Ascent Process Research Articles

A43 諏訪之瀬島火山2000-2003年噴火におけるマグマの火道上昇と噴煙高度変化(火山の岩石学(2),日本火山学会2006年秋季大会)

A43 諏訪之瀬島火山2000-2003年噴火におけるマグマの火道上昇と噴煙高度変化(火山の岩石学(2),日本火山学会2006年秋季大会)

A52 噴出物の含水量測定によるマグマ上昇プロセスの考察 : 北海道駒ケ岳 1929 年噴火の例

A52 噴出物の含水量測定によるマグマ上昇プロセスの考察 : 北海道駒ケ岳 1929 年噴火の例

A unified trajectory optimization framework for lunar ascent

This paper presents a unified trajectory optimization framework for lunar ascent. Compared with prevailing and emerging studies on lunar ascent trajectory optimization with simplified lunar ascent process and simple constraints, our method formulates in detail the lunar ascent process with complex constraints in a unified manner. The kinematics and dynamics model of lunar ascent with mission-specific constraints explicitly expressed through equalities or inequalities form the fuel-optimal lunar ascent trajectory optimization problem. A proper direct trajectory optimization method is chosen to transcribe the original trajectory optimization problem into a nonlinear programming (NLP) problem solved by a highly efficient NLP solver. The homotopy-based backtracking initial value strategy is designed to enhance convergence of the solving process. First, a two-phase trajectory optimization problem including vertical-rise phase and orbit-insertion phase is solved in the proposed unified framework. Subsequently, to obtain terrain clearance, we directly incorporate terrain description into the lunar ascent problem to obtain the optimal lunar ascent trajectory. Simulation results indicate that the proposed unified trajectory optimization framework has enough adaptability to efficiently handle complex lunar ascent scenarios. The proposed framework may benefit future autonomous lunar ascent missions.

Linear Precoding Gain for Large MIMO Configurations with QAM and Reduced Complexity

In this paper, the problem of designing a linear precoder for multiple-input multiple-output (MIMO) systems in conjunction with quadrature amplitude modulation (QAM) is addressed. First, a novel and efficient methodology to evaluate the input–output mutual information for a general MIMO system as well as its corresponding gradients is presented, based on the Gauss–Hermite quadrature rule. Then, the method is exploited in a block coordinate gradient ascent optimization process to determine the globally optimal linear precoder with respect to the MIMO input–output mutual information for QAM systems with relatively moderate MIMO channel sizes. The proposed methodology is next applied in conjunction with the complexity-reducing per-group processing technique to both perfect channel state information (CSI) at the transmitter as well as statistical CSI (Statistical CSI) scenarios, with large transmitting and receiving antenna sizes, and for constellation size up to $M=64$ . We show by the numerical results that the precoders developed offer significantly better performance than the configuration with no precoder as well as the maximum diversity precoder for QAM with constellation sizes $M=16$ , 32, and 64 and for MIMO channel size up to $100\times 100$ .

Fracture problem for an external circumferential crack in a functionally graded superconducting cylinder subjected to a parallel magnetic field

In this study, the multiple isoparametric finite element method (MIFEM) is used to investigate external circumferential crack problem of a functionally graded superconducting cylinder subjected to electromagnetic forces. The superconducting cylinder is composed by Bi2223/Ag composite with material parameters varying. A crack reference region is defined to reflect the effects of crack on flux and current densities, and the magnetically impermeable crack surface condition and the generalized Irie–Yamafuji critical state model outside the crack region are adopted. The distributions of magnetic flux density in the superconducting cylinder are obtained analytically for both the zero-field cooling (ZFC) and the field cooling (FC) activation processes. Based on the MIFEM, the stress intensity factors (SIFs) at crack fronts in the process of field ascent and/or descent are then numerically calculated. It is interesting to note from numerical results that for the present crack model in the ZFC activation process, the crack is easily propagate and grow with the applied field increases, and that in the field descent process of either the ZFC case or FC case, the crack generally does not propagate. In addition, in the field ascent process of the ZFC case, the SIFs depend on not only the crack depths and model parameters but also the applied field. The present study should be helpful to the design and application of high-temperature superconductors with external edge cracks.

Switching control of thrust regulation and inlet unstart protection for scramjet engine based on strategy of integral initial values resetting

A new switching control strategy has been developed to deal with the multi-objective control problem of scramjet engine, which caused by its many safety restrictions during the ascent process. This switching control method is based on the strategy of integral initial values resetting. Firstly, in this paper, the model of each control loop and sub-controller was given on the basis of previous studies. Then the switching criteria and bumpless switching scheme were described separately and the influence of the key parameters of the switching criteria on the control process was discussed using the hardware-in-the-loop simulation. Finally, the validity of switching control was verified on the ground experiment facility. The results showed that it is useful to introduce the switching control based on the strategy of integral initial values resetting to scramjet engine.

