Article
Geosciences, Multidisciplinary
Veronique Gardien, Jean-Emmanuel Martelat, Philippe-Herve Leloup, Gweltaz Maheo, Benoit Bevillard, Pascal Allemand, Patrick Monie, Jean-Louis Paquette, Anne-Sabine Grosjean, Michel Faure, Cyril Chelle-Michou, Clementine Fellah
Summary: A leucogranite sill in the footwall of the extensional Pilat shear zone was emplaced and sheared between 301.8 +/- 3.1 and 303.0 +/- 1.6 Ma. The existence of a relief south of the shear zone and the filling of the St. Etienne Basin confirm the extensional phase. The rapid exhumation of the Velay dome was likely due to localized sub crustal lithospheric mantle dripping.
Article
Geochemistry & Geophysics
Benedict J. R. Harris, Jan C. M. De Hoog, Ralf Halama, Hans-Peter Schertl, Yi-Xiang Chen
Summary: This study investigates the sources and timing of fluid infiltration in the whiteschists from the Dora-Maira massif in the Western Alps. It utilizes boron isotopes and other fluid-mobile trace elements in phengite to understand the metasomatic fluid influx. The results suggest that a B-rich sediment-derived fluid is the main source of B in the whiteschists, while the source of the Mg-rich fluids cannot be determined. This study demonstrates the usefulness of in situ analyses in unraveling complex fluid-rock interaction histories.
CONTRIBUTIONS TO MINERALOGY AND PETROLOGY
(2023)
Article
Geosciences, Multidisciplinary
Irina. V. Karmysheva, Vladimir G. Vladimirov, Sergey N. Rudnev, Vladislav A. Yakovlev, Dina V. Semenova
Summary: Accretionary-collisional events at the western margin of the Tuva-Mongolian microcontinent explain the contradictory Cambrian geodynamic history of the western Central Asian Orogenic Belt. The Erzin metamorphic complex in the tectonic Erzin zone is composed of high-grade metamorphic rocks formed under variable metamorphic conditions. The complex underwent multiple stages of ductile deformation, marking a collisional event at 495 Ma.
JOURNAL OF ASIAN EARTH SCIENCES
(2021)
Article
Geosciences, Multidisciplinary
Abhinaba Roy, Sandip Kumar Roy, H. M. Ramchandra
Summary: The mineral assemblages in ductile shear zones are affected by high-temperature fluids, leading to chemical metasomatism. In the Sakoli Fold Belt of central India, the occurrence of sillimanite in shear zones is influenced by infiltrated high-temperature fluids. The growth of sillimanite in these shear zones coincides with the peak of deformation and metamorphism, possibly due to the high-strain environment.
JOURNAL OF EARTH SYSTEM SCIENCE
(2023)
Article
Geosciences, Multidisciplinary
Kun Zhou, Yi-Xiang Chen, Jia-Wei Xiong, Hans-Peter Schertl, Xiao-Ping Xia
Summary: This study investigates the impact of fluid action on zircon geochemistry in subduction zones, particularly during metamorphic and metasomatic processes. The results show that fluid action significantly affects the U-Pb and O isotope systems of zircon, especially when external metasomatic fluids are involved.
GEOSCIENCE FRONTIERS
(2023)
Article
Geochemistry & Geophysics
Ruth Keppler, Roman Vasin, Michael Stipp, Tomas Lokajicek, Matej Petruzalek, Nikolaus Froitzheim
Summary: The study characterizes the elastic anisotropies of deformed crustal rocks in the Alps, showing a wide range of seismic velocity patterns within the same lithology. Crystallographic preferred orientations and mineral volume fractions are measured to determine the average elastic anisotropy of typical crustal rocks. By modeling the closure of microcracks at increasing depth, an average elastic anisotropy of 4% for gneiss rocks is determined, providing an approximate value for seismic models at a lithospheric scale.
Article
Geochemistry & Geophysics
Stefano Zanchetta, Sofia Locchi, Gregorio Carminati, Manuel Mancuso, Chiara Montemagni, Andrea Zanchi
Summary: Low-angle normal faults (LANFs) are the main structures in the central Southern Alps area of Northern Italy, and they are in contact with the Upper Carboniferous-Permian volcanic-sedimentary succession. Tourmalinites, which are likely of metasomatic origin, frequently replace former cataclasites along LANFs. LANFs, together with high-angle faults, controlled the opening of the Permian Orobic Basin and were potential pathways for hydrothermal fluids. Furthermore, the same fluids may have played a role in the formation of Uranium ore deposits.
