Columbia River Basalt Research Articles

Eclogite-driven subsidence of the Columbia Basin (Washington State, USA) caused by deposition of Columbia River Basalt

Eclogite-driven subsidence of the Columbia Basin (Washington State, USA) caused by deposition of Columbia River Basalt

Modelling groundwater contamination above a potential nuclear waste repository in the Columbia River Basalt, USA

Potential groundwater contamination above the one-time candidate repository for high-level nuclear waste in the Columbia River Basalt (CRB), USA, is evaluated in a flow-transport model with 260,895 elements for a period of 1 million years. The hydrogeologic database originates from the Basalt Waste Isolation Project, which ended in 1987, giving way to the Yucca Mountain project. The CRB data have been scanned recently with the object of finding a storage site for natural gas and a sequestration site for CO2. However, the impact on the nuclear issue in the USA or other countries with similar large flood-basalt provinces has never been evaluated since the suspension of the project. The peak radioactive dose predicted for a potential repository in the CRB is at least eight orders of magnitude lower than the US generic regulatory limit (0.15 mS/a) even for the most pessimistic scenario.

Three‐Phase CO2 Flow in a Basalt Fracture Network

AbstractGeologic CO2 sequestration in basalt reservoirs is predicated on permanent CO2 isolation via rapid mineralization reactions. This process is supported by a substantial body of evidence, including laboratory experiments documenting rapid mineralization rates, regional storage estimates indicating large, accessible storage reservoirs, and two successful pilot‐scale studies. Nevertheless, there remains significant uncertainty in the behavior of CO2 flow within basalt fracture networks, particularly in the context estimating physical trapping potential in early time and as CO2 undergoes phase change. In this study, a Monte Carlo numerical model is designed to simulate a supercritical CO2 plume infiltrating a low‐permeability flood basalt entablature. The fracture network model is based on outcrop‐scale LiDAR mapping of Columbia River Basalt, and CO2 flow is simulated within fifty equally probable realizations of the fracture network. The spatial distribution of fracture permeability for each realization is randomly drawn from a basalt aperture distribution, and ensemble results are analyzed with e‐type estimates to compute mean and standard deviation of fluid pressure and CO2 saturation. Results of this model after 10 years of simulation suggest that (1) CO2 flow converges on a single dominant flow path, (2) CO2 accumulates at fracture intersections, and (3) variability in permeability can account for a 1.6 m depth interval within which free CO2 may change phase from supercritical fluid to subcritical liquid or gas. In the context of CO2 sequestration in basalt, these results suggest that physical CO2 trapping may be substantially enhanced as carbonate minerals precipitate within the basalt fracture network.

Sulfur release from main-phase Columbia River Basalt eruptions

Sulfur release from main-phase Columbia River Basalt eruptions

Geochemistry and mineralogy of a saprolite developed on Columbia River Basalt: Secondary clay formation, element leaching, and mass balance during weathering

This study presents chemical and mineralogical data on weathering trends in a saprolite that is preserved between flows of the Columbia River Basalt Group at Trinidad, Washington. Bulk chemistry, electron imaging, and X-ray mapping indicate early Fe and Mg depletion by dissolution of ferromagnesian minerals, followed by depletion of alkalis, Al, Ti, and P that corresponds to dissolution of feldspars, titanomagnetite, and apatite. Secondary coatings of nontronite clay in the deep saprolite display intricate, submicrometer-scale zoning in Fe and Mg content. Distinct aluminous zones in these clays become more prominent at shallower depths. The primary Fe-containing phase shifts from nontronite in deeper samples to hematite in shallow samples; samples at the boundary contain the assemblage kaolinite + nontronite, which may mark the transition from permeability-limited fluid flow to fully open-system behavior. This shift is observed in rocks that have lost 30–40% of the total rock mass to leaching, and coincides with the disappearance of feldspar, Fe-Ti oxides, and apatite. Rocks in the uppermost saprolite have been converted to an assemblage of Al-smectite + hematite (+kaolinite). These results suggest that the presence of nontronite in weathered samples may indicate weathering under conditions of limited permeability; however, it does not necessarily indicate weathering in a chemically closed system. These observations may be useful in interpreting the clay mineral assemblages observed on Mars and what information they contain about near-surface conditions in the planet’s ancient past.