Distinguishing diapirs from inflated plutons: an integrated rock magnetic fabric and structural study on the Roundstone Pluton, western Ireland

Granitoid plutons account for much of the continental crust and are critical in the generation of several economic resources. Despite over a century of research, the fundamental process by which large felsic bodies intrude remains controversial. Two contrasting models persist: (1) mass ascent and subsequent cooling of magma (diapirism); (2) sheet ascent and subsequent emplacement (laccoliths). The latter hypothesis is different from the former as distinct ascent and emplacement processes must occur and be identifiable; traditional field methods rarely allow this important distinction to be made. We present field, petrographic and anisotropy of magnetic susceptibility data from the Roundstone Pluton, Connemara, western Ireland, which was previously considered a diapiric intrusion. The new data reveal anomalous subvertical magmatic lineations in the core of this circular intrusion as well as a suite of magmatic and submagmatic fabrics that parallel NNW–SSE country rock faults and coeval G2 sheets within the pluton. We deduce that these structures reflect a distinct centralized ascent process along a NNW–SSE conduit. Lateral emplacement and pluton inflation followed, ultimately forming a punched laccolith. We conclude that the combined application of the above techniques provides a unique insight into pluton architecture that removes ambiguity between contrasting diapiric and inflated pluton models. Supplementary material: Complete rock magnetic data tables and sample site coordinates (Irish Grid) are available at http://www.geolsoc.org.uk/SUP18837 .

Rheological transitions in high‐temperature volcanic fault zones

AbstractSilicic magma experiences shear‐induced brittle fracturing during its ascent, resulting in the formation of a magmatic fault at the conduit margin. Once the fault is formed, frictional behavior of the fault controls the magma ascent process. We observed torsional deformation of a magmatic fault gouge in situ at temperatures of 800 and 900°C using synchrotron radiation X‐ray radiography. The torsional deformation rate was set at 0.1–10 rpm, corresponding to equivalent slip velocities of 2.27 × 10−5–1.74 × 10−3 m s−1 and shear strain rates of 0.014–1.16 s−1. The normal stresses used were 1, 5, and 10 MPa. The magmatic fault showed frictional sliding as well as viscous flow even above the glass transition temperature. The transition between frictional sliding and viscous flow depends on temperature, deformation rate, and normal stress on the fault. At 900°C, the fault showed viscous deformation at a normal stress of 10 MPa, while frictional sliding was predominant at 800°C. We propose the ratio of timescales of fault healing and deformation as a criterion for transition between frictional sliding and viscous flow. The experimentally calibrated criterion infers that frictional sliding is predominant from ~500 m in depth during explosive eruption; this may explain rapid magma ascent without efficient outgassing. Frictional heating would in turn enhance fault healing, resulting in the reverse transition from frictional sliding to viscous flow, followed by deceleration of magma ascent. Therefore, cyclic transitions between frictional sliding and viscous flow are a possible explanation for the cyclic behavior of lava effusion.

Petrology and Sr–Nd Isotopic Disequilibrium of the Xiaohaizi Intrusion, NW China: Genesis of Layered Intrusions in the Tarim Large Igneous Province

