by plains formation (Strom et al., 2005). On Venus, the crater density is an order of magnitude less than on Mars. The reason is twofold: (1) only young craters are present due to resurfacing events, which erased older craters;(2) small craters on this planet are rare because the small impactors cannot penetrate the thick atmosphere. Finally, the crater counting can be affected by the potential presence of secondary and multiple craters (Bierhaus et al., 2005).The cratering record of the outer Solar System suffers from e...

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Sediment-Dispersed Extraterrestrial Chromite Traces a Major Asteroid Disruption Event

Cited by 121 publications

References 14 publications

Relict silicate inclusions in extraterrestrial chromite and their use in the classification of fossil chondritic material

Relict silicate inclusions in extraterrestrial chromite and their use in the classification of fossil chondritic material

Asteroid breakup linked to the Great Ordovician Biodiversification Event

Population of Impactors and the Impact Cratering Rate in the Inner Solar System

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