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Lithium is an economically important element that is increasingly extracted from brines accumulated in continental basins. While a number of studies have identified silicic magmatic rocks as the ultimate source of dissolved brine lithium, the processes by which Li is mobilized remain poorly constrained. Here we focus on the potential of low-temperature, post-eruptive processes to remove Li from volcanic glass and generate Li-rich fluids. The rhyolitic glasses in this study (from the Yellowstone-Snake River Plain volcanic province in western North America) have interacted with meteoric water emplacement as revealed by textures and a variety of geochemical and isotopic signatures. Indices of glass hydration correlate with Li concentrations, suggesting Li is lost to the water during the water-rock interaction. We estimate the original Li content upon deposition and the magnitude of Li depletion both by direct in situ glass measurements and by applying a partition-coefficient approach to plagioclase Li contents. Across our whole sample set (19 eruptive units spanning ca. 10 m.y.), Li losses average 8.9 ppm, with a maximum loss of 37.5 ppm. This allows estimation of the dense rock equivalent of silicic volcanic lithologies required to potentially source a brine deposit. Our data indicate that surficial processes occurring post-eruption may provide sufficient Li to form economic deposits. We found no relationship between deposit age and Li loss, i.e., hydration does not appear to be an ongoing process. Rather, it occurs primarily while the deposit is cooling shortly after eruption, with δ18O and δD in our case study suggesting a temperature window of 40° to 70°C.

The separation of immiscible liquids has significant implications for magma evolution and the formation of magmatic ore deposits. We combine high-resolution imaging and electron probe microanalysis with the first use of atom probe tomography on tholeiitic basaltic glass from Hawaii, the Snake River Plain, and Iceland, to investigate the onset of unmixing of basaltic liquids into Fe-rich and Si-rich conjugates. We examine the relationships between unmixing and crystal growth, and the evolution of a nanoemulsion in a crystal mush. We identify the previously unrecognised role played by compositional boundary layers in promoting unmixing around growing crystals at melt-crystal interfaces. Our findings have important implications for the formation of immiscible liquid in a crystal mush, the interpretations of compositional zoning in crystals, and the role of liquid immiscibility in controlling magma physical properties., This study seeks to tackle the question of why intermediate magmatic rock compositions are poorly represented on the Earth’s surface. The authors do so by tracking the evolution of the physical behaviour of immiscible Fe-rich liquids within a sample suite from the lava lake on the Kilauea Iki volcano, Hawaii.

Basalts erupted in the Snake River Plain of central Idaho and sampled in the Kimama drill core link eruptive processes to the construction of mafic intrusions over 5.5 Ma. Cyclic variations in basalt composition reveal temporal chemical heterogeneity related to fractional crystallization and the assimilation of previously-intruded mafic sills. A range of compositional types are identified within 1912 m of continuous drill core: Snake River olivine tholeiite (SROT), low K SROT, high Fe-Ti, and evolved and high K-Fe lavas similar to those erupted at Craters of the Moon National Monument. Detailed lithologic and geophysical logs document 432 flow units comprising 183 distinct lava flows and 78 flow groups. Each lava flow represents a single eruptive episode, while flow groups document chemically and temporally related flows that formed over extended periods of time. Temporal chemical variation demonstrates the importance of source heterogeneity and magma processing in basalt petrogenesis. Low-K SROT and high Fe-Ti basalts are genetically related to SROT as, respectively, hydrothermally-altered and fractionated daughters. Cyclic variations in the chemical composition of Kimama flow groups are apparent as 21 upward fractionation cycles, six recharge cycles, eight recharge-fractionation cycles, and five fractionation-recharge cycles. We propose that most Kimama basalt flows represent typical fractionation and recharge patterns, consistent with the repeated influx of primitive SROT parental magmas and extensive fractional crystallization coupled with varying degrees of assimilation of gabbroic to ferrodioritic sills at shallow to intermediate depths over short durations. Trace element models show that parental SROT basalts were generated by 5-10% partial melting of enriched mantle at shallow depths above the garnet-spinel lherzolite transition. The distinctive evolved and high K-Fe lavas are rare. Found at four depths, 319 m, 1045 m, 1078 m, and 1189 m, evolved and high K-Fe flows are compositionally unrelated to SROT magmas and represent highly fractionated basalt, probably accompanied by crustal assimilation. These evolved lavas may be sourced from the Craters of the Moon/Great Rift system to the northeast. The Kimama drill core is the longest record of geochemical variation in the central Snake River Plain and reinforces the concept of magma processing in a layered complex.

