Magma Evolution in the Primitive, Intra-oceanic Tonga Arc: Petrogenesis of Basaltic Andesites at Tofua Volcano

Tofua volcano is situated midway along the Tonga oceanic arc and has undergone two phases of ignimbrite-forming activity. The eruptive products are almost entirely basaltic andesites (52 center dot 5-57 wt % SiO2) with the exception of a volumetrically minor pre-caldera dacite. The suite displays a strong tholeiitic trend with K2O <1 wt %. Phenocryst assemblages typically comprise plagioclase + clinopyroxene +/- orthopyroxene with microlites of Ti-magnetite. Olivine (Fo(83-88)) is rare and believed to be dominantly antecrystic. An increase in the extent and frequency of reverse zoning in phenocrysts, sieve-textured plagioclase and the occurrence of antecrystic phases in post-caldera lavas record a shift to dynamic conditions, allowing the interaction of magma batches that were previously distinct. Pyroxene thermobarometry suggests crystallization at 950-1200 degrees C and 0 center dot 8-1 center dot 8 kbar. Volatile measurements of glassy melt inclusions indicate a maximum H2O content of 4 center dot 16 wt % H2O, and CO2-H2O saturation curves indicate that crystallization occurred at two levels, at depths of 4-5 center dot 5 km and 1 center dot 5-2 center dot 5 km. Major and trace element models suggest that the compositions of the majority of the samples represent a differentiation trend whereby the dacite was produced by 65% fractional crystallization of the most primitive basaltic andesite. Trace element models suggest that the sub-arc mantle source is the residuum of depleted Indian mid-ocean ridge basalt mantle (IDMM-1% melt), whereas radiogenic isotope data imply addition of 0 center dot 2% average Tongan sediment melt and a fluid component derived from the subducted altered Pacific oceanic crust. A horizontal array on the U-Th equiline diagram and Ra excesses of up to 500% suggest fluid addition to the mantle wedge within the last few thousand years. Time-integrated (Ra-226/Th-230) vs Sr/Th and Ba/Th fractionation models imply differentiation timescales of up to 4500 years for the dacitic magma compositions at Tofua.

Magma Evolution in the Primitive, Intra-oceanic Tonga Arc: Rapid Petrogenesis of Dacites at Fonualei Volcano

Fonualei is unusual amongst subaerial volcanoes in the Tonga arc because it has erupted dacitic vesicular lavas, tuffs and phreomagmatic deposits for the last 165 years. The total volume of dacite may approach 5 km(3) and overlies basal basaltic andesite and andesite lavas that are constrained to be less than a few millennia in age. All of the products are crystal-poor and formed from relatively low-viscosity magmas inferred to have had temperatures of 1100-1000 degrees C, 2-4 wt % H2O and oxygen fugacities 1-2 log units above the quartz-fayalite-magnetite buffer. Major and trace element data, along with Sr-Nd-Pb and U-Th-Ra isotope data, are used to assess competing models for the origin of the dacites. Positive correlations between Sc and Zr and Sr rule out evolution of the within-dacite compositional array by closed-system crystal fractionation of a single magma batch. An origin by partial melting of lower crustal amphibolites cannot reproduce these data trends or, arguably, any of the dacites either. Instead, we develop a model in which the dacites reflect mixing between two dacitic magmas, each the product of fractional crystallization of basaltic andesite magmas formed by different degrees of partial melting. Mixing was efficient because the two magmas had similar temperatures and viscosities. This is inferred to have occurred at shallow (2-6 km) depths beneath the volcano. U-Th-Ra disequilibria in the basaltic andesite and andesite indicate that the parental magmas had fluids added to their mantle source regions less than 8 kyr ago and that fractionation to the dacitic compositions took less than a few millennia. The 165 year eruption period for the dacites implies that mixing occurred on a similar timescale, possibly during ascent in conduits. The composition of the dacites renders them unsuitable candidates as contributors to average continental crust.

Octave Uzanne’s L’Éventail: a literary mythology of the fan

In the last half of the nineteenth century, the folding fan was phenomenally popular in France. The accessory was a ubiquitous component of women’s dress, yet it also attracted the attention of some prominent collectors and Orientalists as well as acquiring an importance in the art and literature of the period. In many plastic works and literary texts devoted to it, the fan retains a link with femininity, and particularly with feminine sexuality, even as its identity as an art object is emphasized. Octave Uzanne’s L’Éventail (1882), a self-professed literary history of the fan, exemplifies this dualistic treatment as it presents the fan both as a titillating intimate companion of women and as a literary and (although to a lesser extent) art historical subject. This article focuses on Uzanne’s treatment of the fan’s early history in the Far and Middle East. By comparing his text with other contemporary histories of the fan, it demonstrates that the “history” of the accessory may be more accurately described as a mythology.

