ERUPTIVE VOLUME AND EXPLOSION ENERGY ESTIMATES FROM KILBOURNE HOLE, SOUTHERN AXIS OF THE RIO GRANDE RIFT, SOUTHCENTRAL NEW MEXICO

The magmatic history of the Rio Grande rift (RGR) is complex, transitioning from early intermediate-composition magmatism to bimodal volcanism dominated by lithosphere-derived magma, and eventually to dominantly asthenosphere-derived alkalic basalts. Kilbourne Hole, a late-Pleistocene maar volcano adjacent to the Potrillo Volcanic Field, broadly fits into the later portion of the magmatic history of the rift. Maars are a common monogenetic volcano type associated with small volumes of magma interacting shallowly with external water but remain lesser understood than other volcano types.

Traditional field methods are implemented for determining surge deposit extent and variations in thickness, as well as locating, measuring, and sampling of ejected volcanic bombs/blocks at Kilbourne Hole. Complementary modern remote sensing mapping through false-color composite imagery from Landsat 8 OLI and Worldview-3 is used as reconnaissance for determining the furthest surge extents and bomb/block locations. This study presents a preliminary minimum eruptive volume from deposit thickness, explosion energies based on bomb/block ballistics, and changes in deposit characteristics throughout the eruptive lifespan of the maar-diatreme. High-precision GPS measurements made in the field are utilized to accurately assess deposit location and variations in thickness around the maar crater rim to make an isopach map and a paleosurface of the study area. Constraints on a minimum eruptive volume and eruption energies provide insight into the evolution and behavior of the eruption of Kilbourne during the later magmatic history of the RGR. Additionally, this project demonstrates the validity of using remote sensing complementary to field work and utilizing the unique reflectance properties of different surface materials to accurately assess and map young volcanic deposits.

Although Kilbourne makes up a small portion of the magmatic history of the RGR, it is associated with an abundance of mantle xenoliths that have provided vital geochemical data on the mantle composition beneath the rift. Constraining an eruptive volume and explosion energies involved in the transport of the xenoliths is vital in understanding rift-related volcanism as well as the broader formation and growth of maar-diatreme volcanoes.