Iron, IAB complex
(Stony iron-ung in MetBull 86)
(Achondrite-ung recommended in MetBull DB)
Found October 1999
27° 11.88' N., 16° 24.51' E.
While hunting in a well-searched area of the southeastern Dar al Gani plateau, Libya, the Pelisson's of Sahara Meteorite Prospecting found a 130 g stony-iron meteorite. Although they returned to the area, they failed to find any other pieces of this unique meteorite (R. Pelisson, pers. comm.). It is their opinion that the high density of this meteorite might be responsible for a deeper penetration into the soil; luckily, this single individual was only half buried. Another factor that could frustrate attempts to locate more fragments of this meteorite is its proximity to a basaltic massif, which consists completely of black rocks, likely rendering any future searches futile.
In a collaboration among research groups (Cole and Sipiera of the
Schmitt Meteorite Research Group; Jerman and Hoover of the NASA Marshall Space
Flight Center; Dod of the Mercer University Department of Physics; the Pelisson's of SaharaMet), an analysis of DaG 962 published in an abstract at the 65th MetSoc (2002) resulted in a classification of anomalous mesosiderite.
This meteorite is composed of 55 vol% metallic matrix and 45 vol% angular silicate clasts (MetBull 86). The silicates are primarily magnesian olivine (Fa1.0) and enstatite (Fs0.84), which are often intruded by veinlets of FeNi-metal (kamacite and taenite). Minor clinopyroxene and plagioclase are present, as well as troilite. Newly conducted electron microprobe studies conducted by Kuehner et al. (2011) identified accessory phases of daubreelite, schreibersite, and magnesiochromite. The internal structure is more similar to the pallasites than the mesosiderites in having a continuous network of FeNi-metal enclosing silicates, consistent with an igneous origin in a coremantle boundary. However, the silicates are more Mg-rich than those in main-group pallasites or any other pallasites; they are more similar to irons of group IAB. O-isotope data collected by D. Rumble III (Carnegie Institution, Washington DC) also plot near the IAB iron complex and winonaites. Dar al Gani 962 may be comparable to the Landes IAB silicated iron, and shows some similarity to Woodbine.
The photo above shows a 1.3 g partial slice of DaG 962, the mirror slice of the portion used for the thin section that was utilized for the analysis. The top photo below shows the meteorite in situ, while the bottom photo shows the main mass, illustrating the staining on the portion previously embedded below soil level.
Photos courtesy of R & R PelissonSahara Meteorite Prospecting