Lunar magma transport phenomena

Science.gov (United States)

Spera, Frank J.

1992-01-01

An outline of magma transport theory relevant to the evolution of a possible Lunar Magma Ocean and the origin and transport history of the later phase of mare basaltic volcanism is presented. A simple model is proposed to evaluate the extent of fractionation as magma traverses the cold lunar lithosphere. If Apollo green glasses are primitive and have not undergone significant fractionation en route to the surface, then mean ascent rates of 10 m/s and cracks of widths greater than 40 m are indicated. Lunar tephra and vesiculated basalts suggest that a volatile component plays a role in eruption dynamics. The predominant vapor species appear to be CO CO2, and COS. Near the lunar surface, the vapor fraction expands enormously and vapor internal energy is converted to mixture kinetic energy with the concomitant high-speed ejection of vapor and pyroclasts to form lunary fire fountain deposits such as the Apollo 17 orange and black glasses and Apollo 15 green glass.

A Thermodynamic Approach for Modeling H2O-CO2 Solubility in Alkali-rich Mafic Magmas at Mid-crustal Pressures

Science.gov (United States)

Allison, C. M.; Roggensack, K.; Clarke, A. B.

2017-12-01

Volatile solubility in magmas is dependent on several factors, including composition and pressure. Mafic (basaltic) magmas with high concentrations of alkali elements (Na and K) are capable of dissolving larger quantities of H2O and CO2 than low-alkali basalt. The exsolution of abundant gases dissolved in alkali-rich mafic magmas can contribute to large explosive eruptions. Existing volatile solubility models for alkali-rich mafic magmas are well calibrated below 200 MPa, but at greater pressures the experimental data is sparse. To allow for accurate interpretation of mafic magmatic systems at higher pressures, we conducted a set of mixed H2O-CO2 volatile solubility experiments between 400 and 600 MPa at 1200 °C in six mafic compositions with variable alkali contents. Compositions include magmas from volcanoes in Italy, Antarctica, and Arizona. Results from our experiments indicate that existing volatile solubility models for alkali-rich mafic magmas, if extrapolated beyond their calibrated range, over-predict CO2 solubility at mid-crustal pressures. Physically, these results suggest that volatile exsolution can occur at deeper levels than what can be resolved from the lower-pressure experimental data. Existing thermodynamic models used to calculate volatile solubility at different pressures require two experimentally derived parameters. These parameters represent the partial molar volume of the condensed volatile species in the melt and its equilibrium constant, both calculated at a standard temperature and pressure. We derived these parameters for each studied composition and the corresponding thermodynamic model shows good agreement with the CO2 solubility data of the experiments. A general alkali basalt solubility model was also constructed by establishing a relationship between magma composition and the thermodynamic parameters. We utilize cation fractions from our six compositions along with four compositions from the experimental literature in a linear

Eruptive dynamics during magma decompression: a laboratory approach

Science.gov (United States)

Spina, L.; Cimarelli, C.; Scheu, B.; Wadsworth, F.; Dingwell, D. B.

2013-12-01

A variety of eruptive styles characterizes the activity of a given volcano. Indeed, eruptive styles can range from effusive phenomena to explosive eruptions, with related implications for hazard management. Rapid changes in eruptive style can occur during an ongoing eruption. These changes are, amongst other, related to variations in the magma ascent rate, a key parameter affecting the eruptive style. Ascent rate is in turn dependent on several factors such as the pressure in the magma chamber, the physical properties of the magma and the rate at which these properties change. According to the high number of involved parameters, laboratory decompression experiments are the best way to achieve quantitative information on the interplay of each of those factors and the related impact on the eruption style, i.e. by analyzing the flow and deformation behavior of the transparent volatile-bearing analogue fluid. We carried out decompression experiments following different decompression paths and using silicone oil as an analogue for the melt, with which we can simulate a range of melt viscosity values. For a set of experiments we added rigid particles to simulate the presence of crystals in the magma. The pure liquid or suspension was mounted into a transparent autoclave and pressurized to different final pressures. Then the sample was saturated with argon for a fixed amount of time. The decompression path consists of a slow decompression from the initial pressure to the atmospheric condition. Alternatively, samples were decompressed almost instantaneously, after established steps of slow decompression. The decompression path was monitored with pressure transducers and a high-speed video camera. Image analysis of the videos gives quantitative information on the bubble distribution with respect to depth in the liquid, pressure and time of nucleation and on their characteristics and behavior during the ongoing magma ascent. Furthermore, we also monitored the evolution of

Carbon dioxide in magmas and implications for hydrothermal systems

Science.gov (United States)

Lowenstern, J. B.

2001-01-01

This review focuses on the solubility, origin, abundance, and degassing of carbon dioxide (CO2) in magma-hydrothermal systems, with applications for those workers interested in intrusion-related deposits of gold and other metals. The solubility of CO2 increases with pressure and magma alkalinity. Its solubility is low relative to that of H2O, so that fluids exsolved deep in the crust tend to have high CO2/H2O compared with fluids evolved closer to the surface. Similarly, CO2/H2O will typically decrease during progressive decompression- or crystallization-induced degassing. The temperature dependence of solubility is a function of the speciation of CO2, which dissolves in molecular form in rhyolites (retrograde temperature solubility), but exists as dissolved carbonate groups in basalts (prograde). Magnesite and dolomite are stable under a relatively wide range of mantle conditions, but melt just above the solidus, thereby contributing CO2 to mantle magmas. Graphite, diamond, and a free CO2-bearing fluid may be the primary carbon-bearing phases in other mantle source regions. Growing evidence suggests that most CO2 is contributed to arc magmas via recycling of subducted oceanic crust and its overlying sediment blanket. Additional carbon can be added to magmas during magma-wallrock interactions in the crust. Studies of fluid and melt inclusions from intrusive and extrusive igneous rocks yield ample evidence that many magmas are vapor saturated as deep as the mid crust (10-15 km) and that CO2 is an appreciable part of the exsolved vapor. Such is the case in both basaltic and some silicic magmas. Under most conditions, the presence of a CO2-bearing vapor does not hinder, and in fact may promote, the ascent and eruption of the host magma. Carbonic fluids are poorly miscible with aqueous fluids, particularly at high temperature and low pressure, so that the presence of CO2 can induce immiscibility both within the magmatic volatile phase and in hydrothermal systems

Mantle to surface degassing of carbon- and sulphur-rich alkaline magma at El Hierro, Canary Islands

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Longpré, Marc-Antoine; Stix, John; Klügel, Andreas; Shimizu, Nobumichi

2017-02-01

Basaltic volcanoes transfer volatiles from the mantle to the surface of the Earth. The quantification of deep volatile fluxes relies heavily on estimates of the volatile content of primitive magmas, the best archive of which is provided by melt inclusions. Available data from volcanoes producing mafic alkaline lavas in a range of tectonic settings suggest high volatile fluxes, but information remains sparse, particularly for intraplate ocean islands. Here we present measurements of volatile and trace element concentrations, as well as sulphur speciation, in olivine-hosted melt inclusions and matrix glasses from quenched basanite lava balloon samples from the 2011-2012 submarine eruption at El Hierro, Canary Islands. The results reveal remarkably high concentrations of dissolved volatiles and incompatible trace elements in this magma, with ∼80 ppm Nb and up to 3420 ppm CO2, 3.0 wt.% H2O and 5080 ppm S. Reconstructed primitive CO2 contents, considering CO2/Nb systematics and possible CO2 sequestration in shrinkage bubbles, reach weight percent levels, indicating that carbon is a major constituent of Canary Island magmas at depth and that exsolution of a CO2-rich fluid begins in the mantle at pressures in excess of 1 GPa. Correlations between sulphur concentration, sulphur speciation and water content suggest strong reduction of an initially oxidised mantle magma, likely controlled by coupled H2O and S degassing. This late-stage redox change may have triggered sulphide saturation, recorded by globular sulphide inclusions in clinopyroxene and ulvöspinel. The El Hierro basanite thus had a particularly high volatile-carrying capacity and released a minimum of 1.3-2.1 Tg CO2 and 1.8-2.9 Tg S to the environment, causing substantial stress on the local submarine ecosystem. These results highlight the important contribution of alkaline ocean island volcanoes, such as the Canary Islands, to volatile fluxes from the mantle.

Intraplate mantle oxidation by volatile-rich silicic magmas

Energy Technology Data Exchange (ETDEWEB)

Martin, Audrey M.; Médard, Etienne; Righter, Kevin; Lanzirotti, Antonio

2017-11-01

The upper subcontinental lithospheric mantle below the French Massif Central is more oxidized than the average continental lithosphere, although the origin of this anomaly remains unknown. Using iron oxidation analysis in clinopyroxene, oxybarometry, and melt inclusions in mantle xenoliths, we show that widespread infiltration of volatile (HCSO)-rich silicic melts played a major role in this oxidation. We propose the first comprehensive model of magmatism and mantle oxidation at an intraplate setting. Two oxidizing events occurred: (1) a 365–286 Ma old magmatic episode that produced alkaline vaugnerites, potassic lamprophyres, and K-rich calc-alkaline granitoids, related to the N–S Rhenohercynian subduction, and (2) < 30 Ma old magmatism related to W–E extension, producing carbonatites and hydrous potassic trachytes. These melts were capable of locally increasing the subcontinental lithospheric mantle fO2 to FMQ + 2.4. Both events originate from the melting of a metasomatized lithosphere containing carbonate + phlogopite ± amphibole. The persistence of this volatile-rich lithospheric source implies the potential for new episodes of volatile-rich magmatism. Similarities with worldwide magmatism also show that the importance of volatiles and the oxidation of the mantle in intraplate regions is underestimated.

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.

Magmas near the critical degassing pressure drive volcanic unrest towards a critical state

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Chiodini, Giovanni; Paonita, Antonio; Aiuppa, Alessandro; Costa, Antonio; Caliro, Stefano; De Martino, Prospero; Acocella, Valerio; Vandemeulebrouck, Jean

2016-01-01

During the reawaking of a volcano, magmas migrating through the shallow crust have to pass through hydrothermal fluids and rocks. The resulting magma–hydrothermal interactions are still poorly understood, which impairs the ability to interpret volcano monitoring signals and perform hazard assessments. Here we use the results of physical and volatile saturation models to demonstrate that magmatic volatiles released by decompressing magmas at a critical degassing pressure (CDP) can drive volcanic unrest towards a critical state. We show that, at the CDP, the abrupt and voluminous release of H2O-rich magmatic gases can heat hydrothermal fluids and rocks, triggering an accelerating deformation that can ultimately culminate in rock failure and eruption. We propose that magma could be approaching the CDP at Campi Flegrei, a volcano in the metropolitan area of Naples, one of the most densely inhabited areas in the world, and where accelerating deformation and heating are currently being observed. PMID:27996976

Phenomena associated with magma expansion into a drift

International Nuclear Information System (INIS)

Gaffney, E.S.

2002-01-01

One of the significant threats to the proposed Yucca Mountain nuclear waste repository has been identified as the possibility of intersection of the underground structure by a basaltic intrusion. Based on the geology of the region, it is assumed that such an intrusion would consist of an alkali basalt similar to the nearby Lathrop Wells cone, which has been dated at about 78 ka. The threat of radioactive release may be either from eruption through the surface above the repository of basalt that had been contaminated or from migration through ground water of radionucleides released as a result of damage to waste packages that interact with the magma. As part of our study of these threats, we are analyzing the phenomena associated with magma expansion into drifts in tuff. The early phenomena of the encounter of volatile-rich basaltic magma with a drift are discussed here.

Bubble accumulation and its role in the evolution of magma reservoirs in the upper crust.

Science.gov (United States)

Parmigiani, A; Faroughi, S; Huber, C; Bachmann, O; Su, Y

2016-04-28

Volcanic eruptions transfer huge amounts of gas to the atmosphere. In particular, the sulfur released during large silicic explosive eruptions can induce global cooling. A fundamental goal in volcanology, therefore, is to assess the potential for eruption of the large volumes of crystal-poor, silicic magma that are stored at shallow depths in the crust, and to obtain theoretical bounds for the amount of volatiles that can be released during these eruptions. It is puzzling that highly evolved, crystal-poor silicic magmas are more likely to generate volcanic rocks than plutonic rocks. This observation suggests that such magmas are more prone to erupting than are their crystal-rich counterparts. Moreover, well studied examples of largely crystal-poor eruptions (for example, Katmai, Taupo and Minoan) often exhibit a release of sulfur that is 10 to 20 times higher than the amount of sulfur estimated to be stored in the melt. Here we argue that these two observations rest on how the magmatic volatile phase (MVP) behaves as it rises buoyantly in zoned magma reservoirs. By investigating the fluid dynamics that controls the transport of the MVP in crystal-rich and crystal-poor magmas, we show how the interplay between capillary stresses and the viscosity contrast between the MVP and the host melt results in a counterintuitive dynamics, whereby the MVP tends to migrate efficiently in crystal-rich parts of a magma reservoir and accumulate in crystal-poor regions. The accumulation of low-density bubbles of MVP in crystal-poor magmas has implications for the eruptive potential of such magmas, and is the likely source of the excess sulfur released during explosive eruptions.

Temperature evolution during magma ascent in basaltic effusive eruptions: A numerical application to Stromboli volcano

Science.gov (United States)

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

2015-09-01

The dynamics of magma ascent are controlled by the complex, interdependent processes of crystallisation, rheological evolution, gas exsolution, outgassing, non-ideal gas expansion and temperature evolution. Temperature changes within the conduit, in particular, play a key role on ascent dynamics, since temperature strongly controls the crystallisation process, which in turn has an impact on viscosity and thus on magma ascent rate. The cooling produced by gas expansion is opposed by the heat produced by crystallisation, and therefore the temperature profile within the conduit is quite complex. This complexity means that unravelling the dynamics controlling magma ascent requires a numerical model. Unfortunately, comprehensive, integrated models with full thermodynamic treatment of multiple phases and rheological evolution are challenging to produce, due to the numerical challenges involved. Until now, models have tended to focus on aspects of the problem, without a holistic approach in which petrological, thermodynamic, rheological and degassing processes, and their interactions, were all explicitly addressed and quantified. Here, we present a new, multiphase steady-state model for magma ascent in which the main physical and chemical processes, such as crystallisation, degassing, outgassing, rheological evolution and temperature variations, are quantitatively calculated. Basaltic magma's crystallisation and flow are sensitive to initial temperature and volatile content, and therefore we investigate temperature variations during magma ascent in a basaltic system with a range of volatile contents. As a test case, we use one of the most well-studied recent basaltic effusive eruptions: the 2007 eruption of Stromboli, Italy. Assuming equilibrium crystallisation and exsolution, we compare the solutions obtained both with and without an isothermal constraint, finding that temperature variations within the conduit have a significant influence on the ascent dynamics and

Experimental Study of Lunar and SNC Magmas

Science.gov (United States)

Rutherford, Malcolm J.

1998-01-01

The research described in this progress report involved the study of petrological, geochemical and volcanic processes that occur on the Moon and the SNC parent body, generally accepted to be Mars. The link between these studies is that they focus on two terrestrial-type parent bodies somewhat smaller than earth, and the fact that they focus on the role of volatiles in magmatic processes and on processes of magma evolution on these planets. The work on the lunar volcanic glasses has resulted in some exciting new discoveries over the years of this grant. We discovered small metal blebs initially in the Al5 green glass, and determined the significant importance of this metal in fixing the oxidation state of the parent magma (Fogel and Rutherford, 1995). More recently, we discovered a variety of metal blebs in the Al7 orange glass. Some of these Fe-Ni metal blebs were in the glass; others were in olivine phenocrysts. The importance of these metal spheres is that they fix the oxidation state of the parent magma during the eruption, and also indicate changes during the eruption (Weitz et al., 1997) They also yield important information about the composition of the gas phase present, the gas which drove the lunar fire-fountaining. One of the more exciting and controversial findings in our research over the past year has been the possible fractionation of H from D during shock (experimental) of hornblende bearing samples (Minitti et al., 1997). This research is directed at explaining some of the low H2O and high D/H observed in hydrous phases in the SNC meteorites.

Magma flow instability and cyclic activity at soufriere hills volcano, montserrat, british west indies

Science.gov (United States)

Voight; Sparks; Miller; Stewart; Hoblitt; Clarke; Ewart; Aspinall; Baptie; Calder; Cole; Druitt; Hartford; Herd; Jackson; Lejeune; Lockhart; Loughlin; Luckett; Lynch; Norton; Robertson; Watson; Watts; Young

1999-02-19

Dome growth at the Soufriere Hills volcano (1996 to 1998) was frequently accompanied by repetitive cycles of earthquakes, ground deformation, degassing, and explosive eruptions. The cycles reflected unsteady conduit flow of volatile-charged magma resulting from gas exsolution, rheological stiffening, and pressurization. The cycles, over hours to days, initiated when degassed stiff magma retarded flow in the upper conduit. Conduit pressure built with gas exsolution, causing shallow seismicity and edifice inflation. Magma and gas were then expelled and the edifice deflated. The repeat time-scale is controlled by magma ascent rates, degassing, and microlite crystallization kinetics. Cyclic behavior allows short-term forecasting of timing, and of eruption style related to explosivity potential.

Mantle to surface degassing of alkalic magmas at Erebus volcano, Antarctica

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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.

The decompression of basaltic magma into a sub-surface repository

NARCIS (Netherlands)

Bokhove, Onno; Woods, A.W.

2002-01-01

We examine the ascent of volatile-rich basaltic magma through a vertical dike that intersects a horizontal tunnel of comparable cross-sectional area to the dike and located 300 $m$ below the surface and initially filled with air at atmospheric pressure. This process is a simplified representation of

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

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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.

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.

2016-10-01

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.

Chemical consequences of compaction within the freezing front of a crystallizing magma ocean

Science.gov (United States)

Hier-Majumder, S.; Hirschmann, M. M.

2013-12-01

The thermal and compositional evolution of planetary magma oceans have profound influences on the early development and differentiation of terrestrial planets. During crystallization, rejection of elements incompatible in precipitating solids leads to petrologic and geochemical planetary differentiation, including potentially development of a compositionally stratified early mantle and evolution of thick overlying atmospheres. In cases of extremely efficient segregation of melt and crystals, solidified early mantles can be nearly devoid of key incompatible species including heat-producing (U, Th, K) and volatile (H,C,N,& noble gas) elements. A key structural component of a crystallizing magma ocean is the partially molten freezing front. The dynamics of this region influences the distribution of incompatible elements between the earliest mantle and the initial surficial reservoirs. It also can be the locus of heating owing to the dissipation of large amounts of tidal energy potentially available from the early Moon. The dynamics are influenced by the solidification rate, which is coupled to the liberation of volatiles owing to the modulating greenhouse effects in the overlying thick atmosphere. Compaction and melt retention in the freezing front of a magma ocean has received little previous attention. While the front advances during the course of crystallization, coupled conservation of mass, momentum, and energy within the front controls distribution and retention of melt within this layer. Due to compaction within this layer, melt distribution is far from uniform, and the fraction of melt trapped within this front depends on the rate of freezing of the magma ocean. During phases of rapid freezing, high amount of trapped melt within the freezing front retains a larger quantity of dissolved volatiles and the reverse is true during slow periods of crystallization. Similar effects are known from inferred trapped liquid fractions in layered mafic intrusions. Here we

Oxygen isotope study of the Long Valley magma system, California: isotope thermometry and convection in large silicic magma bodies

Science.gov (United States)

Bindeman, Ilya; Valley, John

2002-07-01

of their longevity (>105 years) and convection. However, remaining isotopic zoning in some quartz phenocrysts, trace element gradients in feldspars, and quartz and zircon crystal size distributions are more consistent with far shorter timescales (102-104 years). We propose a sidewall-crystallization model that promotes convective homogenization, roofward accumulation of more evolved and stagnant, volatile-rich liquid, and develops compositional and temperature gradients in pre-climactic magma chamber. Crystal + melt + gas bubbles mush near chamber walls of variable δ18O gets periodically remobilized in response to chamber refill by new hotter magmas. One such episode of chamber refill by high-Ti, Sr, Ba, Zr, and volatile-richer magma happened 103-104 years prior to the 0.76-Ma caldera collapse that caused magma mixing at the base, mush thawing near the roof and walls, and downward settling of phenocrysts into this hybrid melt.

NanoSIMS results from olivine-hosted melt embayments: Magma ascent rate during explosive basaltic eruptions

Science.gov (United States)

Lloyd, Alexander S.; Ruprecht, Philipp; Hauri, Erik H.; Rose, William; Gonnermann, Helge M.; Plank, Terry

2014-08-01

The explosivity of volcanic eruptions is governed in part by the rate at which magma ascends and degasses. Because the time scales of eruptive processes can be exceptionally fast relative to standard geochronometers, magma ascent rate remains difficult to quantify. Here we use as a chronometer concentration gradients of volatile species along open melt embayments within olivine crystals. Continuous degassing of the external melt during magma ascent results in diffusion of volatile species from embayment interiors to the bubble located at their outlets. The novel aspect of this study is the measurement of concentration gradients in five volatile elements (CO2, H2O, S, Cl, F) at fine-scale (5-10 μm) using the NanoSIMS. The wide range in diffusivity and solubility of these different volatiles provides multiple constraints on ascent timescales over a range of depths. We focus on four 100-200 μm, olivine-hosted embayments erupted on October 17, 1974 during the sub-Plinian eruption of Volcán de Fuego. H2O, CO2, and S all decrease toward the embayment outlet bubble, while F and Cl increase or remain roughly constant. Compared to an extensive melt inclusion suite from the same day of the eruption, the embayments have lost both H2O and CO2 throughout the entire length of the embayment. We fit the profiles with a 1-D numerical diffusion model that allows varying diffusivities and external melt concentrations as a function of pressure. Assuming a constant decompression rate from the magma storage region at approximately 220 MPa to the surface, H2O, CO2 and S profiles for all embayments can be fit with a relatively narrow range in decompression rates of 0.3-0.5 MPa/s, equivalent to 11-17 m/s ascent velocity and an 8 to 12 minute duration of magma ascent from ~ 10 km depth. A two stage decompression model takes advantage of the different depth ranges over which CO2 and H2O degas, and produces good fits given an initial stage of slow decompression (0.05-0.3 MPa/s) at high

Petrology of the 1995/2000 Magma of Copahue, Argentina

Science.gov (United States)

Goss, A.; Varekamp, J. C.

2001-05-01

Phreatomagmatic eruptions of Copahue in July/August,1995 and July/August 2000 produced mixed juvenile clasts, silica-rich debris from the hydrothermal system, and magmatic scoria with 88 percent SiO2. These high-SiO2 clasts carry an as yet unidentified (crystobalite?), euhedral silica phase in great abundance, which is riddled with tan, primary melt inclusions. The mixed clasts have bands of mafic material with small euhedral olivine, clinopyroxene, and plagioclase that are mixed with an intermediate magma with coarser, resorbed phenocrysts of olivine, plagioclase, clino- and ortho- pyroxene, and rare occurrences of the silica phase. These ejecta are intimate mixtures of a relatively felsic magma similar to Pleistocene Copahue lavas and a mafic basaltic andesite, with minor contributions of a magma contaminated with silica-rich hydrothermal wallrock material. Two-pyroxene geothermometry indicates crystallization temperatures of 1020 deg - 1045 deg C. Glass inclusions (59-63 percent SiO2) in plagioclase and olivine crystals yield very low volatile contents in the melt (0.4-1.5 percent H2O). The 1995/2000 magmas resided at shallow level and degassed into the active volcano-hydrothermal system which discharges acid fluids into the Copahue crater lake and hot springs. More mafic magma intruded this shallow batch and the mixture rose into the hydrothermal system and assimilated siliceous wall rock. A Ti-diffusion profile in a magnetite crystal suggests that the period between magma mixing and eruption was on the order of 4-10 weeks, and the temperature difference between resident and intruding magma was about 50-60 oC.

Storage, Ascent, and Release of Silicic Magma in Caldera-forming Eruptions

Science.gov (United States)

Myers, Madison Logan

The mechanisms and timescales associated with the triggering of caldera-forming eruptions remain ambiguous and poorly constrained. Do such eruptions start vigorously, then escalate, or can there be episodicity? Are they triggered through internal processes (e.g. recharge, buoyancy), or can external modulations play an important role? Key to answering these questions is the ability to reconstruct the state of the magma body immediately prior to eruption. My dissertation research seeks to answer these questions through detailed investigation of four voluminous caldera-forming eruptions: (1) 650 km3, 0.767 Ma Bishop Tuff, Long Valley, (2) 530 km3, 25.4 ka Oruanui eruption, Taupo, (3) 2,500 km3, 2.08 Ma Huckleberry Ridge Tuff, Yellowstone and (4) 250 km3, 26.91 Ma Cebolla Creek Tuff, Colorado. The main techniques I applied integrated glass geochemistry (major, trace and volatile), diffusion modeling, and detailed field sampling. In chapters two, three, and four these methods are applied to the initial fall deposits of three supereruptions (Bishop, Oruanui and Huckleberry Ridge) that preserve field-evidence for different opening behaviors. These behaviors range from continuous deposition of fall deposits and ignimbrite (Bishop), to repetitive start/stop behavior, with time breaks between eruptive episodes on the order of weeks to months (Oruanui, Huckleberry Ridge). To reconstruct the timescales of opening activity and relate this to conduit processes, I used two methods that exploit diffusion of volatiles through minerals and melt, providing estimates for the rate at which magmas ascended to the surface. This knowledge is then integrated with the pre-eruptive configuration of the magma body, based on melt inclusion chemistry, to interpret what triggered these systems into unrest. Finally, in chapter five I take a different approach by integrating geochemical data for melt inclusions and phenocryst minerals to test whether the mechanism of heat and volatile recharge

Diffusive exchange of trace elements between basaltic-andesite and dacitic melt: Insights into potential metal fractionation during magma mixing

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Fiege, A.; Ruprecht, P.; Simon, A. C.; Holtz, F.

2017-12-01

Mafic magma recharge is a common process that triggers physical and chemical mixing in magmatic systems and drives their evolution, resulting in, e.g., hybridization and volcanic eruptions. Once magma-magma contact is initiated, rapid heat-flux commonly leads to the formation of a cooling-induced crystal mush on the mafic side of the interface. Here, on a local scale (µm to cm), at the magma-magma interface, melt-melt diffusive exchange is required to approach equilibrium. Significant chemical potential gradients drive a complex, multi-element mass flux between the two systems (Liang, 2010). This diffusive-equilibration often controls crystal dissolution rates within the boundary layers and, thus, the formation of interconnected melt or fluid networks. Such networks provide important pathways for the transport of volatiles and trace metals from the mafic recharge magma to the felsic host magma, where the latter may feed volcanic activities and ore deposits. While major element diffusion in silicate melts is mostly well understood, even in complex systems, the available data for many trace element metals are limited (Liang, 2010; Zhang et al., 2010). Differences in diffusivity in a dynamic, mixing environment can cause trace element fractionation, in particular during crystallization and volatile exsolution and separation. This may affect trace element signatures in phenocrysts and magmatic volatile phases that can form near a magma-magma boundary. As a result, the chemistry of volcanic gases and magmatic-hydrothermal ore deposits may be partially controlled by such mixing phenomena. We performed melt-melt diffusion-couple experiments at 150 MPa, 1100°C, FMQ, FMQ+1 and FMQ+3 (FMQ: fayalite-magnetite-quartz oxygen fugacity buffer). Hydrated, sulfur-bearing cylinders of dacite and basaltic andesite were equilibrated for up to 20 h. Major and trace element gradients were measured by using laser-ablation ICP-MS and electron microprobe analyses. The results we will

Long term storage of explosively erupted magma at Nevado de Toluca volcano, Mexico

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Arce, J. L.; Gardner, J.; Macias, J. L.

2007-12-01

Dacitic magmas production is common in subduction-related volcanoes, occurring in those with a long period of activity as a result of the magmatic evolution. However, in this evolution many factors (i.e. crystal fractionation, assimilation, magma mixing) can interact to produce dacites. Nevado de Toluca volcano (4,680 masl; 19°09'N; 99°45'W) Central Mexico has recorded a long period of time producing dacites explosively, at least during 42 ka of activity, involving several km3 of magma, with two important Plinian-type eruptions occurred at ~21.7 ka (Lower Toluca Pumice) and ~10.5 ka (Upper Toluca Pumice). Questions like, what was the mechanism responsible to produce voluminous dacitic magma and how the volatiles and pressure changed in the Nevado de Toluca system, remain without answers. Dacites from the Lower Toluca Pumice (LTP) contain plagioclase, amphibole, iron-titanium oxides, and minor resorbed biotite, set in a glassy-vesicular matrix and the Upper Toluca Pumice (UTP) dacites contain the same mineral phases plus orthopyroxene. Ilmenite- ulvospinel geothermometry yielded a temperature of ~860°C for the LTP dacite, a little hotter than the UTP (~ 840°C). Based on hydrothermal experiments data, amphibole is stable above 100 MPa under 900°C, while plagioclase crystallizes up to 250-100 MPa at temperatures of 850-900°C. Pyroxene occurs only at pressures of 200-100 MPa with its respective temperatures of 825-900°C. Water contents in the LTP magma (2-3.5 wt %) are similar to that calculated for the UTP magma (1.3-3.6 wt %). So, there are only small changes in temperature and pressure from ~21.7 ka to 10.5 ka. It is noteworthy that orthopyroxene is absent in the LTP, however reaction-rimmed biotite (probably xenocrystic) is commonly observed in all dacites. Hence, almost all dacitic magmas seem to be stored at relatively similar pressures, water contents, and temperatures. All of these data could suggest repetitive basic magma injections producing the

Influence of volatile degassing on the eruptibility of large igneous province magmatic systems

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Mittal, T.; Richards, M. A.

2017-12-01

Magmatic volatiles, in particular their buoyancy, may play a critical role in determining whether a magma reservoir can build up enough overpressure leading to drive flood basalt eruptions (Black & Manga 2017). Thus, it is important to understand the extent to which volatiles can remain trapped in a magmatic system and how they influence the eruptibility. Although the high-temperature metamorphic aureloe around a magma chamber is typically considered to have low permeability due to ductile creep, recent theoretical, experimental, and field work (e.g. Noriaki et al. 2017) have highlighted the role of dynamic permeability in magmatic systems. Consequently, the effective permeability of the crust when magma is present in the system can be orders of magnitude larger than that of exhumed rock samples. We model dynamic permeability changes as a competition between hydro-fracturing (increased porosity) and fracture closure by ductile creep and hydrothermal mineral precipitation (reduced porosity) and find yearly-to-decadal time-scales for periodic fracturing and fluid loss events and an increase in average permeability. We then use a fully coupled poro-thermo-elastic framework to model to explore the macroscopic influence of volatile loss on the stress state of the crust in this higher time-averaged permeability setting. We derive new semi-analytical solutions and combine them with a magma chamber box model (modified from Degruyter & Huber 2014) to analyze system-scale dynamics for both basaltic and silicic magmatic systems. We find that passive degassing likely has a substantial temporal influence on the stress distribution in the crust and the highly crystalline mush zone immediately surrounding a magma reservoir, and find an additional scale : pore-pressure diffusion timescale that exerts a first-order control on the magnitude and frequency of volcanic eruptions. We also explore how disconnected magma batches interact indirectly with each other and its implications for

Magma addition rates in continental arcs: New methods of calculation and global implications

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Ratschbacher, B. C.; Paterson, S. R.

2017-12-01

The transport of mass, heat and geochemical constituents (elements and volatiles) from the mantle to the atmosphere occurs via magma addition to the lithosphere. Calculation of magma addition rates (MARs) in continental arcs based on exposed proportions of igneous arc rocks is complex and rarely consistently determined. Multiple factors influence MAR calculations such as crust versus mantle contributions to magmas, a change in MARs across the arc and with depths throughout the arc crustal column, `arc tempos' with periods of high and low magmatic activity, the loss of previous emplaced arc rocks by subsequent magmatism and return to the mantle, arc migration, variations in the intrusive versus extrusive additions and evolving arc widths and thicknesses during tectonism. All of these factors need to be considered when calculating MARs.This study makes a new attempt to calculate MARs in continental arcs by studying three arc sections: the Famatinian arc, Argentina, the Sierra Nevada batholith, California and the Coast Mountain batholith, Washington and British Columbia. Arcs are divided into fore-arc, main arc and back arc sections and `boxes' with a defined width, length and thickness spanning upper middle and lower crustal levels are assigned to each section. Representative exposed crustal slices for each depth are then used to calculate MARs based on outcrop proportions for each box. Geochemical data is used to infer crustal recycling percentages and total thickness of the arc. Preliminary results show a correlation between MARs, crustal thicknesses and magmatic flare-up durations. For instance, the Famatinian arc shows a strong decrease in MARs between the main arc section (9.4 km3/Ma/arc-km) and the fore-arc (0.61 km3/Ma/arc-km) and back-arc (1.52 km3/Ma/arc-km) regions and an increase in the amount of magmatism with depth.Global MARs over geologic timescales have the potential to investigate mantle melt generation rates and the volatile outgassing contribution

Evolution of C-O-H-N volatile species in the magma ocean during core formation.

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Dalou, C.; Le Losq, C.; Hirschmann, M. M.; Jacobsen, S. D.; Fueri, E.

2017-12-01

understanding of species abundances and gas phase equilibria should constrain the contribution of magma ocean degassing to the Hadean atmosphere. As reactions involving CO, N2, and OH are sufficient to form amino acids, and NH2, NH3, CH3, and CH4 are amino acid components, the availability of such reduced molecules for outgassing from the magma ocean suggest a central role in the formation of the first organic molecules.

Slab melting and magma formation beneath the southern Cascade arc

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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

Magma Chamber Model of Batur Caldera, Bali, Indonesia: Compositional Variation of Two Facies, Large-Volume Dacitic Ignimbrites

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Igan S. Sutawidjaja

2015-05-01

Full Text Available DOI:10.17014/ijog.2.2.111-124Batur is one of the finest known calderas on Earth, and is the source of at least two major ignimbrite eruptions with a combined volume of some 84 km3 and 19 km3. These ignimbrites have a similar compositions, raising the question of whether they are geneticaly related. The Batur Ignimbrite-1 (BI-1 is crystal poor, containing rhyodacitic (68 - 70wt % SiO2, white to grey pumices and partly welded and unwelded. The overlying Batur Ignimbrite-2 (BI-2 is a homogeneous grey to black dacitic pumices (64 - 66 wt % SiO2, unwelded and densely welded (40 - 60% vesicularity, crystal and lithic rich. Phase equilibria indicate that the Batur magma equilibrated at temperatures of 1100 - 1300oC with melt water contents of 3 - 6 wt%. The post-eruptive Batur magma was cooler (<1100oC and it is melt more water rich (> 6 wt % H2O. A pressure of 20 kbar is infered from mineral barometry for the Batur magma chamber. Magmatic chamber model is one in which crystals and melt separate from a convecting Batur magma by density differences, resulting in a stratified magma chamber with a homogeneous central zone, a crystal-rich accumulation zone near the walls or base, and a buoyant, melt-rich zone near the top. This is consistent with the estimated magma temperatures and densities: the pre-eruptive BI-1 magma was hoter (1300oC and more volatile rich (6 wt % H2O with density 2.25 g/cm3 than the BI-2 magma (1200oC; 4 wt % H2O in density was higher (2.50 g/cm3. Batur melt characteristics and intensive parameters are consistent with a volatile oversaturation-driven eruption. However, the higher H2O content, high viscosity and low crystal content of the BI-1 magma imply an external eruption trigger.

Io's theothermal (sulfur) - Lithosphere cycle inferred from sulfur solubility modeling of Pele's magma supply

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Battaglia, Steven M.; Stewart, Michael A.; Kieffer, Susan W.

2014-06-01

Surface deposits of volatile compounds such as water (Earth) or sulfur (Io) on volcanically active bodies suggest that a magmatic distillation process works to concentrate volatiles in surface reservoirs. On Earth, this is the combined hydrologic and tectonic cycle. On Io, sulfurous compounds are transferred from the interior to the surface reservoirs through a combination of a mantle-sourced magmatic system, vertical cycling of the lithosphere, and a sulfur-dominated crustal thermal system that we here call the "theothermal" system. We present a geochemical analysis of this process using previously inferred temperature and oxygen fugacity constraints of Pele's basaltic magma to determine the behavior of sulfur in the ionian magmas. Sulfate to sulfide ratios of Pele's magma are -4.084 ± 0.6 and -6.442 ± 0.7 log10 units, comparable to or lower than those of mid-ocean ridge basalts. This reflects the similarity of Io's oxidation state with Earth's depleted mantle as previously suggested by Zolotov and Fegley (Zolotov, M.Y., Fegley, B. [2000]. Geophys. Res. Lett. 27, 2789-2792). Our calculated limits of sulfur solubility in melts from Pele's patera (˜1100-1140 ppm) are also comparable to terrestrial mid-ocean ridge basalts, reflecting a compositional similarity of mantle sources. We propose that the excess sulfur obvious on Io's surface comes from two sources: (1) an insoluble sulfide liquid phase in the magma and (2) theothermal near-surface recycling.

Rapid Crystallization of the Bishop Magma

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Gualda, G. A.; Anderson, A. T.; Sutton, S. R.

2007-12-01

is 2 orders of magnitude smaller than the shortest durations derived from geochronology. In the current paradigm, this implies that the Bishop magma existed virtually free of crystals for 100-200 ka. Occasional recharge of the system could cause resorption of crystals. The challenge, however, is to explain how a large- volume, liquid- and volatile-rich system, was prevented from erupting for over 100 ka. The trouble is such that it puts into question the whole concept of a long-lived, liquid-rich magma body. Evidence has accumulated to show that the Bishop magma was stratified and did not convect during crystallization, the stratification was established prior to phenocryst crystallization, and crystal migration did not significantly perturb the stratification. All these are simpler to explain if liquid-rich magma only existed for a short period of time, and we estimate the time as being on the order of 1 ka. The geospeedometric timescale inferred can be reconciled with the geochronological evidence if we interpret zircon crystallization ages as reflecting episodic growth in response to waxing and waning of a mushy body, rather than continuous crystallization from liquid-rich magma in a long-lived, large-volume magma body. We speculate that only after 100-200 ka did favorable conditions emerge and allowed for the generation of a large volume of liquid-rich magma. Once such a body of magma was established, it progressed rather quickly towards eruption.

A magma ocean and the Earth's internal water budget

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Ahrens, Thomas J.

1992-01-01

There are lines of evidence which relate bounds on the primordial water content of the Earth's mantle to a magma ocean and the accompanying Earth accretion process. We assume initially (before a magma ocean could form) that as the Earth accreted, it grew from volatile- (H2O, CO2, NH3, CH4, SO2, plus noble) gas-rich planetesimals, which accreted to form an initial 'primitive accretion core' (PAC). The PAC retained the initial complement of planetesimal gaseous components. Shock wave experiments in which both solid, and more recently, the gaseous components of materials such as serpentine and the Murchison meteorite have demonstrated that planetesimal infall velocities of less than 0.5 km/sec, induce shock pressures of less than 0.5 GPa and result in virtually complete retention of planetary gases.

A Physical Model for Three-Phase Compaction in Silicic Magma Reservoirs

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Huber, Christian; Parmigiani, Andrea

2018-04-01

We develop a model for phase separation in magma reservoirs containing a mixture of silicate melt, crystals, and fluids (exsolved volatiles). The interplay between the three phases controls the dynamics of phase separation and consequently the chemical and physical evolution of magma reservoirs. The model we propose is based on the two-phase damage theory approach of Bercovici et al. (2001, https://doi.org/10.1029/2000JB900430) and Bercovici and Ricard (2003, https://doi.org/10.1046/j.1365-246X.2003.01854.x) because it offers the leverage of considering interface (in the macroscopic limit) between phases that can deform depending on the mechanical work and phase changes taking place locally in the magma. Damage models also offer the advantage that pressure is defined uniquely to each phase and does not need to be equal among phases, which will enable us to consider, in future studies, the large capillary pressure at which fluids are mobilized in mature, crystal-rich, magma bodies. In this first analysis of three-phase compaction, we solve the three-phase compaction equations numerically for a simple 1-D problem where we focus on the effect of fluids on the efficiency of melt-crystal separation considering the competition between viscous and buoyancy stresses only. We contrast three sets of simulations to explore the behavior of three-phase compaction, a melt-crystal reference compaction scenario (two-phase compaction), a three-phase scenario without phase changes, and finally a three-phase scenario with a parameterized second boiling (crystallization-induced exsolution). The simulations show a dramatic difference between two-phase (melt crystals) and three-phase (melt-crystals-exsolved volatiles) compaction-driven phase separation. We find that the presence of a lighter, significantly less viscous fluid hinders melt-crystal separation.

Eruption Depths, Magma Storage and Magma Degassing at Sumisu Caldera, Izu-Bonin Arc: Evidence from Glasses and Melt Inclusions

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Johnson, E. R.

2015-12-01

Island arc volcanoes can become submarine during cataclysmal caldera collapse. The passage of a volcanic vent from atmospheric to under water environment involves complex modifications of the eruption style and subsequent transport of the pyroclasts. Here, we use FTIR measurements of the volatile contents of glass and melt inclusions in the juvenile pumice clasts in the Sumisu basin and its surroundings (Izu-Bonin arc) to investigate changes in eruption depths, magma storage and degassing over time. This study is based on legacy cores from ODP 126, where numerous unconsolidated (250 m), massive to normally graded pumice lapilli-tuffs were recovered over four cores (788C, 790A, 790B and 791A). Glass and clast geochemistry indicate the submarine Sumisu caldera as the source of several of these pumice lapilli-tuffs. Glass chips and melt inclusions from these samples were analyzed using FTIR for H2O and CO2 contents. Glass chips record variable H2O contents; most chips contain 0.6-1.6 wt% H2O, corresponding to eruption depths of 320-2100 mbsl. Variations in glass H2O and pressure estimates suggest that edifice collapse occurred prior-to or during eruption of the oldest of these samples, and that the edifice may have subsequently grown over time. Sanidine-hosted melt inclusions from two units record variably degassed but H2O-rich melts (1.1-5.6 wt% H2O). The lowest H2O contents overlap with glass chips, consistent with degassing and crystallization of melts until eruption, and the highest H2O contents suggest that large amounts of degassing accompanied likely explosive eruptions. Most inclusions, from both units, contain 2-4 wt% H2O, which further indicates that the magmas crystallized at pressures of ~50-100 MPa, or depths ~400-2800 m below the seafloor. Further glass and melt inclusion analyses, including major element compositions, will elucidate changes in magma storage, degassing and evolution over time.

Re-appraisal of the Magma-rich versus Magma-poor Paradigm at Rifted Margins: consequences for breakup processes

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Tugend, J.; Gillard, M.; Manatschal, G.; Nirrengarten, M.; Harkin, C. J.; Epin, M. E.; Sauter, D.; Autin, J.; Kusznir, N. J.; McDermott, K.

2017-12-01

Rifted margins are often classified based on their magmatic budget only. Magma-rich margins are commonly considered to have excess decompression melting at lithospheric breakup compared with steady state seafloor spreading while magma-poor margins have suppressed melting. New observations derived from high quality geophysical data sets and drill-hole data have revealed the diversity of rifted margin architecture and variable distribution of magmatism. Recent studies suggest, however, that rifted margins have more complex and polyphase tectono-magmatic evolutions than previously assumed and cannot be characterized based on the observed volume of magma alone. We compare the magmatic budget related to lithospheric breakup along two high-resolution long-offset deep reflection seismic profiles across the SE-Indian (magma-poor) and Uruguayan (magma-rich) rifted margins. Resolving the volume of magmatic additions is difficult. Interpretations are non-unique and several of them appear plausible for each case involving variable magmatic volumes and mechanisms to achieve lithospheric breakup. A supposedly 'magma-poor' rifted margin (SE-India) may show a 'magma-rich' lithospheric breakup whereas a 'magma-rich' rifted margin (Uruguay) does not necessarily show excess magmatism at lithospheric breakup compared with steady-state seafloor spreading. This questions the paradigm that rifted margins can be subdivided in either magma-poor or magma-rich margins. The Uruguayan and other magma-rich rifted margins appear characterized by an early onset of decompression melting relative to crustal breakup. For the converse, where the onset of decompression melting is late compared with the timing of crustal breakup, mantle exhumation can occur (e.g. SE-India). Our work highlights the difficulty in determining a magmatic budget at rifted margins based on seismic reflection data alone, showing the limitations of margin classification based solely on magmatic volumes. The timing of

Influence of extrusion rate and magma rheology on the growth of lava domes: Insights from particle-dynamics modeling

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Husain, Taha; Elsworth, Derek; Voight, Barry; Mattioli, Glen; Jansma, Pamela

2014-09-01

Lava domes are structures that grow by the extrusion of viscous silicic or intermediate composition magma from a central volcanic conduit. Repeated cycles of growth are punctuated by collapse, as the structure becomes oversized for the strength of the composite magma that rheologically stiffens and strengthens at its surface. Here we explore lava dome growth and failure mechanics using a two-dimensional particle-dynamics model. The model follows the evolution of fractured lava, with solidification driven by degassing induced crystallization of magma. The particle-dynamics model emulates the natural development of dome growth and rearrangement of the lava dome which is difficult in mesh-based analyses due to mesh entanglement effects. The deformable talus evolves naturally as a frictional carapace that caps a ductile magma core. Extrusion rate and magma rheology together with crystallization temperature and volatile content govern the distribution of strength in the composite structure. This new model is calibrated against existing observational models of lava dome growth. Results show that the shape and extent of the ductile core and the overall structure of the lava dome are strongly controlled by the infusion rate. The effects of extrusion rate on magma rheology are sensitive to material stiffness, which in turn is a function of volatile content and crystallinity. Material stiffness and material strength are key model parameters which govern magma rheology and subsequently the morphological character of the lava dome and in turn stability. Degassing induced crystallization causes material stiffening and enhances material strength reflected in non-Newtonian magma behavior. The increase in stiffness and strength of the injected magma causes a transition in the style of dome growth, from endogenous expansion of a ductile core, to stiffer and stronger intruding material capable of punching through the overlying material and resulting in the development of a spine or

INTERACTIONS BETWEEN GABBROID AND GRANITOID MAGMAS DURING FORMATION OF THE PREOBRAZHENSKY INTRUSION, EAST KAZAKHSTAN

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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

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

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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

The crustal magma storage system of Volcán Quizapu, Chile, and the effects of magma mixing on magma diversity

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Bergantz, George W.; Cooper, Kari M.; Hildreth, Edward; Ruprecht, Phillipp

2012-01-01

Crystal zoning as well as temperature and pressure estimates from phenocryst phase equilibria are used to constrain the architecture of the intermediate-sized magmatic system (some tens of km3) of Volcán Quizapu, Chile, and to document the textural and compositional effects of magma mixing. In contrast to most arc magma systems, where multiple episodes of open-system behavior obscure the evidence of major magma chamber events (e.g. melt extraction, magma mixing), the Quizapu magma system shows limited petrographic complexity in two large historical eruptions (1846–1847 and 1932) that have contrasting eruptive styles. Quizapu magmas and peripheral mafic magmas exhibit a simple binary mixing relationship. At the mafic end, basaltic andesite to andesite recharge magmas complement the record from peripheral cones and show the same limited range of compositions. The silicic end-member composition is almost identical in both eruptions of Quizapu. The effusive 1846–1847 eruption records significant mixing between the mafic and silicic end-members, resulting in hybridized andesites and mingled dacites. These two compositionally simple eruptions at Volcán Quizapu present a rare opportunity to isolate particular aspects of magma evolution—formation of homogeneous dacite magma and late-stage magma mixing—from other magma chamber processes. Crystal zoning, trace element compositions, and crystal-size distributions provide evidence for spatial separation of the mafic and silicic magmas. Dacite-derived plagioclase phenocrysts (i.e. An25–40) show a narrow range in composition and limited zonation, suggesting growth from a compositionally restricted melt. Dacite-derived amphibole phenocrysts show similar restricted compositions and furthermore constrain, together with more mafic amphibole phenocrysts, the architecture of the magmatic system at Volcán Quizapu to be compositionally and thermally zoned, in which an andesitic mush is overlain by a homogeneous dacitic

Upward migration of Vesuvius magma chamber over the past 20,000 years.

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Scaillet, B; Pichavant, M; Cioni, R

2008-09-11

Forecasting future eruptions of Vesuvius is an important challenge for volcanologists, as its reawakening could threaten the lives of 700,000 people living near the volcano. Critical to the evaluation of hazards associated with the next eruption is the estimation of the depth of the magma reservoir, one of the main parameters controlling magma properties and eruptive style. Petrological studies have indicated that during past activity, magma chambers were at depths between 3 and 16 km (refs 3-7). Geophysical surveys have imaged some levels of seismic attenuation, the shallowest of which lies at 8-9 km depth, and these have been tentatively interpreted as levels of preferential magma accumulation. By using experimental phase equilibria, carried out on material from four main explosive events at Vesuvius, we show here that the reservoirs that fed the eruptive activity migrated from 7-8 km to 3-4 km depth between the ad 79 (Pompeii) and ad 472 (Pollena) events. If data from the Pomici di Base event 18.5 kyr ago and the 1944 Vesuvius eruption are included, the total upward migration of the reservoir amounts to 9-11 km. The change of preferential magma ponding levels in the upper crust can be attributed to differences in the volatile content and buoyancy of ascending magmas, as well as to changes in local stress field following either caldera formation or volcano spreading. Reservoir migration, and the possible influence on feeding rates, should be integrated into the parameters used for defining expected eruptive scenarios at Vesuvius.

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

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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 < 1??MPa, equivalent to < ~ 35??m in the conduit. Fluid-melt partition coefficients for Cl and F are low (< 1.5); F only degasses appreciably at < 0.1??MPa above atmospheric 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.

Magmatic Volatiles as an Amplifier of Centrifugal Volcanism

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Pratt, V. R.

2017-12-01

There is a striking correlation between negated Length of Day -LOD and the 60-70 year period in 20th century global climate, associated by some with the so-called Atlantic Multidecadal Oscillation or AMO. A number of authors have suggested mechanisms by which the former might cause the latter. One such that this author finds quite compelling is that gravity fluctuations at low latitudes increase essentially linearly with LOD fluctuations and therefore moves magma towards or away from the surface as LOD decreases or increases, i.e. angular velocity increases or decreases, respectively. At AGU FM2016 we proposed the term "centrifugal volcanism" for this mechanism and listed four possible objections to it, explaining three to our satisfaction. The remaining objection is the very obvious one that the 4 ms increase in LOD between 1880 and 1910 seems far too small to be able to account for the observed variation of about a quarter of a degree. A basic mechanism underlying many violent eruptions is the strong positive feedback between reduction of pressure in magma and evaporation of dissolved volatiles found in some magmas, driving the magma outwards and thereby further reducing the pressure. The normal state of magma is equilibrium. Any fluctuation in gravity, even a very small one, can be sufficient to shift this equilibrium sufficiently far to set this positive feedback in motion. The relevant electrical analogy would be an operational amplifier whose amplification is greatly increased by a positive feedback. We therefore propose that the same mechanism responsible for some violent eruptions also serves to amplify the tiny changes in gravity sufficiently to increase or decrease the vertical component of the movement of magma in general. This movement, felt throughout the planet albeit most strongly at low latitudes, influences the temperature at ocean bottoms wherever there is a significant level of magmatic volatiles. This in turn creates thermals that are large

Noble gas solubility in silicate melts:a review of experimentation and theory, and implications regarding magma degassing processes

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A. Paonita

2005-06-01

Full Text Available Noble gas solubility in silicate melts and glasses has gained a crucial role in Earth Sciences investigations and in the studies of non-crystalline materials on a micro to a macro-scale. Due to their special geochemical features, noble gases are in fact ideal tracers of magma degassing. Their inert nature also allows them to be used to probe the structure of silicate melts. Owing to the development of modern high pressure and temperature technologies, a large number of experimental investigations have been performed on this subject in recent times. This paper reviews the related literature, and tries to define our present state of knowledge, the problems encountered in the experimental procedures and the theoretical questions which remain unresolved. Throughout the manuscript I will also try to show how the thermodynamic and structural interpretations of the growing experimental dataset are greatly improving our understanding of the dissolution mechanisms, although there are still several points under discussion. Our improved capability of predicting noble gas solubilities in conditions closer to those found in magma has allowed scientists to develop quantitative models of magma degassing, which provide constraints on a number of questions of geological impact. Despite these recent improvements, noble gas solubility in more complex systems involving the main volatiles in magmas, is poorly known and a lot of work must be done. Expertise from other fields would be extremely valuable to upcoming research, thus focus should be placed on the structural aspects and the practical and commercial interests of the study of noble gas solubility.

Can Fractional Crystallization of a Lunar Magma Ocean Produce the Lunar Crust?

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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

Magma heating by decompression-driven crystallization beneath andesite volcanoes.

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Blundy, Jon; Cashman, Kathy; Humphreys, Madeleine

2006-09-07

Explosive volcanic eruptions are driven by exsolution of H2O-rich vapour from silicic magma. Eruption dynamics involve a complex interplay between nucleation and growth of vapour bubbles and crystallization, generating highly nonlinear variation in the physical properties of magma as it ascends beneath a volcano. This makes explosive volcanism difficult to model and, ultimately, to predict. A key unknown is the temperature variation in magma rising through the sub-volcanic system, as it loses gas and crystallizes en route. Thermodynamic modelling of magma that degasses, but does not crystallize, indicates that both cooling and heating are possible. Hitherto it has not been possible to evaluate such alternatives because of the difficulty of tracking temperature variations in moving magma several kilometres below the surface. Here we extend recent work on glassy melt inclusions trapped in plagioclase crystals to develop a method for tracking pressure-temperature-crystallinity paths in magma beneath two active andesite volcanoes. We use dissolved H2O in melt inclusions to constrain the pressure of H2O at the time an inclusion became sealed, incompatible trace element concentrations to calculate the corresponding magma crystallinity and plagioclase-melt geothermometry to determine the temperature. These data are allied to ilmenite-magnetite geothermometry to show that the temperature of ascending magma increases by up to 100 degrees C, owing to the release of latent heat of crystallization. This heating can account for several common textural features of andesitic magmas, which might otherwise be erroneously attributed to pre-eruptive magma mixing.

Making mushy magma chambers in the lower continental crust: Cold storage and compositional bimodality

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Jackson, Matthew; Blundy, Jon; Sparks, Steve

2017-04-01

the local melt fraction is too low to form a mobile magma. The model results are consistent with geochemical data suggesting that lower crustal magma reservoirs supply silicic and mafic melts to arc volcanoes, but intermediate magmas are formed by mixing in shallower reservoirs. We suggest here that lower crustal magma chambers primarily form in response to changes in bulk composition caused by melt migration and chemical reaction in a mush reservoir. This process is different to the conventional and widely applied models of magma chamber formation. Similar processes are likely to operate in shallow mush reservoirs, but will likely be further complicated by the presence of volatile phases, and mixing of different melt compositions sourced from deeper mush reservoirs.

Magma Chambers, Thermal Energy, and the Unsuccessful Search for a Magma Chamber Thermostat

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Glazner, A. F.

2015-12-01

Although the traditional concept that plutons are the frozen corpses of huge, highly liquid magma chambers ("big red blobs") is losing favor, the related notion that magma bodies can spend long periods of time (~106years) in a mushy, highly crystalline state is widely accepted. However, analysis of the thermal balance of magmatic systems indicates that it is difficult to maintain a significant portion in a simmering, mushy state, whether or not the system is eutectic-like. Magma bodies cool primarily by loss of heat to the Earth's surface. The balance between cooling via energy loss to the surface and heating via magma accretion can be denoted as M = ρLa/q, where ρ is magma density, L is latent heat of crystallization, a is the vertical rate of magma accretion, and q is surface heat flux. If M>1, then magma accretion outpaces cooling and a magma chamber forms. For reasonable values of ρ, L, and q, the rate of accretion amust be > ~15 mm/yr to form a persistent volume above the solidus. This rate is extremely high, an order of magnitude faster than estimated pluton-filling rates, and would produce a body 10 km thick in 700 ka, an order of magnitude faster than geochronology indicates. Regardless of the rate of magma supply, the proportion of crystals in the system must vary dramatically with depth at any given time owing to transfer of heat. Mechanical stirring (e.g., by convection) could serve to homogenize crystal content in a magma body, but this is unachievable in crystal-rich, locked-up magma. Without convection the lower part of the magma body becomes much hotter than the top—a process familiar to anyone who has scorched a pot of oatmeal. Thermal models that succeed in producing persistent, large bodies of magma rely on scenarios that are unrealistic (e.g., omitting heat loss to the planet's surface), self-fulfilling prophecies (e.g., setting unnaturally high temperatures as fixed boundary conditions), or physically unreasonable (e.g., magma is intruded

Involvement of a volatile metabolite during phosphoramide mustard-induced ovotoxicity

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Madden, Jill A. [Department of Animal Science, Iowa State University, Ames, IA 50011 (United States); Hoyer, Patricia B. [Department of Physiology, University of Arizona, Tucson, AZ 85724 (United States); Devine, Patrick J. [INRS—Institut Armand-Frappier Research Centre, University of Quebec, Laval, QC H7V 1B7 (Canada); Keating, Aileen F., E-mail: akeating@iastate.edu [Department of Animal Science, Iowa State University, Ames, IA 50011 (United States); Department of Physiology, University of Arizona, Tucson, AZ 85724 (United States)

2014-05-15

The finite ovarian follicle reserve can be negatively impacted by exposure to chemicals including the anti-neoplastic agent, cyclophosphamide (CPA). CPA requires bioactivation to phosphoramide mustard (PM) to elicit its therapeutic effects however; in addition to being the tumor-targeting metabolite, PM is also ovotoxic. In addition, PM can break down to a cytotoxic, volatile metabolite, chloroethylaziridine (CEZ). The aim of this study was initially to characterize PM-induced ovotoxicity in growing follicles. Using PND4 Fisher 344 rats, ovaries were cultured for 4 days before being exposed once to PM (10 or 30 μM). Following eight additional days in culture, relative to control (1% DMSO), PM had no impact on primordial, small primary or large primary follicle number, but both PM concentrations induced secondary follicle depletion (P < 0.05). Interestingly, a reduction in follicle number in the control-treated ovaries was observed. Thus, the involvement of a volatile, cytotoxic PM metabolite (VC) in PM-induced ovotoxicity was explored in cultured rat ovaries, with control ovaries physically separated from PM-treated ovaries during culture. Direct PM (60 μM) exposure destroyed all stage follicles after 4 days (P < 0.05). VC from nearby wells depleted primordial follicles after 4 days (P < 0.05), temporarily reduced secondary follicle number after 2 days, and did not impact other stage follicles at any other time point. VC was determined to spontaneously liberate from PM, which could contribute to degradation of PM during storage. Taken together, this study demonstrates that PM and VC are ovotoxicants, with different follicular targets, and that the VC may be a major player during PM-induced ovotoxicity observed in cancer survivors. - Highlights: • PM depletes all stage ovarian follicles in a temporal pattern. • A volatile ovotoxic compound is liberated from PM. • The volatile metabolite depletes primordial follicles.

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

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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.

Degassing vs. eruptive styles at Mt. Etna volcano (Sicily, Italy): Volatile stocking, gas fluxing, and the shift from low-energy to highly-explosive basaltic eruptions

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Moretti, Roberto; Métrich, Nicole; Di Renzo, Valeria; Aiuppa, Alessandro; Allard, Patrick; Arienzo, Ilenia

2017-04-01

Basaltic magmas can transport and release large amounts of volatiles into the atmosphere, especially in subduction zones, where slab-derived fluids enrich the mantle wedge. Depending on magma volatile content, basaltic volcanoes thus display a wide spectrum of eruptive styles, from common Strombolian-type activity to Plinian events. Mt. Etna in Sicily, is a typical basaltic volcano where the volatile control on such a variable activity can be investigated. Based on a melt inclusion study in products from Strombolian or lava-fountain activity to Plinian eruptions, here we show that for the same initial volatile content, different eruptive styles reflect variable degassing paths throughout the composite Etnean plumbing system. The combined influence of i) crystallization, ii) deep degassing and iii) CO2 gas fluxing can explain the evolution of H2O, CO2, S and Cl in products from such a spectrum of activity. Deep crystallization produces the CO2-rich gas fluxing the upward magma portions, which will become buoyant and easily mobilized in small gas-rich batches stored within the plumbing system. When reaching gas dominated conditions (i.e., a gas/melt mass ratio of 0.3 and CO2,gas/H2Ogas molar ratio 5 ), these will erupt effusively or mildly explosively, whilst in case of the 122 BC Plinian eruption, open-system degassing conditions took place within the plumbing system, such that continuous CO2-fluxing determined gas accumulation on top of the magmatic system. The emission of such a cap in the early eruptive phase triggered the arrival of deep H2O-rich whose fast decompression and bubble nucleation lead to the highly explosive character, enhanced by abundant microlite crystallization and consequent increase of magma effective viscosity. This could explain why open system basaltic systems like Etna may experience highly explosive or even Plinian episodes during eruptions that start with effusive to mildly explosive phases. The proposed mechanism also determines a

Tube pumices as strain markers of the ductile-brittle transition during magma fragmentation

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Martí, J.; Soriano, C.; Dingwell, D. B.

1999-12-01

Magma fragmentation-the process by which relatively slow-moving magma transforms into a violent gas flow carrying fragments of magma-is the defining feature of explosive volcanism. Yet of all the processes involved in explosively erupting systems, fragmentation is possibly the least understood. Several theoretical and laboratory studies on magma degassing and fragmentation have produced a general picture of the sequence of events leading to the fragmentation of silicic magma. But there remains a debate over whether magma fragmentation is a consequence of the textural evolution of magma to a foamed state where disintegration of walls separating bubbles becomes inevitable due to a foam-collapse criterion, or whether magma is fragmented purely by stresses that exceed its tensile strength. Here we show that tube pumice-where extreme bubble elongation is observed-is a well-preserved magmatic `strain marker' of the stress state immediately before and during fragmentation. Structural elements in the pumice record the evolution of the magma's mechanical response from viscous behaviour (foaming and foam elongation) through the plastic or viscoelastic stage, and finally to brittle behaviour. These observations directly support the hypothesis that fragmentation occurs when magma undergoes a ductile-brittle transition and stresses exceed the magma's tensile strength.

Implications of magma transfer between multiple reservoirs on eruption cycling.

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Elsworth, Derek; Mattioli, Glen; Taron, Joshua; Voight, Barry; Herd, Richard

2008-10-10

Volcanic eruptions are episodic despite being supplied by melt at a nearly constant rate. We used histories of magma efflux and surface deformation to geodetically image magma transfer within the deep crustal plumbing of the Soufrière Hills volcano on Montserrat, West Indies. For three cycles of effusion followed by discrete pauses, supply of the system from the deep crust and mantle was continuous. During periods of reinitiated high surface efflux, magma rose quickly and synchronously from a deflating mid-crustal reservoir (at about 12 kilometers) augmented from depth. During repose, the lower reservoir refilled from the deep supply, with only minor discharge transiting the upper chamber to surface. These observations are consistent with a model involving the continuous supply of magma from the deep crust and mantle into a voluminous and compliant mid-crustal reservoir, episodically valved below a shallow reservoir (at about 6 kilometers).

