http://hdl.handle.net/10150/641300 2026-04-20T19:27:58Z http://hdl.handle.net/10150/655699 Petrography and mineral chemistry of the anhydrous component of the Tagish Lake carbonaceous chondrite Simon, S. B.; Grossman, L. Most studies of Tagish Lake have considered features that were either strongly affected by or formed during the extensive hydrous alteration experienced by this meteorite. This has led to some ambiguity as to whether Tagish Lake should be classified a CI, a CM, or something else. Unlike previous workers, we have focused upon the primary, anhydrous component of Tagish Lake, recovered through freeze-thaw disaggregation and density separation and located by thin section mapping. We found many features in common with CMs that are not observed in CIs. In addition to the presence of chondrules and refractory forsterite (which distinguish Tagish Lake from the CIs), we found hibonite-bearing refractory inclusions, spinel-rich inclusions, forsterite aggregates, Cr-, Al-rich spinel, and accretionary mantles on many clasts, which clearly establishes a strong link between Tagish Lake and the CM chondrites. The compositions of isolated olivine crystals in Tagish Lake are also like those found in CMs. We conclude that the anhydrous inclusion population of Tagish Lake was, originally, very much like that of the known CM chondrites and that the inclusions in Tagish Lake are heavily altered, more so than even those in Mighei, which are more heavily altered than those in Murchison. 2003-01-01T00:00:00Z http://hdl.handle.net/10150/655700 Book Review: Solar System Evolution: A New Perspective, Stuart Ross Taylor Taylor, L. Book Review: Solar System Evolution: A New Perspective, Stuart Ross Taylor. Second edition. Cambridge University Press (2001). 2003-01-01T00:00:00Z http://hdl.handle.net/10150/655695 Detection of terrestrial fluorine by proton induced gamma emission (PIGE): A rapid quantification for Antarctic meteorites Noll, K.; Döbeli, M.; Krähenbühl, U.; Grambole, D.; Herrmann, F.; Koeberl, C. The enrichment of fluorine on the surface of Antarctic meteorites is investigated by applying the nuclear reactions 19F(p, alpha x gamma)16O or 19F(p, p'gamma)19F with the proton induced gamma emission (PIGE) technique, a class of nuclear reaction analysis (NRA). Results for the Antarctic meteorites ALHA77294, TIL 82409, LEW 86015, ALHA77003, and ALH 83108 are presented. Possible sources of terrestrial F are: volcanic exhalation, tephra layers (volcanic glass), continental soil dust, or sea spray. Material from blue-ice dust-band samples also shows concentrations of F that are significantly higher than the bulk concentrations of meteorites. Finally, a quick investigation for Antarctic meteorites by external PIGE is proposed, leading to a F-contamination index that supplements the qualitative ABC-weathering index. 2003-01-01T00:00:00Z http://hdl.handle.net/10150/655697 New eucrite Dar al Gani 872: Petrography, chemical composition, and evolution Patzer, A.; Hill, D. H.; Boynton, W. V. Dar al Gani 872 (DaG 872) is a new meteorite from Libya that we classified by means of Instrumental Neutron Activation Analysis (INAA), electron microprobe, and optical microscopy. According to our results, DaG 872 is a Mg-rich main group eucrite, i.e., a monomict noncumulate basaltic eucrite displaying a predominant coarse-grained relict subophitic and a fine-grained granulitic texture. The meteorite also shows pockets of late-stage mesostasis and is penetrated by several calcite veins due to terrestrial weathering. Finally, it exhibits shock phenomena of stage 1-2 including heavily fractured mineral components, undulose extinction of plagioclase, kinked lamellae, and mosaicism in pyroxenes corresponding to peak pressures of ~20 GPa. In view of petrographic criteria as well as compositional and exsolution characteristics of its pyroxenes, the sample represents a metamorphic type 5 eucrite. Assuming the metamorphic type to be a function of burial depth on the parent body and taking into account the relatively high shock stage, the excavation of DaG 872 was likely induced by a major impact event. Prior to this point, DaG 872 apparently underwent a 4-stage geological evolution that is reflected by intricate textural and mineralogical features. 2003-01-01T00:00:00Z