3&). We infer that dmisteinbergite, together with the other secondary minerals, formed by replacement of melilite as a result of fluid-assisted thermal metamorphism experienced by the CV chondrite parent asteroid. Based on the textural appearance of dmisteinbergite in NWA 2086 and petrographic observations of altered CAIs from the Allende meteorite, we suggest that dmisteinbergite is a common secondary mineral in CAIs from the oxidized Allende-like CV3 chondrites that has been previously misidentified as a secondary anorthite.

Abstract-Highly forsteritic olivine (Fo: 99.2-99.7) in the Kaba meteorite emits bright cathodoluminescence (CL). CL spectra of red luminescent forsterite grains have two broad emission bands at approximately 630 nm (impurity center of divalent Mn ions) in the red region and above 700 nm (trivalent Cr ions) in the red-IR region. The cores of the grains show CL blue luminescence giving a characteristic broad band emission at 400 nm, also associated with minor red emissions related to Mn and Cr ions. CL color variation of Kaba forsterite is attributed to structural defects. Electron probe microanalyzer (EPMA) analysis shows concentrations of Ca, Al, and Ti in the center of the forsterite grain. The migration of diffusible ions of Mn, Cr, and Fe to the rim of the Kaba meteoritic forsterite was controlled by the hydrothermal alteration at relatively low temperature (estimated at about 250°C), while Ca and Al ions might still lie in the core. A very unusual phase of FeO (w€ ustite) was also observed, which may be a terrestrial alteration product of FeNi-metal.

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We investigated three types of shocked feldspar in the Asuka-881757,531-2 sample with midinfrared spectroscopy (reflectance mode). Under the petrographic microscope three types of site were characterized by (1) undulatory extinction, (2) undulatory extinction with isotropic patches and decreased interference color, and (3) isotropic, lath-shaped feldspars, which is indicative of maskelynite. The IR emissivity maximum (Christiansen feature=CF) changes with the chemical composition of feldspar. One of the Christiansen composition features exhibits a wave length peak of 1234 cm -1 for anorthite; another feature appears at 1245 cm -1 for maskelynite (Palomba et al. 2006).With the help of IR spectroscopy we observed three vibrational types in our spectra: (1) peaks of depolimerization of SiO 4 tetrahedra (500-650 cm -1 , 950-1150 cm -1 ), (2) peaks of stretching and bending vibrational modes of SiO 6 octahedra (750-850 cm -1 ), and (3) Si-O stretching vibration of SiO 4 units Johnson et al. , 2007. All these vibration types were observed at the less shocked sites. In the spectrum of highly shocked maskelynite only a broader band close to 1000 cm -1 was observed, which is the main vibrational band of maskelynite (Palomba et al. 2006). The calculated FWHM showed the disordering rate of shocked feldspars. On the basis of the measurements it could be concluded that the estimated shock pressure range gradually increases from 17-35 GPa for different degrees of undulatory sites, to 35-45 GPa for maskelynite sites.

Ringwoodite, produced by shock metamorphism, is common in and adjacent to melt veins in highly shocked chondrites. Although ringwoodite can be crystallized from the silicate melt in the shock-veins or pockets, a major part of the easily observed ringwoodite in shock veins is formed by the transformation of olivine in host-rock fragments entrained in the melt or olivine along shock-vein margins. In this paper we examine the microstructures and textures of ringwoodites from NWA 5011 L-chondrite in order to better understanding the transformation mechanisms of ringwoodite by optical microscope. Finally, we attempt to locate the source region of L-type chondrites in three different impact scenarios of the L parent body.