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  • 1
    Electronic Resource
    Electronic Resource
    Geologic model of the magmatichydrothermal system of vulcano (Aeolian Islands, Italy) (1998)
    Springer
    Mineralogy and petrology 62 (1998), S. 195-222 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Diese Arbeit stellt ein Modell für das aktive magmatisch-hydrothermale (highsulfidation) System des La Fossa Vulkans vor. Dieses beruht auf mineralogischen und geochemischen Studien der hydrothermalen Umwandlung an der Oberfläche und im Untergrund (geothermale Bohrungen und lithische Klasten von explosiven Eruptionen). Als Energiequelle fungiert das seichte magmatische Zufuhrsystem von La Fossa, das signifikante Entgasung volatiler Phasen (H2O, S, HCl) mit sich bringt. Das Eindringen magmatischer Fluide in die Zufuhrkanäle verursacht Rekristallisation und Metasomatose der vulkanischen und subvulkanischen Gesteine bei hohen Temperaturen. In lateralen Bereichen der vulkanischen Zufuhrkanäle erfahren die magmatischen Fluide eine primäre Neutralisation, wobei neutrale hydrothermale Zonen niedriger Permeabilität entstehen. Während des Aufstiegs an die Oberfläche können die magmatischen Fluide im Grundwasser kondensiert werden, wobei sie saure Lösungen bilden, die wiederum mit den Gesteinen reagieren und zu Hydrothermalalteration führen. Dabei entstehen silizische, fortgeschrittene argillische und intermediäre agillische Umwandlungsfazies. Dies entspricht der zunehmenden Neutralisation extrem saurer Fluide. Hohe Gehalte an Spurenelementen, wie TI und Bi können als zusätzliche Hinweise für magmatischen Fluidtransport gesehen werden, sie treten in der Nähe der HochTemperatur-Fumarolen (bis 500'C) in der silizischen Alterationszone von La Fossa auf.
    Notes: Summary This paper presents a model of the active magmatic-hydrothermal (high-sulfidation) system of La Fossa volcano, based on mineralogical and geochemical studies of hydrothermal alteration on the surface and in the subsoil (geothermal wells and lithic clasts from explosive eruptions). The main engine of this system is represented by the shallow magmatic feeding system of La Fossa, which produces substantial degassing of volatiles (H2O, S, Cl). The introduction of magmatic fluids into the conduit system causes high temperature recrystallisation and metasomatism of the volcanic and sub-volcanic rocks. Lateraly to the volcanic conduits, the magmatic fluids undergo a primary neutralization, forming neutral low permeability hydrothermal zones. During their rise to the surface, the magmatic vapours may condense in groundwater, forming acid solutions that react with rocks to form superficial hydrothermal alteration. Silicic, advanced argillic and intermediate argillic alteration facies develop. This reflects the progressive neutralisation of extremely acid fluids. High contents of trace elements, like TI and Bi, supporting evidence for magmatic fluid transport, were found close to the high temperature fumaroles (up to 500°Q in the silicic alteration zone of La Fossa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01178029
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  • 2
    Electronic Resource
    Electronic Resource
    Assessment of a shallow magmatic system: the 1888–90 eruption, Vulcano Island, Italy (1994)
    Springer
    Bulletin of volcanology 56 (1994), S. 466-486 
    Details
    ISSN: 1432-0819
    Keywords: Key words Magma chambers ; Isotope geochemistry ; Fluid inclusions ; Geochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The magmatic system feeding the last eruption of the volcano La Fossa, Vulcano Island, Italy was studied. The petrogenetic mechanisms controlling the differentiation of erupted rocks were investigated through petrography, mineral chemistry, major, trace and rare earth element and Sr, Nd and Pb isotopic geochemistry. In addition, melt inclusion and fluid inclusion data were collected on both juvenile material and xenolithic partially melted metamorphic clasts to quantify the P–T conditions of the magma chamber feeding the eruption. A regular and continuous chemical zoning has been highlighted: rhyolites are the first erupted products, followed by trachytes and latites, whereas rhyolitic compositions were also found in the upper part of the sequence. The chemical and isotopic composition of the rhyolites indicates that they originated by fractional crystallization from latitic magmas plus the assimilation of crustal material; the trachytes represent hybrid magmas resulting from the mixing of latites and