Yellowstone Plume Research Articles

Cause of Enigmatic Upper-Mantle Earthquakes in Central Wyoming

Abstract Earthquakes deeper than 60 km generally occur in subducting slabs. However, on 21 September 2013 two earthquakes (M 4.8 and 3.0) occurred at ∼71 to 75 km depths in the upper mantle beneath central Wyoming in the stable North American continent, where there is no actively subducting slab at present. The cause of the two events is still unclear. Here, we present detailed 3D P-wave isotropic and anisotropic tomography down to 750 km depth under Wyoming and adjacent areas. Our result shows that the two Wyoming events took place within a high-velocity (high-V) body at 0–160 km depths, which may be part of dense continental lithosphere. Another high-V body exists at ∼300 to 500 km depths, which may reflect a remnant of the subducted Farallon slab. A significant low-velocity (low-V) zone appears at ∼200 to 300 km depths between the two high-V bodies, and the low-V zone exhibits seismic anisotropy that VP is greater in the vertical direction than that in the horizontal direction. The low-V zone may include ascending fluids from dehydration of the subducted slab remnant, which was promoted by the nearby hot Yellowstone plume. It is highly possible that the ascending fluids induced the 2013 Wyoming upper-mantle earthquakes.

Plume‐Lithosphere Interaction and Delamination at Yellowstone and Its Implications for the Boundary of Craton Stability

AbstractDelamination of the lower lithosphere has occurred under different tectonic settings, thereby inducing strong lateral lithospheric strength heterogeneities. Here, we examine a recent case of plume‐induced lithosphere delamination associated with the Yellowstone plume. We propose that interaction between the Yellowstone plume and western North American lithosphere is what led to delamination of the lower lithosphere beneath the Columbia River Basalt (CRB) roughly ∼17 Myr ago. The excess melting that occurred when this “hole” was being filled by Yellowstone plume material was the primary trigger for the CRB excess melting event. The delaminated lower lithosphere currently lies to the northeast of the CRB; it can be clearly identified in recent seismic tomographic models. We suggest that both weak zones, for example, lithosphere‐crossing faults or suture zones, or vertical weaknesses associated with hotspot tracks, and strong zones (regions not underlain by weak mid‐lithosphere discontinuity material) can become the lateral boundaries of lithosphere delamination.

Seismic Evidence of Mid‐Mantle Water Transport Beneath the Yellowstone Region

AbstractEarth's mantle transition zone (MTZ) is a possible global water reservoir and may be responsible for long‐term (∼100 Ma) ocean‐mass regulation. Estimates of water capacities in MTZ minerals are ∼1 wt%, far greater than that of rocks of the surrounding mantle. When water‐rich material is displaced from the MTZ, partial melting occurs, generating a sharp reduction in seismic velocities detectable with seismic receiver functions (RFs). We estimated RFs for the MTZ beneath the Yellowstone region using earthquakes recorded by ∼200 stations of the Earthscope Transportable Array. We found many LVZs both above and below the MTZ, consistent with water release upon phase transformation of hydrated MTZ rock into upper‐ and lower‐mantle mineral assemblages with low water capacities. The locations of LVZs are consistent with mid‐mantle flow induced by descent of a Farallon‐slab fragment and ascent of the deeply rooted Yellowstone plume as imaged by seismic tomography.

Continental Tectonics Inferred From High‐Resolution Imaging of the Mantle Beneath the United States, Through the Combination of USArray Data Types

AbstractA comprehensive North American upper mantle seismic‐tomographic model, NA13, was inferred from a combination of several decades of seismic data from early North American seismic networks and USArray data. This data‐driven modeling inverted a combination of regional waveform fits, teleseismic S delay times, and point constraints on Moho depths. The joint inversion model combines the contrasting and overlapping resolving power of the different data sets, and demonstrates enhanced resolution over regional models created with a single geophysical data set. Resolution in the upper mantle is achieved on the scale of ∼100 km, although travel time delay studies suggest that anomalies in parts of the western United States are smaller. In NA13, velocities beneath the Yellowstone plume are low enough to require the presence of partial melt. NA13 also models a variety of smaller scale velocity variations beneath the Central and Eastern United States that reveal remnant velocity anomalies related to lithospheric variations in the upper mantle between Proterozoic units.

