Abstract
At arc volcanoes, deep crustal magma plumbing controls the volume, frequency, and composition of magma being transported to and stored in the upper crust. However, the mid-to-lower crust remains a challenging region to image. We explore the mid-to-lower crustal velocity structure beneath the Christiana-Santorini-Kolumbo Volcanic Chain (CSKVC) to better understand how an established stratovolcano and flanking volcano (Santorini and Kolumbo) are fed through the mid-to-lower crust. We use active-source seismic data to obtain a P-wave velocity model of the crust below the CSKVC. We invert direct and reflected P phases to cover the entire depth extent of the crust and solve for Moho interface depth. Results show a high Vp anomaly in the lower crust under Santorini and a mid-crustal low Vp anomaly offset from both Santorini and Kolumbo. Resolution is limited in the mid-crust below the Santorini caldera. We find that accumulation of magma correlates with local extension in the upper mid-crust (<10 km) but is offset at deeper depths. Our model requires a curved Moho interface, representative of crustal thickening via underplating. We find evidence for melt storage at 11-13 km depth associated with volcanism at Kolumbo. To reconcile our results with geochemical evidence, we favor entirely separate crustal plumbing for Santorini and Kolumbo despite their proximity. What remains uncertain is how melt is transported through the mid-to-lower crust to recharge the shallow melt at Santorini. Our study supports that vents nearby established stratovolcanoes can have separate systems of melt transport and storage in the crust.
Plain Language Summary
This study examines how magma is stored and transported through the Earth’s mid-to-lower crust beneath the Santorini and Kolumbo volcanoes, which are part of the Christiana-Santorini-Kolumbo Volcanic Chain. The mid-to-lower crust is a difficult area to study but is crucial for determining how magma is transported from the mantle through the crust at arc volcanoes. We use seismic data to create a model that shows the speed of seismic waves in the crust, known as a P-wave velocity model. This model helps visualize the structure of the crust beneath the volcanic chain. We identified a high-velocity area in the lower crust beneath Santorini and a lower-velocity area in the mid-crust that is not directly below either volcano. This low-velocity area is likely a region of melt storage for Kolumbo. By combining our results with previous studies of Santorini and Kolumbo’s chemical signatures, we find that the volcanic systems of Santorini and Kolumbo likely operate independently, even though they are geographically close. This suggests that each volcano has its own pathway for transporting and storing magma. However, there is still uncertainty regarding how magma is transported through the mid-to-lower crust to recharge the shallow melt at Santorini.