1,721,055 research outputs found
Dataset for thesis "Constraining Cu-(Co) mineralisation in sediment-hosted copper deposits using rutile, apatite, and carbonate geochronology"
No full textFinal trace element geochemistry spreadsheet for rutile and apatite including standards and accuracy and precision. Final geochronology tables for rutile, apatite and calcite including standards. Final electron microprobe data tables and bonus petrography/geochemistry figures.</span
Constraining Cu-(Co) mineralisation in sediment-hosted copper deposits using rutile, apatite and carbonate geochemistry
No full textTransitioning to a green economy requires unprecedented metal supply rates, highlighting the need for the discovery of new ore deposits. Sediment-hosted Cu deposits (SSHC’s) are attractive, high-grade deposits however, despite decades of research, lack indicator and vectoring mineral exploration tools relative to other deposit types whilst controversy still surrounds the timing of mineralisation. To address these issues, this thesis explores the potential of rutile, apatite, and calcite as effective U-Pb geochronometers to constrain mineralisation in the Zambian Copperbelt (ZCB) and Neuquén basin. Furthermore, trace element geochemistry and machine learning are used to assess the potential of rutile and apatite as indicator minerals for SSHC deposits.Rutile is intergrown with chalcopyrite-bornite, defining a broad window of mineralisation from ~570-520 Ma, supporting previous molybdenite Re-Os constraints. No evidence for syndiagenetic mineralisation is observed and Cu mineralisation is interpreted as syn-orogenic, linked to K-Mg metasomatism caused by circulation of high temperature, potassic basinal brines during the Lufilian Orogeny. A 2nd hydrothermal event between 490-470 Ma is constrained by rutile and apatite, aligned with post-orogenic uplift of the Lufilian Orogeny and existing Re-Os bornite constraints. Late-stage Ca-Na metasomatism, caused by infiltration of halite undersaturated brines derived from evaporite dissolution is invoked to explain this stage, indicating mineralisation in the ZCB is episodic rather than one single event.Similar, syn-orogenic mineralisation is constrained by calcite U-Pb geochronology in the Neuquén basin at ~27 Ma, linked to Oligocene-Miocene basin inversion during Andean tectonism. Earlier calcite generations at ~95 Ma and ~77 Ma align with diagenesis and hydrocarbon and formation water migration respectively, showcasing calcite U-Pb geochronology as an effective tool, defining different stages of basin evolution. Overall, a model linking Cu mineralisation with redox reactions involving hydrocarbons and oxidised brines is invoked, with the Neuquén basin potentially representing a younger analogue to the ZCB.Textural and trace element geochemical characteristics support a metasomatic origin for rutile and apatite. Hydrothermal rutile is W, Ta, Sn, Th and potentially Cu enriched but Zr, Hf and Mo poor compared to metamorphic and detrital rutile, offering distinction between hydrothermal and metamorphic environments. Orebody apatite at Nchanga and Mindola North display convex upward, MREE enriched profiles and are separated from most metamorphic apatite using principal component analysis, based on LREE depletion and low Sr/Y ratios. However, neither mineral displays definitive criteria distinguishing SSHC deposits from other ore deposit types. Hence, the ability for these mineral phases to act as indicator minerals is limited on a global basis but may demonstrate more success on a deposit scale.</div
A girlie from the U. S. A., by lieut. Jamie Kelly
No full textChansons anglaises -- États-Unis -- +* 1900......- 1999......+:20e siècle
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
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