WorldWideScience

Sample records for rapid magma ascent

  1. Failed magmatic eruptions: Late-stage cessation of magma ascent

    Science.gov (United States)

    Moran, S.C.; Newhall, C.; Roman, D.C.

    2011-01-01

    When a volcano becomes restless, a primary question is whether the unrest will lead to an eruption. Here we recognize four possible outcomes of a magmatic intrusion: "deep intrusion", "shallow intrusion", "sluggish/viscous magmatic eruption", and "rapid, often explosive magmatic eruption". We define "failed eruptions" as instances in which magma reaches but does not pass the "shallow intrusion" stage, i. e., when magma gets close to, but does not reach, the surface. Competing factors act to promote or hinder the eventual eruption of a magma intrusion. Fresh intrusion from depth, high magma gas content, rapid ascent rates that leave little time for enroute degassing, opening of pathways, and sudden decompression near the surface all act to promote eruption, whereas decreased magma supply from depth, slow ascent, significant enroute degassing and associated increases in viscosity, and impingement on structural barriers all act to hinder eruption. All of these factors interact in complex ways with variable results, but often cause magma to stall at some depth before reaching the surface. Although certain precursory phenomena, such as rapidly escalating seismic swarms or rates of degassing or deformation, are good indicators that an eruption is likely, such phenomena have also been observed in association with intrusions that have ultimately failed to erupt. A perpetual difficulty with quantifying the probability of eruption is a lack of data, particularly on instances of failed eruptions. This difficulty is being addressed in part through the WOVOdat database. Papers in this volume will be an additional resource for scientists grappling with the issue of whether or not an episode of unrest will lead to a magmatic eruption.

  2. Magma ascent pathways associated with large mountains on Io

    Science.gov (United States)

    McGovern, P. J.; Kirchoff, M. R.; White, O. L.; Schenk, P.

    2013-12-01

    While Jupiter's moon Io is the most volcanically active body in the solar system, the largest mountains seen on Io are created by tectonic forces rather than volcanic construction. Pervasive compression, brought about by subsidence induced by sustained volcanic resurfacing and aided by thermal stress, creates the mountains, but at the same time inhibits magma ascent in vertical conduits (dikes). We superpose stress solutions for subsidence and thermal stress (from the 'crustal conveyor belt' resurfacing) in Io's lithosphere with stresses from Io mountain-sized loads (in a shallow spherical shell solution) in order to evaluate magma ascent pathways. We use stress orientation (least compressive stress horizontal) and stress gradient (compression decreasing upwards) criteria to identify ascent pathways through the lithosphere. For nominal 'conveyor belt' stress states, the ascent criteria are satisfied only in a narrow (5 km or so), roughly mid-lithosphere band. Superposed stresses from loading of a 150-km wide mountain (comparable to Boösaule Mons) on a lithosphere with thickness Te = 50 km results in a thickening of the ascent-favorable (AF) zone beneath the center of the edifice, with a total thickness of 38 km for an 18 km tall (post-flexure) edifice. Most of the thickening is upward, although some is downward. Widening the edifice to 200 km produces a 'U-shaped' AF zone, thin and depressed at r = 0 but intersecting the surface at distances of about 20 to 40 km from the center. Increasing edifice width increases the radial distance at which the AF zone intersects the surface. Thinner lithospheres create generally thinner AF zones, and U-shaped AF zones for narrower edifices. There are several configurations for which viable ascent paths transit nearly the entire lithosphere, arriving at the base of the mountain, where magma can be transported through thrust faults or perhaps thermally erode flank sections, the latter consistent with observations of paterae in

  3. Predicting changes in volcanic activity through modelling magma ascent rate.

    Science.gov (United States)

    Thomas, Mark; Neuberg, Jurgen

    2013-04-01

    It is a simple fact that changes in volcanic activity happen and in retrospect they are easy to spot, the dissimilar eruption dynamics between an effusive and explosive event are not hard to miss. However to be able to predict such changes is a much more complicated process. To cause altering styles of activity we know that some part or combination of parts within the system must vary with time, as if there is no physical change within the system, why would the change in eruptive activity occur? What is unknown is which parts or how big a change is needed. We present the results of a suite of conduit flow models that aim to answer these questions by assessing the influence of individual model parameters such as the dissolved water content or magma temperature. By altering these variables in a systematic manner we measure the effect of the changes by observing the modelled ascent rate. We use the ascent rate as we believe it is a very important indicator that can control the style of eruptive activity. In particular, we found that the sensitivity of the ascent rate to small changes in model parameters surprising. Linking these changes to observable monitoring data in a way that these data could be used as a predictive tool is the ultimate goal of this work. We will show that changes in ascent rate can be estimated by a particular type of seismicity. Low frequency seismicity, thought to be caused by the brittle failure of melt is often linked with the movement of magma within a conduit. We show that acceleration in the rate of low frequency seismicity can correspond to an increase in the rate of magma movement and be used as an indicator for potential changes in eruptive activity.

  4. Role for syn-eruptive plagioclase disequilibrium crystallisation in basaltic magma ascent dynamics

    Science.gov (United States)

    La Spina, Giuseppe; Burton, Mike; de'Michieli Vitturi, Mattia; Arzilli, Fabio

    2017-04-01

    Magma ascent dynamics in volcanic conduits play a key role in determining the eruptive style of a volcano. The lack of direct observations inside the conduit means that numerical conduit models, constrained with observational data, provide invaluable tools for quantitative insights into complex magma ascent dynamics. The highly nonlinear, interdependent processes involved in magma ascent dynamics require several simplifications when modelling their ascent. For example, timescales of magma ascent in conduit models are typically assumed to be much longer than crystallisation and gas exsolution for basaltic eruptions. However, it is now recognized that basaltic magmas may rise fast enough for disequilibrium processes to play a key role on the ascent dynamics. The quantification of the characteristic times for crystallisation and exsolution processes are fundamental to our understanding of such disequilibria and ascent dynamics. Using observations from Mount Etna's 2001 eruption and a magma ascent model we are able to constrain timescales for crystallisation and exsolution processes. Our results show that plagioclase reaches equilibrium in 1-2 h, whereas ascent times were 1 h. Furthermore, we have related the amount of plagioclase in erupted products with the ascent dynamics of basaltic eruptions. We find that relatively high plagioclase content requires crystallisation in a shallow reservoir, whilst a low plagioclase content reflects a disequilibrium crystallisation occurring during a fast ascent from depth to the surface. Using these new constraints on disequilibrium plagioclase crystallisation we also reproduce observed crystal abundances for different basaltic eruptions: Etna 2002/2003, Stromboli 2007 (effusive eruption) and 1930 (paroxysm) and different Pu'u' O'o eruptions at Kilauea (episodes 49-53). Therefore, our results show that disequilibrium processes play a key role on the ascent dynamics of basaltic magmas and cannot be neglected when describing basaltic

  5. Determination of Magma Ascent Rates From D/H Fractionation in Olivine-Hosted Melt Inclusions

    Science.gov (United States)

    Gaetani, G. A.; Bucholz, C. E.; Le Roux, V.; Klein, F.; Ghiorso, M. S.; Wallace, P. J.; Sims, K. W. W.

    2016-12-01

    The depths at which magmas are stored and the rates at which they ascend to Earth's surface are important controls on the dynamics of volcanic eruptions. Eruptive style is influenced by the rate at which magma ascends from the reservoir to the surface through its effect on vapor bubble nucleation, growth, and coalescence. However, ascent rates are difficult to quantify because few accurate geospeedometers are appropriate for a process occurring on such short timescales. We developed a new approach to determining ascent rates on the basis of D/H fraction associated with diffusive H2O loss from olivine-hosted melt inclusions. The utility of this approach was demonstrated on olivine-hosted melt inclusions in a hyaloclastite recovered from within Dry Valley Drilling Project core 3 from Hut Point Peninsula, Antarctica. All of the melt inclusions are glassy and contain vapor bubbles. The volumes of melt inclusions and vapor bubbles were determined by X-ray microtomography, and the density of CO2 within each bubble was determined using Raman spectroscopy. Olivines were then polished to expose individual inclusions and analyzed for volatiles and dDVSMOW by secondary ion mass spectrometry. Total CO2 was reconstructed by summing CO2 in the included glass and vapor bubble. Entrapment pressures calculated on the basis of reconstructed CO2 and maximum H2O concentrations using the MagmaSat solubility model [1] indicate a depth of origin of 24 km - in good agreement with the seismically determined depth to the Moho beneath Ross Island [2]. Magma ascent rates were determined using a finite difference model for melt inclusion dehydration during magma ascent. The positive correlation between H2O and CO2 is consistent with diffusive loss during ascent, but does not provide direct information on magma ascent rate. In contrast, the slope of the negative correlation between H2O and dDVSMOW is a reflection of transport time and, therefore, ascent rate. If it is assumed that magmas did

  6. Magma buoyancy and volatile ascent driving autocyclic eruptivity at Hekla Volcano (Iceland)

    Science.gov (United States)

    Hautmann, Stefanie; Sacks, I. Selwyn; Linde, Alan T.; Roberts, Matthew J.

    2017-09-01

    Volcanic eruptions are typically accompanied by ground deflation due to the withdrawal of magma from depth and its effusion at the surface. Here, based on continuous high-resolution borehole strain data, we show that ground deformation was absent during the major effusion phases of the 1991 and 2000 eruptions of Hekla Volcano, Iceland. This lack of surface deformation challenges the classic model of magma intrusion/withdrawal as source for volcanic ground uplift/subsidence. We incorporate geodetic and geochemical observables into theoretical models of magma chamber dynamics in order to constrain quantitatively alternative co- and intereruptive physical mechanisms that govern magma propagation and system pressurization. We find the lack of surface deformation during lava effusion to be linked to chamber replenishment from below whilst magma migrates as a buoyancy-driven flow from the magma chamber towards the surface. We further demonstrate that intereruptive pressure build-up is likely to be generated by volatile ascent within the chamber rather than magma injection. Our model explains the persistent periodic eruptivity at Hekla throughout historic times with self-initiating cycles and is conceptually relevant to other volcanic systems.

  7. Ascent Rates of Rhyolitic Magma During the Opening Stages of Explosive Caldera-Forming Eruptions

    Science.gov (United States)

    Myers, M.; Wallace, P. J.; Wilson, C. J. N.; Watkins, J. M.; Liu, Y.; Morgan, D. J.

    2016-12-01

    We investigate the timescales of rhyolitic magma ascent for three supereruptions that show contrasting eruptive behavior at eruption onset: (1) the Bishop Tuff, CA where early fallout graded directly into climactic eruption, (2) the Oruanui eruption, Taupo NZ, which experienced a significant time break between the initial fallout and subsequent activity and (3) the Huckleberry Ridge, Yellowstone where initial activity was episodic, with eruptive pauses totaling days to weeks. During ascent, decompression causes volatile exsolution from the host melt, creating H2O and CO2 gradients in reentrants (REs; unsealed inclusions) that can be modeled to estimate ascent timescales1,2,3. Using a code1 refined to include an error minimization function, we present modeled ascent rates for REs from Huckleberry Ridge (n=10), Bishop (n=14), and Oruanui (n=4), measured using FTIR (20 μm resolution, 4-15 points per RE). Best-fit profiles for the Bishop REs give ascent rates of 0.6-30 m/s, which overlap with those of the Huckleberry (0.3-5.5 m/s), but extend to higher values. Although ascent rate and initial eruptive behavior are somewhat decoupled, there is an increase in the number of faster ascent rates and greater starting depths with higher stratigraphic height in the Huckleberry Ridge and Bishop fall deposits. Preliminary work on Oruanui REs indicates rates of 0.15-2.0 m/s, which overlie the lower end of the Bishop and Huckleberry REs, in agreement with previous data1. Overall, there is significant overlap between the three datasets (average 4±7 m/s). Our calculated ascent rates fall towards the lower end of ascent rates that have been estimated (5-40 m/s4) using theoretical and numerical modeling of conduit flow for Plinian rhyolitic eruptions below the fragmentation depth. 1 Liu Y et al. 2007: J Geophys Res 112, B06204; 2 Humphreys MCS et al. 2008: Earth Planet Sci Lett 270, 25; 3 Lloyd et al., 2014: J Volcanol Geotherm Res 283, 1; 4Rutherford MJ 2008: Rev Mineral Geochem 69

  8. Mechanical Anisotropies and Mechanisms of Mafic Magma Ascent in Middle Continental Crust: The Sondalo Gabbroic Complex (N Italy)

    Science.gov (United States)

    Petri, B.; Mohn, G.; Skrzypek, E.; Mateeva, T.; Robion, P.; Schulmann, K.; Manatschal, G.; Müntener, O.

    2016-12-01

    The ascent mechanisms of magma through the continental crust remain a long standing controversy. The pathways of intermediate to felsic magmas can be continuously traced through the crust, however mafic magma transfer between lower and upper crustal levels is rarely documented. To fill this gap, we explore the mechanisms of mafic magma ascent and emplacement in middle continental crust. We characterize the structure and anisotropy of magnetic susceptibility (AMS) fabrics of a mid-crustal mafic complex (Sondalo gabbroic complex, N-Italy) together with Anisotropy of Anhysteretic Remanent Magnetization (AARM) and Crystallographic Preferred Orientation (CPO) data. Field data indicate concentric gabbroic to dioritic intrusions emplaced in sub-vertically foliated metasedimentary host-rocks. The petrofabrics and magnetic fabrics of the pluton (foliations and lineations) are coaxial, syn-magmatic and sub-vertical. U-Pb dating of zircons along with the structural record of the plutonic rocks indicate two major pulses of magma emplacement in sub-vertical channels. (1) The concordant orientation between the magmatic foliation and the host-rock xenoliths in the center of the pluton suggest that the early emplacement phase occurred through magma fracture opening subparallel to the vertical fabric of the host rocks at 289-288 Ma. (2) The second magma ascent phase was controlled by a change in the rheology of the host-rock and the mafic magma. The temperature increase in the contact aureole induced partial melting and decreased its mechanical strength, whereas the viscosity of the mafic magma increased due to progressive cooling and crystallization. This caused an en-masse rise of the crystal mush and drag forces resulting in the formation of a vertical foliation in the metamorphic aureole and a weaker but concordant magmatic foliation at the rim of the pluton. This ascent phase is slightly younger (288-285 Ma) and accounts for the contrasted P-T evolution recorded by

  9. Morphological Transition in Rapidly Expanding Magmas

    Science.gov (United States)

    Kolinski, J.; Chakraborty, P.; Gioia, G.; Kieffer, S. W.

    2008-12-01

    Many explosive eruptions are initiated by rapid decompression of bubbly magma, which behaves as an elastic material during the decompression and fragments into discrete pieces following the decompression. To emulate the rapid decompression of bubbly magma, we subject a two-dimensional foam of soap bubbles to quasi-static expansion. A recent theory predicts that where a two-dimensional foam of soap bubbles is first subjected to expansion, the foam expands homogeneously. After a critical value of expansion is attained, the foam undergoes a morphological transition and separates into a large number of small bubbles immersed in a background of a few large bubbles [Vainchtein and Aref, Physics of Fluids 13, 2001]. In our experiments we verify the phenomenon of morphological transition under area expansion. We verity the predictions of Vainchtein and Aref, compare our results with the experimental results on rapidly expanding bubble-bearing viscoelastic fluids reported by [Namiki and Manga, Earth and Planetary Science Letters 236, 2005], and discuss the implications of our results for the rapid decompression of magmas.

  10. Prolonged ascent and episodic venting of discrete magma batches at the onset of the Huckleberry Ridge supereruption, Yellowstone

    Science.gov (United States)

    Myers, Madison L.; Wallace, Paul J.; Wilson, Colin J. N.; Morter, Beth K.; Swallow, Elliot J.

    2016-10-01

    How exceedingly large, volcanic supereruptions begin provides crucial information on the storage, ascent and release of silica-rich magma in catastrophic events. Initial fall deposits of the 2.08 Ma, 2500 km3 Huckleberry Ridge eruption are multiply bedded and in several places contain reworked intervals, indicating time breaks in the opening phases of the eruption. A 2.5 m section of these fall deposits was sampled at nine levels below the earliest ignimbrite (member A) at Mount Everts (Mammoth, Wyoming). We analyzed major and trace elements and volatiles in quartz-hosted melt inclusions (MIs), reentrants (REs; unsealed melt inclusions) and associated obsidian pyroclasts (thick-walled shards) to establish quartz crystallization and storage depths and melt compositional groupings. Systematic relationships between Rb and other incompatible elements (U, Cl, B) indicate ∼55% fractional crystallization between the least and most evolved glass compositions. In contrast, H2O concentrations in MIs show scattered relationships with trace elements and are interpreted to reflect variable loss of H2O by diffusion through the quartz host during magma ascent. The wide H2O variations (1.0-4.7 wt.%) in MIs from individual fall horizons imply as much as ∼14 days of diffusive loss, reflecting highly variable and surprisingly slow decompression conditions. Water and CO2 gradients in reentrants, however, are consistent with final ascent times of erupted crystals mirrors that of intermittent explosive activity at Mount St. Helens in summer 1980, and implies that the Huckleberry Ridge magma body was not strongly overpressured at eruption onset. Restored entrapment pressures and geochemical data for MIs provide evidence for six distinct populations of quartz that originally crystallized in geochemically distinct magma domains. The compositions of REs and obsidian pyroclasts, by comparison, show that by the onset of eruption, the quartz had been brought together into three discrete

  11. Halogen degassing during ascent and eruption of water-poor basaltic magma

    Science.gov (United States)

    Edmonds, M.; Gerlach, T.M.; Herd, Richard A.

    2009-01-01

    A study of volcanic gas composition and matrix glass volatile concentrations has allowed a model for halogen degassing to be formulated for K??lauea Volcano, Hawai'i. Volcanic gases emitted during 2004-2005 were characterised by a molar SO2/HCl of 10-64, with a mean of 33; and a molar HF/HCl of 0-5, with a mean of 1.0 (from approximately 2500 measurements). The HF/HCl ratio was more variable than the SO2/HCl ratio, and the two correlate weakly. Variations in ratio took place over rapid timescales (seconds). Matrix glasses of Pele's tears erupted in 2006 have a mean S, Cl and F content of 67, 85 and 173??ppm respectively, but are associated with a large range in S/F. A model is developed that describes the open system degassing of halogens from parental magmas, using the glass data from this study, previously published results and parameterisation of sulphur degassing from previous work. The results illustrate that halogen degassing takes place at pressures of pressure, virtually at the top of the magma column. This model reproduces the volcanic gas data and other observations of volcanic activity well and is consistent with other studies of halogen degassing from basaltic magmas. The model suggests that variation in volcanic gas halogen ratios is caused by exsolution and gas-melt separation at low pressures in the conduit. There is no evidence that either diffusive fractionation or near-vent chemical reactions involving halogens is important in the system, although these processes cannot be ruled out. The fluxes of HCl and HF from K??lauea during 2004-5 were ~ 25 and 12??t/d respectively. ?? 2008 Elsevier B.V.

  12. Magma ascent and lava dome evolution at Volcán de Colima, Mexico

    Science.gov (United States)

    Varley, N. R.; Arámbula, R.; Lavallée, Y.; Bernstein, M.; Ryan, A. G.; Maskell, A.

    2009-12-01

    The transition between explosive and effusive activity can be triggered by subtle variations in parameters which dictate the efficiency and speed of degassing from an ascending magma body. Indirect methods have to be utilized to constrain these parameters, to test and refine numerical models, which ultimately permit a more powerful interpretation of monitoring data. Recent activity at Volcán de Colima has included many transitions between different regimes, offering a great opportunity to examine conduit processes. Explosive activity peaked in 2005 with 30 Vulcanian eruptions producing pyroclastic flows, some reaching >5km from the volcano. Each event was associated with a swarm of long-period (LP) seismic events. A poor correlation between swarm characteristics and the size of the explosion suggests independence between the source mechanisms of each phenomenon. The LP events were divided into 10 families, all of which reappeared in different swarms and the majority continued to occur after the Vulcanian explosion. This is evidence of the complexity of the upper edifice, with the source regions for the LP events remaining unaffected by the explosions. We believe they are produced by brittle deformation once a certain strain-rate threshold has been surpassed. The explosions were associated with rapidly ascending magma bodies that were degassing and crystallizing near the surface, each one being destroyed in the subsequent explosion. Magma sometimes reached the crater, with small short-lived domes being observed. In some cases a post-explosion increase in amplitude of the LP events might have reflected an increase in effusion rate after an unloading of material higher in the vent. Volcán de Colima has produced 5 episodes of effusive activity in the last 11 years. These have been of variable duration and intensity, with over 2 orders of magnitude variation in the effusion rate. The current phase has been characterised by a remarkably sustained (from Jan. 07 to at

  13. Copious Volcanism on a Compression-dominated Planet? Insights into Magma Ascent and Mountain Building on Io from Numerical Modeling

    Science.gov (United States)

    McGovern, Patrick J.; Kirchoff, M. R.

    2012-10-01

    Jupiter's moon Io is the most volcanically active body in the solar system. However, the largest mountains on Io are not massive shield volcanoes, but rather tabular features with a characteristic tilted-block morphology created by compressional faulting. A global bias towards compression may be produced by a vertical “conveyor belt” of repeated burial and subsidence of volcanic units, but this hypothesis begs the question of how the magma ascends to the surface in apparent violation of the long-standing principle that compression inhibits eruption. Here we explore the twin paradoxes of “copious volcanism on a compression-dominated planet” and “dominance of compression-built mountains on a volcanic planet” via quantitative modeling of the evolution of stresses in and deformation of Io’s lithosphere. Consideration of the pressure balance on a vertical magma conduit (dike) reveals that the vertical stress gradient associated with the conveyor belt stress state (compression decreasing upward) actually provides a driving force for magma ascent. Unfortunately, the components of the conveyor belt stress state (thermal, Poisson, and subsidence stresses) add together to produce horizontal compression in the lower lithosphere. This is inconsistent with vertical conduits, instead favoring horizontal ones (sills). However, the combined flexural (bending) and membrane (stretching) responses to loading produce stress changes beneath and surrounding large loads that can alter the principal stress orientations, re-enabling magma ascent. The particle-based Distinct Element Method (DEM) provides another way to model the response of Io’s lithosphere to the conveyor belt stress state. We model the lithosphere as a gravitationally loaded and bonded assemblage of particles, subject to horizontal displacements that increase with depth. The resulting deformation produces intact triangular blocks with tilted margins that resemble Ionian mountains. This work is sponsored by

  14. From the Slab to the Surface: Origin, Storage, Ascent, and Eruption of Volatile-Bearing Magmas in the Aleutian arc

    Science.gov (United States)

    Roman, D.; Plank, T. A.; Hauri, E. H.; Rasmussen, D. J.; Power, J. A.; Lyons, J. J.; Haney, M. M.; Werner, C. A.; Kern, C.; Lopez, T. M.; Izbekov, P. E.; Stelling, P. L.

    2016-12-01

    We present initial results from an integrated geochemical-geophysical study of the Unimak-Cleveland corridor of the Aleutian volcanic arc, which encompasses six volcanoes spanning 450 km of the arc that have erupted in the past 25 years with a wide range of magmatic water contents. This relatively small corridor also exhibits a range of deep and upper-crustal seismicity, apparent magma storage depths, and depths to the subducting tectonic plate. The ultimate goal of this study is to link two normally disconnected big-picture problems: 1) the deep origin of magmas and volatiles, and 2) the formation and eruption of crustal magma reservoirs, which we will do by establishing the depth(s) of crustal magma reservoirs and pre-eruptive volatile contents throughout the corridor. Our preliminary work focuses on the geographic end members Shishaldin Volcano, which last erupted in 2014-2015, and Cleveland Volcano, which last erupted in April-May of this year (2016). Both systems are persistently degassing, open-vent volcanoes whose frequent eruptions are typically characterized by minimal precursory seismicity, making eruption forecasting challenging. At Cleveland, we analyze data from a 12-station broadband seismic network deployed from August 2015-July 2016, which is complemented by two permanent seismo-acoustic stations operated by the Alaska Volcano Observatory (AVO). We also analyze tephras from recent eruptions (including 2016) and conducted ground- and helicopter-based gas emission surveys. At Shishaldin, we analyze data from the permanent AVO network, which is comprised of mainly short-period, single-component seismic stations. We also present preliminary analyses of samples of recent eruptive deposits and gas emission data. Through integration of these various datasets we present preliminary interpretations related to the origin, storage, ascent and eruption of volatile-bearing magmas at Cleveland and Shishaldin volcanoes.

  15. Magma ascent and emplacement in a continental rift setting: lessons from alkaline complexes in active and ancient rift zones

    Science.gov (United States)

    Hutchison, William; Lloyd, Ryan; Birhanu, Yelebe; Biggs, Juliet; Mather, Tamsin; Pyle, David; Lewi, Elias; Yirgu, Gezahgen; Finch, Adrian

    2017-04-01

    overlying country rock. These new constraints on magma ascent and volatile ponding in alkaline plutonic systems complement the deformation mechanisms and conceptual models developed for active systems in the Ethiopian Rift. Volcanic-plutonic pairs are rarely considered together but these data demonstrate the power of using constraints from 'fossil' magma chambers to infer sub-volcanic processes at active complexes and vice-versa.

  16. Volcanological evolution of the Rivi-Capo Volcanic Complex at Salina, Aeolian Islands: magma storage processes and ascent dynamics

    Science.gov (United States)

    Nicotra, Eugenio; Viccaro, Marco; De Rosa, Rosanna; Sapienza, Marco

    2014-08-01

    Lava flows and pyroclastic deposits from strombolian fallout related to the activity of the Rivi and Capo volcanoes, which are representative of early subaerial volcanoes on Salina (Aeolian Islands), have been investigated through a geological-petrological approach. Our geological field survey shows that Rivi and Capo volcanoes are part of a single N50°E aligned volcanic complex, here named Rivi-Capo Volcanic Complex (RCVC). Stratigraphically specific rock sampling has allowed reconstruction of the magma feeding processes through time. Whole rock major element compositions, together with core-to-rim profiles of plagioclase and clinopyroxene crystals, show a general evolution toward more basic compositions through the three formations constituting the Capo volcano and within the Rivi center. MELTS simulations and mass balance modeling suggest that the RCVC rocks are the result of fractional crystallization of plagioclase, clinopyroxene, and olivine (ca. 45 % of solid removed) from a primary magma. In addition to fractional crystallization, continuous recharge and mixing with more basic magma coming from deeper parts of the magmatic plumbing system contributed to the final volcanic rock compositions. Our textural and microanalytical data on plagioclase and clinopyroxene crystals allow the definition of a multilevel magmatic storage system with reservoirs at ~20 and ~3 km below sea level. When processes of magma differentiation, ascent, and storage are considered together with the stratigraphic position of each sample, a history of continuous modification of the RCVC plumbing system can be constructed. Volcanism may have been characterized by fissure-type eruptions during the early stages (Lower Capo, Lower Rivi, and Middle Capo Formations), gradually changing later to central-type volcanism (Upper Capo and Upper Rivi Formations).

  17. Generation, ascent and eruption of magma on the Moon: New insights into source depths, magma supply, intrusions and effusive/explosive eruptions (Part 1: Theory)

    Science.gov (United States)

    Wilson, Lionel; Head, James W.

    2017-02-01

    We model the ascent and eruption of lunar mare basalt magmas with new data on crustal thickness and density (GRAIL), magma properties, and surface topography, morphology and structure (Lunar Reconnaissance Orbiter). GRAIL recently measured the broad spatial variation of the bulk density structure of the crust of the Moon. Comparing this with the densities of lunar basaltic and picritic magmas shows that essentially all lunar magmas were negatively buoyant everywhere within the lunar crust. Thus positive excess pressures must have been present in melts at or below the crust-mantle interface to enable them to erupt. The source of such excess pressures is clear: melt in any region experiencing partial melting or containing accumulated melt, behaves as though an excess pressure is present at the top of the melt column if the melt is positively buoyant relative to the host rocks and forms a continuously interconnected network. The latter means that, in partial melt regions, probably at least a few percent melting must have taken place. Petrologic evidence suggests that both mare basalts and picritic glasses may have been derived from polybaric melting of source rocks in regions extending vertically for at least a few tens of km. This is not surprising: the vertical extent of a region containing inter-connected partial melt produced by pressure-release melting is approximately inversely proportional to the acceleration due to gravity. Translating the ∼25 km vertical extent of melting in a rising mantle diapir on Earth to the Moon then implies that melting could have taken place over a vertical extent of up to 150 km. If convection were absent, melting could have occurred throughout any region in which heat from radioisotope decay was accumulating; in the extreme this could have been most of the mantle. The maximum excess pressure that can be reached in a magma body depends on its environment. If melt percolates upward from a partial melt zone and accumulates as a magma

  18. Magma evolution and ascent at the Craters of the Moon and neighboring volcanic fields, southern Idaho, USA: implications for the evolution of polygenetic and monogenetic volcanic fields

    Science.gov (United States)

    Putirka, Keith D.; Kuntz, Mel A.; Unruh, Daniel M.; Vaid, Nitin

    2009-01-01

    The evolution of polygenetic and monogenetic volcanic fields must reflect differences in magma processing during ascent. To assess their evolution we use thermobarometry and geochemistry to evaluate ascent paths for neighboring, nearly coeval volcanic fields in the Snake River Plain, in south-central Idaho, derived from (1) dominantly Holocene polygenetic evolved lavas from the Craters of the Moon lava field (COME) and (2) Quaternary non-evolved, olivine tholeiites (NEOT) from nearby monogenetic volcanic fields. These data show that NEOT have high magmatic temperatures (1205 + or - 27 degrees C) and a narrow temperature range (50 degrees C). Prolonged storage of COME magmas allows them to evolve to higher 87Sr/86Sr and SiO2, and lower MgO and 143Nd/144Nd. Most importantly, ascent paths control evolution: NEOT often erupt near the axis of the plain where high-flux (Yellowstone-related), pre-Holocene magmatic activity replaces granitic middle crust with basaltic sills, resulting in a net increase in NEOT magma buoyancy. COME flows erupt off-axis, where felsic crustal lithologies sometimes remain intact, providing a barrier to ascent and a source for crustal contamination. A three-stage ascent process explains the entire range of erupted compositions. Stage 1 (40-20 km): picrites are transported to the middle crust, undergoing partial crystallization of olivine + or - clinopyroxene. COME magmas pass through unarmored conduits and assimilate 1% or less of ancient gabbroic crust having high Sr and 87Sr/86Sr and low SiO2. Stage 2 (20-10 km): magmas are stored within the middle crust, and evolve to moderate MgO (10%). NEOT magmas, reaching 10% MgO, are positively buoyant and migrate through the middle crust. COME magmas remain negatively buoyant and so crystallize further and assimilate middle crust. Stage 3 (15-0 km): final ascent and eruption occurs when volatile contents, increased by differentiation, are sufficient (1-2 wt % H2O) to provide magma buoyancy through the

  19. The implications of gas slug ascent in a stratified magma for acoustic and ground deformation source mechanisms in Strombolian eruptions

    Science.gov (United States)

    Capponi, Antonio; Lane, Stephen J.; James, Mike R.

    2017-06-01

    The interpretation of geophysical measurements at active volcanoes is vital for hazard assessment and for understanding fundamental processes such as magma degassing. For Strombolian activity, interpretations are currently underpinned by first-order fluid dynamic models which give relatively straightforward relationships between geophysical signals and gas and magma flow. However, recent petrological and high-speed video evidence has indicated the importance of rheological stratification within the conduit and, here, we show that under these conditions, the straightforward relationships break down. Using laboratory analogue experiments to represent a rheologically-stratified conduit we characterise the distinct variations in the shear stress exerted on the upper sections of the flow tube and in the gas pressures measured above the liquid surface, during different degassing flow configurations. These signals, generated by varying styles of gas ascent, expansion and burst, can reflect field infrasonic measurements and ground motion proximal to a vent. The shear stress signals exhibit timescales and trends in qualitative agreement with the near-vent inflation-deflation cycles identified at Stromboli. Therefore, shear stress along the uppermost conduit may represent a plausible source of near-vent tilt, and conduit shear contributions should be considered in the interpretation of ground deformation, which is usually attributed to pressure sources only. The same range of flow processes can produce different experimental infrasonic waveforms, even for similar masses of gas escape. The experimental data resembled infrasonic waveforms acquired from different vents at Stromboli associated with different eruptive styles. Accurate interpretation of near-vent ground deformation, infrasonic signal and eruptive style therefore requires detailed understanding of: a) spatiotemporal magma rheology in the shallow conduit, and b) shallow conduit geometry, as well as bubble

  20. Timescales of magma ascent and degassing and the role of crustal assimilation at Merapi volcano (2006-2010), Indonesia: Constraints from uranium-series and radiogenic isotopic compositions

    Science.gov (United States)

    Handley, H. K.; Reagan, M.; Gertisser, R.; Preece, K.; Berlo, K.; McGee, L. E.; Barclay, J.; Herd, R.

    2018-02-01

    the more explosive behaviour of Merapi in 2010 (as has been previously suggested) and instead indicate that relatively rapid ascent of a more undegassed magma was the primary difference responsible for the transition in explosive behaviour. This interpretation is in good agreement with gas monitoring data, previous petrological studies (mineral, microlite and melt inclusion work) and maximum calculated timescale estimates using Fe-Mg compositional gradients in clinopyroxene, that also suggest more rapid movement of relatively undegassed magma in 2010 relative to 2006.

  1. Generation, ascent and eruption of magma on the Moon: New insights into source depths, magma supply, intrusions and effusive/explosive eruptions (Part 2: Predicted emplacement processes and observations)

    Science.gov (United States)

    Head, James W.; Wilson, Lionel

    2017-02-01

    rapidly decreasing integrated flux of mare basalts is a result of the thermal evolution of the Moon; continued cooling decreased diapiric rise and mantle melting, thickened the lithosphere, and caused the global state of stress to be increasingly contractional, all factors progressively inhibiting the generation, ascent and eruption of basaltic magma. Late-stage volcanic eruptions are typically widely separated in time and characterized by high-volume, high-effusion rate eruptions producing extensive volume-limited flows, a predictable characteristic of deep source regions below a thick lithosphere late in lunar history. This improved paradigm for the generation, ascent, intrusion and eruption of basaltic magma provides the basis for the broader interpretation of the lunar volcanic record in terms of variations in eruption conditions in space and time, and their relation to mantle heterogeneity and a more detailed understanding of lunar thermal evolution.

  2. Downward Crustal Flow During Magma Ascent in the Central Sierran Arc

    Science.gov (United States)

    Anderson, J. L.; Paterson, S. R.; Zhang, T.; Economos, R.; Memeti, V.; Pignotta, G. S.; Mundil, R.

    2008-12-01

    pluton emplacement, yield metamorphic temperatures ranging from 640 to 717 C, thus exhibiting near thermal equilibration with adjacent plutons and indicative of geothermal gradients in excess of 70 C/km. In the Cinko Lake area, metavolcanic rocks descended to their maximum depths (10 km) in the mid-Cretaceous shortly after their surface deposition. In the Soldier Lake area, metavolcanic rocks achieved their maximum depth of 12 km coincident with Jurassic plutonism, and subsequently began a return toward more shallow levels during Cretaceous plutonism. Our evidence for downward displacement of Jurassic and Cretaceous volcanic strata during the rise of slightly younger magma raises questions about how widespread this event is and the processes by which it occurred. Saleeby and colleagues have argued for identical downward flow of host rock during rise of magma in the southern Sierras and further examples apparently exist in the central Sierra suggesting that this may be a major, Sierra-wide event. Careful documentation of the ages of juxtaposed volcanic-plutonic packages, thermobarometry, and host rock displacement processes are necessary to fully understand the significance of this process.

  3. Petrological constraints on the recycling of mafic crystal mushes, magma ascent and intrusion of braided sills in the Torres del Paine mafic complex (Patagonia)

    Science.gov (United States)

    Leuthold, Julien; Müntener, Othmar; Baumgartner, Lukas; Putlitz, Benita

    2014-05-01

    Cumulate and crystal mush disruption and reactivation are difficult to recognise in coarse grained shallow plutonic rocks. Mafic minerals included in hornblende and zoned plagioclase provide snapshots of early crystallization and cumulate formation, but are difficult to interpret in terms of the dynamics of magma ascent and possible links between silicic and mafic rock emplacement. We will present the field relations, the microtextures and the mineral chemistry of the Miocene mafic sill complex of the Torres del Paine intrusive complex (Patagonia, Chile) and its sub-vertical feeder-zone. The mafic sill complex was built up by a succession of braided sills of shoshonitic and high-K calc-alkaline porphyritic hornblende-gabbro and fine grained monzodioritic sills. The mafic units were over-accreted over 41±11 ka, underplating the overlying granite. Local diapiric structures and felsic magma accumulation between sills indicate limited separation of intercumulus liquid from the mafic sills. Anhedral hornblende cores, with olivine + clinopyroxene ± plagioclase ± apatite inclusions, crystallized at temperatures >900°C and pressures of ~300 to ~500 MPa. The corresponding rims and monzodiorite matrix crystallized at 950°C) from the middle crust reservoir to the emplacement level. We show that hornblende-plagioclase thermobarometry is a useful monitor for the determination of segregation conditions of granitic magmas from gabbroic crystal mushes, and for monitoring the evolution of shallow crustal magmatic crystallization, decompression and cooling.

  4. Rapid Mantle Ascent Rates Beneath Brazil: Diamond Bullets from a Smoking Plume?

    Science.gov (United States)

    Walter, M. J.; Frost, D. J.

    2010-12-01

    The concept of upwelling plumes of mantle material is, for many, integral to plate tectonics theory. However, proving that plumes exist has been frustrating, and a growing cadre of geoscientists either deny their existence, or remain uncomfortably agnostic. To the uninitiated, seismic tomography can seem a game of now-you-see-it, now-you-don’t, and igneous petrology a malarial fever of now-it's-hot, now-it's-cold. We suggest that diamonds and their mineral inclusions from Juina, Brazil, may provide direct evidence for rapid mantle ascent caused by an upwelling plume. Cretaceous kimberlites in Juina are famous for producing diamonds with inclusions that originated at transition zone and lower mantle depths [1]. Many of these sublithospheric inclusions show evidence of un-mixing of original single-phase minerals into composite inclusions during ascent in the mantle unrelated to kimberlite eruption [2,3]. What is not known is the timeframe or causality of mantle ascent. Diamonds are notoriously hard to date, but Re/Os dates of sulfide inclusions in lithospheric diamonds are generally Early Proterozoic or older, whereas host kimberlites are typically much younger [4]. If the Brazilian diamonds were also ancient, then un-mixing could have been the result of a couple billion years of passive upward migration in the mantle, unrelated to anything so torrid as a mantle plume. Diamond J1 from the Collier4 kimberlite has a composite CaTiO3+CaSiO3 inclusion in a core growth zone (originally perovskite) and a majoritic garnet inclusion in a rim zone. On the basis of excess silica in its formula, the garnet crystallized at 6-7 GPa (about 200 km), consistent with the un-mixing pressure obtained from the perovskite [5]. Experimental phase relations show that the original single-phase perovskite must have formed deeper, between about 300 and 700 km [5]. Thus, diamond J1 exhibits polybaric growth, having ascended some 100 to 500 km during its growth history. Many other mineral

  5. High altitude illness in pilgrims after rapid ascent to 4380 M.

    Science.gov (United States)

    Zafren, Ken; Pun, Matiram; Regmi, Nirajan; Bashyal, Gobinda; Acharya, Bhuwan; Gautam, Subarna; Jamarkattel, Sujan; Lamichhane, Shankar Raj; Acharya, Suman; Basnyat, Buddha

    The goal of the study was to characterize high altitude illness in Nepali pilgrims. We kept standardized records at the Himalayan Rescue Association (HRA) Temporary Health Camp at Gosainkund Lake (4380 m) in the Nepal Himalaya during the annual Janai Purnima Festival in 2014. Records included rate of ascent and Lake Louise Score (LLS). We defined High Altitude Headache (HAH) as headache alone or LLS = 2. Acute Mountain Sickness (AMS) was LLS≥3. High Altitude Cerebral Edema (HACE) was AMS with ataxia or altered mental status. An estimated 10,000 pilgrims ascended rapidly, most in 1-2 days, from Dhunche (1960 m) to Gosainkund Lake (4380 m). We saw 769 patients, of whom 86 had HAH. There were 226 patients with AMS, including 11 patients with HACE. We treated patients with HACE using dexamethasone and supplemental oxygen prior to rapid descent. Each patient with HACE descended carried by a porter. There were no fatalities due to HACE. There were no cases of High Altitude Pulmonary Edema (HAPE). HAH and AMS were common in pilgrims ascending rapidly to 4380 m. There were 11 cases of HACE, treated with dexamethasone, supplemental oxygen and descent. There were no fatalities. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Thermo-mechanical two-phase flow models of magma ascent in the continental crust with and without extension

    Science.gov (United States)

    Schmeling, Harro; Maruqart, Gabriele; Weinberg, Roberto; Cruden, Sandy

    2017-04-01

    Melting within the lower continental crust with and without extension and subsequent ascent of silicic melts is modelled by a thermo-mechanical two-phase flow approach. The approach is based on the conservation equations of mass, momentum, and energy for melt and solid, respectively, and includes a simplified binary melting model, as well as compaction / decompaction of the solid matrix. The rheology is based on dislocation creep of quartzite or granite, and includes plasticity. 2D models are carried out for cases without and with differential melt-matrix flow. As control parameter the heat flow is varied between 75 and 90 mW m-2 at the base of a thickened continental crust. In the case of no differential flow (batch melting) the model predicts episodic melting, rise and freezing of partially molten magmatic bodies. The recurrence time inversely scales with the bottom heat flux. In the case of allowing for melt migration, no such episodicity is observed anymore. Melt accumulates within melt rich layers and bodies, which subsequently rise through the crust by a combination of diapirism and decompaction related sinking of solid material through the melt rich layer. Final emplacement depths are between 30 and 15 km, shapes of the resulting plutons are visualized by the evolved enrichment and depletion fields. They show a strong dependence on the applied bottom heat fluxes.

  7. 238U–230Th–226Ra–210Pb–210Po disequilibria constraints on magma generation, ascent, and degassing during the ongoing eruption of Kīlauea

    Science.gov (United States)

    Girard, Guillaume; Reagan, Mark K.; Sims, Kenneth W. W.; Thornber, Carl; Waters, Christopher L.; Phillips, Erin H.

    2017-01-01

    The timescales of magma genesis, ascent, storage and degassing at Kīlauea volcano, Hawai‘i are addressed by measuring 238U-series radionuclide abundances in lava and tephra erupted between 1982 and 2008. Most analyzed samples represent lavas erupted by steady effusion from Pu‘u ‘Ō‘ō and Kūpahianaha from 1983 to 2008. Also included are samples erupted at the summit in April 1982 and March 2008, along the East Rift Zone at the onset of the ongoing eruption in January 1983, and during vent shifting episodes 54 and 56, at Nāpau crater in January 1997, and Kane Nui O Hamo in June 2007. In general, samples have small (∼4%) excesses of (230Th) over (238U) and ∼3 to ∼17% excesses of (226Ra) over (230Th), consistent with melting of a garnet peridotite source at melting rates between 1 × 10–3 and 5 × 10–3 kg m–3 a–1, and melting region porosity between ∼2 and ∼10%, in agreement with previous studies of the ongoing eruption and historical eruptions. A small subset of samples has near-equilibrium (230Th/238U) values, and thus were generated at higher melting rates. Based on U–Th–Ra disequilibria and Th isotopic data from this and earlier studies, melting processes and sources have been relatively stable over at least the past two centuries or more, including during the ongoing unusually long (>30 years) and voluminous (4 km3) eruption. Lavas recently erupted from the East Rift Zone have average initial (210Pb/226Ra) values of 0·80 ± 0·11 (1σ), which we interpret to be the result of partitioning of 222Rn into a persistently generated CO2-rich gas phase over a minimum of 8 years. This (210Pb) deficit implies an average magma ascent rate of ≤3·7 km a–1 from ∼30 km depth to the surface. Spatter and lava associated with vent-opening episodes erupt with variable (210Pb) deficits ranging from 0·7 to near-equilibrium values in some samples. The samples with near-equilibrium (210Pb/226Ra) are typically more

  8. Rapid heterogeneous assembly of multiple magma reservoirs prior to Yellowstone supereruptions

    Science.gov (United States)

    Wotzlaw, Jörn-Frederik; Bindeman, Ilya N.; Stern, Richard A.; D'Abzac, Francois-Xavier; Schaltegger, Urs

    2015-09-01

    Large-volume caldera-forming eruptions of silicic magmas are an important feature of continental volcanism. The timescales and mechanisms of assembly of the magma reservoirs that feed such eruptions as well as the durations and physical conditions of upper-crustal storage remain highly debated topics in volcanology. Here we explore a comprehensive data set of isotopic (O, Hf) and chemical proxies in precisely U-Pb dated zircon crystals from all caldera-forming eruptions of Yellowstone supervolcano. Analysed zircons record rapid assembly of multiple magma reservoirs by repeated injections of isotopically heterogeneous magma batches and short pre-eruption storage times of 103 to 104 years. Decoupled oxygen-hafnium isotope systematics suggest a complex source for these magmas involving variable amounts of differentiated mantle-derived melt, Archean crust and hydrothermally altered shallow-crustal rocks. These data demonstrate that complex magma reservoirs with multiple sub-chambers are a common feature of rift- and hotspot related supervolcanoes. The short duration of reservoir assembly documents rapid crustal remelting and two to three orders of magnitude higher magma production rates beneath Yellowstone compared to continental arc volcanoes. The short pre-eruption storage times further suggest that the detection of voluminous reservoirs of eruptible magma beneath active supervolcanoes may only be possible prior to an impending eruption.

  9. Rapid heterogeneous assembly of multiple magma reservoirs prior to Yellowstone supereruptions

    Science.gov (United States)

    Wotzlaw, Jörn-Frederik; Bindeman, Ilya N.; Stern, Richard A.; D’Abzac, Francois-Xavier; Schaltegger, Urs

    2015-01-01

    Large-volume caldera-forming eruptions of silicic magmas are an important feature of continental volcanism. The timescales and mechanisms of assembly of the magma reservoirs that feed such eruptions as well as the durations and physical conditions of upper-crustal storage remain highly debated topics in volcanology. Here we explore a comprehensive data set of isotopic (O, Hf) and chemical proxies in precisely U-Pb dated zircon crystals from all caldera-forming eruptions of Yellowstone supervolcano. Analysed zircons record rapid assembly of multiple magma reservoirs by repeated injections of isotopically heterogeneous magma batches and short pre-eruption storage times of 103 to 104 years. Decoupled oxygen-hafnium isotope systematics suggest a complex source for these magmas involving variable amounts of differentiated mantle-derived melt, Archean crust and hydrothermally altered shallow-crustal rocks. These data demonstrate that complex magma reservoirs with multiple sub-chambers are a common feature of rift- and hotspot related supervolcanoes. The short duration of reservoir assembly documents rapid crustal remelting and two to three orders of magnitude higher magma production rates beneath Yellowstone compared to continental arc volcanoes. The short pre-eruption storage times further suggest that the detection of voluminous reservoirs of eruptible magma beneath active supervolcanoes may only be possible prior to an impending eruption. PMID:26356304

  10. Rapid heterogeneous assembly of multiple magma reservoirs prior to Yellowstone supereruptions.

    Science.gov (United States)

    Wotzlaw, Jörn-Frederik; Bindeman, Ilya N; Stern, Richard A; D'Abzac, Francois-Xavier; Schaltegger, Urs

    2015-09-10

    Large-volume caldera-forming eruptions of silicic magmas are an important feature of continental volcanism. The timescales and mechanisms of assembly of the magma reservoirs that feed such eruptions as well as the durations and physical conditions of upper-crustal storage remain highly debated topics in volcanology. Here we explore a comprehensive data set of isotopic (O, Hf) and chemical proxies in precisely U-Pb dated zircon crystals from all caldera-forming eruptions of Yellowstone supervolcano. Analysed zircons record rapid assembly of multiple magma reservoirs by repeated injections of isotopically heterogeneous magma batches and short pre-eruption storage times of 10(3) to 10(4) years. Decoupled oxygen-hafnium isotope systematics suggest a complex source for these magmas involving variable amounts of differentiated mantle-derived melt, Archean crust and hydrothermally altered shallow-crustal rocks. These data demonstrate that complex magma reservoirs with multiple sub-chambers are a common feature of rift- and hotspot related supervolcanoes. The short duration of reservoir assembly documents rapid crustal remelting and two to three orders of magnitude higher magma production rates beneath Yellowstone compared to continental arc volcanoes. The short pre-eruption storage times further suggest that the detection of voluminous reservoirs of eruptible magma beneath active supervolcanoes may only be possible prior to an impending eruption.

  11. Rapid differentiation in a sill-like magma reservoir: a case study from the campi flegrei caldera.

    Science.gov (United States)

    Pappalardo, Lucia; Mastrolorenzo, Giuseppe

    2012-01-01

    In recent decades, geophysical investigations have detected wide magma reservoirs beneath quiescent calderas. However, the discovery of partially melted horizons inside the crust is not sufficient to put constraints on capability of reservoirs to supply cataclysmic eruptions, which strictly depends on the chemical-physical properties of magmas (composition, viscosity, gas content etc.), and thus on their differentiation histories. In this study, by using geochemical, isotopic and textural records of rocks erupted from the high-risk Campi Flegrei caldera, we show that the alkaline magmas have evolved toward a critical state of explosive behaviour over a time span shorter than the repose time of most volcanic systems and that these magmas have risen rapidly toward the surface. Moreover, similar results on the depth and timescale of magma storage were previously obtained for the neighbouring Somma-Vesuvius volcano. This consistency suggests that there might be a unique long-lived magma pool beneath the whole Neapolitan area.

  12. The location and timing of magma degassing during Plinian eruptions

    Science.gov (United States)

    Giachetti, T.; Gonnermann, H. M.

    2014-12-01

    Water is the most abundant volatile species in explosively erupting silicic magmas and significantly affects magma viscosity, magma fragmentation and the dynamics of the eruption column. The effect that water has on these eruption processes can be modulated by outgassing degassing from a permeable magma. The magnitude, rate and timing of outgassing during magma ascent, in particular in relation to fragmentation, remains a subject of debate. Here we constrain how much, how fast and where the erupting magma lost its water during the 1060 CE Plinian phase of the Glass Mountain eruption of Medicine Lake Volcano, California. Using thermogravimetric analysis coupled with numerical modeling, we show that the magma lost >90% of its initial water upon eruption. Textural analyses of natural pumices, together with numerical modeling of magma ascent and degassing, indicate that 65-90% of the water exsolved before fragmentation, but very little was able to outgas before fragmentation. The magma attained permeability only within about 1 to 10 seconds before fragmenting and during that time interval permeable gas flow resulted in only a modest amount of gas flux from the un-fragmented magma. Instead, most of the water is lost shortly after fragmentation, because gas can escape rapidly from lapilli-size pyroclasts. This results in an efficient rarefaction of the gas-pyroclast mixture above the fragmentation level, indicating that the development of magma permeability and ensuing permeable outgassing are a necessary condition for sustain explosive eruptions of silicic magma. Magma permeability is thus a double-edged sword, it facilitates both, the effusive and the explosive eruption of silicic magma.

  13. Linking rapid magma reservoir assembly and eruption trigger mechanisms at evolved Yellowstone-type supervolcanoes

    Science.gov (United States)

    Wotzlaw, J.F.; Bindeman, I.N.; Watts, Kathryn E.; Schmitt, A.K.; Caricchi, L.; Schaltegger, U.

    2014-01-01

    The geological record contains evidence of volcanic eruptions that were as much as two orders of magnitude larger than the most voluminous eruption experienced by modern civilizations, the A.D. 1815 Tambora (Indonesia) eruption. Perhaps nowhere on Earth are deposits of such supereruptions more prominent than in the Snake River Plain–Yellowstone Plateau (SRP-YP) volcanic province (northwest United States). While magmatic activity at Yellowstone is still ongoing, the Heise volcanic field in eastern Idaho represents the youngest complete caldera cycle in the SRP-YP, and thus is particularly instructive for current and future volcanic activity at Yellowstone. The Heise caldera cycle culminated 4.5 Ma ago in the eruption of the ∼1800 km3 Kilgore Tuff. Accessory zircons in the Kilgore Tuff display significant intercrystalline and intracrystalline oxygen isotopic heterogeneity, and the vast majority are 18O depleted. This suggests that zircons crystallized from isotopically distinct magma batches that were generated by remelting of subcaldera silicic rocks previously altered by low-δ18O meteoric-hydrothermal fluids. Prior to eruption these magma batches were assembled and homogenized into a single voluminous reservoir. U-Pb geochronology of isotopically diverse zircons using chemical abrasion–isotope dilution–thermal ionization mass spectrometry yielded indistinguishable crystallization ages with a weighted mean 206Pb/238U date of 4.4876 ± 0.0023 Ma (MSWD = 1.5; n = 24). These zircon crystallization ages are also indistinguishable from the sanidine 40Ar/39Ar dates, and thus zircons crystallized close to eruption. This requires that shallow crustal melting, assembly of isolated batches into a supervolcanic magma reservoir, homogenization, and eruption occurred extremely rapidly, within the resolution of our geochronology (103–104 yr). The crystal-scale image of the reservoir configuration, with several isolated magma batches, is very similar to the

  14. Mantle xenolith-xenocryst-bearing monogenetic alkali basaltic lava field from Kutch Basin, Gujarat, Western India: Estimation of magma ascent rate

    Science.gov (United States)

    Ray, Arijit; Hatui, Kalyanbrata; Paul, Dalim Kumar; Sen, Gautam; Biswas, S. K.; Das, Brindaban

    2016-02-01

    Kutch rift basin of northwestern India is characterized by a topography that is controlled by a number of fault controlled uplifted blocks. Kutch Mainland Uplift, the largest uplifted block in the central part of the basin, contains alkali basalt plugs and tholeiitic basalt flows of the Deccan age. Alkali plugs often contain small, discoidal mantle xenoliths of spinel lherzolite and spinel wehrlite composition. Olivine occurs as xenocrysts (coarse, fractured, broken olivine grains with embayed margin; Fo> 90), phenocrysts (euhedral, smaller, and less forsteritic ~ Fo80), and as groundmass grains (small, anhedral, Fo75) in these alkali basalts. In a few cases, the alkali plugs are connected with feeder dykes. Based on the width of feeder dykes, on the sizes of the xenocrysts and xenoliths, thickness of alteration rim around olivine xenocryst, we estimate that the alkali magmas erupted at a minimum speed of 0.37 km per hour. The speed was likely greater because of the fact that the xenoliths broke up into smaller fragments as their host magma ascended through the lithosphere.

  15. Magnetic fabrics in sub-caldera plutons recording magma ascent and fault-caldera interactions, the Etiavnica volcano-plutonic complex, Western Carpathians

    Science.gov (United States)

    Tomek, Filip; Žák, Jiří

    2013-04-01

    the two different magnetic fabrics in these sub-caldera plutons as recording magma emplacement interacting with tectonic deformation of the volcano basement. In the diorite, the steep fabric results from intrusive strain during vertical magma flow along a steep segment of the pluton roof. On the contrary, fabric in the granodiorite presumably reflects inclined magma flow converted from up-dip to subhorizontal stretching during synchronous dextral strike-slip faulting in the pluton roof. Such a conclusion is in agreement with published paleostress estimations. Finally, using the Štiavnica volcano-plutonic complex as a case example, we develop a general model for three-dimensional fabric and inferred strain patterns in the crestal portions of granitoid plutons as a response to main modes of caldera collapse in various tectonic settings.

  16. Rapid heterogeneous assembly of multiple magma reservoirs prior to Yellowstone supereruptions

    OpenAIRE

    Jörn-Frederik Wotzlaw; Bindeman, Ilya N.; Richard A. Stern; Francois-Xavier D’Abzac; Urs Schaltegger

    2015-01-01

    Large-volume caldera-forming eruptions of silicic magmas are an important feature of continental volcanism. The timescales and mechanisms of assembly of the magma reservoirs that feed such eruptions as well as the durations and physical conditions of upper-crustal storage remain highly debated topics in volcanology. Here we explore a comprehensive data set of isotopic (O, Hf) and chemical proxies in precisely U-Pb dated zircon crystals from all caldera-forming eruptions of Yellowstone supervo...

  17. Age as a risk factor for acute mountain sickness upon rapid ascent to 3,700 m among young adult Chinese men

    Directory of Open Access Journals (Sweden)

    Tang XG

    2014-08-01

    Full Text Available Xu-gang Tang,1 Ji-hang Zhang,1 Jun Qin,1 Xu-bin Gao,1 Qian-ning Li,2 Jie Yu,1 Xiao-han Ding,1 Lan Huang1 1Institute of Cardiovascular Diseases, 2Department of Neurology, Xinqiao Hospital, Third Military Medical University, Chongqing, People’s Republic of China Background: The aim of this study was to explore the relationship between age and acute mountain sickness (AMS when subjects are exposed suddenly to high altitude.Methods: A total of 856 young adult men were recruited. Before and after acute altitude exposure, the Athens Insomnia Scale score (AISS was used to evaluate the subjective sleep quality of subjects. AMS was assessed using the Lake Louise scoring system. Heart rate (HR and arterial oxygen saturation (SaO2 were measured.Results: Results showed that, at 500 m, AISS and insomnia prevalence were higher in older individuals. After acute exposure to altitude, the HR, AISS, and insomnia prevalence increased sharply, and the increase in older individuals was more marked. The opposite trend was observed for SaO2. At 3,700 m, the prevalence of AMS increased with age, as did severe AMS, and AMS symptoms (except gastrointestinal symptoms. Multivariate logistic regression analysis showed that age was a risk factor for AMS (adjusted odds ratio [OR] 1.07, 95% confidence interval [CI] 1.01–1.13, P<0.05, as well as AISS (adjusted OR 1.39, 95% CI 1.28–1.51, P<0.001.Conclusion: The present study is the first to demonstrate that older age is an independent risk factor for AMS upon rapid ascent to high altitude among young adult Chinese men, and pre-existing poor subjective sleep quality may be a contributor to increased AMS prevalence in older subjects. Keywords: acute mountain sickness, age, Athens Insomnia Scale, rapid ascent, sleep

  18. The Chaitén rhyolite lava dome: Eruption sequence, lava dome volumes, rapid effusion rates and source of the rhyolite magma

    Science.gov (United States)

    Pallister, John S.; Diefenbach, Angela K.; Burton, William C.; Munoz, Jorge; Griswold, Julia P.; Lara, Luis E.; Lowenstern, Jacob B.; Valenzuela, Carolina E.

    2013-01-01

    and relatively low viscosity enabled rapid magma ascent and high effusion rates during the dome-forming phases of the 2008-2009 eruption.

  19. Radiographic visualization of magma dynamics in an erupting volcano.

    Science.gov (United States)

    Tanaka, Hiroyuki K M; Kusagaya, Taro; Shinohara, Hiroshi

    2014-03-10

    Radiographic imaging of magma dynamics in a volcanic conduit provides detailed information about ascent and descent of magma, the magma flow rate, the conduit diameter and inflation and deflation of magma due to volatile expansion and release. Here we report the first radiographic observation of the ascent and descent of magma along a conduit utilizing atmospheric (cosmic ray) muons (muography) with dynamic radiographic imaging. Time sequential radiographic images show that the top of the magma column ascends right beneath the crater floor through which the eruption column was observed. In addition to the visualization of this magma inflation, we report a sequence of images that show magma descending. We further propose that the monitoring of temporal variations in the gas volume fraction of magma as well as its position in a conduit can be used to support existing eruption prediction procedures.

  20. Rapid changes in magma storage beneath the Klyuchevskoy group of volcanoes inferred from time-dependent seismic tomography

    Science.gov (United States)

    Koulakov, Ivan; Gordeev, Evgeniy I.; Dobretsov, Nikolay L.; Vernikovsky, Valery A.; Senyukov, Sergey; Jakovlev, Andrey; Jaxybulatov, Kayrly

    2013-08-01

    We present the results of time-dependent local earthquake tomography for the Kluchevskoy group of volcanoes in Kamchatka, Russia. We consider the time period from 1999 to 2009, which covers several stages of activity of Kluchevskoy and Bezymianny volcanoes. The results are supported by synthetic tests that recover a common 3D model based on data corresponding to different time windows. Throughout the period, we observe a robust feature below 25 km depth with anomalously high Vp/Vs values (up to 2.2). We interpret this feature as a channel bringing deep mantle materials with high fluid and melt content to the bottom of the crust. This mantle channel directly or indirectly determines the activity of all volcanoes of the Kluchevskoy group. In the crust, we model complex structure that varies over time. During the pre-eruptive period, we detected two levels of potential magma storage: one in the middle crust at 10-12 km depth and one close to the surface just below Kluchevskoy volcano. In 2005, a year of powerful eruptions of Kluchevskoy and Besymiyanny volcanoes, we observe a general increase in Vp/Vs throughout the crust. In the relaxation period following the eruption, the Vp/Vs values are generally low, and no strong anomalous zones in the crust are observed. We propose that very rapid variations in Vp/Vs are most likely due to abrupt changes in the stress and deformation states, which cause fracturing and the active transport of fluids. These fluids drive more fracturing in a positive feedback system that ultimately leads to eruption. We envision the magma reservoirs beneath the Kluchevskoy group as sponge-structured volumes that may quickly change the content of the molten phases as fluids pulse rapidly through the system.

  1. Upper mantle magma storage and transport under a Canarian shield-volcano, Teno, Tenerife (Spain)

    Science.gov (United States)

    Longpré, Marc-Antoine; Troll, Valentin R.; Hansteen, Thor H.

    2008-08-01

    We use clinopyroxene-liquid thermobarometry, aided by petrography and mineral major element chemistry, to reconstruct the magma plumbing system of the late Miocene, largely mafic Teno shield-volcano on the island of Tenerife. Outer rims of clinopyroxene and olivine phenocrysts show patterns best explained by decompression-induced crystallization upon rapid ascent of magmas from depth. The last equilibrium crystallization of clinopyroxene occurred in the uppermost mantle, from ˜20 to 45 km depth. We propose that flexural stresses or, alternatively, thermomechanical contrasts create a magma trap that largely confines magma storage to an interval roughly coinciding with the Moho at ˜15 km and the base of the long-term elastic lithosphere at ˜40 km below sea level. Evidence for shallow magma storage is restricted to the occurrence of a thick vitric tuff of trachytic composition emplaced before the Teno shield-volcano suffered large-scale flank collapses. The scenario developed in this study may help shed light on some unresolved issues of magma supply to intraplate oceanic volcanoes characterized by relatively low magma fluxes, such as those of the Canary, Madeira and Cape Verde archipelagoes, as well as Hawaiian volcanoes in their postshield stage. The data presented also support the importance of progressive magmatic underplating in the Canary Islands.

  2. A review of the ascent and emplacement of granitoid bodies into the crust

    Directory of Open Access Journals (Sweden)

    Katarína Bónová

    2005-03-01

    Full Text Available This paper relates to basic information (i.e. mechanical aspects of ascent, indicators faciliting the discriminability of various ascent styles about the models of ascent and emplacement of granitoid bodies, since the purely mechanical aspect of intrusion of magmas is a fascinating subject and it has generated a considerable controversy over many years. Individual models are demonstrated by world-known occurrences and examples from Western Carpathian’s region. The conditions of magma migration are demonstrated as well.

  3. Mapping the ductile-brittle transition of magma

    Science.gov (United States)

    Kendrick, J. E.; Lavallee, Y.; Dingwell, D. B.

    2010-12-01

    During volcanic unrest, eruptive activity can switch rapidly from effusive to explosive. Explosive eruptions require the fragmentation of magma, in which, if deformation rate is too fast to be relaxed, magma undergoes a transition in deformation mechanism from viscous and/or ductile to brittle. Our knowledge of the deformation mechanisms of magma ascent and eruption remains, to date, poor. Many studies have constrained the glass transition (Tg) of the interstitial melt phase; yet the effect of crystals and bubbles are unresolved. During ascent, magma undergoes P-T changes which induce crystallization, thereby inducing a transition from viscous to ductile and, in some cases, to brittle deformation. Here, we explore the deformation mechanisms of magma involved in the dome-building eruptions and explosions that occurred at Volcán de Colima (Mexico) since 1998. For this purpose, we investigated the rheology of dome lavas, containing 10-45 vol.% rhyolitic interstitial melt, 55-90 vol.% crystals and 5-20 vol.% bubbles. The interstitial glass is characterized by electron microprobe and Tg is characterized using a differential scanning calorimeter and a dilatometer. The population of crystals (fraction, shape and size distribution) is described optically and quantified using ImageJ and AMOCADO. The rheological effects of crystals on the deformation of magmas are constrained via acoustic emission (AE) and uniaxial deformation experiments at temperature above Tg (900-980 °C) and at varied applied stresses (and strain rates: 10-6 to 10-2 s-1). The ratio of ductile to brittle deformation across the ductile-brittle transition is quantified using the output AE energy and optical and SEM analysis. We find that individual dome lava sample types have different mechanical responses, yielding a significant range of measured strain rates under a given temperature and applied stress. Optical analysis suggests that at low strain rates, ductile deformation is mainly controlled by the

  4. Change in Magma Dynamics at Okataina Rhyolite Caldera revealed by Plagioclase Textures and Geochemistry

    Science.gov (United States)

    Shane, P. A. R.

    2015-12-01

    A fundamental reorganization of magma dynamics at Okataina volcano, New Zealand, occurred at 26 ka involving a change from smaller volume, high-temperature rhyodacite magmas to a lower eruptive tempo of larger volume, low-temperature, rhyolite magmas. Zircon studies demonstrate the presence of a periodically active, long-lived (100,000 yr) magmatic reservoir. However, there is little correlation between periods of zircon crystallization and eruption events. In contrast, the changing magmatic dynamics is revealed in plagioclase growth histories. Crystals from the ~0.7 ka Kaharoa eruption are characterized by resorbed cores displaying a cellular-texture of high-An (>40) zones partially replaced by low-An (cellular texture of variable An content (An 40-50). The crystals display step-wise re-growth of successively higher An, Fe, Mg and Ti content, consistent with progressive mafic recharge. Two crystal groups are distinguished by trace element chemistry indicating growth in separate melts and co-occurrence via magma-mingling. The contrasting zoning patterns in plagioclase correspond to the evolutionary history of magmatism at Okataina. Emptying of the magma reservoir following caldera eruption at 46 ka reduced barriers to mafic magma ascent. This is recorded by the frequent resorption and recharge episodes in Hauparu crystals. Subsequent re-development of a more silicic reservoir zone (post-26 ka) dampened thermal and mass perturbations, resulting in simpler growth histories of the Kaharoa crystals. The plagioclase lack features associated with rapid decompression events that are common in andesite systems.

  5. Outgassing from Open and Closed Magma Foams

    Directory of Open Access Journals (Sweden)

    Felix W. von Aulock

    2017-06-01

    Full Text Available During magma ascent, bubbles nucleate, grow, coalesce, and form a variably permeable porous network. The reorganization, failing and sealing of bubble walls may contribute to the opening and closing of the volcanic system. In this contribution we cause obsidian to nucleate and grow bubbles to high gas volume fraction at atmospheric pressure by heating samples to 950°C for different times and we image the growth through a furnace. Following the experiment, we imaged the internal pore structure of selected samples in 3D and then dissected for analysis of textures and dissolved water content remnant in the glass. We demonstrate that in these high viscosity systems, during foaming and subsequent foam-maturation, bubbles near a free surface resorb via diffusion to produce an impermeable skin of melt around a foam. The skin thickens non-linearly through time. The water concentrations at the outer and inner skin margins reflect the solubility of water in the melt at the partial pressure of water in atmospheric and water-rich bubble conditions, respectively. In this regime, mass transfer of water out of the system is diffusion limited and the sample shrinks slowly. In a second set of experiments in which we polished off the skin of the foamed samples and placed them back in the furnace to allow open system outgassing, we observe rapid sample contraction and collapse of the connected pore network under surface tension as the system efficiently outgasses. In this regime, mass transfer of water is permeability limited. We conclude that diffusion-driven skin formation can efficiently seal connectivity in foams. When rupture of melt film around gas bubbles (i.e., skin removal occurs, then rapid outgassing and consequent foam collapse modulate gas pressurization in the vesiculated magma. The mechanisms described here are relevant to the evolution of pore network heterogeneity in permeable magmas.

  6. From a long-lived upper-crustal magma chamber to rapid porphyry copper emplacement: Reading the geochemistry of zircon crystals at Bajo de la Alumbrera (NW Argentina)

    Science.gov (United States)

    Buret, Yannick; von Quadt, Albrecht; Heinrich, Christoph; Selby, David; Wälle, Markus; Peytcheva, Irena

    2016-09-01

    cathodoluminescence imaging reveals the presence of intermediate low luminescent (dark) growth zones in many crystals from all intrusions, characterised by anomalously high Th, U and REE concentrations and transient excursions in trace element ratios. A return to the same fractionation trend after this excursion excludes external compositional forcing such as magma mixing. Instead we interpret the ;dark-zones; to record zircon crystallisation during a transient event of rapid growth that resulted from mafic magma injection into the base of the magma chamber, releasing a CO2-rich vapour phase into the dacitic crystal mush. We propose that this vapour phase then migrated upwards to the apical part of the magma chamber from where it was expelled, together with successive batches of magma, to form the porphyry copper deposit within a short time-span of less than a few 10,000 years. The short duration of host rock emplacement, hydrothermal alteration and mineralisation presented in this study provides critical constraints on fluid storage in magma chambers and the genesis of large porphyry copper deposits.

  7. Source-Related Chemical And Isotopic Heterogeneities In Granitoid Magmas

    Science.gov (United States)

    Helps, P. A.; Clemens, J. D.; Petford, N.

    2004-12-01

    A survey of a large number of post-orogenic plutons, shows that regional-scale, intraplutonic isotope heterogeneities (initial 87Sr/86Sr and/or eNd) are common in crustally derived granitic rocks. This is expected since the source materials, from which the granitic magmas were created by partial melting, are themselves heterogeneous, especially from metasedimentary sources. If we accept models of granite emplacement involving the rapid ascent of magma along dykes, there must be potential for the preservation of source-inherited chemical and isotopic heterogeneities. However, their preservation will depend on the extent of post-emplacement homogenisation processes, such as diffusion and convective mixing, in the magma chambers. Micro-sampling of feldspar crystals in granites has revealed complex internal Sr and Nd isotope variations thought to reveal subtle variations in the isotopic composition of the melt from which particular zones crystallised. We therefore have evidence of both macro-scale (regional) and micro-scale isotopic variation within granitic magmas. What is unknown is the extent of chemical and isotopic variation on the meso-scale. We have obtained high-precision geochemical and isotopic (Sr, Nd, and O) analyses for spatially well constrained samples, from two granitic intrusions from the UK, to study the scales over which isotope heterogeneities are preserved, and the maximum volumes of magma over which isotope and elemental homogenisation may have been achieved. These data provide important constraints on the physical and chemical characteristics of processes that occur during magma genesis, ascent, and emplacement. The Criffell pluton (SW Scotland) has previously been shown to be isotopically heterogeneous on the regional scale, with initial 87Sr/86Sr varying from 0.70521 to 0.70728, generally increasing inward, towards the centre of the pluton. This was interpreted as representing isotopic heterogeneity within the source region. Our study has

  8. Steepest Ascent Tariff Reform

    DEFF Research Database (Denmark)

    Raimondos-Møller, Pascalis; Woodland, Alan

    2014-01-01

    The policy reform literature is primarily concerned with the construction of reforms that yield welfare gains. By contrast, this paper’s contribution is to develop a theoretical concept for which the focus is upon the sizes of welfare gains accruing from policy reforms rather than upon their signs....... In undertaking this task, and by focusing on tariff reforms, we introduce the concept of a steepest ascent policy reform, which is a locally optimal reform in the sense that it achieves the highest marginal gain in utility of any feasible local reform. We argue that this reform presents itself as a natural...... benchmark for the evaluation of the welfare effectiveness of other popular tariff reforms such as the proportional tariff reduction and the concertina rules, since it provides the maximal welfare gain of all possible local reforms. We derive properties of the steepest ascent tariff reform, construct...

  9. Steepest Ascent Tariff Reforms

    DEFF Research Database (Denmark)

    Raimondos-Møller, Pascalis; Woodland, Alan D.

    2006-01-01

    a theoretical concept where the focus is upon the size of welfare gains accruing from tariff reforms rather than simply with the direction of welfare effects that has been the concern of theliterature.JEL code: F15.Keywords: Steepest ascent tariff reforms; piecemeal tariff policy; welfare; market access; small...... for the evaluation of the welfare effectiveness of other well known tariff reform rules, as e.g. the proportional and the concertina rules. We develop the properties of this tariff reform, characterize the sources of the potential welfare gains from tariff reform, use it to establish conditions under which some...... existing reforms are locally optimal, provide geometric illustrations and compare welfare effectiveness of reforms using numerical examples. Moreover, being a general concept, we apply it to the issue of market access and examine its implications. Overall, the paper's contribution lies in presenting...

  10. Two populations of amphibole in dacite magmas at Volcan Aucanquilcha, Chile: A case for rapid and repeated mixing of a tiered magmatic system

    Science.gov (United States)

    Klemetti, E. W.; Grunder, A. L.

    2006-12-01

    Magmatic amphibole is a ubiquitous phase in most dacitic magmas in continental arc systems. Amphibole can react quickly to changes in P, T and water content caused by processes such as underplating of new magma, degassing, ascension and mixing of magma. This allows amphibole to be a valuable and sensitive barometer, thermometer and hygrometer in silicic magmatic systems. It can be especially suitable for disentangling the potential geometry of subvolcanic systems and limiting the timescales that these processes can occur. Volcán Aucanquilcha (Chile) is a Quaternary volcano that has erupted dacite lavas (63-67 wt% SiO2) that contain two populations of amphibole during its entire 1 M.y. eruptive history. The amphibole is found as phenocrysts of hornblende and pargasite that range in size from 0.5 mm to 1 cm. The amphibole populations exhibit a variety of textures: (1) thin opacite rims; (2) thick reaction rims of pyroxene, plagioclase and opaque oxides; (3) cored" with other phases such as plagioclase, biotite and anhydride; and (4) unrimmed. Representative electron microprobe analyses of amphibole find that very few of the phenocrysts are compositionally zoned, i.e., the two populations are not pargasite cores with hornblende rims. The presence of two populations of amphibole such as those found at Aucanquilcha appears to be rare; there are documented occurrences of two amphibole populations found in lavas from continental-arc related volcanoes. Sajama, Parinacota and Porquesa in Central Andes of Chile exhibit the same two populations of amphibole phenocrysts as Aucanquilcha. Evidence from Aucanquilcha suggest that the populations of amphibole crystallized at different pressures: 0.5-2 kb and 3-6 kb. Textures of the amphibole imply that the processes that mix the amphibole occur quickly before eruption, possibly in a timescales of days. The constant presence of these amphibole in all Aucanquilcha lavas indicate that the processes that juxtapose pargasite and

  11. Complex subvolcanic magma plumbing system of an alkali basaltic maar-diatreme volcano (Elie Ness, Fife, Scotland)

    Science.gov (United States)

    Gernon, T. M.; Upton, B. G. J.; Ugra, R.; Yücel, C.; Taylor, R. N.; Elliott, H.

    2016-11-01

    Alkali basaltic diatremes such as Elie Ness (Fife, Scotland) expose a range of volcanic lithofacies that points to a complex, multi-stage emplacement history. Here, basanites contain phenocrysts including pyrope garnet and sub-calcic augites from depths of 60 km. Volcanic rocks from all units, pyroclastic and hypabyssal, are characterised by rare earth element (REE) patterns that show continuous enrichment from heavy REE (HREE) to light REE (LREE), and high Zr/Y that are consistent with retention of garnet in the mantle source during melting of peridotite in a garnet lherzolite facies. Erupted garnets are euhedral and unresorbed, signifying rapid ascent through the lithosphere. The magmas also transported abundant pyroxenitic clasts, cognate with the basanite host, from shallower depths ( 35-40 km). These clasts exhibit wide variation in texture, mode and mineralogy, consistent with growth from a range of compositionally diverse melts. Further, clinopyroxene phenocrysts from both the hypabyssal and pyroclastic units exhibit a very wide compositional range, indicative of polybaric fractionation and magma mixing. This is attributed to stalling of earlier magmas in the lower crust - principally from 22 to 28 km - as indicated by pyroxene thermobarometry. Many clinopyroxenes display chemical zoning profiles, occasionally with mantles and rims of higher magnesium number (Mg#) suggesting the magmas were mobilised by juvenile basanite magma. The tuffs also contain alkali feldspar megacrysts together with Fe-clinopyroxene, zircon and related salic xenoliths, of the 'anorthoclasite suite' - inferred to have crystallised at upper mantle to lower crustal depths from salic magma in advance of the mafic host magmas. Despite evidence for entrainment of heterogeneous crystal mushes, the rapidly ascending melts experienced negligible crustal contamination. The complex association of phenocrysts, megacrysts and autoliths at Elie Ness indicates thorough mixing in a dynamic system

  12. Compressible magma flow in a two-dimensional elastic-walled dike

    NARCIS (Netherlands)

    Woods, A.W.; Bokhove, Onno; de Boer, A; Hill, B.E.

    2006-01-01

    The ascent of magma to the Earth's surface is commonly modeled by assuming a fixed dike or flow geometry from a deep subsurface reservoir to the surface. In practice, however, this flow geometry is produced by deformation of the crust by ascending overpressured magma. Here, we explore how this

  13. Contrasting plagioclase textures and geochemistry in response to magma dynamics in an intra-caldera rhyolite system, Okataina volcano

    Science.gov (United States)

    Shane, Phil

    2015-05-01

    The changing magmatic dynamics of the rhyolite caldera volcano, Okataina Volcanic Centre, New Zealand, is revealed in plagioclase growth histories. Crystals from the ~ 0.7 ka Kaharoa eruption are characterized by resorbed cores displaying a cellular texture of high-An (> 40) zones partially replaced by low-An (cellular texture of variable An content (An40-50). The crystals display step-wise regrowth of successively higher An, Fe, Mg, and Ti content, consistent with progressive mafic recharge. Two crystal groups are distinguished by trace element chemistry, indicating growth in separate melts and co-occurrence via magma mingling. For plagioclase in both eruption deposits, partition coefficients (D) estimated from crystal rim-groundmass glass analyses, produce melt compositions similar to the array of rock and glass compositions erupted and are consistent with the processes of fractional crystallization and recharge. However, D values estimated from some published formulations based on An content and temperature produce unrealistic melts. The contrasting zoning patterns in plagioclase correspond to the evolutionary history of magmatism at Okataina. Emptying of the magma reservoir following caldera eruption at 46 ka reduced barriers to mafic magma ascent. This is recorded by the frequent resorption and recharge episodes in Hauparu crystals. Subsequent redevelopment of a more silicic reservoir zone (post-26 ka) dampened thermal and mass perturbations, resulting in simpler growth histories of the Kaharoa crystals. The plagioclase lack features associated with rapid decompression events that are common in andesite systems. This reflects the rapid ascent of the rhyolite magmas and lack of precursory eruptions that could decompressed the system.

