The Zakłodzie enstatite meteorite: Mineralogy, petrology, origin, and classification

Abstract

Abstract-The Zak≥odzie meteorite was found in September 1998, about 40 km west of ZamoúÊ, in southeast Poland. Macroscopic and microscopic observations (in transmitted and reflected light), microprobe analyses, cathodoluminescence images, and X-ray diffraction data show that the meteorite is composed of clino-and orthoenstatite, two generations of feldspars, relict olivine (forsterite), a polymorph of SiO 2 (apparently cristobalite), and opaque minerals: Fe-Ni alloy (kamacite and taenite), troilite, schreibersite, graphite, and sulfide (Mg, Mn, Fe)S, which is probably keilite. The texture is fine-to inequigranular of cumulate type, locally intergranular. The MgS-FeS thermometer indicates that the sulfides crystallized at ∼580-600 ºC. Thus, the Zak≥odzie meteorite formed by the nearly complete melting of an enstatite chondrite protolith, probably at ∼4.4 Ga; the process was likely caused by the decay of the 26 Al nuclide in the planetesimal interior. The second stage of its evolution, which could have happened at ∼2.1 Ga, involved partial re-melting of most fusible components, probably due to collision with another body. The structure, composition, and origin of the meteorite and its relation to the parent rock indicate that Zak≥odzie may represent a primitive enstatite achondrite.

Northwest Africa 2526: A partial melt residue of enstatite chondrite parentage

“…After partial melting and annealing, NWA 2526 experienced a second, relatively mild impact event (<~20 GPa) that caused formation of the polysynthetic twinning in the enstatite. We suggest that the meteorite Zak≥odzie, which has been referred to as a "primitive enstatite achondrite" (Przylibski et al 2005), did not form from a magma of internal origin, but that it is an impact-melt breccia of enstatite chondrite-like parentage, as previously discussed by Burbine et al (2000) and Keil (2007).…”

“…Specifically, Keil (2007) noted that the relict chondrule shown in Fig. 2 in Przylibski et al (2005) and identified as such by these authors is a common feature of impact-melt breccias of enstatite chondrite parentage (e.g., . Keil (2007) also noted that the euhedral enstatite laths surrounded by metallic Fe,Ni are typical for enstatite chondrite impact-melt rocks and breccias and are indicators of impact melting followed by relatively fast cooling (e.g., .…”

“…The Zak≥odzie enstatite meteorite has been called a "primitive enstatite achondrite," but one that is interpreted to have formed on its parent body from a magma of internal origin (Przylibski et al 2005). These authors did not propose that Zak≥odzie formed by partial melting of an enstatite chondrite precursor lithology and, in a follow-up paper state that the meteorite "is not an enstatite chondrite" (Karwowski et al 2007).…”

“…After partial melting and annealing, NWA 2526 experienced a second, relatively mild impact event (<~20 GPa) that caused formation of the polysynthetic twinning in the enstatite. We suggest that the meteorite Zak≥odzie, which has been referred to as a "primitive enstatite achondrite" (Przylibski et al 2005), did not form from a magma of internal origin, but that it is an impact-melt breccia of enstatite chondrite-like parentage, as previously discussed by Burbine et al (2000) and Keil (2007).Finally, the "metal-rich enstatite meteorite with achondritic texture" Itqiy (Patzer et al 2001) formed by processes very similar to those responsible for formation of NWA 2526 and is also the residue of ~20 vol% partial melting of an enstatite chondrite-like parent lithology, with the FeS-Fe,Ni and plagioclase-enstatite partial melts having been removed from the residue. It also experienced an impact event after partial melting that was responsible for the formation of the mixed Mg-Mn-Fesulfides and the shock stage S3 features of the enstatite.…”

Mössbauer studies of Polish enstatite meteorite—Zakłodzie

“…There are some differences in results obtained using Mössbauer spectroscopy [1] and other methods [2,3]. The biggest difference is relatively small amount of metal (FeNi) in Mössbauer spectrum comparing to other techniques.…”