Bilanga meteorite, Bilanga-Yanga, Bilanga Department, Gnagna Province, Est Region, Burkina Fasoi

Regional Level Types
Bilanga meteorite	Meteorite Fall Location
Bilanga-Yanga	Town
Bilanga Department	Department
Gnagna Province	Province
Est Region	Region
Burkina Faso	Country

Diogenite, severely brecciated
Fell 27 Oct1999; 25 kg

A number of black stones covered with fresh fusion crusts were collected after a widely observed meteorite shower fell near the villages of Bilanga-Yanga and Gomponsago. The meteorite is one of only 11 witnessed diogenite falls recorded before 2014 and is the second most massive of all recovered diogenites. Like the great majority of diogenites, Bilanga is a plutonic pyroxenite compositionally dominated by orthopyroxene which crystallized well below (10-25 km??) the surface of its original parent body. Bilanga is somewhat unusual among diogenites as it contains significant amounts of accessory plagioclase (mostly bytownite), diopside, and silica which appear to have crystallized somewhat later than the predominant orthopyroxene. Bilanga is even more unusual because it is one of the most severely brecciated diogenites. Brecciation features include chemically related diogenite lithologies of varying grain size, partially recrystallized melt pockets, and some Si-,K-rich glass. It is also somewhat richer in its entourage of minor phases which have apparently crystallized in the interstices between the various assemblages and comminuted clasts which were partially reequilibrated and reassembled after brecciating events. Minor phases include K-Feldspar, Co-containing kamacite, tetrataenite, pentlandite, native copper, a light rare earth element-bearing phosphate, and several quench phases.

As an apparently 'geochemically normal' member of the HED Clan (Howardites-Eucrites-Diogenites) Bilanga may very well be a fragment of the asteroid 4 Vesta. However, more definitive work with O-isotope and Fe-Mn ratios and other geochemical and chronological markers is apparently needed before we can confidently declare which specific HED meteorites are fragments of Vesta and which are exceptions. O-isotope and Fe/Mn ratios clearly indicate that a few anomalous HED meteorites (e.g., Ibitira, Pasamonte) are from separate homeworlds, but definitive evidence for a putative 'main group' of HED meteorites derived only from Vesta is a work still in progress.

Other Regions, Features and Areas containing this locality

References