Role of iron content on serpentinite dehydration depth in subduction zones: Experiments and thermodynamic modeling

Lithos ◽  
2016 ◽  
Vol 264 ◽  
pp. 441-452 ◽  
Author(s):  
Margarita Merkulova ◽  
Manuel Muñoz ◽  
Olivier Vidal ◽  
Fabrice Brunet
Keyword(s):  
Thermodynamic Modeling ◽  
Iron Content ◽  
Subduction Zones

Petrologic and geochemical role of serpentinite in subduction zones and plate interface domains

2015 ◽  
Vol 37 ◽  
pp. 61-64
Author(s):  
Marco Scambelluri ◽  
Enrico Cannaò ◽  
Mattia Gilio ◽  
Marguerite Godard
Keyword(s):  
Subduction Zones ◽  
Plate Interface

scholarly journals The role of sulphur on the melting of Ca-poor sediment and on trace element transfer in subduction zones: an experimental investigation

2021 ◽  
Author(s):  
Anne-Aziliz Pelleter ◽  
Gaëlle Prouteau ◽  
Bruno Scaillet
Keyword(s):  
Trace Element ◽  
Partial Melting ◽  
Subduction Zones ◽  
Sediment Flux ◽  
Arc Magmas ◽  
Trace Element Contents ◽  
The Stability ◽  
Element Transfer ◽  
High Sediment

Abstract We performed phase equilibrium experiments on a natural Ca-poor pelite at 3 GPa, 750-1000 °C, under moderately oxidizing conditions, simulating the partial melting of such lithologies in subduction zones. Experiments investigated the effect of sulphur addition on phase equilibria and compositions, with S contents of up to ∼ 2.2 wt. %. Run products were characterized for their major and trace element contents, in order to shed light on the role of sulphur on the trace element patterns of melts produced by partial melting of oceanic Ca-poor sediments. Results show that sulphur addition leads to the replacement of phengite by biotite along with the progressive consumption of garnet, which is replaced by an orthopyroxene-kyanite assemblage at the highest sulphur content investigated. All Fe-Mg silicate phases produced with sulphur, including melt, have higher MgO/(MgO+FeO) ratios (relative to S-free/poor conditions), owing to Fe being primarily locked up by sulphide in the investigated redox range. Secular infiltration of the mantle wedge by such MgO and K2O-rich melts may have contributed to the Mg and K-rich character of the modern continental crust. Addition of sulphur does not affect significantly the stability of the main accessory phases controlling the behaviour of trace elements (monazite, rutile and zircon), although our results suggest that monazite solubility is sensitive to S content at the conditions investigated. The low temperature (∼ 800 °C) S-bearing and Ca-poor sediment sourced slab melts show Th and La abundances, Th/La systematics and HFSE signatures in agreement with the characteristics of sediment-rich arc magmas. Because high S contents diminish phengite and garnet stabilities, S-rich and Ca-poor sediment sourced slab melts have higher contents of Rb, B, Li (to a lesser extent), and HREE. The highest ratios of La/Yb are observed in sulphur-poor runs (with a high proportion of garnet, which retains HREE) and beyond the monazite out curve (which retains LREE). Sulphides appear to be relatively Pb-poor and impart high Pb/Ce ratio to coexisting melts, even at high S content. Overall, our results show that Phanerozoic arc magmas from high sediment flux margins owe their geochemical signature to the subduction of terrigenous, sometimes S-rich, sediments. In contrast, subduction of such lithologies during Archean appears unlikely or unrecorded.

scholarly journals The role of thermal analysis in the development of high-iron-content kaolinite-based photocatalysts

2020 ◽  
Vol 142 (1) ◽  
pp. 289-299
Author(s):  
Veronika Vágvölgyi ◽  
Katalin Győrfi ◽  
Balázs Zsirka ◽  
Erzsébet Horváth ◽  
János Kristóf
Keyword(s):  
Iron Content ◽  
Adsorbed Water ◽  
Acid Base ◽  
High Iron Content ◽  
High Iron ◽  
Defect Sites ◽  
Heating Water ◽  
Coordinated Water