The new Wallula CO2 project may revive the old Columbia River Basalt (western USA) nuclear-waste repository project

A novel CO2 sequestration project at Wallula, Washington, USA, makes ample use of the geoscientific data collection of the old nuclear waste repository project at the Hanford Site nearby. Both projects target the Columbia River Basalt (CRB). The new publicity for the old project comes at a time when the approach to high-level nuclear waste disposal has undergone fundamental changes. The emphasis now is on a technical barrier that is chemically compatible with the host rock. In the ideal case, the waste container is in thermodynamic equilibrium with the host-rock groundwater regime. The CRB groundwater has what it takes to represent the ideal case.

Wallula Basalt Pilot Demonstration Project: Post-injection Results and Conclusions

Deep underground geologic formations are being evaluated for long-term storage of CO2, including large continental flood basalt formations. At the GHGT-11 and GHGT-12 conferences, progress was reported on the initial phases for Wallula Basalt Pilot demonstration test (located in Eastern Washington state), where nearly 1,000 metric tons of CO2 was injected over a 3-week period during July/August 2013. The target CO2 injection intervals were two permeable basalt interflow reservoir zones with a combined thickness of ∼20 m that occur within a layered basalt sequence between a depth of 830-890 m below ground surface. During the two-year post-injection monitoring period, downhole fluid samples were periodically collected, coupled with limited wireline borehole logging surveys that provided indirect evidence of on-going chemical geochemical reactions/alterations and CO2 distribution. A detailed pre-closure field characterization program included downhole fluid sampling, and performance of hydrologic tests and wireline geophysical surveys. Side-wall cores also were retrieved from within the targeted injection zones. Visual observations of the core material identified small globular nodules, translucent to yellow in color, residing within vugs and small cavities, which were not evident in pre-injection side-wall cores obtained from the native basalt formation. Characterization by x-ray diffraction identified these nodular precipitates as ankerite, the identical iron and calcium rich carbonate observed to form in laboratory tests with Columbia River basalts. Isotopic characterization (δ13C, δ18O) conducted on the ankerite nodules indicate a distinct isotopic signature that is closely aligned with that of the injected CO2. Final post-injection wireline geophysical logging results also indicate the presence of free-phase CO2 at the top of the two injection interflow zones, with no vertical migration of CO2 above the injection horizons. These findings support previous assumptions regarding storage feasibility and rapid mineralization of CO2 injected into a suitable basalt formation.

A crustal-scale integrated geophysical and tectonic study of the Snake River Plain region, northwestern U.S.A.

ABSTRACTThe Pacific Northwest region of North America is a site of very complex tectonomagmatic activity. This activity is due to subduction of the Pacific plate, the associated Cascade chain of volcanoes, micro-plate interactions, and mantle plume activity to the east of the plate margin that produced the Yellowstone hotspot track along the Eastern Snake River Plain (ESRP). A number of recent geophysical and geological studies have produced new results that have drawn attention to the complex tectonic setting of the region east of the Cascade Range, and its tectonic evolution is the subject of considerable scientific interest and debate. Numerous seismic studies have specifically focused on the crustal and upper mantle structure of the ESRP and Yellowstone area. However, crustal-scale studies of the Western Snake River Plain (WSRP) are limited. We undertook an integrated analysis of new and existing geophysical data and geologic constraints to study the crustal structure of the WSRP and generated two-dimensional crustal models across it. We observed both differences and similarities in the structural and tectonic evolution of the eastern and western arms of the SRP based on our integrated analysis. From a broader perspective based on recent geological and geophysical studies in the surrounding region, the intersection of the two arms of the SRP emerges as a major element of a complex tectonic intersection that includes the High Lava Plains of eastern Oregon, the Northern Nevada rift, a southwestern extension of the ESRP into northern Nevada, as well as, faulting and volcanism extending north-westward to connect with the Columbia River basalt plateau region. Thus, the goal of this study is to advance our understanding of the tectonomagmatic evolution of the region and to encourage further studies in the region.