Yellowstone Plume Drives Neogene North American Plate Motion Change

AbstractPlate motion changes provide powerful constrains on plate tectonic forces. North America is ideal to explore these forces. We use recently published high‐temporal resolution plate reconstructions of North America, which reveal a velocity slow‐down at 17 Ma, roughly coeval with the eruption of the Yellowstone plume, together with a stratigraphic analysis of hiatus surfaces across the continent, which provides proxy information for paleotopography. Using a simple Couette/Poiseuille flow models we estimate asthenosphere flow beneath North America and its impact on Neogene plate motion. We find that North America's Neogene plate motion change can be explained by Poiseuille flow in the asthenosphere generated upon the arrival of the Yellowstone plume and that the flow length‐scale matches the extent of hiatus surfaces. While plume driven upper mantle flow constitutes a geodynamically viable model to explain North America's Neogene plate motion change it provides an intrinsic link between vertical and horizontal plate motions.

Hydrothermal 15N15N abundances constrain the origins of mantle nitrogen.

Nitrogen is the main constituent of the Earth's atmosphere, but its provenance in the Earth's mantle remains uncertain. The relative contribution of primordial nitrogen inherited during theEarth's accretion versus that subducted from the Earth's surface is unclear1-6. Here we show that the mantle may have retained remnants of such primordial nitrogen. We use the rare 15N15N isotopologue of N2 as a new tracer of air contamination in volcanic gas effusions. By constraining air contamination in gases from Iceland, Eifel (Germany) and Yellowstone (USA), we derive estimates of mantle δ15N (the fractional difference in 15N/14N from air), N2/36Ar and N2/3He. Our results show that negative δ15N values observed in gases, previously regarded as indicating a mantle origin for nitrogen7-10, in fact represent dominantly air-derived N2 that experienced 15N/14N fractionation in hydrothermal systems. Using two-component mixing models to correct for this effect, the 15N15N data allow extrapolations that characterize mantle endmember δ15N, N2/36Ar and N2/3He values. We show that the Eifel region has slightly increased δ15N and N2/36Ar values relative to estimates for the convective mantle provided by mid-ocean-ridge basalts11, consistent with subducted nitrogen being added to the mantle source. In contrast, we find that whereas the Yellowstone plume has δ15N values substantially greater than that of the convective mantle, resembling surface components12-15, its N2/36Ar and N2/3He ratios are indistinguishable from those of the convective mantle. This observation raises the possibility that the plume hosts a primordial component. We provide a test of the subduction hypothesis with a two-box model, describing the evolution of mantle and surface nitrogen through geological time. We show that the effect of subduction on the deep nitrogen cycle may be less important than has been suggested by previous investigations. We propose instead that high mid-ocean-ridge basalt and plume δ15N values may both be dominantly primordial features.

Yellowstone Plume Conduit Tilt Caused by Large‐Scale Mantle Flow

AbstractMantle plumes are hot upwellings of rock thought to originate at the core‐mantle boundary. As they rise through the mantle, their conduits may become tilted due to lateral large‐scale mantle flow. Recent tomographic images have revealed a strongly tilted plume conduit starting at the core‐mantle boundary beneath northern Baja California rising toward the Yellowstone hot spot from the southwest. Here we perform numerical computations of plumes deflected in large‐scale mantle flow with the aim of finding if realistic model parameter ranges exist that yield a good fit with the tomographically observed conduit. We restrict ourselves to models that yield reasonable results for plume conduit tilt and hot spot motion globally. These models require high viscosity ≈1023 Pa s at some lower mantle depths. For a plume head reaching the surface 17 Ma, corresponding to the start of the Columbia River Basalts, our models require rise times ≈80 Myr or longer to match the tilt of the conduit observed by tomography. We used several tomography models to determine mantle density with almost all models predicting southwestward flow in the lowermost mantle beneath the western United States. Exact details of the shape of the predicted conduit's southwesterly tilt vary, depending on the density and viscosity structures we used. In many cases we find comparatively strong tilts in two depth ranges, in the upper and lower portions of the mantle, which is also a characteristic of the tomographically observed conduit. We expect that future models may help to constrain large‐scale flow by matching these corresponding depth ranges.

