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The evolution of young silicic lavas at Medicine Lake Volcano, California: Implications for the origin of compositional gaps in calc-alkaline series lavas (1986)

Grove, T. L. ; Donnelly-Nolan, J. M.

Springer

Contributions to mineralogy and petrology 92 (1986), S. 281-302

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ISSN: 1432-0967

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences

Notes: Abstract At Medicine Lake Volcano, California, the compositional gap between andesite (57–62 wt.% SiO2) and rhyolite (73–74 wt.% SiO2) has been generated by fractional crystallization. Assimilation of silicic crust has also occurred along with fractionation. Two varieties of inclusions found in Holocene rhyolite flows, hornblende gabbros and aphyric andesites, provide information on the crystallization path followed by lavas parental to the rhyolite. The hornblende gabbros are magmatic cumulate residues and their mineral assemblages are preserved evidence of the phases that crystallized from an andesitic precursor lava to generate the rhyolite lavas. The andesitic inclusions represent samples of a parental andesite and record the early part of the differentiation history. Olivine, plagioclase and augite crystallization begins the differentiation history, followed by the disappearance of olivine and augite through reaction with the liquid to form orthopyroxene and amphibole. Further crystallization of the assemblage plagioclase, amphibole, orthopyroxene, magnetite, and apatite from a high-SiO2 andesite leads to rhyolite. This final crystallization process occurs on a cotectic that is nearly horizontal in temperature-composition space. Since a large amount of crystallization occurs over a limited temperature interval, a compositional gap develops between rhyolite and high SiO2 andesite. Liquidus surfaces with shallow slopes in temperature-composition space are characteristic of several late-stage crystallization assemblages in the andesite to rhyolite compositional range. Experimentally produced plagioclase+ amphibole+orthopyroxene+magnetite and plagioclase+ augite+low-Ca pyroxene+magnetite cotectics have liquidus slopes that are nearly flat. At other calc-alkaline volcanic centers crystallization processes involving large compositional changes over small temperature intervals may also be important in the development of bimodal volcanism (i.e. the existence of a composition gap). At Mt. Mazama and Mt. St. Helens, USA and Aso Caldera and Shikotsu, Japan the amphibole-bearing assemblage was important. At Krakatau, Indonesia and Katmai, USA, an augite+orthopyroxene-bearing assemblage was important. In addition to its role in the production of a compositional gap between intermediate and rhyolitic lavas, the crystallization process increases the H2O content of the residual liquid. This rapid increase in residual liquid volatile content which results from the precipitation of a large proportion of crystalline solids may be an important factor among several that lead to explosive silicic eruptions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00572157

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Assimilation of granite by basaltic magma at Burnt Lava flow, Medicine Lake volcano, northern California: Decoupling of heat and mass transfer (1988)

Grove, T. L. ; Kinzler, R. J. ; Baker, M. B. ; [et al.]

Springer

Contributions to mineralogy and petrology 99 (1988), S. 320-343

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ISSN: 1432-0967

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences

Notes: Abstract At Medicine Lake volcano, California, andesite of the Holocene Burnt Lava flow has been produced by fractional crystallization of parental high alumina basalt (HAB) accompanied by assimilation of granitic crustal material. Burnt Lava contains inclusions of quenched HAB liquid, a potential parent magma of the andesite, highly melted granitic crustal xenoliths, and xenocryst assemblages which provide a record of the fractional crystallization and crustal assimilation process. Samples of granitic crustal material occur as xenoliths in other Holocene and Pleistocene lavas, and these xenoliths are used to constrain geochemical models of the assimilation process. A large amount of assimilation accompanied fractional crystallization to produce the contaminated Burnt lava andesites. Models which assume that assimilation and fractionation occurred simultaneously estimate the ratio of assimilation to fractional crystallization (R) to be 〉1 and best fits to all geochemical data are at an R value of 1.35 at F=0.68. Petrologic evidence, however, indicates that the assimilation process did not involve continuous addition of granitic crust as fractionation occurred. Instead, heat and mass transfer were separated in space and time. During the assimilation process, HAB magma underwent large amounts of fractional crystallization which was not accompanied by significant amounts of assimilation. This fractionation process supplied heat to melt granitic crust. The models proposed to explain the contamination process involve fractionation, replenishment by parental HAB, and mixing of evolved and parental magmas with melted granitic crust.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00375365

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3

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Abrupt shift in δ18O values at Medicine Lake Volcano (California, USA) (1998)

Donnelly-Nolan, J. M.

