Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEpu

Azumendi García, Oscar

García Guinea, Javier

Ruiz Pérez, Javier

Tormo, L.

Docta Complutense

MADRID L6 CHONDRITE (FALL 1896): ESEM-CATHODOLUMINESCENCE SURVEY.  O. Azumendi1, L. Tormo2, J. Ruiz1, J. Garcia-Guinea2, 1Departamento de Geodinamica, Universidad Complutense de Madrid. Ma-drid 28040 Spain. oscarazumendi@yahoo.es, 2Museo Nacional Ciencias Naturales. CSIC. 28006 Madrid. Spain. ltormo@mncn.csic.es  Introduction: The Madrid meteorite fell in Madrid downtown the 10th of February of 1896, seconds be-fore 9:30 am. Ten samples were recovered in the city, just after a bright white-blue light and a strong explo-sion scared and advertised the people of the meteorite fallen. The heaviest and lightest weight 143.79 and 1.3 respectively. The meteorites distribution formed an ellipse NW/SE orientated, where the largest meteorites fell in the NW. The compositions of olivines (Fa25) and low-Ca pyroxenes (Fs24) in Madrid meteorite are within the range of equilibrated L chondrite. The amount of troilite (5.02 wt. %) and metallic Fe-Ni (5.95 wt. %) support this classification. The material is highly crystallized and brecciated, with chondrules poorly defined and clearly visible (bigger than 50µm across) feldspars. This classify the meteorite in the petrographic type 6: the Madrid meteorite is therefore an impact melt breccia L6 ordinary chondrite. The main aim of this work is to analyse feldspars and whitlockites from Madrid meteorite by cathodolumi-nescence and to determine the trap structure. The im-pact events of this chondrite have also been using the mineralogy and ESEM images interpretations.   ESEM-BackScattering Image showing a schock vein composed by a mixture of Olivine, Troilite and infilled iron in very thin veins sized from 1 to 3 microns.  Schock veins:  In similar cases have been demon-strated: (i) the presence of eutectic Fe and FeS indi-cates that the temperature during melt formation ex-ceeded  988ºC, (ii) the troillite nodules occurred in many shocked chondrites being characteristic of the shock stage S3-S6. This L6-chondrite suffered two main impacts episodes. The first one produced the breccia, with thick dark areas, very heterogeneous, mixed with the unmelted minerals. This shock is been dated by 40Ar/39Ar in 470 Ma, when a big body im-pacted L6 parent body (all L6 meteorites have the same porphyritic to holocristaline texture, produced by this impact), and a mayor degassing event occurred. The second shock melted the Fe and FeS, propagating the hot liquid and gaseous metals through the breccia, entering into the minerals background  in very thin shock veins of few microns.   Merrilite cathodoluminescence: This CaPO4 phase  is related with mesostasis processes having a late crys-tallization. The characteristic emission peaks of the CL spectra from 300 nm to 1000 nm has been associated to specific activators such as Ce3+, Eu2+, Mn2+, Dy3+, Sm3+ and Sm2+ the two structural positions of calcium.    This merrilite (CaPO4) from Madrid L6 Chrondrite emits cathodoluminescence peaks attributed to Ce3+ (360-380 nm peak), Dy3+ (499 nm peak and 666nm peak), Sm (590 nm peak) and Tm3+ (366 nm peak).    4020.pdfCORALS II Conference (2011)

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Madrid L6 chondrite (fall 1896): ESEM-cathodoluminescence survey

http://eprints.ucm.es/34281/1/43-Met2.pdf

Madrid L6 chondrite (fall 1896): ESEM-cathodoluminescence survey

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