Plume-modified mantle flow in the northern Basin and Range and southern Cascadia back-arc region since ca. 12 Ma

AbstractBimodal volcanism and rhyolite migration along the High Lava Plains in central Oregon (United States) lie above a broader feature defined by low seismic velocity in the upper mantle that emanates from the Yellowstone hotspot (northwest United States) and extends westward across the northern Basin and Range. It was emplaced by a westward current, driven in part by rapid buoyancy-driven flow across the east-west cratonic boundary of North America. Geothermometry studies and geochemical considerations suggest that the low-velocity feature may be composed of moderately hot, low-density mantle derived from the Yellowstone plume but diluted by thermomechanical erosion and entrainment of colder mantle lithosphere. Finger-like conduits of plume-modified mantle beneath Quaternary eruption sites delineate flow-line channels that have developed across the broader mantle structure since 2 Ma. These channels have allowed low-density mantle to accumulate against the Cascades arc, thus providing a heated mantle source for mafic magmatism in the Newberry (Oregon) and Medicine Lake (California) volcanic fields.

Spatially Variable Increase in Rock Uplift in the Northern U.S. Cordillera Recorded in the Distribution of River Knickpoints and Incision Depths

AbstractLandscape evolution is driven by factors like tectonics and climate, and unraveling such factors can reveal the history recorded in landscape morphology. The northern U.S. Cordillera features many potential drivers, such as the Yellowstone plume, the extrusion of a large igneous province, and the drainage of large lakes. Among this complex geologic history, the drivers of transient incision in the Clearwater and Salmon watersheds of central Idaho are not well understood. To constrain the pattern of regional incision, we analyze the morphologies of 80 individual tributaries underlain by single lithologies. From north to south across our study area, knickpoint elevations increase from about 800 to 2,200 m, and incision depths increase from about 300 to 1,200 m. We use both numerical and analytical models to demonstrate that such a gradient could represent spatial variations in rock uplift. These findings suggest that transience is driven by a spatially variable increase in rock uplift that has disrupted a low‐relief paleolandscape, and the high steepness values of main drainages suggest that high rock‐uplift rates are still maintained to the present. Changes in rock uplift may be related to interactions between the Yellowstone plume and the lithosphere, although base level fall from the drainage of the Lake Idaho down the proto‐Snake River may be superimposed over these patterns in rock uplift. We show that careful, quantitative analyses of river profiles in geologically complex regions can differentiate between the influences of rock uplift and far‐field base level changes.

Thermomechanical Modeling of the Formation of a Multilevel, Crustal‐Scale Magmatic System by the Yellowstone Plume

AbstractGeophysical imaging of the Yellowstone supervolcano shows a broad zone of partial melt interrupted by an amagmatic gap at depths of 15–20 km. We reproduce this structure through a series of regional‐scale magmatic‐thermomechanical forward models which assume that magmatic dikes stall at rheologic discontinuities in the crust. We find that basaltic magmas accumulate at the Moho and at the brittle‐ductile transition, which naturally forms at depths of 5–10 km. This leads to the development of a 10‐ to 15‐km thick midcrustal sill complex with a top at a depth of approximately 10 km, consistent with geophysical observations of the pre‐Yellowstone hot spot track. We show a linear relationship between melting rates in the mantle and rhyolite eruption rates along the hot spot track. Finally, melt production rates from our models suggest that the Yellowstone plume is ~175°C hotter than the surrounding mantle and that the thickness of the overlying lithosphere is ~80 km.