  14. Segregating gas from melt: an experimental study of the Ostwald ripening of vapor bubbles in magmas

    Science.gov (United States)

    Lautze, Nicole C.; Sisson, Thomas W.; Mangan, Margaret T.; Grove, Timothy L.

    2011-01-01

    Diffusive coarsening (Ostwald ripening) of H2O and H2O-CO2 bubbles in rhyolite and basaltic andesite melts was studied with elevated temperature–pressure experiments to investigate the rates and time spans over which vapor bubbles may enlarge and attain sufficient buoyancy to segregate in magmatic systems. Bubble growth and segregation are also considered in terms of classical steady-state and transient (non-steady-state) ripening theory. Experimental results are consistent with diffusive coarsening as the dominant mechanism of bubble growth. Ripening is faster in experiments saturated with pure H2O than in those with a CO2-rich mixed vapor probably due to faster diffusion of H2O than CO2 through the melt. None of the experimental series followed the time1/3 increase in mean bubble radius and time-1 decrease in bubble number density predicted by classical steady-state ripening theory. Instead, products are interpreted as resulting from transient regime ripening. Application of transient regime theory suggests that bubbly magmas may require from days to 100 years to reach steady-state ripening conditions. Experimental results, as well as theory for steady-state ripening of bubbles that are immobile or undergoing buoyant ascent, indicate that diffusive coarsening efficiently eliminates micron-sized bubbles and would produce mm-sized bubbles in 102–104 years in crustal magma bodies. Once bubbles attain mm-sizes, their calculated ascent rates are sufficient that they could transit multiple kilometers over hundreds to thousands of years through mafic and silicic melt, respectively. These results show that diffusive coarsening can facilitate transfer of volatiles through, and from, magmatic systems by creating bubbles sufficiently large for rapid ascent.

  15. Timescales of mixing and storage for Keanakāko`i Tephra magmas (1500-1820 C.E.), Kīlauea Volcano, Hawai`i

    Science.gov (United States)

    Lynn, Kendra J.; Garcia, Michael O.; Shea, Thomas; Costa, Fidel; Swanson, Donald A.

    2017-09-01

    The last 2500 years of activity at Kīlauea Volcano (Hawai`i) have been characterized by centuries-long periods dominated by either effusive or explosive eruptions. The most recent period of explosive activity produced the Keanakāko`i Tephra (KT; ca. 1500-1820 C.E.) and occurred after the collapse of the summit caldera (1470-1510 C.E.). Previous studies suggest that KT magmas may have ascended rapidly to the surface, bypassing storage in crustal reservoirs. The storage conditions and rapid ascent hypothesis are tested here using chemical zoning in olivine crystals and thermodynamic modeling. Forsterite contents (Fo; [Mg/(Mg + Fe) × 100]) of olivine core and rim populations are used to identify melt components in Kīlauea's prehistoric (i.e., pre-1823) plumbing system. Primitive (≥Fo88) cores occur throughout the 300+ years of the KT period; they originated from mantle-derived magmas that were first mixed and stored in a deep crustal reservoir. Bimodal olivine populations (≥Fo88 and Fo83-84) record repeated mixing of primitive magmas and more differentiated reservoir components shallower in the system, producing a hybrid composition (Fo85-87). Phase equilibria modeling using MELTS shows that liquidus olivine is not stable at depths >17 km. Thus, calculated timescales likely record mixing and storage within the crust. Modeling of Fe-Mg and Ni zoning patterns (normal, reverse, complex) reveal that KT magmas were mixed and stored for a few weeks to several years before eruption, illustrating a more complex storage history than direct and rapid ascent from the mantle as previously inferred for KT magmas. Complexly zoned crystals also have smoothed compositional reversals in the outer 5-20 µm rims that are out of Fe-Mg equilibrium with surrounding glasses. Diffusion models suggest that these rims formed within a few hours to a few days, indicating that at least one additional, late-stage mixing event may have occurred shortly prior to eruption. Our study

  16. Rapid magma evolution constrained by zircon petrochronology and 40Ar/39Ar sanidine ages for the Huckleberry Ridge Tuff, Yellowstone, USA

    DEFF Research Database (Denmark)

    Rivera, Tiffany; Storey, Michael; Schmitz, Mark

    2014-01-01

    Understanding the time scales of magmatic differentiation, storage, and eruption of large volume silicic magmas is a primary goal of igneous petrology. Within the Huckleberry Ridge Tuff (HRT; Idaho, USA), representing the earliest and largest caldera-forming eruption associated with Yellowstone...... of single zircon crystals demonstrates an absence of pre-Pleistocene xenocrysts, but reveals the presence of antecrysts recycled from pre-caldera rhyolites in the HRT magma. The petrochronologic interpretation of autocrystic zircon thermal, chemical, and temporal characteristics suggests that HRT member B...

  17. The effect of nonlinear decompression history on H2O/CO2 vesiculation in rhyolitic magmas

    Science.gov (United States)

    Su, Yanqing; Huber, Christian

    2017-04-01

    Magma ascent rate is one of the key parameters that control volcanic eruption style, tephra dispersion, and volcanic atmospheric impact. Many methods have been employed to investigate the magma ascent rate in volcanic eruptions, and most rely on equilibrium thermodynamics. Combining the mixed H2O-CO2 solubility model with the diffusivities of both H2O and CO2 for normal rhyolitic melt, we model the kinetics of H2O and CO2 in rhyolitic eruptions that involve nonlinear decompression rates. Our study focuses on the effects of the total magma ascent time, the nonlinearity of decompression paths, and the influence of different initial CO2/H2O content on the posteruptive H2O and CO2 concentration profiles around bubbles within the melt. Our results show that, under most circumstances, volatile diffusion profiles do not constrain a unique solution for the decompression rate of magmas during an eruption, but, instead, provide a family of decompression paths with a well-defined trade-off between ascent time and nonlinearity. An important consequence of our analysis is that the common assumption of a constant decompression rate (averaged value) tends to underestimate the actual magma ascent time.

  18. Degassing of basaltic magma: decompression experiments and implications for interpreting the textures of volcanic rocks

    Science.gov (United States)

    Le Gall, Nolwenn; Pichavant, Michel; Cai, Biao; Lee, Peter; Burton, Mike

    2017-04-01

    Decompression experiments were performed to simulate the ascent of basaltic magma, with the idea of approaching the textural features of volcanic rocks to provide insights into degassing processes. The experiments were conducted in an internally heated pressure vessel between NNO-1.4 and +0.9. H2O-only (4.9 wt%) and H2O-CO2-bearing (0.71-2.45 wt% H2O, 818-1094 ppm CO2) melts, prepared from Stromboli pumice, were synthesized at 1200°C and 200 MPa, continuously decompressed between 200 and 25 MPa at a rate of either 39 or 78 kPa/s (or 1.5 and 3 m/s, respectively), and rapidly quenched. Run products were characterized both texturally (by X-ray computed tomography and scanning electron microscopy) and chemically (by IR spectroscopy and electron microprobe analysis), and then compared with products from basaltic Plinian eruptions and Stromboli paroxysms (bubble textures, glass inclusions). The obtained results demonstrate that textures are controlled by the kinetics of nucleation, growth, coalescence and outgassing of the bubbles, as well as by fragmentation, which largely depend on the presence of CO2 in the melt and the achievement in chemical equilibrium. Textures of the H2O-only melts result from two nucleation events, the first at high pressure (200 X-ray imaging. The obtained 4D (3D + time) data will help us refine our understanding of magma ascent processes. This experimental programme requires first technology adaptation and development, which is in progress.

  19. Hydrogen isotope investigation of amphibole and glass in dacite magmas erupted in 1980-1986 and 2005 at Mount St. Helens, Washington

    Science.gov (United States)

    Underwood, S.J.; Feeley, T.C.; Clynne, M.A.

    2013-01-01

    In active, shallow, sub-volcanic magma conduits the extent of the dehydrogenation–oxidation reaction in amphibole phenocrysts is controlled by energetic processes that cause crystal lattice damage or conditions that increase hydrogen diffusivity in magmatic phases. Amphibole phenocrysts separated from dacitic volcanic rocks erupted from 1980 to 1986 and in 2005 at Mount St. Helens (MSH) were analyzed for δD, water content and Fe3+/Fe2+, and fragments of glassy groundmass were analyzed for δD and water content. Changes in amphibole δD values through time are evaluated within the context of carefully observed volcanic eruption behavior and published petrological and geochemical investigations. Driving forces for amphibole dehydrogenation include increase in magma oxygen fugacity, decrease in amphibole hydrogen fugacity, or both. The phenocryst amphibole (δD value c. –57‰ and 2 wt % H2O) in the white fallout pumice of the May 18, 1980 plinian eruptive phase is probably little modified during rapid magma ascent up an ∼7 km conduit. Younger volcanic rocks incorporate some shallowly degassed dacitic magma from earlier pulses, based on amphibole phenocryst populations that exhibit varying degrees of dehydrogenation. Pyroclastic rocks from explosive eruptions in June–October 1980 have elevated abundances of mottled amphibole phenocrysts (peaking in some pyroclastic rocks erupted on July 22, 1980), and extensive amphibole dehydrogenation is linked to crystal damage from vesiculation and pyroclastic fountain collapse that increased effective hydrogen diffusion in amphibole. Multiple amphibole δD populations in many 1980 pyroclastic rocks combined with their groundmass characteristics (e.g. mixed pumice textures) support models of shallow mixing prior to, or during, eruption as new, volatile-rich magma pulses blended with more oxidized, degassed magma. Amphibole dehydrogenation is quenched at the top surface of MSH dacite lava lobes, but the diversity in the

  20. Meniscus ascent by thrips (Thysanoptera).

    Science.gov (United States)

    Ortega-Jiménez, Victor Manuel; Arriaga-Ramirez, Sarahi; Dudley, Robert

    2016-09-01

    Meniscus climbing using a fixed body posture has been well documented for various aquatic and neustonic insects, but is not known from small flying insects that inadvertently become trapped on water surfaces. Here, we show that thrips (order Thysanoptera) can ascend a meniscus by arching their non-wetting bodies to translate head-first and upward along a water surface; if initially oriented backwards, they can turn by 180° to ascend head-first, and climb upward on a surrounding boundary. Using variable-concentration sucrose solutions, we show that translational and climbing speeds during meniscus ascent vary inversely with fluid viscosity. Becoming trapped in water is a frequent event for flying insects, and given that most of them are very small, dedicated behaviours to escape water may be commonplace among pterygotes. © 2016 The Author(s).

  1. Rapid pre-eruptive thermal rejuvenation in a large silicic magma body: the case of the Masonic Park Tuff, Southern Rocky Mountain volcanic field, CO, USA

    Science.gov (United States)

    Sliwinski, J. T.; Bachmann, O.; Dungan, M. A.; Huber, C.; Deering, C. D.; Lipman, P. W.; Martin, L. H. J.; Liebske, C.

    2017-05-01

    Determining the mechanisms involved in generating large-volume eruptions (>100 km3) of silicic magma with crystallinities approaching rheological lock-up ( 50 vol% crystals) remains a challenge for volcanologists. The Cenozoic Southern Rocky Mountain volcanic field, in Colorado and northernmost New Mexico, USA, produced ten such crystal-rich ignimbrites within 3 m.y. This work focuses on the 28.7 Ma Masonic Park Tuff, a dacitic ( 62-65 wt% SiO2) ignimbrite with an estimated erupted volume of 500 km3 and an average of 45 vol% crystals. Near-absence of quartz, titanite, and sanidine, pronounced An-rich spikes near the rims of plagioclase, and reverse zoning in clinopyroxene record the reheating (from 750 to >800 °C) of an upper crustal mush in response to hotter recharge from below. Zircon U-Pb ages suggest prolonged magmatic residence, while Yb/Dy vs temperature trends indicate co-crystallization with titanite which was later resorbed. High Sr, Ba, and Ti concentrations in plagioclase microlites and phenocryst rims require in-situ feldspar melting and concurrent, but limited, mass addition provided by the recharge, likely in the form of a melt-gas mixture. The larger Fish Canyon Tuff, which erupted from the same location 0.7 m.y. later, also underwent pre-eruptive reheating and partial melting of quartz, titanite, and feldspars in a long-lived upper crustal mush following the underplating of hotter magma. The Fish Canyon Tuff, however, records cooler pre-eruptive temperatures ( 710-760 °C) and a mineral assemblage indicative of higher magmatic water contents (abundant resorbed sanidine and quartz, euhedral amphibole and titanite, and absence of pyroxene). These similar pre-eruptive mush-reactivation histories, despite differing mineral assemblages and pre-eruptive temperatures, indicate that thermal rejuvenation is a key step in the eruption of crystal-rich silicic volcanics over a wide range of conditions.

  2. The origin of plagioclase phenocrysts in basalts from continental monogenetic volcanoes of the Kaikohe-Bay of Islands field, New Zealand: implications for magmatic assembly and ascent

    Science.gov (United States)

    Coote, Alisha; Shane, Phil; Stirling, Claudine; Reid, Malcolm

    2018-02-01

    Late Quaternary, porphyritic basalts erupted in the Kaikohe-Bay of Islands area, New Zealand, provide an opportunity to explore the crystallization and ascent history of small volume magmas in an intra-continental monogenetic volcano field. The plagioclase phenocrysts represent a diverse crystal cargo. Most of the crystals have a rim growth that is compositionally similar to groundmass plagioclase ( An65) and is in equilibrium with the host basalt rock. The rims surround a resorbed core that is either less calcic ( An20-45) or more calcic (> An70), having crystallized in more differentiated or more primitive melts, respectively. The relic cores, particularly those that are less calcic (< An45), have 87Sr/86Sr ratios that are either mantle-like ( 0.7030) or crustal-like ( 0.7040 to 0.7060), indicating some are antecrysts formed in melts fractionated from plutonic basaltic forerunners, while others are true xenocrysts from greywacke basement and/or Miocene arc volcanics. It is envisaged that intrusive basaltic forerunners produced a zone where various degrees of crustal assimilation and fractional crystallization occurred. The erupted basalts represent mafic recharge of this system, as indicated by the final crystal rim growths around the entrained antecrystic and xenocrystic cargo. The recharge also entrained cognate gabbros that occur as inclusions, and produced mingled groundmasses. Multi-stage magmatic ascent and interaction is indicated, and is consistent with the presence of a partial melt body in the lower crust detected by geophysical methods. This crystallization history contrasts with traditional concepts of low-flux basaltic systems where rapid ascent from the mantle is inferred. From a hazards perspective, the magmatic system inferred here increases the likelihood of detecting eruption precursor phenomena such as seismicity, degassing and surface deformation.

  3. Rheology of Magma at Tungurahua, from the Magma Chamber to the Eruption

    Science.gov (United States)

    Hanson, J. B.; Goldstein, F.; Lavallee, Y.; Kueppers, U.; Hess, K.; Castro, J. M.; Dingwell, D. B.

    2010-12-01

    Tungurahua volcano (Ecuador) is one of the most active volcanoes in the world, and since 1999 has posed a large threat to the local population as well as to air traffic in South America. Notable explosive eruptions have generated pyroclastic density currents in July and August 2006, February 2008 and May 2010. The August 2006 Plinian eruption triggered 10s of pyroclastic density currents. Markedly, the activity terminated with the effusion of a 3-km long lava flow. Rheological behaviour of ascending magma is a chief determinant of eruptive style. The viscosity of magma is strongly dependent on temperature and chemical composition of the melt; moreover, it is heavily influenced by the presence of crystals and bubbles, inducing strain rate dependence. Rheologically, crystallization is especially important as it selectively modifies the composition of the interstitial melt while adding rigid particles. The varied eruptive style at Tungurahua represents an excellent opportunity to characterize the evolution of the rheological properties of the magma as it ascended and crystallized. Here, we combine geothermobarometry and rheology measurements using a concentric cylinder rheometer, a dilatometer, a uniaxial deformation press and a fragmentation apparatus to map the flow behavior of magma through its ascent from the magma chamber until eruption. The temperature conditions for the progression of the eruption have been bracketed using two methods. First, a combination of pyroxene geothermobarometers helped constrain conditions in the magma chamber to ca. 1025 °C and ~700 MPa. Second, differential scanning calorimetry was used to estimate the glass transition temperature (~730°C); the temperature at which viscous behavior ceased. Chemically, eruptive products during 2006-2008 have been highly homogeneous in terms of bulk composition(57% SiO2). It follows that the rheological properties of the crystal-free magma present in the reservoir before onset of crystallization

  4. Effects of magma and conduit conditions on transitions between effusive and explosive activity: a numerical modeling approach

    Science.gov (United States)

    Carr, B. B.; De'Michieli Vitturi, M.; Clarke, A. B.; Voight, B.

    2013-12-01

    Transitions between effusive and explosive eruptions, common at silicic volcanoes, can occur between distinct eruptive episodes or can occur as changes between effusive and explosive phases within a single episode. The precise causes of these transitions are difficult to determine due to the multitude of mechanisms and variables that can influence fragmentation thresholds. Numerical modeling of magma ascent within a volcanic conduit allows the influence of key variables to be extensively tested. We study the effect of different variables on the mass eruption rate at the vent using a conservative, 1-D, two-phase, steady-state model that allows for lateral gas loss at shallow depths. Several fragmentation criteria are also tested. We are able to generate a number of regime diagrams for a variety of magma and conduit conditions that constrain transitions from effusive to explosive episodes. We show that a transition to explosive activity can occur without changes in the bulk chemistry, crystal volume fraction, or gas mass fraction of the magma. Eruptive style can be controlled by the pressure gradient within the conduit caused by either overpressure in the chamber or varying lava dome size at the vent. Specific results are sensitive to both magma temperature and conduit geometry. It is important that these variables are well constrained when applying this model to different volcanic systems. We apply our model to the recent activity at Merapi Volcano in Indonesia. We constrain model input and output parameters using current petrologic, seismic, and geodetic studies of the Merapi system, and vary critical parameters over reasonable ranges as documented in the literature. Our model is able to reproduce eruption rates observed during both the 2006 effusive and 2010 explosive/effusive eruptions. Our modeling suggests that a combination of chamber overpressure, increased volatile content, and decreased crystal content due to the voluminous injection of new magma into the

  5. Pressure evolution in shallow magma chambers upon buoyancy-driven replenishment

    Science.gov (United States)

    Papale, P.; Montagna, C. P.; Longo, A.

    2017-03-01

    The invasion of active magma chambers by primitive magma of deeper provenance is a frequent occurrence in volcanic systems, and it is commonly associated with pressurization. Chamber replenishment is driven by pressure and buoyancy forces that cause magma ascent towards shallow depths. We examine the end-member case of pure buoyancy-driven (natural) convection in crustal reservoirs deriving from the presence of degassed, dense magma at shallow level, that can originate a gravitational instability. Space-time-dependent numerical simulations of magma dynamics in composite underground systems reveal highly nonlinear pressure evolution dominated by decompression at shallow depths. This counterintuitive result originates from the compressible nature of multiphase magmas and their complex convection and mixing dynamics. Shallow magma chamber decompression on replenishment is favored by large volatile contents of the uprising magma, resulting in large density contrasts among the resident and the incoming components. These results show that the intuitive concept of magma chamber pressurization upon replenishment may not always hold in real situations dominated by buoyancy, and provide new perspectives for the interpretation of geophysical records at active volcanoes.Plain Language SummaryA common process at active volcanoes worldwide is the arrival of magma from depth of tens of kilometers into shallower (depths of some km) reservoirs ("magma chambers"), containing themselves magma that can be different in terms of gas content and composition. We present numerical simulations that describe this process, with particular reference to the Campi Flegrei volcano in Italy. Our results show that, depending on the specific conditions and the gas contents of the two magma types, this process can lead to a decrease in pressure of the shallow chamber. When interpreting ground deformation signals, very often magma rise toward shallow depths is linked to inflation, caused by pressure

  6. The Meaning of "Magma"

    Science.gov (United States)

    Bartley, J. M.; Glazner, A. F.; Coleman, D. S.

    2016-12-01

    Magma is a fundamental constituent of the Earth, and its properties, origin, evolution, and significance bear on issues ranging from volcanic hazards to planetary evolution. Unfortunately, published usages indicate that the term "magma" means distinctly different things to different people and this can lead to miscommunication among Earth scientists and between scientists and the public. Erupting lava clearly is magma; the question is whether partially molten rock imaged at depth and too crystal-rich to flow should also be called magma. At crystal fractions > 50%, flow can only occur via crystal deformation and solution-reprecipitation. As the solid fraction increases to 90% or more, the material becomes a welded crystal framework with melt in dispersed pores and/or along grain boundaries. Seismic images commonly describe such volumes of a few % melt as magma, yet the rheological differences between melt-rich and melt-poor materials make it vital not to confuse a large rock volume that contains a small melt fraction with melt-rich material. To ensure this, we suggest that "magma" be reserved for melt-rich materials that undergo bulk fluid flow on timescales consonant with volcanic eruptions. Other terms should be used for more crystal-rich and largely immobile partially molten rock (e.g., "crystal mush," "rigid sponge"). The distinction is imprecise but useful. For the press, the public, and even earth scientists who do not study magmatic systems, "magma" conjures up flowing lava; reports of a large "magma" body that contains a few percent melt can engender the mistaken perception of a vast amount of eruptible magma. For researchers, physical processes like crystal settling are commonly invoked to account for features in plutonic rocks, but many such processes are only possible in melt-rich materials.

  7. Volatile Evolution of Magma Associated with the Solchiaro Eruption in the Phlegrean Volcanic District (Italy)

    Science.gov (United States)

    Esposito, R.; Bodnar, R. J.; de Vivo, B.; Lima, A.; Fedele, L.; Shimizu, N.; Hunter, J.

    2009-12-01

    assuming a pressure gradient of 270 bar/Km. Pressures of crystallization of intermediate melts correlate with magma evolution associated with FCA processes. At the moment of the eruption, melt saturated in volatiles at 8 km continuously lost volatiles during its rapid ascent to the surface. Glass embayments and glass at the crystal/melt interface shows higher volatiles (especially CO2), compared to highly vesiculated matrix glass. Magma compositions relative to some MIs hosted in forsterite-rich olivine show extremely low contents of both K2O and Na2O and high CaO (0.5, 1.90 and 13.89 wt% respectively). Similar compositions have not been previously reported from the PVD but are characteristic of the Aeolian Arc.

  8. Crew Exploration Vehicle Ascent Abort Overview

    Science.gov (United States)

    Davidson, John B., Jr.; Madsen, Jennifer M.; Proud, Ryan W.; Merritt, Deborah S.; Sparks, Dean W., Jr.; Kenyon, Paul R.; Burt, Richard; McFarland, Mike

    2007-01-01

    One of the primary design drivers for NASA's Crew Exploration Vehicle (CEV) is to ensure crew safety. Aborts during the critical ascent flight phase require the design and operation of CEV systems to escape from the Crew Launch Vehicle and return the crew safely to the Earth. To accomplish this requirement of continuous abort coverage, CEV ascent abort modes are being designed and analyzed to accommodate the velocity, altitude, atmospheric, and vehicle configuration changes that occur during ascent. The analysis involves an evaluation of the feasibility and survivability of each abort mode and an assessment of the abort mode coverage. These studies and design trades are being conducted so that more informed decisions can be made regarding the vehicle abort requirements, design, and operation. This paper presents an overview of the CEV, driving requirements for abort scenarios, and an overview of current ascent abort modes. Example analysis results are then discussed. Finally, future areas for abort analysis are addressed.

  9. Discovering Mathematics with Magma Reducing the Abstract to the Concrete

    CERN Document Server

    Bosma, Wieb

    2006-01-01

    With a design based on the ontology and semantics of algebra, Magma enables users to rapidly formulate and perform calculations in the more abstract parts of mathematics. This book introduces the role Magma plays in advanced mathematical research through 14 case studies which, in most cases, describe computations underpinning theoretical results.

  10. Kinematics of stair ascent in healthy dogs.

    Science.gov (United States)

    Durant, A M; Millis, D L; Headrick, J F

    2011-01-01

    The purpose of the study was to evaluate the kinematic characteristics of pelvic limb joints in orthopaedically normal dogs during stair ascent. Prospective study. Eight hound-type dogs were fitted with reflective spheres at palpable landmarks, including the tuber ischium, greater trochanter, cranial dorsal iliac spine, lateral epicondyle of the femur, lateral malleolus, and the base of the fifth metatarsal bone. Each dog was walked up a set of custom made stairs consisting of four steps and then trotted across a level test space. Data were recorded for the right and left pelvic limbs during ascent. Maximum and minimum joint angles and total joint motion were calculated for all joints and evaluated statistically. Pelvic limb joints had a greater total joint excursion during stair ascent. There was greater extension of the coxofemoral and tibiotarsal joints during ascent, whereas the stifle joint had less extension. Maximum flexion of the stifle and tarsal joints was significantly greater in stair ascent. There was not any significant difference between the right and left limbs. All joints of the pelvic limb undergo a greater joint motion to ascend stairs.

  11. Subterranean fragmentation of magma during conduit initiation and evolution in the shallow plumbing system of the small-volume Jagged Rocks volcanoes (Hopi Buttes Volcanic Field, Arizona, USA)

    Science.gov (United States)

    Re, Giuseppe; White, James D. L.; Muirhead, James D.; Ort, Michael H.

    2016-08-01

    Monogenetic volcanoes have limited magma supply and lack long-lived sustained magma plumbing systems. They erupt once, often from multiple vents and sometimes over several years, and are rarely or never re-activated. Eruptive behavior is very sensitive to physical processes (e.g., volatile exsolution, magma-water interaction) occurring in the later stages of magma ascent at shallow crustal depths (shapes, dense groundmasses, and composite clasts (loaded and cored). The extent of fragmentation and the formation of subterranean open space controlled the nature of the particles and the architecture and geometry of these conduit structures and their deposits.

  12. Numerical investigation of permeability models for low viscosity magmas: Application to the 2007 Stromboli effusive eruption

    Science.gov (United States)

    La Spina, G.; Polacci, M.; Burton, M.; de'Michieli Vitturi, M.

    2017-09-01

    Magma permeability is the most important factor controlling the transition between effusive and explosive styles during magma ascent at active volcanoes. When magma permeability is low, gas bubbles in the melt expand as the pressure decreases; above a critical gas volume fraction threshold, magma fragments, generating an explosive eruption. On the contrary, if magma is sufficiently permeable, gas ascends through the conduit towards the surface faster than the magma ascent speed, producing decoupling of gas and magma and reducing the maximum vesicularity. This decoupled flow inhibits fragmentation and leads to either an effusive eruption or quiescent degassing. Accurate modelling of permeability behaviour is therefore fundamental when simulating magma ascent processes. In this work, we compare different permeability models for low viscosity magmas using a 1D steady-state model. We use, as a test case, the 2007 effusive eruption at Stromboli volcano, Italy. We compare the numerical solutions computed using the linear Darcy's law with those obtained using the non-linear Forchheimer relation. Our numerical results show that, using Darcy's law and appropriate permeability models, it is possible to obtain an effusive eruption in agreement with observations. However, we found that, in the shallow conduit, the limit of applicability of Darcy's law (that is the modified Reynolds number Rem gas flow rates. Furthermore, we show that using Forchheimer's law and some parametric expressions for viscous and inertial permeabilities, results can be compatible with an effusive eruption, once appropriate values are chosen. However, one of the parameters required to obtain an effusive eruption, the friction coefficient between gas and melt, is several orders of magnitude lower than that determined from measurements of solid erupted samples. This result requires further experimental verification. We propose that our novel permeability modelling regime is suitable for basaltic volcanism

  13. Modelling magma-drift interaction at the proposed high-level radioactive waste repository at Yucca Mountain, Nevada, USA

    NARCIS (Netherlands)

    Woods, Andrew W.; Sparks, Steve; Bokhove, Onno; Lejeune, Anne-Marie; Connor, Charles B.; Hill, Britain E.

    2002-01-01

    We examine the possible ascent of alkali basalt magma containing 2 wt percent water through a dike and into a horizontal subsurface drift as part of a risk assessment for the proposed high-level radioactive waste repository beneath Yucca Mountain, Nevada, USA. On intersection of the dike with the

  14. On Small Disturbance Ascent Vent Behavior

    Science.gov (United States)

    Woronowicz, Michael

    2015-01-01

    As a spacecraft undergoes ascent in a launch vehicle, its ambient pressure environment transitions from one atmosphere to high vacuum in a matter of a few minutes. Venting of internal cavities is necessary to prevent the buildup of pressure differentials across cavity walls. These pressure differentials are often restricted to low levels to prevent violation of container integrity. Such vents usually consist of fixed orifices, ducts, or combinations of both. Duct conductance behavior is fundamentally different from that for orifices in pressure driven flows governing the launch vehicle ascent depressurization environment. Duct conductance is governed by the average pressure across its length, while orifice conductance is dictated by a pressure ratio. Hence, one cannot define a valid equivalent orifice for a given duct across a range of pressure levels. This presentation discusses development of expressions for these two types of vent elements in the limit of small pressure differentials, explores conditions for their validity, and compares their features regarding ascent depressurization performance.

  15. Watching magma from space

    Science.gov (United States)

    Lu, Zhong; Wicks, Charles W.; Dzurisin, Daniel; Thatcher, Wayne R.; Freymueller, Jeffrey T.; McNutt, Stephen R.; Mann, Dorte

    2000-01-01

    Westdahl is a broad shield volcano at the western end of Unimak Island in the Aleutian chain. It has apparently been dormant since a 1991-92 eruption and seismicity levels have been low. However, satellite radar imaging shows that in the years following 1992 the upper flanks of Westdahl have risen several centimeters, probably from the influx of new magma deep below its summit. Until now, deep magma reservoirs have been difficult to detect beneath most volcanoes. But using space geodetic technologies, specifically interferometric synthetic aperture radar (InSAR), we have discovered a deep magmatic source beneath Westdahl. 

  16. A reverse energy cascade for crustal magma transport

    Science.gov (United States)

    Karlstrom, Leif; Paterson, Scott R.; Jellinek, A. Mark

    2017-08-01

    Direct constraints on the ascent, storage and eruption of mantle melts come primarily from exhumed, long-frozen intrusions. These structures, relics of a dynamic magma transport network, encode how Earth's crust grows and differentiates over time. Furthermore, they connect mantle melting to an evolving distribution of surface volcanism. Disentangling magma transport processes from the plutonic record is consequently a seminal but unsolved problem. Here we use field data analyses, scaling theory and numerical simulations to show that the size distribution of intrusions preserved as plutonic complexes in the North American Cordillera suggests a transition in the mechanical response of crustal rocks to protracted episodes of magmatism. Intrusion sizes larger than about 100 m follow a power-law scaling expected if energy delivered from the mantle to open very thin dykes and sills is transferred to intrusions of increasing size. Merging, assimilation and mixing of small intrusions into larger ones occurs until irreversible deformation and solidification dissipate available energy. Mantle magma supply over tens to hundreds of thousands of years will trigger this regime, a type of reverse energy cascade, depending on the influx rate and efficiency of crustal heating by intrusions. Identifying regimes of magma transport provides a framework for inferring subsurface magmatic processes from surface patterns of volcanism, information preservation in the plutonic record, and related effects including climate.

  17. Generation of Deccan Trap magmas

    Indian Academy of Sciences (India)

    Deccan Trap; giant Plagioclase basalt; age; contamination; fractional crystallization; magma generation. ... Deccan magmas were produced by 15-30% melting of a Fe-rich lherzolitic source at ∼3-2 GPa;; Parent magmas of the relatively uncontaminated Ambenali formation had a primitive composition with 16% MgO, 47% ...

  18. Mush Column Magma Chambers

    Science.gov (United States)

    Marsh, B. D.

    2002-12-01

    Magma chambers are a necessary concept in understanding the chemical and physical evolution of magma. The concept may well be similar to a transfer function in circuit or time series analysis. It does what needs to be done to transform source magma into eruptible magma. In gravity and geodetic interpretations the causative body is (usually of necessity) geometrically simple and of limited vertical extent; it is clearly difficult to `see' through the uppermost manifestation of the concentrated magma. The presence of plutons in the upper crust has reinforced the view that magma chambers are large pots of magma, but as in the physical representation of a transfer function, actual magma chambers are clearly distinct from virtual magma chambers. Two key features to understanding magmatic systems are that they are vertically integrated over large distances (e.g., 30-100 km), and that all local magmatic processes are controlled by solidification fronts. Heat transfer considerations show that any viable volcanic system must be supported by a vertically extensive plumbing system. Field and geophysical studies point to a common theme of an interconnected stack of sill-like structures extending to great depth. This is a magmatic Mush Column. The large-scale (10s of km) structure resembles the vertical structure inferred at large volcanic centers like Hawaii (e.g., Ryan et al.), and the fine scale (10s to 100s of m) structure is exemplified by ophiolites and deeply eroded sill complexes like the Ferrar dolerites of the McMurdo Dry Valleys, Antarctica. The local length scales of the sill reservoirs and interconnecting conduits produce a rich spectrum of crystallization environments with distinct solidification time scales. Extensive horizontal and vertical mushy walls provide conditions conducive to specific processes of differentiation from solidification front instability to sidewall porous flow and wall rock slumping. The size, strength, and time series of eruptive behavior

  19. Fluid flow and degassing in high temperature magma

    Science.gov (United States)

    Gaunt, H. E.; Sammonds, P.; Kilburn, C.; Meredith, P.; Smith, R.

    2012-04-01

    Dacitic volcanoes such as Mount St Helens are commonly associated with plinian eruptions. They can also erupt magma as lava domes that, in addition to simple effusion, frequently pass through episodes of major collapse and can also explode in vulcanian eruptions under suitable increases in gas pressure. Both dome collapse and vulcanian events can propagate pyroclastic flows and so extend the hazardous range of a dome far beyond the radius of the dome itself. As magma rises in the conduit it becomes supersaturated with dissolved volatiles and, during decompression, exsolution occurs creating gas bubbles within the melt. The ability of gases to escape the rising magma depends strongly on its permeability. It is common in highly viscous magma for gas pressure to build up until, under a sufficient amount of depressurisation, the tensile strength of the magma is exceeded and fragmentation occurs. However effusion of lava domes requires magma to reach the surface in a relatively volatile free state and the processes that control this gas escape in high temperature magma are still poorly understood. To investigate the controls on degassing processes, we have measured how permeability varies progressively with increasing temperature on samples from the 2004-2008 lava dome at Mount St Helens. Permeability was measured on cylindrical samples 25 mm in diameter in a high temperature triaxial deformation apparatus at temperatures up to 900oC, confining pressures of 10 MPa and pore fluid pressures of 5 MPa. Samples of intact dacite from the interior of Spine 4 were used to test temperature effects on fluid flow. Our preliminary results show that fluid flow in the dacite lava at the core of the lava dome is reduced by over two orders of magnitude when the temperature is increased from 30oC to 400oC, with no apparent discontinuity when the pore fluid water flashes to steam at 264oC. During ascent in the conduit the magma is cooled from around 850oC and depressurisation causes

  20. A spatter-forming, large-scale paroxysm at Stromboli Volcano (Aeolian Islands, Italy): insight into magma evolution and eruption dynamics

    Science.gov (United States)

    La Felice, Sonia; Landi, Patrizia

    2011-11-01

    This study focuses on a pyroclastic sequence related to a large-scale paroxysm that occurred during the seventeenth century ad and which can be considered one of the most powerful and hazardous explosive events at the volcano in the past few centuries. Paroxysms are energetic, short-lived explosions which sporadically interrupt normal Strombolian activity at Stromboli and commonly erupt a deep-derived, volatile-rich crystal-poor high-potassium basalt ("low porphyricity" (LP)), together with a shallow, degassed crystal-rich high-potassium to shoshonitic basalt ("high porphyricity" (HP)), which feed normal activity at the volcano. The studied deposit, crops out along the flanks of Sciara del Fuoco and, from base to top, consists of: (1) a layer of HP and LP ash and lapilli; (2) an unwelded layer of coarse HP lapilli and flattened dark scoriae; (3) weakly welded spatter made up of dense HP pyroclasts at the base, overlain by strongly vesicular LP clasts. The textural and chemical zoning of minerals and the glass chemistry of the LP products record repeated mafic recharge events, mixing with an old mushy body and episodes of rapid crystallization due to sudden degassing. Collapse of a foam layer originated by deep degassing probably triggered this large-scale, spatter-forming paroxysm. Decompression induced rapid degassing and vesiculation of the deep volatile-rich magma. The rapid ascent of the foamy magma blob pushed the shallow HP magma out and finally produced a fire fountain that emplaced the LP portion of the spatter.

  1. Long-period seismicity at Redoubt Volcano, Alaska, 1989-1990 related to magma degassing

    Science.gov (United States)

    Morrissey, M.M.

    1997-01-01

    The mass of exsolved magmatic H2O is estimated and compared to the mass of superheated steam (25-50 Mtons) released through the resonating crack producing the December 13-14, 1989 swarm of long-period seismic events at Redoubt Volcano. Results indicate degassing of a H2O-CO2-SO2-saturated magma upon ascending from at least 12 km to 3-4 km beneath the crater as the source of the superheated steam. The mass of exsolved H2O (3.2-250 Mtons) is estimated from solubility diagrams of H2O-CO2-saturated silicate melts for the ascent history of the Redoubt magmas. Crystal size distribution, seismological, petrological, and geochemical data are used to constrain the ascent history of the two andesitic magmas prior to the eruption. Two stages of crystallization are inferred from crystal size distributions of plagioclase crystals in andesites erupted in December 1989. The first stage occurred 30-150 years before the eruption in both magmas and the second stage occurred at least 8 years and 15 years before the eruption in the dacitic andesite and rhyolitic andesite, respectively. The depths of crystallization are constrained from the spatial and temporal variations of volcano-tectonic earthquakes locations (Lahr et al., 1994) and from the P-wave and S-wave velocity structures (Benz et al., 1996). These data suggest that the rhyolitic andesite magma ascended to a depth of 7-8 km within at least 15 years of the eruption. Within at least 8 years of the eruption, the dacitic andesite magma migrated to a depth just below the other magma body where it resided until hours to days of the eruption. At this time, the dacitic andesite magma mixed with the rhyolitic andesite magma and established the reservoir for the eruption. Near the top of the reservoir, some of the mixed magma was displaced into fractures which extended 4-5 km toward the surface. This displaced magma created the eruption conduit and released the fluids related to the resonating crack. This scenario is consistent with

  2. Rocketdyne - Lunar Ascent Engine. Chapter 7, Appendix I

    Science.gov (United States)

    Harmon, Tim

    2009-01-01

    The ascent engine was the last one from the moon, and I want to focus on the idea of redundancy and teams in regard to the engine. By teams, I mean teamwork - not just within Rocketdyne. It was teamwork within Rocketdyne; it was teamwork within Grumman; it was teamwork within NASA. These were all important elements leading to the successful development of the lunar excursion module (LEM) engine. Communication, rapid response, and cooperation were all important. Another aspect that went into the development of the ascent engine was the integration of technology and of lessons learned. We pushed all the above, plus technology and lessons learned, into a program, and that led to a successful result. One of the things that I like to think about - again in retrospect - is how it is very "in" now to have integrated product and process teams. These are buzzwords for teamwork in all program phases. That s where you combine a lot of groups into a single organization to get a job done. The ascent engine program epitomized that kind of integration and focus, and because this was the mid- to late-1960s; this was new ground for Rocketdyne, Grumman, and NASA. Redundancy was really a major hallmark of the Apollo Program. Everything was redundant. Once you got the rocket going, you could even lose one of the big F-1 engines, and it would still make it to orbit. And once the first stage separated from the rest of the vehicle, the second stage could do without an engine and still make a mission. This redundancy was demonstrated when an early Apollo launch shut down a J-2 second-stage engine. Actually, they shut down two J-2 engines on that flight. Even the third stage, with its single J-2 engine, was backed up because the first two stages could toss it into a recoverable orbit. If the third stage didn't work, you were circling the earth, and you had time to recover the command module and crew. Remember how on the Apollo 13 flight, there was sufficient system redundancy even when we

  3. Comparative Magma Oceanography

    Science.gov (United States)

    Jones, J. H.

    1999-01-01

    The question of whether the Earth ever passed through a magma ocean stage is of considerable interest. Geochemical evidence strongly suggests that the Moon had a magma ocean and the evidence is mounting that the same was true for Mars. Analyses of martian (SNC) meteorites have yielded insights into the differentiation history of Mars, and consequently, it is interesting to compare that planet to the Earth. Three primary features of Mars contrast strongly to those of the Earth: (i) the extremely ancient ages of the martian core, mantle, and crust (about 4.55 b.y.); (ii) the highly depleted nature of the martian mantle; and (iii) the extreme ranges of Nd isotopic compositions that arise within the crust and depleted mantle. The easiest way to explain the ages and diverse isotopic compositions of martian basalts is to postulate that Mars had an early magma ocean. Cumulates of this magma ocean were later remelted to form the SNC meteorite suite and some of these melts assimilated crustal materials enriched in incompatible elements. The REE pattern of the crust assimilated by these SNC magmas was LREE enriched. If this pattern is typical of the crust as a whole, the martian crust is probably similar in composition to melts generated by small degrees of partial melting (about 5%) of a primitive source. Higher degrees of partial melting would cause the crustal LREE pattern to be essentially flat. In the context of a magma ocean model, where large degrees of partial melting presumably prevailed, the crust would have to be dominated by late-stage, LREE-enriched residual liquids. Regardless of the exact physical setting, Nd and W isotopic evidence indicates that martian geochemical reservoirs must have formed early and that they have not been efficiently remixed since. The important point is that in both the Moon and Mars we see evidence of a magma ocean phase and that we recognize it as such. Several lines of theoretical inference point to an early Earth that was also hot

  4. Magma decompression rates during explosive eruptions of Kīlauea volcano, Hawaii, recorded by melt embayments

    Science.gov (United States)

    Ferguson, David J.; Gonnermann, Helge M.; Ruprecht, Philipp; Plank, Terry; Hauri, Erik H.; Houghton, Bruce F.; Swanson, Donald A.

    2016-01-01

    The decompression rate of magma as it ascends during volcanic eruptions is an important but poorly constrained parameter that controls many of the processes that influence eruptive behavior. In this study, we quantify decompression rates for basaltic magmas using volatile diffusion in olivine-hosted melt tubes (embayments) for three contrasting eruptions of Kīlauea volcano, Hawaii. Incomplete exsolution of H2O, CO2, and S from the embayment melts during eruptive ascent creates diffusion profiles that can be measured using microanalytical techniques, and then modeled to infer the average decompression rate. We obtain average rates of ~0.05–0.45 MPa s−1 for eruptions ranging from Hawaiian style fountains to basaltic subplinian, with the more intense eruptions having higher rates. The ascent timescales for these magmas vary from around ~5 to ~36 min from depths of ~2 to ~4 km, respectively. Decompression-exsolution models based on the embayment data also allow for an estimate of the mass fraction of pre-existing exsolved volatiles within the magma body. In the eruptions studied, this varies from 0.1 to 3.2 wt% but does not appear to be the key control on eruptive intensity. Our results do not support a direct link between the concentration of pre-eruptive volatiles and eruptive intensity; rather, they suggest that for these eruptions, decompression rates are proportional to independent estimates of mass discharge rate. Although the intensity of eruptions is defined by the discharge rate, based on the currently available dataset of embayment analyses, it does not appear to scale linearly with average decompression rate. This study demonstrates the utility of the embayment method for providing quantitative constraints on magma ascent during explosive basaltic eruptions.

  5. Mars Ascent Vehicle Design for Human Exploration

    Science.gov (United States)

    Polsgrove, Tara; Thomas, Dan; Sutherlin, Steven; Stephens, Walter; Rucker, Michelle

    2015-01-01

    In NASA's evolvable Mars campaign, transportation architectures for human missions to Mars rely on a combination of solar electric propulsion and chemical propulsion systems. Minimizing the Mars ascent vehicle (MAV) mass is critical in reducing the overall lander mass and also eases the requirements placed on the transportation stages. This paper presents the results of a conceptual design study to obtain a minimal MAV configuration, including subsystem designs and mass summaries.

  6. Prediction of acute mountain sickness by monitoring arterial oxygen saturation during ascent.

    Science.gov (United States)

    Karinen, Heikki M; Peltonen, Juha E; Kähönen, Mika; Tikkanen, Heikki O

    2010-01-01

    Acute mountain sickness (AMS) is a common problem while ascending at high altitude. AMS may progress rapidly to fatal results if the acclimatization process fails or symptoms are neglected and the ascent continues. Extensively reduced arterial oxygen saturation at rest (R-Spo₂) has been proposed as an indicator of inadequate acclimatization and impending AMS. We hypothesized that climbers less likely to develop AMS on further ascent would have higher Spo₂ immediately after exercise (Ex-Spo₂) at high altitudes than their counterparts and that these postexercise measurements would provide additional value for resting measurements to plan safe ascent. The study was conducted during eight expeditions with 83 ascents. We measured R-Spo₂ and Ex-Spo₂ after moderate daily exercise [50 m walking, target heart rate (HR) 150 bpm] at altitudes of 2400 to 5300 m during ascent. The Lake Louise Questionnaire was used in the diagnosis of AMS. Ex-Spo₂ was lower at all altitudes among those climbers suffering from AMS during the expeditions than among those climbers who did not get AMS at any altitude during the expeditions. Reduced R-Spo₂ and Ex-Spo₂ measured at altitudes of 3500 and 4300 m seem to predict impending AMS at altitudes of 4300 m (p saturation at rest, especially during exercise, most likely do not develop AMS. The results suggest that daily evaluation of Spo₂ during ascent both at rest and during exercise can help to identify a population that does well at altitude.

  7. Oxygen isotope composition of mafic magmas at Vesuvius

    Science.gov (United States)

    Dallai, L.; Cioni, R.; Boschi, C.; D'Oriano, C.

    2009-12-01

    The oxygen isotope composition of olivine and clinopyroxene from four plinian (AD 79 Pompeii, 3960 BP Avellino), subplinian (AD 472 Pollena) and violent strombolian (Middle Age activity) eruptions were measured to constrain the nature and evolution of the primary magmas of the last 4000 years of Mt. Vesuvius activity. A large set of mm-sized crystals was accurately separated from selected juvenile material of the four eruptions. Crystals were analyzed for their major and trace element compositions (EPMA, Laser Ablation ICP-MS), and for 18O/16O ratios. As oxygen isotope composition of uncontaminated mantle rocks on world-wide scale is well constrained (δ18Oolivine = 5.2 ± 0.3; δ18Ocpx = 5.6 ± 0.3 ‰), the measured values can be conveniently used to monitor the effects of assimilation/contamination of crustal rocks in the evolution of the primary magmas. Instead, typically uncontaminated mantle values are hardly recovered in Italian Quaternary magmas, mostly due to the widespread occurrence of crustal contamination of the primary magmas during their ascent to the surface (e.g. Alban Hills, Ernici Mts., and Aeolian Islands). Low δ18O values have been measured in olivine from Pompeii eruption (δ18Oolivine = 5.54 ± 0.03‰), whereas higher O-compositions are recorded in mafic minerals from pumices or scoria of the other three eruptions. Measured olivine and clinopyroxene share quite homogeneous chemical compositions (Olivine Fo 85-90 ; Diopside En 45-48, respectively), and represent phases crystallized in near primary mafic magmas, as also constrained by their trace element compositions. Data on melt inclusions hosted in crystals of these compositions have been largely collected in the past demonstrating that they crystallized from mafic melt, basaltic to tephritic in composition. Published data on volatile content of these melt inclusions reveal the coexistence of dissolved water and carbon dioxide, and a minimum trapping pressure around 200-300 MPa, suggesting

  8. Hybrid adaptive ascent flight control for a flexible launch vehicle

    Science.gov (United States)

    Lefevre, Brian D.

    controller. In the simulations where the online parameter identification algorithm was disabled, the tracking error based neural network weight update law forced the network's output to diverge despite repeated reductions of the adaptive learning rate. As a result, the modeling error based neural network weight update law (which generated bounded signals) is utilized by the hybrid adaptive controller in all subsequent simulations. Comparing the PID and hybrid adaptive flight controllers under nominal flight conditions in rigid body ascent simulations showed that their tracking error magnitudes are similar for a period of time during the middle of the ascent phase. Though the PID controller performs better for a short interval around the 20 second mark, the hybrid adaptive controller performs far better from roughly 70 to 120 seconds. Elevating the aerodynamic loads by increasing the force and moment coefficients produced results very similar to the nominal case. However, applying a 5% or 10% thrust reduction to the first stage rocket motor causes the tracking error magnitude observed by the PID controller to be significantly elevated and diverge rapidly as the simulation concludes. In contrast, the hybrid adaptive controller steadily maintains smaller errors (often less than 50% of the corresponding PID value). Under the same sets of flight conditions with flexibility enabled, the results exhibit similar trends with the hybrid adaptive controller performing even better in each case. Again, the reduction of the first stage rocket motor's thrust clearly illustrated the superior robustness of the hybrid adaptive flight controller.

  9. Oxygen isotope geochemistry of mafic magmas at Mt. Vesuvius

    Science.gov (United States)

    Dallai, Luigi; Raffaello, Cioni; Chiara, Boschi; Claudia, D'oriano

    2010-05-01

    Pumice and scoria from different eruptive layers of Mt. Vesuvius volcanic products contain mafic minerals consisting of High-Fo olivine and Diopsidic Pyroxene. These phases were crystallized in unerupted trachibasaltic to tephritic magmas, and were brought to surface by large phonolitic/tephri-phonolitic (e.g. Avellino and Pompei) and/or of tephritic and phono-tephritic (Pollena) eruptions. A large set of these mm-sized crystals was accurately separated from selected juvenile material and measured for their chemical compositions (EPMA, Laser Ablation ICP-MS) and 18O/16O ratios (conventional laser fluorination) to constrain the nature and evolution of the primary magmas at Mt. Vesuvius. Uncontaminated mantle δ18O values are hardly recovered in Italian Quaternary magmas, mostly due to the widespread occurrence of crustal contamination of the primary melts during their ascent to the surface (e.g. Alban Hills, Ernici Mts., and Aeolian Islands). At Mt. Vesuvius, measured olivine and clinopyroxene share quite homogeneous chemical compositions (Olivine Fo 85-90 ; Diopside En 45-48, respectively), and represent phases crystallized in near primary mafic magmas. Trace element composition constrains the near primary nature of the phases. Published data on volatile content of melt inclusions hosted in these crystals reveal the coexistence of dissolved water and carbon dioxide, and a minimum trapping pressure around 200-300 MPa, suggesting that crystal growth occurred in a reservoir at about 8-10 km depth. Recently, experimental data have suggested massive carbonate assimilation (up to about 20%) to derive potassic alkali magmas from trachybasaltic melts. Accordingly, the δ18O variability and the trace element content of the studied minerals suggest possible contamination of primary melts by an O-isotope enriched, REE-poor contaminant like the limestone of Vesuvius basement. Low, nearly primitive δ18O values are observed for olivine from Pompeii eruption, although still

  10. Volatile contents of mafic-to-intermediate magmas at San Cristóbal volcano in Nicaragua

    Science.gov (United States)

    Robidoux, P.; Aiuppa, A.; Rotolo, S. G.; Rizzo, A. L.; Hauri, E. H.; Frezzotti, M. L.

    2017-02-01

    San Cristóbal volcano in northwest Nicaragua is one of the most active basaltic-andesitic stratovolcanoes of the Central American Volcanic Arc (CAVA). Here we provide novel constraints on the volcano's magmatic plumbing system, by presenting the first direct measurements of major volatile contents in mafic-to-intermediate glass inclusions from Holocene and historic-present volcanic activity. Olivine-hosted (forsterite [Fo] parental melts at 1889 μg/g, which is consistent with the less-CO2-degassed melt inclusions (MI) (> 1500 μg/g) found in Nicaragua at Cerro Negro, Nejapa, and Granada. Models of H2O and CO2 solubilities constrain the degassing pathway of magmas up to 425 MPa ( 16 km depth), which includes a deep CO2 degassing step (only partially preserved in the MI record), followed by coupled degassing of H2O and S plus crystal fractionation at magma volatile saturation pressures from ∼ 195 to < 10 MPa. The variation in volatile contents from San Cristóbal MI is interpreted to reflect (1) Holocene eruptive cycles characterized by the rapid emplacement of basaltic magma batches, saturated in volatiles, at depths of 3.8-7.4 km, and (2) the ascent of more-differentiated and cogenetic volatile-poor basaltic andesites during historic-present eruptions, having longer residence times in the shallowest (< 3.4 km) and hence coolest regions of the magmatic plumbing system. We also report the first measurements of the compositions of noble-gas isotopes (He, Ne, and Ar) in fluid inclusions in olivine and pyroxene crystals. While the measured 40Ar/36Ar ratios (300-304) and 4He/20Ne ratios (9-373) indicate some degree of air contamination, the 3He/4He ratios (7.01-7.20 Ra) support a common mantle source for Holocene basalts and historic-present basaltic andesites. The magmatic source is interpreted as generated by a primitive MORB-like mantle, that is influenced to variable extents by distinct slab fluid components for basalts (Ba/La 76 and U/Th 0.8) and basaltic

  11. High Performance Monopropellants for Future Planetary Ascent Vehicles Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Physical Sciences Inc. proposes to design, develop, and demonstrate, a novel high performance monopropellant for application in future planetary ascent vehicles. Our...

  12. Human Mars Ascent Configuration and Design Sensitivities

    Science.gov (United States)

    Polsgrove, Tara P.; Gernhardt, Mike; Collins, Tim; Martin, John

    2017-01-01

    Human missions to Mars may utilize several small cabins where crew members could live for days up to a couple of weeks. At the end of a Mars surface mission the Mars Ascent Vehicle (MAV) crew cabin would carry the crew to their destination in orbit in a matter of hours or days. Other small cabins in support of a Mars mission would include pressurized rovers that allow crew members to travel great distances from their primary habitat on Mars while unconstrained by time limits of typical EVAs. An orbital crew taxi could allow for exploration of the moons of Mars with minimum impact to the primary Earth-Mars transportation systems. A common crew cabin design that can perform in each of these applications is desired and could reduce the overall mission cost. However, for the MAV, the crew cabin size and mass can have a large impact on vehicle design and performance. The total ascent vehicle mass drives performance requirements for the Mars descent systems and the Earth to Mars transportation elements. Minimizing MAV mass is a priority and minimizing the crew cabin size and mass is one way to do that. This paper explores the benefits and impacts of using a common crew cabin design for the MAV. Results of a MAV configuration trade study will be presented along with mass and performance estimates for the selected design.

  13. Stair ascent and descent at different inclinations.

    Science.gov (United States)

    Riener, Robert; Rabuffetti, Marco; Frigo, Carlo

    2002-02-01

    The aim of this study was to investigate the biomechanics and motor co-ordination in humans during stair climbing at different inclinations. Ten normal subjects ascended and descended a five-step staircase at three different inclinations (24 degrees, 30 degrees, 42 degrees ). Three steps were instrumented with force sensors and provided 6 dof ground reactions. Kinematics was analysed by a camera-based optoelectronic system. An inverse dynamics approach was applied to compute joint moments and powers. The different kinematic and kinetic patterns of stair ascent and descent were analysed and compared to level walking patterns. Temporal gait cycle parameters and ground reactions were not significantly affected by staircase inclination. Joint angles and moments showed a relatively low but significant dependency on the inclination. A large influence was observed in joint powers. This can be related to the varying amount of potential energy that has to be produced (during ascent) or absorbed (during descent) by the muscles. The kinematics and kinetics of staircase walking differ considerably from level walking. Interestingly, no definite signs could be found indicating that there is an adaptation or shift in the motor patterns when moving from level to stair walking. This can be clearly seen in the foot placement: compared to level walking, the forefoot strikes the ground first--independent from climbing direction and inclination. This and further findings suggest that there is a certain inclination angle or angular range where subjects do switch between a level walking and a stair walking gait pattern.

  14. Mechanical interaction between gas bubbles and micro-crystals in magma

    Science.gov (United States)

    Dinger, Florian; Bobrowski, Nicole; Bredemeyer, Stefan; Arellano, Santiago; Platt, Ulrich; Wagner, Thomas

    2017-04-01

    The magnitude of volcanic gas emissions from low viscosity magmas is controlled by many factors. The buoyancy driven ascent of gas bubbles in the volcanic conduit is one of them. During the ascent the bubbles may collide with micro-crystals, slide along the crystal faces, and finally leave the crystal at the crystal tip. We investigate the mechanical consequences of this interaction in a static volume of magma assuming constant pressure, temperature and chemical composition and neglecting thermodynamic processes between bubbles and crystals. Explicitly, we focus on tabular crystals whose extensions are about one order of magnitude larger than the bubbles. The mechanical interaction changes the motion of both the bubbles and the crystals. The buoyancy force of the bubbles results in a torque on the crystal which ultimately orients the long axis of the crystal to the vertical direction. On the other hand, bubbles change their ascent path and velocity if they slide along a crystal face. This change in the bubble motion may have two opposing impacts on the magnitude of volcanic emissions: First, the reduced ascent velocity results in a bubble accumulation and thus enhanced bubble coalescence rate in the proximity of crystals. Second, the crystals align the bubbles in rise channels starting at the crystal tips while no bubbles access the magma volume immediately located above the crystal cross section, which we call "crystal shadow". Now, volatile degassing from supersaturated magma is a diffusive short-distance process which accelerate in the proximity of pre-existing gas bubbles. We thus infer that the orientation of the crystals influences the bulk volatile degassing rate and thus the volcanic gas emission rate due to the crystal shadow. The mechanical model suggests that all crystals get erected by the bubble-induced torque within time periods in the order of weeks to months. This has to be compared to the crystal nucleation rate in order to obtain a steady state

  15. Permeability of alkaline magmas: a study from Campi Flegrei, Italy

    Science.gov (United States)

    Polacci, M.; Bouvet de Maissoneuve, C.; Giordano, D.; Piochi, M.; Degruyter, W.; Bachmann, O.; Mancini, L.

    2012-04-01

    Knowledge of permeability is of paramount importance for understanding the evolution of magma degassing during pre-, syn- and post-eruptive volcanic processes. Most permeability estimates existing to date refer to magmas of calc-alkaline compositions. We report here the preliminary results of permeability measurements performed on alkali-trachyte products erupted from the Campanian Ignimbrite (CI) and Monte Nuovo (MTN), two explosive eruptions from Campi Flegrei (CF), an active, hazardous caldera west of Naples, Southern Italy. Darcian (viscous) permeability spans a wide range between 10^-11 and 10^-14 m^2. We observe that the most permeable samples are the scoria clasts from the upper units of MTN; pumice samples from the Breccia Museo facies of CI are instead the least permeable. Non-Darcian (inertial) permeability follows the same trend as Darcian permeability. The first implication of this study is that porosity in alkaline as well as calc-alkaline magmas does not exert a first order control on permeability (e.g. the MTN samples are the most permeable but not the most porous). Second, sample geometry exhibits permeability anisotropy (higher permeability in the direction of vesicle elongation), suggesting stronger degassing in the vertical direction in the conduit. In addition, inertial effects are higher across the sample. As inertial effects are potentially generated by tortuosity (or tortuous vesicle paths), tortuosity is likely higher horizontally than vertically in the conduit. Finally, the measured CF permeability values overlap with those of rhyolitic pumice clasts from the Kos Plateau Tuff (Bouvet de Maisonneuve et al., 2009), together with CI one of the major Quaternary explosive eruptions of the Mediterranean region. This indicates that gas flow is strongly controlled by the geometry of the porous media, which is generated by the bubble dynamics during magma ascent. Therefore, permeability will depend on composition through the rheological properties

  16. THE VISCOUS TO BRITTLE TRANSITION IN CRYSTAL- AND BUBBLE-BEARING MAGMAS

    Directory of Open Access Journals (Sweden)

    Mattia ePistone

    2015-11-01

    Full Text Available The transition from viscous to brittle behaviour in magmas plays a decisive role in determining the style of volcanic eruptions. While this transition has been determined for one- or two-phase systems, it remains poorly constrained for natural magmas containing silicic melt, crystals, and gas bubbles. Here we present new experimental results on shear-induced fracturing of three-phase magmas obtained at high-temperature (673-1023 K and high-pressure (200 MPa conditions over a wide range of strain-rates (5·10-6 s-1 to 4·10-3 s-1. During the experiments bubbles are deformed (i.e. capillary number are in excess of 1 enough to coalesce and generate a porous network that potentially leads to outgassing. A physical relationship is proposed that quantifies the critical stress required for magmas to fail as a function of both crystal (0.24 to 0.65 and bubble volume fractions (0.09 to 0.12. The presented results demonstrate efficient outgassing for low crystal fraction ( 0.44 promote gas bubble entrapment and inhibit outgassing. The failure of bubble-free, crystal-bearing systems is enhanced by the presence of bubbles that lower the critical failure stress in a regime of efficient outgassing, while the failure stress is increased if bubbles remain trapped within the crystal framework. These contrasting behaviours have direct impact on the style of volcanic eruptions. During magma ascent, efficient outgassing reduces the potential for an explosive eruption and favours brittle behaviour, contributing to maintain low overpressures in an active volcanic system resulting in effusion or rheological flow blockage of magma at depth. Conversely, magmas with high crystallinity experience limited loss of exsolved gas, permitting the achievement of larger overpressures prior to a potential sudden transition to brittle behaviour, which could result in an explosive volcanic eruption.

  17. The percolation threshold and permeability evolution of ascending magmas

    Science.gov (United States)

    Burgisser, Alain; Chevalier, Laure; Gardner, James E.; Castro, Jonathan M.

    2017-07-01

    The development of gas permeability in magmas is a complex phenomenon that directly influences the style of a volcanic eruption. The emergence of permeability is linked to the concept of percolation threshold, which is the point beyond which gas bubbles are connected in a continuous network that allows gas escape. Measurements of the percolation threshold, however, range from ∼30 to 78 vol%. No known combination of parameters can explain such a wide range of threshold values, which affects our understanding of the relationship between percolation and permeability. We present permeability calculations on bubble-bearing rhyolitic melts that underwent experimental decompression. Samples were analyzed by X-ray microtomography to image the bubble networks in 3D. We develop a percolation threshold for magmas that depends on the bubble network characteristics of this sample set. This relationship recovers the behavior of a wide range of volcanic samples by separating permeable samples from impermeable ones with a success rate of 88%. We use this percolation threshold to propose simplified permeability relationships that rely on parameters widely used in numerical modeling of magma flow. These relationships are valid within one order of magnitude for the viscous permeability coefficient and within two orders of magnitude for the inertial coefficient. They recover the ranges of values previously covered by isolated relationships, reassembling them within a single framework. We test the implications of such unification on eruptive dynamics with a 1D, two-phase conduit flow model. This test shows that varying the percolation threshold has little influence on vertical gas loss and ascent dynamics.

  18. Hot Gas TVC For Planetary Ascent Vehicle Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A Mars ascent vehicle (MAV) uses solid rocket motors to propel soil samples into orbit, but the motors cannot provide steering. Cold gas thrusters are used for...

  19. Hot Gas TVC For Planetary Ascent Vehicle Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A Mars ascent vehicle (MAV) uses solid rocket motors to propel soil samples into orbit, but the motors cannot provide steering. Flexseal TVC control is planned for...

  20. The role of dyking and fault control in the rapid onset of eruption at Chaitén volcano, Chile.

    Science.gov (United States)

    Wicks, Charles; de la Llera, Juan Carlos; Lara, Luis E; Lowenstern, Jacob

    2011-10-19

    Rhyolite is the most viscous of liquid magmas, so it was surprising that on 2 May 2008 at Chaitén Volcano, located in Chile's southern Andean volcanic zone, rhyolitic magma migrated from more than 5 km depth in less than 4 hours (ref. 1) and erupted explosively with only two days of detected precursory seismic activity. The last major rhyolite eruption before that at Chaitén was the largest volcanic eruption in the twentieth century, at Novarupta volcano, Alaska, in 1912. Because of the historically rare and explosive nature of rhyolite eruptions and because of the surprisingly short warning before the eruption of the Chaitén volcano, any information about the workings of the magmatic system at Chaitén, and rhyolitic systems in general, is important from both the scientific and hazard perspectives. Here we present surface deformation data related to the Chaitén eruption based on radar interferometry observations from the Japan Aerospace Exploration Agency (JAXA) DAICHI (ALOS) satellite. The data on this explosive rhyolite eruption indicate that the rapid ascent of rhyolite occurred through dyking and that melt segregation and magma storage were controlled by existing faults.

  1. Percolating magmas in three dimensions

    Directory of Open Access Journals (Sweden)

    H. Gaonac'h

    2007-11-01

    Full Text Available The classical models of volcanic eruptions assume that they originate as a consequence of critical stresses or critical strain rates being exceeded in the magma followed by catastrophic fragmentation. In a recent paper (Gaonac'h et al., 2003 we proposed an additional mechanism based on the properties of complex networks of overlapping bubbles; that extreme multibubble coalescence could lead to catastrophic changes in the magma rheology at a critical vesicularity. This is possible because at a critical vesicularity Pc (the percolation threshold, even in the absence of external stresses the magma fragments. By considering 2-D percolation with the (observed extreme power law bubble distributions, we showed numerically that P2c had the apparently realistic value ≈0.7.

    The properties of percolating systems are, however, significantly different in 2-D and 3-D. In this paper, we discuss various new features relevant to 3-D percolation and compare the model predictions with empirical data on explosive volcanism. The most important points are a bubbles and magma have different 3-D critical percolation points; we show numerically that with power law bubble distributions that the important magma percolation threshold P3c,m has the high value ≈0.97±0.01, b a generic result of 3-D percolation is that the resulting primary fragments will have power law distributions with exponent B3f≈1.186±0.002, near the empirical value (for pumice ≈1.1±0.1; c we review the relevant percolation literature and point out that the elastic properties may have lower – possibly more realistic – critical vesicularities relevant to magmas; d we explore the implications of long range correlations (power law bubble distributions and discuss this in combination with bubble anisotropy; e we propose a new kind of intermediate "elliptical" dimensional percolation involving differentially

  2. Ascent Velocity of Plasmoids Generated by Surface Discharges

    Science.gov (United States)

    Wenzel, Uwe

    The ascent velocity of long-lived plasmoids generated under atmospheric conditions to simulate ball lightning was estimated in [Fussmann et al., Phys. Unserer Zeit 39, 246 (2008) and Jegorov et al., Tech. Phys. 53, 688 (2008): Refs. 1 and 2 in the text, respectively], using a rigid sphere model with poor agreement with the experiment. The plasmoids were, however, deformed. Much better agreement is obtained using the Davies and Taylor formula, which describes the ascent velocity of large spherical-cap bubbles.

  3. Seismometer reading from impact made by Lunar Module ascent stage

    Science.gov (United States)

    1969-01-01

    The seismometer reading from the impact made by the Lunar Module ascent stage when it struck the lunar surface. The impact was registered by the Passive Seismic Experiment Package (PSEP) which was deployed on the Moon by the Apollo 12 astronauts. The Lunar module's ascent stage was jettisoned and sent toward impact on the Moon after Astronauts Charles Conrad Jr. and Alan L. Bean returned to lunar orbit and rejoined Astronaut Richard F. Gordon Jr., in the Command/Service Modules.

  4. Mars Ascent Vehicle-First Stage Motor

    Science.gov (United States)

    Dankanich, John; Doudrick, Scott; Williams, Jacob

    2015-01-01

    This project is development effort of a first stage solid motor based on a two-stage solid motor Mars Ascent Vehicle (MAV) design for the robotic Mars Sample Return (MSR) mission (fig. 1). The MSR MAV has been studied for decades and multiple concepts have been shown to meet the mission objectives as posed.1 However, there remains significant uncertainty with the MAV requirements. The sample container and sample cache itself is immature. Additionally, MAV-specific requirements ranging from full three-axis controlled and strict communication requirements to minimal capability concepts are still under consideration. Given the maturity of the overall mission requirements, the MAV has been limited to a large number of parametric analyses and paper studies. Recently, a Jet Propulsion Laboratory study highlighted the flexibility of a two-stage solid motor concept. The MAV itself is driven by the constraints of the Entry, Decent, and Landing (EDL) system. Within the EDL constraints, there is a range of MAV options ranging in complexity from simple spun upper stage options to higher capability three-axis controlled solutions. There are also options to trade the ratio of mission (Delta)V between the first and second stage. Finally, sensitivity studies also indicated that solid motors with a high percentage of off-load flexability only had minor impact on the total system mass over a single point design optimized motor. This flexibility in the first stage motor has allowed NASA to mature the design of the motor beyond parametric analyses and start to address known design challenges of the motor.

  5. Generation of Deccan Trap magmas

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Para˜na basalts of South America, Siberian Traps. (Russia), Karoo (Africa), Columbia River Basalts. (North America), Caribbean Sea-floor basalts, and the Ontong Java plateau (western Pacific Ocean). Keywords. Deccan Trap; giant Plagioclase basalt; age; contamination; fractional crystallization; magma generation. Proc.

  6. In situ visualization of magma deformation at high temperature using time-lapse 3D tomography

    Science.gov (United States)

    Godinho, jose; Lee, Peter; Lavallee, Yan; Kendrick, Jackie; Von-Aulock, Felix

    2016-04-01

    We use synchrotron based x-ray computed micro-tomography (sCT) to visualize, in situ, the microstructural evolution of magma samples 3 mm diameter with a resolution of 3 μm during heating and uniaxial compression at temperatures up to 1040 °C. The interaction between crystals, melt and gas bubbles is analysed in 4D (3D + time) during sample deformation. The ability to observe the changes of the microstructure as a function of time allow us to: a) study the effect of temperature in the ability of magma to fracture or deform; b) quantify bubble nucleation and growth rates during heating; c) study the relation between crystal displacement and volatile exsolution. We will show unique beautiful videos of how bubbles grow and coalescence, how samples and crystals within the sample fracture, heal and deform. Our study establishes in situ sCT as a powerful tool to quantify and visualize with micro-scale resolution fast processes taking place in magma that are essential to understand ascent in a volcanic conduit and validate existing models for determining the explosivity of volcanic eruptions. Tracking simultaneously the time and spatial changes of magma microstructures is shown to be primordial to study disequilibrium processes between crystals, melt and gas phases.

  7. Mars Ascent Vehicle-Propellant Aging

    Science.gov (United States)

    Dankanich, John; Rousseau, Jeremy; Williams, Jacob

    2015-01-01

    This project is to develop and test a new propellant formulation specifically for the Mars Ascent Vehicle (MAV) for the robotic Mars Sample Return mission. The project was initiated under the Planetary Sciences Division In-Space Propulsion Technology (ISPT) program and is continuing under the Mars Exploration Program. The two-stage, solid motor-based MAV has been the leading MAV solution for more than a decade. Additional studies show promise for alternative technologies including hybrid and bipropellant options, but the solid motor design has significant propellant density advantages well suited for physical constraints imposed while using the SkyCrane descent stage. The solid motor concept has lower specific impulse (Isp) than alternatives, but if the first stage and payload remain sufficiently small, the two-stage solid MAV represents a potential low risk approach to meet the mission needs. As the need date for the MAV slips, opportunities exist to advance technology with high on-ramp potential. The baseline propellant for the MAV is currently the carboxyl terminated polybutadiene (CTPB) based formulation TP-H-3062 due to its advantageous low temperature mechanical properties and flight heritage. However, the flight heritage is limited and outside the environments, the MAV must endure. The ISPT program competed a propellant formulation project with industry and selected ATK to develop a new propellant formulation specifically for the MAV application. Working with ATK, a large number of propellant formulations were assessed to either increase performance of a CTPB propellant or improve the low temperature mechanical properties of a hydroxyl terminated polybutadiene (HTPB) propellant. Both propellants demonstrated potential to increase performance over heritage options, but an HTPB propellant formulation, TP-H-3544, was selected for production and testing. The test plan includes propellant aging first at high vacuum conditions, representative of the Mars transit

  8. DK UMa: A Star on the Ascent

    Science.gov (United States)

    Simon, Theodore

    1999-01-01

    DK UMa (= 24 UMa = HD 82210) is a G4 IV-III star. According to its M(sub v) and B - V color, it is located at the base of the red giant branch, having recently exited from the Hertzsprung Gap. Now poised to start its first ascent along the giant branch, DK UMa is at a significant juncture in its post-main-sequence evolution, offering an important evolutionary comparison for magnetic activity with stars like 31 Comae, which is just entering the Hertzsprung Gap, and older stars like the Hyades giants or P Ceti, which have passed the tip of the giant branch and lie in the so-called 'clump'. As part of a major survey of the ultraviolet and X ray properties of a well-defined sample of evolved giant stars, DK UMa was observed with the Extreme Ultraviolet Explorer (EUVE) spacecraft in March 1997, for a total exposure time of 230 kiloseconds. A plot of the extracted short-wavelength (SW) spectrum of this star is shown, where it is compared with similar EUVE exposures for other yellow and red giant stars in the activity survey. In terms of the spectral lines of different ionization stages present in these spectra, the transition region and coronal temperature of DK UMa appears to be intermediate between those of 31 Com and P Ceti. Combining the relative strengths of the EUVE lines with Hubble Space Telescope (HST) data at near UV wavelengths and with ROSAT X-ray fluxes, the differential emission measure (DEM) distributions of these stars form a sequence in coronal temperature, which peaks at 10(exp 7.2) K for 31 Com, at 10(exp 6.8) K for B Ceti, and at intermediate temperatures for DK UMa - consistent with the evolutionary stages represented by the three stars. The integrated fluxes of the strongest emission lines found in the EUVE spectrum of DK UMa are listed, again compared with similar measurements for other giant stars that were observed in the course of other EUVE Guest Observer programs.

  9. The Melt Segregation During Ascent of Buoyant Diapirs in Subduction Zones

    Science.gov (United States)

    Zhang, N.; Behn, M. D.; Parmentier, E. M.; Kincaid, C. R.

    2014-12-01

    Cold, low-density diapirs arising from hydrated mantle and/or subducted sediments on the top of subducting slabs may transport key chemical signatures from the slab to the shallow source region for arc magmas. These chemical signatures are strongly influenced by melting of this buoyant material during its ascent. However, to date there have been relatively few quantitative models to constrain melting and melt segregation in an ascending diapir, as well as the induced geochemical signature. Here, we use a two-phase Darcy-Stokes-energy model to investigate thermal evolution, melting, and melt segregation in buoyant diapirs as they ascend through the mantle wedge. Using a simplified 2-D axi-symmetric circular geometry we investigate diapir evolution in three scenarios with increasing complexity. First, we consider a case without melting in which the thermal evolution of the diapir is controlled solely by thermal diffusion during ascent. Our results show that for most cases (e.g., diapir radius ≤ 3.7 km and diapir generation depths of ~ 75 km) thermal diffusion times are smaller than the ascent time—implying that the diapir will thermal equilibrate with the mantle wedge. Secondly, we parameterize melting within the diapir, but without melt segregation, and add the effect of latent heat to the thermal evolution of the diapir. Latent heat significantly buffers heating of the diapir. For the diapir with radius ~3.7 km, the heating from the outside is slowed down ~30%. Finally, we include melt segregation within the diapir in the model. Melting initiates at the boundaries of the diapir as the cold interior warms in response to thermal equilibration with the hot mantle wedge. This forms a high porosity, high permeability rim around the margin of the diapir. As the diapir continues to warm and ascend, new melts migrate into this rim and are focused upward, accumulating at the top of the diapir. The rim thus acts like an annulus melt channel isolating the central part of

  10. The 12.4 ka Upper Apoyeque Tephra, Nicaragua: stratigraphy, dispersal, composition, magma reservoir conditions and trigger of the plinian eruption

    Science.gov (United States)

    Wehrmann, Heidi; Freundt, Armin; Kutterolf, Steffen

    2016-06-01

    Upper Apoyeque Tephra (UAq) was formed by a rhyodacitic plinian eruption in west-central Nicaragua at 12.4 ka BP. The fallout tephra was dispersed from a progressively rising plinian eruption column that became exposed to different wind speeds and directions at different heights in the stratosphere, leading to an asymmetric tephra fan with different facies in the western and southern sector. Tephra dispersal data integrated with geochemical compositions of lava flows in the area facilitate delimitation of the source vent to the south of Chiltepe Peninsula. UAq, Lower Apoyeque Tephra, Apoyeque Ignimbrite, and two lava lithic clasts in San Isidro Tephra together form a differentiation trend distinct from that of the younger tephras and lavas at Chiltepe Volcanic Complex in a TiO2 versus K2O diagram, compositionally precluding a genetic relationship of UAq with the present-day Apoyeque stratovolcano. Apoyeque Volcano in its present shape did not exist at the time of the UAq eruption. The surface expression of the UAq vent is now obscured by younger eruption products and lake water. Pressure-temperature constraints based on mineral-melt equilibria and fluid inclusions in plagioclase indicate at least two magma storage levels. Clinopyroxenes crystallised in a deep crustal reservoir at ˜24 km depth as inferred from clinopyroxene-melt inclusion pairs. Chemical disequilibrium between clinopyroxenes and matrix glasses indicates rapid magma ascent to the shallower reservoir at ˜5.4 km depth, where magnesiohornblendes and plagioclase fractionated at a temperature of ˜830 °C. Water concentrations were ˜5.5 wt.% as derived from congruent results of amphibole and plagioclase-melt hygrometry. The eruption was triggered by injection of a hotter, more primitive melt into a water-supersaturated reservoir.