Springer

Bulletin of volcanology 59 (1998), S. 529-536

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ISSN: 1432-0819

Keywords: Key words Medicine Lake volcano ; Oxygen isotopes ; California ; Cascade range ; Assimilation

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences

Notes: Abstract Oxygen-isotope analyses of lavas from Medicine Lake volcano (MLV), in the southern Cascade Range, indicate a significant change in δ18O in Holocene time. In the Pleistocene, basaltic lavas with 〈52% SiO2 averaged +5.9‰, intermediate lavas averaged +5.7‰, and silicic lavas (≥63.0% SiO2) averaged +5.6‰. No analyzed Pleistocene rhyolites or dacites have values greater than +6.3‰. In post-glacial time, basalts were similar at +5.7‰ to those erupted in the Pleistocene, but intermediate lavas average +6.8‰ and silicic lavas +7.4‰ with some values as high as +8.5‰. The results indicate a change in the magmatic system supplying the volcano. During the Pleistocene, silicic lavas resulted either from melting of low-18O crust or from fractionation combined with assimilation of very-low-18O crustal material such as hydrothermally altered rocks similar to those found in drill holes under the center of the volcano. By contrast, Holocene silicic lavas were produced by assimilation and/or wholesale melting of high-18O crustal material such as that represented by inclusions of granite in lavas on the upper flanks of MLV. This sudden shift in assimilant indicates a fundamental change in the magmatic system. Magmas are apparently ponding in the crust at a very different level than in Pleistocene time.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004450050207

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Evidence of hydrous differentiation and crystal accumulation in the low-MgO, high-Al2O3 Lake Basalt from Medicine Lake volcano, California (1995)

Wagner, T. P. ; Donnelly-Nolan, J. M. ; Grove, T. L.

Springer

Contributions to mineralogy and petrology 121 (1995), S. 201-216

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ISSN: 1432-0967

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences

Notes: Abstract The late Pleistocene Lake Basalt of Medicine Lake volcano, California is comprised of variably porphyritic basalt and basaltic andesite flows and scoria. These eruptives are similar in composition and phenocryst abundance to the low-MgO, high-Al2O3 mafic magmas common in convergent margin settings. The petrogenesis of the magmas that produced the Lake Basalt has been inferred from field relations, melting experiments and subsequent major and trace element modeling. Their formation involved both hydrous differentiation and plagioclase accumulation and thus the Lake Basalt can be used to constrain the relative contributions of these processes to the production of high-Al2O3 arc basalt. Phenocryst-poor lavas of the Lake Basalt formed by hydrous differentiation; their compositions and observed phenocrysts were reproduced in 1 kbar, H2O-saturated melting experiments. Anorthite-rich plagioclase compositions of the lavas of the Lake Basalt necessitate crystallization from melts with between 4 and 6 wt% dissolved H2O. Phenocryst-rich lavas of the Lake Basalt, with 18 modal% phenocrysts and greater, formed by plagioclase accumulation in magmas similar to the phenocryst-poor lavas. This interpretation is supported by the depleted incompatible element abundances and enriched Sr/Zr ratio of the more porphyritic lavas relative to the phenocryst-poor lavas. We model the formation of the Lake Basalt as a two-stage process that combines a differentiation model and a plagioclase accumulation model. Stage one involved hydrous fractionation, granitic assimilation and mixing with undifferentiated parent magma. This process generated lavas with up to 19.2 wt% Al2O3 and 7 modal% phenocrysts. In stage two, plagioclase accumulated in these liquids and produced more aluminous and porphyritic lavas with up to 21.8 wt% Al2O3 and 33 modal% phenocrysts.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/

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5

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Late Holocene hydrous mafic magmatism at the Paint Pot Crater and Callahan flows, Medicine Lake Volcano, N. California and the influence of H2O in the generation of silicic magmas (2000)

Kinzler, R. J. ; Donnelly-Nolan, J. M. ; Grove, T. L.

