Itqiy: A metal‐rich enstatite meteorite with achondritic texture

Abstract

Abstract-Itqiy is a unique coarse-grained, metal-rich enstatite meteorite that was found in the Western Sahara and consists of two rocks together weighing 4.72 kg, which are both completely coated with fusion crust. We report results from our electron microprobe and instrumental neutron activation analysis techniques.Itqiy consists of subhedral, equigranular, millimeter-sized enstatite, -25 vol% of millimeter-sized kamacite and a few tiny intergrowths of sulfides and kamacite. Relic chondrules are absent. Pyroxene (Fs0.2) is chemically similar to enstatite in EL chondrites, but the metal is closer in composition to that in EH chondrites. Sulfides resemble those in E chondrites but their compositions are distinct from those in both EL and EH chondrites. Itqiy clearly formed under very reducing conditions, but it does not appear to have formed from EH or EL chondrites.Two thermal events can be distinguished. Silicate compositions including rare earth element abundances indicate loss of partial melt and slow cooling. Heterogeneous sulfides indicate a subsequent reheating and quenching event, which may have been due to shock as many enstatite grains show shock stage S3 features.

Testing an integrated chronology: I‐Xe analysis of enstatite meteorites and a eucrite

“…Metal also passes through silicate as a network of veinlets. Patzer et al (2001) also observed regions of sulfide and metal intergrowths consisting of intergranular assemblages of 3 different sulfides and metal globules. Different features in pyroxene indicate shock stages between 2 and 4 (Patzer et al 2001).…”

“…Patzer et al (2001) also observed regions of sulfide and metal intergrowths consisting of intergranular assemblages of 3 different sulfides and metal globules. Different features in pyroxene indicate shock stages between 2 and 4 (Patzer et al 2001). Itqiy enstatite shows no evidence for zoning and has Na 2 O, FeO and MnO abundances similar to EL chondrite pyroxenes, though CaO content is considerably higher than in ELs, whereas kamacite is compositionally identical to that of EH chondrites.…”

“…Modal analysis yields 78% silicate, 14% metal, and 8% "rust" (Patzer et al 2001). Silicate (En 96.8 Fs 0.2 Wo 3.0 ), which has been extensively recrystallized, forms subhedral, equigranular grains (0.5-4 mm), while the metal grains range from 0.2 to 2 mm.…”

“…The sulfide assemblages consist of a Mg-Mn-Fe sulfide host with oldhamite, Fe-Cr sulfide (consistent with ELs) and metal droplets embedded in it. The host sulfide has a very variable composition that falls within neither the EL or EH fields (Patzer et al 2001). Itqiy therefore shows no clear affinity to either the EH or EL groups, and hence is classed as anomalous.…”

“…The petrology of Itqiy indicates a complex thermal history recording at least two major events: crystallization of large silicate grains and later heating indicated by the mixed sulfide assemblage (Patzer et al 2001). The most enstatite rich separate, ItC, shows the best defined isochron which is associated with early silicate formation or recrystallization.…”