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Auteur : Grafiati
Publié le 10 mars 2023

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1

Segall, Paul. « Magma chambers : what we can, and cannot, learn from volcano geodesy ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 377, no 2139 (7 janvier 2019) : 20180158. http://dx.doi.org/10.1098/rsta.2018.0158.

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Geodetic observations on volcanoes can reveal important aspects of crustal magma chambers. The rate of decay of deformation with distance reflects the centroid depth of the chamber. The amplitude of the deformation is proportional to the product of the pressure change and volume of the reservoir. The ratio of horizontal to vertical displacement is sensitive to chamber shape: sills are efficient at generating vertical displacement, while stocks produce more horizontal deformation. Geodesy alone cannot constrain important parameters such as chamber volume or pressure; furthermore, kinematic models have no predictive power. Elastic response combined with influx proportional to pressure gradient predicts an exponentially decaying flux, leading to saw-tooth inflation cycles observed at some volcanoes. Yet many magmatic systems exhibit more complex temporal behaviour. Wall rock adjacent to magma reservoirs cannot behave fully elastically. Modern conceptual models of magma chambers also include cumulate and/or mush zones, with potentially multi-level melt lenses. A viscoelastic shell surrounding a spherical magma chamber significantly modifies the predicted time-dependent response; post-eruptive inflation can occur without recharge if the magma is sufficiently incompressible relative to the surrounding crust (Segall P. 2016 J. Geophys. Res. Solid Earth , 121 , 8501–8522). Numerical calculations confirm this behaviour for both oblate and prolate ellipsoidal chambers surrounded by viscoelastic aureoles. Interestingly, the response to a nearly instantaneous pressure drop during an explosive eruption can be non-monotonic as the rock around the chamber relaxes at different rates. Pressure-dependent recharge of a non-Newtonian magma in an elastic crust leads to an initially high rate of inflation which slows over time; behaviour that has been observed in some magmatic systems. I close by discussing future challenges in volcano geodesy. This article is part of the Theo Murphy meeting issue ‘Magma reservoir architecture and dynamics’.
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2

Townsend, Meredith, et Christian Huber. « A critical magma chamber size for volcanic eruptions ». Geology 48, no 5 (6 février 2020) : 431–35. http://dx.doi.org/10.1130/g47045.1.

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Abstract We present a model for a coupled magma chamber–dike system to investigate the conditions required to initiate volcanic eruptions and to determine what controls the size of eruptions. The model combines the mechanics of dike propagation with internal chamber dynamics including crystallization, volatile exsolution, and the elastic response of the magma and surrounding crust to pressure changes within the chamber. We find three regimes for dike growth and eruptions: (1) below a critical magma chamber size, eruptions are suppressed because chamber pressure drops to lithostatic before a dike reaches the surface; (2) at an intermediate chamber size, the erupted volume is less than the dike volume (“dike-limited” eruption regime); and (3) above a certain chamber size, dikes can easily reach the surface and the erupted volume follows a classic scaling law, which depends on the attributes of the magma chamber (“chamber-limited” eruption regime). The critical chamber volume for an eruption ranges from ∼0.01 km3 to 10 km3 depending on the water content in the magma, depth of the chamber, and initial overpressure. This implies that the first eruptions at a volcano likely are preceded by a protracted history of magma chamber growth at depth, and that the crust above the magma chamber may have trapped several intrusions or “failed eruptions.” Model results can be combined with field observations of erupted volume, pressure, and crystal and volatile content to provide tighter constraints on parameters such as the eruptible chamber size.
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3

Huppert, Herbert E., et Andrew W. Woods. « The role of volatiles in magma chamber dynamics ». Nature 420, no 6915 (décembre 2002) : 493–95. http://dx.doi.org/10.1038/nature01211.

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4

Carrigan, Charles R., et Randall T. Cygan. « Implications of magma chamber dynamics for Soret-related fractionation ». Journal of Geophysical Research 91, B11 (1986) : 11451. http://dx.doi.org/10.1029/jb091ib11p11451.

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5

Asmerom, Yemane, S. Andrew DuFrane, Samuel B. Mukasa, Hai Cheng et R. Lawrence Edwards. « Time scale of magma differentiation in arcs from protactinium-radium isotopic data ». Geology 33, no 8 (1 août 2005) : 633–36. http://dx.doi.org/10.1130/g21638ar.1.

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Abstract Absolute chronology of magma differentiation processes has been a long-desired goal, given its importance in understanding magma chamber dynamics and its connection to a fundamental understanding of the style and frequency of volcanic eruptions. Broad estimates of the duration of magma differentiation and overall crustal residence times have been made based on a variety of indirect approaches, such as physical models of magma chamber cooling, rates of crystal growth and settling, and long-lived radiogenic isotopes. In contrast, combined 231Pa-235U data may provide a robust measure of the time scale of magma differentiation. Based on 231Pa-235U, 230Th-238U and 226Ra-230Th data from Taal volcano, Luzon Arc, Philippine Archipelago, we show that 231Pa-235U data may provide a robust direct measure of the time scale of magma differentiation. A closed-system magma fractionation model gives a 231Pa-235U differentiation time scale in the range of 30 k.y., while the 226Ra-230Th time scale is considerably younger. The time scales are reconciled if we consider either fluid-mixing or magma-mixing models. The fluid-mixing model gives a time scale of differentiation similar to the 231Pa-235U closed-system time scale and is supported by the 230Th-238U data. The magma-mixing model gives a considerably longer time, in the range of 55 k.y. The combined observations support the robustness of the 231Pa-235U chronology, indicating a differentiation time scale in the range of 30 k.y., although this time scale for other volcanoes may vary depending on size and thermal state of the magma chamber. The 226Ra-230Th closed-system model ages, which yield much younger estimates for magma differentiation, are not likely to reflect time scales of magma differentiation.
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6

Sigmarsson, O., I. Vlastelic, R. Andreasen, I. Bindeman, J. L. Devidal, S. Moune, J. K. Keiding, G. Larsen, A. Höskuldsson et Th Thordarson. « Remobilization of silicic intrusion by mafic magmas during the 2010 Eyjafjallajökull eruption ». Solid Earth 2, no 2 (2 décembre 2011) : 271–81. http://dx.doi.org/10.5194/se-2-271-2011.

