First Results from HOTSPOT: The Snake River Plain Scientific Drilling Project, Idaho, U.S.A.

Abstract

HOTSPOT is an international collaborative effort to understand the volcanic history of the Snake River Plain (SRP). The SRP overlies a thermal anomaly, the Yellowstone-Snake River hotspot, that is thought to represent a deep-seated mantle plume under North America. The primary goal of this project is to document the volcanic and stratigraphic history of the SRP, which represents the surface expression of this hotspot, and to understand how it affected the evolution of continental crust and mantle. An additional goal is to evaluate the geothermal potential of southern Idaho.Project HOTSPOT has completed three drill holes.(1) The Kimama site is located along the central volcanic axis of the SRP; our goal here was to sample a long-term record of basaltic volcanism in the wake of the SRP hotspot.(2) The Kimberly site is located near the margin of the plain; our goal here was to sample a record of high-temperature rhyolite volcanism associated with the underlying plume. This site was chosen to form a nominally continuous record of volcanism when paired with the Kimama site. (3) The Mountain Home site is located in the western plain; our goal here was to sample the Pliocene-Pleistocene transition in lake sediments at this site and to sample older basalts that underlie the sediments.We report here on our initial results for each site, and on some of the geophysical logging studies carried out as part of this project.

Rheomorphic ignimbrites of the Rogerson Formation, central Snake River plain, USA: record of mid-Miocene rhyolitic explosive eruptions and associated crustal subsidence along the Yellowstone hotspot track

“…Castleford Crossing Ignimbrite, 70 m, Balanced Rock Rhyolite lava, 80 m; Late-Miocene and Pliocene to Pleistocene basalts, ≥100 m, Bonnichsen et al 2008;Othberg et al 2012). The net differential elevation across the Brown's Bench monocline could exceed our estimate if, as we expect, some individual ignimbrites reach over 1 km thick in the Snake River Basin, as demonstrated by a ≥1.3-km-thick ponded ignimbrite in the Kimberly deep drill core to the east (Shervais et al 2013;Knott et al 2016). Similar estimates of elevation change across the basin margins are described in the eastern Snake River Plain (Rodgers et al 2002) and around Kimberly (Knott et al 2016).…”

“…Boroughs et al 2012;Colón et al 2015). Interest centres upon how the magmas formed in such volume Shervais et al 2013) and upon the unusual physical volcanology of the eruptions, their scale, frequency and environmental impact (Branney et al Editorial responsibility: R.J. Brown…”

Drilling Into the Track of the Yellowstone Hot Spot

“…Project HOTSPOT is an international collaborative drilling effort focused on understanding the Yellowstone hot spot and its interactions with the continental lithosphere ( Figure 1) [Shervais et al, 2006;Shervais et al, 2013]. Previous seismic observations have measured the Yellowstone magma plume as extending to depths greater than 1000 kilometers, well into the lower mantle [Smith et al, 2009;Obrebski et al, 2010;Schmandt et al, 2012], although other investigators propose a shallower mantle origin for the anomaly [James et al, 2011].…”

Drilling to investigate processes in active tectonics and magmatism

“…These projects have presented, and will continue to present, significant opportunities. An example of the opportunities provided by alternative funding sources is the Snake River Geothermal Drilling Project, funded by US Department of Energy, which produced ∼ 5.3 km of core (Shervais et al, 2013b).…”

“…Unzen Scientific Drilling Project (Nakada et al, 2005) and the Iceland Deep Drilling Project (IDDP: Friðleifssona et al, 2014;. Projects focusing on chemical geodynamics include the Hawai'i Scientific Drilling Project (DePaolo et al, 1996 and Hotspot: the Snake River Drilling Project (Shervais et al, 2006(Shervais et al, , 2013b.…”