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Portales Valley meteorite, Portales, Roosevelt Co., New Mexico, USA

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Latitude & Longitude (WGS84): 34° 10' 30'' North , 103° 17' 42'' West
Latitude & Longitude (decimal): 34.175, -103.295


Ordinary Chondrite (H6; S1-3; W0)
Fell June 13, 1998. Total mass >100 kg (by 2000.

After detonations and a smoky trail, a shower of stones (over 50 stones recovered) were found near Portales, New Mexico over an ~8 x 2 km ellipse. Largest recovered fragments were 34.0, 17.0, and 16.5 kg. While classified as an ordinary H chondrite, Portales Valley is by no means an ordinary 'ordinary chondrite'. The meteorite consists partially of large angular silicate clasts composed primarily of H-like material. Homogeneous olivine (Fa18.4), orthopyroxene (Fs16.3), and albitic plagioclase are quite normal for H chondrites. However, it is also characterized by unusually large and conspicuous Fe-Ni metal veins which are chemically quite similar — but not identical in detail — to the metal in most H chondrites. Petrographically peaking, however, the large veins are unique — they often have essentially straight line borders with the silicate clasts. Indeed, the appearance of some regions are much more like some classical stony-irons (pallasite, mesosiderites) than a 'stony' chondrite. A number of the opaques (notably troilite and chromite) are distributed in uneven fashion between the silicate-rich and metal-rich regions. Also curious are occasional concentrations along phase borders — copper rinds between metal and troilite, tetrataenite between kamacite and taenite, swathing kamacite along silicate boundaries.

There is ample evidence of varying levels of shock — especially in olivine. Small curvilinear veins of tiny kamacite, troilite, and chromite grins are also present. One way to account for many of these features has been to describe Portales Valley as an 'impact breccia.' It should be noted, however, that the central conundrum of the meteorite, the simultaneous presence of equilibrated, relatively undisturbed silicates in close proximity to once very active molten metal is not an assemblage which leads itself to an easy and obvious explanation.

While the 16.5 kg mass was purchased by a consortium of scientific institutions, much of the meteorite has been distributed though commercial meteorite dealers.

Mineral List


10 valid minerals.

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References

Rubin, A.E., Ulff-Møller, F., W., J.T. & C, W.D. (2001) Article: Geochimica et Cosmochimica Acta 65(2): 323-342. (Jan 2001).

Ruzicka, A., Killgore, M., Mittlefehldt, D. W. & Fries, M. D. (2005) Portales Valley: Petrology of a metallic-melt meteorite breccia. Meteoritics & Planetary Science 40 (2): 261-295. (Feb 2005).

Ruzicka, A. & Hutson, M. (2005) Portales Valley: Not Just Another Ordinary Chondrite. Planetary Science Research Discoveries. (Sept 2005).

Scott, E.R.D., Krot, T.V., Goldstein, J.I. & Wakita, S. (2014) Thermal and impact history of the H chondrite parent asteroid during metamorphism: Constraints from metallic Fe-Ni. Geochimica et Cosmochimica Acta 136: 13-37. (July 2014).

Grady, M.M., Pratesi, G. & Moggi-Cecchi, V. (2015) Atlas of Meteorites. Cambridge University Press: Cambridge, United Kingdom. 373 pages.

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