A rapid lake-shallowing event terminated preservation of the Miocene Clarkia Fossil Konservat-Lagerstätte (Idaho, USA)

Abstract The world-renowned middle Miocene Clarkia lacustrine deposits (15.4–16.0 Ma) in northern Idaho, United States, known as Fossil Lagerstätten, yield extraordinary fossils that preserve in situ ancient biomolecules and organic biomarkers. The sudden formation of the Clarkia Lake basin by means of the Columbia River Basalt damming the proto–St. Maries River is well documented, but less is known about the tempo and mode of the lake environmental succession which impacted on the preservation of these Fossil Lagerstätten. Here, we present evidence for a previously unrecognized, geologically instantaneous drop in the Clarkia Lake water level, using tetraether-based water-depth proxies from a continuous sedimentary sequence at the classic P-33 site. Terrestrial hydrological conditions inferred from compound-specific hydrogen isotope compositions (δD) and tetraether-derived temperature estimates from the same sequence show that the rapid shallowing by >10 m was independent of regional climatic changes. We hypothesize that a volcanic-related geological event was primarily responsible for the rapid reduction of Clarkia Lake water depth—an event that played a decisive role in switching depositional conditions for Clarkia Fossil Lagerstätten from a conservation deposit to a concentration deposit.

Introduction: EarthScope IDOR project (deformation and magmatic modification of a steep continental margin, western Idaho–eastern Oregon) themed issue

The EarthScope IDOR (Idaho-Oregon) project was designed to investigate the formation of the steep accretionary boundary associated with the Salmon River suture zone and western Idaho shear zone (WISZ), in western Idaho and eastern Oregon (western USA). The research was designed to test three hypotheses concerning the present geometry of the boundary: (1) a crustal detachment; (2) a lithospheric detachment; and (3) a curved original geometry for the WISZ. The data presented in this volume indicate that none of these original three models is correct. Rather, the WISZ continues vertically downward through the entire crust, its steep orientation consistent with a significant component of strike-slip and/or transpressional tectonism. Moreover, the western Idaho shear zone is extremely well preserved despite abundant subsequent magmatism (Idaho batholith, Challis event, Columbia River Basalt Group) and tectonism (Cretaceous contraction, Eocene extension, Miocene–present extension). The ten research papers in this volume report on various aspects of this history. Four papers address the kinematics and tectonic history of rocks spatially associated with the WISZ, including its along-strike northward continuation. Two papers address the tectonic history of the accreted terranes, including geochemical arguments for different lithospheres sampled during magmatic episodes. Three papers document deformation, exhumation, and emplacement rates in the Idaho batholith. The final paper constrains the modern crustal architecture along a transect from the accreted terranes in the west to cratonic North America in the east. Together, these studies constrain the tectonic history of a subvertical tectonic boundary in the North American Cordillera.

A strong contrast in crustal architecture from accreted terranes to craton, constrained by controlled-source seismic data in Idaho and eastern Oregon

Crustal structure was derived from EarthScope Idaho-Oregon (IDOR) controlled-source seismic data across the Precambrian continental margin in the Idaho and Oregon region of the U.S. Cordillera. Refraction and wide-angle reflection traveltimes were inverted to derive a seismic velocity model that constrains the contact between oceanic accreted terranes and craton. The seismic data reveal that the boundary is a near-vertical, through-going feature of the crust, represented by the transpressional western Idaho shear zone (WISZ). The WISZ separates crust with different seismic velocities at all depths, implying a contrast in lithology, and extends to an ∼7 km offset of the Moho. The thinner, ∼32-km-thick accreted terrane crust to the west is characterized by faster seismic velocities that correspond to an intermediate composition. We interpret a high-velocity layer below a high-amplitude seismic reflection as mafic magmatic underplating associated with the feeder system of the Columbia River Basalts. The cratonic crust east of the WISZ is 37–40 km thick, with a felsic composition to ∼29 km subsurface depth, underlain by an intermediate-composition layer above the Moho. The strong contrasts in lithology and crustal thickness across the WISZ have influenced subsequent magmatism and extension in the region. The northwestern extent of the Archean Grouse Creek cratonic block beneath the Atlanta lobe of the Idaho batholith is interpreted based on continuity of crustal architecture in the seismic model. The velocity structure and crustal thickness east of the WISZ are consistent with the Atlanta lobe melting within a thickened crust.

