1,720,964 research outputs found
Ore geology, fluid inclusions and four-stage hydrothermal mineralization of the Shangfanggou giant Mo-Fe deposit in Eastern Qinling, central China
No full textThe Eastern Qinling, Central China, containing more than 20 Mesozoic porphyry +/- skarn systems, is the most important Mo province in the world. The Shangfanggou giant Mo deposit, Luanchuan County, Henan Province, is a porphyry-skam system hosted in a lithologic association comprising carbonaceous sandstone, shale, carbonate and chert within the Neoproterozoic Luanchuan Group. Mo ores are mainly altered porphyry, skam and hornfels, with minor altered gabbro. The mineralization process includes four stages, potassic alteration of the porphyry and skamization of dolomite marble in stage 1, stockworlcs of quartz + molybdenite +/- sulfide (stage 2), pyrite + quartz +/- sulfides (stage 3), and carbonate +/- quartz +/- fluorite (stage 4), respectively. Mo mineralization was generally associated with strong silicification and/or phyllic alteration. The fluid inclusions in minerals include three compositional types, i.e., CO2-bearing (C-type), aqueous (W-type) and daughter mineral-bearing (S-type). Minerals formed in stages I to 3 contain all the three types of Fls, but the stage 4 minerals only contain the W-type Fls. Oxides and Cu-phosphate are recognized as daughter minerals in S-type inclusions in minerals of stage 1, whereas the daughter sulfide and reducing gases such as CO, CH4, H2S and C2H6 can be observed in quartz of stages 2 and 3, suggesting that the ore-forming fluids were initially oxidizing and then evolved to reducing. Boiling fluid inclusion assemblages can be observed in minerals formed in stage 2 or earlier, but not in stage 3 or later. Fluid boiling caused CO2 escape, oxygen fugacity decrease and rapid precipitation of ore minerals, and was a key factor causing Mo-mineralization at Shangfanggou. Data and interpretations presented in this contribution show that the fluids forming the Shangfanggou Mo deposit evolved from CO2-rich, high-salinity hypothermal, to CO2-poor, low-salinity epithermal (low-T). The Mo mineralization at the Shangfanggou deposit mainly occurred at depth of 6.6-7.0 km, deeper than the majority of porphyry systems in volcanic arcs, which resulted from a CO2-rich magma-fluid system originating from partial melting of thickened lower crust The Shangfanggou mineral system developed during 158-134 Ma when the Yangtze-North China continental collision began to evolve from compression to extension. Magmatic hydrothermal deposits developed in a continental collision regime are generally formed by CO2-rich, high-salinity fluids. (C) 2013 Elsevier B.V. All rights reserved.GeologyMineralogyMining & Mineral ProcessingSCI(E)EI11REVIEWC146-1615
Re-Os and Sr-Nd-Pb isotope constraints on source of fluids in the Zhifang Mo deposit, Qinling Orogen, China
No full textThe Zhifang Mo deposit is located in the northeastern Qinling Orogen along the southern margin of the North China Craton. The deposit represents a quartz-vein system hosted in the Mesoproterozoic Xiong'er Group volcanic rocks. We identify three hydrothermal stages (early, middle and late), characterized by veinlets of quartz-pyrite, quartz-molybdenite-pyrite-chalcopyrite-galena-sphalerite, and quartz-carbonate assemblages, respectively. Five molybdenite samples from the Zhifang deposit yield Re-Os ages ranging from 241.2 +/- 1.6 Ma to 247.4 +/- 2.5 Ma, with an isochron age of 246.0 +/- 5.2 Ma (2 sigma, MSWD = 7.4), and a weighted mean age of 243.8 +/- 2.8 Ma (26, MSWD = 5.5). The Re-Os age shows that the Mo mineralization occurred during the Indosinian Orogeny, and suggests that the mineralization is unrelated to the Yanshanian magmatism or the Paleo-Mesoproterozoic volcanic-hydrothermal event. This study also reports a new Sr-Nd-Pb