Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Teddy Parra is active.

Publication


Featured researches published by Teddy Parra.


Journal of Geophysical Research | 1998

Midcrustal shear zones in postorogenic extension: Example from the northern Tyrrhenian Sea

Laurent Jolivet; Claudio Faccenna; Bruno Goffé; Massimo Mattei; Federico Rossetti; Christophe Brunet; Fabrizio Storti; R Funiciello; Jean Cadet; N. D'Agostino; Teddy Parra

Metamorphic core complexes of the Aegean region have revealed midcrustal, shallow-dipping extensional shear zones. These shear zones display constant kinematic indicators over large regions (100–200 km). We analyze the example of the northern Tyrrhenian Sea and then compare it to the Aegean region. We first summarize our observations on ductile extension and metamorphic evolution in the northern Tyrrhenian Sea from Alpine Corsica to Tuscany. (1) Extension migrated from west to east from the early Miocene in Corsica to the Recent in the Apennines; (2) Extension is accommodated by shallow east dipping extensional shear zones at the depth of the brittle-ductile transition, from the early Miocene to the Pliocene. (3) West dipping normal faults accommodate extension on the eastern side of the volcanic arc. (4) Extension is preceded along the convergence front by the formation of a thrust wedge, where high-pressure and low-temperature conditions are recorded; maximum PT conditions decrease toward the east, and PT paths are systematically very cold, suggesting that a large part of the exhumation occurred during synorogenic extension. We discuss the possible mechanisms that account for constant shear sense over large domains. The model involves retreat of the slab and migration of the volcanic arc. Partially molten lower crust acts as a low strength zone where extensional strain is localized. Eastward motion of the upper mantle as a consequence of the migration of the slab induced a component of shear toward the volcanic arc at the base of the stronger upper crust. In the weak upper mantle and lower crust, to the west of the volcanic arc, extensional stresses are not transmitted; this produces a top-to-the-east sense of shear at the base of the upper crust that migrates eastward, following arc migration.


Lithos | 2002

Relation between the intensity of deformation and retrogression in blueschist metapelites of Tinos Island (Greece) evidenced by chlorite–mica local equilibria

Teddy Parra; Olivier Vidal; Laurent Jolivet

The late greenschist deformation of the Cycladic Blueschists unit on Tinos Island evolves along a NE–SW gradient of non-coaxial strain across a major extensional shear zone. Deformation is more intense and the greenschist overprint is also more severe close to the shear zone that separates the Cycladic Blueschists from the upper ophiolitic unit in the NE of the island. The compositional variability of chlorite and K-white mica (KWM) in metapelites sampled along a NE–SW cross-section is characteristic of their P–T conditions of crystallization and is mainly characterized by variations of their Si, Al, Fe and Mg contents due to the Tschermak substitution (SiIV(Fe, Mg)VI=AlVIAlIV). Multi-equilibrium P–T estimates based on the assumption of local equilibrium indicate that each sample recorded a part of the P–T history, which depends on the distance to the contact to the main shear zone, i.e. the intensity and the pattern of deformation. The combination of P–T estimates obtained from all the samples collected along the transect provides a continuous P–T path which is composed of two parts. It provides insights on the syn- and post-orogenic exhumation for some of the Cycladic Blueschists. In particular, we could distinguish two stages in the exhumation process. A first stage in the blueschist facies occurred along a cold P–T path during the construction of the Hellenides. The second exhumation stage occurred along a warmer P–T path during the formation of the Aegean sea. Between the two stages of exhumation, there is a thermal reequilibration of the crust and a partial thermal overprint of the blueschist parageneses.


American Mineralogist | 2005

Thermodynamic properties of the Tschermak solid solution in Fe-chlorite: Application to natural examples and possible role of oxidation

Olivier Vidal; Teddy Parra; Philippe Vieillard

Abstract The standard-state thermodynamic properties of 14 Å Fe-amesite [Fe4Al4Si2O10(OH)8] were calculated from the reequilibration experiments of Pana et al. (2005) and natural data bearing on the Fe-Mg partitioning between chlorite and chloritoid over a wide range of pressure (P). temperature (7), and rock composition. The combination of these data with the three-site mixing model and thermodynamic properties of daphnite proposed by Vidal et al. (2001) led us to reappraise the evolution of the Margules parameter WGAlFe with pressure and temperature. The new data [H0fFe-Am = -7607460 J/mol, .S0Fe-Am = 514.8 J/(mol·K), V0Fe-Am = 20.90 J/bar, WGAlFe = 1200 - 31T + 0.7(P - 1)] are compatible with all the natural data and reequilibration experiments, and in fair agreement with the results of synthesis. They are used to calculate the compositional evolution of chlorite with T. P, or αO2 at different bulk-system compositions. The calculated phase relations and chlorite compositions are compared with previous experiments conducted in the FeO-Al2O3-SiO2-H2O system. The addition of the Fe-amesite end-member increases the number of equilibria that can be calculated for any natural assemblage involving chlorite. Two independent equilibria are obtained for natural (Fe-Mg)-chlorite-quartz or diaspore assemblages. It is therefore possible to estimate metamorphic conditions for high-variance assemblages from the composition of chlorite. We discuss the reliability of such P-T estimates using natural chlorites occurring in low-pressure and low-temperature or medium- to high-pressure and temperature samples. Assuming that the proposed model and thermodynamic parameters are correct, these various natural data suggest that XFe3+ [= Fe3+/(Fe2+ + Fe3+)] in metamorphic chlorites is low (<0.1), whereas it can be as high as 0.3 in Si- and Mg-rich chlorites formed at low -P-T conditions.