The Bruneau Woodpile site has long been popular among fossil collectors; however, the deposit has received scant attention from scientists. Our research reveals that the fossilized wood was deposited ca. 6.85 Ma, within the Chalk Hills Formation, and was mineralized with carbonate-fluorapatite. The diverse assemblage of conifers and hardwoods is representative of the warm temperate forests that flourished in southwest Idaho, USA during the late Miocene. Limb and trunk fragments preserved in a single thin sandstone bed appear to represent woody debris that was transported by streams. One possible explanation is that wood, pumice, and sandy volcaniclastic sediment arrived separately as a result of ordinary stream action, and later were combined into a single assemblage during a subsequent high-energy sedimentation event. We favor an alternate hypothesis: a catastrophic event (e.g., a windstorm) damaged trees on slopes bordering the ancient lake. Branches and small trunk fragments were carried by wind and rain into local streams and ponds where they became waterlogged. After a delay that allowed pumice and wood to become saturated, storm water transported these materials, along with finer volcaniclastic sediment, into a lake. The resulting density current produced a fining-upward sedimentary cycle where wood was preserved in the lowest, coarsest stratum.

Understanding irrigator responses to previous changes in water availability is critical to building effective institutions that allow for efficient and resilient management of water resources in the face of potentially increasing scarcity due to climate change. Using remote sensing data, I examined irrigator responses to seasonal changes in water availability in Idaho's Snake River Plain over the past 33 years. Google Earth Engine's high performance cloud computing and big data processing capabilities were used to compare the performance of three spectral indices, three compositing algorithms and two sensors for 2002 and 2007 for distinguishing between irrigated and non-irrigated parcels. We demonstrate that, on average, the seasonal-maximum algorithm yields a 60% reduction in county scale root mean square error (RMSE) over the accepted single-date approach. We use the best performing classification method, a binary threshold of the seasonal maximum of the Normalized Difference Moisture Index (NDMI), to identify irrigated and non-irrigated lands in Idaho's Snake River Basin for 1984-2016 using Landsat 5-8 data. NDMI of irrigated lands was found to generally increase over time, likely as a result of changes in agricultural practices increasing crop productivity. Furthermore, we find that irrigators with rights to small areas, and those with only surface water rights are more likely to have a major reduction (>25%) in irrigated area and conversely those with a large, groundwater rights are more likely to have major increases (>25%) in the extent of their irrigation. Master of Science

There are pressing concerns about the interplay between agricultural productivity, water demand, and water availability in semi-arid to arid regions of the world. Currently, irrigated agriculture is the dominant water user in these regions and is estimated to consume approximately 80% of the world’s diverted freshwater resources. We develop an improved irrigated land-use mapping algorithm that uses the seasonal maximum value of a spectral index to distinguish between irrigated and non-irrigated parcels in Idaho’s Snake River Plain. We compare this approach to two alternative algorithms that differentiate between irrigated and non-irrigated parcels using spectral index values at a single date or the area beneath spectral index trajectories for the duration of the agricultural growing season. Using six different pixel and county-scale error metrics, we evaluate the performance of these three algorithms across all possible combinations of two growing seasons (2002 and 2007), two datasets (MODIS and Landsat 5), and three spectral indices, the Normalized Difference Vegetation Index, Enhanced Vegetation Index and Normalized Difference Moisture Index (NDVI, EVI, and NDMI). We demonstrate that, on average, the seasonal-maximum algorithm yields an improvement in classification accuracy over the accepted single-date approach, and that the average improvement under this approach is a 60% reduction in county scale root mean square error (RMSE), and modest improvements of overall accuracy in the pixel scale validation. The greater accuracy of the seasonal-maximum algorithm is primarily due to its ability to correctly classify non-irrigated lands in riparian and developed areas of the study region. Published version

The 1895 discovery of a petrified tree near Clover Creek in south-central Idaho, USA, attracted worldwide attention and resulted in the naming of a new species of ancient oak, Quercinium pliocaenicum Schuster. For more than a century, the discovery has largely been forgotten, even though specimens reside in reputable museums. Reinvestigation of the locality in 2014/2015 resulted in newly-collected specimens and a wealth of new data. Optical microscopy confirms the cellular anatomy used for the original taxonomic study. X-ray diffraction, scanning electron microscopy, energy-dispersive electron spectroscopy, Raman spectroscopy and cathodoluminescence microscopy reveal details of the mineralization, showing the presence of opal-CT as the primary component, with chalcedony as a lesser constituent. This mineralogy suggests petrifaction occurred in at least two stages, beginning with opalization of cellular tissue, leaving open vessels that became filled with chalcedony during a later mineralization episode. Clover Creek oak represents relict flora growing in a wetter climate before the uplift of the Cascade Range created a rain shadow that caused profound desertification of the inland Pacific Northwest.