Abstract Dynamic and controlled-rate thermogravimetric analyses have been carried out on acid-treated (11 and 5.8 M HCl), high-iron-content kaolinites as potential photocatalysts. The mineral contaminants were determined by XRD, while the defect sites of reduced coordination number obtained by surface treatments were identified with 27Al MAS NMR spectroscopy. Upon heating, water is evolved from the surface-treated samples in three main stages: (1) removal of adsorbed water up to ~ 200 °C, (2) goethite dehydroxylation between 200 and 350 °C and (3) dehydroxylation of the clay in the 300–700 °C temperature range. Identification of water released from the above mass loss steps is difficult due to the significant overlap of steps 2 and 3, as well as to the presence of coordinated water at broken edges and defect sites (–OH2+ groups). As a result, the thermal behavior of surface-treated kaolinites should be taken into account both in the preparation of hybrids/composites and in the acid–base characterization of the catalytic surface.

scholarly journals Ineffective erythropoiesis in β-thalassemia is characterized by increased iron absorption mediated by down-regulation of hepcidin and up-regulation of ferroportin

Blood ◽  
2007 ◽  
Vol 109 (11) ◽  
pp. 5027-5035 ◽  
Author(s):  
Sara Gardenghi ◽  
Maria F. Marongiu ◽  
Pedro Ramos ◽  
Ella Guy ◽  
Laura Breda ◽  
...  
Keyword(s):  
Iron Overload ◽  
Iron Content ◽  
Iron Absorption ◽  
Regulatory Gene ◽  
Regulatory Genes ◽  
Ineffective Erythropoiesis ◽  
Transfusion Therapy ◽  
Iron Distribution ◽  
Tissue Iron

Abstract Progressive iron overload is the most salient and ultimately fatal complication of β-thalassemia. However, little is known about the relationship among ineffective erythropoiesis (IE), the role of iron-regulatory genes, and tissue iron distribution in β-thalassemia. We analyzed tissue iron content and iron-regulatory gene expression in the liver, duodenum, spleen, bone marrow, kidney, and heart of mice up to 1 year old that exhibit levels of iron overload and anemia consistent with both β-thalassemia intermedia (th3/+) and major (th3/th3). Here we show, for the first time, that tissue and cellular iron distribution are abnormal and different in th3/+ and th3/th3 mice, and that transfusion therapy can rescue mice affected by β-thalassemia major and modify both the absorption and distribution of iron. Our study reveals that the degree of IE dictates tissue iron distribution and that IE and iron content regulate hepcidin (Hamp1) and other iron-regulatory genes such as Hfe and Cebpa. In young th3/+ and th3/th3 mice, low Hamp1 levels are responsible for increased iron absorption. However, in 1-year-old th3/+ animals, Hamp1 levels rise and it is rather the increase of ferroportin (Fpn1) that sustains iron accumulation, thus revealing a fundamental role of this iron transporter in the iron overload of β-thalassemia.

scholarly journals 11B-rich fluids in subduction zones: The role of antigorite dehydration in subducting slabs and boron isotope heterogeneity in the mantle

2014 ◽  
Vol 376 ◽  
pp. 20-30 ◽  
Author(s):  
Jason Harvey ◽  
Carlos J. Garrido ◽  
Ivan Savov ◽  
Samuele Agostini ◽  
José Alberto Padrón-Navarta ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Boron Isotope

scholarly journals Pacific subduction control on Asian continental deformation including Tibetan extension and eastward extrusion tectonics

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
W. P. Schellart ◽  
Z. Chen ◽  
V. Strak ◽  
J. C. Duarte ◽  
F. M. Rosas
Keyword(s):  
Subduction Zones ◽  
Large Scale ◽  
Active Role ◽  
The Pacific ◽  
Slab Rollback ◽  
Continental Deformation ◽  
Basin Formation ◽  
Backarc Basins ◽  
East West

Abstract The India-Asia collision has formed the highest mountains on Earth and is thought to account for extensive intraplate deformation in Asia. The prevailing explanation considers the role of the Pacific and Sunda subduction zones as passive during deformation. Here we test the hypothesis that subduction played an active role and present geodynamic experiments of continental deformation that model Indian indentation and active subduction rollback. We show that the synchronous activity and interaction of the collision zone and subduction zones explain Asian deformation, and demonstrate that east-west extension in Tibet, eastward continental extrusion and Asian backarc basin formation are controlled by large-scale Pacific and Sunda slab rollback. The models require 1740 ± 300 km of Indian indentation such that backarc basins form and central East Asian extension conforms estimates. Indentation and rollback produce ~260–360 km of eastward extrusion and large-scale clockwise upper mantle circulation from Tibet towards East Asia and back to India.

