alexander simakin | Institute of Physics of the Earth, Russian Academy of Sciences (original) (raw)
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Petrology
This paper presents the results of theoretical and experimental investigations of the system rubi... more This paper presents the results of theoretical and experimental investigations of the system rubidium feldspar-quartz-water at a pressure of 1 kbar. It was found that rubidium leucite (RbAlSi2O6) rather than feldspar is stable both in the dry and hydrous systems. Near the eutectic point of the dry system, the liquidas of RbAlSiO4 approaches that of RbAlSi2O6. The latter phase crystallizes owing to the heterogeneity of initial glass obtained at a temperature of 1500°C. The water solubility in RbAlSi3O8 melt is 4.2 ± 0.15 wt % at 1300°C and a water pressure of 1 kbar. The eutectic composition contains 53 ± 2 mol % quartz (recalculated to RbAlSi3O 8 and Si6O12) at a water pressure of 1 kbar. A comparison of the sodium, potassium, and rubidium systems reveals a systematic shift of eutectic composition toward quartz and simultaneous depression of the quartz liquidus. This is related to an increase in the activity of an aluminosilicate phase (leucite in the rubidium system) and a concurre...
Geochemistry International, 2008
Sodium-silicate glasses with varying water contents were studied by 23Na NMR and 1H NMR spectrosc... more Sodium-silicate glasses with varying water contents were studied by 23Na NMR and 1H NMR spectroscopy. The 23Na NMR spectrum is made up of two Gaussian-Lorentzian components corresponding to rigidly bound and free Na ions. The rigidly bound Na is allocated in the disilicate-like domains corresponding to Q3 species of sodium-silicate glasses. Unbound Na is associated with Q2 and Q1 species. It was shown that, during water dissolution, some hydroxyls are incorporated into the disilicate unit of the structure to form NaHSi2O5, while others hydrate silica (Q4species). Our 23Na NMR data are consistent with available data on Q speciation and the proportions of water species in sodium-silicate glasses in the frameworks of a proposed detailed structural scheme of water dissolution.
Volcanoes - Geological and Geophysical Setting, Theoretical Aspects and Numerical Modeling, Applications to Industry and Their Impact on the Human Health, 2018
As the magma ascends from its depth of generation to the surface, it is often stored in a series ... more As the magma ascends from its depth of generation to the surface, it is often stored in a series of chambers along the way. The rheological contrast between the viscous magma in the magmatic chambers and the surrounding rocks disturbed the stress field which can give rise to various modes of rock failure at magmatic pressures less than the lithostatic stress, leading to an eruption. Different modes of mechanical failure of the chamber walls are considered depending on the geometry and the sign the relative pressure. Relaxation of viscous stress around magmatic chambers, which is important on the time scale of weeks to months is considered in the analysis of stability with application to both large and extra-large magmatic chambers such as Yellowstone. The effects of a strong deep CO2 flux in Yellowstone are considered in detail. The analysis shows that variations in the flow rate around the observed mean value of 40 kg/m2/yr in the hydrothermally active areas can change the composition of the magma for several hundred thousand years, and cause periodic uplift and subsidence of the caldera surface with a period of several decades.
The solubility of Pt in CO-CO2 fluid was studied experimentally at P = 50–200 MPa and T = 950 °C.... more The solubility of Pt in CO-CO2 fluid was studied experimentally at P = 50–200 MPa and T = 950 °C. A mixture of MgC2O4 and MgCO3 was used as a source of the fluid. Upon the reaction of the Pt capsule walls and the fluid, a carbonyl of platinum is formed. The use of the high-temperature quartz ceramics as a fluid trap avoids the effect of mechanical contamination with Pt from the eroded capsule walls. The total content of platinum in the porous fluid traps was measured by the Electrothermal Atomic Absorption (ET-AAS) method. In some experiments, the local analysis of traps was carried out by the Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) method. The composition of fluid in bubbles captured in an albite glass trap was studied by micro-Raman spectroscopy. On the capsule walls and MgO, Pt “whiskers” of submicron diameter were observed, which were formed as a product of carbonyl decomposition during quenching. About 5–15% of carbonyl withstands quenching resul...
