  Northwest Africa (NWA) 11042 is a heavily shocked achondrite with
medium-grained cumulate textures. Its olivine and pyroxene compositions, oxygen
isotopic composition, and chromium isotopic composition are consistent with L
chondrites. Sm-Nd dating of its primary phases shows a crystallization age of
4100 +/- 160 Ma. Ar-Ar dating of its shocked mineral maskelynite reveals an age
of 484.0 +/- 1.5 Ma. This age coincides roughly with the breakup event of the L
chondrite parent body evident in the shock ages of many L chondrites and the
terrestrial record of fossil L chondritic chromite. NWA 11042 shows large
depletions in siderophile elements (<0.01 times CI) suggestive of a complex
igneous history involving extraction of a Fe-Ni-S liquid on the L chondrite
parent body. Due to its relatively young crystallization age, the heat source
for such an igneous process is most likely impact. Because its mineralogy,
petrology, and O isotopes are similar to the ungrouped achondrite NWA 4284
(this work), the two meteorites are likely paired and derived from the same
parent body.