American Mineralogist | 2005

Experimental data on the Tschermak substitution in Fe-chlorite

Teddy Parra; Olivier Vidal; Thomas Theye

Abstract Iron chlorite with compositions intermediate between the two end-members daphnite [Fe5Al2Si3O10(OH)8] and Fe-amesite [Fe4Al4Si2O10(OH)8] were synthesized from gels, under fO₂ conditions defined by the solid oxygen buffer Fe-FeO. The unit-cell parameters and volume of chlorite with Si-content ranging from 2.3 to 2.7 were calculated. A least-squares fit of these data yields V0Fe-ames = 213.06 cm3 and V0daph = 216.50 cm3. The molar volume of daphnite is similar to that estimated by Vidal et al. (2001), but the volume difference between Fe-amesite and daphnite is too low. The experimental data were also fitted for reasonable values of V0Daph - V0Fe-ames and VFeMg-1, with linear (ideal) or non-ideal volume models involving a positive excess volume. With these models we obtain V0Daph between 216 cm3 and 217.49 cm3, and V0Fe-ames between 209 and 211.35 cm3. Equilibration experiments involving chlorite with almandine-hercynite/fayalite or chloritoidhercynite/ fayalite provide data on the chlorite composition as a function of T and P at temperatures between 420 and 520 °C and pressures between 3 and 20 kbar, at fO₂ buffered by the assemblage Fe- FeO. Initial Si-rich and Si-poor chlorite compositions converged in most cases toward an equilibrium composition during the experiments. The results show that the Si-content of chlorite is sensitive to temperature for the various divariant assemblages. The most definitive results, obtained for the assemblage chlorite-almandine-fayalite, were used to estimate H0fFe-amesite and the Al-Fe Margules parameter for the various sets of daphnite and Fe-amesite molar volumes constrained from the synthetic chlorites. The results indicate that H0fFe-amesite = -7616 ± 3 kJ and WGAlFe ~ -10 kJ.


European Journal of Mineralogy | 2003

Room temperature compressibility of clinochlore and chamosite

Thomas Theye; Teddy Parra; Christian Lathe

The room temperature compressibility of one synthetic chamosite and two intermediate iron magnesium chlorites has been measured up to 87 kbar in situ using a MAX-80 multi-anvil press and synchrotron radiation. The Murnaghan bulk compressibility moduli range between 690 and 911 kbar. These values are much higher than data previously published by Hazen & Finger (1978).


American Journal of Science | 2001

A Thermodynamic Model for Fe-Mg Aluminous Chlorite Using Data from Phase Equilibrium Experiments and Natural Pelitic Assemblages in the 100° to 600°c, 1 to 25 kb Range

Olivier Vidal; Teddy Parra; Fabien Trotet


Contributions to Mineralogy and Petrology | 2002

A thermodynamic model for Fe-Mg dioctahedral K white micas using data from phase-equilibrium experiments and natural pelitic assemblages

Teddy Parra; Olivier Vidal; Phillipe Agard


Journal of Petrology | 2005

Exhumation Paths of High-Pressure-Low- Temperature Metamorphic Rocks from the Lycian Nappes and the Menderes Massif (SW Turkey): a Multi-Equilibrium Approach

Gaëtan Rimmelé; Teddy Parra; Bruno Goffé; Roland Oberhänsli; Laurent Jolivet; Osman Candan


Geological Society of America Special Papers | 2004

Strain localization during crustal-scale boudinage to form extensional metamorphic domes in the Aegean Sea

Laurent Jolivet; Vincent Famin; Caroline Mehl; Teddy Parra; Charles Aubourg; Ronan Hébert; Pascal Philippot


Lithos | 2018

Nanoscale chemical zoning of chlorite and implications for low-temperature thermometry: Application to the Glarus Alps (Switzerland)

Franck Bourdelle; Olivier Beyssac; Teddy Parra; Christian Chopin

Collaboration


Dive into the Teddy Parra's collaboration.

Top Co-Authors

Avatar

Olivier Vidal

Centre national de la recherche scientifique

View shared research outputs
Top Co-Authors

Avatar

Bruno Goffé

École Normale Supérieure

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Vincent Famin

Institut de Physique du Globe de Paris

View shared research outputs
Top Co-Authors

Avatar

Ronan Hébert

Centre national de la recherche scientifique

View shared research outputs
Top Co-Authors

Avatar

Christian Chopin

École Normale Supérieure

View shared research outputs
Top Co-Authors

Avatar

Christophe Brunet

Institut de Physique du Globe de Paris

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Fabien Trotet

École Normale Supérieure

View shared research outputs
Researchain Logo
Decentralizing Knowledge