Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Geology

Supervisor

Dr. Phil McCausland

2nd Supervisor

Dr. Matthew Izawa

Joint Supervisor

3rd Supervisor

Dr. Roberta Flemming

Co-Supervisor

Abstract

This thesis investigates the processes and environments of formation of the anomalous enstatite achondrites NWA 4301, Zakłodzie, and NWA 8173 to determine how they relate to other enstatite meteorites (chondrites, impact melt rocks, aubrites, and so-called “primitive enstatite achondrites”). Observations of Zakłodzie and NWA 4301 showed both meteorites may share a common parent body, but experienced different metamorphic conditions. Different zonation patterns in plagioclase, silica polymorphs and associations, and sulfide assemblages indicate Zakłodzie experienced higher metamorphic temperatures and cooled faster than NWA 4301, therefore NWA 4301 was buried deeper in the parent body relative to Zakłodzie. In NWA 8173, mineral assemblages and textures indicate it formed at high temperatures, and underwent subsolidus annealing. Detailed mineral, chemical and structural classification of fluorophlogopite in NWA 8173 was made, to determine the role of halogens in formation mechanisms of enstatite meteorites. Overall findings showed that incipient partial melting and annealing following impact melting can both form the anomalous enstatite meteorites. However, a model is proposed where halogens can act as a fluxing agent in the melt and are represented by NWA 8173 and cause a thermally metamorphosed rock such as Zaklodzie and NWA 4301 to melt, fractionally crystallize and ultimately differentiate.

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