Formation of the ferruginous smectite SWa-1 by alteration of soil clays

Clay minerals found in and near the surface of Mars contain unique information about the geo-chemical environment in the martian near-surface in the ancient past. To interpret this information, it is necessary to fully understand the environments in which different clay minerals form. Studies of terrestrial analog materials and environments are a useful way to address such questions, and some terrestrial materials are also important standards for remote sensing and in situ chemical and mineralogical analyses. This study presents new information on the formation environment of an unusual standard clay, the Clay Minerals Society source clay SWa-1 ferruginous smectite of Grant County. The SWa-1 collection locality is in the Columbia River Basalts (CRB), at the contact between a paleosol and a capping basalt flow. Features at the contact indicate the paleosol soil was wet when the capping flow was emplaced, that lava-sediment mixing occurred, and that both the soil and the capping lava were hydrothermally altered. The soil was hydrothermally enriched in Fe, Mn, and Si. The SWa-1 sample was collected from within the altered zone, suggesting it formed through alteration of paleosol clays by addition of Fe. Similar environments are widespread in the CRB, particularly at the plateau margins, suggesting that altered clays may occur frequently at lava-sediment contacts. Such environments are likely to occur wherever basalt flows are emplaced under warm, wet conditions promoting weathering—such as Mars >3.5 Ga before the present, when clay minerals were forming at its surface. This information has important implications for the use of clay compositions to inform clay formation environments on Mars.

Measuring and modelling water transport on Skaftafellsheiði, Iceland

Areas with thick basaltic aquifers are used for drinking water supply and irrigation purposes, such as the Columbia River Basalt group in northwest USA and the Deccan Traps in India. However, rainfall-runoff processes in these basaltic areas are poorly understood. Cooling joints can transport large amounts of water, but – due to their limited porosity – they are vulnerable for over-abstraction. On Iceland, in the small Skaftafellsheiði basaltic catchment (4 x 6 km), field data were collected in 2014 and 2015. Two small streams discharge the rain surplus. Precipitation was measured at various elevations on the ridge. Also, the discharge of the streams was measured. A groundwater flow model was constructed in order to get more insight in the physical properties of the basalt aquifer and its rainfall-runoff properties. The field experiments showed that precipitation increases linearly with surface elevation. On average, the precipitation at 800 m+msl was almost double, relative to the precipitation at 200 m+msl. Calculated ETpot was rather high, due to the 19 potential sun hours per day during the Icelandic summer. Field experiments revealed quick discharge response on rainfall events, but also rather constant base flow during dryer periods. This indicates a limited infiltration capacity, but also a considerable storage capacity in the subsequent layers. The peat layer is believed to be the dominant storage/reservoir. Peat, regolith and an organic layer formed the top layer in the GMS-Modflow groundwater model. The thick basaltic aquifer was split in a series of model layers. Best results were obtained by using a decreasing hydraulic conductivity to depth. The transient model overestimated the groundwater levels at the outlet, but managed to reproduce the wet/dry conditions in the catchment rather well. This indicates that it is possible to model complex basaltic aquifers, by taking a large Representative Elementary Volume (REV) as starting point

Using 40Ar/39Ar ages of intercalated silicic tuffs to date flood basalts: Precise ages for Steens Basalt Member of the Columbia River Basalt Group

To establish causality between flood basalt eruptions and extinction events and global environmental effects recorded by isotopic excursions in marine sediments, highly accurate and precise ages for the flood basalts are required. But flood basalts are intrinsically difficult to date. We illustrate how 40Ar/39Ar feldspar ages for silicic tuffs intercalated with and overlying sections of Steens Basalt, the earliest lavas of the Middle Miocene Columbia River Basalt Group in the northwestern United States, provide high-precision ages that, for the first time, make it possible to resolve age differences with stratigraphic position within a section of these flood lavas. The stratigraphically lowest rhyolitic tuff, a fall deposit, yielded an age of 16.592±±0.028 Ma (FCs = 28.02 Ma), and the uppermost, the alkali rhyolite ignimbrite Tuff of Oregon Canyon, is 16.468±±0.014 Ma. The argon and stratigraphic data indicate that Steens Basalt eruptions occurred from ∼16.64 to 16.43 Ma in the southern end of its distribution. We estimate that the Steens Mountain geomagnetic reversal occurred at 16.496±±0.028 Ma (±0.18 Ma total error). Our estimates of the timing for initiation of volcanism and volumetric eruptive rates do not seem to support volcanic forcing by the initial stages of Columbia River Basalt Group eruptions as an explanation for the abrupt warming and carbonate dissolution at the beginning of the Miocene Climatic Optimum.

