TY - JOUR A1 - Duesterhoeft, Erik A1 - Quinteros, Javier A1 - Oberhänsli, Roland A1 - Bousquet, Romain A1 - de Capitani, Christian T1 - Relative impact of mantle densification and eclogitization of slabs on subduction dynamics: A numerical thermodynamic/thermokinematic investigation of metamorphic density evolution JF - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth N2 - Understanding the relationships between density and spatio-thermal variations at convergent plate boundaries is important for deciphering the present-day dynamics and evolution of subduction zones. In particular, the interaction between densification due to mineralogical phase transitions and slab pull forces is subject to ongoing investigations. We have developed a two-dimensional subduction zone model that is based on thermodynamic equilibrium assemblage calculations and includes the effects of melting processes on the density distribution in the lithosphere. Our model calculates the "metamorphic density" of rocks as a function of pressure, temperature and chemical composition in a subduction zone down to 250 km. We have used this model to show how the hydration, dehydration, partial melting and fractionation processes of rocks all influence the metamorphic density and greatly depend on the temperature field within the subduction system. These processes are largely neglected by other approaches that reproduce the density distribution within this complex tectonic setting. Our model demonstrates that the initiation of edogitization (i.e., when crustal rocks reach higher densities than the ambient mantle) of the slab is not the only significant process that makes the descending slab denser and generates the slab pull force. Instead, the densification of the lithospheric mantle of the sinking slab starts earlier than eclogitization and contributes significantly to slab pull in the early stages of subduction. Accordingly, the complex metamorphic structure of the slab and the mantle wedge has an important impact on the development of subduction zones. (C) 2014 Elsevier B.V. All rights reserved. KW - Density KW - Melt KW - Metamorphism KW - Subduction KW - Thermodynamic modeling KW - Thermo-mechanical modeling Y1 - 2014 U6 - https://doi.org/10.1016/j.tecto.2014.09.009 SN - 0040-1951 SN - 1879-3266 VL - 637 SP - 20 EP - 29 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Lambert, Ian A1 - Oberhänsli, Roland T1 - Towards more effective risk reduction: Catastrophic tsunami JF - Episodes : journal of international geosciences N2 - The International Union of Geological Sciences (JUGS) is evaluating whether there are additional geoscientific activities that would be beneficial in helping mitigate the impacts of tsunami. Public concerns about poor decisions and inaction, and advances in computing power and data mining call for new scientific approaches. Three fundamental requirements for mitigating impacts of natural hazards are defined. These are: (1) improvement of process-oriented understanding, (2) adequate monitoring and optimal use of data, and (3) generation of advice based on scientific, technical and socio-economic expertise. International leadership/coordination is also important. To increase the capacity to predict and mitigate the impacts of tsunami and other natural hazards a broad consensus is needed. The main needs include the integration of systematic geological inputs - identifying and studying paleo-tsunami deposits for all subduction zones; optimising coverage and coordination of geodetic and seismic monitoring networks; underpinning decision making at national and international scales by developing appropriate mechanisms for gathering, managing and communicating authoritative scientific and technical advice information; international leadership for coordination and authoritative statements of best approaches. All these suggestions are reflected in the Sendai Agreement, the collective views of the experts at the International Workshop on Natural Hazards, presented later in this volume. Y1 - 2014 SN - 0705-3797 VL - 37 IS - 4 SP - 229 EP - 233 PB - Geological Society of India CY - Bangalore ER - TY - JOUR A1 - Pourteau, Amaury A1 - Bousquet, Romain A1 - Vidal, Olivier A1 - Plunder, Alexis A1 - Duesterhoeft, Erik A1 - Candan, Osman A1 - Oberhänsli, Roland T1 - Multistage growth of Fe-Mg-carpholite and Fe-Mg-chloritoid, from field evidence to thermodynamic modelling JF - Contributions to mineralogy and petrology N2 - We provide new insights into the prograde evolution of HP/LT metasedimentary rocks on the basis of detailed petrologic examination, element-partitioning analysis, and thermodynamic modelling of well-preserved Fe-Mg-carpholite- and Fe-Mg-chloritoid-bearing rocks from the Afyon Zone (Anatolia). We document continuous and discontinuous compositional (ferromagnesian substitution) zoning of carpholite (overall X-Mg = 0.27-0.73) and chloritoid (overall X-Mg = 0.07-0.30), as well as clear equilibrium and disequilibrium (i.e., reaction-related) textures involving carpholite and chloritoid, which consistently account for the consistent enrichment in Mg of both minerals through time, and the progressive replacement of carpholite by chloritoid. Mg/Fe distribution coefficients calculated between carpholite and chloritoid vary widely within samples (2.2-20.0). Among this range, only values of 7-11 correlate with equilibrium textures, in agreement with data from the literature. Equilibrium phase diagrams for metapelitic compositions are calculated using a newly modified thermodynamic dataset, including most recent data for carpholite, chloritoid, chlorite, and white mica, as well as further refinements for Fe-carpholite, and both chloritoid end-members, as required to reproduce accurately petrologic observations (phase relations, experimental constraints, Mg/Fe partitioning). Modelling reveals that Mg/Fe partitioning between carpholite and chloritoid is greatly sensitive to temperature and calls for a future evaluation of possible use as a thermometer. In addition, calculations show significant effective bulk composition changes during prograde metamorphism due to the fractionation of chloritoid formed at the expense of carpholite. We retrieve P-T conditions for several carpholite and chloritoid growth stages (1) during prograde stages using unfractionated, bulk-rock XRF analyses, and (2) at peak conditions using compositions fractionated for chloritoid. The P-T paths reconstructed for the Kutahya and Afyon areas shed light on contrasting temperature conditions for these areas during prograde and peak stages. KW - HP/LT metamorphism KW - Carpholite KW - Chloritoid KW - Growth zoning KW - Element partitioning KW - Chemical fractionation Y1 - 2014 U6 - https://doi.org/10.1007/s00410-014-1090-7 SN - 0010-7999 SN - 1432-0967 VL - 168 IS - 6 PB - Springer CY - New York ER - TY - INPR A1 - Scheffler, Franziska A1 - Oberhänsli, Roland A1 - Pourteau, Amaury A1 - Candan, Osman A1 - Di Lucia, Matteo T1 - The rosetta marbles from feslegen, A-ren unit, SW Anatolia T2 - International journal of earth sciences Y1 - 2014 U6 - https://doi.org/10.1007/s00531-013-0936-y SN - 1437-3254 SN - 1437-3262 VL - 103 IS - 2 SP - 485 EP - 486 PB - Springer CY - New York ER -