Article
Physics, Multidisciplinary
S. Borsanyi, Z. Fodor, J. N. Guenther, R. Kara, S. D. Katz, P. Parotto, A. Pasztor, C. Ratti, K. K. Szabo
Summary: This Letter introduces a new scheme for extrapolating the equation of state of QCD to finite chemical potential with improved convergence properties, allowing extension to high baryonic chemical potentials. The continuum extrapolated lattice results for the new expansion coefficients are presented, showing thermodynamic observables up to mu(B)/T <= 3.5. This novel expansion overcomes the limitations of traditional Taylor expansion methods, providing a solution to the poor signal-to-noise ratio in determining Taylor coefficients from lattice calculations.
PHYSICAL REVIEW LETTERS
(2021)
Article
Geosciences, Multidisciplinary
Susobhan Neogi, Tapan Pal
Summary: The Sonapahar sillimanite-corundum deposit in Meghalaya, Northeast India, is associated with high-grade metapelites and features an unusual occurrence of sillimanite-quartz, corundum-quartz, sapphirine-phlogopite-corundum-sillimanite rock. The pockets of sillimanite and corundum within the host quartz sillimanite schist have contrasting chemical signatures, suggesting a significant role of metasomatism in modifying the host rocks during post-peak metamorphism. Structural features and mineral enrichments near shear zones indicate that metasomatism played a key role in the formation of sillimanite-corundum rocks.
JOURNAL OF EARTH SYSTEM SCIENCE
(2021)
Article
Geochemistry & Geophysics
Martin Kubes, Jaromir Leichmann, Jana Kotkova, Renata Copjakova, Marketa Hola, Jiri Slama
Summary: A variable assemblage of rocks in the Bohemian Massif reflects the incorporation of contrasting mantle domains during the Variscan orogeny. This study provides important insights into the mantle history during the formation of the Variscan orogenic belt in Central Europe.
Article
Geochemistry & Geophysics
M. Dumanska-Slowik, T. Powolny, G. Nguyen Khac
Summary: The alkaline Cho Don complex in NE Vietnam is formed by mafic-felsic suites that resulted from widespread magmatism in the early Permian-late Triassic period. This study investigates the petrogenesis of nepheline syenite and its relationship with cogenetic scapolite-rich gabbro in the Bang Phuc massif. The nepheline syenite formed through fractional crystallization of mantle-derived basaltic melt modified by subduction-related components, and magma evolution involved the contribution of asthenospheric-derived melts. The presence of different minerals and their alteration patterns indicate fluid-rock interactions and changes in the crystalline structure of the rock.
JOURNAL OF PETROLOGY
(2023)
Article
Geosciences, Multidisciplinary
Alberto Vasquez-Serrano, Angel Francisco Nieto-Samaniego, Elizabeth Rangel-Granados, Susana Alaniz-Alvarez, Maria de Jesus Paulina Olmos-Moya
Summary: Detachment zones play a significant role in the geometry, structural style, and amount of shortening in fold and thrust belts by accommodating deformation through brittle-ductile structures. Detailed structural analysis of an ancient detachment zone in Mexico reveals a sub-simple shear mechanism of deformation and the presence of complex shear structures. The study highlights the importance of weak layers and the development of detachment zones in contraction of sedimentary packages.
JOURNAL OF STRUCTURAL GEOLOGY
(2021)
Article
Geosciences, Multidisciplinary
Matej Machek, Igor Soejono, Jiri Slama, Eliska Zackova
Summary: The high-grade metamorphic complexes along the northern Moldanubian periphery of the central Bohemian Massif provide a detailed structural record of the collisional evolution of the Variscan Orogeny. Multiple tectonic events were identified through the analysis of rock structures and microstructures, as well as geochronology.
JOURNAL OF THE GEOLOGICAL SOCIETY
(2022)
Article
Geosciences, Multidisciplinary
Sofia Locchi, Stefano Zanchetta, Andrea Zanchi
Summary: Well-preserved Permian extensional structures have been found in the central Southern Alps, providing important insights into the tectonics of the region during the Permian period.
INTERNATIONAL JOURNAL OF EARTH SCIENCES
(2022)
Article
Geosciences, Multidisciplinary
Jean-Baptiste Jacob, Emilie Janots, Carole Cordier, Stephane Guillot
Summary: Small bodies of mantle-derived peridotites and other ultramafic rocks in exhumed lower crustal units provide evidence of the geodynamic evolution of an orogen. Petrographic diversity, thermobarometric calculations, and geochemical analyses suggest a complex history of the peridotites before their incorporation in the lower crust during the Variscan Orogeny. Metasomatism, both cryptic and modal, is observed in these peridotites, likely resulting from the percolation of fluids or melts related to Variscan subduction. This study provides important insights into the mantle evolution and geodynamic processes during orogeny.