Retrograde carbon sequestration in orogenic complexes: a case study from the Chinese Southwestern Tianshan

2021 ◽  
Author(s):  
Han Hu ◽  
Alberto Vitale Brovarone ◽  
Lifei Zhang ◽  
Francesca Piccoli ◽  
Weigang Peng ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
Thermodynamic Modeling ◽  
Subduction Zones ◽  
Greenschist Facies ◽  
Water Model ◽  
Chinese Tianshan ◽  
Silicate Dissolution ◽  
Carbon Release ◽  
Oxygen Isotopic ◽  
Stage 1

<p>The interaction between ascending carbonic fluids and rocks at shallow depths in orogenic systems plays an important role in carbon flux regulation. In subduction zones, most works have focused on processes related to carbon release from the subducting slab or sequestration via high-pressure (HP) carbonation of mafic or ultramafic lithologies. A significant fraction of the carbonic fluids released by deep metamorphic reactions can also reach orogenic complexes and react with crustal and exhumed metamorphic rocks. However, the amount of fluid-mediated carbonation that may take place at crustal depths in orogenic complexes is still poorly constrained.</p><p>We report the occurrence of retrograde mafic eclogites and metasomatic marbles in UHP units in the Chinese Tianshan orogenic belt. The mafic eclogites recorded two successive, superimposed metamorphic–metasomatic stages: graphite precipitation along fractures and veins at eclogite facies (Stage#1) and pervasive rock carbonation (i.e., Stage#2: silicate dissolution and carbonate precipitation) at retrograde amphibolite to greenschist facies. This work focuses on Stage#2 carbonation, which consists of the transformation of Stage#1 graphite-bearing eclogites into carbonate + paragonite (± zoisite) + quartz. We present field, microstructural, petrological, and geochemical results of carbonic fluid–rock interactions affecting exhumed mafic eclogites. These results are supported by thermodynamic modeling for low-pressure carbonation of mafic eclogite obtained by means of EQ3/6 and the Deep Earth Water model. Carbon and oxygen isotopic data and thermodynamic modeling suggest an external metasedimentary source for the Stage#2 carbonation. This deep carbon sequestration event can be referred to retrograde, greenschist-facies conditions at about 10 kbar and 450 °C, and redox conditions similar or more oxidized than the quartz–fayalite–magnetite (QFM) buffer. Our findings provide new insights into the reactivity of metastable, exhumed metamafic rocks with ascending carbonic fluids in orogenic systems. We conclude that retrograde, fluid-mediated rock carbonation can significantly impact on carbon fluxes from active collisional belts. </p>

How Good is a Paleoseismic Record of Megathrust Earthquakes for Probabilistic Forecasting?

2021 ◽  
Author(s):  
Francisco Acuña ◽  
Gonzalo A. Montalva ◽  
Daniel Melnick
Keyword(s):  
Subduction Zones ◽  
Weibull Model ◽  
Time Dependent ◽  
Probabilistic Forecasting ◽  
Future Event ◽  
Earthquake Forecast ◽  
Megathrust Earthquakes ◽  
Chile Earthquake ◽  
Hazard Assessments

Abstract Time-dependent earthquake forecast depends on the frequency and number of past events and time since the last event. Unfortunately, only a few past events are historically documented along subduction zones where forecasting relies mostly on paleoseismic catalogs. We address the role of dating uncertainty and completeness of paleoseismic catalogs on probabilistic estimates of forthcoming earthquakes using a 3.6-ka-long catalog including 11 paleoseismic and 1 historic (Mw≥8.6) earthquakes that preceded the great 1960 Chile earthquake. We set the clock to 1940 and estimate the conditional probability of a future event using five different recurrence models. We find that the Weibull model predicts the highest forecasting probabilities of 44% and 72% in the next 50 and 100 yr, respectively. Uncertainties in earthquake chronologies due to missing events and dating uncertainties may produce changes in forecast probabilities of up to 50%. Our study provides a framework to use paleoseismic records in seismic hazard assessments including epistemic uncertainties.

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