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  • 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology  (6)
  • Springer Verlag Germany  (5)
  • MDPI Publishing
  • Nature Publishing Group
Collection
Keywords
Publisher
Years
  • 1
    facet.materialart.
    Unknown
    Origin of crystal-poor, differentiated magmas: insights from thermal gradient experiments (2012)
    Springer Verlag Germany
    Details
    Publication Date: 2017-04-03
    Description: Crystal-poor, differentiated magmas are com- monly erupted from shallow, thermally zoned magma chambers. In order to constrain the origin of these magmas, we have experimentally investigated crystallization, differentiation and crystal-melt separation in presence of a thermal gradient. Experiments have been designed taking advantage of the innate temperature gradient of the piston cylinder apparatus and carried out on a phonolitic system at 0.3 GPa and temperature ranging from 1,050 to 800 C. Crystallization degree and melt composition in experi- mental products vary as a function of the temperature gradient. In particular, melt composition differentiates from tephri-phonolite (starting material) to phonolite moving from the hotter, glassy zone (T B 1,050 C) towards the cooler, heterogeneously crystallized zone (T B 900 C) of the charge. The heterogeneously crystal- lized zone is made up of: (1) a crystal-rich, mushy region (crystallinity [30 vol%), (2) a rigid crystal framework (crystallinity B80 vol%) and (3) glassy belts of phonolitic glass at the top. Thermal gradient experiments picture crystallization, differentiation and crystal-melt separation processes occurring in a thermally zoned environment and reveal that relatively large volumes of crystal-poor melt (glassy belts) can originate as a consequence of the instability and collapse of the rigid crystal framework. Analogously, in thermally zoned magma chambers, the development and collapse of a solidification front may represent the controlling mechanism originating large volumes of crystal-poor, differentiated magmas.
    Description: Sapienza Universita` di Roma,Istituto Nazionale di Geofisica e Vulcanologia.
    Description: Published
    Description: 49-65
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: restricted
    Keywords: Explosive eruptions ; Crystal-poor magma ; Thermal gradient ; Solidification front ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    The control of cooling rate on titanomagnetite composition: implications for a geospeedometry model applicable to alkaline rocks from Mt. Etna volcano (2012)
    Springer Verlag Germany
    Details
    Publication Date: 2017-04-04
    Description: In this study, we have investigated the control of cooling rate on the composition of titanomagnetite formed from a trachybasaltic melt. Results show that disequilibrium growth conditions exert a primary control on the abundance, texture, and composition of the crystals. As the degree of cooling is increased, titanomagnetites show immature textures and are progressively enriched in Al ? Mg and depleted in Ti. Thus, early-formed titanomagnetite nuclei do not re-equilibrate with the melt over faster cooling rates; instead, their compositions are far from equilibrium. On the basis of the different intra-crystal redistribution rates for Ti, Al, and Mg, we have calibrated a geospeedometer that represents the first quantitative description of the effect of cooling rate on titanomagnetite composition. This model was tested using the compositions of titanomagnetites in lava and dike samples from Mt. Etna volcano whose crystallization conditions resemble those of our experiments. Cooling rates calculated for lava samples are comparable with those measured in several volcanic complexes. At Mt. Etna, compositional variations of titanomagnetite grains from the innermost to the outermost part of a dike testify to progressively higher degrees of cooling, in agreement with numerical simulations of thermal gradients in and around magmatic intrusions.
    Description: Published
    Description: 457-475
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: restricted
    Keywords: Titanomagnetite; cooling rate ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    The partitioning of trace elements between clinopyroxene and trachybasaltic melt during rapid cooling and crystal growth (2014)
    Springer Verlag Germany
    Details
    Publication Date: 2017-04-04
    Description: We present the variation in trace element partition coefficients measured at the interface between rapidly cooled clinopyroxene crystals and co-existing melts. Results indicate that, as the cooling rate is increased, clinopyroxene crystals are progressively depleted in Si, Ca and Mg counterbalanced by enrichments in Al (mainly tetrahedral Aliv), Na and Ti. Partition coefficients (Ds) for rare earth elements (REE), high field strength elements (HFSE) and transition elements (TE) increase with increasing cooling rate, in response to clinopyroxene compositional variations. The entry of REE into the M2 site is facilitated by a coupled substitution where either Na substitutes for Ca on the M2 site or Aliv substitutes for Si in the tetrahedral site. The latter substitution reflects an increased ease of locally balancing the excess charge at M2 as the number of surrounding Aliv atoms increases. Due to the lower concentration of Ca in rapidly cooled clinopyroxenes, divalent large ion lithophile elements (LILE) on M2 decrease at the expense of monovalent cations. Conversely, higher concentrations of HFSE and TE on the M1 site are facilitated as the average charge on this site increases with the replacement of divalent-charged cations by Alvi. Although crystallization kinetics modify clinopyroxene composition, deviations from equilibrium partitioning are insufficient to change the tendency of a trace element to be compatible or incompatible. Consequently, there are regular relationships between ionic radius, valence of the trace element and D. At both equilibrium and cooling rate conditions, Ds for isovalent cations define parabola-like curves when plotted against ionic radius, consistent with the lattice strain model, demonstrating that the partitioning of trace elements is driven by charge balance mechanisms; cation substitution reactions can be treated in terms of the energetics of the various chargeimbalanced configurations.
