Iron Meteorites Derrick Peak

The iron meteorites are of special interest because this group of meteorites is under-represented among Antarctic meteorites (Table 18.5). Several large fragments of the Derrick Peak iron meteorite (DRP 78001-78009) fell about 1 million years ago and have lain on a substrate of soil and rock fragments ever since. Therefore, these specimens were not transported in the ice of the polar plateau to their present location like most other meteorites in Antarctica, but they actually landed on rocks where they were found. 

When the geologists who made the original discovery reported by radio that they had found several iron 

Fig 18 21 Derrick Peak at 80°04 S and 156°23 E is the site where a small group of iron meteorites was found by a team of New Zealand geologists. The principal meteorite-discovery site is outlined in red. The Hatherton Glacier is a southern tributary to the Darwin Glacier which flows between the Brown Hills and the Britannia Range before merging into the Ross Ice Shelf (Adapted from U.S.G.S. map SU 56-60/1, Mount Olympus, Antarctica with information from Shiraishi 1979) 

The rocks exposed on Derrick Peak consist of a basal conglomerate overlain by quartz sandstones and 

Antarctica (Section 18.6.2) has an even older terrestrial age of 5 million years (Nishiizumi et al. 1989). 

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Fig. 18.22 This specimen of the Derrick Peak iron meteorite has a mass of 10 kg and is highly corroded as a result of chemical weathering after it fell about 1 million years ago. The upper surface is dark brown in color and is characterized by protruding crystals of schreibersite [(Fe.NiljP] which are more resistant to chemical weathering than kamacite (Fe-Ni alloy). The original fusion crust and heat-altered surface layer are no longer present. The Derrick Peak meteorite is a member of group IlAB (coarse octahedrite) (Courtesy of NASA, JSC, Houston, Texas)...

The Derrick Peak iron meteorite was more extensively altered by chemical weathering than most other Antarctic meteorites which remained frozen until they were exposed by ablation of the ice in which they were embedded. The weathering products of DRP78009 (138.1 kg) include Cl-bearing akaganeite (f)-FeOOH) and goethite (a-FeOOH) with smaller amonnts of lepido-crocite (y-FeOOH) and maghemite (y-Fe Oj) (Buchwald and Clarke 1989). 

The properties of meteorites collected in Antarctica that have been measured include their chemical and mineralogical compositions as well as their textures, isotopic ages, and cosmic-ray exposure histories. The scientific value of the accumulated data is exemplified in this chapter by selected specimens of Antarctic meteorites such as the Derrick Peak iron, by the first lunar meteorite recovered on the icefields of fhe Allan Hills (ALHA 81005), and by the martian rock ALH 84001. The interpretation of data derived from these and other meteorites collected in Antarctica contribute to the on-going exploration of the solar system. 

Qarke RS Jr (1982) The Derrick Peak, Antarctica, iron meteorites. Meteoritics 17(3) 129-134... 

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