A comparative study of glaciovolcanic palagonitization of tholeiitic and alkaline sideromelane in Helgafell, Iceland and Wells Gray-Clearwater Volcanic Field, BC, Canada ...

• Main Author: Massey, Erica A.
• Format: Text
• Language: English
• Published: University of British Columbia 2017
• Subjects: Iceland
• Online Access: https://dx.doi.org/10.14288/1.0347288; https://doi.library.ubc.ca/10.14288/1.0347288

Pleistocene glaciovolcanic eruptions occurred frequently beneath continental-scale ice sheets producing vitric, fragmental volcanic deposits in Helgafell, Iceland (tholeiitic basalt) and Wells Gray, BC, Canada (alkali olivine basalt). They are highly susceptible to hydrothermal alteration that transforms sideromelane (basaltic volcanic glass) into palagonite (early amorphous material) and secondary minerals (i.e. zeolites, clays and sulfides). Compositional controls, mass transfer and geochemical-textural relationships are investigated by optical microscopy and analyses of major (12) and trace (32) elements in glass-palagonite pairs by Electron Microprobe Analysis (EMPA), Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), and geochemical modelling. Helgafell’s thinner (6-10 m vs. 10-20 m) palagonite rims demarcate highly vesicular (30.2% vs. 4.9%) sideromelane that has more secondary minerals (1.4% vs. 0.5%) than Wells Gray’s microlite-rich (12.3% vs. 0.1%) sideromelane. The thicknesses ...