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Philip Kyle - One of the best experts on this subject based on the ideXlab platform.
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Storage and Evolution of Mafic and Intermediate Alkaline Magmas beneath Ross Island, Antarctica
Journal of Petrology, 2016Co-Authors: Kayla Iacovino, Clive Oppenheimer, Bruno Scaillet, Philip KyleAbstract:We present the results of phase equilibrium experiments carried out on Basanite and phonotephrite lavas from Ross Island, Antarctica. Experiments were designed to reproduce the P–T–X–f O 2 conditions of deep and intermediate magma storage and to place constraints on the differentiation of each of the two predominant lava suites on the island, which are thought to be derived from a common parent melt. The Erebus Lineage (EL) consists of lava erupted from the Erebus summit and the Dry Valley Drilling Project (DVDP) lineage is represented by lavas sampled by drill core on Hut Point Peninsula. Experiments were performed in internally heated pressure vessels over a range of temperatures (1000–1150°C) and pressures (200–400 MPa), under oxidized conditions (NNO to NNO + 3, where NNO is the nickel–nickel oxide buffer), with XH2O of the H 2 O–CO 2 mixture added to the experimental capsule varying between zero and unity. The overall mineralogy and mineral compositions of the natural lavas were reproduced, suggesting oxidizing conditions for the deep magma plumbing system, in marked contrast to the reducing conditions (QFM to QFM – 1, where QFM is the quartz–fayalite–magnetite buffer) in the Erebus lava lake. In Basanite, crystallization of spinel is followed by olivine and clinopyroxene; olivine is replaced by kaersutitic amphibole below ∼1050°C at intermediate water contents. In phonotephrite, the liquidus phase is kaersutite except in runs with low water content ( X H 2 O fluid
Kayla Iacovino - One of the best experts on this subject based on the ideXlab platform.
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Storage and Evolution of Mafic and Intermediate Alkaline Magmas beneath Ross Island, Antarctica
Journal of Petrology, 2016Co-Authors: Kayla Iacovino, Clive Oppenheimer, Bruno Scaillet, Philip KyleAbstract:We present the results of phase equilibrium experiments carried out on Basanite and phonotephrite lavas from Ross Island, Antarctica. Experiments were designed to reproduce the P–T–X–f O 2 conditions of deep and intermediate magma storage and to place constraints on the differentiation of each of the two predominant lava suites on the island, which are thought to be derived from a common parent melt. The Erebus Lineage (EL) consists of lava erupted from the Erebus summit and the Dry Valley Drilling Project (DVDP) lineage is represented by lavas sampled by drill core on Hut Point Peninsula. Experiments were performed in internally heated pressure vessels over a range of temperatures (1000–1150°C) and pressures (200–400 MPa), under oxidized conditions (NNO to NNO + 3, where NNO is the nickel–nickel oxide buffer), with XH2O of the H 2 O–CO 2 mixture added to the experimental capsule varying between zero and unity. The overall mineralogy and mineral compositions of the natural lavas were reproduced, suggesting oxidizing conditions for the deep magma plumbing system, in marked contrast to the reducing conditions (QFM to QFM – 1, where QFM is the quartz–fayalite–magnetite buffer) in the Erebus lava lake. In Basanite, crystallization of spinel is followed by olivine and clinopyroxene; olivine is replaced by kaersutitic amphibole below ∼1050°C at intermediate water contents. In phonotephrite, the liquidus phase is kaersutite except in runs with low water content ( X H 2 O fluid
Andreas Klugel - One of the best experts on this subject based on the ideXlab platform.
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Basanite to phonolite differentiation within 1550 1750 yr u th ra isotopic evidence from the a d 1585 eruption on la palma canary islands
Geology, 2005Co-Authors: Torsigvald Johansen, Andreas Klugel, Kaj Hoernle, Folkmar Hauff, Thomas KokfeltAbstract:U-Th-Ra disequilibria of Basanites, tephrites, and phonolites from the A.D. 1585 eruption on La Palma, Canary Islands, constrain magma differentiation times in an ocean-island rift zone. The insignificant difference in (230Th)/(232Th) implies differentiation from Basanite to phonolite in <15 k.y. 226Ra has a half-life of 1600 yr, however, and permits higher temporal resolution; (226Ra)/(230Th) disequilibria are highest in the phonolites (46%–54%) and Basanites (44%–47%) and lowest in the tephrites (38%–41%). The higher 226Ra excesses in the end-member compositions model Basanite-phonolite differentiation within 1550–1750 yr at a rate of 0.04% fractional crystallization per year. Such a short time interval is in sharp contrast to the ∼200 k.y. proposed for phonolite differentiation on the neighboring island of Tenerife and could reflect different volcanic systems, with a mantle-fed rift system on La Palma versus a crustal magma reservoir on Tenerife.
