Using Zircon Morphology to Understand Metasomatic Fluid Alteration During the Big Sky Orogeny

Undergraduate Honors Thesis

Citations

Citeable URL: https://scholar.colorado.edu/concern/undergraduate_honors_theses/0r9674034

Abstract

Metasomatism is a metamorphic process that changes the bulk composition and morphology of a lithology. By understanding the differences between the protolith and altered rock, specifics about the composition of the fluid and its effects on the host rock can be understood. Metasomatic fluids have altered a lithology in Bear Basin, within the Northern Madison Range, in southwest Montana. This study utilizes zircon morphology from this altered lithology to constrain the effect of metasomatic alterations. Indicated by the zircon characteristics, albitization facilitates the formation of zircon glomerocrysts. The cores of the glomerocrysts are inherited from the protolith and are sutured together by new, metasomatic zircon growth. The inherited zircon cores are indicative of the zircon from the granodioritic body which contacts the albitite. The lithologic contact of the granodiorite and a dissimilar body acted as a crustal weakness which was exploited by the metasomatic fluid.

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