Abstract

Braedvikir is a hyaloclastite dominated tindar in the Prestahnukur fissure swarm in the Western Volcanic Zone of Iceland. Major & trace element chemistry shows that Braedvikir is geochemically different from the region’s glaciovolcanic edifices, characterized by its highly depleted levels of FeO* and MgO and enrichment in SiO2. Samples show limited variation in incompatible elements, suggesting little differentiation in melting conditions. Major elements establish a variation in chemistry between lithostratigraphic units on the ridge. Units are genetically related by a 3-kb fractional crystallization model (Rhyolite-MELTS), which generates two pyroxenes and a range of plagioclase compositions. Plagioclase compositions could be indicative of a variety of crustal processes, but the data used in this study cannot conclusively point to any given process. A two-stage eruptive model was formulated using major element distinctions and cross-cutting relationships on the ridge. This model separates the initial explosive event which formed the bulk of the ridge (Unit LT) from a secondary event consisting of an explosive phase (TB1-2) followed by the intrusion of pipes (Lb1-8), a dike set (Ld1-2), and pillows (Lp1). This secondary event is hypothesized to be caused by a recharge event in the magma lens. This supply of more primitive magma could explain the difference in MgO levels between unit LT and all other units.

Advisor

Pollock, Meagen

Department

Geology

Disciplines

Geochemistry | Geology | Volcanology

Keywords

Petrology, Glaciovolcanism, Geochemistry, Iceland, Braedvikir, Basalt

Publication Date

2019

Degree Granted

Bachelor of Arts

Document Type

Senior Independent Study Thesis

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© Copyright 2019 Simon E. Crawford-Muscat