Paleolimnology and diatom flora of the Miocene Quincy Diatomite, Washington, USA

The Quincy Diatomite, central Washington, USA, is a middle Miocene (∼15 Ma) lacustrine deposit located between flows of the Columbia River Basalt Group. Two primary localities along the western margin of the deposit are examined for stratigraphic and geographic variation. Three lithologic units are recognized in the deposit and are distinguished by distinct diatom floras and subtle lithologic differences. Diatom assemblages vary geographically along the western margin of the basin. Distinctions between these assemblages are confirmed through analysis of point count data using nonMetric Multidimensional Scaling and cluster analyses. Three stages of lake development, directly influenced by the regional geology and geography, are recognized. The earliest stage was likely deposited in a series of small-interconnected pocket lakes that were eutrophic and slightly alkaline. This lake stage was succeeded by a period of shallower water depth, and dominated by benthic species. The latest stage of the lake is interpreted as representing a deepening and expansion of the lake, based on the dominance of planktonic diatom species. Tectonic uplift of the western Frenchman Hills Anticline combined with overall subsidence of the Quincy Basin during intermediate and late stages of lake development is interpreted to be the driver for relative changes in lake bathymetry.

Identifying groundwater recharge connections in the Moscow (USA) sub-basin using isotopic tracers and a soil moisture routing model

Globally, aquifers are suffering from large abstractions resulting in groundwater level declines. These declines can be caused by excessive abstraction for drinking water, irrigation purposes or industrial use. Basaltic aquifers also face these conflicts. A large flood basalt area (1.1 × 105 km2) can be found in the Northwest of the USA. This Columbia River Basalt Group (CRBG) consists of a thick series of basalt flows of Miocene age. The two major hydrogeological units (Wanapum and Grand Ronde formations) are widely used for water abstraction. The mean decline over recent decades has been 0.6 m year−1. At present day, abstraction wells are drying up, and base flow of rivers is reduced. At the eastern part of CRBG, the Moscow sub-basin on the Idaho/Washington State border can be found. Although a thick poorly permeable clay layer exists on top of the basalt aquifer, groundwater level dynamics suggest that groundwater recharge occurs at certain locations. A set of wells and springs has been monitored bi-weekly for 9 months for δ18O and δ2H. Large isotopic fluctuations and d-excess values close to the meteoric water line in some wells are indicating that recharge occurs at the granite/basalt interface through lateral flow paths in and below the clay. A soil moisture routing (SMR) model showed that most recharge occurs on the granitic mountains. The basaltic aquifer receives recharge from these sedimentary zones around the granite/basalt interface. The identification of these types of areas is of major importance for future managed-aquifer recharge solutions to solve problems of groundwater depletion.

Anomalous density and elastic properties of basalt at high pressure: Reevaluating of the effect of melt fraction on seismic velocity in the Earth's crust and upper mantle

AbstractIndependent measurements of the volumetric and elastic properties of Columbia River basalt glass were made up to 5.5 GPa by high‐pressure X‐ray microtomography and GHz‐ultrasonic interferometry, respectively. The Columbia River basalt displays P and S wave velocity minima at 4.5 and 5 GPa, respectively, violating Birch's law. These data constrain the pressure dependence of the density and elastic moduli at high pressure, which cannot be modeled through usual equations of state nor determined by stepwise integrating the bulk sound velocity as is common practice. We propose a systematic variation in compression behavior of silicate glasses that is dependent on the degree of polymerization and arises from the flexibility of the aluminosilicate network. This behavior likely persists into the liquid state for basaltic melts resulting in weak pressure dependence for P wave velocities perhaps to depths of the transition zone. Modeling the effect of partial melt on P wave velocity reductions suggests that melt fraction determined by seismic velocity variations may be significantly overestimated in the crust and upper mantle.