isotope dataset from ore sulfides in an attempt to constrain the source of the ore-forming fluids. Ten sulfide samples from middle stage of the Zhifang Mo deposit yield I-sr(t) ratios of 0.710286-0.711943, with an average of 0.711004; epsilon(Nd)(t) values between -19.5 and -14.8, with an average of -16.7; and ((206)pb/(204)pb)(i), ((207)pb/(204)pb)(i) and ((208)pb/(204),pb)(i) ratios of 17.126-17.535, 15.374-15.466 and 37.485-37.848, with averages of 17.380,15.410 and 37.631, respectively. One pyrite from the early stage yield I-sr(t) of 0.722711-0.722855, with an average of 0.722783, which is higher than those of the middle stage sulfides and suggests equilibration with wallrocks. The epsilon Nd(t) values are in the range of -173 to -16.6 with a mean at -17.0; and ((206)pb/(204)pb)(i), ((207)pb/(204)pb)(i) and (Pb-208/Pb-204)(i) ratios are 17386,15.405 and 37.622, respectively. The ore sulfides show higher Pb-isotope ratios, higher epsilon(Nd)(t) and lower I-sr(t) values than the host rocks. The results suggest that the ore-forming fluids had lower I-sr(t), and higher epsilon(Nd)(t) values than the ore sulfides, and were possibly sourced from the Dengfeng Complex. The southward subduction of the North China Craton beneath the Huaxiong Block during the Triassic was possibly responsible for the formation of the Waifangshan orogenic Mo system. (C) 2015 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.National Basic Research Program [2012CB416602, 2006CB403508]; National Natural Science Foundation of China [41202050, 41372085, 41403032]; China Postdoctoral Science Foundation [2012M510261]; Chinese GovernmentSCI(E)[email protected],SI132-1433
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
Pb-Sr-Nd isotope constraints on the fluid source of the Dahu Au-Mo deposit in Qinling Orogen, central China, and implication for Triassic tectonic setting
No full textThe Dahu Au-Mo deposit is a structure-controlled lode system occurring in the northern Xiaoqinling terrane, Huaxiong Block, Qinling Orogen. This paper reports a new Sr-Nd-Pb isotope dataset obtained for ore sulfides and the hostrocics within the Taihua Supergroup, in an attempt to constrain the source of the ore-forming fluids from a new dimension. 16 sulfide samples yield I-Sr ratios of 0.70470-0.71312, with an average of 0.70854; epsilon(Nd)(t) values between -13.5 and -18.1, with average of -15.1; and (Pb-206/Pb-204)(i), (Pb-207/Pb-204)(i) and (Pb-208/Pb-204)i ratios of 17.033-17.285, 15.358-15.438, and 37.307-37.582, with averages of 17.162, 15.405, and 37.440, respectively. 5 gneiss samples from the Taihua Supergroup yield I-Sr ratios of 0.70947-0.73201, averaging 0.72294; epsilon(Nd)(t) values of -20.0 to -31.1. averaging -25.1; and (Pb-206/Pb-204)(i), (Pb-207/Pb-204)(i), (Pb-208/Pb-204)(i) ratios of 17.127-18.392, 15.416-15.604 and 37.498-37.814, with averages of 17.547, 15.470 and 37.616, respectively. These data show that the ore sulfides have less radiogenic Sr-Nd-Pb isotope systematics than the hostrocks, and suggest that the ore-forming fluids, which interacted with the wallrocks to form ores, must be sourced from a depleted mantle or a depleted, subducted oceanic slab. In combination with the spatial scenario and geochemical signatures of the Triassic magmatites and mineral systems, we argue that in the Triassic the Mianlue Ocean was not completely closed, and that the northward oceanic plate subduction still survived along the Mian-Lue suture, which caused the Late Triassic magmatism and associated mineralization in Qinling Orogen, including the Au-Mo Dahu deposit. (c) 2012 Elsevier B.V. All rights reserved.GeologyMineralogyMining & Mineral ProcessingSCI(E)EI0REVIEW60-674
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
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
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