Western US volcanism due to intruding oceanic mantle driven by ancient Farallon slabs

The origin of late Cenozoic intraplate volcanism over the western United States is debated. One important reason is the lack of a clear understanding of the mantle dynamics during this volcanic history. Here we reconstruct the mantle thermal states beneath North America since 20 million years ago using a hybrid inverse geodynamic model with data assimilation. The model simultaneously satisfies the past subduction kinematics, present mantle tomographic image and the volcanic history. We find that volcanism in both the Yellowstone volcanic province and the Basin and Range province corresponds to a similar eastward-intruding mantle derived from beneath the Pacific Ocean and driven mostly by the sinking Farallon slab below the central-eastern United States. The hot mantle that forms the Columbia River flood basalt and subsequent Yellowstone–Newberry hotspot tracks first enters the western United States through tears within the Juan de Fuca slab. Subsequent coexistence of the westward asthenospheric flow above the retreating Juan de Fuca slab and eastward-propagating mantle beyond the back-arc region reproduces the bifurcating hotspot chains. A similar but weaker heat source intrudes below the Basin and Range around the southern edge of the slab, and can explain the diffuse basaltic volcanism in this region. According to our models, the putative Yellowstone plume contributes little to the formation of the Yellowstone volcanic province. Volcanism in the western US may result from warm oceanic mantle beneath the Pacific Ocean being drawn eastwards by mantle flow induced by the sinking of Farallon slabs, according to numerical model simulations.

The Role of the Ancestral Yellowstone Plume in the Tectonic Evolution of the Western United States

The Role of the Ancestral Yellowstone Plume in the Tectonic Evolution of the Western United States

Insights for the melt migration, the volcanic activity and the ultrafast lithosphere delamination related to the Yellowstone plume (Western USA)

The Yellowstone–East Snake River Plain hotspot track has been intensely studied since several decades and is widely considered to result from the interaction of a mantle plume with the North American plate. An integrated conclusive geodynamic interpretation of this extensive data set is however presently still lacking, and our knowledge of the dynamical processes beneath Yellowstone is patchy. It has been argued that the Yellowstone plume has delaminated the lower part of the thick Wyoming cratonic lithosphere. We derive an original dynamic model to quantify delamination processes related to mantle plume–lithosphere interactions. We show that fast (∼300 ka) lithospheric delamination is consistent with the observed timing of formation of successive volcanic centres along the Yellowstone hotspot track and requires (i) a tensile stress regime within the whole lithosphere exceeding its failure threshold, (ii) a purely plastic rheology in the lithosphere when stresses reach this yield limit, (iii) a dense lower part of the 200 km thick Wyoming lithosphere and (iv) a decoupling melt horizon inside the median part of the lithosphere. We demonstrate that all these conditions are verified and that ∼150 km large and ∼100 km thick lithospheric blocks delaminate within 300 ka when the Yellowstone plume ponded below the 200 km thick Wyoming cratonic lithosphere. Furthermore, we take advantage of the available extensive regional geophysical and geological observation data sets to design a numerical 3-D upper-mantle convective model. We propose a map of the ascending convective sheets contouring the Yellowstone plume. The model further evidences the development of a counter-flow within the lower part of the lithosphere centred just above the Yellowstone mantle plume axis. This counter-flow controls the local lithospheric stress field, and as a result the trajectories of feeder dykes linking the partial melting source within the core of the mantle plume with the crust by crosscutting the lithospheric mantle. This counter-flow further explains the 50 km NE shift observed between the mantle plume axis and the present-day Yellowstone Caldera as well as the peculiar shaped crustal magma chambers.

Yellowstone plume trigger for Basin and Range extension, and coeval emplacement of the Nevada–Columbia Basin magmatic belt