The Meaning of "Magma"

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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.

Improving Student Understanding of Magmatic Differentiation Using an M&M Magma Chamber

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Wirth, K. R.

2003-12-01

Many students, especially those in introductory geology courses, have difficulty developing a deep understanding of the processes of magmatic differentiation. In particular, students often struggle to understand Bowen's reaction series and fractional crystallization. The process of fractional crystallization by gravity settling can be illustrated using a model magma chamber consisting of M&M's. In this model, each major cation (e.g., Si, Ti, Al, Fe, Mg, Ca, Na, K) is represented by a different color M&M; other kinds of differently colored or shaped pieces could also be used. Appropriate numbers of each color M&M are combined to approximate the cation proportions of a basaltic magma. Students then fractionate the magma by moving M&M's to the bottom of the magma chamber forming a series of cumulus layers; the M&M's are removed in the stoichiometric proportions of cations in the crystallizing minerals (e.g., olivine, pyroxene, feldspars, quartz, magnetite, ilmenite). Students observe the changing cation composition (proportions of colors of M&M's) in the cumulus layers and in the magma chamber and graph the results using spreadsheet software. More advanced students (e.g., petrology course) can classify the cumulates and resulting liquid after each crystallization step, and they can compare the model system with natural magmatic systems (e.g., absence of important fractionating phases, volatiles). Students who have completed this exercise generally indicate a positive experience and demonstrate increased understanding of Bowen's reaction series and fractionation processes. They also exhibit greater familiarity with mineral stoichiometry, classification, solid-solution in minerals, element behavior (e.g., incompatibility), and chemical variation diagrams. Other models (e.g., paths of equilibrium and fractional crystallization on phase diagrams) can also be used to illustrate differentiation processes in upper level courses (e.g., mineralogy and petrology).

Magma-derived CO2 emissions in the Tengchong volcanic field, SE Tibet: Implications for deep carbon cycle at intra-continent subduction zone

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Zhang, Maoliang; Guo, Zhengfu; Sano, Yuji; Zhang, Lihong; Sun, Yutao; Cheng, Zhihui; Yang, Tsanyao Frank

2016-09-01

Active volcanoes at oceanic subduction zone have long been regard as important pathways for deep carbon degassed from Earth's interior, whereas those at continental subduction zone remain poorly constrained. Large-scale active volcanoes, together with significant modern hydrothermal activities, are widely distributed in the Tengchong volcanic field (TVF) on convergent boundary between the Indian and Eurasian plates. They provide an important opportunity for studying deep carbon cycle at the ongoing intra-continent subduction zone. Soil microseepage survey based on accumulation chamber method reveals an average soil CO2 flux of ca. 280 g m-2 d-1 in wet season for the Rehai geothermal park (RGP). Combined with average soil CO2 flux in dry season (ca. 875 g m-2 d-1), total soil CO2 output of the RGP and adjacent region (ca. 3 km2) would be about 6.30 × 105 t a-1. Additionally, we conclude that total flux of outgassing CO2 from the TVF would range in (4.48-7.05) × 106 t a-1, if CO2 fluxes from hot springs and soil in literature are taken into account. Both hot spring and soil gases from the TVF exhibit enrichment in CO2 (>85%) and remarkable contribution from mantle components, as indicated by their elevated 3He/4He ratios (1.85-5.30 RA) and δ13C-CO2 values (-9.00‰ to -2.07‰). He-C isotope coupling model suggests involvement of recycled organic metasediments and limestones from subducted Indian continental lithosphere in formation of the enriched mantle wedge (EMW), which has been recognized as source region of the TVF parental magmas. Contamination by crustal limestone is the first-order control on variations in He-CO2 systematics of volatiles released by the EMW-derived melts. Depleted mantle and recycled crustal materials from subducted Indian continental lithosphere contribute about 45-85% of the total carbon inventory, while the rest carbon (about 15-55%) is accounted by limestones in continental crust. As indicated by origin and evolution of the TVF

Geochemical evidences of magma dynamics at Campi Flegrei (Italy)

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Caliro, S.; Chiodini, G.; Paonita, A.

2014-05-01

Campi Flegrei caldera, within the Neapolitan area of Italy, is potentially one of the most dangerous volcanoes in the world, and during the last decade it has shown clear signs of reactivation, marked by the onset of uplift and changes in the geochemistry of gas emissions. We describe a 30-year-long data set of the CO2-He-Ar-N2 compositions of fumarolic emissions from La Solfatara crater, which is located in the center of the caldera. The data display continuous decreases in both the N2/He and N2/CO2 ratios since 1985, paralleled by an increase in He/CO2. These variations cannot be explained by either processes of boiling/condensation in the local hydrothermal system or with changes in the mixing proportions between a magmatic vapor and hydrothermal fluids. We applied the magma degassing model of Nuccio and Paonita (2001, Earth Planet. Sci. Lett. 193, 467-481) using the most recent inert-gas solubilities in order to interpret these peculiar features in accordance with petrologic constraints derived from the ranges of the melt compositions and reservoir pressures at Campi Flegrei. The model simulations for mafic melts (trachybasalt and shoshonite) show a remarkably good agreement with the measured data. Both decompressive degassing of an ascending magma and mixing between magmatic fluids exsolved at various levels along the ascent path can explain the long-term geochemical changes. Recalling that (i) a sill-like reservoir of gases at a depth of 3-4 km seems to be the main source of ground inflation and (ii) there is petrologic and geophysical evidence for a reservoir of magma at about 8 km below Campi Flegrei, we suggest that the most-intense episodes of inflation occur when the gas supply to the sill-like reservoir comes from the 8 km-deep magma, although fluids exsolved by magma bodies at shallower depths also contribute to the gas budget. Our work highlights that, in caldera systems where the presence of hydrothermal aquifers commonly masks the magmatic signature

It's the little things that matter most: The role of volatiles in volcanoes and their magmatic roots

Science.gov (United States)

Keller, T.; Suckale, J.

2017-12-01

Many volcanic eruptions are driven by volatiles - mostly H2O and CO2 - that degas from magmas rising up beneath the volcano. Gas expands during ascent, thus frequently creating lavas with upward of 50% vesicularity. That is a particularly compelling observation considering that volatiles are only present at concentrations of order 100 ppm in the mantle source. Yet, even at these small concentrations, volatiles significantly lower the peridotite solidus. That leads to the production of reactive volatile-rich melts at depth, which has important consequences for melt transport in the asthenosphere. Thus, volatiles have a pivotal role both at the beginning and the end of the magmatic storyline. A growing amount of observational evidence provides various perspectives on these systems. Volcanic products are characterised increasingly well by geochemical and petrological data. And, volcano monitoring now often provides continuous records of degassing flux and composition. What is missing to better interpret these data are coupled fluid mechanic and thermodynamic models that link melt production and reactive transport in the mantle and crust with degassing-driven volcanic activity at the surface. Such models need to describe the deformation and segregation of multiple material phases (liquids, solids, gases) and track the reactive transport of diverse chemical components (major elements, trace elements, volatiles). I will present progress towards a generalization of existing two-phase model for melt transport in the mantle, extending them to three-phase flows appropriate for magma circulation and degassing in volcanoes. What sets the two environments apart is the presence of a compressible vapor in volcanoes. Also, volcanic degassing may occur by convecting suspensions as well as porous segregation. The model framework we are developing for these processes is based on mixture theory. Uncovering the underlying physics that connects these diverse expressions of magma

Degassing during magma ascent in the Mule Creek vent (USA)

Science.gov (United States)

Stasiuk, M.V.; Barclay, J.; Carroll, M.R.; Jaupart, Claude; Ratte, J.C.; Sparks, R.S.J.; Tait, S.R.

1996-01-01

The structures and textures of the rhyolite in the Mule Creek vent (New Mexico, USA) indicate mechanisms by which volatiles escape from silicic magma during eruption. The vent outcrop is a 300-m-high canyon wall comprising a section through the top of a feeder conduit, vent and the base of an extrusive lava dome. Field relations show that eruption began with an explosive phase and ended with lava extrusion. Analyses of glass inclusions in quartz phenocrysts from the lava indicate that the magma had a pre-eruptive dissolved water content of 2.5-3.0 wt% and, during eruption, the magma would have been water-saturated over the vertical extent of the present outcrop. However, the vesicularity of the rhyolite is substantially lower than that predicted from closed-system models of vesiculation under equilibrium conditions. At a given elevation in the vent, the volume fraction of primary vesicles in the rhyolite increases from zero close to the vent margin to values of 20-40 vol.% in the central part. In the centre the vesicularity increases upward from approximately 20 vol.% at 300 m below the canyon rim to approximately 40 vol.% at 200 m, above which it shows little increase. To account for the discrepancy between observed vesicularity and measured water content, we conclude that gas escaped during ascent, probably beginning at depths greater than exposed, by flow through the vesicular magma. Gas escape was most efficient near the vent margin, and we postulate that this is due both to the slow ascent of magma there, giving the most time for gas to escape, and to shear, favouring bubble coalescence. Such shear-related permeability in erupting magma is supported by the preserved distribution of textures and vesicularity in the rhyolite: Vesicles are flattened and overlapping near the dense margins and become progressively more isolated and less deformed toward the porous centre. Local zones have textures which suggest the coalescence of bubbles to form permeable

Behavior of volatiles in arc volcanism : geochemical and petrologic evidence from active volcanoes in Indonesia

NARCIS (Netherlands)

Hoog, J.C.M. de

2001-01-01

Large amounts of material are recycled along subduction zones by uprising magmas, of which volcanoes are the surface expression. This thesis focuses on the behavior of volatiles elements (S, Cl, H) during these recycling processes. The study area is the Indonesian arc system, which

Juvenile pumice and pyroclastic obsidian reveal the eruptive conditions necessary for the stability of Plinian eruption of rhyolitic magma

Science.gov (United States)

Giachetti, T.; Shea, T.; Gonnermann, H. M.; McCann, K. A.; Hoxsie, E. C.

2016-12-01

Significant explosive activity generally precedes or coexists with the large effusion of rhyolitic lava (e.g., Mono Craters; Medicine Lake Volcano; Newberry; Chaitén; Cordón Caulle). Such explosive-to-effusive transitions and, ultimately, cessation of activity are commonly explained by the overall waning magma chamber pressure accompanying magma withdrawal, albeit modulated by magma outgassing. The tephra deposits of such explosive-to-effusive eruptions record the character of the transition - abrupt or gradual - as well as potential changes in eruptive conditions, such as magma composition, volatiles content, mass discharge rate, conduit size, magma outgassing. Results will be presented from a detailed study of both the gas-rich (pumice) and gas-poor (obsidian) juvenile pyroclasts produced during the Plinian phase of the 1060 CE Glass Mountain eruption of Medicine Lake Volcano, California. In the proximal deposits, a multitude of pumice-rich sections separated by layers rich in dense clasts suggests a pulsatory behavior of the explosive phase. Density measurements on 2,600 pumices show that the intermediate, most voluminous deposits have a near constant median porosity of 65%. However, rapid increase in porosity to 75-80% is observed at both the bottom and the top of the fallout deposits, suggestive of rapid variations in magma degassing. In contrast, a water content of pyroclastic obsidians of approximately 0.6 wt% does remain constant throughout the eruption, suggesting that the pyroclastic obsidians degassed up to a constant pressure of a few megapascals. Numerical modeling of eruptive magma ascent and degassing is used to provide constraints on eruption conditions.

Intrusion of basaltic magma into a crystallizing granitic magma chamber: The Cordillera del Paine pluton in southern Chile

Science.gov (United States)

Michael, Peter J.

1991-10-01

The Cordillera del Paine pluton in the southernmost Andes of Chile represents a deeply dissected magma chamber where mafic magma intruded into crystallizing granitic magma. Throughout much of the 10x15 km pluton, there is a sharp and continuous boundary at a remarkably constant elevation of 1,100 m that separates granitic rocks (Cordillera del Paine or CP granite: 69 77% SiO2) which make up the upper levels of the pluton from mafic and comingled rocks (Paine Mafic Complex or PMC: 45 60% SiO2) which dominate the lower exposures of the pluton. Chilled, crenulate, disrupted contacts of mafic rock against granite demonstrate that partly crystallized granite was intruded by mafic magma which solidified prior to complete crystallization of the granitic magma. The boundary at 1,100 m was a large and stable density contrast between the denser, hotter mafic magma and cooler granitic magma. The granitic magma was more solidified near the margins of the chamber when mafic intrusion occurred, and the PMC is less disrupted by granites there. Near the pluton margins, the PMC grades upward irregularly from cumulate gabbros to monzodiorites. Mafic magma differentiated largely by fractional crystallization as indicated by the presence of cumulate rocks and by the low levels of compatible elements in most PMC rocks. The compositional gap between the PMC and CP granite indicates that mixing (blending) of granitic magma into the mafic magma was less important, although it is apparent from mineral assemblages in mafic rocks. Granitic magma may have incorporated small amounts of mafic liquid that had evolved to >60% SiO2 by crystallization. Mixing was inhibited by the extent of crystallization of the granite, and by the thermal contrast and the stable density contrast between the magmas. PMC gabbros display disequilibrium mineral assemblages including early formed zoned olivine (with orthopyroxene coronas), clinopyroxene, calcic plagioclase and paragasite and later-formed amphibole

Magma-poor vs. magma-rich continental rifting and breakup in the Labrador Sea

Science.gov (United States)

Gouiza, M.; Paton, D.

2017-12-01

Magma-poor and magma-rich rifted margins show distinct structural and stratigraphic geometries during the rift to breakup period. In magma-poor margins, crustal stretching is accommodated mainly by brittle faulting and the formation of wide rift basins shaped by numerous graben and half-graben structures. Continental breakup and oceanic crust accretion are often preceded by a localised phase of (hyper-) extension where the upper mantle is embrittled, serpentinized, and exhumed to the surface. In magma-rich margins, the rift basin is narrow and extension is accompanied by a large magmatic supply. Continental breakup and oceanic crust accretion is preceded by the emplacement of a thick volcanic crust juxtaposing and underplating a moderately thinned continental crust. Both magma-poor and magma-rich rifting occur in response to lithospheric extension but the driving forces and processes are believed to be different. In the former extension is assumed to be driven by plate boundary forces, while in the latter extension is supposed to be controlled by sublithospheric mantle dynamics. However, this view fails in explaining observations from many Atlantic conjugate margins where magma-poor and magma-rich segments alternate in a relatively abrupt fashion. This is the case of the Labrador margin where the northern segment shows major magmatic supply during most of the syn-rift phase which culminate in the emplacement of a thick volcanic crust in the transitional domain along with high density bodies underplating the thinned continental crust; while the southern segment is characterized mainly by brittle extension, mantle seprentinization and exhumation prior to continental breakup. In this work, we use seismic and potential field data to describe the crustal and structural architectures of the Labrador margin, and investigate the tectonic and mechanical processes of rifting that may have controlled the magmatic supply in the different segments of the margin.

Coupled interactions between volatile activity and Fe oxidation state during arc crustal processes

Science.gov (United States)

Humphreys, Madeleine C.S.; Brooker, R; Fraser, D.C.; Burgisser, A; Mangan, Margaret T.; McCammon, C

2015-01-01

Arc magmas erupted at the Earth’s surface are commonly more oxidized than those produced at mid-ocean ridges. Possible explanations for this high oxidation state are that the transfer of fluids during the subduction process results in direct oxidation of the sub-arc mantle wedge, or that oxidation is caused by the effect of later crustal processes, including protracted fractionation and degassing of volatile-rich magmas. This study sets out to investigate the effect of disequilibrium crustal processes that may involve coupled changes in H2O content and Fe oxidation state, by examining the degassing and hydration of sulphur-free rhyolites. We show that experimentally hydrated melts record strong increases in Fe3+/∑Fe with increasing H2O concentration as a result of changes in water activity. This is relevant for the passage of H2O-undersaturated melts from the deep crust towards shallow crustal storage regions, and raises the possibility that vertical variations in fO2 might develop within arc crust. Conversely, degassing experiments produce an increase in Fe3+/∑Fe with decreasing H2O concentration. In this case the oxidation is explained by loss of H2 as well as H2O into bubbles during decompression, consistent with thermodynamic modelling, and is relevant for magmas undergoing shallow degassing en route to the surface. We discuss these results in the context of the possible controls on fO2 during the generation, storage and ascent of magmas in arc settings, in particular considering the timescales of equilibration relative to observation as this affects the quality of the petrological record of magmatic fO2.

Noble Gas Isotope Evidence for Mantle Volatiles in the Cu-Mo Porphyry and Main Stage Polymetallic Veins at Butte, Montana

Science.gov (United States)

Hofstra, A. H.; Rusk, B. G.; Manning, A. H.; Hunt, A. G.; Landis, G. P.

2017-12-01

Recent studies suggest that volatiles released from mafic intrusions may be important sources of heat, sulfur, and metals in porphyry Cu-Mo-Au and epithermal Au-Ag deposits associated with intermediate to silicic stocks. The huge Cu-Mo porphyry and Main Stage polymetallic vein deposits at Butte are well suited to test this hypothesis because there is no geologic or isotopic evidence of basaltic intrusions in the mine or drill holes. The Butte porphyry-vein system is associated with quartz monzonite stocks and dikes within the southwest part of the Late Cretaceous Boulder batholith. The Boulder batholith was emplaced into Mesoproterozoic to Mesozoic sedimentary rocks and Late Cretaceous volcanic rocks. The Boulder batholith and Butte intrusions have Sri and eNd values indicative of crustal contamination. Eu and Ce anomalies in zircon from Butte intrusions provide evidence of oxidation due to magma degassing. To ascertain the source of volatiles in this system, 11 samples from the Cu-Mo porphyry and 16 from Main Stage veins were selected. The isotopic composition of Ar, Ne, and He extracted from fluid inclusions in quartz, magnetite, pyrite, chalcopyrite, sphalerite, galena, enargite, and covellite were determined. Helium isotopes exceed blank levels in all samples and Ne and Ar in some samples. On a 38Ar/36Ar vs. 40Ar/36Ar diagram, data plot near air. On a 20Ne/22Ne vs. 21Ne/22Ne diagram, data extend from air along the trajectories of OIB and MORB. On a 36Ar/4He vs. 3He/4He RA diagram, data extend from crust toward the air-mantle mixing line. The maximum 3He/4He RA values in the Cu-Mo porphyry (2.86) and Main Stage veins (3.46) are from pyrite and these values correspond to 36 and 43 % mantle helium. The Ne and He results show that fluid inclusions contain volatiles discharged from mantle magmas and that these volatiles were diluted by groundwater containing He derived from country rocks. Despite the lack of mafic intrusions in the Butte magmatic center, noble gas

Shallow magma diversions during explosive maar-diatreme eruptions in mafic volcanic fields

Science.gov (United States)

Le Corvec, N.; Muirhead, J.; White, J. D. L.

2017-12-01

Maar-diatremes are inverted conical structures formed by subterranean excavation and remobilization of country rocks during explosive volcanism and common in mafic volcanic fields. We focus on impacts of excavation and filling of maar-diatremes on the local state of stress, and its subsequent influence on underlying feeder dikes, which are critical for understanding the development of intrusive networks that feed surface eruptions. We address this issue using finite element models in COMSOL Multiphysics®. Inverted conical structures of varying sizes are excavated in a gravitationally loaded elastic half-space, and then progressively filled with volcaniclastic material, resulting in changes in the orientations and magnitudes of stresses generated within surrounding rocks and within the filling portion of the maar-diatreme. Our results show that rapid unloading during maar-diatreme excavation generates a horizontal compressive stress state beneath diatremes. These stresses allow magma to divert laterally as saucer-shaped sills and circumferential dikes at varying depths in the shallow feeder system, and produce intrusion geometries consistent with both field observations from exhumed volcanic fields and conceptual models of diatreme growth. Stresses generated in these models also provide an explanation for the evolving locations of fragmentation zones over the course of diatreme's filling. In particular, results from this study suggest that: (1) extensional stresses at the base of the diatreme fill favor magma ascent in the lower half of the structure, and possibly promote volatile exsolution and magma fragmentation; and (2) increased filling of diatremes creates a shallow compressive stress state that can inhibit magma ascent to the surface, promoting widespread intra-diatreme explosions, efficient mixing of host rock, and upward widening of the diatreme structure.

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, Judith

2016-01-01

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 surface.

Magma emplacement in 3D

Science.gov (United States)

Gorczyk, W.; Vogt, K.

2017-12-01

Magma intrusion is a major material transfer process in Earth's continental crust. Yet, the mechanical behavior of the intruding magma and its host are a matter of debate. In this study, we present a series of numerical thermo-mechanical experiments on mafic magma emplacement in 3D.In our model, we place the magmatic source region (40 km diameter) at the base of the mantle lithosphere and connect it to the crust by a 3 km wide channel, which may have evolved at early stages of magmatism during rapid ascent of hot magmatic fluids/melts. Our results demonstrate continental crustal response due to magma intrusion. We observe change in intrusion geometries between dikes, cone-sheets, sills, plutons, ponds, funnels, finger-shaped and stock-like intrusions as well as injection time. The rheology and temperature of the host-rock are the main controlling factors in the transition between these different modes of intrusion. Viscous deformation in the warm and deep crust favours host rock displacement and magma pools along the crust-mantle boundary forming deep-seated plutons or magma ponds in the lower to middle-crust. Brittle deformation in the cool and shallow crust induces cone-shaped fractures in the host rock and enables emplacement of finger- or stock-like intrusions at shallow or intermediate depth. A combination of viscous and brittle deformation forms funnel-shaped intrusions in the middle-crust. Low-density source magma results in T-shaped intrusions in cross-section with magma sheets at the surface.

Fault-Magma Interactions during Early Continental Rifting: Seismicity of the Magadi-Natron-Manyara basins, Africa

Science.gov (United States)

Weinstein, A.; Oliva, S. J.; Ebinger, C.; Aman, M.; Lambert, C.; Roecker, S. W.; Tiberi, C.; Muirhead, J.

2017-12-01

Although magmatism may occur during the earliest stages of continental rifting, its role in strain accommodation remains weakly constrained by largely 2D studies. We analyze seismicity data from a 13-month, 39-station broadband seismic array to determine the role of magma intrusion on state-of-stress and strain localization, and their along-strike variations. Precise earthquake locations using cluster analyses and a new 3D velocity model reveal lower crustal earthquakes along projections of steep border faults that degas CO2. Seismicity forms several disks interpreted as sills at 6-10 km below a monogenetic cone field. The sills overlie a lower crustal magma chamber that may feed eruptions at Oldoinyo Lengai volcano. After determining a new ML scaling relation, we determine a b-value of 0.87 ± 0.03. Focal mechanisms for 66 earthquakes, and a longer time period of relocated earthquakes from global arrays reveal an along-axis stress rotation of 50 o ( N150 oE) in the magmatically active zone. Using Kostrov summation of local and teleseismic mechanisms, we find opening directions of N122ºE and N92ºE north and south of the magmatically active zone. The stress rotation facilitates strain transfer from border fault systems, the locus of early stage deformation, to the zone of magma intrusion in the central rift. Our seismic, structural, and geochemistry results indicate that frequent lower crustal earthquakes are promoted by elevated pore pressures from volatile degassing along border faults, and hydraulic fracture around the margins of magma bodies. Earthquakes are largely driven by stress state around inflating magma bodies, and more dike intrusions with surface faulting, eruptions, and earthquakes are expected.

Disclosing Multiple Magma Degassing Sources Offers Unique Insights of What's Behind the Campi Flegrei Caldera Unrest

Science.gov (United States)

Moretti, R.; Civetta, L.; Orsi, G.; Arienzo, I.; D'Antonio, M.; Di Renzo, V.

2013-12-01

The definition of the structure and evolution of the magmatic system of Campi Flegrei caldera (CFc), Southern Italy, has been a fundamental tool for the assessment of the short-term volcanic hazard. The ensemble of geophysical and petrologic data show that the CFc magmatic system has been -and still is- characterized by two major reservoirs at different depths. From the deep one (around 8 km), less evolved magmas crystallize and degas, supplying fluids and magmas to the shallow (3-4 km) reservoirs. A thorough reconstruction of processes occurring in magma chamber/s prior and/or during the CFc eruptions has shown that magmas entering shallow reservoirs mixed with resident and crystallized batches. Also the 1982-85 unrest episode has been related to a magma intrusion of 2.1 x 10^7 m^3 at 3-4 km depth, on the basis of geophysical data (ground deformation, gravimetry, seismic imaging) and their interpretation. Thermodynamic evaluation of magma properties, at the time of emplacement, suggests for such an intrusion a bulk density of 2.000 kg/m^3 . Such a value testifies the high amount of exsolved volatiles within the system. The available record of geochemical and isotopic data on surface fumaroles, coupled with melt inclusion data, has already shown that dual (deep and shallow) magma degassing from such two reservoirs, as well as their interaction with the hydrothermal system, allows explaining the relevant fluctuations observed at crater fumaroles after the 1982-85 magma intrusion. An important role was played by the rapid crystallization (around 30 years) of the shallow magma, such that in the recent years gas discharges should be fuelled mostly by the deep magma. Such a process is well recorded in the fumarolic gas composition of the last ~10 years, but has to be reconciled with the unrest dynamics which took place after year 2000, characterized by a slow but continuous ground uplift. All geochemical indicators (major species and noble gases) point to three possible

Isotopic disequilibrium among commingled hybrid magmas: Evidence for a two-stage magma mixing-commingling process in the Mt. Perkins Pluton, Arizona

International Nuclear Information System (INIS)

Metcalf, R.V.; Smith, E.I.; Reed, R.C.

1995-01-01

The syn-extensional Miocene Mt. Perkins pluton, northwestern Arizona, cooled rapidly due to its small size (6 km 2 ) and shallow emplacement (7.5 km) and allows examination of commingled rocks that experienced little isotopic exchange. Within the pluton, quartz dioritic to granodioritic host rocks (58-68 wt% SiO 2 ) enclose dioritic enclaves (50-55 wt% SiO 2 ) and a portion contains enclave-free granodiorite (70-74 wt% SiO 2 ). Fine-grained, crenulate enclave margins and a lack of advanced mixing structures (e.g., schlieren, flow fabrics, etc.) indicate an incipient stage of commingling. Isotopic variation between enclaves and enclosing host rocks is large (6.8 to 10.6 ε Nd units; 0.0036 to 0.0046 87 Sr/ 86 Sr units), suggesting isotopic disequilibrium. Comparison of an enclave core and rim suggests that isotopic exchange with the host magma was limited to the enclave rim. Enclaves and hosts collectively form a calc-alkaline suite exhibiting a large range of ε Nd (+1.2 to -12.5) and initial 87 Sr/ 86 Sr (0.705 to 0.71267) with a correlation among ε Nd , initial 87 Sr/ 86 Sr, and major and trace element compositions. Modeling suggests that the suite formed by magma hybridization involving magma mixing accompanied by fractional crystallization. The magma mixing must have predated commingling at the present exposure level and indicates a larger mixing chamber at depth. Isotopic and trace element data suggests mixing end-members were asthenospheric mantle-derived mafic and crustal-derived felsic magmas. Fractional crystallization facilitated mixing by reducing the rheological contrasts between the mafic and felsic mixing end-members. 58 refs., 11 figs., 3 tabs

Magma evolution inside the 1631 Vesuvius magma chamber and eruption triggering

Directory of Open Access Journals (Sweden)

Stoppa Francesco

2017-03-01

Full Text Available 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.

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.

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.

Why Is There an Abrupt Transition from Solid Rock to Low Crystallinity Magma in Drilled Magma Bodies?

Science.gov (United States)

Eichelberger, J. C.; Carrigan, C. R.; Sun, Y.; Lavallée, Y.

2017-12-01

We report on a preliminary evaluation, from basic principles of heat and mass transfer, on the unexpectedly abrupt transition from cuttings of solid rock to fragments of crystal poor glass during drilling into magma bodies. Our analysis is based on conditions determined and inferred for the 2009 IDDP-1 well in Krafla Caldera, which entered apparently liquidus rhyolite magma at about 900oC at a depth of 2104 m. Simple conduction would predict some 30 m of crystallization and partial crystallization since the latest time the magma could have been intruded, approximately 30 years prior to discovery by drilling. Option 1: The expected crystallization of magma has occurred but interstitial melt remains. The pressure difference between lithostatic load of about 50 MPa on the mush and 20 MPa hydrostatic pressure in the well causes pore melt to flow from the permeable mush into the borehole, where it becomes the source of the quenched melt chips. To be viable, this mechanism must work over the time frame of a day. Option 2: The expected crystallization is occurring, but high Rayleigh number thermal convection in the magma chamber continuously displaces crystallizing roof magma by liquidus magma from the interior of the body. To be viable, this mechanism must result in overturning magma in the chamber on a time scale that is much shorter than that of crystallization. Option 3: Flow-induced crystal migration away from zones of high shear created during drilling into magma may preferentially produce low-crystal-content melt at the boundary of the borehole, which is then sampled.

Experimental simulation of magma-carbonate interaction beneath Mt. Vesuvius, Italy

Science.gov (United States)

Jolis, E. M.; Freda, C.; Troll, V. R.; Deegan, F. M.; Blythe, L. S.; McLeod, C. L.; Davidson, J. P.

2013-11-01

We simulated the process of magma-carbonate interaction beneath Mt. Vesuvius in short duration piston-cylinder experiments under controlled magmatic conditions (from 0 to 300 s at 0.5 GPa and 1,200 °C), using a Vesuvius shoshonite composition and upper crustal limestone and dolostone as starting materials. Backscattered electron images and chemical analysis (major and trace elements and Sr isotopes) of sequential experimental products allow us to identify the textural and chemical evolution of carbonated products during the assimilation process. We demonstrate that melt-carbonate interaction can be extremely fast (minutes), and results in dynamic contamination of the host melt with respect to Ca, Mg and 87Sr/86Sr, coupled with intense CO2 vesiculation at the melt-carbonate interface. Binary mixing between carbonate and uncontaminated melt cannot explain the geochemical variations of the experimental charges in full and convection and diffusion likely also operated in the charges. Physical mixing and mingling driven by exsolving volatiles seems to be a key process to promote melt homogenisation. Our results reinforce hypotheses that magma-carbonate interaction is a relevant and ongoing process at Mt. Vesuvius and one that may operate not only on a geological, but on a human timescale.

Magma flow through elastic-walled dikes

NARCIS (Netherlands)

Bokhove, Onno; Woods, A.W.; de Boer, A

2005-01-01

A convection–diffusion model for the averaged flow of a viscous, incompressible magma through an elastic medium is considered. The magma flows through a dike from a magma reservoir to the Earth’s surface; only changes in dike width and velocity over large vertical length scales relative to the

Fault-magma interactions during early continental rifting: Seismicity of the Magadi-Natron-Manyara basins, Africa

Science.gov (United States)

Weinstein, A.; Oliva, S. J.; Ebinger, C. J.; Roecker, S.; Tiberi, C.; Aman, M.; Lambert, C.; Witkin, E.; Albaric, J.; Gautier, S.; Peyrat, S.; Muirhead, J. D.; Muzuka, A. N. N.; Mulibo, G.; Kianji, G.; Ferdinand-Wambura, R.; Msabi, M.; Rodzianko, A.; Hadfield, R.; Illsley-Kemp, F.; Fischer, T. P.

2017-10-01

Although magmatism may occur during the earliest stages of continental rifting, its role in strain accommodation remains weakly constrained by largely 2-D studies. We analyze seismicity data from a 13 month, 39-station broadband seismic array to determine the role of magma intrusion on state-of-stress and strain localization, and their along-strike variations. Precise earthquake locations using cluster analyses and a new 3-D velocity model reveal lower crustal earthquakes beneath the central basins and along projections of steep border faults that degas CO2. Seismicity forms several disks interpreted as sills at 6-10 km below a monogenetic cone field. The sills overlie a lower crustal magma chamber that may feed eruptions at Oldoinyo Lengai volcano. After determining a new ML scaling relation, we determine a b-value of 0.87 ± 0.03. Focal mechanisms for 65 earthquakes, and 13 from a catalogue prior to our array reveal an along-axis stress rotation of ˜60° in the magmatically active zone. New and prior mechanisms show predominantly normal slip along steep nodal planes, with extension directions ˜N90°E north and south of an active volcanic chain consistent with geodetic data, and ˜N150°E in the volcanic chain. The stress rotation facilitates strain transfer from border fault systems, the locus of early-stage deformation, to the zone of magma intrusion in the central rift. Our seismic, structural, and geochemistry results indicate that frequent lower crustal earthquakes are promoted by elevated pore pressures from volatile degassing along border faults, and hydraulic fracture around the margins of magma bodies. Results indicate that earthquakes are largely driven by stress state around inflating magma bodies.

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.

A temporal record of pre-eruptive magmatic volatile contents at Campi Flegrei: Insights from texturally-constrained apatite analyses

Science.gov (United States)

Stock, Michael J.; Isaia, Roberto; Humphreys, Madeleine C. S.; Smith, Victoria C.; Pyle, David M.

2016-04-01

Apatite is capable of incorporating all major magmatic volatile species (H2O, CO2, S, Cl and F) into its crystal structure. Analysis of apatite volatile contents can be related to parental magma compositions through the application of pressure and temperature-dependent exchange reactions (Piccoli and Candela, 1994). Once included within phenocrysts, apatite inclusions are isolated from the melt and preserve a temporal record of magmatic volatile contents in the build-up to eruption. In this work, we measured the volatile compositions of apatite inclusions, apatite microphenocrysts and pyroxene-hosted melt inclusions from the Astroni 1 eruption of Campi Flegrei, Italy (Stock et al. 2016). These data are coupled with magmatic differentiation models (Gualda et al., 2012), experimental volatile solubility data (Webster et al., 2014) and thermodynamic models of apatite compositional variations (Piccoli and Candela, 1994) to decipher pre-eruptive magmatic processes. We find that apatite halogen/OH ratios decreased through magmatic differentiation, while melt inclusion F and Cl concentrations increased. Melt inclusion H2O contents are constant at ~2.5 wt%. These data are best explained by volatile-undersaturated differentiation over most of the crystallisation history of the Astroni 1 melt, with melt inclusion H2O contents reset at shallow levels during ascent. Given the high diffusivity of volatiles in apatite (Brenan, 1993), the preservation of volatile-undersaturated melt compositions in microphenocrysts suggests that saturation was only achieved 10 - 103 days before eruption. We suggest that late-stage transition into a volatile-saturated state caused an increase in magma chamber overpressure, which ultimately triggered the Astroni 1 eruption. This has major implications for monitoring of Campi Flegrei and other similar volcanic systems. Piccoli and Candela, 1994. Am. J. of Sc., 294, 92-135. Stock et al., 2016, Nat. Geosci. Gualda et al., 2012. J. Pet., 53, 875

Volatile-rich komatiitic and picritic melt inclusions in Cr-spinel beach sand from Gorgona Island, Colombia

Science.gov (United States)

Shimizu, K.; Shimizu, N.; Suzuki, K.; Tatsumi, Y.; Komiya, T.; Maruyama, S.

2007-12-01

Volatile content of komatiite is a key to constrain thermal evolution of the deep Earth. We report volatile contents with major and trace element compositions of melt inclusions (MIs) in chromian spinel (Cr-spinel) from beach sands of Gorgona Island, Colombia. Gorgona Island is ~90 Ma volcanic island, where picrites and the world-youngest komatiites occur. As Cr-spinel is dense and rigid oxide mineral that crystallizes only at early stages of crystallization, it is considered to be a superior container for retaining primitive melt, even including volatiles. Volatile (H2O, CO2, S, F and Cl) and trace element (K2O, Sr, Y, Zr, Nb, Ba, La, Ce, Sm, Dy, Yb) compositions of ~80 MIs were analyzed by SIMS (Cameca-1280 and 3f, respectively) at WHOI. MIs in the Cr-spinel from Gorgona Is. are classified into three types by their host Cr-spinel compositions such as low-Ti (P-type), high-Ti with high-Cr# (BK-type) and high-Ti with low-Cr# (K-type). MIs of P-type, BK-type and K-type are mostly in compositional ranges of picrite, high TiO2 komatiite (some basalt) and low TiO2 komatiite in Gorgona Island, respectively. Water content of P-type MIs is variable, ranging from 0.05 to 0.9 wt%, whereas those of BK and K-type MIs are limited (500 ppm) do not contain (shrinkage) bubbles and many of them are low in K2O. H2O/K2O, CO2/K2O, S/K2O and F/K2O ratios are positively correlated with Y/Sr ratios, indicating degassing trends of melt at crystallization, magma mixing and/or assimilation. Undegassed H2O/K2O, CO2/K2O, S/K2O and F/K2O ratios of komatiitic (picritic) melt are estimated to be ~10 (~40), ~80 (n.d.), ~7(~3) and ~1(~0.5), respectively, which are much higher than those estimated for the depleted source mantle of the MORB [1.6, 0.7, 1.6 and 0.2, respectively; Salters, V. & Stracke, A. (2004), Composition of the depleted mantle. Geochem. Geophys. Geosys. 5 (2003GC000597)]. The results suggest that Gorgona komatiite and picrite magmas were derived from volatile-rich sources. CO2

Ilchulbong tuff cone, Jeju Island, Korea, revisited: A compound monogenetic volcano involving multiple magma batches, shifting vents, and discrete eruptive phases

Science.gov (United States)

Sohn, Y.; Brenna, M.; Smith, I. E.; Nemeth, K.; White, J. D.; Murtagh, R.; Jeon, Y.; Kwon, C.; Cronin, S. J.

2010-12-01

Ilchulbong (Sunrise Peak) tuff cone is a UNESCO World Heritage site that owes its scientific importance to the outstanding coastal exposures that surround it. It is also one of the classic sites that provided the sedimentary evidence for the primary pyroclastic processes that occur during phreatomagmatic basaltic eruptions. It has been long considered, based on the cone morphology, that this classic cone was produced via eruption from a single vent site. Reanalysis of the detailed sedimentary sequence has now revealed that two subtle paraconformities occur in this deposition sequence, one representing a significant time break of perhaps days to weeks or months, during which erosion and compaction of the lower cone occurred, the conduit cooled and solidified and a subsequent resumption of eruption took place in a new vent location. Detailed geochemical study of the juvenile clasts through this cone reveals that three separate alkali basaltic magma batches were erupted, the first and third erupted may be genetically related, with the latter showing evidence for longer periods of shallow-level fractionation. The second magma batch erupted was generated in a different mantle source area. Reconstructing the eruption sequence, the lower Ilchulbong cone was formed by eruption of magma 1. Cessation of eruption was accompanied by erosion to generate a volcano-wide unconformity, associated with reworked deposits in the lower cone flanks. The eruption resumed with magma 2 that, due to the cooled earlier conduit, was forced to erupt in a new site to the west of the initial vent. This formed the middle cone sequence over the initially formed structure. The third magma batch erupted with little or no interval after magma 2 from the same vent location, associated with cone instability and slumping, and making up the deposits of the upper cone. These results demonstrate how critical the examination for sedimentary evidence for time breaks in such eruption sequences is for

Time-resolved seismic tomography detects magma intrusions at Mount Etna.

Science.gov (United States)

Patanè, D; Barberi, G; Cocina, O; De Gori, P; Chiarabba, C

2006-08-11

The continuous volcanic and seismic activity at Mount Etna makes this volcano an important laboratory for seismological and geophysical studies. We used repeated three-dimensional tomography to detect variations in elastic parameters during different volcanic cycles, before and during the October 2002-January 2003 flank eruption. Well-defined anomalous low P- to S-wave velocity ratio volumes were revealed. Absent during the pre-eruptive period, the anomalies trace the intrusion of volatile-rich (>/=4 weight percent) basaltic magma, most of which rose up only a few months before the onset of eruption. The observed time changes of velocity anomalies suggest that four-dimensional tomography provides a basis for more efficient volcano monitoring and short- and midterm eruption forecasting of explosive activity.

One hundred volatile years of volcanic gas studies at the Hawaiian Volcano Observatory: Chapter 7 in Characteristics of Hawaiian volcanoes

Science.gov (United States)

Sutton, A.J.; Elias, Tamar; Poland, Michael P.; Takahashi, T. Jane; Landowski, Claire M.

2014-01-01

The first volcanic gas studies in Hawai‘i, beginning in 1912, established that volatile emissions from Kīlauea Volcano contained mostly water vapor, in addition to carbon dioxide and sulfur dioxide. This straightforward discovery overturned a popular volatile theory of the day and, in the same action, helped affirm Thomas A. Jaggar, Jr.’s, vision of the Hawaiian Volcano Observatory (HVO) as a preeminent place to study volcanic processes. Decades later, the environmental movement produced a watershed of quantitative analytical tools that, after being tested at Kīlauea, became part of the regular monitoring effort at HVO. The resulting volatile emission and fumarole chemistry datasets are some of the most extensive on the planet. These data indicate that magma from the mantle enters the shallow magmatic system of Kīlauea sufficiently oversaturated in CO2 to produce turbulent flow. Passive degassing at Kīlauea’s summit that occurred from 1983 through 2007 yielded CO2-depleted, but SO2- and H2O-rich, rift eruptive gases. Beginning with the 2008 summit eruption, magma reaching the East Rift Zone eruption site became depleted of much of its volatile content at the summit eruptive vent before transport to Pu‘u ‘Ō‘ō. The volatile emissions of Hawaiian volcanoes are halogen-poor, relative to those of other basaltic systems. Information gained regarding intrinsic gas solubilities at Kīlauea and Mauna Loa, as well as the pressure-controlled nature of gas release, have provided useful tools for tracking eruptive activity. Regular CO2-emission-rate measurements at Kīlauea’s summit, together with surface-deformation and other data, detected an increase in deep magma supply more than a year before a corresponding surge in effusive activity. Correspondingly, HVO routinely uses SO2 emissions to study shallow eruptive processes and effusion rates. HVO gas studies and Kīlauea’s long-running East Rift Zone eruption also demonstrate that volatile emissions can

Eruption and Degassing Processes in a Supervolcanic System: The Volatile Record Preserved in Melt Inclusions from the 3.49Ma Tara Ignimbrite in the Central Andes

Science.gov (United States)

Grocke, S.; de Silva, S. L.; Schmitt, A. K.; Wallace, P. J.

2010-12-01

Analysis of H2O and CO2 in quartz and sanidine-hosted melt inclusions from one of the youngest supervolcanic eruptions in the Altiplano Puna Volcanic Complex (APVC) in the Central Andes provides information on crystallization depths and eruption and degassing processes. At least 740 km3 of high-K, metaluminous, rhyodacite to rhyolite magma erupted from the Guacha Caldera in southwest Bolivia, producing three phases of the 3.49 Ma Tara Ignimbrite: a Plinian fall-deposit, an extensive ignimbrite, and several post-caldera domes. Infrared spectroscopic analyses of quartz-hosted melt inclusions from Tara Plinian pumice have H2O contents of ~4.5 wt % and variable CO2 contents (110-300 ppm), corresponding to vapor saturation pressures up to 180 MPa. In contrast, sanidine-hosted melt inclusions from the Plinian-fall deposit contain bubbles, lower water contents (1.4-2.2 wt %) and lower CO2 (87-143 ppm). These vesiculated melt inclusions and low volatile contents suggest that the sanidine crystals leaked on their ascent to the surface and therefore do not record accurate pre-eruptive melt volatile contents. In contrast, quartz-hosted melt inclusions from post-caldera dome samples contain lower H2O contents of 2.5-3.5 wt % (average 2.9 wt %) and no detectable CO2, corresponding to vapor saturation pressures of 50-90 MPa. These data indicate that the preeruptive plinian stage Tara magma was vapor saturated at the time of melt inclusion entrapment and stored between 5-6 km, while those from the post-caldera domes were trapped at 2-3 km. Differences in CO2 between Plinian and dome melt inclusions require that the post-caldera dome quartzes represent a different generation of crystals that grew as the magma slowly rose and progressively degassed at 2-3 km. During this shallow crystallization, the magma evolved further and eventually fed the post-caldera domes, one of which is a high-Si rhyolite. Consistent with this interpretation, melt inclusions from post-caldera dome samples

Evidence for degassing of fresh magma during the 2004-2008 eruption of Mount St. Helens: Subtle signals from the hydrothermal system

Science.gov (United States)

Bergfeld, Deborah; Evans, William C.; Spicer, Kurt R.; Hunt, Andrew G.; Kelly, Peter

2017-01-01

Results from chemical and isotopic analyses of water and gas collected between 2002 and 2016 from sites on and around Mount St. Helens are used to assess magmatic degassing related to the 2004-2008 eruption. During 2005 the chemistry of hot springs in The Breach of Mount St. Helens showed no obvious response to the eruption, and over the next few years, changes were subtle, giving only slight indications of perturbations in the system. By 2010 however, water chemistry, temperatures, and isotope compositions (δD and δ18O) clearly indicated some inputs of volatiles and heat associated with the eruption, but the changes were such that they could be attributed to a pre-existing, gas depleted magma. An increase of ~ 1.5‰ in the δ13C values of dissolved carbon in the springs was noted in 2006 and continued through 2009, a change that was mirrored by a similar shift in δ13C-CO2 in bubble gas emissions. These changes require input of a new source of carbon to the hydrothermal system and provide clear evidence of CO2 from an undegassed body of magma. Rising trends in 3He/4He ratios in gas also accompanied the increases in δ13C. Since 2011 maximum RC/RA values are ≥ 6.4 and are distinctly higher than 5 samples collected between 1986 and 2002, and provide additional evidence for some involvement of new magma as early as 2006, and possibly earlier, given the unknown time needed for CO2 and He to traverse the system and arrive at the springs.

Constraining the volatile budget of the lunar interior

Science.gov (United States)

Potts, N. J.; Bromiley, G. D.

2017-12-01

Measurements of volatiles (F, Cl, S, H2O) in a range of lunar samples confirm the presence of volatile material in lunar magmas. It remains unknown, however, where this volatile material is stored and when it was delivered to the Moon. On Earth, point defects within mantle olivine, and its high-pressure polymorphs, are thought to be the largest reservoir of volatile material. However, as volatiles have been cycled into and out of the Earth's mantle throughout geological time, via subduction and volcanism, this masks any original volatile signatures. As the Moon has no plate tectonics, it is expected that any volatile material present in the deep lunar interior would have been inherited during accretion and differentiation, providing insight into the delivery of volatiles to the early Earth-Moon system. Our aim was, therefore, to test the volatile storage capacity of the deep lunar mantle and determine mineral/melt partitioning for key volatiles. Experiments were performed in a primitive lunar mantle composition and run at relevant T, P, and at fO2 below the IW buffer. Experiments replicated the initial stages of LMO solidification with either olivine + melt, olivine + pyroxene + melt, or pyroxene + melt as the only phases present. Mineral-melt partition coefficients (Dx) derived for volatile material (F, Cl, S, H2O) vary significantly compared to those derived for terrestrial conditions. An order of magnitude more H2O was found to partition into lunar olivine compared to the terrestrial upper mantle. DF derived for lunar olivine are comparable to the highest terrestrial derived values whilst no Cl was found to partition into lunar olivine under these conditions. Furthermore, an inverse trend between DF and DOH hints towards coupled-substitution mechanisms between H and F under low-fO2/lunar bulk composition. These results suggest that if volatile material was present in the LMO a significant proportion could be partitioned into the lower lunar mantle. The

Subsurface Connections and Magma Mixing as revealed by Olivine- and Pyroxene-Hosted Melt Inclusions from Cerro Negro Volcano and the Las Pilas-El Hoyo Complex, Nicaragua.

Science.gov (United States)

Venugopal, S.; Moune, S.; Williams-Jones, G.

2015-12-01

Cerro Negro, the youngest volcano in the Central American Volcanic Belt, is a polygenetic cinder cone with relatively frequent explosive basaltic eruptions. Las Pilas, on the other hand, is a much larger and older complex with milder and less frequent eruptions. Based on historical data, these two closely spaced volcanoes have shown concurrent eruptive behavior, suggesting a subsurface connection. To further investigate this link, melt inclusions, which are blebs of melt trapped in growing crystals, were the obvious choice for optimal comparison of sources and determination of pre-eruptive volatile contents and magmatic conditions. Olivine-hosted inclusions were chosen for both volcanoes and pyroxene-hosted inclusions were also sampled from Las Pilas to represent the evolved melt. Major, volatile and trace elements reveal a distinct geochemical continuum with Cerro Negro defining the primitive end member and Las Pilas representing the evolved end member. Volatile contents are high for Cerro Negro (up to 1260 ppm CO2, 4.27 wt% H2O and 1700 ppm S) suggesting that volatile exsolution is likely the trigger for Cerro Negro's explosive eruptions. Las Pilas volatile contents are lower but consistent with degassing and evolutionary trends shown by major oxides. Trace element contents are rather unique and suggest Cerro Negro magmas fractionally crystallize while Las Pilas magmas are the products of mixing. Magmatic conditions were estimated with major and volatile contents: at least 2.4 kbar and 1170 °C for Cerro Negro melts and 1.3 kbar and 1130 °C for Las Pilas melts with an overall oxygen fugacity at the NNO buffer. In combination with available literature data, this study suggests an interconnected subsurface plumbing system and thus Cerro Negro should be considered as the newest vent within the Las Pilas-El Hoyo Complex.

Artificial magma and applications of the blasting technique

Energy Technology Data Exchange (ETDEWEB)

Ichioka, K [Chugoku Kaki KK, Japan

1974-01-01

Artifical magma is discussed. Solid magma is a high temperature source and fluid magma is also a heat carrier. Iron ores are examples of solid magma, silica-borate is an example of a hydrophobic heat carrier magma assuming a liquid phase at 600/sup 0/C, and S, Ag, Pb, etc. are also examples of heat carrier magma. In addition to these examples, basic salts such as NaNO/sub 3/, KNO/sub 3/, NaCl, CaCl, KCl, BaCl, and Na/sub 4/B/sub 4/O/sub 7/ can be used as artifical magma. These are artifical magmas or heat mediums capable of capturing geothermal heat when circulated inside volcanoes. The blasting technique's applications in geothermal wells are also discussed. The technique can be used to expand a well's diameter, repair the well bottom, regenerate old wells, clean wells, or cut steel pipe. Two figures and one table are provided.

Examining shear processes during magma ascent

Science.gov (United States)

Kendrick, J. E.; Wallace, P. A.; Coats, R.; Lamur, A.; Lavallée, Y.

2017-12-01

Lava dome eruptions are prone to rapid shifts from effusive to explosive behaviour which reflects the rheology of magma. Magma rheology is governed by composition, porosity and crystal content, which during ascent evolves to yield a rock-like, viscous suspension in the upper conduit. Geophysical monitoring, laboratory experiments and detailed field studies offer the opportunity to explore the complexities associated with the ascent and eruption of such magmas, which rest at a pivotal position with regard to the glass transition, allowing them to either flow or fracture. Crystal interaction during flow results in strain-partitioning and shear-thinning behaviour of the suspension. In a conduit, such characteristics favour the formation of localised shear zones as strain is concentrated along conduit margins, where magma can rupture and heal in repetitive cycles. Sheared magmas often record a history of deformation in the form of: grain size reduction; anisotropic permeable fluid pathways; mineral reactions; injection features; recrystallisation; and magnetic anomalies, providing a signature of the repetitive earthquakes often observed during lava dome eruptions. The repetitive fracture of magma at ( fixed) depth in the conduit and the fault-like products exhumed at spine surfaces indicate that the last hundreds of meters of ascent may be controlled by frictional slip. Experiments on a low-to-high velocity rotary shear apparatus indicate that shear stress on a slip plane is highly velocity dependent, and here we examine how this influences magma ascent and its characteristic geophysical signals.

Zircon crytallization and recycling in the magma chamber of the rhyolitic Kos Plateau Tuff (Aegean arc)

Science.gov (United States)

Bachman, O.; Charlier, B.L.A.; Lowenstern, J. B.

2007-01-01

In contrast to most large-volume silicic magmas in continental arcs, which are thought to evolve as open systems with significant assimilation of preexisting crust, the Kos Plateau Miff magma formed dominantly by crystal fractionation of mafic parents. Deposits from this ??? 60 km3 pyroclastic eruption (the largest known in the Aegean arc) lack xenocrystic zircons [secondary ion mass spectrometry (SIMS) U-Pb ages on zircon cores never older than 500 ka] and display Sr-Nd whole-rock isotopic ratios within the range of European mantle in an area with exposed Paleozoic and Tertiary continental crust; this evidence implies a nearly closed-system chemical differentiation. Consequently, the age range provided by zircon SIMS U-Th-Pb dating is a reliable indicator of the duration of assembly and longevity of the silicic magma body above its solidus. The age distribution from 160 ka (age of eruption by sanidine 40Ar/39Ar dating; Smith et al., 1996) to ca. 500 ka combined with textural characteristics (high crystal content, corrosion of most anhydrous phenocrysts, but stability of hydrous phases) suggest (1) a protracted residence in the crust as a crystal mush and (2) rejuvenation (reduced crystallization and even partial resorption of minerals) prior to eruption probably induced by new influx of heat (and volatiles). This extended evolution chemically isolated from the surrounding crust is a likely consequence of the regional geodynamics because the thinned Aegean microplate acts as a refractory container for magmas in the dying Aegean subduction zone (continent-continent subduction). ?? 2007 Geological Society of America.

Zircon crystallization and recycling in the magma chamber of the rhyolitic Kos Plateau Tuff (Aegean arc)

Science.gov (United States)

Bachman, O.; Charlier, B.L.A.; Lowenstern, J. B.

2007-01-01

In contrast to most large-volume silicic magmas in continental arcs, which are thought to evolve as open systems with significant assimilation of preexisting crust, the Kos Plateau Tuff magma formed dominantly by crystal fractionation of mafic parents. Deposits from this ~60 km3 pyroclastic eruption (the largest known in the Aegean arc) lack xenocrystic zircons [secondary ion mass spectrometry (SIMS) U-Pb ages on zircon cores never older than 500 ka] and display Sr-Nd whole-rock isotopic ratios within the range of European mantle in an area with exposed Paleozoic and Tertiary continental crust; this evidence implies a nearly closed-system chemical differentiation. Consequently, the age range provided by zircon SIMS U-Th-Pb dating is a reliable indicator of the duration of assembly and longevity of the silicic magma body above its solidus. The age distribution from 160 ka (age of eruption by sanidine 40Ar/39Ar dating; Smith et al., 1996) to ca. 500 ka combined with textural characteristics (high crystal content, corrosion of most anhydrous phenocrysts, but stability of hydrous phases) suggest (1) a protracted residence in the crust as a crystal mush and (2) rejuvenation (reduced crystallization and even partial resorption of minerals) prior to eruption probably induced by new influx of heat (and volatiles). This extended evolution chemically isolated from the surrounding crust is a likely consequence of the regional geodynamics because the thinned Aegean microplate acts as a refractory container for magmas in the dying Aegean subduction zone (continent-continent subduction).

Evolution of silicic magmas in the Kos-Nisyros volcanic center, Greece: a petrological cycle associated with caldera collapse

Science.gov (United States)

Bachmann, Olivier; Deering, Chad D.; Ruprecht, Janina S.; Huber, Christian; Skopelitis, Alexandra; Schnyder, Cedric

2012-01-01

Multiple eruptions of silicic magma (dacite and rhyolites) occurred over the last ~3 My in the Kos-Nisyros volcanic center (eastern Aegean sea). During this period, magmas have changed from hornblende-biotite-rich units with low eruption temperatures (≤750-800°C; Kefalos and Kos dacites and rhyolites) to hotter, pyroxene-bearing units (>800-850°C; Nisyros rhyodacites) and are transitioning back to cooler magmas (Yali rhyolites). New whole-rock compositions, mineral chemistry, and zircon Hf isotopes show that these three types of silicic magmas followed the same differentiation trend: they all evolved by crystal fractionation and minor crustal assimilation (AFC) from parents with intermediate compositions characterized by high Sr/Y and low Nb content, following a wet, high oxygen fugacity liquid line of descent typical of subduction zones. As the transition between the Kos-Kefalos and Nisyros-type magmas occurred immediately and abruptly after the major caldera collapse in the area (the 161 ka Kos Plateau Tuff; KPT), we suggest that the efficient emptying of the magma chamber during the KPT drew out most of the eruptible, volatile-charged magma and partly solidified the unerupted mush zone in the upper crust due to rapid unloading, decompression, and coincident crystallization. Subsequently, the system reestablished a shallow silicic production zone from more mafic parents, recharged from the mid to lower crust. The first silicic eruptions evolving from these parents after the caldera collapse (Nisyros units) were hotter (up to >100°C) than the caldera-forming event and erupted from reservoirs characterized by different mineral proportions (more plagioclase and less amphibole). We interpret such a change as a reflection of slightly drier conditions in the magmatic column after the caldera collapse due to the decompression event. With time, the upper crustal intermediate mush progressively transitioned into the cold-wet state that prevailed during the Kefalos

Finite-element modeling of magma chamber-host rock interactions prior to caldera collapse

Science.gov (United States)

Kabele, Petr; Žák, Jiří; Somr, Michael

2017-06-01

Gravity-driven failure of shallow magma chamber roofs and formation of collapse calderas are commonly accompanied by ejection of large volumes of pyroclastic material to the Earth's atmosphere and thus represent severe volcanic hazards. In this respect, numerical analysis has proven as a key tool in understanding the mechanical conditions of caldera collapse. The main objective of this paper is to find a suitable approach to finite-element simulation of roof fracturing and caldera collapse during inflation and subsequent deflation of shallow magma chambers. Such a model should capture the dominant mechanical phenomena, for example, interaction of the host rock with magma and progressive deformation of the chamber roof. To this end, a comparative study, which involves various representations of magma (inviscid fluid, nearly incompressible elastic, or plastic solid) and constitutive models of the host rock (fracture and plasticity), was carried out. In particular, the quasi-brittle fracture model of host rock reproduced well the formation of tension-induced radial and circumferential fractures during magma injection into the chamber (inflation stage), especially at shallow crustal levels. Conversely, the Mohr-Coulomb shear criterion has shown to be more appropriate for greater depths. Subsequent magma withdrawal from the chamber (deflation stage) results in further damage or even collapse of the chamber roof. While most of the previous studies of caldera collapse rely on the elastic stress analysis, the proposed approach advances modeling of the process by incorporating non-linear failure phenomena and nearly incompressible behaviour of magma. This leads to a perhaps more realistic representation of the fracture processes preceding roof collapse and caldera formation.

Evidence for seismogenic fracture of silicic magma.

Science.gov (United States)

Tuffen, Hugh; Smith, Rosanna; Sammonds, Peter R

2008-05-22

It has long been assumed that seismogenic faulting is confined to cool, brittle rocks, with a temperature upper limit of approximately 600 degrees C (ref. 1). This thinking underpins our understanding of volcanic earthquakes, which are assumed to occur in cold rocks surrounding moving magma. However, the recent discovery of abundant brittle-ductile fault textures in silicic lavas has led to the counter-intuitive hypothesis that seismic events may be triggered by fracture and faulting within the erupting magma itself. This hypothesis is supported by recent observations of growing lava domes, where microearthquake swarms have coincided with the emplacement of gouge-covered lava spines, leading to models of seismogenic stick-slip along shallow shear zones in the magma. But can fracturing or faulting in high-temperature, eruptible magma really generate measurable seismic events? Here we deform high-temperature silica-rich magmas under simulated volcanic conditions in order to test the hypothesis that high-temperature magma fracture is seismogenic. The acoustic emissions recorded during experiments show that seismogenic rupture may occur in both crystal-rich and crystal-free silicic magmas at eruptive temperatures, extending the range of known conditions for seismogenic faulting.

The Boycott effect in magma chambers

Science.gov (United States)

Blanchette, F.; Peacock, T.; Bush, J. W. M.

2004-03-01

We investigate the plausibility of the stratified Boycott effect as a source of layering in magma chambers. Crystal settling within the magma chamber will generate buoyant fluid near the sloping sidewalls whose vertical ascent may be limited by the ambient stratification associated with vertical gradients in SiO2. The resulting flow may be marked by a layered structure, each layer taking the form of a convection cell spanning the lateral extent of the magma chamber. Using parameters relevant to magma chambers, we estimate that such convection cells would be established over a timescale of a month and have a depth on the order of 4m, which is roughly consistent with field observations of strata within solidified chambers.

Volatile elements - water, carbon, nitrogen, noble gases - on Earth

Science.gov (United States)

Marty, B.

2017-12-01

Understanding the origin and evolution of life-bearing volatile elements (water, carbon, nitrogen) on Earth is a fruitful and debated area of research. In his pioneering work, W.W. Rubey inferred that the terrestrial atmosphere and the oceans formed from degassing of the mantle through geological periods of time. Early works on noble gas isotopes were consistent with this view and proposed a catastrophic event of mantle degassing early in Earth's history. We now have evidence, mainly from noble gas isotopes, that several cosmochemical sources contributed water and other volatiles at different stages of Earth's accretion. Potential contributors include the protosolar nebula gas that equilibrated with magma oceans, inner solar system bodies now represented by chondrites, and comets. Stable isotope ratios suggest volatiles where primarily sourced by planetary bodies from the inner solar system. However, recent measurements by the European Space Agency Rosetta probe on the coma of Comet 67P/Churyumov-Gerasimenko permit to set quantitative constraints on the cometary contribution to the surface of our planet. The surface and mantle reservoirs volatile elements exchanged volatile elements through time, with rates that are still uncertain. Some mantle regions remained isolated from whole mantle convection within the first tens to hundreds million years after start of solar system formation. These regions, now sampled by some mantle plumes (e.g., Iceland, Eifel) preserved their volatile load, as indicated by extinct and extant radioactivity systems. The abundance of volatile elements in the mantle is still not well known. Different approaches, such as high pressure experimental petrology, noble gas geochemistry, modelling, resulted in somewhat contrasted estimates, varying over one order of magnitude for water. Comparative planetology, that is, the study of volatiles on the Moon, Venus, Mars, Vesta, will shed light on the sources and strengths of these elements in the

Seismic Tremors and Three-Dimensional Magma Wagging

Science.gov (United States)

Liao, Y.; Bercovici, D.