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Abstract. Injection of basaltic magmas into silicic crustal holding chambers and subsequent magma mingling or mixing is a process that has been recognised since the late seventies as resulting in explosive eruptions. Detailed reconstruction and assessment of the mixing process caused by such intrusion is now possible because of the exceptional time-sequence sample suite available from the tephra fallout of the 2010 summit eruption at Eyjafjallajökull volcano in South Iceland. Fallout from 14 to 19 April contains three glass types of basaltic, intermediate, and silicic compositions recording rapid magma mingling without homogenisation, involving evolved FeTi-basalt and silicic melt with composition identical to that produced by the 1821–1823 AD Eyjafjallajökull summit eruption. The time-dependent change in the magma composition suggests a binary mixing process with changing end-member compositions and proportions. Beginning of May, a new injection of primitive basalt was recorded by deep seismicity, appearance of Mg-rich olivine phenocrysts together with high sulphur dioxide output and presence of sulphide crystals. Thus, the composition of the basaltic injection became more magnesian and hotter with time provoking changes in the silicic mixing end-member from pre-existing melt to the solid carapace of the magma chamber. Finally, decreasing proportions of the mafic end-member with time in the erupted mixed-magma demonstrate that injections of Mg-rich basalt was the motor of the 2010 Eyjafjallajökull explosive eruption, and that its decreasing inflow terminated the eruption. Significant quantity of silicic magma is thus still present in the interior of the volcano. Our results show that detailed sampling during the entire eruption was essential for deciphering the complex magmatic processes at play, i.e. the dynamics of the magma mingling and mixing. Finally, the rapid compositional changes in the eruptive products suggest that magma mingling occurs on a timescale of a few hours to days whereas the interval between the first detected magma injection and eruption was several months.
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Vestergaard, Rikke, Gro Birkefeldt Møller Pedersen et Christian Tegner. « The 1845–46 and 1766–68 eruptions at Hekla volcano : new lava volume estimates, historical accounts and emplacement dynamics ». JOKULL 70 (8 avril 2021) : 35–56. http://dx.doi.org/10.33799/jokull2020.70.035.

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We use new remote sensing data, historical reports, petrology and estimates of viscosity based on geochemical data to illuminate the lava emplacement flow-lines and vent structure changes of the summit ridge of Hekla during the large eruptions of 1845–46 and 1766–68. Based on the planimetric method we estimate the bulk volumes of these eruptions close to 0.4 km3 and 0.7 km3, respectively. However, comparison with volume estimates from the well-recorded 1947–48 eruption, indicates that the planimetric method appears to underestimate the lava bulk volumes by 40–60%. Hence, the true bulk volumes are more likely 0.5–0.6 km3 and 1.0–1.2 km3, respectively. Estimated melt viscosity averages for the 1766–68 eruption amount to 2.5 x10**2 Pa s (pre-eruptive) and 2.5x10**3 Pa s (degassed), and for the 1845–46 eruption 2.2x10**2 Pa s (pre-eruptive) and 1.9x10**3 Pa s (degassed). Pre-eruptive magmas are about one order of magnitude more fluid than degassed magmas. In the 1845–46 and 1947–48 eruptions, SiO2 decreased from 58–57 to 55–54 wt% agreeing with a conventional model that Hekla erupts from a large, layered magma chamber with the most evolved (silica-rich) magmas at the top. In contrast, the lava-flows from 1766–68 reveal a more complicated SiO2 trend. The lava fields emplaced in 1766 to the south have SiO2 values 54.9–56.5%, while the Hringlandahraun lava-flow that erupted from younger vents on the NE end of the Hekla ridge in March 1767 has higher SiO2 of 57.8%. This shows that the layered magma chamber model is not suitable for all lava-flows emplaced during Hekla eruptions.
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8

Utkin, I. S., O. E. Mel’nik, A. A. Afanas’ev et Yu D. Tsvetkova. « Effect of Quartz Deposition on the Dynamics of Magma Chamber Degassing ». Moscow University Mechanics Bulletin 73, no 6 (novembre 2018) : 129–34. http://dx.doi.org/10.3103/s0027133018060018.

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9

Mollo, Silvio, Flavio Di Stefano et Francesca Forni. « Editorial for the Special Issue “Mineral Textural and Compositional Variations as a Tool for Understanding Magmatic Processes” ». Minerals 11, no 2 (21 janvier 2021) : 102. http://dx.doi.org/10.3390/min11020102.

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This Special Issue of Minerals collects seven different scientific contributions highlighting how magma chamber processes and eruption dynamics studied either in the laboratory or in nature may ultimately control the evolutionary histories and geochemical complexities of igneous rocks [...]
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10

Marsh, Bruce D. « Solidification fronts and magmatic evolution ». Mineralogical Magazine 60, no 398 (février 1996) : 5–40. http://dx.doi.org/10.1180/minmag.1996.060.398.03.