Layered mafic intrusions (LMI) are sporadically distributed in the Early Permian Tarim large igneous province (LIP), NW China, and are crosscut by numerous contemporaneous dykes. The Xiaohaizi wehrlite intrusion is composed mainly of olivine (Fo69–75), clinopyroxene (Mg# = 75–84), intercumulus plagioclase (An53–86) and Fe–Ti oxides. Both petrography and mineral compositions suggest that olivine and clinopyroxene crystallized earlier than plagioclase and Fe–Ti oxides. The dykes are of alkali basalt to trachyandesite with low Mg# (35–39). The least-contaminated dykes display strong rare earth element (REE) fractionation, enrichment of Nb and Ta, and depletion of Pb relative to other similarly incompatible elements, bearing strong similarity to ocean island basalts (OIB). This, together with their positive εNdi values (4·3–4·8), is consistent with derivation from an enriched asthenospheric mantle source. Clinopyroxenes in the wehrlites display convex-upward chondrite-normalized REE patterns. The melts in equilibrium with these clinopyroxenes have very similar trace element compositions to those of the crosscutting dykes, suggesting a similar mantle source shared by the Xiaohaizi wehrlite intrusion and dykes. The Xiaohaizi wehrlite intrusion is characterized by Sr–Nd isotopic disequilibrium between clinopyroxene and plagioclase separates: 87Sr/86Sri (0·7038–0·7041) and εNdi (1·0–1·9) of clinopyroxene are lower and higher than the respective ratios of intercumulus plagioclase (87Sr/86Sri = 0·7042–0·7043, εNdi = 0·4–1·0). The 87Sr/86Sri and εNdi of clinopyroxene separates correlate positively and negatively with Zr/Nb, respectively, implying variable degrees of crustal contamination during the formation of the Xiaohaizi wehrlite intrusion. 87Sr/86Sri increases and εNdi decreases with increasing Ca content of plagioclase, indicating that higher An plagioclases experienced higher degrees of contamination. This can be explained by assimilation of continental crust through a turbulent magma ascent (ATA) process. However, this ATA model fails to account for the positive correlation between the Mg# and εNdi of clinopyroxene separates. The isotopic disequilibrium in the Xiaohaizi LMI is more probably generated during an assimilation and fractional crystallization process involving Archean–Neoproterozoic basement and carbonates as contaminants.

B2-28 黒曜石溶岩中のマイクロライトの形態から推定されるマグマ上昇過程(浅部マグマ上昇過程,口頭発表)

B2-28 黒曜石溶岩中のマイクロライトの形態から推定されるマグマ上昇過程(浅部マグマ上昇過程,口頭発表)

Seismicity and magma supply rate of the 1998 failed eruption at Iwate volcano, Japan

Iwate volcano, Japan, showed significant volcanic activity including earthquake swarms and volcano inflation from the beginning of 1998. A large earthquake of magnitude 6.1 hit the south-west of the volcano on September 3. Although a 1 km2 fumarole field formed, blighting plants on the ridge in the western part of the volcano in the spring of 1999, no magmatic eruptions occurred. We reconcile the spatio-temporal distributions of volcanic pressure sources determined by previously reported studies in which GPS, strain and tilt data from dense geodetic station networks are analyzed (Miura et al. Earth Planet Space 52:1003–1008, 2000; Sato and Hamaguchi J Volcanol Geotherm Res 155:244–262, 2006). We calculate the magma supply rates from their results and compare them with the occurrence rates of volcanic earthquakes. The results show that the magma supply rates are almost constant or even decrease with time while the earthquake occurrence rate increases with time. This contrast in their temporal changes is interpreted to result from stress accumulation in the volcanic edifice caused by constant magma supply without effusion of magma to the surface. We further show that data showing slight acceleration in strain can be best explained by magma ascent at a constant velocity, and that there is no evidence for increased magma buoyancy resulting from gas bubble growth. This consideration supports the interpretation that the magma stayed at 2 km depth and horizontally migrated. These findings relating magma supply rate and seismicity to magma ascent process are clues to understanding why no magmatic eruption occurred at Iwate volcano in 1998.

Magma Evolution and Ascent at the Craters of the Moon and Neighboring Volcanic Fields, Southern Idaho, USA: Implications for the Evolution of Polygenetic and Monogenetic Volcanic Fields

The evolution of polygenetic and monogenetic volcanic fields must reflect differences in magma processing during ascent.To assess their evolution we use thermobarometry and geochemistry to evaluate ascent paths for neighboring, nearly coeval volcanic fields in the Snake River Plain, in south^central Idaho, derived from (1) dominantly Holocene polygenetic evolved lavas from the Craters of the Moon lava field (COME) and (2) Quaternary non-evolved, olivine tholeiites (NEOT) from nearby monogenetic volcanic fields. These data show that NEOT have high magmatic temperatures (1205 278C) and a narrow temperature range (5258C) at any given depth; NEOT parent magmas partially crystallize within the middle crust (14^17 km), but with little time for cooling or assimilation. In contrast, COME magmas partially crystallize at similar depths, but at any given depth exhibit lower temperatures (by 408C), and wider temperature ranges (4508C). Prolonged storage of COME magmas allows them to evolve to higher Sr/Sr and SiO2, and lower MgO and Nd/Nd. Most importantly, ascent paths control evolution: NEOT often erupt near the axis of the plain where high-flux (Yellowstone-related), pre-Holocene magmatic activity replaces granitic middle crust with basaltic sills, resulting in a net increase in NEOT magma buoyancy. COME flows erupt off-axis, where felsic crustal lithologies sometimes remain intact, providing a barrier to ascent and a source for crustal contamination. A three-stage ascent process explains the entire range of erupted compositions. Stage 1 (40^20 km): picrites are transported to the middle crust, undergoing partial crystallization of olivine clinopyroxene. COME magmas pass through unarmored conduits and assimilate 1% or less of ancient gabbroic crust having high Sr and Sr/Sr and low SiO2. Stage 2 (20^10 km): magmas are stored within the middle crust, and evolve to moderate MgO (10%). NEOT magmas, reaching 10% MgO, are positively buoyant and migrate through the middle crust. COMEmagmas remain negatively buoyant and so crystallize further and assimilate middle crust. Stage 3 (15^0 km): final ascent and eruption occurs when volatile contents, increased by differentiation, are sufficient (1^2 wt % H2O) to provide magma buoyancy through the middle (and upper) crust.

