DaG 055

(C3-ung in MetBull 80)
standby for dar al gani 055 photo
Found June 1995
27° 16.03′ N., 16° 25.22′ E. A stone weighing 451 g was found in the Libyan Sahara. It is shocked to stage S1 and has a weathering grade of W1. The main mass is at the University of Humboldt in Berlin. A 703 g stone recovered nearby, designated DaG 056, is thought to be paired with DaG 055 based on similar cosmic-ray exposure ages (6.1 and 6.3 m.y. respectively), similar bulk compositions, and their close proximity when found. In 1998, stones were found nearby that might also be paired with DaG 055—DaG 429 (253 g) and DaG 430 (572 g; CRE age of 5.9 m.y.). Notably, only DaG 056 has been found to contain solar-type rare gases indicative of a regolith origin. Another type-3 carbonaceous chondrite, NWA 1665, has an O-isotope composition that plots near the DaG 055 pairing group, and it has been suggested that it could also be related.

Characteristics observed in DaG 055 and 056 are similar to those of reduced CV chondrites, but significant differences suggest the use of an ‘anomalous’ suffix. Chondrule sizes of DaG 055 are large (ave. 790 µm), similar to sizes found in CV chondrites (ave. 750 µm; Choe et al., 2010). Igneous rims are present on chondrules in both meteorites, attesting to their formation in a dusty region of the nebula. A low abundance of AOAs along with rare CAIs are present in DaG 055 as well as CV chondrites. The opaques consist of FeNi-metal and sulfide at abundances consistent with reduced CV chondrites. The O-isotope values of DaG 055 plot along the CCAM line within the CO and CV fields. Clayton and Mayeda (1999) describe a similar oxygen plot in the middle of the CK field.

According to one research team, refractory lithophile element abundances fall within the CV-group range, while another team concluded that they plot higher than all chondrite groups. By comparison, siderophile and chalcophile abundances are more CV-like (Huber et al., 2006). Certain moderately volatile elements plot near the CV field, as do volatile siderophile and chalcophile elements. DaG 055 has unequilibrated olivines with a composition of Fa0.432, in the range of equilibrated CV-group members (Fa31 ±3). It also shows similarities to the CK3 Camel Donga 003, but exhibits lower than normal 129Xe/132Xe ratios. A porosity measurememt was made for the probable pairing DaG 056, and it was determined to be 2.25 (±1.42) vol% (M. Strait, 2010).

It has been proposed by some (e.g., Greenwood et al.,2009 and Wasson et al., 2013) that the CK group is consistent with a metamorphic extension of the CV group (see the Dhofar 015 page for more detailed information). The specimen of DaG 055 shown above is a 0.8 g fragment partially covered by fusion crust.

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