Abstract-The study of chondrules provides information about processes occurring in the early solar system. In order to ascertain to what extent these processes played a role in determining the properties of the enstatite chondrites, the physical and chemical properties of chondrules from three EL3 chondrites and three EH3 chondrites have been examined by optical, cathodoluminescence (CL), and electron microprobe techniques. Properties examined include size, texture, CL, and composition of both individual phases and bulk chondrules. The textures, distribution of textures, and composition of silicates of the EL3 chondrules resemble those of EH3 chondrules. However, the chondrules from the two classes differ in that (1) the size distribution of the EL chondrules is skewed to larger values than EH chondrules, (2) the enstatite in EL chondrules displays varying shades of red CL due to the presence of fine-grained sulfides and metal in the silicates, and (3) the mesostasis of EH chondrules is enriched in Na relative to that of EL chondrules. The similarities between the chondrules of the two classes suggest similar precursor materials, while the differences suggest that there was not a single reservoir of meteoritic chondrules, but that their origin was fairly local. The differences in the size distribution of chondrules in EH and EL chondrites may be explained by aerodynamic and gravitational sorting during accumulation of the meteoric material, while differences in CL and mesostasis properties may reflect differences in formation conditions and cooling rate following chondrule formation. We argue that our observations are consistent with the formation of enstatite chondrites in a thick dynamic regolith on their parent body.

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[1] EL chondrites exhibit larger average metal grain sizes than EH chondrites, a difference attributed by Easton [1983] to metamorphic coarsening, as most EL chondrites are equilibrated, and most EH chondrites are unequilibrated. In this paper, we present metal grain size data for three unequilbrated EL3 chondrites (PCA 91020; ALH 85119; MAC 88180) , and three EH3 chondrites (ALH 84170; PCA 91085; PCA 91238). We find that EL3 chondrites have larger average metal grain sizes than EH3 chondrites, and that grain sizes of the unequilibrated enstatite chondrites are similar to those of equilibrated chondrites of the same class. We thus interpret the metal size distributions of enstatite chondrites as primarily reflecting their pre-metamorphic distributions. Shock processing appears to have had only minor influence on metal grain size distributions in these meteorites.

Abstract-A new 2.8 kg meteorite find fiom the United States, Kansas University, is classified as an L6 (S3) chondrite based on optical microscopy and electron microprobe analysis of mafic minerals. Natural thermoluminescence (TL) and 14C measurements suggest that the Kansas University meteorite has a short terrestrial age compared to other meteorite finds fiom this area and is not paired with the other local meteorite finds, Densmore (1 879), Lawrence, Kansas and Long Island, Kansas. HISTORYAround the turn of the century, a single stone weighing 2.8 kg was recovered by Mr. Handel Tong Martin. Martin was curator of Paleontology at the University of Kansas at the time and acquired the stone while searching for fossils in an unknown location. The stone was given to Mr. William H. Martin, son of Handel Martin, who in turn gave the stone to his son, Mr. William H. Martin, Jr. The stone was brought to the University of Arkansas in December of 1990, where it was identified as a meteorite. The specific location of where the meteorite was found is unknown, but we presume it to be in the Lawrence, Kansas area. The main mass of the stone remains on loan at the University of Arkansas; a small sample weighing 8.0 g and the thin section studied are in the meteorite collection of the University of Arkansas. PETROGRAPHIC DESCRIPTIONThe Kansas University meteorite is roughly cube-shaped with one face covered by an extensively scalloped fusion crust (Fig. 1). There is no apparent fusion crust on the other faces. The meteorite is only moderately weathered, and one corner bears saw marks where a sample of >50 g was probably removed prior to its arrival at the University of Arkansas. Fragments broken from the main mass are fairly lightly colored, with only a few areas of rust stains, and metal grains are prominent on polished surfaces.In thin section, the meteorite shows only scattered instances of weathering. In general, the meteorite displays an interlocking texture of olivine and pyroxene. A few chondrules were noted, but these were indistinct, with blurred edges. On this basis, we classify the Kansas University meteorite as petrologic type 6, following the scheme of Van Schmus and Wood ( 1967).Examination of the thin section suggests that the meteorite is moderately shocked. Undulatory extinction and occasional planar fractures are noted in both olivine and pyroxene grains. A few small opaque shock veins were observed, but no melt pockets were noted in our section. Using the criteria of St6ffler et al. (1991), we suggest that the Kansas University meteorite is shock stage S3. MINERALOGYElectron microprobe analysis of the meteorite was conducted at Johnson Space Center (JSC) using a 15 keV, 30 nA beam. Marjalahti olivine was used as the standard. The olivine has a mean composition of Fa26,0 (N = 10, u = 1.4), and the pyroxene has a mean composition of Fs21,~ (N = 3, u = 0.8) and W01.2 (N = 3, CJ = 0.1). Minor amounts of highCa pyroxene were noted. These data are consistent with the classification of this meteorite as an L chondri...