Drilling Into the Track of the Yellowstone Hot Spot

Shervais, John W.; Evans, James P.; Schmitt, Douglas R.; Christiansen, Eric H.; Prokopenko, Alexander A.

doi:10.1002/2014eo100001

Cited by 7 publications

(4 citation statements)

References 3 publications

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“…The remainder of the drill core samples extremely thick, welded rhyolite ash flows to a total depth of 1958 m depth (Knott et al, 2016). show that basalts and sediments below the Shoshone Falls Rhyolite (from to 420 m) in the Kimberly drill core are slightly older (≥6.37 Ma) than basalts recovered at the base of the Kimama drill core (Shervais et al, 2014;Knott et al, 2016). If we add this 181 m of basalt + sediment in the Kimberly drill core to the 1912 m section penetrated by the Kimama borehole, we can estimate a thickness of 2093 m for Pliocene through Quaternary basalts in the CSRP.…”

Section: Volcanic Stratigraphymentioning

confidence: 96%

“…A typical sequence of continental plume volcanism begins with intrusions of mafic, plume-derived magmas that drive the melting of continental lithosphere. Eruptions of silica-rich rhyolitic magmas occur over 2-4 m.y., after which the continental lithosphere is sufficiently depleted to allow the eruption of mantle-derived basalts (Jean et al, 2018;Shervais et al, 2014). The sequence of rhyolite, basalt, and sedimentary rocks that comprise the SRP spans 17 m.y.…”

Section: Regional Settingmentioning

confidence: 99%

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Volcanic stratigraphy and age model of the Kimama deep borehole (Project Hotspot): Evidence for 5.8 million years of continuous basalt volcanism, central Snake River Plain, Idaho

et al. 2019

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The Snake River Plain of central Idaho represents the world's best example of a mantle hotspot track impinging upon continental crust and provides a record of bimodal volcanism extending over 12 Ma to the present. Project Hotspot recovered almost 2 km of continuous drill core from the Kimama borehole, located in central Idaho on the axial volcanic zone. The Kimama drill core represents the most complete record of mafic volcanism along the Yellowstone-Snake River Plain hotspot track. A total of 432 basalt flow units, representing 183 basalt flows, 78 basalt flow groups, and 34 super groups, along with 42 sediment interbeds are recognized using volcanic facies observations, stratigraphic relationships, borehole geophysical logs, and paleosecular variation in magnetostratigraphy. Rhyolite and other non-basaltic volcanic materials were not encountered in the drill core. Ages for six basalt lava flows were determined by 40 Ar/ 39 Ar using incremental heating experiments. Paleomagnetic inclination was measured on over 1200 samples collected at roughly 2-m-depth intervals, yielding mean values of paleosecular variation between ±50° to ±70° in Kimama flow groups, close to the expected 61° axial dipole average for the Kimama borehole location. Twenty-three magnetic reversals were identified and correlated to dated geomagnetic chrons and subchrons and compared with the 40 Ar/ 39 Ar radiometric ages. A linear fit to 40 Ar/ 39 Ar dates, geomagnetic chron and subchron boundaries, and volcanogenic zircon U-Pb ages defines a mean accumulation rate of ~320 m/m.y. and extrapolates to a bottom hole age of 6.3 Ma. Average thicknesses of lithologic units increase from 2.7 m (sediment), 4 m (flow units), 10 m (flows), 23 m (flow groups), to 53 m (super groups). On average, one lava flow inundated the Kimama borehole location every 33 k.y. Intercalated sediments, ranging from 0.06 to 24.5 m thick, make up roughly 6% of the drill core and indicate lulls in local volcanic activity that may have lasted up to 77 k.y. Neutron and gamma-ray logs supplement observations from the drill cores: neutron logs document individual flow units through the contrast between massive flow interiors and more porous flow surfaces, and gamma-ray logs document the depth and thickness of sedimentary interbeds and high-K-Fe basalts. The 5.8 m.y. duration of basaltic volcanism in the Kimama drill core implies a steady rate of volcanism, indicating a relatively stable rate of mantle upflow along the lithosphere-mantle boundary in the wake of Yellowstone-Snake River Plain plume volcanism.

