1,721,210 research outputs found
High-pressure metamorphism in Taiwan: from oceanic subduction to arc-continent collision?
No full textThermal Evolution of the Permo-Triassic Karakaya Subduction- Accretion Complex from the Biga Peninsula to the Tokat Massif (Anatolia)
No full textThe results of the combined application of a series of analytical methods (clay mineralogy, vitrinite reflectance, Raman microspectroscopy) placed tight constraints on the thermal evolution of the Karakaya Complex of northern Anatolia, a mostly Permo-Triassic subduction-accretion complex resulting from the progressive closure of the Palaeotethys. The thermal evolution of the Karakaya Complex is the result of Permian-Triassic subduction-accretion processes, and was not significantly affected by later Alpine-age tectonism, as shown by Liassic shallow-water siliciclastic and carbonate deposits overlying unconformably the Karakaya Complex which did not undergo any significant burial. The Lower Karakaya Complex, comprising metabasite and subordinate marble and phyllite, experienced maximum temperatures ranging from 340 to 497 degrees C, in agreement with independently determined thermobarometric reconstructions. The entire Upper Karakaya Complex, previously considered unmetamorphosed or slightly metamorphosed, was affected by zeolite to lower greenschist facies metamorphism (120-376 degrees C). The coherent results of this study show that Raman thermometry has great potential for palaeotemperature determination at low temperature ranges (200-350 degrees C)
Thermal architecture and deformation structures in the Alpi Apuane (NW Tuscany Italy): new insights for the metamorphic and tectonic history of the inner northern Apennines
Full text linkA Raman spectroscopy study on carbonaceous material (RSCM) has been applied in the Northern Apennines
with particular focus on the Alpi Apuane (NW Tuscany, Italy) and surrounding areas in order to constrain peak
metamorphic temperatures and their variability in the different continent-derived units of the nappe stack. Peak
temperatures in the range of ∼ 530–320 °C were found in the Alpi Apuane, whereas in the nearby metamorphic
core of the Monte Pisano and Punta Bianca lower peak temperatures of 305–315 °C and 350 °C were found,
respectively. The Tuscan Nappe in La Spezia area (west of Alpi Apuane) shows temperatures in the range of
295–246 °C, whereas the same unit in the Lima Valley (east of the Alpi Apuane) shows temperatures lower
than 230 °C.
Using the presented data will discuss the thermal architecture of the inner northern Apennines and the
relationships with regional-scale deformation structures to provide new contraints for the thermo-mechanical
evolution and exhumation history of the inner Northern Apennine and its geodynamic setting. In particular
we support the interpretation of the Alpi Apuane as a cold metamorphic core complex in which the preserved
paleothermal structure and part of the exhumation are related with crustal thickening while the final exhumation
stages (depth ≤15 km and ambient crustal temperature ≤350 °C) are associated with crustal thinning still
ongoing in the area
Thermal Evolution of the Permo-Triassic Karakaya Subduction-accretion Complex between the Biga Peninsula and the Tokat Massif (Anatolia)
No full textThe results of the combined application of a series of analytical methods (clay mineralogy, vitrinite reflectance, Raman microspectroscopy) placed tight constraints on the thermal evolution of the Karakaya Complex of northern Anatolia, a mostly Permo−Triassic subduction-accretion complex resulting from the progressive closure of the Palaeotethys. The thermal evolution of the Karakaya Complex is the result of Permian−Triassic subductionaccretion processes, and was not significantly affected by later Alpine-age tectonism, as shown by Liassic shallow-water siliciclastic and carbonate deposits overlying unconformably the Karakaya Complex which did not undergo any significant burial. The Lower Karakaya Complex, comprising metabasite and subordinate marble and phyllite, experienced maximum temperatures ranging from 340 to 497° C, in agreement with independently determined thermobarometric reconstructions. The entire Upper Karakaya Complex, previously considered unmetamorphosed or slightly metamorphosed, was affected by zeolite to lower greenschist facies metamorphism (120−376° C). The coherent results of this study show that Raman thermometry has great potential for palaeotemperature determination at low temperature ranges (200−350° C)
Carbonation by fluid-rock interactions at high-pressure conditions: Implications for carbon cycling in subduction zones
No full textCarbonate-bearing lithologies are the main carbon carrier into subduction zones. Their evolution during metamorphism largely controls the fate of carbon, regulating its fluxes between shallow and deep reservoirs. Recent estimates predict that almost all subducted carbon is transferred into the crust and lithospheric mantle during subduction metamorphism via decarbonation and dissolution reactions at high-pressure conditions. Here we report the occurrence of eclogite-facies marbles associated with metasomatic systems in Alpine Corsica (France). The occurrence of these marbles along major fluid- conduits as well as textural, geochemical and isotopic data indicating fluid–mineral reactions are compelling evidence for the precipitation of these carbonate-rich assemblages from carbonic fluids during metamorphism. The discovery of metasomatic marbles brings new insights into the fate of carbonic fluids formed in subducting slabs. We infer that rock carbonation can occur at high-pressure conditions by either vein-injection or chemical replacement mechanisms. This indicates that carbonic fluids produced by decarbonation reactions and carbonate dissolution may not be directly transferred to the mantle wedge, but can interact with slab and mantle-forming rocks. Rock-carbonation by fluid–rock interactions may have an important impact on the residence time of carbon and oxygen in subduction zones and lithospheric mantle reservoirs as well as carbonate isotopic signatures in subduction zones. Furthermore, carbonation may modulate the emission of CO2 at volcanic arcs over geological time scales
Fluid-mediated selective dissolution of subducting carbonaceous material: Implications for carbon recycling and fluid fluxes at forearc depths
Full text linkSubduction of crustal C governs the long-term global C cycling. The role of carbonates recycling in subduction zones and the related dissolution of C at various depths have been the subject of a large body of literature over the last decades. Much less is known about the contribution of carbonaceous material (CM) to the deep C cycling in subduction zones. This paper presents natural evidence for intense fluid-mediated leaching of CM in pelitic schists at high-pressure/low-temperature conditions relevant to the forearc region of subducting slabs. Manifestations of such process were identified along fluid pathways at various scales in the blueschist-facies subduction complexes of both Alpine Corsica and the Western Alps. Microstructural, whole-rock and Raman analyses across a selected metasomatic aureole were used to quantify the amount and mechanisms of C loss during fluid-rock interaction. In samples affected by intense fluid infiltration, > 90% of the initial CM was removed from the rock. Microstructural and micro-Raman data indicate selective leaching of disordered CM relative to nearly crystalline graphite. The collected data allowed constraining the magnitude of fluid fluxes required to bleach the studied CM-bearing lithologies at different P-T-fO2 conditions, which corresponds to rather high time-integrated fluid fluxes in the order of ~106 m3/m2. In settings of large-scale fluid channeli- zation, such as along regional-scale, lithological/tectonic boundaries or at the top of the subducted sedimentary pile, intense dissolution of subducted CM is expected. This process may thus exert a negative feedback on the sink of C phases into the deep mantle over the geological timescales and contribute to the release of isotopically light C from subducting slabs in forearc regions
Stacking and metamorphism of continuous segments of subducted lithosphere in a high-pressure wedge: The example of Alpine Corsica (France)
No full text
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
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