Northwest Africa 3340

Algeria or Morocco

Find: April 2006

Carbonaceous chondrite (CM2, anomalous)

History: Purchased by F. Kuntz in April 2006 in Erfoud, Morocco and subsequently acquired for the DuPont Collection at PSF.

Physical characteristics: Two pieces from a very fresh, broken, black, porous stone (total weight 12.7 g) with shiny fusion crust on one side.

Petrography: (A. Irving and S. Kuehner, UWS; T. Bunch, NAU) Sparse mineral grains, carbon-rich objects, dust-armored chondrules and rare refractory inclusion occur in a heterogeneous, very fine grained, porous matrix composed mainly of bladed phyllosilicates with some pentlandite and calcite (clearly visible under incident UV light). Olivine grains (up to 2 mm across) are commonly armored by fine, polycrystalline "dust" and contain inclusions of Ni-rich troilite, chromite, millerite, kamacite and taenite.Both pentlandite and magnesian olivine occur as separate smaller, angular grains. The carbon-rich objects (up to 50 mm across) consist of either pure graphite or a chlorine-rich organic phase. Chondrules consist of PO and POP, many having a fine-grained polycrystalline "dust" rims. One small refractory inclusion is composed of Mg-Al spinel with inclusions of perovskite.

Mineral compositions and geochemistry: Larger zoned olivine grains (e.g., Fa_17.9-33.9, Fa_39.9-66); smaller homogeneous olivine grains (e.g. Fa_1.5, Fa_19.9); pentlandite (Ni = 26.2 wt%). Matrix phyllosilicate material could not be analyzed quantitatively, but has very consistent proportions of Mg, Fe, Si and S. The chlorine-rich organic phase contains ~17 wt% Cl and ~32 wt% C, but no detectable N and minor O. Oxygen Isotopes: (D. Rumble, CIW) Replicate analyses by laser fluorination gave, respectively, [values redacted]*.

Classification: Carbonaceous chondrite (CM2, anomalous); minimal weathering. The presence of chlorine-rich carbon compounds, which may be enigmatic chlorinated hydrocarbons, makes this specimen potentially unique among CM chondrites.

Specimens: A total of 2.7 g of sample is on deposit at UWS and the remainder of the mass (10 g) is at PSF.

*) See erratum in MB103