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Abstract

The historical Madrid meteorite chondrite fell in 1896 showing thin melt veins with a 65% of brecciated forsterite fragments surrounded by a fine grained matrix formed by troilite, chromite and Fe-Ni blebs. It exhibits a delicate iron infill, neo-formation of troilite in pockets and shock veins and neo-formation of Na-feldspar formed at high temperature and fast quenching. The semi-quantitative mineral determinations were performed with IMAGEJ freeware and chemical mappings resulting in the following approximated compositions: olivine (∼55%); augite (∼10%); enstatite (∼10%); plagioclase (∼10%); chromite (∼2%); troilite (∼4%), kamacite-taenite α-γ-(Fe, Ni) (∼7%) and merrillite (∼7%). The specimen was also studied by computer tomography, micro-Raman spectroscopy and spectral cathodoluminescence. X-ray diffraction patterns were also recorded in non-destructive way on a polished surface because of the small size of the specimen. This combination of non-destructive techniques provides an improved knowledge on the Madrid-1896 meteorite compared to the previous study performed on the same specimen carried out twenty years ago by electron probe microanalysis and optical microscopy in destructive way. Limits of these techniques are the specimen's size in the analytical chambers and the threshold resolution of the microscopes analyzing shock veins micro-crystals.

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... These major bands are accompanied by minor bands between 1000 and 1080 cm −1 , which are related to asymmetric υ3 vibrations. Minor peaks can be observed at around 550 to 620 cm −1 , and are also characteristic of both phosphates [12,19,20]. Characteristic bands related to the presence of OH − (near 3600 cm −1 ; graphical spectra end at 3650 cm −1 ) were not observed in chlorapatite or in merrillite. ...
... Moreover, peaks with variable intensity appear in the merrillite spectra between 2050 and 2750 cm −1 . These bands were interpreted as photoluminescence of REE, replacing structural Ca 2+ in the crystallographic structure of merrillite [20,21]. In the case of chloroapatite, no defined peaks can be observed in this region, but a generalized intensity anomaly is usually present in the same area, interpreted by the same mechanism as in the case of merrillite. ...
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Chapter
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A method for the non-destructive observation of extraterrestrial materials using X-ray computed tomography (CT) is discussed. This method allows to image texture of objects in meteorites without destructive methods of sample preparation. Quantitative analysis of X-ray CT data was achieved by measuring X-ray linear attenuation coefficients (LACs). The histogram of the LAC value provides information regarding the meteorite structure, such as the internal components and their chemical composition. The change of the signal-to-noise ratio (S/N ratio) of CT data is investigated by optimizing the CT measurement conditions. These results form an important baseline for the initial analysis of extraterrestrial materials.
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Six ordinary chondrite breccias from the Museo Nacional de Ciencias Naturales, Madrid (Spain), are described and classified as follows: the solar gas-rich regolith breccia Oviedo (H5); the premetamorphic fragmental breccias Cabezo de Mayo (type 6, L-LL), and Sevilla (LL4); the fragmental breccias Canellas (H4) and Gerona (H5); and the impact melt breccia, Madrid (L6). It is confirmed that chondrites with typical light-dark structures and petrographic properties typical of regolith breccias may (Oviedo) or may not (Canellas) be solar gas-rich. Cabezo de Mayo and Sevilla show convincing evidence that they were assembled prior to peak metamorphism and were equilibrated during subsequent reheating. Compositions of olivine and low-Ca pyroxene in host chondrite and breccia clasts in Cabezo de Mayo are transitional between groups L and LL. It is suggested, based on mineralogic and oxygen isotopic compositions of host and clasts, that the rock formed on the L parent body by mixing, prior to peak metamorphism. This was followed by partial equilibrium of two different materials: the indigenous L chondrite host and exotic LL melt rock clasts.
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