Super-eruptions generating hundreds of cubic kilometers of pyroclastic density currents are commonly recorded by thick, welded and lava-like ignimbrites. Despite the huge environmental impact inferred for this type of eruption, little is yet known about the timescales of deposition and post-depositional flow. Without these timescales, the critical question of the duration of any environmental impact, and the ensuing gravity of its effects for the Earth system, eludes us. The eruption and welding of ignimbrites requires three transects of the glass transition. Magma needs to: (1) fragment during ascent, (2) liquefy and relax during deposition, agglutination and welding (sintering), and (3) quench by cooling into the glassy state. Here we show that welding is a rapid, syn-depositional process and that the welded ignimbrite sheet may flow for up to a few hours before passing through the glass transition a final time. Geospeedometry reveals that the basal vitrophyre of the Grey’s Landing ignimbrite underwent the glass transition at a rate of ∼0.1°C.min−1 at 870°C; that is, 30–180°C below pre-eruptive geothermometric estimates. Application of a 1-D cooling model constrains the timescale of deposition, agglutination, and welding of the basal vitrophyre to less than 1 h, and possibly even tens of minutes. Thermo-mechanical iteration of the sintering process indicates an optimal temperature solution for the emplacement of the vitrophyres at 966°C. The vitrophyres reveal a Newtonian rheology up to 46 MPa, which suggests that the ash particles annealed entirely during welding and that viscous energy dissipation is unlikely from loading conditions alone, unless shear stresses imposed by the overlying ash flow were excessively high and sustained over long distances. The findings underline the value of the term “lava-like” flow to describe the end rheology of Snake River-type ignimbrites, fully consistent with the typical lithofacies observed.

The Snake River Plain (SRP) is one of the best-preserved examples of continental hotspot volcanis, with a continuous record of volcanism that extends over 16 Ma to the present. Yellowstone-Snake River Plain records the migration of plume-tail volcanism from inception at the Bruneau-Jarbridge caldera complex at 12.6 Ma to its present locus, under the Yellowstone Plateau. Records kept by the Snake River Plain volcanic actions include rhyolite lavas and ignimbritesm minor coeval basalts, and an overlying veneer of younger basalts. The central SRP has received comparatively little attention in the past. The Kimama core hole was drilled as part of Project Hotspot, the Snake River Scientific Drilling Project, which seeks to understand the long-term volcanic and sediment logical history of the SRP volcanic province. The Kimama core hole is the only part of the SRP that has not been scientifically drilled and cored to a significant depth in the past. Investigations of subsurface stratigraphy in continental volcanic provinces such as the SRP-YP are limited by the by the relatively low depth and spatial distribution of cored wells. The study of the Kimama core provides us with a continuous record of basalt and minor sediment deposition. The long-term volcanic history of the SRP, documented by moving magma and its composition, demonstrates that magmatism is mantle plume-derived. Our investigation of the Kimama core, combined with new mantle tomography, provides evidence that refutes non-plume models for the origin of the Snake River Plain volcanic province.

The role of bison in the prehistoric subsistence in southern Idaho is not fully understood. Bison remains from Baker Cave, a late Holocene archaeological site dating to cal A.D. 1042-1265, however, provide evidence of pre-contact subsistence strategies in the region. This thesis focuses on the paleoecology of bison and their role in prehistoric subsistence on the Snake River Plain (SRP). The ecological study of bison focuses on the hypothesized trans-Holocene diminution in bison body size in southern Idaho, while a second study focuses on how these animals figured into prehistoric responses to seasonal fat scarcity. Although bison diminution and its ecological determinants are well understood on the Great Plains, the history of diminution west of the Rocky Mountains is less clear. Bison morphometrics from Baker Cave present the opportunity to assess bison diminution on the Snake River Plain. Bison morphometrics from Baker Cave are indistinguishable not only from other late Holocene bison on the Snake River Plain but iv also from late Holocene bison from the Great Plains. Further, the Baker Cave bison are smaller than early Holocene bison from the Great Plains and Snake River Plain. These results suggest morphological similarity between Snake River Plain bison and Great Plains bison through the Holocene, pointing to similar bottom up ecological constraints on body size. Although bison are common components of SRP archaeofaunas, their role in prehistoric subsistence is poorly understood. To shed light on this problem, I hypothesize that the Baker Cave bison assemblage resulted from hunters seeking skeletal fat. I test predictions drawn from this hypothesis with assemblage-level patterns in element representation, impact scar distribution, and fragmentation. These assemblage-level patterns track the skeletal fat utility of elements. These patterns, combined with winter procurement evidenced by fetal remains, support the hypothesis that fat-seeking behavior was a response to winter fat scarcity. A comparison with smaller bison assemblages from southern Idaho suggests that this fat-seeking behavior might have persisted as far back as the middle Holocene, although this requires confirmation from future studies.