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AbstractFrom G. F. Becker's and L. V. Pirsson's early enunciations linking the dynamics of magma chambers to the rock records of sills and plutons to this day, two features stand at the centre of nearly every magmatic process: solidification fronts and phenocrysts. The structure and behaviour of the envisioned solidification front, however, has been mostly that akin to non-silicate, non-multiply-saturated systems, which has led to confusion in appreciating its role in magmatic evolution. The common habit of intruding magmas to carry significant amounts of phenocrysts, which can lead to efficient fractionation, layering, and interstitial melt flow within extensive mush piles, when coupled with solidification fronts, allows a broad understanding of the processes leading to the rock records of sills and lava lakes. These same processes are fundamental to understanding all magmas.The spatial manifestation of the liquidus and solidus is the Solidification Front (SF); all magmas, stationary or in transit, are encased by SFs. In the ideal case of an initially crystal-free, cooling magma, crystallinity increases from nucleation on the leading liquidus edge to a holocrystalline rock at the trailing solidus. The package of SF isotherms advances inward, thickening with time and, depending on location — roof, floor, or walls — and the initial crystallinity of the magma, is instrumental in controlling magmatic evolution. Bimodal volcanism as well as much of the structure of the oceanic crust may arise from the behaviour of SFs.In mafic magmas, somewhere near a crystallinity (N) of 55% (vol), depending on the phase assemblage, the SF changes from a viscous fluid (suspension (0<N<25) and mush (25<N<55%)) to an elastic crystalline network (rigid crust (55<N<100%)) of some strength containing interstitial residual melt. With thickening of the roofward SF of some mafic magmas, the weight of the leading, viscous portion repeatedly tears the crust near N ∼ 55–60%, efficiently segregating the local residual melt into zones of interdigitating silicic lenses. This is SF instability (SFI), a process of possible importance in continental crust initiation and evolution, in producing silicic segregations in oceanic crust, and in recording the inability of the viscous part of the upper SF ever to detach wholly in typical (<∼ 1 km) sheet-like magmas. These granophyric and pegmatitic segregations, individually reaching 1–2 m in thickness and 30–50 m in length, form thick (∼ 50–75 m) zones that can be misconstrued as sandwich horizons where the last liquids might have accumulated. In effectively splitting the magma chemically and spatially, SFI is, in essence, a form of chaos (i.e. silicic chaos).Differentiation of initially crystal-free, stationary magmas is limited to processes occurring within SFs, which operate in competition with the rate of inward advancement of solidification. Local processes operating on characteristic time scales longer than the time for the SF to advance a distance equal to its own thickness are suppressed. Enormous increases in viscosity outward within the viscous, leading portion of the SF efficiently partition the distribution of melt accessible to eruption. Eruptible melts lie essentially inward of the SF and are thus severely restricted in silica enrichment. The silica-enriched SFI melts are thus generally inaccessible to collection and eviction unless the host SF is reprocessed or “burned back” through, respectively, later regional magmatism or massive, late-stage re-injection. And because of large viscosity contrasts between SFI melts and host basalts, once freed, SFI melts are literally impossible to homogenize back into the system and may collect and compact against the roof to form large silicic masses. Unusually voluminous, bulbous masses of silicic granophyre present along, and sometimes warping, the roofs of large diabase sills may reflect collections of remobilized blobs of SFI melts. These bulbous masses may be later added to the continental crust through solid state creep.In sheets made of phenocryst-rich, singly saturated magma, most phenocrysts are able through settling or floating to avoid capture by the advancing SFs. Significant differentiation is possible through extensive settling of initial phenocrysts and upward leakage of interstitial residual melt from the associated cumulate pile, which over-thickens the lower SF, greatly tipping the competitive edge against suppression of melt leakage by advancing solidification. Dense interstitial melts may similarly drain from roofward cumulates of light phenocrysts. The variation in crystal size and modal abundance in these cumulate piles are intimate records of prior crystallization, transport, and filling.Magmas in transit erode SFs and thoroughly charge the magma with crystals, facilitating fractionation and differentiation, especially if the body occasionally comes to rest. The key to protracted differentiation through fractional crystallization is not crystallization in stationary, closed chambers, but the repeated transport and chambering of magma or the periodic resupply to chambers of phenocryst-rich magma. This is punctuated differentiation, which may be the general case. Close corollaries are that thick, closed sheets of initially crystal-free, multiply-saturated magma undergo precious little overall differentiation, and that deciphering the sequence and crystallinity, including in transit phenocryst entrainment, growth, and sorting, of the filling events is central to unravelling intrusive history.Variations in temperature, whether on phase diagrams or in actual magmas, are intrinsically linked to commensurate variations in space and time in magmatic systems. The spectrum of all physical and chemical processes associated with magma is accordingly strongly partitioned in space and time.The idea of a magma chamber as a vat of low crystallinity melt crystallizing everywhere within and differentiating through crystal settling is unrealistic. A magma chamber formed of any number of crystal-laden inputs, encased by inward-propagating, dynamic solidification fronts, and where significant differentiation is tied to the dynamics of late-stage, interstitial melt within extensive mush piles is more in accord with the rock record.
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11

Calanchi, Natale, Rosanna De Rosa, Roberto Mazzuoli, Pierluigi Rossi, Roberto Santacroce et Guido Ventura. « Silicic magma entering a basaltic magma chamber : eruptive dynamics and magma mixing — an example from Salina (Aeolian islands, Southern Tyrrhenian Sea) ». Bulletin of Volcanology 55, no 7 (septembre 1993) : 504–22. http://dx.doi.org/10.1007/bf00304593.

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12

Cattell, A. C. « The Skye Main Lava Series : liquid density and the absence of basaltic hawaiites ». Geological Magazine 126, no 6 (novembre 1989) : 681–84. http://dx.doi.org/10.1017/s001675680000697x.

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AbstractBasaltic hawaiite lavas are virtually absent in the Eocene Skye Main Lava Series, in contrast to relatively abundant basalts and hawaiites. Fractional crystallization from basalt to basaltic hawaiite involves extraction of a large proportion of plagioclase, and liquid densities thereby increase. From basaltic hawaiite to hawaiite titanomagnetite is a significant fractionating phase, and liquid densities decline. The coincidence between a gap in erupted compositions and a density maximum implies that liquid density exerted a strong control on ‘eruptibility’ of magmas; basaltic hawaiites were too dense to be erupted. Density maxima occur in basalt suites if plagioclase fractionates before Fe–Ti oxides, and may explain compositional gaps in erupted magmas. Compositional gaps are not the inevitable result of density maxima; the density of the rock column above, and the fluid dynamics within, the magma chamber where differentiation occurs are also critical factors.
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13

Bain, A. A., A. M. Jellinek et R. A. Wiebe. « Quantitative field constraints on the dynamics of silicic magma chamber rejuvenation and overturn ». Contributions to Mineralogy and Petrology 165, no 6 (24 février 2013) : 1275–94. http://dx.doi.org/10.1007/s00410-013-0858-5.

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14

Holness, Marian B., Michael J. Stock et Dennis Geist. « Magma chambers versus mush zones : constraining the architecture of sub-volcanic plumbing systems from microstructural analysis of crystalline enclaves ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 377, no 2139 (7 janvier 2019) : 20180006. http://dx.doi.org/10.1098/rsta.2018.0006.

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There are clear microstructural differences between mafic plutonic rocks that formed in a dynamic liquid-rich environment, in which crystals can be moved and re-arranged by magmatic currents, and those in which crystal nucleation and growth are essentially in situ and static. Crystalline enclaves, derived from deep crustal mushy zones and erupted in many volcanic settings, afford a unique opportunity to use the understanding of microstructural development, established from the study of intrusive plutons, to place constraints on the architecture of sub-volcanic systems. Here, we review the relevant microstructural literature, before applying these techniques to interrogate the crystallization environments of enclaves from the Kameni Islands of Santorini and Rábida Volcano in the Galápagos. Crystals in samples of deep-sourced material from both case studies preserve evidence of at least some time spent in a liquid-rich environment. The Kameni enclaves appear to record an early stage of crystallization during which crystals were free to move, with the bulk of crystallization occurring in a static, mushy environment. By contrast, the Rábida enclaves were sourced from an environment in which hydrodynamic sorting and re-arrangement by magmatic currents were common, consistent with a liquid-rich magma chamber. While presently active volcanoes are thought to be underlain by extensive regions rich in crystal mush, these examples preserve robust evidence for the presence of liquid-rich magma chambers in the geological record. This article is part of the Theo Murphy meeting issue ‘Magma reservoir architecture and dynamics'.
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Yosifov, Dimcho. « Magma chamber structures in the East Rhodopes – geophysical characteristic and metallogenic significimce ». Geologica Balcanica 21, no 6 (30 décembre 1991) : 91–106. http://dx.doi.org/10.52321/geolbalc.21.6.91.