2015-12-01

Seismic tremor is a feature shared by many silicic volcanoes and is a precursor of volcanic eruption. Many of the characteristics of tremors, including their frequency band from 0.5 Hz to 7 Hz, are common for volcanoes with very different geophysical and geochemical properties. The ubiquitous characteristics of tremor imply that it results from some generation mechanism that is common to all volcanoes, instead of being unique to each volcano. Here we present new analysis on the magma-wagging mechanism that has been proposed to generate tremor. The model is based on the suggestion given by previous work (Jellinek & Bercovici 2011; Bercovici et.al. 2013) that the magma column is surrounded by a compressible, bubble-rich foam annulus while rising inside the volcanic conduit, and that the lateral oscillation of the magma inside the annulus causes observable tremor. Unlike the previous two-dimensional wagging model where the displacement of the magma column is restricted to one vertical plane, the three-dimensional model we employ allows the magma column to bend in different directions and has angular motion as well. Our preliminary results show that, without damping from viscous deformation of the magma column, the system retains angular momentum and develops elliptical motion (i.e., the horizontal displacement traces an ellipse). In this ''inviscid'' limit, the magma column can also develop instabilities with higher frequencies than what is found in the original two-dimensional model. Lateral motion can also be out of phase for various depths in the magma column leading to a coiled wagging motion. For the viscous-magma model, we predict a similar damping rate for the uncoiled magma column as in the two-dimensional model, and faster damping for the coiled magma column. The higher damping thus requires the existence of a forcing mechanism to sustain the oscillation, for example the gas-driven Bernoulli effect proposed by Bercovici et al (2013). Finally, using our new 3

The impairment of MAGMAS function in human is responsible for a severe skeletal dysplasia.

Directory of Open Access Journals (Sweden)

Cybel Mehawej

2014-05-01

Full Text Available Impairment of the tightly regulated ossification process leads to a wide range of skeletal dysplasias and deciphering their molecular bases has contributed to the understanding of this complex process. Here, we report a homozygous mutation in the mitochondria-associated granulocyte macrophage colony stimulating factor-signaling gene (MAGMAS in a novel and severe spondylodysplastic dysplasia. MAGMAS, also referred to as PAM16 (presequence translocase-associated motor 16, is a mitochondria-associated protein involved in preprotein translocation into the matrix. We show that MAGMAS is specifically expressed in trabecular bone and cartilage at early developmental stages and that the mutation leads to an instability of the protein. We further demonstrate that the mutation described here confers to yeast strains a temperature-sensitive phenotype, impairs the import of mitochondrial matrix pre-proteins and induces cell death. The finding of deleterious MAGMAS mutations in an early lethal skeletal dysplasia supports a key role for this mitochondrial protein in the ossification process.

An attempt to model the timing of magma formation by means of radioactive disequilibria

International Nuclear Information System (INIS)

Cortini, M.

1985-01-01

In order to quantitatively determine the timing of magma formation, the Th series radioactive disequilibria for the Etna and Stromboli volcanoes have been re-examined in the light of new isotopic evidence that shows that magma formation is a chemically open-system process. This aim was but partially reached. It is shown that single-stage models of magma formation are not consistent with the experimental data. Short-life disequilibria require that magma formation undergoes: (1) a Th and Ra enrichment stage (a few years long); (2) a closed-system stage (a few tens to some hundreds years long); (3) a second Th and Ra enrichment stage (a few years long), different from the former in terms of Ra/Th ratio. The whole process can be described by a group of equations, derived from open-system non-equilibrium thermodynamics, which were integrated with numerical methods. However, too many unknowns are involved to allow a one-to-one solution based on the available data. (orig.)

Numerical modeling of bubble dynamics in magmas

Science.gov (United States)

Huber, Christian; Su, Yanqing; Parmigiani, Andrea

2014-05-01

Understanding the complex non-linear physics that governs volcanic eruptions is contingent on our ability to characterize the dynamics of bubbles and its effect on the ascending magma. The exsolution and migration of bubbles has also a great impact on the heat and mass transport in and out of magma bodies stored at shallow depths in the crust. Multiphase systems like magmas are by definition heterogeneous at small scales. Although mixture theory or homogenization methods are convenient to represent multiphase systems as a homogeneous equivalent media, these approaches do not inform us on possible feedbacks at the pore-scale and can be significantly misleading. In this presentation, we discuss the development and application of bubble-scale multiphase flow modeling to address the following questions : How do bubbles impact heat and mass transport in magma chambers ? How efficient are chemical exchanges between the melt and bubbles during magma decompression? What is the role of hydrodynamic interactions on the deformation of bubbles while the magma is sheared? Addressing these questions requires powerful numerical methods that accurately model the balance between viscous, capillary and pressure stresses. We discuss how these bubble-scale models can provide important constraints on the dynamics of magmas stored at shallow depth or ascending to the surface during an eruption.

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.

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

Drilling Magma for Science, Volcano Monitoring, and Energy

Science.gov (United States)

Eichelberger, J. C.; Lavallée, Y.; Blankenship, D.

2017-12-01

Magma chambers are central to understanding magma evolution, formation of continental crust, volcanism, and renewal of hydrothermal systems. Information from geology, petrology, laboratory experiments, and geophysical imagery has led to little consensus except a trend to see magma systems as being crystal-dominant (mush) rather than melt dominant. At high melt viscosities, crystal-liquid fractionation may be achieved by separation of melt from mush rather than crystals from liquid suspension. That the dominant volume has properties more akin to solid than liquid might explain the difficulty in detecting magma geophysically. Recently, geothermal drilling has intersected silicic magma at the following depths and SiO2 contents are: Puna, Hawaii, 2.5 km, 67 wt%; Menengai, Kenya 2.1 km, 67 wt%; Krafla, Iceland, 2.1 km, 75 wt%. Some similarities are: 1) Drillers encountered a "soft", sticky formation; 2) Cuttings or chips of clear quenched glass were recovered; 3) The source of the glass flowed up the well; 4) Transition from solid rock to recovering crystal-poor glass occurred in tens of meters, apparently without an intervening mush zone. Near-liquidus magma at the roof despite rapid heat loss there presents a paradox that may be explained by very recent intrusion of magma, rise of liquidus magma to the roof replacing partially crystallized magma, or extremely skewed representation of melt over mush in cuttings (Carrigan et al, this session). The latter is known to occur by filter pressing of ooze into lava lake coreholes (Helz, this session), but cannot be verified in actual magma without coring. Coring to reveal gradients in phase composition and proportions is required for testing any magma chamber model. Success in drilling into and controlling magma at all three locations, in coring lava lakes to over 1100 C, and in numerical modeling of coring at Krafla conditions (Su, this session) show this to be feasible. Other unprecedented experiments are using the known

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

Timescale of Petrogenetic Processes Recorded in the Mount Perkins Magma System, Northern Colorado River Extension Corridor, Arizona

Science.gov (United States)

Danielson, Lisa R.; Metcalf, Rodney V.; Miller, Calvin F.; Rhodes Gregory T.; Wooden, J. L.

2013-01-01

The Miocene Mt. Perkins Pluton is a small composite intrusive body emplaced in the shallow crust as four separate phases during the earliest stages of crustal extension. Phase 1 (oldest) consists of isotropic hornblende gabbro and a layered cumulate sequence. Phase 2 consists of quartz monzonite to quartz monzodiorite hosting mafic microgranitoid enclaves. Phase 3 is composed of quartz monzonite and is subdivided into mafic enclave-rich zones and enclave-free zones. Phase 4 consists of aphanitic dikes of mafic, intermediate and felsic compositions hosting mafic enclaves. Phases 2-4 enclaves record significant isotopic disequilibrium with surrounding granitoid host rocks, but collectively enclaves and host rocks form a cogenetic suite exhibiting systematic variations in Nd-Sr-Pb isotopes that correlate with major and trace elements. Phases 2-4 record multiple episodes of magma mingling among cogenetic hybrid magmas that formed via magma mixing and fractional crystallization at a deeper crustal. The mafic end-member was alkali basalt similar to nearby 6-4 Ma basalt with enriched OIB-like trace elements and Nd-Sr-Pb isotopes. The felsic end-member was a subalkaline crustal-derived magma. Phase 1 isotropic gabbro exhibits elemental and isotopic compositional variations at relatively constant SiO2, suggesting generation of isotropic gabbro by an open-system process involving two mafic end-members. One end-member is similar in composition to the OIB-like mafic end-member for phases 2-4; the second is similar to nearby 11-8 Ma tholeiite basalt exhibiting low epsilon (sub Nd), and depleted incompatible trace elements. Phase 1 cumulates record in situ fractional crystallization of an OIB-like mafic magma with isotopic evidence of crustal contamination by partial melts generated in adjacent Proterozoic gneiss. The Mt Perkins pluton records a complex history in a lithospheric scale magma system involving two distinct mantle-derived mafic magmas and felsic magma sourced in the

Pigeonholing pyroclasts: Insights from the 19 March 2008 explosive eruption of Kīlauea volcano

Science.gov (United States)

Houghton, Bruce F.; Swanson, D.A.; Carey, R.J.; Rausch, J.; Sutton, A.J.

2011-01-01

We think, conventionally, of volcanic explosive eruptions as being triggered in one of two ways: by release and expansion of volatiles dissolved in the ejected magma (magmatic explosions) or by transfer of heat from magma into an external source of water (phreatic or phreatomagmatic explosions). We document here an event where neither magma nor an external water source was involved in explosive activity at K??lauea. Instead, the eruption was powered by the expansion of decoupled magmatic volatiles released from deeper magma, which was not ejected by the eruption, and the trigger was a collapse of near-surface wall rocks that then momentarily blocked that volatile flux. Mapping of the advected fall deposit a day after this eruption has highlighted the difficulty of constraining deposit edges from unobserved or prehistoric eruptions of all magnitudes. Our results suggest that the dispersal area of advected fall deposits could be miscalculated by up to 30% of the total, raising issues for accurate hazard zoning and assessment. Eruptions of this type challenge existing classification schemes for pyroclastic deposits and explosive eruptions and, in the past, have probably been interpreted as phreatic explosions, where the eruptive mechanism has been assumed to involve flashing of groundwater to steam. ?? 2011 Geological Society of America.

Artificial magma program: Report on workshop held in Oak Ridge, Tennessee on March 29-30, 1994

International Nuclear Information System (INIS)

Naney, M.T.; Jacobs, G.K.

1995-03-01

A workshop was organized and conducted in Oak Ridge, Tennessee, on March 29 and 30, 1994, to evaluate the use of in situ vitrification (ISV) technology to produce large silicate melts that would serve as analogs for natural magmas for the study of magmatic properties and processes. ISV technology would permit experiments to test hypotheses or provide new data that cannot be tested or obtained through bench-top experimentation or the study of natural systems. The scale of ISV melts is intermediate between that of natural lava lakes and laboratory crucible experiments, with melt volumes from 15 to 300 m 3 easily obtained. This approach permits investigation of dynamic processes which operate on scales difficult to simulate through bench-top experimentation and that are not amenable to direct observation or control in natural systems (e.g., degassing, convection, and crystal settling). Several aspects of the ISV process make it uniquely applicable for the study of magma systems. The process produces open-quotes containerlessclose quotes silicate melts, which permits development of important analog components of natural magma systems including: partial melt zones, stopping, contact metamorphic haloes, and open-quotes hydrothermalclose quotes fluids. The lack of a melt open-quotes containerclose quotes also enables use of standard field-scale geophysical instrumentation for studying the seismic and electrical properties of the melt and host materials. In addition, volatile and particulate emissions from the melt can be sampled using methods that avoid reaction with, and contamination by, host rocks. The consensus of the group was that the use of melts generated by ISV technology provided unique opportunities to advance the understanding of magmas and magmatic processes and warranted development of a proposal

Xe isotopic constraints on cycling of deep Earth volatiles

Science.gov (United States)

Parai, R.; Mukhopadhyay, S.

2017-12-01

The modern deep Earth volatile budget reflects primordial volatiles delivered during accretion, radiogenic ingrowth of volatile species (e.g., 40Ar produced by 40K decay), outgassing in association with mantle processing, and regassing via subduction. The noble gases are unique volatile tracers in that they are chemically inert, but are thought to be trapped within hydrous alteration phases in downwelling lithologies. Noble gases thus provide a tracer of volatile transport between the deep Earth and surface reservoirs. Constraints on the fluxes of noble gases between deep Earth and surface reservoirs over time can accordingly be used to provide insight into temperature conditions at subduction zones, limits on volatile cycling, and the evolving distribution of major volatile species in terrestrial reservoirs over time. Xe isotope systematics in mantle-derived rocks show that 80-90% of the mantle Xe budget is derived from recycling of atmospheric Xe, indicating that atmospheric Xe is retained in subducting slabs beyond depths of magma generation in subduction zones over Earth history. We present an integrated model of Xe cycling between the mantle and atmosphere in association with mantle processing over Earth history. We test a wide variety of outgassing and regassing rates and take the evolution of the atmospheric Xe isotopic composition [e.g., 1] into account. Models in which the deep Earth transitions from a net outgassing to net regassing regime best satisfy Xe isotopic constraints from mantle-derived rocks [2-6]. [1] Avice et al., 2017; Nature Communications, 8; [2] Mukhopadhyay, 2012, Nature 486, 101-104; [3] Parai et al., 2012, EPSL 359-360, 227-239; [4] Parai and Mukhopadhay, 2015, G-cubed 16, 719-735; [5] Peto et al., 2013, EPSL 369-370, 13-23; [6] Tucker et al., 2012, EPSL 355-356, 244-254.

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

Indian Academy of Sciences (India)

66

20 crystallization of the latter, results in hybrid magmas under the influence of thermal and. 21 chemical exchange. The mechanical exchange occurs between the coexisting magmas due to. 22 viscosity contrast, if the mafic magma enters slightly later into the magma chamber, when the. 23 felsic magma started to crystallize.

Depth of origin of magma in eruptions.

Science.gov (United States)

Becerril, Laura; Galindo, Ines; Gudmundsson, Agust; Morales, Jose Maria

2013-09-26

Many volcanic hazard factors--such as the likelihood and duration of an eruption, the eruption style, and the probability of its triggering large landslides or caldera collapses--relate to the depth of the magma source. Yet, the magma source depths are commonly poorly known, even in frequently erupting volcanoes such as Hekla in Iceland and Etna in Italy. Here we show how the length-thickness ratios of feeder dykes can be used to estimate the depth to the source magma chamber. Using this method, accurately measured volcanic fissures/feeder-dykes in El Hierro (Canary Islands) indicate a source depth of 11-15 km, which coincides with the main cloud of earthquake foci surrounding the magma chamber associated with the 2011-2012 eruption of El Hierro. The method can be used on widely available GPS and InSAR data to calculate the depths to the source magma chambers of active volcanoes worldwide.

Mantle enrichment by volatiles as the Nazca plate subducts beneath the Payenia backarc of the Southern Volcanic Zone, Argentina

DEFF Research Database (Denmark)

Brandt, Frederik Ejvang

The thesis is a contribution towards the understanding of the generation of the source mantle for magmas related to the subduction of the Nazca plate under South America with an emphasis on the geochemistry of the volatiles Cl, F, S, H2O and CO2. The study presents analytical data for tephra, min...

Constraining magma physical properties and its temporal evolution from InSAR and topographic data only: a physics-based eruption model for the effusive phase of the Cordon Caulle 2011-2012 rhyodacitic eruption

Science.gov (United States)

Delgado, F.; Kubanek, J.; Anderson, K. R.; Lundgren, P.; Pritchard, M. E.

2017-12-01

The 2011-2012 eruption of Cordón Caulle volcano in Chile is the best scientifically observed rhyodacitic eruption and is thus a key place to understand the dynamics of these rare but powerful explosive rhyodacitic eruptions. Because the volatile phase controls both the eruption temporal evolution and the eruptive style, either explosive or effusive, it is important to constrain the physical parameters that drive these eruptions. The eruption began explosively and after two weeks evolved into a hybrid explosive - lava flow effusion whose volume-time evolution we constrain with a series of TanDEM-X Digital Elevation Models. Our data shows the intrusion of a large volume laccolith or cryptodome during the first 2.5 months of the eruption and lava flow effusion only afterwards, with a total volume of 1.4 km3. InSAR data from the ENVISAT and TerraSAR-X missions shows more than 2 m of subsidence during the effusive eruption phase produced by deflation of a finite spheroidal source at a depth of 5 km. In order to constrain the magma total H2O content, crystal cargo, and reservoir pressure drop we numerically solve the coupled set of equations of a pressurized magma reservoir, magma conduit flow and time dependent density, volatile exsolution and viscosity that we use to invert the InSAR and topographic data time series. We compare the best-fit model parameters with independent estimates of magma viscosity and total gas content measured from lava samples. Preliminary modeling shows that although it is not possible to model both the InSAR and the topographic data during the onset of the laccolith emplacement, it is possible to constrain the magma H2O and crystal content, to 4% wt and 30% which agree well with published literature values.

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.

Using fumarolic inert gas composition to investigate magma dynamics at Campi Flegrei (Italy)

Science.gov (United States)

Chiodini, G.; Caliro, S.; Paonita, A.; Cardellini, C.

2013-12-01

volatiles, inert gases are the preferred species to achieve information on the dynamics and structure of the magma plumbing systems.

Variations in magma supply rate at Kilauea Volcano, Hawaii

Science.gov (United States)

Dvorak, John J.; Dzurisin, Daniel

1993-01-01

When an eruption of Kilauea lasts more than 4 months, so that a well-defined conduit has time to develop, magma moves freely through the volcano from a deep source to the eruptive site at a constant rate of 0.09 km3/yr. At other times, the magma supply rate to Kilauea, estimated from geodetic measurements of surface displacements, may be different. For example, after a large withdrawal of magma from the summit reservoir, such as during a rift zone eruption, the magma supply rate is high initially but then lessens and exponentially decays as the reservoir refills. Different episodes of refilling may have different average rates of magma supply. During four year-long episodes in the 1960s, the annual rate of refilling varied from 0.02 to 0.18 km3/yr, bracketing the sustained eruptive rate of 0.09 km3/yr. For decade-long or longer periods, our estimate of magma supply rate is based on long-term changes in eruptive rate. We use eruptive rate because after a few dozen eruptions the volume of magma that passes through the summit reservoir is much larger than the net change of volume of magma stored within Kilauea. The low eruptive rate of 0.009 km3/yr between 1840 and 1950, compared to an average eruptive rate of 0.05 km3/yr since 1950, suggests that the magma supply rate was lower between 1840 and 1950 than it has been since 1950. An obvious difference in activity before and since 1950 was the frequency of rift zone eruptions: eight rift zone eruptions occurred between 1840 and 1950, but more than 20 rift zone eruptions have occurred since 1950. The frequency of rift zone eruptions influences magma supply rate by suddenly lowering pressure of the summit magma reservoir, which feeds magma to rift zone eruptions. A temporary drop of reservoir pressure means a larger-than-normal pressure difference between the reservoir and a deeper source, so magma is forced to move upward into Kilauea at a faster rate.

MAGMA: analysis of two-channel microarrays made easy.

Science.gov (United States)

Rehrauer, Hubert; Zoller, Stefan; Schlapbach, Ralph

2007-07-01

The web application MAGMA provides a simple and intuitive interface to identify differentially expressed genes from two-channel microarray data. While the underlying algorithms are not superior to those of similar web applications, MAGMA is particularly user friendly and can be used without prior training. The user interface guides the novice user through the most typical microarray analysis workflow consisting of data upload, annotation, normalization and statistical analysis. It automatically generates R-scripts that document MAGMA's entire data processing steps, thereby allowing the user to regenerate all results in his local R installation. The implementation of MAGMA follows the model-view-controller design pattern that strictly separates the R-based statistical data processing, the web-representation and the application logic. This modular design makes the application flexible and easily extendible by experts in one of the fields: statistical microarray analysis, web design or software development. State-of-the-art Java Server Faces technology was used to generate the web interface and to perform user input processing. MAGMA's object-oriented modular framework makes it easily extendible and applicable to other fields and demonstrates that modern Java technology is also suitable for rather small and concise academic projects. MAGMA is freely available at www.magma-fgcz.uzh.ch.

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.

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

Depositional features and stratigraphic sections in granitic plutons: implications for the emplacement and crystallization of granitic magma

Science.gov (United States)

Wiebe, R. A.; Collins, W. J.

1998-09-01

Many granitic plutons contain sheet-like masses of dioritic to gabbroic rocks or swarms of mafic to intermediate enclaves which represent the input of higher temperature, more mafic magma during crystallization of the granitic plutons. Small-scale structures associated with these bodies (e.g. load-cast and compaction features, silicic pipes extending from granitic layers into adjacent gabbroic sheets) indicate that the sheets and enclave swarms were deposited on a floor of the magma chamber (on granitic crystal mush and beneath crystal-poor magma) while the mafic magma was incompletely crystallized. These structures indicate 'way up', typically toward the interior of the intrusions, and appear to indicate that packages of mafic sheets and enclave concentrations in these plutons are a record of sequential deposition. Hence, these plutons preserve a stratigraphic history of events involved in the construction (filling, replenishment) and crystallization of the magma chamber. The distinctive features of these depositional portions of plutons allow them to be distinguished from sheeted intrusions, which usually preserve mutual intrusive contacts and 'dike-sill' relations of different magma types. The considerable thickness of material that can be interpreted as depositional, and the evidence for replenishment, suggest that magma chamber volumes at any one time were probably much less than the final size of the pluton. Thus, magma chambers may be constructed much more slowly than presently envisaged. The present steep attitudes of these structures in many plutons may have developed gradually as the floor of the chamber (along with the underlying solidified granite and country rock) sank during continuing episodes of magma chamber replenishment. These internal magmatic structures support recent suggestions that the room problem for granites could be largely accommodated by downward movement of country rock beneath the magma chamber.

Volatile and non-volatile/semi-volatile compounds and in vitro bioactive properties of Chilean Ulmo (Eucryphia cordifolia Cav.) honey.

Science.gov (United States)

Acevedo, Francisca; Torres, Paulina; Oomah, B Dave; de Alencar, Severino Matias; Massarioli, Adna Prado; Martín-Venegas, Raquel; Albarral-Ávila, Vicenta; Burgos-Díaz, César; Ferrer, Ruth; Rubilar, Mónica

2017-04-01

Ulmo honey originating from Eucryphia cordifolia tree, known locally in the Araucania region as the Ulmo tree is a natural product with valuable nutritional and medicinal qualities. It has been used in the Mapuche culture to treat infections. This study aimed to identify the volatile and non-volatile/semi-volatile compounds of Ulmo honey and elucidate its in vitro biological properties by evaluating its antioxidant, antibacterial, antiproliferative and hemolytic properties and cytotoxicity in Caco-2 cells. Headspace volatiles of Ulmo honey were isolated by solid-phase microextraction (SPME); non-volatiles/semi-volatiles were obtained by removing all saccharides with acidified water and the compounds were identified by GC/MS analysis. Ulmo honey volatiles consisted of 50 compounds predominated by 20 flavor components. Two of the volatile compounds, lyrame and anethol have never been reported before as honey compounds. The non-volatile/semi-volatile components of Ulmo honey comprised 27 compounds including 13 benzene derivatives accounting 75% of the total peak area. Ulmo honey exhibited weak antioxidant activity but strong antibacterial activity particularly against gram-negative bacteria and methicillin-resistant Staphylococcus aureus (MRSA), the main strain involved in wounds and skin infections. At concentrations >0.5%, Ulmo honey reduced Caco-2 cell viability, released lactate dehydrogenase (LDH) and increased reactive oxygen species (ROS) production in a dose dependent manner in the presence of foetal bovine serum (FBS). The wide array of volatile and non-volatile/semi-volatile constituents of Ulmo honey rich in benzene derivatives may partly account for its strong antibacterial and antiproliferative properties important for its therapeutic use. Our results indicate that Ulmo honey can potentially inhibit cancer growth at least partly by modulating oxidative stress. Copyright © 2017 Elsevier Ltd. All rights reserved.

Silicic magma generation at Askja volcano, Iceland

Science.gov (United States)

Sigmarsson, O.

2009-04-01

Rate of magma differentiation is an important parameter for hazard assessment at active volcanoes. However, estimates of these rates depend on proper understanding of the underlying magmatic processes and magma generation. Differences in isotope ratios of O, Th and B between silicic and in contemporaneous basaltic magmas have been used to emphasize their origin by partial melting of hydrothermally altered metabasaltic crust in the rift-zones favoured by a strong geothermal gradient. An alternative model for the origin of silicic magmas in the Iceland has been proposed based on U-series results. Young mantle-derived mafic protolith is thought to be metasomatized and partially melted to form the silicic end-member. However, this model underestimates the compositional variations of the hydrothermally-altered basaltic crust. New data on U-Th disequilibria and O-isotopes in basalts and dacites from Askja volcano reveal a strong correlation between (230Th/232Th) and delta 18O. The 1875 AD dacite has the lowest Th- and O isotope ratios (0.94 and -0.24 per mille, respectively) whereas tephra of evolved basaltic composition, erupted 2 months earlier, has significantly higher values (1.03 and 2.8 per mille, respectively). Highest values are observed in the most recent basalts (erupted in 1920 and 1961) inside the Askja caldera complex and out on the associated fissure swarm (Sveinagja basalt). This correlation also holds for older magma such as an early Holocene dacites, which eruption may have been provoked by rapid glacier thinning. Silicic magmas at Askja volcano thus bear geochemical signatures that are best explained by partial melting of extensively hydrothermally altered crust and that the silicic magma source has remained constant during the Holocene at least. Once these silicic magmas are formed they appear to erupt rapidly rather than mixing and mingling with the incoming basalt heat-source that explains lack of icelandites and the bi-modal volcanism at Askja

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, 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 either the lower crust or metasomatized mantle. The origin of sulfur remains unresolved

Short-circuiting magma differentiation from basalt straight to rhyolite?

Science.gov (United States)

Ruprecht, P.; Winslow, H.

2017-12-01

Silicic magmas are the product of varying degrees of crystal fractionation and crustal assimilation/melting. Both processes lead to differentiation that is step-wise rather than continuous for example during melt separation from a crystal mush (Dufek and Bachmann, 2010). However, differentiation is rarely efficient enough to evolve directly from a basaltic to a rhyolitic magma. At Volcán Puyehue-Cordón Caulle, Chile, the magma series is dominated by crystal fractionation where mixing trends between primitive and felsic end members in the bulk rock compositions are almost absent (e.g. P, FeO, TiO2 vs. SiO2). How effective fraction is in this magmatic system is not well-known. The 2011-12 eruption at Cordón Caulle provides new constraints that rhyolitic melts may be derived directly from a basaltic mush. Minor, but ubiquitous mafic, crystal-rich enclaves co-erupted with the predominantly rhyolitic near-aphyric magma. These enclaves are among the most primitive compositions erupted at Puyehue-Cordón Caulle and geochemically resemble closely basaltic magmas that are >10 ka old (Singer et al. 2008) and that have been identified as a parental tholeiitic mantle-derived magma (Schmidt and Jagoutz, 2017) for the Southern Andean Volcanic Zone. The vesiculated nature, the presence of a microlite-rich groundmass, and a lack of a Eu anomaly in these encalves suggest that they represent recharge magma/mush rather than sub-solidus cumulates and therefore have potentially a direct petrogenetic link to the erupted rhyolites. Our results indicate that under some conditions crystal fractionation can be very effective and the presence of rhyolitic magmas does not require an extensive polybaric plumbing system. Instead, primitive mantle-derived magmas source directly evolved magmas. In the case, of the magma system beneath Puyehue-Cordón Caulle, which had three historic rhyolitic eruptions (1921-22, 1960, 2011-12) these results raise the question whether rhyolite magma extraction

Sixty thousand years of magmatic volatile history before the caldera-forming eruption of Mount Mazama, Crater Lake, Oregon

Science.gov (United States)

Wright, Heather M.; Bacon, Charles R.; Vazquez, Jorge A.; Sisson, Thomas W.

2012-01-01

The well-documented eruptive history of Mount Mazama, Oregon, provides an excellent opportunity to use pre-eruptive volatile concentrations to study the growth of an explosive silicic magmatic system. Melt inclusions (MI) hosted in pyroxene and plagioclase crystals from eight dacitic–rhyodacitic eruptive deposits (71–7.7 ka) were analyzed to determine variations in volatile-element concentrations and changes in magma storage conditions leading up to and including the climactic eruption of Crater Lake caldera. Temperatures (Fe–Ti oxides) increased through the series of dacites, then decreased, and increased again through the rhyodacites (918–968 to ~950 to 845–895 °C). Oxygen fugacity began at nickel–nickel-oxide buffer (NNO) +0.8 (71 ka), dropped slightly to NNO +0.3, and then climbed to its highest value with the climactic eruption (7.7 ka) at NNO +1.1 log units. In parallel with oxidation state, maximum MI sulfur concentrations were high early in the eruptive sequence (~500 ppm), decreased (to ~200 ppm), and then increased again with the climactic eruption (~500 ppm). Maximum MI sulfur correlates with the Sr content (as a proxy for LREE, Ba, Rb, P2O5) of recharge magmas, represented by basaltic andesitic to andesitic enclaves and similar-aged lavas. These results suggest that oxidized Sr-rich recharge magmas dominated early and late in the development of the pre-climactic dacite–rhyodacite system. Dissolved H2O concentrations in MI do not, however, correlate with these changes in dominant recharge magma, instead recording vapor solubility relations in the developing shallow magma storage and conduit region. Dissolved H2O concentrations form two populations through time: the first at 3–4.6 wt% (with a few extreme values up to 6.1 wt%) and the second at ≤2.4 wt%. CO2 concentrations measured in a subset of these inclusions reach up to 240 ppm in early-erupted deposits (71 ka) and are below detection in climactic deposits (7.7 ka). Combined H2O and

Loki Patera: A Magma Sea Story

Science.gov (United States)

Veeder, G. J.; Matson, D. L.; Rathbun, A. G.

2005-01-01

We consider Loki Patera on Io as the surface expression of a large uniform body of magma. Our model of the Loki magma sea is some 200 km across; larger than a lake but smaller than an ocean. The depth of the magma sea is unknown, but assumed to be deep enough that bottom effects can be ignored. Edge effects at the shore line can be ignored to first order for most of the interior area. In particular, we take the dark material within Loki Patera as a thin solidified lava crust whose hydrostatic shape follows Io's isostatic surface (approx. 1815 km radius of curvature). The dark surface of Loki appears to be very smooth on both regional and local (subresolution) scales. The thermal contrast between the low and high albedo areas within Loki is consistent with the observed global correlation. The composition of the model magma sea is basaltic and saturated with dissolved SO2 at depth. Its average, almost isothermal, temperature is at the liquidus for basalt. Additional information is included in the original extended abstract.

Ardnamurchan 3D cone-sheet architecture explained by a single elongate magma chamber.

Science.gov (United States)

Burchardt, Steffi; Troll, Valentin R; Mathieu, Lucie; Emeleus, Henry C; Donaldson, Colin H

2013-10-08

The Palaeogene Ardnamurchan central igneous complex, NW Scotland, was a defining place for the development of the classic concepts of cone-sheet and ring-dyke emplacement and has thus fundamentally influenced our thinking on subvolcanic structures. We have used the available structural information on Ardnamurchan to project the underlying three-dimensional (3D) cone-sheet structure. Here we show that a single elongate magma chamber likely acted as the source of the cone-sheet swarm(s) instead of the traditionally accepted model of three successive centres. This proposal is supported by the ridge-like morphology of the Ardnamurchan volcano and is consistent with the depth and elongation of the gravity anomaly underlying the peninsula. Our model challenges the traditional model of cone-sheet emplacement at Ardnamurchan that involves successive but independent centres in favour of a more dynamical one that involves a single, but elongate and progressively evolving magma chamber system.

Pb isotopes during crustal melting and magma mingling - A cautionary tale from the Miki Fjord macrodike, central east Greenland

DEFF Research Database (Denmark)

Waight, Tod Earle; Lesher, Charles

2010-01-01

Pb isotopic data are presented for hybrid rocks formed by mingling between mantle-derived tholeiitic magma of the Eocene Miki Fjord macrodike (East Greenland) and melt derived from the adjacent Precambrian basement. Bulk mixing and AFC processes between end-members readily identified in the field...... grain boundaries during disequilibrium melting of the host rock by the mafic magma. The crustal melt involved in magma interactions was therefore heterogeneous with respect to Pb isotopes on a metre-scale. These results illustrate the difficulties inherent in interpreting isotopic variations...... in contaminated mafic magmas even when the end-members are well constrained by field relations. We show that the Pb isotopic composition of the crustal contaminants and contamination trajectories for the Miki Fjord hybrid magmatic lithologies are markedly different from regional basement gneisses and contaminated...

Ground surface deformation patterns, magma supply, and magma storage at Okmok volcano, Alaska, from InSAR analysis: 1. Intereruption deformation, 1997–2008

Science.gov (United States)

Lu, Zhong; Dzurisin, Daniel; Biggs, Juliet; Wicks, Charles; McNutt, Steve

2010-01-01

Starting soon after the 1997 eruption at Okmok volcano and continuing until the start of the 2008 eruption, magma accumulated in a storage zone centered ~3.5 km beneath the caldera floor at a rate that varied with time. A Mogi-type point pressure source or finite sphere with a radius of 1 km provides an adequate fit to the deformation field portrayed in time-sequential interferometric synthetic aperture radar images. From the end of the 1997 eruption through summer 2004, magma storage increased by 3.2–4.5 × 107 m3, which corresponds to 75–85% of the magma volume erupted in 1997. Thereafter, the average magma supply rate decreased such that by 10 July 2008, 2 days before the start of the 2008 eruption, magma storage had increased by 3.7–5.2 × 107 m3 or 85–100% of the 1997 eruption volume. We propose that the supply rate decreased in response to the diminishing pressure gradient between the shallow storage zone and a deeper magma source region. Eventually the effects of continuing magma supply and vesiculation of stored magma caused a critical pressure threshold to be exceeded, triggering the 2008 eruption. A similar pattern of initially rapid inflation followed by oscillatory but generally slowing inflation was observed prior to the 1997 eruption. In both cases, withdrawal of magma during the eruptions depressurized the shallow storage zone, causing significant volcano-wide subsidence and initiating a new intereruption deformation cycle.

Major and trace element and volatile constraints on magma systematics of seamounts and axial ridge glasses from the East Pacific Rise between 8°N and 12°N

Science.gov (United States)

Lytle, M. L.; Kelley, K. A.; Wanless, V. D.; Hauri, E. H.

2017-12-01

The East Pacific Rise is a fast spreading mid-ocean ridge system (6-16cm/yr) consisting of many spreading ridges and transform faults. Focusing on a well-studied segment between 8-12°N, we present new SIMS measurements of magmatic volatiles (H2O, CO2, S, Cl, F) and new LA-ICP-MS trace element data in both on-axis and off-axis glasses, coupled with previously published data and use these data to relate melt composition to crystallization and melting processes. The seamounts range in composition from evolved (MgO = 5.54 wt%) to fairly primitive (MgO = 9.70 wt%), whereas on-axis samples have a narrower range of MgO (5.85 - 8.83 wt%). Seamounts span a wide range of enrichment in trace element compositions (La/Sm 0.45 - 4.63; Th/La 0.02 - 0.14; K/Ti 0.02 - 0.66), whereas on-axis glasses reflect NMORB compositions (La/Sm 0.5 - 1; Th/La 0.035 - 0.07; K/Ti 0.05 - 0.15). Light rare earth elements in the seamounts vary from depleted to enriched and have variable Eu anomalies (0.79 - 1.10), while on-axis samples have NMORB patterns with more negative Eu anomalies (0.74 - 1.00). The H2O content of the seamounts ranges from dry (0.05 wt%) to fairly wet (0.96 wt%), whereas on-axis samples have a narrower range (0.15 - 0.31 wt%). Cl contents show variable mixing between seawater and a magmatic component, with seamounts assimilating more seawater. Magmatic liquid lines of descent (LLD), recorded in glass, reflect fractional crystallization of olivine, plagioclase, and clinopyroxene, consistent with modal phenocryst abundances of the rocks. A multi-element approach (e.g., MgO vs. Al2O3, CaO, CaO/Al2O3), constrains LLDs, providing fractionation slopes, allowing mafic basalt compositions to be accurately corrected back to primary melts in equilibrium with Fo90. Using these melts, pressures and temperatures of melt equilibration can be constrained using melt thermobarometry. On-axis samples reflect higher PT conditions (1371°C; 1.37 GPa), although within error of seamounts (1340�

Oxygen isotopes and volatile contents of the Gorgona komatiites, Colombia: A confirmation of the deep mantle origin of H2O

Science.gov (United States)

Gurenko, Andrey A.; Kamenetsky, Vadim S.; Kerr, Andrew C.

2016-11-01

We report O isotopes in olivine grains (Fo89-93) and volatile contents (CO2, H2O, F, S, Cl) in olivine-hosted melt inclusions from one Gorgona picrite and five komatiites with the aim of constraining the origin of H2O in these magmas. These samples have previously been analysed for major and trace elements and volatile concentrations (H2O, S, Cl) and B isotopes in melt inclusions. A distinctive feature of the included melts is relatively high contents of volatile components and boron, which show positive anomalies in, otherwise depleted, primitive mantle normalised trace and rare earth element patterns and range in δ11 B from -11.5 to 15.6‰. In this study, the olivines were systematically analysed for O isotopes (1) in the centre of grains, (2) near the grain boundaries and, (3) as close as possible to the studied melt inclusions. The majority of olivines (∼66%) are ;mantle;-like, 4.8 ‰ ≤δ18 O ≤ 5.5 ‰, with a subordinate but still significant number (∼33%) above, and only 2 grains below, this range. There is no systematic difference between the central and marginal parts of the grains. Higher than ;mantle; δ18OOl values are ascribed to low-T (Gorgona mafic and ultramafic magmas.

Magma Reservoirs Feeding Giant Radiating Dike Swarms: Insights from Venus

Science.gov (United States)

Grosfils, E. B.; Ernst, R. E.

2003-01-01

Evidence of lateral dike propagation from shallow magma reservoirs is quite common on the terrestrial planets, and examination of the giant radiating dike swarm population on Venus continues to provide new insight into the way these complex magmatic systems form and evolve. For example, it is becoming clear that many swarms are an amalgamation of multiple discrete phases of dike intrusion. This is not surprising in and of itself, as on Earth there is clear evidence that formation of both magma reservoirs and individual giant radiating dikes often involves periodic magma injection. Similarly, giant radiating swarms on Earth can contain temporally discrete subswarms defined on the basis of geometry, crosscutting relationships, and geochemical or paleomagnetic signatures. The Venus data are important, however, because erosion, sedimentation, plate tectonic disruption, etc. on Earth have destroyed most giant radiating dike swarm's source regions, and thus we remain uncertain about the geometry and temporal evolution of the magma sources from which the dikes are fed. Are the reservoirs which feed the dikes large or small, and what are the implications for how the dikes themselves form? Does each subswarm originate from a single, periodically reactivated reservoir, or do subswarms emerge from multiple discrete geographic foci? If the latter, are these discrete foci located at the margins of a single large magma body, or do multiple smaller reservoirs define the character of the magmatic center as a whole? Similarly, does the locus of magmatic activity change with time, or are all the foci active simultaneously? Careful study of giant radiating dike swarms on Venus is yielding the data necessary to address these questions and constrain future modeling efforts. Here, using giant radiating dike swarms from the Nemesis Tessera (V14) and Carson (V43) quadrangles as examples, we illustrate some of the dike swarm focal region diversity observed on Venus and briefly explore some

Magma chamber interaction giving rise to asymmetric oscillations

Science.gov (United States)

Walwer, D.; Ghil, M.; Calais, E.

2017-12-01

Geodetic time series at four volcanoes (Okmok, Akutan, Shishaldin, and Réunion) are processed using Multi-channel Singular Spectrum Analysis (M-SSA) and reveal sawtooth-shaped oscillations ; the latter are characterized by short intervals of fast inflations followed by longer intervals of slower deflations. At Okmok and Akutan, the oscillations are first damped and then accentuated. At Okmok, the increase in amplitude of the oscillations is followed by an eruption. We first show that the dynamics of these four volcanoes bears similarities with that of a simple nonlinear, dissipative oscillator, indicating that the inflation-deflation episodes are relaxation oscillations. These observations imply that ab initio dynamical models of magma chambers should possess an asymmetric oscillatory regime. Next, based on the work of Whitehead and Helfrich [1991], we show that a model of two magma chambers — connected by a cylindrical conduit in which the magma viscosity depends on temperature — gives rise to asymmetric overpressure oscillations in the magma reservoirs. These oscillations lead to surface deformations that are consistent with those observed at the four volcanoes in this study. This relaxation oscillation regime occurs only when the vertical temperature gradient in the host rock between the two magma chambers is large enough and when the magma flux entering the volcanic system is sufficiently high. The magma being supplied by a deeper source region, the input flux depends on the pressure difference between the source and the deepest reservoir. When this difference is not sufficiently high, the magma flux exponentially decreases, leading to damped oscillations as observed at Akutan and Okmok. The combination of observational and modeling results clearly supports the role of relaxation oscillations in the dynamics of volcanic systems.

Magma-sponge hypothesis and stratovolcanoes: Case for a compressible reservoir and quasi-steady deep influx at Soufrière Hills Volcano, Montserrat

Science.gov (United States)

Voight, Barry; Widiwijayanti, Christina; Mattioli, Glen; Elsworth, Derek; Hidayat, Dannie; Strutt, M.

2010-02-01

We use well-documented time histories of episodic GPS surface deformation and efflux of compressible magma to resolve apparent magma budget anomalies at Soufrière Hills volcano (SHV) on Montserrat, WI. We focus on data from 2003 to 2007, for an inflation succeeded by an episode of eruption-plus-deflation. We examine Mogi-type and vertical prolate ellipsoidal chamber geometries to accommodate both mineralogical constraints indicating a relatively shallow pre-eruption storage, and geodetic constraints inferring a deeper mean-pressure source. An exsolved phase involving several gas species greatly increases andesite magma compressibility to depths >10 km (i.e., for water content >4 wt%, crystallinity ˜40%), and this property supports the concept that much of the magma transferred into or out of the crustal reservoir could be accommodated by compression or decompression of stored reservoir magma (i.e., the “magma-sponge”). Our results suggest quasi-steady deep, mainly mafic magma influx of the order of 2 m3s-1, and we conclude that magma released in eruptive episodes is approximately balanced by cumulative deep influx during the eruptive episode and the preceding inflation. Our magma-sponge model predicts that between 2003 and 2007 there was no evident depletion of magma reservoir volume at SHV, which comprises tens of km3 with radial dimensions of order ˜1-2 km, in turn implying a long-lived eruption.

Helium isotope data from the Goldfield epithermal system, Nevada: Evidence for volatile input from a primitive mantle source during ore formation

Science.gov (United States)

Hofstra, A. H.; Manning, A. H.

2013-12-01

Goldfield is the largest high sulfidation epithermal gold mining district in the United States with over 130 t of gold production and 23 sq. km. of argillic alteration (with alunite, pyrophyllite, or kaolinite). It formed at 20.0×0.5 Ma in an andesite to rhyolite volcanic field in the ancestral Cascades continental magmatic arc. Previous stable isotope studies of quartz, alunite, and sulfide minerals suggest that the gold ores formed in a magmatic vapor plume derived from a subjacent porphyry intrusion, which displaced and mixed with meteoric groundwater at shallow levels. The isotopic compositions of He, Ne, and Ar trapped in fluid inclusions in hydrothermal minerals (Cu-sulfides and sulfosalts, pyrite, quartz) were measured to further constrain volatile source and migration processes. Gases were released by thermal decrepitation at 300°C and analyzed using a high resolution static sector mass spectrometer. The isotopic compositions of Ne and Ar are typical of air-saturated water (ASW), indicating that the samples contain little nucleogenic Ne or radiogenic Ar derived from underlying old crustal sources. In contrast, He/Ne and He/Ar ratios are much greater than ASW, indicating that a component of He was produced in the subsurface. The wide range of He R/Ra values, 0.4 to 20, suggests that He was derived from both crustal and mantle sources. 4He/40Ar* and 4He/21Ne* systematics are characteristic of magma degassing. The highest R/Ra values (15-20) are well above those previously reported for modern volcanic rocks and geothermal fluids in subduction-related arcs. Such R/Ra values indicate a primitive mantle source, perhaps below the subducting slab. We hypothesize that the discharge of metal-laden fluids from the subjacent porphyry intrusion was influenced by the input of hot volatiles from mafic mantle-derived magmas. This scenario implies a magma column that remained open to the flux of volatiles over a considerable depth range, from the mantle to the shallow

Magma Mixing: Why Picrites are Not So Hot

Science.gov (United States)

Natland, J. H.

2010-12-01

Oxide gabbros or ferrogabbros are the late, low-temperature differentiates of tholeiitic magma and usually form as cumulates that can have 2-30% of the magmatic oxides, ilmenite and magnetite. They are common in the ocean crust and are likely ubiquitous wherever extensive tholeiitic magmatism has occurred, especially beneath thick lava piles such as at Hawaii, Iceland, oceanic plateaus, island arcs and ancient continental crust. When intruded by hot primitive magma including picrite, the oxide-bearing portions of these rocks are readily partially melted or assimilated into the magma and contribute to it a degree of iron and titanium enrichment that is not reflective of the mantle source of the primitive magma. The most extreme examples of such mixing are meimechites and ferropicrites, but this type of end-member mixing is even common in MORB. To the extent this process occurs, the eruptive picrite cannot be used to estimate compositions of partial melts of mantle rocks, nor their eruptive or potential temperatures, using olivine-liquid FeO-MgO backtrack procedures. Most picrites have glasses with compositions approximating those expected from low-pressure multiphase cotectic crystallization, and olivine that on average crystallized from liquids of nearly those compositions. The hallmark of such rocks is the presence of minerals other than olivine among phenocrysts (plagioclase at Iceland, clinopyroxene at many oceanic islands), Fe- and Ti-rich chromian spinel (ankaramites, ferropicrites and meimichites), and in some cases the presence of iron-rich olivine (hortonolite ~Fo65 in ferropicrites), Ti-rich kaersutitic amphibole and even apatite (meimechites); the latter two derive from late-stage, hydrous and geochemically enriched metamorphic or alkalic assimilants. This type of mixing, however, does not necessarily involve depleted and enriched mixing components. To avoid such mixing, primitive melts have to rise primarily through upper mantle rocks of near-zero melt

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.

Modelling of Magma Density and Viscocity Changes and Their Influences towards the Characteristic of Kelud Volcano Eruption

Directory of Open Access Journals (Sweden)

Hanik Humaida

2014-06-01

Full Text Available DOI: 10.17014/ijog.v6i4.129The effusive eruption of Kelud Volcano in 2007 was different from the previous ones, which in general were more explosive. Among others, density and viscosity are factors that determine the type of eruption. Therefore, the study on the difference of the recent eruption style based on the density and viscosity of magma was carried out. The method used in this study was based on geochemical analysis of the rock and then a modeling was established by using the above parameter. The study on the explosive eruption was emphasized on the data of 1990 eruption, whereas the effusive eruption was based on the data of 2007 eruption. The result shows that the magma viscosity of Kelud Volcano depend on the H O concentration as one of the volatile compound in magma, and temperature which gives the exponential equation. The higher the increase of H O content the smaller the value of its viscosity as well as the higher the temperature. The H O content in silica fluid can break the polymer bond of the silica fluid, because a shorter polymer will produce a lower viscosity. The density of the silica content of Kelud Volcano ranges between andesitic and basaltic types, but andesite is more likely. The fluid density of the material of 1990 eruption is different from 2007 eruption. Compared to the 2007, the 1990 eruption material gave a lower density value in its silica fluid than that of the 2007 one. The low density value of the silica fluid of the 1990 eruption material was reflecting a more acid magma. The level of density value of silica fluid depends on its temperature. At the temperature of 1073 K the density of the 1990 Kelud magma is 2810 kg/m3 and the 2007 magma is 2818 kg/m3, whereas at a temperature of 1673 K, the density is 2672 kg/m3 and 2682 kg/m3 of the 1990 and 2007 eruptions respectively. A modeling by using an ideal gas law of Henry’s Law illustrated that the ascent of Kelud’s magma to the surface may cause changes

Magma Dynamics in Dome-Building Volcanoes

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Kendrick, J. E.; Lavallée, Y.; Hornby, A. J.; Schaefer, L. N.; Oommen, T.; Di Toro, G.; Hirose, T.

2014-12-01

The frequent and, as yet, unpredictable transition from effusive to explosive volcanic behaviour is common to active composite volcanoes, yet our understanding of the processes which control this evolution is poor. The rheology of magma, dictated by its composition, porosity and crystal content, is integral to eruption behaviour and during ascent magma behaves in an increasingly rock-like manner. This behaviour, on short timescales in the upper conduit, provides exceptionally dynamic conditions that favour strain localisation and failure. Seismicity released by this process can be mimicked by damage accumulation that releases acoustic signals on the laboratory scale, showing that the failure of magma is intrinsically strain-rate dependent. This character aids the development of shear zones in the conduit, which commonly fracture seismogenically, producing fault surfaces that control the last hundreds of meters of ascent by frictional slip. High-velocity rotary shear (HVR) experiments demonstrate that at ambient temperatures, gouge behaves according to Byerlee's rule at low slip velocities. At rock-rock interfaces, mechanical work induces comminution of asperities and heating which, if sufficient, may induce melting and formation of pseudotachylyte. The viscosity of the melt, so generated, controls the subsequent lubrication or resistance to slip along the fault plane thanks to non-Newtonian suspension rheology. The bulk composition, mineralogy and glass content of the magma all influence frictional behaviour, which supersedes buoyancy as the controlling factor in magma ascent. In the conduit of dome-building volcanoes, the fracture and slip processes are further complicated: slip-rate along the conduit margin fluctuates. The shear-thinning frictional melt yields a tendency for extremely unstable slip thanks to its pivotal position with regard to the glass transition. This thermo-kinetic transition bestows the viscoelastic melt with the ability to either flow or

Cost-benefit analyses for the development of magma power

International Nuclear Information System (INIS)

Haraden, John

1992-01-01

Magma power is the potential generation of electricity from shallow magma bodies in the crust of the Earth. Considerable uncertainty still surrounds the development of magma power, but most of that uncertainty may be eliminated by drilling the first deep magma well. The uncertainty presents no serious impediments to the private drilling of the well. For reasons unrelated to the uncertainty, there may be no private drilling and there may be justification for public drilling. In this paper, we present cost-benefit analyses for private and public drilling of the well. Both analyses indicate there is incentive for drilling. (Author)

A nonparametric approach to forecasting realized volatility

OpenAIRE

Adam Clements; Ralf Becker

2009-01-01

A well developed literature exists in relation to modeling and forecasting asset return volatility. Much of this relate to the development of time series models of volatility. This paper proposes an alternative method for forecasting volatility that does not involve such a model. Under this approach a forecast is a weighted average of historical volatility. The greatest weight is given to periods that exhibit the most similar market conditions to the time at which the forecast is being formed...

Magma wagging and whirling in volcanic conduits

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Liao, Yang; Bercovici, David; Jellinek, Mark

2018-02-01

Seismic tremor characterized by 0.5-7 Hz ground oscillations commonly occur before and during eruptions at silicic volcanoes with widely ranging vent geometries and edifice structures. The ubiquitous characteristics of this tremor imply that its causes are potentially common to silicic volcanoes. Here we revisit and extend to three dimensions the magma-wagging model for tremor (Jellinek and Bercovici, 2011; Bercovici et al., 2013), wherein a stiff magma column rising in a vertical conduit oscillates against a surrounding foamy annulus of bubbly magma, giving rise to tremor. While prior studies were restricted to two-dimensional lateral oscillations, here we explore three-dimensional motion and additional modes of oscillations. In the absence of viscous damping, the magma column undergoes 'whirling' motion: the center of each horizontal section of the column traces an elliptical trajectory. In the presence of viscous effect we identify new 'coiling' and 'uncoiling' column bending shapes with relatively higher and comparable rates of dissipation to the original two-dimensional magma wagging model. We also calculate the seismic P-wave response of the crustal material around the volcanic conduit to the new whirling motions and propose seismic diagnostics for different wagging patterns using the time-lag between seismic stations. We test our model by analyzing pre-eruptive seismic data from the 2009 eruption of Redoubt Volcano. In addition to suggesting that the occurrence of elliptical whirling motion more than 1 week before the eruption, our analysis of seismic time-lags also implies that the 2009 eruption was accompanied by qualitative changes in the magma wagging behavior including fluctuations in eccentricity and a reversal in the direction of elliptical whirling motion when the eruption was immediately impending.

Magma paths at Piton de la Fournaise Volcano

OpenAIRE

Michon , Laurent; Ferrazzini , Valérie; Di Muro , Andrea

2016-01-01

International audience; Several patterns of magma paths have been proposed since the 1980s for Piton de la Fournaise volcano. Given the significant differences, which are presented here, we propose a reappraisal of the magma intrusion paths using a 17-years-long database of volcano-tectonic seismic events and a detailed mapping of the scoria cones. At the edifice scale, the magma propagates along two N120 trending rift zones. They are wide, linear, spotted by small to large scoria cones and r...

Silicic magma differentiation in ascent conduits. Experimental constraints

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Rodríguez, Carmen; Castro, Antonio

2017-02-01

Crystallization of water-bearing silicic magmas in a dynamic thermal boundary layer is reproduced experimentally by using the intrinsic thermal gradient of piston-cylinder assemblies. The standard AGV2 andesite under water-undersaturated conditions is set to crystallize in a dynamic thermal gradient of about 35 °C/mm in 10 mm length capsules. In the hotter area of the capsule, the temperature is initially set at 1200 °C and decreases by programmed cooling at two distinct rates of 0.6 and 9.6 °C/h. Experiments are conducted in horizontally arranged assemblies in a piston cylinder apparatus to avoid any effect of gravity settling and compaction of crystals in long duration runs. The results are conclusive about the effect of water-rich fluids that are expelled out the crystal-rich zone (mush), where water saturation is reached by second boiling in the interstitial liquid. Expelled fluids migrate to the magma ahead of the solidification front contributing to a progressive enrichment in the fluxed components SiO2, K2O and H2O. The composition of water-rich fluids is modelled by mass balance using the chemical composition of glasses (quenched melt). The results are the basis for a model of granite magma differentiation in thermally-zoned conduits with application of in-situ crystallization equations. The intriguing textural and compositional features of the typical autoliths, accompanying granodiorite-tonalite batholiths, can be explained following the results of this study, by critical phenomena leading to splitting of an initially homogeneous magma into two magma systems with sharp boundaries. Magma splitting in thermal boundary layers, formed at the margins of ascent conduits, may operate for several km distances during magma transport from deep sources at the lower crust or upper mantle. Accordingly, conduits may work as chromatographic columns contributing to increase the silica content of ascending magmas and, at the same time, leave behind residual mushes that

Na, Rb and Cs partitioning between metal, silicate and sulfide: Implications for volatile depletion in terrestrial planets

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Boujibar, A.; Fei, Y.; Du, Z.; Righter, K.; Bullock, E. S.

2017-12-01

Inner Solar System materials are known for their depletion in volatile elements, including the moderately volatile alkalis: Na, K, Rb, and Cs. The origin of this depletion is still uncertain, as several processes could have been involved, during the nebular condensation or planetary accretion. Volatile depletion is commonly estimated through comparison of alkali concentrations relatively to those of chondrites, assuming they remain in planetary mantles during core segregation. However, experimental studies show that substantial K can partition into metals that are enriched in sulfur and oxygen. Several models have also suggested that sulfides may have played an important role during episodes of sulfide segregation from a crystallizing magma ocean (sulfide matte) or accretion of S-rich planetary embryos. For Mercury, a sulfide layer could be present between core and mantle, due to immiscibility between Si-rich and S-rich metals. Therefore, here we investigate whether alkali elements (Na, Cs and Rb) could be partly sequestered in planetary cores during their differentiation. We conducted experiments at high pressure and temperature (1 to 5 GPa and up to 1900 °C) to determine partition coefficients of Na, Rb and Cs between metal and silicate. Our results show that pressure, temperature, sulfur and oxygen in metals enhance the partitioning of Na, Rb and Cs into metals, as previously found for K. For all three investigated alkalis (Na, Rb and Cs), we found a maximum partition coefficient of 1 between sulfides containing 13 wt% O and silicate melt. Therefore, S-rich cores or sulfide layers formed due to immiscibility in Fe-S-O systems could have acted as important geochemical reservoirs for alkali elements. Using our experimental data and different assumptions on initial bulk abundances, we evaluate volatile depletion in terrestrial planets, by comparing resulting mantle alkali concentrations after core segregation, with actual concentrations in the Earth's mantle.

Orientation of the eruption fissures controlled by a shallow magma chamber in Miyakejima

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Nobuo Geshi

2016-11-01

Full Text Available Orientation of the eruption fissures and composition of the lavas of the Miyakejima volcano indicate tectonic influence of a shallow magma chamber on the distribution of eruption fissures. We examined the distributions and magmatic compositions of 23 fissures that formed within the last 2800 years, based on a field survey and a new dataset of 14C ages. The dominant orientation of the eruption fissures in the central portion of the volcano was found to be NE-SW, which is perpendicular to the direction of regional maximum horizontal compressive stress (σHmax. Magmas that show evidences of magma mixing between basaltic and andesitic magmas erupted mainly from the eruption fissures with a higher offset angle from the regional σHmax direction. The presence of a shallow dike-shaped magma chamber controls the distribution of the eruption fissures. The injection of basaltic magma into the shallow andesitic magma chamber caused the temporal rise of internal magmatic pressure in the shallow magma chamber. Dikes extending from the andesitic magma chamber intrude along the local compressive stress field which is generated by the internal excess pressure of the andesitic magma chamber. As the result, the eruption fissures trend parallel to the elongation direction of the shallow magma chamber. Injection of basaltic magma into the shallow andesitic magma chamber caused the magma mixing. Some basaltic dikes from the deep-seated magma chamber reach the ground surface without intersection with the andesitic magma chamber. The patterns of the eruption fissures can be modified in the future as was observed in the case of the destruction of the shallow magma chamber during the 2000 AD eruption.

The Surtsey Magma Series.

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Schipper, C Ian; Jakobsson, Sveinn P; White, James D L; Michael Palin, J; Bush-Marcinowski, Tim

2015-06-26

The volcanic island of Surtsey (Vestmannaeyjar, Iceland) is the product of a 3.5-year-long eruption that began in November 1963. Observations of magma-water interaction during pyroclastic episodes made Surtsey the type example of shallow-to-emergent phreatomagmatic eruptions. Here, in part to mark the 50(th) anniversary of this canonical eruption, we present previously unpublished major-element whole-rock compositions, and new major and trace-element compositions of sideromelane glasses in tephra collected by observers and retrieved from the 1979 drill core. Compositions became progressively more primitive as the eruption progressed, with abrupt changes corresponding to shifts between the eruption's four edifices. Trace-element ratios indicate that the chemical variation is best explained by mixing of different proportions of depleted ridge-like basalt, with ponded, enriched alkalic basalt similar to that of Iceland's Eastern Volcanic Zone; however, the systematic offset of Surtsey compositions to lower Nb/Zr than other Vestmannaeyjar lavas indicates that these mixing end members are as-yet poorly contained by compositions in the literature. As the southwestern-most volcano in the Vestmannaeyjar, the geochemistry of the Surtsey Magma Series exemplifies processes occurring within ephemeral magma bodies on the extreme leading edge of a propagating off-axis rift in the vicinity of the Iceland plume.

Deep magma transport at Kilauea volcano, Hawaii

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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

Solubility of reduced C-O-H volatiles in basalt as a function of fCO: Implications for the early Earth, the moon, and Mars

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Armstrong, L. S.; Hirschmann, M. M.

2013-12-01

Magmatic C-O-H volatiles influence the evolution of planetary atmospheres and, when precipitated and stored in solidified mantles, the dynamical evolution of planetary interiors. In the case of the Earth, the fO2 of the mantle near the end of core formation should have been ~IW-2, and subsequently increased to present-day values [1]. In experiments with fO2 ≤ IW, a variety of reduced volatile species have been found dissolved in magmas, including H2, CH4, CO, Fe(CO)5 and possibly Fe(CO)62+. However, there remains significant disagreement regarding the identity and concentrations of these volatiles in natural magmas, as well as their dependencies on intensive variables (T, P, fO2, fCO, fH2)[2-6]. Previous experiments document the importance of CO-related species [2,6], but were conducted over a limited range of fCO and had potentially interfering effects from poorly controlled variations in H2O. We aim to experimentally determine the solubility of C-O-H volatiles in basaltic magmas under reduced, C-saturated conditions while minimizing water content. The relationship between volatile speciation, fO2, and fCO at 1.2 GPa and 1400°C are constrained, laying the groundwork for a more extensive study at a range of conditions relevant to the interiors of the terrestrial planets and the moon. Both MORB and a martian basalt were studied, contained in Pt-C capsules with Fe × Pt × Si metal added to generate reducing conditions and to monitor fO2. A nominal amount of H2O is unavoidable in experimental charges, but was minimized by drying capsules prior to welding. Phase compositions were determined by electron microprobe and volatile concentrations were measured by FTIR spectroscopy. In preliminary experiments with fO2 of IW-0.70 to +1.75 (corresponding to log fCO of 3.3-4.5), H2O and CO2 concentrations as determined by FTIR are 113-13283 and 12-721 ppm, respectively. Most experiments also display a small FTIR peak at 2205 cm-1, whereas the most reduced experiments lack

Viscosity controlled magma-carbonate interaction: a comparison of Mt. Vesuvius (Italy) and Mt. Merapi (Indonesia).

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Blythe, L. S.; Misiti, V.; Masotta, M.; Taddeucci, J.; Freda, C.; Troll, V. R.; Deegan, F. M.; Jolis, E. M.

2012-04-01

Magma-carbonate interaction is increasingly seen as a viable and extremely important cause of magma contamination, and the generation of a crustally sourced CO2 phase (Goff et al., 2001; Freda et al., 2010). Even though the process is well recognized at certain volcanoes e.g. Popocatépetl, (Mexico); Merapi, (Indonesia); and Colli Albani, (Italy) (Goff et al., 2001; Deegan et al., 2010; Freda et al., 2010), neither the kinetics of carbonate assimilation nor its consequences for controlling the explosivity of eruptions have been constrained. Here we show the results of magma-carbonate interaction experiments conducted at 1200 °C and 0.5 GPa for varying durations (0 s, 60 s, 90 s and 300 s) for the Mt. Merapi (Indonesia) and Mt. Vesuvius (Italy) volcanic systems. We performed experiments using glassy starting materials specific to each volcano (shoshonite for Mt. Vesuvius, basaltic-andesite for Mt. Merapi) with different degrees of hydration (anhydrous vs hydration with ~ 2 wt % water) and using carbonate fragments of local origin; see Deegan et al., (2010) and Jolis et al., (2011). Experimental products include a gas phase (CO2-rich) and two melt phases, one pristine (Ca-normal) and one contaminated (Ca-rich) separated by a 'contamination front' which propagates outwards from the carbonate clast. Vesicles appear to nucleate in the contaminated glass and then migrate into the pristine one. Both contamination front propagation and bubble migration away from the carbonate are slower in anhydrous basaltic-andesite (Merapi anhydrous series) than in hydrated basaltic-andesite and shoshonite (Merapi and Vesuvius hydrated series), suggesting that assimilation speed is strongly controlled by the degree of hydration and the SiO2 content, both of which influence melt viscosity and hence diffusivity. As the carbonate dissolution proceeds in our experiments, initially dissolved and eventually exsolved CO2 builds up in the contaminated Ca-rich melt phase. Once melt volatile

Partially molten magma ocean model

International Nuclear Information System (INIS)

Shirley, D.N.