  11. Optimization of the medium for Lactobacillus acidophilus by Plackett-Burman and steepest ascent experiment.

    Science.gov (United States)

    Chen, He; Niu, Jinfeng; Qin, Tao; Ma, Qi; Wang, Lei; Shu, Guowei

    2015-01-01

    Lactobacillus acidophilus not only improves the intestinal flora balance but also inhabits the growth of undesirable microorganisms in intestine, which is benefit to the health of humans and animals. Plackett-Burman and steepest ascent experiment are the rapid and concise ways of screening the main effective factors. This study is aimed to select the main influence factors and optimize the medium for Lactobacillus acidophilus by Plackett-Burman experiment and steepest ascent experiment. The ideal carbon source was screened among glucose, maltose, lactose and whey powder, and the ideal nitrogen source was screened among casein hydrolysate, peptone, yeast extract powder, fish meal, carbamide, ammonium sulfate and sodium nitrate by single factor experiment. Plackett-Burman and steepest ascent experiment were applied to screen the main effective factors of Lactobacillus acidophilus among peptone, beef extract, yeast extract powder, glucose, K2HPO4, C6H14O7N2, CH3COONa, MgSO4 and Tween-80. Result. The results indicated that glucose (p = 0.01510) as negative factor and K2HPO4 (p = 0.02017) as positive effect were the significant growth factors of Lactobacillus acidophilus, CH3COONa (p = 0.09273) as positive effect was an important factor, and the optimized medium was as follows: glucose - 21 g/L, K2HPO4 - 3.5 g/L, CH3COONa - 6.5 g/L, peptone - 10 g/L, beef extract - 8 g/L, yeast extract pow. nd. Lactobacillus acidophilus not only improves the intestinal flora balance but also inhabits the growth of undesirable microorganisms in intestine, which is benefit to the health of humans and animals. Plackett-Burman and steepest ascent experiment are the rapid and concise ways of screening the main effective factors. This study is aimed to select the main influence factors and optimize the medium for Lactobacillus acidophilus by Plackett-Burman experiment and steepest ascent experiment. Material and methods. The ideal carbon source was screened among glucose, maltose, lactose and

  12. Factors affecting stair-ascent patterns in unilateral transfemoral amputees.

    Science.gov (United States)

    Hobara, Hiroaki; Kobayashi, Yoshiyuki; Tominaga, Shuichi; Nakamura, Takashi; Yamasaki, Nobuya; Ogata, Toru

    2013-06-01

    Patterns and ease of stair ambulation influence amputees' level of satisfaction with their rehabilitation, confidence level, and motivation for continued rehabilitation, demonstrating the importance of stair-ascent data for rehabilitation. However, little is known about the determinants of stair-ascent patterns in unilateral transfemoral amputees. To investigate the factors affecting stair-ascent patterns in transfemoral amputees. Cross-sectional survey. Stair-ascent patterns were evaluated using the Stair Assessment Index. We collected Stair Assessment Index data as well as demographic and clinical data (sex, age, height, mass, amputation side, reason for amputation, time since amputation, and residual limb length) from 25 transfemoral amputees. Statistical analyses revealed that age was negatively correlated and time since amputation was positively correlated with Stair Assessment Index. In contrast, height, body mass, and residual limb lengths were not correlated with Stair Assessment Index. The results of this study suggest that in unilateral transfemoral amputee, (1) both age and time since amputation could affect stair-climbing patterns and (2) residual limb length should not be a limiting factor for stair climbing if the transfemoral amputee has a certain minimum residual limb length. Rehabilitation teams should carefully consider nonmodifiable predisposing factors such as age and time since amputation. However, they may be able to carry on stair-ascent rehabilitation for transfemoral amputees disregarding residual limb length (depending on the length).

  13. Caldera resurgence driven by magma viscosity contrasts.

    Science.gov (United States)

    Galetto, Federico; Acocella, Valerio; Caricchi, Luca

    2017-11-24

    Calderas are impressive volcanic depressions commonly produced by major eruptions. Equally impressive is the uplift of the caldera floor that may follow, dubbed caldera resurgence, resulting from magma accumulation and accompanied by minor eruptions. Why magma accumulates, driving resurgence instead of feeding large eruptions, is one of the least understood processes in volcanology. Here we use thermal and experimental models to define the conditions promoting resurgence. Thermal modelling suggests that a magma reservoir develops a growing transition zone with relatively low viscosity contrast with respect to any newly injected magma. Experiments show that this viscosity contrast provides a rheological barrier, impeding the propagation through dikes of the new injected magma, which stagnates and promotes resurgence. In explaining resurgence and its related features, we provide the theoretical background to account for the transition from magma eruption to accumulation, which is essential not only to develop resurgence, but also large magma reservoirs.

  14. Physiological responses in rock climbing with repeated ascents over a 10-week period.

    Science.gov (United States)

    España-Romero, Vanesa; Jensen, Randall L; Sanchez, Xavier; Ostrowski, Megan L; Szekely, Jay E; Watts, Phillip B

    2012-03-01

    The purpose was to analyze the physiological responses and energy expenditure during repeated ascents of the same climbing route over a 10-week period. Nine climbers completed nine ascents of a specific route spaced 1 week apart. Expired air was analyzed continuously during each ascent, and time of ascent was recorded to the nearest second. Energy expenditure during climbing (EE(CLM)), and during climbing +10 min recovery (EE(TOT)) was calculated by the Weir and Zuntz equations. Differences among ascents 1, 4, 6 and 9 were analyzed by repeated measures ANOVA. Climbing time was longer for ascent 1 compared with ascents 4, 6 and 9 (P climbing route decreased the climbing time and absolute energy expenditure during climbing. Initially, the decrease in climbing energy expenditure is accompanied by an increase in energy expenditure during recovery; however, by the ninth ascent, the total energy expenditure of the task is lower than for ascent 1.

  15. Mantle Calcium Dominates Continental Magmas

    Science.gov (United States)

    Simon, J. I.; Depaolo, D. J.; Bachmann, O.

    2009-12-01

    Trace element and isotopic compositions of continental igneous rocks are often used to model the generation and evolution of crustal magmas. Here we report new Ca isotopic measurements of crystal-poor (35%) rhyolites from the Oligocene San Juan Volcanic Field (SJVF) and Pliocene to Pleistocene tuffs from Yellowstone Caldera. Because both volcanic fields are located within the North American craton the extruded magmas could have assimilated old crustal source components with radiogenic Ca that would be clearly distinguishable from that of the mantle. New Ca data are also reported for two crustal xenoliths found within the 28.2 Ma Fish Canyon Tuff (FCT) of the SJVF that yield ɛCa values of 3.8±0.6 (2 σ, n=3) and 7.5±0.4 (2 σ, n=3), respectively. The 40Ca excesses of these possible source rocks are due to long-term in situ 40K decay and suggest that they are Precambrian in age. In contrast to the excess radiogenic Ca signatures, most Cenozoic basalts and many silicic igneous rocks from Earth yield initial ɛCa values close to zero, which indicates that the 40Ca/44Ca ratio of the Earth’s mantle is well defined and virtually invariant at the resolution of our measurements. The crystal-rich FCT, inferred to result from batholith-scale remobilization of a shallow subvolcanic magma chamber, exhibits an ɛCai value of 0.32±0.02 (2 σ, n=5) that is indistinguishable from Ca in clinopyroxene from an ultramafic xenolith that has a mantle-like ɛCai value of -0.35±0.62 (2 σ, n=2). Simple mass balance calculations indicate that Ca in the FCT is greater than ~75% mantle derived. Similar mixing models based on published Nd data for the FCT that consider the range of possible crustal source components can deviate substantially from the Ca models. At face value the Nd data indicate that the FCT magma underwent significant crustal assimilation (i.e., at least ~10% and possibly ~75% of the Nd appears to have come from an enriched source component). So even in cases where a

  16. The petrogenesis of anorogenic felsic magmas and AMCG suites: Insights on element mobility and mutual cryptic contamination from polythermal experiments

    Science.gov (United States)

    Martin, Robert F.

    2012-10-01

    The close association of mantle-derived mafic rocks and crust-derived felsic rocks in AMCG suites the world over is now interpreted in terms of delamination of the lithospheric keel of an orogen within a short time after the cessation of a major collision. The stage is set for the ascent of an asthenospheric diapir, which is accompanied by the ascent of a stream of H2O-CO2 representing regional degassing of the mantle in the ensuing extensional setting. The crust gets variably metasomatized prior to melting, and this episode of melting seems to involve almost complete melting rather than the expected films of leucosome. Results of polythermal experiments with a large array of target rocks (pulverized) + H2O show that it is possible to mobilize the major elements K, Na, Al, Si and Fe such that the transported fractions resembles an A-type granite or syenite. The open-system process increases in efficiency with increasing temperature and increasing pressure. A stream of such fluid interacting with gabbro or basic magma could create anorthositic and ultrabasic assemblages that are candidates for contamination of pools of basic magma in the uppermost mantle and lower crust. The same stream continues its buoyant rise and makes over the sterile granulitic lower and middle crust into a geochemically fertile protolith for the generation of A-type felsic magmas by wholesale anatexis.

  17. Dynamics of Bubbly-magma Flow in Conduits: Stress and Expansion Regimes of Magma Fragmentation

    Science.gov (United States)

    Mitani, N. K.; Koyaguchi, T.; Ida, Y.

    2002-12-01

    Explosive volcanic eruptions are characterized by magma fragmentation, that is, the process through which a bubbly magma is changed into a gas-pyroclast dispersion. Two criteria of mechanisms have been proposed for the magma fragmentation so far. First, magma fragments when stress or strain rate of magma around bubbles exceeds a critical value. Second, magma disrupts due to the instability of thin magma-foam. Which criterion is actually applicable is not yet known. In order to clarify the physics of the magma fragmentation, we numerically study one-dimensional steady flows with bubble growth in conduits. The spherical cell model is used to calculate expansion of bubbles in ascending visco-elastic magma. The stress around bubbles generally grows as magma ascends and the pressure difference between bubbles and surrounding magma increases. In some conditions, the stress becomes critically large only when the flow velocity approaches the sound speed meeting the choking condition. In other conditions, the stress becomes large enough as magma pressure drops with bubble pressure kept almost unchanged. These two distinct types may correspond to the above two criteria of fragmentation mechanisms. In the former case, void fraction becomes close to unity before the stress reaches the strength of magma. In such case, the magma does not fragment due to the visco-elastic deformations but fragments by the instability of the thin magma-foam (`expansion' regime). In the latter case, on the other hand, the stress reaches the magma strength at much lower void fractions. In such case, the magma fragments due to the visco-elastic deformation around bubbles (`stress' regime). The `expansion' and `stress' regimes occur when the ratio of the initial wall-friction stress to the magma strength is sufficiently smaller and greater than unity, respectively.

  18. Pulses of earthquake activity in the mantle wedge track the route of slab fluid ascent

    Science.gov (United States)

    White, Lloyd; Rawlinson, Nicholas; Lister, Gordon; Tanner, Dominique; Macpherson, Colin; Morgan, Jason

    2016-04-01

    Earthquakes typically record the brittle failure of part of the Earth at a point in space and time. These almost invariably occur within the crust or where the upper surface of subducting lithosphere interacts with the overriding mantle. However, there are also reports of rare, enigmatic earthquakes beneath rifts, above mantle plumes or very deep in the mantle. Here we report another type of mantle earthquake and present three locations where earthquake clusters occur in the mantle wedge overlying active subduction zones. These earthquake clusters define broadly circular to ellipsoidal columns that are 50 km or greater in diameter from depths between ~150 km and the surface. We interpret these rare pulses of earthquakes as evidence of near vertical transport of fluids (and associated flux-melts) from the subducted lithosphere through the mantle wedge. Detailed temporal analysis shows that most of these earthquakes occur over two-year periods, with the majority of events occurring in discrete month-long flurries of activity. As the time and location of each earthquake is recorded, pulses of seismic activity may provide information about the rate of magma ascent from the dehydrated subducted slab to sub-arc/backarc crust. This work indicates that fluids are not transported through the mantle wedge by diapirism, but through sub-vertical pathways facilitated by fracture networks and dykes on monthly to yearly time scales. These rare features move us toward solving what has until now represented a missing component of the subduction factory.

  19. Lithospheric magma dynamics beneath the El Hierro Volcano, Canary Islands: insights from fluid inclusions

    Science.gov (United States)

    Oglialoro, E.; Frezzotti, M. L.; Ferrando, S.; Tiraboschi, C.; Principe, C.; Groppelli, G.; Villa, I. M.

    2017-10-01

    At active volcanoes, petrological studies have been proven to be a reliable approach in defining the depth conditions of magma transport and storage in both the mantle and the crust. Based on fluid inclusion and mineral geothermobarometry in mantle xenoliths, we propose a model for the magma plumbing system of the Island of El Hierro (Canary Islands). The peridotites studied here were entrained in a lava flow exposed in the El Yulan Valley. These lavas are part of the rift volcanism that occurred on El Hierro at approximately 40-30 ka. The peridotites are spinel lherzolites, harzburgites, and dunites which equilibrated in the shallow mantle at pressures between 1.5 and 2 GPa and at temperatures between 800 and 950 °C (low-temperature peridotites; LT), as well as at higher equilibration temperatures of 900 to 1100 °C (high-temperature peridotites; HT). Microthermometry and Raman analyses of fluid inclusions reveal trapping of two distinct fluid phases: early type I metasomatic CO2-N2 fluids ( X N2 = 0.01-0.18; fluid density (d) = 1.19 g/cm3), coexisting with silicate-carbonate melts in LT peridotites, and late type II pure CO2 fluids in both LT (d = 1.11-1.00 and 0.75-0.65 g/cm3) and HT ( d = 1.04-1.11 and 0.75-0.65 g/cm3) peridotites. While type I fluids represent metasomatic phases in the deep oceanic lithosphere (at depths of 60-65 km) before the onset of magmatic activity, type II CO2 fluids testify to two fluid trapping episodes during the ascent of xenoliths in their host mafic magmas. Identification of magma accumulation zones through interpretation of type II CO2 fluid inclusions and mineral geothermobarometry indicate the presence of a vertically stacked system of interconnected small magma reservoirs in the shallow lithospheric mantle between a depth of 22 and 36 km (or 0.67 to 1 GPa). This magma accumulation region fed a short-lived magma storage region located in the lower oceanic crust at a depth of 10-12 km (or 0.26-0.34 GPa). Following our model

  20. Magma evolution along the East Pacific Rise between 11⁰N and 15⁰N

    Science.gov (United States)

    Miyakawa, Y.; Zerda, C.; Barton, M.

    2015-12-01

    The fast spreading East Pacific Rise (EPR) between 11°N and 14°N is characterized by several discontinuities. Previous work suggests that magmas erupted at ridge discontinuities partially crystallize at higher pressures than magmas erupted along "normal" ridge segments. We have determined the pressures of partial crystallization of erupted magmas using 922 glass analyses compiled from Gale et al., (2013). The results indicate crystallization at a wide range of pressures (1 bar to ~ 700 MPa) over the whole length of this ridge segment with no apparent correlation between pressure and ridge discontinuities. This might indicate that some magmas begin to crystallize in the mantle. Alternatively, the compositions of some magmas have been modified by interaction with preexisting crust so that the calculated pressures may not represent the true pressure of partial crystallization. We compiled geochemical data for 178 whole-rock samples from Gale et al., (2013) to examine the possibility that some magmas have interacted with oceanic crust. We found no systematic changes in composition with latitude or ridge discontinuities, and values of Na8 suggest near-constant degrees of melting at near constant temperature in the mantle beneath the ridge. However, normalizing trace element concentrations to the composition of average NMORB reveals that the southern and northern ridge segments have compositions similar to NMORB, although some samples are enriched in highly incompatible elements. In contrast, samples from the middle segment are depleted in highly incompatible elements relative to NMORB. The simplest interpretation is that magmas were ultimately derived from mantle sources variably depleted in highly incompatible elements. Plots of P2O5 and TiO2 versus K2O suggest that crystallization was not the only process occurring in the crust, and some magmas assimilated preexisting oceanic crust during ascent. This suggests the possibility that all magmas were ultimately derived

  1. Global Search and Local Ascent for Large Cournot Games

    Directory of Open Access Journals (Sweden)

    Maria Sarasan

    2010-12-01

    Full Text Available Equilibria detection in large games is a fundamental problem in computational game theory. A memetic algorithm, Global Search and Local Ascent (GSLA, is proposed. GSLA's performance is evaluated by means of numerical experiments within the framework of a Cournot game involving up to 100 players and by comparison with an evolutionary multiobjective optimization algorithm adapted for Nash equilibria detection.

  2. Silicic magma entering a basaltic magma chamber: eruptive dynamics and magma mixing — an example from Salina (Aeolian islands, Southern Tyrrhenian Sea)

    Science.gov (United States)

    Calanchi, Natale; de Rosa, Rosanna; Mazzuoli, Roberto; Rossi, Pierluigi; Santacroce, Roberto; Ventura, Guido

    1993-09-01

    The Pollara tuff-ring resulted from two explosive eruptions whose deposits are separated by a paleosol 13 Ka old. The oldest deposits (LPP, about 0.2 km3) consist of three main fall units (A, B, C) deposited from a subplinian column whose height (7 14 km) increased with time from A to C, as a consequence of the increased magma discharge rate during the eruption (1 8x106 kg/s). A highly variable juvenile population characterizes the eruption. Black, dense, highly porphyritic, mafic ejecta (SiO2=50 55%) almost exclusively form A deposits, whereas grey, mildly vesiculated, mildly porphyritic pumice (SiO2=56 67%) and white, highly vesiculated, nearly aphyric pumice (SiO2=66 71%) predominate in B and C respectively. Mafic cumulates are abundant in A, while crystalline lithic ejecta first appear in B and increase upward. The LPP result from the emptying of an unusual and unstable, compositionally zoned, shallow magma chamber in which high density mafic melts capped low density salic ones. Evidence of the existence of a short crystal fractionation series is found in the mafic rocks; the andesitic pumice results from complete blending between rhyolitic and variously fractionated mafic melts (salic component up to 60 wt%), whereas bulk dacitic compositions mainly result from the presence of mafic xenocrysts within rhyolitic glasses. Viscosity and composition-mixing diagrams show that blended liquids formed when the visosities of the two end members had close values. The following model is suggested: 1. A rhyolitic magma rising through the metamorphic basement enterrd a mafic magma chamber whose souter portions were occupied by a highly viscous, mafic crystal mush. 2. Under the pressure of the rhyolitic body the nearly rigid mush was pushed upwards and mafic melts were squeezed against the walls of the chamber, beginning roof fracturing and mingling with silicic melts. 3. When the equilibrium temperature was reached between mafic and silicic melts, blended liquids rapidly

  3. Physiological responses in rock climbing with repeated ascents over a 10-week period

    NARCIS (Netherlands)

    Espana-Romero, Vanesa; Jensen, Randall L.; Sanchez, Xavier; Ostrowski, Megan L.; Szekely, Jay E.; Watts, Phillip B.

    The purpose was to analyze the physiological responses and energy expenditure during repeated ascents of the same climbing route over a 10-week period. Nine climbers completed nine ascents of a specific route spaced 1 week apart. Expired air was analyzed continuously during each ascent, and time of

  4. Fe in magma - An overview

    Directory of Open Access Journals (Sweden)

    M. Wilke

    2005-06-01

    Full Text Available The strong influence of physical conditions during magma formation on Fe equilibria offers a large variety of possibilities to deduce these conditions from Fe-bearing phases and phase assemblages found in magmatic rocks. Conditions of magma genesis and their evolution are of major interest for the understanding of volcanic eruptions. A brief overview on the most common methods used is given together with potential problems and limitations. Fe equilibria are not only sensitive to changes in intensive parameters (especially T and fO2 and extensive parameters like composition also have major effects, so that direct application of experimentally calibrated equilibria to natural systems is not always possible. Best estimates for pre-eruptive conditions are certainly achieved by studies that relate field observations directly to experimental observations for the composition of interest using as many constraints as possible (phase stability relations, Fe-Ti oxides, Fe partitioning between phases, Fe oxidation state in glass etc.. Local structural environment of Fe in silicate melts is an important parameter that is needed to understand the relationship between melt transport properties and melt structure. Assignment of Fe co-ordination and its relationship to the oxidation state seems not to be straightforward. In addition, there is considerable evidence that the co-ordination of Fe in glass differs from that in the melt, which has to be taken into account when linking melt structure to physical properties of silicate melts at T and P.

  5. Design and Analysis of Optimal Ascent Trajectories for Stratospheric Airships

    Science.gov (United States)

    Mueller, Joseph Bernard

    Stratospheric airships are lighter-than-air vehicles that have the potential to provide a long-duration airborne presence at altitudes of 18-22 km. Designed to operate on solar power in the calm portion of the lower stratosphere and above all regulated air traffic and cloud cover, these vehicles represent an emerging platform that resides between conventional aircraft and satellites. A particular challenge for airship operation is the planning of ascent trajectories, as the slow moving vehicle must traverse the high wind region of the jet stream. Due to large changes in wind speed and direction across altitude and the susceptibility of airship motion to wind, the trajectory must be carefully planned, preferably optimized, in order to ensure that the desired station be reached within acceptable performance bounds of flight time and energy consumption. This thesis develops optimal ascent trajectories for stratospheric airships, examines the structure and sensitivity of these solutions, and presents a strategy for onboard guidance. Optimal ascent trajectories are developed that utilize wind energy to achieve minimum-time and minimum-energy flights. The airship is represented by a three-dimensional point mass model, and the equations of motion include aerodynamic lift and drag, vectored thrust, added mass effects, and accelerations due to mass flow rate, wind rates, and Earth rotation. A representative wind profile is developed based on historical meteorological data and measurements. Trajectory optimization is performed by first defining an optimal control problem with both terminal and path constraints, then using direct transcription to develop an approximate nonlinear parameter optimization problem of finite dimension. Optimal ascent trajectories are determined using SNOPT for a variety of upwind, downwind, and crosswind launch locations. Results of extensive optimization solutions illustrate definitive patterns in the ascent path for minimum time flights across

  6. CO2-crystal wettability in potassic magmas: implications for eruptive dynamics in light of experimental evidence for heterogeneous nucleation

    Science.gov (United States)

    Sottili, Gianluca; Fanara, Sara; Silleni, Aurora; Palladino, Danilo M.; Schmidt, Burkhard C.

    2017-05-01

    The volatile content in magmas is fundamental for the triggering and style of volcanic eruptions. Carbon dioxide, the second most abundant volatile component in magmas after H2O, is the first to reach saturation upon ascent and depressurization. We investigate experimentally CO2-bubble nucleation in trachybasalt and trachyte melts at high temperature and high pressure (HT and HP) through wetting-angle measurements on different (sialic, mafic or oxide) phenocryst phases. The presence of crystals lowers the supersaturation required for CO2-bubble nucleation up to 37 per cent (heterogeneous nucleation, HeN), with a minor role of mineral chemistry. Different from H2O-rich systems, feldspar crystals are effective in reducing required supersaturation for bubble nucleation. Our data suggest that leucite, the dominant liquidus phase in ultrapotassic systems at shallow depth (i.e. explosive behaviour.

  7. Incremental growth of an upper crustal, A-type pluton, Argentina: Evidence of a re-used magma pathway

    Science.gov (United States)

    Alasino, Pablo H.; Larrovere, Mariano A.; Rocher, Sebastián; Dahlquist, Juan A.; Basei, Miguel A. S.; Memeti, Valbone; Paterson, Scott; Galindo, Carmen; Macchioli Grande, Marcos; da Costa Campos Neto, Mario

    2017-07-01

    Carboniferous igneous activity in the Sierra de Velasco (NW Argentina) led to the emplacement of several magmas bodies at shallow levels (< 2 kbar). One of these, the San Blas intrusive complex formed over millions of years (≤ 2-3 m.y.) through three periods of magma additions that are characterized by variations in magma sources and emplacement style. The main units, mostly felsic granitoids, have U-Pb zircon crystallization ages within the error range. From older to younger (based on cross-cutting relationships) intrusive units are: (1) the Asha unit (340 ± 7 Ma): a tabular to funnel-shaped intrusion emplaced during a regional strain field dominated by WSW-ENE shortening with contacts discordant to regional host-rock structures; (2) the San Blas unit (344 ± 2 Ma): an approximate cylindrical-shaped intrusion formed by multiple batches of magmas, with a roughly concentric fabric pattern and displacement of the host rock by ductile flow of about 35% of shortening; and (3) the Hualco unit (346 ± 6 Ma): a small body with a possible mushroom geometry and contacts concordant to regional host-rock structures. The magma pulses making up these units define two groups of A-type granitoids. The first group includes the peraluminous granitic rocks of the Asha unit generated mostly by crustal sources (εNdt = - 5.8 and εHft in zircon = - 2.9 to - 4.5). The second group comprises the metaluminous to peraluminous granitic rocks of the youngest units (San Blas and Hualco), which were formed by a heterogeneous mixture between mantle and crustal sources (εNdt = + 0.6 to - 4.8 and εHft in zircon = + 3 to - 6). Our results provide a comprehensive view of the evolution of an intrusive complex formed from multiple non-consanguineous magma intrusions that utilized the same magmatic plumbing system during downward transfer of host materials. As the plutonic system matures, the ascent of magmas is governed by the visco-elastic flow of host rock that for younger batches include

  8. Magma Energy Research Project, FY80 annual progress report

    Energy Technology Data Exchange (ETDEWEB)

    Colp, J.L. (ed.)

    1982-04-01

    The technical feasibility of extracting energy from magma bodies is explored. Five aspects of the project are studied: resource location and definition, source tapping, magma characterization, magma/material compatibility, and energy extraction.

  9. A fast ascent trajectory optimization method for hypersonic air-breathing vehicles

    Science.gov (United States)

    Murillo, Oscar J., Jr.

    The objective of this dissertation is to investigate a fast and reliable method to generate three-dimensional optimal ascent trajectories for hypersonic air-breathing vehicles. The problem is notoriously difficult because of the strong nonlinear coupling amongst aerodynamics, propulsion, vehicle attitude and trajectory state. As such an algorithm matures, the ultimate goal is to realize optimal closed-loop ascent guidance for hypersonic air-breathing vehicles. The problem is formulated as a fuel-optimal control problem. The corresponding necessary conditions are given. It is shown how the original problem of search for the optimal control commands can be reduced to a univariate root-finding problem at each point along the trajectory. A finite difference scheme is used to numerically solve the associated two-point-boundary-value problem. Evaluation of the approach is done through open-loop solutions and closed-loop simulations. The results show promising potential of the proposed approach as a rapid trajectory optimization tool for the class of hypersonic air-breathing vehicles.

  10. Multiple rhyolite magmas and basalt injection in the 17.7 ka Rerewhakaaitu eruption episode from Tarawera volcanic complex, New Zealand

    Science.gov (United States)

    Shane, Phil; Martin, S. B.; Smith, V. C.; Beggs, K. F.; Darragh, M. B.; Cole, J. W.; Nairn, I. A.

    2007-07-01

    The 17.7 ka Rerewhakaaitu eruption episode (volume ˜ 5 km 3 DRE rhyolite magma) was the second of five major episodes that have built the Tarawera volcanic complex in the Okataina Volcanic Centre over the past 22 kyr. The Rerewhakaaitu episode produced a widespread tephra fall deposit, associated proximal pyroclastic flow deposits, and voluminous rhyolite lava extrusions. Two different rhyolite magmas (T1 and T2) were simultaneously erupted from the main vent area throughout much of the eruption episode. T1 magma was a crystal-poor orthopyroxene-hornblende rhyolite that is highly evolved (whole rock SiO 2 = 77 wt.%), with a moderate temperature (˜ 760 °C, based on Fe-Ti oxides). T2 is a crystal-rich biotite-hornblende rhyolite that is less evolved (SiO 2 = 75 wt.%), with a Fe-Ti oxide temperature of ˜ 700 °C. Ejecta from the simultaneous and sequential eruption of these two magmas include some pumice clasts with mixed (hybrid) and mingled glass compositions and crystal populations. A third rhyolite magma (T3) was extruded from another vent 3 km distant to form an apparently contemporaneous lava dome. T3 was the least evolved (SiO 2 = 74 wt.%) and hottest (˜ 820 °C) of the three magmas. Saturation pressures calculated using dissolved H 2O and CO 2 contents of melt inclusions in quartz crystals indicate that T2 magma stagnated and crystallised at about 12 km depth, while small quartz crystals in T1 magma grew during ascent through ˜ 8 km depths. Some T1 and T2 rhyolite clasts contain vesicular brown blebs with widely variable (andesite to rhyolite) glass compositions, accompanied by olivine, clinopyroxene and calcic plagioclase crystals that are interpreted as xenocrysts derived from injected basalt. Temperatures over 1000 °C estimated from pyroxene phase equilibria in these clasts reflect intrusion of the more mafic magma, which is now identified as the priming and triggering mechanism for three of the four post-22 ka Tarawera rhyolite eruption episodes

  11. Human Mars Ascent Vehicle Configuration and Performance Sensitivities

    Science.gov (United States)

    Polsgrove, Tara P.; Thomas, Herbert D.; Stephens, Walter; Collins, Tim; Rucker, Michelle; Gernhardt, Mike; Zwack, Matthew R.; Dees, Patrick D.

    2017-01-01

    The total ascent vehicle mass drives performance requirements for the Mars descent systems and the Earth to Mars transportation elements. Minimizing Mars Ascent Vehicle (MAV) mass is a priority and minimizing the crew cabin size and mass is one way to do that. Human missions to Mars may utilize several small cabins where crew members could live for days up to a couple of weeks. A common crew cabin design that can perform in each of these applications is desired and could reduce the overall mission cost. However, for the MAV, the crew cabin size and mass can have a large impact on vehicle design and performance. This paper explores the sensitivities to trajectory, propulsion, crew cabin size and the benefits and impacts of using a common crew cabin design for the MAV. Results of these trades will be presented along with mass and performance estimates for the selected design.

  12. The nanofluidics can explain ascent of water in tallest trees

    CERN Document Server

    Gouin, Henri

    2012-01-01

    In Amazing numbers in biology, Flindt reports a giant, 128 meter-tall eucalyptus, and a 135 meter-tall sequoia. However, the explanation of the maximum altitude of the crude sap ascent and consequently the main reason of the maximum size that trees can reach is not well understood. According to tree species, the crude sap is driven in xylem microtubes with diameters ranging between 50 and 400 micrometers. The sap contains diluted salts but its physical properties are roughly those of water; consequently, hydrodynamic, capillarity and osmotic pressure yield a crude sap ascent of a few tens of meters only. Today, we can propound a new understanding of the ascent of sap to the top of very tall trees thanks to a new comparison between experiments associated with the cohesion-tension theory and the disjoining pressure concept. Here we show that the pressure in the water-storing tracheids of leaves can be strongly negative whereas the pressure in the xylem microtubes of stems may remain positive when, at high level...

  13. Age-related arrhythmogenesis on ascent and descent: "autonomic conflicts" on hypoxia/reoxygenation at high altitude?

    Science.gov (United States)

    Behn, Claus; Dinamarca, Gustavo A; De Gregorio, Nicole F; Lips, Viviana; Vivaldi, Ennio A; Soza, Daniel; Guerra, Manuel A; Jiménez, Raúl F; Lecannelier, Eduardo A; Varela, Héctor; Silva-Urra, Juan A

    2014-09-01

    To discern whether arrhythmogenesis at high-altitude (HA) may differ depending on ascent or descent, as well as on age. Male subjects (37.9±12.0 SD y, n=33) were separated into a young (Y) group (29.6±5.73 SD y, n=18) and an older (O) one (47.9±9.83 SD y, n=15). All subjects were monitored by Holter electrocardiography while successively ascending (41.2±7.51 SD min) and descending (38.7±6.68 SD min) between 2950 and 5050 m as car passengers on a 25 km road in Northern Chile. Arrhythmic events (AE) ensued when the difference between two consecutive RR intervals exceeded 0.16 sec. From 311 AE registered, 29% occurred on ascent and 71% on descent, the sinusal type predominating in both age groups. AE incidence, RR interval duration, and heart rate variability (HRV) in the time domain (RMSSD) increased during descent, as compared to ascent, in the Y group (p<0.05), but not in the O one. Independently of age, AE incidence along descent associates with the time previously spent at 5050 m (p<0.001). Rapid transitions at HA favor arrhythmogenesis, the latter becoming evident particularly in the Y group on descent. Age-dependent changes of autonomic activity appear to be involved in arrhythmogenesis on transitions at HA.

  14. Effect of Acetazolamide and Gingko Biloba on the Human Pulmonary Vascular Response to an Acute Altitude Ascent

    Science.gov (United States)

    Ke, Tao; Wang, Jiye; Swenson, Erik R.; Zhang, Xiangnan; Hu, Yunlong; Chen, Yaoming; Liu, Mingchao; Zhang, Wenbin; Zhao, Feng; Shen, Xuefeng; Yang, Qun

    2013-01-01

    Abstract Ke, Tao, Jiye Wang, Erik R. Swenson, Xiangnan Zhang, Yunlong Hu, Yaoming Chen, Mingchao Liu, Wenbin Zhang, Feng Zhao, Xuefeng Shen, Qun Yang, Jingyuan Chen, and Wenjing Luo. Effect of acetazolamide and gingko biloba on the human pulmonary vascular response to an acute altitude ascent. High Alt Med Biol 14:162–167, 2013.—Acetazolamide and gingko biloba are the two most investigated drugs for the prevention of acute mountain sickness (AMS). Evidence suggests that they may also reduce pulmonary artery systolic pressure (PASP). To investigate whether these two drugs for AMS prevention also reduce PASP with rapid airlift ascent to high altitude, a randomized controlled trial was conducted on 28 healthy young men with acetazolamide (125 mg bid), gingko biloba (120 mg bid), or placebo for 3 days prior to airlift ascent (397 m) and for the first 3 days at high altitude (3658 m). PASP, AMS, arterial oxygen saturation (Sao2), mean arterial pressure (MAP), heart rate (HR), forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), and peak expiratory flow (PEF) were assessed both at 397 m and 3658 m. HR, PEF, and PASP increased with altitude exposure (pbiloba (mean at 3658 m, 33.7 mm Hg, p=0.001; incremental change, 13.1 mm Hg, 95%CI., 9.6–16.5 mm Hg, p=0.002), and with placebo (mean at 3658 m, 34.7 mm Hg, pgingko biloba, mitigates the early increase of PASP in a quick ascent profile. PMID:23795737

  15. Syneruptive deep magma transfer and shallow magma remobilization during the 2011 eruption of Shinmoe-dake, Japan—Constraints from melt inclusions and phase equilibria experiments

    Science.gov (United States)

    Suzuki, Yuki; Yasuda, Atsushi; Hokanishi, Natsumi; Kaneko, Takayuki; Nakada, Setsuya; Fujii, Toshitsugu

    2013-05-01

    The 2011 Shinmoe-dake eruption started with a phreatomagmatic eruption (Jan 19), followed by climax sub-Plinian events and subsequent explosions (Jan 26-28), lava accumulation in the crater (end of January), and vulcanian eruptions (February-April). We have studied a suite of ejecta to investigate the magmatic system beneath the volcano and remobilization processes in the silicic magma mush. Most of the ejecta, including brown and gray colored pumice clasts (Jan 26-28), ballistically ejected dense lava (Feb 1), and juvenile particles in ash from the phreatomagmatic and vulcanian events are magma mixing products (SiO2 = 57-58 wt.%; 960-980 °C). Mixing occurred between silicic andesite (SA) and basaltic andesite (BA) magmas at a fixed ratio (40%-30% SA and 60%-70% BA). The SA magma had SiO2 = 62-63 wt.% and a temperature of 870 °C, and contains 43 vol.% phenocrysts of pyroxene, plagioclase, and Fe-Ti oxide. The BA magma had SiO2 = 55 wt.% and a temperature of 1030 °C, and contains 9 vol.% phenocrysts of olivine and plagioclase. The SA magma partly erupted without mixing as white parts of pumices and juvenile particles. The two magmatic end-members crystallized at different depths, requiring the presence of two separate magma reservoirs; shallower SA reservoir and deeper BA reservoir. An experimental study reveals that the SA magma had been stored at a pressure of 125 MPa, corresponding to a depth of 5 km. The textures and forms of phenocrysts from the BA magma indicate rapid crystallization directly related to the 2011 eruptive activity. The wide range of H2O contents of olivine melt inclusions (5.5-1.6 wt.%) indicates that rapid crystallization was induced by decompression, with olivine crystallization first (≤ 250 MPa), followed by plagioclase addition. The limited occurrence of olivine melt inclusions trapped at depths of existed in the SA reservoir in the precursor stage, were finally erupted together. Magnetite phenocrysts in the Feb 18 ash reveal the

  16. Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano.

    Science.gov (United States)

    Druitt, T H; Costa, F; Deloule, E; Dungan, M; Scaillet, B

    2012-02-01

    Caldera-forming volcanic eruptions are low-frequency, high-impact events capable of discharging tens to thousands of cubic kilometres of magma explosively on timescales of hours to days, with devastating effects on local and global scales. Because no such eruption has been monitored during its long build-up phase, the precursor phenomena are not well understood. Geophysical signals obtained during recent episodes of unrest at calderas such as Yellowstone, USA, and Campi Flegrei, Italy, are difficult to interpret, and the conditions necessary for large eruptions are poorly constrained. Here we present a study of pre-eruptive magmatic processes and their timescales using chemically zoned crystals from the 'Minoan' caldera-forming eruption of Santorini volcano, Greece, which occurred in the late 1600s BC. The results provide insights into how rapidly large silicic systems may pass from a quiescent state to one on the edge of eruption. Despite the large volume of erupted magma (40-60 cubic kilometres), and the 18,000-year gestation period between the Minoan eruption and the previous major eruption, most crystals in the Minoan magma record processes that occurred less than about 100 years before the eruption. Recharge of the magma reservoir by large volumes of silicic magma (and some mafic magma) occurred during the century before eruption, and mixing between different silicic magma batches was still taking place during the final months. Final assembly of large silicic magma reservoirs may occur on timescales that are geologically very short by comparison with the preceding repose period, with major growth phases immediately before eruption. These observations have implications for the monitoring of long-dormant, but potentially active, caldera systems.

  17. Shallow and deep crustal control on differentiation of calc-alkaline and tholeiitic magma

    Science.gov (United States)

    Hora, John M.; Singer, Brad S.; Wörner, Gerhard; Beard, Brian L.; Jicha, Brian R.; Johnson, Clark M.

    2009-07-01

    The role of changing crustal interaction and plumbing geometry in modulating calc-alkaline vs. tholeiitic magma affinity is well illustrated by the influence of 70 km thick crust beneath Volcán Parinacota. Changes in petrologic affinity correlate with periods of cone-building, sector collapse, and rebuilding of the volcano over the last 52 ka, and are well explained by changes in magma recharge regime. With increasing recharge and magma output, lavas transition from low-Fe, strongly calc-alkaline, phenocryst-rich silicic compositions to medium-Fe, near-tholeiitic, mafic, and aphanitic characteristics. Strontium isotope data show that the change in magma regime did not affect all parts of the system simultaneously; these are characterized by distinctive 87Sr/ 86Sr ratios, which suggest an initially compartmentalized system. Relatively high ( 230Th/ 232Th) activity ratios of ~ 0.72 in early-erupted calc-alkaline lavas are consistent with interaction with high-U upper crust. Low ( 230Th/ 232Th) activity ratios of ~ 0.55 and up to 33% Th-excess in younger near-tholeiitic lavas correlate with steep REE patterns, indicating lower-crustal interaction. Thorium-excesses at the time of eruption approach the maximum that can be generated via small-degree garnet-residual melting in the lower crust or mantle and imply that transit time through the crustal column for the most tholeiitic magmas had to be short, on the order of secular equilibrium, suggesting stagnation times > 3 × 10 5 yr in the upper crust. In addition to more traditional explanations tied to magma source, expression of low-Fe 'calc-alkaline' (CA) vs. medium-Fe 'near-tholeiitic' (TH) magma series at the scale of individual volcanoes is likely to be modulated by transitions from compartmentalized, stagnant, assimilation-prone 'dirty' systems (CA) to 'clean' systems (TH) that are characterized by rapid magma throughput and minimal opportunity for upper-crustal contamination.

  18. Magma Beneath Yellowstone National park.

    Science.gov (United States)

    Eaton, G P; Christiansen, R L; Iyer, H M; Pitt, A D; Mabey, D R; Blank, H R; Zietz, I; Gettings, M E

    1975-05-23

    The Yellowstone plateau volcanic field is less than 2 million years old, lies in a region of intense tectonic and hydrothermal activity, and probably has the potential for further volcanic activity. The youngest of three volcanic cycles in the field climaxed 600,000 years ago with a voluminous ashflow eruption and the collapse of two contiguous cauldron blocks. Doming 150,000 years ago, followed by voluminous rhyolitic extrusions as recently as 70,000 years ago, and high convective heat flow at present indicate that the latest phase of volcanism may represent a new magmatic insurgence. These observations, coupled with (i) localized postglacial arcuate faulting beyond the northeast margin of the Yellowstone caldera, (ii) a major gravity low with steep bounding gradients and an amplitude regionally atypical for the elevation of the plateau, (iii) an aeromagnetic low reflecting extensive hydrothermal alteration and possibly indicating the presence of shallow material above its Curie temperature, (iv) only minor shallow seismicity within the caldera (in contrast to a high level of activity in some areas immediately outside), (v) attenuation and change of character of seismic waves crossing the caldera area, and (vi) a strong azimuthal pattern of teleseismic P-wave delays, strongly suggest that a body composed at least partly of magma underlies the region of the rhyolite plateau, including the Tertiary volcanics immediately to its northeast. The Yellowstone field represents the active end of a system of similar volcanic foci that has migrated progressively northeastward for 15 million years along the trace of the eastern Snake River Plain (8). Regional aeromagnetic patterns suggest that this course was guided by the structure of the Precambrian basement. If, as suggested by several investigators (24), the Yellowstone magma body marks a contemporary deep mantle plume, this plume, in its motion relative to the North American plate, would appear to be "navigating" along a

  19. Volatiles Which Increase Magma Viscosity

    Science.gov (United States)

    Webb, S.

    2015-12-01

    The standard model of an erupting volcano is one in which the viscosity of a decompressing magma increases as the volatiles leave the melt structure to form bubbles. It has now been observed that the addition of the "volatiles" P, Cl and F result in an increase in silicate melt viscosity. This observation would mean that the viscosity of selected degassing magmas would decrease rather than increase. Here we look at P, Cl and F as three volatiles which increase viscosity through different structural mechanisms. In all three cases the volatiles increase the viscosity of peralkaline composition melts, but appear to always decrease the viscosity of peraluminous melts. Phosphorus causes the melt to unmix into a Na-P rich phase and a Na-poor silicate phase. Thus as the network modifying Na (or Ca) are removed to the phosphorus-rich melt, the matrix melt viscosity increases. With increasing amounts of added phosphorus (at network modifying Na ~ P) the addition of further phosphorus causes a decrease in viscosity. The addition of chlorine to Fe-free aluminosilicate melts results in an increase in viscosity. NMR data on these glass indicates that the chlorine sits in salt-like structures surrounded by Na and/or Ca. Such structures would remove network-modifying atoms from the melt structure and thus result in an increase in viscosity. The NMR spectra of fluorine-bearing glasses shows that F takes up at least 5 different structural positions in peralkaline composition melts. Three of these positions should result in a decrease in viscosity due to the removal of bridging oxygens. Two of the structural positons of F, however, should result in an increase in viscosity as they require the removal of network-modifying atoms from the melt structure (with one of the structures being that observed for Cl). This would imply that increasing amounts of F might result in an increase in viscosity. This proposed increase in viscosity with increasing F has now been experimentally confirmed.

  20. Pre-1991 sulfur transfer between mafic injections and dacite magma in the Mt. Pinatubo reservoir

    Science.gov (United States)

    Di, Muro A.; Pallister, J.; Villemant, B.; Newhall, C.; Semet, M.; Martinez, M.; Mariet, C.

    2008-01-01

    Before the 1991-1992 activity, a large andesite lava dome belonging to the penultimate Pinatubo eruptive period (Buag ??? 500??BP) formed the volcano summit. Buag porphyritic andesite contains abundant amphibole-bearing microgranular enclaves of basaltic-andesite composition. Buag enclaves have lower K2O and incompatible trace element (LREE, U, Th) contents than mafic pulses injected in the Pinatubo reservoir during the 1991-1992 eruptive cycle. This study shows that Buag andesite formed by mingling of a hot, water-poor and reduced mafic magma with cold, hydrous and oxidized dacite. Depending on their size, enclaves experienced variable re-equilibration during mixing/mingling. Re-equilibration resulted in hydration, oxidation and transfer of mobile elements (LILE, Cu) from the dacite to the mafic melts and prompted massive amphibole crystallization. In Buag enclaves, S-bearing phases (sulfides, apatite) and melt inclusions in amphibole and plagioclase record the evolution of sulfur partition among melt, crystal and fluid phases during magma cooling and oxidation. At high temperature, sulfur is partitioned between andesitic melt and sulfides (Ni-pyrrhotite). Magma cooling, oxidation and hydration resulted in exsolution of a S-Cl-H2O vapor phase at the S-solubility minimum near the sulfide-sulfate redox boundary. Primary magmatic sulfide (pyrrhotite) and xenocrystic sulfide grains (pyrite), recycled together with olivines and pyroxenes from old mafic intrusives, were replaced by Cu-rich phases (chalcopyrite, cubanite) and, partially, by Ba-Sr sulfate. Sulfides degassed and transformed into residual spongy magnetite in response to fS2 drop during final magma ascent and decompression. Our research suggests that a complete evaluation of the sulfur budget at Pinatubo must take into account the en route S assimilation from the country rocks. Moreover, this study shows that the efficiency of sulfur transfer between mafic recharges and injected magmas is controlled by the

  1. Interaction of coeval felsic and mafic magmas from the Kanker ...

    Indian Academy of Sciences (India)

    Blobs of mafic magma form as MMEs in the felsic magma and they scatter throughout the pluton due to convection. At a later stage, if mafic magma enters the system after partial crystallization of felsic phase, mechanical interaction between the magmas leads to the formation of fragmented dyke or syn-plutonic mafic dyke.

  2. Thermal stress fracturing of magma simulant materials

    Energy Technology Data Exchange (ETDEWEB)

    Wemple, R.P.; Longcope, D.B.

    1986-10-01

    Direct contact heat exchanger concepts for the extraction of energy from magma chambers are being studied as part of the DOE-funded Magma Energy Research Program at Sandia National Laboratories. These concepts require the solidification of molten material by a coolant circulated through a borehole drilled into the magma and subsequent fracture of the solid either as a natural consequence of thermal stress or by deliberate design (intentional flaws, high pressure, etc.). This report summarizes the results of several thermal stress fracturing experiments performed in the laboratory and compares the results with an analysis developed for use as a predictive tool. Information gained from this test series has been the basis for additional work now under way to simulate magma melt solidification processes.

  3. A Ground Deformation Monitoring Approach to Understanding Magma Chamber Systems and Eruptive Cycles of Mount Cameroon

    Science.gov (United States)

    Riley, S.; Clarke, A.

    2005-05-01

    Mount Cameroon is a 13,400ft basanite volcano on the passive margin of West Africa. It has erupted seven times in the past century making it one of the most active volcanoes in Africa. Most recently Mount Cameroon erupted in 1999 and 2000 first issuing strombolian explosions from vents near the summit, and later erupting effusively from a fissure running southwest from the summit (Suh et al., 2003). Prior to 2004, the only monitoring equipment on Mount Cameroon was a small seismometer network installed following the 1982 eruption. By 1999 only a single seismometer in the network was functional. Seismic activity did not rise above background levels until the few days immediately preceding the eruption. In an effort to raise awareness of the volcano's condition and provide a more efficient warning of impending eruptions we have begun constructing a ground deformation network on Mount Cameroon. The new network currently consists of two Applied Geomechanics 711-2A(4X) biaxial tiltmeters capable of resolving 0.1 microradians of tilt. One station is located approximately 500 m from the 2000 summit vent, and the other is approximately 1km away from the central fissure approximately 5km southwest of the 2000 summit vent. Three primary processes could precede eruptions at Mt. Cameroon, offering the opportunity for detection and prediction by our network. These processes are magma chamber pressurization, magma ascent via a central conduit, and/or propagation of magma along the central fissure. Magma chamber location, if a significant chamber exists, is poorly constrained, however, previous petrologic studies on Mount Cameroon (Suh et al., 2003; Fitton et al., 1983) suggest Mount Cameroon magmas originate at a depth less than 40km. Published seismic data (Ambeh, 1989) contains evidence of magmatic activity and possible chambers at depths ranging from 10km to 70km. Preliminary calculations using a simple Mogi model suggest deformation caused by pressurization of a large

  4. Regional and temporal variability of melts during a Cordilleran magma pulse: Age and chemical evolution of the jurassic arc, eastern mojave desert, California

    Science.gov (United States)

    Barth, A.P.; Wooden, J.L.; Miller, David; Howard, Keith A.; Fox, Lydia; Schermer, Elizabeth R.; Jacobson, C.E.

    2017-01-01

    Intrusive rock sequences in the central and eastern Mojave Desert segment of the Jurassic Cordilleran arc of the western United States record regional and temporal variations in magmas generated during the second prominent pulse of Mesozoic continental arc magmatism. U/Pb zircon ages provide temporal control for describing variations in rock and zircon geochemistry that reflect differences in magma source components. These source signatures are discernible through mixing and fractionation processes associated with magma ascent and emplacement. The oldest well-dated Jurassic rocks defining initiation of the Jurassic pulse are a 183 Ma monzodiorite and a 181 Ma ignimbrite. Early to Middle Jurassic intrusive rocks comprising the main stage of magmatism include two high-K calc-alkalic groups: to the north, the deformed 183–172 Ma Fort Irwin sequence and contemporaneous rocks in the Granite and Clipper Mountains, and to the south, the 167–164 Ma Bullion sequence. A Late Jurassic suite of shoshonitic, alkali-calcic intrusive rocks, the Bristol Mountains sequence, ranges in age from 164 to 161 Ma and was emplaced as the pulse began to wane. Whole-rock and zircon trace-element geochemistry defines a compositionally coherent Jurassic arc with regional and secular variations in melt compositions. The arc evolved through the magma pulse by progressively greater input of old cratonic crust and lithospheric mantle into the arc magma system, synchronous with progressive regional crustal thickening.

  5. Characterization of the Space Shuttle Ascent Debris using CFD Methods

    Science.gov (United States)

    Murman, Scott M.; Aftosmis, Michael J.; Rogers, Stuart E.

    2005-01-01

    After video analysis of space shuttle flight STS-107's ascent showed that an object shed from the bipod-ramp region impacted the left wing, a transport analysis was initiated to determine a credible flight path and impact velocity for the piece of debris. This debris transport analysis was performed both during orbit, and after the subsequent re-entry accident. The analysis provided an accurate prediction of the velocity a large piece of foam bipod ramp would have as it impacted the wing leading edge. This prediction was corroborated by video analysis and fully-coupled CFD/six degree of freedom (DOF) simulations. While the prediction of impact velocity was accurate enough to predict critical damage in this case, one of the recommendations of the Columbia Accident Investigation Board (CAIB) for return-to-flight (RTF) was to analyze the complete debris environment experienced by the shuttle stack on ascent. This includes categorizing all possible debris sources, their probable geometric and aerodynamic characteristics, and their potential for damage. This paper is chiefly concerned with predicting the aerodynamic characteristics of a variety of potential debris sources (insulating foam and cork, nose-cone ablator, ice, ...) for the shuttle ascent configuration using CFD methods. These aerodynamic characteristics are used in the debris transport analysis to predict flight path, impact velocity and angle, and provide statistical variation to perform risk analyses where appropriate. The debris aerodynamic characteristics are difficult to determine using traditional methods, such as static or dynamic test data, due to the scaling requirements of simulating a typical debris event. The use of CFD methods has been a critical element for building confidence in the accuracy of the debris transport code by bridging the gap between existing aerodynamic data and the dynamics of full-scale, in-flight events.

  6. Algorithm for Determination of Orion Ascent Abort Mode Achievability

    Science.gov (United States)

    Tedesco, Mark B.

    2011-01-01

    For human spaceflight missions, a launch vehicle failure poses the challenge of returning the crew safely to earth through environments that are often much more stressful than the nominal mission. Manned spaceflight vehicles require continuous abort capability throughout the ascent trajectory to protect the crew in the event of a failure of the launch vehicle. To provide continuous abort coverage during the ascent trajectory, different types of Orion abort modes have been developed. If a launch vehicle failure occurs, the crew must be able to quickly and accurately determine the appropriate abort mode to execute. Early in the ascent, while the Launch Abort System (LAS) is attached, abort mode selection is trivial, and any failures will result in a LAS abort. For failures after LAS jettison, the Service Module (SM) effectors are employed to perform abort maneuvers. Several different SM abort mode options are available depending on the current vehicle location and energy state. During this region of flight the selection of the abort mode that maximizes the survivability of the crew becomes non-trivial. To provide the most accurate and timely information to the crew and the onboard abort decision logic, on-board algorithms have been developed to propagate the abort trajectories based on the current launch vehicle performance and to predict the current abort capability of the Orion vehicle. This paper will provide an overview of the algorithm architecture for determining abort achievability as well as the scalar integration scheme that makes the onboard computation possible. Extension of the algorithm to assessing abort coverage impacts from Orion design modifications and launch vehicle trajectory modifications is also presented.

  7. Space Shuttle Ascent Flight Design Process: Evolution and Lessons Learned

    Science.gov (United States)

    Picka, Bret A.; Glenn, Christopher B.

    2011-01-01

    The Space Shuttle Ascent Flight Design team is responsible for defining a launch to orbit trajectory profile that satisfies all programmatic mission objectives and defines the ground and onboard reconfiguration requirements for this high-speed and demanding flight phase. This design, verification and reconfiguration process ensures that all applicable mission scenarios are enveloped within integrated vehicle and spacecraft certification constraints and criteria, and includes the design of the nominal ascent profile and trajectory profiles for both uphill and ground-to-ground aborts. The team also develops a wide array of associated training, avionics flight software verification, onboard crew and operations facility products. These key ground and onboard products provide the ultimate users and operators the necessary insight and situational awareness for trajectory dynamics, performance and event sequences, abort mode boundaries and moding, flight performance and impact predictions for launch vehicle stages for use in range safety, and flight software performance. These products also provide the necessary insight to or reconfiguration of communications and tracking systems, launch collision avoidance requirements, and day of launch crew targeting and onboard guidance, navigation and flight control updates that incorporate the final vehicle configuration and environment conditions for the mission. Over the course of the Space Shuttle Program, ascent trajectory design and mission planning has evolved in order to improve program flexibility and reduce cost, while maintaining outstanding data quality. Along the way, the team has implemented innovative solutions and technologies in order to overcome significant challenges. A number of these solutions may have applicability to future human spaceflight programs.

  8. Light-Weight Injector Technology for Cryogenic Mars Ascent Engines

    Science.gov (United States)

    Trihn, Huu Phuoc; Cramer, John M.

    1998-01-01

    Preliminary mission studies for human exploration of Mars have been performed at Marshall Space Flight Center (MSFC). These studies indicate that for chemical rockets only a cryogenic propulsion system would provide high enough performance to be considered for a Mars ascent vehicle. Although the mission is possible with Earth-supplied propellants for this vehicle, utilization of in-situ propellants is highly attractive. This option would significantly reduce the overall mass of launch vehicles. Consequently, the cost of the mission would be greatly reduced because the number and size of the Earth launch vehicle(s) needed for the mission decrease. NASA/Johnson Space Center has initiated several concept studies of in-situ propellant production plants. Liquid oxygen (LOX) is the primary candidate for an in-situ oxidizer. In-situ fuel candidates include methane (CH4), ethylene (C2H4), and methanol (CH3OH). MSFC initiated a technology development program for a cryogenic propulsion system for the Mars human exploration mission in 1998. One part of this technology program is the effort described here: an evaluation of propellant injection concepts for a LOX/liquid methane Mars Ascent Engine (MAE) with an emphasis on light-weight, high efficiency, reliability, and thermal compatibility. In addition to the main objective, hot-fire tests of the subject injectors will be used to test other key technologies including light-weight combustion chamber materials and advanced ignition concepts. This state-of-the-art technology will then be applied to the development of a cryogenic propulsion system that will meet the requirements of the planned Mars sample return (MSR) mission. The current baseline propulsion system for the MSR mission uses a storable propellant combination [monomethyl hydrazine/mixed oxides of nitrogen-25. However, a mission option that incorporates in-situ propellant production and utilization for the ascent stage is being carefully considered as a subscale

  9. Crew Exploration Vehicle Service Module Ascent Abort Coverage

    Science.gov (United States)

    Tedesco, Mark B.; Evans, Bryan M.; Merritt, Deborah S.; Falck, Robert D.

    2007-01-01

    The Crew Exploration Vehicle (CEV) is required to maintain continuous abort capability from lift off through destination arrival. This requirement is driven by the desire to provide the capability to safely return the crew to Earth after failure scenarios during the various phases of the mission. This paper addresses abort trajectory design considerations, concept of operations and guidance algorithm prototypes for the portion of the ascent trajectory following nominal jettison of the Launch Abort System (LAS) until safe orbit insertion. Factors such as abort system performance, crew load limits, natural environments, crew recovery, and vehicle element disposal were investigated to determine how to achieve continuous vehicle abort capability.

  10. Effects of ascent to high altitude on human antimycobacterial immunity.

    Directory of Open Access Journals (Sweden)

    Sarah Eisen

    Full Text Available Tuberculosis infection, disease and mortality are all less common at high than low altitude and ascent to high altitude was historically recommended for treatment. The immunological and mycobacterial mechanisms underlying the association between altitude and tuberculosis are unclear. We studied the effects of altitude on mycobacteria and antimycobacterial immunity.Antimycobacterial immunity was assayed in 15 healthy adults residing at low altitude before and after they ascended to 3400 meters; and in 47 long-term high-altitude residents. Antimycobacterial immunity was assessed as the extent to which participants' whole blood supported or restricted growth of genetically modified luminescent Bacille Calmette-Guérin (BCG mycobacteria during 96 hours incubation. We developed a simplified whole blood assay that could be used by a technician in a low-technology setting. We used this to compare mycobacterial growth in participants' whole blood versus positive-control culture broth and versus negative-control plasma.Measurements of mycobacterial luminescence predicted the number of mycobacterial colonies cultured six weeks later. At low altitude, mycobacteria grew in blood at similar rates to positive-control culture broth whereas ascent to high altitude was associated with restriction (p ≤ 0.002 of mycobacterial growth to be 4-times less than in culture broth. At low altitude, mycobacteria grew in blood 25-times more than negative-control plasma whereas ascent to high altitude was associated with restriction (p ≤ 0.01 of mycobacterial growth to be only 6-times more than in plasma. There was no evidence of differences in antimycobacterial immunity at high altitude between people who had recently ascended to high altitude versus long-term high-altitude residents.An assay of luminescent mycobacterial growth in whole blood was adapted and found to be feasible in low-resource settings. This demonstrated that ascent to or residence at high altitude was

  11. Steepest-Ascent Constrained Simultaneous Perturbation for Multiobjective Optimization

    DEFF Research Database (Denmark)

    McClary, Dan; Syrotiuk, Violet; Kulahci, Murat

    2011-01-01

    The simultaneous optimization of multiple responses in a dynamic system is challenging. When a response has a known gradient, it is often easily improved along the path of steepest ascent. On the contrary, a stochastic approximation technique may be used when the gradient is unknown or costly...... that leverages information about the known gradient to constrain the perturbations used to approximate the others. We apply SP(SA)(2) to the cross-layer optimization of throughput, packet loss, and end-to-end delay in a mobile ad hoc network (MANET), a self-organizing wireless network. The results show that SP...

  12. Habitable Mars Ascent Vehicle (MAV) Concept. [Mars Ascent Vehicle (MAV) Layout and Configuration: 6-Crew, Habitable, Nested Tank Concept

    Science.gov (United States)

    Dang, Victor; Rucker, Michelle

    2013-01-01

    NASA's ultimate goal is the human exploration of Mars. Among the many difficult aspects of a trip to Mars is the return mission that would transport the astronauts from the Martian surface back into Mars orbit. One possible conceptual design to accomplish this task is a two-stage Mars Ascent Vehicle (MAV). In order to assess this design, a general layout and configuration for the spacecraft must be developed. The objective of my internship was to model a conceptual MAV design to support NASA's latest human Mars mission architecture trade studies, technology prioritization decisions, and mass, cost, and schedule estimates.

  13. Granite ascent in convergent orogenic belts: Testing a model

    Science.gov (United States)

    Solar, Gary S.; Pressley, Rachel A.; Brown, Michael; Tucker, Robert D.

    1998-08-01

    The common spatial relationship in convergent orogenic belts between a crustal-scale shear-zone system, high-grade metamorphic rocks, and granites suggests a feedback relation between crustal anatexis and contractional deformation that helps granite extraction and focuses granite ascent. Such a feedback relation has been proposed for ascent of Early Devonian granites in west-central Maine. This interpretation requires that deformation, metamorphism, and plutonism were synchronous. We have determined precise U-Pb zircon and monazite ages that we interpret to record time of crystallization of syntectonic granite in metric to decametric sheets and kilometric plutons, and of schlieric granite within migmatites. Ages are in the range ca. 408 404 Ma, within 1 m.y. at 95% confidence limits. These ages are similar to extant U-Pb monazite ages of ca. 405 399 ± 2 Ma for syntectonic regional metamorphism in the same area. The coincidence between the age of peak metamorphism and crystallization ages of granite shows tectonics, metamorphism, and magmatism were contemporaneous, in support of the feedback model.

  14. Petrological cannibalism: the chemical and textural consequences of incremental magma body growth

    Science.gov (United States)

    Cashman, Kathy; Blundy, Jon

    2013-09-01

    fluxing the reservoir with CO2-rich vapors that are either released from deeper in the system or transported with the recharge magma. Temperature fluctuations of 20-40 °C, on the other hand, are an inevitable consequence of incremental, or pulsed, assembly of crustal magma bodies wherein each pulse interacts with ancestral, stored magmas. We venture that this "petrological cannibalism" accounts for much of the plagioclase zoning and textural complexity seen not only at Mount St. Helens but also at arc magmas generally. More broadly we suggest that the magma reservoir below Mount St. Helens is dominated by crystal mush and fed by frequent inputs of hotter, but compositionally similar, magma, coupled with episodes of magma ascent from one storage region to another. This view both accords with other independent constraints on the subvolcanic system at Mount St. Helens and supports an emerging view of many active magmatic systems as dominantly super-solidus, rather than subliquidus, bodies.

  15. Stress barriers controlling lateral migration of magma revealed by seismic tomography

    Science.gov (United States)

    Martí, J.; Villaseñor, A.; Geyer, A.; López, C.; Tryggvason, A.

    2017-01-01

    Understanding how monogenetic volcanic systems work requires full comprehension of the local and regional stresses that govern magma migration inside them and why/how they seem to change from one eruption to another. During the 2011-2012 El Hierro eruption (Canary Islands) the characteristics of unrest, including a continuous change in the location of seismicity, made the location of the future vent unpredictable, so short term hazard assessment was highly imprecise. A 3D P-wave velocity model is obtained using arrival times of the earthquakes occurred during that pre-eruptive unrest and several latter post-eruptive seismic crises not related to further eruptions. This model reveals the rheological and structural complexity of the interior of El Hierro volcanic island. It shows a number of stress barriers corresponding to regional tectonic structures and blocked pathways from previous eruptions, which controlled ascent and lateral migration of magma and, together with the existence of N-S regional compression, reduced its options to find a suitable path to reach the surface and erupt.

  16. Driving magma to the surface: The 2011-2012 El Hierro Volcanic Eruption

    Science.gov (United States)

    López, Carmen; Benito-Saz, Maria A.; Martí, Joan; del-Fresno, Carmen; García-Cañada, Laura; Albert, Helena; Lamolda, Héctor

    2017-08-01

    We reanalyzed the seismic and deformation data corresponding to the preeruptive unrest on El Hierro (Canary Islands) in 2011. We considered new information about the internal structure of the island. We updated the seismic catalog to estimate the full evolution of the released seismic energy and demonstrate the importance of nonlocated earthquakes. Using seismic data and GPS displacements, we characterized the shear-tensile type of the predominant fracturing and modeled the strain and stress fields for different time periods. This enabled us to identify a prolonged first phase characterized by hydraulic tensile fracturing, which we interpret as being related to the emplacement of new magma below the volcanic edifice on El Hierro. This was followed by postinjection unidirectional migration, probably controlled by the stress field and the distribution of the structural discontinuities. We identified the effects of energetic magmatic pulses occurring a few days before the eruption that induced shear seismicity on preexisting faults within the volcano and raised the Coulomb stress over the whole crust. We suggest that these magmatic pulses reflect the crossing of the Moho discontinuity, as well as changes in the path geometry of the dyke migration toward the surface. The final phase involved magma ascent through a prefractured crust.

  17. Magma Emplacement Rates and Porphyry Copper Deposits: Thermal Modelling of the Yerington Batholith, Nevada, USA

    Science.gov (United States)

    Schöpa, Anne; Annen, Catherine; Dilles, John H.; Sparks, R. Stephen J.; Blundy, Jon D.

    2017-04-01

    Many porphyry copper deposits are associated with granitoid plutons. Their genesis is attributed to the degassing of pluton-forming intermediate to silicic magma chambers. These plutons are commonly envisioned as resulting from the slow cooling and crystallization of large magma chambers. Most of the models combine the formation of ore deposits and the cooling of a magma chamber. However, they do not consider neither how typically hundreds of cubic kilometres of magma were emplaced into the upper crust, nor the prolonged growth of plutons involving simultaneous cooling and crystallization together with the release of exsolved volatiles, which may contribute to ore formation. We use numerical simulations of thermal evolution due to pluton growth to investigate the links between pluton construction, magma accumulation, solidification, volatile exsolution, volatile release and porphyry copper formation. The Jurassic Yerington batholith in western Nevada, USA, is used as a case study because it is associated with economic porphyry copper deposits, it shows an exceptional exposure revealing the geometry of the intrusion, and petrological and geochronological analysis have shed light on its emplacement style and duration. Our conductive heat flow model simulates the growth of the ˜1000 km3 batholith emplaced at 2-8 km crustal depth by step-wise intrusions of vertically stacked sills. Different emplacement rates and repose times of no melt injection between the three main Yerington intrusions were tested. Our numerical simulations show that to comply with the conceptual model linking porphyry copper deposits with the presence of large, highly molten magma chambers, magmas must be emplaced at a high rate of several cm/yr. In plutonic records, such high rates are uncommon. It follows that either the current conceptual model is incorrect or that porphyry copper deposits are only produced by the rare, rapidly emplaced plutons. The fact that many granitoid plutons are barren

  18. Juvenile magma recognition and eruptive dynamics inferred from the analysis of ash time series: The 2015 reawakening of Cotopaxi volcano

    Science.gov (United States)

    Gaunt, H. Elizabeth; Bernard, Benjamin; Hidalgo, Silvana; Proano, Antonio; Wright, Heather M.; Mothes, Patricia; Criollo, Evelyn; Kueppers, Ulrich

    2016-01-01

    Forecasting future activity and performing hazard assessments during the reactivation of volcanoes remain great challenges for the volcanological community. On August 14, 2015 Cotopaxi volcano erupted for the first time in 73 years after approximately four months of precursory activity, which included an increase in seismicity, gas emissions, and minor ground deformation. Here we discuss the use of near real-time petrological monitoring of ash samples as a complementary aid to geophysical monitoring, in order to infer eruption dynamics and evaluate possible future eruptive activity at Cotopaxi. Twenty ash samples were collected between August 14 and November 23, 2015 from a monitoring site on the west flank of the volcano. These samples contain a range of grain types that we classified as: hydrothermal/altered, lithic, juvenile, and free crystals. The relative proportions of theses grains evolved as the eruption progressed, with increasing amounts of juvenile material and a decrease in hydrothermally altered material. In samples from the initial explosion, juvenile grains are glassy, microlite-poor and contain hydrothermal minerals (opal and alunite). The rising magma came in contact with the hydrothermal system under confinement, causing hydro-magmatic explosions that cleared the upper part of the plumbing system. Subsequently, the magmatic column produced a thermal aureole in the conduit and dried out the hydrothermal system, allowing for dry eruptions. Magma ascent rates were low enough to allow for efficient outgassing and microlite growth. Constant supply of magma from below caused quasi-continuous disruption of the uppermost magma volume through a combination of shear-deformation and gas expansion. The combination of increasing crystallinity of juvenile grains, and high measured SO2 flux indicate decreasing integrated magma ascent rates and clearing of the hydrothermal system along transport pathways in a system open to gas loss. The near real

  19. Sulfur isotopic zoning in apatite crystals: A new record of dynamic sulfur behavior in magmas

    Science.gov (United States)

    Economos, Rita; Boehnke, Patrick; Burgisser, Alain

    2017-10-01

    The mobility and geochemical behavior of sulfur in magmas is complex due to its multi-phase (solid, immiscible liquid, gaseous, dissolved ions) and multi-valent (from S2- to S6+) nature. Sulfur behavior is closely linked with the evolution of oxygen fugacity (fO2) in magmas; the record of fO2 evolution is often enigmatic to extract from rock records, particularly for intrusive systems. We apply a novel method of measuring S isotopic ratios in zoned apatite crystals that we interpret as a record of open-system magmatic processes. We interrogate the S concentration and isotopic variations preserved in multiple apatite crystals from single hand specimens from the Cadiz Valley Batholith, CA via electron microprobe and ion microprobe. Isotopic variations in single apatite crystals ranged from 0 to 3.8‰ δ34S and total variation within a single hand sample was 6.1‰ δ34S. High S concentration cores yielded high isotopic ratios while low S concentration rims yielded low isotopic ratios. We discuss a range of possible natural scenarios and favor an explanation of a combination of magma mixing and open-system, ascent-driven degassing under moderately reduced conditions: fO2 at or below NNO+1, although the synchronous crystallization of apatite and anhydrite is also a viable scenario. Our conclusions have implications for the coupled S and fO2 evolution of granitic plutons and suggest that in-situ apatite S isotopic measurements could be a powerful new tool for evaluating redox and S systematics in magmatic systems.

  20. Pressure of Partial Crystallization of Katla Magmas: Implications for Magma Chamber Depth and for the Magma Plumbing System

    Science.gov (United States)

    Tenison, A.; Kelley, D. F.; Barton, M.

    2012-12-01

    Iceland is home to some of the most active volcanoes in the world, and recent eruptions emphasize the need for additional studies to better understand the volcanism and tectonics in this region. Historical patterns of eruptive activity and an increase in seismic activity suggest that Katla is showing signs of an impending eruption. The last major eruption in 1918 caused massive flooding and deposited enough sediment to extend part of Iceland's southern shoreline by 5 km. It also generated sufficient ash over many weeks to cause a brief drop in global temperature. A future eruption similar to the 1918 event could have serious global consequences, including severe disruptions in air travel, short-term global cooling, and shortened growing seasons. Relatively few studies have focused on establishing the depth of the main magma chamber beneath Katla, although knowledge of magma chamber depth is essential for constraining models for magma evolution and for understanding the eruption dynamics of this volcano. The results of seismic and geodetic studies suggest the presence of a shallow magma body at a depth of 2-4 km, but do not provide firm evidence for the presence of deeper chambers in contrast to results obtained for other volcanoes in Iceland. Studies of volcanic ash layers reveal a history of alternating cycles of basaltic and silicic eruptions. We suggest that the shallow magma chamber is primarily the source of silica-rich magma, and postulate that there must be one or more additional chambers in the middle or deep crust that serve as the storage site of the basaltic magma erupted as lava and ash. We have tested this proposal by calculating the pressures of partial crystallization for basalts erupted at Katla using petrological methods. These pressures can be converted to depths and the results provide insight into the likely configuration of the magma plumbing system. Published analyses of volcanic glasses (lava, ash and hyaloclastite) were used as input data

  1. Timescales between mantle metasomatism and kimberlite ascent indicated by diffusion profiles in garnet crystals from peridotite xenoliths

    Science.gov (United States)

    Jollands, Michael C.; Hanger, Brendan J.; Yaxley, Gregory M.; Hermann, Jörg; Kilburn, Matthew R.

    2018-01-01

    Rare garnet crystals from a peridotite xenolith from the Wesselton kimberlite, South Africa, have distinct zones related to two separate episodes of mantle metasomatism. The garnet cores were firstly depleted through melt extraction, then equilibrated during metasomatism by a potentially diamond-forming carbonate-bearing or proto-kimberlitic fluid at 1100-1300 °C and 4.5-5.5 GPa. The garnet rim chemistry, in contrast, is consistent with later overgrowth in equilibrium with a kimberlite at around 1025 ± 25 °C and 4.2 ± 0.5 GPa. This suggests that the rock was physically moved upwards by up to tens of kilometres between the two metasomatic episodes. Preserved high Ca, Al and Cr contents in orthopyroxenes suggest this uplift was tectonic, rather than magmatic. Diffusion profiles were measured over the transitions between garnet cores and rims using electron microprobe (Mg, Ca, Fe for modelling, plus Cr, Mn, Ti, Na, Al) and nano Secondary Ion Mass Spectrometry (NanoSIMS; 89Y, along with 23Na, Ca, Cr, Fe, Mn and Ti) analyses. The short profile lengths (generally interaction of the mantle xenolith with the host kimberlite magma during a single-stage ascent to the crust (hours to days). The samples offer a rare opportunity to study metasomatic processes associated with failed eruption attempts in the cratonic lithosphere.

  2. Multicriteria steepest ascent in a design space consisting of both mixture and process variables

    NARCIS (Netherlands)

    Duineveld, CAA; Coenegracht, PMJ

    1995-01-01

    Steepest ascent is shown to be a feasible method for problems where two or more responses are to be optimized. With the aid of Pareto optimality the (one response) standard method is adapted for the use of more responses. A special kind of steepest ascent problem involves the presence of both

  3. Large-volume lateral magma transport from the Mull volcano: An insight to magma chamber processes

    Science.gov (United States)

    Ishizuka, Osamu; Taylor, Rex N.; Geshi, Nobuo; Mochizuki, Nobutatsu

    2017-04-01

    Long-distance lateral magma transport within the crust has been inferred for various magmatic systems including oceanic island volcanoes, mid-oceanic ridges, and large igneous provinces. However, studying the physical and chemical properties of active fissure systems is difficult. Hence, this study investigates the movement of magma away from the Mull volcano in the North Atlantic Igneous Province, where erosion has exposed its upper crustal dike networks. Magmatic lineations within dikes indicate that the magma flow in the Mull dike suite changed from near vertical to horizontal within 30 km of the volcanic center. This implies that distal dikes were fed by lateral magma transport from Mull. Geochemical characteristics indicate that many assimilation in Lewisian basement. Following crystallization and assimilation in the lower crust, magma fed an upper crustal reservoir, where further fractionation and incorporation of Moinian rocks generated felsic compositions. Distal dikes are andesitic and reflect events in which large volumes of mafic and felsic magma were combined by mixing between lower and upper crustal reservoirs to generate the 30-80 km3 required to supply the long-distance dikes. Once propagated, compositions along dikes were not significantly affected by assimilation and crystallization. Supplying the distal dikes with magma would have required a large-scale evacuation of the crustal reservoirs that acted as a potential trigger for explosive volcanism and the caldera formation recorded in Mull central complex.

  4. Defining the Mars Ascent Problem for Sample Return

    Energy Technology Data Exchange (ETDEWEB)

    Whitehead, J

    2008-07-31

    Lifting geology samples off of Mars is both a daunting technical problem for propulsion experts and a cultural challenge for the entire community that plans and implements planetary science missions. The vast majority of science spacecraft require propulsive maneuvers that are similar to what is done routinely with communication satellites, so most needs have been met by adapting hardware and methods from the satellite industry. While it is even possible to reach Earth from the surface of the moon using such traditional technology, ascending from the surface of Mars is beyond proven capability for either solid or liquid propellant rocket technology. Miniature rocket stages for a Mars ascent vehicle would need to be over 80 percent propellant by mass. It is argued that the planetary community faces a steep learning curve toward nontraditional propulsion expertise, in order to successfully accomplish a Mars sample return mission. A cultural shift may be needed to accommodate more technical risk acceptance during the technology development phase.

  5. Pump Fed Propulsion for Mars Ascent and Other Challenging Maneuvers

    Energy Technology Data Exchange (ETDEWEB)

    Whitehead, J C

    2007-05-09

    Returning Mars geology samples to Earth within science mission budgets requires a miniature launch vehicle (100-200 kg) for ascending from Mars to an orbital rendezvous. A Mars Ascent Vehicle must deliver a velocity change exceeding 4 km/s within minutes, entirely outside the capabilities of satellite propulsion. A possible solution is to scale down liquid launch vehicle principles to achieve stage propellant mass fractions near 90 percent. Feeding a high-pressure engine from thin-walled low pressure tanks permits stage hardware to be sufficiently lightweight and compact, if very high performance pumps can be made available. NASA's Mars Technology Program has funded refinement and testing of a miniature piston pump, powered by reacted propellant. A pump-fed bipropellant rocket stage remains to be developed. The technology could also benefit other future lunar and planetary science programs.

  6. Metabolics of stair ascent with a powered transfemoral prosthesis.

    Science.gov (United States)

    Ledoux, E D; Lawson, B E; Shultz, A H; Bartlett, H L; Goldfarb, M

    2015-01-01

    This paper evaluates the effectiveness of a powered knee and ankle prosthesis for stair ascent through a metabolic assessment comparing energy expenditure of a single transfemoral amputee subject while ascending stairs with the powered prosthesis relative to his passive daily use device, as well as comparing the kinematics and kinetics obtained with the passive prosthesis to healthy biomechanics. The subject wore a portable system that measured pulmonary gaseous exchange rates of oxygen and carbon dioxide while he ascended stairs with each of the prostheses in alternating tests. The results indicated that the amputee's energy expenditure decreased by 32 percent while climbing with the powered prosthesis as compared to his passive one, and the kinematics and kinetics achieved were representative of healthy biomechanics.

  7. Mars Ascent Vehicle Gross Lift-off Mass Sensitivities for Robotic Mars Sample Return

    Science.gov (United States)

    Dux, Ian J.; Huwaldt, Joseph A.; McKamey, R. Steve; Dankanich, John W.

    2011-01-01

    The Mars ascent vehicle is a critical element of the robotic Mars Sample Return (MSR) mission. The Mars ascent vehicle must be developed to survive a variety of conditions including the trans-Mars journey, descent through the Martian atmosphere and the harsh Martian surface environments while maintaining the ability to deliver its payload to a low Mars orbit. The primary technology challenge of developing the Mars ascent vehicle system is designing for all conditions while ensuring the mass limitations of the entry descent and landing system are not exceeded. The NASA In-Space Propulsion technology project has initiated the development of Mars ascent vehicle technologies with propulsion system performance and launch environments yet to be defined. To support the project s evaluation and development of various technology options the sensitivity of the Mars ascent vehicle gross lift-off mass to engine performance, inert mass, target orbits, and launch conditions has been completed with the results presented herein.

  8. Volatile Abundances and Magma Geochemistry of Recent (2006) Through Ancient Eruptions (Less Than 2100 aBP) of Augustine Volcano, Alaska

    Science.gov (United States)

    Webster, J. D.; Mandeville, C. W.; Gerard, T.; Goldoff, B.; Coombs, M. L.