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Chamber structures of Paleogene magmatism are a characteristic element of the structure or collisional depressions in the East Rhodopes. The following larger chamber structures are distinguished as circular heterogeneities of a 'different' type and class in the geophysical fields: Borovitsa, Zvezdel-Krumovgrad, Madzharovo and Lozen. Except for the Zvezdel-Krumovgrad structure the others coincide, in their larger part, with gravitation minima or occupy parts of them like Madzharovo caldera. In the magnetic field they are an ensemble of local anomalies, circular in shape and of different polarlties. In accord with the magnetic field morphology, the Zveztlel-Krumovgrad siructure consists of two partially overlapping chamber structures. Besides that, within their range sharply enhanced concentrations of potassium-40 – have been established. The petrophysical analysis and interpretation of geophysical fields show that the chamber structures lie in tectonic nodes - areas of crossing of depth magma-conduit faults. They are characterized by enhanced endogenous activity – high tectonic dynamics, intensive magmatic hydrothermal metasomatic activity. Mineralization often develops against this background. Lead-zinc deposits and ore fields determining the metallogenic nature of the East Rhodopes are directly connected with the chamber structures considered above. Geophysical data show that certain industrial deposits practically lie within the area of intermediate magmatites and even in the immediate proximity of their largest centres. All this corroborates the concept about the lead-zinc mineralization most probably being in a paragenetic relation with intermediate Upper Eocene and Oligocene collision magmatism.
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Paterson, Scott, Valbone Memeti, Roland Mundil et Jiří Žák. « Repeated, multiscale, magmatic erosion and recycling in an upper-crustal pluton : Implications for magma chamber dynamics and magma volume estimates ». American Mineralogist 101, no 10 (octobre 2016) : 2176–98. http://dx.doi.org/10.2138/am-2016-5576.

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17

Lucci, Federico, Gerardo Carrasco-Núñez, Federico Rossetti, Thomas Theye, John Charles White, Stefano Urbani, Hossein Azizi, Yoshihiro Asahara et Guido Giordano. « Anatomy of the magmatic plumbing system of Los Humeros Caldera (Mexico) : implications for geothermal systems ». Solid Earth 11, no 1 (23 janvier 2020) : 125–59. http://dx.doi.org/10.5194/se-11-125-2020.

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Abstract. Understanding the anatomy of magma plumbing systems of active volcanoes is essential not only for unraveling magma dynamics and eruptive behaviors but also to define the geometry, depth, and temperature of the heat sources for geothermal exploration. The Pleistocene–Holocene Los Humeros volcanic complex is part of the eastern Trans-Mexican Volcanic Belt (central Mexico), and it constitutes one of the most important exploited geothermal fields in Mexico with ca. 90 MW of produced electricity. With the aim to decipher the anatomy (geometry and structure) of the magmatic plumbing system feeding the geothermal field at Los Humeros, we carried out a field-based petrological and thermobarometric study of the exposed Holocene lavas. Textural analysis, whole-rock major-element data, and mineral chemistry are integrated with a suite of mineral-liquid thermobarometric models. Our results support a scenario characterized by a heterogeneous multilayered system, comprising a deep (depth of ca. 30 km) basaltic reservoir feeding progressively shallower and smaller discrete magma stagnation layers and batches, up to shallow-crust conditions (depth of ca. 3 km). The evolution of melts in the feeding system is mainly controlled by differentiation processes through fractional crystallization (plagioclase + clinopyroxene + olivine + spinel). We demonstrate the inadequacy of the existing conceptual models, where a single voluminous melt-controlled magma chamber (or “Standard Model”) at shallow depths was proposed for the magmatic plumbing system at Los Humeros. We instead propose a magmatic plumbing system made of multiple, more or less interconnected, magma transport and storage layers within the crust, feeding small (ephemeral) magma chambers at shallow-crustal conditions. This revised scenario provides a new configuration of the heat source feeding the geothermal reservoir at Los Humeros, and it should be taken into account to drive future exploration and exploitation strategies.
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Bachmann, O., et G. W. Bergantz. « Deciphering Magma Chamber Dynamics from Styles of Compositional Zoning in Large Silicic Ash Flow Sheets ». Reviews in Mineralogy and Geochemistry 69, no 1 (1 janvier 2008) : 651–74. http://dx.doi.org/10.2138/rmg.2008.69.17.

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Pearce, T. H., M. P. Griffin et A. M. Kolisnik. « Magmatic crystal stratigraphy and constraints on magma chamber dynamics : Laser interference results on individual phenocrysts ». Journal of Geophysical Research : Solid Earth 92, B13 (10 décembre 1987) : 13745–52. http://dx.doi.org/10.1029/jb092ib13p13745.

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Gutiérrez, Francisco, et Miguel A. Parada. « Numerical Modeling of Time-dependent Fluid Dynamics and Differentiation of a Shallow Basaltic Magma Chamber ». Journal of Petrology 51, no 3 (8 février 2010) : 731–62. http://dx.doi.org/10.1093/petrology/egp101.

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Agangi, Andrea, Jocelyn McPhie et Vadim S. Kamenetsky. « Magma chamber dynamics in a silicic LIP revealed by quartz : The Mesoproterozoic Gawler Range Volcanics ». Lithos 126, no 1-2 (septembre 2011) : 68–83. http://dx.doi.org/10.1016/j.lithos.2011.06.005.

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Aulinas, M., L. Civetta, M. A. Di Vito, G. Orsi, D. Gimeno et J. L. Férnandez-Turiel. « The “Pomici di mercato” Plinian eruption of Somma-Vesuvius : magma chamber processes and eruption dynamics ». Bulletin of Volcanology 70, no 7 (20 novembre 2007) : 825–40. http://dx.doi.org/10.1007/s00445-007-0172-z.

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Ayub, Syahrial, Muhammad Zuhdi et Muhammad Taufik. « PARAMETER-PARAMETER FISIKA UNTUK MENGUNGKAP STRUKTUR STATIS BAWAH PERMUKAAN GUNUNGAPI ». ORBITA : Jurnal Kajian, Inovasi dan Aplikasi Pendidikan Fisika 7, no 1 (9 mai 2021) : 181. http://dx.doi.org/10.31764/orbita.v7i1.4358.

