Meteoritics zyxwvutsrqpon & Planefury zyxwvutsrqpo Science 36, 1495-1 505 (2001) Available online at http://www.uark.edu/meteor zyxwvutsrq Itqiy: A metal-rich enstatite meteorite with achondritic texture ANDREA PATZER*, DOLORES H. HILL AND WILLIAM V. BOYNTON Lunar and Planetary Laboratory, University of Arizona, Tucson Arizona 8572 zyxw 1, USA *Correspondence author's e-mail address: apatzer@lpl.arizona.edu (Received zyxwvutsrq 2001 May 9; accepted in revised form 2001 August zyxw 15) 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. INTRODUCTION Enstatite meteorites represent the most reduced naturally- occurring material of our solar system (Keil, 1968). They comprise two main groups, chondrites and achondrites (aubrites), as well as several ungrouped samples that exhibit anomalous characteristics. The enstatite chondrites (E chondrites) are subdivided into EL chondrites with relatively low metal abundances and EH chondrites with comparatively high metal contents (e.g., Sears zyxwvutsr et al., 1982; Kallemeyn and Wasson, 1986; Keil, 1989; Zhang et al., 1995; Kong et al., 1997). Both subgroups essentially consist of nearly FeO-free enstatite zyxwvutsr as a major component and lesser amounts of Si-bearing kamacite and troilite (Table 1). Some E chondritic samples show intermediate chemical features between the EH and EL subgroupsand might represent a new grouplet (e.g., Lin and Kimura, 1998; Kimura and Lin, 1999). Others were melted once and therefore only ambiguously match the characteristics of either EH or EL chondrites (Lin and Kimura, 1998). In addition, several melt breccias are known among E chondrites (e.g., McCoy et al., 1995; Rubin et al., 1997; Weisberg et al., 1997). One of the ungrouped, anomalous enstatite meteorites is Zaklodzie, which was found in Poland recently (Stepniewski et al., 2000). Similar to Itqiy, it has been classified as an ungrouped enstatite-rich meteorite (Grossman, 2000; Grossman and Zipfel, 2001) and is composed mainly of euhedral and subhedral enstatite. Unlike Itqiy though, interstices are filled with plagioclase actingas a groundmass. Additional accessory phases are kamacite and troilite. Schreibersite was also identified. Overall, the chemical composition and mineralogy of Zaklodzie reveals parallels to EL chondriteswhereas its texture can be described as either highly metamorphosed or achondritic. We will shortly discuss mineralogical-chemical similarities between Itqiy and Zaklodzie. A supplementary comparisonofthe noble gas records will be published in a second paper. Aubrites are pyroxenites consisting of primarily FeO-free enstatite that underwent igneous processing and brecciation. Modally, they are related to E chondritesand might have formed from an E chondritic precursor (e.g., Watters and Prinz, 1979; Okada et al., 1988; Keil, 1989; Casanova et al., 1993a,b; McCoy et al., 1997). A variety of lithic clasts found in aubrites reveal igneous textures and testifL to the igneous parentage as well as complex fractionation and crystallization history of these meteorites. The dominance of enstatite and depletion or absence of feldspar (relative to chondrites) are characteristic for both aubrites and Itqiy. SAMPLES AND ANALYTICAL METHODS Itqiy consists of two separate pieces of 410 and 43 10 g, respectively. A nomad of Western Sahara recovered the 4 10 g Prelude preprint MW4545 1495 zyxwv 0 Meteoritical Society, 2001. Printed in USA.