Widespread extension began across the northern and central Basin and Range Province at 17–16 Ma, contemporaneous with magmatism along the Nevada–Columbia Basin magmatic belt, a linear zone of dikes and volcanic centers that extends for >1000 km, from southern Nevada to the Columbia Basin of eastern Washington. This belt was generated above an elongated sublithospheric melt zone associated with arrival of the Yellowstone mantle plume, with a north-south tabular shape attributed to plume ascent through a propagating fracture in the Juan de Fuca slab. Dike orientation along the magmatic belt suggests an extension direction of 245°–250°, but this trend lies oblique to the regional extension direction of 280°–300° during coeval and younger Basin and Range faulting, an ∼45° difference. Field relationships suggest that this magmatic trend was not controlled by regional stress in the upper crust, but rather by magma overpressure from below and forceful dike injection with an orientation inherited from a deeper process in the sublithospheric mantle. The southern half of the elongated zone of mantle upwelling was emplaced beneath a cratonic lithosphere with an elevated surface derived from Late Cretaceous to mid-Tertiary crustal thickening. This high Nevadaplano was primed for collapse with high gravitational potential energy under the influence of regional stress, partly derived from boundary forces due to Pacific–North American plate interaction. Plume arrival at 17–16 Ma resulted in advective thermal weakening of the lithosphere, mantle traction, delamination, and added buoyancy to the northern and central Basin and Range. It was not the sole cause of Basin and Range extension, but rather the catalyst for extension of the Nevadaplano, which was already on the verge of regional collapse.

The earliest low and high δ18O caldera-forming eruptions of the Yellowstone plume: implications for the 30–40 Ma Oregon calderas and speculations on plume-triggered delaminations

We present new isotopic and trace element data for four eruptive centers in Oregon: Wildcat Mountain (40 Ma), Crooked River (32–28 Ma), Tower Mountain (32 Ma), and Mohawk River (32 Ma). The first three calderas are located too far east to be sourced through renewed subduction of the Farallon slab following accretion of the Yellowstone-produced Siletzia terrane at ~50 Ma. Basalts of the three eastern eruptive centers yield high Nb/Yb and Th/Yb ratios, indicating an enriched sublithospheric mantle source, while Mohawk River yields trace element and isotopic (δ18O and εHf) values that correlate with its location above a subduction zone. The voluminous rhyolitic tuffs and lavas of Crooked River (41 x 27 km) have δ18Ozircon values that include seven low δ18Ozircon units (1.8–4.5 ‰), one high δ18Ozircon unit (7.4–8.8 ‰), and two units with heterogeneous zircons (2.0–9.0 ‰), similar to younger Yellowstone-Snake River Plain rhyolites. In order to produce these low δ18O values, a large heat source, widespread hydrothermal circulation, and repeated remelting are all required. In contrast, Wildcat Mountain and Tower Mountain rocks yield high δ18Ozircon values (6.4–7.9 ‰) and normal to low εHfi values (5.2–12.6), indicating crustal melting of high-δ18O supracrustal rocks. We propose that these calderas were produced by the first appearance of the Yellowstone plume east of the Cascadia subduction zone, which is supported by plate reconstructions that put the Yellowstone plume under Crooked River at 32–28 Ma. Given the eastern location of these calderas along the suture of the accreted Siletzia terrane and North America, we suggest that the Yellowstone hotspot is directly responsible for magmatism at Crooked River, and for plume-assisted delamination of portions of the edge of the Blue Mountains that produced the Tower Mountain magmas, while the older Wildcat Mountain magmas are related to suture zone instabilities that were created following accretion of the Siletzia terrane.

Bifurcation of the Yellowstone plume driven by subduction-induced mantle flow

In the northwestern United States, two neighbouring volcanic chains—the Snake River Plain and High Lava Plains—decrease in age in opposing directions. Laboratory experiments show that diverging volcanic chains can form where vigorous mantle circulation beneath a subduction zone causes an upwelling mantle plume to split into two.

Upper mantle seismic structure beneath the Pacific Northwest: A plume-triggered delamination origin for the Columbia River flood basalt eruptions

We invert teleseismic P and S body waves constrained by an ambient-noise surface wave model and Moho depth inferred from receiver function analysis (Gao et al., 2011) to image mantle structures continuously from the surface to the base of the upper mantle. The major structures coincide with prominent geological features. We focus on a NE-Oregon structure, termed here the Wallowa anomaly, which coincides with the source area for the ∼16Ma Columbia River flood basalt eruptions and a circular area of topographic relief created during and after these eruptions. Resolution tests indicate that the curtain-like structure previously interpreted as Farallon lithosphere connects with the Wallowa anomaly above 150km along the northeast margin of the Wallowa anomaly. This connection, along with the pre-flood basalt magmatic and tectonic history of the Pacific Northwest, lead us to conclude that arrival of the Yellowstone plume to south-central Oregon initiated delamination of remnant Farallon lithosphere from the base of NE Oregon, exposing ocean crust to Yellowstone asthenosphere. This hypothesis accounts for the propagation of flood basalt volcanism far north of the Yellowstone hotspot track, and for the high-silica composition of most of the flood basalt magmas.

