HYPOTHESIS OF ORIGIN
The Granada material has oxygen isotope values that are exceedingly high, when compared to the oxygen isotope analyses of meteorites representing that of a planetary origin (fig. 9). It has been noted that high values of 18O and 17O are a result of an interaction with a 16O poor gas source (Clayton, 1993; Frias et al., 1999). Moreover, Clayton (1984) found that the earliest solar system gases reached values of 30.0‰ for 18O and 24.2‰ for 17O (Frias et al., 1999). The only presumed extraterrestrial material similar to the Granada material is the Getafe pseudometeorite, which was documented fall in Madrid Spain (Frias et al., 1999). Despite the well documented fall, the term pseudometeorite was allocated to the specimen after analysis of the material could not provide conclusive evidence of an extraterrestrial origin (Frias et al., 1999).
The Getafe material closely matches that of the Granada material, with oxygen isotope values of 16.3‰ for 18O and 8.1‰ for 17O (Frias et al., 1999). Moreover, like the Granada material the Getafe material is composed of refractory components of larnite and wustite bearing assemblages (Frias et al., 1999). Thus, a strong extraterrestrial correlation exists between the Granada and Getafe material. It is important to note that oxygen isotope analyses of slags will be variable, reflecting the protolith of the source material being melted. Thus, it would be unlikely that two slags from separate continents would have nearly the same oxygen isotope values. Though it is important to note that the composition of the Granada material matches that of an steel slag, which is typically composed of: 42% CaO, 24% FeO, 15% SiO2, 8% MgO, 5% MnO, 5% Al2O3, and 0.8% P2O5 (National Slag Association, 2004). However, steel slag always contains an abundance of free CaO occurring as lime, which is absent in both the Granada material and the Getafe material (after Frias et al., 1999).
Studies conducted by Bunch and Chang (1980) have concluded that a strong correlation exists between industrial refractory materials and CAIs (Frias et al., 1999). Such a study found that although industrial refractory inclusions are simpler in composition, the thermal alteration textures are similar to CAI rims; such as in the Allende chondrite (Bunch and Chang, 1980; Frias et al., 1999).
Figure 9. 18O and 17O values of the Granada material with comparisons to planetary bodies. Oxygen isotope values are reproduced from Anand et al. (2003).