| Large Igneous Provinces (LIPs) produce highly voluminous lava flows in geologically
short periods. Little is known about the duration of the individual LIP eruptions. Here, I use
thermochronology to constrain the eruptive timescales of four dike segments in the Maxwell
Lake Dike Complex, which fed magma to the surface during the main phase of the 16-million-
year-old LIP called Columbia River Basalts. I found that these four dike segments erupted
magma from 0.5 to 9.5 years. In the field, I mapped meter-scale partial-melt zones in the
wallrocks next to dike segments. At one outcrop, I observed that the partial-melt zone tapers
from 5 m to no partial melt, which I interpret as evidence of magma focusing at an individual
dike segment. This result suggests that modern fissure eruptions in Iceland and Hawai’i are
reasonable analogs for LIP eruptions.
Key Words: Columbia River Basalts, thermochronology, magma flow duration, ambient
background temperature, numerical modeling, partial melt |