rhyolites, contaminated in the shallow magmatic system. The erupted products, primarily compositionally zoned from latites to rhyolites, are heterogeneous due to syn-eruptive mingling. The occurrence of magma–crust interaction processes, evidenced by isotopic variations (87Sr/86Sr = 0.70474±3 to 0.70511±3;143Nd/144Nd = 0.512550±6 to 0.512614±8;206Pb/204Pb = 19.318–19.489;207Pb/204Pb=15.642–15.782;208Pb/204Pb = 39.175–39.613), is confirmed by the presence of partially melted metamorphic xenoliths, with 87Sr/86Sr = 0.71633±6 to 0.72505±2 and 143Nd/144Nd = 0.51229±7, in rhyolites and trachytes. AFC calculations indicate a few percentage contribution of crustal material to the differentiating magmas. Thermometric measurements on melt inclusions indicate that the crystallization temperatures of the latites and trachytes were in the range of 1050–1100°  C, whereas the temperature of the rhyolites appears to have been around 1000°  C at the time of the eruption. Compositional data on melt inclusions reveal that the magmas involved in the eruption contained about 1–1.5 wt.% dissolved H2O in pre-eruptive conditions. Secondary fluid inclusions found in metamorphic xenoliths give low equilibration pressure data (30–60 MPa), giving the location of the higher portions of the chamber at around 1500–2000 m of depth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004450050056
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  • 3
    Electronic Resource
    Electronic Resource
    Assessment of a shallow magmatic system: the 1888–90 eruption, Vulcano Island, Italy (1994)
    Springer
    Bulletin of volcanology 56 (1994), S. 466-486 
    Details
    ISSN: 1432-0819
    Keywords: Magma chambers ; Isotope geochemistry ; Fluid inclusions ; Geochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The magmatic system feeding the last eruption of the volcano La Fossa, Vulcano Island, Italy was studied. The petrogenetic mechanisms controlling the differentiation of erupted rocks were investigated through petrography, mineral chemistry, major, trace and rare earth element and Sr, Nd and Pb isotopic geochemistry. In addition, melt inclusion and fluid inclusion data were collected on both juvenile material and xenolithic partially melted metamorphic clasts to quantify the P-T conditions of the magma chamber feeding the eruption. A regular and continuous chemical zoning has been highlighted: rhyolites are the first erupted products, followed by trachytes and latites, whereas rhyolitic compositions were also found in the upper part of the sequence. The chemical and isotopic composition of the rhyolites indicates that they originated by fractional crystallization from latitic magmas plus the assimilation of crustal material; the trachytes represent hybrid magmas resulting from the mixing of latites and rhyolites, contaminated in the shallow magmatic system. The erupted products, primarily compositionally zoned from latites to rhyolites, are heterogeneous due to syn-eruptive mingling. The occurrence of magmacrust interaction processes, evidenced by isotopic variations (87Sr/86Sr=0.70474±3 to 0.70511±3; 143Nd/144Nd=0.512550±6 to 0.512614±8; 206Pb/204Pb=19.318–19.489; 207Pb/204Pb=15.642–15.782; 208Pb/204Pb=39.175–39.613), is confirmed by the presence of partially melted metamorphic xenoliths, with 87Sr/86Sr=0.71633±6 to 0.72505±2 and 143Nd/144Nd=0.51229±7, in rhyolites and trachytes. AFC calculations indicate a few percentage contribution of crustal material to the differentiating magmas. Thermometric measurements on melt inclusions indicate that the crystallization temperatures of the latites and trachytes were in the range of 1050–1100° C, whereas the temperature of the rhyolites appears to have been around 1000°C at the time of the eruption. Compositional data on melt inclusions reveal that the magmas involved in the eruption contained about 1–1.5 wt.% dissolved H2O in pre-eruptive conditions. Secondary fluid inclusions found in metamorphic xenoliths give low equilibration pressure data (30–60 MPa), giving the location of the higher portions of the chamber at around 1500–2000 m of depth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00302828
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  • 4
    Electronic Resource
    Electronic Resource
    A study of melt inclusions at Vulcano (Aeolian Islands, Italy): insights on the primitive magmas and on the volcanic feeding system (1998)
    Springer
    Bulletin of volcanology 60 (1998), S. 286-306 
    Details
    ISSN: 1432-0819