ACCUMULATION OF SECONDARY CARBONATE EVIDENCE BY ASCENDING CAPILLARY IN MEDITERRANEAN ARGILLIC HORIZONS (CORDOBA, ANDALUSIA, SPAIN)

The physicochemical properties of a red Mediterranean soil profile (Chromic Luvisol) developed on a fluvial terrace 20 m above the Guadalquivir river, near the city of Cordoba, Spain, were examined with emphasis on finding evidence of translocation of carbonates affecting preexisting Bt red horizons in the selected soil profile. The high concentration of carbonate nodules below the argillic horizon and the vertical distribution of carbonate supported the hypothesis that capillary ascent process explained this phenomenon. Two phases are suggested for this carbonation process. First, a Mediterranean pedogenesis occurred, with illuviation, rubification, and lixivied carbonates, which are accumulated in deep calcic horizons with nodules more than 350 ky. This was followed by a second phase with important processes of capillarity ascent affecting preexisting Bt horizons and carbonate nodules with chronology dated 114 (8.9) ky.

Shallow resistivity structure of Asama Volcano and its implications for magma ascent process in the 2004 eruption

Asama volcano is an active volcano with many historical records of Vulcanian eruptions. Its most recent eruptions occurred in 2004 at the summit crater. In this paper, we argue the resistivity structure shallower than 3 km obtained by a dense magnetotelluric survey. The magnetotelluric data were obtained at 74 measurement sites mainly along the four survey lines across the volcano. The resistivity profiles obtained by two-dimensional inversions are characterized by a resistive surface layer and an underlying conductive layer. The dominant feature of the profiles is the existence of resistive bodies at a depth range of a few hundred meters to a few kilometers surrounded by a highly conductive region. Considering that the location of resistive bodies correspond to the old eruption centers (one corresponds to the 24 ka collapse caldera and the other to the 21 ka lava dome), the resistive bodies imply zones of old and solidified intrusive magma with low porosity. Because geothermal activities exist near the resistive bodies, the enclosing highly conductive regions are interpreted as a hydrothermal system driven by the heat from the old solidified magma. Beneath the resistive body under the collapsed caldera, intrusion of magma is inferred from the studies of volcano-tectonic earthquakes and continuous global positioning system (GPS) observation, implying the structural control of magma activity within the volcano. In this study, we propose that the magma ascent was impeded by the old and solidified remnant magma and partly migrated horizontally to the east and finally ascended to the summit, resulting in the 2004 eruptions.

Driving force of lateral permeable gas flow in magma and the criterion of explosive and effusive eruptions

The release of gas from ascending magma is one of the most important factors that controls the style of volcanic eruptions. It is proposed in this paper that the viscous resistance of decompressed magma to gas expansion coupled with the lateral gradient of the ascent velocity can work as a driving force of the permeable gas flow that may transport gas in magma toward the country rock. Based on this idea, the rate of gas loss from magma is calculated in terms of the mean ascent velocity, the gas volume fraction and the ‘degassing factor’ that is proportional to the magma viscosity and the permeability in the limit of the large gas volume fraction. This formulation of gas loss is applied to a simulation of the magma ascent process to examine the eruption style. For the simulation we employ a model of one-dimensional, non-stationary conduit flow in which volatiles are assumed to move upward with the same speed as the liquid magma and to deposit on bubbles in an amount exceeding the solubility. The simulation reveals that the gas volume fraction in the erupting magma sharply drops from nearly unity to significantly lower values as the dimensionless degassing factor increases and crosses a critical value that is only slightly dependent on various conditions. This consequence yields a simple criterion of the eruption style that displays the ranges of explosive and effusive eruptions on the viscosity–permeability plane separated by a boundary line that shifts following the size and geometry type of the conduit.

