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Articles 1 - 12 of 12
Full-Text Articles in Volcanology
Extreme Differentiation Along Multiple Liquid Lines Of Descent In Strongly Peralkaline Magma Series At Pantelleria (Italy), John C. White, Ray Macdonald, Bogusław Bagiński, Katarzyna M. Liszewska
Extreme Differentiation Along Multiple Liquid Lines Of Descent In Strongly Peralkaline Magma Series At Pantelleria (Italy), John C. White, Ray Macdonald, Bogusław Bagiński, Katarzyna M. Liszewska
EKU Faculty and Staff Scholarship
The liquid line of descent from trachyte to pantellerite is controlled primarily by fractional crystallization of alkali feldspar, with whole rock compositions following a fractionation path along the ‘thermal valley’ in the peralkaline haplogranite system Qz-Ab-Or-Ac-Ns and terminating at a minimum on the feldspar-quartz cotectic. Although whole-rock compositions for different pantelleritic suites follow nearly identical paths in a Qz-Ab-Or projection that terminate near the experimental minimum (Qz40.5Or34.5Ab25 at 100 MPa, projected from Ac-Ns), matrix glass from samples with near-minimum compositions record extreme differentiation and form a ‘cotectic delta’ beyond the terminus of the ‘thermal valley’. Although each glass trend shows …
Contrasting Styles Of Inter-Caldera Volcanism In A Peralkaline System: Case Studies From Pantelleria (Sicily Channel, Italy), Pierangelo Romano, John C. White, Silvio G. Rotolo, Nina J. Jordan, Rosolino Cirrincione, Giovanni De Giorgio, Patrizia Fiannacca, Epifanio Vaccaro
Contrasting Styles Of Inter-Caldera Volcanism In A Peralkaline System: Case Studies From Pantelleria (Sicily Channel, Italy), Pierangelo Romano, John C. White, Silvio G. Rotolo, Nina J. Jordan, Rosolino Cirrincione, Giovanni De Giorgio, Patrizia Fiannacca, Epifanio Vaccaro
EKU Faculty and Staff Scholarship
The recent (<190 ka) volcanic history of Pantelleria is characterized by the eruption of nine peralkaline ignimbrites, ranging in composition from comenditic trachyte to comendite to pantellerite. The ~46 ka Green Tuff (GT) was the last of these ignimbrites, which was followed by many effusive and explosive low-volume eruptions of pantellerite from vents within the caldera moat and along the caldera rim. Although recent studies have shed additional light on the age, petrochemistry, and volcanology of the older ignimbrites, there is very little knowledge of magmatism that occurred between these older ignimbrites, primarily due to the very scarce exposures. In this paper, we present new field descriptions and geochemical data for three local peralkaline centers never studied before, two pre-GT and one post-GT, which share a similar setting with respect to the caldera scarps but differ in terms of their age, composition, and eruptive style. These centers include: (i) the older (~125 ka) Giache center (comenditic trachyte), (ii) the ~67 ka Attalora center (comendite, pantellerite), and (iii) the younger (~14 ka) Patite center (pantellerite).
Volcanological Evolution Of Pantelleria Island (Strait Of Sicily) Peralkaline Volcano: A Review, Silvio G. Rotolo, Stéphane Scaillet, Fabio Speranza, John C. White, Rebecca Williams, Nina J. Jordan
Volcanological Evolution Of Pantelleria Island (Strait Of Sicily) Peralkaline Volcano: A Review, Silvio G. Rotolo, Stéphane Scaillet, Fabio Speranza, John C. White, Rebecca Williams, Nina J. Jordan
EKU Faculty and Staff Scholarship
Pantelleria volcano has a particularly intriguing evolutionary history intimately related to the peralkaline composition of its explosively erupted magmas. Due to the stratigraphic complexity, studies over the last two decades have explored either only the pre-Green Tuff ignimbrite volcanism or the post-Green Tuff activity. We here focus on the whole evolutionary history, detailing the achievements since the first pioneering studies, in order to illustrate how the adoption and integration of progressively more accurate methods (40Ar/39Ar, paleomagnetism, petrography, and detailed field study) have provided many important independent answers to unresolved questions. We also discuss rheomorphism, a distinct feature at Pantelleria, at …
Peralkaline Silicic Extrusive Rocks: Magma Genesis, Evolution, Plumbing Systems, And Eruption., Ray Macdonald, John C. White, Harvey E. Belkin
Peralkaline Silicic Extrusive Rocks: Magma Genesis, Evolution, Plumbing Systems, And Eruption., Ray Macdonald, John C. White, Harvey E. Belkin