REMOBILIZED GEOCHEMICAL ANOMALIES RELATED TO DEEP GOLD ZONES, CARLIN TREND, NEVADA

A near-vertical fracture set in Miocene Carlin Formation tuffaceous sediments occurs approximately 800 m above a deep Carlin-type gold ore zone of Eocene age at the Ren property on the northern Carlin trend, Nevada. The fractures, 0.2 to 2 cm wide, are filled with brown montmorillonite clays and contain a distinctive Carlin-type geochemical assemblage including Au, As, Sb, Hg, Tl, and S. These young, in situ geochemical anomalies are thought to originate from a paleogeothermal event that may have been seismically triggered by Yellowstone plume bulge-relaxation dynamics. The passage of the plume immediately north of the Carlin trend would have provided increased heat flow, which, coupled with crustal extension, may have allowed metal-charged geothermal vapor to be released from depth. The hydrothermal remobilization filled dilational fractures in surficial units with vapor-phase alteration clays containing the geochemical signature of the deep gold ore zone. Such fractures, if found in other areas of northern Nevada’s great mineral trends, may provide important exploration guidance for deep ore systems.

Mantle dynamics beneath the Pacific Northwest and the generation of voluminous back‐arc volcanism

The Pacific Northwest (PNW) has a complex tectonic history and over the past ∼17 Ma has played host to several major episodes of intraplate volcanism. These events include the Steens/Columbia River flood basalts (CRB) and the striking spatiotemporal trends of the Yellowstone/Snake River Plain (Y/SRP) and High Lava Plains (HLP) regions. Several different models have been proposed to explain these features, which variously invoke the putative Yellowstone plume, rollback and steepening of the Cascadia slab, extensional processes in the lithosphere, or a combination of these. Here we integrate seismologic, geodynamic, geochemical, and petrologic results from the multidisciplinary HLP project and associated analyses of EarthScope USArray seismic data to propose a conceptual model for post‐20 Ma mantle dynamics beneath the PNW and the relationships between mantle flow and surface tectonomagmatic activity. This model invokes rollback subduction as the main driver for mantle flow beneath the PNW beginning at ∼20 Ma. A major pulse of upwelling due to slab rollback and upper plate extension and consequent melting produced the Steens/CRB volcanism, and continuing trench migration enabled mantle upwelling and hot, shallow melting beneath the HLP. An additional buoyant mantle upwelling is required to explain the Y/SRP volcanism, but subduction‐related processes may well have played a primary role in controlling its timing and location, and this upwelling likely continues today in some form. This conceptual model makes predictions that are broadly consistent with seismic observations, geodynamic modeling experiments, and petrologic and geochemical constraints.

Initial impingement of the Yellowstone plume located by widespread silicic volcanism contemporaneous with Columbia River flood basalts

During the main phase of Steens and Columbia River (United States) flood basalt eruptions between 16.7 and 15.0 Ma, ∼3900 km 3 of silicic magma erupted from centers dispersed across ∼25,000 km 2 . The largest and oldest silicic centers, High Rock, McDermitt, and Lake Owyhee caldera complexes, lie along a narrow NNE trend at the transition between the craton and accreted oceanic crust, suggesting that silicic magma generation was greatest where mafic magma intruded more-felsic crust. Less voluminous and younger silicic centers track the spread of mafic dikes to the north. The High Rock caldera complex forms the western end of the Snake River Plain–Yellowstone trend of eastward-younging silicic centers. We attribute a regional lull in volcanism between ca. 23 and 7 Ma to lifting of the Juan de Fuca slab by a mantle plume beginning at ca. 25 Ma, and the distribution of main-stage flood basalts and coeval rhyolites to breakthrough of plume material at ca. 17 Ma to form a smaller plume head centered beneath Steens Mountain.