Fresh magma input is necessary attribute of the volcanic activity. Ascending from the depth magma... more Fresh magma input is necessary attribute of the volcanic activity. Ascending from the depth magma would come into the contact with cooled partially solidified one and may cause its melting (e.g., Izbekov et al., 2004). Viscosity contrast can prevent continuous mixing in the system to keep gravity unstable stratification for some period of time. We consider condition of the convective overturn in the two-layered system composed of the layer of superheated rhyolitic magma overlaid by partially solidified denser counterpart. Temperature at the lower contact of the system is set constant and larger than liquidus one due to contact with more basic and hotter magma. At first problem is treated analytically via analysis of the growth of infinitesimal exponential disturbance of interface in the two layer system with variable viscosity contrast and thicknesses ratio with proper boundary conditions. Time of RTI exponent and melting time for layer half width (at H=200 m, rhyolite material para...
Large-volume sub-liquidus silicic rocks are erupted in caldera environments with short repose tim... more Large-volume sub-liquidus silicic rocks are erupted in caldera environments with short repose time. Modern in situ isotopic methods have recently permitted analysis of isotopic and trace elemental abundances on micron to smaller scale and demonstrate strong crystalline heterogeneity. We review recent discoveries of isotopically (O, U-Pb) zircons in large volume ignimbrites (Snake River Plain, Kamchatka, and Iceland). We report results from a long-duration isotope exchange experiment with natural zircon and rutile that was held for 4 months at 850°C and 0.3 kbars in a silica-rich solution doped with 18O, 2H, 7Li and 10B. The length-scales of in-diffusion were examined by depth profiling using time-of-flight (TOF) and Cameca 1270 high sensitivity dynamic SIMS. Rutile and zircon developed ~2 µm and ≤0.13µm Fickian profiles, respectively, suggesting that rutile diffusion coefficients were at ~400 times greater than zircon's, and both are consistent with the wet diffusion coefficient...
Geochemistry International, 2015
The paper presents newly obtained chemical analyses of metamorphosed mafic volcanic rocks from th... more The paper presents newly obtained chemical analyses of metamorphosed mafic volcanic rocks from the upper reaches of the Krutogorova River, southwestern Kamchatka. According to their geochemistry, these mafic rocks and the ore bearing mafic rocks of the cortlandite-gabbro-norite association at the Kuval orog occurrence of Ni mineralization in Kamchatka were produced by melting undepleted mantle at its adi abatic decompression (without involvement of subduction related fluids and melts). The significant crystal lization depths of the small cortlandite-gabbro-norite intrusions are confirmed by our pressure evaluations (P = 8 kbar) by a newly developed amphibole barometer; the crystallization depths of the small subvolcanic intrusions was much shallower. The physical mechanism of derivation of the primitive partial mantle melts is discussed using simple numerical simulations of processes related to the onset of subduction and oceanic slab break off. Geochemical data and results of our numerical simulations testify that the picrobasaltic magmas were generated in ascending flows induced in the upper mantle by complicated geodynamic processes during the accretion of the Achaivaam-Valaginskii island arc to the Eurasian continent in the Eocene.
Processes of the intrachamber magma degassing precede degassing in the conduit on the final stage... more Processes of the intrachamber magma degassing precede degassing in the conduit on the final stages of eruption and may be of no less importance. Appearance of the free fluid phase at the depth can be responsible for intrachamber elements transport, pressure buildup and local magma oxidation. We interpret phenocrysts zonality in Shiveluch andesites in terms of such degassing based on our experimental data. High magnesium andesite of Shiveluch volcano (Kamchatka) was studied at PH2O=2 kbar. Bulk hydrous glass was prepared in the series of operations including hydrothermal reducing of the initially melted oxidized rock powder under hydrothermal conditions and remelting. The Fe2+/Fe3+ ratio in the final hydrous glass was estimated with Mossbauer spectroscopy. It corresponds to fO2 = NNO - NNO+2 in the andesite melt at the experimental PT parameters. Short experiments yield crystals grown from the melt with Fe2+/Fe3+ ratio close to the initial value. Liquidus temperature of amphibole was...