EKU Faculty and Staff Scholarship
Peralkaline silicic extrusive rocks are an important component of the volcanological record. Here we review several aspects of their formation and evolution, including the tectonic settings in which they occur, their main petrological and geochemical features, the magmatic lineages along which they evolve, and the parameters (T, P, fO2, melt water contents) that control the lineages. Particular attention is paid to the composition of the extraordinary melts formed at the lowest temperatures. Various lines of evidence are presented to explain the silica-gaps in some lineages. The partial melting of continental crust and the role of crustal contamination …
Experimental And Thermodynamic Constraints On Mineral Equilibrium In Pantelleritic Magmas., Pierangelo Romano, Bruno Scaillet, John C. White, Joan Andujar, Ida Di Carlo, Silvio G. Rotolo
Experimental And Thermodynamic Constraints On Mineral Equilibrium In Pantelleritic Magmas., Pierangelo Romano, Bruno Scaillet, John C. White, Joan Andujar, Ida Di Carlo, Silvio G. Rotolo
EKU Faculty and Staff Scholarship
Crystallization experiments on two pantellerites from Pantelleria, Italy, provide new evidence for the relation-ships between mineral phases in pantelleritic rocks as well as the influence of temperature and redox conditionson mineral assemblages. Experiments were performed at 1 kbar with temperature ranging between 750–900°C,andfluid saturation conditions with XH2O (=H2O/H2O+CO2) between 0 and 1. Redox conditions were fixed at, or slightly below, the FMQ buffer. Results show that at temperature of 900 °C pantelleritic magmas are well above the liquidus regardless their water content; we also observed a decrease in liquidus temperature (800°C) with increasingly reducing conditions. Mineral assemblages of the natural …
Geochemical Constraints On Mantle Sources And Basalt Petrogenesis In The Strait Of Sicily Rift Zone (Italy): Insights Into The Importance Of Short Lengthscale Mantle Heterogeneity., John C. White, David A. Neave, Silvio G. Rotolo, Don F. Parker
Geochemical Constraints On Mantle Sources And Basalt Petrogenesis In The Strait Of Sicily Rift Zone (Italy): Insights Into The Importance Of Short Lengthscale Mantle Heterogeneity., John C. White, David A. Neave, Silvio G. Rotolo, Don F. Parker
EKU Faculty and Staff Scholarship
Igneous activity from the late Miocene to historic time (most recently 1891 ce) in the Strait of Sicily has created two islands (Pantelleria and Linosa) and several seamounts. These volcanoes are dominated by transitional (ol+hy-normative) to alkaline (ne-normative) basaltic lavas and scoriae; peralkaline felsic rocks (trachyte-rhyolite) crop out only on Pantelleria. Although most likely erupted through continental crust, basalts demonstrate no evidence of crustal contamination and are geochemically similar to oceanic island basalts (OIB). Despite their isotopic similarities, there are considerable compositional differences with respect to major and trace element geochemistry both between and within the two islands that are …
Anatomy Of The Magmatic Plumbing System Of Los Humeros Caldera (Mexico): Implications For Geothermal Systems., Federico Lucci, Gerardo Carrasco-Nuñez, Federico Rossetti, Thomas Theye, John C. White, Stefano Urbani, Hossein Azzizi, Yosihiro Asahara, Guido Giordano
Anatomy Of The Magmatic Plumbing System Of Los Humeros Caldera (Mexico): Implications For Geothermal Systems., Federico Lucci, Gerardo Carrasco-Nuñez, Federico Rossetti, Thomas Theye, John C. White, Stefano Urbani, Hossein Azzizi, Yosihiro Asahara, Guido Giordano
EKU Faculty and Staff Scholarship
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. 90MWof 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 …
The Leyva Canyon Volcano, Big Bend Ranch State Park, Presidio Co., Texas., John C. White, Kevin M. Urbanczyk, Kelly Watson
The Leyva Canyon Volcano, Big Bend Ranch State Park, Presidio Co., Texas., John C. White, Kevin M. Urbanczyk, Kelly Watson
EKU Faculty and Staff Scholarship
Leyva Canyon volcano is an Oligocene (37.3 to 27.1 Ma) trachyte shield volcano whose eruptive and volcaniclastic deposits of rhyolite and trachyte lavas, ash-flow tuffs, lahars, and associated sedimentary rocks comprise the Leyva Canyon Member of the Rawls Formation. The lavas and tuffs originated from vents located near the present-day "Bofecillos vent" in the central Bofecillos Mountains, approximately 5 km west of the Sauceda Ranger Station in Big Bend Ranch State Park in southernmost Presidio County, Texas. The pyroclastic and volcaniclastic units form the distinctive cliffs and caves at the periphery of the Bofecillos Mountains, with the caves developing in …
