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Electron microprobe data of carbonate fluorapatite pellets from the Phosphate Hill phosphorite prospect in the Georgina Basin
No full textSample locations and whole rock geochemistry for phosphorite samples from the Cambrian Georgina Basin
No full textLaser ablation ICPMS trace element data of microcrystalline carbonate fluorapatite and individual peloids (phosclasts) of the granular phosphorites from the Georgina Basin phosphorite prospects
No full textWhole rock geochemistry, electron microprobe and laser ablation ICP-MS geochemistry of the Georgina Basin phosphorites
No full textThis dataset comprises whole rock geochemistry of the Georgina Basin (Queensland, northern Australia) phosphorites and their locations, along with the underlying basement rocks (Sybella Granites, Proterozoic Schists and McNamarra Group metasediments of the Lawn Hill Platform). Phosphorite samples were collected in 2020 by the Geological Survey of Queensland from drillholes provided by individual companies that hold the tenements over the analysed prospects (Ardmore, Phosphate Hill, Duchess, Lily Creek, Sherrin Creek, DTREE, Barr Creek, Paradise North and Paradise South). Basement rock sample were collected during a field campaign in June-July 2021. Whole rock geochemistry was obtained through external laboratory (ALS Global) using lithium borate fusion method, with full dataset published previously by authors (Valetich et al., 2022 - Chemical Geology, v.588, 120654). Laser ablation and microprobe geochemistry of the individual phosphate (carbonate fluorapatite) clasts (phosclasts and microcrystalline carbonate fluorapatite) was carried out at Adelaide Microscopy (The University of Adelaide) using the procedures detailed in the publication linked to this dataset in the Geochemistry, Geophysics, Geosystems (G Cubed) journal
High-pressure veins in eclogite from New Caledonia and their significance for fluid migration in subduction zones
No full textThis paper describes the petrology and geochemistry of high-pressure veins and associated metasomatic selvages that are hosted by eclogite in the Pouébo Eclogite Melange of northern New Caledonia. Isotopic and geochemical evidence indicates that the mafic host rock represents seafloor-altered fractionated MORB that underwent eclogite–facies metamorphism in a subduction zone. Within the host rock are cm-thick garnet–quartz–phengite veins that are enveloped by garnet-poor, omphacite-rich selvages or bleach zones. Petrography, thermometry, oxygen isotope characteristics, and mass balance calculations are used to show that the
veins largely formed by fluid-mediated mass transfer from the bleach zones during prograde metamorphism. Minerals in the veins are free of inclusions, but the vein garnets preserve complex chemical zoning features that are not present in the host rock garnets. Vein garnets have Mn and HREE zoning patterns that are indicative of progressive garnet growth during prograde metamorphism,
whereas Mg and Ca contents reveal prominent sector zoning and fine-scale intergrowth features. We propose that the veins formed over a prolonged period during subduction by local circulation of fluid that was sourced from
prograde dehydration of minerals in the host rock. Fluid circulation may have been driven by episodic microcracking/sealing around garnet porphyroblasts, which led to significant mass transfer and progressive vein growth. Mass balance calculations and phengite trace element compositions also require the additional of pelite-derived components to the veins. These components were
probably introduced into the veins at conditions close to peak metamorphism via a relatively small external fluid flux. This model for vein formation is consistent with previous studies that suggest fluid flow in deeply subducted oceanic crust is highly restricted in many cases. The delay of fluid migration after hydrous mineral breakdown may provide an important source of water for arc magmas as free fluid is transported to deeper levels in subduction zones
Experimental constraints on element mobility from subducted sediments using high-P synthetic fluid/melt inclusions
No full textA series of hydrothermal piston-cylinder experiments have been performed to determine the composition of representative fluids and fluid/melt/rock interaction in subduction zones. Experiments were conducted under H2O saturated conditions at 2.2 GPa over a temperature range from 600–750 °C. The experiments contained synthetic, trace-element-doped pelitic starting material and fractured quartz chips to trap and preserve synthetic fluid/melt inclusions. Pelite residues from the subsolidus experiments (600–650 °C) consist of an eclogite-facies mineral assemblage including quartz, phengite, epidote, rutile, garnet, amphibole, apatite, and zircon. Coexisting hydrous fluids are expected to be completely buffered for trace elements by this mineral assemblage. At 2.2 GPa the wet solidus for the pelitic starting material is located at approximately 675 °C and hydrous fluid and melt coexist as immiscible phases at least up to 750 °C. Residue phases in the supersolidus experiments (700–750 °C) are garnet, rutile, and zircon, which suggest that HREE and HFSE are largely retained in slab residues during very high degrees of H2O saturated melting. Laser ablation ICPMS analysis and quantification of trapped fluid inclusions from the experiments indicate that subsolidus hydrous fluids released from subducted sediments have relatively high LILE contents compared to REE and HFSE, but overall are
remarkably dilute. Total solute contents are approximately 5 wt.%, of which N75% is SiO2 and around 15% is Na2O+Al2O3. The experimental results are used to show that subducting sedimentary rocks do not undergo significant element loss during metamorphic dehydration up to eclogite facies. If these fluids are representative of aqueous fluids released at sub-arc depths then simple slab dehydration models may be unable to account for element transfer from the slab to arc magmas. Instead, element recycling through subduction zones may be a product of complex fluid-melt-rock interaction processes involving multiple slab components
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
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