    Keywords: Key words Melt inclusions ; Vulcano ; Shoshonitic basalts ; Magmatic differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  This work presents the results of a microthermometric and EPMA-SIMS study of melt inclusions in phenocrysts of rocks of the shoshonitic eruptive complex of Vulcano (Aeolian Islands, Italy). Different primitive magmas related to two different evolutionary series, an older one (50–25 ka) and a younger one (15 ka to 1890 A.D.), were identified as melt inclusions in olivine Fo88–91 crystals. Both are characterized by high Ca/Al ratio and present very similar Rb/Sr, B/Be and patterns of trace elements, with Nb and Ti anomalies typical of a subduction zone. The two basalts present the same temperature of crystallization (1180±20  °C) and similar volatile abundances. The H2O, S and Cl contents are relatively high, whereas magmatic CO2 concentrations are very low, probably due to CO2 loss before low-pressure crystallization and entrapment of melt inclusions. The mineral chemistry of the basaltic assemblages and the high Ca/Al ratio of melt inclusions indicate an origin from a depleted, metasomatized clinopyroxene-rich peridotitic mantle. The younger primitive melt is characterized with respect to the older one by higher K2O and incompatible element abundances, by lower Zr/Nb and La/Nb, and by higher Ba/Rb and LREE enrichment. A different degree of partial melting of the same source can explain the chemical differences between the two magmas. However, some anomalies in Sr, Rb and K contents suggest either a slightly different source for the two magmas or differing extents of crustal contamination. Low-pressure degassing and cooling of the basaltic magmas produce shoshonitic liquids. The melt inclusions indicate evolutionary paths via fractional crystallization, leading to trachytic compositions during the older activity and to rhyolitic compositions during the recent one. The bulk-rock compositions record a more complex history than do the melt inclusions, due to the syneruptive mixing processes commonly affecting the magmas erupted at Vulcano. The composition and temperature data on melt inclusions suggest that in the older period of activity several shallow magmatic reservoirs existed; in the younger one a relatively homogeneous feeding system is active. The shallow magmatic reservoir feeding the recent eruptive activity probably has a vertical configuration, with basaltic magma in the deeper zones and differentiated magmas in shallower, low-volume, dike-like reservoirs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004450050233
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  • 5
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    Chemical and petrographic fingerprinting of volcanic ashes as a tool for high-resolution stratigraphy of the upper Miocene Pisco Formation (Peru) (2018)
    Geological Society of London
    Details
    Publication Date: 2018
    Description: 〈span〉〈div〉Abstract〈/div〉Tephra layers are a unique tool for stratigraphy. Their geologically instantaneous deposition across wide areas makes them a powerful instrument for dating and correlating distant localities. In this paper, we apply tephra fingerprinting for high-resolution stratigraphic purposes in the upper Miocene portion of the Pisco Formation, which crops out along the southern Peruvian coast. The Pisco Formation diatomaceous strata host an important marine vertebrate Fossil-Lagerstätte, whose palaeontological relevance has entailed the necessity of reconstructing a detailed chronostratigraphic framework using 〈sup〉39〈/sup〉Ar–〈sup〉40〈/sup〉Ar dating and tephra correlations. Distal ashes from the Central Andes volcanoes are frequent in the Pisco Formation, but their similar glass composition and mineral assemblage, together with the shallow marine environment limiting tephra preservation, could be unpromising for tephra-based correlations. In this study, tephra layers from measured stratigraphic sections were fingerprinted with a combined petrographic and microanalytical approach, including glass shard morphology and granulometric analyses. Based on the obtained results, we correlated sections several kilometres apart, greatly increasing the chronostratigraphic detail. Major element composition of biotite proved a valuable tool to discriminate the Central Andes metaluminous to peraluminous tephra deposited in the Peruvian forearc basins. This study highlights the applicability of tephra fingerprinting in unfavourable shallow marine environments.〈strong〉Supplementary material:〈/strong〉 A compilation of tephra data (field observations, granulometric parameters, petrographic data and EPMA analyses on glass), EPMA single analyses on glass and biotite, 〈sup〉39〈/sup〉Ar–〈sup〉40〈/sup〉Ar step heating results, measured stratigraphic logs and biotite chemical diagrams are available at 〈a href="https://doi.org/10.6084/m9.figshare.c.4201484"〉https://doi.org/10.6084/m9.figshare.c.4201484〈/a〉〈/span〉