Springer

Contributions to mineralogy and petrology 138 (2000), S. 1-16

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ISSN: 1432-0967

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences

Notes: Abstract This paper characterizes late Holocene basalts and basaltic andesites at Medicine Lake volcano that contain high pre-eruptive H2O contents inherited from a subduction related hydrous component in the mantle. The basaltic andesite of Paint Pot Crater and the compositionally zoned basaltic to andesitic lavas of the Callahan flow erupted approximately 1000 14C years Before Present (14C years b.p.). Petrologic, geochemical and isotopic evidence indicates that this late Holocene mafic magmatism was characterized by H2O contents of 3 to 6 wt% H2O and elevated abundances of large ion lithophile elements (LILE). These hydrous mafic inputs contrast with the preceding episodes of mafic magmatism (from 10,600 to ∼3000 14C years b.p.) that was characterized by the eruption of primitive high alumina olivine tholeiite (HAOT) with low H2O (〈0.2 wt%), lower LILE abundance and different isotopic characteristics. Thus, the mantle-derived inputs into the Medicine Lake system have not always been low H2O, primitive HAOT, but have alternated between HAOT and hydrous subduction related, calc-alkaline basalt. This influx of hydrous mafic magma coincides temporally and spatially with rhyolite eruption at Glass Mountain and Little Glass Mountain. The rhyolites contain quenched magmatic inclusions similar in character to the mafic lavas at Callahan and Paint Pot Crater. The influence of H2O on fractional crystallization of hydrous mafic magma and melting of pre-existing granite crust beneath the volcano combined to produce the rhyolite. Fractionation under hydrous conditions at upper crustal pressures leads to the early crystallization of Fe-Mg silicates and the suppression of plagioclase as an early crystallizing phase. In addition, H2O lowers the saturation temperature of Fe and Mg silicates, and brings the temperature of oxide crystallization closer to the liquidus. These combined effects generate SiO2-enrichment that leads to rhyodacitic differentiated lavas. In contrast, low H2O HAOT magmas at Medicine Lake differentiate to iron-rich basaltic liquids. When these Fe-enriched basalts mix with melted granitic crust, the result is an andesitic magma. Since mid-Holocene time, mafic volcanism has been dominated primarily by hydrous basaltic andesite and andesite at Medicine Lake Volcano. However, during the late Holocene, H2O-poor mafic magmas continued to be erupted along with hydrous mafic magmas, although in significantly smaller volumes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/PL00007657

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Using Jackson's Return Potential Model to Explore the Normativeness of Recycling (2015)

Nolan, J. M.

Sage

In: Environment and Behavior

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Publication Date: 2015-08-25

Description: In this article, a novel theoretical model, Jackson’s Return Potential Model (RPM), is applied to examine social norms for recycling. Unlike other theoretical models that emphasize the causal relationship between norms and behavior, Jackson’s RPM provides a conceptual model for thinking about the "normativeness" of recycling and other pro-environmental behaviors. Convenience samples of recycling experts and university students were surveyed about their approval and disapproval for different levels of recycling. The results showed that both students and experts approved of high levels of recycling and disapproved of low levels of recycling. However, for partial-recycling (the descriptively normative level of recycling among students and most Americans), the social climate was one of indifference. It is argued that the lack of disapproval for partial-recycling may partly explain the gap between real and ideal recycling rates. The practical utility of Jackson’s RPM and the implications of the results for recycling outreach and education are discussed.

Print ISSN: 0013-9165

Electronic ISSN: 1552-390X

Topics: Energy, Environment Protection, Nuclear Power Engineering , Psychology

Published by Sage

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Quadrupole moments of coexisting collective shapes at high spin in ^{154}Er (2013)

J. P. Revill, E. S. Paul, X. Wang, M. A. Riley, J. Simpson, R. V. F. Janssens, J. Ollier, A. J. Boston, M. P. Carpenter, C. J. Chiara, C. R. Hoffman, F. G. Kondev, T. Lauritsen, P. J. Nolan, J. M. Rees, S. V. Rigby, C. Unsworth, S. Zhu, and I. Ragnarsson

American Physical Society (APS)

In: Physical Review C

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Publication Date: 2013-09-10

Description: Author(s): J. P. Revill, E. S. Paul, X. Wang, M. A. Riley, J. Simpson, R. V. F. Janssens, J. Ollier, A. J. Boston, M. P. Carpenter, C. J. Chiara, C. R. Hoffman, F. G. Kondev, T. Lauritsen, P. J. Nolan, J. M. Rees, S. V. Rigby, C. Unsworth, S. Zhu, and I. Ragnarsson Four high-spin collective bands have been populated in 68 154 Er 86 via the 110 Pd( 48 Ti,4 n γ ) 154 Er reaction. Average transition quadrupole moments Q t have been measured for three of the bands by using the Doppler-shift attenuation method. The strongest band has a value of Q t =11.0±1.0 e b, similar to val... [Phys. Rev. C 88, 031304] Published Mon Sep 09, 2013

Keywords: Nuclear Structure

Print ISSN: 0556-2813

Electronic ISSN: 1089-490X

Topics: Physics