Enstatite chondrite (EH4; S2-S5)
Fall of 9 June 1953; 107 kg

In the long twilight of early June a fireball brighter than the full moon, accompanied by sonic booms, lit up the skys of Alberta for a few moments. Six days later a meteorite was excavated from a small crater (diameter, 1.7 m; Depth 1.5 m). Abee is not only an unusual meteorite (an Enstatite Chondrite), its 107 kg mass is nearly 4 times that of the next largest observed Enstatite Chondrite fall (Pillistfer). Enstatite chondrites are formally defined by their bulk elemental and oxygen isotope ratio, but their extremely reduced mineralogical assemblages often draws the most attention. Like most Enstatite chondrites, Abee’s most prominent mineral is Enstatite, an iron poor pyroxene — found in chondrules and in the surrounding matrix. Nickel-iron (mostly Kamacite) and Troilite are the most important accessory phases, but small amounts of Daubréelite, Oldhamite, Osbornite and other phases rarely — if ever — found on earth are also present. Indeed the minerals Keilite and Niningerite were first discovered in Abee. The presence of Niningerite is usually a sure indicator that the meteorite is an EH (high-iron) Enstatite Chondrite rather than a related EL (low iron) Enstatite Chondrite. Abee is usually classified as petrologic type EH4 as it has abundant chondrules which lack glass and many of its mineral assemblages are homogenized.

Some caveats. Tiny magnetite crystals found in Abee’s fusion crust are a result of heating and oxidation which occurred during Abee’s brief fiery passage thru the earth’s atmosphere. Long before Abee’s encounter with the earth, it had apparently experienced both strong impacts and metamorphic heating. For two decades Alan Rubin (Rubin, 2008; Rubin et al., 1997) has been working to disentangle such shock effects from endogenous heating. He and others frequently used the term impact-melt breccia to emphasize that sufficiently strong impacts create (local) heat sources whose effects often mimic more ‘normal’ metamorphism.

Addendum. Tiny Diamonds and various other phases are quite sparse. Such phases may be only infrequently observed in other, smaller Enstatite Chondrites.

Other Regions, Features and Areas containing this locality

References