Crustal Structure and Tectono-magmatic Processes of the Yellowstone-Snake River Plain Volcanic System from Gravity-density and Lithospheric Strength Modeling with Seismic and Heat Flow Constraints PDF Download
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Author: Katrina Robb Settles
Publisher:
ISBN:
Category : Plate tectonics
Languages : en
Pages : 468
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Author: Katrina Robb Settles
Publisher:
ISBN:
Category : Plate tectonics
Languages : en
Pages : 468
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Author: Robert Baer Smith
Publisher:
ISBN:
Category : Calderas
Languages : en
Pages : 122
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Direct evidence for a plume-plate interaction as the mechanism responsible for the Yellowstone-Snake River Plain (YSRP), 16 Ma volcanic system is observation of a linear age-progression of silicic volcanic centers along the Snake River Plain 800 km to the Yellowstone caldera-- the track of the Yellowston hotspot. Caldera-forming rhyolitic volcanism, active crustal deformation, extremely high heat flow (30 times the continental average), and intensive earthquake activity in Yellowstone National Park mark the surface manifestations of the hotspot. Anomalously low, P-wave velocities in the upper-crust of the Yellowstone caldera are interpreted as solidified but still hot granitic rocks, partial melts, hydrothermal fluids and sediments. Unprecedented deformation of the Yellowstone caldera of up to 1 m of uplift from 1923 to 1984, followed by subsidence of as much as ~12 cm from 1985 to 1991, clearly reflects a giant caldera unrest. The regional signature of the Yellowstone hotspot is highlighted by an anomalous, 600 m high, topographic bulge centered on the caldera and that extends across a ~600 km-wide region. We suggest that this feature reflecs long-wavelength tumescence of the hotspot. Yellowstone is also the center of a +20 m geoid anomaly, the largest in North America, and extends ~500 km laterally from the caldera, similar in width to the geoid anomalies of many oceanic hotspots and swells. The 16 Ma trace of the Yellowstone hotspot, the seismically quiescent Snake River Plain, is surrounded by "bow-wave" or parabolic shaped regions of earthquakes and high topography. Whereas systematic topographic decay along the Snake River Plain, totaling 1,300 m, fits a model of lithospheric cooling and subsidence which is consistent with passage of the North American plate across a mantle heat source. We note that the rate of 4.5 cm/yr silicic, volcanic age progression of the YSRP includes a component of southwest motion of the North American plate, modeled at ~2.5 cm/yr, and a component of concomitant crustal extension estimated to be 1 to 2 cm/yr. The USRP also exhibits anomalous crustal structure which we believe is inherited from magmatic and thermal processes associated which the Yellowstone hotspot. This includes a thin, 2-5 km-thick surface layer compses of basalts and rhyolites and an unusually high-velocity, 6.5 km/s, mid-crustal mafic layer that we suggest reflects extinct "Yellowstone" magma systems that have replaced much of the normal granite upper-crust. Direct evidence for a mantle connection for the YSRP system is from anomalously low, P-wave velocities which extend from the crust to depths of ~200km. These properties and the kinematics of teh YSRP are consistent with an analytic model for plume-plate interaction that produces a "bow-wave" or parabolic patter of upper-mantle flow southwesterly from the hotspot, similar to the systematic patterns of regional topography and seismicity. Our unified model for the origin of the YSRP is consistent with the geologic evidence where basaltic magmas ascend from a mantle plume to interact with a silicic-rich continental crust producing partial melts of rhyolite composition and the characteristic caldera-forming volcanism of Yellowstone. Cooling and contraction of the lithosphere follows the passage of the plate over the hotspot with continuing episodic eruptions of mantle-derived basalts along the SRP.