Modulating mythology in a post-traumatic era: Murals and re-imaging in Northern Ireland.

Arguably the most ancient of the social media, wall paintings have been a persistent vehicle of cultural meaning management. The dynamics of myth markets are reflected in the sectarian murals of Northern Ireland. In this paper, we draw from consumer research literature on mythology and street art to explore the continuous revision of these wallscapes that seeks to address the enduring contradictions of civic ideology in contested political space. In particular, we focus on the use of classical, historical and pop-cultural mythologies to transform private space into public place. We examine the decommissioning of murals occurring in the wake of the Peace Accords, and speculate on the implications of the creation of a shared mythology for the future of mural painting and the state.

Acoustic-oceanographic data fusion for prediction of oceanic acoustic elds

Tese de doutoramento, Engenharia Electrónica e Telecomunicações (Processamento de Sinal), Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2014

Sympatric speciation in palms on an oceanic island.

The origin of species diversity has challenged biologists for over two centuries. Allopatric speciation, the divergence of species resulting from geographical isolation, is well documented. However, sympatric speciation, divergence without geographical isolation, is highly controversial. Claims of sympatric speciation must demonstrate species sympatry, sister relationships, reproductive isolation, and that an earlier allopatric phase is highly unlikely. Here we provide clear support for sympatric speciation in a case study of two species of palm (Arecaceae) on an oceanic island. A large dated phylogenetic tree shows that the two species of Howea, endemic to the remote Lord Howe Island, are sister taxa and diverged from each other well after the island was formed 6.9 million years ago. During fieldwork, we found a substantial disjunction in flowering time that is correlated with soil preference. In addition, a genome scan indicates that few genetic loci are more divergent between the two species than expected under neutrality, a finding consistent with models of sympatric speciation involving disruptive/divergent selection. This case study of sympatric speciation in plants provides an opportunity for refining theoretical models on the origin of species, and new impetus for exploring putative plant and animal examples on oceanic islands.

Oceanic intraplate volcanoes exposed: Example from seamounts accreted in Panama

Two Paleogene ocean islands are exposed in the Azuero Peninsula, west Panama, within sequences accreted in the early-Middle Eocene. A multidisciplinary approach involving litho-logic mapping, paleontological age determinations, and petrological study allows reconstruction of the stratigraphy and magmatic evolution of one of these intraplate oceanic volcanoes. From base to top, the volcano's structure comprises submarine basaltic lava flows locally interlayered with hemipelagic sediments, basaltic breccias, shallow-water limestones, and subaerial basaltic lava. Gabbros and basaltic dikes were emplaced along a rift zone of the island. Geochemical trends of basaltic lavas include decreased Mg# {[Mg/(Mg + Fe)] * 100} and, with time, increased incompatible element contents thought to be representative of many poorly documented intraplate volcanoes in the Pacific. Our results show that, in addition to deep drilling, the roots of oceanic islands can be explored through studies of accreted and subaerially exhumed oceanic sequences.

The newly defined "Greenstone Unit'' of the Aiguilles Rouges massif (western Alps): remnant of an Early Palaeozoic oceanic island-arc ?

In the southwestern part of the Aiguilles Rouges massif (pre-Alpine basement of the Helvetic realm, western Alps), a metavolcanic sequence, newly defined as the ``Greenstone Unit'',is exposed in two NS trending belts of several 100 metres in thickness. It consists of epidote amphibolites, partly epidote and/or calcic amphibole-bearing greenschists, and small amounts of alkali feldspar-bearing greenschists, which underwent low- to medium-grade metamorphism during Visean oblique collision. Metamorphic calcic amphiboles and epidotes show strong chemical zoning, whereas metamorphic plagioclase is exclusively albitic in composition (An 1-3). The SiO2 content of the subalkaline tholeiitic to calc-alkaline suite ranges continuously from 44 wt% to 73 wt%,but andesitic rocks predominate. The majority of samples have chemical compositions close to recent subduction-related lavas; some are even restricted to recent oceanic arcs (extremely low Ta and Nb contents, high La/Nb and Th/Ta ratios). But several basaltic to basalto-andesitic samples resemble continental tholeiites (low Th/Ta, La/Nb ratio). As it is very probable that both lava types are to some extent contemporaneous, it is proposed that the Greenstone Unit represents a former oceanic volcanic are which temporarily underwent extension during which emplacement of continental tholeiite-like rocks occurred. The cause of the extension remains ambiguous. Considering palaeotectonic significance and age of other metavolcanic units in the Aiguilles Rouges massif, the Greenstone Unit most likely formed in the Early Palaeozoic.