    Print ISSN: 0370-291X
    Topics: Geosciences
    Published by Geological Society of London
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  • 6
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    Inside baleen: Exceptional microstructure preservation in a late Miocene whale skeleton from Peru (2016)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publication Date: 2016-10-08
    Description: Exceptionally preserved delicate baleen microstructures have been found in association with the skeleton of a late Miocene balaenopteroid whale in a dolomite concretion of the Pisco Formation, Peru. Microanalytical data (scanning electron microscopy, electron probe microanalysis, X-ray diffraction) on fossil baleen are provided and the results are discussed in terms of their taphonomic and paleoecological implications. Baleen fossilization modes at this site include molding of plates and tubules, and phosphatization. A rapid formation of the concretion was fundamental for fossilization. We suggest that the whale foundered in a soft sediment chemically favorable to rapid dolomite precipitation, allowing the preservation of delicate structures. Morphometric considerations on the baleen plates and bristles coupled with the reconstructed calcification of the latter permit speculation on the trophic preferences of this balaenopteroid whale: the densely spaced plates and the fine and calcified bristles provide evidence for feeding on small-sized plankton, as does the modern sei whale.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 7
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    Inside baleen: Exceptional microstructure preservation in a late Miocene whale skeleton from Peru (2016)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publication Date: 2016-10-14
    Description: Exceptionally preserved delicate baleen microstructures have been found in association with the skeleton of a late Miocene balaenopteroid whale in a dolomite concretion of the Pisco Formation, Peru. Microanalytical data (scanning electron microscopy, electron probe microanalysis, X-ray diffraction) on fossil baleen are provided and the results are discussed in terms of their taphonomic and paleoecological implications. Baleen fossilization modes at this site include molding of plates and tubules, and phosphatization. A rapid formation of the concretion was fundamental for fossilization. We suggest that the whale foundered in a soft sediment chemically favorable to rapid dolomite precipitation, allowing the preservation of delicate structures. Morphometric considerations on the baleen plates and bristles coupled with the reconstructed calcification of the latter permit speculation on the trophic preferences of this balaenopteroid whale: the densely spaced plates and the fine and calcified bristles provide evidence for feeding on small-sized plankton, as does the modern sei whale.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 8
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    Allostratigraphy and paleontology of the lower Miocene Chilcatay Formation in the Zamaca area, East Pisco basin, southern Peru (2019)
    Taylor & Francis
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    Publication Date: 2019-05-05
    Electronic ISSN: 1744-5647
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Taylor & Francis
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  • 9
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    Facies analysis, stratigraphy and marine vertebrate assemblage of the lower Miocene Chilcatay Formation at Ullujaya (Pisco basin, Peru) (2018)
    Taylor & Francis
    Details
    Publication Date: 2018-04-10
    Electronic ISSN: 1744-5647
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Taylor & Francis
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  • 10
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    Stratigraphic framework of the late Miocene to Pliocene Pisco Formation at Cerro Colorado (Ica Desert, Peru) (2015)
    Taylor & Francis
    Details
    Publication Date: 2015-05-26
    Electronic ISSN: 1744-5647
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Taylor & Francis
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