Article
Geochemistry & Geophysics
Hans-Joachim Massonne, Botao Li
Summary: The study examined the pressure-temperature path of eclogite from Les Essarts high-pressure unit in western France and identified unusual atoll garnet. Through mineral chemistry characterization and thermodynamic modeling, the metamorphic evolution of eclogite was revealed. A geodynamic scenario was outlined to explain the formation and evolution of eclogite in two different geotectonic environments.
Article
Geosciences, Multidisciplinary
Stephen Collett, Karel Schulmann, Pierig Deiller, Pavla Stipska, Vit Peresty, Marc Ulrich, Yingde Jiang, Luc de Hoym de Marien, Jitka Mikova
Summary: This article investigates the high-pressure and high-temperature metamorphism during the Mid-Devonian period in the Variscan Orogeny, focusing on the geological characteristics of the Marianske Lazne Complex (MLC). The unique position of MLC at the base of its original upper plate is highlighted. The study reveals that both MLC and the upper plate developed above a relatively unaltered Neoproterozoic lithospheric mantle, which is important for reconstructing the original architecture of the Variscan terranes.
GEOSCIENCE FRONTIERS
(2022)
Article
Geosciences, Multidisciplinary
Lukas Krmicek, Milan Novak, Robert B. Trumbull, Jan Cempirek, Stanislav Houzar
Summary: Various metacarbonate and calc-silicate rocks in the Bohemian Massif of the Variscan orogen contain tourmaline in different paragenetic settings, each showing distinctive compositional features. The presence of tourmaline with different B-isotope compositions in specific units suggests regional variations and possible metamorphic processes within the studied areas.
GEOSCIENCE FRONTIERS
(2021)
Article
Geochemistry & Geophysics
Johannes E. Pohlner, Afife El Korh, Reiner Klemd, Bernard Grobety, Thomas Pettke, Massimo Chiaradia
Summary: Eclogites, metagabbros, and paragneisses in the Variscan Munchberg Massif underwent a complex succession of igneous, hydrothermal, and metamorphic processes, with geochemical signatures revealing a varied history. The light and dark eclogites were likely formed from different parental magmas, with the former interpreted as plagioclase-rich cumulates and the latter as complementary differentiates. Metagabbros showed an enriched trace element signature and origin from a more enriched mantle source than the eclogites. The rocks experienced limited metamorphic fluid-rock interactions, possibly due to the lack of lawsonite dehydration.
Article
Geology
Florent Cheval-Garabedian, Eric Marcoux, Hugues Raimbourg, Michel Faure
Summary: By studying the La Lucette deposit in the French Armorican Massif, the relationship between Sb-Au-W and the metallogenic processes of the deposit were revealed. The deposit is characterized by four ore deposition stages with different mineral assemblages. The formation of the deposit is closely related to the temperature and mixing processes of the fluids, and does not require significant burial or involvement of late magmatic events.
ORE GEOLOGY REVIEWS
(2023)
Article
Geology
Luc de Hoym de Marien, Pavel Pitra, Marc Poujol, Nathan Cogne, Florence Cagnard, Benjamin Le Bayon
Summary: Two eclogites from the French Massif Central underwent prograde evolution, heating, partial melting, and subsequent exhumation, revealing a complex tectonic history involving an Ordovician rifting event, Devonian subduction, and Carboniferous exhumation. The previously proposed Silurian age for the subduction has been definitively rejected. The petrochronological record of zircon shows a complex pattern of metamorphic ages, while apatite and rutile yield a well-defined age of about 350 Ma. Fractures filled with analcite, thomsonite, plagioclase, and biotite indicate late interaction with alkaline fluids at relatively low temperatures.
JOURNAL OF METAMORPHIC GEOLOGY
(2023)
Article
Geology
R. Arenas, I. Novo-Fernandez, A. Garcia-Casco, Fernandez R. Diez, J. M. Fuenlabrada, M. F. Pereira, J. Abati, Martinez S. Sanchez, F. J. Rubio Pascual
Summary: The Badajoz-Cordoba Unit is a Variscan high-P unit mainly composed of metapelites, metagreywackes, orthogneisses, Grt-amphibolites, and retrogressed eclogites. The unit underwent high-P metamorphism at around 377 Ma, forming rare metapelites with well-preserved high-P mineral assemblages. Pseudosection modelling suggests formation in blueschist facies under high pressure conditions, followed by exhumation and moderate heating, similar to other units in the Variscan Orogen.
INTERNATIONAL GEOLOGY REVIEW
(2021)
Article
Geosciences, Multidisciplinary
R. Dias, C. Coke, A. Ribeiro
Summary: The formation of the Ibero-Armorican Arc played an important role in the Variscan orogeny. The study revealed a heterogeneous sinistral transpressive regime and observed strain partitioning at different scales. The research also identified the coeval development of sedimentary rocks and fold structures related to the deformation.
