No abstract

) and chromite, embedded in an Fe-rich, Al-poor basaltic to picro-basaltic glass. Within the melt pockets strong thermal gradients (minimum 1 °C/μm) existed at the onset of crystallization, giving rise to a heterogeneous distribution of nucleation sites, resulting in gradational textures of olivine and chromite. Dendritic and skeletal olivine, crystallized in the melt pocket center, has a nucleation density (1.0 × 10 3 crystals/mm 2 ) that is two orders of magnitude lower than olivine euhedra near the melt margin (1.6 × 10 5 crystals/mm 2 ). Based on petrography and minor element abundances, melt pocket formation occurred by in situ melting of host rock constituents by shock, as opposed to melt injected into the lherzolitic target. Despite a common origin, NWA 1950 is shocked to a lesser extent compared to Allan Hills (ALH) 77005 (45-55 GPa). Assuming ejection in a single shock event by spallation, this places NWA 1950 near to ALH 77005, but at a shallower depth within the Martian subsurface. Extensive shock melt networks, the interconnectivity between melt pockets, and the ubiquitous presence of highly vesiculated plagioclase glass in ALH 77005 suggests that this meteorite may be transitional between discreet shock melting and bulk rock melting.

Executive summary provided in lieu of abstract.

Until 2016 only 38 Italian meteorites have been classified and published on the Meteoritical Bulletin Database. Among these, only 4 were irons. We here report the results of the analyses performed on two iron meteorites recovered in Italy. The first one, Castiglione del Lago, weighing 667 g, was recovered in 1970. The textural features observed by means of both optical microscope and SEM, as well as SEM-EDX and ICP-MS analyses, allowed to classify it as IAB-MG iron. The second one, named Castelvecchio, has been recovered at Lignana, near Pontito, in August 2015. In the same locality a fireball was witnessed on October 23, 1986, by Mario Goiorani, a meteorite collector. The main mass, weighing 49.5 g, was recovered inside a hollow. A chip, observed with both optical metallographic microscope and SEM, displayed no kamacite lamellae at the centimetric scale, suggesting a classification as IIAB iron. This classification was confirmed by ICP-MS analyses. Both meteorites have been approved by the Meteoritical Society in 2016 and published in the on-line Meteoritical Bulletin Database (https://www.lpi.usra.edu/meteor).

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.