![]() ![]() In the course of their work two different sets of exposure ages were determined by Honda et al. (2008) and also Honda et al (2008) stated that samples of the Gibeon meteorite show an extraordinary low concentration of cosmogenic noble gases and radio-nuclides.įor example, the activity levels of 10Be in Gibeon were as low as 5E-5 dpm/kg, which indicates a shielding of the sample in a depth of up to 2 meters. While there is little doubt on the solidification age, the cosmic exposure history is extremely difficult to determine due to deep shielding of samples from cosmic irradiation. (1961) determined the solidification age of Gibeon by the Os/Ir method to be about 4.0 x 10 9 years. Questions remain: cosmic exposure, terrestrial age Recently Wasson (2008) delivered an extensive survey on the genesis of iron magmas and described Gibeon as consistent with the genesis of IVA irons by impact-driven partial melting of an L-LL chondritic precursor, leading to loss of volatile Ge and Ga and the reduction of FeO to lower the Ni content of the metal phase. Unfortunately the paper lacks substantial evidence in favour for such creative model. This resulted in electrical discharges between this levels to form diatremes. To enable the readers to draw their own conclusions we quote the Khazanovich-Wulff hypothesis: A large iron-meteoroid Gibeon having entered the earth’s atmosphere induced a powerful electrical charge on the earth’s surface which interacted with electrical fields in the earth’s interiors. The ages of the Kimberlite pipes and the Brukarros structure, to which Khazanovich-Wulff denied a volcanic origin, are given with 75 Ma and Khazanovich-Wulff speculated that a regular arid climate may have existed on the Nama plateau during 75 Ma, which may have preserved the large meteorite debris among dry eolic sands. Khazanovich-Wulff added an interesting viewpoint to the current Gibeon research in suggesting that Kimberlite fields in the Gibeon area and around the Brukarros structure are related to the Gibeon meteorite strewn field (Khazanovich-Wulff 2001). (1998) detected terrestrial magnetic contamination on a Gibeon sample and the authors noted that any analysis of iron meteorites based on their magnetic properties may be compromised considerably by terrestrial influences. On occasion of their research on remnant magnetization, Fukuhara et al. Petaev concluded that the formation of these rare objects was a planetary-wide process on the IVA parent Body. Petaev suggested their formation due to accumulation of detrital mineral fragments and intergrowths without subsequent cementation, rather than crystallization from a melt or condensation from a fluid phase. In Gibeon the sulfides occur in the shape of loosely packed inequigranular, irregular metal and sulfide grains and aggregates. A feature which had previously been discovered in the Albion IVA fine octahedrite. also discovered brassy metal-troilite-daubrelite masses and sulfide bearing vugs in Gibeon cut sections (Petaev et al. The mineral, which was previously described in terrestrial occurrences, was discovered in a Gibeon section. delivered the first report on eskolaite in meteorites. Considering the trace amounts of silicia Scott stated that either a small size of the mother body caused inefficient removal of trapped silicate liquid, or, alternatively, that temperatures occurring on the Gibeon mother body were never sufficient to melt the mantle entirely (Scott et al. Several researchers noted the unusual content of silicates in Gibeon (e.g. Pools this size quickly sink through the silicate and the authors conclude that the Gibeon IVA material very probably comes from an asteroidal core. pointed out that the parental liquid pool of the Gibeon meteorite on the IVA mother body was at least many meters in size. In addition to the work of Malvin et al., Scott et al. 16 Psyche) as a possible source of origin for Gibeon and other IVA iron meteorites. Matsui’s results underlined that the brittle behavior of iron-like planetesimals in the low-temperature asteroid zone prevents the growth of these bodies into full-size planets.īased on their study of bidirectional reflectance properties including Gibeon samples Britt et al. Consequently, even if IVA iron meteorites were originally the core of a layered parent body, they might be subsequently destroyed in a brittle manner. Their experiments revealed the brittle behaviour of the material at low temperatures. (1984) simulated high and low-velocity impacts into Gibeon material. ![]() Several researchers investigated the brittle-ductile systematics of the IVA mother body with interesting results. ![]()
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