Date of Award
Master of Science
Northwest Africa 6963 (NWA 6963) is an intriguing new coarse grained, gabbroic Martian meteorite that further extends our sample collection both compositionally and texturally. Basaltic shergottites offer insight to volcanic igneous processes on the Martian surface and can be used to predict subsurface conditions. Gabbroic shergottite NWA 6963 provides direct petrologic evidence of intrusive igneous conditions within the Martian crust that extrusive meteorite samples cannot match. NWA 6963 is composed of coarse grained clinopyroxenes and maskelynite with sub-ophitic textures supporting its intrusive origin. Zoning textures in clinopyroxenes, augite and pigeonite, are analyzed to determine the crystallization history of NWA 6963. Compositional zoning profiles reveal pyroxenes with augite or pigeonite cores mantled by Fe-rich pigeonite rims. In NWA 6963 the pyroxenes cores are in equilibrium with one another, but cores are not in equilibrium with respective Fe-rich pigeonite rims in the same grain. This study suggests reasons for complex pyroxene textures and compositions observed in NWA 6963 are due to magma undercooling and possibly volatile expulsion during two distinct stages of crystallization history.
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