Geochmica et Cosmochimica Acta
Terra Nova, 2013
The resumption of subduction of an oceanic plate at a contact with a docked island (continental) ... more The resumption of subduction of an oceanic plate at a contact with a docked island (continental) margin is modeled numerically in 2D. The mechanical properties of the crustal and mantle rock masses are treated with visco-plastic rheologies where the viscosities are described by a Dynamic Power Law phenomenologically accounting for the transient texture evolution of the deforming rock masses. The study is limited to the extreme case of a fluid weakened lithosphere characterized by a uniform effective yield stress. At a constant push of 8 cm/yr the shear zones split the oceanic slab into blocks at the contact with the island. At a moderate yield stress (σ Y < 80 MPa) and normal relaxation rate of viscosity, subduction resumes in less than ca 1 Ma. High σ Y = 100 MPa leads to the island edge bending. A detached block of the island is subducted after the plunge of the oceanic plate reverses.
Earth Science Research, 2012
Amphibole crystallization from hydrous high-magnesium andesite (Shiveluch volcano, Kamchatka) mel... more Amphibole crystallization from hydrous high-magnesium andesite (Shiveluch volcano, Kamchatka) melt has been studied experimentally at pressures 2, 3, 5 kbar. Slightly subliquidus temperatures have been selected for amphibole crystallization. Amphiboles with close to the equilibrium composition have been obtained at low undercoolings in short 4 hours experiments. We select octahedral aluminium content and sum of high charged cations (Ti 4+ , Fe 3+) all evaluated with the 13eCNK method as master parameters reflecting pressure of amphibole formation. Asymptotic maximum of Al VI content at the sum Ti+Fe 3+ =0 as a function of pressure was calculated following negative linear correlation trend for each run of the original and published experimental data sets. The derived novel Al VI in amphibole barometer is calibrated in the pressure range of 2-12 kbar for andesitic and basaltic magmas. Reliability and validity of the new geobarometer were tested on the amphibolized ultramafic xenoliths from the Shiveluch Volcano (Kamchatka) and Dish Hill (California). In both cases our estimates appear to be equal within the uncertainty of the method to the predictions done by two-pyroxene geo-thermo-barometer (Putirka, 2008).
Terra Nova, 2010
Abstract We present the results of coupled analogue and numerical models that provide new insight... more Abstract We present the results of coupled analogue and numerical models that provide new insights into the relationships between volcanoes and thrusts. The effects of both upper-crustal magma chambers and the load of volcanoes on the geometry of thrust systems were investigated. Analogue modelling points to a strong influence exerted by a magma chamber on thrust geometry, which, as suggested by the numerical models used to rationalize these results, is related to the stress redistribution around the weak heterogeneity. The low- ...