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ABSTRAKParameter-parameter fisika gunungapi diungkap dengan metode geofisika. Survei kakas gravitasi dan magnetik yang menghasilkan anomali positive bagi medan gravitasi dan magnetiknya, mengungkap struktur statis bawah permukaannya. Analisis tremor volkanik mengungkap dinamika internalnya. Gerakan-gerakan (aliran) fluida magma di dalam gunungapi menjadi sumber getar yang memancarkan gelombang seismik yang di sebut tremor volkanik. Lokasi, migrasi, daya pancar, bentuk geometri sistem pipa-kantong magma, periodisasi, model matematis dan sebagainya. Gempa volkanik yang disebabkan aktivitas magma dapat dijadikan indikator. Hasil pengeplotan posisi hiposenter dan episenter terhadap gempa volkanik yang terjadi, juga dapat mengungkap struktur statis bawah permukaan gunungapi. Kata Kunci : parameter-parameter fisika gunungapi; struktur statis bawah permukaanbawah permukaan ABSTRACTUsing methods of geophysics, physical parameters of volcano are described. Gravity and magnetic surveys yield positive anomaly on their fields, which can be interpreted as an accumulated material beneath the surface with certain values of its mass density and magnetic susceptibility. Analysis of volcanic tremor at the volcano to the knowledge of its internal dynamics. Fluid magma movements inside a volcano acts as source of vibrations which radiate sesmic wave called volcanic tremor. Location, migration, radiation power, geometry of magma chamber-pipe system, periodicities, mathematical models, etc. Volcanic earthquakes caused by magma activity can also be used as indicators. The results of the hypocenter and epicenter position of the volcanic earthquake that occurred, can also reveal the subsurface static structure of the volcano. Keywords : physical parameters;subsurface static structure
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Chalokwu, Christopher I., Alexei A. Ariskin et Evgeny V. Koptev-Dvornikov. « Magma dynamics at the base of an evolving mafic magma chamber : Incompatible element evidence from the Partridge River intrusion, Duluth Complex, Minnesota, USA ». Geochimica et Cosmochimica Acta 60, no 24 (décembre 1996) : 4997–5011. http://dx.doi.org/10.1016/s0016-7037(96)00294-3.

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Schwindinger, Kathleen R. « Particle dynamics and aggregation of crystals in a magma chamber with application to Kilauea Iki olivines ». Journal of Volcanology and Geothermal Research 88, no 4 (mars 1999) : 209–38. http://dx.doi.org/10.1016/s0377-0273(99)00009-8.

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Strehlow, K., J. H. Gottsmann et A. C. Rust. « Poroelastic responses of confined aquifers to subsurface strain and their use for volcano monitoring ». Solid Earth 6, no 4 (10 novembre 2015) : 1207–29. http://dx.doi.org/10.5194/se-6-1207-2015.

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Abstract. Well water level changes associated with magmatic unrest can be interpreted as a result of pore pressure changes in the aquifer due to crustal deformation, and so could provide constraints on the subsurface processes causing this strain. We use finite element analysis to demonstrate the response of aquifers to volumetric strain induced by pressurized magma reservoirs. Two different aquifers are invoked – an unconsolidated pyroclastic deposit and a vesicular lava flow – and embedded in an impermeable crust, overlying a magma chamber. The time-dependent, fully coupled models simulate crustal deformation accompanying chamber pressurization and the resulting hydraulic head changes as well as flow through the porous aquifer, i.e. porous flow. The simulated strain leads to centimetres (pyroclastic aquifer) to metres (lava flow aquifer) of hydraulic head changes; both strain and hydraulic head change with time due to substantial porous flow in the hydrological system. Well level changes are particularly sensitive to chamber volume, shape and pressurization strength, followed by aquifer permeability and the phase of the pore fluid. The depths of chamber and aquifer, as well as the aquifer's Young's modulus also have significant influence on the hydraulic head signal. While source characteristics, the distance between chamber and aquifer and the elastic stratigraphy determine the strain field and its partitioning, flow and coupling parameters define how the aquifer responds to this strain and how signals change with time. We find that generic analytical models can fail to capture the complex pre-eruptive subsurface mechanics leading to strain-induced well level changes, due to aquifer pressure changes being sensitive to chamber shape and lithological heterogeneities. In addition, the presence of a pore fluid and its flow have a significant influence on the strain signal in the aquifer and are commonly neglected in analytical models. These findings highlight the need for numerical models for the interpretation of observed well level signals. However, simulated water table changes do indeed mirror volumetric strain, and wells are therefore a valuable addition to monitoring systems that could provide important insights into pre-eruptive dynamics.
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Woods, Andrew W., et Michael J. Stock. « Some fluid mechanical constraints on crystallization and recharge within sills ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 377, no 2139 (7 janvier 2019) : 20180007. http://dx.doi.org/10.1098/rsta.2018.0007.

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The injection of hot magma into a sill can lead to heating and melting of the walls and roof of the reservoir while the injected magma cools and crystallizes. If the crystals are relatively dense, they will try to sediment from the injected magma to form a cumulate layer. In this cumulate layer, the crystals form a porous framework which traps the melt as it is built up. As the melt within the sill continually cools and precipitates dense crystals, there will be a gradual reduction in the density of the remaining silicate liquid. As a result, the melt which is progressively trapped in the pore space of the cumulate layer will become stably stratified in density. Using an idealized model of the fluid mechanical and thermodynamical principles, we explore some of the controls on the thickness and density stratification of cumulate layers following replenishment of a sill-like magma chamber. We show the balance between jamming of the crystal laden melt to form a homogeneous layer and the formation of a stratified cumulate zone depends on the cooling time scale compared to the sedimentation time scale. A key finding is that the composition and stratification in a packed crystal–melt suspension and the associated cumulate layer formed by cooling an intrusion of hot melt injected into the crust may have considerable variability, depending on the properties of the overlying roof melt and the size and hence fall speed of crystals which form in the melt. This article is part of the Theo Murphy meeting issue ‘Magma reservoir architecture and dynamics’.
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Kamiyama, Hiroyuki, Takashi Nakajima et Hikari Kamioka. « Magmatic Stratigraphy of the Tilted Tottabetsu Plutonic Complex, Hokkaido, North Japan : Magma Chamber Dynamics and Pluton Construction ». Journal of Geology 115, no 3 (mai 2007) : 295–314. http://dx.doi.org/10.1086/512754.

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Furnes, H., B. Hellevang, B. Robins et A. Gudmundsson. « Geochemical stratigraphy of the lavas of the Solund-Stavfjord Ophiolite Complex, W. Norway, and magma-chamber dynamics ». Bulletin of Volcanology 65, no 6 (1 août 2003) : 441–57. http://dx.doi.org/10.1007/s00445-002-0271-9.

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Kouli, Maria, et Karen St. Seymour. « Plagioclase microtextures and their importance for magma chamber dynamics – examples from Lesvos, Hellas and Teide, Canary Islands ». Neues Jahrbuch für Mineralogie - Abhandlungen 182, no 3 (1 août 2006) : 323–36. http://dx.doi.org/10.1127/0077-7757/2006/0054.

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31

Tepley, Frank J., et Jon P. Davidson. « Mineral-scale Sr-isotope constraints on magma evolution and chamber dynamics in the Rum layered intrusion, Scotland ». Contributions to Mineralogy and Petrology 145, no 5 (20 juin 2003) : 628–41. http://dx.doi.org/10.1007/s00410-003-0481-y.

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Kogarko, Lia N., et Troels F. D. Nielsen. « Compositional Variation of Eudialyte-Group Minerals from the Lovozero and Ilímaussaq Complexes and on the Origin of Peralkaline Systems ». Minerals 11, no 6 (21 mai 2021) : 548. http://dx.doi.org/10.3390/min11060548.

