H chondrite

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H chondrite
— Group —
Weston meteorite.jpg
Type Chondrite
Structural classification ?
Class Ordinary chondrite
Subgroups
  • H3
  • H4
  • H5
Parent body Possibly 6 Hebe, less likely 3 Juno & 7 Iris
Composition Iron ~25-31%, bronzite (an orthopyroxene), olivine (with characteristic fayalite (Fa) content 16 to 20 mol%), nickel-iron 15-19%, troilite 5%
Petrologic type 3 (~2.5%), 5 (40%), 4 & 6 (57.5%)
Alternative names Bronzite chondrites, Olivine bronzite chondrites
Tetrataenite-138026.jpg
Nuevo Mercurio, H5

The H type ordinary chondrites are the most common type of meteorite, accounting for approximately 40% of all those catalogued, 46% of the ordinary chondrites, and 44% of the chondrites.[1] The ordinary chondrites are thought to have originated from three parent asteroids, with the fragments making up the H chondrite, L chondrite and LL chondrite groups respectively.[2]

Name[edit]

The name comes from their High iron abundance, with respect to other ordinary chondrites.

Historically, the H chondrites have been named bronzite chondrites or olivine bronzite chondrites for the dominant minerals, but these terms are now obsolete.

Parent body[edit]

A probable parent body for this group is the S-type asteroid 6 Hebe, with less likely candidates being 3 Juno and 7 Iris.[3] It is supposed that these meteorites arise from impacts onto small near-Earth asteroids broken off from 6 Hebe in the past, rather than originating from 6 Hebe directly.

The H chondrites have very similar trace element abundances and Oxygen isotope ratios to the IIE iron meteorites, making it likely that they both originate from the same parent body.

Iron[edit]

Their high iron abundance is about 25-31% by weight. Over half of this is present in metallic form, making these meteorites strongly magnetic despite the stony chondritic appearance.

Mineralogy[edit]

The most abundant minerals are bronzite (an orthopyroxene), and olivine. Characteristic is the fayalite (Fa) content of the olivine of 16 to 20 mol%. They contain also 15-19% of nickel-iron metal and about 5% of troilite. The majority of these meteorites have been significantly metamorphosed, with over 40% being in petrologic class 5, most of the rest in classes 4 and 6. Only a few (about 2.5%) are of the largely unaltered petrologic class 3.

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See also[edit]

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