Petrology, 2009
This paper reports the results of an experimental investigation of the influence of iron oxidatio... more This paper reports the results of an experimental investigation of the influence of iron oxidation state in the water-saturated andesite melt of Shiveluch Volcano (Kamchatka) on amphibole composition. Experiments with durations of 2–4 h were carried out at a pressure of 2 kbar and temperatures close to the amphibole liquidus (950°C). The degree of iron oxidation (NNO and NNO +
Materiales de Construcción, 2001
Los fundidos de alumino-silicato son una fase parcialmente ordenada. Su estructura puede ser desc... more Los fundidos de alumino-silicato son una fase parcialmente ordenada. Su estructura puede ser descrita en términos de la coordinación de tetraedros de alúmina-sílice también denominados especies Q. La proporción de tetraedros con diferente grado de conectividad entre si se ha investigado por espectroscopias de RMN e IR en fundidos de silicatos alcalinos, fundamentalmente de sodio. Así, la estructura de medio alcance puede caracterizarse por el tamaño de los anillos compuestos de tetraedros de alúmina-sílice. La distribución de tamaño se puede deducir por IR observándose un aumento sistemático de la secuencia en el binario Albita-Anortita. Se ha observado además la destrucción parcial de la estructura por la disolución de agua que sustituye a los grupos de cuatro anillos por anillos de seis grupos. Los cambios bruscos en viscosidad y difusividad se detectan cuando aumenta el contenido de oxígenos no-puente. De la misma manera, se presentan y discuten los resultados en vidrios de silicato de litio con diferentes contenidos en moléculas de agua en el fundido original. La presencia de agua en la red de vidrios susceptibles de ser convertidos en materiales vitrocerámicos y petrúrgicos como materiales de construcción tiene repercusión en los procesos de nucleación y crecimiento cristalino que son necesarios para la fabricación de este tipo de materiales. Se discute, pues, el efecto de este contenido en agua sobre las velocidades de nucleación y cristalización de manera que al rebajarse la viscosidad se incrementan los valores de tipo cinético en estos procesos.
Journal of Volcanology and Geothermal Research, 2001
A new model is proposed for passive degassing from sub-volcanic magma chambers. The water content... more A new model is proposed for passive degassing from sub-volcanic magma chambers. The water content in stably stratified shallow magma chamber will be equated to its solubility at the upper boundary by convection. Water from a lower layer high in water content can enrich the contact zone of the upper layer and lead to further convective overturn of this boundary
Geophysical Research Letters, 2003
Doklady Earth Sciences, 2014
Petrology
This paper presents the results of theoretical and experimental investigations of the system rubi... more This paper presents the results of theoretical and experimental investigations of the system rubidium feldspar-quartz-water at a pressure of 1 kbar. It was found that rubidium leucite (RbAlSi2O6) rather than feldspar is stable both in the dry and hydrous systems. Near the eutectic point of the dry system, the liquidas of RbAlSiO4 approaches that of RbAlSi2O6. The latter phase crystallizes owing to the heterogeneity of initial glass obtained at a temperature of 1500°C. The water solubility in RbAlSi3O8 melt is 4.2 ± 0.15 wt % at 1300°C and a water pressure of 1 kbar. The eutectic composition contains 53 ± 2 mol % quartz (recalculated to RbAlSi3O 8 and Si6O12) at a water pressure of 1 kbar. A comparison of the sodium, potassium, and rubidium systems reveals a systematic shift of eutectic composition toward quartz and simultaneous depression of the quartz liquidus. This is related to an increase in the activity of an aluminosilicate phase (leucite in the rubidium system) and a concurre...
Geochemistry International, 2008
Sodium-silicate glasses with varying water contents were studied by 23Na NMR and 1H NMR spectrosc... more Sodium-silicate glasses with varying water contents were studied by 23Na NMR and 1H NMR spectroscopy. The 23Na NMR spectrum is made up of two Gaussian-Lorentzian components corresponding to rigidly bound and free Na ions. The rigidly bound Na is allocated in the disilicate-like domains corresponding to Q3 species of sodium-silicate glasses. Unbound Na is associated with Q2 and Q1 species. It was shown that, during water dissolution, some hydroxyls are incorporated into the disilicate unit of the structure to form NaHSi2O5, while others hydrate silica (Q4species). Our 23Na NMR data are consistent with available data on Q speciation and the proportions of water species in sodium-silicate glasses in the frameworks of a proposed detailed structural scheme of water dissolution.