1983-01-01

The properties of the lunar crust and upper mantle can be explained if the outer 300-400 km of the moon was initially only partially molten rather than fully molten. The top of the partially molten region contained about 20% melt and decreased to 0% at 300-400 km depth. Nuclei of anorthositic crust formed over localized bodies of magma segregated from the partial melt, then grew peripherally until they coverd the moon. Throughout most of its growth period the anorthosite crust floated on a layer of magma a few km thick. The thickness of this layer is regulated by the opposing forces of loss of material by fractional crystallization and addition of magma from the partial melt below. Concentrations of Sr, Eu, and Sm in pristine ferroan anorthosites are found to be consistent with this model, as are trends for the ferroan anorthosites and Mg-rich suites on a diagram of An in plagioclase vs. mg in mafics. Clustering of Eu, Sr, and mg values found among pristine ferroan anorthosites are predicted by this model

Dynamics of differentiation in magma reservoirs

Science.gov (United States)

Jaupart, Claude; Tait, Stephen

1995-09-01

In large magma chambers, gradients of temperature and composition develop due to cooling and to fractional crystallization. Unstable density differences lead to differential motions between melt and crystals, and a major goal is to explain how this might result in chemical differentiation of magma. Arriving at a full description of the physics of crystallizing magma chambers is a challenge because of the large number of processes potentially involved, the many coupled variables, and the different geometrical shapes. Furthermore, perturbations are caused by the reinjection of melt from a deep source, eruption to the Earth's surface, and the assimilation of country rock. Physical models of increasing complexity have been developed with emphasis on three fundamental approaches. One is, given that large gradients in temperature and composition may occur, to specify how to apply thermodynamic constraints so that coexisting liquid and solid compositions may be calculated. The second is to leave the differentiation trend as the solution to be found, i.e., to specify how cooling occurs and to predict the evolution of the composition of the residual liquid and of the solid forming. The third is to simplify the physics so that the effects of coupled heat and mass transfer may be studied with a reduced set of variables. The complex shapes of magma chambers imply that boundary layers develop with density gradients at various angles to gravity, leading to various convective flows and profiles qf liquid stratification. Early studies were mainly concerned with describing fluid flow in the liquid interior of large reservoirs, due to gradients developed at the margins. More recent work has focused on the internal structure and flow field of boundary layers and in particular on the gradients of solid fraction and interstitial melt composition which develop within them. Crystal settling may occur in a surprisingly diverse range of regimes and may lead to intermittent deposition

Thermally-assisted Magma Emplacement Explains Restless Calderas.

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Amoruso, Antonella; Crescentini, Luca; D'Antonio, Massimo; Acocella, Valerio

2017-08-11

Many calderas show repeated unrest over centuries. Though probably induced by magma, this unique behaviour is not understood and its dynamics remains elusive. To better understand these restless calderas, we interpret deformation data and build thermal models of Campi Flegrei caldera, Italy. Campi Flegrei experienced at least 4 major unrest episodes in the last decades. Our results indicate that the inflation and deflation of magmatic sources at the same location explain most deformation, at least since the build-up of the last 1538 AD eruption. However, such a repeated magma emplacement requires a persistently hot crust. Our thermal models show that this repeated emplacement was assisted by the thermal anomaly created by magma that was intruded at shallow depth ~3 ka before the last eruption. This may explain the persistence of the magmatic sources promoting the restless behaviour of the Campi Flegrei caldera; moreover, it explains the crystallization, re-melting and mixing among compositionally distinct magmas recorded in young volcanic rocks. Our model of thermally-assisted unrest may have a wider applicability, possibly explaining also the dynamics of other restless calderas.

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.

«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.

Chondritic Mn/Na ratio and limited post-nebular volatile loss of the Earth

Science.gov (United States)

Siebert, Julien; Sossi, Paolo A.; Blanchard, Ingrid; Mahan, Brandon; Badro, James; Moynier, Frédéric

2018-03-01

The depletion pattern of volatile elements on Earth and other differentiated terrestrial bodies provides a unique insight as to the nature and origin of planetary building blocks. The processes responsible for the depletion of volatile elements range from the early incomplete condensation in the solar nebula to the late de-volatilization induced by heating and impacting during planetary accretion after the dispersion of the H2-rich nebular gas. Furthermore, as many volatile elements are also siderophile (metal-loving), it is often difficult to deconvolve the effect of volatility from core formation. With the notable exception of the Earth, all the differentiated terrestrial bodies for which we have samples have non-chondritic Mn/Na ratios, taken as a signature of post-nebular volatilization. The bulk silicate Earth (BSE) is unique in that its Mn/Na ratio is chondritic, which points to a nebular origin for the depletion; unless the Mn/Na in the BSE is not that of the bulk Earth (BE), and has been affected by core formation through the partitioning of Mn in Earth's core. Here we quantify the metal-silicate partitioning behavior of Mn at deep magma ocean pressure and temperature conditions directly applicable to core formation. The experiments show that Mn becomes more siderophile with increasing pressure and temperature. Modeling the partitioning of Mn during core formation by combining our results with previous data at lower P-T conditions, we show that the core likely contains a significant fraction (20 to 35%) of Earth's Mn budget. However, we show that the derived Mn/Na value of the bulk Earth still lies on the volatile-depleted end of a trend defined by chondritic meteorites in a Mn/Na vs Mn/Mg plot, which tend to higher Mn/Na with increasing volatile depletion. This suggests that the material that formed the Earth recorded similar chemical fractionation processes for moderately volatile elements as chondrites in the solar nebula, and experienced limited post

Magma ascent, fragmentation and depositional characteristics of "dry" maar volcanoes: Similarities with vent-facies kimberlite deposits

Science.gov (United States)

Berghuijs, Jaap F.; Mattsson, Hannes B.

2013-02-01

Several maar craters within the Lake Natron-Engaruka monogenetic volcanic field (LNE-MVF) of northern Tanzania show compelling evidence for magmatic fragmentation and dry deposition. This is in contradiction of the common belief that most maars are formed through the explosive interaction between ascending magma and ground- or surface water. We here present a detailed study on the eruptive and depositional characteristics of the Loolmurwak and Eledoi maar volcanoes, two of the largest craters in the LNE-MVF, focusing on high-resolution stratigraphy, sedimentology, grain size distribution, pyroclast textures and morphologies, bulk geochemistry and mineral chemistry. At both maars, ejected material has been emplaced by a combination of pyroclastic surges and fallout. Indicators of phreatomagmatic fragmentation and wet deposition, such as impact sags, accretionary lapilli, vesiculated tuffs and plastering against obstacles, are absent in the deposits. Juvenile material predominantly occurs as fluidal-shaped vesicular melt droplets and contains no glass shards produced by the breakage of bubble walls. The Eledoi deposits comprise a large amount of inversely graded beds and lenses, which result from grain flow in a dry depositional environment. Preferential deposition of fine material toward the northern side of its crater can be related to effective wind winnowing in a dry eruption plume. This large variety of observations testifies to the dominance of magmatic fragmentation as well as dry deposition at the Loolmurwak and Eledoi maars, which is in line with what has been found for other structures in the LNE-MVF but contrasts with current ideas on maar formation. We infer that a volatile-rich, olivine melilitic magma was formed by small amounts of partial melting at upper mantle depths. With minimum average ascent rates of 5.3 m s- 1 for Loolmurwak and 26.2 m s- 1 for Eledoi, this magma rapidly moved toward the surface and exsolved a substantial amount of volatiles

The Relationship Between Carbonatitic, Melilititic and Potassic Trachytic Magma Types at the Saltpeterkop Carbonatite Complex, Sutherland, South Africa

Science.gov (United States)

Janney, P. E.; Marageni, M.

2016-12-01

The 74 Ma Saltpeterkop Carbonatite Complex near Sutherland, South Africa, is unusual in that it is one of the few southern African carbonatites with preserved volcanic features, including a 1 km-diameter tuff ring composed of silicified volcaniclastic breccia. Around the complex, the regionally flat-lying Karoo strata have been dramatically upwarped, with dips away from the Complex as high as 45°. Further, within about a 10 km radius of the center of the complex are hundreds of dikes, sills and diatremes composed mainly of carbonatite, potassic trachyte and olivine melilitite, with the spatial density of these intrusions decreasing with increasing distance. We have recently completed an in-depth geochemical reconnaissance of the Saltpeterkop complex, involving field sampling and whole-rock major and trace element analysis, with radiogenic and stable isotope measurements in progress. While the association with potassic trachytes is relatively common in southern African carbonatites, the presence of significant amounts of primitive olivine melilitite (30-40 wt.% SiO2, Mg# = 61-74) is unusual. Our preliminary model for the origin of the complex involves (1) ascent and intrusion of a mantle-derived carbonated and potassic magma into the mid-to upper crust, (2a) separation of an alkali carbonatite phase from this magma, resulting in intensive local fenitization and partial melting of mid-crustal rocks (thereby forming potassic trachytes), and possibly triggering the initial eruption, (2b) small amounts of primitive, but now less potassic, mantle-derived magma are emplaced as olivine melilitite dikes and diatremes, and (3) differentiation of the mantle-derived magma to generate significant quantities of mainly calcio- and ferro-carbonatite magmas emplaced as dykes and sills.

Crystalline heterogeneities and instabilities in thermally convecting magma chamber

Science.gov (United States)

Culha, C.; Suckale, J.; Qin, Z.

2016-12-01

A volcanic vent can supply different densities of crystals over an eruption time period. This has been seen in Hawai'i's Kilauea Iki 1959 eruption; however it is not common for all Kilauea or basaltic eruptions. We ask the question: Under what conditions can homogenous magma chamber cultivate crystalline heterogeneities? In some laboratory experiments and numerical simulations, a horizontal variation is observed. The region where crystals reside is identified as a retention zone: convection velocity balances settling velocity. Simulations and experiments that observe retention zones assume crystals do not alter the convection in the fluid. However, a comparison of experiments and simulations of convecting magma with crystals suggest that large crystal volume densities and crystal sizes alter fluid flow considerably. We introduce a computational method that fully resolves the crystalline phase. To simulate basaltic magma chambers in thermal convection, we built a numerical solver of the Navier-Stoke's equation, continuity equation, and energy equation. The modeled magma is assumed to be a viscous, incompressible fluid with a liquid and solid phase. Crystals are spherical, rigid bodies. We create Rayleigh-Taylor instability through a cool top layer and hot bottom layer and update magma density while keeping crystal temperature and size constant. Our method provides a detailed picture of magma chambers, which we compare to other models and experiments to identify when and how crystals alter magma chamber convection. Alterations include stratification, differential settling and instabilities. These characteristics are dependent on viscosity, convection vigor, crystal volume density and crystal characteristics. We reveal that a volumetric crystal density variation may occur over an eruption time period, if right conditions are met to form stratifications and instabilities in magma chambers. These conditions are realistic for Kilauea Iki's 1959 eruption.

Complexities in Shallow Magma Transport at Kilauea (Invited)

Science.gov (United States)

Swanson, D. A.

2013-12-01

The standard model of Kilauea's shallow plumbing system includes magma storage under the caldera and conduits in the southwest rift zone (SWRZ) and the east rift zone (ERZ). As a field geologist, I find that seemingly aberrant locations and trends of some eruptive vents indicate complexities in shallow magma transport not addressed by the standard model. This model is not wrong but instead incomplete, because it does not account for the development of offshoots from the main plumbing. These offshoots supply magma to the surface at places that tell us much about the complicated stress system within the volcano. Perhaps most readily grasped are fissures peripheral to the north and south sides of the caldera. Somehow magma can apparently be injected into caldera-bounding faults from the summit reservoir complex, but the process and pathways are unclear. Of more importance is the presence of fissures with ENE trends on the east side of the caldera, including Kilauea Iki. Is this a rift zone that forms an acute angle with the ERZ? I think there is another explanation: the main part of the ERZ has migrated ~5 km SSE during the past few tens of thousands of years owing to seaward movement of the south flank, but older parts of the rift zone can be reactivated. The fissures east of the caldera have the ERZ trend and may record such reactivation; this interpretation includes the location of the largest eruption (15th century) known from Kilauea. Whether or not this interpretation has validity, the question remains: what changes in the plumbing system allow magma to erupt east of the caldera? The SWRZ can be divided into two sections, the SWRZ proper and the seismically active part (SASWRZ) southeast of the SWRZ. The total width of both sections is ~4 km. The SWRZ might be migrating SSE, as is the ERZ. Fissures in the SWRZ proper trend SW. Fissures in the SASWRZ, however, have ENE trends like that of the ERZ, although, because of en echelon offsets, the fissure zone itself

Better constraints on the size and volatile content of the Mount St. Helens magma reservoir following the end of the 2004-2008 eruption

Science.gov (United States)

Mastin, L. G.; Lisowski, M.; Beeler, N.; Roeloffs, E.

2008-12-01

The October 2004-January 2008 eruption of Mount St. Helens produced about 93 million cubic meters dense-rock equivalent (DRE) lava at a continuous rate that decreased monotonically from ~6 m3 s-1 to zero over its duration. From late October 2004 through the end of the eruption, continuous GPS stations around the mountain recorded inward deflation at a rate that dropped monotonically below the noise level by early 2007. The geodetic signal is consistent with a volume change Δ Vc of ~16-25M m3 in an ellipsoidal reservoir of volume Vc centered at ~9-14 km depth beneath the crater. Throughout the eruption we used physically based models to extrapolate trends in lava-dome volume and deflation, and to forecast the duration and final erupted volume, Ve, using assumed or geologically constrained values of Vc, average recharge rate R into the reservoir, and compressibilities of magma (Km = ( 1/ρ m )( ∂ ρ m /∂ p )) and of the reservoir (Kc = ( 1/Vc )( ∂ Vc /∂ p )), where ρ m is magma density and p is pressure). Curves that neglected recharge consistently under-predicted both the final duration and volume, while those that assumed a constant recharge rate predicted indefinite duration and volume. The fact that the eruption ended several months after deflation stopped suggests that the long-term average recharge was close to zero, or at least much less than the average eruption rate. The discrepancy between Ve (93M m3) and Δ VC (16-25M m3) can be accounted for by the elastic relation Ve /Δ Vc = ( 1 + Km /Kc ), with Km = 3 - 4 × 10- 10 Pa-1 calculated for reservoir magma with 1- 1.5% bubbles (constrained from gas studies of the erupted lava), and Kc = 1.1 - 1.5 × 10 - 10 Pa-1. Assuming that the pressure drop dp in the reservoir was only slightly greater than the ~5 MPa increase in pressure at the 2004 vent elevation due to growth of the 220-m-high lava dome, the elastic relation Ve = VC dp( Kc + Km ) suggests that the eruption could have been fed by a reservoir

Hydrogen isotopic fractionation during crystallization of the terrestrial magma ocean

Science.gov (United States)

Pahlevan, K.; Karato, S. I.

2016-12-01

Models of the Moon-forming giant impact extensively melt and partially vaporize the silicate Earth and deliver a substantial mass of metal to the Earth's core. The subsequent evolution of the terrestrial magma ocean and overlying vapor atmosphere over the ensuing 105-6 years has been largely constrained by theoretical models with remnant signatures from this epoch proving somewhat elusive. We have calculated equilibrium hydrogen isotopic fractionation between the magma ocean and overlying steam atmosphere to determine the extent to which H isotopes trace the evolution during this epoch. By analogy with the modern silicate Earth, the magma ocean-steam atmosphere system is often assumed to be chemically oxidized (log fO2 QFM) with the dominant atmospheric vapor species taken to be water vapor. However, the terrestrial magma ocean - having held metallic droplets in suspension - may also exhibit a much more reducing character (log fO2 IW) such that equilibration with the overlying atmosphere renders molecular hydrogen the dominant H-bearing vapor species. This variable - the redox state of the magma ocean - has not been explicitly included in prior models of the coupled evolution of the magma ocean-steam atmosphere system. We find that the redox state of the magma ocean influences not only the vapor speciation and liquid-vapor partitioning of hydrogen but also the equilibrium isotopic fractionation during the crystallization epoch. The liquid-vapor isotopic fractionation of H is substantial under reducing conditions and can generate measurable D/H signatures in the crystallization products but is largely muted in an oxidizing magma ocean and steam atmosphere. We couple equilibrium isotopic fractionation with magma ocean crystallization calculations to forward model the behavior of hydrogen isotopes during this epoch and find that the distribution of H isotopes in the silicate Earth immediately following crystallization represents an oxybarometer for the terrestrial

Magma Ocean Depth and Oxygen Fugacity in the Early Earth--Implications for Biochemistry.

Science.gov (United States)

Righter, Kevin

2015-09-01

A large class of elements, referred to as the siderophile (iron-loving) elements, in the Earth's mantle can be explained by an early deep magma ocean on the early Earth in which the mantle equilibrated with metallic liquid (core liquid). This stage would have affected the distribution of some of the classic volatile elements that are also essential ingredients for life and biochemistry - H, C, S, and N. Estimates are made of the H, C, S, and N contents of Earth's early mantle after core formation, considering the effects of variable temperature, pressure, oxygen fugacity, and composition on their partitioning. Assessment is made of whether additional, exogenous, sources are required to explain the observed mantle concentrations, and areas are identified where additional data and experimentation would lead to an improved understanding of this phase of Earth's history.

The roles of fractional crystallization, magma mixing, crystal mush remobilization and volatile-melt interactions in the genesis of a young basalt-peralkaline rhyolite suite, the greater Olkaria volcanic complex, Kenya Rift valley

Science.gov (United States)

Macdonald, R.; Belkin, H.E.; Fitton, J.G.; Rogers, N.W.; Nejbert, K.; Tindle, A.G.; Marshall, A.S.

2008-01-01

The Greater Olkaria Volcanic Complex is a young (???20 ka) multi-centred lava and dome field dominated by the eruption of peralkaline rhyolites. Basaltic and trachytic magmas have been erupted peripherally to the complex and also form, with mugearites and benmoreites, an extensive suite of magmatic inclusions in the rhyolites. The eruptive rocks commonly represent mixed magmas and the magmatic inclusions are themselves two-, three- or four-component mixes. All rock types may carry xenocrysts of alkali feldspar, and less commonly plagioclase, derived from magma mixing and by remobilization of crystal mushes and/or plutonic rocks. Xenoliths in the range gabbro-syenite are common in the lavas and magmatic inclusions, the more salic varieties sometimes containing silicic glass representing partial melts and ranging in composition from anorthite ?? corundum- to acmite-normative. The peralkaline varieties are broadly similar, in major element terms, to the eruptive peralkaline rhyolites. The basalt-trachyte suite formed by a combination of fractional crystallization, magma mixing and resorption of earlier-formed crystals. Matrix glass in metaluminous trachytes has a peralkaline rhyolitic composition, indicating that the eruptive rhyolites may have formed by fractional crystallization of trachyte. Anomalous trace element enrichments (e.g. ??? 2000 ppm Y in a benmoreite) and negative Ce anomalies may have resulted from various Na- and K-enriched fluids evolving from melts of intermediate composition and either being lost from the system or enriched in other parts of the reservoirs. A small group of nepheline-normative, usually peralkaline, magmatic inclusions was formed by fluid transfer between peralkaline rhyolitic and benmoreitic magmas. The plumbing system of the complex consists of several independent reservoirs and conduits, repeatedly recharged by batches of mafic magma, with ubiquitous magma mixing. ?? The Author 2008. Published by Oxford University Press. All

Zircon reveals protracted magma storage and recycling beneath Mount St. Helens

Science.gov (United States)

Claiborne, L.L.; Miller, C.F.; Flanagan, D.M.; Clynne, M.A.; Wooden, J.L.

2010-01-01

Current data and models for Mount St. Helens volcano (Washington, United States) suggest relatively rapid transport from magma genesis to eruption, with no evidence for protracted storage or recycling of magmas. However, we show here that complex zircon age populations extending back hundreds of thousands of years from eruption age indicate that magmas regularly stall in the crust, cool and crystallize beneath the volcano, and are then rejuvenated and incorporated by hotter, young magmas on their way to the surface. Estimated dissolution times suggest that entrained zircon generally resided in rejuvenating magmas for no more than about a century. Zircon elemental compositions reflect the increasing influence of mafic input into the system through time, recording growth from hotter, less evolved magmas tens of thousands of years prior to the appearance of mafic magmas at the surface, or changes in whole-rock geochemistry and petrology, and providing a new, time-correlated record of this evolution independent of the eruption history. Zircon data thus reveal the history of the hidden, long-lived intrusive portion of the Mount St. Helens system, where melt and crystals are stored for as long as hundreds of thousands of years and interact with fresh influxes of magmas that traverse the intrusive reservoir before erupting. ?? 2010 Geological Society of America.

A petrogenetic model of the relationships among achondritic meteorites

Science.gov (United States)

Stolper, E.; Hays, J. F.; Mcsween, H. Y., Jr.

1979-01-01

Petrological evidence is used to support the hypothesis that although the magma source regions and parent bodies of basaltic achondrite, shergottite, nakhlite, and chassignite meteorites are clearly distinct, they may be simply related. It is proposed that the peridotites which on partial melting generated the parent magmas of the shergottite meteorites differed from those which gave rise to eucritic magmas by being enriched in a component rich in alkalis and other volatiles. Similarly, the source regions of the parent magmas of the nakhlite and chassignite meteorites differed from those on the shergottite parent body by being still richer in this volatile-rich component. These regions could have been related by processes such as mixture of variable amounts of volatile-rich and volatile-poor components in planetary or nebular settings, or alternatively by variable varying degrees of volatile loss from volatile-rich materials.

Shallow magma diversions during explosive diatreme-forming eruptions.

Science.gov (United States)

Le Corvec, Nicolas; Muirhead, James D; White, James D L

2018-04-13

The diversion of magma is an important mechanism that may lead to the relocation of a volcanic vent. Magma diversion is known to occur during explosive volcanic eruptions generating subterranean excavation and remobilization of country and volcanic rocks. However, feedbacks between explosive crater formation and intrusion processes have not been considered previously, despite their importance for understanding evolving hazards during volcanic eruptions. Here, we apply numerical modeling to test the impacts of excavation and subsequent infilling of diatreme structures on stress states and intrusion geometries during the formation of maar-diatreme complexes. Explosive excavation and infilling of diatremes affects local stress states which inhibits magma ascent and drives lateral diversion at various depths, which are expected to promote intra-diatreme explosions, host rock mixing, and vent migration. Our models demonstrate novel mechanisms explaining the generation of saucer-shaped sills, linked with magma diversion and enhanced intra-diatreme explosive fragmentation during maar-diatreme volcanism. Similar mechanisms will occur at other volcanic vents producing crater-forming eruptions.

Io: Loki Patera as a Magma Sea

Science.gov (United States)

Matson, Dennis L.; Davies, Ashley Gerard; Veeder, Glenn J.; Rathbun, Julie A.; Johnson, Torrence V.; Castillo, Julie C.

2006-01-01

We develop a physical model for Loki Patera as a magma sea. We calculate the total volume of magma moving through the Loki Patera volcanic system every resurfacing cycle (approx.540 days) and the resulting variation in thermal emission. The rate of magma solidification at times reaches 3 x 10(exp 6) kg per second, with a total solidified volume averaging 100 cu km per year. A simulation of gas physical chemistry evolution yields the crust porosity profile and the timescale when it will become dense enough to founder in a manner consistent with observations. The Loki Patera surface temperature distribution shows that different areas are at different life cycle stages. On a regional scale, however, there can be coordinated activity, indicated by the wave of thermal change which progresses from Loki Patera's SW quadrant toward the NE at a rate of approx.1 km per day. Using the observed surface temperature distribution, we test several mechanisms for resurfacing Loki Patera, finding that resurfacing with lava flows is not realistic. Only the crustal foundering process is consistent with observations. These tests also discovered that sinking crust has a 'heat deficit' which promotes the solidification of additional magma onto the sinking plate ("bulking up"). In the limiting case, the mass of sinking material can increase to a mass of approx.3 times that of the foundering plate. With all this solid matter sinking, there is a compensating upward motion in the liquid magma. This can be in excess of 2 m per year. In this manner, solid-liquid convection is occurring in the sea.

Stochastic volatility of volatility in continuous time

DEFF Research Database (Denmark)

Barndorff-Nielsen, Ole; Veraart, Almut

This paper introduces the concept of stochastic volatility of volatility in continuous time and, hence, extends standard stochastic volatility (SV) models to allow for an additional source of randomness associated with greater variability in the data. We discuss how stochastic volatility...... of volatility can be defined both non-parametrically, where we link it to the quadratic variation of the stochastic variance process, and parametrically, where we propose two new SV models which allow for stochastic volatility of volatility. In addition, we show that volatility of volatility can be estimated...

The expected greenhouse benefits from developing magma power at Long Valley, California

International Nuclear Information System (INIS)

Haraden, John.

1995-01-01

Magma power is the production of electricity from shallow magma bodies. Before magma becomes a practical source of power, many engineering problems must still be solved. When they are solved, the most likely site for the first magma power plant is Long Valley, California, USA. In this paper, we examine the greenhouse benefits from developing Long Valley. By generating magma power and by curtailing an equal amount of fossil power, we estimate the expected mass and the expected discounted value of reduced CO 2 emissions. For both measures, the expected benefits seem to be substantial. (author)

Magma chamber processes in central volcanic systems of Iceland

DEFF Research Database (Denmark)

Þórarinsson, Sigurjón Böðvar; Tegner, Christian

2009-01-01

are composed of 2-10 m thick melanocratic layers rich in clinopyroxene and sometimes olivine, relative to the thicker overlying leucocratic oxide gabbros. While the overall compositional variation is limited (Mg# clinopyroxene 72-84; An% plagioclase 56-85), the melanocratic bases display spikes in Mg# and Cr2O......3 of clinopyroxene and magnetite indicative of magma replenishment. Some macrorhythmic units show mineral trends indicative of up-section fractional crystallisation over up to 100 m, whereas others show little variation. Two populations of plagioclase crystals (large, An-rich and small, less An......-rich) indicate that the recharge magma carried plagioclase xenocrysts (high An-type). The lack of evolved gabbros suggests formation in a dynamic magma chamber with frequent recharge, tapping and fractionation. Modelling of these compositional trends shows that the parent magma was similar to known transitional...

The 1994-2001 eruptive period at Rabaul, Papua New Guinea: Petrological and geochemical evidence for basalt injections into a shallow dacite magma reservoir, and significant SO2 flux

Science.gov (United States)

Patia, H.; Eggins, S. M.; Arculus, R. J.; McKee, C. O.; Johnson, R. W.; Bradney, A.

2017-10-01

The eruptions that began at Rabaul Caldera on 19 September 1994 had two focal points, the vents Tavurvur and Vulcan, located 6 km apart on opposing sides of the caldera. Vulcan eruptives define a tight cluster of dacite compositions, whereas Tavurvur eruptives span an array from equivalent dacite compositions to mafic andesites. The eruption of geochemically and mineralogically identical dacites from both vents indicates sourcing from the same magma reservoir. This, together with previously reported H2O-CO2 volatile contents of dacite melt inclusions, a caldera-wide seismic low-velocity zone, and a seismically active caldera ring fault structure are consistent with the presence at 3-6 km depth of an extensive, tabular dacitic magma body having volume of about 15-150 km3. The Tavurvur andesites form a linear compositional array and have strongly bimodal phenocryst assemblages that reflect dacite hybridisation with a mafic basalt. The moderately large volume SO2 flux documented in the Tavurvur volcanic plume (and negligible SO2 flux in the Vulcan plume) combined with high dissolved S contents of basaltic melt inclusions trapped in olivine of Tavurvur eruptives, indicate that the amount of degassed basaltic magma was 0.1 km3 and suggest that the injection of this magma was confined to the Tavurvur-side (eastern to northeastern sector) of the caldera. Circumstantial evidence suggests that the eruption was triggered and evolved in response to a series of basaltic magma injections that may have commenced in 1971 and continued up until at least the start of the 1994 eruptions. The presence of zoned plagioclase phenocrysts reflecting older basalt-dacite interaction events (i.e. anorthite cores overgrown with thick andesine rims), evaluation of limited available data for the products of previous eruptions in 1878 and 1937-1943, and the episodic occurrence of major intra-caldera seismo-deformational events indicates that the shallow magma system at Rabaul Caldera is

Temporal evolution of granitic magmas in the Luanchuan metallogenic belt, east Qinling Orogen, central China: Implications for Mo metallogenesis

Science.gov (United States)

Li, Dong; Han, Jiangwei; Zhang, Shouting; Yan, Changhai; Cao, Huawen; Song, Yaowu

2015-11-01

The Luanchuan metallogenic belt, located within the eastern part of the Qinling Orogen, central China, hosts a number of world-class Mo deposits that are closely related to small late Mesozoic granitic plutons. Zircon U-Pb dating of distinct plutons in the Luanchuan metallogenic belt has yielded ages of 153 ± 1, 154 ± 2, 152 ± 2, and 148 ± 1 Ma. Molybdenite Re-Os isotopic compositions of Yuku ore district in the southern part of Luanchuan metallogenic belt has yielded an isochron age of 146 ± 1 Ma, which is consistent with the large-scale mineralization ages in the northern part of the Luanchuan metallogenic belt. A combination of previous studies and new geochronological and isotopic data show a concordant temporal and genetic link between granitic magmatism and Mo mineralization in the Luanchuan metallogenic belt, suggesting that this mineralization episode formed the most extensive Mo mineralization belt in the east Qinling Orogen. Zircon grains from Mo-related granitic plutons show similar trace element distributions. High-precision Multi Collector-Inductively Coupled Plasma-Mass Spectrometry (MC-ICP-MS) Pb isotope analysis of K-feldspar megacrysts from mineralization-related granites suggest that they were derived from the lower crust. Similarly, the Pb isotopic compositions of pyrite coprecipitated with molybdenite also suggest that the metals were derived form the lower crust, with probably minor mantle contribution. A continuum mineralization model that describes the sourcing of Mo from an evolving granitic magma over successive differentiation events, possibly in separate but connected magma chambers, could explain the remarkable Mo enrichment in the Luanchuan metallogenic belt. The volatile- and Mo-bearing granitic magmas ascended as diapirs from the deep crust, and were emplaced as dikes in the upper crust. Lithological differences between these Mo-bearing granites may relate to different stages in the evolution of individual magmas. Finally, ore

The role of crystallization-driven exsolution on the sulfur mass balance in volcanic arc magmas

Science.gov (United States)

Su, Yanqing; Huber, Christian; Bachmann, Olivier; Zajacz, Zoltán; Wright, Heather M.; Vazquez, Jorge A.

2016-01-01

The release of large amounts of sulfur to the stratosphere during explosive eruptions affects the radiative balance in the atmosphere and consequentially impacts climate for up to several years after the event. Quantitative estimations of the processes that control the mass balance of sulfur between melt, crystals, and vapor bubbles is needed to better understand the potential sulfur yield of individual eruption events and the conditions that favor large sulfur outputs to the atmosphere. The processes that control sulfur partitioning in magmas are (1) exsolution of volatiles (dominantly H2O) during decompression (first boiling) and during isobaric crystallization (second boiling), (2) the crystallization and breakdown of sulfide or sulfate phases in the magma, and (3) the transport of sulfur-rich vapor (gas influx) from deeper unerupted regions of the magma reservoir. Vapor exsolution and the formation/breakdown of sulfur-rich phases can all be considered as closed-system processes where mass balance arguments are generally easier to constrain, whereas the contribution of sulfur by vapor transport (open system process) is more difficult to quantify. The ubiquitous “excess sulfur” problem, which refers to the much higher sulfur mass released during eruptions than what can be accounted for by amount of sulfur originally dissolved in erupted melt, as estimated from melt inclusion sulfur concentrations (the “petrologic estimate”), reflects the challenges in closing the sulfur mass balance between crystals, melt, and vapor before and during a volcanic eruption. In this work, we try to quantify the relative importance of closed- and open-system processes for silicic arc volcanoes using kinetic models of sulfur partitioning during exsolution. Our calculations show that crystallization-induced exsolution (second boiling) can generate a significant fraction of the excess sulfur observed in crystal-rich arc magmas. This result does not negate the important role of

The role of amphibole in Merapi arc magma petrogenesis: insights from petrology and geochemistry of lava hosted xenoliths and xenocrysts

Science.gov (United States)

Chadwick, J. P.; Troll, V. R.; Schulz, B.; Dallai, L.; Freda, C.; Schwarzkopf, L. M.; Annersten, H.; Skogby, H.

2010-05-01

deep- to mid-crustal processes given the stability field of amphibole. The individual amphibole xenocrysts are also co-genetic to the Merapi magma system and indicative of high-pressure crystallisation. Hydrogen isotope analyses of these large amphibole megacrysts, record a broad range of dD ratios (permil deviation of D/H isotope ratio from Standard Mean Ocean Water). The dD values of some of these crystals appear to be modified significantly from expected primary compositions, particularly towards the rims of amphiboles showing breakdown textures. The measured dD values possibly result from H-isotope re-equilibration with surrounding volatile vapour during eruption or via dehydration reactions. Mossbauer analysis of a selected pristine amphibole megacryst from this suite records 67 % of iron as Fe3+ in the M-sites. Complementary IR spectroscopy of this amphibole indicates no serious loss of OH groups. High H2O pressures at formation depth for this crystal have stabilized full hydrous compositions at ~ 2% H2O concentration in the amphibole. Such fully hydrated amphiboles could release their H2O on depressurisation on ascent prior to eruption, a process that consistent with the dD data. Analysis of these samples is ongoing, however this initial data indicates that amphibole is a key phase in Merapi magmatic evolution and is a likely source of volatiles through dehydration on ascent. This is of particular significance given the fact that water content of magma has a considerable impact on the explosive potential of subduction zone volcanism. (1) Davidson et al., 2007. Geology, 35: 787-790. (2) Tiepolo et al., 2002 Contrib. Min. Pet., 144:1-15.

Extensive, water-rich magma reservoir beneath southern Montserrat

Science.gov (United States)

Edmonds, M.; Kohn, S. C.; Hauri, E. H.; Humphreys, M. C. S.; Cassidy, M.

2016-05-01

South Soufrière Hills and Soufrière Hills volcanoes are 2 km apart at the southern end of the island of Montserrat, West Indies. Their magmas are distinct geochemically, despite these volcanoes having been active contemporaneously at 131-129 ka. We use the water content of pyroxenes and melt inclusion data to reconstruct the bulk water contents of magmas and their depth of storage prior to eruption. Pyroxenes contain up to 281 ppm H2O, with significant variability between crystals and from core to rim in individual crystals. The Al content of the enstatites from Soufrière Hills Volcano (SHV) is used to constrain melt-pyroxene partitioning for H2O. The SHV enstatite cores record melt water contents of 6-9 wt%. Pyroxene and melt inclusion water concentration pairs from South Soufriere Hills basalts independently constrain pyroxene-melt partitioning of water and produces a comparable range in melt water concentrations. Melt inclusions recorded in plagioclase and in pyroxene contain up to 6.3 wt% H2O. When combined with realistic melt CO2 contents, the depth of magma storage for both volcanoes ranges from 5 to 16 km. The data are consistent with a vertically protracted crystal mush in the upper crust beneath the southern part of Montserrat which contains heterogeneous bodies of eruptible magma. The high water contents of the magmas suggest that they contain a high proportion of exsolved fluids, which has implications for the rheology of the mush and timescales for mush reorganisation prior to eruption. A depletion in water in the outer 50-100 μm of a subset of pyroxenes from pumices from a Vulcanian explosion at Soufrière Hills in 2003 is consistent with diffusive loss of hydrogen during magma ascent over 5-13 h. These timescales are similar to the mean time periods between explosions in 1997 and in 2003, raising the possibility that the driving force for this repetitive explosive behaviour lies not in the shallow system, but in the deeper parts of a vertically

Magma mixing in granitic rocks of the central Sierra Nevada, California

Science.gov (United States)

Reid, John B.; Evans, Owen C.; Fates, Dailey G.

1983-12-01

The El Capitan alaskite exposed in the North American Wall, Yosemite National Park, was intruded by two sets of mafic dikes that interacted thermally and chemically with the host alaskite. Comparisons of petrographic and compositional data for these dikes and alaskite with published data for Sierra Nevada plutons lead us to suggest that mafic magmas were important in the generation of the Sierra Nevada batholith. Specifically, we conclude that: (1) intrusion of mafic magmas in the lower crust caused partial melting and generation of alaskite (rhyolitic) magmas; (2) interaction between the mafic and felsic magmas lead to the observed linear variation diagrams for major elements; (3) most mafic inclusions in Sierra Nevada plutons represent chilled pillows of mafic magmas, related by fractional crystallization and granitoid assimilation, that dissolve into their felsic host and contaminate it to intermediate (granodioritic) compositions; (4) vesiculation of hydrous mafic magma upon chilling may allow buoyant mafic inclusions and their disaggregation products to collect beneath a pluton's domed ceiling causing the zoning (mafic margins-to-felsic core) that these plutons exhibit.

Molybdenite saturation in silicic magmas: Occurrence and petrological implications

Science.gov (United States)

Audetat, A.; Dolejs, D.; Lowenstern, J. B.

2011-01-01

We identified molybdenite (MoS2) as an accessory magmatic phase in 13 out of 27 felsic magma systems examined worldwide. The molybdenite occurs as small (molybdenite-saturated samples reveal 1-13 ppm Mo in the melt and geochemical signatures that imply a strong link to continental rift basalt-rhyolite associations. In contrast, arc-associated rhyolites are rarely molybdenite-saturated, despite similar Mo concentrations. This systematic dependence on tectonic setting seems to reflect the higher oxidation state of arc magmas compared with within-plate magmas. A thermodynamic model devised to investigate the effects of T, f O2 and f S2 on molybdenite solubility reliably predicts measured Mo concentrations in molybdenite-saturated samples if the magmas are assumed to have been saturated also in pyrrhotite. Whereas pyrrhotite microphenocrysts have been observed in some of these samples, they have not been observed from other molybdenite-bearing magmas. Based on the strong influence of f S2 on molybdenite solubility we calculate that also these latter magmas must have been at (or very close to) pyrrhotite saturation. In this case the Mo concentration of molybdenite-saturated melts can be used to constrain both magmatic f O2 and f S2 if temperature is known independently (e.g. by zircon saturation thermometry). Our model thus permits evaluation of magmatic f S2, which is an important variable but is difficult to estimate otherwise, particularly in slowly cooled rocks. ?? The Author 2011. Published by Oxford University Press. All rights reserved.

Thermal evolution of magma reservoirs in the shallow crust and incidence on magma differentiation: the St-Jean-du-Doigt layered intrusion (Brittany, France)

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Barboni, M.; Bussy, F.; Ovtcharova, M.; Schoene, B.

2009-12-01

Understanding the emplacement and growth of intrusive bodies in terms of mechanism, duration, thermal evolution and rates are fundamental aspects of crustal evolution. Recent studies show that many plutons grow in several Ma by in situ accretion of discrete magma pulses, which constitute small-scale magmatic reservoirs. The residence time of magmas, and hence their capacities to interact and differentiate, are controlled by the local thermal environment. The latter is highly dependant on 1) the emplacement depth, 2) the magmas and country rock composition, 3) the country rock thermal conductivity, 4) the rate of magma injection and 5) the geometry of the intrusion. In shallow level plutons, where magmas solidify quickly, evidence for magma mixing and/or differentiation processes is considered by many authors to be inherited from deeper levels. We show however that in-situ differentiation and magma interactions occurred within basaltic and felsic sills at shallow depth (0.3 GPa) in the St-Jean-du-Doigt bimodal intrusion, France. Field evidence coupled to high precision zircon U-Pb dating document progressive thermal maturation within the incrementally built laccolith. Early m-thick mafic sills are homogeneous and fine-grained with planar contacts with neighbouring felsic sills; within a minimal 0.5 Ma time span, the system gets warmer, adjacent sills interact and mingle, and mafic sills are differentiating in the top 40 cm of the layer. Rheological and thermal modelling show that observed in-situ differentiation-accumulation processes may be achieved in less than 10 years at shallow depth, provided that (1) the differentiating sills are injected beneath consolidated, yet still warm basalt sills, which act as low conductive insulating screens, (2) the early mafic sills accreted under the roof of the laccolith as a 100m thick top layer within 0.5 My, and (3) subsequent and sustained magmatic activity occurred on a short time scale (years) at an injection rate of ca. 0

Volatiles produced by the mycophagous soil bacterium Collimonas

NARCIS (Netherlands)

Garbeva, P.; Hordijk, C.; Gerards, S.; Boer, de W.

2014-01-01

It is increasingly recognized that volatile organic compounds play an import role during interactions between soil microorganisms. Here, we examined the possible involvement of volatiles in the interaction of Collimonas bacteria with soil fungi. The genus Collimonas is known for its ability to grow

Genesis of felsic plutonic magmas and their igneous enclaves

DEFF Research Database (Denmark)

Clemens, John D.; Maas, Roland; Waight, Tod Earle

2016-01-01

-type Pyalong pluton was emplaced, apparently along an east-west-orientated fracture zone. Around 367 Ma, the main I-type Baynton pluton intruded as numerous shallow-dipping sheets. The last plutonic event was the intrusion of the broad, thin, flat-lying, and crosscutting sheet of the I-type Beauvallet pluton...... the relatively high abundance of igneous-textured microgranular enclaves (MEs). The MEs show neither chemical nor isotope mixing trends with each other or with the host magmas. Variations in the Baynton magmas were derived from the heterogeneity of the source terrane, with individual magma batches formed from...

Constraints on timescales and mechanics of magmatic underplating from InSAR observations of large active magma sills in the Earth's crust.

Science.gov (United States)

Fialko, Y.

2002-12-01

Theoretical models of the granitoid magma generation due to magmatic underplating predict that anatectic melts are produced on quite short timescales of the order of the crystallization time of typical mafic underplates (e.g., 102-10^3 years for sill intrusions that are a few tens to a few hundred meters thick). If so, the intrusion of mafic underplates, the volume changes associated with in situ melting, and the subsequent evacuation of the resulting granitoid magmas can each generate geodetically observable deformation. Geodetic measurements in areas of contemporaneous large active magma bodies may therefore provide critical constraints on the timescales and dynamics of crustal anatexis. We use Interferometric Synthetic Aperture Radar (InSAR) observations in regions of the ongoing crustal magmatism to constrain typical rates of the large-scale melt generation and/or migration, and to test the proposed models of the granitic melt production. Our primary targets include large mid-crustal magma bodies imaged by seismic studies, in particular, the Socorro (New Mexico, USA), the Altiplano-Puna (south America), and the south Tibet (Asia) magma bodies. All these magma bodies are located at depth of 19-20 km, suggesting a strong rheological or buoyancy control on the transition from a vertical to a horizontal magma flow. Stacked interferometric data from the Socorro magma body indicate a quasi-steady uplift with a maximum rate of 3-4 mm/yr over the last 10 years covered by the InSAR observations. The uplift morphology can be well described by an elastic inflation of the Socorro sill. We show that deformation models that allow for the viscous-like rheology of the mid-to-lower crust cannot be easily reconciled with the geodetic data. However, thermodynamic modeling, in conjunction with inferences of the nearly constant uplift rates, suggest that the deformations associated with the intrusion emplacement must involve a significant inelastic component. Such inelastic

Magma viscosity estimation based on analysis of erupted products. Potential assessment for large-scale pyroclastic eruptions

International Nuclear Information System (INIS)

Takeuchi, Shingo

2010-01-01

After the formulation of guidelines for volcanic hazards in site evaluation for nuclear installations (e.g. JEAG4625-2009), it is required to establish appropriate methods to assess potential of large-scale pyroclastic eruptions at long-dormant volcanoes, which is one of the most hazardous volcanic phenomena on the safety of the installations. In considering the volcanic dormancy, magma eruptability is an important concept. The magma eruptability is dominantly controlled by magma viscosity, which can be estimated from petrological analysis of erupted materials. Therefore, viscosity estimation of magmas erupted in past eruptions should provide important information to assess future activities at hazardous volcanoes. In order to show the importance of magma viscosity in the concept of magma eruptability, this report overviews dike propagation processes from a magma chamber and nature of magma viscosity. Magma viscosity at pre-eruptive conditions of magma chambers were compiled based on previous petrological studies on past eruptions in Japan. There are only 16 examples of eruptions at 9 volcanoes satisfying data requirement for magma viscosity estimation. Estimated magma viscosities range from 10 2 to 10 7 Pa·s for basaltic to rhyolitic magmas. Most of examples fall below dike propagation limit of magma viscosity (ca. 10 6 Pa·s) estimated based on a dike propagation model. Highly viscous magmas (ca. 10 7 Pa·s) than the dike propagation limit are considered to lose eruptability which is the ability to form dikes and initiate eruptions. However, in some cases, small precursory eruptions of less viscous magmas commonly occurred just before climactic eruptions of the highly viscous magmas, suggesting that the precursory dike propagation by the less viscous magmas induced the following eruptions of highly viscous magmas (ca. 10 7 Pa·s). (author)

Geochemical monitoring of volcano unrest and multi-step magma propagation: the example of the 2007-2011 Piton de la Fournaise activity.

Science.gov (United States)

Di Muro, Andrea; Métrich, Nicole; Deloule, Etienne; Civetta, Lucia

2014-05-01

between our petrological estimates of the potential SO2 release and the remotely derived fluxes, together with absence of hydrothermal signature in bulk rocks and melt inclusions, rule out a significant contribution of external fluids to PdF volatile budget. Regular monitoring of magma, crystal and glass compositions is an effective strategy for monitoring and interpreting magma storage and dynamics at a very active volcano like Piton de la Fournaise.

Understanding the rheology of two and three-phase magmas

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Coats, R.; Cai, B.; Kendrick, J. E.; Wallace, P. A.; Hornby, A. J.; Miwa, T.; von Aulock, F. W.; Ashworth, J. D.; Godinho, J.; Atwood, R. C.; Lee, P. D.; Lavallée, Y.

2017-12-01

The rheology of magma plays a fundamental role in determining the style of a volcanic eruption, be it explosive or effusive. Understanding how magmas respond to changes in stress/ strain conditions may help to enhance eruption forecast models. The presence of crystals and bubbles in magmas alter the viscosity of suspensions and favor a non-Newtonian response. Thus, with the aim of grasping the rheological behavior of volcanic materials, uniaxial compressive tests were performed on natural and synthetic samples. A suite of variably porous (10-32 vol.%), highly crystalline ( 50 vol.%) dacite from the 1991-95 eruption of Mt Unzen, Japan, was selected as the natural material, while synthetic samples were sintered with desired porosities (Diamond Light Source. Unexpectedly, these observations suggest that fractures nucleate in crystals due to crystal interactions, before propagating through the interstitial melt. This ongoing study promises to uncover the way crystal-bearing magmas flow or fail, necessary to constrain magmatic processes and volcanic hazards.

Locating the depth of magma supply for volcanic eruptions, insights from Mt. Cameroon.

Science.gov (United States)

Geiger, Harri; Barker, Abigail K; Troll, Valentin R

2016-10-07

Mt. Cameroon is one of the most active volcanoes in Africa and poses a possible threat to about half a million people in the area, yet knowledge of the volcano's underlying magma supply system is sparse. To characterize Mt. Cameroon's magma plumbing system, we employed mineral-melt equilibrium thermobarometry on the products of the volcano's two most recent eruptions of 1999 and 2000. Our results suggest pre-eruptive magma storage between 20 and 39 km beneath Mt. Cameroon, which corresponds to the Moho level and below. Additionally, the 1999 eruption products reveal several shallow magma pockets between 3 and 12 km depth, which are not detected in the 2000 lavas. This implies that small-volume magma batches actively migrate through the plumbing system during repose intervals. Evolving and migrating magma parcels potentially cause temporary unrest and short-lived explosive outbursts, and may be remobilized during major eruptions that are fed from sub-Moho magma reservoirs.

Shallow system rejuvenation and magma discharge trends at Piton de la Fournaise volcano (La Réunion Island)

Science.gov (United States)

Coppola, D.; Di Muro, A.; Peltier, A.; Villeneuve, N.; Ferrazzini, V.; Favalli, M.; Bachèlery, P.; Gurioli, L.; Harris, A. J. L.; Moune, S.; Vlastélic, I.; Galle, B.; Arellano, S.; Aiuppa, A.

2017-04-01

Basaltic magma chambers are often characterized by emptying and refilling cycles that influence their evolution in space and time, and the associated eruptive activity. During April 2007, the largest historical eruption of Piton de la Fournaise (Île de La Réunion, France) drained the shallow plumbing system (> 240 ×106 m3) and resulted in collapse of the 1-km-wide summit crater. Following these major events, Piton de la Fournaise entered a seven-year long period of near-continuous deflation interrupted, in June 2014, by a new phase of significant inflation. By integrating multiple datasets (lava discharge rates, deformation, seismicity, gas flux, gas composition, and lava chemistry), we here show that the progressive migration of magma from a deeper (below sea level) storage zone gradually rejuvenated and pressurized the above-sea-level portion of the magmatic system consisting of a vertically-zoned network of relatively small-volume magma pockets. Continuous inflation provoked four small (CO2 enrichment of summit fumaroles, and involving emission of less differentiated lavas, to end with, (iii) three short-lived (∼2 day-long) pulses in lava and gas flux, coupled with arrival of cumulative olivine at the surface and deflation. The activity observed at Piton de la Fournaise in 2014 and 2015 points to a new model of shallow system rejuvenation and discharge, whereby continuous magma supply causes eruptions from increasingly deeper and larger magma storage zones. Downward depressurization continues until unloading of the deepest, least differentiated magma triggers pulses in lava and gas flux, accompanied by rapid contraction of the volcano edifice, that empties the main shallow reservoir and terminates the cycle. Such an unloading process may characterize the evolution of shallow magmatic systems at other persistently active effusive centers.

Incremental assembly and prolonged consolidation of Cordilleran magma chambers--Evidence from the Southern Rocky Mountain volcanic field

Science.gov (United States)

Lipman, Peter W.

2007-01-01

Recent inference that Mesozoic Cordilleran plutons grew incrementally during >106 yr intervals, without the presence of voluminous eruptible magma at any stage, minimizes close associations with large ignimbrite calderas. Alternatively, Tertiary ignimbrites in the Rocky Mountains and elsewhere, with volumes of 1–5 × 103 km3, record multistage histories of magma accumulation, fractionation, and solidification in upper parts of large subvolcanic plutons that were sufficiently liquid to erupt. Individual calderas, up to 75 km across with 2–5 km subsidence, are direct evidence for shallow magma bodies comparable to the largest granitic plutons. As exemplified by the composite Southern Rocky Mountain volcanic field (here summarized comprehensively for the first time), which is comparable in areal extent, magma composition, eruptive volume, and duration to continental-margin volcanism of the central Andes, nested calderas that erupted compositionally diverse tuffs document deep composite subsidence and rapid evolution in subvolcanic magma bodies. Spacing of Tertiary calderas at distances of tens to hundreds of kilometers is comparable to Mesozoic Cordilleran pluton spacing. Downwind ash in eastern Cordilleran sediments records large-scale explosive volcanism concurrent with Mesozoic batholith growth. Mineral fabrics and gradients indicate unified flow-age of many pluton interiors before complete solidification, and some plutons contain ring dikes or other textural evidence for roof subsidence. Geophysical data show that low-density upper-crustal rocks, inferred to be plutons, are 10 km or more thick beneath many calderas. Most ignimbrites are more evolved than associated plutons; evidence that the subcaldera chambers retained voluminous residua from fractionation. Initial incremental pluton growth in the upper crust was likely recorded by modest eruptions from central volcanoes; preparation for caldera-scale ignimbrite eruption involved recurrent magma input and

Magma transport and storage at Kilauea volcano, Hawaii I: 1790-1952

Science.gov (United States)

Wright, T. L.; Klein, F.

2011-12-01

former time to 1918-1919 and the latter to 1924. Qualitative Mogi modeling of the 1921-1927 deformation data yields three centers, two shallow ones corresponding to sources 1 and 2, and a third deeper one that we interpret to represent draining of source 3. During recovery from the 1924 intrusion and collapse the tilt remained low, unlike the aftermath of more recent deflations. Small eruptions in Halemaumau between 1924 and 1934 used up the last of the magma that fed the lava lakes, and three passive East rift intrusions without a tilt signal are considered part of the recovery of source 3. Kilauea began inflating in March 1950, leading up to the long 1952 eruption in Halemaumau. Deep earthquakes occurred in 1950 and 1951, resulting in an increased magma supply rate of 0.062 km3/yr. An intense earthquake swarm occurred beneath the offshore south flank in March-April 1952 that unlocked the south flank to initiate the modern spreading regime. We interpret the 1924 intrusion as a critical event in stabilizing the modern magma system beneath the rift zone. Prior to that time it is probable that major caldera draining events in the 19th century involved the entire magmatic system. Measurements made at HVO are critical to the interpretations made in the pre-1952 period.

Seismic tremors and magma wagging during explosive volcanism.

Science.gov (United States)

Jellinek, A Mark; Bercovici, David

2011-02-24

Volcanic tremor is a ubiquitous feature of explosive eruptions. This oscillation persists for minutes to weeks and is characterized by a remarkably narrow band of frequencies from about 0.5 Hz to 7 Hz (refs 1-4). Before major eruptions, tremor can occur in concert with increased gas flux and related ground deformation. Volcanic tremor is thus of particular value for eruption forecasting. Most models for volcanic tremor rely on specific properties of the geometry, structure and constitution of volcanic conduits as well as the gas content of the erupting magma. Because neither the initial structure nor the evolution of the magma-conduit system will be the same from one volcano to the next, it is surprising that tremor characteristics are so consistent among different volcanoes. Indeed, this universality of tremor properties remains a major enigma. Here we employ the contemporary view that silicic magma rises in the conduit as a columnar plug surrounded by a highly vesicular annulus of sheared bubbles. We demonstrate that, for most geologically relevant conditions, the magma column will oscillate or 'wag' against the restoring 'gas-spring' force of the annulus at observed tremor frequencies. In contrast to previous models, the magma-wagging oscillation is relatively insensitive to the conduit structure and geometry, which explains the narrow band of tremor frequencies observed around the world. Moreover, the model predicts that as an eruption proceeds there will be an upward drift in both the maximum frequency and the total signal frequency bandwidth, the nature of which depends on the explosivity of the eruption, as is often observed.

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.

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.

Quantitative evaluation of the effect of H2O degassing on the oxidation state of magmas

Science.gov (United States)

Lange, R. A.; Waters, L.

2014-12-01

The extent to which degassing of the H2O component affects the oxidation state of hydrous magmas is widely debated. Several researchers have examined how degassing of mixed H-C-O-S-Cl fluids may change the Fe3+/FeT ratio of various magmas, whereas our focus is on the H2O component. There are two ways that degassing of H2O by itself may cause oxidation: (1) the reaction: H2O (melt) + 2FeO (melt) = H2 (fluid) + Fe2O3 (melt), and/or (2) if dissolved water preferentially enhances the activity of ferrous vs. ferric iron in magmatic liquids. In this study, a comparison is made between the pre-eruptive oxidation states of 14 crystal-poor, jet-black obsidian samples (obtained from two Fe-Ti oxides) and their post-eruptive values (analyzed with the Wilson 1960 titration method tested against USGS standards). The obsidians are from Medicine Lake (CA), Long Valley (CA), and the western Mexican arc; all have low FeOT (1.1-2.1 wt%), rendering their Fe2+/Fe3+ ratios highly sensitive to the possible effects of substantial H2O degassing. The Fe-Ti oxide thermometer/oxybarometer of Ghiorso and Evans, (2008) gave temperatures for the 14 samples that range for 720 to 940°C and ΔNNO values of -0.9 to +1.4. With temperature known, the plagioclase-liquid hygrometer was applied and show that ≤ 6.5 wt% H2O was dissolved in the melts prior to eruption. In addition, pre-eruptive Cl and S concentrations were constrained on the basis of apatite analyses (Webster et al., 2009) and sulfur concentrations needed for saturation with pyrrhotite (Clemente et al., 2004), respectively. Maximum pre-eruptive chlorine and sulfur contents are 6000 and 200 ppm, respectively. After eruption, the rhyolites lost nearly all of their volatiles. Our results indicate no detectable change between pre- and post-eruptive Fe2+ concentrations, with an average deviation of ± 0.1 wt % FeO. Although degassing of large concentrations of S and/or Cl may affect the oxidation state of magmas, at the pre-eruptive levels

Sodium channels as targets for volatile anesthetics

Directory of Open Access Journals (Sweden)

Karl F. Herold

2012-03-01

Full Text Available The molecular mechanisms of modern inhaled anesthetics although widely used in clinical settings are still poorly understood. Considerable evidence supports effects on membrane proteins such as ligand- and voltage-gated ion channels of excitable cells. Na+ channels are crucial to action potential initiation and propagation, and represent potential targets for volatile anesthetics. Inhibition of presynaptic Na+ channels leads to reduced neurotransmitter release at the synapse and could therefore contribute to the mechanisms by which volatile anesthetics produce their characteristic effects: amnesia, unconsciousness, and immobility. Early studies on crayfish and squid giant axon showed inhibition of Na+ currents by volatile anesthetics. Subsequent studies using native neuronal preparations and heterologous expression systems with various mammalian Na+ channel isoforms implicated inhibition of presynaptic Na+ channels in anesthetic actions. Volatile anesthetics reduce peak Na+ current and shift the voltage of half-maximal steady-state inactivation towards more negative potentials, thus stabilizing the fast-inactivated state. Furthermore recovery from fast-inactivation is slowed together with an enhanced use-dependent block during pulse train protocols. These effects can reduce neurotransmitter release by depressing presynaptic excitability, depolarization and Ca entry, and ultimately transmitter release. This reduction in transmitter release is more portent for glutamatergic vs. GABAergic terminals. Involvement of Na+ channel inhibition in mediating the immobility caused by volatile anesthetics has been demonstrated in animal studies, in which intrathecal infusion of the Na+ channel blocker tetrodotoxin increases volatile anesthetic potency, whereas infusion of the Na+ channels agonist veratridine reduces anesthetic potency. These studies indicate that inhibition of presynaptic Na+ channels by volatile anesthetics is involved in mediating some of

The 2006-2009 activity of the Ubinas volcano (Peru): Petrology of the 2006 eruptive products and insights into genesis of andesite magmas, magma recharge and plumbing system

Science.gov (United States)

Rivera, Marco; Thouret, Jean-Claude; Samaniego, Pablo; Le Pennec, Jean-Luc

2014-01-01

Following a fumarolic episode that started six months earlier, the most recent eruptive activity of the Ubinas volcano (south Peru) began on 27 March 2006, intensified between April and October 2006 and slowly declined until December 2009. The chronology of the explosive episode and the extent and composition of the erupted material are documented with an emphasis on ballistic ejecta. A petrological study of the juvenile products allows us to infer the magmatic processes related to the 2006-2009 eruptions of the andesitic Ubinas volcano. The juvenile magma erupted during the 2006 activity shows a homogeneous bulk-rock andesitic composition (56.7-57.6 wt.% SiO2), which belongs to a medium- to high-K calc-alkaline series. The mineral assemblage of the ballistic blocks and tephra consists of plagioclase > two-pyroxenes > Fe-Ti oxide and rare olivine and amphibole set in a groundmass of the same minerals with a dacitic composition (66-67 wt.% SiO2). Thermo-barometric data, based on two-pyroxene and amphibole stability, records a magma temperature of 998 ± 14 °C and a pressure of 476 ± 36 MPa. Widespread mineralogical and textural features point to a disequilibrium process in the erupted andesite magma. These features include inversely zoned "sieve textures" in plagioclase, inversely zoned clinopyroxene, and olivine crystals with reaction and thin overgrowth rims. They indicate that the pre-eruptive magmatic processes were dominated by recharge of a hotter mafic magma into a shallow reservoir, where magma mingling occurred and triggered the eruption. Prior to 2006, a probable recharge of a mafic magma produced strong convection and partial homogenization in the reservoir, as well as a pressure increase and higher magma ascent rate after four years of fumarolic activity. Mafic magmas do not prevail in the Ubinas pre-historical lavas and tephras. However, mafic andesites have been erupted during historical times (e.g. AD 1667 and 2006-2009 vulcanian eruptions). Hence

Apatite: A New Tool For Understanding The Temporal Variability Of Magmatic Volatile Contents

Science.gov (United States)

Stock, M. J.; Humphreys, M.; Smith, V.; Pyle, D. M.; Isaia, R.

2015-12-01

The apatite crystal structure is capable of incorporating H2O, F and Cl, as well as trace CO2 and sulphur. These can be related to parental magma compositions through application of a series of pressure and temperature-dependent exchange reactions (Piccoli and Candela, 1994), permitting apatite crystals to preserve a record of all major volatile species in the melt. Furthermore, due to the general incompatibility of P in other rock-forming minerals, apatite is ubiquitous in igneous systems and often begins crystallising early, such that apatite inclusions within phenocrysts record melt volatile contents throughout magmatic differentiation. In this work, we compare the compositions of apatite inclusions and microphenocrysts with pyroxene-hosted melt inclusions from the Astroni 1 eruption of Campi Flegrei, Italy. These data are coupled with magmatic differentiation models (Gualda et al., 2012), experimental volatile solubility data (Webster et al., 2014) and thermodynamic models of apatite compositional variations (Piccoli and Candela, 1994) to determine a time-series of magmatic volatile evolution in the build-up to eruption. We find that apatite halogen/OH ratios decreased through magmatic differentiation, while melt inclusion F and Cl concentrations increased. Melt inclusion H2O contents are constant at ~2.5 wt%. These data are best explained by volatile-undersaturated differentiation over most of the crystallisation history of the Astroni 1 melt, with melt inclusion H2O contents reset during ascent, due to rapid H diffusion through the phenocryst hosts (Woods et al., 2000). Given the rapid diffusivity of volatiles in apatite (Brenan, 1993), preservation of undersaturated compositions in microphenocrysts suggests that saturation was only achieved a few days to months before eruption and that it may have been the transition into a volatile-saturated state that ultimately triggered eruption. Piccoli and Candela, 1994. Am. J. of Sc., 294, 92-135. Gualda et al., 2012

Adakitic magmas: modern analogues of Archaean granitoids

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Martin, Hervé

1999-03-01

Both geochemical and experimental petrological research indicate that Archaean continental crust was generated by partial melting of an Archaean tholeiite transformed into a garnet-bearing amphibolite or eclogite. The geodynamic context of tholeiite melting is the subject of controversy. It is assumed to be either (1) subduction (melting of a hot subducting slab), or (2) hot spot (melting of underplated basalts). These hypotheses are considered in the light of modern adakite genesis. Adakites are intermediate to felsic volcanic rocks, andesitic to rhyolitic in composition (basaltic members are lacking). They have trondhjemitic affinities (high-Na 2O contents and K 2O/Na 2O˜0.5) and their Mg no. (0.5), Ni (20-40 ppm) and Cr (30-50 ppm) contents are higher than in typical calc-alkaline magmas. Sr contents are high (>300 ppm, until 2000 ppm) and REE show strongly fractionated patterns with very low heavy REE (HREE) contents (Yb≤1.8 ppm, Y≤18 ppm). Consequently, high Sr/Y and La/Yb ratios are typical and discriminating features of adakitic magmas, indicative of melting of a mafic source where garnet and/or hornblende are residual phases. Adakitic magmas are only found in subduction zone environments, exclusively where the subduction and/or the subducted slab are young (subducted and where the adakitic character of the lavas correlates well with the young age of the subducting oceanic lithosphere. In typical subduction zones, the subducted lithosphere is older than 20 Ma, it is cool and the geothermal gradient along the Benioff plane is low such that the oceanic crust dehydrates before it reaches the solidus temperature of hydrated tholeiite. Consequently, the basaltic slab cannot melt. The released large ion lithophile element (LILE)-rich fluids rise up into the mantle wedge, inducing both its metasomatism and partial melting. Afterwards, the residue is made up of olivine+clinopyroxene+orthopyroxene, such that the partial melts are HREE-rich (low La/Yb and Sr

Aleutian tholeiitic and calc-alkaline magma series I: The mafic phenocrysts

Science.gov (United States)

Kay, S. Mahlburg; Kay, Robert W.