BSGF-EARTH SCIENCES BULLETIN
(2023)
Article
Geochemistry & Geophysics
A. Maffeis, S. Ferrando, J. A. D. Connolly, C. Groppo, M. L. Frezzotti, D. Castelli
Summary: When studying the migration of subduction fluids within rocks, it is essential to consider the complex post-entrapment effects, such as solvent loss, chemical reactions, and water diffusion. Results from fluid inclusion analysis and thermodynamic modeling can qualitatively describe and explain the chemical characteristics of UHP fluid inclusions.
GEOCHIMICA ET COSMOCHIMICA ACTA
(2021)
Article
Geology
Hua Xiang, James A. D. Connolly
Summary: GeoPS is a program that enables the calculation of stable phase relations throughout the mantle and crust of terrestrial planets, with a wide range of phase equilibrium calculations and an intuitive graphical user interface. The novel Gibbs energy minimization algorithm in GeoPS provides robust and efficient solution to the phase equilibrium problem.
JOURNAL OF METAMORPHIC GEOLOGY
(2022)
Article
Geochemistry & Geophysics
Robert Myhill, James A. D. Connolly
Summary: This article presents the mathematical framework common to all Bragg-Williams models and introduces the necessary tools for building and using such models. The first part discusses the definitions of solid solution effective site occupancy space and the linear algebra needed for transforming solution models. The second part focuses on linear algebra for transforming van Laar and subregular solution models and deriving macroscopic endmember interactions.
CONTRIBUTIONS TO MINERALOGY AND PETROLOGY
(2021)
Article
Geology
Jonas Vanardois, Francoise Roger, Pierre Trap, Philippe Goncalves, Pierre Lanari, Jean-Louis Paquette, Didier Marquer, Florence Cagnard, Benjamin Le Bayon, Jeremie Melleton, Fabrice Barou
Summary: This study investigates mafic eclogite relics in the Aiguilles-Rouges massif of the Western Alps and suggests that they are remnants of continental lower crust exhumed and juxtaposed with lower-grade migmatites in crust-scale vertical transpressive shear zones.
JOURNAL OF METAMORPHIC GEOLOGY
(2022)
Article
Geosciences, Multidisciplinary
Elias D. Kempf, Joerg Hermann, James A. D. Connolly
Summary: Petrographic observations and mineral compositional analyses were used to determine the phase relations and reactions in pro-grade metamorphosed serpentinites in the Bergell contact aureole. The study found seven dehydration reactions, including three previously unidentified ones. Computed phase diagrams reproduced the observed mineral parageneses, with some exceptions. Petrography also revealed a retrograde overprint of the prograde parageneses due to metamorphic and magmatic fluids.
SWISS JOURNAL OF GEOSCIENCES
(2022)
Article
Geosciences, Multidisciplinary
J. Vanardois, P. Trap, F. Roger, P. Goncalves, D. Marquer, J. L. Paquette, G. Siron, T. Baudin
Summary: In this study, the spatial and temporal evolution of mid-crustal flow in the Agly Massif was investigated. The results suggest that the middle crust reached high-temperature and suprasolidus conditions at ca. 325-320 Ma and was partially molten until ca. 300 Ma. The D2 thinning and top-to-the-north shearing were active from ca. 325-290 Ma.
INTERNATIONAL JOURNAL OF EARTH SCIENCES
(2022)
Article
Geosciences, Multidisciplinary
Gregory Dumond, Kevin H. Mahan, Philippe Goncalves, Michael L. Williams, Michael J. Jercinovic
Summary: The Ramsay-Graham heterogeneous simple shear zone model revolutionized our understanding of finite strain variation in orogenic belts. In this study, using syn-kinematic monazite, the micro-scale record of shear strain in two shear zones was explored. The results demonstrate that monazite grains can provide important information on the textural and temporal aspects of shear strain, and can also provide absolute ages for kinematics in continental orogens.
