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Interaktion und Vermischung kompositionell unterschiedlicher Silikatschmelzen treten im gesamten Spektrum magmatischer Aktivität auf. Dabei kann es sowohl zu Magma mingling-, als auch zu Magma mixing-Prozessen kommen. Magmatische Enklaven und Dispersionen sind dabei Zeugen der ehemaligen Interaktion und Vermischung der beteiligten Schmelzen. Diese Arbeit präsentiert ein neuartiges Modell zur Genese magmatischer Dispersionen, das auf hydrodynamischen Mischungsprozessen der beteiligten Schmelzen beruht. Es geht davon aus, dass es bei geeigneten, an der Grenzfläche zwischen zwei Schmelzen wirkenden Scherkräften zu mechanischen Mischungsprozessen unter Ausbildung von Dispersionen kommen kann. Die dafür relevanten Parameter umfassen die jeweiligen Viskositäten der Schmelzen, die zwischen ihnen herrschende Grenzflächenspannung, die anliegenden Scherraten bzw. Fließgeschwindigkeiten und die zur Verfügung stehende Zeitspanne. Die praktische Anwendbarkeit und die generelle Gültigkeit für georelevante Silikatschmelzen des Modells zur hydrodynamischen Genese magmatischer Dispersionen wurde experimentell durch Laborversuche und durch die Anwendung auf natürliche Fälle magmatischer Mischungsprozesse bestätigt. Somit steht auch ein tool im Sinne der Geospeedometrie zur Verfügung, mit dem die damaligen Temperaturen, Viskositäten und relativen Strömungsgeschwindigkeiten der beteiligten Magmen zum Zeitpunkt ihrer Vermischung berechnet und rekonstruiert werden können. Es liefert wichtige Daten zur Erfassung der kinematischen Eigenschaften von Silikatschmelzen und trägt so zur weiteren Aufklärung der komplexen magmatischen Systeme bei. / Interaction and comingling of contrasting silicate magmas is a frequent phenomenon occurring in the entire spectrum of magmatic activity. Thereby both magma mingling and mixing processes are to be found. Magmatic enclaves and dispersions appear as a witness for the former interaction and mingling of the involved melts. This work presents a new model for the genesis of magmatic dispersions, which is based on hydrodynamic mingling processes of the participating melts. It is due to the attempt that under suitable shear rates mechanical mingling processes at the interface of two melts can be initiated to form dispersions. The parameters relevant to this process include the viscosities, the interacting interfacial tension, the applied shear rates resp. flow velocities and the available time span. The practical applicability and the general validity for geo-relevant silicate melts of the proposed model was confirmed by experimental laboratory tests and by the application on natural cases of magmatic mingling processes. Thus a tool in the sense of geo-speedometry is available which allows calculation and reconstruction of the former temperatures, viscosities and relative flow velocities of the melts at the time of their conjunction. In doing so it provides important data on the kinematic features of silicate melts and provides insights into the complex magmatic systems.

The Canary islands are formed by a slow moving hotspot, from Fuerteventura 20 Ma to el Hierro 1.2Ma years old and La Palma is in the shield building stage of evolution. La Palma had its last eruption 1971 and has had seven eruptions since 1430, which makes it the most active of the islands in our times. The samples consist of host lavas, basanites, and mafic/ultramafic and felsic xenoliths, alkali gabbros and syenites respectively. Minerals in the lavas and the alkali gabbro xenolith samples are clinopyroxene, olivine, amphibole and plagioclase, the clinopyroxenes are zoned. Forsterite content in the olivines increases at the rim for the xenoliths and decreases for the host lavas. While magnesium number in the clinopyroxenes decreases towards the rim. The Fe-Mg partitioning indicates that there were points of equilibrium between the clinopyroxenes and their host lavas, which was calculated to temperature, pressure and depth indicating 62-74km for the xenoliths and 23-35km for the host lavas. The temperatures and pressures were 1184-1205°C with 6-10 kbar for the host lavas compared to 1316-1341°C and 17-20 kbar for the xenoliths.

