"CHEMICAL VOLCANOES" IN THE SPRINGERVILLE AREA, ARIZONA: USING TRAVERTINES, SPRINGS, AND MICROSEISMICITY TO LINK WATER QUALITY, PALEOHYDROLOGY AND NEOTECTONICS

Large volume travertine accumulations in the Springerville volcanic field, AZ, provide a natural laboratory for studying the interaction of magmatism, deeply sourced fluids, CO₂ flux, neotectonics, and the evolution of drainages. This area is a major center of recent (3.0 – 0.3 Ma) magmatism at the intersection of the southeastern margin of the Colorado Plateau and the Jemez lineament. Travertine mounds with central vents resemble shield volcanoes both in morphology and mode of accumulation. In addition to providing data for models of travertine formation and genesis, these deposits can be used in a manner similar to young volcanic rocks to constrain neotectonics and geomorphic history.

Forty-nine travertine mounds are clustered along the Little Colorado River near Lyman Lake, covering approximately 20 km² with an estimated total travertine volume of 2 km³. Local spring and groundwater chemistries indicate appreciable CO₂ degassing. Travertine vents align with previously mapped northwest-trending Quaternary faults and folds that reflect Quaternary strain at the southern boundary of the Colorado Plateau-Basin and Range transition zone just to the south of the site. CO₂ fields underlie the eastern portion of the study area. In December 2004, a swarm of nearly identical upper crustal microearthquakes ranging in magnitude from ~2.0 to ~4.0 occurred directly south of the youngest basalts in the Springerville volcanic field and of the travertine vents, indicating active tectonics in the region. Travertine-cemented river gravels are preserved 30 m above the paleoelevation of the Little Colorado. These gravels offer the potential to date the incision of the river and to test rate estimates from published K-Ar dates on basalt that suggest average incision rates of ~60 m/Ma for the past 1.98 Ma.

Previous studies of volcano ages, spatial clustering, and geochemistry in the Springerville volcanic field have shown spatial and temporal patterns that suggest multiple magma sources and migrating loci of waxing and waning magmatism. Study of the travertine deposits can add another dimension to the understanding of the complex tectonic evolution of the area.