1985-07-01

Diagnostic mafic silicate assemblages in a continuous spectrum of Aleutian volcanic rocks provide evidence for contrasts in magmatic processes in the Aleutian arc crust. Tectonic segmentation of the arc exerts a primary control on the variable mixing, fractional crystallization and possible assimilation undergone by the magmas. End members of the continuum are termed calc-alkaline (CA) and tholeiitic (TH). CA volcanic rocks (e.g., Buldir and Moffett volcanoes) have low FeO/MgO ratios and contain compositionally diverse phenocryst populations, indicating magma mixing. Their Ni and Cr-rich magnesian olivine and clinopyroxene come from mantle-derived mafic olivine basalts that have mixed with more fractionated magmas at mid-to lower-crustal levels immediately preceding eruption. High-Al amphibole is associated with the mafic end member. In contrast, TH lavas (e.g., Okmok and Westdahl volcanoes) have high FeO/MgO ratios and contain little evidence for mixing. Evolved lavas represent advanced stages of low pressure crystallization from a basaltic magma. These lavas contain groundmass olivine (FO 40 50) and lack Ca-poor pyroxene. Aleutian volcanic rocks with intermediate FeO/MgO ratios are termed transitional tholeiitic (TTH) and calc-alkaline (TCA). TCA magmas are common (e.g., Moffett, Adagdak, Great Sitkin, and Kasatochi volcanoes) and have resulted from mixing of high-Al basalt with more evolved magmas. They contain amphibole (high and low-Al) or orthopyroxene or both and are similar to the Japanese hypersthene-series. TTH magmas (e.g., Okmok and Westdahl) contain orthopyroxene or pigeonite or both, and show some indication of upper crustal mixing. They are mineralogically similar to the Japanese pigeonite-series. High-Al basalt lacks Mg-rich mafic phases and is a derivative magma produced by high pressure fractionation of an olivine tholeiite. The low pressure mineral assemblage of high-Al basalt results from crystallization at higher crustal levels.

Degassing during quiescence as a trigger of magma ascent and volcanic eruptions.

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Girona, Társilo; Costa, Fidel; Schubert, Gerald

2015-12-15

Understanding the mechanisms that control the start-up of volcanic unrest is crucial to improve the forecasting of eruptions at active volcanoes. Among the most active volcanoes in the world are the so-called persistently degassing ones (e.g., Etna, Italy; Merapi, Indonesia), which emit massive amounts of gas during quiescence (several kilotonnes per day) and erupt every few months or years. The hyperactivity of these volcanoes results from frequent pressurizations of the shallow magma plumbing system, which in most cases are thought to occur by the ascent of magma from deep to shallow reservoirs. However, the driving force that causes magma ascent from depth remains unknown. Here we demonstrate that magma ascent can be triggered by the passive release of gas during quiescence, which induces the opening of pathways connecting deep and shallow magma reservoirs. This top-down mechanism for volcanic eruptions contrasts with the more common bottom-up mechanisms in which magma ascent is only driven by processes occurring at depth. A cause-effect relationship between passive degassing and magma ascent can explain the fact that repose times are typically much longer than unrest times preceding eruptions, and may account for the so frequent unrest episodes of persistently degassing volcanoes.

Ultra-high chlorine in submarine Kı̄lauea glasses: Evidence for direct assimilation of brine by magma

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Coombs, Michelle L.; Sisson, Thomas W.; Kimura, Jun-Ichi

2004-01-01

Basaltic glass grains from the submarine south flank of Kı̄lauea, Hawai′i, have Cl concentrations of 0.01–1.68 wt%, the latter being the highest Cl content yet recorded for a Hawaiian glass. The high-Cl glass grains are products of brine assimilation by tholeiite magma. The glasses are grains in a sandstone clast from bedded breccias draping the southwestern margin of Kı̄lauea’s submarine midslope bench. The clast contains two distinct suites of glass grains: abundant degassed tholeiites, perhaps derived from subaerial lavas of Mauna Loa that shattered upon ocean entry, and a smaller population of Kea-type tholeiite (n=17 analyzed) that erupted subaqueously, based on elevated S (780–1050 ppm), H2O (0.42–1.27 wt%), and CO2 (1000 ppm, six >5000 ppm, and two grains have >10 000 ppm dissolved Cl. Abundances of H2O, Na2O, K2O, and several trace elements increase regularly with Cl concentration, and we estimate that Cl enrichment was due to up to 13 wt% addition of a brine consisting of 78% H2O (wt), 13% Cl, 4.4% Na, 2.6% K, 2.6% Ca, 620 ppm Ba, 360 ppm Sr, 65 ppm Rb, and 7 ppm Pb. The large amounts of brine addition argue against bulk assimilation of low-porosity brine-bearing rock. The brine’s composition is appropriate for a seawater-derived hydrothermal fluid that reacted with basaltic wall rocks at T>100°C, losing Mg and S and gaining K, Ca, Rb, Ba, Sr, and Pb, followed by phase separation near 500°C and ∼50 MPa (5 km below sea level at hydrostatic pressure). Brine was assimilated at or near the depth it formed, as estimated on petrologic grounds, but under lithostatic conditions. The highest extents of assimilation either forced volatile saturation of the magma or enriched already coexisting magmatic vapor in H2O. Possible mechanisms for assimilation are: (1) forcible injection of brine into magma during bursting of overpressured pockets heated by new dikes, or (2) intrusion of magma into lenses or sills occupied by trapped brine.

Mars Global Surveyor Data Analysis Program. Origins of Small Volcanic Cones: Eruption Mechanisms and Implications for Water on Mars

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Fagents, Sarah A.; Greeley, Ronald; Thordarson, Thorvaldur

2002-01-01

The goal of the proposed work was to determine the origins of small volcanic cones observed in Mars Global Surveyor (MGS) data, and their implications for regolith ice stores and magma volatile contents. For this 1-year study, our approach involved a combination of: Quantitative morphologic analysis and interpretation of Mars Orbiter Camera (MOC) and Mars Orbiter Laser Altimeter (MOLA) data; Numerical modeling of eruption processes responsible for producing the observed features; Fieldwork on terrestrial analogs in Iceland. Following this approach, this study succeeded in furthering our understanding of (i) the spatial and temporal distribution of near-surface water ice, as defined by the distribution and sizes of rootless volcanic cones ("pseudocraters"), and (ii) the properties, eruption conditions, and volatile contents of magmas producing primary vent cones.

Rapid ascent of rhyolitic magma at Chaitén volcano, Chile.

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Castro, Jonathan M; Dingwell, Donald B

2009-10-08

Rhyolite magma has fuelled some of the Earth's largest explosive volcanic eruptions. Our understanding of these events is incomplete, however, owing to the previous lack of directly observed eruptions. Chaitén volcano, in Chile's northern Patagonia, erupted rhyolite magma unexpectedly and explosively on 1 May 2008 (ref. 2). Chaitén residents felt earthquakes about 24 hours before ash fell in their town and the eruption escalated into a Plinian column. Although such brief seismic forewarning of a major explosive basaltic eruption has been documented, it is unprecedented for silicic magmas. As precursory volcanic unrest relates to magma migration from the storage region to the surface, the very short pre-eruptive warning at Chaitén probably reflects very rapid magma ascent through the sub-volcanic system. Here we present petrological and experimental data that indicate that the hydrous rhyolite magma at Chaitén ascended very rapidly, with velocities of the order of one metre per second. Such rapid ascent implies a transit time from storage depths greater than five kilometres to the near surface in about four hours. This result has implications for hazard mitigation because the rapidity of ascending rhyolite means that future eruptions may provide little warning.

Lunar Magma Ocean Crystallization: Constraints from Fractional Crystallization Experiments

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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

Mezcla de magmas en Vulcanello (Isla Vulcano, Italia

Directory of Open Access Journals (Sweden)

Aparicio, A.

2008-06-01

Full Text Available Volcanic activity in Vulcano starts about 350 ka ago and continues up to present day with the development of thre main episodes corresponding to the calderas of Piano and La Fossa, and Vulcanello. These cover a compositional range from rhyolitic to trachybasaltic rocks. This lithological diversity is produced by different petrogenetic processes such as fractional crystallization, assimilation coupled to fractional crystallization (AFC, mixing, etc.The eruption of Vulcanello area emitted trachyandesitic materials, including shoshonites and latites. A magma-mixing process is established between trachytes and shoshonites to origine latites. Trachytes and rhyolites are produced by fractional crystallization and by ACF processes (assimilation of sedimentary rocks from trachyandesitic magmas.La actividad volcánica de Isla Vulcano comienzó aproximadamente hace 350.000 años y continúa hasta la actualidad con el desarrollo de tres grandes episodios correspondientes a las caldera de Piano, caldera de Fossa y a Vulcanello, que han emitido piroclastos y coladas de composiciones muy variadas, desde riolitas a traquibasaltos. Esta variedad litológica ha sido relacionada con procesos petrogenéticos tan diversos como cristalización fraccionada, asimilación simultánea con cristalización (ACF, mezcla de magmas, etc.El episodio de Vulcanello emite rocas traquiandesíticas, con composiciones shoshoníticas y latíticas. Un proceso de mezcla de magmas es reconocido entre traquitas y shoshonitas para generar latitas. Traquitas y riolitas son producidas por procesos de cristalización fraccionada simple y por ACF con asimilación de rocas sedimentarias a partir de magmas traquiandesíticos.

Growing magma chambers control the distribution of small-scale flood basalts.

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Yu, Xun; Chen, Li-Hui; Zeng, Gang

2015-11-19

Small-scale continental flood basalts are a global phenomenon characterized by regular spatio-temporal distributions. However, no genetic mechanism has been proposed to explain the visible but overlooked distribution patterns of these continental basaltic volcanism. Here we present a case study from eastern China, combining major and trace element analyses with Ar-Ar and K-Ar dating to show that the spatio-temporal distribution of small-scale flood basalts is controlled by the growth of long-lived magma chambers. Evolved basalts (SiO2 > 47.5 wt.%) from Xinchang-Shengzhou, a small-scale Cenozoic flood basalt field in Zhejiang province, eastern China, show a northward younging trend over the period 9.4-3.0 Ma. With northward migration, the magmas evolved only slightly ((Na2O + K2O)/MgO = 0.40-0.66; TiO2/MgO = 0.23-0.35) during about 6 Myr (9.4-3.3 Ma). When the flood basalts reached the northern end of the province, the magmas evolved rapidly (3.3-3.0 Ma) through a broad range of compositions ((Na2O + K2O)/MgO = 0.60-1.28; TiO2/MgO = 0.30-0.57). The distribution and two-stage compositional evolution of the migrating flood basalts record continuous magma replenishment that buffered against magmatic evolution and induced magma chamber growth. Our results demonstrate that the magma replenishment-magma chamber growth model explains the spatio-temporal distribution of small-scale flood basalts.

The Biosynthesis of Unusual Floral Volatiles and Blends Involved in Orchid Pollination by Deception: Current Progress and Future Prospects.

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Wong, Darren C J; Pichersky, Eran; Peakall, Rod

2017-01-01

Flowers have evolved diverse strategies to attract animal pollinators, with visual and olfactory floral cues often crucial for pollinator attraction. While most plants provide reward (e.g., nectar, pollen) in return for the service of pollination, 1000s of plant species, particularly in the orchid family, offer no apparent reward. Instead, they exploit their often specific pollinators (one or few) by mimicking signals of female insects, food source, and oviposition sites, among others. A full understanding of how these deceptive pollination strategies evolve and persist remains an open question. Nonetheless, there is growing evidence that unique blends that often contain unusual compounds in floral volatile constituents are often employed to secure pollination by deception. Thus, the ability of plants to rapidly evolve new pathways for synthesizing floral volatiles may hold the key to the widespread evolution of deceptive pollination. Yet, until now the biosynthesis of these volatile compounds has been largely neglected. While elucidating the biosynthesis in non-model systems is challenging, nonetheless, these cases may also offer untapped potential for biosynthetic breakthroughs given that some of the compounds can be exclusive or dominant components of the floral scent and production is often tissue-specific. In this perspective article, we first highlight the chemical diversity underpinning some of the more widespread deceptive orchid pollination strategies. Next, we explore the potential metabolic pathways and biosynthetic steps that might be involved. Finally, we offer recommendations to accelerate the discovery of the biochemical pathways in these challenging but intriguing systems.

The link between multistep magma ascent and eruption intensity: examples from the recent activity of Piton de la Fournaise (La Réunion Island).

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Di Muro, Andrea

2014-05-01

Caldera collapses represent catastrophic events, which induce drastic modification in a volcano plumbing system and can result in major and fast evolution of the system dynamics. At Piton de la Fournaise (PdF) volcano, the 2007 eruptive sequence extruded the largest lava volume (240 Mm3) since at least 3 centuries, provoking the collapse of a small (1 km wide; 340 m deep) summit caldera. In about 35 days, the 2007 major eruption generated i) the greatest lava output rate, ii) the strongest lava fountaining activity (> 200 m high), iii) the largest SO2 volume (> 230 kt) ever documented at PdF. This event ended a 9 year-long period (1998-2007) of continuous edifice inflation and sustained eruptive activity (3 eruptions per year on average). Unexpectedly and in spite of the large volume of magma erupted in 2007, volcano unrest and eruptive activity resumed quickly in 2008, soon after caldera collapse, and produced several closely spaced intracaldera eruptions and shallow intrusions. The post-2007 activity is associated with a trend of continuous volcano deflation and consists in small-volume (Pele's hairs, coarse ash fragments produced by lava-sea water interaction, glassy crust of lavas, high-temperature lavas quenched in water, matrix glasses) with the geophysical record of volcano unrest. Petro-chemical data suggest that the shallow PdF plumbing system is formed by a network of small sized magma pockets (sills). We explicitly link its formation and emptying with periodic magma recharges from deeper levels and repeated caldera collapses, which frequently affect the central cone of PdF. In spite of the large range in fountain intensity, dissolved volatiles contents are low and almost constant. Multistep ascent of magma inputs is identified as the key mechanism determining the evolution towards open system degassing and in fine controlling eruptive behavior.

Experimental Fractional Crystallization of the Lunar Magma Ocean

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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].

Isotopic composition of carbon in dacitic gases from Usu volcano (Japan). Relationship between the 13C/12C ratio of volatiles and the 87Sr/86Sr ratio of silicates in arc volcanism

International Nuclear Information System (INIS)

Allard, Patrick

1981-01-01

CO 2 emitted at 568 deg C by the new dacitic intrusion in Usu volcano (Japan) has a 13 C/ 12 C ratio of -4.4 per mill vs PDB. Such a value, together with previous isotopic data from other volcanoes in Japan, Indonesia, Central America, Lesser Antilles and New Zealand, enhance that the carbon released by magmas in subduction zones is systematically 13 C-enriched with respect to the primary carbon from rift areas. Such a 13 C enrichment in volatiles is explained in terms of crustal contamination by sedimentary carbon, and can be sowewhat related to a simultaneous increase of 87 Sr in the magma [fr

Magma transfer at Campi Flegrei caldera (Italy) before the 1538 AD eruption.

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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.

Timescales of quartz crystallization and the longevity of the Bishop giant magma body.

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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 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.

Pressure effect on Fe3+/FeT in silicate melts and applications to magma redox, particularly in magma oceans

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Zhang, H.; Hirschmann, M. M.

2014-12-01

The proportions of Fe3+ and Fe2+ in magmas reflect the redox conditions of their origin and influence the chemical and physical properties of natural silicate liquids, but the relationship between Fe3+/FeT and oxygen fugacity depends on pressure owing to different molar volumes and compressibilities of Fe3+ and Fe2+ in silicates. An important case where the effect of pressure effect may be important is in magma oceans, where well mixed (and therefore potentially uniform Fe3+/FeT) experiencses a wide range of pressures, and therefore can impart different ƒO2 at different depths, influencing magma ocean degassing and early atmospheres, as well as chemical gradients within magma oceans. To investigate the effect of pressure on magmatic Fe3+/FeT we conducted high pressure expeirments on ƒO2-buffered andestic liquids. Quenched glasses were analyzed by Mössbauer spectroscopy. To verify the accuracy of Mössbauer determinations of Fe3+/FeT in glasses, we also conducted low temperature Mössbauer studies to determine differences in the recoilless fraction (ƒ) of Fe2+ and Fe3. These indicate that room temperature Mössbauer determinations of on Fe3+/FeT glasses are systematically high by 4% compared to recoilless-fraction corrected ratios. Up to 7 GPa, pressure decreases Fe3+/FeT, at fixed ƒO2 relative to metal-oxide buffers, meaning that an isochemical magma will become more reduced with decreasing pressure. Consequently, for small planetary bodies such as the Moon or Mercury, atmospheres overlying their MO will be highly reducing, consisting chiefly of H2 and CO. The same may also be true for Mars. The trend may reverse at higher pressure, as is the case for solid peridotite, and so for Earth, Venus, and possibly Mars, more oxidized atmospheres above MO are possible. Diamond anvil experiments are underway to examine this hypothesis.

Sources of Magmatic Volatiles Discharging from Subduction Zone Volcanoes

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Fischer, T.

2001-05-01

5.4 Mmol/a of non-mantle N2). Other subduction zone volcanoes are currently degassing a much more substantial amount of volatiles. Popocatepetl, Mexico, has degassed approximately 14 Mt of SO2 to the atmosphere over the past 6 years (Witter et al. 2000). Satsuma-Iwojima, Japan, has degassed for longer than 800 years and is currently releasing 500-1000 tones/day (Kazahaya et al. 2000). At these volcanoes CO2 and N2 discharges from the magma should also be balanced by the supply from slab and crustal sources. The rate of subduction off Mexico and Japan, however, is similar to the rate at the Kuriles. Therefore, large amounts of slab derived volatiles must be, in some fashion, stored in the "subduction factory" to supply the large amounts degassing passively from these volcanoes. Kazahaya et al. (2000) Seventh Field Workshop on Volcanic Gases, IAVCEI. Witter et al (2000) Seventh Field Workshop on Volcanic Gases, IAVCEI.

Depths of Magma Chambers in the Icelandic Crust

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Kelley, D. F.; Kapostasy, D. D.; Barton, M.

2004-05-01

There is considerable interest in the structure and thermal state of the crust in Iceland, which lies across the Mid Atlantic Ridge. However, interpretations of seismic and gravity data yield conflicting views of the nature of the lower crust. Some interpretations prefer a model in which the lower crust (15-25 km) is relatively cool and solid, whereas other interpretations, based largely on gravity data, prefer a model in which the lower crust is relatively warm and possibly partially molten. Knowledge of the depth of magma chambers is critical to constrain the geothermal gradient in Icelandic crust and to resolve discrepancies in interpretation of geophysical data. Analyses of aphyric lavas and of glasses in Icelandic lavas erupted from 11 volcanic centers have been compiled. The compositions are picritic and basaltic with SiO2 - 47 to 50 wt%, MgO - 6 to 15wt%, FeO - 8 to 14wt%, to, Na2O - 1.3 to 3.3 wt%, and K2O - 0.03-46 wt%. The pressures of equilibration of these liquids with ol, high-Ca pyx and plag were estimated qualitatively from projections into the pseudoternary system Ol-Di-Silica using methods described by Walker and coworkers and Grove and coworkers. The results (ca. 0.5 GPa) indicate crystallization in magma chambers located at about 16 km depth. Equilibration pressures were also calculated using the method described by Yang and coworkers and by a modified version of this method. Calculated pressures (0.45±0.15 GPa) indicate magma chambers located at 15±4 km depth. Equilibration pressures for Rekjanes Ridge glasses determined using the same techniques are 0.2±0.1 GPa, corresponding to depths of 7.6±3 km. The results indicate the presence of magma chambers in the deep Icelandic crust and that the latter is relatively warm. Shallower chambers (3-7 km) have been identified from seismic studies suggesting a complex magma plumbing system. The results also confirm that magma chambers beneath Iceland are located at greater depths than those beneath the

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

2016-01-01

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. PMID:27619897

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.

Effects of Rotation on the Differentiation of a terrestrial Magma Ocean

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Maas, C.; Hansen, U.

2014-12-01

It is widely accepted that the Earth experienced several large impacts during its early evolution which led to the formation of one or more magma oceans. Differentiation processes in such a magma ocean are of great importance for the initial conditions of mantle convection and for the subsequent mantle structure. Convection in a magma ocean is most likely very vigorous. Further, rotation of the early Earth is supposed to be very fast. Therefore, and due to the small viscosity, it can be assumed that differentiation is strongly affected by rotation.To study the influence of rotation on the crystallization of a magma ocean, we employed a 3D Cartesian numerical model with low Prandtl number and used a discrete element method to describe silicate crystals.Our results show a crucial dependence on crystal density, rotation rate and latitude. Low rotation at the pole leads to a large fraction of suspended particles. With increasing rotation the particles settle at the bottom and form a stable stratified layer. In contrast to that at the equator at low rotation all particles settle at the bottom, at higher rotation they form a layer of significant thickness and at the highest rotation rate the particles accumulate in the middle of the magma ocean. In addition to that, we observe that due to the Coriolis force silicate crystals with different densities separate from each other. While lighter particles are at the bottom, denser particles accumulate at mid-depth at the same rotation rate. This could result in an unstable stratified mantle in the equatorial region after magma ocean solidification.All in all, rotation could lead to an asymmetrical crystallization of the magma ocean, with a contrary layering at the pole and the equator. This affects the composition of the early mantle and could explain the development of a localized magma ocean at the core-mantle boundary and the development of phase transitions observed in seismology, like the mantle transition zone.

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.

The Earth’s mantle before convection: Effects of magma oceans and the Moon (Invited)

Science.gov (United States)

Elkins-Tanton, L. T.; Smrekar, S. E.; Tobie, G.

2009-12-01

thick solid lid and diminished the likelihood of mantle remixing. Second, on an Earth-sized planet a magma ocean would solidify to produce very dense near-surface solids that also contain the bulk of the water held in the solid state, and the bulk of the incompatible elements. During gravitationally-driven overturn shallow, dense, damp solids carry their water as they sink into the perovskite stability zone and transform the bulk of their mineralogy into perovskite. The last solids that form near the surface exceed the likely water saturation levels of perovskite and will be forced to dewater as they cross the boundary into the lower mantle, leaving water behind in a rapid flux as the dense material sinks. This event will form a kind of “water catastrophe,” and would have the potential to partially melt the upper mantle, to produce a damp asthensosphere, and indeed to encourage convection. These results imply that planets in which perovskite is stable, that is, planets that are larger than Mars, are perhaps more likely to have an early initiation of plate tectonics, and that larger planets may have more violent and near-surface mantle volatile releases during any overturn event.

Water Partitioning in Planetary Embryos and Protoplanets with Magma Oceans

Science.gov (United States)

Ikoma, M.; Elkins-Tanton, L.; Hamano, K.; Suckale, J.

2018-06-01

The water content of magma oceans is widely accepted as a key factor that determines whether a terrestrial planet is habitable. Water ocean mass is determined as a result not only of water delivery and loss, but also of water partitioning among several reservoirs. Here we review our current understanding of water partitioning among the atmosphere, magma ocean, and solid mantle of accreting planetary embryos and protoplanets just after giant collisions. Magma oceans are readily formed in planetary embryos and protoplanets in their accretion phase. Significant amounts of water are partitioned into magma oceans, provided the planetary building blocks are water-rich enough. Particularly important but still quite uncertain issues are how much water the planetary building blocks contain initially and how water goes out of the solidifying mantle and is finally degassed to the atmosphere. Constraints from both solar-system explorations and exoplanet observations and also from laboratory experiments are needed to resolve these issues.

A dynamic balance between magma supply and eruption rate at Kilauea volcano, Hawaii

Science.gov (United States)

Denlinger, R.P.

1997-01-01

The dynamic balance between magma supply and vent output at Kilauea volcano is used to estimate both the volume of magma stored within Kilauea volcano and its magma supply rate. Throughout most of 1991 a linear decline in volume flux from the Kupaianaha vent on Kilauea's east rift zone was associated with a parabolic variation in the elevation of Kilauea's summit as vent output initially exceeded then lagged behind the magma supply to the volcano. The correspondence between summit elevation and tilt established with over 30 years of data provided daily estimates of summit elevation in terms of summit tilt. The minimum in the parabolic variation in summit tilt and elevation (or zero elevation change) occurs when the magma supply to the reservoir from below the volcano equals the magma output from the reservoir to the surface, so that the magma supply rate is given by vent flux on that day. The measurements of vent flux and tilt establish that the magma supply rate to Kilauea volcano on June 19, 1991, was 217,000 ?? 10,000 m3/d (or 0.079 ?? 0.004 km3/yr). This is close to the average eruptive rate of 0.08 km3/yr between 1958 and 1984. In addition, the predictable response of summit elevation and tilt to each east rift zone eruption near Puu Oo since 1983 shows that summit deformation is also a measure of magma reservoir pressure. Given this, the correlation between the elevation of the Puu Oo lava lake (4 km uprift of Kupaianaha and 18 km from the summit) and summit tilt provides an estimate for magma pressure changes corresponding to summit tilt changes. The ratio of the change in volume to the change in reservoir pressure (dV/dP) during vent activity may be determined by dividing the ratio of volume erupted to change in summit tilt (dV/dtilt) by the ratio of pressure change to change in summit tilt (dP/dtilt). This measure of dV/dP, when combined with laboratory measurements of the bulk modulus of tholeitic melt, provides an estimate of 240 ?? 50 km3 for the volume

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.

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

Use of a free-jet expansion, molecular beam mass spectrometer to understand processes involving volatile corrosion products

International Nuclear Information System (INIS)

Jacobson, N.S.

1997-01-01

Many high-temperature corrosion processes generate volatile products in addition to condensed phase products. Examples of these volatile products are chlorides, oxychlorides, and certain oxides and hydroxyl species. One of the best techniques to identify high temperature vapor molecules is mass spectrometry. Most mass spectrometers operate in high vacuum and are generally used to examine processes ocurring at greatly reduced pressures. However, a free-jet expansion, molecular beam mass spectrometer system allows direct sampling of volatile corrosion products. This instrument is described. Several examples from our studies on chlorination/oxidation of metals and ceramics are discussed. In addition, reactions of Cr 2 O 3 , SiO 2 , and Al 2 O 3 with water vapor, which produce volatile hydroxyl species are discussed. (orig.)

Features of the distribution of uranium in igneous rocks - uranium deposits associated with igneous rocks

International Nuclear Information System (INIS)

Soerensen, H.

1977-01-01

The generally accepted main features of the distribution of uranium and thorium in igneous rocks are briefly reviewed. It is pointed out that uranium in most cases examined is strongly partitioned into the melt during consolidation of magmas and that uranium is concentrated in the most volatile-rich parts of magmas. The mode of emplacement and the consolidation of magmas control the retention or the expulsion of the volatile phase from consolidating magmas and also the distribution of uranium between magmas and the volatile phase. After a brief review of the types of uranium deposits associated with igneous rocks it is concluded that it is difficult to establish universally valid exploration criteria to be used in the search of these types of deposit. It is emphasized, however, that detailed petrological and geochemical studies may be useful in outlining exploration targets. (author)

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.

Assimilation of carbonate country rock by the parent magma of the Panzhihua Fe-Ti-V deposit (SW China: Evidence from stable isotopes

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Clément Ganino

2013-09-01

Full Text Available The Panzhihua intrusion in southwest China is part of the Emeishan Large Igneous Province and host of a large Fe-Ti-V ore deposit. During emplacement of the main intrusion, multiple generations of mafic dykes invaded carbonate wall rocks, producing a large contact aureole. We measured the oxygen-isotope composition of the intrusions, their constituent minerals, and samples of the country rock. Magnetite and plagioclase from Panzhihua intrusion have δ18O values that are consistent with magmatic equilibrium, and formed from magmas with δ18O values that were 1–2‰ higher than expected in a mantle-derived magma. The unmetamorphosed country rock has high δ18O values, ranging from 13.2‰ (sandstone to 24.6–28.6‰ (dolomite. The skarns and marbles from the aureole have lower δ18O and δ13C values than their protolith suggesting interaction with fluids that were in exchange equilibrium with the adjacent mafic magmas and especially the numerous mafic dykes that intruded the aureole. This would explain the alteration of δ18O of the dykes which have significantly higher values than expected for a mantle-derived magma. Depending on the exact δ18O values assumed for the magma and contaminant, the amount of assimilation required to produce the elevated δ18O value of the Panzhihua intrusion was between 8 and 13.7 wt.%, assuming simple mixing. The exact mechanism of contamination is unclear but may involve a combination of assimilation of bulk country rock, mixing with a melt of the country rock and exchange with CO2-rich fluid derived from decarbonation of the marls and dolomites. These mechanisms, particularly the latter, were probably involved in the formation of the Fe-Ti-V ores.

The Biosynthesis of Unusual Floral Volatiles and Blends Involved in Orchid Pollination by Deception: Current Progress and Future Prospects

Directory of Open Access Journals (Sweden)

Darren C. J. Wong

2017-11-01

Full Text Available Flowers have evolved diverse strategies to attract animal pollinators, with visual and olfactory floral cues often crucial for pollinator attraction. While most plants provide reward (e.g., nectar, pollen in return for the service of pollination, 1000s of plant species, particularly in the orchid family, offer no apparent reward. Instead, they exploit their often specific pollinators (one or few by mimicking signals of female insects, food source, and oviposition sites, among others. A full understanding of how these deceptive pollination strategies evolve and persist remains an open question. Nonetheless, there is growing evidence that unique blends that often contain unusual compounds in floral volatile constituents are often employed to secure pollination by deception. Thus, the ability of plants to rapidly evolve new pathways for synthesizing floral volatiles may hold the key to the widespread evolution of deceptive pollination. Yet, until now the biosynthesis of these volatile compounds has been largely neglected. While elucidating the biosynthesis in non-model systems is challenging, nonetheless, these cases may also offer untapped potential for biosynthetic breakthroughs given that some of the compounds can be exclusive or dominant components of the floral scent and production is often tissue-specific. In this perspective article, we first highlight the chemical diversity underpinning some of the more widespread deceptive orchid pollination strategies. Next, we explore the potential metabolic pathways and biosynthetic steps that might be involved. Finally, we offer recommendations to accelerate the discovery of the biochemical pathways in these challenging but intriguing systems.

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

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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.

What can Fe stable isotopes tell us about magmas?

DEFF Research Database (Denmark)

Stausberg, Niklas

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......The majority of the Earth’s crust is formed by magmas, and understanding their production and differentiation is important to interpret the geologic rock record. A powerful tool to investigate magmatic processes is the distribution of the stable isotopes of the major redox-sensitive element...... 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...

Reconstructing modalities of magma storage in the crust by thermo-rheological modelling

Science.gov (United States)

Caricchi, L.; Annen, C.; Rust, A.; Blundy, J.

2012-04-01

During my PhD I worked under the supervision of Luigi Burlini studying the rheological behaviour of magma. Luigi was not only a great teacher and friend but he was also able to project the science he was performing beyond the obvious applications. This aspect of Luigi's approach shaped my approach to research and brought me to think to ways of applying the studies we performed together to unravel the complexity of nature that impassioned and inspired him. This contribution comes from the motivation and interest that Luigi created in me during the short, but truly memorable journey we shared together. This study combines petrology, thermal modelling and magma rheology to characterise timescales and modalities of magma emplacement in the Earth's crust. Thermal modelling was performed to determine the influence of magma injection rates in the crust on the temperature evolution of a magmatic body. The injected tonalitic magma was considered to contain dioritic enclaves, common in plutons. The contrast in chemical composition between host and enclaves leads to different crystallinities of these magmas during cooling and produce a rheological contrast that permits reciprocal deformation only in restricted temperature ranges. Characterising the thermal and rheological evolution of host magma and enclaves, we traced the evolution of strain recorded by these inclusions during the construction of an intrusion, showing that the strain recorded by enclaves distributed in different portions of a pluton can be used to constrain thermal evolution in time, magmatic fluxes and timescale of assemblage of magmatic bodies in the crust.

Modeling Magma Mixing: Evidence from U-series age dating and Numerical Simulations

Science.gov (United States)

Philipp, R.; Cooper, K. M.; Bergantz, G. W.

2007-12-01

Magma mixing and recharge is an ubiquitous process in the shallow crust, which can trigger eruption and cause magma hybridization. Phenocrysts in mixed magmas are recorders for magma mixing and can be studied by in- situ techniques and analyses of bulk mineral separates. To better understand if micro-textural and compositional information reflects local or reservoir-scale events, a physical model for gathering and dispersal of crystals is necessary. We present the results of a combined geochemical and fluid dynamical study of magma mixing processes at Volcan Quizapu, Chile; two large (1846/47 AD and 1932 AD) dacitic eruptions from the same vent area were triggered by andesitic recharge magma and show various degrees of magma mixing. Employing a multiphase numerical fluid dynamic model, we simulated a simple mixing process of vesiculated mafic magma intruded into a crystal-bearing silicic reservoir. This unstable condition leads to overturn and mixing. In a second step we use the velocity field obtained to calculate the flow path of 5000 crystals randomly distributed over the entire system. Those particles mimic the phenocryst response to the convective motion. There is little local relative motion between silicate liquid and crystals due to the high viscosity of the melts and the rapid overturn rate of the system. Of special interest is the crystal dispersal and gathering, which is quantified by comparing the distance at the beginning and end of the simulation for all particle pairs that are initially closer than a length scale chosen between 1 and 10 m. At the start of the simulation, both the resident and new intruding (mafic) magmas have a unique particle population. Depending on the Reynolds number (Re) and the chosen characteristic length scale of different phenocryst-pairs, we statistically describe the heterogeneity of crystal populations on the thin section scale. For large Re (approx. 25) and a short characteristic length scale of particle

75 FR 28778 - Magma Flood Retarding Structure (FRS) Supplemental Watershed Plan, Pinal County, AZ

Science.gov (United States)

2010-05-24

... DEPARTMENT OF AGRICULTURE Natural Resources Conservation Service Magma Flood Retarding Structure... statement is not being prepared for the Magma Flood Retarding Structure (FRS) Supplemental Watershed Plan... rehabilitate the Magma FRS to provide for continued flood protection for a portion of the Town of Florence and...

Deformation patterns, magma supply, and magma storage at Karymsky Volcanic Center, Kamchatka, Russia, 2000-2010, revealed by InSAR

Science.gov (United States)

Ji, Lingyun; Izbekov, Pavel; Senyukov, Sergey; Lu, Zhong

2018-02-01

Under a complex geological region influenced by the subduction of the Pacific plate, Kamchatka Peninsula is one of the most active volcanic arcs in the Pacific Rim. Due to logistical difficulty in instrumentation, shallow magma plumbing systems beneath some of the Kamchatkan volcanoes are poorly understood. InSAR offers a safe and quick method for monitoring volcanic deformation with a high spatial resolution. In this study, a group of satellite radar interferograms that span the time interval from 2000 to 2010 shows eruptive and non-eruptive deformation at Karymsky Volcanic Center (KVC), Kamchatka, Russia. All the interferograms provide details of the activity around the KVC during 2000-2010, as follows: (1) from 2000 to 2004, the Karymsky-AN (Akademia Nauk) area deflated and the MS (Maly Semyachik) area inflated, (2) from 2004 to 2006, the Karymsky-AN area deflated with ongoing eruption, while the MS area subsided without eruption, (3) from 2006 to 2008, as with 2000-2004, the Karymsky-AN area deflated and the MS area inflated, (4) from 2008 to 2010, the Karymsky-AN area inflated up to 3 cm, and the MS area subsided. Point source models suggest that two magma reservoirs provide a good fit to the observed deformation. One source is located beneath the area between Karymsky and AN at a depth of approximately 7.0 km, and the other one is situated beneath MS at a depth of around 5.8 km. Synchronous deformation patterns suggest that two magma systems are fed from the same deep magma source and connected by a fracture zone. The InSAR results are consistent with GPS ground deformation measurements, seismic data, and petrological constraints.

Role of syn-eruptive plagioclase disequilibrium crystallization in basaltic magma ascent dynamics.

Science.gov (United States)

La Spina, G; Burton, M; De' Michieli Vitturi, M; Arzilli, F

2016-12-12

Timescales of magma ascent in conduit models are typically assumed to be much longer than crystallization 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 crystallization and exsolution processes are fundamental to our understanding of such disequilibria and ascent dynamics. Here we use observations from Mount Etna's 2001 eruption and a magma ascent model to constrain timescales for crystallization and exsolution processes. Our results show that plagioclase reaches equilibrium in 1-2 h, whereas ascent times were magma ascent rate and disequilibrium crystallization and exsolution plays a key role in controlling eruption dynamics in basaltic volcanism.

Unscrambling the Omlette: a New Bubble and Crystal Clustering Mechanism in Chaotically Mixed Magma Flows

Science.gov (United States)

Robertson, J.; Metcalfe, G.; Wang, S.; Barnes, S. J.

2014-12-01

The concentration of bubbles, crystals or droplets into small volumes of magma is a key trigger for many interesting magmatic processes. For example, gas slugs driving Strombolian eruptions form from the coalesence of exsolved bubbles within a volcanic conduit, while Ni-Cu-PGE magmatic sulfide deposits require a concentration of dense sulfide droplets from a large volume of magma to form a massive ore body. However the physical mechanism for this clustering remains unresolved - especially since small particles in active magma flows are expected to mostly track flow streamlines rather than clustering. We have uncovered a previously unreported clustering mechanism which is applicable to magmatic flows. This mechanism involves the interaction of particles with two kinds of chaotic flow structure: (a) high-strain regions within the well-mixed chaotic zones of the flow, and (b) unmixed islands of stability within the chaotic flow, known as Kolmogorov-Arnold-Moser (KAM) regions. The first figure shows the difference between chaotic and KAM regions in a chaotic laminar pipe flow. Trapping occurs when particles are scattered from high-strain regions in the chaotic zones and become trapped in the KAM regions, leading to a rapid concentration of particles relative to their original distribution (shown in the second series of figures). Using a combination of these analogue experiments and theoretical analysis we outline the conditions under which this clustering process can occur. We examine the onset of secondary density-related instabilities and the effects of increased particle-particle interaction within the clustered particles, and highlight the impact of particle clustering on the dynamics of magma ascent and emplacement.

Mafic-silicic magma interaction in the layered 1.87 Ga Soukkio Complex in Mäntsälä, southern Finland

Directory of Open Access Journals (Sweden)

Toni T. Eerola

2002-01-01

Full Text Available The Svecofennian layered Soukkio Complex (1.87 Ga in Mäntsälä, southern Finland, consists of layered tholeiitic gabbro and porphyritic calc-alkaline monzonite, quartz monzonite and granite, mingled together. The gabbro belongs to a group of ten mafic-ultramafic intrusions of Mäntsälä, part of the 150 km long and 20 km wide, linear, E-W trending Hyvinkää–Mäntsälä Gabbroic Belt(HMGB, representing syn-collisional magmatism. Structures and textures related to magma mingling and mixing occur in a 1–2 km wide zone around Lake Kilpijärvi, located at the center of the Soukkio Complex. The complex is compositionally stratified and consists of four zones:its base, found at the Western Zone, is a dynamically layered gabbro. The followingtonalite is probably a result of magma mixing. Felsic amoeboid layers and pipes, alternating with or cutting the fine-grained gabbro in the Central-Western Zone, resemble those of mafic-silicic layered intrusions in general. Mafic magmatic enclaves (MMEs and pillows form the South-Central Zone and disrupted synplutonic mafic dykes or sheets intruded the granite in the Eastern Zone. The MMEs and disrupted synplutonic mafic dykes or sheets show cuspate and chilled margins against the felsic host, quartz ocelli, corroded K-feldspar xenocrysts with or without plagioclase mantles, and acicular apatite, all typical features of magma mingling and mixing. Mixing is suggested by intermediate composition of MMEs between granitoid and gabbro, as well as by their partly linear trends in some Harker diagrams. REE composition of the MMEs is similar to that of the Soukkio Gabbro, as expected for granite hosted MMEs. The model proposed for evolution of the Soukkio Complex involves intrusion of mafic magma into the crust, causing its partial melting. This generated granitic magma above the mafic chamber. Injections of mafic magma invaded the felsic chamber and those magmas interacted mainly by intermingling. Mingling and

The Krafla International Testbed (KMT): Ground Truth for the New Magma Geophysics

Science.gov (United States)

Brown, L. D.; Kim, D.; Malin, P. E.; Eichelberger, J. C.

2017-12-01

Recent developments in geophysics such as large N seismic arrays , 4D (time lapse) subsurface imaging and joint inversion algorithms represent fresh approaches to delineating and monitoring magma in the subsurface. Drilling at Krafla, both past and proposed, are unique opportunities to quantitatively corroborate and calibrate these new technologies. For example, dense seismic arrays are capable of passive imaging of magma systems with resolutions comparable to that achieved by more expensive (and often logistically impractical) controlled source surveys such as those used in oil exploration. Fine details of the geometry of magma lenses, feeders and associated fluid bearing fracture systems on the scale of meters to tens of meters are now realistic targets for surface seismic surveys using ambient energy sources, as are detection of their temporal variations. Joint inversions, for example of seismic and MT measurements, offer the promise of tighter quantitative constraints on the physical properties of the various components of magma and related geothermal systems imaged by geophysics. However, the accuracy of such techniques will remain captive to academic debate without testing against real world targets that have been directly sampled. Thus application of these new techniques to both guide future drilling at Krafla and to be calibrated against the resulting borehole observations of magma are an important step forward in validating geophysics for magma studies in general.

Nonvolatile, semivolatile, or volatile: redefining volatile for volatile organic compounds.

Science.gov (United States)

Võ, Uyên-Uyén T; Morris, Michael P

2014-06-01

Although widely used in air quality regulatory frameworks, the term "volatile organic compound" (VOC) is poorly defined. Numerous standardized tests are currently used in regulations to determine VOC content (and thus volatility), but in many cases the tests do not agree with each other, nor do they always accurately represent actual evaporation rates under ambient conditions. The parameters (time, temperature, reference material, column polarity, etc.) used in the definitions and the associated test methods were created without a significant evaluation of volatilization characteristics in real world settings. Not only do these differences lead to varying VOC content results, but occasionally they conflict with one another. An ambient evaporation study of selected compounds and a few formulated products was conducted and the results were compared to several current VOC test methodologies: SCAQMD Method 313 (M313), ASTM Standard Test Method E 1868-10 (E1868), and US. EPA Reference Method 24 (M24). The ambient evaporation study showed a definite distinction between nonvolatile, semivolatile, and volatile compounds. Some low vapor pressure (LVP) solvents, currently considered exempt as VOCs by some methods, volatilize at ambient conditions nearly as rapidly as the traditional high-volatility solvents they are meant to replace. Conversely, bio-based and heavy hydrocarbons did not readily volatilize, though they often are calculated as VOCs in some traditional test methods. The study suggests that regulatory standards should be reevaluated to more accurately reflect real-world emission from the use of VOC containing products. The definition of VOC in current test methods may lead to regulations that exclude otherwise viable alternatives or allow substitutions of chemicals that may limit the environmental benefits sought in the regulation. A study was conducted to examine volatility of several compounds and a few formulated products under several current VOC test

Dynamics of an open basaltic magma system: The 2008 activity of the Halema‘uma‘u Overlook vent, Kīlauea Caldera

Science.gov (United States)

Eychenne, Julia; Houghton, Bruce F.; Swanson, Don; Carey, Rebecca; Swavely, Lauren

2015-01-01

On March 19, 2008 a small explosive event accompanied the opening of a 35-m-wide vent (Overlook vent) on the southeast wall of Halema‘uma‘u Crater in Kīlauea Caldera, initiating an eruptive period that extends to the time of writing. The peak of activity, in 2008, consisted of alternating background open-system outgassing and spattering punctuated by sudden, short-lived weak explosions, triggered by collapses of the walls of the vent and conduit. Near-daily sampling of the tephra from this open system, along with exceptionally detailed observations, allow us to study the dynamics of the activity during two eruptive sequences in late 2008. Each sequence includes background activity preceding and following one or more explosions in September and October 2008 respectively. Componentry analyses were performed for daily samples to characterise the diversity of the ejecta. Nine categories of pyroclasts were identified in all the samples, including wall-rock fragments. The six categories of juvenile clasts can be grouped in three classes based on vesicularity: (1) poorly, (2) uniformly highly to extremely, and (3) heterogeneously highly vesicular. The wall-rock and juvenile clasts show dissimilar grainsize distributions, reflecting different fragmentation mechanisms. The wall-rock particles formed by failure of the vent and conduit walls above the magma free surface and were then passively entrained in the eruptive plume. The juvenile componentry reveals consistent contrasts in degassing and fragmentation processes before, during and after the explosive events. We infer a crude ‘layering’ developed in the shallow melt, in terms of both rheology and bubble and volatile contents, beneath a convecting free surface during background activity. A tens-of-centimetres thick viscoelastic surface layer was effectively outgassed and relatively cool, while at depths of less than 100 m, the melt remained slightly supersaturated in volatiles and actively vesiculating

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.

Drilling into Rhyolitic Magma at Shallow depth at Krafla Volcanic Complex, NE-Iceland

Science.gov (United States)

Mortensen, A. K.; Markússon, S. H.; Gudmundsson, Á.; Pálsson, B.

2017-12-01

Krafla volcanic complex in NE-Iceland is an active volcano but the latest eruption was the Krafla Fires in 1975-1984. Though recent volcanic activity has consisted of basaltic fissure eruptions, then it is rhyolitic magma that has been intercepted on at least two occasions while drilling geothermal production wells in the geothermal field suggesting a layered magma plumbing system beneath the Krafla volcanic complex. In 2008 quenched rhyolitic glass was retrieved from the bottom of well KJ-39, which is 2865 m deep ( 2571 m true vertical depth). In 2009 magma was again encountered at an even shallower depth and in more than 2,5 km distance from the bottom of well KJ-39, but in 2009 well IDDP-1 was drilled into magma three times just below 2100 m depth. Only on the last occasion was quenched glass retrieved to confirm that magma had been encountered. In well KJ-39 the quenched glass was rhyolitic in composition. The glass contained resorbed minerals of plagioclase, clinopyroxene and titanomagnetite, but the composition of the glass resembles magma that has formed by partial melting of hydrated basalt. The melt was encountered among cuttings from impermeable, coarse basaltic intrusives at a depth, where the well was anticipated to penetrate the Hólseldar volcanic fissure. In IDDP-1 the quenched glass was also rhyolitic in composition. The glass contained less than 5% of phenocrysts, but the phenocryst assemblage included andesine plagioclase, augite, pigeonite, and titanomagnetite. At IDDP-1 the melt was encountered below a permeable zone composed of fine to coarse grained felsite and granophyre. The disclosure of magma in two wells at Krafla volcanic complex verify that rhyolitic magma can be encountered at shallow depth across a larger area within the caldera. The encounter of magma at shallow depth conforms with that superheated conditions have been found at >2000 m depth in large parts of Krafla geothermal field.

The fluid dynamics of a basaltic magma chamber replenished by influx of hot, dense ultrabasic magma

Science.gov (United States)

Huppert, Herbert E.; Sparks, R. Stephen J.

1981-09-01

This paper describes a fluid dynamical investigation of the influx of hot, dense ultrabasic magma into a reservoir containing lighter, fractionated basaltic magma. This situation is compared with that which develops when hot salty water is introduced under cold fresh water. Theoretical and empirical models for salt/water systems are adapted to develop a model for magmatic systems. A feature of the model is that the ultrabasic melt does not immediately mix with the basalt, but spreads out over the floor of the chamber, forming an independent layer. A non-turbulent interface forms between this layer and the overlying magma layer across which heat and mass are transferred by the process of molecular diffusion. Both layers convect vigorously as heat is transferred to the upper layer at a rate which greatly exceeds the heat lost to the surrounding country rock. The convection continues until the two layers have almost the same temperature. The compositions of the layers remain distinct due to the low diffusivity of mass compared to heat. The temperatures of the layers as functions of time and their cooling rate depend on their viscosities, their thermal properties, the density difference between the layers and their thicknesses. For a layer of ultrabasic melt (18% MgO) a few tens of metres thick at the base of a basaltic (10% MgO) magma chamber a few kilometres thick, the temperature of the layers will become nearly identical over a period of between a few months and a few years. During this time the turbulent convective velocities in the ultrabasic layer are far larger than the settling velocity of olivines which crystallise within the layer during cooling. Olivines only settle after the two layers have nearly reached thermal equilibrium. At this stage residual basaltic melt segregates as the olivines sediment in the lower layer. Depending on its density, the released basalt can either mix convectively with the overlying basalt layer, or can continue as a separate

Terrestrial magma ocean and core segregation in the earth

Science.gov (United States)

Ohtani, Eiji; Yurimoto, Naoyoshi

1992-01-01

According to the recent theories of formation of the earth, the outer layer of the proto-earth was molten and the terrestrial magma ocean was formed when its radius exceeded 3000 km. Core formation should have started in this magma ocean stage, since segregation of metallic iron occurs effectively by melting of the proto-earth. Therefore, interactions between magma, mantle minerals, and metallic iron in the magma ocean stage controlled the geochemistry of the mantle and core. We have studied the partitioning behaviors of elements into the silicate melt, high pressure minerals, and metallic iron under the deep upper mantle and lower mantle conditions. We employed the multi-anvil apparatus for preparing the equilibrating samples in the ranges from 16 to 27 GPa and 1700-2400 C. Both the electron probe microanalyzer (EPMA) and the Secondary Ion Mass spectrometer (SIMS) were used for analyzing the run products. We obtained the partition coefficients of various trace elements between majorite, Mg-perovskite, and liquid, and magnesiowustite, Mg-perovskite, and metallic iron. The examples of the partition coefficients of some key elements are summarized in figures, together with the previous data. We may be able to assess the origin of the mantle abundances of the elements such as transition metals by using the partitioning data obtained above. The mantle abundances of some transition metals expected by the core-mantle equilibrium under the lower mantle conditions cannot explain the observed abundance of some elements such as Mn and Ge in the mantle. Estimations of the densities of the ultrabasic magma Mg-perovskite at high pressure suggest existence of a density crossover in the deep lower mantle; flotation of Mg-perovskite occurs in the deep magma ocean under the lower mantle conditions. The observed depletion of some transition metals such as V, Cr, Mn, Fe, Co, and Ni in the mantle may be explained by the two stage process, the core-mantle equilibrium under the lower

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.

Rapid mixing and short storage timescale in the magma dynamics of a steady-state volcano

Science.gov (United States)

Petrone, Chiara Maria; Braschi, Eleonora; Francalanci, Lorella; Casalini, Martina; Tommasini, Simone

2018-06-01

Steady-state volcanic activity implies equilibrium between the rate of magma replenishment and eruption of compositionally homogeneous magmas, lasting for tens to thousands of years in an open conduit system. The Present-day activity of Stromboli volcano (Aeolian Islands, Southern Italy) has long been recognised as typical of a steady-state volcano, with a shallow magmatic reservoir (highly porphyritic or hp-magma) continuously refilled by more mafic magma (with low phenocryst content or lp-magma) at a constant rate and accompanied by mixing, crystallisation and eruption. Our aim is to clarify the timescale and dynamics of the plumbing system at the establishment of the Present-day steady-state activity (volcanoes.

Ascent Rates from Melt Embayments: Insights into the Eruption Dynamics of Arc Volcanoes

Science.gov (United States)

Ruprecht, P.; Lloyd, A. S.; Hauri, E.; Rose, W. I.; Gonnermann, H. M.; Plank, T. A.

2014-12-01

A significant fraction of the magma that is added from the mantle to the subvolcanic plumbing system ultimately erupts at the surface. The initial volatile content of the magmas as well as the interplay between volatile loss and magma ascent plays a significant role in determining the eruption style (effusive versus explosive) as well as the magnitude of the eruption. The October 17, 1974 sub-Plinian eruption of Volcán de Fuego represents a particularly well-characterized system in terms of volatile content and magma chemistry to investigate the relation between initial water content of the magmas and the ascent rate. By modeling volatile element distribution in melt embayments through diffusion and degassing during ascent we can estimate magma ascent from the storage region in the crust to the surface. The novel aspect is the measurement of concentration gradients multiple volatile elements (in particular CO2, H2O, S) at fine-scale (5-10 μm) using the NanoSIMS. The wide range in diffusivity and solubility of these different volatiles provides multiple constraints on ascent timescales over a range of depths. H2O, CO2, and S all decrease toward the embayment outlet bubble documenting the loss of H2O and CO2 compared to an extensive melt inclusion suite from the same day of the eruption. The data is best described by a two-stage model. At high pressure (>145 MPa) decompression is slow (0.05- 0.3 MPa/s) and CO2 is bled off predominantly. At shallow levels decompression accelerates to 0.3-0.5 MPa/s at the point of H2O exsolution, which strongly affects the buoyancy of the ascending magma. The magma ascent rates presented are among the first for explosive basaltic eruptions and demonstrate the potential of the embayment method for quantifying magmatic timescales associated with eruptions of different vigor. [1] Lloyd et al. (2014) JVGR, http://dx.doi.org/10.1016/j.jvolgeores.2014.06.002

MAGMA: generalized gene-set analysis of GWAS data.

Science.gov (United States)

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

2015-04-01

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.

Tomographic location of potential melt-bearing phenocrysts in lunar glass spherules

International Nuclear Information System (INIS)

Ebel, D.S.; Fogel, R.A.; Rivers, M.L.

2005-01-01

Apollo 17 orange glass spherules contain olivine phenocrysts with melt inclusions from depth. Tomography ( 200 spherules located 1 phenocryst. We will try to find melt inclusions and obtain original magma volatiles and compositions. In 1971, Apollo 17 astronauts collected a 10 cm soil sample (74220) comprised almost entirely of orange glass spherules. Below this, a double drive-tube core sampled a 68 cm thick horizon comprised of orange glass and black beads (crystallized equivalents of orange glass). Primitive lunar glass spherules (e.g.-A17 orange glasses) are thought to represent ejecta from lunar mare fire fountains. The fire-fountains were apparently driven by a combination of C-O gas exsolution from orange glass melt and the oxidation of graphite. Upon eruption, magmas lost their volatiles (e.g., S, CO, CO 2 ) to space. Evidence for volatile escape remains as volatile-rich coatings on the exteriors of many spherules. Moreover, it showed that Type I and II Fe-Ni-rich metal particles found within orange glass olivine phenocrysts, or free-floating in the glass itself, are powerful evidence for the volatile driving force for lunar fire fountains. More direct evidence for the volatile mechanism has yet to be uncovered. Issues remaining include: the exact composition of magmatic volatiles; the hypothesized existence of graphite in the magma; the oxygen fugacity of the magma and of the lunar interior. In 1996 reported a single ∼450 micron, equant olivine phenocryst, containing four glassy melt inclusions (or inclusion cores), the largest ∼30micron in size, in a thin section of the 74001/2 drill core. The melt is assumed to sample the parent magma of the lunar basalts at depth, evidenced by the S content of the inclusion (600 ppm) which is 400 ppm greater than that of the orange glass host. Such melts potentially contain a full complement of the volatile components of the parent magma, which can be analyzed by infrared spectroscopy. Although the A17 orange glass

Shallow-level magma-sediment interaction and explosive behaviour at Anak Krakatau (Invited)

Science.gov (United States)

Troll, V. R.; Jolis, E. M.; Dahren, B.; Deegan, F. M.; Blythe, L. S.; Harris, C.; Berg, S. E.; Hilton, D. R.; Freda, C.

2013-12-01

Crustal contamination of ascending arc magmas is generally thought to be a significant process which occurs at lower- to mid-crustal magma storage levels where magmas inherit their chemical and isotopic character by blending, assimilation and differentiation [1]. Anak Krakatau, like many other volcanoes, erupts shallow-level crustal xenoliths [2], indicating a potential role for upper crustal modification and hence late-stage changes to magma rheology and thus potential eruptive behaviour. Distinguishing deep vs. shallow crustal contamination processes at Krakatau, and elsewhere, is therefore crucial to understand and assess pre-eruptive magmatic conditions and their associated hazard potential. Here we report on a multi-disciplinary approach to unravel the crustal plumbing system of the persistently-active and dominantly explosive Anak Krakatau volcano [2, 3], employing rock-, mineral- and gas-isotope geochemistry and link these results with seismic tomography [4]. We show that pyroxene crystals formed at mid- and lower-crustal levels (9-11 km) and carry almost mantle-like isotope signatures (O, Sr, Nd, He), while feldspar crystals formed dominantly at shallow levels (< 5km) and display unequivocal isotopic evidence for late stage contamination (O, Sr, Nd). This obeservation places a significant element of magma-crust interaction into the uppermost, sediment-rich crust beneath the volcano. Magma storage in the uppermost crust can thus offer a possible explanation for the compositional modifications of primitive Krakatau magmas, and likely provides extra impetus to increased explosivity at Anak Krakatau. [1] Annen, et al., 2006. J. Petrol. 47, 505-539. [2] Gardner, et al., 2013. J. Petrol. 54, 149-182. [3] Dahren, et al., 2012. Contrib. Mineral. Petrol. 163, 631-651. [4] Jaxybulatov, et al., 2011. J. Volcanol. Geoth. Res. 206, 96-105.

Trace element and isotopic effects arising from magma migration beneath mid-ocean ridges

International Nuclear Information System (INIS)

Kenyon, P.M.

1990-01-01

The trace element concentrations and isotopic ratios in the magma erupted on mid-ocean ridges may differ from those in the source material due to physical effects such as porous flow dispersion, exchange of trace elements between the fluid and solid phases during magma migration, and convective mixing in magma chambers. These differences are in addition to those produced by better known processes such as fractional crystallization and partial melting. The effects of the three former processes are described. It is predicted that magma typically reaches the sub-ridge magma chambers with a spatial heterogeneity only slightly reduced from that of the source material, but with a subdued variation in time. Convective mixing then further reduces the spatial heterogeneity. Application of the results for convective mixing to a recent Fourier analysis of 87 Sr/ 86 Sr variations along the Mid-Atlantic Ridge suggests that the falloff in amplitude of variation observed with decreasing wavelength in the Mid-Atlantic Ridge data cannot be explained by convective mixing in magma chambers. Instead, it is postulated that this falloff is due to the mechanics of the production and/or the solid-state convective mixing of chemical and isotopic heterogeneities in the solid mantle. (orig.)

Isolation and quantification of volatiles in fish by dynamic headspace sampling and mass spectrometry

DEFF Research Database (Denmark)

Refsgaard, Hanne; Haahr, Anne-Mette; Jensen, Benny

1999-01-01

A dynamic headspace sampling method for isolation of volatiles in fish has been developed. The sample preparation involved freezing of fish tissue in liquid nitrogen, pulverizing the tissue, and sampling of volatiles from an aqueous slurry of the fish powder. Similar volatile patterns were...

Low-pressure evolution of arc magmas in thickened crust: The San Pedro-Linzor volcanic chain, Central Andes, Northern Chile

Science.gov (United States)

Godoy, Benigno; Wörner, Gerhard; Kojima, Shoji; Aguilera, Felipe; Simon, Klaus; Hartmann, Gerald

2014-07-01

Magmatism at Andean Central Volcanic Zone (CVZ), or Central Andes, is strongly influenced by differentiation and assimilation at high pressures that occurred at lower levels of the thick continental crust. This is typically shown by high light to heavy rare earth element ratios (LREE/HREE) of the erupted lavas at this volcanic zone. Increase of these ratios with time is interpreted as a change to magma evolution in the presence of garnet during evolution of Central Andes. Such geochemical signals could be introduced into the magmas be high-pressure fractionation with garnet on the liquidus and/or assimilation from crustal rocks with a garnet-bearing residue. However, lavas erupted at San Pedro-Linzor volcanic chain show no evidence of garnet fractionation in their trace element patterns. This volcanic chain is located in the active volcanic arc, between 22°00‧S and 22°30‧S, over a continental crust ˜70 km thick. Sampled lavas show Sr/Y and Sm/Yb ratios Chile. We relate our geochemical observations to shallow crustal evolution of primitive magmas involving a high degree of assimilation of upper continental crust. We emphasize that low pressure AFC- (Assimilation Fractional Crystallization) type evolution of the San Pedro-Linzor volcanic chain reflects storage, fractionation, and contamination of mantle-derived magmas at the upper felsic crust (<40 km depth). The ascent of mantle-derived magmas to mid-crustal levels is related with the extensional regime that has existed in this zone of arc-front offset since Late-Miocene age, and the relatively thin portion of mafic lower crust observed below the volcanic chain.

Pricing Volatility of Stock Returns with Volatile and Persistent Components

DEFF Research Database (Denmark)

Zhu, Jie

In this paper a two-component volatility model based on the component's first moment is introduced to describe the dynamic of speculative return volatility. The two components capture the volatile and persistent part of volatility respectively. Then the model is applied to 10 Asia-Pacific stock m......, a positive or risk-premium effect exists between return and the volatile component, yet the persistent component is not significantly priced for return dynamic process....... markets. Their in-mean effects on return are also tested. The empirical results show that the persistent component accounts much more for volatility dynamic process than the volatile component. However the volatile component is found to be a significant pricing factor of asset returns for most markets...

Evidence for crustal recycling during the Archean: the parental magmas of the stillwater complex

International Nuclear Information System (INIS)

McCallum, I.S.

