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The geochemistry and petrogenesis of MARID and PIC xenoliths
Get PDF© 2019 Dr. Angus Pakorn Maclennan FitzpayneMARID (Mica-Amphibole-Rutile-Ilmenite-Diopside) and PIC (Phlogopite-Ilmenite-Clinopyroxene) rocks are rare mantle samples, most often occurring as xenoliths in kimberlites. Both MARID and PIC xenoliths contain high modal abundances of phlogopite, which does not occur in the “depleted mantle” – i.e. the residue that represents the protolith of Archean mantle roots, complementary to the formation of continental crust. Consequently, these rocks are frequently interpreted as the products of extreme mantle metasomatism. Previous studies of these rocks have focussed on acquiring isolated datasets on small sample suites. This approach has made it difficult to explore possible relationships within the spectrum of metasomatised, phlogopite-rich xenoliths, even from a single locality. It therefore remains unclear how MARID and PIC rocks are formed (whether by metasomatism of peridotites, or by melt crystallisation in mantle veins). The nature of MARID parental melts/fluids also remains unidentified. Finally, MARID geochemical compositions (e.g., high K2O content) and “enriched mantle” radiogenic isotope signatures are often cited as evidence for their presence in the source of mantle-derived potassic magmas, such as lamproites. This study seeks a greater understanding of the causes and effects of mantle metasomatism by studying the petrographic, geochemical, and isotopic (radiogenic Sr-Nd-Hf-Pb and stable N-O-S-Tl) features of 26 MARID and PIC samples from southern African kimberlites (Kimberley) and orangeites (Newlands).
Previous inferences of a genetic link between PIC rocks and kimberlite melts are substantiated by clinopyroxene trace element compositions in equilibrium with kimberlite melts, and the similar radiogenic isotopic compositions of PIC clinopyroxene (87Sr/86Sri = 0.7037–0.7041) and southern African Cretaceous kimberlites (87Sr/86Sri = 0.7032–0.7048). Based on petrographic observations of kimberlite groundmass minerals (e.g., calcite, perovskite) as inclusions in secondary clinopyroxene rims, PIC rocks must be the result of kimberlite metasomatism, and not the melt source for kimberlite magmas. Furthermore, PIC rocks appear to be closely related to some phlogopite-bearing peridotites and wehrlites from the lithospheric mantle beneath Kimberley, due to similarities in their mineral geochemical compositions. It can therefore be inferred that these lithologies are the result of variable degrees of interaction between kimberlite melts and the lithospheric mantle.
This study also presents mineralogical, geochemical, and isotopic evidence that kimberlites infiltrate and affect the mineral and bulk-rock compositions of the MARID rocks that they host, complicating interpretations of MARID genesis. By filtering out such contamination effects, new interpretations regarding these rocks can be reached. Although many studies support a magmatic genesis, the ranges in primary MARID mineral major element compositions presented in this thesis overlap with those in extremely metasomatised peridotites, opening the possibility of MARID genesis by metasomatic overprinting of peridotite protoliths. Some lherzolites studied herein have similar geochemical and isotopic signatures to MARIDs, suggestive of a common parental metasomatic fluid. Prior to kimberlite infiltration, MARID rocks appear to have had “enriched mantle” radiogenic isotopic signatures, which may indicate that the source of MARID parental melts contained recycled material – comprising both oceanic and continental crust, based on stable isotope considerations. Finally, bulk-rock reconstructions of MARID compositions were conducted to eliminate secondary features, from which the trace element composition of MARID-derived melts was modelled. These melts closely match the compositions of mantle-derived magmas, such as orangeites, lamproites, and some ultramafic lamprophyres, suggesting that MARID-veined mantle could indeed be the source of alkaline ultramafic magmas in intracontinental settings
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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