JOURNAL OF STRUCTURAL GEOLOGY
(2022)
Article
Geochemistry & Geophysics
Oscar Laurent, Simon Couzinie, Luc S. Doucet
Summary: The study reveals the timescales of lower crustal ultra-high temperature metamorphism and the production and transfer of granitic magmas. Zircon petrochronology of felsic and mafic granulite xenoliths from the Variscan eastern French Massif Central shows that these rocks underwent Variscan UHT peak metamorphism at 940-970°C and 8±2 kbar. The zircon U-Pb dates of the felsic granulites range from -315 to -265 Ma, indicating continuous crystallization of zircon upon cooling from the thermal peak. The emplacement of upper crustal granite started at 340 Ma and peaked at 313±3 Ma, reflecting melt extraction along the prograde path of the lower crust. The crystallization ages of mid-crustal migmatites (315-300 Ma) and lower crustal granulites (315-265 Ma) suggest slow cooling in the presence of melt.
EARTH AND PLANETARY SCIENCE LETTERS
(2023)
Article
Geology
Jochen Roetzler, Martin J. Timmerman
Summary: The Saxon Granulite Massif is a key area for understanding the Palaeozoic Variscan orogeny, with a dome structure comprising high-P granulites and low-P metasedimentary rocks. New age and petrologic data suggest that the metaophiolites developed from early Cambrian protoliths and underwent high-P amphibolite facies metamorphism in the mid- to late-Devonian, followed by thermal overprinting by the exhuming hot granulite body in the early Carboniferous. The exhumation and cooling rates of the granulite body are estimated to be around 8 mm/year and 80 degrees C/Ma, with a significant drop in exhumation rate and a slight rise in cooling rate during the different stages of exhumation.
JOURNAL OF METAMORPHIC GEOLOGY
(2021)
Correction
Geosciences, Multidisciplinary
Vojtech Janousek, Pavel Hanzl, Martin Svojtka, John M. Hora, Yulia V. Erban Kochergina, Petr Gadas, Frantisek V. Holub, Axel Gerdes, Krystof Verner, Kristyna Hrdlickova, J. Stephen Daly, David Burianek
Summary: The authors apologize for inadvertently providing an erroneous version of the recalculated titanite analyses data table.
INTERNATIONAL JOURNAL OF EARTH SCIENCES
(2021)
Article
Geology
Francisco J. Rubio Pascual, Luis M. Martin Parra, Ruben Diez Fernandez, Pablo Valverde-Vaquero, Alejandro Diez-Montes, Manuel P. Hacar Rodriguez, Justo Iglesias, Gloria Gallastegui, L. Roberto Rodriguez Fernandez, Aratz Beranoaguirre
Summary: This study examines the geological structures and metamorphic processes in the NW Iberian section of the Variscan Orogen. By analyzing the metamorphic record of tectonic slices, it reveals the transitional process between subduction and collision zones, providing important clues for understanding the construction of orogens.
INTERNATIONAL GEOLOGY REVIEW
(2022)
Article
Geology
Marine Jouvent, Ondrej Lexa, Vit Peresty, Petr Jerabek
Summary: The study focuses on the transition from low-grade phyllites to medium-grade micaschists in the surrounding metasediments, using thermodynamic modeling to determine the P-T conditions of four deformation fabric events. The evolution of Variscan orogenic processes from continental subduction to orogenic wedge formation is characterized by different metamorphic events with varying geothermal gradients. The Erzgebirge part of the Saxothuringian Domain displays an example of active margin evolution involving accretionary prism formation, orogenic wedge building through subducted continental crust accretion, and subsequent extensional collapse.
JOURNAL OF METAMORPHIC GEOLOGY
(2022)
Article
Geosciences, Multidisciplinary
Yan Yang, Chenyue Liang, Changqing Zheng, Xuechun Xu, Xiao Zhou, Pengyue Hu
Summary: This study investigates the Mashan Complex in the Ximashan area and presents new data to constrain the timing, P-T conditions, and P-T path of the complex. The results reveal important information related to collision orogeny and the crustal evolution of the Jiamusi Massif. The peak of granulite-facies metamorphism is inferred to have occurred at 530-500 Ma.
Article
Geosciences, Multidisciplinary
Camille Dusseaux, Aude Gebelin, Philippe Boulvais, Gilles Ruffet, Marc Poujol, Nathan Cogne, Yannick Branquet, Catherine Mottram, Fabrice Barou, Andreas Mulch
Summary: The study assesses the connection between crustal deformation, thermo-mechanical events, and Variscan mineralization by analyzing the geochemical signature and the role of fluids in a Variscan detachment zone. The findings indicate that meteoric fluid infiltration played a major role in the leaching of uranium and the development of a sustained hydrothermal system.
JOURNAL OF STRUCTURAL GEOLOGY
(2022)