    2006-12-01

    Augustine Volcano, Cook Inlet, Alaska, is a subduction-related Aleutian arc volcano located approximately 275 km southwest of Anchorage. During the past 200 years, Augustine volcano has shown explosive eruptive behavior seven times, with the most recent activity occurring in January through March 2006. Its ash and pumice eruptions pose a threat to commercial air traffic, the local fishing industry, and the inhabitants of the region. Following prior investigations on volatile abundances and processes of evolution for magmas associated with the 1976 (Johnston, 1978) and 1986 (Roman et al., 2005) eruptions of Augustine, we have analyzed phenocrysts, matrix glasses, and silicate melt inclusions in andesites formed during 5 pre-historic eruptions (ranging from 2100 to 1000 years in age) as well as the 1986 and recent 2006 eruptions. Outcrops of basaltic units on Augustine are rare, and basaltic melt inclusions are as well, so most melt inclusions studied range from andesitic to rhyolitic compositions. Comparison of the volatile abundances in felsic melt inclusion glasses shows few differences in H2O, CO2, S, and Cl, respectively, between eruptive materials of the pre- historic, 1976 (Johnston, 1978), and 1986 (Roman et al., 2005; our data) events. The magmas associated with these eruptions contained 1.6 to 8.0 wt.% H2O with 0.21 to 0.84 wt.% Cl, 100 to 1800 ppm CO2, and 100 to 400 ppm S. In contrast, preliminary research on rhyodacitic to rhyolitic melt inclusions in a single 2006 andesite sample collected from a lahar deposit indicates they contain somewhat lower H2O contents and higher Cl and S abundances than felsic melt inclusions from prior eruptions, and they exhibit geochemical trends consonant with magma mixing. Relationships involving H2O, CO2, S, and Cl in prehistoric through 1986 melt inclusions are consistent with fluid-saturated magma evolution of andesitic to rhyolitic melt compositions during closed-system ascent. The various batches of magma rose through

  9. Short residence times for alkaline Vesuvius magmas in a multi-depth supply system: Evidence from geochemical and textural studies

    Science.gov (United States)

    Pappalardo, Lucia; Mastrolorenzo, Giuseppe

    2010-07-01

    It is crucial to understand magma chamber chemico-physical conditions and residence times for high-risk volcanoes because these factors control the occurrence and size of future eruptions. In order to define magmatic pressure-temperature conditions and residence times at the Somma-Vesuvius volcano, we studied the geochemistry and texture of selected past eruptions that are representative of the entire volcanic history. Our petrological model indicates a multi-depth magma chamber composed of a deeper tephritic (350-400 Mpa) magma layer, which fed Strombolian and effusive eruptions during open-conduit activity, and an upper (200-250 Mpa) phonolitic level, which supplied the high explosive events that followed closed-conduit repose time. This upper reservoir matches the inferred transition between sedimentary sequences and metamorphic basement. At this level, the presence of a structural and lithological discontinuity favors magma storage during closed-conduit periods. The prevalent differentiation process was fractional crystallization during the magma cooling associated with upward migration of less dense, evolved liquids. Our results indicate that major steam exolution occurred during the late crystallization stage of phonolites, which accounts for the high Volcanic Explosivity Index (VEI) of eruptions supplied by these melts. Moreover, our phenocryst CSD data reveal the rapid crystallization and differentiation (decades to centuries) of alkaline Somma-Vesuvius magmas. This implies that the 400 km 2 partial melting zone detected by tomography studies at 8-10 km depth beneath Vesuvius should consist of differentiated magma that is already capable of generating a large-scale (plinian) explosive event if renewed activity develops out of the present closed-conduit state. Additionally, because our microlite CSD data indicate rapid magma migration from the chamber toward the surface, precursory activity could appear only short time before a major eruption.

  10. Insights From the Kilgore Tuff: Surprising Homogeneity of Supervolcanic Magmas in Yellowstone Hotspot Calderas

    Science.gov (United States)

    Watts, K. E.; Bindeman, I. N.; Schmitt, A. K.; Morgan, L. A.

    2008-12-01

    Supervolcanic eruptions in the late Miocene Heise volcanic field in eastern Idaho concluded ~4.5Ma with the eruption of the Kilgore Tuff, an extremely voluminous (1,800km3) caldera-forming ignimbrite. The Heise volcanic field represents the most recently extinct phase of volcanism over the Yellowstone hotspot and is the most immediate predecessor to the active Yellowstone Plateau volcanic field in western Wyoming. Thus, the climactic Kilgore Tuff of the Heise field is an important example of silicic magma genesis in the Yellowstone hotspot track, and may serve as an analog to large volume, late-stage magmatism in the Yellowstone Plateau volcanic field. We present major and trace element analyses, oxygen isotope ratios of bulk and individual phenocrysts, strontium isotope ratios of whole rock powders, and uranium-lead zircon crystallization ages of five geographically discrete and compositionally diverse samples of the Kilgore Tuff. Despite the presence of both high and low-silica rhyolites, with and without quartz phenocrysts, our isotopic and geochronologic data indicate that the Kilgore Tuff was erupted from a remarkably homogeneous silicic magma chamber with a constant and low δ18O value of 3.32±0.02‰, a 87Sr/86Sr ratio of 0.7105±0.0001, and a 238U-206Pb crystallization age of 4.64±0.05Ma (uncertainties are 1σ). Our new data support a shallow crustal recycling model of magma genesis for the Kilgore Tuff, in which low-δ18O intracaldera fill, consisting of hydrothermally altered and buried volcanic rocks from three previous caldera-forming eruptions, is remelted in batches and rapidly assembled into one voluminous, well-mixed magma chamber. Following isotopic homogenization by convection, fractional crystallization resulted in low and high-silica magma types in the parental Kilgore batholith. Similar processes may also explain effusive, large volume silicic magma genesis of the low-δ18O Central Plateau Member rhyolites (0.25-0.07Ma, 700km3) in the

  11. Probing magma reservoirs to improve volcano forecasts

    Science.gov (United States)

    Lowenstern, Jacob B.; Sisson, Thomas W.; Hurwitz, Shaul

    2017-01-01

    When it comes to forecasting eruptions, volcano observatories rely mostly on real-time signals from earthquakes, ground deformation, and gas discharge, combined with probabilistic assessments based on past behavior [Sparks and Cashman, 2017]. There is comparatively less reliance on geophysical and petrological understanding of subsurface magma reservoirs.

  12. Iron Redox Systematics of Martian Magmas

    Science.gov (United States)

    Righter, K.; Danielson, L.; Martin, A.; Pando, K.; Sutton, S.; Newville, M.

    2011-01-01

    Martian magmas are known to be FeO-rich and the dominant FeO-bearing mineral at many sites visited by the Mars Exploration rovers (MER) is magnetite [1]. Morris et al. [1] propose that the magnetite appears to be igneous in origin, rather than of secondary origin. However, magnetite is not typically found in experimental studies of martian magmatic rocks [2,3]. Magnetite stability in terrestrial magmas is well understood, as are the stability of FeO and Fe2O3 in terrestrial magmas [4,5]. In order to better understand the variation of FeO and Fe2O3, and the stability of magnetite (and other FeO-bearing phases) in martian magmas we have undertaken an experimental study with two emphases. First we document the stability of magnetite with temperature and fO2 in a shergottite bulk composition. Second, we determine the FeO and Fe2O3 contents of the same shergottite bulk composition at 1 bar and variable fO2 at 1250 C, and at variable pressure. These two goals will help define not only magnetite stability, but pyroxene-melt equilibria that are also dependent upon fO2.

  13. Unusual Iron Redox Systematics of Martian Magmas

    Science.gov (United States)

    Danielson, L.; Righter, K.; Pando, K.; Morris, R. V.; Graff, T.; Agresti, D.; Martin, A.; Sutton, S.; Newville, M.; Lanzirotti, A.

    2012-01-01

    Martian magmas are known to be FeO-rich and the dominant FeO-bearing mineral at many sites visited by the Mars Exploration rovers (MER) is magnetite. Morris et al. proposed that the magnetite appears to be igneous in origin, rather than of secondary origin. However, magnetite is not typically found in experimental studies of martian magmatic rocks. Magnetite stability in terrestrial magmas is well understood, as are the stabilities of FeO and Fe2O3 in terrestrial magmas. In order to better understand the variation of FeO and Fe2O3, and the stability of magnetite (and other FeO-bearing phases) in martian magmas, we have undertaken an experimental study with two emphases. First, we determine the FeO and Fe2O3 contents of super- and sub-liquidus glasses from a shergottite bulk composition at 1 bar to 4 GPa, and variable fO2. Second, we document the stability of magnetite with temperature and fO2 in a shergottite bulk composition.

  14. The mechanics of shallow magma reservoir outgassing

    Science.gov (United States)

    Parmigiani, A.; Degruyter, W.; Leclaire, S.; Huber, C.; Bachmann, O.

    2017-08-01

    Magma degassing fundamentally controls the Earth's volatile cycles. The large amount of gas expelled into the atmosphere during volcanic eruptions (i.e., volcanic outgassing) is the most obvious display of magmatic volatile release. However, owing to the large intrusive:extrusive ratio, and considering the paucity of volatiles left in intrusive rocks after final solidification, volcanic outgassing likely constitutes only a small fraction of the overall mass of magmatic volatiles released to the Earth's surface. Therefore, as most magmas stall on their way to the surface, outgassing of uneruptible, crystal-rich magma storage regions will play a dominant role in closing the balance of volatile element cycling between the mantle and the surface. We use a numerical approach to study the migration of a magmatic volatile phase (MVP) in crystal-rich magma bodies ("mush zones") at the pore scale. Our results suggest that buoyancy-driven outgassing is efficient over crystal volume fractions between 0.4 and 0.7 (for mm-sized crystals). We parameterize our pore-scale results for MVP migration in a thermomechanical magma reservoir model to study outgassing under dynamical conditions where cooling controls the evolution of the proportion of crystal, gas, and melt phases and to investigate the role of the reservoir size and the temperature-dependent viscoelastic response of the crust on outgassing efficiency. We find that buoyancy-driven outgassing allows for a maximum of 40-50% volatiles to leave the reservoir over the 0.4-0.7 crystal volume fractions, implying that a significant amount of outgassing must occur at high crystal content (>0.7) through veining and/or capillary fracturing.

  15. Deep intrusions, lateral magma transport and related uplift at ocean island volcanoes

    Science.gov (United States)

    Klügel, Andreas; Longpré, Marc-Antoine; García-Cañada, Laura; Stix, John

    2015-12-01

    Oceanic intraplate volcanoes grow by accumulation of erupted material as well as by coeval or discrete magmatic intrusions. Dykes and other intrusive bodies within volcanic edifices are comparatively well studied, but intrusive processes deep beneath the volcanoes remain elusive. Although there is geological evidence for deep magmatic intrusions contributing to volcano growth through uplift, this has rarely been demonstrated by real-time monitoring. Here we use geophysical and petrological data from El Hierro, Canary Islands, to show that intrusions from the mantle and subhorizontal transport of magma within the oceanic crust result in rapid endogenous island growth. Seismicity and ground deformation associated with a submarine eruption in 2011-2012 reveal deep subhorizontal intrusive sheets (sills), which have caused island-scale uplift of tens of centimetres. The pre-eruptive intrusions migrated 15-20 km laterally within the lower oceanic crust, opening pathways that were subsequently used by the erupted magmas to ascend from the mantle to the surface. During six post-eruptive episodes between 2012 and 2014, further sill intrusions into the lower crust and upper mantle have caused magma to migrate up to 20 km laterally, resulting in magma accumulation exceeding that of the pre-eruptive phase. A comparison of geobarometric data for the 2011-2012 El Hierro eruption with data for other Atlantic intraplate volcanoes shows similar bimodal pressure distributions, suggesting that eruptive phases are commonly accompanied by deep intrusions of sills and lateral magma transport. These processes add significant material to the oceanic crust, cause uplift, and are thus fundamentally important for the growth and evolution of volcanic islands. We suggest that the development of such a magma accumulation zone in the lower oceanic crust begins early during volcano evolution, and is a consequence of increasing size and complexity of the mantle reservoir system, and potentially

  16. Deep magma transport at Kilauea volcano, Hawaii

    Science.gov (United States)

    Wright, T.L.; Klein, F.W.

    2006-01-01

    The shallow part of Kilauea's magma system is conceptually well-understood. Long-period and short-period (brittle-failure) earthquake swarms outline a near-vertical magma transport path beneath Kilauea's summit to 20 km depth. A gravity high centered above the magma transport path demonstrates that Kilauea's shallow magma system, established early in the volcano's history, has remained fixed in place. Low seismicity at 4-7 km outlines a storage region from which magma is supplied for eruptions and intrusions. Brittle-failure earthquake swarms shallower than 5 km beneath the rift zones accompany dike emplacement. Sparse earthquakes extend to a decollement at 10-12 km along which the south flank of Kilauea is sliding seaward. This zone below 5 km can sustain aseismic magma transport, consistent with recent tomographic studies. Long-period earthquake clusters deeper than 40 km occur parallel to and offshore of Kilauea's south coast, defining the deepest seismic response to magma transport from the Hawaiian hot spot. A path connecting the shallow and deep long-period earthquakes is defined by mainshock-aftershock locations of brittle-failure earthquakes unique to Kilauea whose hypocenters are deeper than 25 km with magnitudes from 4.4 to 5.2. Separation of deep and shallow long-period clusters occurs as the shallow plumbing moves with the volcanic edifice, while the deep plumbing is centered over the hotspot. Recent GPS data agrees with the volcano-propagation vector from Kauai to Maui, suggesting that Pacific plate motion, azimuth 293.5?? and rate of 7.4 cm/yr, has been constant over Kilauea's lifetime. However, volcano propagation on the island of Hawaii, azimuth 325??, rate 13 cm/yr, requires southwesterly migration of the locus of melting within the broad hotspot. Deep, long-period earthquakes lie west of the extrapolated position of Kilauea backward in time along a plate-motion vector, requiring southwesterly migration of Kilauea's magma source. Assumed ages of 0

  17. Carbonate-derived CO 2 purging magma at depth: Influence on the eruptive activity of Somma-Vesuvius, Italy

    Science.gov (United States)

    Dallai, Luigi; Cioni, Raffaello; Boschi, Chiara; D'Oriano, Claudia

    2011-10-01

    Mafic phenocrysts from selected products of the last 4 ka volcanic activity at Mt. Vesuvius were investigated for their chemical and O-isotope composition, as a proxy for primary magmas feeding the system. 18O/ 16O ratios of studied Mg-rich olivines suggest that near-primary shoshonitic to tephritic melts experienced a flux of sedimentary carbonate-derived CO 2, representing the early process of magma contamination in the roots of the volcanic structure. Bulk carbonate assimilation (physical digestion) mainly occurred in the shallow crust, strongly influencing magma chamber evolution. On a petrological and geochemical basis the effects of bulk sedimentary carbonate digestion on the chemical composition of the near-primary melts are resolved from those of carbonate-released CO 2 fluxed into magma. An important outcome of this process lies in the effect of external CO 2 in changing the overall volatile solubility of the magma, enhancing the ability of Vesuvius mafic magmas to rapidly rise and explosively erupt at the surface.

  18. Krafla Magma Testbed: An International Project Crossing The Scientific Frontier From Geothermal System Into Magma

    Science.gov (United States)

    Eichelberger, J. C.; Dingwell, D. B.; Ludden, J. N.; Mandeville, C. W.; Markusson, S.; Papale, P.; Sigmundsson, F.

    2016-12-01

    Few Earth regimes are subject to as much inference and as little direct knowledge as magma. Among the most important mysteries is the transition from hydrothermal to magmatic, i.e. from aqueous fluid-present to silicate melt-present, regimes. Because solid rock is ductile at near-solidus temperature, fractures should have fleeting existence and therefore heat transfer should be by conduction. Heat and mass transport across this zone influences evolution of magma bodies. The hydrothermal regime influences eruptive behavior when magma intrudes it and propagation of the transition zone toward magma is demonstrated by physical and chemical evidence. Both drilling observations and heat-balance considerations indicate that the melt- and fluid-absent transition zone is thin. Drilling of Iceland Deep Drilling Project's IDDP-1, 2 km into Krafla Caldera, showed that the transition from deep-solidus fine-grained granite to liquidus rhyolite is less than 30 m thick, probably much less. For the first time, we have the opportunity to interrogate an entire system of heat and mass transport, from magmatic source through the hydrothermal zone to surface volcanism, and in so doing unite the disciplines of volcanology and geothermal energy. With support from industry, national geoscience agencies, community stakeholders, and the International Continental Scientific Drilling Program (ICDP), we are developing a broad program to push the limits of knowledge and technology in extremely hot Earth. We use the term "testbed" for two reasons: Surface and borehole observations used in volcano monitoring and geothermal exploration will be tested and reinterpreted in light of the first "ground-truth" about magma. More than "observing", magma and the transition zone will be manipulated through fluid injection and extraction to understand time-dependent behavior. Sensor technology will be pushed to measure magmatic conditions directly. Payoffs are in fundamental planetary science, volcano

  19. Launch Vehicle Debris Models and Crew Vehicle Ascent Abort Risk

    Science.gov (United States)

    Gee, Ken; Lawrence, Scott

    2013-01-01

    For manned space launch systems, a reliable abort system is required to reduce the risks associated with a launch vehicle failure during ascent. Understanding the risks associated with failure environments can be achieved through the use of physics-based models of these environments. Debris fields due to destruction of the launch vehicle is one such environment. To better analyze the risk posed by debris, a physics-based model for generating launch vehicle debris catalogs has been developed. The model predicts the mass distribution of the debris field based on formulae developed from analysis of explosions. Imparted velocity distributions are computed using a shock-physics code to model the explosions within the launch vehicle. A comparison of the debris catalog with an existing catalog for the Shuttle external tank show good comparison in the debris characteristics and the predicted debris strike probability. The model is used to analyze the effects of number of debris pieces and velocity distributions on the strike probability and risk.

  20. Mars Ascent Vehicle Test Requirements and Terrestrial Validation

    Science.gov (United States)

    Dankanich, John W.; Cathey, Henry M.; Smith, David A.

    2011-01-01

    The Mars robotic sample return mission has been a potential flagship mission for NASA s science mission directorate for decades. The Mars Exploration Program and the planetary science decadal survey have highlighted both the science return of the Mars Sample Return mission, but also the need for risk reduction through technology development. One of the critical elements of the MSR mission is the Mars Ascent Vehicle, which must launch the sample from the surface of Mars and place it into low Mars orbit. The MAV has significant challenges to overcome due to the Martian environments and the Entry Descent and Landing system constraints. Launch vehicles typically have a relatively low success probability for early flights, and a thorough system level validation is warranted. The MAV flight environments are challenging and in some cases impossible to replicate terrestrially. The expected MAV environments have been evaluated and a first look of potential system test options has been explored. The terrestrial flight requirements and potential validation options are presented herein.

  1. Illuminating magma shearing processes via synchrotron imaging

    Science.gov (United States)

    Lavallée, Yan; Cai, Biao; Coats, Rebecca; Kendrick, Jackie E.; von Aulock, Felix W.; Wallace, Paul A.; Le Gall, Nolwenn; Godinho, Jose; Dobson, Katherine; Atwood, Robert; Holness, Marian; Lee, Peter D.

    2017-04-01

    Our understanding of geomaterial behaviour and processes has long fallen short due to inaccessibility into material as "something" happens. In volcanology, research strategies have increasingly sought to illuminate the subsurface of materials at all scales, from the use of muon tomography to image the inside of volcanoes to the use of seismic tomography to image magmatic bodies in the crust, and most recently, we have added synchrotron-based x-ray tomography to image the inside of material as we test it under controlled conditions. Here, we will explore some of the novel findings made on the evolution of magma during shearing. These will include observations and discussions of magma flow and failure as well as petrological reaction kinetics.

  2. Pressure waves in a supersaturated bubbly magma

    Science.gov (United States)

    Kurzon, I.; Lyakhovsky, V.; Navon, O.; Chouet, B.

    2011-01-01

    We study the interaction of acoustic pressure waves with an expanding bubbly magma. The expansion of magma is the result of bubble growth during or following magma decompression and leads to two competing processes that affect pressure waves. On the one hand, growth in vesicularity leads to increased damping and decreased wave amplitudes, and on the other hand, a decrease in the effective bulk modulus of the bubbly mixture reduces wave velocity, which in turn, reduces damping and may lead to wave amplification. The additional acoustic energy originates from the chemical energy released during bubble growth. We examine this phenomenon analytically to identify conditions under which amplification of pressure waves is possible. These conditions are further examined numerically to shed light on the frequency and phase dependencies in relation to the interaction of waves and growing bubbles. Amplification is possible at low frequencies and when the growth rate of bubbles reaches an optimum value for which the wave velocity decreases sufficiently to overcome the increased damping of the vesicular material. We examine two amplification phase-dependent effects: (1) a tensile-phase effect in which the inserted wave adds to the process of bubble growth, utilizing the energy associated with the gas overpressure in the bubble and therefore converting a large proportion of this energy into additional acoustic energy, and (2) a compressive-phase effect in which the pressure wave works against the growing bubbles and a large amount of its acoustic energy is dissipated during the first cycle, but later enough energy is gained to amplify the second cycle. These two effects provide additional new possible mechanisms for the amplification phase seen in Long-Period (LP) and Very-Long-Period (VLP) seismic signals originating in magma-filled cracks.

  3. Predictive Models of Acute Mountain Sickness after Rapid Ascent to Various Altitudes

    Science.gov (United States)

    2013-01-01

    men and women when se- verity was increased in men. Third, previous history of AMS was not included as a factor in these models. Prior AMS...susceptibility has been shown to be an important predictor of future AMS (26,33). Given the small number of volun- teers with a previous history of AMS in our...3):192–9. 5. Burtscher M, Likar R, Nachbauer W, et al. Effects of aspirin dur- ing exercise on the incidence of high-altitude headache: a ran

  4. Rapid ascent: Rocky Mountain National Park in the Great Acceleration, 1945-present

    Science.gov (United States)

    Boxell, Mark

    After the Second World War's conclusion, Rocky Mountain National Park (RMNP) experienced a massive rise in visitation. Mobilized by an affluent economy and a growing, auto-centric infrastructure, Americans rushed to RMNP in droves, setting off new concerns over the need for infrastructure improvements in the park. National parks across the country experienced similar explosions in visitation, inspiring utilities- and road-building campaigns throughout the park units administered by the National Park Service. The quasi-urbanization of parks like RMNP implicated the United States' public lands in a process of global change, whereby wartime technologies, cheap fossil fuels, and a culture of techno-optimism--epitomized by the Mission 66 development program--helped foster a "Great Acceleration" of human alterations of Earth's natural systems. This transformation culminated in worldwide turns toward mass-urbanization, industrial agriculture, and globalized markets. The Great Acceleration, part of the Anthropocene--a new geologic epoch we have likely entered, which proposes that humans have become a force of geologic change--is used as a conceptual tool for understanding the connections between local and global changes which shaped the park after World War II. The Great Acceleration and its array of novel technologies and hydrocarbon-powered infrastructures produced specific cultures of tourism and management techniques within RMNP. After World War II, the park increasingly became the product and distillation of a fossil fuel-dependent society.

  5. Predicted Hematologic and Plasma Volume Responses Following Rapid Ascent to Progressive Altitudes

    Science.gov (United States)

    2014-06-01

    1835. 55. Hartgens F and Kuipers H: Effects of androgenic- anabolic steroids in athletes. Sports Med. 2014, 34:513-554. 56. Gonzales GF, Gasco M...altitude on second-generation blood tests to detect erythropoietin abuse by athletes. Hematologica 2003, 88:1053-1062. 10. Subudhi AW, Bourdillon N

  6. Ultralightweight Refractory-Lined C/C Ascent Engine Combustion Chambers Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Mars sample return ascent vehicles require a velocity change exceeding 4 km/s within minutes of launch and higher propellant mass fractions than are offered by...

  7. Predictors of energy cost during stair ascent and descent in individuals with chronic stroke

    National Research Council Canada - National Science Library

    Polese, Janaine Cunha; Scianni, Aline Alvim; Teixeira-Salmela, Luci Fuscaldi

    2015-01-01

    [Purpose] This study aimed to determine which clinical measures of walking performance and lower limb muscle strength would predict energy cost during stair ascent and descent in community-dwelling individuals with stroke...

  8. End-tidal partial pressure of carbon dioxide and acute mountain sickness in the first 24 hours upon ascent to Cusco Peru (3326 meters).

    Science.gov (United States)

    Douglas, Danielle J; Schoene, Robert B

    2010-06-01

    To explore the association of end-title partial pressure (Petco(2)) and oxygen saturation (Spo(2)) with the development of AMS in travelers rapidly ascending to Cusco, Peru (3326 m). Using the 715 TIDAL WAVE Sp handheld, portable capnometer/oximeter, we measured Spo(2) and Petco(2) in 175 subjects upon ascent to Cusco, Peru (3326 m) from Lima (sea level) (a mean time of 3.9 hours.) Symptoms of AMS were recorded at the same initial time on arrival to altitude and 24 hours later using the Environmental Symptoms Questionnaire (ESQ). This study showed that no subjects with the lowest Petco(2) of 23 to 30 mm Hg had AMS (P <.044). The data also demonstrate that subjects with a higher Petco(2) (36-40 mm Hg) and lower Sao(2) (72%-86%) have a higher incidence of AMS. The most important finding of this study is that Petco(2) upon ascent was found to have a more significant effect than Spo(2) on a subject's ultimate ESQ score. This study demonstrates that those individuals with a brisk ventilatory response upon ascent to moderate altitude, as measured by Petco(2), did not develop AMS, whereas a blunted ventilatory response, as reflected in the highest Petco(2), was related to the subsequent development of AMS. Copyright (c) 2010. Published by Elsevier Inc.

  9. Geochemical Evidence for a Terrestrial Magma Ocean

    Science.gov (United States)

    Agee, Carl B.

    1999-01-01

    The aftermath of phase separation and crystal-liquid fractionation in a magma ocean should leave a planet geochemically differentiated. Subsequent convective and other mixing processes may operate over time to obscure geochemical evidence of magma ocean differentiation. On the other hand, core formation is probably the most permanent, irreversible part of planetary differentiation. Hence the geochemical traces of core separation should be the most distinct remnants left behind in the mantle and crust, In the case of the Earth, core formation apparently coincided with a magma ocean that extended to a depth of approximately 1000 km. Evidence for this is found in high pressure element partitioning behavior of Ni and Co between liquid silicate and liquid iron alloy, and with the Ni-Co ratio and the abundance of Ni and Co in the Earth's upper mantle. A terrestrial magma ocean with a depth of 1000 km will solidify from the bottom up and first crystallize in the perovskite stability field. The largest effect of perovskite fractionation on major element distribution is to decrease the Si-Mg ratio in the silicate liquid and increase the Si-Mg ratio in the crystalline cumulate. Therefore, if a magma ocean with perovskite fractionation existed, then one could expect to observe an upper mantle with a lower than chondritic Si-Mg ratio. This is indeed observed in modern upper mantle peridotites. Although more experimental work is needed to fully understand the high-pressure behavior of trace element partitioning, it is likely that Hf is more compatible than Lu in perovskite-silicate liquid pairs. Thus, perovskite fractionation produces a molten mantle with a higher than chondritic Lu-Hf ratio. Arndt and Blichert-Toft measured Hf isotope compositions of Barberton komatiites that seem to require a source region with a long-lived, high Lu-Hf ratio. It is plausible that that these Barberton komatiites were generated within the majorite stability field by remelting a perovskite

  10. Augmenting Parametric Optimal Ascent Trajectory Modeling with Graph Theory

    Science.gov (United States)

    Dees, Patrick D.; Zwack, Matthew R.; Edwards, Stephen; Steffens, Michael

    2016-01-01

    It has been well documented that decisions made in the early stages of Conceptual and Pre-Conceptual design commit up to 80% of total Life-Cycle Cost (LCC) while engineers know the least about the product they are designing [1]. Once within Preliminary and Detailed design however, making changes to the design becomes far more difficult to enact in both cost and schedule. Primarily this has been due to a lack of detailed data usually uncovered later during the Preliminary and Detailed design phases. In our current budget-constrained environment, making decisions within Conceptual and Pre-Conceptual design which minimize LCC while meeting requirements is paramount to a program's success. Within the arena of launch vehicle design, optimizing the ascent trajectory is critical for minimizing the costs present within such concerns as propellant, aerodynamic, aeroheating, and acceleration loads while meeting requirements such as payload delivered to a desired orbit. In order to optimize the vehicle design its constraints and requirements must be known, however as the design cycle proceeds it is all but inevitable that the conditions will change. Upon that change, the previously optimized trajectory may no longer be optimal, or meet design requirements. The current paradigm for adjusting to these updates is generating point solutions for every change in the design's requirements [2]. This can be a tedious, time-consuming task as changes in virtually any piece of a launch vehicle's design can have a disproportionately large effect on the ascent trajectory, as the solution space of the trajectory optimization problem is both non-linear and multimodal [3]. In addition, an industry standard tool, Program to Optimize Simulated Trajectories (POST), requires an expert analyst to produce simulated trajectories that are feasible and optimal [4]. In a previous publication the authors presented a method for combatting these challenges [5]. In order to bring more detailed information

  11. Open-path FTIR spectroscopy of magma degassing processes during eight lava fountains on Mount Etna

    Science.gov (United States)

    La Spina, Alessandro; Burton, Mike; Allard, Patrick; Alparone, Salvatore; Murè, Filippo

    2016-04-01

    In June-July 2001 a series of 16 discrete lava fountain paroxysms occurred at the Southeast summit crater (SEC) of Mount Etna, preceding a 28-day long violent flank eruption. Each paroxysm was preceded by lava effusion, growing seismic tremor and a crescendo of Strombolian explosive activity culminating into powerful lava fountaining up to 500m in height. During 8 of these 16 events we could measure the chemical composition of the magmatic gas phase (H2O, CO2, SO2, HCl, HF and CO), using open-path Fourier transform infrared (OP-FTIR) spectrometry at ˜1-2km distance from SEC and absorption spectra of the radiation emitted by hot lava fragments. We show that each fountaining episode was characterized by increasingly CO2-rich gas release, with CO2/SO2and CO2/HCl ratios peaking in coincidence with maxima in seismic tremor and fountain height, whilst the SO2/HCl ratio showed a weak inverse relationship with respect to eruption intensity. Moreover, peak values in both CO2/SO2ratio and seismic tremor amplitude for each paroxysm were found to increase linearly in proportion with the repose interval (2-6 days) between lava fountains. These observations, together with a model of volatile degassing at Etna, support the following driving process. Prior to and during the June-July 2001 lava fountain sequence, the shallow (˜2km) magma reservoir feeding SEC received an increasing influx of deeply derived carbon dioxide, likely promoted by the deep ascent of volatile-rich primitive basalt that produced the subsequent flank eruption. This CO2-rich gas supply led to gas accumulation and overpressure in SEC reservoir, generating a bubble foam layer whose periodical collapse powered the successive fountaining events. The anti-correlation between SO2/HCl and eruption intensity is best explained by enhanced syn-eruptive degassing of chlorine from finer particles produced during more intense magma fragmentation.

  12. Volcanic systems of Iceland and their magma source

    Science.gov (United States)

    Sigmarsson, Olgeir

    2017-04-01

    Several active hot-spot volcanoes produce magma from mantle sources which composition varies on decadal time scale. This is probably best demonstrated by the recent work of Pietruszka and collaborators on Kilauea, Hawaii. In marked contrast, basalt lavas from volcanic system in Iceland located above the presumed centre of the Iceland mantle plume have uniform isotope composition over the last 10 thousand years. Volcanic systems are composed of a central volcano and a fissure swarm, or a combination of both and they represent a fundamental component of the neovolcanic zones in Iceland. Four such systems, those of Askja, Bárðarbunga, Kverkfjöll and Grímsvötn in central Iceland were chosen for investigation. The last three have central volcanoes covered by the Vatnajökull ice-sheet whereas part of their fissure swarms is ice-free. Tephra produced during subglacial eruptions together with lavas from the fissure swarms of Holocene age have been collected and analysed for Sr, Nd and Th isotope ratios. Those volcanic formations that can be univocally correlated to a given volcanic system display uniform isotope ratio but different from one volcanic system to another. An exception to this regularity is that Askja products have isotope ratios indistinguishable from those of Gímsvötn, but since these volcanic systems lies far apart their lava fields do not overlap. A practical aspect of these findings was demonstrated during the rifting event of Bárðarbunga and fissure eruption forming the Holuhraun lava field. Relatively low, O isotope ratios in these basalts and heterogeneous macrocrystal composition have been ascribed to important metabasaltic crustal contamination with or without crystal mush recycling. In that case a surprisingly efficient magma mixing and melt homogenization must have occurred in the past beneath the volcanic systems. One possibility is that during the rapid deglaciation much mantle melting occurred and melts accumulated at the mantle

  13. New Approaches for Identifying the P-T-X-t Histories and Eruption Triggers for Silicic Magmas; An Example Examining the Scaup Lake Rhyolite, Yellowstone Caldera, WY

    Science.gov (United States)

    Till, C. B.; Boyce, J. W.

    2016-12-01

    The crystal cargoes from past eruptions provide petrologic records of the pressure, temperature and composition of a magma body preceding eruption. Recent advances in diffusion chronometry also now enable us to reconstruct the timing of magmatic events shortly before eruption. Here these techniques are combined to unlock detailed P-T-X-t histories of silicic magma bodies leading to eruption, using the 260 ka Scaup Lake rhyolite lava (SCL) from Yellowstone caldera as an example. The SCL contains 30% phenocrysts of reversely zoned quartz, clinopyroxene, orthopyroxene, plagioclase and sanidine. SCL sanidine and plagioclase reveal ubiquitous bright rims that are enriched in Ba, Sr, Ca and in some cases Mg and Ti relative to the grain interior. Major element transects across the full width of the sanidine rims reveal two pronounced changes in composition that can be equated to heating events (older +25°C, younger +100°C) using sanidine-liquid thermometry and compositional relationships predicted by Rhyolite-MELTS. Renewed precipitation of sanidine at higher temperatures could reflect magma ascent and concomitant exsolution of dissolved H2O, the addition of CO2 by new magma, and/or the addition of K-Na-enriched melt derived from melting sanidine-rich cumulates. The increase in magmaphile elements associated with the 25°C heating event indicate this episode of feldspar growth resulted from the injection of a hotter, less evolved magma 10-40 yrs prior to eruption based on diffusion chronometry (Till et al., Geology, 2015). Estimates using natural and experimental crystal growth rates suggest the second heating event of 100°C recorded in the outermost sanidine rims occurred within 1.5-2 yrs of eruption. This is consistent with a subset of the diffusion chronometry results that indicate rejuvenation-eruption timescales of eruption. Instead it appears the necessary overpressure was provided by a second intrusion in the prior several years to months.

  14. Magma Energy Research Project, FY 1979 annual progress report

    Energy Technology Data Exchange (ETDEWEB)

    Colp, J.L.

    1979-12-01

    The objective of the Magma Energy Research Project is to define the scientific feasibility of extracting energy from magma bodies. Activities to accomplish the objective are divided into five tasks: resource location and identification; source tapping; magma characterization; materials compatibility; and energy extraction. The program activities of FY 1979 are summarized here according to the individual tasks. Major emphasis of the program in the last year was on field experimentation with the United States Geological Survey in geoscience and technological studies at the Kilauea Iki lava lake. Other major efforts included installation of the magma simulation facility and magma-metal compatibility studies. The Magma Energy Advisory Panel also met during this period. Efforts and results are summarized.

  15. Magma storage and evolution of the most recent effusive and explosive eruptions from Yellowstone Caldera

    Science.gov (United States)

    Befus, Kenneth S.; Gardner, James E.

    2016-04-01

    Between 70 and 175 ka, over 350 km3 of high-silica rhyolite magma erupted both effusively and explosively from within the Yellowstone Caldera. Phenocrysts in all studied lavas and tuffs are remarkably homogenous at the crystal, eruption, and caldera-scale, and yield QUILF temperatures of 750 ± 25 °C. Phase equilibrium experiments replicate the observed phenocryst assemblage at those temperatures and suggest that the magmas were all stored in the upper crust. Quartz-hosted glass inclusions contain 1.0-2.5 % H2O and 50-600 ppm CO2, but some units are relatively rich in CO2 (300-600 ppm) and some are CO2-poor (50-200 ppm). The CO2-rich magmas were stored at 90-150 MPa and contained a fluid that was 60-75 mol% CO2. CO2-poor magmas were stored at 50-70 MPa, with a more H2O-rich fluid (X_{{{text{CO}}2 }} = 40-60 %). Storage pressures and volatiles do not correlate with eruption age, volume, or style. Trace-element contents in glass inclusions and host matrix glass preserve a systematic evolution produced by crystal fractionation, estimated to range from 36 ± 12 to 52 ± 12 wt%. Because the erupted products contain eruption. In the Tuffs of Bluff Point and Cold Mountain Creek, matrix glass is less evolved than most inclusions, which may indicate that more primitive rhyolite was injected into the reservoir just before those eruptions. The presence and dissolution of granophyre in one flow may record evidence for heating prior to eruption and also demonstrate that the Yellowstone magmatic system may undergo rapid changes. The variations in depth suggest the magmas were sourced from multiple chambers that follow similar evolutionary paths in the upper crust.

  16. Chlorine solubility in evolved alkaline magmas

    Directory of Open Access Journals (Sweden)

    M. R. Carroll

    2005-06-01

    Full Text Available Experimental studies of Cl solubility in trachytic to phonolitic melts provide insights into the capacity of alkaline magmas to transport Cl from depth to the earth?s surface and atmosphere, and information on Cl solubility variations with pressure, temperature and melt or fluid composition is crucial for understanding the reasons for variations in Cl emissions at active volcanoes. This paper provides a brief review of Cl solubility experiments conducted on a range of trachytic to phonolitic melt compositions. Depending on the experimental conditions the melts studied were in equilibrium with either a Cl-bearing aqueous fluid or a subcritical assemblage of low- Cl aqueous fluid + Cl-rich brine. The nature of the fluid phase(s was identified by examination of fluid inclusions present in run product glasses and the fluid bulk composition was calculated by mass balance. Chlorine concentrations in the glass increase with increasing Cl molality in the fluid phase until a plateau in Cl concentration is reached when melt coexists with aqueous fluid + brine. With fluids of similar Cl molality, higher Cl concentrations are observed in peralkaline phonolitic melts compared with peraluminous phonolitic melts; overall the Cl concentrations observed in phonolitic and trachytic melts are approximately twice those found in calcalkaline rhyolitic melts under similar conditions. The observed negative pressure dependence of Cl solubility implies that Cl contents of melts may actually increase during magma decompression if the magma coexists with aqueous fluid and Cl-rich brine (assuming melt-vapor equilibrium is maintained. The high Cl contents (approaching 1 wt% Cl observed in some melts/glasses from the Vesuvius and Campi Flegrei areas suggest saturation with a Cl-rich brine prior to eruption.

  17. Special relativity derived from spacetime magma.

    Science.gov (United States)

    Greensite, Fred

    2014-01-01

    We present a derivation of relativistic spacetime largely untethered from specific physical considerations, in constrast to the many physically-based derivations that have appeared in the last few decades. The argument proceeds from the inherent magma (groupoid) existing on the union of spacetime frame components [Formula: see text] and Euclidean [Formula: see text] which is consistent with an "inversion symmetry" constraint from which the Minkowski norm results. In this context, the latter is also characterized as one member of a class of "inverse norms" which play major roles with respect to various unital [Formula: see text]-algebras more generally.

  18. Special relativity derived from spacetime magma.

    Directory of Open Access Journals (Sweden)

    Fred Greensite

    Full Text Available We present a derivation of relativistic spacetime largely untethered from specific physical considerations, in constrast to the many physically-based derivations that have appeared in the last few decades. The argument proceeds from the inherent magma (groupoid existing on the union of spacetime frame components [Formula: see text] and Euclidean [Formula: see text] which is consistent with an "inversion symmetry" constraint from which the Minkowski norm results. In this context, the latter is also characterized as one member of a class of "inverse norms" which play major roles with respect to various unital [Formula: see text]-algebras more generally.

  19. Breaking the paradigm at magma-poor and magma-rich rifted margins

    Science.gov (United States)

    Tugend, Julie; Manatschal, Gianreto; Gillard, Morgane; Nirrengarten, Michael; Epin, Marie-Eva; Sauter, Daniel; Autin, Julia; Harkin, Caroline; Kusznir, Nick

    2017-04-01

    Rifted margins used to be classified into volcanic or non-volcanic passive margins. Because magmatism is evidenced even in so-called 'non-volcanic' settings, this terminology was later adjusted to magma-poor and magma-rich rifted margins. This classification represents a simplification into end-member magmatic types depending on the magmatic budget related to rifting and/or breakup processes. New observations derived from higher quality geophysical data sets and drill-hole data revealed the great diversity of rifted margin architecture and highly variable distribution of rift-related and/or breakup related magmatism. Recent studies suggest that rifted margins have a more complex tectono-magmatic evolution than previously assumed and cannot be characterized based on the observed volume of magma alone. In this study, we present seismic observations from 2D high resolution long-offset deep reflection seismic profiles across the East-Indian and South-Atlantic rifted margins. We aim to compare structural similarities between rifted margins with different magmatic budgets. We apply a systematic seismic interpretation approach to describe and characterize the first-order architecture and magmatic budget of our case examples. The identification of magmatic additions based on seismic observations only is indeed not unequivocal, in spite of the high-resolution dataset. Interpretations are related to large uncertainties in particular at ocean-continent transitions (i.e. outer highs) where most of the magmatism seems to be located. For each line, we present three different interpretations based on offshore and/or onshore field analogues. These interpretations illustrate scenarios for the nature of the outer highs that we believe are geologically meaningful and reasonable, and imply different magmatic budgets at breakup. Based on these interpretations we discuss different mechanisms for lithospheric breakup involving either a gradual or more instantaneous process independently

  20. Magma evolution inside the 1631 Vesuvius magma chamber and eruption triggering

    Science.gov (United States)

    Stoppa, Francesco; Principe, Claudia; Schiazza, Mariangela; Liu, Yu; Giosa, Paola; Crocetti, Sergio

    2017-03-01

    Vesuvius is a high-risk volcano and the 1631 Plinian eruption is a reference event for the next episode of explosive unrest. A complete stratigraphic and petrographic description of 1631 pyroclastics is given in this study. During the 1631 eruption a phonolite was firstly erupted followed by a tephritic phonolite and finally a phonolitic tephrite, indicating a layered magma chamber. We suggest that phonolitic basanite is a good candidate to be the primitive parental-melt of the 1631 eruption. Composition of apatite from the 1631 pyroclastics is different from those of CO2-rich melts indicating negligible CO2 content during magma evolution. Cross checking calculations, using PETROGRAPH and PELE software, accounts for multistage evolution up to phonolite starting from a phonolitic basanite melt similar to the Vesuvius medieval lavas. The model implies crystal settling of clinopyroxene and olivine at 6 kbar and 1220°C, clinopyroxene plus leucite at a pressure ranging from 2.5 to 0.5 kbar and temperature ranging from 1140 to 940°C. Inside the phonolitic magma chamber K-feldspar and leucite would coexist at a temperature ranging from from 940 to 840°C and at a pressure ranging from 2.5 to0.5 kbar. Thus crystal fractionation is certainly a necessary and probably a sufficient condition to evolve the melt from phono tephritic to phonolitic in the 1631 magma chamber. We speculate that phonolitic tephrite magma refilling from deeper levels destabilised the chamber and triggered the eruption, as testified by the seismic precursor phenomena before 1631 unrest.

  1. Efficacy of pre-ascent climbing route visual inspection in indoor sport climbing.

    Science.gov (United States)

    Sanchez, X; Lambert, Ph; Jones, G; Llewellyn, D J

    2012-02-01

    Pre-ascent climbing route visual inspection (route preview) has been suggested as a key climbing performance parameter although its role has never been verified experimentally. We examined the efficacy of this perceptual-cognitive skill on indoor sport climbing performance. Twenty-nine male climbers, divided into intermediate, advanced and expert climbing level groups, climbed two indoor sport routes matching their climbing level and, where applicable, routes below their climbing level. At each level, one route was climbed with a preview, where participants benefited from a 3-min pre-ascent climbing route visual inspection. Performance was assessed in terms of output (route completion) and form (number and duration of moves and stops). Route preview did not influence the output performance. Climbers using visual inspection were no more likely to finish the ascent than those without the option of using visual inspection. Conversely, route preview did influence form performance; climbers made fewer, and shorter stops during their ascent following a preview of the route. Form performances differences remained when baseline ability levels were taken into account, although for shorter duration of stops only with expert climbers benefiting most from route preview. The ability to visually inspect a climb before its ascent may represent an essential component of performance optimization. © 2010 John Wiley & Sons A/S.

  2. Survey Says...! Women rising above challenges in atmospheric science through ASCENT

    Science.gov (United States)

    Edwards, L. M.; Thiry, H.; Hallar, A. G.; Avallone, L. M.

    2011-12-01

    The Atmospheric Sciences Collaborations and Enriching NeTworks (ASCENT) project is in its third year of connecting early career atmospheric scientists with female senior scientists in related fields. The annual workshops have demonstrated the range of career and personal decisions that current successful senior scientists have made, presented tools and resources, created new networks of collaboration, and provided a forum for informal and formal discussions of issues that face early career female atmospheric scientists. A formal assessment has been ongoing, with participants responding to questions relating to the workshops themselves, in addition to a longitudinal study that asks participants about the impact of ASCENT months or years after their workshop experience. Through this evaluation, the workshop organizers have been able to tailor the workshop schedule, reunion events, and communication, to fit the needs of the participants and manage the project better to achieve their desired outcomes. The results so far have shown that participants felt they enhanced their professional networks, and over 90% had maintained contact with other ASCENT participants six months after the workshop. Participants also reported to have gained knowledge and resources for women scientists and had fewer career obstacles six months after ASCENT. ASCENT organizers will share lessons learned throughout the process and some examples of best practices they have discovered. The assessment design, and most recent results from all three workshop cohorts will also be presented.

  3. Selective entrainment of peritectic garnet into S-type granitic magmas: Evidence from Archaean mid-crustal anatectites

    Science.gov (United States)

    Taylor, Jeanne; Stevens, Gary

    2010-12-01

    Entrainment of restite is commonly invoked to explain both the origin of relatively mafic granites and granodiorites, as well as the chemical connection between granite magmas and their sources. This concept has become linked to models for magma migration out of the source, as restite entrainment is considered to take place when diatexitic sources mobilise en masse. This is at odds with the common occurrence of relatively mafic granites as high level intrusions in the crust or their eruptive equivalents that must have formed from markedly water-undersaturated magmas that ascended through narrow conduits. We investigate pelitic migmatites from the Mkhondo Valley Metamorphic Suite (MVMS) in Swaziland, where a mid-crustal heating event produced metatexitic migmatites with minimal post-anatectic recrystallisation. In these rocks all the garnet is peritectic, having arisen through biotite fluid-absent melting, which produced garnet poikiloblasts characterised by inclusions of melt, quartz and biotite. Leucosomes that represent sites of melt transfer carry similar, smaller (typically accessory phases, while the recrystallised garnet in the larger melt-filled structures became progressively better equilibrated with these minerals. Thus, peritectic garnet in the source grew sufficiently rapidly to prevent trace element equilibrium with the bulk-rock composition, and, concurrent rapid magma segregation prevented the development of diatexitic source conditions. The segregated magma consisted of melt, the peritectic assemblage (principally garnet) and the accessory minerals monazite and zircon. These rocks illustrate that mafic granites may arise purely as mixtures of melt and the peritectic assemblage produced by the incongruent melting reaction. Importantly, under the circumstances which produced the MVMS anatectites, peritectic garnet is entrained as < 1 mm poikiloblasts, demonstrating how mafic granitic magmas can migrate out of the source without the source becoming

  4. Chapter 9 The magma feeding system of Somma-Vesuvius (Italy) strato-volcano: new inferences from a review of geochemical and Sr, Nd, Pb and O isotope data

    Science.gov (United States)

    Piochi, M.; de Vivo, B.; Ayuso, R.A.

    2006-01-01

    A large database of major, trace and isotope (Sr, Nd, Pb, O) data exists for rocks produced by the volcanic activity of Somma-Vesuvius volcano. Variation diagrams strongly suggest a major role for evolutionary processes such as fractional crystallization, contamination, crystal trapping and magma maxing, occurring after magma genesis in the mantle. Most mafic magmas are enriched in LILE (Light Ion Lithophile Elements; K. Rb, Ba), REE (Ce, Sm) and Y, show small Nb-Ta negative anomalies, and have values of Nb/Zr at about 0.15. Enrichments in LILE, REE, Nb and Ta do not correlate with Sr isotope values or degree of both K enrichment and silica undersaturation. The results indicate mantle source heterogeneity produced by slab-derived components beneath the volcano. However, the Sr isotope values of Somma-Vesuvius increase from 0.7071 up to 0.7081 with transport through the uppermost 11-12 km of the crust. The Sr isotope variation suggests that the crustal component affected the magmas during ascent through the lithosphere to the surface. Our new geochemical assessment based on chemical, isotopic and fluid inclusion data points to the existence of three main levels of magma storage. Two of the levels are deep and may represent long-lived reservoirs; the uppermost crustal level probably coincides with the volcanic conduit. The deeper level of magma storage is deeper than 12 km and fed the 1944 AD eruption. The intermediate level coincides with the seismic discontinuity detected by Zollo et al. (1996) at about 8 km. This intermediate level supplies magmas with 87Sr/86Sr values between 0.7071 and 0.7074, and ??O18<8% that typically erupted both during interplinian (i.e. 1906 AD) and sub-plinian (472 AD, 1631 AD) events. The shallowest level of magma storage at about 5 km was the site of magma chambers for the Pompei and Avellino plinian eruptions. New investigations are necessary to verify the proposed magma feeding system. ?? 2006 Elsevier B.V. All rights reserved.

  5. Zircons reveal magma fluxes in the Earth's crust.

    Science.gov (United States)

    Caricchi, Luca; Simpson, Guy; Schaltegger, Urs

    2014-07-24

    Magma fluxes regulate the planetary thermal budget, the growth of continents and the frequency and magnitude of volcanic eruptions, and play a part in the genesis and size of magmatic ore deposits. However, because a large fraction of the magma produced on the Earth does not erupt at the surface, determinations of magma fluxes are rare and this compromises our ability to establish a link between global heat transfer and large-scale geological processes. Here we show that age distributions of zircons, a mineral often present in crustal magmatic rocks, in combination with thermal modelling, provide an accurate means of retrieving magma fluxes. The characteristics of zircon age populations vary significantly and systematically as a function of the flux and total volume of magma accumulated in the Earth's crust. Our approach produces results that are consistent with independent determinations of magma fluxes and volumes of magmatic systems. Analysis of existing age population data sets using our method suggests that porphyry-type deposits, plutons and large eruptions each require magma input over different timescales at different characteristic average fluxes. We anticipate that more extensive and complete magma flux data sets will serve to clarify the control that the global heat flux exerts on the frequency of geological events such as volcanic eruptions, and to determine the main factors controlling the distribution of resources on our planet.

  6. Mantle ingredients for making the fingerprint of Etna alkaline magmas: implications for shallow partial melting within the complex geodynamic framework of Eastern Sicily

    Science.gov (United States)

    Viccaro, Marco; Zuccarello, Francesco

    2017-09-01

    able to produce magmas with variable compositions and volatile contents, which can then undergo distinct histories of ascent and evolution, leading to the wide range of eruptive styles observed at Mt. Etna volcano. Being partial melting confined in the spinel facies of the mantle, our model implies that the source of Mt. Etna magmas might be rather shallow (<2 GPa; i.e., lesser than ca. 60 km), excluding the presence of deep, plume-like mantle structures responsible for magma generation. Partial melting should occur consequently as a response of mantle decompression within the framework of regional tectonics affecting the Eastern Sicily, which could be triggered by extensional tectonics and/or subduction-induced mantle upwelling.

  7. A Multiconstrained Ascent Guidance Method for Solid Rocket-Powered Launch Vehicles

    Directory of Open Access Journals (Sweden)

    Si-Yuan Chen

    2016-01-01

    Full Text Available This study proposes a multiconstrained ascent guidance method for a solid rocket-powered launch vehicle, which uses a hypersonic glide vehicle (HGV as payload and shuts off by fuel exhaustion. First, pseudospectral method is used to analyze the two-stage launch vehicle ascent trajectory with different rocket ignition modes. Then, constraints, such as terminal height, velocity, flight path angle, and angle of attack, are converted into the constraints within height-time profile according to the second-stage rocket flight characteristics. The closed-loop guidance method is inferred by different spline curves given the different terminal constraints. Afterwards, a thrust bias energy management strategy is proposed to waste the excess energy of the solid rocket. Finally, the proposed method is verified through nominal and dispersion simulations. The simulation results show excellent applicability and robustness of this method, which can provide a valuable reference for the ascent guidance of solid rocket-powered launch vehicles.

  8. Photon storage in ¿-type optically dense atomic media. IV. Optimal control using gradient ascent

    DEFF Research Database (Denmark)

    Gorshkov, Alexey V.; Calarco, Tomasso; Lukin, Mikhail D.

    2008-01-01

    We use the numerical gradient ascent method from optimal control theory to extend efficient photon storage in -type media to previouslyinaccessible regimes and to provide simple intuitive explanations for our optimization techniques. In particular, by using gradient ascent to shape classical....... We also demonstrate that the often discussed connection between time reversal andoptimality in photon storage follows naturally from gradient ascent. Finally, we discuss the optimization of controlled reversible inhomogeneous broadening....... control pulses used to mediate photon storage, we open up the possibility of high efficiency photon storage in thenonadiabatic limit, in which analytical solutions to the equations of motion do not exist. This control shaping technique enables an order-of-magnitude increase in the bandwidth of the memory...

  9. Experimental Constraints on a Vesta Magma Ocean

    Science.gov (United States)

    Hoff, C.; Jones, J. H.; Le, L.

    2014-01-01

    A magma ocean model was devised to relate eucrites (basalts) and diogenites (orthopyroxenites), which are found mixed together as clasts in a suite of polymict breccias known as howardites. The intimate association of eucritic and diogenitic clasts in howardites argues strongly that these three classes of achondritic meteorites all originated from the same planetoid. Reflectance spectral evidence (including that from the DAWN mission) has long suggested that Vesta is indeed the Eucrite Parent Body. Specifically, the magma ocean model was generated as follows: (i) the bulk Vesta composition was taken to be 0.3 CV chondrite + 0.7 L chondrite but using only 10% of the Na2O from this mixture; (ii) this composition is allowed to crystallize at 500 bar until approx. 80% of the system is solid olivine + low-Ca pyroxene; (iii) the remaining 20% liquid crystallizes at one bar from 1250C to 1110C, a temperature slightly above the eucrite solidus. All crystallization calculations were performed using MELTS. In this model, diogenites are produced by cocrystallization of olivine and pyroxene in the >1250C temperature regime, with Main Group eucrite liquids being generated in the 1300-1250C temperature interval. Low-Ca pyroxene reappears at 1210C in the one-bar calculations and fractionates the residual liquid to produce evolved eucrite compositions (Stannern Trend). We have attempted to experimentally reproduce the <1250C portion of the MELTS Vesta magma ocean. In the MELTS calculation, the change from 500 bar to one bar results in a shift of the olivine:low-Ca pyroxene boundary so that the 1250C liquid is now in the olivine field and, consequently, olivine should be the first-crystallizing phase, followed by low-Ca pyroxene at 1210C, and plagioclase at 1170C. Because at one bar the olivine:low-Ca pyroxene boundary is a peritectic, fractional crystallization of the 1210C liquid proceeds with only pyroxene crystallization until plagioclase appears. Thus, the predictions of the

  10. The timing of compositionally-zoned magma reservoirs and mafic 'priming' weeks before the 1912 Novarupta-Katmai rhyolite eruption

    Science.gov (United States)

    Singer, Brad S.; Costa, Fidel; Herrin, Jason S.; Hildreth, Wes; Fierstein, Judy

    2016-10-01

    The June, 6, 1912 eruption of more than 13 km3 of dense rock equivalent (DRE) magma at Novarupta vent, Alaska was the largest of the 20th century. It ejected >7 km3 of rhyolite, ∼1.3 km3 of andesite and ∼4.6 km3 of dacite. Early ideas about the origin of pyroclastic flows and magmatic differentiation (e.g., compositional zonation of reservoirs) were shaped by this eruption. Despite being well studied, the timing of events that led to the chemically and mineralogically zoned magma reservoir remain poorly known. Here we provide new insights using the textures and chemical compositions of plagioclase and orthopyroxene crystals and by reevaluating previous U-Th isotope data. Compositional zoning of the magma reservoir likely developed a few thousand years before the eruption by several additions of mafic magma below an extant silicic reservoir. Melt compositions calculated from Sr contents in plagioclase fill the compositional gap between 68 and 76% SiO2 in whole pumice clasts, consistent with uninterrupted crystal growth from a continuum of liquids. Thus, our findings support a general model in which large volumes of crystal-poor rhyolite are related to intermediate magmas through gradual separation of melt from crystal-rich mush. The rhyolite is incubated by, but not mixed with, episodic recharge pulses of mafic magma that interact thermochemically with the mush and intermediate magmas. Hot, Mg-, Ca-, and Al-rich mafic magma intruded into, and mixed with, deeper parts of the reservoir (andesite and dacite) multiple times. Modeling the relaxation of the Fe-Mg concentrations in orthopyroxene and Mg in plagioclase rims indicates that the final recharge event occurred just weeks prior to the eruption. Rapid addition of mass, volatiles, and heat from the recharge magma, perhaps aided by partial melting of cumulate mush below the andesite and dacite, pressurized the reservoir and likely propelled a ∼10 km lateral dike that allowed the overlying rhyolite to reach the

  11. Magma Reservoirs: How Well do We Know Them, Why Does it Matter, and How Can We Do Better?

    Science.gov (United States)

    Lowenstern, J. B.; Sisson, T. W.; Hurwitz, S.

    2016-12-01

    Worldwide, magma erupts through volcanoes scores of times per year, but it remains rare that we successfully image high-melt fraction bodies in pre-eruptive subsurface reservoirs. Largely, this stems from a problem of scale: only a few tenths of a km3 of magma typically erupt, and the resolution of state-of-the-art tomographic images rarely permits imaging such small volumes. Even where we expect significant magma reservoirs, we are challenged to create definitive images. Success is enhanced in the submarine environment where high-resolution seismic reflection experiments have been combined with a suite of other geophysical techniques. But at subaerial volcanoes, where we must forecast hazards and respond to unrest, we cannot reliably incorporate data on the nature and status of subvolcanic magmas. An example is Yellowstone, where we observe anomalously high heat flow covering thousands of square kms, prolific gas discharge, abundant seismicity, and persistent uplift-subsidence cycles. Nowhere on earth is there such compelling evidence for a large crustal magma body. Yet the inferred percentage of "mushbound" melt is still low, 5-15% according to the most recent tomographic study. Other similar studies infer up to 30% melt, still 50% less than melt fractions from lavas and tuffs in the geologic record at Yellowstone. Could there be significant undetected molten regions within a broader batholith of more crystalline residue? Or as suggested by some petrologic studies, can mush transition rapidly to eruptible magma on short timescales (years to decades) prior to eruption? Even so, pre-eruptive reservoirs should be detectable. At Yellowstone, the lower crust is yet more problematic. Mantle gas flux requires degassing of >0.1 cubic km of basalt per year, presumably from >10-km-depths, but tomography infers 2% melt fractions. How can gas transfer through such a crystal-dominated matrix? It seems likely that our ability to image magma in the upper and lower crust remains

  12. China’s ascent and Africa’s environment

    NARCIS (Netherlands)

    Mol, A.P.J.

    2011-01-01

    China’s unprecedented economic growth path over the last two decades has been paralleled by an exponential growth in the consumption of natural resources and in pollution. Initially, China mainly exploited domestic resources to fuel its rapid industrial development. But over the last decade,

  13. MAGMA: a multiagent architecture for metaheuristics.

    Science.gov (United States)

    Milano, Michela; Roli, Andrea

    2004-04-01

    In this work, we introduce a multiagent architecture called the MultiAGent Metaheuristic Architecture (MAGMA) conceived as a conceptual and practical framework for metaheuristic algorithms. Metaheuristics can be seen as the result of the interaction among different kinds of agents: The basic architecture contains three levels, each hosting one or more agents. Level-0 agents build solutions, level-1 agents improve solutions, and level-2 agents provide the high level strategy. In this framework, classical metaheuristic algorithms can be smoothly accommodated and extended. The basic three level architecture can be enhanced with the introduction of a fourth level of agents (level-3 agents) coordinating lower level agents. With this additional level, MAGMA can also describe, in a uniform way, cooperative search and, in general, any combination of metaheuristics. We describe the entire architecture, the structure of agents in each level in terms of tuples, and the structure of their coordination as a labeled transition system. We propose this perspective with the aim to achieve a better and clearer understanding of metaheuristics, obtain hybrid algorithms, suggest guidelines for a software engineering-oriented implementation and for didactic purposes. Some specializations of the general architecture will be provided in order to show that existing metaheuristics [e.g., greedy randomized adaptive procedure (GRASP), ant colony optimization (ACO), iterated local search (ILS), memetic algorithms (MAs)] can be easily described in our framework. We describe cooperative search and large neighborhood search (LNS) in the proposed framework exploiting level-3 agents. We show also that a simple hybrid algorithm, called guided restart ILS, can be easily conceived as a combination of existing components in our framework.

  14. Crystal Histories and Crustal Magmas: Insights into Magma Storage from U-Series Crystal Ages

    Science.gov (United States)

    Cooper, K. M.

    2014-12-01

    The dynamic processes operating within crustal magma reservoirs control many aspects of the chemical composition of erupted magmas, and crystals in volcanic rocks can provide a temporally-constrained archive of these changing environments. A new compilation of 238U-230Th ages of accessory phases and 238U-230Th-226Ra ages of bulk mineral separates of major phases documents that crystals in individual samples often have ages spanning most of the history of a volcanic center. Somewhat surprisingly, this observation holds for surface analyses as well as interior analyses, indicating that the latest stages of growth took place at different times for different grains. Nevertheless, average ages of surfaces are younger than interiors (as expected), and the dominant surface age population is often within error of eruption age. In contrast to accessory phase ages, less than half of the bulk separate 238U-230Th-226Ra ages for major phases are more than 10 kyr older than eruption. This suggests that major phases may in general reflect a later stage of development of an eruptible magma body than do accessory phases, or that the extent of discordance between ages of major and accessory phases reflects the extent to which a crystal mush was remobilized during processes leading to eruption. Crystal ages are most useful for illuminating magmatic processes when combined with crystal-scale trace-element or isotopic data, and I will present several case studies where such combined data sets exist. For example, at Yellowstone and at Okataina Caldera Complex, New Zealand, the combination zircon surface and interior analyses (of age, Hf isotopic, and trace-element data) with bulk dating and in-situ trace-element and isotopic compositions of feldspar allows a comparison of the early history of storage in a crystal mush with the later history of melt extraction and further crystallization prior to eruption, thus tracking development of erupted magma bodies from storage through eruption.

  15. On the longevity of silicic magma based on multi-isotope investigation of zircons and modeling their survivals destinies

    Science.gov (United States)

    Bindeman, I. N.; Wotzlaw, J. F.; Melnik, O. E.

    2015-12-01

    Large volumes of crystal poor, near-liquidus rhyolites are erupted worldwide as tuffs and lavas in rift and hot spots more common previously on early earth, creating temporally very high magma production rates. In this contribution we combine results of IDTIMS dating of zircons with numerical modeling of zircon crystallization. New investigation of zircons in major Yellowstone tuffs: Huckleberry Ridge (Members A,B,C), Mesa Falls, and Lava Creek (A,B) tuffs was done by a combination of in situ measurements of oxygen isotopes followed by ID-TIMS U-Pb dating, Hf isotopes and trace elemental investigation of single crystals. We discover that nearly all zircons are of eruption age, but display significant isotope (O,Hf) diversity and often show decoupled O and Hf isotope systematics. This record rapid (~103yrs) double or triple remelting and sequestration from diverse Archean crust and hydrothermally altered shallow-crustal rocks from previous eruptive cycles, followed by effective mixing of co-existing magma reservoirs with diverse zircons prior to eruptions. Similar results characterize other studied Snake River Plain rhyolites in pre-Yellowstone Heise complex. These results collectively suggest that zircons crystallize after reheating above saturation rejuvenation in isotopically-diverse areas of the crust in the magma plumbing system. Modeling of zircon and quartz dissolution and crystallization trajectories outline conditions of survival (inheritance) vs complete dissolution on conductive timescales, and when combined with a phase diagram, magma T-t paths can be computed. Zircon rejuvenation requires hot, >770-800°C peak temperatures lasting 10-102yrs. We speculate that near liquidus hot and dry Yellowstone rhyolites are kept alive in a multi-batch state by a series of interconnected pods and sills that can rapidly get thermomechanically assembled into large, shallow and eruptable supervolcanoic magma bodies. We suggest that overpressure and roof dynamics and

  16. Fractional crystallization and replenishment of the magma chamber at the East Pacific Rise 9°50' N

    Science.gov (United States)

    Horne, R. C.; Hebert, L. B.; Liu, L.; Lowell, R. P.

    2010-12-01

    observed changes cannot be explained by anhydrous replenishment using more evolved magmas. The conditions that best match the evolution of the 1991-1992 lavas to the 2005-2006 lavas are hydrous replenishment of a more primitive composition with oxygen fugacity at the QFM buffer. The petrological results are consistent with a mathematical model of a rapidly mixed convecting, cooling, replenished magma chamber, in which crystals are assumed to settle rapidly to the floor.

  17. The Perils of Partition: Erroneous Results from Applying D Mineral/Magma to Rocks that Equilibrated Without Magma

    Science.gov (United States)

    Treiman, A. H.

    1995-09-01

    Compositions of extraterrestrial magmas are commonly derived from mineral compositions using, using experimentally determined mineral/basalt partition coefficients, Dmineral/basalt [1]. However, Dmineral/basalts cannot be applied to minerals which have experienced post-magmatic (subsolidus or metamorphic) chemical equilibration [2]. A failure to recognize post-magmatic equilibration can lead to wildly erroneous estimates of magma compositions and unrealistic scenarios of magmatic and planetary evolution [3]. To judge the effects of subsolidus chemical equilibration, consider REE distributions in a eucrite basalt, formed from a magma with CREE = 10 x CI. Let this magma crystallize and chemically equilibrate just below its solidus to a rock consisting of 49.5% plagioclase, 49.5% pigeonite, 0.1% whitlockite (a Ca phosphate), and 0.9% minor phases no REE content (silica, Fe metal, troilite); exact proportions are not critical. The total REE content ofthe rock is unchanged at 10 x CI, and distributions of REE among its minerals can be calculated from solidus-temperature Ds, e.g., Dpigeonite/plagioclase = Dpigeonite/basalt / Dplagioclase/basalt (where Dmineral/basalts are chosen to reflect the same magma compositions and temperature). REE abundances in minerals of this equilibrated rock (Figure 1 [5]) are significantly higher than they would be in the presence of magma. For instance, if this eucrite basalt system consisted of 50% magma, 25% pigeonite, and 25% plagioclase, one calculates C(La)Pigeonite = 0 04 x CI and C(La)Plagioclase = 0.8 x CI; with no magma present (Figure 1), C(La)Pigeonite = 0.4 x CI and CLaPIagioclase = 9 x CI! In the absence of magma, the incompatible REE must go somewhere!! If a mineral grain from this rock were used with Dmineral/basalts to derive a magma composition, that "Hparent basalt" would be rich in REE (130-200 x CI), enrichmed in light REE (La/Lu = 1.6 x CI), and strongly depleted in Eu. Compare this to the original eucrite, with REE at

  18. El Hierro's floating stones as messengers of crust-magma interaction at depth

    Science.gov (United States)

    Burchardt, S.; Troll, V. R.; Schmeling, H.; Koyi, H.; Blythe, L. S.; Longpré, M. A.; Deegan, F. M.

    2012-04-01

    During the early stages of the submarine eruption that started on October 10 2011 south of El Hierro, Canary Islands, Spain, peculiar eruption products were found floating on the sea surface. These centimetre- to decimetre-sized "bombs" have been termed "restingolites" after the nearby village La Restinga and consist of a basaltic rind and a white to light grey core that resembles pumice in texture. According to Troll et al. (2011; see also Troll et al. EGU 2012 Abstracts), this material consists of a glassy matrix hosting extensive vesicle networks, which results in extremely low densities allowing these rocks to float on sea water. Mineralogical and geochemical analyses reveal that the "restingolites" originate from the sedimentary rocks (sand-, silt-, and mudstones) that form layer 1 of the oceanic crust beneath El Hierro. During the onset and early stages of the eruption, magma ponded at the base of this sedimentary sequence, breaking its way through the sedimentary rocks to the ocean floor. The textures of the "restingolites" reveal that crust-magma interaction during fragmentation and transport of the xenoliths involved rapid partial melting and volatile exsolution. Xenoliths strikingly similar to those from El Hierro are known from eruptions on other Canary Islands (e.g. La Palma, Gran Canaria, and Lanzarote). In fact, they resemble in texture xenoliths of various protoliths from volcanic areas worldwide (e.g. Krakatao, Indonesia, Cerro Quemado, Guatemala, Laacher See, Germany). This indicates that the process of partial melting and volatile exsolution, which the "restingolites" bear witness of, is probably occurring frequently during shallow crustal magma emplacement. Thermomechanical numerical models of the effect of the density decrease associated with the formation of vesicle networks in partially molten xenoliths show that xenoliths of crustal rocks initially sink in a magma chamber, but may start to float to the chamber roof once they start to heat up

  19. Crystallization of a compositionally stratified basal magma ocean

    Science.gov (United States)

    Laneuville, Matthieu; Hernlund, John; Labrosse, Stéphane; Guttenberg, Nicholas

    2018-03-01

    Earth's ∼3.45 billion year old magnetic field is regenerated by dynamo action in its convecting liquid metal outer core. However, convection induces an isentropic thermal gradient which, coupled with a high core thermal conductivity, results in rapid conducted heat loss. In the absence of implausibly high radioactivity or alternate sources of motion to drive the geodynamo, the Earth's early core had to be significantly hotter than the melting point of the lower mantle. While the existence of a dense convecting basal magma ocean (BMO) has been proposed to account for high early core temperatures, the requisite physical and chemical properties for a BMO remain controversial. Here we relax the assumption of a well-mixed convecting BMO and instead consider a BMO that is initially gravitationally stratified owing to processes such as mixing between metals and silicates at high temperatures in the core-mantle boundary region during Earth's accretion. Using coupled models of crystallization and heat transfer through a stratified BMO, we show that very high temperatures could have been trapped inside the early core, sequestering enough heat energy to run an ancient geodynamo on cooling power alone.

  20. Advancement of magma fragmentation by inhomogeneous bubble distribution.

    Science.gov (United States)

    Kameda, M; Ichihara, M; Maruyama, S; Kurokawa, N; Aoki, Y; Okumura, S; Uesugi, K

    2017-12-01

    Decompression times reported in previous studies suggest that thoroughly brittle fragmentation is unlikely in actual explosive volcanic eruptions. What occurs in practice is brittle-like fragmentation, which is defined as the solid-like fracture of a material whose bulk rheological properties are close to those of a fluid. Through laboratory experiments and numerical simulation, the link between the inhomogeneous structure of bubbles and the development of cracks that may lead to brittle-like fragmentation was clearly demonstrated here. A rapid decompression test was conducted to simulate the fragmentation of a specimen whose pore morphology was revealed by X-ray microtomography. The dynamic response during decompression was observed by high-speed photography. Large variation was observed in the responses of the specimens even among specimens with equal bulk rheological properties. The stress fields of the specimens under decompression computed by finite element analysis shows that the presence of satellite bubbles beneath a large bubble induced the stress concentration. On the basis of the obtained results, a new mechanism for brittle-like fragmentation is proposed. In the proposed scenario, the second nucleation of bubbles near the fragmentation surface is an essential process for the advancement of fragmentation in an upward magma flow in a volcanic conduit.

  1. How mantle heterogeneity can affect geochemistry of magmas and their styles of emplacement: a fascinating tale revealed by Etna alkaline lavas

    Science.gov (United States)

    Viccaro, Marco; Zuccarello, Francesco

    2016-04-01

    Geochemical investigations of Mt. Etna magmas have led to notable findings on the nature of compositional heterogeneity of the mantle source beneath the volcano. Some of the observed features explain the short-term geochemical variability of volcanic rocks erupted at Mt. Etna in recent times, which are characterized by increase of LILE, 87Sr/86Sr and decrease of 143Nd/144Nd, 206Pb/204Pb,176Hf/177Hf. This compositional behavior has not attributed exclusively to differentiation processes such as fractional crystallization, crustal assimilation and effects of volatile flushing. In this study, based on some geochemical similarities of the Etnean and Hyblean alkaline magmas, we have modeled partial melting of a composite source constituted by two rock types, inferred by various observations performed on some Hyblean xenoliths, namely: a spinel lherzolite bearing phlogopite-amphibole and a garnet pyroxenite in form of veins intruded into lherzolite that is interpreted as metasomatic high-temperature fluids (silicate melts) crystallized at mantle conditions. Partial melting modeling has been applied to each rock type and the resulting primary liquids have been then mixed in various proportions. The concentrations of major and trace elements along with the water obtained from the modeling are remarkably comparable with those of Etnean melts re-equilibrated at primary conditions. Different proportions of spinel lherzolite bearing metasomatic phases and garnet pyroxenite can account for the signature of a large spectrum of Etnean alkaline magmas and for their geochemical variability through time. Our study implies that magmas characterized by variable compositions and volatile contents directly inherited from the source can undergo distinct histories of ascent and evolution in the plumbing system at crustal levels, potentially leading to a wide range of eruptive styles. A rather shallow source inferred from the model also excludes the presence of deep mantle structures

  2. From seismic network optimization to real-time diagnosis of magma migration

    Science.gov (United States)

    Taisne, B.; Aoki, Y.

    2013-12-01

    Triggering mechanism of a seismic swarm has to be identified with great confidence in real time. Crisis response will not be the same whether magma is involved or not. The method based on the Seismic Amplitude Ratio Analysis enables a rapid and unambiguous diagnosis to detect migrating micro-seismicity. Combined with other measurements, this migrating seismicity could be linked to complex motions of magma within the volcanic edifice. The beauty of this method lies in the fact that the ratio of seismic energy recorded at different stations is independent of the seismic energy radiated at the source. Drastic changes in attenuation are unlikely to occur at the time scale of magma intrusion, therefore temporal evolutions in the measured ratio have to be explained by a change in the source location. Based on a simple assumption this technique can be used to assess the potential of existing monitoring seismic network to detect migrating events in real-time. It can also be used to design monitoring seismic network based on the available number of sensors as well as from field constraints. Network capability also depends on the noise level at each station, therefore this noise is used to define the magnitude threshold that can be detected as a function of the distance.

  3. Forecasting magma-chamber rupture at Santorini volcano, Greece.

    Science.gov (United States)

    Browning, John; Drymoni, Kyriaki; Gudmundsson, Agust

    2015-10-28

    How much magma needs to be added to a shallow magma chamber to cause rupture, dyke injection, and a potential eruption? Models that yield reliable answers to this question are needed in order to facilitate eruption forecasting. Development of a long-lived shallow magma chamber requires periodic influx of magmas from a parental body at depth. This redistribution process does not necessarily cause an eruption but produces a net volume change that can be measured geodetically by inversion techniques. Using continuum-mechanics and fracture-mechanics principles, we calculate the amount of magma contained at shallow depth beneath Santorini volcano, Greece. We demonstrate through structural analysis of dykes exposed within the Santorini caldera, previously published data on the volume of recent eruptions, and geodetic measurements of the 2011-2012 unrest period, that the measured 0.02% increase in volume of Santorini's shallow magma chamber was associated with magmatic excess pressure increase of around 1.1 MPa. This excess pressure was high enough to bring the chamber roof close to rupture and dyke injection. For volcanoes with known typical extrusion and intrusion (dyke) volumes, the new methodology presented here makes it possible to forecast the conditions for magma-chamber failure and dyke injection at any geodetically well-monitored volcano.

  4. Compositional evolution of the zoned calcalkaline magma chamber of Mount Mazama, Crater Lake, Oregon

    Science.gov (United States)

    Bacon, C.R.; Druitt, T.H.

    1988-01-01

    The climactic eruption of Mount Mazama has long been recognized as a classic example of rapid eruption of a substantial fraction of a zoned magma body. Increased knowledge of eruptive history and new chemical analyses of ???350 wholerock and glass samples of the climactic ejecta, preclimactic rhyodacite flows and their inclusions, postcaldera lavas, and lavas of nearby monogenetic vents are used here to infer processes of chemical evolution of this late Pleistocene - Holocene magmatic system. The 6845??50 BP climactic eruption vented ???50 km3 of magma to form: (1) rhyodacite fall deposit; (2) welded rhyodacite ignimbrite; and (3) lithic breccia and zoned ignimbrite, these during collapse of Crater Lake caldera. Climactic ejecta were dominantly homogeneous rhyodacite (70.4??0.3% SiO2), followed by subordinate andesite and cumulate scoriae (48-61% SiO2). The gap in wholerock composition reflects mainly a step in crystal content because glass compositions are virtually continuous. Two types of scoriae are distinguished by different LREE, Rb, Th, and Zr, but principally by a twofold contrast in Sr content: High-Sr (HSr) and low-Sr (LSr) scoriae. HSr scoriae were erupted first. Trace element abundances indicate that HSr and LSr scoriae had different calcalkaline andesite parents; basalt was parental to some mafic cumulate scoriae. Parental magma compositions reconstructed from scoria wholerock and glass data are similar to those of inclusions in preclimactic rhyodacites and of aphyric lavas of nearby monogenetic vents. Preclimactic rhyodacite flows and their magmatic inclusions give insight into evolution of the climactic chamber. Evolved rhyodacite flows containing LSr andesite inclusions were emplaced between ???30000 and ???25000 BP. At 7015??45 BP, the Llao Rock vent produced a zoned rhyodacite pumice fall, then rhyodacite lava with HSr andesite inclusions. The Cleetwood rhyodacite flow, emplaced immediately before the climactic eruption and compositionally

  5. A cascade of magmatic events during the assembly and eruption of a super-sized magma body

    Science.gov (United States)

    Allan, Aidan. S. R.; Barker, Simon J.; Millet, Marc-Alban; Morgan, Daniel J.; Rooyakkers, Shane M.; Schipper, C. Ian; Wilson, Colin J. N.

    2017-07-01

    We use comprehensive geochemical and petrological records from whole-rock samples, crystals, matrix glasses and melt inclusions to derive an integrated picture of the generation, accumulation and evacuation of 530 km3 of crystal-poor rhyolite in the 25.4 ka Oruanui supereruption (New Zealand). New data from plagioclase, orthopyroxene, amphibole, quartz, Fe-Ti oxides, matrix glasses, and plagioclase- and quartz-hosted melt inclusions, in samples spanning different phases of the eruption, are integrated with existing data to build a history of the magma system prior to and during eruption. A thermally and compositionally zoned, parental crystal-rich (mush) body was developed during two periods of intensive crystallisation, 70 and 10-15 kyr before the eruption. The mush top was quartz-bearing and as shallow as 3.5 km deep, and the roots quartz-free and extending to >10 km depth. Less than 600 year prior to the eruption, extraction of large volumes of 840 °C low-silica rhyolite melt with some crystal cargo (between 1 and 10%), began from this mush to form a melt-dominant (eruptible) body that eventually extended from 3.5 to 6 km depth. Crystals from all levels of the mush were entrained into the eruptible magma, as seen in mineral zonation and amphibole model pressures. Rapid translation of crystals from the mush to the eruptible magma is reflected in textural and compositional diversity in crystal cores and melt inclusion compositions, versus uniformity in the outermost rims. Prior to eruption the assembled eruptible magma body was not thermally or compositionally zoned and at temperatures of 790 °C, reflecting rapid cooling from the 840 °C low-silica rhyolite feedstock magma. A subordinate but significant volume (3-5 km3) of contrasting tholeiitic and calc-alkaline mafic material was co-erupted with the dominant rhyolite. These mafic clasts host crystals with compositions which demonstrate that there was some limited pre-eruptive physical interaction of mafic

  6. The Role and Behavior of Exsolved Volatiles in Magma Reservoirs

    Science.gov (United States)

    Edmonds, M.; Woods, A.

