H_chondrite Knowpia

H chondrite
H chondrite
— Group —
	Weston meteorite, H4
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
	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 all chondrites.^[1] The ordinary chondrites are thought to have originated from three parent asteroids, whose fragments make 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.

Gallery edit

Gao-Guenie, H5
H5 Dar Bou Nali South Morocco

References edit

^ "Natural History Museum, meteorite catalogue". Archived from the original on 2006-05-03. Retrieved 2005-11-29.
^ NASA (YouTube) – Dr. David Kring – Asteroid Initiative Workshop Cosmic Explorations Speakers Session
^ M. J. Gaffey & S. L. Gilbert Asteroid 6 Hebe: The probable parent body of the H-Type ordinary chondrites and the IIE iron meteorites, Meteoritics & Planetary Science, Vol. 33, p. 1281 (1998).