Volcanoes - Geological and Geophysical Setting, Theoretical Aspects and Numerical Modeling, Applications to Industry and Their Impact on the Human Health, 2018
As the magma ascends from its depth of generation to the surface, it is often stored in a series ... more As the magma ascends from its depth of generation to the surface, it is often stored in a series of chambers along the way. The rheological contrast between the viscous magma in the magmatic chambers and the surrounding rocks disturbed the stress field which can give rise to various modes of rock failure at magmatic pressures less than the lithostatic stress, leading to an eruption. Different modes of mechanical failure of the chamber walls are considered depending on the geometry and the sign the relative pressure. Relaxation of viscous stress around magmatic chambers, which is important on the time scale of weeks to months is considered in the analysis of stability with application to both large and extra-large magmatic chambers such as Yellowstone. The effects of a strong deep CO2 flux in Yellowstone are considered in detail. The analysis shows that variations in the flow rate around the observed mean value of 40 kg/m2/yr in the hydrothermally active areas can change the composition of the magma for several hundred thousand years, and cause periodic uplift and subsidence of the caldera surface with a period of several decades.
The solubility of Pt in CO-CO2 fluid was studied experimentally at P = 50–200 MPa and T = 950 °C.... more The solubility of Pt in CO-CO2 fluid was studied experimentally at P = 50–200 MPa and T = 950 °C. A mixture of MgC2O4 and MgCO3 was used as a source of the fluid. Upon the reaction of the Pt capsule walls and the fluid, a carbonyl of platinum is formed. The use of the high-temperature quartz ceramics as a fluid trap avoids the effect of mechanical contamination with Pt from the eroded capsule walls. The total content of platinum in the porous fluid traps was measured by the Electrothermal Atomic Absorption (ET-AAS) method. In some experiments, the local analysis of traps was carried out by the Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) method. The composition of fluid in bubbles captured in an albite glass trap was studied by micro-Raman spectroscopy. On the capsule walls and MgO, Pt “whiskers” of submicron diameter were observed, which were formed as a product of carbonyl decomposition during quenching. About 5–15% of carbonyl withstands quenching resul...
Fresh magma input is necessary attribute of the volcanic activity. Ascending from the depth magma... more Fresh magma input is necessary attribute of the volcanic activity. Ascending from the depth magma would come into the contact with cooled partially solidified one and may cause its melting (e.g., Izbekov et al., 2004). Viscosity contrast can prevent continuous mixing in the system to keep gravity unstable stratification for some period of time. We consider condition of the convective overturn in the two-layered system composed of the layer of superheated rhyolitic magma overlaid by partially solidified denser counterpart. Temperature at the lower contact of the system is set constant and larger than liquidus one due to contact with more basic and hotter magma. At first problem is treated analytically via analysis of the growth of infinitesimal exponential disturbance of interface in the two layer system with variable viscosity contrast and thicknesses ratio with proper boundary conditions. Time of RTI exponent and melting time for layer half width (at H=200 m, rhyolite material para...
Large-volume sub-liquidus silicic rocks are erupted in caldera environments with short repose tim... more Large-volume sub-liquidus silicic rocks are erupted in caldera environments with short repose time. Modern in situ isotopic methods have recently permitted analysis of isotopic and trace elemental abundances on micron to smaller scale and demonstrate strong crystalline heterogeneity. We review recent discoveries of isotopically (O, U-Pb) zircons in large volume ignimbrites (Snake River Plain, Kamchatka, and Iceland). We report results from a long-duration isotope exchange experiment with natural zircon and rutile that was held for 4 months at 850°C and 0.3 kbars in a silica-rich solution doped with 18O, 2H, 7Li and 10B. The length-scales of in-diffusion were examined by depth profiling using time-of-flight (TOF) and Cameca 1270 high sensitivity dynamic SIMS. Rutile and zircon developed ~2 µm and ≤0.13µm Fickian profiles, respectively, suggesting that rutile diffusion coefficients were at ~400 times greater than zircon's, and both are consistent with the wet diffusion coefficient...