JOURNAL OF STRUCTURAL GEOLOGY
(2022)
Article
Geosciences, Multidisciplinary
Alberto Ceccato, Philippe Goncalves, Luca Menegon
Summary: The study of small-scale shear zones in granitoid rocks provides valuable insights into strain localization processes in the continental crust. Through field, microstructural and petrological analyses, researchers have identified the temperature range (450-500°C) and conditions that promote the nucleation and development of shear zones. The evolution of shear zones in granitoid rocks is influenced by metamorphic reactions, fluid interactions, and mineralogical changes, which in turn affect rheology and fabric evolution. Future research should focus on understanding the feedback processes between deformation, metamorphism, and metasomatism to quantify the evolution of shear zones over time.
JOURNAL OF STRUCTURAL GEOLOGY
(2022)
Article
Geochemistry & Geophysics
Shah Wali Faryad, Josef Jezek, James A. D. Connolly
Summary: This paper presents the application and results of phase diagram and diffusion modelling for constraining metamorphic P-T paths. It discusses the differences between measured garnet zoning profiles and those calculated by phase diagram modelling, as well as the quantification of diffusion in high-grade rocks. The approach allows for the deciphering of reasons behind the discrepancies and the constraint of P-T paths in high-grade rocks.
JOURNAL OF PETROLOGY
(2022)
Article
Geosciences, Multidisciplinary
Jonas Vanardois, Pierre Trap, Francoise Roger, Jeremie Melleton, Didier Marquer, Jean-Louis Paquette, Philippe Goncalves, Florence Cagnard, Benjamin Le Bayon
Summary: This study investigates the dynamics of a crustal-scale shear zone, the mechanisms of pluton emplacement, and the magma sources in the Aiguilles-Rouges and Mont-Blanc massifs in the East Variscan Shear Zone.
JOURNAL OF STRUCTURAL GEOLOGY
(2022)
Article
Geochemistry & Geophysics
Melanie Drilleau, Henri Samuel, Raphael F. Garcia, Attilio Rivoldini, Clement Perrin, Chloe Michaut, Mark Wieczorek, Benoit Tauzin, James A. D. Connolly, Pauline Meyer, Philippe Lognonne, William B. Banerdt
Summary: We present detailed analysis of the structure of Mars using seismic data, revealing the locations of marsquakes and providing insight into the thermal and chemical state of the planet. The results show significant variations in crustal velocity and suggest a relatively hot mantle and a thick lithosphere for Mars.
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2022)
Article
Geochemistry & Geophysics
James A. D. Connolly, Max W. Schmidt
Summary: Centrifuge experiments show evidence of viscous compaction by grain-boundary diffusion-controlled creep in olivine, chromite, and plagioclase aggregates saturated in basaltic liquid. The exponential dependence of shear viscosity on melt fraction observed at low porosities extends to sedimentary porosities. The study suggests that common macroscopic compaction models underestimate the effect of matrix disaggregation and overestimate the viscosities of crystal mushes.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2022)
Article
Geosciences, Multidisciplinary
Michael G. Frothingham, Kevin H. Mahan, Vera Schulte-Pelkum, Philippe Goncalves, Michele Zucali
Summary: Seismic anisotropy is primarily controlled by aligned rock-forming minerals, and previous studies have focused on solid-state shear as the main cause, neglecting the magmatic fabric in plutonic rocks. In this study, we investigate the contributions of magmatic fabric to seismic anisotropy through the analysis of samples from different tectonic settings. Results show that magmatic fabric can lead to significant anisotropy comparable to solid-state deformation, and magmatically aligned feldspar can cause a unique foliation-perpendicular fast velocity. This highlights the importance of considering magmatic fabric in understanding crustal seismic anisotropy.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Mineralogy
Thierry Decrausaz, Marguerite Godard, Manuel D. Menzel, Fleurice Parat, Emilien Oliot, Romain Lafay, Fabrice Barou
Summary: The long-term cycling of carbon on Earth is regulated by mass transfers involving mantle rocks. Through the study of low-grade glass alteration processes along the basal thrust of the Semail Ophiolite in Oman, we found that carbonation occurred in three main stages. The iron and magnesium content of mantle rocks depends on the homogeneity and heterogeneity of the mantle rocks.
EUROPEAN JOURNAL OF MINERALOGY
(2023)
Article
Geochemistry & Geophysics
Fanny Goussin, Stephane Guillot, Gilles Ruffet, Marc Poujol, Emilien Oliot, Anne Replumaz, Carole Cordier, Guillaume Dupont-Nivet, Pierrick Roperch
Summary: This work presents new U-Pb and 40Ar/39Ar ages from the highly deformed units of the Yushu melange in the Tibetan Plateau, helping to refine the chronology of the Paleo-Tethyan oceanic subductions. The study reveals at least three successive tectono-magmatic events in the Yushu melange.