1988-01-01

The petrology and geochemistry of the Stillwater Complex, an Archean (2.7 Ga) layered mafic intrusion in the Beartooth Mountains of Montana, is discussed. Efforts to reconstruct the compositions of possible parental magmas and thereby place some constraints on the composition and history of their mantle source regions was studied. A high-Mg andesite or boninite magma best matches the crystallization sequences and mineral compositions of Stillwater cumulates, and represents either a primary magma composition or a secondary magma formed, for example, by assimilation of crustal material by a very Mg-rich melt such as komatiite. Isotopic data do not support the extensive amounts of assimilation required by the komatiite parent hypothesis, and it is argued that the Stillwater magma was generated from a mantle source that had been enriched by recycling and homogenization of older crustal material over a large area

Testing for Volatility Co-movement in Bivariate Stochastic Volatility Models

OpenAIRE

Chen, Jinghui; Kobayashi, Masahito; McAleer, Michael

2017-01-01

markdownabstractThe paper considers the problem of volatility co-movement, namely as to whether two financial returns have perfectly correlated common volatility process, in the framework of multivariate stochastic volatility models and proposes a test which checks the volatility co-movement. The proposed test is a stochastic volatility version of the co-movement test proposed by Engle and Susmel (1993), who investigated whether international equity markets have volatility co-movement using t...

Endogenous Lunar Volatiles

Science.gov (United States)

McCubbin, F. M.; Liu, Y.; Barnes, J. J.; Boyce, J. W.; Day, J. M. D.; Elardo, S. M.; Hui, H.; Magna, T.; Ni, P.; Tartese, R.;

Oil and stock market volatility: A multivariate stochastic volatility perspective

International Nuclear Information System (INIS)

Vo, Minh

2011-01-01

This paper models the volatility of stock and oil futures markets using the multivariate stochastic volatility structure in an attempt to extract information intertwined in both markets for risk prediction. It offers four major findings. First, the stock and oil futures prices are inter-related. Their correlation follows a time-varying dynamic process and tends to increase when the markets are more volatile. Second, conditioned on the past information, the volatility in each market is very persistent, i.e., it varies in a predictable manner. Third, there is inter-market dependence in volatility. Innovations that hit either market can affect the volatility in the other market. In other words, conditioned on the persistence and the past volatility in their respective markets, the past volatility of the stock (oil futures) market also has predictive power over the future volatility of the oil futures (stock) market. Finally, the model produces more accurate Value-at-Risk estimates than other benchmarks commonly used in the financial industry. - Research Highlights: → This paper models the volatility of stock and oil futures markets using the multivariate stochastic volatility model. → The correlation between the two markets follows a time-varying dynamic process which tends to increase when the markets are more volatile. → The volatility in each market is very persistent. → Innovations that hit either market can affect the volatility in the other market. → The model produces more accurate Value-at-Risk estimates than other benchmarks commonly used in the financial industry.

The magma plumbing system in the Mariana Trough back-arc basin at 18° N

Science.gov (United States)

Lai, Zhiqing; Zhao, Guangtao; Han, Zongzhu; Huang, Bo; Li, Min; Tian, Liyan; Liu, Bo; Bu, Xuejiao

2018-04-01

Mafic magmas are common in back-arc basin, once stalled in the crust, these magmas may undergo different evolution. In this paper, compositional and textural variations of plagioclase as well as mineral-melt geothermobarometry are presented for basalts erupted from the central Mariana Trough (CMT). These data reveal crystallization conditions and we attempt a reconstruction of the magma plumbing system of the CMT. Plagioclase megacrysts, phenocrysts, microphenocrysts, microlites, olivine, spinel, and clinopyroxene have been recognized in basalt samples, using BSE images and compositional features. The last three minerals are homogeneous as microphenocrysts. Mineral-melt barometry indicates that plagioclase crystals crystallized and eventually grew into phenocrysts and megacrysts in mush zone with depth of 5-9 km, in which the normal zoning plagioclases crystallized in the interval of various batches of basic magma recharging. Plagioclase megacrysts and phenocrysts were dissolved and/or resorbed, when new basic magmas injected into the mush zone near Moho depth. It is inferred that magma extracted from the mush zone, and adiabatically ascended via different pathways. Some basaltic magmas underwent plagioclase and clinopyroxene microphenocrysts crystallization in low-pressure before eruption. Plagioclase microlites and outermost rims probably crystallized after eruption.

Parental magmas of Mare Fecunditatis - Evidence from pristine glasses

International Nuclear Information System (INIS)

Jin, Y.; Taylor, L.A.

1990-01-01

Results are presented on the petrography and electron microprobe analyses of 14 discrete glass beads from the Luna 16 core sample (21036,15) from Mare Fecunditatis regolith, that were previously characterized as representing pristine glasses. Compared to Apollo pristine glasses analyzed by Delano (1986), the Luna 16 pristine glasses have higher CaO and Al2O3 contents but lower MgO and Ni. On the basis of their contents of MgO, FeO, Al2O3, and CaO, these pristine glasses could be divided into two groups, A and B. It is suggested that at least two parental magmas are needed to explain the chemical variations among these glasses. The Group B glasses appear to represent primitive parental magma that evolved by olivine fractionation to the compositions of the Luna 16 aluminous mare basalts, whereas the Group A volcanic glasses may represent an unusual new basalt magma type that contains a high plagioclase component. 14 refs

Pricing Volatility of Stock Returns with Volatile and Persistent Components

DEFF Research Database (Denmark)

Zhu, Jie

2009-01-01

This paper introduces a two-component volatility model based on first moments of both components to describe the dynamics of speculative return volatility. The two components capture the volatile and the persistent part of volatility, respectively. The model is applied to 10 Asia-Pacific stock ma...... markets. A positive or risk-premium effect exists between the return and the volatile component, yet the persistent component is not significantly priced for the return dynamic process....... markets. Their in-mean effects on returns are tested. The empirical results show that the persistent component is much more important for the volatility dynamic process than is the volatile component. However, the volatile component is found to be a significant pricing factor of asset returns for most...

Volatility in energy prices

International Nuclear Information System (INIS)

Duffie, D.

1999-01-01

This chapter with 58 references reviews the modelling and empirical behaviour of volatility in energy prices. Constant volatility and stochastic volatility are discussed. Markovian models of stochastic volatility are described and the different classes of Markovian stochastic volatility model are examined including auto-regressive volatility, option implied and forecasted volatility, Garch volatility, Egarch volatility, multivariate Garch volatility, and stochastic volatility and dynamic hedging policies. Other volatility models and option hedging are considered. The performance of several stochastic volatility models as applied to heating oil, light oil, natural gas, electricity and light crude oil are compared

Possible stakeholder concerns regarding volatile organic compound in arid soils integrated demonstration technologies not evaluated in the stakeholder involvement program

International Nuclear Information System (INIS)

Peterson, T.

1995-12-01

The Volatile Organic Compounds in Arid Soils Integrated Demonstration (VOC-Arid ID) supported the demonstration of a number of innovative technologies, not all of which were evaluated in the integrated demonstration's stakeholder involvement program. These technologies have been organized into two categories and the first category ranked in order of priority according to interest in the evaluation of the technology. The purpose of this report is to present issues stakeholders would likely raise concerning each of the technologies in light of commentary, insights, data requirements, concerns, and recommendations offered during the VOC-Arid ID's three-year stakeholder involvement, technology evaluation program. A secondary purpose is to provide a closeout status for each of the technologies associated with the VOC-Arid ID. This report concludes with a summary of concerns and requirements that stakeholders have for all innovative technologies

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.

Mafic microgranular enclave swarms in the Chenar granitoid stock, NW of Kerman, Iran: evidence for magma mingling

Science.gov (United States)

Arvin, M.; Dargahi, S.; Babaei, A. A.

2004-10-01

Mafic microgranular enclaves (MME) are common in the Early to Middle Miocene Chenar granitoid stock, northwest of Kerman, which is a part of Central Iranian Eocene volcanic belt. They occur individually and in homogeneous or heterogeneous swarms. The MME form a number of two-dimensional structural arrangements, such as dykes, small rafts, vortices, folded lens-shapes and late swarms. The enclaves are elongated, rounded to non-elongated and subrounded in shape and often show some size-sorting parallel to direction of flow. Variation in the elongation of enclaves could reflect variations in the viscosity of the enclave, the time available for enclave deformation and differential strain during flow of the host granitoid magma. The most effective mechanism in the formation of enclave swarms in the Chenar granitoid stock was velocity gradient-related convection currents in the granitoid magma chamber. Gravitational sorting and the break-up of heterogeneous dykes also form MME swarms. The MME (mainly diorite to diorite gabbro) have igneous mineralogy and texture, and are marked by sharp contacts next to their host granitoid rocks. The contact is often marked by a chilled margin with no sign of solid state deformation. Evidence of disequilibrium is manifested in feldspars by oscillatory zoning, resorbed rims, mantling and punctuated growth, together with overgrowth of clinopyroxene/amphibole on quartz crystals, the acicular habit of apatites and the development of Fe-Ti oxides along clinopyroxene cleavages. These observations suggest that the MMEs are derived from a hybrid-magma formed as a result of the intrusion of a mafic magma into the base of a felsic magma chamber. The density contrast between hybrid-magma and the overlying felsic magma was reduced by the release of dissolved fluids and the ascent of exsolved gas bubbles from the mafic magma into the hybrid zone. Further convection in the magma chamber dispersed the hybridized magma as globules in the upper parts of

When Magma Meets Carbonate: Explosive Criminals of Climate Change?

Science.gov (United States)

Carter, L. B.

2017-12-01

The natural carbon cycle is a key component of global climate change. Identifying and quantifying all processes in the cycle is essential to determine the effects of human greenhouse gas contributions and make future predictions. Volcanoes are the main natural source of carbon dioxide to the atmosphere [1]. In settings where carbonate rocks underlie the edifice, they can be consumed by magma passing through, which can release extra CO2, potentially explaining the extremely high emissions at Mount Etna in Italy [2-4]. We conduct laboratory experiments, mimicking conditions in the crust, to study how different carbonate rocks interact with hot magmas at pressure, and determine the amount of CO2 generated. We find that some types of magma can raise volcanic gas output and cause more explosive and dangerous eruptions [5-6]. Others are more likely to release hot fluids to the surrounding rocks, releasing CO2 by skarnification, which leaves economically important ores like in the western US [3,7] but can weaken the subsurface, potentially leading to landslides. Gas can also be released on the flanks of a volcano or in regions lacking an active volcano, due to the breakdown of certain carbonate rocks by heat [7], seen as bubbling springs in Yellowstone [8]. Our experiments indicate that if dolostone, not limestone, surrounds a magma chamber, over half the CO2 that was locked in the crust can escape even at lower temperatures a distance away. These processes are perhaps pertinent to why the Earth's climate was warm >50 million years ago, when more magma-carbonate interaction likely occurred than today [3] and thus contributed several times the current volcanic output [4] to the atmosphere. As significant parts of the long-term carbon cycle, it is necessary to include magma-carbonate reactions when considering climate changes before taking into account human input. [1] Aiuppa et al 2017 ESciRev (168) 24-47; [2] Ganino and Arndt 2009 Geol (37) 323-326; [3] Lee et al. 2013

A whiff of death: fatal volatile solvent inhalation abuse.

Science.gov (United States)

Steffee, C H; Davis, G J; Nicol, K K

1996-09-01

Inhalation abuse of volatile solvents, previously known generically as "glue sniffing," is typically pursued by adolescents. A wide range of legal, easily obtained products containing volatile substances are available for abuse. We report two illustrative cases of fatal volatile substance abuse: gasoline sniffing in a 20-year-old man and aerosol propellant gas inhalation (aerosol air freshener) in a 16-year-old girl with underlying reactive airway disease. Although the ratio of deaths to nonfatal inhalation escapades is extremely low, volatile solvent abuse carries the risk of sudden death due to cardiac arrest after a dysrhythmia or vasovagal event, central nervous system respiratory depression, hypoxia and hypercapnia due to the techniques of inhalation, and other mechanisms. Investigation of the patient's substance abuse history, examination of the scene of death, and special toxicologic analyses are critical to identifying volatile substance inhalation abuse as the cause of death because anatomic autopsy findings will typically be nonspecific. Above all, physicians must suspect the diagnosis of volatile substance inhalation abuse, especially in any case of sudden death involving an otherwise healthy young person.

A Hull and White Formula for a General Stochastic Volatility Jump-Diffusion Model with Applications to the Study of the Short-Time Behavior of the Implied Volatility

Directory of Open Access Journals (Sweden)

Elisa Alòs

2008-01-01

Full Text Available We obtain a Hull and White type formula for a general jump-diffusion stochastic volatility model, where the involved stochastic volatility process is correlated not only with the Brownian motion driving the asset price but also with the asset price jumps. Towards this end, we establish an anticipative Itô's formula, using Malliavin calculus techniques for Lévy processes on the canonical space. As an application, we show that the dependence of the volatility process on the asset price jumps has no effect on the short-time behavior of the at-the-money implied volatility skew.

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.

Radioactive equilibria and disequilibria of U-series nuclides in erupting magmas from Izu arc volcanoes

International Nuclear Information System (INIS)

Sato, Jun; Kurihara, Yuichi; Takahashi, Masaomi

2009-01-01

Radioactive disequilibria among U-series nuclides are observed in the magmas from volcanoes in the world. Basaltic products from Izu arc volcanoes, including Izu-Oshima and Fuji volcanoes, show 230 Th 238 U and 226 Ra> 230 Th disequilibria, indicating that the addition of U-and Ra-rich fluid from the subducting slab to the mantle wedge at the magma genesis. The disequilibria of 226 Ra> 230 Th in the erupting magmas suggest that the timescale from magma genesis to the eruption may be less than 8000 years. (author)

Volatility Discovery

DEFF Research Database (Denmark)

Dias, Gustavo Fruet; Scherrer, Cristina; Papailias, Fotis

The price discovery literature investigates how homogenous securities traded on different markets incorporate information into prices. We take this literature one step further and investigate how these markets contribute to stochastic volatility (volatility discovery). We formally show...... that the realized measures from homogenous securities share a fractional stochastic trend, which is a combination of the price and volatility discovery measures. Furthermore, we show that volatility discovery is associated with the way that market participants process information arrival (market sensitivity......). Finally, we compute volatility discovery for 30 actively traded stocks in the U.S. and report that Nyse and Arca dominate Nasdaq....

Noctuidae-induced plant volatiles: current situation and prospects

Directory of Open Access Journals (Sweden)

Vanusa Rodrigues Horas

2014-01-01

Full Text Available Noctuids are phytophagous lepidopterans with some species causing significant damage to agriculture. The host plants, in turn, have developed defense mechanisms to cope with them, for instance chemical defenses. In this study we review the literature on plant volatiles induced by noctuids, and discuss the methodologies used to induce the production of volatiles that are usually employed in plant defense mechanisms. Future prospects involving this line of research in pest control are also discussed.

Thermally-assisted Magma Emplacement Explains Restless Calderas

Science.gov (United States)

Amoruso, A.; Crescentini, L.; D'Antonio, M.; Acocella, V.

2017-12-01

Many calderas show repeated unrest over centuries. Though probably induced by magma, this unique behaviour is not understood and its dynamics remains elusive. To better understand these restless calderas, we interpret deformation data and build thermal models of Campi Flegrei, Italy, which is the best-known, yet most dangerous calderas, lying to the west of Naples and restless since the 1950s at least.Our elaboration of the geodetic data indicates that the inflation and deflation of magmatic sources at the same location explain most deformation, at least since the build-up of the last 1538 AD eruption. However, such a repeated magma emplacement requires a persistently hot crust.Our thermal models show that the repeated emplacement was assisted by the thermal anomaly created by magma that was intruded at shallow depth 3 ka before the last eruption and, in turn, contributed to maintain the thermal anomaly itself. This may explain the persistence of the magmatic sources promoting the restless behaviour of the Campi Flegrei caldera; moreover, it explains the crystallization, re-melting and mixing among compositionally distinct magmas recorded in young volcanic rocks.Available information at other calderas highlights similarities to Campi Flegrei, in the pattern and cause of unrest. All monitored restless calderas have either geodetically (Yellowstone, Aira Iwo-Jima, Askja, Fernandina and, partly, Long Valley) or geophysically (Rabaul, Okmok) detected sill-like intrusions inducing repeated unrest. Some calderas (Yellowstone, Long Valley) also show stable deformation pattern, where inflation insists on and mimics the resurgence uplift. The common existence of sill-like sources, also responsible for stable deformation patterns, in restless calderas suggests close similarities to Campi Flegrei. This suggests a wider applicability of our model of thermally-assisted sill emplacement, to be tested by future studies to better understand not only the dynamics of restless

Isotopic evidence for multiple contributions to felsic magma chambers

DEFF Research Database (Denmark)

Waight, Tod Earle; Wiebe, R.A.; Krogstad, E.J.

2007-01-01

The Gouldsboro Granite forms part of the Coastal Maine Magmatic Province, a region characterized by granitic plutons that are intimately linked temporally and petrogenetically with abundant co-existing mafic magmas. The pluton is complex and preserves a felsic magma chamber underlain...... with identical isotopic compositions to more mafic dikes suggest that closed system fractionation may be occurring in deeper level chambers prior to injection to shallower levels. The granitic portion of the pluton has the highest Nd isotopic composition (eNd=+3.0) of plutons in the region whereas the mafic...

Weak solutions of magma equations

International Nuclear Information System (INIS)

Krishnan, E.V.

1999-01-01

Periodic solutions in terms of Jacobian cosine elliptic functions have been obtained for a set of values of two physical parameters for the magma equation which do not reduce to solitary-wave solutions. It was also obtained solitary-wave solutions for another set of these parameters as an infinite period limit of periodic solutions in terms of Weierstrass and Jacobian elliptic functions

Comments on 'Generation of Deccan Trap magmas'

Indian Academy of Sciences (India)

R.Narasimhan(krishtel emaging)1461 1996 Oct 15 13:05:22

Comments on 'Generation of Deccan Trap magmas' by Gautam Sen ... Department of Geology & Geophysics, School of Ocean & Earth Science & Technology (SOEST), University of .... Mahoney J J, Sheth H C, Chandrasekharan D and Peng Z.

A basal magma ocean dynamo to explain the early lunar magnetic field

Science.gov (United States)

Scheinberg, Aaron L.; Soderlund, Krista M.; Elkins-Tanton, Linda T.

2018-06-01

The source of the ancient lunar magnetic field is an unsolved problem in the Moon's evolution. Theoretical work invoking a core dynamo has been unable to explain the magnitude of the observed field, falling instead one to two orders of magnitude below it. Since surface magnetic field strength is highly sensitive to the depth and size of the dynamo region, we instead hypothesize that the early lunar dynamo was driven by convection in a basal magma ocean formed from the final stages of an early lunar magma ocean; this material is expected to be dense, radioactive, and metalliferous. Here we use numerical convection models to predict the longevity and heat flow of such a basal magma ocean and use scaling laws to estimate the resulting magnetic field strength. We show that, if sufficiently electrically conducting, a magma ocean could have produced an early dynamo with surface fields consistent with the paleomagnetic observations.

Magma degassing triggered by static decompression at Kīlauea Volcano, Hawai‘i

Science.gov (United States)

Poland, Michael P.; Jeff, Sutton A.; Gerlach, Terrence M.

2009-01-01

During mid-June 2007, the summit of Kīlauea Volcano, Hawai‘i, deflated rapidly as magma drained from the subsurface to feed an east rift zone intrusion and eruption. Coincident with the deflation, summit SO2 emission rates rose by a factor of four before decaying to background levels over several weeks. We propose that SO2 release was triggered by static decompression caused by magma withdrawal from Kīlauea's shallow summit reservoir. Models of the deflation suggest a pressure drop of 0.5–3 MPa, which is sufficient to trigger exsolution of the observed excess SO2 from a relatively small volume of magma at the modeled source depth beneath Kīlauea's summit. Static decompression may also explain other episodes of deflation accompanied by heightened gas emission, including the precursory phases of Kīlauea's 2008 summit eruption. Hazards associated with unexpected volcanic gas emission argue for increased awareness of magma reservoir pressure fluctuations.

Level Shifts in Volatility and the Implied-Realized Volatility Relation

DEFF Research Database (Denmark)

Christensen, Bent Jesper; de Magistris, Paolo Santucci

We propose a simple model in which realized stock market return volatility and implied volatility backed out of option prices are subject to common level shifts corresponding to movements between bull and bear markets. The model is estimated using the Kalman filter in a generalization to the mult......We propose a simple model in which realized stock market return volatility and implied volatility backed out of option prices are subject to common level shifts corresponding to movements between bull and bear markets. The model is estimated using the Kalman filter in a generalization...... to the multivariate case of the univariate level shift technique by Lu and Perron (2008). An application to the S&P500 index and a simulation experiment show that the recently documented empirical properties of strong persistence in volatility and forecastability of future realized volatility from current implied...... volatility, which have been interpreted as long memory (or fractional integration) in volatility and fractional cointegration between implied and realized volatility, are accounted for by occasional common level shifts....

Testing for Volatility Co-movement in Bivariate Stochastic Volatility Models

NARCIS (Netherlands)

J. Chen (Jinghui); M. Kobayashi (Masahito); M.J. McAleer (Michael)

2017-01-01

markdownabstractThe paper considers the problem of volatility co-movement, namely as to whether two financial returns have perfectly correlated common volatility process, in the framework of multivariate stochastic volatility models and proposes a test which checks the volatility co-movement. The

Pathways of volatile migration in the crust beneath Harrat Lunayyir (Saudi Arabia) during the unrest in 2009 revealed by attenuation tomography

Science.gov (United States)

El Khrepy, Sami; Koulakov, Ivan; Al-Arifi, Nassir; Sychev, Ilya

2017-04-01

Harrat Lunayyir is a relatively young basaltic field in Saudi Arabia located at the western margin of the Arabian Peninsula. In April-June 2009, strong seismic activity and ground deformations at this site marked the activation of the magma system beneath Harrat Lunayyir. In this study, we present new three-dimensional models of the attenuation of P and S waves during the unrest in 2009 based on the analysis of t*. We measured 1658 and 3170 values of t* for P and S waves, respectively, for the same earthquakes that were previously used for travel time tomography. The resulting anomalies of the P and S wave attenuation look very similar. In the center of the study area, we observe a prominent high-attenuation pattern, which coincides with the most active seismicity at shallow depths and maximum ground deformations. This high-attenuation zone may represent a zone of accumulation and ascending of gases, which originated at depths of 5-7 km due to the decompression of ascending liquid volatiles. Based on these findings and previous tomography studies, we propose that the unrest at Harrat Lunayyir in 2009 was triggered by a sudden injection of unstable liquid volatiles from deeper magma sources. At some depths, they were transformed to gases, which caused the volume to increase, and this led to seismic activation in the areas of phase transformations. The overpressurized gases ultimately found the weakest point in the rigid basaltic cover at the junction of several tectonic faults and escaped to the surface.

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

, inhibiting dike emplacement and surface eruptions. In contrast to small dike volumes and low propagation velocities in terrestrial environments, lunar dike propagation velocities are typically sufficiently high that shallow sill formation is not favored; local low-density breccia zones beneath impact crater floors, however, may cause lateral magma migration to form laccoliths (e.g., Vitello Crater) and sills (e.g., Humboldt Crater) in floor-fractured craters. Dikes emplaced into the shallow crust may stall and produce crater chains due to active and passive gas venting (e.g., Mendeleev Crater Chain) or, if sufficiently shallow, may create a near-surface stress field that forms linear and arcuate graben, often with pyroclastic and small-scale effusive eruptions (e.g., Rima Parry V). Effusive eruptions are modulated by effusion rates, eruption durations, cooling and supply limitations to flow length, and pre-existing topography. Relatively low effusion rate, cooling-limited flows lead to small shield volcanoes (e.g., Tobias Mayer, Milicius); higher effusion rate, cooling-limited flows lead to compound flow fields (e.g., most mare basins) and even higher effusion rate, long-duration flows lead to thermal erosion of the vent, effusion rate enhancement, and thermal erosion of the substrate to produce sinuous rilles (e.g., Rimae Prinz). Extremely high effusion rate flows on slopes lead to volume-limited flow with lengths of many hundreds of kilometers (e.g., the young Imbrium basin flows). Explosive, pyroclastic eruptions are common on the Moon. The low pressure environment in propagating dike crack-tips can cause gas formation at great depths and throughout dike ascent; at shallow crustal depths both the smelting reaction and the recently documented abundant magmatic volatiles in mare basalt magmas contribute to significant shallow degassing and pyroclastic activity associated with the dike as it erupts at the surface. Dikes penetrating to the surface produce a wide range of

Regulatory, Land Ownership, and Water Availability Factors for a Magma Well: Long Valley Caldera and Coso Hot Springs, California

Energy Technology Data Exchange (ETDEWEB)

Blackett, Robert

1985-09-01

The U.S. Department of Energy is currently engaged in a program to demonstrate the engineering feasibility of extracting thermal energy from high-level molten magma bodies. The program is being carried out under the direction of Sandia National Laboratories where a number of individual projects support the overall program. The existing program elements include (1) high-temperature materials compatibility testing; (2) studies of properties of melts of various compositions; and (3) the investigation of the economics of a magma energy extraction system. Another element of the program is being conducted with the cooperation of the U.S. Geological Survey, and involves locating and outlining magma bodies at selected sites using various geophysical techniques. The ultimate goal here will be to define the limits of a magma body as a drilling target. During an earlier phase of the program, more than twenty candidate study sites considered were evaluated based upon: (1) the likelihood of the presence of a shallow magma chamber, (2) the accessibility of the site, and (3) physical and institutional constraints associated with each site with respect to performing long-term experiments. From these early phase activities, the number of candidate sites were eventually narrowed to just 2. The sites currently under consideration are Coso Hot Springs and the Long Valley caldera (Figure 1). This report describes certain attributes of these sites in order to help identify potential problems related to: (1) state and federal regulations pertaining to geothermal development; (2) land ownership; and (3) water resource availability. The information sources used in this study were mainly maps, publications, and informative documents gathered from the California Division of Oil and Gas and the U.S. Department of the Interior. Environmental studies completed for the entire Long Valley caldera study area, and for portions of the Coso Hot Springs study area were also used for reference.

Effect of pressure on Fe3+/ΣFe ratio in a mafic magma and consequences for magma ocean redox gradients

Energy Technology Data Exchange (ETDEWEB)

Zhang, H. L.; Hirschmann, M. M.; Cottrell, E.; Withers, A. C.

2017-05-01

Experiments establishing the effect of pressure on the Fe³⁺/ΣFe ratio of andesitic silicate melts buffered by coexisting Ru and RuO₂ were performed from 100 kPa to 7 GPa and 1400–1750 °C. Fe³⁺/ΣFe ratios were determined by room temperature Mössbauer spectroscopy, but corrected for the effects of recoilless fraction. Fe³⁺/ΣFe ratios in quenched glasses decrease with increasing pressure consistent with previous results between 100 kPa and 3 GPa (O’Neill et al., 2006), but show only small pressure effects above 5 GPa. Ratios also decrease with increasing temperature. Mössbauer hyperfine parameters indicate mean coordination of Fe³⁺ ions of ~5 in glasses, with no dependence on the pressure from which the glasses were quenched, but show an increase with pressure in mean coordination of Fe²⁺ ions, from ~5 to ~6. XANES spectra on these glasses show variations in pre-edge intensities and centroid positions that are systematic with Fe³⁺/ΣFe, but are displaced from those established from otherwise identical andesitic glasses quenched at 100 kPa (Zhang et al., 2016). These systematics permit construction of a new XANES calibration curve relating pre-edge sub-peak intensities to Fe³⁺/ΣFe applicable to high pressure glasses. Consistent with interpretations of the Mössbauer hyperfine parameters, XANES pre-edge peak features in high pressure glasses are owing chiefly to the effects of pressure on the coordination of Fe²⁺ ions from ~5.5 to ~6, with negligible effects evident for Fe³⁺ ions. We use the new data to construct a thermodynamic model relating the effects of oxygen fugacity and pressure on Fe³⁺/ΣFe. We apply this model to calculate variations in oxygen fugacity in isochemical (constant Fe³⁺/ΣFe) columns of magma representative of magma oceans, in which fO2 is fixed at the base by equilibration with molten Fe. These calculations

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.

Automatic Compound Annotation from Mass Spectrometry Data Using MAGMa.

Science.gov (United States)

Ridder, Lars; van der Hooft, Justin J J; Verhoeven, Stefan

2014-01-01

The MAGMa software for automatic annotation of mass spectrometry based fragmentation data was applied to 16 MS/MS datasets of the CASMI 2013 contest. Eight solutions were submitted in category 1 (molecular formula assignments) and twelve in category 2 (molecular structure assignment). The MS/MS peaks of each challenge were matched with in silico generated substructures of candidate molecules from PubChem, resulting in penalty scores that were used for candidate ranking. In 6 of the 12 submitted solutions in category 2, the correct chemical structure obtained the best score, whereas 3 molecules were ranked outside the top 5. All top ranked molecular formulas submitted in category 1 were correct. In addition, we present MAGMa results generated retrospectively for the remaining challenges. Successful application of the MAGMa algorithm required inclusion of the relevant candidate molecules, application of the appropriate mass tolerance and a sufficient degree of in silico fragmentation of the candidate molecules. Furthermore, the effect of the exhaustiveness of the candidate lists and limitations of substructure based scoring are discussed.

Enhancement of eruption explosivity by heterogeneous bubble nucleation triggered by magma mingling.

Science.gov (United States)

Paredes-Mariño, Joali; Dobson, Katherine J; Ortenzi, Gianluigi; Kueppers, Ulrich; Morgavi, Daniele; Petrelli, Maurizio; Hess, Kai-Uwe; Laeger, Kathrin; Porreca, Massimiliano; Pimentel, Adriano; Perugini, Diego

2017-12-04

We present new evidence that shows magma mingling can be a key process during highly explosive eruptions. Using fractal analysis of the size distribution of trachybasaltic fragments found on the inner walls of bubbles in trachytic pumices, we show that the more mafic component underwent fracturing during quenching against the trachyte. We propose a new mechanism for how this magmatic interaction at depth triggered rapid heterogeneous bubble nucleation and growth and could have enhanced eruption explosivity. We argue that the data support a further, and hitherto unreported contribution of magma mingling to highly explosive eruptions. This has implications for hazard assessment for those volcanoes in which evidence of magma mingling exists.

Temperatures and isotopic evolution of silicic magmas, Taupo Volcanic Zone and Coromandel, New Zealand

International Nuclear Information System (INIS)

Blattner, P.; Rui-Zhong, Hu; Graham, I.J.; Houston-Eleftheriadis, C.

1996-01-01

A new set of oxygen and strontium isotope data on rhyolitic lavas and ignimbrites of the Taupo Volcanic Zone (TVZ) and the Coromandel Peninsula provides new limits for petrogenetic models. For oxygen isotopes, the rock matrix is frequently altered, so that values for magma need to be phenocryst based. Within TVZ a trend towards more negative delta 1 8 O values for more recent magmas appears likely (average before about 1 Ma and for Coromandel near 8.0 per thousand; after 1 Ma near 7.5 per thousand). This could indicate the gradual removal of supracrustal contaminants from the zones of magma accumulation and extrusion. Similar trends within Coromandel cannot yet be resolved. A generally positive correlation is found for oxygen and strontium isotopes of magmas. Most magmas have a limited range of isotopic values, which then becomes a useful fingerprint (e.g., the Mamaku, Matahina, and Waiotapu Ignimbrites). A narrow range of eruption temperatures of 880 plus or minus 60degC is derived from quartz-plagioclase fractionations of 0.98 plus or minus 0.25 per thousand delta 1 8 O for 15 magmas. Some delta 1 8 O values of quartz and feldspar phenocrysts are sufficiently low to suggest interaction between surface water and magma. However, large negative oxygen isotope anomalies (such as known from Yellowstone), could be no more than partially concealed by the isotopically less depleted meteoric water of New Zealand, and have not yet been found in New Zealand. (author). 45 refs., 3 tabs., 6 figs

Sr and Nd isotope geochemistry of coexisting alkaline magma series, Cantal, Massif Central, France

International Nuclear Information System (INIS)

Downes, H.

1984-01-01

Sr and Nd isotope analyses are presented for Tertiary continental alkaline volcanics from Cantal, Massif Central, France. The volcanics belong to two main magma series, silica-saturated and silica-undersaturated (with rare nephelinites). Trace element and isotopic data indicate a common source for the basic parental magmas of both major series; the nephelinites in contrast must have been derived from a mantle source which is isotopically and chemically distinct from that which gave rise to the basalts and basanites. 87 Sr/ 86 Sr initial ratios range from 0.7034 to 0.7056 in the main magma series (excluding rhyolites) and 143 Nd/ 144 Nd ratios vary between 0.512927 and 0.512669; both are correlated with increasing SiO 2 in the lavas. The data can be explained by a model of crustal contamination linked with fractional crystallisation. This indicates that crustal magma chambers are the sites of differentiation since only rarely do evolved magmas not show a crustal isotopic signature and conversely basic magmas have primitive isotopic ratios unless they contain obviuos crustal-derived xenocrysts. Potential contaminants include lower crustal granulites or partial melts of upper crustal units. Equal amounts of contamination are required for both magma series, refuting hypotheses of selective contamination of the silica-saturated series. The isotopic characteristics of the apparently primary nephelinite lavas demonstrates widespread heterogeneity in the mantle beneath Cantal. Some rhyolites, previously thought to be extremely contaminated or to be crustally derived, are shown to have undergone post-emplacement hydrothermal alteration. (orig.)

Interactions between magma and the lithospheric mantle during Cenozoic rifting in Central Europe

Science.gov (United States)

Meyer, Romain; Elkins-Tanton, Linda T.

2010-05-01

During the Cenozoic, extensive intraplate volcanic activity occurred throughout Central Europe. Volcanic eruptions extend over France (the Massif Central), central Germany (Eifel, Vogelsberg, Rhön; Heldburg), the Czech Republic (the Eger graben) and SW Poland (Lower Silesia), a region ~1,200 km wide. The origin of this predominantly alkaline intraplate magmatism is often genetically linked to one or several mantle plumes, but there is no convincing evidence for this. We have measured Pb isotope ratios, together with major and trace elements, in a representative set of mafic to felsic igneous rocks from the intra-plate Cenozoic Rhön Mts. and the Heldburg dike swarm in order to gain insight into the melting source and petrogenetic history of these melts. Three different mafic rock types (tholeiitic basalt, alkali basalt, basanite) were distinguished based on petrography and geochemistry within the investigated areas. Except for the lherzolite-bearing phonolite from the Veste Heldburg all other evolved magmas are trachytes. REE geochemistry and calculated partial melting modeling experiments for the three mafic magma types point to different degrees of partial melting in a garnet-bearing mantle source. In addition a new version of the ternary Th-Hf-Ta diagram is presented in this study as a useful petrological tool. This diagram is not only able to define potentially involved melting source end-members (e.g. asthenosphere, sub-continental lithospheric mantle and continental crust) but also interactions between these members are illustrated. An advantage of this diagram compared to partial melting degree sensitive multi-element diagrams is that a ternary diagram is a closed system. An earlier version of this diagram has been recently used to establish the nature and extent of crust mantle melt interaction of volcanic rifted margins magmas (Meyer et al. 2009). The Th-Hf-Ta geochemistry of the investigated magmas is similar to spinel and garnet xenoliths from different

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.

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.

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) offers detailed sections through the now frozen particle microstructure of a congested magma slurry. We simulated the flow regime in two and three dimensions using numerical models built on a finite-element mesh derived from field data. The model captures the flow behaviour of the Basement Sill magma over a viscosity range of 1-10 4  Pa s where the higher end (greater than or equal to 10 2  Pa s) corresponds to a magmatic slurry with crystal fractions varying between 30 and 70%. A novel feature of the model is the discovery of transient, low viscosity (less than or equal to 50 Pa s) high Reynolds number eddies formed along undulating contacts at the floor and roof of the intrusion. Numerical tracing of particle orbits implies crystals trapped in eddies segregate according to their mass density. Recovered shear strain rates (10 -3 -10 -5  s -1 ) at viscosities equating to high particle concentrations (around more than 40%) in the Sill interior point to shear-thinning as an explanation for some types of magmatic layering there. Model transport rates for the Sill magmas imply a maximum emplacement time of ca 10 5 years, consistent with geochemical evidence for long-range lateral flow. It is a theoretically possibility that fast-flowing magma on a continental scale will be susceptible to planetary-scale rotational forces.

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.

Magma shearing and friction in the volcanic conduit: A crystal constraint

Science.gov (United States)

Wallace, P. A.; Kendrick, J. E.; Henton De Angelis, S.; Ashworth, J. D.; Coats, R.; Miwa, T.; Mariani, E.; Lavallée, Y.

2017-12-01

Magma shearing and friction processes in the shallow volcanic conduit are typical manifestations of strain localisation, which in turn can have an influential role on magma ascent dynamics. The thermal consequences of such events could drive the destabilisation of magma and thus dictate the style of activity at the surface. Shear heating and fault friction are prime candidates for the generation of significant quantities of heat. Here we use a combination of field and experimental evidence to investigate how crystals can act as sensitive recorders of both physical and chemical processes occurring in the shallow volcanic conduit. Spine extrusion during the closing of the 1991-95 eruption at Unzen volcano, Japan, provided the unique opportunity to investigate marginal shear zone formation, which preserves a relic of the deformation during magma ascent. Our results show that crystals can effectively act as a deformation marker during magma ascent through the viscous-brittle transition by accommodating strain in the form of crystal plasticity before fracturing (comminution). Electron backscatter diffraction (EBSD) reveals up to 40° lattice distortion of biotite phenocrysts in zones of high shear, with negligible plasticity further away. Plagioclase microlites display a systematic plastic response to an increase in shear intensity, as recorded by an increase in lattice distortion towards the spine margin of up to 9°. This localisation of strain within the shear zone is also accompanied by the destabilisation of hydrous mineral phases (i.e. amphibole), compaction of pores (23-13% Φ), glass devitrification and magnetic anomalies. The narrow zone of disequilibrium textures suggests the likely effect of a thermal input due to strain localisation being the contributing factor. These observations are complimented by high-temperature high-velocity rotary shear experiments which simulate the deformation evolution during shear. Hence, understanding these shallow volcanic

Reaction of Rhyolitic Magma to its Interception by the IDDP-1 Well, Krafla, 2009

Science.gov (United States)

Saubin, É.; Kennedy, B.; Tuffen, H.; Villeneuve, M.; Watson, T.; Nichols, A. R.; Schipper, I.; Cole, J. W.; Mortensen, A. K.; Zierenberg, R. A.

2017-12-01

The unexpected encounter of rhyolitic magma during IDDP-1 geothermal borehole drilling at Krafla, Iceland in 2009, temporarily created the world's hottest geothermal well. This allowed new questions to be addressed. i) How does magma react to drilling? ii) Are the margins of a magma chamber suitable for long-term extraction of supercritical fluids? To investigate these questions, we aim to reconstruct the degassing and deformation behaviour of the enigmatic magma by looking for correlations between textures in rhyolitic material retrieved from the borehole and the recorded drilling data. During drilling, difficulties were encountered in two zones, at 2070 m and below 2093 m depth. Drilling parameters are consistent with the drill bit encountering a high permeability zone and the contact zone of a magma chamber, respectively. Magma was intercepted three times between 2101-2104.4 m depth, which culminated in an increase in standpipe pressure followed by a decrease in weight on bit interpreted as representing the ascent of magma within the borehole. Circulation returned one hour after the last interception, carrying cuttings of glassy particles, felsite with granophyre and contaminant clasts from drilling, which were sampled as a time-series for the following 9 hours. The nature of glassy particles in this time-series varied through time, with a decrease in the proportion of vesicular clasts and a commensurate increase in dense glassy clasts, transitioning from initially colourless to brown glass. Componentry data show a sporadic decrease in felsite (from 34 wt. %), an increase in glassy particles during the first two hours (from 63 wt. % to 94 wt. %) and an increase in contaminant clasts towards the end of the cutting retrieval period. These temporal variations are probably related to the magma body architecture and interactions with the borehole. Transition from vesicular to dense clasts suggests a change in the degassing process that could be related to an early

The evolution of volcanism, tectonics, and volatiles on Mars - An overview of recent progress

Science.gov (United States)

Zimbelman, James R.; Solomon, Sean C.; Sharpton, Virgil L.

1991-01-01

Significant results of the 'Mars: Evolution of Volcanism, Tectonics, and Volatiles' (MEVTV) project are presented. The data for the project are based on geological mapping from the Viking images, petrologic and chemical analyses of SNC meteorites, and both mapping and temporal grouping of major fault systems. The origin of the planet's crustal dichotomy is examined in detail, the kinematics and formation of wrinkle ridges are discussed, and some new theories are set forth. Because the SNC meteorites vary petrologically and isotopically, the sources of the parental Martian magma are heterogeneous. Transcurrent faulting coupled with the extensional strains that form Valles Marineris suggest early horizontal movement of lithospheric blocks. A theory which connects the formation of the crustal dichotomy to the Tharsis region associates the horizontal motions with plate tectonics that generated a new lithosphere.

Magma Mixing: Magmatic Enclaves in Morne Micotrin, Dominica

Science.gov (United States)

Hickernell, S.; Frey, H. M.; Manon, M. R. F.; Waters, L. E.

2017-12-01

Magmatic enclaves in volcanic rocks provide direct evidence of magma mingling/mixing within a magma reservoir and may reinvigorate the system and trigger eruption, as documented at the Soufriere Hills in Montserrat. Lava domes on the neighboring island of Dominica also contain multiple enclave populations and may be evidence for similar magma chamber processes. The central dome of Micotrin is at the head of the Roseau Valley, which was filled with 3 km3 of pyroclastic deposits from eruptions spanning 65 - 25 ka. There appear to be two distinct types of enclaves in the crystal-rich Micotrin andesites (60 wt% SiO2), fine-grained and coarse-grained. Fine-grained mafic enclaves (52 wt% SiO2) vary in size from 1 to 15 cm in diameter, whereas the coarse-grained enclaves are generally larger and range from 3-20 cm. Fine-grained enclaves are saturated in plag (35%) + opx (35%) + cpx (20%) + oxides (10%). Average pyroxenes are 0.01 to 0.02 cm in size, whereas plagioclase averages 0.05 cm and up to 0.1 cm. The texture of the fine-grained enclaves is cumulate-like, devoid of microlites and matrix glass. Coarse-grained enclaves lack cpx and have different modal abundances and textures: plag (75%) + opx (10%) + oxides (5%) + plag microlites (10%). Plagioclase are 0.1 cm in size and orthopyroxenes average 0.05 cm. The coarse-grained enclaves are highly vesicular, a notable difference from the host as well as the fine-grained enclaves. The boundaries of both the fine- and coarse-grained enclaves are quite sharp and distinct and there do not appear to be enclave minerals disaggregated in the host rock. Temperatures were determined by two oxides. The fine-grained enclaves had two populations of magnetite, yielding 847 + 21° and 920 + 17°C. The coarse-grained enclave was 890 + 42 °C, but the oxides were extensively exsolved. Plagioclase composition in both coarse and fine-grained samples was comparable, ranging from An50 to An80. Despite compositional similarity the textures of

Volcanic-plutonic connections and metal fertility of highly evolved magma systems: A case study from the Herberton Sn-W-Mo Mineral Field, Queensland, Australia

Science.gov (United States)

Cheng, Yanbo; Spandler, Carl; Chang, Zhaoshan; Clarke, Gavin

2018-03-01

Understanding the connection between the highly evolved intrusive and extrusive systems is essential to explore the evolution of high silicic magma systems, which plays an important role in discussions of planetary differentiation, the growth of continents, crustal evolution, and the formation of highly evolved magma associated Sn-W-Mo mineral systems. To discern differences between "fertile" and "non-fertile" igneous rocks associated with Sn-W-Mo mineralization and reveal the genetic links between coeval intrusive and extrusive rocks, we integrate whole rock geochemistry, geochronology and Hf isotope signatures of igneous zircons from contemporaneous plutonic and volcanic rocks from the world-class Herberton Mineral Field of Queensland, Australia. The 310-300 Ma intrusive rocks and associated intra-plutonic W-Mo mineralization formed from relatively oxidized magmas after moderate degrees of crystal fractionation. The geochemical and isotopic features of the coeval volcanic succession are best reconciled utilizing the widely-accepted volcanic-plutonic connection model, whereby the volcanic rocks represent fractionated derivatives of the intrusive rocks. Older intrusions emplaced at 335-315 Ma formed from relatively low fO2 magmas that fractionated extensively to produce highly evolved granites that host Sn mineralization. Coeval volcanic rocks of this suite are compositionally less evolved than the intrusive rocks, thereby requiring a different model to link these plutonic-volcanic sequences. In this case, we propose that the most fractionated magmas were not lost to volcanism, but instead were effectively retained at the plutonic level, which allowed further localized build-up of volatiles and lithophile metals in the plutonic environment. This disconnection to the volcanism and degassing may be a crucial step for forming granite-hosted Sn mineralization. The transition between these two igneous regimes in Herberton region over a ∼30 m.y. period is attributed to

Evolution of silicic magmas in the Kos-Nisyros volcanic center: cycles associated with caldera collapse

Science.gov (United States)

Ruprecht, J. S.; Bachmann, O.; Deering, C. D.; Huber, C.; Skopelitis, A.; Schnyder, C.

2010-12-01

Multiple eruptions of silicic magma (dacite and rhyolites) occurred over the last ~ 3 My in the Kos-Nisyros volcanic center (eastern Aegean sea). Over the course of this period, magmas have changed from hornblende-biotite rich units with low eruption temperatures (≤750-800 °C; Kefalos and Kos units) to hotter (>800-850 °C), pyroxene-bearing units (Nisyros units) and are transitioning back to colder magmas (Yali units). Using bulk-rock compositions, mineral chemistry, and zircon Hf isotopes, we show that the two different types of silicic magmas followed the same differentiation trend; they all evolved by crystal fractionation (and minor assimilation) from parents with intermediate compositions characterized by high Sr/Y and low Nb content, following a wet, high oxygen fugacity liquid line of descent typical of subduction zones. As the transition between the Kos-Kefalos and Nisyros-type magmas occurred immediately and abruptly after the major caldera collapse in the area (the 161 ky Kos Plateau Tuff; KPT), we suggest that the efficient emptying of the magma chamber during the KPT drew most of the eruptible magma out and partly froze the silicic magma source zone in the upper crust due to rapid unloading, decompression and resulting crystallization. Therefore, the system had to reinstate a shallow silicic production zone from more mafic parents, recharged at temperatures typically around 850-900 °C from the mid to lower crust. The first silicic eruptions evolving from these parents after the caldera collapse (Nisyros units) were thus slightly hotter and less evolved than the Kefalos-Kos package. However, with time, the upper crustal intermediate mush grew and cooled, leading to interstitial melt compositions reaching again the highly-evolved, cold state that prevailed prior to the Kefalos-Kos. The recent (albeit not precisely dated) eruption of the high-SiO2 rhyolite of Yali suggests that another large, potentially explosive magma chamber is presently building

The emplacement and crystallization of the U-Th-REE-rich agpaitic and hyperagpaitic lujavrites at Kvanefjeld, Ilimaussaq alkaline complex, South Greenland

International Nuclear Information System (INIS)

Soerensen, H.; Bailey, J.C.; Rose-Hansen, J.

2011-01-01

The U-Th-REE deposit located at the Kvanefjeld plateau in the north-west corner of the Ilimaussaq alkaline complex, South Greenland, consists of lujavrites which are melanocratic agpaitic nepheline syenites. The fine-grained lujavrites of the Kvanefjeld plateau can be divided into a northern and a southern part with an intermediate zone between them. The northern part is situated along the north contact of the Ilimaussaq complex and continues east of the Kvanefjeld plateau as a lujavrite belt along the contact. This part has relatively 'low' contents of U, Th, and REE, and hyperagpaitic mineralogy is restricted to its highest-lying parts. The fine-grained lujavrites of the intermediate and southern part of the Kvanefjeld plateau occur between and below huge masses of country rocks which we show are practically in situ remnants of the roof of the lujavrite magma chamber. These lujavrites have high contents of U, Th, and REE, and hyperagpaitic varieties with naujakasite, steenstrupine and villiaumite are widespread. We present a model for the formation of the fine-grained lujavrites of the Kvanefjeld plateau. In this model, an off-shoot from the large lujavrite magma body in the central part of the complex intruded into a fracture zone along the north contact of the Ilimaussaq complex and was forcefully emplaced from north-west to south-east. The intruding lujavrite magma was bounded to the west, north, and at its roof by strong volcanic country rocks, and to the south by the weaker, earlier rocks of the complex. The magma stored in the fracture crystallized, squeezing volatile and residual ele-ments upwards. A subsequent violent explosion opened up fractures in the weaker southern rocks, and the residual volatile-enriched magma was squeezed into fractures in augite syenite, naujaite, and also in the overlying volcanic roof rocks. The removal of the volatile-rich lujavrite magma in the upper part of the fracture-bounded magma chamber made room for the rise of

Magma Odalı Yavaş Yayılan Okyanus Ortası Sırtlarda Isı Modellemesi

OpenAIRE

DÜŞÜNÜR-DOĞAN, Doğa; ESCARTIN, Javier

2012-01-01

Orta Atlantik sırtının yavaş yayılan Lucky Strike segmentinde keşfedilen magma odası, yavaş yayılan okyanus ortası sırtlarında duraylı olabilecek magma odalarınıın varlığını denetleyen parametrelerin araştırılabilmesi için bir motivasyon olmuştur. Bu çalışma kapsamında, segmentteki magma odasından kaynaklanan sıcaklığı 3-boyutlu modelleyebilmek için sonlu farklar yöntemini kullandık. Okyanus ortası sırtlarının sıcaklık yapısını denetleyen ana etmenlerden, toplam magma girdisi, magma giriş geo...

Range-based volatility, expected stock returns, and the low volatility anomaly

Science.gov (United States)

2017-01-01

One of the foundations of financial economics is the idea that rational investors will discount stocks with more risk (volatility), which will result in a positive relation between risk and future returns. However, the empirical evidence is mixed when determining how volatility is related to future returns. In this paper, we examine this relation using a range-based measure of volatility, which is shown to be theoretically, numerically, and empirically superior to other measures of volatility. In a variety of tests, we find that range-based volatility is negatively associated with expected stock returns. These results are robust to time-series multifactor models as well as cross-sectional tests. Our findings contribute to the debate about the direction of the relationship between risk and return and confirm the presence of the low volatility anomaly, or the anomalous finding that low volatility stocks outperform high volatility stocks. In other tests, we find that the lower returns associated with range-based volatility are driven by stocks with lottery-like characteristics. PMID:29190652

Range-based volatility, expected stock returns, and the low volatility anomaly.

Science.gov (United States)

Blau, Benjamin M; Whitby, Ryan J

2017-01-01

One of the foundations of financial economics is the idea that rational investors will discount stocks with more risk (volatility), which will result in a positive relation between risk and future returns. However, the empirical evidence is mixed when determining how volatility is related to future returns. In this paper, we examine this relation using a range-based measure of volatility, which is shown to be theoretically, numerically, and empirically superior to other measures of volatility. In a variety of tests, we find that range-based volatility is negatively associated with expected stock returns. These results are robust to time-series multifactor models as well as cross-sectional tests. Our findings contribute to the debate about the direction of the relationship between risk and return and confirm the presence of the low volatility anomaly, or the anomalous finding that low volatility stocks outperform high volatility stocks. In other tests, we find that the lower returns associated with range-based volatility are driven by stocks with lottery-like characteristics.

Range-based volatility, expected stock returns, and the low volatility anomaly.

Directory of Open Access Journals (Sweden)

Benjamin M Blau

Full Text Available One of the foundations of financial economics is the idea that rational investors will discount stocks with more risk (volatility, which will result in a positive relation between risk and future returns. However, the empirical evidence is mixed when determining how volatility is related to future returns. In this paper, we examine this relation using a range-based measure of volatility, which is shown to be theoretically, numerically, and empirically superior to other measures of volatility. In a variety of tests, we find that range-based volatility is negatively associated with expected stock returns. These results are robust to time-series multifactor models as well as cross-sectional tests. Our findings contribute to the debate about the direction of the relationship between risk and return and confirm the presence of the low volatility anomaly, or the anomalous finding that low volatility stocks outperform high volatility stocks. In other tests, we find that the lower returns associated with range-based volatility are driven by stocks with lottery-like characteristics.

Pricing Volatility Referenced Assets

Directory of Open Access Journals (Sweden)

Alan De Genaro Dario

2006-12-01

Full Text Available Volatility swaps are contingent claims on future realized volatility. Variance swaps are similar instruments on future realized variance, the square of future realized volatility. Unlike a plain vanilla option, whose volatility exposure is contaminated by its asset price dependence, volatility and variance swaps provide a pure exposure to volatility alone. This article discusses the risk-neutral valuation of volatility and variance swaps based on the framework outlined in the Heston (1993 stochastic volatility model. Additionally, the Heston (1993 model is calibrated for foreign currency options traded at BMF and its parameters are used to price swaps on volatility and variance of the BRL / USD exchange rate.

On the conditions of magma mixing and its bearing on andesite production in the crust.

Science.gov (United States)

Laumonier, Mickael; Scaillet, Bruno; Pichavant, Michel; Champallier, Rémi; Andujar, Joan; Arbaret, Laurent

2014-12-15

Mixing between magmas is thought to affect a variety of processes, from the growth of continental crust to the triggering of volcanic eruptions, but its thermophysical viability remains unclear. Here, by using high-pressure mixing experiments and thermal calculations, we show that hybridization during single-intrusive events requires injection of high proportions of the replenishing magma during short periods, producing magmas with 55-58 wt% SiO2 when the mafic end-member is basaltic. High strain rates and gas-rich conditions may produce more felsic hybrids. The incremental growth of crustal reservoirs limits the production of hybrids to the waning stage of pluton assembly and to small portions of it. Large-scale mixing appears to be more efficient at lower crustal conditions, but requires higher proportions of mafic melt, producing more mafic hybrids than in shallow reservoirs. Altogether, our results show that hybrid arc magmas correspond to periods of enhanced magma production at depth.

Computer Simulation To Assess The Feasibility Of Coring Magma

Science.gov (United States)

Su, J.; Eichelberger, J. C.

2017-12-01

Lava lakes on Kilauea Volcano, Hawaii have been successfully cored many times, often with nearly complete recovery and at temperatures exceeding 1100oC. Water exiting nozzles on the diamond core bit face quenches melt to glass just ahead of the advancing bit. The bit readily cuts a clean annulus and the core, fully quenched lava, passes smoothly into the core barrel. The core remains intact after recovery, even when there are comparable amounts of glass and crystals with different coefficients of thermal expansion. The unique resulting data reveal the rate and sequence of crystal growth in cooling basaltic lava and the continuous liquid line of descent as a function of temperature from basalt to rhyolite. Now that magma bodies, rather than lava pooled at the surface, have been penetrated by geothermal drilling, the question arises as to whether similar coring could be conducted at depth, providing fundamentally new insights into behavior of magma. This situation is considerably more complex because the coring would be conducted at depths exceeding 2 km and drilling fluid pressures of 20 MPa or more. Criteria that must be satisfied include: 1) melt is quenched ahead of the bit and the core itself must be quenched before it enters the barrel; 2) circulating drilling fluid must keep the temperature of the coring assembling cooled to within operational limits; 3) the drilling fluid column must nowhere exceed the local boiling point. A fluid flow simulation was conducted to estimate the process parameters necessary to maintain workable temperatures during the coring operation. SolidWorks Flow Simulation was used to estimate the effect of process parameters on the temperature distribution of the magma immediately surrounding the borehole and of drilling fluid within the bottom-hole assembly (BHA). A solid model of the BHA was created in SolidWorks to capture the flow behavior around the BHA components. Process parameters used in the model include the fluid properties and

Contraction or expansion of the Moon's crust during magma ocean freezing?

Science.gov (United States)

Elkins-Tanton, Linda T; Bercovici, David

2014-09-13

The lack of contraction features on the Moon has been used to argue that the Moon underwent limited secular cooling, and thus had a relatively cool initial state. A cool early state in turn limits the depth of the lunar magma ocean. Recent GRAIL gravity measurements, however, suggest that dikes were emplaced in the lower crust, requiring global lunar expansion. Starting from the magma ocean state, we show that solidification of the lunar magma ocean would most likely result in expansion of the young lunar crust, and that viscous relaxation of the crust would prevent early tectonic features of contraction or expansion from being recorded permanently. The most likely process for creating the expansion recorded by the dikes is melting during cumulate overturn of the newly solidified lunar mantle. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

[The spectrum studies of structure characteristics in magma contact metamorphic coal].

Science.gov (United States)

Wu, Dun; Sun, Ruo-Yu; Liu, Gui-Jian; Yuan, Zi-Jiao

2013-10-01

The structural parameters evolution of coal due to the influence of intrusions of hot magma was investigated and analyzed. X-ray diffraction and laser confocal microscope Raman spectroscopy were used to test and analyze 4 coal samples undergoing varying contact-metamorphism by igneous magmas in borehole No. 13-4 of Zhuji coal mine, Huainan coalfield. The result showed that coal XRD spectrum showed higher background intensity, with the 26 degrees and 42 degrees nearby apparent graphite diffraction peak. Two significant vibration peaks of coal Raman spectra were observed in the 1 000-2 000 cm(-1) frequency range: broad "D" peak at 1 328-1 369 cm(-1) and sharp "G" peak at 1 564-1 599 cm(-1). With the influence of magma intrusion, the relationship between coal structural parameters and coal ranks was excellent.

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.

Magma ocean formation due to giant impacts

Science.gov (United States)

Tonks, W. B.; Melosh, H. J.

1993-01-01

The thermal effects of giant impacts are studied by estimating the melt volume generated by the initial shock wave and corresponding magma ocean depths. Additionally, the effects of the planet's initial temperature on the generated melt volume are examined. The shock pressure required to completely melt the material is determined using the Hugoniot curve plotted in pressure-entropy space. Once the melting pressure is known, an impact melting model is used to estimate the radial distance melting occurred from the impact site. The melt region's geometry then determines the associated melt volume. The model is also used to estimate the partial melt volume. Magma ocean depths resulting from both excavated and retained melt are calculated, and the melt fraction not excavated during the formation of the crater is estimated. The fraction of a planet melted by the initial shock wave is also estimated using the model.

Iodine volatility

International Nuclear Information System (INIS)

Beahm, E.C.; Shockley, W.E.

1984-01-01

The ultimate aim of this program is to couple experimental aqueous iodine volatilities to a fission product release model. Iodine partition coefficients, for inorganic iodine, have been measured during hydrolysis and radiolysis. The hydrolysis experiments have illustrated the importance of reaction time on iodine volatility. However, radiolysis effects can override hydrolysis in determining iodine volatility. In addition, silver metal in radiolysis samples can react to form silver iodide accompanied by a decrease in iodine volatility. Experimental data are now being coupled to an iodine transport and release model that was developed in the Federal Republic of Germany

Coupling Thermal and Chemical Signatures of Crustal Magma Bodies: Energy-Constrained Eruption, Recharge, Assimilation, and Fractional Crystallization (E'RAχFC)

Science.gov (United States)

Bohrson, W. A.; Spera, F. J.

2004-12-01

Energy-Constrained Eruption, Recharge, Assimilation and Fractional Crystallization (E'RAχFC) tracks the evolution of an open-system magmatic system by coupling conservation equations governing energy, mass and species (isotopes and trace elements). By linking the compositional characteristics of a composite magmatic system (host magma, recharge magma, wallrock, eruptive reservoir) to its mass and energy fluxes, predictions can be made about the chemical evolution of systems characterized by distinct compositional and thermal characteristics. An interesting application of E'RAχFC involves documenting the influence distinct thermal regimes have on the chemical evolution of magmatic systems. Heat transfer between a magma-country rock system at epizonal depths can be viewed as a conjugate heat transfer problem in which the average country rock-magma boundary temperature, Tb, is governed by the relative vigor of hydrothermal convection in the country rock vs. magma convection. For cases where hydrothermal circulation is vigorous and magmatic heat is efficiently transported away from the boundary, contact aureole temperatures (~Tb) are low. In cases where magmatic heat can not be efficiently transported away from the boundary and hydrothermal cells are absent or poorly developed, Tb is relatively high. Simultaneous solution of the differential equations governing momentum and energy conservation and continuity for the coupled hydrothermal-magmatic conjugate heat transfer system enables calculation of the characteristic timescale for EC-RAFC evolution and development of hydrothermal deposits as a function of material and medium properties, sizes of systems and relative efficiency of hydrothermal vs. magmatic heat transfer. Characteristic timescales lie in the range 102-106 yr depending on system size, magma properties and permeability among other parameters. In E'RAχFC, Tb is approximated by the user-defined equilibration temperature, Teq, which is the temperature at

Temperatures and isotopic evolution of silicic magmas, Taupo Volcanic Zone and Coromandel, New Zealand

International Nuclear Information System (INIS)

Blattner, P.; Rui-Zhong H.; Graham, I.J.; Houston-Eleftheriadis, C.

1996-01-01

A new set of oxygen and strontium isotope data on rhyolitic lavas and ignimbrites of the Taupo Volcanic Zone (TVZ) and the Coromandel Peninsula provides new limits for petrogenic models. For oxygen isotopes, the rock matrix is frequently altered, so that values for magma need to be phenocryst based. Within TVZ a trend towards more negative δ 1 8O values for more recent magmas appears likely (average before about 1 Ma and for Coromandel near 8.0 per mille; after 1 Ma near 7.5 per mille). This could indicate the gradual removal of supracrustal contaminants from the zones of magma accumulation and extrusion. Similar trends within Coromandel cannot yet be resolved. A generally positive correlation is found for oxygen and strontium isotopes of magmas. Most magmas have a limited range of isotopic values, which then becomes a fingerprint (e.g., the Mamaku, Matahina, and Waiotapu Ignimbrites). A narrow range of eruption temperatures of 880 ± 60 o C is derived from quartz-plagioclase fractionations of 0.98 ± 0.25 per mille δ 1 8O values of quartz and feldspar phenocrysts are sufficiently low to suggest interaction between surface water and magma. However, large negative oxygen isotope anomalies (such as known from Yellowstone), could be no more than partially concealed by the isotopically less depleted meteoric water of New Zealand, and have not yet been found in New Zealand. (authors). 45 refs., 6 figs., 3 tabs

The 2nd to 4th century explosive activity of Vesuvius: new data on the timing of the upward migration of the post-A.D. 79 magma chamber

Directory of Open Access Journals (Sweden)

Raffaello Cioni

2013-11-01

Full Text Available We present volcanological data on the deposits of the Santa Maria Member (SMM, the eruption cycle occurred at Vesuvius (Italy in the period between the A.D. 79 plinian and the A.D. 472 subplinan eruptions. Historical accounts report only sporadic, poorly reliable descriptions of the volcanic activity in this period, during which a stratified sequence of ash and lapilli beds, up to 150 cm thick, with a total volume estimated around 0.15 km3, was widely dispersed on the outer slopes of the volcano. Stratigraphic studies and component analyses suggest that activity was characterized by mixed hydromagmatic and magmatic processes. The eruption style has been interpreted as repeated alternations of continuous and prolonged ash emission activity intercalated with short-lived, violent strombolian phases. Analyses of the bulk rock composition reveal that during the entire eruption cycle, magma maintained an homogeneous phonotephritic composition. In addition, the general trends of major and trace elements depicted by the products of the A.D. 79 and A.D. 472 eruptions converge to the SMM composition, suggesting a common mafic end-member for these eruptions. The volatile content measured in pyroxene-hosted melt inclusions indicates two main values of crystallization pressures, around 220 and 70 MPa, roughly corresponding to the previously estimated depth of the magma reservoirs of the A.D. 79 and A.D. 472 eruptions, respectively. The study of SMM eruption cycle may thus contribute to understand the processes governing the volcano reawakening immediately after a plinian event, and the timing and modalities which govern the migration of the magma reservoir.