    2016-12-01

    There is an abundance of evidence for complex, vertically protracted and frequently recharged magma reservoirs in a range of tectonic settings. Geophysical evidence suggests that vertically protracted mushy zones with liquid-rich regions may extend throughout much of the crust and even beyond the Moho. Geochemical evidence suggests that magma mixing, as well as extensive fractional crystallization, dominates the differentiation of crystal-rich magmas. These magmas may reside for long timescales close to their solidus temperatures in the crust before being recharged by mafic magmas, which supply heat and volatiles. The volatile budgets and gas emissions associated with eruptions from these long-lived reservoirs typically show that there is an abundance of magmatic vapor emitted, far above that expected from syn-eruptive degassing of the erupted, crystal-rich intermediate or evolved melts. Eruptions are often associated with muted ground deformation, far less than expected to account for the volumes erupted, suggesting a compressible magma. Breccia pipes in a number of mafic layered intrusion settings, thought to be the expression of diatreme-like volcanism, testify to the importance of gas overpressure in slowly crystallizing magmas. These observations are all consistent with the existence of a substantial fraction of exsolved magmatic vapor throughout much of the upper crustal zones of the magma reservoir, which holds much of the sulfur, as well as carbon dioxide, chlorine and metal species. Reconstruction of the distribution and form of this exsolved vapor phase is a challenge, as there is little geochemical record in the erupted rocks, beyond that which may be established from melt inclusion studies. The most promising approach to understand the distribution and role of exsolved vapor in magma reservoir dynamics is through analogue experiments, which have yielded valuable insights into the role of crystals in modulating gas storage and flow in the plutonic and

  7. Magnetic resonance imaging of water ascent in embolized xylem vessels of grapevine stem segments

    Science.gov (United States)

    Mingtao Wang; Melvin T. Tyree; Roderick E. Wasylishen

    2013-01-01

    Temporal and spatial information about water refilling of embolized xylem vessels and the rate of water ascent in these vessels is critical for understanding embolism repair in intact living vascular plants. High-resolution 1H magnetic resonance imaging (MRI) experiments have been performed on embolized grapevine stem segments while they were...

  8. Efficacy of pre-ascent climbing route visual inspection in indoor sport climbing

    NARCIS (Netherlands)

    Sanchez, X.; Lambert, Ph; Jones, G.; Llewellyn, D. J.

    Pre-ascent climbing route visual inspection (route preview) has been suggested as a key climbing performance parameter although its role has never been verified experimentally. We examined the efficacy of this perceptual-cognitive skill on indoor sport climbing performance. Twenty-nine male

  9. Changes in sublingual microcirculatory flow index and vessel density on ascent to altitude

    NARCIS (Netherlands)

    Martin, Daniel S.; Goedhart, Peter; Vercueil, Andre; Ince, Can; Levett, Denny Z. H.; Grocott, Mike P. W.

    2010-01-01

    We hypothesized that ascent to altitude would result in reduced sublingual microcirculatory flow index (MFI) and increased vessel density. Twenty-four subjects were studied using sidestream dark-field imaging, as they ascended to 5300 m; one cohort remained at this altitude (n = 10), while another

  10. A simple dual ascent algorithm for the multilevel facility location problem

    NARCIS (Netherlands)

    Bumb, A.F.; Kern, Walter; Hurink, Johann L.; Pickl, Stefan; Broersma, Haitze J.; Faigle, U.

    2001-01-01

    We present a simple dual ascent method for the multilevel facility location problem which finds a solution within 6 times the optimum for the uncapacitated case and within f 2 times the optimum for the capacitated one. The algorithm is deterministic and based on the primal-dual techinique

  11. A simple dual ascent algorithm for the multilevel facility location problem

    NARCIS (Netherlands)

    Bumb, A.F.; Kern, Walter

    2001-01-01

    We present a simple dual ascent method for the multilevel facility location problem which finds a solution within $6$ times the optimum for the uncapacitated case and within $12$ times the optimum for the capacitated one. The algorithm is deterministic and based on the primal-dual technique.

  12. Reference mission 3B ascent trajectory. Mission planning, mission analysis and software formulation

    Science.gov (United States)

    Kuhn, A. E.

    1975-01-01

    Mission 3B is designed as a payload retrieval mission with both shuttle launch and orbiter landing to take place at the western test range. The mission is designed for direct rendezvous with a passive satellite in a 100 NMI circular orbit with an inclination of 104 degrees. The ascent portion of mission 3B is described as well as the trajectory simulation.

  13. Bitz, Ginoux, Jacobson, Nizkorodov, and Yang Receive 2013 Atmospheric Sciences Ascent Awards: Citation for Sergey Nizkorodov

    Science.gov (United States)

    Webster, Peter J.

    2014-07-01

    The Atmospheric Sciences section of AGU awards one of the five Ascent Awards to Professor Sergey Nizkorodov of the Department of Chemistry at the University of California, Irvine (UCI) for elucidating at the molecular level the formation, growth, and reactions of organic molecules in the atmosphere.

  14. Enabling Parametric Optimal Ascent Trajectory Modeling During Early Phases of Design

    Science.gov (United States)

    Holt, James B.; Dees, Patrick D.; Diaz, Manuel J.

    2015-01-01

    During the early phases of engineering design, the costs committed are high, costs incurred are low, and the design freedom is high. It is well documented that decisions made in these early design phases drive the entire design's life cycle. In a traditional paradigm, key design decisions are made when little is known about the design. As the design matures, design changes become more difficult -- in both cost and schedule -- to enact. Indeed, the current capability-based paradigm that has emerged because of the constrained economic environment calls for the infusion of knowledge acquired during later design phases into earlier design phases, i.e. bring knowledge acquired during preliminary and detailed design into pre-conceptual and conceptual design. An area of critical importance to launch vehicle design is the optimization of its ascent trajectory, as the optimal trajectory will be able to take full advantage of the launch vehicle's capability to deliver a maximum amount of payload into orbit. Hence, the optimal ascent trajectory plays an important role in the vehicle's affordability posture as the need for more economically viable access to space solutions are needed in today's constrained economic environment. The problem of ascent trajectory optimization is not a new one. There are several programs that are widely used in industry that allows trajectory analysts to, based on detailed vehicle and insertion orbit parameters, determine the optimal ascent trajectory. Yet, little information is known about the launch vehicle early in the design phase - information that is required of many different disciplines in order to successfully optimize the ascent trajectory. Thus, the current paradigm of optimizing ascent trajectories involves generating point solutions for every change in a vehicle's design parameters. This is often a very tedious, manual, and time-consuming task for the analysts. Moreover, the trajectory design space is highly non-linear and multi

  15. Evolution of Space Shuttle Range Safety (RS) Ascent Flight Envelope Design

    Science.gov (United States)

    Brewer, Joan D.

    2011-01-01

    Ascent flight envelopes are trajectories that define the normal operating region of a space vehicle s position from liftoff until the end of powered flight. They fulfill part of the RS data requirements imposed by the Air Force s 45th Space Wing (45SW) on space vehicles launching from the Eastern Range (ER) in Florida. The 45SW is chartered to protect the public by minimizing risks associated with the inherent hazards of launching a vehicle into space. NASA s Space Shuttle program has launched 130+ manned missions over a 30 year period from the ER. Ascent envelopes were delivered for each of those missions. The 45SW envelope requirements have remained largely unchanged during this time. However, the methodology and design processes used to generate the envelopes have evolved over the years to support mission changes, maintain high data quality, and reduce costs. The evolution of the Shuttle envelope design has yielded lessons learned that can be applied to future endevours. There have been numerous Shuttle ascent design enhancements over the years that have caused the envelope methodology to evolve. One of these Shuttle improvements was the introduction of onboard flight software changes implemented to improve launch probability. This change impacted the preflight nominal ascent trajectory, which is a key element in the RS envelope design. While the early Shuttle nominal trajectories were designed preflight using a representative monthly mean wind, the new software changes involved designing a nominal ascent trajectory on launch day using real-time winds. Because the actual nominal trajectory position was not known until launch day, the envelope analysis had to be customized to account for this nominal trajectory variation in addition to the other envelope components.

  16. Frontal joint dynamics when initiating stair ascent from a walk versus a stand.

    Science.gov (United States)

    Vallabhajosula, Srikant; Yentes, Jennifer M; Stergiou, Nicholas

    2012-02-02

    Ascending stairs is a challenging activity of daily living for many populations. Frontal plane joint dynamics are critical to understand the mechanisms involved in stair ascension as they contribute to both propulsion and medio-lateral stability. However, previous research is limited to understanding these dynamics while initiating stair ascent from a stand. We investigated if initiating stair ascent from a walk with a comfortable self-selected speed could affect the frontal plane lower-extremity joint moments and powers as compared to initiating stair ascent from a stand and if this difference would exist at consecutive ipsilateral steps on the stairs. Kinematics data using a 3-D motion capture system and kinetics data using two force platforms on the first and third stair treads were recorded simultaneously as ten healthy young adults ascended a custom-built staircase. Data were collected from two starting conditions of stair ascent, from a walk (speed: 1.42 ± 0.21 m/s) and from a stand. Results showed that subjects generated greater peak knee abductor moment and greater peak hip abductor moment when initiating stair ascent from a walk. Greater peak joint moments and powers at all joints were also seen while ascending the second ipsilateral step. Particularly, greater peak hip abductor moment was needed to avoid contact of the contralateral limb with the intermediate step by counteracting the pelvic drop on the contralateral side. This could be important for therapists using stair climbing as a testing/training tool to evaluate hip strength in individuals with documented frontal plane abnormalities (i.e. knee and hip osteoarthritis, ACL injury). Copyright © 2011 Elsevier Ltd. All rights reserved.

  17. Closed-loop nominal and abort atmospheric ascent guidance for rocket-powered launch vehicles

    Science.gov (United States)

    Dukeman, Greg A.

    2005-07-01

    An advanced ascent guidance algorithm for rocket-powered launch vehicles is developed. The ascent guidance function is responsible for commanding attitude, throttle and setting during the powered ascent phase of flight so that the vehicle attains target cutoff conditions in a near optimal manner while satisfying path constraints such as maximum allowed bending moment and maximum allowed axial acceleration. This algorithm cyclically solves the calculus-of-variations two-point boundary-value problem starting at vertical rise completion through orbit insertion. This is different from traditional ascent guidance algorithms which operate in an open-loop mode until the high dynamic pressure portion of the trajectory is over, at which time there is a switch to a closed loop guidance mode that operates under the assumption of negligible aerodynamic forces. The main contribution of this research is an algorithm of the predictor-corrector type wherein the state/costate system is propagated with known (navigated) initial state and guessed initial costate to predict the state/costate at engine cutoff. The initial costate guess is corrected, using a multi-dimensional Newton's method, based on errors in the terminal state constraints and the transversality conditions. Path constraints are enforced within the propagation process. A modified multiple shooting method is shown to be a very effective numerical technique for this application. Results for a single stage to orbit launch vehicle are given. In addition, the formulation for the free final time multi-arc trajectory optimization problem is given. Results for a two-stage launch vehicle burn-coast-burn ascent to orbit in a closed-loop guidance mode are shown. An abort to landing site formulation of the algorithm and numerical results are presented. A technique for numerically treating the transversality conditions is discussed that eliminates part of the analytical and coding burden associated with optimal control theory.

  18. The Ascent Study - Understanding the Market Environment for the Follow-on to the Space Shuttle

    Science.gov (United States)

    Webber, Derek

    2002-01-01

    The ASCENT Study - Understanding the Market Environment for the Follow-on to NASA's Marshall Space Flight Center in Huntsville, Alabama, awarded a contract (base plus option amounting to twenty months of analysis) to Futron Corporation in June 2001 to investigate the market environment, and explore the price elasticity attributes, relevant for the introduction of the Second Generation Reusable Launch Vehicle (the follow-on to the Space Shuttle) in the second decade of this century. This work is known as the ASCENT Study (Analysis of Space Concepts Enabled by New Transportation) and data collection covering a total of 42 different sectors took place during 2001. Modeling and forecasting activities for 26 of these markets (all of them international in nature) have been taking place throughout 2002, and the final results of the ASCENT Study, which include 20 year forecasts, are due by the end of January, 2003. This paper describes the markets being analyzed for the ASCENT Study, and includes some preliminary findings in terms of launch vehicle demand during the next 20 years, broken down by mass class and mission type. Amongst these markets are the potential public space travel opportunities. When completed, the final report of the ASCENT Study is expected to represent a significant reference document for all business development, financing and planning activities in the space industry for some time to come. One immediate use will be as a key factor in determining the cargo capability and launch rates to be used for designing the follow-on to the Space Shuttle. The Study will also provide NASA with a quantified indication of the extent to which the lower cost to orbit, made possible by a new class of launch vehicle, will bring into being new markets.

  19. Primary magmas and mantle temperatures through time

    Science.gov (United States)

    Ganne, Jérôme; Feng, Xiaojun

    2017-03-01

    Chemical composition of mafic magmas is a critical indicator of physicochemical conditions, such as pressure, temperature, and fluid availability, accompanying melt production in the mantle and its evolution in the continental or oceanic lithosphere. Recovering this information has fundamental implications in constraining the thermal state of the mantle and the physics of mantle convection throughout the Earth's history. Here a statistical approach is applied to a geochemical database of about 22,000 samples from the mafic magma record. Potential temperatures (Tps) of the mantle derived from this database, assuming melting by adiabatic decompression and a Ti-dependent (Fe2O3/TiO2 = 0.5) or constant redox condition (Fe2+/∑Fe = 0.9 or 0.8) in the magmatic source, are thought to be representative of different thermal "horizons" (or thermal heterogeneities) in the ambient mantle, ranging in depth from a shallow sublithospheric mantle (Tp minima) to a lower thermal boundary layer (Tp maxima). The difference of temperature (ΔTp) observed between Tp maxima and minima did not change significantly with time (˜170°C). Conversely, a progressive but limited cooling of ˜150°C is proposed since ˜2.5 Gyr for the Earth's ambient mantle, which falls in the lower limit proposed by Herzberg et al. [2010] (˜150-250°C hotter than today). Cooling of the ambient mantle after 2.5 Ga is preceded by a high-temperature plateau evolution and a transition from dominant plumes to a plate tectonics geodynamic regime, suggesting that subductions stabilized temperatures in the Archaean mantle that was in warming mode at that time.Plain Language SummaryThe Earth's upper mantle constitutes a major interface between inner and outer envelops of the planet. We explore at high resolution its thermal state evolution (potential temperature of the ambient mantle, Tp) in depth and time using a multi-dimensional database of mafic lavas chemistry (>22,000 samples formed in the last 4 billion years

  20. Mixing - Mingling and Modification of Magmas in a Giant Deep Crustal Magmatic Reservoir: The Seiland Igneous Province, Northern Norway

    Science.gov (United States)

    Larsen, R. B.; Grant, T.; Sorensen, B. E.; McEnroe, S. A.

    2016-12-01

    The Seiland Igneous Province (SIP) comprises a giant magmatic reservoir with > 50 .000 km3 of mafic, ultramafic and alkaline rocks emplaced at 25-35 km depth in Igneous Province (LIP), making the region a key location in which to study the ascent, emplacement and modification of dense mantle melts before progressing upwards. 1/5 of SIP comprises ultramafic complexes interpreted to be the de facto conduits along which picritic-komatiitic magmas migrated through the continental lithosphere. As an example, the Reinfjord complex in SIP features a major conduit accommodating picritic-komatiitic melts that were emplaced into gabbros in three major pulses, punctuated by several smaller replenishment events and forming three distinct layered ultramafic series. The final series, the central series (CS), comprises dunitic cumulates in the centre of the intrusion. The CS intruded into a wehrlitic crystal-melt mush where cpx was assimilated under the formation of discordant replacive dunites. Super-imposed upon these major events, cryptical zonation of ol and cpx reveal 15 recharge events over only 700 metres of cumulates. Field observations document smaller replenishment events of pyroxenitic melts. They occur as irregular dykes that intersect semisolid cumulates before dissipating in mushy melts higher up in the stratigraphy. We also observe that the melt-mushes of CS were intruded by several episodes of alkaline CO2-H2O rich melts forming patches and veinlets of feldspars, amphibole, carbonates, opx and cpx. Trace-element modelling on cpx-compositions imply that picritic-komatiitic parental melts formed by 11 - 20 % partial melting of a carbonate metasomatised peridotitic mantle. Together, this rich diversity of igneous rocks documents the complexity of melts that are produced during plume assisted emplacements of very large volumes of mafic-ultramafic melts and also demonstrates the importance of intermittent reservoirs where melts are mixed and modified before further

  1. Magma chamber processes in central volcanic systems of Iceland

    DEFF Research Database (Denmark)

    Þórarinsson, Sigurjón Böðvar; Tegner, Christian

    2009-01-01

    New field work and petrological investigations of the largest gabbro outcrop in Iceland, the Hvalnesfjall gabbro of the 6-7 Ma Austurhorn intrusive complex, have established a stratigraphic sequence exceeding 800 m composed of at least 8 macrorhythmic units. The bases of the macrorhythmic units...... olivine basalts from Iceland that had undergone about 20% crystallisation of olivine, plagioclase and clinopyroxene and that the macrorhythmic units formed from thin magma layers not exceeding 200-300 m. Such a "mushy" magma chamber is akin to volcanic plumbing systems in settings of high magma supply...... rate including the mid-ocean ridges and present-day magma chambers over the Iceland mantle plume. The Austurhorn central volcano likely formed in an off-rift flank zone proximal to the Iceland mantle plume during a major rift relocation....

  2. The Role of Magma Mixing in Creating Magmatic Diversity

    Science.gov (United States)

    Davidson, J. P.; Collins, S.; Morgan, D. J.

    2012-12-01

    Most magmas derived from the mantle are fundamentally basaltic. An assessment of actual magmatic rock compositions erupted at the earth's surface, however, shows greater diversity. While still strongly dominated by basalts, magmatic rock compositions extend to far more differentiated (higher SiO2, LREE enriched) compositions. Magmatic diversity is generated by differentiation processes, including crystal fractionation/ accumulation, crustal contamination and magma mixing. Among these, magma mixing is arguably inevitable in magma systems that deliver magmas from source-to-surface, since magmas will tend to multiply re-occupy plumbing systems. A given mantle-derived magma type will mix with any residual magmas (and crystals) in the system, and with any partial melts of the wallrock which are generated as it is repeatedly flushed through the system. Evidence for magma mixing can be read from the petrography (identification of crystals derived from different magmas), a technique which is now well-developed and supplemented by isotopic fingerprinting (1,2) As a means of creating diversity, mixing is inevitably not efficient as its tendency is to blend towards a common composition (i.e. converging on homogeneity rather than diversity). It may be surprising then that many systems do not tend to homogenise with time, meaning that the timescales of mixing episodes and eruption must be similar to external magma contributions of distinct composition (recharge?). Indeed recharge and mixing/ contamination may well be related. As a result, the consequences of magma mixing may well bear on eruption triggering. When two magmas mix, volatile exsolution may be triggered by retrograde boiling, with crystallisation of anhydrous phase(s) in either of the magmas (3) or volatiles may be generated by thermal breakdown of a hydrous phase in one of the magmas (4). The generation of gas pressures in this way probably leads to geophysical signals too (small earthquakes). Recent work pulling

  3. Magma Dynamics at Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    D. Krier

    2005-08-29

    Small-volume basaltic volcanic activity at Yucca Mountain has been identified as one of the potential events that could lead to release of radioactive material from the U.S. Department of Energy (DOE) designated nuclear waste repository at Yucca Mountain. Release of material could occur indirectly as a result of magmatic dike intrusion into the repository (with no associated surface eruption) by changing groundwater flow paths, or as a result of an eruption (dike intrusion of the repository drifts, followed by surface eruption of contaminated ash) or volcanic ejection of material onto the Earth's surface and the redistribution of contaminated volcanic tephra. Either release method includes interaction between emplacement drifts and a magmatic dike or conduit, and natural (geologic) processes that might interrupt or halt igneous activity. This analysis provides summary information on two approaches to evaluate effects of disruption at the repository by basaltic igneous activity: (1) descriptions of the physical geometry of ascending basaltic dikes and their interaction with silicic host rocks similar in composition to the repository host rocks; and (2) a summary of calculations developed to quantify the response of emplacement drifts that have been flooded with magma and repressurized following blockage of an eruptive conduit. The purpose of these analyses is to explore the potential consequences that could occur during the full duration of an igneous event.

  4. Pre-eruptive conditions of the Hideaway Park topaz rhyolite: Insights into metal source and evolution of magma parental to the Henderson porphyry molybdenum deposit, Colorado

    Science.gov (United States)

    Mercer, Celestine N.; Hofstra, Albert H.; Todorov, Todor I.; Roberge, Julie; Burgisser, Alain; Adams, David T.; Cosca, Michael A.

    2015-01-01

    The Hideaway Park tuff is the only preserved extrusive volcanic unit related to the Red Mountain intrusive complex, which produced the world-class Henderson porphyry Mo deposit. Located within the Colorado Mineral Belt, USA, Henderson is the second largest Climax-type Mo deposit in the world, and is therefore an excellent location to investigate magmatic processes leading to Climax-type Mo mineralization. We combine an extensive dataset of major element, volatile, and trace element abundances in quartz-hosted melt inclusions and pumice matrix glass with major element geochemistry from phenocrysts to reconstruct the pre-eruptive conditions and the source and evolution of metals within the magma. Melt inclusions are slightly peraluminous topaz rhyolitic in composition and are volatile-charged (≤6 wt % H2O, ≤600 ppm CO2, ∼0·3–1·0 wt % F, ∼2300–3500 ppm Cl) and metal-rich (∼7–24 ppm Mo, ∼4–14 ppm W, ∼21–52 ppm Pb, ∼28–2700 ppm Zn, pressures of ≤300 MPa (≤8 km depth), with little to no crystallization upon shallow ascent and eruption. Filter pressing, crystal settling, magma recharge and mixing of less evolved rhyolite melt, and volatile exsolution were important processes during magma evolution; the low estimated viscosities (∼105–1010 Pa s) of these H2O- and F-rich melts probably enhanced these processes. A noteworthy discrepancy between the metal contents in the pumice matrix glass and in the melt inclusions suggests that after quartz crystallization ceased upon shallow magma ascent and eruption, the Hideaway Park magma exsolved an aqueous fluid into which Mo, Bi, Ag, Zn, Mn, Cs, and Y strongly partitioned. Given that the Henderson deposit contains anomalous abundances of not only Mo, but also W, Pb, Zn, Cu, Bi, Ag, and Mn, we suggest that these metals were sourced from similar fluids exsolved from unerupted portions of the same magmatic system. Trace element ratios imply that Mo was sourced deep, from

  5. Diatexite Deformation and Magma Extraction on Kangaroo Island, South Australia

    Science.gov (United States)

    Hasalova, Pavlina; Weinberg, Roberto; Ward, Lindsay; Fanning, Mark

    2013-04-01

    Migmatite terranes are structurally complex because of strong rheological contrast between layers with different melt contents and because of magma migration leading to volume changes. Migmatite deformation is intimately linked with magma extraction and the origin of granitoids. We investigate here the relationships between an evolving deformation and magma extraction in migmatites formed during the ca. 500Ma Delamerian orogeny, exposed on Kangaroo Island, South Australia. Here, several phases of deformation occurred in the presence of melt. During an early upright, non-cylindrical folding event, magma was channeled towards the hinge zones of antiforms. Funnel-shaped networks of leucosomes form a root zone that link up towards a central axial planar channel, forming the main magma extraction paths during folding. Extraction was associated with fold limb collapse, and antiformal hinge disruption by magma accumulation and transfer. During a later deformation phase, melt-rich diatexites were deformed, and schollen were disaggregated into smaller blocks and schlieren, and deformed into asymmetric, sigmoidal shapes indicative of dextral shearing flow. During flow, magma accumulated preferentially along shear planes, indicating a dilatational component during shearing (transtension) and in strain shadows of schollen. As deformation waned, magma extraction from these diatexites gave rise to N-trending, steeply dipping, funnel-shaped channels not associated to any deformational feature. The funnel-shape of these structures indicates the direction of magma flow. Structures developed during this phase are comparable with those formed during dewatering of soft sediments. Despite a high degree of complexity, magma migration and extraction features record distinct responses to the evolving deformation which can be used to understand deformation, and nature and direction of melt extraction. The oldest and youngest magmatic rocks from migmatites were dated (U-Pb monazite, SHRIMP

  6. The role of turbulence in explosive magma-water mixing

    Science.gov (United States)

    Mastin, L. G.; Walder, J. S.; Stern, L. A.

    2003-12-01

    Juvenile tephra from explosive hydromagmatic eruptions differs from that of dry magmatic eruptions by its fine average grain size and highly variable vesicularity. These characteristics are generally interpreted to indicate that fragmentation, which occurs in dry magmas by bubble growth, is supplemented in hydromagmatic eruptions by quench-fracturing. Quench fragmentation is thought to accelerate heat transfer to water, driving violent steam expansion and increasing eruptive violence. Although some observed hydromagmatic events (e.g. at Surtsey) are indeed violent, others (e.g. quiescent entry of lava into the ocean at Kilauea) are not. We suggest that the violence of magma-water mixing and the grain size and dispersal of hydromagmatic tephras are controlled largely by the turbulence of magma-water mixing. At Surtsey, fine-grained, widely dispersed hydromagmatic tephras were produced primarily during continuous uprush events in which turbulent jets of magma and gas passed through shallow water (Thorarinsson, 1967). During Kilauea's current eruption, videos show generation of fine-grained tephras when turbulent jets of magma, steam, and seawater exited through skylights at the coastline. Turbulence intensity, or the fraction of total jet kinetic energy contained in fine-scale turbulent velocity oscillations, has long been known to control the scale of atomization in spray nozzles and the rate of heat transfer and chemical reaction in fuel injectors. We hypothesize that turbulence intensity also influences grain size and heat transfer rate in magma-water mixing, though such processes are complicated by boiling (in water) and quench fracturing (in magma). We are testing this hypothesis in experiments involving turbulent injection of water (a magma analog) into liquid nitrogen (a water analog). We also suggest that turbulent mixing influences relative proportions of magma and water in hydromagmatic eruptions. Empirical studies indicate that pressure-neutral turbulent

  7. A cellular automaton model for the rise of magma

    Science.gov (United States)

    Piegari, Ester; di Maio, Rosa; Milano, Leopoldo; Scandone, Roberto

    2010-05-01

    Eruptions of volcanoes are complex natural events highly variable in size and time. Over the last couple of decades, statistical analyses of erupted volume and repose time catalogues have been performed for a large number of volcanoes. The aim of such analyses is either to predict future eruptive events or to define physical models for improving our understanding of the volcanic processes that cause eruptions. In particular, for this latter purpose we study a statistical model of eruption triggering caused by the fracturing of the crust above a magma reservoir residing in the crust. When the fracturing reaches the reservoir, magma is allowed to ascend because of its buoyancy. It will be found in batches along the transport region and it will ascend as long as fractures are developed to its tip; when a path is opened to the surface, an eruption occurs involving all batches connected to the opening. We model the vertical section of a volcanic edifice by means of a two-dimensional grid and characterize the state of each cell of the grid by assigning the values of two dynamical variables: a time dependent variable e describing the status of the local stress and a time-dependent variable n describing the presence of magma. At first step of approximation, we treat the magma presence field n as a diffusing lattice gas, and, therefore, we assume its value to be either zero or one if the corresponding cell is empty or filled by magma, respectively. We study the probability distribution, P(V), of eruptions of volume V and the probability distribution, P(t), of inter-event time t and find that the model is able to reproduce, at least in a descriptive way, the essential statistical features of the activity of volcanoes. A key component of magma is the quantity of dissolved gas as it gives magma its explosive character, because the volume of gas expands as the pressure decreases on raising towards the surface. Then, to more accurately describe the rise of magma in a volcanic

  8. Experimental Fractional Crystallization of the Lunar Magma Ocean

    Science.gov (United States)

    Rapp, J. F.; Draper, D. S.

    2012-01-01

    The current paradigm for lunar evolution is of crystallization of a global scale magma ocean, giving rise to the anorthositic crust and mafic cumulate interior. It is thought that all other lunar rocks have arisen from this differentiated interior. However, until recently this paradigm has remained untested experimentally. Presented here are the first experimental results of fractional crystallization of a Lunar Magma Ocean (LMO) using the Taylor Whole Moon (TWM) bulk lunar composition [1].

  9. Low- 18O silicic magmas: why are they so rare?

    Science.gov (United States)

    Balsley, Steven D.; Gregory, Robert T.

    1998-10-01

    Low- 18O silicic magmas are reported from only a small number of localities (e.g., Yellowstone and Iceland), yet petrologic evidence points to upper crustal assimilation coupled with fractional crystallization (AFC) during magma genesis for nearly all silicic magmas. The rarity of low- 18O magmas in intracontinental caldera settings is remarkable given the evidence of intense low- 18O meteoric hydrothermal alteration in the subvolcanic remnants of larger caldera systems. In the Platoro caldera complex, regional ignimbrites (150-1000 km 3) have plagioclase δ 18O values of 6.8±0.1‰, whereas the Middle Tuff, a small-volume (est. 50-100 km 3) post-caldera collapse pyroclastic sequence, has plagioclase δ 18O values between 5.5 and 6.8‰. On average, the plagioclase phenocrysts from the Middle Tuff are depleted by only 0.3‰ relative to those in the regional tuffs. At Yellowstone, small-volume post-caldera collapse intracaldera rhyolites are up to 5.5‰ depleted relative to the regional ignimbrites. Two important differences between the Middle Tuff and the Yellowstone low- 18O rhyolites elucidate the problem. Middle Tuff magmas reached water saturation and erupted explosively, whereas most of the low- 18O Yellowstone rhyolites erupted effusively as domes or flows, and are nearly devoid of hydrous phenocrysts. Comparing the two eruptive types indicates that assimilation of low- 18O material, combined with fractional crystallization, drives silicic melts to water oversaturation. Water saturated magmas either erupt explosively or quench as subsurface porphyries before the magmatic 18O can be dramatically lowered. Partial melting of low- 18O subvolcanic rocks by near-anhydrous magmas at Yellowstone produced small-volume, low- 18O magmas directly, thereby circumventing the water saturation barrier encountered through normal AFC processes.

  10. Low-(18)O Silicic Magmas: Why Are They So Rare?

    Energy Technology Data Exchange (ETDEWEB)

    Balsley, S.D.; Gregory, R.T.

    1998-10-15

    LOW-180 silicic magmas are reported from only a small number of localities (e.g., Yellowstone and Iceland), yet petrologic evidence points to upper crustal assimilation coupled with fractional crystallization (AFC) during magma genesis for nearly all silicic magmas. The rarity of 10W-l `O magmas in intracontinental caldera settings is remarkable given the evidence of intense 10W-l*O meteoric hydrothermal alteration in the subvolcanic remnants of larger caldera systems. In the Platoro caldera complex, regional ignimbrites (150-1000 km3) have plagioclase 6180 values of 6.8 + 0.1%., whereas the Middle Tuff, a small-volume (est. 50-100 km3) post-caldera collapse pyroclastic sequence, has plagioclase 8]80 values between 5.5 and 6.8%o. On average, the plagioclase phenocrysts from the Middle Tuff are depleted by only 0.3%0 relative to those in the regional tuffs. At Yellowstone, small-volume post-caldera collapse intracaldera rhyolites are up to 5.5%o depleted relative to the regional ignimbrites. Two important differences between the Middle Tuff and the Yellowstone 10W-180 rhyolites elucidate the problem. Middle Tuff magmas reached water saturation and erupted explosively, whereas most of the 10W-l 80 Yellowstone rhyolites erupted effusively as domes or flows, and are nearly devoid of hydrous phenocrysts. Comparing the two eruptive types indicates that assimilation of 10W-180 material, combined with fractional crystallization, drives silicic melts to water oversaturation. Water saturated magmas either erupt explosively or quench as subsurface porphyrins bejiire the magmatic 180 can be dramatically lowered. Partial melting of low- 180 subvolcanic rocks by near-anhydrous magmas at Yellowstone produced small- volume, 10W-180 magmas directly, thereby circumventing the water saturation barrier encountered through normal AFC processes.

  11. Recent developments and applications of a real-time tool to detect magma migration in different volcanic settings

    Science.gov (United States)

    Taisne, Benoit; Caudron, Corentin; Aoki, Yosuke

    2014-05-01

    Triggering mechanism of a seismic swarm has to be identified with great confidence in real time. Crisis response will not be the same whether magma is involved or not. The recent developments of the method based on the Seismic Amplitude Ratio Analysis enable a rapid and unambiguous diagnosis to detect migrating micro-seismicity. Combined with other measurements, this migrating seismicity could be linked to complex motions of magma within the volcanic edifice. The beauty of this method lies in the fact that the ratio of seismic energy, recorded at different stations, is independent of the seismic energy radiated at the source and depends only on the location of the source and attenuation of the medium. Since drastic changes in attenuation are unlikely to occur at the time scale of magma intrusion, temporal evolutions in the measured ratio have to be explained by a change in the source location. Based on simple assumptions this technique can be used to assess the potential of existing monitoring seismic network to detect migrating events in real-time. It can also be used to design monitoring seismic network based on the available number of sensors as well as from field constraints. Network capability will depend on the noise level at each station, therefore this noise is used to define the magnitude threshold that can be detected as a function of the distance. A basic set of parameters will be implemented in this tool to tackle magma migration in basaltic systems, as well as acidic ones.

  12. Primary and secondary fragmentation of crystal-bearing intermediate magma

    Science.gov (United States)

    Jones, Thomas J.; McNamara, Keri; Eychenne, Julia; Rust, Alison C.; Cashman, Katharine V.; Scheu, Bettina; Edwards, Robyn

    2016-11-01

    Crystal-rich intermediate magmas are subjected to both primary and secondary fragmentation processes, each of which may produce texturally distinct tephra. Of particular interest for volcanic hazards is the extent to which each process contributes ash to volcanic plumes. One way to address this question is by fragmenting pyroclasts under controlled conditions. We fragmented pumice samples from Soufriere Hills Volcano (SHV), Montserrat, by three methods: rapid decompression in a shock tube-like apparatus, impact by a falling piston, and milling in a ball mill. Grain size distributions of the products reveal that all three mechanisms produce fractal breakage patterns, and that the fractal dimension increases from a minimum of 2.1 for decompression fragmentation (primary fragmentation) to a maximum of 2.7 by repeated impact (secondary fragmentation). To assess the details of the fragmentation process, we quantified the shape, texture and components of constituent ash particles. Ash shape analysis shows that the axial ratio increases during milling and that particle convexity increases with repeated impacts. We also quantify the extent to which the matrix is separated from the crystals, which shows that secondary processes efficiently remove adhering matrix from crystals, particularly during milling (abrasion). Furthermore, measurements of crystal size distributions before (using x-ray computed tomography) and after (by componentry of individual grain size classes) decompression-driven fragmentation show not only that crystals influence particular size fractions across the total grain size distribution, but also that free crystals are smaller in the fragmented material than in the original pumice clast. Taken together, our results confirm previous work showing both the control of initial texture on the primary fragmentation process and the contributions of secondary processes to ash formation. Critically, however, our extension of previous analyses to characterisation

  13. The Magma Chamber Simulator: Modeling the Impact of Wall Rock Composition on Mafic Magmas during Assimilation-Fractional Crystallization

    Science.gov (United States)

    Creamer, J. B.; Spera, F. J.; Bohrson, W. A.; Ghiorso, M. S.

    2012-12-01

    Although stoichiometric titration is often used to model the process of concurrent Assimilation and Fractional Crystallization (AFC) within a compositionally evolving magma body, a more complete treatment of the problem involves simultaneous and self-consistent determination of stable phase relationships and separately evolving temperatures of both Magma (M) and Wall Rock (WR) that interact as a composite M-WR system. Here we present results of M-WR systems undergoing AFC forward modeled with the Magma Chamber Simulator (MCS), which uses the phase modeling capabilities of MELTS (Ghiorso & Sack 1995) as the thermodynamic basis. Simulations begin with one of a variety of mafic magmas (e.g. HAB, MORB, AOB) intruding a set mass of Wall Rock (e.g. lherzolite, gabbro, diorite, granite, metapelite), and heat is exchanged as the M-WR system proceeds towards thermal equilibrium. Depending on initial conditions, the early part of the evolution can involve closed system FC while the WR heats up. The WR behaves as a closed system until it is heated beyond the solidus to critical limit for melt fraction extraction (fc), ranging between 0.08 and 0.12 depending on WR characteristics including composition and, rheology and stress field. Once fc is exceeded, a portion of the anatectic liquid is assimilated into the Magma. The MCS simultaneously calculates mass and composition of the mineral assemblage (Magma cumulates and WR residue) and melt (anatectic and Magma) at each T along the equilibration trajectory. Sensible and latent heat lost or gained plus mass gained by the Magma are accounted for by the MCS via governing Energy Constrained- Recharge Assimilation Fractional Crystallization (EC-RAFC) equations. In a comparison of two representative MCS results, consider a granitic WR intruded by HAB melt (51 wt. % SiO2) at liquidus T in shallow crust (0.1 GPa) with a WR/M ratio of 1.25, fc of 0.1 and a QFM oxygen buffer. In the first example, the WR begins at a temperature of 100o

  14. Ascent velocity and dynamics of the Fiumicino mud eruption, Rome, Italy

    Science.gov (United States)

    Vona, A.; Giordano, G.; De Benedetti, A. A.; D'Ambrosio, R.; Romano, C.; Manga, M.

    2015-08-01

    In August 2013 drilling triggered the eruption of mud near the international airport of Fiumicino (Rome, Italy). We monitored the evolution of the eruption and collected samples for laboratory characterization of physicochemical and rheological properties. Over time, muds show a progressive dilution with water; the rheology is typical of pseudoplastic fluids, with a small yield stress that decreases as mud density decreases. The eruption, while not naturally triggered, shares several similarities with natural mud volcanoes, including mud componentry, grain-size distribution, gas discharge, and mud rheology. We use the size of large ballistic fragments ejected from the vent along with mud rheology to compute a minimum ascent velocity of the mud. Computed values are consistent with in situ measurements of gas phase velocities, confirming that the stratigraphic record of mud eruptions can be quantitatively used to infer eruption history and ascent rates and hence to assess (or reassess) mud eruption hazards.

  15. Optic Nerve Sheath Diameter Increase on Ascent to High Altitude: Correlation With Acute Mountain Sickness.

    Science.gov (United States)

    Kanaan, Nicholas C; Lipman, Grant S; Constance, Benjamin B; Holck, Peter S; Preuss, James F; Williams, Sarah R

    2015-09-01

    Elevated optic nerve sheath diameter on sonography is known to correlate with increased intracranial pressure and is observed in acute mountain sickness. This study aimed to determine whether optic nerve sheath diameter changes on ascent to high altitude are associated with acute mountain sickness incidence. Eighty-six healthy adults enrolled at 1240 m (4100 ft), drove to 3545 m (11,700 ft) and then hiked to and slept at 3810 m (12,500 ft). Lake Louise Questionnaire scores and optic nerve sheath diameter measurements were taken before, the evening of, and the morning after ascent. The incidence of acute mountain sickness was 55.8%, with a mean Lake Louise Questionnaire score ± SD of 3.81 ± 2.5. The mean maximum optic nerve sheath diameter increased on ascent from 5.58 ± 0.79 to 6.13 ± 0.73 mm, a difference of 0.91 ± 0.55 mm (P = .09). Optic nerve sheath diameter increased at high altitude regardless of acute mountain sickness diagnosis; however, compared to baseline values, we observed a significant increase in diameter only in those with a diagnosis of acute mountain sickness (0.57 ± 0.77 versus 0.21 ± 0.76 mm; P = .04). This change from baseline, or Δ optic nerve sheath diameter, was associated with twice the odds of developing acute mountain sickness (95% confidence interval, 1.08-3.93). The mean optic nerve sheath diameter increased on ascent to high altitude compared to baseline values, but not to a statistically significant degree. The magnitude of the observed Δ optic nerve sheath diameter was positively associated with acute mountain sickness diagnosis. No such significant association was found between acute mountain sickness and diameter elevation above standard cutoff values, limiting the utility of sonography as a diagnostic tool. © 2015 by the American Institute of Ultrasound in Medicine.

  16. MONOTONICITY IN STEEPEST ASCENT ALGORITHMS FOR POLYHEDRAL L-CONCAVE FUNCTIONS

    OpenAIRE

    Fujishige, Satoru; MUROTA, Kazuo; Shioura, Akiyoshi

    2015-01-01

    For the minimum cost flow problem, Hassin (1983) proposed a dual algorithm, which iteratively updates dual variables in a steepest ascent manner. This algorithm is generalized to the minimum cost submodular flow problem by Chung and Tcha (1991). In discrete convex analysis, the dual of the minimum cost flow problem is known to be formulated as maximization of a polyhedral L-concave function. It is recently pointed out by Murota and Shioura (2014) that Hassin's algorithm can be recognized as a...

  17. Hip, knee, ankle kinematics and kinetics during stair ascent and descent in healthy young individuals.

    Science.gov (United States)

    Protopapadaki, Anastasia; Drechsler, Wendy I; Cramp, Mary C; Coutts, Fiona J; Scott, Oona M

    2007-02-01

    Few studies have reported the biomechanical aspects of stair climbing for this ergonomically demanding task. The purpose of this ethically approved study was to identify normal functional parameters of the lower limb during stair climbing and to compare the actions of stair ascent and descent in young healthy individuals. Thirty-three young healthy subjects, (16 M, 17 F, range 18-39 years) participated in the study. The laboratory staircase consisted of four steps (rise height 18 cm, tread length 28.5 cm). Kinematic data were recorded using 3D motion analysis system. Temporal gait cycle data and ground reaction forces were recorded using a force platform. Kinetic data were standardized to body mass and height. Paired-samples t tests showed significantly greater hip and knee angles (mean difference standard deviation (SD): hip 28.10 degrees (SD 4.08), knee 3.39 degrees (SD 7.20)) and hip and knee moments (hip 0.25 Nm/kg (SD 0.18), knee 0.17 Nm/kg (SD 0.15)) during stair ascent compared to descent. Significantly greater ankle dorsiflexion angles (9.90 degrees (SD 3.80)) and plantarflexion angles (8.78 degrees (SD 4.80)) were found during stair descent compared to ascent. Coefficient of variation (mean (SD)) in percentage between repeated tests varied for joint angles and moments, respectively (2.35% (SD 1.83)-17.53% (SD 13.62)) and (4.65% (SD 2.99)-40.73% (SD 24.77)). Stair ascent was shown to be the more demanding biomechanical task when compared to stair descent for healthy young subjects. The findings from the current study provide baseline measures for pathological studies, theoretical joint modelling, and for mechanical joint simulators.

  18. Six Degrees-of-Freedom Ascent Control for Small-Body Touch and Go

    Science.gov (United States)

    Blackmore, Lars James C.

    2011-01-01

    A document discusses a method of controlling touch and go (TAG) of a spacecraft to correct attitude, while ensuring a safe ascent. TAG is a concept whereby a spacecraft is in contact with the surface of a small body, such as a comet or asteroid, for a few seconds or less before ascending to a safe location away from the small body. The report describes a controller that corrects attitude and ensures that the spacecraft ascends to a safe state as quickly as possible. The approach allocates a certain amount of control authority to attitude control, and uses the rest to accelerate the spacecraft as quickly as possible in the ascent direction. The relative allocation to attitude and position is a parameter whose optimal value is determined using a ground software tool. This new approach makes use of the full control authority of the spacecraft to correct the errors imparted by the contact, and ascend as quickly as possible. This is in contrast to prior approaches, which do not optimize the ascent acceleration.

  19. Performance of a Predictive Model for Calculating Ascent Time to a Target Temperature

    Directory of Open Access Journals (Sweden)

    Jin Woo Moon

    2016-12-01

    Full Text Available The aim of this study was to develop an artificial neural network (ANN prediction model for controlling building heating systems. This model was used to calculate the ascent time of indoor temperature from the setback period (when a building was not occupied to a target setpoint temperature (when a building was occupied. The calculated ascent time was applied to determine the proper moment to start increasing the temperature from the setback temperature to reach the target temperature at an appropriate time. Three major steps were conducted: (1 model development; (2 model optimization; and (3 performance evaluation. Two software programs—Matrix Laboratory (MATLAB and Transient Systems Simulation (TRNSYS—were used for model development, performance tests, and numerical simulation methods. Correlation analysis between input variables and the output variable of the ANN model revealed that two input variables (current indoor air temperature and temperature difference from the target setpoint temperature, presented relatively strong relationships with the ascent time to the target setpoint temperature. These two variables were used as input neurons. Analyzing the difference between the simulated and predicted values from the ANN model provided the optimal number of hidden neurons (9, hidden layers (3, moment (0.9, and learning rate (0.9. At the study’s conclusion, the optimized model proved its prediction accuracy with acceptable errors.

  20. Eddy Flow during Magma Emplacement: The Basemelt Sill, Antarctica

    Science.gov (United States)

    Petford, N.; Mirhadizadeh, S.

    2014-12-01

    The McMurdo Dry Valleys magmatic system, Antarctica, forms part of the Ferrar dolerite Large Igneous Province. Comprising a vertical stack of interconnected sills, the complex provides a world-class example of pervasive lateral magma flow on a continental scale. The lowermost intrusion (Basement Sill) offers detailed sections through the now frozen particle macrostructure of a congested magma slurry1. Image-based numerical modelling where the intrusion geometry defines its own unique finite element mesh allows simulations of the flow regime to be made that incorporate realistic magma particle size and flow geometries obtained directly from field measurements. One testable outcome relates to the origin of rhythmic layering where analytical results imply the sheared suspension intersects the phase space for particle Reynolds and Peclet number flow characteristic of macroscopic structures formation2. Another relates to potentially novel crystal-liquid segregation due to the formation of eddies locally at undulating contacts at the floor and roof of the intrusion. The eddies are transient and mechanical in origin, unrelated to well-known fluid dynamical effects around obstacles where flow is turbulent. Numerical particle tracing reveals that these low Re number eddies can both trap (remove) and eject particles back into the magma at a later time according to their mass density. This trapping mechanism has potential to develop local variations in structure (layering) and magma chemistry that may otherwise not occur where the contact between magma and country rock is linear. Simulations indicate that eddy formation is best developed where magma viscosity is in the range 1-102 Pa s. Higher viscosities (> 103 Pa s) tend to dampen the effect implying eddy development is most likely a transient feature. However, it is nice to think that something as simple as a bumpy contact could impart physical and by implication chemical diversity in igneous rocks. 1Marsh, D.B. (2004), A

  1. Oxygen Isotope Trajectories of Crystallizing Arc Magmas

    Science.gov (United States)

    Bucholz, C. E.; Jagoutz, O. E.; VanTongeren, J. A.; Wang, Z.

    2014-12-01

    Oxygen isotopes are essential to quantify mantle-derived versus 'recycled' crustal contributions to arc magmas. High δ18O values in igneous rocks (i.e., δ18OSMOW > ~5.7) are generally used to identify supra-crustal inputs, but a melt can also become enriched in 18O due to magmatic differentiation [1,2]. To assess magmatic δ18O values of plutonic rocks, δ18Ozircon values, which are resilient to secondary alteration, are often used. Thus, to disentangle the effects of assimilation versus fractionation, both the absolute increase in melt δ18O due to differentiation and ∆18O(WR-zircon) must be determined. However, existing constraints on the effect of magmatic fractionation on melt δ18O are model-based [2] and calculated relationships between WR SiO2, δ18Ozircon, and δ18Omelt do not incorporate complex melt SiO2, H2O, and temperature (T) relationships [3]. To build upon these initial constraints, we combine the first high-precision δ18O data set on natural samples documenting changes in δ18O melt values with increasing extent of differentiation and modeling which incorporates experimentally constrained melt SiO2, H2O, and T relationships. We analyzed 55 mineral separates with infrared laser-fluorination [4] across large fractionation intervals of two well-studied cumulate sequences: (I) a relatively dry (~1 wt.% H2O initial) tholeiitic sequence (analyzed minerals include plag, opx, cpx, & Fe-rich ol) from the Bushveld Complex and (II) a hydrous high-K sequence (analyzed minerals include ol, cpx, bt, fsp, & qtz) from the Dariv paleoarc in Mongolia. Our results indicate that multiple per mil increases in melt δ18O can occur during magmatic fractionation that in detail depend strongly on melt composition and T. Calculated relationships between WR SiO2 and δ18Ozircon for experimental melt compositions show that wet, 'cool' and dry, 'hot' melts are characterized by larger and smaller ∆18O (melt-zircon) fractionations, respectively. Applying our results to

  2. Upper Atmospheric Monitoring for Ares I-X Ascent Loads and Trajectory Evaluation on the Day-of-Launch

    Science.gov (United States)

    Roberts, Barry C.; McGrath, Kevin; Starr, Brett; Brandon, Jay

    2009-01-01

    During the launch countdown of the Ares I-X test vehicle, engineers from Langley Research Center will use profiles of atmospheric density and winds in evaluating vehicle ascent loads and controllability. A schedule for the release of balloons to measure atmospheric density and winds has been developed by the Natural Environments Branch at Marshall Space Flight Center to help ensure timely evaluation of the vehicle ascent loads and controllability parameters and support a successful launch of the Ares I-X vehicle.

  3. Linking magma transport structures at Kīlauea volcano

    Science.gov (United States)

    Wech, Aaron G.; Thelen, Weston A.

    2015-01-01

    Identifying magma pathways is important for understanding and interpreting volcanic signals. At Kīlauea volcano, seismicity illuminates subsurface plumbing, but the broad spectrum of seismic phenomena hampers event identification. Discrete, long-period events (LPs) dominate the shallow (5-10 km) plumbing, and deep (40+ km) tremor has been observed offshore. However, our inability to routinely identify these events limits their utility in tracking ascending magma. Using envelope cross-correlation, we systematically catalog non-earthquake seismicity between 2008-2014. We find the LPs and deep tremor are spatially distinct, separated by the 15-25 km deep, horizontal mantle fault zone (MFZ). Our search corroborates previous observations, but we find broader-band (0.5-20 Hz) tremor comprising collocated earthquakes and reinterpret the deep tremor as earthquake swarms in a volume surrounding and responding to magma intruding from the mantle plume beneath the MFZ. We propose the overlying MFZ promotes lateral magma transport, linking this deep intrusion with Kīlauea’s shallow magma plumbing.

  4. A study to evaluate STS heads-up ascent trajectory performance employing a minimum-Hamiltonian optimization strategy

    Science.gov (United States)

    Sinha, Sujit

    1988-01-01

    A study was conducted to evaluate the performance implications of a heads-up ascent flight design for the Space Transportation System, as compared to the current heads-down flight mode. The procedure involved the use of the Minimum Hamiltonian Ascent Shuttle Trajectory Evaluation Program, which is a three-degree-of-freedom moment balance simulation of shuttle ascent. A minimum-Hamiltonian optimization strategy was employed to maximize injection weight as a function of maximum dynamic pressure constraint and Solid Rocket Motor burnrate. Performance Reference Mission Four trajectory groundrules were used for consistency. The major conclusions are that for heads-up ascent and a mission nominal design maximum dynamic pressure value of 680 psf, the optimum solid motor burnrate is 0.394 ips, which produces a performance enhancement of 4293 lbm relative to the baseline heads-down ascent, with 0.368 ips burnrate solid motors and a 680 psf dynamic pressure constraint. However, no performance advantage exists for heads-up flight if the current Solid Rocket Motor target burnrate of 0.368 ips is used. The advantage of heads-up ascent flight employing the current burnrate is that Space Shuttle Main Engine throttling for dynamic pressure control is not necessary.

  5. Are recycled carbonates essential to explain light Mg isotopes in magmatic rocks? Insights from Late Cenozoic mantle-derived magmas in Iran

    Science.gov (United States)

    Pang, K. N.; Teng, F. Z.; Sun, Y.; Chung, S. L.; Zarrinkoub, M. H.

    2016-12-01

    Mantle-derived magmas at continental collision zones represent probes into the mantle that might have been variably metasomatized prior to collision. To address how and to what extent mantle metasomatism occurred, particularly for the role of recycled carbonates, we conducted a Mg isotopic study of two suites of Late Cenozoic mantle-derived magmas in Iran, part of the Arabia-Eurasia collision zone preceded by the long-lasting Tethyan subduction. The Qal'eh Hasan Ali high-Mg ultrapotassic rocks, low-degree partial melts from the metasomatized lithospheric mantle, have mantle-like δ26Mg (-0.23 to -0.28 ‰) despite high CaO/Al2O3 and Zr/Hf, low Ti/Eu and Hf/Sm, and presence of carbonate globules in devitrified glass indicative of carbonate or carbonatite involvement in their genesis. The absence of light Mg isotopic composition of these rocks indicates that either the recycled carbonates were in the form of calcitic rather than dolomitic melts, or the amount of Mg from the carbonatite was too little to appear in these rocks. The Lut-Sistan alkali basalts, sodic magmas suggested to have derived from low-degree melting of the asthenosphere followed by variable differentiation, display a range of δ26Mg from -0.17 to -0.26 ‰ with three outlying data at -0.37‰, -0.39‰ and -0.56 ‰. The samples with light Mg isotopes do not show greater influence by carbonate or carbonatite in terms of the elemental indices noted above. Instead, they are characterized by lower light and middle REE abundances and slightly lower initial 143Nd/144Nd than the majority of samples. The covariations can be explained by minor incorporation of lower crustal garnet during magma ascent through local thickened crust in the collision zone. We propose that thickened crust where garnet pyroxenites exist is capable of imparting a light Mg isotopic signature to mantle-derived magmas, and that such signature is not unique to the involvement of carbonate or carbonatite in the mantle source.

  6. Iron Redox Systematics of Shergottites and Martian Magmas

    Science.gov (United States)

    Righter, Kevin; Danielson, L. R.; Martin, A. M.; Newville, M.; Choi, Y.

    2010-01-01

    Martian meteorites record a range of oxygen fugacities from near the IW buffer to above FMQ buffer [1]. In terrestrial magmas, Fe(3+)/ SigmaFe for this fO2 range are between 0 and 0.25 [2]. Such variation will affect the stability of oxides, pyroxenes, and how the melt equilibrates with volatile species. An understanding of the variation of Fe(3+)/SigmaFe for martian magmas is lacking, and previous work has been on FeO-poor and Al2O3-rich terrestrial basalts. We have initiated a study of the iron redox systematics of martian magmas to better understand FeO and Fe2O3 stability, the stability of magnetite, and the low Ca/high Ca pyroxene [3] ratios observed at the surface.

  7. The magma ocean as an impediment to lunar plate tectonics

    Science.gov (United States)

    Warren, Paul H.

    1993-01-01

    The primary impediment to plate tectonics on the moon was probably the great thickness of its crust and particularly its high crust/lithosphere thickness ratio. This in turn can be attributed to the preponderance of low-density feldspar over all other Al-compatible phases in the lunar interior. During the magma ocean epoch, the moon's crust/lithosphere thickness ratio was at the maximum theoretical value, approximately 1, and it remained high for a long time afterwards. A few large regions of thin crust were produced by basin-scale cratering approximately contemporaneous with the demise of the magma ocean. However, these regions probably also tend to have uncommonly thin lithosphere, since they were directly heated and indirectly enriched in K, Th, and U by the same cratering process. Thus, plate tectonics on the moon in the form of systematic lithosphere subduction was impeded by the magma ocean.

  8. Magma storage in a strike-slip caldera.

    Science.gov (United States)

    Saxby, J; Gottsmann, J; Cashman, K; Gutiérrez, E

    2016-07-22

    Silicic calderas form during explosive volcanic eruptions when magma withdrawal triggers collapse along bounding faults. The nature of specific interactions between magmatism and tectonism in caldera-forming systems is, however, unclear. Regional stress patterns may control the location and geometry of magma reservoirs, which in turn may control the spatial and temporal development of faults. Here we provide new insight into strike-slip volcano-tectonic relations by analysing Bouguer gravity data from Ilopango caldera, El Salvador, which has a long history of catastrophic explosive eruptions. The observed low gravity beneath the caldera is aligned along the principal horizontal stress orientations of the El Salvador Fault Zone. Data inversion shows that the causative low-density structure extends to ca. 6 km depth, which we interpret as a shallow plumbing system comprising a fractured hydrothermal reservoir overlying a magmatic reservoir with vol% exsolved vapour. Fault-controlled localization of magma constrains potential vent locations for future eruptions.

  9. Magma chamber and mantle reflections - East Pacific Rise

    Science.gov (United States)

    Herron, Thomas J.; Stoffa, Paul L.; Buhl, Peter

    1980-11-01

    A multichannel seismic reflection profile of stacked and migrated common depth point data across the East Pacific Rise near the Siqueiros Fracture Zone supports and extends previous observations (at two crossings 27 to 50 km to the south) of reflections assumed to be from the top of a magma chamber and of reflections from the M-discontinuity. The reflection assumed to be associated with the top of the magma chamber is 1-1/2 to 2 km below the sea floor. The combined results of the three crossings suggest that the chamber is continuous along the Rise crest and that its width, which varies from 2 to 8 km, correlates with the width of the Rise crest as indicated by the bathymetric contours. The reflections from the crust-mantle boundary can be detected beneath the raised axial block of the East Pacific Rise and although weak, can be detected beneath the magma chamber.

  10. Decoding magma plumbing and geochemical evolution beneath the Lastarria volcanic complex (Northern Chile)-Evidence for multiple magma storage regions

    Science.gov (United States)

    Stechern, André; Just, Tobias; Holtz, François; Blume-Oeste, Magdalena; Namur, Olivier

    2017-05-01

    The petrology of quaternary andesites and dacites from Lastarria volcano was investigated to reconstruct the magma plumbing and storage conditions beneath the volcano. The mineral phase compositions and whole-rock major and trace element compositions were used to constrain temperature, pressure and possible mechanisms for magma differentiation. The applied thermobarometric models include two-pyroxene thermobarometry, plagioclase-melt thermometry, amphibole composition thermobarometry, and Fe-Ti oxide thermo-oxybarometry. The overall temperature estimation is in the range 840 °C to 1060 °C. Calculated oxygen fugacity ranges between NNO to NNO + 1. Results of the geo-barometric calculations reveal multiple magma storage regions, with a distinct storage level in the uppermost crust ( 6.5-8 km depth), a broad zone at mid-crustal levels ( 10-18 km depth), and a likely deeper zone at intermediate to lower crustal levels (> 20 km depth). The highest temperatures in the range 940-1040 °C are recorded in minerals stored in the mid-crustal levels ( 10-18 km depth). The whole-rock compositions clearly indicate that magma mixing is the main parameter controlling the general differentiation trends. Complex zoning patterns and textures in the plagioclase phenocrysts confirm reheating and remobilization processes due to magma replenishment.

  11. Lunar Magma Ocean Crystallization: Constraints from Fractional Crystallization Experiments

    Science.gov (United States)

    Rapp, J. F.; Draper, D. S.

    2015-01-01

    The currently accepted paradigm of lunar formation is that of accretion from the ejecta of a giant impact, followed by crystallization of a global scale magma ocean. This model accounts for the formation of the anorthosite highlands crust, which is globally distributed and old, and the formation of the younger mare basalts which are derived from a source region that has experienced plagioclase extraction. Several attempts at modelling the crystallization of such a lunar magma ocean (LMO) have been made, but our ever-increasing knowledge of the lunar samples and surface have raised as many questions as these models have answered. Geodynamic models of lunar accretion suggest that shortly following accretion the bulk of the lunar mass was hot, likely at least above the solidus]. Models of LMO crystallization that assume a deep magma ocean are therefore geodynamically favorable, but they have been difficult to reconcile with a thick plagioclase-rich crust. A refractory element enriched bulk composition, a shallow magma ocean, or a combination of the two have been suggested as a way to produce enough plagioclase to account for the assumed thickness of the crust. Recently however, geophysical data from the GRAIL mission have indicated that the lunar anorthositic crust is not as thick as was initially estimated, which allows for both a deeper magma ocean and a bulk composition more similar to the terrestrial upper mantle. We report on experimental simulations of the fractional crystallization of a deep (approximately 100km) LMO with a terrestrial upper mantle-like (LPUM) bulk composition. Our experimental results will help to define the composition of the lunar crust and mantle cumulates, and allow us to consider important questions such as source regions of the mare basalts and Mg-suite, the role of mantle overturn after magma ocean crystallization and the nature of KREEP

  12. Magma mixing and high fountaining during the 1959 Kīlauea Iki eruption, Hawai‘i

    Science.gov (United States)

    Sides, I.; Edmonds, M.; Maclennan, J.; Houghton, Bruce F.; Swanson, Don; Steele-MacInnis, M.J.

    2014-01-01

    The 1959 Kīlauea Iki eruption provides a unique opportunity to investigate the process of shallow magma mixing, its impact on the magmatic volatile budget and its role in triggering and driving episodes of Hawaiian fountaining. Melt inclusions hosted by olivine record a continuous decrease in H2O concentration through the 17 episodes of the eruption, while CO2 concentrations correlate with the degree of post-entrapment crystallization of olivine on the inclusion walls. Geochemical data, when combined with the magma budget and with contemporaneous eruption observations, show complex mixing between episodes involving hot, geochemically heterogeneous melts from depth, likely carrying exsolved vapor, and melts which had erupted at the surface, degassed and drained-back into the vent. The drained-back melts acted as a coolant, inducing rapid cooling of the more primitive melts and their olivines at shallow depths and inducing crystallization and vesiculation and triggering renewed fountaining. A consequence of the mixing is that the melts became vapor-undersaturated, so equilibration pressures cannot be inferred from them using saturation models. After the melt inclusions were trapped, continued growth of vapor bubbles, caused by enhanced post-entrapment crystallization, sequestered a large fraction of CO2 from the melt within the inclusions. This study, while cautioning against accepting melt inclusion CO2 concentrations “as measured” in mixed magmas, also illustrates that careful analysis and interpretation of post-entrapment modifications can turn this apparent challenge into a way to yield novel useful insights into the geochemical controls on eruption intensity.

  13. Eutectic propeties of primitive Earth's magma ocean

    Science.gov (United States)

    Lo Nigro, G.; Andrault, D.; Bolfan-Casanova, N.; Perillat, J.-P.

    2009-04-01

    It is widely accepted that the early Earth was partially molten (if not completely) due to the high energy dissipated by terrestrial accretion [1]. After core formation, subsequent cooling of the magma ocean has led to fractional crystallization of the primitive mantle. The residual liquid corresponds to what is now called the fertile mantle or pyrolite. Melting relations of silicates have been extensively investigated using the multi-anvil press, for pressures between 3 and 25 GPa [2,3]. Using the quench technique, it has been shown that the pressure affects significantly the solidus and liquidus curves, and most probably the composition of the eutectic liquid. At higher pressures, up to 65 GPa, melting studies were performed on pyrolite starting material using the laser-heated diamond anvil cell (LH-DAC) technique [4]. However, the quench technique is not ideal to define melting criteria, and furthermore these studies were limited in pressure range of investigation. Finally, the use of pyrolite may not be relevant to study the melting eutectic temperature. At the core-mantle boundary conditions, melting temperature is documented by a single data point on (Mg,Fe)2SiO4 olivine, provided by shock wave experiments at around 130-140 GPa [5]. These previous results present large uncertainties of ~1000 K. The aim of this study is to determine the eutectic melting temperature in the chemically simplified system composed of the two major lower mantle phases, the MgSiO3 perovskite and MgO periclase. We investigated melting in-situ using the laser-heated diamond anvil cell coupled with angle dispersive X-ray diffraction at the ID27 beamline of the ESRF [6]. Melting relations were investigated in an extended P-T range comparable to those found in the Earth's lower mantle, i.e. from 25 to 120 GPa and up to more than 5000 K. Melting was evidenced from (a) disappearance of one of the two phases in the diffraction pattern, (b) drastic changes of the diffraction image itself, and

  14. Magma energy research project: state-of-the-project report, October 1, 1978

    Energy Technology Data Exchange (ETDEWEB)

    Colp, J.L.; Traeger, R.K.

    1980-02-01

    The feasibility of extracting energy from magma bodies is investigated. The work done in FY 76, 77, and 78 in the following tasks are summarized; resource location and definition, source tapping, magma characterization and materials compatibility, and energy extraction. (MHR)

  15. Evolution of magma feeding system in Kumanodake agglutinate activity, Zao Volcano, northeastern Japan

    Science.gov (United States)

    Takebe, Yoshinori; Ban, Masao

    2015-10-01

    The Kumanodake agglutinate of Zao Volcano in northeastern Japan consists of pyroclastic surge layers accumulated during the early part of the newest stage of activity (ca. 33 ka to present). Our petrologic study of this agglutinate based on systematically collected samples aims to reveal the evolution of magma feeding system. To understand the magma evolution, we have examined samples from the agglutinate by using petrologic data including, petrography, analysis of minerals (plagioclase, pyroxene, and olivine), glass compositions, and whole rock major element and trace element (Ba, Sr, Cr, Ni, V, Rb, Zr, Nb, and Y) compositions. Agglutinate are mixed, medium-K, calc-alkaline olv-cpx-opx basaltic andesite (55.2-56.2% SiO2). Results show that the magma feeding system comprised a shallow felsic chamber injected by mafic magma from depth. The felsic magma (59-62% SiO2, 950-990 °C), which was stored at a shallower depth, had orthopyroxene (Mg# = 60-69), clinopyroxene (Mg# = 65-71), and low-An plagioclase (Anca. 58-70). The mafic magma is further divisible into two types: less-differentiated and more-differentiated, designed respectively as an initial mafic magma-1 and a second mafic magma-2. The original mafic magma-1 was olivine (Fo 84) basalt (ca. 48-51% SiO2, 1110-1140 °C). The second mafic magma-2, stored occasionally at 4-6 km depth, was basalt (1070-1110 °C) having Foca. 80 olivine and high-An (Anca. 90) plagioclase phenocrysts. These two magmas mixed (first mixing) to form hybrid mafic magma. The forced injections of the hybrid mafic magmas activated the felsic magma, and these two were mixed (second mixing) shortly before eruptions. The explosivity is inferred to have increased over time because the abundance of large scoria increased. Furthermore, the erupted magma composition became more mafic, which reflects increased percentage of the hybrid mafic magma involved in the second mixing. At the beginning of activity, the mafic magma also acted as a heat

  16. An ISRU Propellant Production System to Fully Fuel a Mars Ascent Vehicle

    Science.gov (United States)

    Kleinhenz, Julie; Paz, Aaron

    2017-01-01

    ISRU of Mars resources was base lined in 2009 Design Reference Architecture (DRA) 5.0, but only for Oxygen production using atmospheric CO2The Methane (LCH4) needed for ascent propulsion of the Mars Ascent Vehicle (MAV) would need to be brought from Earth. HOWEVER: Extracting water from the Martian Regolith enables the production of both Oxygen and Methane from Mars resources Water resources could also be used for other applications including: Life support, radiation shielding, plant growth, etc. Water extraction was not base lined in DRA5.0 due to perceived difficulties and complexity in processing regolith. The NASA Evolvable Mars Campaign (EMC) requested studies to look at the quantitative benefits and trades of using Mars water ISRU Phase 1: Examined architecture scenarios for regolith water retrieval. Completed October 2015Phase 2: Deep dive of one architecture concept to look at end-to-end system size, mass, power of a LCH4LO2 ISRU production system.Evolvable Mars CampaignPre-deployed Mars ascent vehicle (MAV)4 crew membersPropellants: Oxygen MethaneGenerate a system model to roll up mass power of a full ISRU system and enable parametric trade studies. Leverage models from previous studies and technology development programs Anchor with mass power performance from existing hardware. Whenever possible used reference-able (published) numbers for traceability.Modular approach to allow subsystem trades and parametric studies. Propellant mass needs taken from most recently published MAV study:Polsgrove, T. et al. (2015), AIAA2015-4416MAV engines operate at mixture ratios (oxygen: methane) between 3:1 and 3.5:1, whereas the Sabatier reactor produces at a 4:1 ratio. Therefore:Methane production is the driving requirement-Excess Oxygen will be produced.

  17. Trunk, pelvis and hip biomechanics in individuals with femoroacetabular impingement syndrome: Strategies for step ascent.

    Science.gov (United States)

    Diamond, Laura E; Bennell, Kim L; Wrigley, Tim V; Hinman, Rana S; Hall, Michelle; O'Donnell, John; Hodges, Paul W

    2018-01-11

    Femoroacetabular impingment (FAI) syndrome is common among young active adults and a proposed risk factor for the future development of hip osteoarthritis. Pain is dominant and drives clinical decision-making. Evidence for altered hip joint function in this patient population is inconsistent, making the identification of treatment targets challenging. A broader assessment, considering adjacent body segments (i.e. pelvis, trunk) and individual movement strategies, may better inform treatment programs. This exploratory study aimed to compare trunk, pelvis, and hip biomechanics during step ascent between individuals with and without FAI syndrome. Fifteen participants diagnosed with symptomatic cam-type or combined (cam plus pincer) FAI who were scheduled for arthroscopic surgery, and 11 age-, and sex-comparable pain- and disease-free individuals, underwent three-dimensional motion analysis during a step ascent task. Trunk, pelvis and hip biomechanics were compared between groups. Participants with FAI syndrome exhibited altered ipsilateral trunk lean and pelvic rise towards the symptomatic side during single-leg support compared to controls. Alterations were not uniformly adopted across all individuals with FAI syndrome; those who exhibited more pronounced alterations to frontal plane pelvis control tended to report pain during the task. There were minimal between-group differences for hip biomechanics. Exploratory data suggest biomechanics at the trunk and pelvis during step ascent differ between individuals with and without FAI syndrome. Those with FAI syndrome implement a range of proximal strategies for task completion, some of which may have relevance for rehabilitation. Longitudinal investigations of larger cohorts are required to evaluate hypothesized clinical and structural consequences. Copyright © 2018 Elsevier B.V. All rights reserved.

  18. Patellofemoral joint stress during stair ascent and descent in persons with and without patellofemoral pain.

    Science.gov (United States)

    Brechter, Jacklyn Heino; Powers, Christopher M

    2002-10-01

    To determine if persons with patellofemoral pain (PFP) demonstrate elevated patellofemoral joint (PFJ) stress during stair ascent and descent when compared to persons without PFP. A cross sectional study utilizing an experimental and a control group. Ascending and descending stairs is one of the most painful activities of daily living for persons with PFP. Whether or not the pain associated with stair ambulation is the result of elevated joint stress (force per unit area) has not been explored. 10 subjects with a diagnosis of PFP and 10 subjects without pain completed two phases of data collection, (1) MRI assessment to determine PFJ contact area and (2) comprehensive motion analysis during stair ambulation at self selected climbing velocities. Data obtained from both data collection sessions were utilized as input variables into a biomechanical model to quantify PFJ stress. Although the knee extensor moment and PFJ reaction force (PFJRF) were significantly reduced in the PFP subjects during stair ascent, there was no difference in PFJ stress between groups. Similarly, there were no differences in PFJ stress during stair descent. Our results do not support the hypothesis that subjects with PFP demonstrate greater joint stress during stair ascent and descent compared to subjects without pain. However, subjects with PFP appeared to maintain normal levels of PFJ stress by minimizing the PFJRF. This was accomplished through a slower cadence and a reduced knee extensor moment. PFP is a common syndrome causing pain and functional limitations during stair climbing and other activities requiring high levels of quadriceps activity. Information obtained from this study will be useful in understanding the biomechanical mechanisms contributing to functional deficits in the PFP population.

  19. Extension by faulting, stretching and magma intrusion in Ethiopia

    Science.gov (United States)

    Bastow, I. D.; Keir, D.

    2012-12-01

    The 2001-2004 Ethiopia Afar Geoscientific Lithospheric Experiment showed that high seismic wavespeed, dense, mafic crustal intrusions exist beneath many zones of Quaternary magmatism in the Main Ethiopian rift, and that crustal thinning is minimal. From these observations, a consensus quickly emerged that extension presently occurs not by ductile stretching and brittle faulting but by magma intrusion. Striking InSAR images and accompanying seismic data from the 2005 Afar diking episode provided further compelling evidence in support of the magma assisted rifting hypothesis. Patterns of mantle seismic anisotropy, constrained by a combination of body and surface-wave analysis showed that melt intrusion likely also plays an important role in accommodating extension at greater depths in the extending plate. Evidence from further north in Afar, however, where crustal thickness decreases abruptly into the Danakil Depression, is not so easily explained by the magma assisted rifting hypothesis. Subsidence of the newly forming margin towards and below sea level, and eruption of voluminous basalt flows, is likely the result of late-stage thinning of the heavily intruded, weakened plate just before the onset of seafloor spreading. Faulting, stretching and magma intrusion are thus each important, but at different times during breakup. Combining, not isolating, these mechanisms of strain in new rifting models and appreciating how plate strength varies during rifting is essential in developing a clearer understanding of the incomplete geological record that documents continental breakup over time.

  20. Launch Vehicle Ascent Trajectory Simulation Using the Program to Optimize Simulated Trajectories II (POST2)

    Science.gov (United States)

    Lugo, Rafael A.; Shidner, Jeremy D.; Powell, Richard W.; Marsh, Steven M.; Hoffman, James A.; Litton, Daniel K.; Schmitt, Terri L.

    2017-01-01

    The Program to Optimize Simulated Trajectories II (POST2) has been continuously developed for over 40 years and has been used in many flight and research projects. Recently, there has been an effort to improve the POST2 architecture by promoting modularity, flexibility, and ability to support multiple simultaneous projects. The purpose of this paper is to provide insight into the development of trajectory simulation in POST2 by describing methods and examples of various improved models for a launch vehicle liftoff and ascent.

  1. Modeling the ascent of sounding balloons: derivation of the vertical air motion

    Directory of Open Access Journals (Sweden)

    A. Gallice

    2011-10-01

    Full Text Available A new model to describe the ascent of sounding balloons in the troposphere and lower stratosphere (up to ∼30–35 km altitude is presented. Contrary to previous models, detailed account is taken of both the variation of the drag coefficient with altitude and the heat imbalance between the balloon and the atmosphere. To compensate for the lack of data on the drag coefficient of sounding balloons, a reference curve for the relationship between drag coefficient and Reynolds number is derived from a dataset of flights launched during the Lindenberg Upper Air Methods Intercomparisons (LUAMI campaign. The transfer of heat from the surrounding air into the balloon is accounted for by solving the radial heat diffusion equation inside the balloon. In its present state, the model does not account for solar radiation, i.e. it is only able to describe the ascent of balloons during the night. It could however be adapted to also represent daytime soundings, with solar radiation modeled as a diffusive process. The potential applications of the model include the forecast of the trajectory of sounding balloons, which can be used to increase the accuracy of the match technique, and the derivation of the air vertical velocity. The latter is obtained by subtracting the ascent rate of the balloon in still air calculated by the model from the actual ascent rate. This technique is shown to provide an approximation for the vertical air motion with an uncertainty error of 0.5 m s−1 in the troposphere and 0.2 m s−1 in the stratosphere. An example of extraction of the air vertical velocity is provided in this paper. We show that the air vertical velocities derived from the balloon soundings in this paper are in general agreement with small-scale atmospheric velocity fluctuations related to gravity waves, mechanical turbulence, or other small-scale air motions measured during the SUCCESS campaign (Subsonic Aircraft: Contrail and Cloud Effects

  2. Analysis of foot clearance in firefighters during ascent and descent of stairs.

    Science.gov (United States)

    Kesler, Richard M; Horn, Gavin P; Rosengren, Karl S; Hsiao-Wecksler, Elizabeth T

    2016-01-01

    Slips, trips, and falls are a leading cause of injury to firefighters with many injuries occurring while traversing stairs, possibly exaggerated by acute fatigue from firefighting activities and/or asymmetric load carriage. This study examined the effects that fatigue, induced by simulated firefighting activities, and hose load carriage have on foot clearance while traversing stairs. Landing and passing foot clearances for each stair during ascent and descent of a short staircase were investigated. Clearances decreased significantly (p stair clearance or an increased risk of over-stepping during descent. Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

  3. The crystal's view of upper-crustal magma reservoirs

    Science.gov (United States)

    Cooper, K. M.; Kent, A. J.; Huber, C.; Stelten, M. E.; Rubin, A. E.; Schrecengost, K.

    2015-12-01

    Upper-crustal magma reservoirs are important sites of magma mixing, crustal refining, and magma storage. Crystals residing in these reservoirs have been shown to represent valuable archives of the chemical and physical evolution of reservoirs, and the time scales of this evolution. This presentation addresses the question of "What do crystals "see" and record about processes within the upper crust? And how is that view similar or different between plutonic and volcanic records?" Three general observations emerge from study of the ages of crystals, combined with crystal-scale geochemical data: 1) Patterns of isotopic and trace-element data over time in zircon crystals from a given magmatic system (e.g., Yellowstone, WY, and Taupo Volcanic Zone, New Zealand) can show systematic changes in the degree of heterogeneity, consistent with extraction of melts from a long-lived (up to 100s of kyr), heterogeneous crystal mush and in some cases continued crystallization and homogenization of the magma during a short period (eruption. 2) Thermal histories of magma storage derived from crystal records also show that the vast majority of time recorded by major phases was spent in storage as a crystal mush, perhaps at near-solidus conditions. 3) Comparison of ages of accessory phases in both plutonic blocks and host magmas that brought them to the surface do not show a consistent relationship between the two. In some cases, zircons from plutonic blocks have age spectra much older than zircon in the host magma. In other cases, host and plutonic block zircons have similar age spectra and chemical characteristics, suggesting a closer genetic connection between the two. These observations suggest that crystals in plutonic bodies, if examined at similar spatial and temporal scales to those in volcanic rocks, would show records that are highly heterogeneous in chemistry and age on the scale of a pluton or a lobe of a pluton, but that local regions of limited chemical and age variability

  4. Staged storage and magma convection at Ambrym volcano, Vanuatu

    Science.gov (United States)

    Sheehan, Fionnuala; Barclay, Jenni

    2016-08-01

    New mineral-melt thermobarometry and mineral chemistry data are presented for basaltic scoriae erupted from the Mbwelesu crater of Ambrym volcano, Vanuatu, during persistent lava lake activity in 2005 and 2007. These data reveal crystallisation conditions and enable the first detailed attempt at reconstruction of the central magma plumbing system of Ambrym volcano. Pressures and temperatures of magma crystallisation at Ambrym are poorly constrained. This study focuses on characterising the magma conditions underlying the quasi-permanent lava lakes at the basaltic central vents, and examines petrological evidence for magma circulation. Mineral-melt equilibria for clinopyroxene, olivine and plagioclase allow estimation of pressures and temperatures of crystallisation, and reveal two major regions of crystallisation, at 24-29 km and 11-18 km depth, in agreement with indications from earthquake data of crustal storage levels at c. 25-29 km and 12-21 km depth. Temperature estimates are 1150-1170 °C for the deeper region, and 1110-1140 °C in the mid-crustal region, with lower temperatures of 1090-1100 °C for late-stage crystallisation. More primitive plagioclase antecrysts are thought to sample a slightly more mafic melt at sub-Moho depths. Resorption textures combined with effectively constant mafic mineral compositions suggest phenocryst convection in a storage region of consistent magma composition. In addition, basalt erupted at Ambrym has predominantly maintained a constant composition throughout the volcanic succession. This, coupled with recurrent periods of elevated central vent activity on the scale of months, suggest frequent magmatic recharge via steady-state melt generation at Ambrym.