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the chemically zoned 1949 eruption on la palma canary islands petrologic evolution and magma supply dynamics of a rift zone eruption
Journal of Geophysical Research, 2000Co-Authors: Andreas Klugel, Kaj Hoernle, Hansulrich Schmincke, James D L WhiteAbstract:The 1949 rift zone eruption along the Cumbre Vieja ridge on La Palma involved three eruptive centers, 3 km spaced apart, and was chemically and mineralogically zoned. Duraznero crater erupted tephrite for 14 days and shut down upon the opening of Llano del Banco, a fissure that issued first tephrite and, after 3 days, Basanite. Hoyo Negro crater opened 4 days later and erupted Basanite, tephrite, and phonotephrite, while Llano del Banco continued to issue Basanite. The eruption ended with Duraznero erupting Basanite with abundant crustal and mantle xenoliths. The tephrites and Basanites from Duraznero and Llano del Banco show narrow compositional ranges and define a bimodal suite. Each batch ascended and evolved separately without significant intermixing, as did the Hoyo Negro Basanite, which formed at lower degrees of melting. The magmas fractionated clinopyroxene +olivine±kaersutite±Ti-magnetite at 600–800 MPa and possibly 800–1100 MPa. Abundant reversely zoned phenocrysts reflect mixing with evolved melts at mantle depths. Probably as early as 1936, Hoyo Negro Basanite entered the deep rift system at 200–350 MPa. Some shallower pockets of this Basanite evolved to phonotephrite through differentiation and assimilation of wall rock. A few months prior to eruption, a mixing event in the mantle may have triggered the final ascent of the magmas. Most of the erupted tephrite and Basanite ascended from mantle depths within hours to days without prolonged storage in crustal reservoirs. The Cumbre Vieja rift zone differs from the rift zones of Kilauea volcano (Hawaii) in lacking a summit caldera or a summit reservoir feeding the rift system and in being smaller and less active with most of the rift magma solidifying between eruptions.
John Adam - One of the best experts on this subject based on the ideXlab platform.
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trace element partitioning between mica and amphibole bearing garnet lherzolite and hydrous basanitic melt 2 tasmanian cainozoic basalts and the origins of intraplate basaltic magmas
Contributions to Mineralogy and Petrology, 2011Co-Authors: John Adam, T H GreenAbstract:Oligocene volcanics from Oatlands in Tasmania, Australia, include olivine tholeiites, alkali olivine basalts, nepheline Basanites and olivine nephelinites. They have compositional characteristics that are typical of intraplate basalts worldwide. They are generally enriched in incom- patible elements relative to the primitive mantle and are strongly enriched in Nb, Ta and light rare earths, but not heavy rare earths. At the same time, they have Sr and Nd isotope compositions that are similar to those in some incompatible-element-depleted mid-ocean ridge basalts (E-type MORB). Experimentally obtained mineral/melt partition coefficients for an Oatlands Basanite allow the relative concentrations of incompatible elements in the volcanics to be produced by small degrees of melting (B1%) of a source similar to the E-type MORB source of Workman and Hart (2005). However, the absolute concentrations that can be achieved in this way are much less than present in the most incompatible-element-enriched Basanites and nephe- linites at Oatlands. This contradiction can be explained by open-system melting under the influence of a conductive geotherm. This would have involved upwardly migrating near-solidus melts from the asthenosphere cooling along a sub-adiabatic geotherm. Cooling of the melts would have caused them to re-crystallize and accumulate in the overlying mantle, thereby enriching both the new host rocks and any residual melts in incompatible elements. This would also have increased the buoyancy of the host rocks leading to upwelling and further (decompression) melting of incom- patible-element-enriched peridotite. We were able to use our partition coefficients to quantitatively model the develop- ment of incompatible-element enrichments in the Oatlands magmas by these processes. Our explanation is consistent with the characteristically scattered but widespread distri- butions and long time scales of intraplate volcanism in a broad variety of tectonic settings. This is because the con- ditions required to initiate volcanism (i.e. those of near-sol- idus melting of the asthenosphere) are relatively easy to produce and can therefore be caused by both near-surface tectonics and deeper mantle processes. Furthermore, the super-enrichments of incompatible elements in some intra- plate volcanics can be attributed to the influence of normal geothermal gradients on melting processes. Without the very strong fractionation imposed by this combination of factors, the Oatlands volcanics would more closely resemble mid- ocean-ridge basalts.