The chemical and isotopic differentiation of an epizonal magma body: Organ Needle pluton, New Mexico

Science.gov (United States)

Verplanck, P.L.; Farmer, G.L.; McCurry, M.; Mertzman, S.A.

1999-01-01

Major and trace element, and Nd and Sr isotopic compositions of whole rocks and mineral separates from the Oligocene, alkaline Organ Needle pluton (ONP), southern New Mexico, constrain models for the differentiation of the magma body parental to this compositionally zoned and layered epizonal intrusive body. The data reveal that the pluton is rimmed by lower ??(Nd) (~-5) and higher 87Sr/86Sr (~0.7085) syenitic rocks than those in its interior (??(Nd) ~ 2, 87Sr/86Sr ~0.7060) and that the bulk compositions of the marginal rocks become more felsic with decreasing structural depth. At the deepest exposed levels of the pluton, the ??(Nd)~-5 lithology is a compositionally heterogeneous inequigranular syenite. Modal, compositional and isotopic data from separates of rare earth element (REE)-bearing major and accesory mineral phases (hornblende, titanite, apatite, zircon) demonstrate that this decoupling of trace and major elements in the inequigranular syenite results from accumulation of light REE (LREE)-bearing minerals that were evidently separated from silicic magmas as the latter rose along the sides of the magma chamber. Chemical and isotopic data for microgranular mafic enclaves, as well as for restite xenoliths of Precambrian granite wall rock, indicate that the isotopic distinction between the marginal and interior facies of the ONP probably reflects assimilation of the wall rock by ??(Nd) ~-2 mafic magmas near the base of the magma system. Fractional crystallization and crystal liquid separation of the crystally contaminated magma at the base and along the margins of the chamber generated the highly silicic magmas that ultimately pooled at the chamber top.

Magmatic structures in the Krkonoše Jizera Plutonic Complex, Bohemian Massif: evidence for localized multiphase flow and small-scale thermal mechanical instabilities in a granitic magma chamber

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Žák, Jiří; Klomínský, Josef

2007-08-01

The present paper examines magmatic structures in the Jizera and Liberec granites of the Krkonoše-Jizera Plutonic Complex, Bohemian Massif. The magmatic structures are here interpreted to preserve direct field evidence for highly localized magma flow and other processes in crystal-rich mushes, and to capture the evolution of physical processes in an ancient granitic magma chamber. We propose that after chamber-wide mixing and hybridization, as suggested by recent petrological studies, laminar magma flow became highly localized to weaker channel-like domains within the higher-strength crystal framework. Mafic schlieren formed at flow rims, and their formation presumably involved gravitational settling and velocity gradient flow sorting coupled with interstitial melt escape. Local thermal or compositional convection may have resulted in the formation of vertical schlieren tubes and ladder dikes whereas subhorizontal tubes or channels formed during flow driven by lateral gradients in magma pressure. After the cessation or deceleration of channel flow, gravity-driven processes (settling of crystals and enclaves, gravitational differentiation, development of downward dripping instabilities), accompanied by compaction, filter pressing and melt segregation, dominated in the crystal mush within the flow channels. Subsequently, magmatic folds developed in schlieren layers and the magma chamber recorded complex, late magmatic strains at high magma crystallinities. Late-stage magma pulsing into localized submagmatic cracks represents the latest events of magmatic history of the chamber prior to its final crystallization. We emphasize that the most favorable environments for the formation and preservation of magmatic structures, such as those hosted in the Jizera and Liberec granites, are slowly cooling crystal-rich mushes. Therefore, where preserved in plutons, these structures may lend strong support for a "mush model" of magmatic systems.

Sensitivity of seafloor bathymetry to climate-driven fluctuations in mid-ocean ridge magma supply.

Science.gov (United States)

Olive, J-A; Behn, M D; Ito, G; Buck, W R; Escartín, J; Howell, S

2015-10-16

Recent studies have proposed that the bathymetric fabric of the seafloor formed at mid-ocean ridges records rapid (23,000 to 100,000 years) fluctuations in ridge magma supply caused by sealevel changes that modulate melt production in the underlying mantle. Using quantitative models of faulting and magma emplacement, we demonstrate that, in fact, seafloor-shaping processes act as a low-pass filter on variations in magma supply, strongly damping fluctuations shorter than about 100,000 years. We show that the systematic decrease in dominant seafloor wavelengths with increasing spreading rate is best explained by a model of fault growth and abandonment under a steady magma input. This provides a robust framework for deciphering the footprint of mantle melting in the fabric of abyssal hills, the most common topographic feature on Earth. Copyright © 2015, American Association for the Advancement of Science.

A model of the primordial lunar atmosphere

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Saxena, Prabal; Elkins-Tanton, Lindy; Petro, Noah; Mandell, Avi

2017-09-01

We create the first quantitative model for the early lunar atmosphere, coupled with a magma ocean crystallization model. Immediately after formation, the moon's surface was subject to a radiative environment that included contributions from the early Sun, a post-impact Earth that radiated like a mid-type M dwarf star, and a cooling global magma ocean. This radiative environment resulted in a largely Earth-side atmosphere on the Moon, ranging from ∼104 to ∼102 pascals, composed of heavy volatiles (Na and SiO). This atmosphere persisted through lid formation and was additionally characterized by supersonic winds that transported significant quantities of moderate volatiles and likely generated magma ocean waves. The existence of this atmosphere may have influenced the distribution of some moderate volatiles and created temperature asymmetries which influenced ocean flow and cooling. Such asymmetries may characterize young, tidally locked rocky bodies with global magma oceans and subject to intense irradiation.

Temporal variations in volumetric magma eruption rates of Quaternary volcanoes in Japan

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Yamamoto, Takahiro; Kudo, Takashi; Isizuka, Osamu

2018-04-01

Long-term evaluations of hazard and risk related to volcanoes rely on extrapolations from volcano histories, including the uniformity of their eruption rates. We calculated volumetric magma eruption rates, compiled from quantitative eruption histories of 29 Japanese Quaternary volcanoes, and analyzed them with respect to durations spanning 101-105 years. Calculated eruption rates vary greatly (101-10-4 km3 dense-rock equivalent/1000 years) between individual volcanoes. Although large basaltic stratovolcanoes tend to have high eruption rates and relatively constant repose intervals, these cases are not representative of the various types of volcanoes in Japan. At many Japanese volcanoes, eruption rates are not constant through time, but increase, decrease, or fluctuate. Therefore, it is important to predict whether eruption rates will increase or decrease for long-term risk assessment. Several temporal co-variations of eruption rate and magmatic evolution suggest that there are connections between them. In some cases, magma supply rates increased in response to changing magma-generation processes. On the other hand, stable plumbing systems without marked changes in magma composition show decreasing eruption rates through time.[Figure not available: see fulltext.

The parent magma of xenoliths in shergottite EETA79001: Bulk and trace element composition inferred from magmatic inclusions

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Treiman, Allan H.; Lindstrom, David J.; Martinez, Rene R.

1994-01-01

The SNC meteorites are samples of the Martian crust, so inferences about their origins and parent magmas are of wide planetologic significance. The EETA79001 shergottite, a basalt, contains xenoliths of pyroxene-olivine cumulate rocks which are possibly related to the ALHA77005 and LEW88516 SNC lherzolites. Olivines in the xenoliths contain magmatic inclusions, relics of magma trapped within the growing crystals. The magmatic inclusions allow a parent magma composition to be retrieved; it is similar to the composition reconstructed from xenolith pyroxenes by element distribution coefficients. The xenolith parent magma is similar but not identical to parent magmas for the shergottite lherzolites.

The parent magma of the Nakhla (SNC) meteorite: Reconciliation of composition estimates from magmatic inclusions and element partitioning

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Treiman, A. H.

1993-01-01

The composition of the parent magma of the Nakhla meteorite was difficult to determine, because it is accumulate rock, enriched in olivine and augite relative to a basalt magma. A parent magma composition is estimated from electron microprobe area analyses of magmatic inclusions in olivine. This composition is consistent with an independent estimate based on the same inclusions, and with chemical equilibria with the cores of Nakhla's augites. This composition reconciles most of the previous estimates of Nakhla's magma composition, and obviates the need for complex magmatic processes. Inconsistency between this composition and those calculated previously suggests that magma flowed through and crystallized into Nakhla as it cooled.

The parent magma of the nakhlite meteorites - Clues from melt inclusions

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Harvey, Ralph P.; Mcsween, Harry Y., Jr.

1992-01-01

Several forms of trapped liquid found within nakhlite meteorites have been examined, including interstitial melt and magmatic inclusions within the cores of large olivine grains. Differences in the mineralogy and texture between two types of trapped melt inclusions, and between these inclusions and the mesostasis, indicate that vitrophyric inclusions are most appropriate for estimating the composition of a nakhlite parental magma in equilibrium with early-forming olivine and augite. Parent liquids were calculated from the mineralogy of large inclusions in Nakhla and Governador Valadares, using a system of mass-balance equations solved by linear regression methods. The chosen parental liquids were cosaturated in olivine and augite and had Mg/Fe values consistent with measured augite/liquid Kds. These parental magma compositions are similar to other published compositions for Nakhla, Chassigny, and Shergotty parental melts, and may correspond to a significant magma type on Mars.

Chaotic behavior of earthquakes induced by a nonlinear magma up flow

International Nuclear Information System (INIS)

Pelap, F.B.; Kagho, L.Y.; Fogang, C.F.

2016-01-01

This paper considers the dynamics of a modified 1D nonlinear spring-block model for earthquake subjected to the strengths induced by the motion of the tectonic plates and the up flow of magma during volcanism. Based on the multiple time scales method, we establish that after the slip, the fault remains active and the frictions increase with the power of the earthquake. We also obtain in the non-resonance case that the appearing probability of an event decreases with these frictions. In the resonance case, the dynamics of harmonic oscillations show that the rocks constituting the block will fracture or resist to the effects induced by the magma motion. Our analytical investigations are complemented by numerical simulations from which it appears that, for given values of the magma thrust strength magnitude, the friction coefficient, the quadratic and cubic nonlinear parameters, the system exhibits chaotic behavior.

Volcano seismicity and ground deformation unveil the gravity-driven magma discharge dynamics of a volcanic eruption.

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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.

The Dovyren Intrusive Complex (Southern Siberia, Russia): Insights into dynamics of an open magma chamber with implications for parental magma origin, composition, and Cu-Ni-PGE fertility

Science.gov (United States)

Ariskin, Alexey; Danyushevsky, Leonid; Nikolaev, Georgy; Kislov, Evgeny; Fiorentini, Marco; McNeill, Andrew; Kostitsyn, Yuri; Goemann, Karsten; Feig, Sandrin T.; Malyshev, Alexey

2018-03-01

The Dovyren Intrusive Complex (DIC, Northern Baikal region, 728 Ma) includes the layered dunite-troctolite-gabbronorite Yoko-Dovyren massif (YDM), associated mafic-ultramafic sills, and dykes of olivine-rich to olivine-free gabbronorite. Major rock types of the DIC are presented, including a diversity of olivine orthocumulates to olivine-plagioclase and gabbroic adcumulates, carbonate-contaminated ultramafics and Cu-Ni-PGE mineralisation. Detailed comparisons of complete cross-sections of the YDM in its centre and at the NE and SW margins demonstrate differences in the cumulate succession, mineral chemistry, and geochemical structure that likely reflect variations in parental magma compositions. Combining petrochemical reconstructions for most primitive rocks and calculations using the COMAGMAT-5 model, it is shown that the central and peripheral parts of the intrusion formed by olivine-laden parental magmas ranged in their temperatures by 100 °C, approximately from 1290 °C ( 11 wt% MgO, olivine Fo88) to 1190 °C ( 8 wt% MgO, olivine Fo86). Thermodynamic modelling suggests that the most primitive high-Mg magma was S-undersaturated, whereas its derivatives became S-saturated at T piles to generate poorly-mineralised plagiodunite. In the troctolite and gabbroic parts of the Dovyren chamber, sulphide immiscibility likely occurred at lower temperatures, producing Cu-rich sulphide precursors, which gave rise to the 'platinum group mineral' (PGM-containing) troctolite and low-mineralised PGE-rich anorthosite in the Main Reef. The geochemical structure of the YDM demonstrates C-shaped distributions of TiO2, K2O, P2O5, and incompatible trace elements, which are 3-5 fold depleted in the cumulate rocks from the inner horizons of the intrusion with respect to the relatively thin lower and upper contact zones. In addition, a marked misbalance between estimates of the average composition of the YDM and that of the proposed olivine-laden parental magmas is established. This

Heterogeneity in lunar anorthosite meteorites: implications for the lunar magma ocean model.

Science.gov (United States)

Russell, Sara S; Joy, Katherine H; Jeffries, Teresa E; Consolmagno, Guy J; Kearsley, Anton

2014-09-13

The lunar magma ocean model is a well-established theory of the early evolution of the Moon. By this model, the Moon was initially largely molten and the anorthositic crust that now covers much of the lunar surface directly crystallized from this enormous magma source. We are undertaking a study of the geochemical characteristics of anorthosites from lunar meteorites to test this model. Rare earth and other element abundances have been measured in situ in relict anorthosite clasts from two feldspathic lunar meteorites: Dhofar 908 and Dhofar 081. The rare earth elements were present in abundances of approximately 0.1 to approximately 10× chondritic (CI) abundance. Every plagioclase exhibited a positive Eu-anomaly, with Eu abundances of up to approximately 20×CI. Calculations of the melt in equilibrium with anorthite show that it apparently crystallized from a magma that was unfractionated with respect to rare earth elements and ranged in abundance from 8 to 80×CI. Comparisons of our data with other lunar meteorites and Apollo samples suggest that there is notable heterogeneity in the trace element abundances of lunar anorthosites, suggesting these samples did not all crystallize from a common magma source. Compositional and isotopic data from other authors also suggest that lunar anorthosites are chemically heterogeneous and have a wide range of ages. These observations may support other models of crust formation on the Moon or suggest that there are complexities in the lunar magma ocean scenario to allow for multiple generations of anorthosite formation. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Numerical modeling of magma-tectonic interactions at Pacaya Volcano, Guatemala

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Wauthier, C.

2017-12-01

Pacaya Volcano is composed of several volcanic cones located along the southern rim of the Amatitlan caldera, approximately 25 km south of Guatemala City. It is a basaltic volcano located in the Central American Volcanic Arc. The shallow magma plumbing system at Pacaya likely includes at least three magma reservoirs: a very shallow ( 0.2-0.4 km depth) reservoir located below and possibly within the MacKenney cone, a 4 km deep reservoir located northwest of the summit, and a shallow dike-like conduit below the summit which fed the recent flank eruptions. Pacaya's western flank is slipping in a stick-slip fashion, and the instability seems associated with larger volume eruptions. Flank instability phases indeed occurred in 2010 and 2014 in coincidence with major intrusive and eruptive phases, suggesting a positive feedback between the flank motion and major intrusions. Simple analytical models are insufficient to fit the geodetic observations and model the flank processes and their mechanical interactions with the magmatic system. Here, numerical modeling approaches are used to characterize the 2014 flank deformation episode and magma-tectonic interactions.

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.

CO2 bubble generation and migration during magma-carbonate interaction

Science.gov (United States)

Blythe, L. S.; Deegan, F. M.; Freda, C.; Jolis, E. M.; Masotta, M.; Misiti, V.; Taddeucci, J.; Troll, V. R.

2015-04-01

We conducted quantitative textural analysis of vesicles in high temperature and pressure carbonate assimilation experiments (1200 °C, 0.5 GPa) to investigate CO2 generation and subsequent bubble migration from carbonate into magma. We employed Mt. Merapi (Indonesia) and Mt. Vesuvius (Italy) compositions as magmatic starting materials and present three experimental series using (1) a dry basaltic-andesite, (2) a hydrous basaltic-andesite (2 wt% H2O), and (3) a hydrous shoshonite (2 wt% H2O). The duration of the experiments was varied from 0 to 300 s, and carbonate assimilation produced a CO2-rich fluid and CaO-enriched melts in all cases. The rate of carbonate assimilation, however, changed as a function of melt viscosity, which affected the 2D vesicle number, vesicle volume, and vesicle size distribution within each experiment. Relatively low-viscosity melts (i.e. Vesuvius experiments) facilitated efficient removal of bubbles from the reaction site. This allowed carbonate assimilation to continue unhindered and large volumes of CO2 to be liberated, a scenario thought to fuel sustained CO2-driven eruptions at the surface. Conversely, at higher viscosity (i.e. Merapi experiments), bubble migration became progressively inhibited and bubble concentration at the reaction site caused localised volatile over-pressure that can eventually trigger short-lived explosive outbursts. Melt viscosity therefore exerts a fundamental control on carbonate assimilation rates and, by consequence, the style of CO2-fuelled eruptions.

Asymmetric Realized Volatility Risk

Directory of Open Access Journals (Sweden)

David E. Allen

2014-06-01

Full Text Available In this paper, we document that realized variation measures constructed from high-frequency returns reveal a large degree of volatility risk in stock and index returns, where we characterize volatility risk by the extent to which forecasting errors in realized volatility are substantive. Even though returns standardized by ex post quadratic variation measures are nearly Gaussian, this unpredictability brings considerably more uncertainty to the empirically relevant ex ante distribution of returns. Explicitly modeling this volatility risk is fundamental. We propose a dually asymmetric realized volatility model, which incorporates the fact that realized volatility series are systematically more volatile in high volatility periods. Returns in this framework display time varying volatility, skewness and kurtosis. We provide a detailed account of the empirical advantages of the model using data on the S&P 500 index and eight other indexes and stocks.

It’s all about volatility of volatility

DEFF Research Database (Denmark)

Grassi, Stefano; Santucci de Magistris, Paolo

2015-01-01

The persistent nature of equity volatility is investigated by means of a multi-factor stochastic volatility model with time varying parameters. The parameters are estimated by means of a sequential matching procedure which adopts as auxiliary model a time-varying generalization of the HAR model f...

VOLATILIZATION RATES FROM WATER TO INDOOR AIR ...

Science.gov (United States)

Contaminated water can lead to volatilization of chemicals to residential indoor air. Previous research has focused on only one source (shower stalls) and has been limited to chemicals in which gas-phase resistance to mass transfer is of marginal significance. As a result, attempts to extrapolate chemical emissions from high-volatility chemicals to lower volatility chemicals, or to sources other than showers, have been difficult or impossible. This study involved the development of two-phase, dynamic mass balance models for estimating chemical emissions from washing machines, dishwashers, and bathtubs. An existing model was adopted for showers only. Each model required the use of source- and chemical-specific mass transfer coefficients. Air exchange (ventilation) rates were required for dishwashers and washing machines as well. These parameters were estimated based on a series of 113 experiments involving 5 tracer chemicals (acetone, ethyl acetate, toluene, ethylbenzene, and cyclohexane) and 4 sources (showers, bathtubs, washing machines, and dishwashers). Each set of experiments led to the determination of chemical stripping efficiencies and mass transfer coefficients (overall, liquid-phase, gas-phase), and to an assessment of the importance of gas- phase resistance to mass transfer. Stripping efficiencies ranged from 6.3% to 80% for showers, 2.6% to 69% for bathtubs, 18% to 100% for dishwashers, and 3.8% to 100% for washing machines. Acetone and cyclohexane al

Two magma bodies beneath the summit of Kilauea Volcano unveiled by isotopically distinct melt deliveries from the mantle

Science.gov (United States)

Pietruszka, Aaron J.; Heaton, Daniel E.; Marske, Jared P.; Garcia, Michael O.

2015-01-01

The summit magma storage reservoir of Kīlauea Volcano is one of the most important components of the magmatic plumbing system of this frequently active basaltic shield-building volcano. Here we use new high-precision Pb isotopic analyses of Kīlauea summit lavas—from 1959 to the active Halema‘uma‘u lava lake—to infer the number, size, and interconnectedness of magma bodies within the volcano's summit reservoir. From 1971 to 1982, the 206Pb/204Pb ratios of the lavas define two separate magma mixing trends that correlate with differences in vent location and/or pre-eruptive magma temperature. These relationships, which contrast with a single magma mixing trend for lavas from 1959 to 1968, indicate that Kīlauea summit eruptions since at least 1971 were supplied from two distinct magma bodies. The locations of these magma bodies are inferred to coincide with two major deformation centers identified by geodetic monitoring of the volcano's summit region: (1) the main locus of the summit reservoir ∼2–4 km below the southern rim of Kīlauea Caldera and (2) a shallower magma body 4 km3 of lava erupted), must therefore be sustained by a nearly continuous supply of new melt from the mantle. The model results show that a minimum of four compositionally distinct, mantle-derived magma batches were delivered to the volcano (at least three directly to the summit reservoir) since 1959. These melt inputs correlate with the initiation of energetic (1959 Kīlauea Iki) and/or sustained (1969–1974 Mauna Ulu, 1983-present Pu‘u ‘Ō‘ō and 2008-present Halema‘uma‘u) eruptions. Thus, Kīlauea's eruptive behavior is partly tied to the delivery of new magma batches from the volcano's source region within the Hawaiian mantle plume.

Latent Integrated Stochastic Volatility, Realized Volatility, and Implied Volatility: A State Space Approach

DEFF Research Database (Denmark)

Bach, Christian; Christensen, Bent Jesper

process is downward biased. Implied volatility performs better than any of the alternative realized measures when forecasting future integrated volatility. The results are largely similar across the stock market (S&P 500), bond market (30-year U.S. T-bond), and foreign currency exchange market ($/£ )....

Evidence of a global magma ocean in Io's interior.

Science.gov (United States)

Khurana, Krishan K; Jia, Xianzhe; Kivelson, Margaret G; Nimmo, Francis; Schubert, Gerald; Russell, Christopher T

2011-06-03

Extensive volcanism and high-temperature lavas hint at a global magma reservoir in Io, but no direct evidence has been available. We exploited Jupiter's rotating magnetic field as a sounding signal and show that the magnetometer data collected by the Galileo spacecraft near Io provide evidence of electromagnetic induction from a global conducting layer. We demonstrate that a completely solid mantle provides insufficient response to explain the magnetometer observations, but a global subsurface magma layer with a thickness of over 50 kilometers and a rock melt fraction of 20% or more is fully consistent with the observations. We also place a stronger upper limit of about 110 nanoteslas (surface equatorial field) on the dynamo dipolar field generated inside Io.

DOES ENERGY CONSUMPTION VOLATILITY AFFECT REAL GDP VOLATILITY? AN EMPIRICAL ANALYSIS FOR THE UK

Directory of Open Access Journals (Sweden)

Abdul Rashid

2013-10-01

Full Text Available This paper empirically examines the relation between energy consumption volatility and unpredictable variations in real gross domestic product (GDP in the UK. Estimating the Markov switching ARCH model we find a significant regime switching in the behavior of both energy consumption and GDP volatility. The results from the Markov regime-switching model show that the variability of energy consumption has a significant role to play in determining the behavior of GDP volatilities. Moreover, the results suggest that the impacts of unpredictable variations in energy consumption on GDP volatility are asymmetric, depending on the intensity of volatility. In particular, we find that while there is no significant contemporaneous relationship between energy consumption volatility and GDP volatility in the first (low-volatility regime, GDP volatility is significantly positively related to the volatility of energy utilization in the second (high-volatility regime.

Measurement of volatiles, semi-volatiles and heavy metals in an oil burn test

International Nuclear Information System (INIS)

Li, K.; Caron, T.; Landriault, M.; Pare, J.R.J.; Fingas, M.

1992-01-01

Tests involving meso-scale burning of Louisiana crude oil were conducted, and during each burn, extensive samples were taken from the oil, residue, and the smoke plume. The detailed analytical work employed to obtain and analyze the burn samples is outlined and discussed. The analytical parameters included volatiles and semi-volatiles of environmental interests as well as heavy metals typically contained in the starting crude oil. Because the smoke plume did not always impinge on the samplers, the ground samplers did not collect sufficient samples for a definitive analysis. Crude/residue analyses showed the burn resulted in a significant reduction of polycyclic aromatic hydrocarbons (PAH) in the original oil. Most of the reduction was thought to be simply evaporation or destruction from combustion. The residue did not have the degree of enrichment of the higher molecular weight PAHs as was the case in bench-scale burn experiments. Volatile organic compound and dioxin/furan measurements likewise did not show high levels of contamination from the burn itself. Most of the elevated levels of contaminants could probably be due to evaporation of the oil itself. Insufficient sampling was conducted to investigate the background levels from the weathering process. A novel means of sampling using a small remote controlled helicopter was attempted and sufficiently interesting results were obtained to indicate the potential of this passive sampling device for future work. 5 refs., 4 figs

Isotopic abundances relevant to the identification of magma sources

International Nuclear Information System (INIS)

O'Nions, R.K.

1984-01-01

The behaviour of natural radiogenic isotope tracers in the Earth that have lithophile and atmophile geochemical affinity is reviewed. The isotope tracer signature of oceanic and continental crust may in favourable circumstances by sufficiently distinct from that of the mantle to render a contribution from these sources resolvable within the isotopic composition of the magma. Components derived from the sedimentary and altered basaltic portion of oceanic crust are recognized in some island arc magmas from their Sr, Nd and Pb isotopic signatures. The rare-gas isotope tracers (He, Ar, Xe in particular) are not readily recycled into the mantle and thus provide the basis of an approach that is complementary to that based on the lithophile tracers. In particular, a small mantle-derived helium component may be readily recognized in the presence of a predominant radiogenic component generated in the continents. The importance of assessing the mass balance of these interactions rather than merely a qualitative recognition is emphasized. The question of the relative, contribution of continental-oceanic crust and mantle to magma sources is an essential part of the problem of generation and evolution of continental crust. An approach to this problem through consideration of the isotopic composition of sediments is briefly discussed. (author)

Concentration variance decay during magma mixing: a volcanic chronometer.

Science.gov (United States)

Perugini, Diego; De Campos, Cristina P; Petrelli, Maurizio; Dingwell, Donald B

2015-09-21

The mixing of magmas is a common phenomenon in explosive eruptions. Concentration variance is a useful metric of this process and its decay (CVD) with time is an inevitable consequence during the progress of magma mixing. In order to calibrate this petrological/volcanological clock we have performed a time-series of high temperature experiments of magma mixing. The results of these experiments demonstrate that compositional variance decays exponentially with time. With this calibration the CVD rate (CVD-R) becomes a new geochronometer for the time lapse from initiation of mixing to eruption. The resultant novel technique is fully independent of the typically unknown advective history of mixing - a notorious uncertainty which plagues the application of many diffusional analyses of magmatic history. Using the calibrated CVD-R technique we have obtained mingling-to-eruption times for three explosive volcanic eruptions from Campi Flegrei (Italy) in the range of tens of minutes. These in turn imply ascent velocities of 5-8 meters per second. We anticipate the routine application of the CVD-R geochronometer to the eruptive products of active volcanoes in future in order to constrain typical "mixing to eruption" time lapses such that monitoring activities can be targeted at relevant timescales and signals during volcanic unrest.

Direct evidence for the origin of low-18O silicic magmas: Quenched samples of a magma chamber's partially-fused granitoid walls, Crater Lake, Oregon

International Nuclear Information System (INIS)

Bacon, C.R.; Adami, L.H.; Lanphere, M.A.

1989-01-01

Partially fused granitoid blocks were ejected in the climactic eruption of Mount Mazama, which was accompanied by collapse of Crater Lake caldera. Quartz, plagioclase, and glass in the granitoids have much lower δ 18 O values (-3.4 to +4.9per mille) than any fresh lavas of Mount Mazama and the surrounding region (+5.8 to +7.0per mille). Oxygen isotope fractionation between phases in granitoids is consistent with equilibrium at T≥900deg C following subsolidus exchange with hydrothermal fluids of meteoric origin. Assimilation of ≅ 10-20% of material similar to these granitoids can account for the O and Sr isotopic compositions of lavas and juvenile pyroclasts derived from the climactic magma chamber, many of which have δ 18 O values ≅ 0.5per mille or more lower than comparable lavas of Mount Mazama. The O isotope data provide the only clear evidence for such assimilation because the mineralogy and chemical and radiogenic isotopic compositions of the granitoids (dominantly granodiorite) are similar to those of erupted juvenile magmas. The granitoid blocks from Crater Lake serve as direct evidence for the origin of 18 O depletion in large, shallow silicic magma bodies. (orig.)

Timing magma migration through the Icelandic Crust: from the Moho to the surface

Science.gov (United States)

Mutch, E. J. F.; Maclennan, J.; Edmonds, M.

2017-12-01

The rate of magma transfer throughout the crust, particularly the amount of time it takes for melt to travel from the upper mantle to the surface, is largely unknown. Only one previous study has investigated the timescales of transport of crystals that were in equilibrium with mantle melts [1]. Despite estimating timescales on the order of months to years, the depths from which these crystals were entrained is poorly constrained. Borgarhraun is an exceptionally well-characterised picrite lava flow in the Theistareykir Volcanic System of Northern Iceland. The crystal-cargo of this lava includes macrocrysts of olivine (Fo86-90), plagioclase (An84-90), clinopyroxene and spinel with much rarer wehrlitic nodules. Crystallisation has been estimated to have taken place in deep sub-Moho magma chambers ( 24 km). Melt inclusions in primitive olivine macrocrysts (Fo88-90) are the result of mixing a suite of geochemically distinct mantle melts that were CO2 undersaturated [2-3]. Zoning in the macrocrysts holds a record of concurrent crystallisation and mixing of these variable mantle melts, as well as ascent through the crust prior to eruption [4]. We have conducted a multi-phase, multi-element approach by applying finite-element diffusion models to wehrlite olivines and plagioclase macrocrysts to constrain the timescales of crystal residence and magma ascent prior to eruption. Model results suggest that at 1250 °C the timescale of final ascent was on the order of 20-50 days, whilst longer-term crystal residence times can exceed 700 years. This analysis shows that magma can ascend from the base of the crust to the surface in under a couple of months, suggesting picrites such as Borgarhraun are the result of high speed conduits to sub-Moho magma chambers. These rapid ascent timescales have important implications for the physical modelling of primitive magmas as well as for understanding the architecture of magma-plumbing systems in the temporal domain. References [1] Ruprecht

Buffered and unbuffered dike emplacement on Earth and Venus - Implications for magma reservoir size, depth, and rate of magma replenishment

Science.gov (United States)

Parfitt, E. A.; Head, J. W., III

1993-01-01

Models of the emplacement of lateral dikes from magma chambers under constant (buffered) driving pressure conditions and declining (unbuffered) driving pressure conditions indicate that the two pressure scenarios lead to distinctly different styles of dike emplacement. In the unbuffered case, the lengths and widths of laterally emplaced dikes will be severely limited and the dike lengths will be highly dependent on chamber size; this dependence suggests that average dike length can be used to infer the dimensions of the source magma reservoir. On Earth, the characteristics of many mafic-dike swarms suggest that they were emplaced in buffered conditions (e.g., the Mackenzie dike swarm in Canada and some dikes within the Scottish Tertiary). On Venus, the distinctive radial fractures and graben surrounding circular to oval features and edifices on many size scales and extending for hundreds to over a thousand km are candidates for dike emplacement in buffered conditions.

The change of magma chamber depth in and around the Baekdu Volcanic area from late Cenozoic

Science.gov (United States)

Lee, S. H.; Oh, C. W.; Lee, Y. S.; Lee, S. G.; Liu, J.

2016-12-01

The Baekdu Volcano is a 2750m high stratovolcanic cone resting on a basaltic shield and plateau and locates on the North Korea-China border. Its volcanic history can be divided into four stages (from the oldest to the youngest): (i) preshield plateau-forming eruptions, (ii) basalt shield formation, (iii) construction of a trachytic composite cone, and (iv) explosive ignimbrite forming eruptions. In the First stage, a fissure eruption produced basalts from the Oligocene to the Miocene (28-13 Ma) forming preshield plateau. Fissure and central eruptions occurred together during the shield-forming eruptions (4.21-1.70 Ma). In the third stage, the trachytic composite volcano formed during the Pleistocene (0.61-0.09 Ma). In this stage, magma changed to an acidic melt. The latest stage has been characterized by explosive ignimbrite-forming eruptions during the Holocene. The composite volcanic part consists of the Xiaobaishan, Lower, Middle and Upper Trachytes with rhyolites. The whole rock and clinopyroxene in basalts, trachytic and rhyolite, are analyzed to study the depth of magma chambers under the Baekdu Volcano. From the rhyolite, 9.8-12.7kbar is obtained for the depth of magma chamber. 3.7-4.1, 8.9-10.5 and 8.7 kbar are obtained from the middle, lower and Xiaobaishan trachytes. From the first and second stage basalts, 16.9-17.0 kbar and 14-14.4kbar are obtained respectively. The first stage basalt give extrusive age of 11.98 Ma whereas 1.12 and 1.09 Ma are obtained from the feldspar and groundmass in the second stage basalt. The Xiaobaishan trachyte and rhyolite give 0.25 and 0.21 Ma whereas the Middle trachyte gives 0.07-0.06 Ma. These data indicate that the magma chambers of the first and second stage basalts were located in the mantle and the magma chamber for the second stage basalt may have been underplated below continental crust. The Xiaobisan trachyte and rhyolite originated from the magma chamber in the depth of ca. 30-40 km and the Middle trachyte

Realized Volatility Risk

NARCIS (Netherlands)

D.E. Allen (David); M.J. McAleer (Michael); M. Scharth (Marcel)

2013-01-01

textabstractIn this paper we document that realized variation measures constructed from highfrequency returns reveal a large degree of volatility risk in stock and index returns, where we characterize volatility risk by the extent to which forecasting errors in realized volatility are substantive.

Origin of silicic magmas along the Central American volcanic front: Genetic relationship to mafic melts

Science.gov (United States)

Vogel, Thomas A.; Patino, Lina C.; Eaton, Jonathon K.; Valley, John W.; Rose, William I.; Alvarado, Guillermo E.; Viray, Ela L.

2006-09-01

Silicic pyroclastic flows and related deposits are abundant along the Central American volcanic front. These silicic magmas erupted through both the non-continental Chorotega block to the southeast and the Paleozoic continental Chortis block to the northwest. The along-arc variations of the silicic deposits with respect to diagnostic trace element ratios (Ba/La, U/Th, Ce/Pb), oxygen isotopes, Nd and Sr isotope ratios mimic the along-arc variation in the basaltic and andesitic lavas. This variation in the lavas has been interpreted to indicate relative contributions from the slab and asthenosphere to the basaltic magmas [Carr, M.J., Feigenson, M.D., Bennett, E.A., 1990. Incompatible element and isotopic evidence for tectonic control of source mixing and melt extraction along the Central American arc. Contributions to Mineralogy and Petrology, 105, 369-380.; Patino, L.C., Carr, M.J. and Feigenson, M.D., 2000. Local and regional variations in Central American arc lavas controlled by variations in subducted sediment input. Contributions to Mineralogy and Petrology, 138 (3), 265-283.]. With respect to along-arc trends in basaltic lavas the largest contribution of slab fluids is in Nicaragua and the smallest input from the slab is in central Costa Rica — similar trends are observed in the silicic pyroclastic deposits. Data from melting experiments of primitive basalts and basaltic andesites demonstrate that it is difficult to produce high K 2O/Na 2O silicic magmas by fractional crystallization or partial melting of low-K 2O/Na 2O sources. However fractional crystallization or partial melting of medium- to high-K basalts can produce these silicic magmas. We interpret that the high-silica magmas associated Central America volcanic front are partial melts of penecontemporaneous, mantle-derived, evolved magmas that have ponded and crystallized in the mid-crust — or are melts extracted from these nearly completely crystallized magmas.

U-series isotopes in arc magma

Energy Technology Data Exchange (ETDEWEB)

Hawkesworth, C.; Turner, S.; McDermott, F.; Peate, D.; Van Calsteren, P.

1997-12-31

Thorium is not readily mobilized in the fluid component along destructive plate margins. Uranium is mobilized, and the resultant fractionation in U/Th can be used to estimate the rates of transfer slab derived components through the mantle wedge. The variations in Th/Yb, and by implication in the fractionation-corrected Th abundances of arc magmas largely depend on the contributions from subducted sediments. It is inferred that the distinctive high Th/Ta ratios of subduction related magmas primarily reflect the Th/Ta ratios of the subducted sediments, and that such high Th/Ta ratios are generated by processes other than those associated with recent subduction-related magmatism. Uranium and thorium isotopes have also been used to evaluate magma residence times within the crust. Thus, separated minerals and groundmass from six rocks erupted in the last 4,000 years from Soufriere on St. Vincent in the Lesser Antilles, scatter about a 50,000 year errorchron on the U-Th equiline diagram (Heath et al., 1977). Models are currently being developed to investigate how such apparent ages may relate to calculated replenishment times in steady state systems. Bulk continental crust has a lower U/Th ratio (0.25) than at least some estimates for the bulk Earth (0.26) and the depleted upper mantle (0.39). However, the island arc rocks with low U/Th ratios appear to have inherited those from subducted sediments, and arc rocks with a low sediment contribution have significantly higher U/Th. Consequently, the U/Th ratios of new crustal material generated along destructive plate margins are significantly higher than those of bulk continental crust. The low average U/Th of bulk crust may be primarily due to different crust generation processes in the Archaean, when U would be less mobile because conditions were less oxidising, and when residual garnet may have had more of a role in crust generation processes. Extended abstract. 4 figs., 23 refs.

Modeling the Daly Gap: The Influence of Latent Heat Production in Controlling Magma Extraction and Eruption

Science.gov (United States)

Nelson, B. K.; Ghiorso, M. S.; Bachmann, O.; Dufek, J.

2011-12-01

A century-old issue in volcanology is the origin of the gap in chemical compositions observed in magmatic series on ocean islands and arcs - the "Daly Gap". If the gap forms during differentiation from a mafic parent, models that predict the dynamics of magma extraction as a function of chemical composition must simulate a process that results in volumetrically biased, bimodal compositions of erupted magmas. The probability of magma extraction is controlled by magma dynamical processes, which have a complex response to magmatic heat evolution. Heat loss from the magmatic system is far from a simple, monotonic function of time. It is modified by the crystallization sequence, chamber margin heat flux, and is buffered by latent heat production. We use chemical and thermal calculations of MELTS (Ghiorso & Sack, 1995) as input to the physical model of QUANTUM (Dufek & Bachmann, 2010) to predict crystallinity windows of most probable magma extraction. We modeled two case studies: volcanism on Tenerife, Canary Islands, and the Campanian Ignimbrite (CI) of Campi Flegrei, Italy. Both preserve a basanitic to phonolitic lineage and have comparable total alkali concentrations; however, CI has high and Tenerife has low K2O/Na2O. Modeled thermal histories of differentiation for the two sequences contrast strongly. In Tenerife, the rate of latent heat production is almost always greater than sensible heat production, with spikes in the ratio of latent to sensible heats of up to 40 associated with the appearance of Fe-Ti oxides at near 50% crystallization. This punctuated heat production must cause magma temperature change to stall or slow in time. The extended time spent at ≈50% crystallinity, associated with dynamical processes that enhance melt extraction near 50% crystallinity, suggests the magma composition at this interval should be common. In Tenerife, the modeled composition coincides with that of the first peak in the bimodal frequency-composition distribution. In our

Formation of anorthosite on the Moon through magma ocean fractional crystallization

Directory of Open Access Journals (Sweden)

Tatsuyuki Arai

2017-03-01

Full Text Available Lunar anorthosite is a major rock of the lunar highlands, which formed as a result of plagioclase-floatation in the lunar magma ocean (LMO. Constraints on the sufficient conditions that resulted in the formation of a thick pure anorthosite (mode of plagioclase >95 vol.% is a key to reveal the early magmatic evolution of the terrestrial planets. To form the pure lunar anorthosite, plagioclase should have separated from the magma ocean with low crystal fraction. Crystal networks of plagioclase and mafic minerals develop when the crystal fraction in the magma (φ is higher than ca. 40–60 vol.%, which inhibit the formation of pure anorthosite. In contrast, when φ is small, the magma ocean is highly turbulent, and plagioclase is likely to become entrained in the turbulent magma rather than separated from the melt. To determine the necessary conditions in which anorthosite forms from the LMO, this study adopted the energy criterion formulated by Solomatov. The composition of melt, temperature, and pressure when plagioclase crystallizes are constrained by using MELTS/pMELTS to calculate the density and viscosity of the melt. When plagioclase starts to crystallize, the Mg# of melt becomes 0.59 at 1291 °C. The density of the melt is smaller than that of plagioclase for P > 2.1 kbar (ca. 50 km deep, and the critical diameter of plagioclase to separate from the melt becomes larger than the typical crystal diameter of plagioclase (1.8–3 cm. This suggests that plagioclase is likely entrained in the LMO just after the plagioclase starts to crystallize. When the Mg# of melt becomes 0.54 at 1263 °C, the density of melt becomes larger than that of plagioclase even for 0 kbar. When the Mg# of melt decreases down to 0.46 at 1218 °C, the critical diameter of plagioclase to separate from the melt becomes 1.5–2.5 cm, which is nearly equal to the typical plagioclase of the lunar anorthosite. This suggests that plagioclase could separate from the

Redox Evolution in Magma Oceans Due to Ferric/Ferrous Iron Partitioning

Science.gov (United States)

Schaefer, L.; Elkins-Tanton, L. T.; Pahlevan, K.

2017-12-01

A long-standing puzzle in the evolution of the Earth is that while the present day upper mantle has an oxygen fugacity close to the QFM buffer, core formation during accretion would have occurred at much lower oxygen fugacities close to IW. We present a new model based on experimental evidence that normal solidification and differentiation processes in the terrestrial magma ocean may explain both core formation and the current oxygen fugacity of the mantle without resorting to a change in source material or process. A commonly made assumption is that ferric iron (Fe3+) is negligible at such low oxygen fugacities [1]. However, recent work on Fe3+/Fe2+ ratios in molten silicates [2-4] suggests that the Fe3+ content should increase at high pressure for a given oxygen fugacity. While disproportionation was not observed in these experiments, it may nonetheless be occurring in the melt at high pressure [5]. Therefore, there may be non-negligible amounts of Fe3+ formed through metal-silicate equilibration at high pressures within the magma ocean. Homogenization of the mantle and further partitioning of Fe2+/Fe3+ as the magma ocean crystallizes may explain the oxygen fugacity of the Earth's mantle without requiring additional oxidation mechanisms. We present here models using different parameterizations for the Fe2+/Fe3+ thermodynamic relationships in silicate melts to constrain the evolution of the redox state of the magma ocean as it crystallizes. The model begins with metal-silicate partitioning at high pressure to form the core and set the initial Fe3+ abundance. Combined with previous work on oxygen absorption by magma oceans due to escape of H from H2O [6], we show that the upper layers of solidifying magma oceans should be more oxidized than the lower mantle. This model also suggests that large terrestrial planets should have more oxidized mantles than small planets. From a redox perspective, no change in the composition of the Earth's accreting material needs to be

Magma at depth: A retrospective analysis of the 1975 unrest at Mount Baker, Washington, USA

Science.gov (United States)

Crider, Juliet G.; Frank, David; Malone, Stephen D.; Poland, Michael P.; Werner, Cynthia; Caplan-Auerbach, Jacqueline

2011-01-01

Mount Baker volcano displayed a short interval of seismically-quiescent thermal unrest in 1975, with high emissions of magmatic gas that slowly waned during the following three decades. The area of snow-free ground in the active crater has not returned to pre-unrest levels, and fumarole gas geochemistry shows a decreasing magmatic signature over that same interval. A relative microgravity survey revealed a substantial gravity increase in the ~30 years since the unrest, while deformation measurements suggest slight deflation of the edifice between 1981-83 and 2006-07. The volcano remains seismically quiet with regard to impulsive volcano-tectonic events, but experiences shallow (10 km) long-period earthquakes. Reviewing the observations from the 1975 unrest in combination with geophysical and geochemical data collected in the decades that followed, we infer that elevated gas and thermal emissions at Mount Baker in 1975 resulted from magmatic activity beneath the volcano: either the emplacement of magma at mid-crustal levels, or opening of a conduit to a deep existing source of magmatic volatiles. Decadal-timescale, multi-parameter observations were essential to this assessment of magmatic activity.

The Lunar Magma Ocean: Sharpening the Focus on Process and Composition

Science.gov (United States)

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

2014-01-01

The currently accepted model for the formation of the lunar anorthositic crust is by flotation from a crystallizing lunar magma ocean (LMO) shortly following lunar accretion. Anorthositic crust is globally distributed and old, whereas the mare basalts are younger and derived from a source region that has experienced plagioclase extraction. Several attempts at modelling such a crystallization sequence have been made [e.g. 1, 2], but our ever-increasing knowledge of the lunar samples and surface have raised as many questions as these models have answered. This abstract presents results from our ongoing ex-periments simulating LMO crystallization and address-ing a range of variables. We investigate two bulk com-positions, which span most of the range of suggested lunar bulk compositions, from the refractory element enriched Taylor Whole Moon (TWM) [3] to the more Earth-like Lunar Primitive Upper Mantle (LPUM) [4]. We also investigate two potential crystallization mod-els: Fully fractional, where crystallizing phases are separated from the magma as they form and sink (or float in the case of plagioclase) throughout magma ocean solidification; and a two-step process suggested by [1, 5] with an initial stage of equilibrium crystalliza-tion, where crystals remain entrained in the magma before the crystal burden increases viscosity enough that convection slows and the crystals settle, followed by fractional crystallization. Here we consider the frac-tional crystallization part of this process; the equilibri-um cumulates having been determined by [6].

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

Advancing dynamic and thermodynamic modelling of magma oceans

Science.gov (United States)

Bower, Dan; Wolf, Aaron; Sanan, Patrick; Tackley, Paul

2017-04-01

The techniques for modelling low melt-fraction dynamics in planetary interiors are well-established by supplementing the Stokes equations with Darcy's Law. But modelling high-melt fraction phenomena, relevant to the earliest phase of magma ocean cooling, necessitates parameterisations to capture the dynamics of turbulent flow that are otherwise unresolvable in numerical models. Furthermore, it requires knowledge about the material properties of both solid and melt mantle phases, the latter of which are poorly described by typical equations of state. To address these challenges, we present (1) a new interior evolution model that, in a single formulation, captures both solid and melt dynamics and hence charts the complete cooling trajectory of a planetary mantle, and (2) a physical and intuitive extension of a "Hard Sphere" liquid equation of state (EOS) to describe silicate melt properties for the pressure-temperature (P-T) range of Earth's mantle. Together, these two advancements provide a comprehensive and versatile modelling framework for probing the far-reaching consequences of magma ocean cooling and crystallisation for Earth and other rocky planets. The interior evolution model accounts for heat transfer by conduction, convection, latent heat, and gravitational separation. It uses the finite volume method to ensure energy conservation at each time-step and accesses advanced time integration algorithms by interfacing with PETSc. This ensures it accurately and efficiently computes the dynamics throughout the magma ocean, including within the ultra-thin thermal boundary layers (modelling capabilities. The thermodynamics of mantle melting are represented using a pseudo-one-component model, which retains the simplicity of a standard one-component model while introducing a finite temperature interval for melting (important for multi-component systems). Our new high P-T liquid EOS accurately captures the energetics and physical properties of the partially molten

Virtual volatility

Science.gov (United States)

Silva, A. Christian; Prange, Richard E.

2007-03-01

We introduce the concept of virtual volatility. This simple but new measure shows how to quantify the uncertainty in the forecast of the drift component of a random walk. The virtual volatility also is a useful tool in understanding the stochastic process for a given portfolio. In particular, and as an example, we were able to identify mean reversion effect in our portfolio. Finally, we briefly discuss the potential practical effect of the virtual volatility on an investor asset allocation strategy.

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.

RAPID TIMESCALES FOR MAGMA OCEAN CRYSTALLIZATION ON THE HOWARDITE-EUCRITE-DIOGENITE PARENT BODY

International Nuclear Information System (INIS)

Schiller, Martin; Paton, Chad; Bizzarro, Martin; Baker, Joel; Creech, John; Millet, Marc-Alban; Irving, Anthony

2011-01-01

Asteroid 4 Vesta has long been postulated as the source for the howardite-eucrite-diogenite (HED) achondrite meteorites. Here we show that Al-free diogenite meteorites record variability in the mass-independent abundance of 26 Mg ( 26 Mg*) that is correlated with their mineral chemistry. This suggests that these meteorites captured the Mg-isotopic evolution of a large-scale differentiating magma body with increasing 27 Al/ 24 Mg during the lifespan of the short-lived 26 Al nuclide (t 1/2 ∼ 730,000 yr). Thus, diogenites and eucrites represent crystallization products of a large-scale magma ocean associated with the differentiation and magmatic evolution of the HED parent body. The 26 Mg* composition of the most primitive diogenites requires onset of the magma ocean crystallization within 0.6 -0.4 +0.5 Myr of solar system formation. Moreover, 26 Mg* variations among diogenites and eucrites imply that near complete solidification of the HED parent body occurred within the following 2-3 Myr. Thermal models predict that such rapid cooling and magma ocean crystallization could only occur on small asteroids (<100 km), implying that 4 Vesta is not the source of the HED meteorites.

The Acoculco caldera magmas: genesis, evolution and relation with the Acoculco geothermal system

Science.gov (United States)

Sosa-Ceballos, G.; Macías, J. L.; Avellán, D.

2017-12-01

The Acoculco Caldera Complex (ACC) is located at the eastern part of the Trans Mexican Volcanic Belt; México. This caldera complex have been active since 2.7 Ma through reactivations of the system or associated magmatism. Therefore the ACC is an excellent case scenario to investigate the relation between the magmatic heat supply and the evolution processes that modified magmatic reservoirs in a potential geothermal field. We investigated the origin and the magmatic processes (magma mixing, assimilation and crystallization) that modified the ACC rocks by petrography, major oxides-trace element geochemistry, and isotopic analysis. Magma mixing is considered as the heat supply that maintain active the magmatic system, whereas assimilation yielded insights about the depth at which processes occurred. In addition, we performed a series of hydrothermal experiments in order to constrain the storage depth for the magma tapped during the caldera collapse. Rocks from the ACC were catalogued as pre, syn and post caldera. The post caldera rocks are peralkaline rhyolites, in contrast to all other rocks that are subalkaline. Our investigation is focus to investigate if the collapse modified the plumbing system and the depth at which magmas stagnate and recorded the magmatic processes.

Polycrystalline magma behaviour in dykes: Insights from high-resolution numerical models

Science.gov (United States)

Yamato, Philippe; Duretz, Thibault; Tartèse, Romain; May, Dave

2013-04-01

The presence of a crystalline load in magmas modifies their effective rheology and thus their flow behaviour. In dykes, for instance, the presence of crystals denser than the melt reduces the ascent velocity and modifies the shape of the velocity profile from a Newtonian Poiseuille flow to a Bingham type flow. Nevertheless, several unresolved issues still remain poorly understood and need to be quantified: (1) What are the mechanisms controlling crystals segregation during magma ascent in dykes? (2) How does crystals transportation within a melt depend on their concentration, geometry, size and density? (3) Do crystals evolve in isolation to each other or as a cluster? (4) What is the influence of considering inertia of the melt within the system? In this study, we present numerical models following the setup previously used in Yamato et al. (2012). Our model setup simulates an effective pressure gradient between the base and the top of a channel (representing a dyke), by pushing a rigid piston into a magmatic mush that comprised crystals and melt and perforated by a hole. The initial resolution of the models (401x1551 nodes) has been doubled in order to ensure that the smallest crystalline fractions are sufficiently well resolved. Results show that the melt phase can be squeezed out from a crystal-rich magma when subjected to a given pressure gradient range and that clustering of crystals might be an important parameter controlling their behaviour. This demonstrates that crystal-melt segregation in dykes during magma ascent constitutes a viable mechanism for magmatic differentiation of residual melts. These results also explain how isolated crystal clusters and melt pockets, with different chemistry, can be formed. In addition, we discuss the impact of taking into account inertia in our models. Reference: Yamato, P., Tartèse, R., Duretz, T., May, D.A., 2012. Numerical modelling of magma transport in dykes. Tectonophysics 526-529, 97-109.

How does the architecture of a fault system controls magma upward migration through the crust?

Science.gov (United States)

Iturrieta, P. C.; Cembrano, J. M.; Stanton-Yonge, A.; Hurtado, D.

2017-12-01

The orientation and relative disposition of adjacent faults locally disrupt the regional stress field, thus enhancing magma flow through previous or newly created favorable conduits. Moreover, the brittle-plastic transition (BPT), due to its stronger rheology, governs the average state of stress of shallower portions of the fault system. Furthermore, the BPT may coincide with the location of transient magma reservoirs, from which dikes can propagate upwards into the upper crust, shaping the inner structure of the volcanic arc. In this work, we examine the stress distribution in strike-slip duplexes with variable geometry, along with the critical fluid overpressure ratio (CFOP), which is the minimum value required for individual faults to fracture in tension. We also determine the stress state disruption of the fault system when a dike is emplaced, to answer open questions such as: what is the nature of favorable pathways for magma to migrate? what is the architecture influence on the feedback between fault system kinematics and magma injection? To this end, we present a 3D coupled hydro-mechanical finite element model of the continental lithosphere, where faults are represented as continuum volumes with an elastic-plastic rheology. Magma flow upon fracturing is modeled through non-linear Stoke's flow, coupling solid and fluid equilibrium. A non-linear sensitivity analysis is performed in function of tectonic, rheology and geometry inputs, to assess which are the first-order factors that governs the nature of dike emplacement. Results show that the CFOP is heterogeneously distributed in the fault system, and within individual fault segments. Minimum values are displayed near fault intersections, where local kinematics superimpose on regional tectonic loading. Furthermore, when magma is transported through a fault segment, the CFOP is now minimized in faults with non-favorable orientations. This suggests that these faults act as transient pathways for magma to

Outgassing From Open And Closed Magma Foams

Science.gov (United States)

von Aulock, Felix W.; Kennedy, Ben M.; Maksimenko, Anton; Wadsworth, Fabian B.; Lavallée, Yan

2017-06-01

During magma ascent, bubbles nucleate, grow, coalesce, and form a variably permeable porous network. The volcanic system opens and closes as bubble walls reorganize, seal or fail. In this contribution we cause obsidian to nucleate and grow bubbles to high gas volume fraction at atmospheric pressure by heating samples to 950 ºC 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 nonlinearly 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, 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. The mechanisms described here are relevant to the evolution of pore network heterogeneity in permeable magmas. 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 pressurisation in the vesiculated magma.

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.

Asymmetric shock heating and the terrestrial magma ocean origin of the Moon.

Science.gov (United States)

Karato, Shun-ichiro

2014-01-01

One of the difficulties of the current giant impact model for the origin of the Moon is to explain the marked similarity in the isotopic compositions and the substantial differences in the major element chemistry. Physics of shock heating is analyzed to show that the degree of heating is asymmetric between the impactor and the target, if the target (the proto-Earth) had a magma-ocean but the impactor did not. The magma ocean is heated much more than the solid impactor and the vapor-rich jets come mainly from the magma-ocean from which the Moon might have been formed. In this scenario, the similarity and differences in the composition between the Moon and Earth would be explained as a natural consequence of a collision in the later stage of planetary formation. Including the asymmetry in shock heating is the first step toward explaining the chemical composition of the Moon.

Realized volatility and absolute return volatility: a comparison indicating market risk.

Science.gov (United States)

Zheng, Zeyu; Qiao, Zhi; Takaishi, Tetsuya; Stanley, H Eugene; Li, Baowen

2014-01-01

Measuring volatility in financial markets is a primary challenge in the theory and practice of risk management and is essential when developing investment strategies. Although the vast literature on the topic describes many different models, two nonparametric measurements have emerged and received wide use over the past decade: realized volatility and absolute return volatility. The former is strongly favored in the financial sector and the latter by econophysicists. We examine the memory and clustering features of these two methods and find that both enable strong predictions. We compare the two in detail and find that although realized volatility has a better short-term effect that allows predictions of near-future market behavior, absolute return volatility is easier to calculate and, as a risk indicator, has approximately the same sensitivity as realized volatility. Our detailed empirical analysis yields valuable guidelines for both researchers and market participants because it provides a significantly clearer comparison of the strengths and weaknesses of the two methods.

Realized volatility and absolute return volatility: a comparison indicating market risk.

Directory of Open Access Journals (Sweden)

Zeyu Zheng

Full Text Available Measuring volatility in financial markets is a primary challenge in the theory and practice of risk management and is essential when developing investment strategies. Although the vast literature on the topic describes many different models, two nonparametric measurements have emerged and received wide use over the past decade: realized volatility and absolute return volatility. The former is strongly favored in the financial sector and the latter by econophysicists. We examine the memory and clustering features of these two methods and find that both enable strong predictions. We compare the two in detail and find that although realized volatility has a better short-term effect that allows predictions of near-future market behavior, absolute return volatility is easier to calculate and, as a risk indicator, has approximately the same sensitivity as realized volatility. Our detailed empirical analysis yields valuable guidelines for both researchers and market participants because it provides a significantly clearer comparison of the strengths and weaknesses of the two methods.

Using Spectroscopy to Infer the Eruption Style and Volatile History of Volcanic Tephras

Science.gov (United States)

McBride, M. J.; Horgan, B. H. N.; Rowe, M. C.; Wall, K. T.; Oxley, B. M.

2017-12-01

The interaction between volatiles and magma strongly influences volcanic eruption styles, and results in an increase in the glass component of volcanic tephra. On Earth, both phreatomagmatic and magmatic explosive eruptions create glassy tephras. Phreatomagmatic eruptions form abundant glass by quickly quenching lava through interaction with meteoric water while magmatic eruptions create less glass through slower cooling within larger pyroclasts or eruption columns. Wall et al. (2014) used X-ray diffraction (XRD) of diverse tephra samples to show that glass content correlates with eruption style, as magmatic samples contain less glass than phreatomagmatic samples. While use of XRD is limited to Earth and the Curiosity rover on Mars, orbital spectroscopy is much a more common technique in the exploration of terrestrial bodies. In this study, we evaluate whether or not spectroscopy can be used to infer eruption style and thus volatile history. Visible/near-infrared (VNIR) and thermal-infrared (TIR) spectra were collected of the Wall et al. (2014) tephra samples, and were analyzed for trends related to glass content and thus eruption style. VNIR spectra can detect glass at high abundances as well as hydrothermal alteration minerals produced during interactions with meteoric water. Using TIR, glass abundances can be derived by deconvolving the spectra with a standard spectral library; however, due to the non-unique spectral shape of glass, intermediate to high glass abundances in tephras are difficult to differentiate using TIR alone. Synthetic mixtures of glass and crystalline minerals verify these results. Therefore, the most effective method for determining glass abundance and thus eruption style from volcanic deposits is a combination of VNIR and TIR spectral analysis. Using standard planetary remote sensing instrumentation to infer eruption styles will provide a new window into the volcanic and volatile histories of terrestrial bodies.

Unstable volatility

DEFF Research Database (Denmark)

Casas, Isabel; Gijbels, Irène

2012-01-01

The objective of this paper is to introduce the break-preserving local linear (BPLL) estimator for the estimation of unstable volatility functions for independent and asymptotically independent processes. Breaks in the structure of the conditional mean and/or the volatility functions are common...... in Finance. Nonparametric estimators are well suited for these events due to the flexibility of their functional form and their good asymptotic properties. However, the local polynomial kernel estimators are not consistent at points where the volatility function has a break. The estimator presented...

Multiple Magma Batches Recorded in Tephra Deposits from the Toba Complex, Sumatra.

Science.gov (United States)

Pearce, N. J. G.; Westgate, J.; Gatti, E.

2015-12-01

The Toba Caldera Complex is the largest Quaternary caldera on Earth, and has generated three voluminous and compositionally similar rhyolitic tuffs, viz. the Oldest (OTT, 800 ka), Middle (MTT, ~500 ka) and Youngest Toba Tuffs (YTT, 75 ka). These tephra deposits are widespread across Indonesia, Malaysia, South China Sea, Sea of Bengal, India and Indian Ocean and provide useful stratigraphic markers in oceanic, lacustrine and terrestrial environments. Single shard trace element analysis of these deposits reveals the changing availability of different batches of magma through time, with Sr, Ba and Y contents defining 5 discrete magma populations in YTT, 4 populations in MTT and only a single, low Ba population in OTT. Within an individual eruption these populations are clearly distinct, but between eruptions (e.g. MTT and YTT) some of these populations overlap while others do not, indicating both the longevity (and/or continuous supply of fresh material) and evolution of these magma batches in the Toba Complex. Major element compositions of the different groups show equilibration at different pressures (based on Q'-Ab'-Or'), with the equilibration of low Ba populations at ~160 MPa, increasing to depths of ~210 MPa for the highest Ba population. The proportions of different populations of glass in distal YTT shows that relatively little of the high Ba population makes it into the distal record across India, and that this population appears to be over-represented in the proximal free glass and pumice from the caldera walls. This data may shed light on magma availability and tephra dispersal during the YTT eruption. Similarly, the glass composition of individual pumices from proximal deposits record regional, compositional and temporal differences in the erupted products. These show, for example, the apparent mingling of some of the magma batches and also that the high Ba population appears early (i.e. stratigraphically lower) in the northern caldera wall.

Magmas in motion: Degassing in volcanic conduits and fabrics of pyroclastic density current

Science.gov (United States)

Burgisser, Alain

Volcanoes are caused by the transport of magma batches from the Earth's crust to the surface. These magmas in motion undergo drastic changes of rheologic properties during their journey to the surface and this work explores how these changes affect volcanic eruptions. The first part of this study is devoted to the dynamic aspects of degassing and permeability in magmas with high pressure, high temperature experiments on natural volcanic rocks. Degassing is measured by the influence of decompression rate on the growth of the bubbles present in the magma while permeability is deduced from the temporal evolution of these bubbles. The parameterization of our results in a numerical model of volcanic conduit flow show that previous models based on equilibrium degassing overestimate the acceleration and the decompression rate of the magma. Assessing permeability effects derived form our results show that the transition between explosive and effusive eruptions is a strong function of the magma initial ascent rate. The second part of this work is a unification of two end-members of pyroclastic currents (highly concentrated pyroclastic flows and dilute, turbulent pyroclastic surges) using theoretical scaling arguments based on multiphase physics. Starting from the dynamics of the particle interactions with a fundamental eddy, we consider the full spectrum of eddies generated within a turbulent current. We demonstrate that the presence of particles with various sizes induces a density stratification of the current, leading to its segregation into a basal concentrated part overlain by a dilute cloud. To verify our predictions on the interactions of such a segregated pyroclastic current with its surroundings (hills and sea), we studied the products of the 2050 BP caldera-forming eruption of Okmok Volcano (Alaska). This field study allowed us to reconstruct the eruptive sequence and to validate the main aspects of our theoretical model, such as the superposition of a dense and

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 (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 older hot magma mush. The latter results in ductile downward flow of older, during rise of younger magma. Such complexes may reflect the plutonic portion of volcanic centers where chemically distinct magmas are erupted.

