The focus of this study is to further develop an understanding of the local petrogenesis and related magmatic processes within Pillow Ridge, located in the Mount Edziza Volcanic Complex (MEVC), northwest British Columbia. This area, in addition to the regional MEVC, is poorly understood with regards to emplacement mechanisms and eruptive history. We examine textural and geochemical indicators from xenolithic samples from pillow units further detailed in Edwards et al., 2008, which are composed of gabbroic xenoliths within host basalts. Textural evidence supports our hypothesis that these xenoliths represent varying degrees of disaggregation and assimilation into the intruding melt. Incompatible elements (Nb, Zr and Y) from xenoliths, host rocks and previous data from Pillow Ridge samples (Franceschi et al., 2014) reveal that these xenoliths are related to the basaltic melt via fractional crystallization, although significant decoupling is seen in most major and trace elements. Furthermore, amphibole cumulus phases are seen in some gabbroic xenoliths, which are atypical of ordinary basalt fractionation. We propose that metasomatism is responsible for both A) decoupling seen in most geochemical comparisons and B) irregular hydrous phases in some xenoliths, through the addition of silica and H2O rich fluids into the basaltic cumulus pile. In addition, we propose that the eruptions that emplaced these pillow units are derived from a common parent magma source, wherein relict fractional byproducts (xenoliths) evolved and were extruded in later eruptions.
Jones, Leo, "Analysis of gabbroic xenoliths in pillow basalts, Pillow Ridge, MEVC, British Columbia: implications for crustal contamination, metasomatic crystallization and petrogenesis." (2015). Senior Independent Study Theses. Paper 6860.
Geology | Volcanology
Bachelor of Arts
Senior Independent Study Thesis
© Copyright 2015 Leo Jones