    Description: Published
    Description: 1633-1654
    Description: 2R. Laboratori sperimentali e analitici
    Description: JCR Journal
    Description: restricted
    Keywords: trace element partitioning ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
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    Rapid differentiation in a sill-like magma reservoir: a case study from the campi flegrei caldera (2012)
    Nature Publishing Group
    Details
    Publication Date: 2017-04-04
    Description: In recent decades, geophysical investigations have detected wide magma reservoirs beneath quiescent calderas. However, the discovery of partially melted horizons inside the crust is not sufficient to put constraints on capability of reservoirs to supply cataclysmic eruptions, which strictly depends on the chemical-physical properties of magmas (composition, viscosity, gas content etc.), and thus on their differentiation histories. In this study, by using geochemical, isotopic and textural records of rocks erupted from the high-risk Campi Flegrei caldera, we show that the alkaline magmas have evolved toward a critical state of explosive behaviour over a time span shorter than the repose time of most volcanic systems and that these magmas have risen rapidly toward the surface. Moreover, similar results on the depth and timescale of magma storage were previously obtained for the neighbouring Somma-Vesuvius volcano. This consistency suggests that there might be a unique long-lived magma pool beneath the whole Neapolitan area.
    Description: Published
    Description: article 712
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: 3.5. Geologia e storia dei vulcani ed evoluzione dei magmi
    Description: 3.6. Fisica del vulcanismo
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: N/A or not JCR
    Description: open
    Keywords: magma ; campi flegrei caldera ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
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    Crystallization and eruption ages of Breccia Museo (Campi Flegrei caldera, Italy) plutonic clasts and their relation to the Campanian ignimbrite (2014)
    Springer Verlag Germany
    Details
    Publication Date: 2017-04-04
    Description: The Campi Flegrei volcanic district (Naples region, Italy) is a 12-km-wide, restless caldera system that has erupted at least six voluminous ignimbrites during the late Pleistocene, including the [300 km3 Campanian ignimbrite (CI) which originated from the largest known volcanic event of the Mediterranean region. The Breccia Museo (BM), a petrologically heterogeneous and stratigraphically complex volcanic deposit extending over 200 km2 in close proximity to Campi Flegrei, has long remained contentious regarding its age and stratigraphic relation to the CI. Here, we present crystallization and eruption ages for BM plutonic ejecta clasts that were determined via uranium decay series and (U–Th)/He dating of zircon, respectively. Despite mineralogical and textural heterogeneity of these syenitic clasts, their U–Th zircon rim crystallization ages are indistinguishable with an average age of 49.7 ± 2.5 ka (2r errors; mean square of weighted deviates MSWD = 1.2; n = 34). A subset of these crystals was used to obtain disequilibrium-corrected (U–Th)/He zircon ages which average 41.7 ± 1.8 ka (probability of fit P = 0.54; n = 15). This age closely overlaps with published CI 40Ar/39Ar eruption ages (40.6 ± 0.1 ka) after recalibration to recently revised flux monitor ages. Concordant eruption ages for BM and CI agree with previous chemostratigraphic and paleomagnetic correlations, suggesting their origin from the same eruption. However, they are at variance with recalibrated 40Ar/39Ar ages which have BM postdate CI by 3 ± 1 ka. BM syenites show similar geochemical and Sr–Nd isotopical features of pre-caldera rocks erupted between 58 and 46 ka, but are distinctive from subsequent calderaforming magmas. Energy-constrained assimilation and fractional crystallization modeling of Nd–Sr isotopic data suggests that pre-caldera magmas formed a carapace of BM-type intrusions in a mid-crust magma chamber (C8 km depth) shielding the younger CI magma from contamination by Hercynian basement wall rocks. An *41–50 ka hiatus in crystallization ages implies rapid solidification of these pre-CI intrusions. This argues against protracted pre-eruptive storage of a large volume of CI magma at shallow crustal levels.
    Description: Published
    Description: 953
    Description: 1V. Storia e struttura dei sistemi vulcanici
    Description: JCR Journal
    Description: restricted
    Keywords: Pleistocene ; Zircon ; Geochronology ; Tephra ; 04. Solid Earth::04.04. Geology::04.04.02. Geochronology ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology ; 04. Solid Earth::04.04. Geology::04.04.07. Rock geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    Clinopyroxene–liquid thermometers and barometers specific to alkaline differentiated magmas (2014)
    Springer Verlag Germany
    Details
    Publication Date: 2022-05-04
    Description: We present new thermometers and barometers based on clinopyroxene–liquid equilibria specific to alkaline differentiated magmas. The new models were calibrated through the regression analyses of experimental datasets obtained by merging phase equilibria experiments from the literature with new experiments performed by using trachytic and phonolitic starting compositions. The regression strategy was twofold: (1) we have tested previous thermometric and barometric equations and recalibrated these models using the new datasets; (2) we have calibrated a new thermometer and a new barometer including only regression parameters that closely describe the compositional variability of the datasets. The new models yield more precise estimates than previous thermometers and barometers when used to predict temperatures and pressures of alkaline differentiated magmas. We have tested the reliability of the new equations by using clinopyroxene–liquid pairs from trachytes and phonolites erupted during major explosive eruptions at the Phlegrean Fields and Mt. Vesuvius (central Italy). The test yielded crystallization conditions comparable to those determined by means of melt and fluid inclusion analyses and phase equilibria studies; this validates the use of the proposed models for precise estimates of crystallization temperatures and pressures in differentiated alkaline magmas. Because these magmas feed some of the most voluminous, explosive, and threatening volcanic eruptions in the world, a better understanding of the environmental conditions of their reservoirs is mandatory and this is now possible with the new models provided here.
    Description: Published
    Description: 1545-1561
    Description: 2R. Laboratori sperimentali e analitici
    Description: JCR Journal
    Description: restricted
    Keywords: Thermometers and barometers ; 04. Solid Earth::04.04. Geology::04.04.05. Mineralogy and petrology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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