Additional Constraints on the Crystallization of Basaltic Shergottite

Introduction: QUE 94201 (QUE) is a basaltic shergottite containing subequal amounts of pyroxene and plagioclase, the latter having been converted to maskelynite by shock (Fig. 1) [e.g., 1-3]. Pyroxene occurs as elongate subhedral to euhedral grains up to several mm in length. It has extensive and complex zoning (Fig 1). Typical grains have Mg-rich pigeonite cores mantled by Mg-rich augite, which is in turn rimmed by Fe-rich pigeonite that is sometimes rimmed by a thin discontinuous layer of hedenbergite. Grains often display sector zoning and complex interlayering of augite and pigeonite. This zoning provides a rich record of the crystallization of this meteorite, a point to which we shall return below.