Northwest Africa 1807

Northwest Africa

Find: 2002

Carbonaceous chondrite (CV3)

History: M. Chinellato purchased a single stone of 274 g in Erfoud, Morocco.

Physical characteristics: The main mass of 54.5 g has no fusion crust. A cut surface on the type specimen shows rather large chondrules and some small white spots.

Petrography: (V. Moggi Cecchi and G. Pratesi, MSP) In thin section, many chondrules of various kinds (BO, PO, POP), accounting for ~50 vol% and ranging in size from 500 to 1200 µm in apparent diameter are visible (mean value 950 µm), set in a dark brown matrix. The chondrule margins are clear and defined. Chondrules contain variable amounts of clear glass. The matrix is composed of olivine and orthopyroxene, with rare clinopyroxene. Fe,Ni-rich metal and troilite are uncommon (less than 5 vol%). CAIs and rare apatite grains are observed.

Mineral compositions and geochemistry: Chondrule olivine (Fo_95–99), matrix olivine (Fo₅₀), orthopyroxene (En_98.14Fs_0.8Wo_1.06), clinopyroxene (Fs_{15.54–28.61}En_{25.12–36.97}Wo_{46.12–47.49}). Chondrule glass is anorthitic (An₈₅). Oxygen isotopes: (I. Franchi and R. Greenwood, OU) δ¹⁷O = -1.64, δ¹⁸O = 2.52, Δ¹⁷O = -2.96 (all ‰).

Classification: Carbonaceous chondrite (CV3); S1, minor weathering.

Type specimen: A total of 20.5 g and one thin section are on deposit at MSP. MChin holds the main mass.