  5. A Terminal Area Analysis of Continuous Ascent Departure Fuel Use at Dallas/Fort Worth International Airport

    Science.gov (United States)

    Roach, Keenan; Robinson, John E., III

    2010-01-01

    Aircraft departing from the Dallas/Fort Worth International Airport (DFW) encounter vertical restrictions that prevent continuous ascent operations. The result of these restrictions are temporary level-offs at 10,000 feet. A combination of flow direction, specific Area Navigation (RNAV) route geometry, and arrival streams have been found to be the biggest factors in the duration and frequency of a temporary level-offs. In total, 20% of DFW departures are affected by these level-offs, which have an average duration of just over 100 seconds. The use of continuous descent approaches at DFW are shown to lessen the impact arrivals have on the departures and allow more continuous ascents. The fuel used in a continuous ascent and an ascent with a temporary level-off have been calculated using a fuel burn rate model created from a combination of actual aircraft track data, aircraft manufacturer flight operations manuals, and Eurocontrol's Base of Aircraft Data (BADA) simulation tool. This model represents the average aggregate burn rates for the current fleet mix at DFW. Continuous ascents would save approximately seven gallons of fuel out of 450 gallons used to climb to a cruise altitude of 31,000ft per departure.

  6. The extimated presence of differentiated higly explosive magmas beneath Vesuvius and Campi Flegrei: evidence from geochemical and textural studies.

    Science.gov (United States)

    Pappalardo, Lucia; Mastrolorenzo, Giuseppe

    2010-05-01

    rapid crystallization and differentiation time for alkaline Campanian magmas (in the order of decades to few centuries). This evidence implies that the 400 km2 partial melting zone detected by tomography study at 8-10 km depth beneath Vesuvius and Campi Flegrei, should consist of differentiated magma already capable to produce also large scale (plinian) explosive events in case of renewal of the activity from the present closed-conduit state.

  7. Simulation of Liquid Injection Thrust Vector Control for Mars Ascent Vehicle

    Science.gov (United States)

    Gudenkauf, Jared

    2017-01-01

    The Jet Propulsion Laboratory is currently in the initial design phase for a potential Mars Ascent Vehicle; which will be landed on Mars, stay on the surface for period of time, collect samples from the Mars 2020 rover, and then lift these samples into orbit around Mars. The engineers at JPL have down selected to a hybrid wax-based fuel rocket using a liquid oxidizer based on nitrogen tetroxide, or a Mixed Oxide of Nitrogen. To lower the gross lift-off mass of the vehicle the thrust vector control system will use liquid injection of the oxidizer to deflect the thrust of the main nozzle instead of using a gimbaled nozzle. The disadvantage of going with the liquid injection system is the low technology readiness level with a hybrid rocket. Presented in this paper is an effort to simulate the Mars Ascent Vehicle hybrid rocket nozzle and liquid injection thrust vector control system using the computational fluid dynamic flow solver Loci/Chem. This effort also includes determining the sensitivity of the thrust vector control system to a number of different design variables for the injection ports; including axial location, number of adjacent ports, injection angle, and distance between the ports.

  8. The space shuttle ascent vehicle aerodynamic challenges configuration design and data base development

    Science.gov (United States)

    Dill, C. C.; Young, J. C.; Roberts, B. B.; Craig, M. K.; Hamilton, J. T.; Boyle, W. W.

    1985-01-01

    The phase B Space Shuttle systems definition studies resulted in a generic configuration consisting of a delta wing orbiter, and two solid rocket boosters (SRB) attached to an external fuel tank (ET). The initial challenge facing the aerodynamic community was aerodynamically optimizing, within limits, this configuration. As the Shuttle program developed and the sensitivities of the vehicle to aerodynamics were better understood the requirements of the aerodynamic data base grew. Adequately characterizing the vehicle to support the various design studies exploded the size of the data base to proportions that created a data modeling/management challenge for the aerodynamicist. The ascent aerodynamic data base originated primarily from wind tunnel test results. The complexity of the configuration rendered conventional analytic methods of little use. Initial wind tunnel tests provided results which included undesirable effects from model support tructure, inadequate element proximity, and inadequate plume simulation. The challenge to improve the quality of test results by determining the extent of these undesirable effects and subsequently develop testing techniques to eliminate them was imposed on the aerodynamic community. The challenges to the ascent aerodynamics community documented are unique due to the aerodynamic complexity of the Shuttle launch. Never before was such a complex vehicle aerodynamically characterized. The challenges were met with innovative engineering analyses/methodology development and wind tunnel testing techniques.

  9. Corticomuscular coherence variation throughout the gait cycle during overground walking and ramp ascent: A preliminary investigation.

    Science.gov (United States)

    Winslow, Anna T; Brantley, Justin; Zhu, Fangshi; Contreras Vidal, Jose L; Huang, He

    2016-08-01

    Recent designs of neural-machine interfaces (NMIs) incorporating electroencephalography (EEG) or electromyography (EMG) have been used in lower limb assistive devices. While the results of previous studies have shown promise, a NMI which takes advantage of early movement-related EEG activity preceding movement onset, as well as the improved signal-to-noise ratio of EMG, could prove to be more accurate and responsive than current NMI designs based solely on EEG or EMG. Previous studies have demonstrated that the activity of the sensorimotor cortex is coupled to the firing rate of motor units in lower limb muscles during voluntary contraction. However, the exploration of corticomuscular coherence during locomotive tasks has been limited. In this study, coupling between the motor cortex and right tibialis anterior muscle activity was preliminarily investigated during self-paced over-ground walking and ramp ascent. EEG at the motor cortex and surface EMG from the tibialis anterior were collected from one able-bodied subject. Coherence between the two signals was computed and studied across gait cycles. The EEG activity led the EMG activity in the low gamma band in swing phase of level ground walking and in stance phase of ramp ascent. These results may inform the future design of EEG-EMG multimodal NMIs for lower limb devices that assist locomotion of people with physical disabilities.

  10. Orion Guidance and Control Ascent Abort Algorithm Design and Performance Results

    Science.gov (United States)

    Proud, Ryan W.; Bendle, John R.; Tedesco, Mark B.; Hart, Jeremy J.

    2009-01-01

    During the ascent flight phase of NASA s Constellation Program, the Ares launch vehicle propels the Orion crew vehicle to an agreed to insertion target. If a failure occurs at any point in time during ascent then a system must be in place to abort the mission and return the crew to a safe landing with a high probability of success. To achieve continuous abort coverage one of two sets of effectors is used. Either the Launch Abort System (LAS), consisting of the Attitude Control Motor (ACM) and the Abort Motor (AM), or the Service Module (SM), consisting of SM Orion Main Engine (OME), Auxiliary (Aux) Jets, and Reaction Control System (RCS) jets, is used. The LAS effectors are used for aborts from liftoff through the first 30 seconds of second stage flight. The SM effectors are used from that point through Main Engine Cutoff (MECO). There are two distinct sets of Guidance and Control (G&C) algorithms that are designed to maximize the performance of these abort effectors. This paper will outline the necessary inputs to the G&C subsystem, the preliminary design of the G&C algorithms, the ability of the algorithms to predict what abort modes are achievable, and the resulting success of the abort system. Abort success will be measured against the Preliminary Design Review (PDR) abort performance metrics and overall performance will be reported. Finally, potential improvements to the G&C design will be discussed.

  11. Controlled weather balloon ascents and descents for atmospheric research and climate monitoring

    Science.gov (United States)

    Kräuchi, Andreas; Philipona, Rolf; Romanens, Gonzague; Hurst, Dale F.; Hall, Emrys G.; Jordan, Allen F.

    2016-03-01

    In situ upper-air measurements are often made with instruments attached to weather balloons launched at the surface and lifted into the stratosphere. Present-day balloon-borne sensors allow near-continuous measurements from the Earth's surface to about 35 km (3-5 hPa), where the balloons burst and their instrument payloads descend with parachutes. It has been demonstrated that ascending weather balloons can perturb the air measured by very sensitive humidity and temperature sensors trailing behind them, particularly in the upper troposphere and lower stratosphere (UTLS). The use of controlled balloon descent for such measurements has therefore been investigated and is described here. We distinguish between the single balloon technique that uses a simple automatic valve system to release helium from the balloon at a preset ambient pressure, and the double balloon technique that uses a carrier balloon to lift the payload and a parachute balloon to control the descent of instruments after the carrier balloon is released at preset altitude. The automatic valve technique has been used for several decades for water vapor soundings with frost point hygrometers, whereas the double balloon technique has recently been re-established and deployed to measure radiation and temperature profiles through the atmosphere. Double balloon soundings also strongly reduce pendulum motion of the payload, stabilizing radiation instruments during ascent. We present the flight characteristics of these two ballooning techniques and compare the quality of temperature and humidity measurements made during ascent and descent.

  12. Evaluation of a Powered Ankle-Foot Prosthesis during Slope Ascent Gait.

    Directory of Open Access Journals (Sweden)

    Christopher A Rábago

    Full Text Available Passive prosthetic feet lack active plantarflexion and push-off power resulting in gait deviations and compensations by individuals with transtibial amputation (TTA during slope ascent. We sought to determine the effect of active ankle plantarflexion and push-off power provided by a powered prosthetic ankle-foot (PWR on lower extremity compensations in individuals with unilateral TTA as they walked up a slope. We hypothesized that increased ankle plantarflexion and push-off power would reduce compensations commonly observed with a passive, energy-storing-returning prosthetic ankle-foot (ESR. We compared the temporal spatial, kinematic, and kinetic measures of ten individuals with TTA (age: 30.2 ± 5.3 yrs to matched abled-bodied (AB individuals during 5° slope ascent. The TTA group walked with an ESR and separately with a PWR. The PWR produced significantly greater prosthetic ankle plantarflexion and push-off power generation compared to an ESR and more closely matched AB values. The PWR functioned similar to a passive ESR device when transitioning onto the prosthetic limb due to limited prosthetic dorsiflexion, which resulted in similar deviations and compensations. In contrast, when transitioning off the prosthetic limb, increased ankle plantarflexion and push-off power provided by the PWR contributed to decreased intact limb knee extensor power production, lessening demand on the intact limb knee.

  13. Evaluation of a Powered Ankle-Foot Prosthesis during Slope Ascent Gait.

    Science.gov (United States)

    Rábago, Christopher A; Aldridge Whitehead, Jennifer; Wilken, Jason M

    2016-01-01

    Passive prosthetic feet lack active plantarflexion and push-off power resulting in gait deviations and compensations by individuals with transtibial amputation (TTA) during slope ascent. We sought to determine the effect of active ankle plantarflexion and push-off power provided by a powered prosthetic ankle-foot (PWR) on lower extremity compensations in individuals with unilateral TTA as they walked up a slope. We hypothesized that increased ankle plantarflexion and push-off power would reduce compensations commonly observed with a passive, energy-storing-returning prosthetic ankle-foot (ESR). We compared the temporal spatial, kinematic, and kinetic measures of ten individuals with TTA (age: 30.2 ± 5.3 yrs) to matched abled-bodied (AB) individuals during 5° slope ascent. The TTA group walked with an ESR and separately with a PWR. The PWR produced significantly greater prosthetic ankle plantarflexion and push-off power generation compared to an ESR and more closely matched AB values. The PWR functioned similar to a passive ESR device when transitioning onto the prosthetic limb due to limited prosthetic dorsiflexion, which resulted in similar deviations and compensations. In contrast, when transitioning off the prosthetic limb, increased ankle plantarflexion and push-off power provided by the PWR contributed to decreased intact limb knee extensor power production, lessening demand on the intact limb knee.

  14. Interaction of coeval felsic and mafic magmas from the Kanker granite, Pithora region, Bastar Craton, Central India

    Science.gov (United States)

    Elangovan, R.; Krishna, Kumar; Vishwakarma, Neeraj; Hari, K. R.; Ram Mohan, M.

    2017-10-01

    Field and petrographic studies are carried out to characterize the interactions of mafic and felsic magmas from Pithora region of the northeastern part of the Bastar Craton. The MMEs, syn-plutonic mafic dykes, cuspate contacts, magmatic flow textures, mingling and hybridization suggest the coeval emplacement of end member magmas. Petrographic evidences such as disequilibrium assemblages, resorption textures, quartz ocelli, rapakivi and poikilitic textures suggest magma mingling and mixing phenomena. Such features of mingling and mixing of the felsic and mafic magma manifest the magma chamber processes. Introduction of mafic magmas into the felsic magmas before initiation of crystallization of the latter, results in hybrid magmas under the influence of thermal and chemical exchange. The mechanical exchange occurs between the coexisting magmas due to viscosity contrast, if the mafic magma enters slightly later into the magma chamber, then the felsic magma starts to crystallize. Blobs of mafic magma form as MMEs in the felsic magma and they scatter throughout the pluton due to convection. At a later stage, if mafic magma enters the system after partial crystallization of felsic phase, mechanical interaction between the magmas leads to the formation of fragmented dyke or syn-plutonic mafic dyke. All these features are well-documented in the study area. Field and petrographic evidences suggest that the textural variations from Pithora region of Bastar Craton are the outcome of magma mingling, mixing and hybridization processes.

  15. A Holistic Model That Physicochemically Links Iron Oxide - Apatite and Iron Oxide - Copper - Gold Deposits to Magmas

    Science.gov (United States)

    Simon, A. C.; Reich, M.; Knipping, J.; Bilenker, L.; Barra, F.; Deditius, A.; Lundstrom, C.; Bindeman, I. N.

    2015-12-01

    Iron oxide-apatite (IOA) and iron oxide-copper-gold deposits (IOCG) are important sources of their namesake metals and increasingly for rare earth metals in apatite. Studies of natural systems document that IOA and IOCG deposits are often spatially and temporally related with one another and coeval magmatism. However, a genetic model that accounts for observations of natural systems remains elusive, with few observational data able to distinguish among working hypotheses that invoke meteoric fluid, magmatic-hydrothermal fluid, and immiscible melts. Here, we use Fe and O isotope data and high-resolution trace element (e.g., Ti, V, Mn, Al) data of individual magnetite grains from the world-class Los Colorados (LC) IOA deposit in the Chilean Iron Belt to elucidate the origin of IOA and IOCG deposits. Values of d56Fe range from 0.08‰ to 0.26‰, which are within the global range of ~0.06‰ to 0.5‰ for magnetite formed at magmatic conditions. Values of δ18O for magnetite and actinolite are 2.04‰ and 6.08‰, respectively, consistent with magmatic values. Ti, V, Al, and Mn are enriched in magnetite cores and decrease systematically from core to rim. Plotting [Al + Mn] vs. [Ti + V] indicates that magnetite cores are consistent with magmatic and/or magmatic-hydrothermal (i.e., porphyry) magnetites. Decreasing Al, Mn, Ti, V is consistent with a cooling trend from porphyry to Kiruna to IOCG systems. The data from LC are consistent with the following new genetic model for IOA and IOCG systems: 1) magnetite cores crystallize from silicate melt; 2) these magnetite crystals are nucleation sites for aqueous fluid that exsolves and scavenges inter alia Fe, P, S, Cu, Au from silicate melt; 3) the magnetite-fluid suspension is less dense that the surrounding magma, allowing ascent; 4) as the suspension ascends, magnetite grows in equilibrium with the fluid and takes on a magmatic-hydrothermal character (i.e., lower Al, Mn, Ti, V); 5) during ascent, magnetite, apatite and

  16. Magma Energy Research Project. Project summary, July 1, 1974--June 30, 1975

    Energy Technology Data Exchange (ETDEWEB)

    Colp, J.L.; Davis, M.J.; Graeber, E.J.; Hardee, H.C.

    1976-03-01

    The objective of the Magma Energy Research Project now under way at Sandia Laboratories is to investigate the feasibility of extracting energy directly from deeply buried circulating magma sources. Project plans describe a concept whereby a fully closed heat exchanger system is inserted directly into such a magma source to allow the heat energy to be brought to the surface with minimal environmental impact. A summary of previous efforts is given. The achievements and future plans for source location and definition, source tapping, magma characterization, magma materials compatibilities studies, and energy extraction studies are outlined. (LBS)

  17. Seismological evidence for Lateral magma intrusion during the July 1978 deflation of the Krafla volcano in NE-Iceland

    Energy Technology Data Exchange (ETDEWEB)

    Einarsson, Pall; Brandsdottir, Bryndis

    1978-07-01

    The July 1978 deflation of the Krafla volcano in the volcanic rift zone of NE-Iceland was in most respects typical of the many deflation events that have occurred at Krafla since December 1975. Separated by periods of slow inflation, the deflation events are characterized by rapid subsidence in the caldera region, volcanic tremor and extensive rifting in the fault swarm that transects the volcano. Earthquakes increase in the caldera region shortly after deflation starts and propagate along the fault swarm away from the central part of the volcano, sometimes as far as 65 km. The deflation events are interpreted as the result of subsurface magmatic movements, when magma from the Krafla reservoir is injected laterally into the fault swarm to form a dyke. In the July 1978 event magma was injected a total distance of 30 km into the northern fault swarm. The dyke tip propagated with the velocity of 0.4-0.5 m/sec during the first 9 hours, but the velocity decreased as the length of the dyke increased. Combined with surface deformation data, these data can be used to estimate the cross sectional area of the dyke and the driving pressure of the magma. The cross sectional area is variable along the dyke and is largest in the regions of maximum earthquake activity. The average value is about 1200 m{sup 2}. The pressure difference between the magma reservoir and the dyke tip was of the order of 10-40 bars and did not change much during the injection.

  18. Degassing and magma mixing during the eruption of Surtsey Volcano (Iceland, 1963-1967): the signatures of a dynamic and discrete rift propagation event

    Science.gov (United States)

    Schipper, C. Ian; Le Voyer, Marion; Moussallam, Yves; White, James D. L.; Thordarson, Thor; Kimura, Jun-Ichi; Chang, Qing

    2016-04-01

    The eruption of Surtsey (Iceland, 1963-1967) is a rare example of observed volcanism at a propagating rift tip, where Iceland's Eastern Volcanic Zone is advancing southwesterly toward the Reykjanes Ridge. We use olivine-hosted melt inclusions, embayments, and matrix glasses to investigate major element, trace element, and volatile characteristics of Surtsey's magmatic system, and to parameterize decompression models that describe degassing of C-H-S-O species during this well-studied eruption. Major elements show that the inclusions represent heterogeneous melts with a range of compositions similar to those of Icelandic lavas. Trace elements discriminate between two groups of inclusions: the majority are compositionally similar to Eastern Volcanic Zone alkalic basalts, and the remainder are notably more depleted in incompatible trace elements and trend toward fields defined by tholeiites on and around Iceland. Strongly correlated Cl and Nb for all inclusions indicates that seawater did not affect Surtsey's volatile budget, despite having clearly affected its eruption style. Both types of inclusions are volatile rich (≤1.47 wt.% H2O; ≤2534 ppm CO2 as measured or ≤5286 ppm once corrected for vapor bubbles and post-entrapment crystallization). They are more hydrous than primary melts in the onshore Eastern Volcanic Zone and have parental CO2/Nb (≤590) at the upper end of regional estimates. Saturation pressures calculated from corrected CO2 values indicate that melts in both inclusion types initially crystallized at similar depths in the upper mantle (17-21 km), and then partially crystallized during ascent through the lower crust (7-13 km). Historical data show that gases emitted on Surtsey shifted from being relatively reduced in 1964/1965 to more oxidized in 1967, after a protracted period of effusive activity and resurgence of pyroclastic activity from satellite vents. Closed-system degassing models predict the compositions and redox states of the 1964

  19. Parametric investigation of a brine lens formation above degassing magma chamber

    Science.gov (United States)

    Afanasyev, Andrey; Melnik, Oleg; Utkin, Ivan; Tsvetkova, Yulia

    2017-04-01

    Formation of porphyry-type ore deposits is associated with degassing of crustal magma chambers. Saline, metal-rich magmatic fluid penetrates into a shallow region saturated with cold meteoric water where the metals concentrate in brine lenses. The formation of the lenses and, thus, of the deposits occurs due to phase transitions [1]. The evaporation of H2O results in enrichment of residual fluid in NaCl. At a depth of 1-2 km precipitation of solid halite blocks the pore space and facilitates formation of concentrated brine lenses. In order to investigate lens formation, we developed an extension of our multiphase simulator MUFITS [2] for NaCl-H2O mixture flows. We applied the code in a simple axisymmetric scenario with a high permeability zone in the central part of the domain surrounded by low permeable rocks. The high permeability zone simulates a volcanic conduit above a magma body. The degassing of magma is simulated with a point source of hot supercritical fluid that ascends rapidly up the conduit, undergoing phase transitions en route. Evaporation and rapid ascend of vapor results in increasing from bottom to top salinity of the fluid. As temperature and pressure decline closer to the surface, solid halite precipitates blocking the conduit. Convection of meteoric water in surrounding rocks favors compact location of the brine lens beneath the region of precipitation. Typical temperature in the lens is 450-550°C and overpressure above lithostatic is a few MPa. We conducted a parametric analysis, investigating the influence of model parameters on accumulation of halite and metals. We found that a higher permeability in the conduit, a smaller permeability in the surrounding rocks and a higher salinity of magmatic fluid favor larger lenses. A smaller magmatic fluid temperature T , i.e. temperature in the chamber, results in a smaller lens that disappears abruptly at a threshold value Ta≈ 650˚ C, and it does not form at T Ta the lens parameters are most

  20. Evolution of the magma feeding system during a Plinian eruption: The case of Pomici di Avellino eruption of Somma-Vesuvius, Italy

    Science.gov (United States)

    Massaro, S.; Costa, A.; Sulpizio, R.

    2018-01-01

    The current paradigm for volcanic eruptions is that magma erupts from a deep magma reservoir through a volcanic conduit, typically modelled with fixed rigid geometries such as cylinders. This simplistic view of a volcanic eruption does not account for the complex dynamics that usually characterise a large explosive event. Numerical simulations of magma flow in a conduit combined with volcanological and geological data, allow for the first description of a physics-based model of the feeding system evolution during a sustained phase of an explosive eruption. The method was applied to the Plinian phase of the Pomici di Avellino eruption (PdA, 3945 ±10 cal yr BP) from Somma-Vesuvius (Italy). Information available from volcanology, petrology, and lithology studies was used as input data and as constraints for the model. In particular, Mass Discharge Rates (MDRs) assessed from volcanological methods were used as target values for numerical simulations. The model solutions, which are non-unique, were constrained using geological and volcanological data, such as volume estimates and types of lithic components in the fall deposits. Three stable geometric configurations of the feeding system (described assuming elliptical cross-section of variable dimensions) were assessed for the Eruptive Units 2 and 3 (EU2, EU3), which form the magmatic Plinian phase of PdA eruption. They describe the conduit system geometry at time of deposition of EU2 base, EU2 top, and EU3. A 7-km deep dyke (length 2 a = 200-4 00 m, width 2 b = 10- 12 m), connecting the magma chamber to the surface, characterised the feeding system at the onset of the Plinian phase (EU2 base). The feeding system rapidly evolved into hybrid geometric configuration, with a deeper dyke (length 2 a = 600- 800 m, width 2 b = 50 m) and a shallower cylindrical conduit (diameter D = 50 m, dyke-to-cylinder transition depth ∼2100 m), during the eruption of the EU2 top. The deeper dyke reached the dimensions of 2 a = 2000 m and

  1. Feasibility of a magma ocean dynamo on Mars

    Science.gov (United States)

    Helffrich, George

    2017-12-01

    Crustal magnetization of rocks in regions of Mars surface testifies to an era of dynamo activity. I examine the possibility that the dynamo that operated then, in the first 400-600 Ma after Mars formed, was powered by a crystallizing subsurface magma ocean. Of the ways that a magma ocean dynamo could operate, on Mars only turbulent and magnetostrophic dynamos seem feasible; geostrophic dynamos do not seem so unless very high heat flows, 100-1000 times present, are invoked. Given the anticipated information from the future InSight lander mission, it will be difficult to assess where the dynamo originated unless an inner core is discovered, rendering the dynamo likely to have operated in the core. [Figure not available: see fulltext.

  2. What can Fe stable isotopes tell us about magmas?

    DEFF Research Database (Denmark)

    Stausberg, Niklas

    in magmas, Fe. Fe isotope compositions of magmatic rocks exhibit systematic differences, where the heaviest compositions are found in rhyolites and granites. Understanding of these systematics is complicated by a lack of constraints on Fe isotope fractionation among minerals and liquids under magmatic...... the differentiation of magmas from the perspective of Fe stable isotopes, integrated with petrology, by studying igneous rocks and their constituent phases (minerals and glasses) from the Bushveld Complex, South Africa, Thingmuli, Iceland, Pantelleria, Italy, and the Bishop Tuff, USA. The findings are interpreted...... in terms of available theory, experiments and forward modeling incorporating petrologic constraints. Mafic cumulate rocks from the Bushveld Complex exhibit resolvable whole rock Fe isotopic variation with modal mineralogy and mineral composition, to a 1st order reflecting partitioning of Fe3+ and Fe2...

  3. Oxygen regime of Siberian alkaline-ultramafic magmas

    Science.gov (United States)

    Ryabchikov, Igor; Kogarko, Liya

    2017-04-01

    Regimes of S2 and O2 are decisive factors controlling behavior of chalcophile and siderophile elements in magmatic processes. These parameters play important role during magmagenesis and in the course of crystallization and fluid mass transfer in magma chamber. Alkaline-ultramafic magmatism in Maymecha-Kotuy Province (Polar Siberia) is represented by giant intrusive complexes as well as by volcanics and dyke rocks, which include a well-known variety - meimechites. The latter are considered primary magmas of alkaline-ultramafic plutons in the region like for instance Guli intrusive complex. Sulfur content in primitive magmas estimated from the analyses of melt inclusions in olivine megacrysts from meimechites is close to 0.1 %. fO2 values calculated using olivine+clinopyroxene+spinel and spinel+melt oxygen barometers (1, 2) are 2-3 log units above QFM buffer. The relatively high oxygen potential at the early magmatic stage of alkaline-ultramafic Guli pluton provide predominance of sulfates among other forms of sulfur in the melt. This leads to the almost complete absence of sulfides in highly magnesian rocks. The oxidizing conditions exert important effect on behavior of many ore metals. At the stage of magma generation absence of sulfides in mantle materialresults in the presence of siderophile elements in metallic form and saturation of primary magmas in respect of metallic phases at an early stage of injection of the melt into the magma chamber. Later, under favorable circumstances during magma crystallization nuggets of precious metals may be formed. During further evolution of magmatic system fO2 and activity of oxidized sulfur decrease due to intensive crystallization of magnetite during the formation of koswites, then oxygen fugacity becomes even lower as a result serpentinization at a postmagmatic stage. These serpentization processes are caused by the displacement of reactions in the aqueous phase due to cooling towards the formation of methane and other

  4. MAGMA: Generalized Gene-Set Analysis of GWAS Data

    Science.gov (United States)

    de Leeuw, Christiaan A.; Mooij, Joris M.; Heskes, Tom; Posthuma, Danielle

    2015-01-01

    By aggregating data for complex traits in a biologically meaningful way, gene and gene-set analysis constitute a valuable addition to single-marker analysis. However, although various methods for gene and gene-set analysis currently exist, they generally suffer from a number of issues. Statistical power for most methods is strongly affected by linkage disequilibrium between markers, multi-marker associations are often hard to detect, and the reliance on permutation to compute p-values tends to make the analysis computationally very expensive. To address these issues we have developed MAGMA, a novel tool for gene and gene-set analysis. The gene analysis is based on a multiple regression model, to provide better statistical performance. The gene-set analysis is built as a separate layer around the gene analysis for additional flexibility. This gene-set analysis also uses a regression structure to allow generalization to analysis of continuous properties of genes and simultaneous analysis of multiple gene sets and other gene properties. Simulations and an analysis of Crohn’s Disease data are used to evaluate the performance of MAGMA and to compare it to a number of other gene and gene-set analysis tools. The results show that MAGMA has significantly more power than other tools for both the gene and the gene-set analysis, identifying more genes and gene sets associated with Crohn’s Disease while maintaining a correct type 1 error rate. Moreover, the MAGMA analysis of the Crohn’s Disease data was found to be considerably faster as well. PMID:25885710

  5. Apatite: a new redox proxy for silicic magmas?

    OpenAIRE

    Miles, A.J.; Graham, C M; Hawkesworth, C.J.; Gillespie, M.R.; Hinton, R.W.; Bromiley, G.D.

    2014-01-01

    The oxidation states of magmas provide valuable information about the release and speciation of volatile elements during volcanic eruptions, metallogenesis, source rock compositions, open system magmatic processes, tectonic settings and potentially titanium (Ti) activity in chemical systems used for Ti-dependent geothermometers and geobarometers. In this paper we explore the use of Mn in apatite as an oxybarometer in intermediate and silicic igneous rocks. Increased Mn concentrations in apati...

  6. The chlorine isotope fingerprint of the lunar magma ocean.

    Science.gov (United States)

    Boyce, Jeremy W; Treiman, Allan H; Guan, Yunbin; Ma, Chi; Eiler, John M; Gross, Juliane; Greenwood, James P; Stolper, Edward M

    2015-09-01

    The Moon contains chlorine that is isotopically unlike that of any other body yet studied in the Solar System, an observation that has been interpreted to support traditional models of the formation of a nominally hydrogen-free ("dry") Moon. We have analyzed abundances and isotopic compositions of Cl and H in lunar mare basalts, and find little evidence that anhydrous lava outgassing was important in generating chlorine isotope anomalies, because (37)Cl/(35)Cl ratios are not related to Cl abundance, H abundance, or D/H ratios in a manner consistent with the lava-outgassing hypothesis. Instead, (37)Cl/(35)Cl correlates positively with Cl abundance in apatite, as well as with whole-rock Th abundances and La/Lu ratios, suggesting that the high (37)Cl/(35)Cl in lunar basalts is inherited from urKREEP, the last dregs of the lunar magma ocean. These new data suggest that the high chlorine isotope ratios of lunar basalts result not from the degassing of their lavas but from degassing of the lunar magma ocean early in the Moon's history. Chlorine isotope variability is therefore an indicator of planetary magma ocean degassing, an important stage in the formation of terrestrial planets.

  7. Deep degassing and the eruptibility of flood basalt magmas

    Science.gov (United States)

    Black, B. A.; Manga, M.

    2015-12-01

    Individual flood basalt lavas often exceed 103 km3 in volume, and many such lavas erupt during emplacement of flood basalt provinces. The large volume of individual flood basalt lavas demands correspondingly large magma reservoirs within or at the base of the crust. To erupt, some fraction of this magma must become buoyant and overpressure must be sufficient to encourage failure and dike propagation. Because the overpressure associated with a new injection of magma is inversely proportional to the total reservoir volume, buoyancy overpressure has been proposed as a trigger for flood basalt eruptions. To test this hypothesis, we develop a new one-dimensional model for buoyancy overpressure-driven eruptions that combines volatile exsolution, bubble growth and rise, assimilation, and permeable fluid escape through the surrounding country rocks. Degassing during emplacement of flood basalt provinces may have major environmental repercussions. We investigate the temporal evolution of permeable degassing through the crust and degassing during eruptive episodes. We find that assimilation of volatile-rich country rocks strongly enhances flood basalt eruptibility, implying that the eruptive dynamics of flood basalts may be intertwined with their climatic consequences.

  8. Flow mechanism and viscosity in basaltic magma chambers

    Science.gov (United States)

    Nicolas, A.; Ildefonse, B.

    Magmatic flow in the dense suspension of crystallizing gabbros below the free surface of basaltic magma chambers is considered from the point of view of flow mechanisms and rheology. Hyperdense suspensions (˜20% melt fraction) may arise if flat plagioclase crystals develop a strong preferred orientation induced by magmatic flow. With the help of Nomarski differential interference contrast and back scattered electron figures, we show that suspension flow is possible even for smaller melt fractions if impingements between moving crystals are reduced by chemical dissolution at their contact points. This dissolution process is rate controlling. With strain rates near 10-9 s-1 and viscosities near 1014-16 Pa.s, such crystalline mushes should be closer to plastically deforming solids than to the overlying basaltic suspension. If we characterize magma chambers by suspension flow, no matter how small the melt fraction, magma chambers below oceanic fast spreading centers should not be restricted to a perched melt lens, but should extend to the Moho and comprise the entire volume of observed strong seismic attenuation.

  9. The shallow magma chamber of Stromboli Volcano (Italy)

    Science.gov (United States)

    Patanè, D.; Barberi, G.; De Gori, P.; Cocina, O.; Zuccarello, L.; Garcia-Yeguas, A.; Castellano, M.; D'Alessandro, A.; Sgroi, T.

    2017-07-01

    In this work, we integrate artificial and natural seismic sources data to obtain high-resolution images of the shallow inner structure of Stromboli Volcano. Overall, we used a total of 21,953 P readings from an active seismic experiment and an additional 2731 P and 992 S readings deriving from 269 local events. The well-defined Vp, Vs, and Vp/Vs tomograms have highlighted the following: (i) the region where magma cumulates at shallow depths (2-4 km below sea level (bsl)), forming an elongated NE-SW high-velocity body (Vp ≥ 6.0 km/s and Vs ≥ 3.5 km/s), with a very fast velocity core (6.5 ≤ Vp vertical pipe-like structures, characterized by relatively high P velocities values, mainly linked to past activity (e.g., Strombolicchio); and (iii) a near-vertical pipe-like volume with high Vp/Vs (1.78 ÷ 1.85), located beneath to the craters (down to 1.0 km bsl), overlying a deeper region (1.0 to 3.0 km bsl) with low Vp/Vs (1.64 ÷ 1.69), interpreted as the actual and preferential pathway of magma toward the surface. Our results demonstrate the importance of combining passive and active seismic data to improve, in a tomographic inversion, the resolution of the volcanic structures and to discover where magma may be stored.

  10. Design of Launch Vehicle Flight Control Systems Using Ascent Vehicle Stability Analysis Tool

    Science.gov (United States)

    Jang, Jiann-Woei; Alaniz, Abran; Hall, Robert; Bedossian, Nazareth; Hall, Charles; Jackson, Mark

    2011-01-01

    A launch vehicle represents a complicated flex-body structural environment for flight control system design. The Ascent-vehicle Stability Analysis Tool (ASAT) is developed to address the complicity in design and analysis of a launch vehicle. The design objective for the flight control system of a launch vehicle is to best follow guidance commands while robustly maintaining system stability. A constrained optimization approach takes the advantage of modern computational control techniques to simultaneously design multiple control systems in compliance with required design specs. "Tower Clearance" and "Load Relief" designs have been achieved for liftoff and max dynamic pressure flight regions, respectively, in the presence of large wind disturbances. The robustness of the flight control system designs has been verified in the frequency domain Monte Carlo analysis using ASAT.

  11. An indefinite ascent towards God. The mystical landscape of Fray Guillermo Butler

    Directory of Open Access Journals (Sweden)

    Valeria Nougues

    2015-04-01

    Full Text Available At work I intend to develop a short life journey of Brother William Butler op, emphasizing basic choices for which he devoted his life to preaching the mystery of God through art, demonstrating the freedom of the Spirit in their aesthetic choice and the way inserted in the construction of national identity in the early twentieth century. From the analysis of some of his writings and art criticism, I will develop an outline of theological hermeneutics called “Mystical landscape” of Butler, as was described aptly by critics of the time, to stop reading any of his works in which the author invites us, through the aesthetic and symbolic language, to an indefinite ascent towards God.

  12. Wallops Low Elevation Link Analysis for the Constellation Launch/Ascent Links

    Science.gov (United States)

    Cheung, Keith; Ho, C.; Kantak, A.; Lee, C.; Tye, R.; Richards, E.; Sham, C.; Schlesinger, A.; Barritt, B.

    2011-01-01

    To execute the President's Vision for Space Exploration, the Constellation Program (CxP) was formed to build the next generation spacecraft Orion and launch vehicles Ares, to transport human and cargo to International Space Station (ISS), moon, and Mars. This paper focuses on the detailed link analysis for Orion/Ares s launch and ascent links with Wallops 11.3m antenna (1) Orion's Dissimilar Voice link: 10.24 Kbps, 2-way (2) Ares Developmental Flight Instrument link, 20 Mbps, downlink. Three launch trajectories are considered: TD7-E, F (Feb), and G (Aug). In certain launch scenarios, the critical events of main engine cutoff (MECO) and Separation occur during the low elevation regime of WFF s downrange -- less than 5 degree elevation angle. The goal of the study is to access if there is enough link margins for WFF to track the DV and DFI links.

  13. A real-time guidance algorithm for aerospace plane optimal ascent to low earth orbit

    Science.gov (United States)

    Calise, A. J.; Flandro, G. A.; Corban, J. E.

    1989-01-01

    Problems of onboard trajectory optimization and synthesis of suitable guidance laws for ascent to low Earth orbit of an air-breathing, single-stage-to-orbit vehicle are addressed. A multimode propulsion system is assumed which incorporates turbojet, ramjet, Scramjet, and rocket engines. An algorithm for generating fuel-optimal climb profiles is presented. This algorithm results from the application of the minimum principle to a low-order dynamic model that includes angle-of-attack effects and the normal component of thrust. Maximum dynamic pressure and maximum aerodynamic heating rate constraints are considered. Switching conditions are derived which, under appropriate assumptions, govern optimal transition from one propulsion mode to another. A nonlinear transformation technique is employed to derived a feedback controller for tracking the computed trajectory. Numerical results illustrate the nature of the resulting fuel-optimal climb paths.

  14. An optimal Space Shuttle ascent trajectory for the first orbital flight test

    Science.gov (United States)

    Johnson, I. L., Jr.

    1977-01-01

    An optimal solution of the ascent trajectory of the Space Shuttle for the first orbital flight test is presented; the optimization is a minimum propellant, four-control problem in yaw angle, roll angle, pitch angle and vacuum thrust of each Space Shuttle main engine. Piecewise linear segments with juncture points treated as parameters are employed to model the controls. Equations of motion for a three-dimensional flight with pitch plane moment balance about an oblate are integrated numerically with a fourth-order Runge-Kutta method; two- and one-dimensional cubic spline function curve fits of aerodynamic coefficients are used during the first and second stages, respectively. The constraint minimization problem is solved with the Davidon-Fletcher-Powell function method.

  15. Shuttle STS-2 mission communication systems RF coverage and performance predictions. Volume 1: Ascent

    Science.gov (United States)

    Porter, J. A.; Gibson, J. S.; Kroll, Q. D.; Loh, Y. C.

    1981-10-01

    The RF communications capabilities and nominally expected performance for the ascent phase of the second orbital flight of the shuttle are provided. Predicted performance is given mainly in the form of plots of signal strength versus elapsed mission time for the STDN (downlink) and shuttle orbiter (uplink) receivers for the S-band PM and FM, and UHF systems. Performance of the NAV and landing RF systems is treated for RTLS abort, since in this case the spacecraft will loop around and return to the launch site. NAV and landing RF systems include TACAN, MSBLS, and C-band altimeter. Signal strength plots were produced by a computer program which combines the spacecraft trajectory, antenna patterns, transmit and receive performance characteristics, and system mathematical models. When available, measured spacecraft parameters were used in the predictions; otherwise, specified values were used. Specified ground station parameter values were also used. Thresholds and other criteria on the graphs are explained.

  16. The Ascent of Educational Psychology in Denmark in the Interwar Years

    DEFF Research Database (Denmark)

    Hamre, Bjørn; Ydesen, Christian

    2014-01-01

    and deviation in particular. The establishment of the educational psychologist’s office at Frederiksberg in Denmark, the introduction of IQ testing, and the related psychological files of students provide an image of a period of measurement in schools during which IQ testing was decisive in decisions...... to transfer students to the remedial school. The testing and filing were the foremost important technologies of the period. We draw on sources that allow us to view educational psychology and testing in their local, national, and political context. The sources applied are primarily obtained from Frederiksberg......In this article, we argue that an understanding of the interwar years and the ascent of educational psychology contribute valuable knowledge about the inner workings of modern-day education with regard to the links between society and education in general and the boundary between normality...

  17. Differential Evolution Based Ascent Phase Trajectory Optimization for a Hypersonic Vehicle

    Science.gov (United States)

    Giri, Ritwik; Ghose, D.

    In this paper, a new method for the numerical computation of optimal, or nearly optimal, solutions to aerospace trajectory problems is presented. Differential Evolution (DE), a powerful stochastic real-parameter optimization algorithm is used to optimize the ascent phase of a hypersonic vehicle. The vehicle has to undergo large changes in altitude and associated aerodynamic conditions. As a result, its aerodynamic characteristics, as well as its propulsion parameters, undergo drastic changes. Such trajectory optimization problems can be solved by converting it to a non-linear programming (NLP) problem. One of the issues in the NLP method is that it requires a fairly large number of grid points to arrive at an optimal solution. Differential Evolution based algorithm, proposed in this paper, is shown to perform equally well with lesser number of grid points. This is supported by extensive simulation results.

  18. The Yellowstone magma reservoir is 50% larger than previously imaged

    Science.gov (United States)

    Farrell, J.; Smith, R. B.; Husen, S.

    2013-12-01

    Earlier tomographic studies of the Yellowstone crustal magma system have revealed a low P-wave crustal anomaly beneath the 0.64 Ma Yellowstone caldera that has been interpreted to be the magma reservoir of partial melt that provides the thermal energy for Yellowstone's youthful volcanic and hydrothermal systems. The Yellowstone seismic network has evolved over the last decade into a modern real-time volcano monitoring system that consists of 36 short-period, broadband, and borehole seismometers that cover the entire Yellowstone volcanic field and surrounding tectonic areas. Until recently, limited seismograph coverage did not provide for adequate resolution of the velocity structure northeast of the caldera, an area of the largest negative Bouguer gravity field of -60 mGal whose 3D density model reveals a shallow, low density body that extends ~20 km northeast of the caldera. Recent upgrades to the Yellowstone Seismic Network (YSN), including the addition of nine 3-component and broadband seismic stations providing much better ray coverage of the entire Yellowstone area with greater bandwidth data. This allows much-expanded and improved resolution coverage of the Yellowstone crustal velocity structure. We have compiled waveforms for the Yellowstone earthquake catalog from 1984-2011 with 45,643 earthquakes and 1,159,724 waveforms to analyze P-wave arrival times with an automatic picker based on an adaptive high-fidelity human mimicking algorithm. Our analysis reduced the data to the 4,520 best-located earthquakes with 48,622 P-wave arrival times to invert for the velocity structure. The resulting 3D P-wave model reveals a low Vp body (up to -7% ΔVp) that is interpreted to be the Yellowstone crustal magma reservoir and is ~50% larger than previously imaged. It extends as an oblong shaped anomalous body ~90 km NE-SW, ~20 km NE of the 0.64 Ma caldera, and up to 30 km wide and markedly shallowing from 15 km depth beneath the caldera to less than ~2 km deep northeast of

  19. Aerothermal Protuberance Heating Design and Test Configurations for Ascent Vehicle Design

    Science.gov (United States)

    Martin, Charles E.; Neumann, Richard D.; Freeman, Delma

    2010-01-01

    A series of tests were conducted to evaluate protuberance heating for the purposes of vehicle design and modification. These tests represent a state of the art approach to both testing and instrumentation for defining aerothermal protuberance effects on the protuberance and surrounding areas. The testing was performed with a number of wind tunnel entries beginning with the proof of concept "pathfinder" test in the Test Section 1 (TS1) tunnel in the Langley Unitary Plan Wind Tunnel (UPWT). The TS1 section (see Figures 1a and 1b) is a lower Mach number tunnel and the Test Section 2 (TS2) has overlapping and higher Mach number capability as showin in Figure 1c. The pathfinder concept was proven and testing proceeded for a series of protuberance tests using an existing splitter aluminum protuberance mounting plate, Macor protuberances, thin film gages, total temperature and pressure gages, Kulite pressure transducers, Infra-Red camera imaging, LASER velocimetry evaluations and the UPWT data collection system. A boundary layer rake was used to identify the boundary layer profile at the protuberance locations for testing and helped protuberance design. This paper discusses the techniques and instrumentation used during the protuberance heating tests performed in the UPWT in TS1 and TS2. Runs of the protuberances were made Mach numbers of 1.5, 2.16, 2.65, and 3.51. The data set generated from this testing is for ascent protuberance effects and is termed Protuberance Heating Ascent Data (PHAD) and this testing may be termed PHAD-1 to distinguish it from future testing of this type.

  20. A Densified Liquid Methane Delivery System for the Altair Ascent Stage

    Science.gov (United States)

    Tomsik, Thomas M.; Johnson, Wesley L.; Smudde, Todd D.; Femminineo, Mark F.; Schnell, Andrew R.

    2010-01-01

    The Altair Lunar Lander is currently carrying options for both cryogenic and hypergolic ascent stage propulsion modules. The cryogenic option uses liquid methane and liquid oxygen to propel Altair from the lunar surface back to rendezvous with the Orion command module. Recent studies have determined that the liquid methane should be densified by subcooling it to 93 K in order to prevent over-pressurization of the propellant tanks during the 210 day stay on the lunar surface. A trade study has been conducted to determine the preferred method of producing; loading, and maintaining the subcooled, densified liquid methane onboard Altair from a ground operations perspective. The trade study took into account the limitations in mass for the launch vehicle and the mobile launch platform as well as the historical reliability of various components and their thermal efficiencies. Several unique problems were encountered, namely delivering a small amount of a cryogenic propellant to a flight tank that is positioned over 350 ft above the launch pad as well as generating the desired delivery temperature of the methane at 93 K which is only 2.3 K above the methane triple point of 90.7 K. Over 20 methods of subcooled liquid methane production and delivery along with the associated system architectures were investigated to determine the best solutions to the problem. The top four cryogenic processing solutions were selected for further evaluation and detailed thermal modeling. This paper describes the results of the preliminary trade analysis of the 20 plus methane densification methods considered. The results of the detailed analysis will be briefed to the Altair Project Office and their propulsion team as well as the Ground Operations Project Office before the down-select is made between cryogenic and hypergolic ascent stages in August 2010.

  1. Transfer of volatiles and metals from mafic to felsic magmas in composite magma chambers: An experimental study

    Science.gov (United States)

    Guo, Haihao; Audétat, Andreas

    2017-02-01

    In order to determine the behavior of metals and volatiles during intrusion of mafic magma into the base of silicic, upper crustal magma chambers, fluid-rock partition coefficients (Dfluid/rock) of Li, B, Na, S, Cl, K, Mn, Fe, Rb, Sr, Ba, Ce, Cu, Zn, Ag, Cd, Mo, As, Se, Sb, Te, W, Tl, Pb and Bi were determined experimentally at 2 kbar and 850 °C close to the solidus of mafic magma. In a first step, volatile-bearing mafic glasses were prepared by melting a natural basaltic trachyandesite in the presence of volatile-bearing fluids at 1200 °C/10 kbar in piston cylinder presses. The hydrous glasses were then equilibrated in subsequent experiments at 850 °C/2 kbar in cold-seal pressure vessels, which caused 80-90% of the melt to crystallize. After 0.5-2.0 days of equilibration, the exsolved fluid was trapped by means of in-situ fracturing in the form of synthetic fluid inclusions in quartz. Both the mafic rock residue and the fluid inclusions were subsequently analyzed by laser-ablation ICP-MS for major and trace elements. Reverse experiments were conducted by equilibrating metal-bearing aqueous solutions with rock powder and then trapping the fluid. In two additional experiments, information on relative element mobilities were obtained by reacting fluids that exsolved from crystallizing mafic magma with overlying silicic melts. The combined results suggest that under the studied conditions S, Cl, Cu, Se, Br, Cd and Te are most volatile (Dfluid/rock >10), followed by Li, B, Zn, As, Ag, Sb, Cs, W, Tl, Pb and Bi (Dfluid/rock = 1-10). Less volatile are Na, Mg, K, Ca, Mn, Fe, Rb, Sr, Mo and Rb (Dfluid/rock 0.1-1), and the least fluid-mobile elements are Al, Si, Ti, Zr, Ba and Ce (Dfluid/rock apatite.

  2. Origin of magmas in subduction zones: a review of experimental studies.

    Science.gov (United States)

    Kushiro, Ikuo

    2007-02-01

    Studies of the origin of magmas in subduction zones, particularly in the Japanese island arc, have been significantly advanced by petrological, geochemical, geophysical and experimental studies during last 50 years. Kuno's original model(1)) for magma generation in the Japanese island arc, that tholeiite magmas are formed at relatively shallow levels in the mantle on the Pacific Ocean side whereas alkali basalt magmas are formed in deeper levels on the Japan Sea side, stimulated subsequent studies, particularly high-pressure experimental studies in which the author participated. Recent seismic tomographic studies of regions beneath the Japanese island arc demonstrate that seismic low-velocity zones where primary magmas are formed have finger-like shapes and rise obliquely from the Japan Sea side toward the Pacific Ocean side. Based on experimental studies, it is suggested that the compositions of primary magmas depend mainly on the H2O content and degree of melting in the melting zones, and that primary tholeiite magmas are formed by 10-25% melting of the source mantle containing less than 0.2 wt.% H2O. High-alumina basalt and alkali basalt magmas are formed by smaller degrees of melting of similar mantle, whereas primary boninite magmas are formed by more than 20% melting of the source mantle with more than 0.2 wt.% H2O, and finally, high-magnesia andesite magmas are formed by smaller degrees of melting of similar mantle.

  3. Anticipatory kinematics and muscle activity preceding transitions from level-ground walking to stair ascent and descent.

    Science.gov (United States)

    Peng, Joshua; Fey, Nicholas P; Kuiken, Todd A; Hargrove, Levi J

    2016-02-29

    The majority of fall-related accidents are during stair ambulation-occurring commonly at the top and bottom stairs of each flight, locations in which individuals are transitioning to stairs. Little is known about how individuals adjust their biomechanics in anticipation of walking-stair transitions. We identified the anticipatory stride mechanics of nine able-bodied individuals as they approached transitions from level ground walking to stair ascent and descent. Unlike prior investigations of stair ambulation, we analyzed two consecutive "anticipation" strides preceding the transitions strides to stairs, and tested a comprehensive set of kinematic and electromyographic (EMG) data from both the leading and trailing legs. Subjects completed ten trials of baseline overground walking and ten trials of walking to stair ascent and descent. Deviations relative to baseline were assessed. Significant changes in mechanics and EMG occurred in the earliest anticipation strides analyzed for both ascent and descent transitions. For stair descent, these changes were consistent with observed reductions in walking speed, which occurred in all anticipation strides tested. For stair ascent, subjects maintained their speed until the swing phase of the latest anticipation stride, and changes were found that would normally be observed for decreasing speed. Given the timing and nature of the observed changes, this study has implications for enhancing intent recognition systems and evaluating fall-prone or disabled individuals, by testing their abilities to sense upcoming transitions and decelerate during locomotion. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Interface pressure in transtibial socket during ascent and descent on stairs and its effect on patient satisfaction.

    Science.gov (United States)

    Ali, Sadeeq; Abu Osman, Noor Azuan; Eshraghi, Arezoo; Gholizadeh, Hossein; Abd Razak, Nasrul Anwar Bin; Wan Abas, Wan Abu Bakar Bin

    2013-01-01

    Transtibial amputees encounter stairs and steps during their daily activities. The excessive pressure between residual limb/socket may reduce the walking capability of transtibial prosthetic users during ascent and descent on stairs. The purposes of the research were to evaluate the interface pressure between Dermo (shuttle lock) and Seal-In X5 (prosthetic valve) interface systems during stair ascent and descent, and to determine their satisfaction effects on users. Ten amputees with unilateral transtibial amputation participated in the study. Interface pressure was recorded with F-socket transducer (9811E) during stair ascent and descent at self-selected speed. Each participant filled in a questionnaire about satisfaction and problems encountered with the use of the two interface systems. The resultant mean peak pressure (kPa) was significantly lower for the Dermo interface system compared to that of the Seal-In X5 interface system at the anterior, posterior and medial regions during stair ascent (63.14 vs. 80.14, 63.14 vs. 90.44, 49.21 vs. 66.04, respectively) and descent (67.11 vs. 80.41, 64.12 vs. 88.24, 47.33 vs. 65.11, respectively). Significant statistical difference existed between the two interface systems in terms of satisfaction and problems encountered (Pstair negotiation. The qualitative survey also showed that the prosthesis users experienced fewer problems and increased satisfaction with the Dermo interface system. © 2013. Published by Elsevier Ltd. All rights reserved.

  5. Research and development for Onboard Navigation (ONAV) ground based expert/trainer system: Preliminary ascent knowledge requirements

    Science.gov (United States)

    Bochsler, Daniel C.

    1988-01-01

    The preliminary version of expert knowledge for the Onboard Navigation (ONAV) Ground Based Expert Trainer Ascent system for the space shuttle is presented. Included is some brief background information along with the information describing the knowledge the system will contain. Information is given on rules and heuristics, telemetry status, landing sites, inertial measurement units, and a high speed trajectory determinator (HSTD) state vector.

  6. Shear zone-controlled magma emplacement or magma-assisted nucleation of shear zones? Insights from northeast Brazil

    Science.gov (United States)

    Neves, S. P.; Vauchez, A.; Archanjo, C. J.

    1996-09-01

    In the Borborema province of northeast Brazil, neoproterozoic granitoids and large-scale transcurrent shear zones are spatially associated, suggesting a genetic link between magma bodies and shear zones. In some cases magma emplacement was clearly favored by shear zone activity, but for several plutons this model is not satisfactory. In these plutons, pre-full crystallization strike-slip deformation, evidenced by parallelism of magmatic foliations and lineations with the solid-state mylonitic fabric, and by a transition from magmatic to solid-state flow, is restricted to the vicinity of the shear zones. Evidence of shear zone activity prior to magma emplacement is lacking, and the magmatic foliation away from the shear zones is in most cases shallowly dipping and concordant with the slightly older, gently-dipping, regional gneissic foliation. Field and anisotropy of magnetic susceptibility mapping, together with petrographic and geochemical studies performed in one of the magmatic complexes of the Borborema province have revealed a structure and a magmatic fabric incompatible with the shear zone-controlled emplacement model. Away from the shear zones, this complex has retained a stratification inherited from the mixing of crystal-poor magmas of contrasting composition, and a magmatic fabric characterized by low-to moderate-dip magmatic foliations bearing a NW-trending lineation, which contrast with vertical foliations bearing NE- or E-W-trending stretching lineations in the shear zones and indicates that crystallization started prior to shear zone development. Based on evidence that magma emplacement predated strike-slip shearing and on information about the transition from magmatic to solid-state deformation observed in the studied plutons, we suggest that incompletely solidified plutons within the crust represent rheological heterogeneities that may induce strain localization and favor shear zone nucleation. We propose that in the studied cases deformation first

  7. Mathematical and numerical modelling of fractional crystallization coupled with chemical exchanges and differential magma-solid transport in magma chambers

    Science.gov (United States)

    Lakhssassi, Morad; Guy, Bernard; Cottin, Jean-Yves; Touboul, Eric

    2010-05-01

    The knowledge of the chemical evolution of magmas is a major concern in geochemistry and petrology. The jumps (or discontinuities) of chemical composition observed in volcanic series from the same province are also the subject of many studies. In particular the phenomenon of "Daly gap" (Daly 1910, 1925), the name given to the jump in chemical composition between the mafic rocks (basalt) and felsic rocks (trachyte, rhyolite, phonolite), corresponding to the absence or scarcity of rocks of intermediate composition (andesite), in both ocean and continental series. Some authors explain these compositional jumps thanks to the intervention of various geological phenomena which follow in time. For example, when a magma chamber turns from a closed to an open system, the lava of a specific composition is ejected to the surface, favoring the rise of the lightest, the most volatile-rich and the less sticky magmas to the surface of the earth (Geist et al., 1995, Thompson et al., 2001). The various explanations offered, although they agree satisfactorily with the natural data, most often lead us away from basic phenomena of melting / solidification, relative migration and chemical equilibrium between solid and liquid and involve various additional phenomena. In our study, we propose a numerical modelling of the crystallization of a closed magma chamber. The physical and mathematical model distinguishes three main classes of processes occurring simultaneously: - heat transfer and solidification, - relative migration between the solid and the liquid magma, - chemical reactions between the two (solid and liquid) phases. Writing the partial differential equations with dimensionless numbers makes two parameters appear, they express the respective ratios of the solidification velocity on the transport velocity, and the kinetics of chemical exchange on the transport velocity. The speed of relative movement between the solid and the liquid, the solidification velocity and the chemical

  8. The Phillips pluton, Maine, USA: evidence of heterogeneous crustal sources and implications for granite ascent and emplacement mechanisms in convergent orogens

    Science.gov (United States)

    Pressley, Rachel A.; Brown, Michael

    1999-03-01

    two sources. The data are consistent with these sources being CMB metasedimentary rocks ( ɛNd (404 Ma)-4) for the granodiorite. The range of Nd isotope compositions within each granite type most likely reflects isotopic heterogeneity inherited from the source. These data imply that the integrity of individual melt batches was maintained during ascent, and that extensive mixing of melt batches during emplacement at this level in the pluton did not occur, although centimetric enclaves have intermediate Nd isotope compositions consistent with small-scale interactions between magmas. We infer that the Phillips pluton represents the root of a larger pluton, and that what remains of this larger pluton is the feeder constructed from multiple melt batches arrested during waning flow of granite magma through a crustal-scale shear zone system.

  9. Xenocryst assimilation and formation of peritectic crystals during magma contamination: An experimental study

    OpenAIRE

    Erdmann, Saskia; Scaillet, Bruno; Kellett, D.A.

    2010-01-01

    International audience; Contamination of magmas by country rocks may contribute xenoliths and xenocrysts to the magma, but also melt and peritectic crystals that form through incongruent melting or dissolution of the original contaminants. Identifying contaminant-derived peritectic crystals and former melt components in igneous rocks is particularly challenging, but also particularly important, because their assimilation significantly affects melt composition and magma temperature. To facilit...

  10. Lithospheric Evolution of Magmas from the Northern Galapagos Province

    Science.gov (United States)

    Miller, M.; Geist, D.; Harpp, K. S.; Mittelstaedt, E. L.

    2010-12-01

    Volcanoes of the Northern Galapagos Providence (NGP) are crucial to understanding the interaction between the Galapagos Plume and the Galapagos Spreading Center (GSC). The NGP consists of five islands and nine volcanic lineaments, all located south of the GSC. Major and trace element compositions of seamounts within the NGP provide insight into the lithospheric evolution of magma within the province. The FLAMINGO cruise (June, 2010) dredged forty-seven localities in the NGP. Major element compositions were determined by XRF and microprobe analysis of submarine rocks and glasses. Crystallization as a function of pressure and temperature is modeled with MELTS and projections into ternary phase diagrams. The Wolf-Darwin Lineament (WDL) is divided into three groups for evaluation of the lavas’ petrology: Northern Wolf-Darwin lineament (that closest to the GSC including Darwin Island), Middle Wolf-Darwin lineament (MWDL, which includes Wolf Island), and Southern Wolf-Darwin lineament (that closest to the Galapagos Platform). Lavas from two other lineaments to the east of the WDL and around Pinta Island are assessed as well. Two parental compositions are modeled, one enriched and one depleted (K2O/TiO2 >0.23 as enriched and K2O/TiO2 =0.04 as depleted). CaO/Al2O3 and Al2O3 variations with Mg# vary considerably as a function of pressure. Magmas from most of the subregions of the NGP evolved by crystallization of olivine and plagioclase, with little CPX crystallization. This indicates that crystallization beneath these volcanoes is limited to pressures 16.5% could be from very low extents of partial melting. The dominantly shallow crystallization depths within the NGP contrast with the deep crustal crystallization that characterizes magmas from the Galapagos Platform. We attribute the rarity of deep crustal fractionation as due to the relatively thin lithosphere south of the GSC as well as the extensional tectonic regime.

  11. Workshop on magma/hydrothermal drilling and instrumentation

    Energy Technology Data Exchange (ETDEWEB)

    Varnado, S.G.; Colp, J.L. (eds.)

    1978-07-01

    The discussions, conclusions, and recommendations of the Magma/Hydrothermal Drilling and Instrumentation Workshop, Albuquerque, NM, May 31--June 2, 1978 are summarized. Three working groups were organized as follows: Drilling Location and Environment, Drilling and Completion Technology, and Logging and Instrumentation Technology. The first group discussed potential drilling sites and the environment that could be expected in drilling to magma depth at each site. Sites suggested for early detailed evaluation as candidate drilling sites were The Geysers-Clear Lake, CA, Kilauea, HI, Long Valley-Mono Craters, CA, and Yellowstone, WY. Magma at these sites is expected to range from 3 to 10 km deep with temperatures of 800 to 1100{sup 0}C. Detailed discussions of the characteristics of each site are given. In addition, a list of geophysical measurements desired for the hole is presented. The Drilling and Completion Group discussed limitations on current rotary drilling technology as a function of depth and temperature. The group concluded that present drilling systems can be routinely used to temperatures of 200{sup 0}C and depths to 10 km; drilling to 350{sup 0}C can be accomplished with modifications of present techniques, drilling at temperatures from 350{sup 0}C to 1100{sup 0}C will require the development of new drilling techniques. A summary of the limiting factors in drilling systems is presented, and recommendations for a program directed at correcting these limitations is described. The third group discussed requirements for instrumentation and established priorities for the development of the required instruments. Of highest priority for development were high resolution temperature tools, sampling techniques (core, formation fluids), chemical probes, and communications techniques. A description of instrumentation requirements for the postulated hole is given, and the tasks necessary to develop the required devices are delineated.

  12. Growth rates of lava domes with respect to viscosity of magmas

    Directory of Open Access Journals (Sweden)

    I. Yokoyama

    2005-06-01

    Full Text Available In the discussion of lava dome formation, viscosity of magma plays an important role. Measurements of viscosity of magmas in field and laboratory are briefly summarized. The types of lava dome emplacements are classified into two, squeeze- and spine-type, by kinetic processes. The squeeze-type is the formation of a dome as a result of squeezes of magma through conduits and the latter is solidified magma forced to ascend by underlying fluid magma. An important parameter in the formation of such lava domes is their growth rates. Lava domes of squeeze-type are governed by the Hagen-Poiseuille Law which involves their viscosoties and other eruption parameters. At present, the real viscosity of magmas at the site of lava dome is still inaccessible. In order to avoid uncertainty in viscosity of magmas, a conception of «macroscopic viscosity» is proposed, which involves effects of chemical components, mainly SiO2 and volatile material, crystals and temperature, and their changes with time. Lava dome formations during the 20th century are briefly examined and their growth rates are estimated. The relationship between the growth rates and the SiO2 content of the magma is statistically studied, and the macroscopic viscosity is empirically expressed as a function of SiO2 content. The linearity between the two parameters is reasonably interpreted. This means that formation processes of lava domes are dominantly controlled by macroscopic viscosity of magma.

  13. Silicic magmas from the Emeishan large igneous province, Southwest China: Petrogenesis and their link with the end-Guadalupian biological crisis

    Science.gov (United States)

    Xu, Yi-Gang; Chung, Sun-Lin; Shao, Hui; He, Bin

    2010-09-01

    The Emeishan large igneous province in SW China comprises a bimodal mafic-silicic suite with the silicic rocks occurring at the uppermost part of the thick lava sequence. The silicic rocks have an age of 257-263 Ma, and are thus roughly coeval with the Guadalupian-Loping (G-L) boundary event. Most silicic rocks (trachyte and rhyolite) from the Emeishan province have rather uniform ɛNd values (+ 1 to + 2.9) that are comparable with the uncontaminated high-Ti basalts. This fact and the remarkably narrow ranges of incompatible element ratios (e.g., Zr/Nb) of the basalt-silicic suite indicate a genetic relationship between basalt and silicic members. The significant difference between the Emeishan rocks and the experimental melts of hydrated basaltic crust, suggests the fractional crystallization of basaltic magma, rather than crustal melting, as the major petrogenetic process for the formation of silicic rocks. Indeed, their major and trace element trends can be modeled by fractionation of the observed mineral phases (feldspar, clinopyroxene, Fe-Ti oxide and apatite). In contrast to the virtually closed system differentiation processes associated with trachytes, the rhyolites may have experienced interaction with upper crustal material during ascent. The geochemical characteristics and recent assessment of timing of the Emeishan volcanism suggest the Emeishan rhyolites as the potential source of the widespread clay bed at the G-L boundary in south China. This enhanced the causal link between the Emeishan eruption and the end-Guadalupian biological crisis.

  14. Grain to outcrop-scale frozen moments of dynamic magma mixing in the syenite magma chamber, Yelagiri Alkaline Complex, South India

    Directory of Open Access Journals (Sweden)

    M.L. Renjith

    2014-11-01

    Full Text Available Magma mixing process is unusual in the petrogenesis of felsic rocks associated with alkaline complex worldwide. Here we present a rare example of magma mixing in syenite from the Yelagiri Alkaline Complex, South India. Yelagiri syenite is a reversely zoned massif with shoshonitic (Na2O + K2O=5–10 wt.%, Na2O/K2O = 0.5–2, TiO2 <0.7 wt.% and metaluminous character. Systematic modal variation of plagioclase (An11–16 Ab82–88, K-feldspar (Or27–95 Ab5–61, diopside (En34–40Fs11–18Wo46–49, biotite, and Ca-amphibole (edenite build up three syenite facies within it and imply the role of in-situ fractional crystallization (FC. Evidences such as (1 disequilibrium micro-textures in feldspars, (2 microgranular mafic enclaves (MME and (3 synplutonic dykes signify mixing of shoshonitic mafic magma (MgO = 4–5 wt.%, SiO2 = 54–59 wt.%, K2O/Na2O = 0.4–0.9 with syenite. Molecular-scale mixing of mafic magma resulted disequilibrium growth of feldspars in syenite. Physical entity of mafic magma preserved as MME due to high thermal-rheological contrast with syenite magma show various hybridization through chemical exchange, mechanical dilution enhanced by chaotic advection and phenocryst migration. In synplutonic dykes, disaggregation and mixing of mafic magma was confined within the conduit of injection. Major-oxides mass balance test quantified that approximately 0.6 portions of mafic magma had interacted with most evolved syenite magma and generated most hybridized MME and dyke samples. It is unique that all the rock types (syenite, MME and synplutonic dykes share similar shoshonitic and metaluminous character; mineral chemistry, REE content, coherent geochemical variation in Harker diagram suggest that mixing of magma between similar composition. Outcrop-scale features of crystal accumulation and flow fabrics also significant along with MME and synplutonic dykes in syenite suggesting that Yelagiri syenite magma chamber had evolved

  15. Iron isotopic compositions of adakitic and non-adakitic granitic magmas: Magma compositional control and subtle residual garnet effect

    Science.gov (United States)

    He, Yongsheng; Wu, Hongjie; Ke, Shan; Liu, Sheng-Ao; Wang, Qiang

    2017-04-01

    Here we present iron (Fe) isotopic compositions of 51 well-characterized adakitic and non-adakitic igneous rocks from the Dabie orogen, Central China and Panama/Costa Rica, Central America. Twelve I-type non-adakitic granitoid samples from the Dabie orogen yield δ56Fe ranging from -0.015‰ to 0.184‰. The good correlations between δ56Fe and indices of magma differentiation (e.g., SiO2, FeOt, Mg#, and Fe3+/ΣFe) suggest Fe2+-rich silicate and oxide minerals dominated fractional crystallization with Δ56Femelt-crystal ∼ 0.06‰ may account for the δ56Fe variation in these samples. One A-type granite sample from the Dabie orogen has δ56Fe as high as 0.447‰, likely indicating less magnetite crystallization and an increase in 103lnβmelt with magma (Na + K)/(Ca + Mg). Combined with the literature data, most high silica (SiO2 ⩾ 71 wt.%) granitic rocks define a good positive linear correlation between δ56Fe and (Na + K)/(Ca + Mg): δ56Fe = 0.0062‰ × (Na + K)/(Ca + Mg) + 0.130‰ (R2 = 0.66). Given that fractional crystallization also tends to increase δ56Fe with (Na + K)/(Ca + Mg), this correlation can serve as the maximum estimate of the magma compositional control on Fe isotope fractionation. Low-Mg adakitic samples (LMA) have δ56Fe ranging from 0.114‰ to 0.253‰. The melt compositional control on LMA δ56Fe could be insignificant due to their limited (Na + K)/(Ca + Mg) variation. Except for one sample that may be affected by late differentiation, 14 out of 15 LMA have δ56Fe increasing with (Dy/Yb)N, reflecting a subtle but significant effect of residual garnet proportion. This serves as evidence for that source mineralogy may play an important role in fractionating Fe isotopes during partial melting. Dabie and Central America high-Mg adakitic samples have homogeneous Fe isotopic compositions with mean δ56Fe of 0.098 ± 0.038‰ (2SD, N = 11) and 0.085 ± 0.045‰ (2SD, N = 11), respectively. These samples have undergone melt-mantle interaction

  16. Initiation of Magma Fragmentation Leading to Vulcanian Explosions

    Science.gov (United States)

    Sacks, S. I.; Hidayat, D.; Linde, A. T.; Voight, B.

    2009-12-01

    The SHV volcano on Montserrat island in the Caribbean has been active since 1995. More than half the island has been made uninhabitable because of continuing dome collapses, pyroclastic flows and vulcanian explosions. In 2003, a small network of borehole strainmeters was installed at ~5 km to ~9 km from the volcano. Since then the strain changes caused by many vulcanian explosions have been recorded. These explosions are short-lived, and result from a sudden decompression of high pressure, vesiculated magma in the conduit. The strain data indicates a decrease in conduit pressure throughout the fragmentation and ejection process that typically occurs in less than 200 seconds. The dense rock equivalent material ejected is usually in the range pressure reduction in the conduit of ~0.5 MPa. This is followed by a strong strain change and vigorous seismic disturbance as is usually observed during vulcanian explosions. The initial pressure reduction is rather similar to the pressure threshold determined for equivalent conditions in the laboratory study. We postulate that a crack in the plug sealing the conduit allows gas to escape, decreasing the pressure at the top of the magma column sufficiently to initiate fragmentation.

  17. Triple oxygen isotope composition of the Campi Flegrei magma systems

    Science.gov (United States)

    Iovine, Raffaella Silvia; Wörner, Gerhard; Pack, Andreas; Sengupta, Sukanya; Carmine Mazzeo, Fabio; Arienzo, Ilenia; D'Antonio, Massimo

    2017-04-01

    Sr-O isotope relationships in igneous rocks are a powerful tool to distinguish magma sources and quantify assimilation processes in magmatic rocks. Isotopic (87Sr/86Sr and 18O/16O-17O/16O) data have been acquired on whole rocks and separated minerals (feldspar, Fe-cpx, Mg-cpx, olivine phenocrysts) from pyroclastic products of the Campi Flegrei volcanic complex (Gulf of Naples, Southern Italy). Oxygen isotope ratios were measured by infrared laser fluorination using a Thermo MAT253 gas source isotope ratio mass spectrometer in dual inlet mode, on ˜2 mg of hand-picked phenocrysts. Variations in triple oxygen isotope ratios (17O/16O, 18O/16O) are expressed as the δ notation relative to VSMOW. Sr isotopic compositions were determined by thermal ionization mass spectrometry after standard cation-exchange methods on separated hand-picked phenocrysts (˜300 mg), and on whole rocks, in case of insufficient sample size to separate crystals. Sr-isotopes in Campi Flegrei minerals range from 0.707305 to 0.707605 and δ18O varies from 6.5 to 8.3‰ . Recalculated δ18Omelt values accordingly show a large range between 7.2 and 8.6‰ . Our data, compared with published δ18O-isotope data from other Italian volcanic centers (Alban Hills, Mts. Ernici, Ischia, Mt. Vesuvius, Aeolian Islands, Tuscany and Sardinia) and from subduction zones worldwide (Kamchatka, Lesser Antilles, Indonesia and Central Andean ignimbrites), show compositions that are very different from typical mantle values. Distinct trends and sources are recognized in our compilation from global data: (1) serpentinized mantle (Kamchatka), (2) sediment-enrichment in the mantle source (Indonesia, Lesser Antilles, Eolian arc), (3) assimilation of old radiogenic continental crust affecting magmas derived from sediment-modified mantle sources (Tuscany, Sardinia), (4) assimilation of lower crustal lithologies (Central Andes, Alban Hills, Mts. Ernici, Ischia). Sr-O-isotope values of Campi Flegrei and Vesuvius magmas

  18. Temporal Evolution of Surface Deformation and Magma Sources at Pacaya Volcano, Guatemala Revealed by InSAR

    Science.gov (United States)

    Wnuk, K.; Wauthier, C.

    2016-12-01

    Pacaya Volcano, Guatemala is a persistently active volcano whose western flank is unstable. Despite continuous activity since 1961, a lack of high temporal resolution geodetic surveying has prevented detailed modeling of Pacaya's underlying magmatic plumbing system. A new, temporally dense dataset of Interferometric Synthetic Aperture Radar (InSAR) RADARSAT-2 images, spanning December 2012 to March 2014, shows magmatic deformation before and during major eruptions in January and March 2014. Inverse modeling of InSAR surface displacements suggest that three magma bodies are responsible for observed deformation: (1) a 3.7 km deep spherical reservoir located northwest of the summit, (2) a 0.4 km deep spherical source located directly west of the summit, and (3) a shallow dike below the summit that provides the primary transport pathway for erupted materials. Periods of heightened activity are brought on by magma pulses at depth, which result in rapid inflation of the edifice. We observe an intrusion cycle at Pacaya that consists of deflation of one or both magma reservoirs followed by dike intrusion. Intrusion volumes are proportional to reservoir volume loss, and do not always result in an eruption. Periods of increased activity culminate with larger dike fed eruptions. Large eruptions are followed by inter eruptive periods marked by a decrease in crater explosions and a lack of deformation. A full understanding of magmatic processes at Pacaya is required to assess potential impacts on other aspects of the volcano such as the unstable western flank. Co-eruptive flank motion appears to have initiated a new stage of volcanic rifting at Pacaya defined by repeated NW-SE dike intrusions. This creates a positive feedback relationship whereby magmatic forcing from eruptive dike intrusions induces flank motion

  19. Changes in Mitral Annular Ascent with Worsening Echocardiographic Parameters of Left Ventricular Diastolic Function

    Directory of Open Access Journals (Sweden)

    Paula M. Hernández Burgos

    2016-01-01

    Full Text Available Background. While the mitral annular plane systolic excursion (MAPSE has been suggested as a surrogate measurement of left ventricular ejection fraction, less is known about the relative value of mitral annular ascent (MAa. Methods. Our database was queried for complete transthoracic echocardiograms performed for any clinical indication. Baseline echocardiographic measurements were compared to determine any correlation between MAa and traditional Echo-Doppler echocardiographic measures to characterize left ventricular diastolic dysfunction (LVDD. Results. Patients with normal LV diastolic function were younger (41±13 years than patients with LVDD (stage 1: 61±13 years; stage 2: 57±14 years; and stage 3: 66±17 years; p=0.156. LV ejection fraction decreased in patients with stage 2 LVDD (63±17% and was further reduced in patients with stage 3 LVDD (28±21; p=0.003. Discussion. While a vigorous MAa excursion was seen in patients with stage 1 LVDD, MAa significantly decreased in stage 2 and stage 3 LVDD patients. Our results highlight the importance of atrioventricular coupling, as MAa motion seems to reflect changes in left atrial pressure. Additional studies are now required to better examine atrioventricular interactions and electromechanical coupling that might improve our assessment of LV diastolic function.

  20. Error Estimates of the Ares I Computed Turbulent Ascent Longitudinal Aerodynamic Analysis

    Science.gov (United States)

    Abdol-Hamid, Khaled S.; Ghaffari, Farhad

    2012-01-01

    Numerical predictions of the longitudinal aerodynamic characteristics for the Ares I class of vehicles, along with the associated error estimate derived from an iterative convergence grid refinement, are presented. Computational results are based on an unstructured grid, Reynolds-averaged Navier-Stokes analysis. The validity of the approach to compute the associated error estimates, derived from a base grid to an extrapolated infinite-size grid, was first demonstrated on a sub-scaled wind tunnel model at representative ascent flow conditions for which the experimental data existed. Such analysis at the transonic flow conditions revealed a maximum deviation of about 23% between the computed longitudinal aerodynamic coefficients with the base grid and the measured data across the entire roll angles. This maximum deviation from the wind tunnel data was associated with the computed normal force coefficient at the transonic flow condition and was reduced to approximately 16% based on the infinite-size grid. However, all the computed aerodynamic coefficients with the base grid at the supersonic flow conditions showed a maximum deviation of only about 8% with that level being improved to approximately 5% for the infinite-size grid. The results and the error estimates based on the established procedure are also presented for the flight flow conditions.

  1. Modeling of the Lightning Plasma Channel Stroke to a Spacecraft during Ascent

    Science.gov (United States)

    Tarditi, Alfonso; Norgard, John

    2009-11-01

    Lightning protection is an important aspect of modern aerospace design: the increased use of composite materials (vs. metals) reduces the shielding and robustness of the conducting path that the outer shell of a vehicle can present to a lightning discharge. A spacecraft during ascent becomes vulnerable to lightning strokes immediately after leaving the launch pad: in addition to natural lightning conditions, there is the possibility of triggered lightning events, caused by a perturbation of the atmospheric electric field [1]. The purpose of this study, in support of the NASA Constellation program, is to determine the evolution of the plasma current and its distribution on the spacecraft surface. Following earlier ``gas dynamic'' approaches [2], the model considers a plasma channel attached to the ascending spacecraft after a return stroke is established. The conductive exhaust plume [3] is an integral part of the model. The NIMROD 3D plasma fluid code [4] is used to model the plasma channel, reproducing the full transient due to the self-consistent magnetic field and the possibility of sweeping of the attachment point along the moving structure [5]. References: [1] M.A. Uman, Proc. IEEE, 76, 1548 (1988). [2] V. A. Rakov, M. A. Uman, IEEE Trans. EMC, EMC-2940, 403 (1998). [3] J. D. Norgard, G.S. Smith, IEEE Trans. EMC, EMC-29, 157 (1987) [4] C. R. Sovinec et al., J. Comput. Phys. 195, 355 (2004). [5] Larsson et al., J. Phys. D, 33, 1876 (2000)

  2. Independent Orbiter Assessment (IOA): Assessment of the ascent thrust vector control actuator subsystem FMEA/CIL

    Science.gov (United States)

    Wilson, R. E.