Author: William Prescott Leeman
Publisher:
ISBN:
Category : Calderas
Languages : en
Pages : 11
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Basaltic magmatism associated with the Yellowstone hotspot has been widely attributed to upwelling of a mantle plume, yet the temporal and spatial distribution of these magmas and their compositional characteristics are distinctive from oceanic hotspot magmatism. Fundamental questions concern the influence of continental cratonic lithosphere in producing the differences, and the extent to which upper plate processes contribute to magma production. To better understand scenarios of melt generation, P?T conditions are estimated for segregation of primitive Snake River Plain (SRP) basalts from the mantle. Combined with analysis of trace element and seismic constraints, we conclude from this that (1) melt production was concentrated at depths between roughly 70?100 km, (2) mantle temperature was only slightly higher than ambient conditions with a maximum potential temperature of 1450 °C, and (3) the mantle source was relatively fertile (Mg#b90). These results suggest that the seismically imaged plume below Yellowstone is significantly cooler than upwellings beneath Hawaii, Iceland and many other oceanic ?hotspots?. Our findings, in combination with other geochemical and geodynamic considerations, are permissive of magma generation within the ancient lithospheric mantle keel associated with the Wyoming craton. Plume contributions, while not excluded, involve physical and geochemical implications that suggest they are subordinate.
Author: Xiaohua Peng
Publisher:
ISBN:
Category : Snake River Plain (Idaho and Or.)
Languages : en
Pages : 16
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Teleseismic receiver functions are used to estimate the crustal structure beneath a 36-station, 500-km-long, NW oriented linear array centered on the eastern Snake River Plain and crossing the Yellowstone hotspot swell 250 km SW of Yellowstone. Structure derived previously for this region from wide-angle reflection data is used as an initial model, and this structure explains most features observed in our receiver functions. Based on a combination of forward and inverse modeling, our data require several modifications to the initial structure: (1) Moho depth is ~42 km beneath most of the Snake River Plain, shallows to ~37 km to either side, and thickens abruptly to ~47 km beneath SW Wyoming; (2) a midcrustal layer interpreted previously as a ~9-km-thick gabbroic sill is flat topped across the entire ~90 km width of the Snake River Plain; and (3) a low-velocity layer is found beneath and southeast of the Snake River Plain, which probably is partially molten lower-most crust. Using the seismic structure of the crust to estimate the crustal load upon the mantle, and assuming local isostasy, we calculate that mantle beneath the Yellowstone swell is approximately uniformly as buoyant as 12-million-year-old ocean mantle, and more buoyant than the adjacent Wyoming mantle by an amount equivalent of ~1.5 km of elevation. The transition between these regions of greatly different mantle occurs across a major Paleozoic boundary that now separates the Basin and Range from the Rocky Mountains.
Author: Mattia Pistone
Publisher: Frontiers Media SA
ISBN: 2889637778
Category :
Languages : en
Pages : 207
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Author: Bill Bonnichsen
Publisher: Idaho Geological Survey
ISBN:
Category : Geology, Structural
Languages : en
Pages : 508
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Author: Jian Wang
Publisher:
ISBN:
Category : Magmatism
Languages : en
Pages : 14
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The western North American lithosphere experienced extensive magmatism and large-scale crustal deformation due to the interactions between the Farallon and North American plates. To further understand such subduction-related dynamic processes, we characterize crustal structure, magmatism and lithospheric thermal state of western North America based on various data processing and interpretation of gravimetric, magnetic and surface heat flow data. A fractal exponent of 2.5 for the 3D magnetization model is used in the Curie-point depth inversion. Curie depths are mostly small to the north of the Yellowstone-Snake River Plain hotspot track, including the Steens Mountain and McDermitt caldera that are the incipient eruption locations of the Columbia River Basalts and Yellowstone hotspot track. To the south of the Yellowstone hotspot track, larger Curie depths are found in the Great Basin. The distinct Curie depths across the Yellowstone-Snake River Plain hotspot track can be attributed to subduction-related magmatism induced by edge flow around fractured slabs. Curie depths confirm that the Great Valley ophiolite is underlain by the Sierra Nevada batholith, which can extend further west to the California Coast Range. The Curie depths, thermal lithospheric thickness and surface heat flow together define the western edge of the North American craton near the Roberts Mountains Thrust (RMT). To the east of the RMT, large Curie depths, large thermal lithospheric thickness, and low thermal gradient are found. From the differences between Curie-point and Moho depth, we argue that the uppermost mantle in the oceanic region is serpentinized. The low temperature gradients beneath the eastern Great Basin, Montana and Wyoming permit magnetic uppermost mantle, either by serpentinization/metasomatism or in-situ magnetization, which can contribute to long-wavelength and low-amplitude magnetic anomalies and thereby large Curie-point depths.