Seismic data from the intermediate-spreading Endeavour segment of the Juan de Fuca Ridge reveal several crustal-level, low-velocity, high-attenuation regions on the eastern and western ridge flanks 7 to 16 km from the neovolcanic zone. I examine Pg amplitude anomalies for a wide variety of source-receiver azimuths in the Endeavour active source seismic tomography data. I use finite difference waveform forward modeling to estimate the dimensions, depth, and seismic properties of the best-observed inferred anomalous regions. The attenuating regions extend 10-15 km beneath axis-parallel bathymetric highs and from 2 to 4 km below the seafloor. The velocity reduction is small (~8%) and the attenuation large (QP ≈ 8-40) suggesting the presence of partial melt. I infer that melt focusing toward the neovolcanic zone is incomplete and that tectonic interactions with the Heckle seamount chain and/or the large segment-bounding overlapping spreading centers may promote off-axis melt delivery at the Endeavour segment.

Submitted by MARIA DO SOCORRO GOMES TORRES null (liuregis@hotmail.com) on 2016-12-14T21:24:44Z No. of bitstreams: 1 Maria do Socorro Gomes Torres -Repositório UNESP.pdf: 2204441 bytes, checksum: 0b5463c8eca6265e1cdec54da9ed7532 (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-12-15T16:46:42Z (GMT) No. of bitstreams: 1 torres_msgt_dr_sjrp.pdf: 2204441 bytes, checksum: 0b5463c8eca6265e1cdec54da9ed7532 (MD5) / Made available in DSpace on 2016-12-15T16:46:42Z (GMT). No. of bitstreams: 1 torres_msgt_dr_sjrp.pdf: 2204441 bytes, checksum: 0b5463c8eca6265e1cdec54da9ed7532 (MD5) Previous issue date: 2016-08-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Magma, gênese poética do escritor João Guimarães Rosa, constitui-se a base sólida desta tese de doutoramento, em Teoria da Literatura. Tem-se como corpus os poemas da coletânea que apesar de premiada em, 1937, não obteve a recepção merecida, em virtude do autor não ter publicado a obra. O estudo aprofundado dos poemas mostra que o lirismo voltado para os rios, a água e as cores é aspecto crucial em sua composição. Não é novidade vincular a produção rosiana ao Modernismo, o que é novo é abordar uma obra inicial como Magma, tendo em vista os aspectos anteriores. Optamos por realizar uma abordagem que contempla (i) a análise da fortuna crítica; (ii) o contexto de produção, relacionando a gênese poética de João Guimarães Rosa às demais produções poéticas do Modernismo, sobretudo, do primeiro e do segundo momentos; (iii) a análise dos poemas. Para a construção da tese partimos do estudo da fortuna crítica de Magma, atendo-nos à recepção da mesma e às análises que da coletânea foram feitas. O suporte teórico e crítico para a realização desta tese ateve-se a estudos acerca do Modernismo brasileiro, entre eles Affonso Ávila (2013), José Guilherme Merquior (1965), aos estudos voltados para a compreensão do texto poético como Octavio Paz (1982). Além disso, buscamos contextualizar Magma no universo do Modernismo brasileiro, de modo a estabelecer pontos de aproximação e distanciamento entre o que faz João Guimarães Rosa e o que fazem os modernos. Em seguida, organizamos os poemas da obra em vertentes, apoiando-nos em parte nos trabalhos de Maria Célia Leonel. As fronteiras entre tais vertentes não são firmemente delimitadas, porém, acreditamos que há um ganho analítico na organização do livro segundo essa perspectiva, pois, são temas que percorrem toda a coletânea, também, toda a obra subsequente do autor. Por fim, coube investigar em que medida, tais temas, que se apresentam na obra com fronteiras pouco fluidas, se articulam, a partir de um discurso moderno que os aproxima. Ou seja, a partir dos instrumentos fornecidos pelas etapas anteriores procuramos responder à seguinte pergunta: em que medida aspectos do Modernismo articulam-se em Magma, para garantir o diálogo entre as vertentes apontadas e, para, além disso, garantir a originalidade e a riqueza da obra poética de João Guimarães Rosa?. / Magma, poetic genesis of the writer João Guimarães Rosa, constitutes the solid foundation of this doctoral thesis in Literary Theory. There have as corps poems that make up the collection, which despite awarded in 1937, did not get the deserved reception, and this, perhaps, hindered the development of researches on / from it, that situated within the context of Brazilian Modernism. Researches that show at the same time, the extent to which collection moves away from that same literary context, since the poems are linked by a discourse that tenses the very idea of Modernism, responsible for ensuring the originality of the work. The in-depth study of the poems shows that primitivism / nationalism, playful, philosophical, lyrical are crucial aspects in its composition. Unsurprisingly link to Rosa's production to Modernism, what is new is to approach an initial work as Magma, in view of the previous aspects. We decided to use an approach that includes (I) the analysis of the critical fortune; (II) the context of production, linking the poetic genesis of João Guimarães Rosa to other modernist poetic productions, especially the first and second times; (III) the analysis of poems. For the construction of the thesis we start from the study of criticism of Magma fortune, especially the study of Maria Célia Leonel (2000), being guided by the receipt of the same and the analyzes of the work they were made. The theoretical and critical support for the realization of this thesis it is adhered to studies of Brazilian modernism, including Affonso Avila, studies aimed at understanding the poetic text as Octavio Paz (1982). In addition, we seek to contextualize Magma in the universe of Brazilian modernism, in order to establish points of approximation and distancing between what is João Guimarães Rosa and what do the Modernists. Then we organized the poems of the work areas: primitivist / nationalist, lyrical, playful and philosophical. The boundaries between the strands are not firmly defined, but we believe that there is an analytical gain in book organization according to this view, because the themes run throughout the collection, too, all the subsequent work of the author. Finally, we investigate to what extent these issues, which are present in the work with little fluid boundaries, articulate, from a modernist discourse approaching them. That is, from the tools provided by the previous steps seek to answer the following question: to what extent modernist aspects are articulated in Magma to ensure dialogue between the identified aspects and to also ensure the originality and richness of work poetic of João Guimarães Rosa?.