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The Lovozero complex, Kola peninsula, Russia and the Ilímaussaq complex in Southwest Greenland are the largest known layered peralkaline intrusive complexes. Both host world-class deposits rich in REE and other high-tech elements. Both complexes expose spectacular layering with horizons rich in eudialyte group minerals (EGM). We present a detailed study of the composition and cryptic variations in cumulus EGM from Lovozero and a comparison with EGM from Ilímaussaq to further our understanding of peralkaline magma chambers processes. The geochemical signatures of Lovozero and Ilímaussaq EGM are distinct. In Lovozero EGMs are clearly enriched in Na + K, Mn, Ti, Sr and poorer Fe compared to EGM from Ilímaussaq, whereas the contents of ΣREE + Y and Cl are comparable. Ilímaussaq EGMs are depleted in Sr and Eu, which points to plagioclase fractionation and an olivine basaltic parent. The absence of negative Sr and Eu anomalies suggest a melanephelinitic parent for Lovozero. In Lovozero the cumulus EGMs shows decrease in Fe/Mn, Ti, Nb, Sr, Ba and all HREE up the magmatic layering, while REE + Y and Cl contents increase. In Lovozero EGM spectra show only a weak enrichment in LREE relative to HREE. The data demonstrates a systematic stratigraphic variation in major and trace elements compositions of liquidus EGM in the Eudialyte Complex, the latest and uppermost part of Lovozero. The distribution of elements follows a broadly linear trend. Despite intersample variations, the absence of abrupt changes in the trends suggests continuous crystallization and accumulation in the magma chamber. The crystallization was controlled by elemental distribution between EGM and coexisting melt during gravitational accumulation of crystals and/or mushes in a closed system. A different pattern is noted in the Ilimaussaq Complex. The elemental trends have variable steepness up the magmatic succession especially in the uppermost zones of the Complex. The differences between the two complexes are suggested to be related dynamics of the crystallization and accumulation processes in the magma chambers, such as arrival of new liquidus phases and redistributions by mush melts.
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33

Strehlow, K., J. H. Gottsmann et A. C. Rust. « Poroelastic responses of confined aquifers to subsurface strain changes and their use for volcano monitoring ». Solid Earth Discussions 7, no 2 (9 juin 2015) : 1673–729. http://dx.doi.org/10.5194/sed-7-1673-2015.

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Abstract. Well water level changes associated with magmatic unrest can be interpreted as a result of pore pressure changes in the aquifer due to crustal deformation, and so could provide constraints on the subsurface processes causing this strain. We use Finite Element Analysis to demonstrate the response of aquifers to volumetric strain induced by pressurised magma reservoirs. Two different aquifers are invoked – an unconsolidated pyroclastic deposit and a vesicular lava flow – and embedded in an impermeable crust, overlying a magma chamber. The time-dependent, fully coupled models simulate crustal deformation accompanying chamber pressurisation and the resulting hydraulic head changes as well as porous flow in the aquifer. The simulated deformational strain leads to centimetres (pyroclastic aquifer) to meters (lava flow aquifer) of hydraulic head changes; both strain and hydraulic head change with time due to substantial porous flow in the hydrological system. Well level changes are particularly sensitive to chamber volume and shape, followed by chamber depth and the phase of the pore fluid. The Young's Modulus and permeability of the aquifer, as well as the strength of pressurisation also have significant influence on the hydraulic head signal. While source characteristics, the distance between chamber and aquifer and the elastic stratigraphy determine the strain field and its partitioning, flow and coupling parameters define how the aquifer responds to this strain and how signals change with time. We investigated a period of pre-eruptive head changes recorded at Usu volcano, Japan, where well data were interpreted using an analytical deformation model. We find that generic analytical models can fail to capture the complex pre-eruptive subsurface mechanics leading to well level changes, due to aquifer pressure changes being sensitive to chamber shape and lithological heterogeneities. In addition, the presence of a pore fluid and its flow have a significant influence on the strain signal in the aquifer and are commonly neglected in analytical models. These findings highlight the need for numerical models for the interpretation of observed well level signals. However, simulated water table changes do mirror volumetric strain and wells can therefore serve as comparatively cheap strain meters that could provide important insights into pre-eruptive dynamics.
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Piegari, E., R. Di Maio, R. Carbonari et R. Scandone. « Simulations of the emptying of a closed chamber by magma ascent dynamics based on self-organized fracture mechanisms ». Journal of Volcanology and Geothermal Research 369 (janvier 2019) : 113–20. http://dx.doi.org/10.1016/j.jvolgeores.2018.11.025.

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Casalini, Martina, Riccardo Avanzinelli, Arnd Heumann, Sandro de Vita, Fabio Sansivero, Sandro Conticelli et Simone Tommasini. « Geochemical and radiogenic isotope probes of Ischia volcano, Southern Italy : Constraints on magma chamber dynamics and residence time ». American Mineralogist 102, no 2 (février 2017) : 262–74. http://dx.doi.org/10.2138/am-2017-5724.

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Ariskin, Alexey, Leonid Danyushevsky, Georgy Nikolaev, Evgeny Kislov, Marco Fiorentini, Andrew McNeill, Yuri Kostitsyn, Karsten Goemann, Sandrin T. Feig et Alexey Malyshev. « 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 ». Lithos 302-303 (mars 2018) : 242–62. http://dx.doi.org/10.1016/j.lithos.2018.01.001.

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Elardo, S. M., et C. K. Shearer. « Magma chamber dynamics recorded by oscillatory zoning in pyroxene and olivine phenocrysts in basaltic lunar meteorite Northwest Africa 032 ». American Mineralogist 99, no 2-3 (1 février 2014) : 355–68. http://dx.doi.org/10.2138/am.2014.4552.

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Vachon, Rémi, Mohsen Bazargan, Christoph F. Hieronymus, Erika Ronchin et Bjarne Almqvist. « Crystal rotations and alignment in spatially varying magma flows : 2-D examples of common subvolcanic flow geometries ». Geophysical Journal International 226, no 1 (31 mars 2021) : 709–27. http://dx.doi.org/10.1093/gji/ggab127.

