Lodranite
Lodranites are coarse-grained primitive achondrites that lost some of their metal–sulfide and basaltic melts.
If acapulcoites are lightly cooked, lodranites are their well-done relatives. The group takes its name from Lodran, which fell on 1 October 1868 near Lodhran in present-day Pakistan. They are coarser-grained than acapulcoites, typically with grains of roughly half a millimetre to a millimetre, and consist mainly of orthopyroxene and olivine with iron-nickel metal, troilite and chromite. Lodran itself contains broadly similar proportions of metal, olivine and pyroxene.
Lodranites experienced higher degrees of partial melting than acapulcoites. Their depletion in plagioclase and in troilite relative to chondrites shows that both a basaltic silicate melt and an iron-nickel-sulfide melt formed and then drained away. They are therefore residues: what remained after melts were extracted. Matching oxygen isotopes and cosmic-ray exposure ages tie them to the acapulcoites, and lodranites are thought to come from deeper, hotter levels of the same parent body.
This acapulcoite–lodranite body offers a snapshot of a planetesimal caught in the act of differentiating, before forming a full core and crust. Recognition rests on coarse recrystallised textures, depletion in plagioclase and troilite, mineral chemistry, and oxygen isotopes. Rocks transitional between the two groups are also known.
Related terms
Level: Expert Advanced