シリケイトメルト中の水の拡散

Water diffusion in silicate melts is a controlling factor of magma ascent process in volcanic eruption, because it dominates the rates of bubble nucleation and growth in magmas and the decrease of water contents by water diffusion causes drastic changes in the physical properties of silicate melts (viscosity and density). This paper reviews experimental studies for water diffusion in rhyolitic to basaltic melts and glasses. In rhyolitic and dacitic melts (polymerized silicate melts), water mainly dissolves as hydroxyl group (OH) and molecular water (H2O), but only H2O is considered as the mobile species. The H2O diffusivities in rhyolite and dacite increase with water contents and temperature. The mechanism of water diffusion in andesite to basalt (depolymerized silicate melts) is still unclear, but some studies presented the data of total water (OH + H2O) diffusivities in andesite and basalt by assuming the diffusion of one component water. Those data show that the diffusivity of total water increases with melt depolymerization (from rhyolite to basalt) at high temperatures (e.g., > 1400 °C at 0.7 wt% water), but the magnitude relation inverts at the lower temperatures due to the difference of temperature dependences of total water diffusivity in rhyolite to basalt. Recently, a few studies explored the compositional dependence of total water diffusivity and expressed the total water diffusivity as a function of the SiO2 content or the NBO/T value. To test and develop those models, additional experimental data are needed in the future studies, and the developed-comprehensive model for water diffusion in silicate melts and glasses will make a significant contribution to understanding of volcanic eruptions.

On the use of the group SO(4, 2) in atomic and molecular physics

The dynamical non-invariance group SO(4, 2) for a hydrogen-like atom is derived through two different approaches. The first one is by an established traditional ascent process starting from the symmetry group SO(3). This approach is presented in a mathematically oriented original way with a special emphasis on maximally superintegrable systems, N-dimensional extension and little groups. The second approach is by a new symmetry descent process starting from the non-invariance dynamical group Sp(8, R) for a four-dimensional harmonic oscillator. It is based on the little known concept of a Lie algebra under constraints and corresponds in some sense to a symmetry breaking mechanism. This paper ends with a brief discussion of the interest of SO(4, 2) for a new group-theoretical approach to the periodic table of chemical elements. In this connection, a general ongoing programme based on the use of a complete set of commuting operators is briefly described. It is believed that the present paper could be useful not only to the atomic and molecular community but also to people working in theoretical and mathematical physics.

Hydrogen and oxygen isotope compositions of eclogites from the Dabie Mountains and geodynamic implications

Heterogeneous δ18O values as low as - 2.6‰ to+7.0% are observed for ultrahigh pressure eclogites from the Dabie Mountains in East China. Oxygen isotope equilibrium has been approached between the eclogite minerals, suggesting that the rocks would have acquired the unusual δ18O values prior to ultrahigh pressure metamorphism by interaction with18O-depleted fluid. δD values of hydroxyl-bearing are between — 51% and - 83‰, precluding the possibility of paleoseawater involvement. The only likely fluid is ancient meteoric water that exchanged oxygen isotopes with the eclogite precursor (a kind of basaltic rocks) formerly resident on the continental crust. This suggests a crustal recycling process in the suture zone of late subduction. Because silicate minerals undergo rapid oxygen isotope exchange at mantle pressures, preservation of the isotopic signature of meteoric water in the eclogites indicates limited crust-mantle interaction and thus a short residence time (<20 Ma) when the plate containing the eclogite precursor was subducted to mantle depths. The agreement in oxygen isotope temperatures for different mineral pairs suggests a rapid cooling and ascent process for the eclogites subsequent to their formation at mantle depths.

Simulation of balloon ascent process by the computer

In the standard dynamic launch, the balloon bubble is held by a spool instrument when inflated and released to a vertical position. This is an important process of balloon launching. The actual movement of the ascending balloons is quite complex. We used a simplified model to describe it. A computer program was developed to simulate the balloon raising process successfully. The results included the balloon shapes, tension distributions, touch ground positions, taking-off durations etc. in different wind conditions. It is helpful to understand the launch operation. The assumptions of the model, the basic equations, the computing method as well as the main conclusions are described in this paper. The possible improvements in the future are also discussed.

P29 1989 年伊東沖海底噴火に伴う群発地震活動 : (5) 震源分布から推定されるマグマ上昇過程

P29 1989 年伊東沖海底噴火に伴う群発地震活動 : (5) 震源分布から推定されるマグマ上昇過程