Department or Program

Geology

Abstract

Philpotts (1972) suggests the presence of an immiscible liquid (ocelli) crystallized within the Sté Dorothée Sill near Montréal, Canada. To test this hypothesis, I use the alphaMELTS program (Antoshechkina et al., 2012) which combines thermodynamic data and bulk compositional data to mimic natural magmas as they crystallize in the crust. Isobaric and isentropic models are used to simulate both the emplacement conditions and the source conditions of the parent magma that formed the Sté Dorothée Sill. The isobaric model uses temperature constraints that are unrealistic for emplacement, however ensure the composition is entirely liquid upon emplacement in order to compare the modal minerology of the sill. The mineral groups that crystallize from the isobaric trials are largely similar to the mineral groups observed in the Sté Dorothée Sill. Isentropic trials present a more realistic representation of the sill’s emplacement. Upon ascent from 1 GPa to 300 bars, the minerology of the crystallized portion of the melt in both trials suggest a mineralogy similar to the host fourchite which surrounds the ocelli. The remaining liquid upon reaching the suggested emplacement depth closely resembles the chemical composition of the hypothesized immiscible liquid. This evidence suggests that the liquid, which was previously thought to be of immiscible origin, was instead the result of fractional crystallization.

Level of Access

Open Access

First Advisor

Genevieve Robert

Date of Graduation

5-2020

Degree Name

Bachelor of Science

Number of Pages

65

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