Geochemistry International, 2015
The paper presents newly obtained chemical analyses of metamorphosed mafic volcanic rocks from th... more The paper presents newly obtained chemical analyses of metamorphosed mafic volcanic rocks from the upper reaches of the Krutogorova River, southwestern Kamchatka. According to their geochemistry, these mafic rocks and the ore bearing mafic rocks of the cortlandite-gabbro-norite association at the Kuval orog occurrence of Ni mineralization in Kamchatka were produced by melting undepleted mantle at its adi abatic decompression (without involvement of subduction related fluids and melts). The significant crystal lization depths of the small cortlandite-gabbro-norite intrusions are confirmed by our pressure evaluations (P = 8 kbar) by a newly developed amphibole barometer; the crystallization depths of the small subvolcanic intrusions was much shallower. The physical mechanism of derivation of the primitive partial mantle melts is discussed using simple numerical simulations of processes related to the onset of subduction and oceanic slab break off. Geochemical data and results of our numerical simulations testify that the picrobasaltic magmas were generated in ascending flows induced in the upper mantle by complicated geodynamic processes during the accretion of the Achaivaam-Valaginskii island arc to the Eurasian continent in the Eocene.
Processes of the intrachamber magma degassing precede degassing in the conduit on the final stage... more Processes of the intrachamber magma degassing precede degassing in the conduit on the final stages of eruption and may be of no less importance. Appearance of the free fluid phase at the depth can be responsible for intrachamber elements transport, pressure buildup and local magma oxidation. We interpret phenocrysts zonality in Shiveluch andesites in terms of such degassing based on our experimental data. High magnesium andesite of Shiveluch volcano (Kamchatka) was studied at PH2O=2 kbar. Bulk hydrous glass was prepared in the series of operations including hydrothermal reducing of the initially melted oxidized rock powder under hydrothermal conditions and remelting. The Fe2+/Fe3+ ratio in the final hydrous glass was estimated with Mossbauer spectroscopy. It corresponds to fO2 = NNO - NNO+2 in the andesite melt at the experimental PT parameters. Short experiments yield crystals grown from the melt with Fe2+/Fe3+ ratio close to the initial value. Liquidus temperature of amphibole was...
Geochmica et Cosmochimica Acta
Terra Nova, 2013
The resumption of subduction of an oceanic plate at a contact with a docked island (continental) ... more The resumption of subduction of an oceanic plate at a contact with a docked island (continental) margin is modeled numerically in 2D. The mechanical properties of the crustal and mantle rock masses are treated with visco-plastic rheologies where the viscosities are described by a Dynamic Power Law phenomenologically accounting for the transient texture evolution of the deforming rock masses. The study is limited to the extreme case of a fluid weakened lithosphere characterized by a uniform effective yield stress. At a constant push of 8 cm/yr the shear zones split the oceanic slab into blocks at the contact with the island. At a moderate yield stress (σ Y < 80 MPa) and normal relaxation rate of viscosity, subduction resumes in less than ca 1 Ma. High σ Y = 100 MPa leads to the island edge bending. A detached block of the island is subducted after the plunge of the oceanic plate reverses.
Earth Science Research, 2012
Amphibole crystallization from hydrous high-magnesium andesite (Shiveluch volcano, Kamchatka) mel... more Amphibole crystallization from hydrous high-magnesium andesite (Shiveluch volcano, Kamchatka) melt has been studied experimentally at pressures 2, 3, 5 kbar. Slightly subliquidus temperatures have been selected for amphibole crystallization. Amphiboles with close to the equilibrium composition have been obtained at low undercoolings in short 4 hours experiments. We select octahedral aluminium content and sum of high charged cations (Ti 4+ , Fe 3+) all evaluated with the 13eCNK method as master parameters reflecting pressure of amphibole formation. Asymptotic maximum of Al VI content at the sum Ti+Fe 3+ =0 as a function of pressure was calculated following negative linear correlation trend for each run of the original and published experimental data sets. The derived novel Al VI in amphibole barometer is calibrated in the pressure range of 2-12 kbar for andesitic and basaltic magmas. Reliability and validity of the new geobarometer were tested on the amphibolized ultramafic xenoliths from the Shiveluch Volcano (Kamchatka) and Dish Hill (California). In both cases our estimates appear to be equal within the uncertainty of the method to the predictions done by two-pyroxene geo-thermo-barometer (Putirka, 2008).