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Section: Volcanic Stratigraphymentioning

confidence: 96%

Section: Regional Settingmentioning

confidence: 99%

Volcanic stratigraphy and age model of the Kimama deep borehole (Project Hotspot): Evidence for 5.8 million years of continuous basalt volcanism, central Snake River Plain, Idaho

et al. 2019

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“…The third hole documents two phases of volcanism separated by a quiescent phase of lake deposition during the Pliocene-Pleistocene transition. Over 5,320 m of core was recovered from the three holes (Shervais et al 2014). Black and white blocks represent basalt, yellow is sediment, blue is rhyolite within a precise stratigraphic context that typically cannot be duplicated in outcrop; in others, drilling can provide samples of rocks that are not exposed due to lack of uplift and erosion, or where uplift is accompanied by deformation that masks primary relationships.…”

Section: Futurementioning

confidence: 99%

Drilling the solid earth: global geodynamic cycles and earth evolution

Shervais

Arndt

Goodenough

2014

Int J Earth Sci (Geol Rundsch)

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“…The Snake River Scientific Drilling Project (International Continental Scientific Drilling Program, Project HOTSPOT) examined the potential for the presence of commercial geothermal energy resources in the central and western portions of the Snake River Plain (SRP; Idaho, USA) (Nielson et al, 2012Shervais, 2014;Shervais et al, 2013Shervais et al, , 2014aShervais et al, , 2014b. Three boreholes were drilled to examine the geothermal gradient, in situ fluid chemistry and temperature, core geochemistry and lithology, geomechanical properties of the core, and borehole stress states at sites that exhibit potential for geothermal resources.…”

Section: Introductionmentioning

confidence: 99%

Geology and in situ stress of the MH-2 borehole, Idaho, USA: Insights into western Snake River Plain structure from geothermal exploration drilling

et al. 2017

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Project HOTSPOT, the Snake River Scientific Drilling Project (International Continental Scientific Drilling Program), tested for deep geothermal resources and examined the petrology of volcanic rocks with three drillholes in the central and western Snake River Plain (western USA). The MH-2 drillhole targeted fractured crystalline and hydrothermally altered basalt in the area of the Mountain Home Air Force Base (Idaho) to a total depth of 1821 m. At 1745 m depth the drillhole encountered flowing artesian hydrothermal fluids of at least 150 °C. We integrate geological analyses of core, image log, and borehole geophysical data, and in situ stress analyses to describe the structural environment that produces permeability for artesian flow. The rocks in the lower 540 m of the drillhole consist of basalt flows as much as 30 m thick, altered basalt, and thin sedimentary horizons. The mechanical stratigraphy is defined by nine mechanical horizons that are in three ranges of rock strength on the basis of experimentally determined strength data, core logging, and geophysical log signatures. Hydrothermal alteration products and mineralization in the core are associated with three highly faulted sections; the lowermost section is associated with the zone of flowing thermal water. Shear slip indicators on faults observed in core indicate slip ranging from pure strike slip to normal failure mechanisms in the stronger horizons. The borehole breakouts indicate that the maximum horizontal stress, S H , is oriented 047° ± 7°, and drilling-induced tensile fractures indicate that S H is oriented at 67° ± 21°. The in situ stress orientations exhibit little variation over the depth of the measured interval, but the S H magnitude varies with depth, and is best explained by an oblique normal fault stress regime. The geomechanical model indicates that if pore pressures at depth are elevated above the normal hydrostatic gradient, as observed here, the system has the potential to deform by mixed normal and strike-slip failure. Our observations and interpretations suggest that the MH-2 borehole was drilled into oblique normal faults that intersect a buried 300°-trending fault block masked by the basaltic volcanic complex. These data indicate that the transition from the central to western Snake River Plain is characterized by complex structures developed in response to a transitional stress state related to Snake River Plain and western Basin and Range stress regimes. The western Basin and Range stress and tectonic regime may extend from northern Nevada into western Idaho and may enhance the potential for geothermal resources by creating interconnected fracture and fault-related permeability at depth.

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Drilling Into the Track of the Yellowstone Hot Spot

Cited by 7 publications

References 3 publications

Volcanic stratigraphy and age model of the Kimama deep borehole (Project Hotspot): Evidence for 5.8 million years of continuous basalt volcanism, central Snake River Plain, Idaho

Volcanic stratigraphy and age model of the Kimama deep borehole (Project Hotspot): Evidence for 5.8 million years of continuous basalt volcanism, central Snake River Plain, Idaho

Drilling the solid earth: global geodynamic cycles and earth evolution

Geology and in situ stress of the MH-2 borehole, Idaho, USA: Insights into western Snake River Plain structure from geothermal exploration drilling

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