Crystallization history of gabbroic shergottite NWA 6963 as revealed by pyroxene zoning

NorthWest Africa (NWA) 6963 is an intriguing new coarse grained Martian meteorite that further extends our sample collection both compositionally and texturally. It was originally documented as a basaltic shergottite because the pyroxene compositions and modal abundances are similar to Shergotty. However, recent work reclassified NWA 6963 as an intrusive, gabbroic Martian meteorite because of the large oriented pyroxene crystals. This investigation will focus on NWA 6963 pyroxene zoning profiles and interpreting igneous processes related to its crystallization history. Compositional zoning of pyroxene crystals in basaltic shergottites have previously been interpreted for petrology and degrees of undercooling. In addition, cooling rates of Martian magmas have been determined experimentally to constrain volcanic processes based on both pyroxene and olivine zoning. These studies interpret crystallization histories of basaltic shergottites and provide valuble insight of volcanic flows on Mars. However, igneous conditions below the Martian surface can now be constrained with instrusive shergottite NWA 6963. The crystallization history of a gabbroic shergottite is expected to differ from basaltic Martian meteorites due to the nature of instrusive and extrusive igneous conditions. Determining rates of cooling from pyroxene zoning will further constrain the petrogenetic history of NWA 6963. This will provide new information on the nature of instrusive igneous processes within the shallow Martian subsurface