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Summary Elongate inclusions immersed in a viscous fluid generally rotate at a rate that is different from the local angular velocity of the flow. Often, a net alignment of the inclusions develops, and the resulting shape preferred orientation of the particle ensemble can then be used as a strain marker that allows reconstruction of the fluid’s velocity field. Much of the previous work on the dynamics of flow-induced particle rotations has focused on spatially homogeneous flows with large-scale tectonic deformations as the main application. Recently, the theory has been extended to spatially varying flows, such as magma with embedded crystals moving through a volcanic plumbing system. Additionally, an evolution equation has been introduced for the probability density function of crystal orientations. Here, we apply this new theory to a number of simple, 2-D flow geometries commonly encountered in magmatic intrusions, such as flow from a dyke into a reservoir or from a reservoir into a dyke, flow inside an inflating or deflating reservoir, flow in a dyke with a sharp bend, and thermal convection in a magma chamber. The main purpose is to provide a guide for interpreting field observations and for setting up more complex flow models with embedded crystals. As a general rule, we find that a larger aspect ratio of the embedded crystals causes a more coherent alignment of the crystals, while it has only a minor effect on the geometry of the alignment pattern. Due to various perturbations in the crystal rotation equations that are expected in natural systems, we show that the time-periodic behaviour found in idealized systems is probably short-lived in nature, and the crystal alignment is well described by the time-averaged solution. We also confirm some earlier findings. For example, near channel walls, fluid flow often follows the bounding surface and the resulting simple shear flow causes preferred crystal orientations that are approximately parallel to the boundary. Where pure shear deformation dominates, there is a tendency for crystals to orient themselves in the direction of the greatest tensile strain rate. Where flow impinges on a boundary, for example in an inflating magma chamber or as part of a thermal convection pattern, the stretching component of pure shear aligns with the boundary, and the crystals orient themselves in that direction. In the field, this local pattern may be difficult to distinguish from a boundary-parallel simple shear flow. Pure shear also dominates along the walls of a deflating magma chamber and in places where the flow turns away from the reservoir walls, but in these locations, the preferred crystal orientation is perpendicular to the wall. Overall, we find that our calculated patterns of crystal orientations agree well with results from analogue experiments where similar geometries are available.
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Petrova, V. V., et V. A. Rashidov. « Composition and origin of lavas from the Minami-Hiyoshi submarine volcano (Mariana arc) ». Доклады Академии наук 485, no 2 (20 mai 2019) : 198–201. http://dx.doi.org/10.31857/s0869-56524852198-201.

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This work is a link in a series of studies of Late Cenozoic submarine volcanoes of the island arcs in the western part of the Pacific Ocean, representing the first detailed Russian-language description of the material composition of the Minami-Hiyoshi submarine volcano, which is involved in the Hiyoshi volcanic complex (the northern part of the Mariana arc). This study was based on rock material dragged from the volcano during the 5th cruise of the R/V Vulkanolog. New original data on the structure, chemical and mineral compositions, and origin of volcanic lava were obtained. It was shown that all the lava flows studied are genetically linked and originated from the same magma chamber. Structural-petrographic differences in the lava flows are explained by different dynamics in the melt transportation to the surface of the bottom of the ocean.
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Martí, Joan, Silvia Zafrilla, Joan Andújar, María Jiménez-Mejías, Bruno Scaillet, Dario Pedrazzi, Domenico Doronzo et Stephane Scaillet. « Controls of magma chamber zonation on eruption dynamics and deposits stratigraphy : The case of El Palomar fallout succession (Tenerife, Canary Islands) ». Journal of Volcanology and Geothermal Research 399 (juillet 2020) : 106908. http://dx.doi.org/10.1016/j.jvolgeores.2020.106908.

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Gauthier, Pierre-J., et Michel Condomines. « 210Pb–226Ra radioactive disequilibria in recent lavas and radon degassing : inferences on the magma chamber dynamics at Stromboli and Merapi volcanoes ». Earth and Planetary Science Letters 172, no 1-2 (octobre 1999) : 111–26. http://dx.doi.org/10.1016/s0012-821x(99)00195-8.

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Patel, Rahul, Raghav Gadgil et D. Srinivasa Sarma. « Role of dyke geometry in understanding dyke-emplacement mechanisms and magma-chamber dynamics : A critical appraisal from the Chotanagpur Gneissic Complex, India ». Journal of Volcanology and Geothermal Research 418 (octobre 2021) : 107344. http://dx.doi.org/10.1016/j.jvolgeores.2021.107344.

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Tsepelev, I. A., A. T. Ismail-Zadeh et O. E. Melnik. « 3D Numerical Modeling of the Summit Lake Lava Flow, Yellowstone, USA ». Izvestiya, Physics of the Solid Earth 57, no 2 (mars 2021) : 257–65. http://dx.doi.org/10.1134/s1069351321020129.

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Abstract—Volcanic eruptions belong to the extreme events that change the Earth’s landscape and affect global climate and environment. Although special attention is given to super-eruptions, the non-explosive rhyolitic (highly viscous) eruptions and large lava flows are no less important. In this paper, we study an ancient lava flow with a volume of ~50 km3 in the Summit Lake region, ​​Yellowstone, which is one of the best studied large intraplate igneous provinces. We develop three-dimensional (3D) numerical models of isothermal lava flow to analyze the influence of the underlying surface and lava flow viscosity on the advancement and duration of the flow. The modeled dynamics of flow propagation fairly well agrees with the measured values provided that the average angle of inclination of the underlying surface slightly differs from the present-day value (by ~1.3°) presumably due to the pressure change in the magma chamber during the eruption. With the increase in lava viscosity, the flow slows down and its thickness increases leading to a change in the flow morphology.
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Cardoso, Silvana S. S., et Andrew W. Woods. « Mixing by a turbulent plume in a confined stratified region ». Journal of Fluid Mechanics 250 (mai 1993) : 277–305. http://dx.doi.org/10.1017/s0022112093001466.

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An experimental and theoretical study of the mixing produced by a plume rising in a confined stratified environment is presented. As a result of the pre-existing stable stratification, the plume penetrates only part way into the region; at an intermediate level it intrudes laterally forming a horizontal layer. As time evolves, this layer of mixed fluid is observed to increase in thickness. The bottom front advects downward in a way analogous to the first front in the filling box of Baines & Turner (1969), while the lateral spreading of the plume occurs at an ever-increasing level and an ascending top front results. We develop a model of this stratified filling box; the model predicts the rate at which the two fronts advance into the environment.It is found that stratification in the environment, when smooth, has no significant influence on the dynamics of the descending front. We show that the rate of rise of the ascending front is determined by the turbulent mixing occurring at the spreading level. Entrainment of environmental fluid from above into the overshooting plume is significant; as a result, a density interface develops at this level. Asymptotically, the system reaches a state in which a bottom convecting layer, with an almost homogeneous density, deepens in a stratified background. The model proposed for this large-time behaviour is based on the simple energetic formulation that a constant fraction of the kinetic energy supplied by the plume, for mixing across the interface, is converted into potential energy of the convective layer. Our experimental results suggest an efficiency of approximately 50 % for this conversion.We discuss our results in the light of previous studies on turbulent penetrative convection and conclude that the theory developed should be valid for an intermediate range of values of the Richardson number characterizing the dynamic conditions at the interface. The model is applied quantitatively to the process of cooling of a room wherein stratification is relevant. The geological problem of replenishment of a magma chamber by a light input of magma is also analysed.
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Kamacı, Ömer, et Şafak Altunkaynak. « Magma chamber processes and dynamics beneath northwestern Anatolia : Insights from mineral chemistry and crystal size distributions (CSDs) of the Kepsut volcanic complex (NW Turkey) ». Journal of Asian Earth Sciences 181 (septembre 2019) : 103889. http://dx.doi.org/10.1016/j.jseaes.2019.103889.