Terra Nova, 2010
Abstract We present the results of coupled analogue and numerical models that provide new insight... more Abstract We present the results of coupled analogue and numerical models that provide new insights into the relationships between volcanoes and thrusts. The effects of both upper-crustal magma chambers and the load of volcanoes on the geometry of thrust systems were investigated. Analogue modelling points to a strong influence exerted by a magma chamber on thrust geometry, which, as suggested by the numerical models used to rationalize these results, is related to the stress redistribution around the weak heterogeneity. The low- ...
Petrology, 2009
This paper reports the results of an experimental investigation of the influence of iron oxidatio... more This paper reports the results of an experimental investigation of the influence of iron oxidation state in the water-saturated andesite melt of Shiveluch Volcano (Kamchatka) on amphibole composition. Experiments with durations of 2–4 h were carried out at a pressure of 2 kbar and temperatures close to the amphibole liquidus (950°C). The degree of iron oxidation (NNO and NNO +
Materiales de Construcción, 2001
Los fundidos de alumino-silicato son una fase parcialmente ordenada. Su estructura puede ser desc... more Los fundidos de alumino-silicato son una fase parcialmente ordenada. Su estructura puede ser descrita en términos de la coordinación de tetraedros de alúmina-sílice también denominados especies Q. La proporción de tetraedros con diferente grado de conectividad entre si se ha investigado por espectroscopias de RMN e IR en fundidos de silicatos alcalinos, fundamentalmente de sodio. Así, la estructura de medio alcance puede caracterizarse por el tamaño de los anillos compuestos de tetraedros de alúmina-sílice. La distribución de tamaño se puede deducir por IR observándose un aumento sistemático de la secuencia en el binario Albita-Anortita. Se ha observado además la destrucción parcial de la estructura por la disolución de agua que sustituye a los grupos de cuatro anillos por anillos de seis grupos. Los cambios bruscos en viscosidad y difusividad se detectan cuando aumenta el contenido de oxígenos no-puente. De la misma manera, se presentan y discuten los resultados en vidrios de silicato de litio con diferentes contenidos en moléculas de agua en el fundido original. La presencia de agua en la red de vidrios susceptibles de ser convertidos en materiales vitrocerámicos y petrúrgicos como materiales de construcción tiene repercusión en los procesos de nucleación y crecimiento cristalino que son necesarios para la fabricación de este tipo de materiales. Se discute, pues, el efecto de este contenido en agua sobre las velocidades de nucleación y cristalización de manera que al rebajarse la viscosidad se incrementan los valores de tipo cinético en estos procesos.
Journal of Volcanology and Geothermal Research, 2001
A new model is proposed for passive degassing from sub-volcanic magma chambers. The water content... more A new model is proposed for passive degassing from sub-volcanic magma chambers. The water content in stably stratified shallow magma chamber will be equated to its solubility at the upper boundary by convection. Water from a lower layer high in water content can enrich the contact zone of the upper layer and lead to further convective overturn of this boundary
Geophysical Research Letters, 2003
Doklady Earth Sciences, 2014
As the magma ascends from its depth of generation to the surface, it is often stored in a series ... more As the magma ascends from its depth of generation to the surface, it is often stored in a series of chambers along the way. The rheological contrast between the viscous magma in the magmatic chambers and the surrounding rocks disturbed the stress field which can give rise to various modes of rock failure at magmatic pressures less than the lithostatic stress, leading to an eruption. Different modes of mechanical failure of the chamber walls are considered depending on the geometry and the sign the relative pressure. Relaxation of viscous stress around magmatic chambers, which is important on the time scale of weeks to months is considered in the analysis of stability with application to both large and extra‐large magmatic chambers such as Yellowstone. The effects of a strong deep CO2 flux in Yellowstone are considered in detail. The analysis shows that variations in the flow rate around the observed mean value of 40 kg/m2/yr in the hydrothermally active areas can change the composition of the magma for several hundred thousand years, and cause periodic uplift and subsidence of the caldera surface with a period of several decades.