Following a detonation with accompanying light, a stone weighing 410 g was recovered by a nomad in Saguia el Hamra, Western Sahara. In July of 2000, the Labenne family searched for meteorites in the same area near Itqiy and recovered a second stone that weighed 4,310 g. The large, smooth stone was covered with a thin, black fusion crust still exhibiting flow lines. Although this meteorite has a low weathering grade (W1–2) consistent with a recent fall, 14C results infer a terrestrial age for Itqiy of 5,800 (±500) years. Initial classification of Itqiy was completed at the Lunar & Planetary Laboratory, University of Arizona.
Itqiy consists of ~78 vol% equigranular silicates composed of coarse-grained enstatite with a size range of 0.5–4 mm. These are chemically similar to those in EL chondrites but have a significantly higher CaO content. These pyroxene grains form 120° triple junctions which are consistent with an extended annealing process and a high degree of recrystallization. Undulose extinction, irregular fractures, and occasional mosaicism within the grains reflect severe shock exposure consistent with a shock stage of S2–4. However, other evidence of deformation and a lack of twinning, leads to a shock classification of S3.
Kamacite forms 0.2–2 mm diameter grains and vein networks comprising ~22 vol% of the meteorite, with a compositional range similar to the EH chondrites. In contrast, kamacite spherules embedded within sulfide have a composition similar to EL chondrites. No taenite is present and only rare troilite occurs. The Mg–Mn–Fe-sulfides present in Itqiy are compositionally different from those in EH or EL chondrites, and the Fe–Cr sulfides are unusual as well. Furthermore, the Mg/Si and Fe/Si ratios are significantly higher than those in EH or EL chondrites. Plagioclase and relict chondrules are absent.
An absence of radiogenic gases in Itqiy probably reflects a recent loss through an impact melting event, likely related to shock heating during its excavation. The signature of trapped noble gases in Itqiy shows a subsolar component similar to that of E chondrites of petrologic grades 4–6 (as opposed to the sub-Q signature of type-3 E chondrites), which suggests a possible genetic relationship to equilibrated E chondrites. Moreover, from the similar CRE ages between Itqiy (30.1 ±3.0 m.y.) and E chondrites (28.8 m.y.), as well as by their corresponding O-isotopic compositions, it may be concluded that they formed in a similar region of the solar nebula.
While similarities do exist between Itqiy and the EH and EL chondrites, the many inconsistencies make a definitive assignment tenuous—the assignment of Itqiy to the EH group is followed here as recommended in the Meteoritical Bulletin Database. The compositional and textural characteristics of Itqiy may be analogous to those observed in the lodranites, i.e., derivation from a residual melt from which an ~20% basaltic partial melt rich in plagioclase and sulfide had been removed. This occurred under highly reducing conditions on a metal-enriched, E chondrite parent body, where subsequent cooling over a long period allowed extensive equilibration to occur. Other mineralogical features of Itqiy, including the shock features, are consistent with a late impact-heating event to temperatures below 900°C, followed by rapid cooling.
Studies of the 42.9 g enstatite achondrite NWA 2526, which were published by Keil and Bischoff (2008), determined that this meteorite shares many textural and mineralogical characteristics with Itqiy and possibly QUE 94204, potentially forming a grouplet of meteorites that formed as residues of a low degree partial melt, possibly on the same parent body. This object would could represent a fifth enstatite chondrite parent body distinct from those associated with the EH, EL, Shallowater, and aubrite meteorites (Keil and Bischoff, 2008; Izawa et al., 2011). The photo above shows a 1.3 g interior slice of Itqiy. Below is a picture of the complete mass in situ.
