Thesis Defense: Trevor Cole, Master’s Candidate
Defense Date: Tuesday, April 14th, 2020
Time: 1:30 p.m.
The hydrochemical signatures of (in)congruent weathering in Iceland
Silicate weathering is often invoked as the dominant mechanism for sequestering CO2 over geologic timescales. Basaltic terrains such as Iceland are thought to disproportionately contribute to global silicate weathering fluxes since extrusive lithologies chemically weather faster than intrusive substrate. While Iceland is largely monolithologic, compiled solute and bedrock measurements herein suggest that river water is enriched in Na and Ca relative to a bedrock array comprised of rhyolite and basalt. To explore this relationship, we evaluate environmental factors that could explain the solute trends including clay precipitation (type-I incongruent weathering), variable dissolution rates of primary minerals (type-II incongruent weathering), and rhyolite dissolution/ groundwater contributions. Through forward models we conclude that the precipitation of high-Mg smectite exerts the most control on solute movement relative to type-II incongruency or dissolution of rhyolite. However, more direct measurements of clay mineralogy are needed to better constrain this dataset.