Regional Volcanic Extinction as a Mechanism for Subsidence in the Vatnsdalur Structural Basin, Skagi Peninsula, Northwest Iceland

• Main Author: Silverstein, Adam M
• Format: Text
• Language: English
• Published: Open Works 2016
• Subjects: Geology; Volcanology; Iceland; Vatnsdalur Structural Basin; Mid Atlantic Ridge; Mantle Plume; Geochemistry; Mid-Atlantic Ridge; Skagafjörður; Vatnsdalur
• Online Access: https://openworks.wooster.edu/independentstudy/7177; https://openworks.wooster.edu/cgi/viewcontent.cgi?article=8248&context=independentstudy

The Vatnsdalur Structural Basin (VSB) is located on the Skagi Peninsula in Northwest Iceland. It was formed ~7-9 Ma in the Skagafjörður, near the extinct Hunafloi-Skagi rift. The VSB is composed of three distinct sequences, emplaced at different points in time. During the emplacement of the second sequence, there was a massive subsidence event, causing the two sequences to rotate to 60°W/SW. It is possible to determine if this subsidence event was caused by the volcanic system going extinct during a rift jump event. This study hypothesizes that as a volcanic system goes extinct in Iceland, the magma loses its plume signature as it becomes less Oceanic Island Basalt (OIB)-like from moving away from the plume in space. This change in signature can be seen in isotopes as well as in trace element ratios of La/Sm and Th/Yb vs. Nb/Yb. This study expects to see the isotopes change from resembling plume basalts to resembling rift basalts, for the La/Sm ratio to decrease, and Th/Yb vs. Nb/Yb concentrations to decrease from sequence to sequence. The trace element results diverged from the expected trend, becoming more OIB-like from Sequence 1 to Sequence 3. An REE diagram was created to see if a change in the degree of melting had enriched the trace elements and diverged from showing the loss of plume signature. A Batch melting diagram was also created to further see the effect the amount of melt produced has on the concentration of trace elements. This divergence in data can be explained by a decrease in melting, which remains consistent with the hypothesis that the rift jumped and the volcanic system went extinct.