Winonaites are a group of
primitive achondrite meteorites
A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon. When the original object en ...
. Like all primitive achondrites, winonaites share similarities with
chondrites
A chondrite is a stony (non-Metallicity, metallic) meteorite that has not been modified, by either melting or planetary differentiation, differentiation of the parent body. They are formed when various types of dust and small grains in the ea ...
and
achondrites
An achondrite is a stony meteorite that does not contain chondrules. It consists of material similar to terrestrial basalts or plutonic rocks and has been differentiated and reprocessed to a lesser or greater degree due to melting and recrystalli ...
.
They show signs of metamorphism, partial melting, brecciation and relic chondrules. Their chemical and mineralogical composition lies between H and E chondrites.
Naming and history
The winonaite group is named after the type specimen, the
Winona meteorite
The Winona meteorite is a primitive achondrite meteorite. It is the type specimen and by far the largest meteorite of the winonaite group.
Discovery and naming
The Winona meteorite is named after Winona, Arizona. The meteorite is said to be disc ...
. The name itself derived from
Winona, Arizona where the type specimen was said to be found during an archaeological excavation of the
Sinagua village
Elden Pueblo in September 1928. The Sinagua lived in the village between 1150 and 1275. The meteorite was said to be retrieved from the
cist of one of the rooms.
However, a later study indicates the meteorite was found at another Sinagua site and not in Elden Pueblo.
[A. L. Christenson "J. W. Simmons' account of the discovery of the Winona meteorite."''Meteorite'' 10(3):14–16, 2004.]
As of 2021, 54 meteorites are included in the winonaite group.
Description
Winonaites are
achondrites
An achondrite is a stony meteorite that does not contain chondrules. It consists of material similar to terrestrial basalts or plutonic rocks and has been differentiated and reprocessed to a lesser or greater degree due to melting and recrystalli ...
that have a chemical and mineral composition similar to
chondrites
A chondrite is a stony (non-Metallicity, metallic) meteorite that has not been modified, by either melting or planetary differentiation, differentiation of the parent body. They are formed when various types of dust and small grains in the ea ...
. Their composition lies between H and E chondrites.
Their isotopic ratios are similar to the silicate inclusions in
IAB meteorites. In
thin section, the mineral grains show microstructures of extensive thermal metamorphism and signs of partial melting.
Some winonaite specimen appear to have relics of chondrules (e.g. Pontlyfni and Mount Morris).
Parent body
Winonaites and the two iron meteorite groups
IAB and
IIICD are thought to be derived from the same parent body. The iron meteorites formed part of the core of the
planetesimal and the winonaites were closer to the surface. The reasoning is that the silicate inclusions in IAB meteorites are similar to winonaites, especially in their oxygen isotope ratios. It is less clear whether IIICD meteorites are also part this parent body.
The winonaites show that the parent body was affected by impacts that formed
breccias of different lithologies. Later these breccias were heated and
Ar-Ar radiometric ages have constrained the
metamorphism on the parent body to between 4.40 and 4.54 billion years. The parent body also reached temperatures where partial melting took place.
Cosmic ray exposure ages show that the meteorites took about 20 to 80 million years to reach earth.
Notable winonaite meteorites
* Hammadah al Hamra 193:
Amphibole
Amphibole () is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is A ...
bearing.
* Pontlyfni: Chondrule relics.
* Mount Morris: Chondrule relics.
*
Winona meteorite
The Winona meteorite is a primitive achondrite meteorite. It is the type specimen and by far the largest meteorite of the winonaite group.
Discovery and naming
The Winona meteorite is named after Winona, Arizona. The meteorite is said to be disc ...
See also
*
Glossary of meteoritics
References
{{Meteorites
Achondrite meteorites