Volcan Sollipulli is a Quaternary stratovolcano situated at 38'50'S in the Southern Volcanic Zone of the Andes of Chile, about 25 km east of the volcanic front. The volcano is capped by a large (25 km2 approx. ) ice-filled caldera. Sollipulli is unusual in this region of predominantly basic to intermediate magmatism in that it has erupted a wide range of magmas from high-MgO (9%) basalt to rhyolite (74% Si02). The last major eruption, the Alpehue eruption, occurred at about 2,900 B. P, ejecting about 4.7 km3 (D. R. E) of homogeneous high-Si dacite pumice, forming an extensive plinian airfall deposit and ignimbrite. The caldera predates the Alpehue eruption and is believed to have formed by passive subsidence combined with erosion rather than by catastrophic collapse. Withdrawal of magma from beneath the centre of the structure and effusive eruption induced subsidence. Magma mixing, fractional crystallisation and crustal assimilation are important evolutionary mechanisms. Some mixed dacite lavas contain primitive basaltic magmatic inclusions with diktytaxitic textures indicative of rapid quenching. Strongly resorbed, reverse zoned sodic plagioclase of dacitic origin occurs in basic inclusions and high-Mg olivine occurs in dacites. Other sequences appeart o have evolved predominantly by fractional crystallisation with some crustal assimilation. The amount of crustal assimilation increasesw ith decreasinga gei n somec ases. Older Sollipulli basic magmash ave evolved as small batchesp redominantlya t moderatet o high pressurein the mid-lower crust whereas younger basic magmas have experienced protracted upper crustal histories in a large magma chamber, fractionating and assimilating crust to produce abundant high-Si dacite. Sollipulli magmas have an anhydrous mineralogy except for the occurrence of very minor amphibolei n somem ixed rocks. Magma temperaturesra ngef rom about 118 0'C in basalts to about 900'C in dacites. The most primitive samples represent hot and relatively water-poor (<1-2% H20) high-Al basaltic magmas. Crystal-rich andesitesa nd dacites record lower temperaturesth an crystal-poore quivalents. The cooler porphyritic magmas appear to have assimilated more crust than the hotter crystal-poor magmas. Most magmas have evolved at oxygen fugacities close to the NNO buffer curve. Large volcanic front centres in the region erupt magmas with lower incompatible elementa bundancea nd higher Ba/Nb than magmase rupteda t minor monogeneticc entresa, nd at stratovolcanoesto the easto f the front, which have incompatiblee lements ignatures transitional towards back-arc alkaline magmas (e. g. high Nb, Ce/Y). Older Sollipulli magmas also have high Ce/Y and Nb similar to magmas at some monogenetic centres but have lower Ti and Y. Younger Sollipulli magmas have even lower Ti and Y. Sollipulli basic magmasa re also characterisedb y higher Mg/Ni than all regional magmas. The simplest explanation is that the high Nb, Ce/Y magmas have assimilated enriched mantle lithosphere. The Ti, Y, Mg/Ni systematics suggest that the Sollipulli magmasa re generated by higher degrees of melting of a similar MORB-source-type mantle than the regional magmas. In the case of the younger Sollipulli magmas, generation from mantle which was slightly depleted during the earlier phase is also possible but the older magmas show no evidence in their spinel compositions for derivation from refractory mantle.

