Comparative Study of Equilibrated and Unequilibrated Eucrites: Subsolidus Thermal History of Haraiya and Pasamonte Eucrites

Introduction: The source and duration of the heating event responsible for eucrite metamorphism is not well constrained. Three hypotheses have been proposed for the source of heat: Impact, conduction from the mantle, and rapid production of successive flows [1]. Textural and chemical relationships of noncumulate eucrites are investigated to constrain the thermal and temporal conditions responsible for eucrite equilibration to provide insight into the evolution of the HED parent body. Pasamonte and Haraiya were chosen as they represent extremes on the metamorphic scale [2]. Pasamonte (Type 2) retains primary textures and compositions, but has been partially equilibrated during metasomatism. Haraiya (Type 7), with coarsely exsolved, partially inverted pigeonite, experienced prolonged metamorphism at subsolidus temperatures. 0 0.2 0.4 0.6 0.8 1 1.2