Bulletin of Volcanology, 75 (8), ISSN:0258-8900, ISSN:1432-0819

The work in this thesis was based on analyzing water samples collected from three exploratory boreholes drilled during Project Hotspot. The water samples were analyzed for their chemical properties. The chemical properties of the water samples were used as a basis for further analysis. Geophysical logs, mainly temperature logs, were also analyzed for this project. Temperature logs measure temperature in relation to depth within a borehole. All the analyses were made in order to estimate the geothermal potential of the project areas. The exploratory boreholes were all drilled in different areas and each had unique characteristics. The Mountain Home borehole provided the most promising evidence for future geothermal potential. Geothermal energy is a form of renewable energy and potential production areas are difficult and expensive to locate.

The Snake River Plain is located in the southern part of the state of Idaho. The eastern plain, on which this study focuses, is a trail of volcanics from the Yellowstone hotspot. Three exploratory geothermal wells were drilled on the Snake River Plain. This project analyzes basaltic core from the first well at Kimama, north of Burley, Idaho. The objectives of this project are to establish zones of geothermal alteration and analyze the potential for geothermal power production using sub-aquifer resources on the axial volcanic zone of the Snake River Plain. Thirty samples from 1,912 m of core were sampled and analyzed for clay content and composition using X-ray diffraction. Observations from core samples and geophysical logs are also used to establish alteration zones. Mineralogical data, geophysical log data and physical characteristics of the core suggest that the base of the Snake River Plain aquifer at the axial zone is located 960m below the surface, much deeper than previously suspected. Swelling smectite clay clogs pore spaces and reduces porosity and permeability to create a natural base to the aquifer. Increased temperatures favor the formation of smectite clay and other secondary minerals to the bottom of the hole. Below 960 m the core shows signs of alteration including color change, formation of clay, and filling of other secondary minerals in vesicles and fractured zones of the core. The smectite clay observed is Fe-rich clay that is authigenic in some places. Geothermal power generation may be feasible using a low temperature hot water geothermal system if thermal fluids can be attained near the bottom of the Kimama well. (113 pages)

[1] This study presents paleomagnetic results from the Snake River Plain (SRP) in southern Idaho as a contribution to the time-averaged field global database. Paleomagnetic samples were measured from 26 sites, 23 of which ( 13 normal, 10 reverse) yielded site mean directions meeting our criteria for acceptable paleomagnetic data. Flow ages (on 21 sites) range from 5 ka to 5.6 Ma on the basis of Ar-40/Ar-39 dating methods. The age and polarity for the 21 dated sites are consistent with the Geomagnetic Reversal Time Scale except for a single reversely magnetized site dated at 0.39 Ma. This is apparently the first documented excursion associated with a period of low paleointensity detected in both sedimentary and igneous records. Combining the new data from the SRP with data published from the northwest United States between the latitudes of 40degrees and 50degreesN, there are 183 sites in all that meet minimum acceptability criteria for legacy and new data. The overall mean direction of 173 normally magnetized sites has a declination of 2.3degrees, inclination of 61.4degrees, a Fisher concentration parameter (kappa) of 58, and a radius of 95% confidence (alpha(95)) of 1.4degrees. Reverse sites have a mean direction of 182.4degrees declination, -58.6degrees inclination, kappa of 50, and alpha(95) of 6.9degrees. Normal and reversed mean directions are antipodal and indistinguishable from a geocentric axial dipole field at the 95% confidence level. Virtual geomagnetic pole dispersion was found to be circularly symmetric, while the directional data were elongate north-south. An updated and corrected database for the northwestern U. S. region has been contributed to the Magnetics Information Consortium (MagIC) database at http://earthref.org.