    1988-01-01

    The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the Ascent Thrust Vector Control Actuator (ATVD) hardware, generating draft failure modes and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The IOA results were then compared to the NASA FMEA/CIL baseline with proposed Post 51-L updates included. A resolution of each discrepancy from the comparison is provided through additional analysis as required. This report documents the results of that comparison for the Orbiter ATVC hardware. The IOA product for the ATVC actuator analysis consisted of 25 failure mode worksheets that resulted in 16 potential critical items being identified. Comparison was made to the NASA baseline which consisted of 21 FMEAs and 13 CIL items. This comparison produced agreement on all CIL items. Based on the Pre 51-L baseline, all non-CIL FMEAs were also in agreement.

  3. Ascent and emplacement dynamics of obsidian lavas inferred from microlite textures

    Science.gov (United States)

    Befus, Kenneth S.; Manga, Michael; Gardner, James E.; Williams, Matthew

    2015-10-01

    To assess the eruption and emplacement of volumetrically diverse rhyolite lavas, we measured microlite number densities and orientations from samples collected from nine lavas in Yellowstone Caldera and two from Mono Craters, USA. Microlite populations are composed of Fe-Ti oxides ± alkali feldspar ± clinopyroxene. Number densities range from 108.11 ± 0.03 to 109.45 ± 0.15 cm-3 and do not correlate with distance from the vent across individual flows and are remarkably similar between large- and small-volume lavas. Together, those observations suggest that number densities are unmodified during emplacement and that ascent rates in the conduit are similar between small domes and large lava flows. Microtextures produced by continuous decompression experiments best replicate natural textures at decompression rates of 1-2 MPa hr-1. Acicular microlites have a preferred orientation in all natural samples. Because the standard deviation of microlite orientation does not become better aligned with distance travelled, we conclude that microlites exit the conduit aligned and that strain during subaerial flow was insufficient to further align microlites. The orientations of microlite trend and plunge in near-vent samples indicate that pure shear was the dominant style of deformation in the conduit. We speculate that collapsing permeable foam(s) provides a mechanism to concurrently allow microlite formation and alignment in response to the combination of degassing and flattening by pure shear.

  4. A Proposed Ascent Abort Flight Test for the Max Launch Abort System

    Science.gov (United States)

    Tartabini, Paul V.; Gilbert, Michael G.; Starr, Brett R.

    2016-01-01

    The NASA Engineering and Safety Center initiated the Max Launch Abort System (MLAS) Project to investigate alternate crew escape system concepts that eliminate the conventional launch escape tower by integrating the escape system into an aerodynamic fairing that fully encapsulates the crew capsule and smoothly integrates with the launch vehicle. This paper proposes an ascent abort flight test for an all-propulsive towerless escape system concept that is actively controlled and sized to accommodate the Orion Crew Module. The goal of the flight test is to demonstrate a high dynamic pressure escape and to characterize jet interaction effects during operation of the attitude control thrusters at transonic and supersonic conditions. The flight-test vehicle is delivered to the required test conditions by a booster configuration selected to meet cost, manufacturability, and operability objectives. Data return is augmented through judicious design of the boost trajectory, which is optimized to obtain data at a range of relevant points, rather than just a single flight condition. Secondary flight objectives are included after the escape to obtain aerodynamic damping data for the crew module and to perform a high-altitude contingency deployment of the drogue parachutes. Both 3- and 6-degree-of-freedom trajectory simulation results are presented that establish concept feasibility, and a Monte Carlo uncertainty assessment is performed to provide confidence that test objectives can be met.

  5. Liquefaction Study of Gaseous Oxygen Inside Mars Ascent Vehicle Propellant Tank

    Science.gov (United States)

    Wang, Xiao-Yen

    2017-01-01

    The in-situ production of propellants for Mars missions will utilize carbon dioxide (CO2) in the Mars atmosphere to produce oxygen. The oxygen then needs to be cooled, liquefied, and stored to be available for Mars ascent propulsion, which could be up to 2 years after liquefaction starts. Recent investigations have demonstrated the feasibility of both achieving zero boiloff and controlling the pressure of oxygen within a tank using high-efficiency reverse turbo-Brayton-cycle cryocoolers. A tube-on-tank configuration is being studied in this work. The cooling fluid circulating in the cryocooler system is routed through a network of cooling tubes on the oxygen tank. The oxygen gas produced from the in-situ production process is introduced into the chilled tank. A series of analysis of this configuration has been performed to investigate the liquefaction rate inside the tank, the thermal gradient near the top of the tank where the oxygen gas feeding tubing is located. The analyses include 2D axisymmetric CFD analysis using ANSYS Fluent, 1D thermal analysis using Matlab, and 3D thermal analysis using MSC Patran/pthermal. These three models correlate and validate each other.

  6. Stair ascent and descent biomechanical adaptations while using a custom ankle-foot orthosis.

    Science.gov (United States)

    Aldridge Whitehead, Jennifer M; Russell Esposito, Elizabeth; Wilken, Jason M

    2016-09-06

    The ability to navigate stairs step-over-step is an important functional outcome following severe lower leg injury and is difficult for many patients. Ankle-foot orthoses, such as the Intrepid Dynamic Exoskeletal Orthosis (IDEO), are often prescribed to improve function. This study compared stair climbing mechanics between IDEO users and able-bodied control participants. Thirteen IDEO users who sustained severe lower leg injury and 13 controls underwent biomechanical gait analysis. Participants ascended and descended a 16-step instrumented staircase without handrail use at a controlled cadence of 80 steps/min. Peak joint angles, moments, powers, and ground reaction forces, and integrated mechanical work were calculated. Independent t-tests with Bonferroni-Holm corrections were used to compare controls to IDEO and sound limbs. Reduced ankle range of motion on the IDEO limb resulted in compensatory strategies while ascending or descending stairs. During ascent, IDEO users had greater bilateral hip power during pull-up (pIDEO limb׳s reduced ankle dorsiflexion (pIDEO limb had was trailing, it had less ankle dorsiflexion during controlled lowering (pIDEO limb ankle power absorption during weight acceptance (pIDEO users were able to climb stairs step-over-step unassisted. Published by Elsevier Ltd.

  7. Technology Development and Design of a Hybrid Mars Ascent Vehicle Concept

    Science.gov (United States)

    Karp, Ashley C.; Redmond, Matt; Nakazono, Barry; Vaughan, David; Shotwell, Robert; Story, George; Jackson, Dale; Young, David

    2016-01-01

    Hybrid propulsion has been investigated as an enhancing technology for a Mars Ascent Vehicle (MAV) concept as part of potential Mars Sample Return (MSR) because of its high specific impulse, restartability, and the ability to operate and survive at extremely low temperatures. A new wax-based hybrid fuel formulation has been developed that could withstand the harsh and variable Mars environment protected solely by a minimal layer of passive insulation. This formulation could provide substantial energy savings for a notional lander and is critical for rover mobility. Preliminary thermal cycle testing has determined that the formulation can survive the expected temperature extremes and lifetime thermal testing is currently underway. A complete preliminary design using this new fuel formulation combined with a low temperature oxidizer such as Mixed Oxides of Nitrogen (MON30) is presented. Several key features associated with a complete hybrid MAV concept are investigated to determine their mission suitability (e.g. Thrust Vector Control and restartable ignition options). Potential challenges along a path towards developing such a system are outlined and future work is suggested as a means of technology maturation. The hybrid design presented here was the lowest Gross Lift Off Mass (GLOM) result of a 2015 Jet Propulsion Laboratory (JPL) led MAV concept study.

  8. Ascent, Transition, Entry, and Abort Guidance Algorithm Design for the X-33 Vehicle

    Science.gov (United States)

    Hanson, John M.; Coughlin, Dan J.; Dukeman, Gregory A.; Mulqueen, John A.; McCarter, James W.

    1998-01-01

    One of the primary requirements for X-33 is that it be capable of flying autonomously. That is, onboard computers must be capable of commanding the entire flight from launch to landing, including cases where a single engine failure abort occurs. Guidance algorithms meeting these requirements have been tested in simulation and have been coded into prototype flight software. These algorithms must be sufficiently robust to account for vehicle and environmental dispersions, and must issue commands that result in the vehicle operating, within all constraints. Continual tests of these algorithms (and modifications as necessary) will occur over the next year as the X-33 nears its first flight. This paper describes the algorithms in use for X-33 ascent, transition, and entry flight, as well as for the powered phase of PowerPack-out (PPO) aborts (equivalent in thrust impact to losing an engine). All following discussion refers to these phases of flight when discussing guidance. The paper includes some trajectory results and results of dispersion analysis.

  9. The engineering of a nuclear thermal landing and ascent vehicle utilizing indigenous Martian propellant

    Science.gov (United States)

    Zubrin, Robert M.

    1991-01-01

    The following paper reports on a design study of a novel space transportation concept known as a 'NIMF' (Nuclear rocket using Indigenous Martian Fuel). The NIMF is a ballistic vehicle which obtains its propellant out of the Martian air by compression and liquefaction of atmospheric CO2. This propellant is subsequently used to generate rocket thrust at a specific impulse of 264 s by being heated to high temperature (2800 K) gas in the NIMFs' nuclear thermal rocket engines. The vehicle is designed to provide surface to orbit and surface to surface transportation, as well as housing, for a crew of three astronauts. It is capable of refueling itself for a flight to its maximum orbit in less than 50 days. The ballistic NIMF has a mass of 44.7 tonnes and, with the assumed 2800 K propellant temperature, is capable of attaining highly energetic (250 km by 34,000 km elliptical) orbits. This allows it to rendezvous with interplanetary transfer vehicles which are only very loosely bound into orbit around Mars. If a propellant temperature of 2000 K is assumed, then low Mars orbit can be attained; while if 3100 K is assumed, then the ballistic NIMF is capable of injecting itself onto a minimum energy transfer orbit to Earth in a direct ascent from the Martian surface.

  10. A bivariate gamma probability distribution with application to gust modeling. [for the ascent flight of the space shuttle

    Science.gov (United States)

    Smith, O. E.; Adelfang, S. I.; Tubbs, J. D.

    1982-01-01

    A five-parameter gamma distribution (BGD) having two shape parameters, two location parameters, and a correlation parameter is investigated. This general BGD is expressed as a double series and as a single series of the modified Bessel function. It reduces to the known special case for equal shape parameters. Practical functions for computer evaluations for the general BGD and for special cases are presented. Applications to wind gust modeling for the ascent flight of the space shuttle are illustrated.

  11. Timescales of Quartz Crystallization and the Longevity of the Bishop Giant Magma Body

    Science.gov (United States)

    Gualda, Guilherme A. R.; Pamukcu, Ayla S.; Ghiorso, Mark S.; Anderson, Alfred T.; Sutton, Stephen R.; Rivers, Mark L.

    2012-01-01

    Supereruptions violently transfer huge amounts (100 s–1000 s km3) of magma to the surface in a matter of days and testify to the existence of giant pools of magma at depth. The longevity of these giant magma bodies is of significant scientific and societal interest. Radiometric data on whole rocks, glasses, feldspar and zircon crystals have been used to suggest that the Bishop Tuff giant magma body, which erupted ∼760,000 years ago and created the Long Valley caldera (California), was long-lived (>100,000 years) and evolved rather slowly. In this work, we present four lines of evidence to constrain the timescales of crystallization of the Bishop magma body: (1) quartz residence times based on diffusional relaxation of Ti profiles, (2) quartz residence times based on the kinetics of faceting of melt inclusions, (3) quartz and feldspar crystallization times derived using quartz+feldspar crystal size distributions, and (4) timescales of cooling and crystallization based on thermodynamic and heat flow modeling. All of our estimates suggest quartz crystallization on timescales of crystal-poor magma bodies are ephemeral features that, once established, evolve on millennial timescales. We also suggest that zircon crystals, rather than recording the timescales of crystallization of a large pool of crystal-poor magma, record the extended periods of time necessary for maturation of the crust and establishment of these giant magma bodies. PMID:22666359

  12. Timescales of Quartz Crystallization and the Longevity of the Bishop Giant Magma Body

    Energy Technology Data Exchange (ETDEWEB)

    Gualda, Guilherme A.R.; Pamukcu, Ayla S.; Ghiorso, Mark S.; Anderson, Jr. , Alfred T.; Sutton, Stephen R.; Rivers, Mark L. (OFM Res.); (Vanderbilt); (UC)

    2013-04-08

    Supereruptions violently transfer huge amounts (100 s-1000 s km{sup 3}) of magma to the surface in a matter of days and testify to the existence of giant pools of magma at depth. The longevity of these giant magma bodies is of significant scientific and societal interest. Radiometric data on whole rocks, glasses, feldspar and zircon crystals have been used to suggest that the Bishop Tuff giant magma body, which erupted {approx}760,000 years ago and created the Long Valley caldera (California), was long-lived (>100,000 years) and evolved rather slowly. In this work, we present four lines of evidence to constrain the timescales of crystallization of the Bishop magma body: (1) quartz residence times based on diffusional relaxation of Ti profiles, (2) quartz residence times based on the kinetics of faceting of melt inclusions, (3) quartz and feldspar crystallization times derived using quartz+feldspar crystal size distributions, and (4) timescales of cooling and crystallization based on thermodynamic and heat flow modeling. All of our estimates suggest quartz crystallization on timescales of <10,000 years, more typically within 500-3,000 years before eruption. We conclude that large-volume, crystal-poor magma bodies are ephemeral features that, once established, evolve on millennial timescales. We also suggest that zircon crystals, rather than recording the timescales of crystallization of a large pool of crystal-poor magma, record the extended periods of time necessary for maturation of the crust and establishment of these giant magma bodies.

  13. Timescales of quartz crystallization and the longevity of the Bishop giant magma body.

    Science.gov (United States)

    Gualda, Guilherme A R; Pamukcu, Ayla S; Ghiorso, Mark S; Anderson, Alfred T; Sutton, Stephen R; Rivers, Mark L

    2012-01-01

    Supereruptions violently transfer huge amounts (100 s-1000 s km(3)) of magma to the surface in a matter of days and testify to the existence of giant pools of magma at depth. The longevity of these giant magma bodies is of significant scientific and societal interest. Radiometric data on whole rocks, glasses, feldspar and zircon crystals have been used to suggest that the Bishop Tuff giant magma body, which erupted ~760,000 years ago and created the Long Valley caldera (California), was long-lived (>100,000 years) and evolved rather slowly. In this work, we present four lines of evidence to constrain the timescales of crystallization of the Bishop magma body: (1) quartz residence times based on diffusional relaxation of Ti profiles, (2) quartz residence times based on the kinetics of faceting of melt inclusions, (3) quartz and feldspar crystallization times derived using quartz+feldspar crystal size distributions, and (4) timescales of cooling and crystallization based on thermodynamic and heat flow modeling. All of our estimates suggest quartz crystallization on timescales of <10,000 years, more typically within 500-3,000 years before eruption. We conclude that large-volume, crystal-poor magma bodies are ephemeral features that, once established, evolve on millennial timescales. We also suggest that zircon crystals, rather than recording the timescales of crystallization of a large pool of crystal-poor magma, record the extended periods of time necessary for maturation of the crust and establishment of these giant magma bodies.

  14. Protracted near-solidus storage and pre-eruptive rejuvenation of large magma reservoirs

    Science.gov (United States)

    Szymanowski, Dawid; Wotzlaw, Jörn-Frederik; Ellis, Ben S.; Bachmann, Olivier; Guillong, Marcel; von Quadt, Albrecht

    2017-10-01

    Building super-eruptive magma reservoirs in the cold, upper parts of Earth's crust requires a significant influx of magma over an extended period, sufficient to allow the magma to accumulate, differentiate and periodically erupt. Some models favour magma storage in a cold non-eruptible state, requiring extensive reactivation of the reservoirs before eruption, whereas others suggest storage at higher temperature and lower crystallinity, implying that magma in such reservoirs is readily eruptible. Consequently, constraining volcanic hazards requires observations directly linking magma residence timescales to the thermal state and crystallinity of storage. Here we simultaneously determine crystallization temperatures and ages of magmatic crystals of zircon and titanite in the 900 km3 Kneeling Nun Tuff (New Mexico, USA), which allows us to place tight constraints on the long-term thermal evolution of the magma reservoir. We show that zircon and titanite crystals record more than 600,000 years of magma assembly and constrain the dominant storage conditions to low temperatures, set between the granitic solidus (680 to 700 °C) and the temperature of the onset of titanite crystallization (about 720 to 730 °C). We apply the zircon-titanite systematics to a suite of other super-eruptions and suggest that protracted low-temperature storage culminating in late-stage reheating is a widespread feature of large crystal-rich eruptions.

  15. Trunk kinetic effort during step ascent and descent in patients with transtibial amputation using angular momentum separation.

    Science.gov (United States)

    Gaffney, Brecca M M; Christiansen, Cory L; Murray, Amanda M; Davidson, Bradley S

    2017-10-01

    Patients with transtibial amputation adopt trunk movement compensations that alter effort and increase the risk of developing low back pain. However, the effort required to achieve high-demand tasks, such as step ascent and descent, remains unknown. Kinematics were collected during bilateral step ascent and descent tasks from two groups: 1) seven patients with unilateral transtibial amputation and 2) seven healthy control subjects. Trunk kinetic effort was quantified using translational and rotational segmental moments (time rate of change of segmental angular momentum). Peak moments during the loading period were compared across limbs and across groups. During step ascent, patients with transtibial amputation generated larger sagittal trunk translational moments when leading with the amputated limb compared to the intact limb (P=0.01). The amputation group also generated larger trunk rotational moments in the frontal and transverse planes when leading with either limb compared to the healthy group (P=0.01, Pamputation group generated larger trunk translational and rotational moments in all three planes when leading with the intact limb compared to the healthy group (Ptranstibial amputation compared to healthy individuals. Compensations that produce identified increased and asymmetric trunk segmental moments, may increase the risk of the development of low back pain in patients with amputation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. The ASCENT (Allocation System Changes for Equity in Kidney Transplantation Study: A Randomized Effectiveness-Implementation Study to Improve Kidney Transplant Waitlisting and Reduce Racial Disparity

    Directory of Open Access Journals (Sweden)

    Rachel E. Patzer

    2017-05-01

    Discussion: The results from the ASCENT study will demonstrate the feasibility and effectiveness of a multicomponent intervention designed to increase access to the deceased donor kidney waitlist and to reduce racial disparities in waitlisting.

  17. The magma budget of Volcan Arenal, Costa Rica from 1968 to 1980

    Science.gov (United States)

    Wadge, G.

    1983-01-01

    The magma volume emitted by Volcan Arenal, Costa Rica, has been calculated to be 304 x 10 to the 6th cu m. A near-continuous rise from very deep within the crust is proposed as an explanation for Arenal's magma supply, and the long-term seismic pattern is interpreted as individual batches of magma using previously fractured pathways. During a break in activity (1973) the effusion site moved from Crater A to Crater C, approximately 400 m higher. It is maintained that the steady downward tilting of the volcano's summit was caused by the loading of the volcano's western side by about 19 x 10 to the 6th cu m of lava. Also noted is the abrupt decrease in effusion rate compatible with the increased magmatic head needed to reach Crater C. It is concluded that the constancy of magma composition and effusion rate from 1974 to 1980 indicates a homogeneous magma reservoir.

  18. Evidence for variations in magma production along oceanic spreading centers - A critical appraisal

    Science.gov (United States)

    Karson, J. A.; Elthon, D.

    1987-01-01

    Recent studies of the oceanic lithosphere near fracture zones have resulted in the proposal that the 'magma budget', defined as the amount of magma delivered to magma chambers or conduits beneath a spreading center for a given amount of spreading, decreases as fracture zones are approached. Geochemical variations in basaltic glasses collected near fracture zones are consistent with a decrease in partial melting as fracture zones are approached, but they could also be produced by variations in open-system magmatic processes with no change in the extent of partial melting. Although a decrease in the magma budget as fracture zones are approached is consistent with these data, so are alternative models that incorporate a constant magma budget.

  19. «Magma»: as origens de Guimarães Rosa

    Directory of Open Access Journals (Sweden)

    Luiz Cláudio Vieira de Oliveira

    2011-10-01

    Full Text Available Resumo: Leitura de Magma, de Guimarães Rosa, com o objetivo de indicar a presença de temas, fragmentos, personagens, expressões e recursos estilísticos ali existentes, em outros textos do autor, cronologicamente posteriores.Palavras-chave: Literatura brasileira; Guimarães Rosa; Magma.Résumé: Lecture de Magma, de Guimarães Rosa, ayant l’objectif de montrer la présence de quelques sujets, fragments, personnages, expressions et traits stylistiques, que y sont présents, et aussi dans autres textes du même auteur, chronologiquement postérieurs.Mots-clés: Littérature brésilienne; Guimarães Rosa; Magma.Keywords: Brazilian literature; Guimarães Rosa; Magma.

  20. The Effect of Thermal Cycling on Crystal-Liquid Separation During Lunar Magma Ocean Differentiation

    Science.gov (United States)

    Mills, Ryan D.

    2013-01-01

    Differentiation of magma oceans likely involves a mixture of fractional and equilibrium crystallization [1]. The existence of: 1) large volumes of anorthosite in the lunar highlands and 2) the incompatible- rich (KREEP) reservoir suggests that fractional crystallization may have dominated during differentiation of the Moon. For this to have occurred, crystal fractionation must have been remarkably efficient. Several authors [e.g. 2, 3] have hypothesized that equilibrium crystallization would have dominated early in differentiation of magma oceans because of crystal entrainment during turbulent convection. However, recent numerical modeling [4] suggests that crystal settling could have occurred throughout the entire solidification history of the lunar magma ocean if crystals were large and crystal fraction was low. These results indicate that the crystal size distribution could have played an important role in differentiation of the lunar magma ocean. Here, I suggest that thermal cycling from tidal heating during lunar magma ocean crystallization caused crystals to coarsen, leading to efficient crystal-liquid separation.

  1. Slab melting and magma formation beneath the southern Cascade arc

    Science.gov (United States)

    Walowski, Kristina J.; Wallace, Paul J.; Clynne, Michael A.; Rasmussen, D.J.; Weis, D.

    2016-01-01

    The processes that drive magma formation beneath the Cascade arc and other warm-slab subduction zones have been debated because young oceanic crust is predicted to largely dehydrate beneath the forearc during subduction. In addition, geochemical variability along strike in the Cascades has led to contrasting interpretations about the role of volatiles in magma generation. Here, we focus on the Lassen segment of the Cascade arc, where previous work has demonstrated across-arc geochemical variations related to subduction enrichment, and H-isotope data suggest that H2O in basaltic magmas is derived from the final breakdown of chlorite in the mantle portion of the slab. We use naturally glassy, olivine-hosted melt inclusions (MI) from the tephra deposits of eight primitive (MgO>7 wt%) basaltic cinder cones to quantify the pre-eruptive volatile contents of mantle-derived melts in this region. The melt inclusions have B concentrations and isotope ratios that are similar to mid-ocean ridge basalt (MORB), suggesting extensive dehydration of the downgoing plate prior to reaching sub-arc depths and little input of slab-derived B into the mantle wedge. However, correlations of volatile and trace element ratios (H2O/Ce, Cl/Nb, Sr/Nd) in the melt inclusions demonstrate that geochemical variability is the result of variable addition of a hydrous subduction component to the mantle wedge. Furthermore, correlations between subduction component tracers and radiogenic isotope ratios show that the subduction component has less radiogenic Sr and Pb than the Lassen sub-arc mantle, which can be explained by melting of subducted Gorda MORB beneath the arc. Agreement between pMELTS melting models and melt inclusion volatile, major, and trace element data suggests that hydrous slab melt addition to the mantle wedge can produce the range in primitive compositions erupted in the Lassen region. Our results provide further evidence that chlorite-derived fluids from the mantle portion of the

  2. Magma-Assisted Continental Break-up Encroached on Previously Stretched Continental Lithosphere - the NE Greenland Composite Passive Margin

    Science.gov (United States)

    Mazur, S.; Rippington, S.; Houghton, P.

    2014-12-01

    Volcanic continental margins have a number of distinctive features that are different from those typical of magma-poor continental margins. However, in some places volcanic margins may develop parallel to older, highly extended rift systems. In such situations the resultant continental margin shows a complex structure that merges the characteristics of volcanic and non-volcanic margins. Furthermore, the evolution of this younger magma-rich margin is restricted by the pre-existing lithospheric architecture, causing it to diverge from the generally assumed formation model. We use the case of NE Greenland to demonstrate the structure of a composite margin firstly subjected to extensive extension and later overprinted by magma-assisted continental break-up. The NE Greenland continental margin is a highly extended margin, that is up to 250km wide, with crystalline crust attaining the maximum thickness near to the coast of Greenland and at the Danmarkshaven Ridge. The latter represents a major basement horst formed during an Early Cretaceous rifting event. To the east of the Danmarkshaven Ridge, crust is stretched and onlapped by the Early Cretaceous sedimentary basin. The effects of Tertiary break-up are observable in a relatively narrow zone 80 km wide that usually includes an extended edge of continental crust and an adjacent section of oceanic crust. A volcano-sedimentary succession produced during the break-up reaches the maximum thickness of c. 8000 m above a continent-ocean transition (COB). Oceanic crust overlain by mixed volcanic and sedimentary rocks is thicker than usual. No observable SDRs or igneous transitional crust are present near to the COB. Instead, a chain of high density bodies follow the COB at the base of crust. The features observed suggest relatively little extension associated with the Tertiary break-up. Instead localised mantle melting presumably led to rapid break-up with crustal dilatation promptly balanced by production of thick oceanic

  3. Thermal and Chemical Gradients Along the Slab Interface Control Across-Arc Patterns in Compositions of Primitive Arc Magmas

    Science.gov (United States)

    Mather, T. A.; Pyle, D. M.; Watt, S. F.; Naranjo, J. A.

    2014-12-01

    Several studies of primitive mafic arc rocks have shown systematic across-arc variations in the volatile and trace element contents of primary arc magmas. Most of these studies used olivine-hosted melt inclusions in mafic scoria that had been transported rapidly to the surface from depth. These inclusions bypass upper crustal modifications, and constrain the chemical composition of parental magmas in equilibrium with the mantle. The patterns preserved in these melts can be used to explore spatial variation in the volatile-rich flux that enters the mantle wedge, sourced from the subducting plate. Variability in the composition of this flux provides information about fluid and melt transport through the mantle wedge, and of the mineral breakdown or melting processes occurring within the downgoing slab. We analysed olivine-hosted melt inclusions from scoria cones in southern Chile (40 - 42 S), including picrites with unzoned Mg-rich olivine (Fo88) from volcan Apagado. Samples show systematic variations in water, CO2, and trace element content that suggests that the primary-melt chemistry reflects the pattern of element release at the subducting slab interface. This down-slab chemical gradient is consistent with predictions from modelling and experiments. Down-slab, the flux feeding the arc magmas becomes progressively water-poor over a distance of a few km. We suggest that this change marks the onset of significant water-fluxed melting of sediment at the downgoing slab-surface. The short length scale of the across-arc chemical patterns in southern Chile is surprising. The fact that such changes are preserved within our sampled rocks suggests that there is limited across-arc mixing and focussing of fluids or melts as they ascend through the mantle wedge. Our results suggest that slab-surface inputs exert a first-order control on arc-magma chemistry. The chemical patterns that we observe are replicated in other arcs (e.g. Kamchatka, Izu-Bonin), despite the plate

  4. Diapir versus along-channel ascent of crustal material during plate convergence: Constrained by the thermal structure of subduction zones

    Science.gov (United States)

    Liu, Ming-Qi; Li, Zhong-Hai; Yang, Shao-Hua

    2017-09-01

    Subduction channel processes are crucial for understanding the material and energy exchange between the Earth's crust and mantle. Crustal rocks can be subducted to mantle depths, interact with the mantle wedge, and then exhume to the crustal depth again, which is generally considered as the mechanism for the formation of ultrahigh-pressure metamorphic rocks in nature. In addition, the crustal rocks generally undergo dehydration and melting at subarc depths, giving rise to fluids that metasomatize and weaken the overlying mantle wedge. There are generally two ways for the material ascent from subarc depths: one is along subduction channels; the other is through the mantle wedge by diapir. In order to study the conditions and dynamics of these contrasting material ascent modes, systematic petrological-thermo-mechanical numerical models are constructed with variable thicknesses of the overriding and subducting continental plates, ages of the subducting oceanic plate, as well as the plate convergence rates. The model results suggest that the thermal structures of subduction zones control the thermal condition and fluid/melt activity at the slab-mantle interface in subcontinental subduction channels, which further strongly affect the material transportation and ascent mode. The thick overriding continental plate and the low-angle subduction style induced by young subducting oceanic plate both contribute to the formation of relatively cold subduction channels with strong overriding mantle wedge, where the along-channel exhumation occurs exclusively to result in the exhumation of HP-UHP metamorphic rocks. In contrast, the thin overriding lithosphere and the steep subduction style induced by old subducting oceanic plate are the favorable conditions for hot subduction channels, which lead to significant hydration and metasomatism, melting and weakening of the overriding mantle wedge and thus cause the ascent of mantle wedge-derived melts by diapir through the mantle wedge

  5. Compositional dependence of sulfur speciation in Terrestrial and Martian magmas

    Science.gov (United States)

    Nash, William; Wood, Bernard; Smythe, Duane

    2016-04-01

    The capacity of magmas to transport sulfur from mantle to crust strongly influences a planet's surface chemistry. Sulfur is perhaps exceptional among the elements in the diversity of it's chemical speciation, exhibiting four redox species at geologically relevant conditions: sulfide (2-), elemental sulfur (0), sulfite (4+) and sulphate (6+). Furthermore, the solubility of sulfur in a magma (and hence the magma's capacity for delivering mantle-derived sulfur to the crust) depends critically on it's oxidation state. Our aim with this experimental study was to quantitatively determine the chemical speciation of sulfur within several common magmas, as a function of oxygen fugacity (fO2). We have performed a series of experiments on six sulfur-bearing silicate melts, which together represent a broad range of naturally occurring compositions: two putative Martian basalts, two terrestrial MORBs (one primitive, one evolved), an andesite, and a dacite. These melts were equilibrated together (at one-atmosphere pressure, 1300°C) with various CO-CO2-SO2 gas mixtures, which imposed a range of fO2s. This range spanned -2 to +1.6 log units (relative to the Quartz-Fayalite-Magnetite or QFM buffer), and the step-size was 0.25 log units. The quenched glasses were analyzed by X-ray Absorption Spectroscopy (specifically XANES) at the Diamond synchrotron (UK), and the spectra obtained were used to determine the species of sulfur present in each glass. The chemical composition of each glass (including their sulfur contents) was characterized by electron-probe microanalysis. Despite the generally low concentrations of sulfur in our glasses (never exceeding 0.24 wt%), we have clearly resolved the crossover between reduced (S2-) and oxidized (S6+) species for three of our basalts. The other three melts yielded more noisy XANES spectra, and as a result their redox crossovers are visible, but less clearly resolved. For every melt composition, the redox crossover is a continuous (though

  6. Skaergaard parental magma constrained by melt inclusions of cumulus plagioclase

    Science.gov (United States)

    Jakobsen, J. K.; Kent, A. J. R.; Tegner, C.; Brooks, C. K.

    2003-04-01

    Cumulus plagioclase of the 55 Ma Skaergaard intrusion, East Greenland, contains two types melt inclusions. Their form varies from rounded to elongate bodies up to 250 micrometer long often parallel to albite twins. Type-1 inclusions are polycrystalline and composed of plagioclase, augite, magnetite, ilmenite and accessory K-feldspar, biotite, and amphibole. Their abundance varies throughout the intrusion but it is greatest in the Middle Zone but absent in the Hidden Zone. A previous study of type-1 inclusions of the Middle Zone estimated they represent SiO2-poor (46 wt%) and FeO-rich (17 wt%) ferrobasalt calculated by summing mineral compositions weighted by mode (Hanghøj et al., 1995, CMP 120, 265-269). Our study aims to homogenise the crystallised melt inclusion by experimental reheating. Preliminary data of Lower Zone C shows higher SiO2 (50 wt%) and lower FeO (11-12 wt%) and lower titanium than Hanghøj et al. (1995) and all other estimates of Skaergaard magmas. We presently speculate that the unusual composition of the homogenised inclusions is an artefact of overshooting the homogenization temperature (1160°C which is higher than the expected liquidus temperature of 1100 °C) and/or diffusional exchange between host crystal and the melt inclusions. We will continue to test these hypothesis. Type-2 inclusions are glassy or microcrystalline with small oxide crystals. They are found in very high abundance in autoliths thought to represent the Hidden Zone. Homogenised type-2 inclusions have 48 wt% SiO2 and 12 wt% FeO which is similar to chilled margin samples suggested as parental Skaergaard magmas. The rare earth element patterns of the type-2 inclusions are similar to coeval continental flood basalts of the Blosseville coast. We conclude that type-2 melt inclusions represent the parental liquid to the Skaergaard intrusion.

  7. Deciphering magma histories through phosphorus zoning in olivine

    Science.gov (United States)

    Ersoy, Ö.; Nikogosian, I.; Mason, P. R. D.; van Bergen, M.

    2015-12-01

    Since olivine is usually the first major phase to crystallize from basaltic magma, its primary chemistry is a sensitive tracer of the early evolution of volcanic systems. However, fast diffusion and homogenization under magmatic conditions frequently modifies the original composition of olivine, which hampers the reconstruction of cooling histories and magma evolution from the chemistry and zoning patterns of phenocrysts in erupted products. Phosphorous is a notable exception due to its sluggish diffusion in olivine crystals and silicate melts, as igneous olivines almost always display complex zoning patterns. Phosphorus zoning in olivine has been linked either to crystallization rate variations and diffusion controlled growth or to strong compositional controls on melt-mineral partitioning. We illuminate the versatility of P-in-olivine with a comprehensive EPMA and LA-ICPMS dataset on olivines from Italian potassium rich mafic lavas and the primitive melt inclusions (MI) that they host. The olivines are characterized by P concentrations from limit of quantification (22 ppm) to 435 ppm P with MIs containing up to 2.2 wt.% P2O5. High resolution (1-2 μm per pixel) element maps show both fine oscillatory and large scale sector zoning in P, which is uncorrelated with zoning in any other element. The MIs are virtually always surrounded by P-depleted zones that are also depleted in Cr and enriched in Al and Ti, which we attribute to a combination of supply-limited slow growth and melt compositional controls on partitioning behavior imposed by the boundary layer. We demonstrate that P zoning carries valuable information on the nature and timing of magmatic events such as mingling/mixing, wall-rock assimilation and subsequent re-equilibration processes. P-in-olivine is most promising to distinguish multiple generations of MIs, as a guide to study their mode of entrapment and to disclose the origin of primary heterogeneities.

  8. Covariance Analysis Tool (G-CAT) for Computing Ascent, Descent, and Landing Errors

    Science.gov (United States)

    Boussalis, Dhemetrios; Bayard, David S.

    2013-01-01

    G-CAT is a covariance analysis tool that enables fast and accurate computation of error ellipses for descent, landing, ascent, and rendezvous scenarios, and quantifies knowledge error contributions needed for error budgeting purposes. Because GCAT supports hardware/system trade studies in spacecraft and mission design, it is useful in both early and late mission/ proposal phases where Monte Carlo simulation capability is not mature, Monte Carlo simulation takes too long to run, and/or there is a need to perform multiple parametric system design trades that would require an unwieldy number of Monte Carlo runs. G-CAT is formulated as a variable-order square-root linearized Kalman filter (LKF), typically using over 120 filter states. An important property of G-CAT is that it is based on a 6-DOF (degrees of freedom) formulation that completely captures the combined effects of both attitude and translation errors on the propagated trajectories. This ensures its accuracy for guidance, navigation, and control (GN&C) analysis. G-CAT provides the desired fast turnaround analysis needed for error budgeting in support of mission concept formulations, design trade studies, and proposal development efforts. The main usefulness of a covariance analysis tool such as G-CAT is its ability to calculate the performance envelope directly from a single run. This is in sharp contrast to running thousands of simulations to obtain similar information using Monte Carlo methods. It does this by propagating the "statistics" of the overall design, rather than simulating individual trajectories. G-CAT supports applications to lunar, planetary, and small body missions. It characterizes onboard knowledge propagation errors associated with inertial measurement unit (IMU) errors (gyro and accelerometer), gravity errors/dispersions (spherical harmonics, masscons), and radar errors (multiple altimeter beams, multiple Doppler velocimeter beams). G-CAT is a standalone MATLAB- based tool intended to

  9. Evolution of complex life cycles in trophically transmitted helminths. I. Host incorporation and trophic ascent.

    Science.gov (United States)

    Parker, G A; Ball, M A; Chubb, J C

    2015-02-01

    Links between parasites and food webs are evolutionarily ancient but dynamic: life history theory provides insights into helminth complex life cycle origins. Most adult helminths benefit by sexual reproduction in vertebrates, often high up food chains, but direct infection is commonly constrained by a trophic vacuum between free-living propagules and definitive hosts. Intermediate hosts fill this vacuum, facilitating transmission to definitive hosts. The central question concerns why sexual reproduction, and sometimes even larval growth, is suppressed in intermediate hosts, favouring growth arrest at larval maturity in intermediate hosts and reproductive suppression until transmission to definitive hosts? Increased longevity and higher growth in definitive hosts can generate selection for larger parasite body size and higher fecundity at sexual maturity. Life cycle length is increased by two evolutionary mechanisms, upward and downward incorporation, allowing simple (one-host) cycles to become complex (multihost). In downward incorporation, an intermediate host is added below the definitive host: models suggest that downward incorporation probably evolves only after ecological or evolutionary perturbations create a trophic vacuum. In upward incorporation, a new definitive host is added above the original definitive host, which subsequently becomes an intermediate host, again maintained by the trophic vacuum: theory suggests that this is plausible even under constant ecological/evolutionary conditions. The final cycle is similar irrespective of its origin (upward or downward). Insights about host incorporation are best gained by linking comparative phylogenetic analyses (describing evolutionary history) with evolutionary models (examining selective forces). Ascent of host trophic levels and evolution of optimal host taxa ranges are discussed. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary

  10. Timescale and morphology of Martian mantle overturn immediately following magma ocean solidification

    Science.gov (United States)

    Scheinberg, A.; Elkins-Tanton, L. T.; Zhong, S. J.

    2014-03-01

    Energy of accretion in terrestrial planets is expected to create liquid silicate magma oceans. Their solidification processes create silicate differentiation and set the initial mantle structure for the planet. Solidification may result in a compositionally unstable density profile, leading to cumulate Rayleigh-Taylor overturn if a sluggish rather than stagnant lithosphere existed in the early stages of planetary history. The pattern and timescale of overturn, in which cold, dense surface material sinks to the core-mantle boundary, have implications for core dynamo production, volatile escape, and fundamental differences between differently sized bodies. Our fully spherical mantle models reaffirm previous work suggesting that harmonic degree of overturn is dependent on viscosity contrast and layer thickness. We find that cumulate overturn would likely have occurred with short wavelengths. In an isoviscous model, thermal convection ensues rapidly after overturn; however, when viscosity is temperature dependent, compositional stability in the mantle suppresses the onset of whole-mantle thermal convection. For a viscosity of 1018 Pa s, the mantle could fully overturn in as little as 3 Ma.

  11. Lifetime and size of shallow magma bodies controlled by crustal-scale magmatism

    Science.gov (United States)

    Karakas, Ozge; Degruyter, Wim; Bachmann, Olivier; Dufek, Josef

    2017-06-01

    Magmatic processes on Earth govern the mass, energy and chemical transfer between the mantle, crust and atmosphere. To understand magma storage conditions in the crust that ultimately control volcanic activity and growth of continents, an evaluation of the mass and heat budget of the entire crustal column during magmatic episodes is essential. Here we use a numerical model to constrain the physical conditions under which both lower and upper crustal magma bodies form. We find that over long durations of intrusions (greater than 105 to 106 yr), extensive lower crustal mush zones develop, which modify the thermal budget of the upper crust and reduce the flux of magma required to sustain upper crustal magma reservoirs. Our results reconcile physical models of magma reservoir construction and field-based estimates of intrusion rates in numerous volcanic and plutonic localities. Young igneous provinces (less than a few hundred thousand years old) are unlikely to support large upper crustal reservoirs, whereas longer-lived systems (active for longer than 1 million years) can accumulate magma and build reservoirs capable of producing super-eruptions, even with intrusion rates smaller than 10-3 to 10-2 km3 yr-1. Hence, total duration of magmatism should be combined with the magma intrusion rates to assess the capability of volcanic systems to form the largest explosive eruptions on Earth.

  12. Magma transfer at Campi Flegrei caldera (Italy) before the 1538 AD eruption.

    Science.gov (United States)

    Di Vito, Mauro A; Acocella, Valerio; Aiello, Giuseppe; Barra, Diana; Battaglia, Maurizio; Carandente, Antonio; Del Gaudio, Carlo; de Vita, Sandro; Ricciardi, Giovanni P; Ricco, Ciro; Scandone, Roberto; Terrasi, Filippo

    2016-08-25

    Calderas are collapse structures related to the emptying of magmatic reservoirs, often associated with large eruptions from long-lived magmatic systems. Understanding how magma is transferred from a magma reservoir to the surface before eruptions is a major challenge. Here we exploit the historical, archaeological and geological record of Campi Flegrei caldera to estimate the surface deformation preceding the Monte Nuovo eruption and investigate the shallow magma transfer. Our data suggest a progressive magma accumulation from ~1251 to 1536 in a 4.6 ± 0.9 km deep source below the caldera centre, and its transfer, between 1536 and 1538, to a 3.8 ± 0.6 km deep magmatic source ~4 km NW of the caldera centre, below Monte Nuovo; this peripheral source fed the eruption through a shallower source, 0.4 ± 0.3 km deep. This is the first reconstruction of pre-eruptive magma transfer at Campi Flegrei and corroborates the existence of a stationary oblate source, below the caldera centre, that has been feeding lateral eruptions for the last ~5 ka. Our results suggest: 1) repeated emplacement of magma through intrusions below the caldera centre; 2) occasional lateral transfer of magma feeding non-central eruptions within the caldera. Comparison with historical unrest at calderas worldwide suggests that this behavior is common.

  13. The influences of incremental pluton growth on magma crystallinity and aureole rheology: numerical modeling of growth of the Papoose Flat pluton, California

    Science.gov (United States)

    Chen, Yanying; Nabelek, Peter I.

    2017-10-01

    The Papoose Flat pluton in the White-Inyo Range, California, is one of the best examples of forcefully emplaced plutons within an arc crust, having internal fabrics and a contact aureole that deformed in a ductile manner. A 2-D numerical model for the thermo-rheological evolution of the pluton-wall rock system is proposed. We explore how the frequency of magma input, from instantaneous, episodic to continuous, affects magma chamber crystallinity and rheology of both the pluton and its contact aureole. We model pluton growth in the depth range of 10-13 km, which is at the brittle-ductile transition of the crust, and in the 7-4 km depth range, where the host rocks are initially brittle. For incremental growth (episodic and continuous), the pluton begins as a sill. With subsequent injections to the bottom, the pluton grows into a laccolith. Results of mid-crustal models show that the ductile region above the Papoose Flat pluton is related to thermal weakening. The ductile region during incremental growth is 100-150 m thick, matching the observed thickness. It is ten times thinner than in the instantaneous growth model. In episodic and continuous models, the upper part of the pluton is fully or quasi-crystalline throughout growth. During continuous growth, it is likely to remain ductile with potential for the development of solid-state fabrics. During episodic growth, strain rates within the pluton during each injection may become sufficiently high to cause embrittlement of magma. In no case a ductile aureole develops above the pluton at the upper-crustal level, but may develop below the pluton, which serves as thermal insulator. Thus, the pluton's floor may sag. During incremental growth, most of the pluton is below the solidus and brittle. The results suggest that large volcanic eruptions are unlikely to occur by slow pressurization of magma chambers; instead they require rapid injections of large melt volumes.

  14. Deep mixing of mantle melts beneath continental flood basalt provinces: Constraints from olivine-hosted melt inclusions in primitive magmas

    Science.gov (United States)

    Jennings, Eleanor S.; Gibson, Sally A.; Maclennan, John; Heinonen, Jussi S.

    2017-01-01

    We present major and trace element compositions of 154 re-homogenised olivine-hosted melt inclusions found in primitive rocks (picrites and ferropicrites) from the Mesozoic Paraná-Etendeka and Karoo Continental Flood Basalt (CFB) provinces. The major element compositions of the melt inclusions, especially their Fe/Mg ratios, are variable and erratic, and attributed to the re-homogenisation process during sample preparation. In contrast, the trace element compositions of both the picrite and ferropicrite olivine-hosted melt inclusions are remarkably uniform and closely reflect those of the host whole-rocks, except in a small subset affected by hydrothermal alteration. The Paraná-Etendeka picrites and ferropicrites are petrogenetically related to the more evolved and voluminous flood basalts, and so we propose that compositional homogeneity at the melt inclusion scale implies that the CFB parental mantle melts were well mixed prior to extensive crystallisation. The incompatible trace element homogeneity of olivine-hosted melt inclusions in Paraná-Etendeka and Karoo primitive magmatic rocks has also been identified in other CFB provinces and contrasts with findings from studies of basalts from mid-ocean ridges (e.g. Iceland and FAMOUS on the Mid Atlantic Ridge), where heterogeneity of incompatible trace elements in olivine-hosted melt inclusions is more pronounced. We suggest that the low variability in incompatible trace element contents of olivine-hosted melt inclusions in near-primitive CFB rocks, and also ocean island basalts associated with moderately thick lithosphere (e.g. Hawaii, Galápagos, Samoa), may reflect mixing along their longer transport pathways during ascent and/or a temperature contrast between the liquidus and the liquid when it arrives in the crust. These thermal paths promote mixing of mantle melts prior to their entrapment by growing olivine crystals in crustal magma chambers. Olivine-hosted melt inclusions of ferropicrites from the Paran

  15. Shallow Chamber & Conduit Behavior of Silicic Magma: A Thermo- and Fluid- Dynamic Parameterization Model of Physical Deformation as Constrained by Geodetic Observations: Case Study; Soufriere Hills Volcano, Montserrat

    Science.gov (United States)

    Gunn de Rosas, C. L.

    2013-12-01

    The Soufrière Hills Volcano, Montserrat (SHV) is an active, mainly andesitic and well-studied stratovolcano situated at the northern end of the Lesser Antilles Arc subduction zone in the Caribbean Sea. The goal of our research is to create a high resolution 3D subsurface model of the shallow and deeper aspects of the magma storage and plumbing system at SHV. Our model will integrate inversions using continuous and campaign geodetic observations at SHV from 1995 to the present as well as local seismic records taken at various unrest intervals to construct a best-fit geometry, pressure point source and inflation rate and magnitude. We will also incorporate a heterogeneous media in the crust and use the most contemporary understanding of deep crustal- or even mantle-depth 'hot-zone' genesis and chemical evolution of silicic and intermediate magmas to inform the character of the deep edifice influx. Our heat transfer model will be constructed with a modified 'thin shell' enveloping the magma chamber to simulate the insulating or conducting influence of heat-altered chamber boundary conditions. The final forward model should elucidate observational data preceding and proceeding unrest events, the behavioral suite of magma transport in the subsurface environment and the feedback mechanisms that may contribute to eruption triggering. Preliminary hypotheses suggest wet, low-viscosity residual melts derived from 'hot zones' will ascend rapidly to shallower stall-points and that their products (eventually erupted lavas as well as stalled plutonic masses) will experience and display two discrete periods of shallow evolution; a rapid depressurization crystallization event followed by a slower conduction-controlled heat transfer and cooling crystallization. These events have particular implications for shallow magma behaviors, notably inflation, compressibility and pressure values. Visualization of the model with its inversion constraints will be affected with Com

  16. FY 1984 and FY 1985 geochemistry and materials studies in support of the Magma Energy Extraction Program

    Energy Technology Data Exchange (ETDEWEB)

    Westrich, H.R.; Weirick, L.J.; Cygan, R.T.; Reece, M.; Hlava, P.F.; Stockman, H.W.; Gerlach, T.M.

    1986-04-01

    Geochemistry and materials studies are being performed in support of the Magma Energy Extraction Program. The work is largely restricted to: (1) characterizing magmatic environments at sites of interest, (2) testing engineering materials in laboratory simulated magmatic environments, (3) investigating chemical mass transport effects inherent in designs for direct contact heat exchangers, and (4) evaluating degassing hazards associated with drilling into and extracting energy from shallow magma. Magma characterization studies have been completed for shallow magma at Long Valley, Coso volcanic field, and Kilauea volcano. The behavior of 17 commercially available materials has been examined in rhyolite magma at 850/sup 0/C and 200 MPa for periods up to seven days. Analysis of reaction products from materials tests to date indicate that oxidation is the main corrosion problem for most alloys in rhyolitic magma. Considerations of corrosion resistance, high-temperature strength, and cost indicate nickel-base superalloys offer the most promise as candidates for use in rhyolitic magma.

  17. Regional cerebral blood flow in humans at high altitude: gradual ascent and 2 wk at 5,050 m.

    Science.gov (United States)

    Willie, C K; Smith, K J; Day, T A; Ray, L A; Lewis, N C S; Bakker, A; Macleod, D B; Ainslie, P N

    2014-04-01

    The interindividual variation in ventilatory acclimatization to high altitude is likely reflected in variability in the cerebrovascular responses to high altitude, particularly between brain regions displaying disparate hypoxic sensitivity. We assessed regional differences in cerebral blood flow (CBF) measured with Duplex ultrasound of the left internal carotid and vertebral arteries. End-tidal Pco2, oxyhemoglobin saturation (SpO2), blood pressure, and heart rate were measured during a trekking ascent to, and during the first 2 wk at, 5,050 m. Transcranial color-coded Duplex ultrasound (TCCD) was employed to measure flow and diameter of the middle cerebral artery (MCA). Measures were collected at 344 m (TCCD-baseline), 1,338 m (CBF-baseline), 3,440 m, and 4,371 m. Following arrival to 5,050 m, regional CBF was measured every 12 h during the first 3 days, once at 5-9 days, and once at 12-16 days. Total CBF was calculated as twice the sum of internal carotid and vertebral flow and increased steadily with ascent, reaching a maximum of 842 ± 110 ml/min (+53 ± 7.6% vs. 1,338 m; mean ± SE) at ∼ 60 h after arrival at 5,050 m. These changes returned to +15 ± 12% after 12-16 days at 5,050 m and were related to changes in SpO2 (R(2) = 0.36; P < 0.0001). TCCD-measured MCA flow paralleled the temporal changes in total CBF. Dilation of the MCA was sustained on days 2 (+12.6 ± 4.6%) and 8 (+12.9 ± 2.9%) after arrival at 5,050 m. We observed no significant differences in regional CBF at any time point. In conclusion, the variability in CBF during ascent and acclimatization is related to ventilatory acclimatization, as reflected in changes in SpO2.

  18. Trunk muscle activity during wheelchair ramp ascent and the influence of a geared wheel on the demands of postural control.

    Science.gov (United States)

    Howarth, Samuel J; Polgar, Jan M; Dickerson, Clark R; Callaghan, Jack P

    2010-03-01

    To quantify levels of torso muscular demand during wheelchair ramp ascent and the ability of a geared wheel to influence trunk muscle activity. Repeated-measures design. Each participant completed manual wheelchair ramp ascents for each combination of 4 ramp grades (1:12, 1:10, 1:8, and 1:6) and 3 wheel conditions (in gear, out of gear, and a standard spoked wheel) in a block randomized order by wheel condition. Biomechanics laboratory. Healthy novice wheelchair users (N=13; 6 men) from a university student population. Not applicable. Peak electromyographic activity, expressed as a percentage of maximal voluntary isometric contraction (MVIC) of the abdominals, latissimus dorsi, and erector spinae during ramp ascent. Temporal location of peak electromyographic activity (EMG) within a propulsive cycle and integrated electromyographic activity for a single propulsive cycle. Abdominal peak activity increased 13.9% MVIC while peak posterior trunk muscle activity increased 4.9% MVIC between the shallowest and steepest ramp grades (Pwheel prevented increased peak activity of the rectus abdominis and external oblique (P>.05). Only peak electromyographic timing of the erector spinae was influenced during the push phase by increasing ramp slope. Increased trunk muscular demand as a result of increasing ramp slope is required to enhance stiffness of the spinal column and provide a stable base during manual propulsion. Manual wheelchair users with compromised activity capacity, compromised abdominal muscle strength, or both, may be able to navigate more difficult terrains while using a geared wheelchair wheel because of reduced demands from the abdominal musculature in the geared wheel condition. Copyright 2010 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  19. Contribution of altered hip, knee and foot kinematics to dynamic postural impairments in females with patellofemoral pain during stair ascent.

    Science.gov (United States)

    de Oliveira Silva, Danilo; Magalhães, Fernando Henrique; Pazzinatto, Marcella Ferraz; Briani, Ronaldo Valdir; Ferreira, Amanda Schenatto; Aragão, Fernando Amâncio; de Azevedo, Fábio Mícolis

    2016-06-01

    Altered hip, knee and foot kinematics have been systematically observed in individuals with patellofemoral pain (PFP). However, less attention has been given to the altered dynamic postural control associated with PFP. Additionally, the relative contribution of kinematic impairments to the postural behavior of subjects with PFP remains an open question that warrants investigation. The aims of this study were: i) to investigate possible differences in hip adduction, rearfoot eversion, knee flexion and displacement area of the center of pressure (COP) in individuals with PFP in comparison to controls during stair ascent; and (ii) to determine which kinematic parameter is the best predictor of the displacement area of the COP measured during the stance phase of the stair ascent. Twenty-nine females with PFP and 25 asymptomatic pain-free females underwent three-dimensional kinematic and COP analyses during stair ascent. Between-group comparisons were made using independent t-tests. Regression models were performed to identify the capability of each kinematic factor in predicting the displacement area of the COP. Reduced knee flexion and displacement area of the COP as well as increased peak hip adduction and peak rearfoot eversion were observed in individuals with PFP as compared to controls. Peak hip adduction was the best predictor of the displacement area of the COP (r(2)=23.4%). The excessive hip adduction was the biggest predictor of the displacement area of the COP. Based on our findings, proximally targeted interventions may be of major importance for the functional reestablishment of females with PFP. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Deciphering Magma Flow Directions From Complex Magnetic Fabrics

    Science.gov (United States)

    Plenier, G.; Glen, J. M.

    2005-12-01

    A simple relation is generally presumed to exist between an igneous rock's anisotropy of magnetic susceptibility (AMS) fabric and magma flow. In such cases (termed " normal "), the magnetic fabric displays a magnetic foliation pole, given by the minimum AMS axis, that lies perpendicular to the flow plane (i.e., dike walls, or lava flow top or bottom) and a magnetic lineation (AMS maximum axis) aligned with the flow direction. However, abnormal fabrics differing significantly from the normal case are more common than is generally accepted, possibly biasing the interpretation of flow directions. Surprisingly, such cases often have AMS axes that are aligned with the flow coordinates but are flipped (through 90 degrees) with respect to each other. One of the most compelling causes for these " permuted " fabrics involves mixtures of uniaxial single domain (SD) and multi-domain (MD) titanomagnetites (Rochette et al., 1992; Ferre, 2002). In cases where grain size mixtures are responsible for the permuted fabrics, magnetic anisotropy techniques, that isolate the influence of different grain size fractions on magnetic fabric, might allow the true flow directions to be recovered (Plenier and Glen 2005). We will present two such methods that can be used to achieve this goal. The first method acts on the pseudo-single domain (PSD) grain size fraction. The presence of a sub-saturating field tends to saturate the PSD grains that in turn behave more like SD grains. The second method is particularly suited for samples that contain a fraction of super paramagnetic (SP) grains. It involves cooling samples below the SP-blocking temperature in order to increase their fraction of single domain grains. These treatments both result in changes of the sample's AMS fabric that might allow one to recover the true flow directions. We will discuss results from both of these methods, along with independent measurements made to assess magnetic mineralogy and grain size, to determine magma flow

  1. NVP melt/magma viscosity: insight on Mercury lava flows

    Science.gov (United States)

    Rossi, Stefano; Morgavi, Daniele; Namur, Olivier; Vetere, Francesco; Perugini, Diego; Mancinelli, Paolo; Pauselli, Cristina

    2016-04-01

    After more than four years of orbiting Mercury, NASA's MESSENGER spacecraft came to an end in late April 2015. MESSENGER has provided many new and surprising results. This session will again highlight the latest results on Mercury based on MESSENGER observations or updated modelling. The session will further address instrument calibration and science performance both retrospective on MESSENGER and on the ESA/JAXA BepiColombo mission. Papers covering additional themes related to Mercury are also welcomed. Please be aware that this session will be held as a PICO session. This will allow an intensive exchange of expertise and experience between the individual instruments and mission. NVP melt/magma viscosity: insight on Mercury lava flows S. Rossi1, D. Morgavi1, O. Namur2, D. Perugini1, F.Vetere1, P. Mancinelli1 and C. Pauselli1 1 Dipartimento di Fisica e Geologia, Università di Perugia, piazza Università 1, 06123 Perugia, Italy 2 Uni Hannover Institut für Mineralogie, Leibniz Universität Hannover, Callinstraβe 3, 30167 Hannover, Germany In this contribution we report new measurements of viscosity of synthetic komatitic melts, used the behaviour of silicate melts erupted at the surface of Mercury. Composition of Mercurian surface magmas was calculated using the most recent maps produced from MESSENGER XRS data (Weider et al., 2015). We focused on the northern hemisphere (Northern Volcanic Province, NVP, the largest lava flow on Mercury and possibly in the Solar System) for which the spatial resolution of MESSENGER measurements is high and individual maps of Mg/Si, Ca/Si, Al/Si and S/Si were combined. The experimental starting material contains high Na2O content (≈7 wt.%) that strongly influences viscosity. High temperature viscosity measurements were carried out at 1 atm using a concentric cylinder apparatus equipped with an Anton Paar RheolabQC viscometer head at the Department of Physics and Geology (PVRG_lab) at the University of Perugia (Perugia, Italy

  2. Seismic tomography reveals magma chamber location beneath Uturuncu volcano (Bolivia)

    Science.gov (United States)

    Kukarina, Ekaterina; West, Michael; Koulakov, Ivan

    2014-05-01

    Uturuncu volcano belongs to the Altiplano-Puna Volcanic Complex in the central Andes, the product of an ignimbrite ''flare-up''. The region has been the site of large-scale silicic magmatism since 10 Ma, producing 10 major eruptive calderas and edifices, some of which are multiple-eruption resurgent complexes as large as the Yellowstone or Long Valley caldera. Satellite measurements show that the hill has been rising more than half an inch a year for almost 20 years, suggesting that the Uturuncu volcano, which has erupted last time more than 300,000 years ago, is steadily inflating, which makes it fertile ground for study. In 2009 an international multidisciplinary team formed a project called PLUTONS to study Uturuncu. Under this project a 100 km wide seismic network was set around the volcano by seismologists from University of Alaska Fairbanks. Local seismicity is well distributed and provides constraints on the shallow crust. Ray paths from earthquakes in the subducting slab complement this with steep ray paths that sample the deeper crust. Together the shallow and deep earthquakes provide strong 3D coverage of Uturuncu and the surrounding region. To study the deformation source beneath the volcano we performed simultaneous tomographic inversion for the Vp and Vs anomalies and source locations, using the non-linear passive source tomographic code, LOTOS. We estimated both P and S wave velocity structures beneath the entire Uturuncu volcano by using arrival times of P and S waves from more than 600 events registered by 33 stations. To show the reliability of the results, we performed a number of different tests, including checkerboard synthetic tests and tests with odd/even data. Obtained Vp/Vs ratio distribution shows increased values beneath the south Uturuncu, at a depth of about 15 km. We suggest the high ratio anomaly is caused by partial melt, presented in expanding magma chamber, responsible for the volcano inflation. The resulting Vp, Vs and the ratio

  3. Apatite: a new redox proxy for silicic magmas?

    Science.gov (United States)

    Miles, Andrew; Graham, Colin; Hawkesworth, Chris; Gillespie, Martin; Bromiley, Geoff; Hinton, Richard

    2015-04-01

    The oxidation states of magmas provide valuable information about the release and speciation of volatile elements during volcanic eruptions, metallogenesis, source rock compositions, open system magmatic processes, tectonic settings and potentially titanium (Ti) activity in chemical systems used for Ti-dependent geothermometers and geobarometers. In this presentation we explore the use of Mn in apatite as an oxybarometer in intermediate and silicic igneous rocks. Increased Mn concentrations in apatite in granitic rocks from the zoned Criffell granitic pluton (southern Scotland) correlate with decreasing Fe2O3 (Fe3+) and Mn in the whole-rock and likely reflect increased Mn2+/Mn3+and greater compatibility of Mn2+ relative to Mn3+ in apatite under reduced conditions. Fe3+/Fe2+ ratios in biotites have previously been used to calculate oxygen fugacities (fO2) in the outer zone granodiorites and inner zone granites where redox conditions have been shown to change from close to the magnetite-hematite buffer to close to the nickel-nickel oxide buffer respectively[1]. This trend is apparent in apatite Mn concentrations from a range of intermediate to silicic volcanic rocks that exhibit varying redox states and are shown to vary linearly and negatively with log fO2, such that logfO2=-0.0022(±0.0003)Mn(ppm)-9.75(±0.46) Variations in the Mn concentration of apatites appear to be largely independent of differences in the Mn concentration of the melt. Apatite Mn concentrations may therefore provide an independent oxybarometer that is amenable to experimental calibration, with major relevance to studies on detrital mineral suites, particularly those containing a record of early Earth redox conditions, and on the climatic impact of historic volcanic eruptions[2]. [1] Stephens, W. E., Whitley, J. E., Thirlwall, M. F. and Halliday, A. N. (1985) The Criffell zoned pluton: correlated behaviour of rare earth element abundances with isotopic systems. Contributions to Mineralogy and

  4. Individual magma batches related to the origin of Yellowstone 516-70 ka post-caldera rhyolitic lava flows : results from glass geochemistry.

    Science.gov (United States)

    Stix, J.; Girard, G.

    2007-12-01

    would therefore decrease. However, Y generally increases from 60 ppm in bulk rock at 516 ka to 65-70 ppm at 165-147 ka and 85 ppm at 70 ka. Of the analyzed elements, only Rb exhibits concentrations higher in glass than bulk rock and therefore is incompatible. Although it increases slightly over time in bulk rocks from 160 ppm in the most primitive of the 516 ka lavas to 170 ppm at 198 ka, it is generally buffered at 180-200 ppm from 165 to 70 ka. In addition, spatial compositional differences are observed between the flows, despite comparable mineralogy and crystal contents. For instance, during the 165-147 ka period, Ba in the western lavas ranges from 50 to 70 ppm, while it varies from 95 to 120 ppm in the eastern lavas. During the 117-102 ka period, two western lavas erupted at 6 km distance from each other at 112 and 108 ka have respective contents of 40 vs 80 ppm Ba in glass, 40 vs 160 ppm Ba in bulk rock and 65 vs 80 ppm La in glass. These spatial compositional differences, together with the decoupled temporal changes in various trace elements, suggest that these lava flows did not originate from a single homogeneous long-lived liquid reservoir. It is possible that eruptions are the result of localized magma injections at various depths into the mush, which mixed with the mush or merely provided heat to remelt the mush and initiate magma ascent. Each batch of magma may then have undergone variable degrees of differentiation before eruption.

  5. Magma-poor and magma-rich segments along the hyperextended, pre-Caledonian passive margin of Baltica

    Science.gov (United States)

    Andersen, Torgeir B.; Alsaif, Manar; Corfu, Fernando; Jakob, Johannes; Planke, Sverre; Tegner, Christian

    2015-04-01

    The Scandinavian Caledonides constitute a more than 1850 km long 'Himalayan-type' orogen, formed by collision between Baltica-Avalonia and Laurentia. Subduction-related magmatism in the Iapetus ended at ~430 Ma and continental convergence continued for ~30 Myr until ~400 Ma. The collision produced a thick orogenic wedge comprising the stacked remnants of the rifted to hyperextended passive Baltican margin (Andersen et al. 2012), as well as suspect, composite and outboard terranes, which were successively emplaced as large-scale nappe complexes onto Baltica during the Scandian collision (see Corfu et al. 2014 for a recent review). Large parts (~800 km) of the mountain-belt in central Scandinavia, particularly in the Särv and Seve Nappes and their counterparts in Troms, are characterised by spectacular dyke complexes emplaced into continental sediments (e.g. Svenningsen 2001, Hollocher et al. 2007). These constitute a magma-rich segment formed along the margin of Baltica or within hyperextended continental slivers outboard of Baltica. The intensity of the pre-Caledonian magmatism is comparable to that of the present NE-Atlantic and other volcanic passive margins. The volumes and available U-Pb ages of 610-597 Ma (Baird et al. 2014 and refs therein) suggest that the magmatism was short lived, intense and therefore compatible with a large igneous province (LIP). By analogy with present-day margins this LIP may have been associated with continental break-up and onset of sea-floor spreading. The remnants of the passive margin both north and south of the magma-rich segment have different architectures, and are almost devoid of rift/drift related magmatic rocks. Instead, these magma-poor segments are dominated by heterogeneous sediment-filled basins characterised by the abundant presence of solitary bodies of variably altered mantle peridotites, also commonly present as detrital serpentinites. These basins are interpreted to have formed by hyperextension. We suggest that

  6. Crystallization conditions in the Upper Pollara magma chamber, Salina Island, Southern Tyrrhenian Sea

    Science.gov (United States)

    Donato, P.; Behrens, H.; de Rosa, R.; Holtz, F.; Parat, F.

    2006-01-01

    Pyroclastites erupted from the Upper Pollara magma chamber (13 ka, Salina Island, Aeolian Archipelago) resulted from mingling and mixing of rhyolitic and andesitic magmas. An experimental study has been conducted on the rhyolitic end-member to constrain the pre-eruptive conditions of the magma. In order to check for the role of mixing on the equilibrium phase assemblage, three different starting compositions, corresponding to three different mixing degrees, have been used. The crystallization experiments were conducted at two different oxygen fugacities and at variable temperature and fluid contents. The results indicate that the natural mineralogical assemblage can only be reproduced from a composition showing a certain degree of mixing. Assuming a pressure of 200 MPa (generally accepted for the Aeolian Islands), the pre-eruptive temperature of the magmas is estimated between 755 and 800 °C and the water content of the melt was higher than 4 4.5 wt.%.

  7. Are Ferroan Anorthosites Direct Products of the Lunar Magma Ocean?

    Science.gov (United States)

    Neal, C. R.; Draper, D. S.

    2016-01-01

    According to Lunar Magma Ocean (LMO) theory, lunar samples that fall into the ferroan anorthosite (FAN) category represent the only samples we have of of the primordial crust of the Moon. Modeling indicates that plagioclase crystallizes after >70% LMO crystallization and formed a flotation crust, depending upon starting composition. The FAN group of highlands materials has been subdivided into mafic-magnesian, mafic-ferroan, anorthositic- sodic, and anorthositic-ferroan, although it is not clear how these subgroups are related. Recent radiogenic isotope work has suggested the range in FAN ages and isotopic systematics are inconsistent with formation of all FANs from the LMO. While an insulating lid could have theoretically extend the life of the LMO to explain the range of the published ages, are the FAN compositions consistent with crystallization from the LMO? As part of a funded Emerging Worlds proposal (NNX15AH76G), we examine this question through analysis of FAN samples. We compare the results with various LMO crystallization models, including those that incorporate the influence of garnet.

  8. Mantles of terrestrial planets immediately following magma ocean solidification

    Science.gov (United States)

    Scheinberg, A. L.; Elkins-Tanton, L. T.; Zhong, S.; Parmentier, E.

    2010-12-01

    Energy of accretion in terrestrial planets is expected to create liquid silicate magma oceans. Their solidification processes create silicate differentiation and set the initial mantle structure for the planet. Solidification results in a compositionally unstable density profile, leading to cumulate Rayleigh-Taylor overturn in the early stages of planetary history. The pattern and timescale of overturn, in which cold, dense surface material sinks to the core mantle boundary, has implications for core dynamo production, volatile escape and fundamental differences between differently-sized bodies. Our fully spherical mantle models reaffirm previous work suggesting harmonic degree of overturn is dependent on viscosity contrast and layer thickness. We then explore the dependence of overturn morphology in the early mantles of Mars, Earth, Mercury and the Moon on these parameters and on the respective planets’ characteristics using a composition- and temperature-dependent viscosity model. Initial results indicate that fractional solidification and overturn in terrestrial planets always creates some radius range in which the mantle is azimuthally compositionally heterogeneous. After overturn, compositional stability in the mantle suppresses the onset of thermal convection; the broad conclusions of this work indicate that the earliest solid mantle of terrestrial planets is compositionally differentiated and stable.

  9. Chlorine and hydrogen degassing in Vesta's magma ocean

    Science.gov (United States)

    Sarafian, Adam R.; John, Timm; Roszjar, Julia; Whitehouse, Martin J.

    2017-02-01

    The hydrophilic nature of halogens makes these elements ideal for probing potential hydrous geologic processes. Generally, in magmatic settings the stable isotopes of Cl may fractionate when H is in low concentrations and little fractionation occurs when the H concentration is high. We determined the Cl isotope composition and halogen content (F, Cl, Br, and I) of apatite and merrillite in seven basaltic eucrites, which are meteorites linked to the asteroid 4-Vesta, by using secondary ion mass spectrometry. We compare our halogen results with H isotope data, existing bulk rock concentrations, and petrologic models. The inferred Cl isotope composition of eucrites from this study, expressed in standard δ37 Cl notation, which ranges from -3.8 to 7.7‰, correlates with the bulk major- and trace-element content, e.g., the Cl isotope composition positively correlates with Mg and Sc, while Cl isotope composition negatively correlates with K, V, and Cr. Here we suggest that eucrites preserve evidence of a degassing magma ocean as evidenced by the decreasing bulk rock K content with increasing δ37 Cl . If the eucrite parent body, 4-Vesta, accreted with a negative δ37 Cl of - 3.8 ± 1.1 ‰, at least some parts of the solar nebula would have been isotopically light compared to most estimates of the Earth, which on average is close to 0‰.

  10. Magma Storage, Recharge and the Caldera Cycle at Rabaul, Papua New Guinea

    Science.gov (United States)

    Fabbro, G.; Bouvet de Maisonneuve, C.; Sindang, M.

    2015-12-01

    Many calderas have a history of repeated caldera-forming eruptions, interspersed with periods of more minor activity. Rabaul, for instance, has had at least 11 ignimbrite-forming eruptions over the last 200 ky. The most recent of these was the '1400 BP' eruption, which led to caldera collapse. Since then, there has been multiple smaller eruptions, including the ongoing activity from Tavurvur and Vulcan. An important question facing volcanology today is what controls the size of eruptions at calderas such as Rabaul.Detailed stratigraphic sampling of the 1400BP eruption reveals that prior to eruption, the magma reservoir below Rabaul contained a well-mixed dacite with whole-rock SiO2 contents of 65.0-66.4 wt%. The dacite contains a single phenocryst assemblage of plag (An44-52), cpx (En43-46Fs13-15Wo40-41), opx (En69-71Fs25-28Wo3) and magnetite, along with minor apatite. The homogeneity of the dacite is underscored by the narrow range of compositions of both the matrix glass and the melt inclusions (67.8-69.0 wt% SiO2). The only exception to this is at the top of the ignimbrite, representing some of the last magma to have been withdrawn. Dispersed throughout the dacitic pumices are darker, more mafic blebs. Streaks of mingled magma with a range of SiO2 contents, down to 59.9 wt% SiO2 are also found in the pumice, suggesting that a mafic recharge magma was intruded into the base of the reservoir shortly before eruption. High TiO2 contents rule out the direct involvement of basalt, and instead imply the magma that intruded into the reservoir was an andesite with at least 56 wt% SiO2. Phenocrysts related to this recharge magma are rare, and the crystals found in the dark blebs are identical in composition to those found in the dacite, indicating that the recharge was aphyric. The present-day, post-caldera recharge magma is different to the pre-1400 BP recharge magma: it is basaltic. This suggests that the plumbing system of Rabaul is different during the pre-caldera and

  11. Lithium enrichment in intracontinental rhyolite magmas leads to Li deposits in caldera basins

    OpenAIRE

    Benson, Thomas R.; Coble, Matthew A.; Rytuba, James J.; Mahood, Gail A.

    2017-01-01

    The omnipresence of lithium-ion batteries in mobile electronics, and hybrid and electric vehicles necessitates discovery of new lithium resources to meet rising demand and to diversify the global lithium supply chain. Here we demonstrate that lake sediments preserved within intracontinental rhyolitic calderas formed on eruption and weathering of lithium-enriched magmas have the potential to host large lithium clay deposits. We compare lithium concentrations of magmas formed in a variety of te...

  12. Lifetime and size of shallow magma bodies controlled by crustal-scale magmatism

    OpenAIRE

    Karakas, Ozge; Degruyter, Wim; Bachmann, Olivier; Dufek, Josef

    2017-01-01

    Magmatic processes on Earth govern the mass, energy and chemical transfer between the mantle, crust and atmosphere. To understand magma storage conditions in the crust that ultimately control volcanic activity and growth of continents, an evaluation of the mass and heat budget of the entire crustal column during magmatic episodes is essential. Here we use a numerical model to constrain the physical conditions under which both lower and upper crustal magma bodies form. We find that over long d...

  13. A Microsoft Excel interface for rhyolite-MELTS: a tool for research and teaching of magma properties and evolution

    Science.gov (United States)

    Gualda, G. A.; Ghiorso, M. S.

    2013-12-01

    The thermodynamic modeling software MELTS (and its derivatives) is a powerful and much utilized tool for investigating crystallization and melting in natural magmatic systems. Rhyolite-MELTS (Gualda et al. 2012, J. Petrol. 53:875-890) is a recent recalibration of MELTS aimed at better capturing the evolution of magmas present in the upper crust (up to ~400 MPa pressure). Currently, most users of rhyolite-MELTS rely on a graphical user interface (GUI), which can be run on UNIX/LINUX and Mac OS X computers. While the interface is powerful and flexible, it can be somewhat cumbersome for the novice and the output is in the form of text files that need to be processed offline. This situation is probably the main reason why MELTS - despite great potential - has not been used more frequently for teaching purposes. We are currently developing an alternative GUI for rhyolite-MELTS using web services consumed by a VBA backend in Microsoft Excel©. The goal is to create a much more interactive tool, that is easy to use that can be made available to a widespread audience, and that will be useful for both research and teaching. The interface is contained within a macro-enabled workbook, which includes editable cells where the user can insert the model input information. Interface buttons initiate computations that are executed on a central server at OFM Research in Seattle (WA). Results of simple calculations are shown immediately within the interface itself. For instance, a user can very rapidly determine the temperature at which a magma of a given composition is completely molten (i.e. find the liquidus); or determine which phases are present, in what abundances, their compositions, and their physical properties (e.g. density, viscosity) at any given combination of temperature, pressure and oxygen fugacity. We expect that using the interface in this mode will greatly facilitate building intuition about magmas and their properties. It is also possible to combine a sequence of

  14. Superhot fluids circulating close to magma intrusions: a contribution from analogue modelling

    Science.gov (United States)

    Montanari, Domenico; Agostini, Andrea; Bonini, Marco; Corti, Giacomo

    2017-04-01

    Magma overpressure at the time of the emplacement at shallow crustal levels may lead to deformation (i.e. forced folding, fracturing and faulting) in the country rock, both at local and regional scale. To get insights into this process, we reproduced and analysed in the laboratory the fracture/fault network associated with the emplacement of magma at shallow crustal levels. We used a mixture of quartz sand and K-feldspar fine sand as an analogue for the brittle crust, and polyglycerols for the magma. The models were able to reproduce complex 3D architectures of deformation resulting from magma emplacement, with different deformation patterns -invariably dominated by forced folding and associated brittle faulting/fracturing- resulting from variable parameters. These results provide useful hints into geothermal researches. Fractures and faults associated with magma emplacement are indeed expected to significantly influence the distribution and migration of superhot geothermal fluids near the edge of the magma intrusion. These structures can therefore be considered as potential targets for geothermal or mineral deposits exploration. In this perspective, the results of analogue models may provide useful geometric and conceptual constraints for field work, numerical modeling, and particularly seismic interpretation for achieving a better understanding and tuning of the integrated conceptual model concerning the circulation of supercritical fluids. The research leading to these results has received funding from the European Community's Seventh Framework Programme under grant agreement No. 608553 (Project IMAGE).

  15. Thermomechanical controls on magma supply and volcanic deformation: application to Aira caldera, Japan.

    Science.gov (United States)

    Hickey, James; Gottsmann, Joachim; Nakamichi, Haruhisa; Iguchi, Masato

    2016-09-13

    Ground deformation often precedes volcanic eruptions, and results from complex interactions between source processes and the thermomechanical behaviour of surrounding rocks. Previous models aiming to constrain source processes were unable to include realistic mechanical and thermal rock properties, and the role of thermomechanical heterogeneity in magma accumulation was unclear. Here we show how spatio-temporal deformation and magma reservoir evolution are fundamentally controlled by three-dimensional thermomechanical heterogeneity. Using the example of continued inflation at Aira caldera, Japan, we demonstrate that magma is accumulating faster than it can be erupted, and the current uplift is approaching the level inferred prior to the violent 1914 Plinian eruption. Magma storage conditions coincide with estimates for the caldera-forming reservoir ~29,000 years ago, and the inferred magma supply rate indicates a ~130-year timeframe to amass enough magma to feed a future 1914-sized eruption. These new inferences are important for eruption forecasting and risk mitigation, and have significant implications for the interpretations of volcanic deformation worldwide.

  16. Ascent phase trajectory optimization for vehicle with multi-combined cycle engine based on improved particle swarm optimization

    Science.gov (United States)

    Zhou, Hongyu; Wang, Xiaogang; Bai, Yuliang; Cui, Naigang

    2017-11-01

    An improved particle swarm optimization (IPSO) algorithm is proposed to optimize the ascent phase trajectory for vehicle with multi-combined cycle engine. Aerodynamic and thrust models are formulated in couple with flying states and environment. Conventional PSO has advantages in solving complicated optimization problems but has troubles in constraints handling and premature convergence preventing. To handle constraints, a modification in the fitness function of infeasible particles is executed based on the constraints violation and a comparation is executed to choose the better particle according to the fitness. To prevent premature, a diminishing number of particles are chosen to be mutated on the velocity by random times and directions. The ascent trajectory is divided into sub-phases according to engine modes. Different constraints, control parameters and engine models are considered in each sub-phase. Though the proposed algorithm is straightforward in comprehension and implementation, the numerical examples demonstrate that the algorithm has better performance than other PSO variants. In comparation with the commercial software GPOPS, the performance index of IPSO is almost the same as GPOPS but the results are less oscillating and dependent on initial values.