Bonds away : baseball mythology and the 2007 home run chase

In 2007, Barry Bonds hit his 75 6th home run, breaking Hank Aaron's all-time record for most home runs in a Major League career. While it would be expected that such an accomplishment would induce unending praise and adulationfor the new record-holder, Bonds did not receive the treatment typically reserved for a beloved baseball hero. The purpose of this thesis is to assess media representations of the 2007 home run chase in order to shed light upon the factors which led to the mixed representations which accompanied BOlTds ' assault on Aaron's record. Drawingfrom Roland Barthes ' concept of myth, this thesis proposes that Bonds was portrayed in predominantly negative ways because he was seen as failing to embody the values of baseball's mythology. Using a qualitative content analysis of three major American newspapers, this thesis examines portrayals of Bonds and how he was shown both to represent and oppose elements from baseball's mythology, such as youth, and a distant, agrarian past. Recognizing the ways in which baseball is associated with American life, the media representations of Bonds are also evaluated to discern whether he was portrayed as personifYing a distinctly American set of values. The results indicate that, in media coverage of the 2007 home run chase, Bonds was depicted as a player of many contradictions. Most commonly, Bonds' athletic ability and career achievements were contrasted with unflattering descriptions of his character, including discussions of his alleged use of performance-enhancing substances. However, some coverage portrayed Bonds as embodying baseball myth. The findings contribute to an appreciation of the importance of historical context in examining media representations. This understanding is enhanced by an analysis of a selection of articles on Mark McGwire 's record-breaking season in 1998, and careful consideration of, and comparison to, the context under which Bonds performed in 2007. Findings are also shown to support the contemporary existence of a strong American baseball mythology. That Bonds is both condemned for failing to uphold the mythology and praised for personifYing it suggests that the values seen as inherent to baseball continue to act as an American cultural benchmark.

Conflits sur un navire de croisière : étude descriptive

Cette étude vise à comprendre les motifs qui peuvent s’avérer source de conflits dans une situation où il est le plus inattendu : les navires de croisières. Nous analysons les constructions de la propagande de vente de croisières avec l’utilisation des mythes marins. Nous nous questionnons ensuite sur la relation entre l’être humain et la mer à partir de la grande diversité mythologique entourant celle-ci ainsi que l’expérience empirique de la vie sur un navire de croisière (également sur un paquebot, cargo et bateau militaire). Dans ce contexte touristique, nous abordons le thème de la rencontre de l’Autre : l’Autre étant les personnes habitant les destinations visitées, les touristes, et principalement, les employés sur le navire responsables du service à la clientèle. Enfin, nous analysons plusieurs conflits représentatifs vécus à bord d’une croisière afin de comprendre les structures conflictuelles ; l’espace, la subordination, les jeux de rôle, les classes sociales, etc.

A Study on Aerosol Transport Dynamics over the Indian Landmass and the Adjoining Oceanic Regions Using Satellite Data

The present study brings out the influence of transport dynamics on the aerosol distribution over the Indian region at a few selected geographically distinct locations. Over the Bay of Bengal the dominant pathway of aerosol transport during the pre-monsoon period is through higher altitudes (~ 3 km); directed from the Indian main land. In contrast, the aerosol pathways over the Arabian Sea during the same period are quite complex. They are directed from geographically different environments around the ocean through different altitudes. However in general, the day-to-day variability of AOD at both these regions is significantly influenced by the features of atmospheric circulation especially, the wind convergence at higher altitudes (around 3 km). Over the Ganga Basin during the winter period, the wind convergence at lower altitudes (< I km) govems the shon term variations in AOD, while the mean AOD distribution at this location is mainly governed by the local anthropogenic sources.

Studies On Oxygen Minimum Layer In The Arabian Sea In Relation To The Oceanic Circulation

The thesis is divided into six chapters, with Further subdivisions.’ Chapter one has two sections. Section one deals with a general introduction, and section two,with the material and treatment of data For the present investigation. The second chapter concerns with the distribution of oxyty in the oxygen minimum layer and its topography during the southwest and northeast monsoons. The distribution of oxyty at various isanosteric surfaces within which the oxygen minimum layer lies during southwest and northeast monsoons and their topographies Form chapter three. In the fourth chapter the Flow pattern and its influence on the oxygen minimum layer are discussed. The fifth chapter presents the scatter diagrams of oxyty against temperature at the various isanosteric surfaces. The sixth chapter summarises the results of the investigation and presents the conclusions drawn therefrom