No description available.

Please read the abstract in the section front of this document / Dissertation (MSc (Geology))--University of Pretoria, 2008. / Geology / unrestricted

<p> The Proterozoic' Coldwell Alkaline Complex is the southernmost intrusion of a number of N -S trending igneous bodies occurring in the Midcontinental Rift system exposed in the Lake Superior area. The Coldwell complex is host to several Ni-Cu-PGEbearing intrusions two of which; the Two-Duck Lake intrusion (Marathon deposit) and the Geordie Lake gabbro (MacRae occurrence) have been investigated in some detail with respect to PGE mineralisation. Both of these have been suggested to have experienced crustal contamination in conjunction with mineralisation. As a test of this possibility, a detailed Sm-Nd, oxygen isotope, and whole-rock geochemical study of these mineralised occurrences as well as of the Dunlop occurrence and the Middleton occurrence, together with unmineralised rocks of the complex was undertaken. The primary objectives are to determine whether crustal contamination is indicated in mineralised rocks and to try and ascertain the nature of the magma which formed the complex. </p> <p> The Coldwell complex is thought to have been formed by emplacement of magma at three intrusive centres. Sm-Nd data for rocks from these three centres reveal similar isotopic values, with slight variations; samples taken from the western gabbros exhibit eNd values averaging -0.9 ranging from -2.9 to 0.9, whereas rocks from the eastern margin and centre of the complex have eNd values of about an average of 0.5 ranging from -0.5 to 1.2 suggesting that the magma that formed these rocks has undergone a lesser degree of crustal contamination. This data, supported by oxygen isotope and wholerock geochemical information indicates that crustal contamination seems to play a small, and varied role in the genesis of the Coldwell magmas. The Nd isotope data all clusters at values for CHUR, which indicates that it has been enriched relative to the depleted mantle. It has been postulated that an enriched mantle plume resided under the rift and promoted rift-related magmatism. The data from this study would seem to support this supposition. </p> <p> Geochemical parameters utilised to define fields to geochemically delineate possible end member contributors to this primarily plume-derived magma indicate, that in addition to small, variable amounts of assimilation of upper and lower crust, the plume magmas also interacted with the lithospheric upper mantle to a small degree. </p> / Thesis / Master of Science (MSc)

Field evidence from exposed plutonic rocks indicates that mafic-felsic magma interaction is an important process during the construction and evolution of magma chambers. The exhumed, ~140 Ma, Halfmoon Pluton of Stewart Island, New Zealand is characterized by a sequence of mingled mafic sheets and enclaves preserved within an intermediate-felsic host, and provides a unique opportunity to directly investigate the physico-chemical processes that operate within an arc setting. Interpretation of mingling structures and textures in the field, in combination with extensive petrographic, geochemical and geochronological data, allow for conclusions to be reached regarding the nature of the mafic-felsic magma interactions, and the physical, chemical and thermal processes responsible for the generation and evolution of the calc-alkaline magmas. Detailed documentation and interpretation of mafic-felsic magma mingling structures and textures reveal that the Halfmoon Pluton formed incrementally as the result of episodic replenishments of mafic magma emplaced onto the floor of an aggrading intermediate-felsic magma chamber. Physico-chemical processes identified include fractional crystallization and accumulation of a plagioclase – hornblende – apatite – zircon mineral assemblage, episodic replenishment by hot, wet basaltic magmas, magmatic flow and compaction. Early amphibole and apatite crystallization played an important role in the compositional diversity within the Halfmoon Pluton. Variations in the style of magma mingling preserved within the magmatic “stratigraphy” indicate that processes operating within the chamber varied in space and time. Variations in mineral zoning and composition within hornblende indicate that the Halfmoon Pluton crystallized within a magma in which melt composition fluctuated in response to repeated mafic magma replenishments, fractionation, crystal settling and convection. Mineral assemblages, chemical characteristics, isotopic data and geochronological evidence indicate that the amphibole-rich calc-alkaline Halfmoon Pluton was emplaced into a juvenile arc setting, most probably an island-arc. Data are consistent with a model whereby ‘wet’ amphibole-rich basaltic magmas pond at the crust-mantle interface and episodically rise, inject and mingle with an overlying intermediate-felsic magma chamber that itself represents the fractionated product of the mantle melts.