  17. Water ascent in trees and lianas: the cohesion-tension theory revisited in the wake of Otto Renner.

    Science.gov (United States)

    Bentrup, Friedrich-Wilhelm

    2017-03-01

    The cohesion-tension theory of water ascent (C-T) has been challenged over the past decades by a large body of experimental evidence obtained by means of several minimum or non-invasive techniques. The evidence strongly suggests that land plants acquire water through interplay of several mechanisms covered by the multi-force theory of (U. Zimmermann et al. New Phytologist 162: 575-615, 2004). The diversity of mechanisms includes, for instance, water acquisition by inverse transpiration and thermodynamically uphill transmembrane water secretion by cation-chloride cotransporters (L.H. Wegner, Progress in Botany 76:109-141, 2014). This whole plant perspective was opened by Otto Renner at the beginning of the last century who supported experimentally the strictly xylem-bound C-T mechanism, yet anticipated that the water ascent involves both the xylem conduit and parenchyma tissues. The survey also illustrates the known paradigm that new techniques generate new insights, as well as a paradigm experienced by Max Planck that a new scientific idea is not welcomed by the community instantly.

  18. Mushy magma processes in the Tuolumne intrusive complex, Sierra Nevada, California

    Science.gov (United States)

    Memeti, V.; Paterson, S. R.

    2012-12-01

    Debates continue on the nature of volcanic-plutonic connections and the mechanisms of derivation of large volcanic eruptions, which require large volumes of magma to be readily available within a short period of time. Our focus to understand these magma plumbing systems has been to study the nature of their mid-to upper crustal sections, such as the 1,000 km2, 95-85 Ma old Tuolumne intrusive complex in the Sierra Nevada, California, USA. The Tuolumne intrusive complex is a great example where the magma mush model nicely explains observations derived from several datasets. These data suggest that a magma mush body was present and may have been quite extensive especially at times when the Tuolumne intrusive complex was undergoing waxing periods of magmatism (increased magma input), which alternated with waning periods of magmatism (decreased magma addition) and thus a smaller mush body, essentially mimicking in style periodic flare-ups and lulls at the arc scale. During waxing stages, magma erosion and mixing were the dominant processes, whereas waning stages allowed mush domains to continue to undergo fractional crystallization creating additional compositional variations. Over time, the imprint left behind by previous waxing and waning stages was partly overprinted, but individual crystals successfully recorded the compositions of these earlier magmas. Waxing periods in the Tuolumne intrusive complex during which large magma mush bodies formed are supported by the following evidence: 1) Hybrid units and gradational contacts are commonly present between major Tuolumne units. 2) CA-TIMS U/Pb zircon geochronology data demonstrate that antecrystic zircon recycling took place unidirectional from the oldest, marginal unit toward the younger, interior parts of the intrusion, where increasing zircon age spread encompasses the entire age range of the Tuolumne. 3) The younger, interior units also show an increasing scatter and complexity in geochemical element and isotope

  19. Experimental Study into the Stability of Whitlockite in Basaltic Magmas

    Science.gov (United States)

    McCubbin, F. M.; Barnes, J. J.; Srinivasan, P.; Whitson, E. S.; Vander Kaaden, K. E.; Boyce, J. W.

    2017-01-01

    latter treatment resulted in the dehydrogenation of whitlockite to form merrillite. The presence of merrillite vs. whitlockite was widely thought to serve as an indication that magmas were anhydrous [e.g., 6-7]. However, McCubbin et al., [8] determined that merrillite in the martian meteorite Shergotty had no discernible whitlockite component despite its coexistence with OH-rich apatite. Consequently, McCubbin et al., (2014) speculated that the absence of a whitlockite component in Shergotty merrillite and other planetary merrillites may be a consequence of the limited thermal stability of H in whitlockite (stable only at T less than1050degC), which would prohibit merrillite-whitlockite solid-solution at high temperatures. In the present study, we have aimed to test this hypothesis experimentally by examining the stability of whitlockite in basaltic magmas at 1.2 GPa and a temperature range of -1000- 1300degC.

  20. Bonding of xenon to oxygen in magmas at depth

    Science.gov (United States)

    Leroy, Clémence; Sanloup, Chrystèle; Bureau, Hélène; Schmidt, Burkhard C.; Konôpková, Zuzana; Raepsaet, Caroline

    2018-02-01

    The field of noble gases chemistry has witnessed amazing advances in the last decade with over 100 compounds reported including Xe oxides and Xe-Fe alloys stable at the pressure-temperature conditions of planetary interiors. The chemistry of Xe with planetary materials is nonetheless still mostly ignored, while Xe isotopes are used to trace a variety of key planetary processes from atmosphere formation to underground nuclear tests. It is indeed difficult to incorporate the possibility of Xe reactivity at depth in isotopic geochemical models without a precise knowledge of its chemical environment. The structure of Xe doped hydrous silica-rich melts is investigated by in situ high energy synchrotron X-ray diffraction using resistive heating diamond anvil cells. Obtained pair distribution functions reveal the oxidation of Xe between 0.2 GPa and 4 GPa at high T up to 1000 K. In addition to the usual interatomic distances, a contribution at 2.05 ± 0.05 Å is observed. This contribution is not observed in the undoped melt, and is interpreted as the Xe-O bond, with a coordination number of about 12 consistent with Xe insertion in rings of the melt structure. Xe solubility measurements by electron microprobe and particle induced X-rays emission analysis confirm that Xe and Ar have similar solubility values in wt% in silicate melts. These values are nonetheless an order of magnitude higher than those theoretically calculated for Xe. The formation of Xe-O bonds explains the enhanced solubility of Xe in deep continental crust magmas, revealing a mechanism that could store Xe and fractionate its isotopes. Xenon is indeed atypical among noble gases, the atmosphere being notably depleted in elemental Xe, and very strongly depleted in Xe light isotopes. These observations are known as the 'missing' Xe paradox, and could be solved by the present findings.

  1. Phenocryst complexity in andesites and dacites from the Tequila volcanic field, Mexico: resolving the effects of degassing vs. magma mixing

    Science.gov (United States)

    Frey, Holli M.; Lange, Rebecca A.

    2011-08-01

    The petrology of five phenocryst-poor (2-5%) andesites and dacites, all of which were erupted from different short-lived, monogenetic vents, is compared to that of phenocryst-rich (10-25%) andesites erupted from the adjacent stratovolcano, Volcán Tequila, in the Mexican arc. Despite differences in phenocryst abundances, these magmas have comparable phase assemblages (plagioclase + orthopyroxene + titanomagnetite + ilmenite + apatite ± augite ± hornblende), and similarly wide variations in phenocryst compositions, coupled to complex zoning patterns. For the phenocryst-poor lavas, equilibrium pairs of two Fe-Ti oxides lead to a narrow range of calculated temperatures for each sample that range from 934 (±24) to 1,073 (±6)°C and oxygen fugacities that range from +0.1 to +0.7 log units relative to the Ni-NiO buffer. Application of the plagioclase-liquid hygrometer to each sample at these calculated temperatures leads to maximum melt water concentrations of 4.6-3.1 wt% during plagioclase crystallization, indicating that the magmas were fluid saturated at depths ≥6.4-4.5 km. There is a wide, continuous range in the composition of plagioclase (≤44 mol% An) and orthopyroxene (≤16% Mg#) phenocrysts in each sample, which is consistent with a loss of dissolved water (≤2.8 wt%) from the melt phase during degassing as the magmas ascended rapidly to the surface. Evidence is presented that shows the effect of dissolved water is to reduce the activity of MgO relative to FeO in the melt phase, which indicates that degassing will also affect the Mg# of pyroxene phenocrysts, with higher melt water concentrations favoring Fe-rich pyroxene. Both plagioclase and orthopyroxene commonly display diffusion-limited growth textures (e.g., skeletal and hopper crystals, large interior melt hollows, and swallow tails), which are consistent with large undercoolings produced by degassing-induced crystallization. Therefore, degassing is proposed as a possible cause for the phenocryst

  2. Volcanic flood simulation of magma effusion using FLO-2D for drainage of a caldera lake at the Mt. Baekdusan

    Science.gov (United States)

    Lee, Khil-Ha; Kim, Sung-Wook; Kim, Sang-Hyun

    2014-05-01

    Many volcanic craters and calderas are filled with large amounts of water that can pose significant flood hazards to downstream communities due to their high elevation and the potential for catastrophic releases of water. Recent reports pointed out the Baekdusan volcano that is located between the border of China and North Korea as a potential active volcano. Since Millennium Eruption around 1000 AD, smaller eruptions have occurred at roughly 100-year intervals, with the last one in 1903. Sudden release of huge volume of water stored in temporarily elevated caldera lakes are a recurrent feature of volcanic environments, due to the case with which outlet channels are blocked by and re-cut through, unwelded pyroclastic deposits. The volcano is showing signs of waking from a century-long slumber recently. Volcanic floods, including breakouts from volcanic lakes, can affect communities beyond the areas immediately affected by a volcanic eruption and cause significant hydrological hazards because floods from lake-filled calderas may be particularly large and high. Although a number of case studies have been presented in the literature, investigation of the underlying physical processes is required as well as a method for interpreting the process of the rapid release of water stored in a caldera lake. The development of various forecasting techniques to prevent and minimize economic and social damage is in urgent need. This study focuses on constructing a flood hazard map triggered by the magma effusion in the Baekdusan volcano. A physically-based uplift model was developed to compute the amount of water and time to peak flow. The ordinary differential equation was numerically solved using the finite difference method and Newton-Raphson iteration method was used to solve nonlinear equation. The magma effusion rate into the caldera lake is followed by examples at other volcanic activities. As a result, the hydrograph serves as an upper boundary condition when hydrodynamic

  3. Hydrogen, Oxygen and Silicon Isotope Systematics of Groundwater-Magma Interaction in Icelandic Hydrothermal Systems

    Science.gov (United States)

    Kleine, B. I.; Stefansson, A.; Halldorsson, S. A.; Martin, W.; Barnes, J.; Jónasson, K.; Franzson, H.

    2016-12-01

    Magma often encounters groundwater (meteoric or seawater derived) when intruded into the crust. Magma-groundwater interactions result in the formation of hydrothermal fluids which can lead to contact metamorphism and elemental transport in the country rock. In fact, magma-hydrothermal fluid interaction (rather than magma-magmatic fluid interaction) may lead to classic contact metamorphic reactions. In order to explore the importance of hydrothermal fluid during contact metamorphism we use stable isotopes (δD, δ18O, δ30Si) from both active and extinct magma chambers and hydrothermal systems from across Iceland. Quartz grains from various hydrothermal systems, from crustal xenoliths from the Askja central volcano and from the Hafnarfjall pluton, as well as quartz grains associated with low-T zeolites were analysed for δ18O and δ30Si in-situ using SIMS. Whole rock material of these samples was analysed for δD values using a TCEA coupled to an IRMS. Our results indicate that low-T quartz (300°C). Combining the results from the analyses of δ18O and δD allows further division of samples into (i) seawater and/or rock dominated and (ii) meteoric water dominated hydrothermal systems. In order to isolate the effects of fluid-rock interaction, fluid source and formation temperature at the magma-groundwater contact, δD, δ18O and δ30Si values of rocks and fluids were modeled using the PHREEQC software. Comparison of analytical and model results shows that the isotopic compositions are influenced by multiple processes. In some cases, groundwater penetrates the contact zone and causes alteration at >400°C by groundwater-magma heat interaction. Other cases document "baked" contact zones without groundwater. Our analyses and modeling demonstrates that groundwater flow and permeability are crucial in setting the style of contact metamorphism around high T intrusions.

  4. Rapid laccolith intrusion driven by explosive volcanic eruption.

    Science.gov (United States)

    Castro, Jonathan M; Cordonnier, Benoit; Schipper, C Ian; Tuffen, Hugh; Baumann, Tobias S; Feisel, Yves

    2016-11-23

    Magmatic intrusions and volcanic eruptions are intimately related phenomena. Shallow magma intrusion builds subsurface reservoirs that are drained by volcanic eruptions. Thus, the long-held view is that intrusions must precede and feed eruptions. Here we show that explosive eruptions can also cause magma intrusion. We provide an account of a rapidly emplaced laccolith during the 2011 rhyolite eruption of Cordón Caulle, Chile. Remote sensing indicates that an intrusion began after eruption onset and caused severe (>200 m) uplift over 1 month. Digital terrain models resolve a laccolith-shaped body ∼0.8 km3. Deformation and conduit flow models indicate laccolith depths of only ∼20-200 m and overpressures (∼1-10 MPa) that likely stemmed from conduit blockage. Our results show that explosive eruptions may rapidly force significant quantities of magma in the crust to build laccoliths. These iconic intrusions can thus be interpreted as eruptive features that pose unique and previously unrecognized volcanic hazards.

  5. International Inequality in the Age of Globalization: Japanese Economic Ascent and the Restructuring of the Capitalist World-Economy

    Directory of Open Access Journals (Sweden)

    Paul S. Ciccantell

    2015-08-01

    Full Text Available This paper shows how Japanese ?rms and the Japanese state constructed a development model based on the steel industry as a generative sector that drove Japan’s economic ascent in the world-historical context of U.S. hegemony. We make three arguments in this paper. First, there is a new model of capital accumulation that does create new forms of social inequality by redistributing costs and bene?ts in very di?erent ways than earlier models. Second, Japanese ?rms and the Japanese state created this new model of capital accumulation and social inequality via mechanisms including joint ventures, long term contracts, and other forms of international trade and investment, not U.S.-based transnational corporations, as is usually assumed. Third, world-systems theory reconstructed through the lens of the new historical materialism explains this restructuring of the capitalist world-economy as the outcome of Japan’s economic ascent over the last ?fty years. Further, we argue that this new model of capital accumulation has had similar impacts on redistributing the costs and bene?ts of development between core and peripheral regions of the capitalist world-economy in a wide range of global industries. These strategies created a tightly linked set of technological and organizational innovations to overcome the natural and social obstacles to Japanese development, dramatically increase Japan’s international economic competitiveness by lowering production costs in all sectors of the economy, turn Japan into the world’s largest exporter of manufactured products, restructure a range of global industries, and recreate the world-system hierarchy in support of Japanese development. In particular, organizational inno-vations in the use of long term contracts and joint ventures in raw materials industries to foster global excess capacity and lower rents to resource extracting ?rms and states reallocated the costs of providing the material building blocks of

  6. INTERACTIONS BETWEEN GABBROID AND GRANITOID MAGMAS DURING FORMATION OF THE PREOBRAZHENSKY INTRUSION, EAST KAZAKHSTAN

    Directory of Open Access Journals (Sweden)

    S. V. Khromykh

    2017-01-01

    Full Text Available The paper reports on studies of the Preobrazhensky gabbro‐granitoid intrusion, East Kazakhstan, com‐ posed of the rocks that belong to four phases of intrusion, from quartz monzonites and gabbroids to granite‐ leucogranites. Specific relationships between basite and granitoid rocks are usually classified as the result of interac‐ tions and mixing of liquid magmas, i.e. magma mingling and mixing. Basite rocks are represented by a series from biotite gabbros to monzodiorites. Granitoids rocks are biotite‐amphibole granites. Porphyric granosyenites, com‐ bining the features of both granites and monzodiorites, are also involved in mingling. It is established that the primary granitoid magmas contained granosyenite/quartz‐monzonite and occurred in the lower‐medium‐crust conditions in equilibrium with the garnet‐rich restite enriched with plagioclase. Monzodiorites formed during fractionation of the parent gabbroid magma that originated from the enriched mantle source. We propose a magma interaction model describing penetration of the basite magma into the lower horizons of the granitoid source, which ceased below the viscoplastic horizon of granitoids. The initial interaction assumes the thermal effect of basites on the almost crystal‐ lized granitic magma and saturation of the boundary horizons of the basite magma with volatile elements, which can change the composition of the crystallizing melt from gabbroid to monzodiorite. A ‘boundary’ layer of monzodiorite melt is formed at the boundary of the gabbroid and granitoid magmas, and interacts with granitoids. Due to chemical interactions, hybrid rocks – porphyric granosyenites – are formed. The heterogeneous mixture of monzodiorites and granosyenites is more mobile in comparison with the overlying almost crystallized granites. Due to contraction frac‐ turing in the crystallized granites, the heterogeneous mixture of monzodiorites and granosyenites penetrate into the

  7. Numerical Simulation of Magma Effects on Hydrothermal Venting at Ultra-Slow Spreading Southwest Indian Ridge

    Science.gov (United States)

    Zang, Hong; Niu, Xiongwei; Ruan, Aiguo; Li, Jiabiao; Meng, Lin

    2017-04-01

    Finite element method is used to numerically simulate oceanic crust thermal dynamics in order to understand the hydrothermal venting mechanism at ultra-slow spreading ridge, whether is the ancient magma chamber still living and supplying hot magma for vents or have surrounding hotspots been affecting on the ridge continually with melting and hot magma. Two models are simulated, one is a horizontal layered oceanic crust model and the other is a model derived from wide angle seismic experiment of OBS at the ultra-slow spreading Southwest Indian Ridge (50°E, Zhao et al., 2013; Li et al., 2015; Niu et al., 2015). For the former two cases are simulated: without magma from upper mantel or with continuous magma supply, and for the latter supposing magma supply occurs only once in short period. The main conclusions are as follows: (1) Without melt magma supply at the oceanic crust bottom, a magma chamber can live only thousands ten thousand years. According to the simulated results in this case, the magma chamber revealed by seismic data at the mid-east shallow section of the Southwest Indian Ridge could only last 0.8Ma, the present hydrothermal venting is impossible to be the caused by the magma activity occurred during 8-11Ma (Sauter et al., 2009). (2) The magma chamber can live long time with continuous hot magma supply beneath the oceanic crust due to the melting effects of surrounding ridge hotspots, and would result hydrothermal venting with some tectonic structures condition such as detachment faults. We suggest that the present hydrothermal activities at the mid-east shallow section of the Southwest Indian Ridge are the results of melting effects or magma supply from surrounding hotspots. This research was granted by the National Basic Research program of China (grant 2012CB417301) and the National Natural Science Foundation of China (grants 41176046, 91228205). References Zhao, M., Qiu, X., Li, J., et al., 2013. Three-dimensional seismic structure of the Dragon

  8. A mantle-driven surge in magma supply to Kīlauea Volcano during 2003--2007

    Science.gov (United States)

    Poland, Michael P.; Miklius, Asta; Sutton, A. Jeff; Thornber, Carl R.

    2012-01-01

    The eruptive activity of a volcano is fundamentally controlled by the rate of magma supply. At Kīlauea Volcano, Hawai‘i, the rate of magma rising from a source within Earth’s mantle, through the Hawaiian hotspot, was thought to have been relatively steady in recent decades. Here we show that the magma supply to Kīlauea at least doubled during 2003–2007, resulting in dramatic changes in eruptive activity and the formation of new eruptive vents. An initial indication of the surge in supply was an increase in CO2 emissions during 2003–2004, combined with the onset of inflation of Kīlauea’s summit, measured using the Global Positioning System and interferometric synthetic aperture radar. Inflation was not limited to the summit magma reservoirs, but was recorded as far as 50 km from the summit, implying the existence of a connected magma system over that distance. We also record increases in SO2 emissions, heightened seismicity, and compositional and temperature variations in erupted lavas. The increase in the volume of magma passing through and stored within Kīlauea, coupled with increased CO2 emissions, indicate a mantle source for the magma surge. We suggest that magma supply from the Hawaiian hotspot can vary over timescales of years, and that CO2 emissions could be a valuable aid for assessing variations in magma supply at Kīlauea and other volcanoes.

  9. Multiple magma emplacement and its effect on the superficial deformation: hints from analogue models

    Science.gov (United States)

    Montanari, Domenico; Bonini, Marco; Corti, Giacomo; del Ventisette, Chiara

    2017-04-01

    To test the effect exerted by multiple magma emplacement on the deformation pattern, we have run analogue models with synchronous, as well as diachronous magma injection from different, aligned inlets. The distance between injection points, as well as the activation in time of injection points was varied for each model. Our model results show how the position and activation in time of injection points (which reproduce multiple magma batches in nature) strongly influence model evolution. In the case of synchronous injection at different inlets, the intrusions and associated surface deformation were elongated. Forced folds and annular bounding reverse faults were quite elliptical, and with the main axis of the elongated dome trending sub-parallel to the direction of the magma input points. Model results also indicate that the injection from multiple aligned sources could reproduce the same features of systems associated with planar feeder dikes, thereby suggesting that caution should be taken when trying to infer the feeding areas on the basis of the deformation features observed at the surface or in seismic profiles. Diachronous injection from different injection points showed that the deformation observed at surface does not necessarily reflect the location and/or geometry of their feeders. Most notably, these experiments suggest that coeval magma injection from different sources favor the lateral migration of magma rather than the vertical growth, promoting the development of laterally interconnected intrusions. Recently, some authors (Magee et al., 2014, 2016; Schofield et al., 2015) have suggested that, based on seismic reflection data analysis, interconnected sills and inclined sheets can facilitate the transport of magma over great vertical distances and laterally for large distances. Intrusions and volcanoes fed by sill complexes may thus be laterally offset significantly from the melt source. Our model results strongly support these findings, by reproducing

  10. Storage of Explosive versus Effusive Rhyolite Magma at the Yellowstone Volcanic Center

    Science.gov (United States)

    Gardner, J. E.

    2007-12-01

    The Yellowstone volcanic center has erupted more than 900 km3 of rhyolitic magma in the last 600,000 years (1). Most of that magma extruded as large lava flows, with only a few known explosive eruptions. Why have explosive eruptions been so rare in the recent history of the Yellowstone volcanic system? To explore that question, we focus on the Tuff of Bluff Point (TBP), about 50 km3 of magma that explosively erupted 173 ka, forming the West Thumb caldera (1). Like most other recent eruptions of Yellowstone, TBP is high silica rhyolite, with phenocrysts of quartz, sanidine, and minor ferro-pyroxenes and Fe-Ti oxides. Fe-Ti oxide and pyroxene compositions indicate that the magma had equilibrated at an oxygen fugacity equal to the QFM buffer. Rehomogenized glass inclusions (n=7) in quartz contain 2.2-3.1 wt.% water and between 400-650 ppm CO2. Those volatile contents indicate storage pressures of 90-160 MPa. Ubiquitous pyrrhotite shows that the magma was sulfur saturated, and most likely volatile saturated. The co-existing fluid would be only 42-47% water. Cathodoluminescence (CL) images of quartz phenocrysts reveal mainly concentric growth zones, with occasional dissolution boundaries present. Ti contents in quartz generally decrease from core to rim, indicating cooling of the magma, although the relative temperature changes recorded are only 10-15°, with only minor changes across dissolution boundaries. To put our observations in perspective of the recent Yellowstone magma system, we have begun examining some of the recent rhyolitic lavas, including the Pitchstone Plateau (PP), a single homogeneous lava flow of 70 km3 that erupted 79 ka (1). CL images also reveal mainly concentric quartz growth, with few dissolution boundaries obvious. Ti contents in quartz also generally decrease from core to rim, but are uniformly lower than in those in TBP, suggesting that PP magma was colder than TBP magma. Glass inclusions (n=20) in PP are generally water poor and rarely

  11. Slip on serpentine detachments at magma-poor margins

    Science.gov (United States)

    Reston, Timothy; Lymer, Gael; Cresswell, Derren; Stevenson, Carl; Bull, Jonathan; Sawyer, Dale; Morgan, Julia; Galicia 3D working Group

    2017-04-01

    At magma-poor margins, the structures formed during rifting are not obscured by thick lavas, allowing detailed analysis of the tectonics of rifting and breakup. At most of these margins, the mantle beneath the thin crust has unusually low velocities, interpreted as a consequence of serpentinization following the embrittlement of the crust during rifting; models for the onset of serpentinization predict the thicknesses of crust that are observed at the landward limit of the serpentinized mantle. At a handful of margins the top of the serpentinized mantle appears to have acted as a detachment or decollement: faults that bound the overlying crustal blocks root on a bright reflection at the base of these blocks. Examples include the P reflection west of Ireland, the H reflection west of northern Portugal, and the S reflector west of Galicia. Corrugations observed on a 3D volume collected in 2013 above the S reflector strongly support its interpretation as a slip surface. A remaining question is whether slip on these "serpentine detachments" occurred at low-angle or not: for typical friction coefficients of 0.7, normal faults should lock-up and be replaced by steeper faults once they have rotated to perhaps 35°, an observation consistent with earthquake data. This angle can be reduced to 20-25° if the fault zone is composed of weak minerals such as serpentine. One possibility is that the detachment is actually composed of segments of faults that were active sequentially in a rolling hinge model. Beneath the centre of the Porcupine basin, the P reflection is sub-horizontal but its western continuation dips beneath the Porcupine bank at 20-25°, consistent with slip on serpentine-weakened rolling hinge system. West of Galicia, based on the geometrical relationships between late synrift wedges and their bounding faults which root on S, S has been interpreted to have slipped at angles below 20-25°. However, a 3D dataset collected over S in 2013 provides the opportunity

  12. Rapid Prototyping

    Science.gov (United States)

    1999-01-01

    Javelin, a Lone Peak Engineering Inc. Company has introduced the SteamRoller(TM) System as a commercial product. The system was designed by Javelin during a Phase II NASA funded small commercial product. The purpose of the invention was to allow automated-feed of flexible ceramic tapes to the Laminated Object Manufacturing rapid prototyping equipment. The ceramic material that Javelin was working with during the Phase II project is silicon nitride. This engineered ceramic material is of interest for space-based component.

  13. Magmatic architecture within a rift segment: Articulate axial magma storage at Erta Ale volcano, Ethiopia

    Science.gov (United States)

    Xu, Wenbin; Rivalta, Eleonora; Li, Xing

    2017-10-01

    Understanding the magmatic systems beneath rift volcanoes provides insights into the deeper processes associated with rift architecture and development. At the slow spreading Erta Ale segment (Afar, Ethiopia) transition from continental rifting to seafloor spreading is ongoing on land. A lava lake has been documented since the twentieth century at the summit of the Erta Ale volcano and acts as an indicator of the pressure of its magma reservoir. However, the structure of the plumbing system of the volcano feeding such persistent active lava lake and the mechanisms controlling the architecture of magma storage remain unclear. Here, we combine high-resolution satellite optical imagery and radar interferometry (InSAR) to infer the shape, location and orientation of the conduits feeding the 2017 Erta Ale eruption. We show that the lava lake was rooted in a vertical dike-shaped reservoir that had been inflating prior to the eruption. The magma was subsequently transferred into a shallower feeder dike. We also find a shallow, horizontal magma lens elongated along axis inflating beneath the volcano during the later period of the eruption. Edifice stress modeling suggests the hydraulically connected system of horizontal and vertical thin magmatic bodies able to open and close are arranged spatially according to stresses induced by loading and unloading due to topographic changes. Our combined approach may provide new constraints on the organization of magma plumbing systems beneath volcanoes in continental and marine settings.

  14. Timing of Crystallisation of the Lunar Magma Ocean Constrained by the Oldest Zircon

    Science.gov (United States)

    Nemchin, A.; Timms, N.; Pidgeon, R.; Geisler, T.; Reddy, S.; Meyer, C.

    2009-01-01

    The presently favoured concept for the early evolution of the Moon involves consolidation of debris from a giant impact of a Mars sized body with Earth forming a primitive Moon with a thick global layer of melt referred to as the Lunar Magma Ocean1 . It is widely accepted that many significant features observed on the Moon today are the result of crystallisation of this magma ocean. However, controversy exists over the precise timing and duration of the crystallisation process. Resolution of this problem depends on the establishment of precise and robust key crystallisation time points. We report a 4417 6 Myr old zircon in lunar breccia sample 72215,195, which provides a precisely determined younger limit for the solidification of the Lunar Magma Ocean. A model based on these data, together with the age of the Moon forming giant impact, defines an exponential time frame for crystallisation and suggests formation of anorthositic crust after about 80-85% of the magma ocean was solidified. In combination with other zircon ages the 4417 +/- 6 Myr age also suggests that the very small (less than a few per cent) residual portion of the magma ocean continued to solidify during the following 300-500 m.y.

  15. Onset of solid state mantle convection and mixing during magma ocean solidification

    Science.gov (United States)

    Maurice, Maxime; Tosi, Nicola; Samuel, Henri; Plesa, Ana-Catalina; Hüttig, Christian; Breuer, Doris

    2017-04-01

    The fractional crystallization of a magma ocean can cause the formation of a compositional layering that can play a fundamental role for the subsequent long-term dynamics of the interior, for the evolution of geochemical reservoirs, and for surface tectonics. In order to assess to what extent primordial compositional heterogeneities generated by magma ocean solidification can be preserved, we investigate the solidification of a whole-mantle Martian magma ocean, and in particular the conditions that allow solid state convection to start mixing the mantle before solidification is completed. To this end, we performed 2-D numerical simulations in a cylindrical geometry. We treat the liquid magma ocean in a parametrized way while we self-consistently solve the conservation equations of thermochemical convection in the growing solid cumulates accounting for pressure-, temperature- and, where it applies, melt-dependent viscosity as well as parametrized yield stress to account for plastic yielding. By testing the effects of different cooling rates and convective vigor, we show that for a lifetime of the liquid magma ocean of 1 Myr or longer, the onset of solid state convection prior to complete mantle crystallization is likely and that a significant part of the compositional heterogeneities generated by fractionation can be erased by efficient mantle mixing.

  16. Forcings and Feedbacks on Convection in the 2010 Pakistan Flood: Modeling Extreme Precipitation with Interactive Large-Scale Ascent

    CERN Document Server

    Nie, Ji; Sobel, Adam H

    2016-01-01

    Extratropical extreme precipitation events are usually associated with large-scale flow disturbances, strong ascent and large latent heat release. The causal relationships between these factors are often not obvious, however, and the roles of different physical processes in producing the extreme precipitation event can be difficult to disentangle. Here, we examine the large-scale forcings and convective heating feedback in the precipitation events which caused the 2010 Pakistan flood within the Column Quasi-Geostrophic framework. A cloud-revolving model (CRM) is forced with the large-scale forcings (other than large-scale vertical motion) computed from the quasi-geostrophic omega equation with input data from a reanalysis data set, and the large-scale vertical motion is diagnosed interactively with the simulated convection. Numerical results show that the positive feedback of convective heating to large-scale dynamics is essential in amplifying the precipitation intensity to the observed values. Orographic li...

  17. Changes in labial capillary density on ascent to and descent from high altitude [version 1; referees: 2 approved

    Directory of Open Access Journals (Sweden)

    Edward Gilbert-Kawai

    2016-08-01

    Full Text Available Present knowledge of how the microcirculation is altered by prolonged exposure to hypoxia at high altitude is incomplete and modification of existing analytical techniques may improve our knowledge considerably. We set out to use a novel simplified method of measuring in vivo capillary density during an expedition to high altitude using a CytoCam incident dark field imaging video-microscope. The simplified method of data capture involved recording one-second images of the mucosal surface of the inner lip to reveal data about microvasculature density in ten individuals. This was done on ascent to, and descent from, high altitude. Analysis was conducted offline by two independent investigators blinded to the participant identity, testing conditions and the imaging site.  Additionally we monitored haemoglobin concentration and haematocrit data to see if we could support or refute mechanisms of altered density relating to vessel recruitment. Repeated sets of paired values were compared using Kruskall Wallis Analysis of Variance tests, whilst comparisons of values between sites was by related samples Wilcoxon Signed Rank Test. Correlation between different variables was performed using Spearman’s rank correlation coefficient, and concordance between analysing investigators using intra-class correlation coefficient. There was a significant increase in capillary density from London on ascent to high altitude; median capillaries per field of view area increased from 22.8 to 25.3 (p=0.021. There was a further increase in vessel density during the six weeks spent at altitude (25.3 to 32.5, p=0.017. Moreover, vessel density remained high on descent to Kathmandu (31.0 capillaries per field of view area, despite a significant decrease in haemoglobin concentration and haematocrit. Using a simplified technique, we have demonstrated an increase in capillary density on early and sustained exposure to hypobaric hypoxia at thigh altitude, and that this remains

  18. Mechanical energy transfers across lower limb segments during stair ascent and descent in young and healthy older adults.

    Science.gov (United States)

    Novak, Alison C; Li, Qingguo; Yang, Shuozhi; Brouwer, Brenda

    2011-07-01

    Older adults present with altered movement patterns during stair negotiation although the extent to which modifications in pattern and speed influence mechanical efficiency is unknown. This study evaluated mechanical energy transfers attributed to active force production during stair negotiation in young and older adults to provide insight into age-related changes in mechanical efficiency. Secondary analysis on data obtained from 23 young (23.7±3.0 years) and 32 older adults (67.0±8.2 years) during self-paced stair ascent and descent was conducted. Mechanical energy expenditures (MEE) during concentric transfer, eccentric transfer and no-transfer phases were determined for the ankle, knee and hip power profiles in the sagittal plane. Mechanical energy compensations (MEC) were also determined at each joint. During ascent, MEEs were similar for young and older adults although older adults compensated ankle muscles to a lesser extent during concentric muscle action. Controlling for cadence eliminated this difference. During descent, older adults demonstrated lower energy expenditures at the ankle and hip and similar expenditures at the knee compared to young adults. Changes in joint MEE in the older group resulted in reduced energy compensation at the ankle during concentric and eccentric activity and at the knee during eccentric activity. These age-related differences in mechanical energy transfers and related adjustments in MEC were not a function of the slower cadence in older adults and suggest a loss in mechanical efficiency. These results provide a benchmark against which physical impairments in older adults may be explored. Copyright © 2011 Elsevier B.V. All rights reserved.

  19. Volatile constraints on the magma supply, dynamics and plumbing system of a top-ranking basaltic gas emitter: Ambrym volcano, Vanuatu Arc

    Science.gov (United States)

    Allard, Patrick

    2016-04-01

    P. Allard1,2, A. Aiuppa3,4, P. Bani5, N. Métrich1,6, A. Bertagnini6, M. Burton7, P-J. Gauthier5, F. Parello3, H. Shinohara8, G. Sawyer9, E. Bagnato3, E. Garaebiti10 1IPGP, UMR7154 CNRS, Paris France; 2INGV, Sezione di Catania, Italy; 3DiSTEM, Palermo University, Italy; 4INGV, Sezione di Palermo, Italy; 5LMV-OPGC, Clermont-Ferrand, France; 6INGV, Sezione di Pisa, Italy; 7SEAES, University of Manchester, UK; 8Geological Survey of Japan, Tsukuba, Japan; 9Department of Geography, University of Cambridge, UK; 10GEOHAZARD, Port Vila, Vanuatu. Ambrym basaltic volcano (central Vanuatu arc) is one of the most active volcanic systems of the Southwest Pacific region, where recurrent lava lake activity sustains voluminous gas release from two main cones, Benbow and Marum, in a 12 km-wide summit caldera. In 2007-2008 we could perform the first detailed investigations of gas emissions from this very active but remote and hardly accessible intra-oceanic arc volcano, combining ground-based and airborne measurements and using both in situ and remote sensing tools. The degassing budget of major, minor, trace and radioactive volatile species reveals that Ambrym ranks amongst the three most powerful persistent emitters of magmatic volatiles at global scale [1]. Coupled with the analysis of dissolved volatiles in the feeding basalt (olivine-hosted melt inclusions), the gas emission rates imply a very high average magma supply/degassing rate of 25 m3/s - 6 times the rate at Mount Etna - from a reservoir emplaced at about 4 km depth beneath the caldera floor. The chemical composition of emitted volcanic gases is compatible with dominant closed-system ascent and degassing of the basalt, followed by open degassing at shallow depth as water exsolution becomes extensive. The modest time-averaged extrusion rate, estimated from caldera infilling over the past 2 ka, requires convective downward recycling of the denser degassed magma in conduits with diameter of order 10 m. High resolution OP

  20. Short Magma Residence Times at Mt. Rainier and the Probable Absence of a Large, Integrated, and Long-lived Magma Reservoir System

    Science.gov (United States)

    Sisson, T. W.; Lanphere, M. A.

    2003-12-01

    Intensive, high-precision K-Ar and 40Ar/39Ar geochronology have proven essential for producing modern geologic maps of volcanoes and from these determining the volcanoes' time-volume histories. If sufficiently abundant, these data can also reveal aspects of the magma supply system. For Cascade volcanoes a general result has been the demonstration that edifice growth is highly episodic. Mount Rainier grew in the last 500,000 years atop the remains of an ancestral edifice that was active in the same location 1 - 2 Myr ago. The 500,000 year history of the modern edifice falls into four stages of alternating high and low magmatic output of subequal duration, but major and trace element compositions of eruptives show no correlation with volcano growth stages. Instead, the same spectrum of magmas (andesite to low-Si dacite) erupted throughout the history of the volcano with compositions in the same relative abundances. Superimposed on this seemingly null result are at least 6 brief but pronounced excursions in magma trace-element compositions. Concentrations of Zr, Ba, or Sr can double and then return to background values passing into and out of a single flow or flow-group. Some excursions are tightly bracketed by mapping and by measured ages and have durations no more than the geochronologic measurement precision of about 10,000 years. True excursion durations are potentially much shorter. The brevity and abrupt onsets and cessations of these compositional excursions are evidence against the presence of a sizeable, long-lived magma reservoir anywhere beneath the volcano, including a MASH zone in the lower crust, that would have attenuated, dampened, and homogenized compositional excursions introduced into the magmatic system. Instead, we take 10,000 years as a probable upper limit to the average residence time of magma batches transiting the crustal portion of Mount Rainier's plumbing system. A consistent scenario is that parental magmas enter the crust, differentiate

  1. Integrating cut-and-solve and semi-Lagrangean based dual ascent for the single-source capacitated facility location problem

    DEFF Research Database (Denmark)

    Gadegaard, Sune Lauth

    This paper describes how the cut-and-solve framework and semi-Lagrangean based dual ascent algorithms can be integrated in two natural ways in order to solve the single source capacitated facility location problem. The first uses the cut-and-solve framework both as a heuristic and as an exact...

  2. Petrogenesis of the Elephant Moraine A79001 meteorite Multiple magma pulses on the shergottite parent body

    Science.gov (United States)

    Mcsween, H. Y., Jr.; Jarosewich, E.

    1983-01-01

    The EETA 79001 achondrite consists of two distinct igneous lithologies joined along a planar, non-brecciated contact. Both are basaltic rocks composed primarily of pigeonite, augite, and maskelynite, but one contains zoned megacrysts of olivine, orthopyroxene, and chromite that represent disaggregated xenoliths of harzburzite. Both lithologies probably formed from successive volcanic flows or multiple injections of magma into a small, shallow chamber. Many similarities between the two virtually synchronous magmas suggest that they are related. Possible mechanisms to explain their differences involve varying degrees of assimilation, fractionation from similar parental magmas, or partial melting of a similar source peridotite; of these, assimilation of the observed megacryst assemblage seems most plausible. However, some isotopic contamination may be required in any of these petrogenetic models. The meteorite has suffered extensive shock metamorphism and localized melting during a large impact event that probably excavated and liberated it from its parent body.

  3. The 2009 paroxysmal explosions at Stromboli (Italy): magma mixing and eruption dynamics

    Science.gov (United States)

    La Felice, Sonia; Landi, Patrizia

    2011-11-01

    Three small-scale paroxysmal explosions (also called major explosions) interrupted ordinary mild Strombolian activity at Stromboli on May 3, November 8 and 24, 2009. Products were largely confined to the summit area, except in the November 24 event, during which coarse pumiceous lapilli reached the coast. Emission of crystal-poor pumice closely mingled with crystal-rich products characterized the three events. The textural and chemical study of minerals and glassy matrices revealed that the two end-members are mingled together physically in the May 3 and November 24 pumice, whereas November 8 products contain heterogeneous glass with intermediate compositions derived from chemical mixing between crystal-rich and crystal-poor magmas. We here discuss the different degrees of interaction between the two magmas in the three explosions in terms of magma dynamics during small-scale paroxysms.

  4. Lava lake level as a gauge of magma reservoir pressure and eruptive hazard

    Science.gov (United States)

    Patrick, Matthew R.; Anderson, Kyle R.; Poland, Michael P.; Orr, Tim R.; Swanson, Donald A.

    2015-01-01

    Forecasting volcanic activity relies fundamentally on tracking magma pressure through the use of proxies, such as ground surface deformation and earthquake rates. Lava lakes at open-vent basaltic volcanoes provide a window into the uppermost magma system for gauging reservoir pressure changes more directly. At Kīlauea Volcano (Hawaiʻi, USA) the surface height of the summit lava lake in Halemaʻumaʻu Crater fluctuates with surface deformation over short (hours to days) and long (weeks to months) time scales. This correlation implies that the lake behaves as a simple piezometer of the subsurface magma reservoir. Changes in lava level and summit deformation scale with (and shortly precede) changes in eruption rate from Kīlauea's East Rift Zone, indicating that summit lava level can be used for short-term forecasting of rift zone activity and associated hazards at Kīlauea.

  5. Quantitative 3D evaluation of step ascent and descent in individuals with Down syndrome--analysis of a daily challenging task.

    Science.gov (United States)

    Galli, M; Cimolin, V; Ferrario, D; Patti, P; Heaney, G; Freedland, R; Albertini, G; Brown, W T

    2013-12-01

    Step ascent and descent can perturb stability increasing the incidence of falls, especially in older individuals with functional limitations and intellectual disabilities, such as those with Down syndrome (DS). The aim of this study was to investigate the biomechanics and motor coordination of step ascent and descent in adults with DS and compare them with a group of healthy individuals, considering movement kinematics and kinetics. Fourteen adults with DS and 12 similarly aged adults without DS who were free of known motor problems were quantitatively assessed during ascending and descending a step using an optoelectronic system (BTS SMART-D), force platforms and video recording. Kinematic and kinetic parameters were identified and calculated for each study participant and comparisons were made between the DS and a control group (CG). Despite similar age ranges, subjects in the DS group performed the step ascent and descent movements slower, with longer duration and with a more accentuated range of motion of the trunk and of the ankle joint than those in the CG. Additionally, the double stance phase on the step was substantially longer in the DS group when represented as a percentage of the entire stepping sequence (ascent, double stance on the step and descent). In terms of kinetics, ground force platform data revealed that the DS subjects showed higher instability in the medio-lateral direction during double support phase than similarly aged CG subjects and cannot be attributed to age-associated changes in stability. These findings help to elucidate the complex biomechanical strategy of people with DS during a step ascent and descent movement task and may have a major role in the multidimensional evaluation and tailored management for them. © 2012 The Authors. Journal of Intellectual Disability Research © 2012 John Wiley & Sons Ltd, MENCAP & IASSID.

  6. Syn-eruptive breakdown of pyrrhotite: a record of magma fragmentation, air entrainment, and oxidation

    Science.gov (United States)

    Matsumoto, Keiko; Nakamura, Michihiko

    2017-10-01

    Air entrainment in fragmented magmas controls the dynamics of volcanic eruptions. Pyroclast oxidation kinetics may be applied to quantify the degree of magma-air interaction. Pyrrhotite (Po) in volcanic rocks is often oxidized to form magnetite (Mt) and hematite (Hm), and its reaction mechanisms are well constrained. To test utilizing Po oxidation as a marker for magma-air interactions, we compared the occurrence of Po oxidation products from three different eruption styles during the Sakurajima 1914-1915 eruption. Pumices from the Plinian eruption include columnar-type Fe oxides (Mt with subordinate width of Hm) often accompanied by relict Po. This columnar type is also found in clastogenic lava, where it is almost completely oxidized to Hm. The effusive lava contains framboidal aggregates of subhedral to anhedral Mt crystals without Hm. The formation mechanisms of columnar and framboidal Fe oxides were estimated. The columnar type Fe oxides were formed syn-eruptively through gaseous reactions, as opposed to the melt in a magma chamber, as demonstrated by the Ti-free nature of the columnar Mt and its synchronous oxidation to Hm. By contrast, the framboidal type was formed in a melt with decreasing fS2. The calculation of Hm growth in a conductively cooling pumice clast constrains the surface temperature of pumice in the eruption column. The paragenesis and oxidation degree of Po and Fe oxides are consistent with the eruption processes in terms of magma fragmentation, air entrainment, and welding, and can, therefore, be a responsive marker for the magma-air interaction.

  7. Phase equilibria and trace element partitioning in a magma ocean to 260 kilobars

    Science.gov (United States)

    Herzberg, Claude

    1992-01-01

    A magma ocean can solidify in a way that is intermediate between perfect equilibrium and perfect fractional crystallization. In order to model quantitatively any fractional crystallization scenario, it is necessary to understand the geochemical characteristics of the phases that crystallize from a magma ocean, and how they vary with pressure. The crystallizing phase is called the liquidus phase, and their identities were determined by numerous experiments utilizing the multianvil apparatus. For chondritic compositions the liquidus phases are as follows: olivine at 1 atmosphere to 100 kilobars; garnet from 100 to about 260 kilobars; silicate perovskite from 260 kilobars to possibly the core-mantle boundary in the Earth.

  8. The Donkerhuk batholith (Namibia): Evolution of and processes in a giant magma reservoir

    Science.gov (United States)

    Clemens, John; Jung, Stefan; Kisters, Alex; Buick, Ian

    2016-04-01

    The Donkerhuk batholith represents a gigantic accumulation of felsic magma and thus provides insight into the processes and outcomes in at least some huge felsic magma bodies. The largely S-type batholith, which intrudes amphibolite-facies metaturbidites of the Kuiseb Formation, was emplaced at about 530 Ma, in the Southern Zone of the Damara Belt, following the collision of the Kalahari Craton with the Congo Craton (to the north) in the earliest Phanerozoic. It is a vast, elongate body, > 200 km long and 15 to 40 km wide, trending NE-SW, parallel to the Okahandja Lineament and the general structural grain of the Belt. Our current tectonic model for the Donkerhuk magmatism involves intense and prolonged crustal heating due to the opening of a slab window. Over large areas, the granitic rocks carry variably developed magmatic foliations and, in places, solid-state fabrics, underlining its syn- to late-tectonic emplacement, during northwest shortening and pure-shear-dominated transpression. The magmas were not derived through melting of the Kuiseb schists, but rather from older metasedimentary crust just a few km below emplacement level. They were added to the 'magma chamber' as thousands of separate pulses, preserved as sheets that retain their individuality, at least near the margins and roof zones. In the core of the batholith there was evidently some greater degree of thermal insulation and individual sheets are less easily identified. Thus, the 'magma reservoir' was never a large molten mass, but grew over perhaps 14 Myr, in small increments. This set of processes meant that only very local differentiation look place, that there was little or no mixing between magma batches, even in the core of the batholith where the individuality of the pulses became blurred due to a prolonged crystallisation history. As a result, the Donkerhuk rocks preserve a remarkably high degree of source-inherited elemental and isotopic heterogeneity. We suggest that great caution be

  9. Evaluation of magma mixing in the subvolcanic rocks of Ghansura Felsic Dome of Chotanagpur Granite Gneiss Complex, eastern India

    Science.gov (United States)

    Gogoi, Bibhuti; Saikia, Ashima; Ahmad, Mansoor; Ahmad, Talat

    2017-10-01

    The subvolcanic rocks exposed in the Ghansura Felsic Dome (GFD) of the Bathani volcano-sedimentary sequence at the northern fringe of the Rajgir fold belt in the Proterozoic Chotanagpur Granite Gneiss Complex preserves evidence of magma mixing and mingling in mafic (dolerite), felsic (microgranite) and intermediate (hybrid) rocks. Structures like crenulated margins of mafic enclaves, felsic microgranular enclaves and ocelli with reaction surfaces in mafic rocks, hybrid zones at mafic-felsic contacts, back-veining and mafic flows in the granitic host imply magma mingling phenomena. Textural features like quartz and titanite ocelli, acicular apatite, rapakivi and anti-rapakivi feldspar intergrowths, oscillatory zoned plagioclase, plagioclase with resorbed core and intact rim, resorbed crystals, mafic clots and mineral transporting veins are interpreted as evidence of magma mixing. Three distinct hybridized rocks have formed due to varied interactions of the intruding mafic magma with the felsic host, which include porphyritic diorite, mingled rocks and intermediate rocks containing felsic ocelli. Geochemical signatures confirm that the hybrid rocks present in the study area are mixing products formed due to the interaction of mafic and felsic magmas. Physical parameters like temperature, viscosity, glass transition temperature and fragility calculated for different rock types have been used to model the relative contributions of mafic and felsic end-member magmas in forming the porphyritic diorite. From textural and geochemical investigations it appears that the GFD was a partly solidified magma chamber when mafic magma intruded it leading to the formation of a variety of hybrid rock types.

  10. Petrogenesis of the granitic Donkerhuk batholith in the Damara Belt of Namibia: protracted, syntectonic, short-range, crustal magma transfer

    Science.gov (United States)

    Clemens, J. D.; Buick, I. S.; Kisters, A. F. M.; Frei, D.

    2017-07-01

    The areally extensive (>5000 km2), syn-tectonic, ca. 520 Ma, mainly S-type Donkerhuk batholith was constructed through injection of thousands of mainly sheet-like magma pulses over 20-25 Myr. It intruded schists of the Southern Zone accretionary prism in the Damara Belt of Namibia. Each magma pulse had at least partly crystallised prior to the arrival of the following batch. However, much of the batholith may have remained partially molten for long periods, close to the H2O-saturated granite solidus. The batholith shows extreme variation in chemistry, while having limited mineralogical variation, and seems to be the world's most heterogeneous granitic mass. The Nd model ages of 2 Ga suggest that Eburnean rocks of the former magmatic arc, structurally overlain by the accretionary wedge, are the most probable magma sources. Crustal melting was initiated by mantle heat flux, probably introduced by thermal diffusion rather than magma advection. The granitic magmas were transferred from source to sink, with minimal intermediate storage; the whole process having occurred in the middle crust, resulting in feeble crustal differentiation despite the huge volume of silicic magma generated. Source heterogeneity controlled variation in the magmas and neither mixing nor fractionation was prominent. However, due to the transpressional emplacement régime, local filter pressing formed highly silicic liquids, as well as felsic cumulate rocks. The case of the Donkerhuk batholith demonstrates that emplacement-level tectonics can significantly influence compositional evolution of very large syn-tectonic magma bodies.

  11. Rapid Ascent From Zero Quality to International Organization for Standardization Accreditation: A Case Study of Hai Duong Preventive Medicine Center in Vietnam, 2012-2013.

    Science.gov (United States)

    Duong, Cuong Ngoc; Bond, Kyle B; Carvalho, Humberto; Thi Thu, Hien Bui; Nguyen, Thuong; Rush, Thomas

    2017-04-01

    In 2012, the Vietnam Ministry of Health sought to improve the quality of health laboratories by introducing international quality standards. Strengthening Laboratory Management Toward Accreditation (SLMTA), a year-long, structured, quality improvement curriculum (including projects and mentorship) was piloted in 12 laboratories. Progress was measured using a standardized audit tool (Stepwise Laboratory Quality Improvement Process Towards Accreditation). All 12 pilot laboratories (a mix of hospital and public health) demonstrated improvement; median scores rose from 44% to 78% compliance. The public health laboratory in Hai Duong Province entered the program with the lowest score of the group (28%) yet concluded with the highest score (86%). Five months after the completion of the program, without any additional external support, they were accredited. Laboratory management/staff describe factors key to their success: support from the facility senior management, how-to guidance provided by SLMTA, support from the site mentor, and strong commitment of laboratory staff. Hai Duong preventive medical center is one of only a handful of laboratories to reach accreditation after participation in SLMTA and the only laboratory to do so without additional support. Due to the success seen in Hai Duong and other pilot laboratories, Vietnam has expanded the use of SLMTA.

  12. Analysis of High-altitude Syndrome and the Underlying Gene Polymorphisms Associated with Acute Mountain Sickness after a Rapid Ascent to High-altitude

    Science.gov (United States)

    Yu, Jie; Zeng, Ying; Chen, Guozhu; Bian, Shizhu; Qiu, Youzhu; Liu, Xi; Xu, Baida; Song, Pan; Zhang, Jihang; Qin, Jun; Huang, Lan

    2016-12-01

    To investigated the objective indicators and potential genotypes for acute mountain sickness (AMS). 176 male subjects were evaluated for symptoms scores and physiological parameters at 3700 m. EPAS1 gene polymorphisms were explored and verified effects of potential genotypes on pulmonary function by inhaled budesonide. The incidence of AMS was 53.98% (95/176). The individuals who suffered from headache with anxiety and greater changes in heart rate (HR), the forced vital capacity (FVC), and mean flow velocity of basilar artery (Vm-BA), all of which were likely to develop AMS. The rs4953348 polymorphism of EPAS1 gene had a significant correlation with the SaO2 level and AMS, and a significant difference in the AG and GG genotype distribution between the AMS and non-AMS groups. The spirometric parameters were significantly lower, but HR (P = 0.036) and Vm-BA (P = 0.042) significantly higher in the AMS subjects with the G allele than those with the A allele. In summary, changes in HR (≥82 beats/min), FVC (≤4.2 Lt) and Vm-BA (≥43 cm/s) levels may serve as predictors for diagnosing AMS accompanied by high-altitude syndrome. The A allele of rs4953348 is a protective factor for AMS through HR and Vm-BA compensation, while the G allele may contribute to hypoxic pulmonary hypertension in AMS.

  13. Volcano seismicity and ground deformation unveil the gravity-driven magma discharge dynamics of a volcanic eruption.

    Science.gov (United States)

    Ripepe, Maurizio; Donne, Dario Delle; Genco, Riccardo; Maggio, Giuseppe; Pistolesi, Marco; Marchetti, Emanuele; Lacanna, Giorgio; Ulivieri, Giacomo; Poggi, Pasquale

    2015-05-18

    Effusive eruptions are explained as the mechanism by which volcanoes restore the equilibrium perturbed by magma rising in a chamber deep in the crust. Seismic, ground deformation and topographic measurements are compared with effusion rate during the 2007 Stromboli eruption, drawing an eruptive scenario that shifts our attention from the interior of the crust to the surface. The eruption is modelled as a gravity-driven drainage of magma stored in the volcanic edifice with a minor contribution of magma supplied at a steady rate from a deep reservoir. Here we show that the discharge rate can be predicted by the contraction of the volcano edifice and that the very-long-period seismicity migrates downwards, tracking the residual volume of magma in the shallow reservoir. Gravity-driven magma discharge dynamics explain the initially high discharge rates observed during eruptive crises and greatly influence our ability to predict the evolution of effusive eruptions.

  14. Nonexplosive and explosive magma/wet-sediment interaction during emplacement of Eocene intrusions into Cretaceous to Eocene strata, Trans-Pecos igneous province, West Texas

    Science.gov (United States)

    Befus, K.S.; Hanson, R.E.; Miggins, D.P.; Breyer, J.A.; Busbey, A.B.

    2009-01-01

    Eocene intrusion of alkaline basaltic to trachyandesitic magmas into unlithified, Upper Cretaceous (Maastrichtian) to Eocene fluvial strata in part of the Trans-Pecos igneous province in West Texas produced an array of features recording both nonexplosive and explosive magma/wet-sediment interaction. Intrusive complexes with 40Ar/39Ar dates of ~ 47-46??Ma consist of coherent basalt, peperite, and disrupted sediment. Two of the complexes cutting Cretaceous strata contain masses of conglomerate derived from Eocene fluvial deposits that, at the onset of intrusive activity, would have been > 400-500??m above the present level of exposure. These intrusive complexes are inferred to be remnants of diatremes that fed maar volcanoes during an early stage of magmatism in this part of the Trans-Pecos province. Disrupted Cretaceous strata along diatreme margins record collapse of conduit walls during and after subsurface phreatomagmatic explosions. Eocene conglomerate slumped downward from higher levels during vent excavation. Coherent to pillowed basaltic intrusions emplaced at the close of explosive activity formed peperite within the conglomerate, within disrupted Cretaceous strata in the conduit walls, and within inferred remnants of the phreatomagmatic slurry that filled the vents during explosive volcanism. A younger series of intrusions with 40Ar/39Ar dates of ~ 42??Ma underwent nonexplosive interaction with Upper Cretaceous to Paleocene mud and sand. Dikes and sills show fluidal, billowed, quenched margins against the host strata, recording development of surface instabilities between magma and groundwater-rich sediment. Accentuation of billowed margins resulted in propagation of intrusive pillows into the adjacent sediment. More intense disruption and mingling of quenched magma with sediment locally produced fluidal and blocky peperite, but sufficient volumes of pore fluid were not heated rapidly enough to generate phreatomagmatic explosions. This work suggests that

  15. Recent developments and applications of a real-time tool to detect magma migration in different volcanic settings and network optimization.

    Science.gov (United States)

    Taisne, B.; Aoki, Y.; Caudron, C.

    2014-12-01

    Triggering mechanism of a seismic swarm has to be identified with great confidence in real time. Crisis response will not be the same whether magma is involved or not. The recent developments of a method based on the Seismic Amplitude Ratio Analysis enable a rapid and unambiguous diagnosis to detect migrating micro-seismicity. The beauty of this method lies in the fact that the ratio of seismic energy, recorded at different stations, is independent of the seismic energy radiated at the source and depends only on the location of the source and attenuation of the medium. Since drastic changes in attenuation are unlikely to occur at the time scale of magma intrusion, temporal evolutions in the measured ratio have to be explained by a change in the source location. Based on simple assumptions, this technique can be used to assess the potential of existing monitoring seismic network to detect migrating events in real-time. Of much importance, it can also be used to design monitoring seismic network based on the available number of sensors, as well as from field constraints. The method will be implemented in MSNoise software (http://www.msnoise.org/). This allows us to mine existing datasets, to compare the different noise-based techniques, but also to use the method for monitoring purposes. We will present how the key question: "Migration or No Migration" could be answered in real time without need of complex calculation nor full knowledge of the site effect and attenuation of the medium.

  16. Formation and evolution of a lunar core from ilmenite-rich magma ocean cumulates

    NARCIS (Netherlands)

    de Vries, J.; van den Berg, A.P.; van Westrenen, W.

    2010-01-01

    In the absence of comprehensive seismic data coverage, the size, composition and physical state of the lunar core are still debated. It has been suggested that a dense ilmenite-rich layer, which originally crystallised near the top of the lunar magma ocean, may have sunk to the centre of the Moon to

  17. Can Fractional Crystallization of a Lunar Magma Ocean Produce the Lunar Crust?

    Science.gov (United States)

    Rapp, Jennifer F.; Draper, David S.

    2013-01-01

    New techniques enable the study of Apollo samples and lunar meteorites in unprecedented detail, and recent orbital spectral data reveal more about the lunar farside than ever before, raising new questions about the supposed simplicity of lunar geology. Nevertheless, crystallization of a global-scale magma ocean remains the best model to account for known lunar lithologies. Crystallization of a lunar magma ocean (LMO) is modeled to proceed by two end-member processes - fractional crystallization from (mostly) the bottom up, or initial equilibrium crystallization as the magma is vigorously convecting and crystals remain entrained, followed by crystal settling and a final period of fractional crystallization [1]. Physical models of magma viscosity and convection at this scale suggest that both processes are possible. We have been carrying out high-fidelity experimental simulations of LMO crystallization using two bulk compositions that can be regarded as end-members in the likely relevant range: Taylor Whole Moon (TWM) [2] and Lunar Primitive Upper Mantle (LPUM) [3]. TWM is enriched in refractory elements by 1.5 times relative to Earth, whereas LPUM is similar to the terrestrial primitive upper mantle, with adjustments made for the depletion of volatile alkalis observed on the Moon. Here we extend our earlier equilibrium-crystallization experiments [4] with runs simulating full fractional crystallization

  18. The Yellowstone hotspot in space and time: Nd and Hf isotopes insilici magmas

    Energy Technology Data Exchange (ETDEWEB)

    Nash, Barbara P.; Perkins, Michael E.; Christensen, John N.; Lee,Den-Chuen; Halliday, A.N.

    2006-04-19

    Over the course of its 16 m.y. history, the Yellowstonehotspot has produced silicic magmas exhibiting systematic, and oftensympathetic, variations in isotopic and chemical composition, temperatureand frequency of eruption. Nd and Hf isotopic ratios vary systematicallyfrom initial eruptions at ~;16 Ma, contemporaneous with basalticvolcanism in eastern Oregon and Washington, to the present dayYellowstone Volcanic Plateau. Nd and Hf isotopic ratios co-vary and spanthe range of most terrestrial samples, reflecting mixing of mantle andcrustal sources. Earliest erupted silicic magmas were hot (in excess of1050oC), relatively less evolved and have isotopic ratios within therange of contemporaneous Columbia River flood basalts. The transit of thehotspot across the lithospheric boundary between the western accretedoceanic terrain and the Precambrian craton at 15 Ma is marked by shiftsin eNd from +4 to -11 and in ?Hf from +10 to -10. The duration of thetransit yields a crustal magma source diameter of ~;70 km. In theinterval from 14 to 9 Ma, ?Nd systematically increases from -11 to -7,recording a minimum increase in the mantle component from 5 percent to 30percent. The mantle component could be twice as great, depending upon theisotopic composition of crust and mantle reservoirs. In this sameinterval, peak temperatures of ~;1000oC occurred at 9 Ma. The last 8 m.y.are characterized by less frequent eruption of lower temperature(830-900oC) and more compositionally evolved magmas.

  19. Mantle to surface degassing of alkalic magmas at Erebus volcano, Antarctica

    Science.gov (United States)

    Oppenheimer, C.; Moretti, R.; Kyle, P.R.; Eschenbacher, A.; Lowenstern, J. B.; Hervig, R.L.; Dunbar, N.W.

    2011-01-01

    Continental intraplate volcanoes, such as Erebus volcano, Antarctica, are associated with extensional tectonics, mantle upwelling and high heat flow. Typically, erupted magmas are alkaline and rich in volatiles (especially CO2), inherited from low degrees of partial melting of mantle sources. We examine the degassing of the magmatic system at Erebus volcano using melt inclusion data and high temporal resolution open-path Fourier transform infrared (FTIR) spectroscopic measurements of gas emissions from the active lava lake. Remarkably different gas signatures are associated with passive and explosive gas emissions, representative of volatile contents and redox conditions that reveal contrasting shallow and deep degassing sources. We show that this unexpected degassing signature provides a unique probe for magma differentiation and transfer of CO2-rich oxidised fluids from the mantle to the surface, and evaluate how these processes operate in time and space. Extensive crystallisation driven by CO2 fluxing is responsible for isobaric fractionation of parental basanite magmas close to their source depth. Magma deeper than 4kbar equilibrates under vapour-buffered conditions. At shallower depths, CO2-rich fluids accumulate and are then released either via convection-driven, open-system gas loss or as closed-system slugs that ascend and result in Strombolian eruptions in the lava lake. The open-system gases have a reduced state (below the QFM buffer) whereas the closed-system gases preserve their deep oxidised signatures (close to the NNO buffer). ?? 2011 Elsevier B.V.

  20. Lithium enrichment in intracontinental rhyolite magmas leads to Li deposits in caldera basins.

    Science.gov (United States)

    Benson, Thomas R; Coble, Matthew A; Rytuba, James J; Mahood, Gail A

    2017-08-16

    The omnipresence of lithium-ion batteries in mobile electronics, and hybrid and electric vehicles necessitates discovery of new lithium resources to meet rising demand and to diversify the global lithium supply chain. Here we demonstrate that lake sediments preserved within intracontinental rhyolitic calderas formed on eruption and weathering of lithium-enriched magmas have the potential to host large lithium clay deposits. We compare lithium concentrations of magmas formed in a variety of tectonic settings using in situ trace-element measurements of quartz-hosted melt inclusions to demonstrate that moderate to extreme lithium enrichment occurs in magmas that incorporate felsic continental crust. Cenozoic calderas in western North America and in other intracontinental settings that generated such magmas are promising new targets for lithium exploration because lithium leached from the eruptive products by meteoric and hydrothermal fluids becomes concentrated in clays within caldera lake sediments to potentially economically extractable levels.Lithium is increasingly being utilized for modern technology in the form of lithium-ion batteries. Here, using in situ measurements of quartz-hosted melt inclusions, the authors demonstrate that preserved lake sediments within rhyolitic calderas have the potential to host large lithium-rich clay deposits.

  1. Geometry Properties of Porosity Waves during Magma Migration: The Influence of Viscosities and Damage

    Science.gov (United States)

    Cai, Z.; Bercovici, D.

    2014-12-01

    Partial melting occurs along grain boundaries and migrates through porous flow, leading to magma segregation in the mantle. Solitary porosity waves created by a perturbation in melting have been studied in the flow of a low viscosity fluid in a deformable matrix (McKenzie 1984, Scott and Stevenson 1986, Barcilon and Richter 1986, Spiegelman 1993, Wiggins and Spiegelman 1995). However, in a fairly complicated multi-physics, multi-scale process of magma migration, the geometry and instability of porosity waves can be affected by both mechanical and thermal factors, leaving different propagation signatures. In this work we develop a two-dimensional, two-phase damage model of magma-fracturing, and study the influence of viscosities and damage (void generation and microcracking) on the geometry properties of porosity waves. We first benchmark our solitary solutions with previous works and solve 2-D finite-amplitude waves numerically using spectral and semi-spectral method. We show that damage, decompaction weakening of the matrix and porosity-driven viscosities can alter the geometry of stable porosity waves, and result in an elongated or flattened wave front with a trail of smaller porosity. Such trails may localize subsequent waves and form porosity passage in the matrix. Scaling analysis of the time-dependent porosity waves are conducted and amount of magma reaching to the top of the melting region are estimated. Future work will include evaluating the thermal and seismic signatures during and after melt migration in two-phase porous flow.

  2. Tüüri "Magma" kuuplaat. Pärt Saksa romaani kangelasena

    Index Scriptorium Estoniae

    2007-01-01

    Erkki-Sven Tüüri heliplaat "Magma" oli kuuplaat nii BBC Music Magazine'is kui ka Gramophone'is. Saksa kirjanik Adam Thorpe avaldas romaani "Taktverschiebung" ("Taktimuutus"), mille peategelast, inglise heliloojat Jack Middletoni iseloomustatakse Arvo Pärdi suure austajana

  3. Chemical evolution of a high-level magma system: the Black Mountain volcanic center, southern Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, T.A.; Noble, D.C.; Younker, L.W.

    1983-09-01

    A comprehensive study of stratigraphically controlled samples of both lavas and ash-flow tuffs from the Black Mountain volcanic center enables us to evaluate magmatic processes. The results of this study are used to: (1) determine how this high-level magma system developed; (2) compare this system with other similar systems; and (3) correlate ash-flow sheets using their chemical characteristics.

  4. Magma ocean fractional crystallization and cumulate overturn in terrestrial planets: Implications for Mars

    Science.gov (United States)

    Elkins-Tanton, L. T.; Parmentier, E. M.; Hess, P. C.

    2003-12-01

    Crystallization of a magma ocean on a large terrestrial planet that is significantly melted by the energy of accretion may lead to an unstable cumulate density stratification, which may overturn to a stable configuration. Overturn of the initially unstable stratification may produce an early basaltic crust and differentiated mantle reservoirs. Such a stable compositional stratification can have important implications for the planet's subsequent evolution by delaying or suppressing thermal convection and by influencing the distribution of radiogenic heat sources. We use simple models for fractional crystallization of a martian magma ocean, and calculate the densities of the resulting cumulates. While the simple models presented do not include all relevant physical processes, they are able to describe to first order a number of aspects of martian evolution. The models describe the creation of magma source regions that differentiated early in the history of Mars, and present the possibility of an early, brief magnetic field initiated by cold overturned cumulates falling to the core- mantle boundary. In a model that includes the density inversion at about 7.5 GPa, where olivine and pyroxene float in the remaining magma ocean liquids while garnet sinks, cumulate overturn sequesters alumina in the deep martian interior. The ages and compositions of source regions are consistent with SNC meteorite data.

  5. Duration of the Banco Bonito Rhyolite Eruption, Vales Caldera, New Mexico based on magma transport modeling

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Benjamin R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Baldridge, W. Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gable, Carl W. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sicilian, James M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2007-03-05

    Finite volume calculations of the flow of rhyolite are presented to investigate the fate of viscous magmas flowing in planar fractures with realistic length to width ratios of up to 2500:1. Heat and mass transfer for a melt with a temperature dependent viscosity and the potential to undergo phase change are considered. Magma driving pressures and dike widths are chosen to satisfy simple elastic considerations. These models are applied within a parameter space relevant to the Banco Bonito rhyolite flow, Valles caldera, New Mexico. We estimate a maximum eruption duration for the event of ~200 days, realized at a minimum possible dike width of 5-6 m and driving pressure of 7-8 MPa. Simplifications in the current model may warrant scaling of these results. However, we demonstrate the applicability of our model to magma dynamics issues and suggest that such models may be used to infer information about both the timing of an eruption and the evolution of the associated magma source.

  6. There's more than one way to build a caldera magma chamber: Evidence from volcanic-plutonic relationships at three faulted Rio-Grande-rift calderas

    Science.gov (United States)

    Zimmerer, M. J.; McIntosh, W. C.

    2011-12-01

    The temporal and chemical relationships of volcanic and plutonic rocks of the Questa (NM), Mt. Aetna (CO), and Organ caldera (NM) complexes were investigated to establish the origin of these silicic magmas. Rio Grande Rift faulting at these systems has exposed both intracaldera sequences and subvolcanic plutons. Ar/Ar and U/Pb ages reveal the timing of volcanic activity and pluton emplacement and cooling. We observe a link between ignimbrite zoning patterns and the temporal-chemical relationship of volcanic and plutonic rocks. The Questa caldera erupted the high-SiO2 peralkaline Amalia Tuff (AT) at 25.4 Ma. Volumetrically minor phases of two resurgent plutons and a ring dike are compositionally similar to the AT. The age of the ring dike (25.4 Ma) is indistinguishable to AT, suggesting that the peralkaline intrusions are nonerupted AT. The remaining pluton ages are 100 ka to 6.1 Ma younger than AT and are too young to be the AT residual crystal mush. The Mt. Princeton batholith and nested Mt. Aetna caldera are interpreted to be the sources for the 37.3 Ma, low-SiO2 rhyolitic Wall Mountain Tuff (WMT) and the 34.3 Ma, dacitic Badger Creek Tuff (BCT). U/Pb and Ar/Ar ages of Mt. Princeton batholith (36.5 to 35.1 Ma) indicate that it was emplaced and rapidly cooled during the interval between the WMT and BCT eruptions, and that any WMT age intrusions are now eroded. During the eruption of the BCT, the fully crystallized Mt. Princeton batholith collapsed into the Mt. Aetna caldera. Intrusions along the margins of the Mt. Aetna caldera are compositionally identical the BCT and contain zircons 100 to 500 ka older than the tuff, suggesting that the BCT magma chamber was incrementally emplaced prior to caldera eruption. The Organ caldera complex erupted three ignimbrites: a basal high-silica 36.5 Ma rhyolite, a middle intermediate-silica 36.2 Ma rhyolite, and an upper 36.0 Ma low-silica rhyolite. The intracaldera sequence is intruded by the Organ Needle pluton. U/Pb zircon

  7. Petrology of the zoned calcalkaline magma chamber of Mount Mazama, Crater Lake, Oregon

    Science.gov (United States)

    Druitt, T.H.; Bacon, C.R.

    1989-01-01

    Evolution of the magma chamber at Mount Mazama involved repeated recharge by two types of andesite (high-Sr and low-Sr), crystal fractionation, crystal accumulation, assimilation, and magma mixing (Bacon and Druitt 1988). This paper addresses the modal compositions, textures, mineral chemistry and magmatic temperatures of (i) products of the 6845??50 BP climactic eruption, (ii) blocks of partially fused granitoid wallrock found in the ejecta, and (iii) preclimactic rhyodacitic lavas leaked from the chamber in late Pleistocene and early Holocene time. Immediately prior to the climactic eruption the chamber contained ??? 40 km3 of rhyodacite (10 vol% plag + opx + aug + hb + mt + ilm, ???880?? C) overlying high-Sr andesite and cumulus-crystal mush (28-51 vol% plag + hb ?? opx ?? aug + mt ?? ilm, 880?? to ???950?? C), which in turn overlay low-Sr crystal mush (50-66 vol% plag + opx + aug ?? hb ?? ol + mt + ilm, 890?? to ???950??? C). Despite the well known compositional gap in the ejecta, no thermal discontinuity existed in the chamber. Pre-eruptive water contents of pore liquids in most high-Sr and low-Sr mushes were 4-6 wt%, but on average the high-Sr mushes were slightly richer in water. Although parental magmas of the crystal mushes were andesitic, xenocrysts of bytownite and Ni-rich magnesian olivine in some scoriae record the one-time injection of basalt into the chamber. Textures in ol-bearing scoriae preserve evidence for the reactions ol + liq = opx and ol + aug + liq(+ plag?) = hb, which occurred in andesitic liquids at Mount Mazama. Strontium abundances in plagioclase phenocrysts constrain the petrogenesis of preclimactic and climactic rhyodacites. Phenocryst cores derived from high-Sr and low-Sr magmas have different Sr contents which can be resolved by microprobe. Partition coefficients for plagioclase in andesitic to rhyolitic glasses range from 2 to 7, and increase as glass %SiO2 increases. Evolved Pleistocene rhyodacites (???30-25,000 BP) and

  8. Magma dynamics during the 2007 Stromboli eruption (Aeolian Islands, Italy): Mineralogical, geochemical and isotopic data

    Science.gov (United States)

    Landi, P.; Corsaro, R. A.; Francalanci, L.; Civetta, L.; Miraglia, L.; Pompilio, M.; Tesoro, R.

    2009-05-01

    After the 6 month-long effusive event of 2002-2003, a new lava effusion occurred at Stromboli between 27 February and 2 April 2007. Despite the different durations, approximately the same volume of magma was emitted in both eruptions, in the order of 10 7 m 3. A paroxysmal eruption occurred at the summit craters in both the 2002-2003 and 2007 episodes, during which a significant amount of low porphyritic (LP), volatile-rich magma was erupted. In both cases, the paroxysm did not interrupt the lava emission. Here, we present compositional data, including texture, mineralogy, chemistry and Sr and Nd isotope ratios of bulk-rock, groundmass and separated minerals of lavas erupted in 2007, together with chemistry and Sr and Nd isotope composition of the pumices emitted during the 15 March paroxysm. As a whole, the lavas have the same texture and chemistry that characterize the highly porphyritic (HP) products usually erupted at Stromboli during normal Strombolian activity and effusive events. Compared to the previous HP products, the 2007 lavas show minor but systematic mineralogical and isotopic variations which are consistent with a modest increase of the magma supply rate of the volcano. Compositional variations during the entire duration of the event are very modest. Glass chemistry changes in lavas erupted in the second half of March can be explained by the minor mixing between the volatile-rich LP magma rising through the shallow magmatic system during the 15 March paroxysm and the degassed residing HP magma. A first conclusion of this study is that there is no compositional evidence supporting major changes in the magma dynamics of the volcano accompanying the effusive activity, as also suggested for the 2002-2003 event. The activity of Stromboli is controlled by a steady state feeding system in which refilling, mixing, degassing and crystallization at shallow level continuously operate, with modest oscillations in the magma supply rate. Switching between normal

  9. Fractal hierarchies of magma transport in Hawaii and critical self-organization of tremor

    Science.gov (United States)

    Shaw, Herbert R.; Chouet, Bernard

    1991-06-01

    A hierarchical model of magma transport in Hawaii is developed from the seismic records of deep (30-60 km) and intermediate-depth (5-15 km) harmonic tremor between January 1, 1962, and December 31, 1983. We find two kinds of spatial distributions of magma fractions at depths below 5 km, defined by the fractal dimension D3, where the subscript is the embedding dimension. The first is a focused distribution with D3 = 0.28, and the second is a dispersed distribution with D3 = 1.52. The former dimension reflects conduitlike structures where the magma flow converges toward a summit magma chamber and the fractal dimension tends to zero. The latter dimension reflects multifractal clustering of dendritic fractures where hypocentral domains represent subsets of fractures within spherical domains with an average radius of about 1 km. These geometries constitute a percolation network of clustered intermittent fracture and magma transport. The magma volume of the average fracture is about 2 × 104 m3. A tremor model of magma transport is developed from mass balances of percolation that are proportional to tremor durations. It gives reasonable magma fractions and residence times for a vertical drift velocity of 4 km yr-1 and yields patterns of intermittency that are in accord with singularity analyses of the 22-year time series record. According to the model, sustained tremor is generated by the relaxation oscillations of the percolation network with a dominant frequency of about 1 Hz to obtain internally consistent values of fracture geometry, fracture opening force, and magma supply rate. Calculated tremor frequencies are higher in fracture networks of small volume in harmony with the observed relation between seismic amplitude and dominant frequency of tremor. Tectonic relaxation times of rock stresses versus magma pressures are in fair agreement with the average length of tremor episodes and average period of tremor intermittencies. These observations suggest that a high

  10. Assimilation of preexisting Pleistocene intrusions at Long Valley by periodic magma recharge accelerates rhyolite generation: rethinking the remelting model

    Science.gov (United States)

    Simon, Justin I.; Weis, Dominique; DePaolo, Donald J.; Renne, Paul R.; Mundil, Roland; Schmitt, Axel K.

    2014-01-01

    Rhyolite flows and tuffs from the Long Valley area of California, which were erupted over a two-million-year time period, exhibit systematic trends in Nd, Hf, and Pb isotopes, trace element composition, erupted volume, and inferred magma residence time that provide evidence for a new model for the production of large volumes of silica-rich magma. Key constraints come from geochronology of zircon crystal populations combined with a refined eruption chronology from Ar-Ar geochronology; together these data give better estimates of magma residence time that can be evaluated in the context of changing magma compositions. Here, we report Hf, Nd, and Sr isotopes, major and trace element compositions, 40Ar/39Ar ages, and U-Pb zircon ages that combined with existing data suggest that the chronology and geochemistry of Long Valley rhyolites can be explained by a dynamic interaction of crustal and mantle-derived magma. The large volume Bishop Tuff represents the culmination of a period of increased mantle-derived magma input to the Long Valley volcanic system; the effect of this input continued into earliest postcaldera time. As the postcaldera evolution of the system continued, new and less primitive crustal-derived magmas dominated the system. A mixture of varying amounts of more mafic mantle-derived and felsic crustal-derived magmas with recently crystallized granitic plutonic materials offers the best explanation for the observed chronology, secular shifts in Hf and Nd isotopes, and the apparently low zircon crystallization and saturation temperatures as compared to Fe-Ti oxide eruption temperatures. This scenario in which transient crustal magma bodies remained molten for varying time periods, fed eruptions before solidification, and were then remelted by fresh recharge provides a realistic conceptual framework that can explain the isotopic and geochemical evidence. General relationships between crustal residence times and magma sources are that: (1) precaldera rhyolites

  11. Image-based modelling of lateral magma flow: the Basement Sill, Antarctica.

    Science.gov (United States)

    Petford, Nick; Mirhadizadeh, Seyed

    2017-05-01

    The McMurdo Dry Valleys magmatic system, Antarctica, provides a world-class example of pervasive lateral magma flow on a continental scale. The lowermost intrusion (Basement Sill) off