Using rocks to reveal the inner workings of magma chambers below volcanoes in Alaska’s National Parks

Science.gov (United States)

Coombs, Michelle L.; Bacon, Charles R.

2012-01-01

Alaska is one of the most vigorously volcanic regions on the planet, and Alaska’s national parks are home to many of the state’s most active volcanoes. These pose both local and more distant hazards in the form of lava and pyroclastic flows, lahars (mudflows), ash clouds, and ash fall. Alaska’s volcanoes lie along the arc of the Aleutian-Alaskan subduction zone, caused as the oceanic Pacific plate moves northward and dips below the North American plate. These volcanoes form as water-rich fluid from the down-going Pacific plate is released, lowering the melting temperature of rock in the overlying mantle and enabling it to partially melt. The melted rock (magma) migrates upward, collecting at the base of the approximately 25 mile (40 km) thick crust, occasionally ascending into the shallow crust, and sometimes erupting at the earth’s surface.During volcanic unrest, scientists use geophysical signals to remotely visualize volcanic processes, such as movement of magma in the upper crust. In addition, erupted volcanic rocks, which are quenched samples of magmas, can tell us about subsurface magma characteris-tics, history, and the processes that drive eruptions. The chemical compositions of and the minerals present in the erupted magmas can reveal conditions under which these magmas were stored in crustal “chambers”. Studies of the products of recent eruptions of Novarupta (1912), Aniakchak (1931), Trident (1953-74), and Redoubt (2009) volcanoes reveal the depths and temperatures of magma storage, and tell of complex interactions between magmas of different compositions. One goal of volcanology is to determine the processes that drive or trigger eruptions. Information recorded in the rocks tells us about these processes. Here, we demonstrate how geologists gain these insights through case studies from four recent eruptions of volcanoes in Alaska national parks.

Shear thinning behaviors in magmas

Science.gov (United States)

Vetere, F. P.; Cassetta, M.; Perugini, D.

2017-12-01

Studies on magma rheology are of fundamental importance to understanding magmatic processes from depth to surface. Since viscosity is one of the most important parameter controlling eruption mechanisms, as well as lava flow emplacement, a comprehensive knowledge on the evolution of magma viscosities during crystallization is required. We present new viscosity data on partly crystalized basalt, andesite and analogue lavas comparable to those erupted on Mercury's northern volcanic plains. High-temperature viscosity measurements were performed using a rotational Anton Paar RheolabQC viscometer head at the PVRG labs, in Perugia (Italy) (http://pvrg.unipg.it). The relative proportion of phases in each experimental run were determined by image analysis on BS-SEM images at different magnifications; phases are glasses, clinopyroxene, spinel, plagioclase for the basalt, plagioclase and spinel for the andesite and pure enstatite and clinopyroxenes, for the analogue Mercury's composition. Glass and crystalline fractions determined by image analysis well correlate with compositions of residual melts. In order to constrain the viscosity (η) variations as a function of crystallinity, shear rate (γ) was varied from 0.1 to 5 s-1. Viscosity vs. time at constant temperature shows a typical S-shape curve. In particular, for basaltic composition η vary from 3.1-3.8 Pa s [log η] at 1493 K and crystallinity of 19 area % as γ vary from 1.0 to 0.1 s-1; the andesite viscosity evolution is 3.2 and 3.7 Pa s [log η] as γ varies from 1 to 0.1 at 1493 K and crystal content of 17 area %; finally, Mercury's analogue composition was investigated at different temperature ranging from 1533 to 1502 K (Vetere et al., 2017). Results, for γ = 0.1, 1.0 and 5.0 s-1, show viscosity variation between 2.7-4.0, 2.5-3.4 and 2.0-3.0 [log η inPa s] respectively while crystallinity vary from 9 to 27 (area %). As viscosity decreases as shear rate increases, these data points to a shear thinning behaviour

Influences of magma chamber ellipticity on ring fracturing and eruption at collapse calderas

International Nuclear Information System (INIS)

Holohan, Eoghan P; Walsh, John J; Vries, Benjamin van Wyk de; Troll, Valentin R; Walter, Thomas R

2008-01-01

Plan-view ellipticity of a pre-caldera magma reservoir, and its influence on the development of caldera ring fracturing and eruptive behaviour, have not previously been subjected to dedicated evaluation. We experimentally simulated caldera collapse into elliptical magma chambers and found that collapse into highly-elliptical chambers produced a characteristic pattern of ring-fault localization and lateral propagation. Although results are preliminary, the general deformation pattern for elliptical resurgence shows strong similarities to elliptical collapse. Ring faults accommodating uplift again initiate around the chamberos short axis and are reverse, but dip inward. Field and geophysical observations at several elliptical calderas of varying scale (e.g. Long Valley, Katmai, and Rabaul calderas) are consistent with a control from elliptical magma chamber geometry on ring fracturing and eruption, as predicted from our experiments.

Magnetotelluric Investigations of the Yellowstone Caldera: Understanding the Emplacement of Crustal Magma Bodies

Science.gov (United States)

Gurrola, R. M.; Neal, B. A.; Bennington, N. L.; Cronin, R.; Fry, B.; Hart, L.; Imamura, N.; Kelbert, A.; Bowles-martinez, E.; Miller, D. J.; Scholz, K. J.; Schultz, A.

2017-12-01

Wideband magnetotellurics (MT) presents an ideal method for imaging conductive shallow magma bodies associated with contemporary Yellowstone-Snake River Plain (YSRP) magmatism. Particularly, how do these magma bodies accumulate in the mid to upper crust underlying the Yellowstone Caldera, and furthermore, what role do hydrothermal fluids play in their ascent? During the summer 2017 field season, two field teams from Oregon State University and the University of Wisconsin-Madison installed forty-four wideband MT stations within and around the caldera, and using data slated for joint 3-D inversion with existing seismic data, two 2-D vertical conductivity sections of the crust and upper mantle were constructed. These models, in turn, provide preliminary insight into the emplacement of crustal magma bodies and hydrothermal processes in the YSRP region.

Influences of magma chamber ellipticity on ring fracturing and eruption at collapse calderas

Energy Technology Data Exchange (ETDEWEB)

Holohan, Eoghan P; Walsh, John J [Fault Analysis Group, School of Geological Sciences, University College Dublin, Belfield, Dublin 4 (Ireland); Vries, Benjamin van Wyk de [Laboratoire Magmas et Volcans, 5 rue Kessler, 63038 Clermont-Ferrand (France); Troll, Valentin R [Department of Earth Sciences, Uppsala University, SE-752 36, Uppsala (Sweden); Walter, Thomas R [GFZ Potsdam, Telegrafenberg, Potsdam, D-14473 (Germany)], E-mail: Eoghan.Holohan@ucd.ie

2008-10-01

Plan-view ellipticity of a pre-caldera magma reservoir, and its influence on the development of caldera ring fracturing and eruptive behaviour, have not previously been subjected to dedicated evaluation. We experimentally simulated caldera collapse into elliptical magma chambers and found that collapse into highly-elliptical chambers produced a characteristic pattern of ring-fault localization and lateral propagation. Although results are preliminary, the general deformation pattern for elliptical resurgence shows strong similarities to elliptical collapse. Ring faults accommodating uplift again initiate around the chamberos short axis and are reverse, but dip inward. Field and geophysical observations at several elliptical calderas of varying scale (e.g. Long Valley, Katmai, and Rabaul calderas) are consistent with a control from elliptical magma chamber geometry on ring fracturing and eruption, as predicted from our experiments.

Conditions of deep magma chamber beneath Fuji volcano estimated from high- P experiments

Science.gov (United States)

Asano, K.; Takahashi, E.; Hamada, M.; Ushioda, M.; Suzuki, T.

2012-12-01

Fuji volcano, the largest in volume and eruption rate in Japan, is located at the center of Honshu, where North America, Eurasia and Philippine Sea plates meets. Because of the significance of Fuji volcano both in tectonic settings and potential volcanic hazard (particularly after the M9 earthquake in 2011), precise knowledge on its magma feeding system is essentially important. Composition of magma erupted from Fuji volcano in the last 100ky is predominantly basalt (SiO2=50-52wt%, FeO/MgO=1.5-3.0). Total lack of silica-rich magma (basaltic andesite and andesite) which are always present in other nearby volcanoes (e.g., Hakone, Izu-Oshima, see Fig.1) is an important petrologic feature of Fuji volcano. Purpose of this study is to constrain the depth of magma chamber of Fuji volcano and explain its silica-nonenrichment trend. High pressure melting experiments were carried out using two IHPVs at the Magma Factory, Tokyo Institute of Technology (SMC-5000 and SMC-8600, Tomiya et al., 2010). Basalt scoria Tr-1 which represents the final ejecta of Hoei eruption in AD1707, was adopted as a starting material. At 4kbar, temperature conditions were 1050, 1100 and 1150C, and H2O contents were 1.3, 2.7 and 4.7 wt.%, respectively. At 7kbar, temperature conditions were 1075, 1100 and 1125C, and H2O contents were 1.0, 1.1, 3.6 and 6.3wt.%, respectively. The fO2 was controlled at NNO buffer. At 4kbar, crystallization sequence at 3 wt% H2O is magnetite, plagioclase, clinopyroxene and finally orthopyroxene. At 7 kbar, and ~3 wt% H2O, the three minerals (opx, cpx, pl) appears simultaneously near the liquidus. Compositional trend of melt at 4 kbar and 7 kbar are shown with arrows in Fig.1. Because of the dominant crystallization of silica-rich opx at 7 kbar, composition of melt stays in the range SiO2=50-52wt% as predicted by Fujii (2007). Absence of silica-rich rocks in Fuji volcano may be explained by the tectonic setting of the volcano. Because Fuji volcano locates on the plate

Continental rift architecture and patterns of magma migration: a dynamic analysis based on centrifuge models.

NARCIS (Netherlands)

Corti, G.; Bonini, M.; Sokoutis, D.; Innocenti, F.; Manetti, P.; Cloetingh, S.A.P.L.; Mulugeta, G.

2004-01-01

Small-scale centrifuge models were used to investigate the role of continental rift structure in controlling patterns of magma migration and emplacement. Experiments considered the reactivation of weakness zones in the lower crust and the presence of magma at Moho depths. Results suggest that

Pluto's Volatile Transport

Science.gov (United States)

Young, Leslie

2012-10-01

Pluto's varying subsolar latitude and heliocentric distance leads to large variations in the surface volatile distribution and surface pressure. I present results of new volatile transport models (Young 2012a, b). The models include insolation, thermal emission, subsurface conduction, heating of a volatile slab, internal heat flux, latent heat of sublimation, and strict global mass balance. Numeric advances include initial conditions that allow for rapid convergence, efficient computation with matrix arithmetic, and stable Crank-Nicholson timesteps for both bare and volatile-covered areas. Runs of the model show six distinct seasons on Pluto. (1) As Pluto approaches perihelion, the volatiles on the old winter pole (the Rotational North Pole, RNP) becomes more directly illuminated , and the pressure and albedo rise rapidly. (2) When a new ice cap forms on the Rotational South Pole, RSP, volatiles are exchanged between poles. The pressure and albedo change more slowly. (3) When all volatiles have sublimed from the RNP, the albedo and pressure drop rapidly. (4-6) A similar pattern is repeated near aphelion with a reversal of the roles and the poles. I will compare results with earlier Pluto models of Hansen and Paige (1996), show the dependence on parameters such as substrate inertia, and make predictions for the New Horizons flyby of Pluto in 2015. This work was supported, in part, by funding from NASA Planetary Atmospheres Grant NNG06GF32G and the Spitzer project (JPL research support Agreement 1368573). Hansen, C. J. and D. A. Paige 1996. Seasonal Nitrogen Cycles on Pluto. Icarus 120, 247-265. Young, L. A. 2012a. Volatile transport on inhomogeneous surfaces: I - Analytic expressions, with application to Pluto’s day. Icarus, in press Young, L. A. 2012b. Volatile transport on inhomogeneous surfaces: II. Numerical calculations, with application to Pluto's season. In preparation.

Geophysical Evidence for the Locations, Shapes and Sizes, and Internal Structures of Magma Chambers beneath Regions of Quaternary Volcanism

Science.gov (United States)

Iyer, H. M.

1984-04-01

This paper is a review of seismic, gravity, magnetic and electromagnetic techniques to detect and delineate magma chambers of a few cubic kilometres to several thousand cubic kilometres volume. A dramatic decrease in density and seismic velocity, and an increase in seismic attenuation and electrical conductivity occurs at the onset of partial melting in rocks. The geophysical techniques are based on detecting these differences in physical properties between solid and partially molten rock. Although seismic refraction techniques, with sophisticated instrumentation and analytical procedures, are routinely used for detailed studies of crustal structure in volcanic regions, their application for magma detection has been quite limited. In one study, in Yellowstone National Park, U.S.A., fan-shooting and time-term techniques have been used to detect an upper-crustal magma chamber. Attenuation and velocity changes in seismic waves from explosions and earthquakes diffracted around magma chambers are observed near some volcanoes in Kamchatka. Strong attenuation of shear waves from regional earthquakes, interpreted as a diffraction effect, has been used to model magma chambers in Alaska, Kamchatka, Iceland, and New Zealand. One of the most powerful techniques in modern seismology, the seismic reflection technique with vibrators, was used to confirm the existence of a strong reflector in the crust near Socorro, New Mexico, in the Rio Grande Rift. This reflector, discovered earlier from data from local earthquakes, is interpreted as a sill-like magma body. In the Kilauea volcano, Hawaii, mapping seismicity patterns in the upper crust has enabled the modelling of the complex magma conduits in the crust and upper mantle. On the other hand, in the Usu volcano, Japan, the magma conduits are delineated by zones of seismic quiescence. Three-dimensional modelling of laterally varying structures using teleseismic residuals is proving to be a very promising technique for detecting and

Storage conditions of the mafic and silicic magmas at Cotopaxi, Ecuador

Science.gov (United States)

Martel, Caroline; Andújar, Joan; Mothes, Patricia; Scaillet, Bruno; Pichavant, Michel; Molina, Indira

2018-04-01

The 2015 reactivation of the Cotopaxi volcano urges us to understand the complex eruptive dynamics of Cotopaxi for better management of a potential major crisis in the near future. Cotopaxi has commonly transitioned from andesitic eruptions of strombolian style (lava flows and scoria ballistics) or nuées ardentes (pyroclastic flows and ash falls) to highly explosive rhyolitic ignimbrites (pumiceous pyroclastic flows), which entail drastically different risks. To better interpret geophysical and geochemical signals, Cotopaxi magma storage conditions were determined via existing phase-equilibrium experiments that used starting materials chemically close to the Cotopaxi andesites and rhyolites. The results suggest that Cotopaxi's most mafic andesites (last erupted products) can be stored over a large range of depth from 7 km to ≥16 km below the summit (pressure from 200 to ≥400 MPa), 1000 °C, NNO +2, and contain 4.5-6.0±0.7 wt% H2O dissolved in the melt in equilibrium with 30-40% phenocrysts of plagioclase, two pyroxenes, and Fe-Ti oxides. These mafic andesites sometimes evolve towards more silicic andesites by cooling to 950 °C. Rhyolitic magmas are stored at 200-300 MPa (i.e. 7-11 km below the summit), 750 °C, NNO +2, and contain 6-8 wt% H2O dissolved in a nearly aphyric melt (<5% phenocrysts of plagioclase, biotite, and Fe-Ti oxides). Although the andesites produce the rhyolitic magmas by fractional crystallization, the Cotopaxi eruptive history suggests reactivation of either reservoirs at distinct times, likely reflecting flux or time fluctuations during deep magma recharge.

Density of alkaline magmas at crustal and upper mantle conditions by X-ray absorption

Science.gov (United States)

Seifert, R.; Malfait, W.; Petitgirard, S.; Sanchez-Valle, C.

2011-12-01

Silicate melts are essential components of igneous processes and are directly involved in differentiation processes and heat transfer within the Earth. Studies of the physical properties of magmas (e.g., density, viscosity, conductivity, etc) are however challenging and experimental data at geologically relevant pressure and temperature conditions remain scarce. For example, there is virtually no data on the density at high pressure of alkaline magmas (e.g., phonolites) typically found in continental rift zone settings. We present in situ density measurements of alkaline magmas at crustal and upper mantle conditions using synchrotron X-ray absorption. Measurements were conducted on ID27 beamline at ESRF using a panoramic Paris-Edinburgh Press (PE Press). The starting material is a synthetic haplo-phonolite glass similar in composition to the Plateau flood phonolites from the Kenya rift [1]. The glass was synthesized at 1673 K and 2.0 GPa in a piston-cylinder apparatus at ETH Zurich and characterized using EPMA, FTIR and density measurements. The sample contains less than 200 ppm water and is free of CO2. Single-crystal diamond cylinders (Øin = 0.5 mm, height = 1 mm) were used as sample containers and placed in an assembly formed by hBN spacers, a graphite heater and a boron epoxy gasket [2]. The density was determined as a function of pressure (1.0 to 3.1 GPa) and temperature (1630-1860 K) from the X-ray absorption contrast at 20 keV between the sample and the diamond capsule. The molten state of the sample during the data collection was confirmed by X-ray diffraction measurements. Pressure and temperature were determined simultaneously from the equation of state of hBN and platinum using the the double isochor method [3].The results are combined with available density data at room conditions to derive the first experimental equation of state (EOS) of phonolitic liquids at crustal and upper mantle conditions. We will compare our results with recent reports of the

Finite automata over magmas: models and some applications in Cryptography

Directory of Open Access Journals (Sweden)

Volodymyr V. Skobelev

2018-05-01

Full Text Available In the paper the families of finite semi-automata and reversible finite Mealy and Moore automata over finite magmas are defined and analyzed in detail. On the base of these models it is established that the set of finite quasigroups is the most acceptable subset of the set of finite magmas at resolving model problems in Cryptography, such as design of iterated hash functions and stream ciphers. Defined families of finite semi-automata and reversible finite automata over finite $T$-quasigroups are investigated in detail. It is established that in this case models time and space complexity for simulation of the functioning during one instant of automaton time can be much lower than in general case.

Magma Fertility is the First-Order Factor for the Formation of Porphyry Cu±Au Deposits

Science.gov (United States)

Park, J. W.; Campbell, I. H.; Malaviarachchi, S. P. K.; Cocker, H.; Nakamura, E.; Kay, S. M.

2017-12-01

Magma fertility, the metal abundance in magma, has been considered to be one of the key factors for the formation of porphyry Cu±Au deposits. In this study we provide clear evidence to support the hypothesis that the platinum group element (PGE) can be used to distinguish barren from ore-bearing Cu±Au felsic suites. We determined the PGE contents of three barren volcanic and subvolcanic suites from Argentina and Japan, and compare the results with two porphyry Cu-bearing subvolcanic suites from Chile and two porphyry Cu-Au-bearing suites from Australia. The barren suites are significantly depleted in PGE abundances by the time of fluid exsolution, which is attributed to early sulfide saturation at mid to lower crust depths or assimilation of chalcophile element-poor crustal materials. Barren magma, produced by melting continental crust, may have been initially deficient in chalcophile elements. In contrast, the Cu±Au ore-bearing suites contain at least an order of magnitude higher PGE contents than those of the barren suites by the time of fluid saturation. They are characterized by late sulfide saturation in a shallow magma chamber, which allows the chalcophile elements to concentrate in the fractionating magma from which they are sequestered by ore-forming fluids. We suggest the Pd/MgO and Pd/Pt ratios of igneous rocks can be used as magma fertility indicators, and to distinguish between barren, porphyry Cu and porphyry Cu-Au magmatic systems.

The Origin of Tholeiitic and Calc-Alkaline Trends in Arc Magmas

Science.gov (United States)

Luffi, P. I.; Lee, C.

2012-12-01

It has long been recognized that tholeiitic (TH, high-Fe/Mg) and calc-alkaline (CA, low-Fe/Mg) magmatic series define the two most important igneous differentiation trends shaping Earth's crust. While oceanic crust formation at mid-ocean ridges is typically confined to a TH trend, arc magmatism at convergent margins, considered to significantly contribute to continent formation, generates both TH and CA trends. Thus, the origin of these trends - a key issue to understanding how continental crust forms - is matter of ongoing debate. Prevalent factors thought to contribute to the TH-CA duality are: 1) redox conditions (oxygen fugacity, fO2) and H2O contents in magmas, which control the onset and abundance of high-Fe/Mg oxide mineral fractionation; 2) crystallization depths that regulate the fractionating solid assemblage and thereby the solid/liquid Kd(Fe-Mg). Relying on an extensive geochemical dataset of modern arc volcanics and thermodynamic phase equilibria modeling, here we examine the validity and relative importance of these factors in arc petrogenesis. First, to discriminate igneous rocks more efficiently, we formulate an improved CA/TH index solely based on FeO-MgO systematics. We then confirm on a quantitative basis that, on regional scales, arcs formed on thick crust tend to be more calk-alkaline than those emplaced on thinner crust are, and show that the effect of fO2 on the CA/TH index in arc magmas is more significant than that of H2O. Importantly, we demonstrate that CA trends typical for continental arcs only form when crystal fractionation is accompanied by the assimilation of oxidized crustal components; in the absence of buffering oxidized assimilants fractionating magmas follow a TH trend more common in island arcs, irrespective of their H2O content and initial fO2 level. We find that high-pressure fractionation of amphibole and garnet in arc magmas occurs too late to have a significant influence on the CA/TH index; in addition, garnet-melt and

Redox systematics of a magma ocean with variable pressure-temperature gradients and composition.

Science.gov (United States)

Righter, K; Ghiorso, M S

2012-07-24

Oxygen fugacity in metal-bearing systems controls some fundamental aspects of the geochemistry of the early Earth, such as the FeO and siderophile trace element content of the mantle, volatile species that influence atmospheric composition, and conditions for organic compounds synthesis. Redox and metal-silicate equilibria in the early Earth are sensitive to oxygen fugacity (fO(2)), yet are poorly constrained in modeling and experimentation. High pressure and temperature experimentation and modeling in metal-silicate systems usually employs an approximation approach for estimating fO(2) that is based on the ratio of Fe and FeO [called "ΔIW (ratio)" hereafter]. We present a new approach that utilizes free energy and activity modeling of the equilibrium: Fe + SiO(2) + O(2) = Fe(2)SiO(4) to calculate absolute fO(2) and relative to the iron-wüstite (IW) buffer at pressure and temperature [ΔIW (P,T)]. This equilibrium is considered across a wide range of pressures and temperatures, including up to the liquidus temperature of peridotite (4,000 K at 50 GPa). Application of ΔIW (ratio) to metal-silicate experiments can be three or four orders of magnitude different from ΔIW (P,T) values calculated using free energy and activity modeling. We will also use this approach to consider the variation in oxygen fugacity in a magma ocean scenario for various thermal structures for the early Earth: hot liquidus gradient, 100 °C below the liquidus, hot and cool adiabatic gradients, and a cool subsolidus adiabat. The results are used to assess the effect of increasing P and T, changing silicate composition during accretion, and related to current models for accretion and core formation in the Earth. The fO(2) in a deep magma ocean scenario may become lower relative to the IW buffer at hotter and deeper conditions, which could include metal entrainment scenarios. Therefore, fO(2) may evolve from high to low fO(2) during Earth (and other differentiated bodies) accretion. Any

Magma fluxes and recurreance rate of eruptions at Nevado de Toluca volcano (Mexico)

Science.gov (United States)

Weber, Gregor; Probst, Line; Arce, José L.; Caricchi, Luca

2017-04-01

Forecasting the frequency and size of volcanic eruptions is a long-term goal for hazard mitigation. The frequency at which a given crustal magmatic system is driven towards a critical state and the magnitude of the resulting volcanic events are linked to the supply rate of fresh magma, crustal properties, and tectonic setting. Our ability to forecast the recurrence rate of eruptions is hampered by the lack of data on key variables such as the average magma flux locally and globally. The aim of this project is to identify the average magma supply rate and injection frequency for eruptions of different magnitude and eruptive style. We centred our study at Nevado de Toluca in Mexico, a subduction-related volcano with an eruptive history spanning about 1.5 million years of comparatively well documented effusive and explosive eruptions dominantly of dacitic composition. We carry out in-situ high precision zircon geochronology for a sequence of eruptions of different magnitude to obtain a distribution of crystal ages from which average crustal magma fluxes can be calculated. Eruptive fluxes will be constrained by extracting lava flow volumes from a digital elevation model. A combination of whole rock and mineral chemistry will provide quantitative insights on petrogenetic processes and on the frequency at which intensive parameters changed within the magma reservoir before the eruptions. Our results will be integrated in a global database including other volcanic systems and literature data to attempt to identify similarities and differences between magmatic reservoirs feeding volcanic eruptions of different magnitude. The final target of this project is to identify the physical factors controlling the recurrence rate of volcanic eruptions at regional and global scale.

Magma transport in sheet intrusions of the Alnö carbonatite complex, central Sweden.

Science.gov (United States)

Andersson, Magnus; Almqvist, Bjarne S G; Burchardt, Steffi; Troll, Valentin R; Malehmir, Alireza; Snowball, Ian; Kübler, Lutz

2016-06-10

Magma transport through the Earth's crust occurs dominantly via sheet intrusions, such as dykes and cone-sheets, and is fundamental to crustal evolution, volcanic eruptions and geochemical element cycling. However, reliable methods to reconstruct flow direction in solidified sheet intrusions have proved elusive. Anisotropy of magnetic susceptibility (AMS) in magmatic sheets is often interpreted as primary magma flow, but magnetic fabrics can be modified by post-emplacement processes, making interpretation of AMS data ambiguous. Here we present AMS data from cone-sheets in the Alnö carbonatite complex, central Sweden. We discuss six scenarios of syn- and post-emplacement processes that can modify AMS fabrics and offer a conceptual framework for systematic interpretation of magma movements in sheet intrusions. The AMS fabrics in the Alnö cone-sheets are dominantly oblate with magnetic foliations parallel to sheet orientations. These fabrics may result from primary lateral flow or from sheet closure at the terminal stage of magma transport. As the cone-sheets are discontinuous along their strike direction, sheet closure is the most probable process to explain the observed AMS fabrics. We argue that these fabrics may be common to cone-sheets and an integrated geology, petrology and AMS approach can be used to distinguish them from primary flow fabrics.

Autoradiographic methods for studying marked volatile substances (1961)

International Nuclear Information System (INIS)

Cohen, Y.; Wepierre, J.

1961-01-01

The autoradiographic methods for animals used up to the present do not make it possible to localise exactly the distribution of marked volatile molecules. The Ullberg method (1954) which we have modified (Cohen, Delassue, 1959) involves cold desiccant. The method due to Pellerin (1957) avoids this desiccant but the histological comparison of the autoradiography with the biological document itself is difficult, if not impossible. Nevertheless, we have adopted certain points in the two methods and propose the following technique for the autoradiographic study of marked volatile molecules: 1- The surface of the frozen sample to be studied is prepared using a freezing microtome. 2- The last section, which is 20 μ thick and whose histological elements are parallel to those of the block, is dried by cooling and is used as the biological reference document for the autoradiography obtained, as is indicated in 3; 3- The radiography films are applied to the frozen block at -30 deg. C. The autoradiographs correspond to the radioactivity of the volatile molecule and of its non-volatile degradation products. 4- The radiographic film is also applied to the 20 μ section previously dried at -20 deg. C. This autoradiography corresponds to the radioactivity of the non-volatile degradation products of the molecule. 5- We confirmed the absence of diffusion of the volatile molecule and of pseudo-radiographic effects (photochemical and others). This method, which has enabled us to study the distribution of a carbide, para-cymene (C 14 ) 7, macroscopically in the case of a whole mouse and microscopically on the skin of a dog, can find general applications. (authors) [fr

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.

The evolution of magma during continental rifting: New constraints from the isotopic and trace element signatures of silicic magmas from Ethiopian volcanoes

Science.gov (United States)

Hutchison, William; Mather, Tamsin A.; Pyle, David M.; Boyce, Adrian J.; Gleeson, Matthew L. M.; Yirgu, Gezahegn; Blundy, Jon D.; Ferguson, David J.; Vye-Brown, Charlotte; Millar, Ian L.; Sims, Kenneth W. W.; Finch, Adrian A.

2018-05-01

Magma plays a vital role in the break-up of continental lithosphere. However, significant uncertainty remains about how magma-crust interactions and melt evolution vary during the development of a rift system. Ethiopia captures the transition from continental rifting to incipient sea-floor spreading and has witnessed the eruption of large volumes of silicic volcanic rocks across the region over ∼45 Ma. The petrogenesis of these silicic rocks sheds light on the role of magmatism in rift development, by providing information on crustal interactions, melt fluxes and magmatic differentiation. We report new trace element and Sr-Nd-O isotopic data for volcanic rocks, glasses and minerals along and across active segments of the Main Ethiopian (MER) and Afar Rifts. Most δ18 O data for mineral and glass separates from these active rift zones fall within the bounds of modelled fractional crystallization trajectories from basaltic parent magmas (i.e., 5.5-6.5‰) with scant evidence for assimilation of Pan-African Precambrian crustal material (δ18 O of 7-18‰). Radiogenic isotopes (εNd = 0.92- 6.52; 87Sr/86Sr = 0.7037-0.7072) and incompatible trace element ratios (Rb/Nb productivity or where crustal structure inhibits magma ascent). This has important implications for understanding the geotectonic settings that promote extreme melt evolution and, potentially, genesis of economically-valuable mineral deposits in ancient rift-settings. The limited isotopic evidence for assimilation of Pan-African crustal material in Ethiopia suggests that the pre-rift crust beneath the magmatic segments has been substantially modified by rift-related magmatism over the past ∼45 Ma; consistent with geophysical observations. We argue that considerable volumes of crystal cumulate are stored beneath silicic volcanic systems (>100 km3), and estimate that crystal cumulates fill at least 16-30% of the volume generated by crustal extension under the axial volcanoes of the MER and Manda Hararo

Nature of the magma storage system beneath the Damavand volcano (N. Iran): An integrated study

Science.gov (United States)

Eskandari, Amir; Amini, Sadraddin; De Rosa, Rosanna; Donato, Paola

2018-02-01

Damavand intraplate stratovolcano constructed upon a moderately thick crust (58-67 km) over the last 2 Ma. The erupted products are dominantly trachyandesite-trachyte (TT) lavas and pyroclasts, with minor mafic magmas including tephrite-basanite-trachybasalt and alkali olivine basalts emplaced as cinder cones at the base of the stratovolcano. The TT products are characterized by a mineral assemblage of clinopyroxene (diopside-augite), orthopyroxene (clinoenstatite), feldspar (An2-58, Ab6-69, Or2-56), high Ti phlogopite, F-apatite, Fesbnd Ti oxides, and minor amounts of olivine (Fo73-80), amphibole and zircon, whereas olivine (Fo78-88), high Mg# (80-89) diopside, feldspar, apatite and Fesbnd Ti oxide occur in the mafic magmas. The presence of hydrous and anhydrous minerals, normal zonings, mafic cumulates, and the composition of magmatic inclusions in the TT products suggest evolutionary processes in polybaric conditions. In the same way, disequilibrium textures - including orthopyroxene mantled with clinopyroxene, reaction rim of phlogopite and amphibole, the coexistence of olivine and orthopyroxene, reverse, oscillatory and complex zonings of pyroxene and feldspar crystals - suggest magmatic evolutions in open systems with a varying temperature, oxygen fugacity, water as well as pressure and, to a lesser extent, melt chemistry. Mineral assemblages are used to model the physicochemical conditions and assess default parameters for the thermodynamic simulation of crystallization using MELTS software to track the P-T-H2O-ƒO2 evolution of the magma plumbing system. Thermobarometry and MELTS models estimated the initial nucleation depth at 16-17 kb (56-60 km) for olivine (Fo89) and high Al diopside crystals occurring in the mafic primary magma; it then stopped and underwent fractionation between 8 and 10 kb (28-35 km), corresponding with Moho depth, and continued to differentiate in the lower crust, in agreement with the geophysical models. The mafic rocks were formed

Normalization for Implied Volatility

OpenAIRE

Fukasawa, Masaaki

2010-01-01

We study specific nonlinear transformations of the Black-Scholes implied volatility to show remarkable properties of the volatility surface. Model-free bounds on the implied volatility skew are given. Pricing formulas for the European options which are written in terms of the implied volatility are given. In particular, we prove elegant formulas for the fair strikes of the variance swap and the gamma swap.

Money growth volatility and the demand for money in Germany: Friedman's volatility hypothesis revisited

OpenAIRE

Brüggemann, Imke; Nautz, Dieter

1997-01-01

Recently, the Bundesbank claimed that monetary targeting has become considerably more diffcult by the increased volatility of short-term money growth. The present paper investigates the impact of German money growth volatility on income velocity and money demand in view of Friedman's money growth volatility hypothesis. Granger-causality tests provide some evidence for a velocity-volatility linkage. However the estimation of volatility-augmented money demand functions reveals that - in contras...

Chasing volatility

DEFF Research Database (Denmark)

Caporin, Massimiliano; Rossi, Eduardo; Santucci de Magistris, Paolo

The realized volatility of financial returns is characterized by persistence and occurrence of unpreditable large increments. To capture those features, we introduce the Multiplicative Error Model with jumps (MEM-J). When a jump component is included in the multiplicative specification, the condi......The realized volatility of financial returns is characterized by persistence and occurrence of unpreditable large increments. To capture those features, we introduce the Multiplicative Error Model with jumps (MEM-J). When a jump component is included in the multiplicative specification...... estimate alternative specifications of the model using a set of daily bipower measures for 7 stock indexes and 16 individual NYSE stocks. The estimates of the jump component confirm that the probability of jumps dramatically increases during the financial crisis. Compared to other realized volatility...... models, the introduction of the jump component provides a sensible improvement in the fit, as well as for in-sample and out-of-sample volatility tail forecasts....

Somma-Vesuvius Plinian Eruptions fed by mafic magma: insights from bubbles in melt inclusions

Science.gov (United States)

Esposito, R.; Redi, D.; Cannatelli, C.; Danyushevsky, L. V.; Lima, A.; Bodnar, R. J.; De Vivo, B.

2014-12-01

Mt. Somma-Vesuvius Plinian eruptions were first described by Pliny the younger in 79 AD during the infamous eruption that destroyed Pompeii. Today, such eruptions are still a concern to the nearly 3 million people living in the Naples metropolitan area. Understanding the source for Mt. Somma-Vesuvius magma and the coexisting volatile phase is vital to better constrain the long-term eruptive behavior of this volcano. In the present study, ~ 50 olivine phenocrysts were selected from lavas and pumices produced during mild effusive events referred to as inter-Plinian eruptions, and from highly explosive Plinian eruptions that occurred at Mt. Somma-Vesuvius between 33000 ka and 1631 AD. Selected olivine phenocrysts containing MI were examined petrographically and analyzed for Fo content. Fo varies from 69 to 73 mole% for inter-Plinian olivine crystals and from 84 to 90 mole% with one zoned olivine containing 76-81 mole% Fo, for Plinian olivine crystals. Investigated MI vary from slightly crystallized to highly crystallized. Selected crystallized MI were reheated using the Vernadsky stage, and quenched to a homogeneous glass (Group 1) or glass plus a vapor bubble (Group 2). On one hand, MI of Group 1 are hosted in olivine ranging from Fo72 to Fo76 and were all erupted from the Pompeii eruption (white pumice deposit). On the other hand, MI of Group 2 are trapped in olivine ranging from Fo69 to Fo81 and from Fo84 to Fo90, and the hosts are representative of both Plinian and inter-Plinian events. The only eruption where Group-1 and Group-2 MI coexist is the Pompeii eruption. Group 2 MIs were further analyzed by Raman to test for the presence of volatiles (CO2 or H2O) in the vapor bubbles. CO2 was detected in all MI analyzed. CO2 density was determined using the distance between the two Fermi-diad peaks, and ranges between 0.14 and 0.55 g/cm3. Six MI also showed evidence for H2O in the vapor bubble. In addition, carbonates were detected at the glass-vapor interface of five

Autoradiographic methods for studying marked volatile substances (1961); Methode.d'etude autoradiographique de substances marquees volatiles (1961)

Energy Technology Data Exchange (ETDEWEB)

Cohen, Y; Wepierre, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1961-07-01

The autoradiographic methods for animals used up to the present do not make it possible to localise exactly the distribution of marked volatile molecules. The Ullberg method (1954) which we have modified (Cohen, Delassue, 1959) involves cold desiccant. The method due to Pellerin (1957) avoids this desiccant but the histological comparison of the autoradiography with the biological document itself is difficult, if not impossible. Nevertheless, we have adopted certain points in the two methods and propose the following technique for the autoradiographic study of marked volatile molecules: 1- The surface of the frozen sample to be studied is prepared using a freezing microtome. 2- The last section, which is 20 {mu} thick and whose histological elements are parallel to those of the block, is dried by cooling and is used as the biological reference document for the autoradiography obtained, as is indicated in 3; 3- The radiography films are applied to the frozen block at -30 deg. C. The autoradiographs correspond to the radioactivity of the volatile molecule and of its non-volatile degradation products. 4- The radiographic film is also applied to the 20 {mu} section previously dried at -20 deg. C. This autoradiography corresponds to the radioactivity of the non-volatile degradation products of the molecule. 5- We confirmed the absence of diffusion of the volatile molecule and of pseudo-radiographic effects (photochemical and others). This method, which has enabled us to study the distribution of a carbide, para-cymene (C{sup 14}) 7, macroscopically in the case of a whole mouse and microscopically on the skin of a dog, can find general applications. (authors) [French] Les methodes d'autoradiographies sur l'animal, proposees jusqu'a present, ne permettent pas de localiser de facon precise la distribution de molecules marquees volatiles. En effet, la methode de Ullberg (1954) que nous avons modifiee (Cohen, Delassue, 1959) necessite la dessiccation par le froid. La methode

Transport of metals and sulphur in magmas by flotation of sulphide melt on vapour bubbles

Science.gov (United States)

Mungall, J. E.; Brenan, J. M.; Godel, B.; Barnes, S. J.; Gaillard, F.

2015-03-01

Emissions of sulphur and metals from magmas in Earth’s shallow crust can have global impacts on human society. Sulphur-bearing gases emitted into the atmosphere during volcanic eruptions affect climate, and metals and sulphur can accumulate in the crust above a magma reservoir to form giant copper and gold ore deposits, as well as massive sulphur anomalies. The volumes of sulphur and metals that accumulate in the crust over time exceed the amounts that could have been derived from an isolated magma reservoir. They are instead thought to come from injections of multiple new batches of vapour- and sulphide-saturated magmas into the existing reservoirs. However, the mechanism for the selective upward transfer of sulphur and metals is poorly understood because their main carrier phase, sulphide melt, is dense and is assumed to settle to the bottoms of magma reservoirs. Here we use laboratory experiments as well as gas-speciation and mass-balance models to show that droplets of sulphide melt can attach to vapour bubbles to form compound drops that float. We demonstrate the feasibility of this mechanism for the upward mobility of sulphide liquids to the shallow crust. Our work provides a mechanism for the atmospheric release of large amounts of sulphur, and contradicts the widely held assumption that dense sulphide liquids rich in sulphur, copper and gold will remain sequestered in the deep crust.

Crystallization sequence of the Upper Border Series of the Skaergaard Intrusion: Revised subdivision and implications for Chamber-Scale Magma Homogeneity

DEFF Research Database (Denmark)

Salmonsen, Lars Peter; Tegner, Christian

2013-01-01

from the roof of the magma chamber, differs from that in the Layered Series formed at the floor. The proposed deviation would require chemical stratification of the magma, and a reexamination of the crystallization sequence therefore has important implications for understanding the dynamics...... of the crystallization sequences and the anorthite contents of plagioclase cores in the three series imply that the Skaergaard magma chamber solidified by in situ crystallization along the floor, walls and roof from one, largely homogenous, convecting magma body....

Long-Term Volumetric Eruption Rates and Magma Budgets

Energy Technology Data Exchange (ETDEWEB)

Scott M. White Dept. Geological Sciences University of South Carolina Columbia, SC 29208; Joy A. Crisp Jet Propulsion Laboratory, California Institute of Technology Pasadena, CA 91109; Frank J. Spera Dept. Earth Science University of California, Santa Barbara Santa Barbara, CA 93106

2005-01-01

A global compilation of 170 time-averaged volumetric volcanic output rates (Qe) is evaluated in terms of composition and petrotectonic setting to advance the understanding of long-term rates of magma generation and eruption on Earth. Repose periods between successive eruptions at a given site and intrusive:extrusive ratios were compiled for selected volcanic centers where long-term (>104 years) data were available. More silicic compositions, rhyolites and andesites, have a more limited range of eruption rates than basalts. Even when high Qe values contributed by flood basalts (9 ± 2 Å~ 10-1 km3/yr) are removed, there is a trend in decreasing average Qe with lava composition from basaltic eruptions (2.6 ± 1.0 Å~ 10-2 km3/yr) to andesites (2.3 ± 0.8 Å~ 10-3 km3/yr) and rhyolites (4.0 ± 1.4 Å~ 10-3 km3/yr). This trend is also seen in the difference between oceanic and continental settings, as eruptions on oceanic crust tend to be predominately basaltic. All of the volcanoes occurring in oceanic settings fail to have statistically different mean Qe and have an overall average of 2.8 ± 0.4 Å~ 10-2 km3/yr, excluding flood basalts. Likewise, all of the volcanoes on continental crust also fail to have statistically different mean Qe and have an overall average of 4.4 ± 0.8 Å~ 10-3 km3/yr. Flood basalts also form a distinctive class with an average Qe nearly two orders of magnitude higher than any other class. However, we have found no systematic evidence linking increased intrusive:extrusive ratios with lower volcanic rates. A simple heat balance analysis suggests that the preponderance of volcanic systems must be open magmatic systems with respect to heat and matter transport in order to maintain eruptible magma at shallow depth throughout the observed lifetime of the volcano. The empirical upper limit of Å`10-2 km3/yr for magma eruption rate in systems with relatively high intrusive:extrusive ratios may be a consequence of the fundamental parameters

The evolution of hydrous magmas in the Tongariro Volcanic Centre : the 10 ka Pahoka-Mangamate eruptions

International Nuclear Information System (INIS)

Auer, A.; Palin, J.M.; White, J.D.L.; Nakagawa, M.; Stirling, C.

2015-01-01

The majority of arc-type andesites in the Tongariro Volcanic Centre are highly porphyritic, hornblende-free, two-pyroxene andesites. An exception is tephras from the c. 10,000 ka Pahoka-Mangamate event. Magmas of these Plinian eruptions bypassed the extensive crustal mush columns under the central volcanoes and sequentially derived a series of almost aphyric rocks spanning a compositional range from dacite to basaltic andesite. Mineral composition, trace element and isotopic data suggest that this eruptive series tapped a mid-crustal magma reservoir, resulting in the initial eruption of an hydrous dacitic magma and several following eruptions characterised by less-evolved and less-hydrous compositions at progressively higher temperatures and substantially lower 87 Sr/ 86 Sr ratios. Systematic changes in magma chemistry are also reflected in a sequential change in phenocryst content starting with an early hornblende-plagioclase-dominated assemblage to a late olivine-plagioclase-dominated assemblage. (author).

Biogenic volatile organic compounds in the Earth system.

Science.gov (United States)

Laothawornkitkul, Jullada; Taylor, Jane E; Paul, Nigel D; Hewitt, C Nicholas

2009-01-01

Biogenic volatile organic compounds produced by plants are involved in plant growth, development, reproduction and defence. They also function as communication media within plant communities, between plants and between plants and insects. Because of the high chemical reactivity of many of these compounds, coupled with their large mass emission rates from vegetation into the atmosphere, they have significant effects on the chemical composition and physical characteristics of the atmosphere. Hence, biogenic volatile organic compounds mediate the relationship between the biosphere and the atmosphere. Alteration of this relationship by anthropogenically driven changes to the environment, including global climate change, may perturb these interactions and may lead to adverse and hard-to-predict consequences for the Earth system.

Ground surface deformation patterns, magma supply, and magma storage at Okmok volcano, Alaska, from InSAR analysis: 2. Coeruptive deflation, July-August 2008

Science.gov (United States)

Lu, Zhong; Dzurisin, Daniel

2010-01-01

A hydrovolcanic eruption near Cone D on the floor of Okmok caldera, Alaska, began on 12 July 2008 and continued until late August 2008. The eruption was preceded by inflation of a magma reservoir located beneath the center of the caldera and ∼3 km below sea level (bsl), which began immediately after Okmok's previous eruption in 1997. In this paper we use data from several radar satellites and advanced interferometric synthetic aperture radar (InSAR) techniques to produce a suite of 2008 coeruption deformation maps. Most of the surface deformation that occurred during the eruption is explained by deflation of a Mogi-type source located beneath the center of the caldera and 2–3 km bsl, i.e., essentially the same source that inflated prior to the eruption. During the eruption the reservoir deflated at a rate that decreased exponentially with time with a 1/e time constant of ∼13 days. We envision a sponge-like network of interconnected fractures and melt bodies that in aggregate constitute a complex magma storage zone beneath Okmok caldera. The rate at which the reservoir deflates during an eruption may be controlled by the diminishing pressure difference between the reservoir and surface. A similar mechanism might explain the tendency for reservoir inflation to slow as an eruption approaches until the pressure difference between a deep magma production zone and the reservoir is great enough to drive an intrusion or eruption along the caldera ring-fracture system.

Fusarium oxysporum volatiles enhance plant growth via affecting auxin transport and signaling

Directory of Open Access Journals (Sweden)

Vasileios eBitas

2015-11-01

Full Text Available Volatile organic compounds (VOCs have well-documented roles in plant-plant communication and directing animal behavior. In this study, we examine the less understood roles of VOCs in plant-fungal relationships. Phylogenetically and ecologically diverse strains of Fusarium oxysporum, a fungal species complex that often resides in the rhizosphere of assorted plants, produce volatile compounds that augment shoot and root growth of Arabidopsis thaliana and tobacco. Growth responses of A. thaliana hormone signaling mutants and expression patterns of a GUS reporter gene under the auxin-responsive DR5 promoter supported the involvement of auxin signaling in F. oxysporum volatile-mediated growth enhancement. In addition, 1-naphthylthalamic acid, an inhibitor of auxin efflux, negated F. oxysporum volatile-mediated growth enhancement in both plants. Comparison of the profiles of volatile compounds produced by F. oxysporum strains that differentially affected plant growth suggests that the relative compositions of both growth inhibitory and stimulatory compounds may determine the degree of plant growth enhancement. Volatile-mediated signaling between fungi and plants may represent a potentially conserved, yet mostly overlooked, mechanism underpinning plant-fungus interactions and fungal niche adaption.

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

High magma storage rates before the 1983 eruption of kilauea, hawaii

Science.gov (United States)

Cayol; Dieterich; Okamura; Miklius

2000-06-30

After a magnitude 7.2 earthquake in 1975 and before the start of the ongoing eruption in 1983, deformation of Kilauea volcano was the most rapid ever recorded. Three-dimensional numerical modeling shows that this deformation is consistent with the dilation of a dike within Kilauea's rift zones coupled with creep over a narrow area of a low-angle fault beneath the south flank. Magma supply is estimated to be 0.18 cubic kilometers per year, twice that of previous estimates. The 1983 eruption may be a direct consequence of the high rates of magma storage within the rift zone that followed the 1975 earthquake.

Numerical linear algebra on emerging architectures: The PLASMA and MAGMA projects

International Nuclear Information System (INIS)

Agullo, Emmanuel; Demmel, Jim; Dongarra, Jack; Hadri, Bilel; Kurzak, Jakub; Langou, Julien; Ltaief, Hatem; Luszczek, Piotr; Tomov, Stanimire

2009-01-01

The emergence and continuing use of multi-core architectures and graphics processing units require changes in the existing software and sometimes even a redesign of the established algorithms in order to take advantage of now prevailing parallelism. Parallel Linear Algebra for Scalable Multi-core Architectures (PLASMA) and Matrix Algebra on GPU and Multics Architectures (MAGMA) are two projects that aims to achieve high performance and portability across a wide range of multi-core architectures and hybrid systems respectively. We present in this document a comparative study of PLASMA's performance against established linear algebra packages and some preliminary results of MAGMA on hybrid multi-core and GPU systems.

Geochemical differentiation processes for arc magma of the Sengan volcanic cluster, Northeastern Japan, constrained from principal component analysis

Science.gov (United States)

Ueki, Kenta; Iwamori, Hikaru

2017-10-01

In this study, with a view of understanding the structure of high-dimensional geochemical data and discussing the chemical processes at work in the evolution of arc magmas, we employed principal component analysis (PCA) to evaluate the compositional variations of volcanic rocks from the Sengan volcanic cluster of the Northeastern Japan Arc. We analyzed the trace element compositions of various arc volcanic rocks, sampled from 17 different volcanoes in a volcanic cluster. The PCA results demonstrated that the first three principal components accounted for 86% of the geochemical variation in the magma of the Sengan region. Based on the relationships between the principal components and the major elements, the mass-balance relationships with respect to the contributions of minerals, the composition of plagioclase phenocrysts, geothermal gradient, and seismic velocity structure in the crust, the first, the second, and the third principal components appear to represent magma mixing, crystallizations of olivine/pyroxene, and crystallizations of plagioclase, respectively. These represented 59%, 20%, and 6%, respectively, of the variance in the entire compositional range, indicating that magma mixing accounted for the largest variance in the geochemical variation of the arc magma. Our result indicated that crustal processes dominate the geochemical variation of magma in the Sengan volcanic cluster.

Magma evolution in the Pliocene Pleistocene succession of Kos, South Aegean arc (Greece)

Science.gov (United States)

Pe-Piper, Georgia; Moulton, Ben

2008-11-01

This study investigates the petrogenesis of Pliocene-Quaternary andesites, dacites and rhyolites of the island of Kos. These volcanic rocks differ from other volcanic centres in the South Aegean arc in the narrow range of Pliocene volcanic products, the abundance of high-silica rhyolite, the lower ɛNd for a given Sr isotope composition, and greater depth to the subducting slab. Pliocene and early Pleistocene dacite stocks and rhyolite domes are succeeded by younger tuffs, notably the 0.16 Ma Kos Plateau Tuff derived from a super-eruption of an andesite stratocone now subsided beneath the sea south of Kos. Volcanic products in tuffs have been sampled from lithic clasts. Andesite, dacite and rhyolite all have ɛNd ˜+ 1.5 to -1.5 and 86Sr/ 87Sr ˜ 0.7042; this unusual composition is argued to be the result of subduction of sediments derived from the River Nile. All rock types show structures indicative of widespread magma mixing, including complexly zoned plagioclase, clinopyroxene and amphibole containing glass inclusions of trachyte and rhyolite compositions. The observed rocks result from fractionation and mixing of three principal magma types: (a) calc-alkaline high-Al basalt that fractionated to andesite at the base of crust; (b) partially melted metabasaltic amphibolite underplated at the base of crust, that fractionated to produce high-SiO 2 rhyolite; and (c) a minor component of trachytic magma from partial melting of enriched subcontinental lithospheric mantle. The complexly zoned phenocrysts with glass inclusions provide specific evidence for mixing of these three components. Specifically, it was the emplacement of the andesite into a voluminous rhyolite magma in a mid-crustal magma chamber that led to the explosive Kos Plateau Tuff super-eruption.

Production and Preservation of Sulfide Layering in Mercury's Magma Ocean

Science.gov (United States)

Boukare, C.-E.; Parman, S. W.; Parmentier, E. M.; Anzures, B. A.

2018-05-01

Mercury's magma ocean (MMO) would have been sulfur-rich. At some point during MMO solidification, it likely became sulfide saturated. Here we present physiochemical models exploring sulfide layer formation and stability.

Volatility in Equilibrium

DEFF Research Database (Denmark)

Bollerslev, Tim; Sizova, Natalia; Tauchen, George

Stock market volatility clusters in time, carries a risk premium, is fractionally inte- grated, and exhibits asymmetric leverage effects relative to returns. This paper develops a first internally consistent equilibrium based explanation for these longstanding empirical facts. The model is cast i......, and the dynamic cross-correlations of the volatility measures with the returns calculated from actual high-frequency intra-day data on the S&P 500 aggregate market and VIX volatility indexes....

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 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 MELTS calculation are clear and

Crystallization of Magma. CEGS Programs Publication Number 14.

Science.gov (United States)

Berry, R. W.

Crystallization of Magma is one of a series of single-topic problem modules intended for use in undergraduate geology and earth science courses. Through problems and observations based on two sets of experiments, this module leads to an understanding of how an igneous rock can form from molten material. Environmental factors responsible for…

American options under stochastic volatility

NARCIS (Netherlands)

Chockalingam, A.; Muthuraman, K.

2011-01-01

The problem of pricing an American option written on an underlying asset with constant price volatility has been studied extensively in literature. Real-world data, however, demonstrate that volatility is not constant, and stochastic volatility models are used to account for dynamic volatility

Numerical modeling perspectives on zircon crystallization and magma reservoir growth at the Laguna del Maule volcanic field, central Chile

Science.gov (United States)

Andersen, N. L.; Dufek, J.; Singer, B. S.

2017-12-01

Magma reservoirs in the middle to upper crust are though to accumulate incrementally over 104 -105 years. Coupled crystallization ages and compositions of zircon are a potentially powerful tracer of reservoir growth and magma evolution. However, complex age distributions and disequilibrium trace element partitioning complicate the interpretation of the zircon record in terms of magmatic processes. In order to make quantitative predictions of the effects of magmatic processes that contribute reservoir growth and evolution—such as cooling and crystallization, magma recharge and mixing, and rejuvenation and remelting of cumulate-rich reservoir margins—we develop a model of zircon saturation and growth within a numerical framework of coupled thermal transfer, phase equilibrium, and magma dynamics. We apply this model to the Laguna del Maule volcanic field (LdM), located in central Chile. LdM has erupted at least 40 km3 of rhyolite from 36 vents distributed within a 250 km2 lake basin. Ongoing unrest demonstrates the large, silicic magma system beneath LdM remains active to this day. Zircon from rhyolite erupted between c. 23 and 1.8 ka produce a continuous distribution of 230Th-238U ages ranging from eruption to 40 ka, as well as less common crystal domains up to 165 ka and rare xenocrysts. Zircon trace element compositions fingerprint compositionally distinct reservoirs that grew within the larger magma system. Despite the dominantly continuous distributions of ages, many crystals are characterized by volumetrically substantial, trace element enriched domains consistent with rapid crystal growth. We utilize numerical simulations to assess the magmatic conditions required to catalyze these "blooms" of crystallization and the magma dynamics that contributed to the assembly of the LdM magma system.

Oxidation State of Iron in the Izu-Bonin Arc Initial Magma and Its Influence Factors

Science.gov (United States)

Li, H.; Arculus, R. J.; Brandl, P. A.; Hamada, M.; Savov, I. P.; Zhu, S.; Hickey-Vargas, R.; Tepley, F. J., III; Meffre, S.; Yogodzinski, G. M.; McCarthy, A.; Barth, A. P.; Kanayama, K.; Kusano, Y.; Sun, W.

2014-12-01

The redox state of mantle-derived magmas is a controversial issue, especially whether island arc basalts are more oxidized than those from mid-ocean ridges. Usually, arc magmas have higher Fe3+/Fe2+ and calculated oxygen fugacity (fO2) than mid-ocean ridge basalts (MORB). It is the high fO2 of arc magma that apparently delays onset of sulfide fractionation and sequestration of precious/base metals thereby facilitating the formation of many giant gold-copper deposits typically associated with subduction zones. But due to a paucity of Fe3+/Fe2+ data for primary mantle-derived arc magmas, the cause for high fO2 of these magma types is still controversial; causes may include inter alia subduction-released oxidized material addition to the mantle wedge source of arc magma, partial melting of subducted slab, and redox changes occurring during ascent of the magma. Fortunately, IODP expedition 351 drilling at IODP Site U1438 in the Amami-Sankaku Basin of the northwestern Philipine Sea, adjacent to the proto-Izu-Bonin Arc at the Kyushu-Palau Ridge (KPR), recovered not only volcaniclastics derived from the inception of Izu-Bonin Mariana (IBM) arc in the Eocene, but also similar materials for the Arc's subsequent evolution through to the Late Oligocene and abandonment of the KPR as a remnant arc. Samples of the pre-Arc oceanic crustal basement were also recovered enabling us to determine the fO2of the mantle preceding arc inception. As the oxidation state of iron in basaltic glass directly relates to the fO2 , the Fe3+/∑Fe ratio [Fe3+/(Fe3++ Fe2+)] of basaltic glass are quantified by synchrotron-facilitated micro X-ray Absorption Near Edge Structure (XANES) spectroscopy to reflect its fO2. Fe K-edge µ-XANES spectra were recorded in fluorescence mode at Beamline 15U1, Shanghai Synchrotron Radiation Facility (SSRF). Synthetic silicate glass with known Fe3+/∑Fe ratio was used in data handling. The experimental results as well as preliminary data from IODP Expedition 351

On the source material of magmas - with special reference to Nd isotopic ratios of igneous rocks

International Nuclear Information System (INIS)

Shuto, Kenji

1980-01-01

In 1973, the Sm-Nd method was first used for the measurement of the absolute age of igneous rocks and meteorites. Subsequently in the following years, the research works by means of the Nd isotopic ratio in igneous rocks have been made strenuously in order to reveal the chemistry of the source materials of magma giving rise to the igneous rocks and further the evolution process of mantle and earth's crust. The fundamental items for the Sm-Nd method are explained. Then, the research results more important in the above connection are given. Finally, the ideas by the author concerning the source materials of magma are presented from the data available on the Nd isotopes in meteorites and igneous rocks. The following matters are described: the fundamentals of Sm-Nd method, the Nd content in seawater, the negative correlation between Nd and Sr isotopic ratios in igneous rocks, magma source materials and Nd isotopes, and considerations on magma source materials. (J.P.N.)

Proboscis extension reflex platform for volatiles and semi-volatiles detection

Energy Technology Data Exchange (ETDEWEB)

Wingo, Robert M. (Los Alamos, NM); McCabe, Kirsten J. (Los Alamos, NM); Haarmann, Timothy K. (Jemez Pueblo, NM)

2010-11-30

The present invention provides an apparatus for the detection of volatile and semi-volatile chemicals using the olfactory abilities of honey bees that are trained to respond to the presence of a specific chemical in a sample of gas with the proboscis extension reflex (PER). In particular, the geometry and arrangement of the parts of the apparatus are such that the amount of surface area in contact with the sample of gas prior to its introduction to the bees is minimized to improve the detection of particular volatile and semi-volatile that have a tendency to "stick" to contacting surfaces, especially certain chemicals associated with explosives and narcotics. According to another aspect of the present invention, a pre-concentrating means is incorporated with the device to effectively increase the concentration of "sticky" chemicals presented to the insects.

The Largs high-latitude oxygen isotope anomaly (New Zealand) and climatic controls of oxygen isotopes in magma

International Nuclear Information System (INIS)

Blattner, P.; Williams, J.G.

1991-01-01

In northern Fiordland the Brook Street terrane of New Zealand consists of two units - the predominantly basaltic Plato and the predominantly andesitic Largs terrane. The Permian Plato terrane has normal to slightly enriched δ 18 O values, whereas the Largs terrane, which is of similar pre-early Triassic age, has not yielded a single normal δ 18 O SMOW result, with all of 17 total rocks showing less than 3.2per mille, seven less than -4per mille, and two less than -9per mille. These strongly anomalous data confirm an earlier suggested terrestrial character of Largs deposition, and demand the presence of Permo-Triassic geothermal systems running on subAntarctic to Antarctic meteoric water. The skewed data spectrum suggests a relatively immature flow system and likely values for the recharge water are -20per mille δ 18 O or less. For a climate distribution similar to the present one, inlcuding polar ice caps, this would indicate over 70deg of southern latitude. Rafts and xenoliths of Largs rocks have been entrained within Mackay Intrusives in the early Triassic. On field evidence the Mackay magmas have also intruded an early Darran Complex, but this complex has been substantially reactivated in the Cretaceous. It has δ 18 O values near 5.0per mille, which is distinctly low for island arc magmas. Since the complex is isotopically homogenous, its δ 18 O is unlikely to be a direct effect of the relatively shallow Largs terrane. More probable is a climate related slight depression of the δ 18 O of magma sources, in which other high-latitude, low-δ 18 O sediments and geothermal systems have been involved. (orig.)

Magma evolution at Copahue volcano (Chile/Argentina border): insights from melt inclusions

Science.gov (United States)

Cannatelli, C.; Aracena, C.; Leisen, M.; Moncada, D.; Roulleau, E.; Vinet, N.; Petrelli, M.; Paolillo, A.; Barra, F.; Morata, D.

2016-12-01

Copahue volcano is an active stratovolcano in the Andean Southern Volcanic Zone (SVZ), straddling at the border between Central Chile and Argentina. The volcano's eruptive style during its history has changed from mainly effusive in the Pleistocene to explosive in the Holocene. The prehistoric eruptions can be divided into pre-glacial (PG), syn-glacial (SG) and post-glacial (PM) stages, with products ranging from basaltic andesites to andesites. In order to investigate the evolution of the magma source and volatiles through time, we have focused our study on the eruptive products from the SG to the 2014 eruption (SUM2014). Sampled rocks are glomero-porphyritic, with a paragenetic mineral sequence of feldspars, ortho- and clinopyroxene, and olivine in order of abundance. All samples present a variable number of vesicles, with SUM2014 samples containing the biggest amount. Feldspar composition varies from Na-rich (andesine) in SG to Ca-rich (labradorite) in SUM2014. Two pyroxene types are present in SG and PM samples (augite and enstatite), while SUM2014 presents augite, pigeonite and enstatite. Thermobarometric estimation, based on mineral chemistry, show a bimodal distribution for SG and SUM2014 (P=10-12 kbars and 5-8 kbars) and only one interval for PM (P=7-8 kbars). Melt Inclusions Assemblages (MIAs) are found in all mineral phases, mostly re-crystallized, with one or more bubbles and daughter oxide minerals. Compositions vary from trachy-andesitic to dacitic for SG, andesitic to trachydacitic for PM, and basaltic andesitic to trachydacitic for SUM2014. Major elements systematics show the existence of a bimodal distribution of pyroxene and feldspar hosted-MIA in SUM2014, which together with the co-presence of pigeonite (low-Ca pyroxene) and augite and the bimodal distribution of P, can be interpreted as evidence of mixing of two types of magmas, evolving at different depths. Trace elements systematics for MIA in SG, PM and SUM2014 show a negative anomaly for Nb

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.