Author: Mark Hill Anders
Publisher:
ISBN:
Category : Lava flows
Languages : en
Pages :
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Currently, there is a parabolic-shaped pattern of seismicity and latest Quaternary faulting which centers on the axis of the eastern Snake River Plain (SRP) and has its apex at the Yellowstone Plateau. The pattern of activity surrounds a region of aseismicity that includes the eastern SRP. Geologic evidence suggests that this pattern has migrated in tandem with rhyolitic volcanism induced by the Yellowstone hotspot during its 16 m.y. trek across western North America. Similarly there is a migration in the onset of basaltic lava flows and the emplacement of up to 12 km of midcrustal mafic intrusions that follows the track of rhyolitic volcanism. These observations suggest that the intrusion of magmas has a significant influence on the pattern of seismicity and faulting. We present a one-dimensional, finite-difference, thermomechanical model that accounts for the observed pattern of increased faulting followed by fault quiescence within the circum-eastern SRP. In this model, mafic magmas are intruded into a lithosphere that is already extending. The intrusions heat the surrounding rocks resulting in locally increased strain rates. As the intruded magmas solidify, the length of time required to return strain rates to their pre-intrusion level is then determined. The model assumes constant horizontal tectonic forces and maps strain rate as a function of yield strength and time since intrusion. We vary model parameters such as crustal thickness, initial geothermal gradient, and amount of magma intruded, in order to assess how they affect turnaround time for strain rates. The amount and timing of intruded material allowed by the model are constrained by seismic refraction data as well as by regional geochronologic and petrologic studies. We assume intruded rock rheology to be a Maryland diabase; mantle rheology we base on dry olivine; we represent the crust by both dry granite and dry anorthosite rheologies. Our results suggest that 2 to 3 m.y. appears to be a reasonable length of time for strain rates to return to levels present before a midcrustal mafic intrusion equivalent in magnitude to the Yellowstone intrusion. This corresponds closely to the length of time between the onset of along-axis accelerated faulting and subsequent fault quiescence, assuming a hotspot velocity of 3.5 to 4.0 cm/yr relative to the North American Plate.
Author: V. C. Manea
Publisher:
ISBN:
Category : Calderas
Languages : en
Pages : 18
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Although commonly attributed to a mantle plume, time-transgressive magmatism of the Snake River Plain?Yellowstone (SRPY) province differs in important ways from that associated with typical oceanic hotspots. A fundamental question concerns the relative contributions of lithosphere vs. upwelling sub-lithospheric mantle to formation of SRPY basaltic magmas. Specifically, association of this province with initially thick and cold Archean lithosphere (Wyoming craton) poses a problem in that this lid will hinder and possibly prevent melting of rising plume material. Assuming an anhydrous peridotite mantle, melting can only occur if (1) the lid can be substantially thinned over geologically reasonable time and/or (2) the upwelling material is exceptionally warm, or (3) the lid was suitably thin to begin with. Petrologic modeling indicates that SRPY primitive basalts last segregated from mantle at conditions (b1500 °C and ~100 km depth; Leeman, W.P., Schutt, D.L., Hughes, S.S., 2009. Thermal structure beneath the Snake River Plain: implications for the Yellowstone hotspot. J. Volcanol. Geotherm. Res.) only slightly warmer than MORB-source mantle and significantly cooler than sources of many oceanic hotspot magmas. In this study, geodynamic models were developed to evaluate lithospheric thinning processes. The motivation for the modeling is the observation that if the lithosphere is initially more than 200 km thick ? typical of many cratons ? then thinning by at least a factor of two is required to allow decompression melting of an ascending plume, assuming low volatile content and high excess temperature (potential temperature N1500 °C). Fully dynamic models were applied to investigate the extent and rate of lithosphere thinning assuming an initial structure representative of the Wyoming craton. We find that thermal erosion by plume impingement alone appears incapable of providing the required lithospheric thinning. Alternative models (e.g., low-angle Laramide subduction, lithospheric delamination) also conflict with geochemical evidence that SRPY basalts contain a dominant contribution of old, isotopically evolved mantle material ? presumably derived from subcontinental lithospheric mantle (SCLM). We conclude that SCLM is likely to be preserved, that the thick SCLM lid prevents substantial melting of rising plume material (tomographically imaged), and that SRPY basalts are predominantly derived by melting of lithospheric mantle.
Author: Tanya Marie Blacic
Publisher:
ISBN:
Category :
Languages : en
Pages : 352
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