Volatiles And Trace Element Contents In Melt Inclusions From The Zoned Green Tuff Ignimbrite (Pantelleria, Sicily): Petrological Inferences., Pierangelo Romano, John C. White, Alessandro Ciulla, Ida Di Carlo, Claudia D'Oriano, Patrizia Landi, Silvio G. Rotolo
Volatiles And Trace Element Contents In Melt Inclusions From The Zoned Green Tuff Ignimbrite (Pantelleria, Sicily): Petrological Inferences., Pierangelo Romano, John C. White, Alessandro Ciulla, Ida Di Carlo, Claudia D'Oriano, Patrizia Landi, Silvio G. Rotolo
EKU Faculty and Staff Scholarship
The island of Pantelleria is one of the best known localities of bimodal mafic-felsic magmatism (alkali basalt and trachyte-pantellerite). Among the felsic rocks, the coexistence in a single eruption of products of both trachyte and pantellerite compositions is limited to few occurrences, the Green Tuff (GT) ignimbrite being one of these. The GT is compositionally zoned from pantellerite (70.1 wt% SiO2, mol Na+K/Al = 1.86, 1871 ppm Zr) at the base to crystal-rich (>30 vol%) comenditic trachyte (63.4 wt% SiO2, mol Na+K/Al = 1.10, 265 ppm Zr) at the top, although the pantellertic compositions dominate the erupted volume. We …
Compositional And Thermodynamic Variability In A Stratified Magma Chamber: Evidence From The Green Tuff Ignimbrite (Pantelleria, Italy)., Katarzyna M. Liszewska, John C. White, Ray Macdonald, Bogusław Bagiński
Compositional And Thermodynamic Variability In A Stratified Magma Chamber: Evidence From The Green Tuff Ignimbrite (Pantelleria, Italy)., Katarzyna M. Liszewska, John C. White, Ray Macdonald, Bogusław Bagiński
EKU Faculty and Staff Scholarship
The Green Tuff Ignimbrite, Pantelleria, is compositionally zoned from pantellerite at the base to comenditic trachyte at the top, the variation apparently representing an inverted vertical zonation in the pre-eruptive reservoir. The main phenocryst assemblages are alkali feldspar + olivine + clinopyroxene + ilmenite + apatite in the trachytes and alkali feldspar + aenigmatite + clinopyroxene + quartz in the rhyolites. Thermodynamic modelling indicates that the temperature range was ~900–700°C, fO2 FMQ –1.5 to FMQ –0.5 (where FMQ is fayalite–magnetite–quartz buffer) and aSiO2 (relative to quartz saturation) 0.74–1.00. Melt water contents ranged from ~1wt % in the trachytes to ~4wt …
Tuhualite In A Peralkaline Rhyolitic Ignimbrite From Pantelleria, Italy, Boguslaw Baginski, Ray Macdonald, John C. White, Lidia Jezak
Tuhualite In A Peralkaline Rhyolitic Ignimbrite From Pantelleria, Italy, Boguslaw Baginski, Ray Macdonald, John C. White, Lidia Jezak
EKU Faculty and Staff Scholarship
An occurrence of the rare mineral tuhualite (NaFe3+Fe2+Si6O15) is reported in a peralkaline rhyolitic ignimbrite from the 11 island of Pantelleria, Italy. The mineral formed during devitrification of glassy fiamme and varies in form from anhedral plates to 12 perfect euhedral in open vesicles. There is significant replacement of Fe2+ by Mn (FMQ in the presence of a 14 hydrous fluid.
Peralkaline Felsic Magmatism At The Nemrut Volcano, Turkey: Impact Of Volcanism On The Evolution Of Lake Van (Anatolia), Ray Macdonald, Mari Sumita, Hans-Ulrich Schmincke, Boguslaw Baginski, John C. White, Slawomir S. Ilnicki
Peralkaline Felsic Magmatism At The Nemrut Volcano, Turkey: Impact Of Volcanism On The Evolution Of Lake Van (Anatolia), Ray Macdonald, Mari Sumita, Hans-Ulrich Schmincke, Boguslaw Baginski, John C. White, Slawomir S. Ilnicki
EKU Faculty and Staff Scholarship
Nemrut volcano, adjacent to Lake Van (Turkey), is one of the most important peralkaline silicic centres in the world, where magmatism for ~570,000 years has been dominated by peralkaline trachytes and rhyolites. Using onshore and Lake Van drill site tephra samples, we document the phenocryst and glass matrix compositions, confirming a complete spectrum from very rare mafic to dominantly silicic magmas. Magma mixing has been common and, along with the multi-lineage nature of the magmas, indicates that Nemrut has been a very open system where, nevertheless, compositionally zoned caps developed during periods of relative eruptive quiescence. Geothermometry suggests that the …