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Melluso, Leone, Vincenzo Morra, Annamaria Perrotta, Claudio Scarpati et Mariarosaria Adabbo. « The eruption of the Breccia Museo (Campi Flegrei, Italy) : Fractional crystallization processes in a shallow, zoned magma chamber and implications for the eruptive dynamics ». Journal of Volcanology and Geothermal Research 68, no 4 (novembre 1995) : 325–39. http://dx.doi.org/10.1016/0377-0273(95)00020-5.

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47

Wolff, J. A. « Physical properties of carbonatite magmas inferred from molten salt data, and application to extraction patterns from carbonatite–silicate magma chambers ». Geological Magazine 131, no 2 (mars 1994) : 145–53. http://dx.doi.org/10.1017/s0016756800010682.

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AbstractLittle is known about the physical properties of carbonatite magmas, making it difficult to predict dynamic behaviour in carbonatite-bearing magmatic systems. The viscosity of calcium-rich carbonatite magma is approximately estimated from molten salt data to be 0.1 Pa s at 700–800°C, while density is estimated at 2.3−2.5 × 103 kg m−3. The corresponding values for natrocarbonatite are 0.01 Pa s and 2.0−2.1 × 103 kg m−3. It is thus possible for carbonatite to be negatively buoyant with respect to some silicate magmas. The surface tension in air of carbonatite magmas is estimated at 0.25 and 0.21 N m−1 for Ca-carbonatite and natrocarbonatite respectively. Knowledge of the interfacial tension between carbonatite and silicate liquids is critical before the formation and behaviour of silicate–carbonatite emulsions can be properly understood. Interfacial tension is constrained to < 0.09 N m−1 by the application of multiphase drop theory to experimentally-produced textures, and this value receives some support from geological observations. The mechanics of extraction from layered carbonatite-silicate magma chambers are briefly examined using the recommended density and viscosity values and the equations of Blake & Ivey (1986); the degree of eruptive mingling is dependent on which liquid was uppermost in the chamber.
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GINIBRE, CATHERINE, GERHARD WÖRNER et ANDREAS KRONZ. « Structure and Dynamics of the Laacher See Magma Chamber (Eifel, Germany) from Major and Trace Element Zoning in Sanidine : a Cathodoluminescence and Electron Microprobe Study ». Journal of Petrology 45, no 11 (9 septembre 2004) : 2197–223. http://dx.doi.org/10.1093/petrology/egh053.

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Mahood, Gail A., et Paula C. Cornejo. « Evidence for ascent of differentiated liquids in a silicic magma chamber found in a granitic pluton ». Earth and Environmental Science Transactions of the Royal Society of Edinburgh 83, no 1-2 (1992) : 63–69. http://dx.doi.org/10.1017/s0263593300007756.

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ABSTRACTFluid dynamic modelling of crystallising calc-alkalic magma bodies has predicted that differentiated liquids will ascend as boundary layers and that accumulation of these buoyant liquids near chamber roofs will result in compositionally stratified magma chambers. This paper reports physical features in La Gloria Pluton that can be interpreted as trapped ascending differentiated liquids. Leucogranitic layers decimetres thick, which are locally stratified, are trapped beneath overhanging wall contacts. The same felsic magmas were also preserved where they were injected into the wall rocks as dykes and as large sill complexes. These rocks do not represent differentiated magmas produced by crystallisation along the exposed walls because the felsic layers occur at the wall rock contact, not inboard of it. Rather, we speculate that evolved felsic liquids are generated by crystallisation all across the deep levels of chambers and that initial melt segregation occurs by flowage of melt into tension fractures. Melt bodies so formed may be large enough to have significant ascent velocities as diapirs and/or dykes. The other way in which the leucogranite occurrence is at variance with the convective fractionation model is that the ascending liquids did not feed a highly differentiated cap to the chamber, as the composition at the roof, although the most felsic in this vertically and concentrically zoned pluton, is considerably more mafic than the trapped leucogranitic liquids. This suggests that these evolved liquids were usually mixed back into the main body of the chamber. Backmixing may be general in continental-margin calc-alkalic magmatic systems, which, in contrast to those in intracontinental settings, rarely produce volcanic rocks more silicic than rhyodacite. That the highly differentiated liquids are preserved at all at La Gloria is a result of the unusual stepped nature of the contact and the entirely passive mode of emplacement of the pluton, which, in contrast to ballooning in place, does not result in wall zones being “scoured”.
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Sigmarsson, O., I. Vlastelic, R. Andreasen, I. Bindeman, J. L. Devidal, S. Moune, J. K. Keiding, G. Larsen, A. Höskuldsson et Th Thordarson. « Dynamic magma mixing revealed by the 2010 Eyjafjallajökull eruption ». Solid Earth Discussions 3, no 2 (8 juillet 2011) : 591–613. http://dx.doi.org/10.5194/sed-3-591-2011.

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Abstract. Injection of basaltic magmas into silicic crustal holding chambers and subsequent mixing of the two components is a process that has been recognised since the late seventies to have resulted in explosive eruptions. Detailed reconstruction and assessment of the mixing process caused by such intrusion is now possible because of the exceptional time-sequence sample suite available from the tephra fallout of the 2010 summit eruption at Eyjafjallajökull volcano in South Iceland. From 14 to 19 April the tephra contains three glass types of basaltic, intermediate, and silicic compositions recording rapid magma mingling without homogenisation, involving evolved FeTi-basalt and dacite with composition identical to that produced by the 1821–1823 AD Eyjafjallajökull summit eruption. The time-dependent change in the magma composition suggests a binary mixing process with changing end-member compositions and proportions, or dynamic magma mixing. Beginning of May, a new injection of deep-derived basalt was recorded by deep seismicity, appearance of magnesium-rich olivine phenocrysts together with high sulphur output and presence of sulphide crystals. Thus the composition of the basaltic injection became more primitive and hotter with time prowoking changes in the silicic mixing end-member from pre-existing melt to the solid carapace of the magma chamber. Decreasing proportions of the mafic end-member with time in the erupted mixed-magma, demonstrate that injections of Mg-rich basalt was the motor of the 2010 Eyjafjallajökull explosive eruption, and that its decreasing inflow terminated the eruption. Significant quantity of silicic magma is thus still present in the interior of the volcano. Our results show that detailed sampling during the entire eruption was essential for deciphering the complex magmatic processes at play, namely the dynamic magma mixing. Finally, the rapid compositional changes in the eruptive products suggest that magma mingling occurs on a timescale of few hours to days whereas the interval between the first detected magma injection and eruption was several months.
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