Miocene global change recorded in Columbia River basalt–hosted paleosols

Paleosols preserved between flows of the Columbia River Basalt Province record hiatuses in basalt emplacement and provide detailed information about paleoclimatic and pedogenic conditions during pedogenesis. The relatively long duration of pedogenesis (104 to >106 yr) for these paleosols makes them unlikely to have been influenced by short-duration climate fluctuations and allows them to accurately reflect long-term climate trends related to global climate change. Ten paleosols hosted by the Grande Ronde and Wanapum Formations of the Columbia River Basalts were identified on the basis of pedogenic features such as horizon development, root traces, and saprolitization, and they were studied as paleoclimatic indicators. Relationships between the ages of the paleosols and their clay-mineral compositions suggest that pedogenic processes changed in the eastern Columbia River Basalt Province at ca. 15.8 Ma. Analyses of mass-balance trends and chemical alteration in a ca. 16.0 Ma paleosol indicate that it formed under warm, humid climate conditions. We suggest that the absence of similar warm, humid paleosols and the presence of 2:1 clay-rich paleosols that formed after ca. 15.8 Ma represent a cooling and drying climate change related to the termination of the middle Miocene climate optimum, a development not previously captured in paleosol studies. In addition, the well-constrained dates of the basalts provide better resolution on the timing of this termination. When combined with other middle Miocene paleoclimate estimates from the Columbia River Basalt Province, our results suggest a geographic control on mean annual precipitation in the middle Miocene Columbia River Basalt Province leading to an increasing-to-the-east precipitation gradient.

Meteorite Impact Origin of Yellowstone Hotspot

Origin of the Yellowstone hotspot & Columbia River Basalts has remained uncertain until now. Here, we present evidence of meteorite impact origin. The hotspot is shallow, only 200 km deep, invalidating a theory of mantle plume origin. The hotspot track runs from the Yellowstone National Park in NW Wyoming to the volcanic Modoc Plateau in NE California. We present evidence of apparent remnants of an impact crater existing in the Modoc, a large multi-ring structure at least 160 km diameter. Much of the complex crater has become obliterated by later Cascadia and Sierra orogenies. The crater has a tall 4,100 foot central uplift cone, locally known as Chalk Mountain, consisting of diatomaceous earth, presumably the rebound cone of a meteorite impact. This falsifies a theoretical prohibition of cosmic impact volcanism. Based on recent insights into explosive volcanism a plausible mechanism is proposed for how meteorite impacts can lead to resurgent calderas of the Yellowstone type, & of apparent LIP origin from thin crust ET impacts, invalidating theoretical constructs of mantle plumes. We mention chaotic terrains, including plutons, arising antipodal to impacts.

Dendrochronology and middle Miocene petrified oak: Modern counterparts and interpretation

This study reports the first successful statistical ‘crossdating’ among many ring width time series from petrified wood, thus providing a replicable continuous annual resolution window into tree growth and environmental influences during the middle Miocene. The petrified samples, of the genus Quercus, originated at the Stinking Water (SW) locality in Oregon, a Miocene-aged exposure associated with the Columbia River Basalts. 40AR/39AR dating on pillow basalt from the locality yielded a weighted Plateau Age of 13.79±0.09Ma placing the death of the trees at the end of the Langhian Stage of the Middle Miocene (15.97±0.05 to 13.65±0.05Ma), during the middle Miocene Climate Transition (MMCT). Ring width time series from 26 radii, 17 different trees, show significant intercorrelation. A Modified Coexistence Approach was applied to determine the likely climate range when the SW trees were growing. The modified approach included regression of site-mean ring width time series statistic values on estimated soil moisture for the site locations, using site-mean data from 126 modern Quercus sites from across the United States. Identification of highly significant linearities indicated strong relationships between ring width intercorrelation and soil moisture and ring width variability and soil moisture. Comparison of individual modern site-mean statistical values with values calculated for the SW locality suggests a mesic growing environment for the SW Quercus, with moderate temperatures. Geographic placement of modern Quercus sites with site-mean statistics similar to the SW values indicates a modern analogue in the eastern United States. Modern distributions of mesic species in the genera present at the SW locality suggest similarities with the central and southern Appalachian Mountains and the Ozark/Ouachita Mountains, indicating a mean annual temperature range of ≅10 °C to ≅15 °C and a mean annual precipitation range of ≅750 mm to ≅1200 mm when the SW Quercus were growing.