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Trace element partitioning between mica- and amphibole-bearing garnet lherzolite and hydrous basanitic melt: 1. Experimental results and the investigation of controls on partitioning behaviour
Contributions to Mineralogy and Petrology, 2006Co-Authors: John Adam, Trevor GreenAbstract:Thirty five minor and trace elements (Li, Be, B, Sc, Cu, Zn, Ga, Ge, As, Rb, Nb, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, La, Ce, Nd, Sm, Tb, Ho, Tm, Lu, Hf, Ta, W, Tl, Pb, Bi, Th and U) in experimentally produced near-liquidus phases, from a primitive nelpheline Basanite from Bow Hill in Tasmania (Australia), were analysed by LAM ICP-MS. A number of halogens (F, Cl and I) were also analysed by electron microprobe. The analyses were used to determine mineral/melt partition coefficients for mica, amphibole, garnet, clinopyroxene, orthopyroxene and olivine for conditions close to multiple saturation of the Basanite liquidus with garnet lherzolite (approximately 2.6 GPa and 1,200°C with 7.5 wt% of added H_2O). A broader range of conditions was also investigated from 1.0 GPa and 1,025°C to 3.5 GPa and 1,190°C with 5–10 wt% of added H_2O. The scope and comprehensiveness of the data allow them to be used for two purposes, these include the following: an investigation of some of the controlling influences on partition coefficients; and the compilation of a set partition coefficients that are directly relevant to the formation of the Bow Hill Basanite magma by partial melting of mantle peridotite. Considering clinopyroxene, the mineral phase for which the most data were obtained, systematic correlations were found between pressure and temperature, mineral composition, cation radius and valence, and Δ G ^coulb (the coulombic potential energy produced by substituting a cation of mismatched valence into a crystallographic site). Δ G ^coulb is distinctly different for different crystallographic sites, including the M2 and M1 sites in clinopyroxene. These differences can be modelled as a function of variations in optimum valence (expressed as 1 sigma standard deviations) within individual M1 and M2 site populations.
Eumenio Ancochea - One of the best experts on this subject based on the ideXlab platform.
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The historical Basanite - alkali basalt - tholeiite suite at Lanzarote, Canary Islands: Carbonated melts of heterogeneous mantle source?
Chemical Geology, 2018Co-Authors: Alejandra Gómez-ulla, Olgeir Sigmarsson, María José Huertas, Jean-luc Devidal, Eumenio AncocheaAbstract:For the last three decades recycled oceanic lithosphere has been proposed as the principal mantle source for mafic magma erupting on oceanic islands. However, the composition of this lithosphere, as well as how and what part of it melts, is a matter of debate. Several melting experiments show that a mafic pyroxenite/eclogite lithology melts at higher pressure than that of ultramafic peridotite/lherzolite. In addition, the role of carbonate recycling and a carbon-rich fluxing agent producing carbonated silicate melt is increasingly being discussed. The historical Timanfaya eruption (1730–1736) at Lanzarote, Canary Islands, produced a range of mafic magmas that evolved with time from Basanite trough alkali basalt to silica-saturated tholeiite, whereas only Basanite was erupted in the smaller 1824 eruption. Mantle nodules are common and most lavas and tephra are characterised by abundant olivine macrocrysts. Variable trace element ratios of whole-rock tephra (Rb/Th: 3.3–7.7; La/Yb: 12–44; Nb/Ta: 16–21), and more especially those of olivine-bearing melt inclusions (Rb/Th: 2.5–12; La/Yb: 9–77; Nb/Ta: 14–22) suggest rapid melt extraction from a heterogeneous mantle source beneath the island. Increasing (Nb,Ta)/Th, Zr/Hf and decreasing Nb/Ta from Basanite through alkali basalt to tholeiite reflect decreasing carbon-rich fluxing on a time scale of less than a few years. Increasing K, Rb, Cs, and Ba over Th with time during the Timanfaya eruption most likely result from diminishing phlogopite control during the production of increasingly silica-saturated magma. Highly variable melt inclusion compositions are compatible with fractional melting of carbonated pyroxenite, with the whole-rock composition most likely representing the amalgamation of these fractional melts at the asthenosphere-lithosphere boundary beneath the eastern Canary Islands.
