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Building new crust in a nascent arc setting: the example of the New Caledonia gabbronorites
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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
Highly siderophile and chalcophile element behaviour in abyssal-type and supra-subduction zone mantle: constraints from the New Caledonia ophiolite
No full textExposures of arc-related mantle sections preserved in ophiolites constitute a natural laboratory for investigating subduction zone processes. The New Caledonia ophiolite consists primarily of harzburgites, locally overlain by mafic-ultramafic cumulates, and minor spinel and plagioclase lherzolites (Secchiari et al., 2016). Recent studies have shown that the harzburgites and the associated cumulates represent a crust-mantle transect formed in a nascent arc environment (Marchesi et al., 2009; Pirard et al., 2013; Secchiari et al., submitted). However, scarce geochemical data are available for the harzburgites, so that the processes recorded by this mantle section are still poorly constrained.
In order to unravel the evolution of the New Caledonia harzburgite, a comprehensive geochemical dataset (major and trace element, Sr-Nd-Pb isotopes) has been obtained on a new set of fresh samples unaffected by serpentinization.
The studied harzburgites are low-strain tectonites showing porphyroclastic textures, locally grading into promylonitic textures. They exhibit a refractory nature, as attested by the notable absence of primary clinopyroxene, very high Fo content of olivine (90.9-92.9 mol.%), high Mg# of orthopyroxene (89.8-94.2) and Cr# of spinel (39-71). Thin films of undeformed clinopyroxene with very low Na2O (0.03-0.13 wt.%) and TiO2 (0.04-0.10 wt.%) contents have been also recognized in association with Al2O3- (0.88-1.53 wt.%) and CaO- (0.37-0.97 wt.%) poor secondary orthopyroxene.
The harzbugites display U-shaped REE profiles (GdN/YbN=0.06-0.48) with remarkably low REE concentrations (< 0.1 chondritic values), in the range of modern subduction zone peridotites. Geochemical models shows that the HREE composition of the harzburgites can be reproduced with high degrees (up to ~25%) of fractional melting of a DMM source in the spinel stability field. Extended trace element diagrams highlights depleted compositions coupled with strong positive anomalies for Pb and FME (i.e. Cs, Ba, Sr).
Nd isotopic ratios range from poorly to slightly radiogenic (-0.8≤Ndi≤+13.3) and negatively correlate with Sr isotopes (0.70257≤87Sr/86Sr≤0.70770). Pb isotopes cover a wide range, trending from DMM toward enriched, sediment-like, compositions.
We interpret the geochemical signature displayed by the New Caledonia harzburgite as reflecting a highly depleted sub-arc mantle source variably modified by fluid input and/or hydrous melts percolation during Eocene subduction.
REFERENCES
Marchesi, C., Garrido, C.J., Godard, M., Belley, F., Ferré, E. (2009): Migration and accumulation of ultra-depleted subduction-related melts in the Massif du Sud ophiolite (New Caledonia). Chem Geol, 266, 3-4, 171-186
Pirard, C., Hermann, J., O’ Neill H. (2013): Petrology and Geochemistry of the Crust–Mantle Boundary in a Nascent Arc, Massif du Sud Ophiolite, New Caledonia, SW Pacific. J Petrol, 54, 9, 1759–1792
Secchiari, A., Montanini, A., Bosch, D., Macera, P., Cluzel, D. (2016): Melt extraction and enrichment processes in the New Caledonia lherzolites: Evidence from geochemical and Sr–Nd isotope data. Lithos, 260, 28-43
Secchiari A., Montanini, A., Bosch, D., Macera, P., Cluzel, D. (2018): The contrasting geochemical message from the New Caledonia gabbronorites: insights on depletion and contamination processes of the sub-arc mantle in a nascent arc setting. Submitt. to Contrib Mineral Pet
Evidence from the New Caledonia peridotites for contrasting behavior of highly siderophile and chalcophile elements in supra-subduction zone and normal upper mantle
No full textThe New Caledonia Peridotitic Nappe represents one of the largest exposures of mantle rocks worldwide and
provides unique insight on upper mantle processes. The Peridotitic Nappe is dominated by a harzburgite-dunite
association forming the Massif du Sud, but also includes minor lherzolites in the northern part of the island. The
geochemical features of the harzburgites require a complex history, including episodes of melting and local overprint by
fluids or hydrous melts in a supra-subduction zone setting, while lherzolites are relatively homogeneous, abyssal-type
peridotites (Secchiari, 2016). In order to examine how these mantle processes affected the behavior of highly
siderophile (HSE: Os, Ir, Ru, Rh, Pt, Pd, Au, Re) and chalcophile elements (S, Se, Te), a set of fully characterized (i.e.,
major and trace elements; Sr, Nd and Pb isotopes) peridotites has been studied. The lherzolites display homogeneous
187Os/188Osi (0.1273-0.1329), slightly subchondritic to chondritic Re/Os (0.04-0.11) and PGE, Au, Se and Te
abundances, similar to other lherzolites from normal upper mantle. Sulfur contents are variable (202-1268 mg/g) and
were likely increased by serpentinization. Harzburgites can be grouped in two sub-types. Type-A harzburgites
(epsilonNdi=9.3-13.3) have subchondritic 187Os/188Osi (0.1203-0.1254) coupled with low Os (0.554-1.513 ppb) and Re
contents (0.017-0.021 ppb) and somewhat fractionated HSE patterns. The HSE display lower concentrations than in
lherzolites, with Os-Ru enrichments over Ir (OsN/IrN = 1.6-1.9; RuN/IrN = 1.5-1.7) and positive anomalies of Pt and Au.
S-Se-Te have low contents (< 0.1 x primitive mantle) and approximately flat patterns, likely reflecting the presence of
small amounts of sulphides. These features are consistent with high melting degrees that led to sulphide exhaustion and
Os-Ru and Pt alloy stabilization. Type-B harzburgites (-0.8 ≤ εNdi ≤ +4.0) are fresh rocks showing chondritic to
suprachondritic measured 187Os/188Os (0.1273-0.1524) coupled with very low Os concentrations (0.003-0.277 ppb) and
high 187Re/188Os ratios of up to 30. The HSE have melt-like patterns with low concentrations of Os and Ir, strong
negative Pt anomalies and positive Au spikes. Sulfur, Se and Te concentrations are remarkably low (e.g., a few mg/g S).
HSE patterns are interpreted to reflect localized interaction and modification of type A harzburgites with oxidized (?)
subduction-related fluids or melts, which destabilized residual mantle sulphides and PGE alloys, causing strong
depletion of compatible PGE and S, Se, Te. The complex element patterns of these peridotites are unknown from
mantle rocks that were exhumed in extensional environments. The data suggest that HSE fractionations (e.g., Pt
anomalies and A
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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