NORTHWEST AFRICA 960


Ordinary Chondrite, type 3, metal-poor
(ungrouped)
standby for nwa 960 photo
Purchased December 2001
no coordinates recorded

A single stone weighing 997 g was found in Northwest Africa and purchased by A. and G. Hupé in Erfoud, Morocco. Samples were sent for analysis to the University of Washington, Seattle (A. Irving and S. Kuehner) and the Johnson Space Center, Houston (M. Zolensky). This meteorite contains mostly sub-mm-sized chondrules which are primarily olivine-rich, but a minor component of low-Ca pyroxene chondrules is present. It was determined that olivine and pyroxene have Fa and Fs values that lie outside of the range of the ordinary–rumurutiite chondrite clan. Minor mineral phases include magnetite, troilite, pentlandite, chromite and glass. FeNi-metal is absent, possibly due to its complete oxidation to magnetite.

In an effort to resolve the group to which this meteorite belongs, two separate labs were employed for oxygen isotope analysis—the University of Chicago (R. Clayton) and the Carnegie Institution, Washington D.C. (D. Rumble, III). On an oxygen three-isotope diagram, the values plot outside of the field of the ordinary–rumurutiite chondrite clan, and after five years of study, it was decided that NWA 960 is best considered an anomalous, metal-poor, non-carbonaceous chondrite. Along with NWA 960, a small number of anomalous, ungrouped, non-carbonaceous chondrites have been studied and classified to date including HaH 180, NWA 2335, and NWA 2336, for which O-isotopic comparisons have been made to explore any possible genetic relationships (i.e., same parent body) among them. As shown on an oxygen three-isotope diagram, constructed by Achim Raphael, these meteorites plot very close to each other and might constitute a distinct field.

An additional small number of metal-poor, ungrouped non-carbonaceous chondrites have also been studied and classified to date, including the following members of the NWA-series: 2040 [LL], 2041 [L], 3114 [L], 3127 [LL], 3157 [L], 4294 [LL], 4298 [LL], 4486 [L], 4531 [LL], and 5717 [L+LL]). Oxygen isotopic analyses infer a possible "supra-TFL" genetic grouping for these meteorites, which have a slope distinct from the ordinary chondrites (H, L, and LL) as illustrated on the oxygen three-isotope diagram below.

standby for metal-poor oxygen plot
Diagram credit: Rumble, III et al., 38th LPSC, #2230 (2007)

See further details about this "supra-TFL" grouping of meteorites on the HaH 180 page. Northwest Africa 960 is very weakly shocked to stage S1, and weathered to grade W1–2. The photo above shows a 5.2 g partial slice of this anomalous chondrite.