Ou sont les nappes dans le massif central francais?

Ledru, Patrick; Lardeaux, J. M.; Santallier, Danielle; Autran, Albert; Quenardel, Jean-Michel; Floc'h, Jean-Pierre; Lerouge, Gilles; Maillet, N.; Marchand, J.; Ploquin, Alain

doi:10.2113/gssgfbull.v.3.605

Cited by 158 publications

(68 citation statements)

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“…360 to 290 Ma. In the northern part of the Massif Central, these three units are superposed [32,33], forming what is known as the Sioule series, bounded to the west by the major Sillon Houiller strike-slip fault, to the south by the Saint-Gervais granite, to the north by migmatite and granite of Tréban, and to the east by Cenozoic sediments. The Sioule series display Barrovian metamorphism, with maximal recorded temperatures and pressures of ca.…”

Section: Geological Settingmentioning

confidence: 99%

Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)

et al. 2019

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The Echassières district in central France contains complex rare-element ore deposits, whose formation is related to exotic igneous events and several hydrothermal episodes that are not entirely understood to date. Tungsten mineralization consists of three generations of wolframite, characterized by distinct Fe/Mn ratios (8.4; 3.5 and 0.3, for wolframite a, b and c, respectively), formed during three separate hydrothermal episodes related to the Variscan orogeny. Wolframite a occurs in quartz veins of the La Bosse stockwork where it crystallized before the Barrovian metamorphism that affected these veins and the host rock. After metamorphism, before intrusion of the Beauvoir and Colettes granites, wolframite b crystallized in the stockwork during massive topazification. High concentrations of wolframite c occur in the proximal quartz veins in the Mazet area, while only scant amounts are found in the La Bosse stockwork. In both settings, wolframite c precipitated from the fluid responsible for greisen alteration that massively affected the Beauvoir granite. In the La Bosse stockwork, greisen alteration is characterized by hydrothermal topaz that is texturally and chemically distinct from that precipitated during topazification. Supergene alteration responsible for kaolinization of Beauvoir and Colettes granites caused remobilization of a non-negligible amount of tungsten (W) during replacement of wolframite by W-rich goethite in all units of the Echassières district. This model for multiple W mineralizing events is novel and can prove essential in distinguishing potential economic deposits worldwide.

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Section: Geological Settingmentioning

confidence: 99%

Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)

et al. 2019

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“…Paleogeographic setting of major and minor plates, subduction vergence and number of oceans (e.g., Rheic, Moldanubicum Central Massif (MCM), and Paleotethys), consumed during continents convergence, are still debated [e.g., Oliver et al , 1993; Finger and Quadt , 1995; Tait et al , 1997; Torsvik , 1998; Neubauer et al , 1999; von Raumer et al , 2002, 2003]. In general, the geodynamic evolution of the European Paleozoic chain has been explained with two major classes of models: monocyclic [e.g., Matte , 1986; Ledru et al , 1989] and polycyclic models [e.g., Faure et al , 1997, and references therein].…”

Section: Geological Outlinementioning

confidence: 99%

“…In the monocyclic models the Variscan evolution can be subdivided in three main orogenic periods, corresponding to different tectonic styles and metamorphic conditions. They were accurately defined for the French Massif Central evolution [e.g., Ledru et al , 1989], but used as a reference also for the other sectors of the European Variscan chain. An early Variscan period (≥400 Ma) corresponding to a phase of oceanic and continental crust subduction; a meso‐Variscan period (400–340 Ma) characterized by intermediate pressure and temperature metamorphism interpreted as the record of thermal gradient change induced by continental collision; a Neovariscan period (350–280 Ma) characterized by the development of strike‐slip mylonitic belts, accompanying granitoids emplacement between 350 and 320 Ma [ Matte , 1986], followed by the opening of Stephanian and Westphalian basins.…”

Section: Geological Outlinementioning

confidence: 99%

“…In spite of these model divergences, some shared characters can be recognized: the occurrence of a ∼2500 km wide ocean between the Avalonia‐Armorica plates and the Alpine Paleozoic terrains (belonging to Gondwana or to Hunich terranes); the occurrence of active subduction between 425 and 380–370 Ma, followed by continental collision and late orogenic collapse [ Ledru et al , 1989; Malavieille , 1993; Tait et al , 1997; Torsvik , 1998; von Raumer et al , 2003; Faure et al , 2004]. This Variscan geodynamic scenario, assuming solely two facing continents, although simplified, satisfies the different interpretation envisaging Alpine Paleozoic terranes as deriving either from the northern margin of Gondwana (coherent, for example, with the results of Tait et al [1997]) or from the microcontinent (Hunich terranes of von Raumer et al [2003]).…”

Section: Geological Outlinementioning

confidence: 99%

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Permian‐Triassic high thermal regime in the Alps: Result of late Variscan collapse or continental rifting? Validation by numerical modeling

Marotta

Spalla

2007

Tectonics

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[1] The Permian-Triassic igneous activity, associated with regional scale deformation developed under high-temperature/low-pressure (HT-LP) metamorphic conditions and widely recorded in the pre-Alpine crust of the European Alps, can result from late orogenic collapse of a collisional belt or from lithospheric thinning leading to a continental rifting process. In order to reduce this ambiguity, we use a two-dimensional finite element model to give new insights on the sequence of mechanisms operating during active ocean-continent convergence, followed by continental collision and pure gravitational evolution and on the regional geodynamic interpretation of the Paleozoic-Mesozoic evolution of the Alpine area. The modeling predictions are compared with the PT climax conditions of Variscan and Permian-Triassic metamorphism affecting the continental crust of the Helvetic to Southalpine domains. The good agreement between model predictions and natural data realized for the early to Neovariscan evolution indicates that during Paleozoic, the pre-Alpine crust of the Alps was part of an active ocean-continent convergence margin and an intracontinental suture zone. Furthermore, modeling results support the interpretation envisaging a Permian-Triassic lithospheric extension as responsible for the HT metamorphism and related intense igneous activity. This evolution was precursor of the Mesozoic oceanization, during which the tectonic units, coupled and accreted during the Variscan subduction and collision, were separated to form the two passive European and Adriatic continental margins.

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“…It preserves not only evidence of progressive metamorphism, but a changing structural regime from early D 1 ‐D 2 nappe stacking via D 3 folding and anatexis to granite emplacement related to D 4 ( Macaudiere et al ., 1992 ; Montel et al ., 1992 ). This study focuses on the southern part of the Velay Massif where the large Velay pluton (size 6000 km 2 ) cross‐cuts orthogneiss and paragneiss of the Lower Gneiss Unit defined by Ledru et al . (1989 , 1994) (Fig.…”

Section: Geological Settingmentioning

confidence: 99%

Textural evolution in the transition from subsolidus annealing to melting process, Velay Dome, French Massif Central

Dallain

Schulmann

Ledru

1999

Journal Metamorphic Geology

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Petrographic analysis is a useful, but underused tool to aid in distinguishing between subsolidus and anatetic-related textures in migmatites. This study focuses on assessing the relative contributions of these two processes in the development of migmatitic orthogneiss textures in the Velay Massif, French Massif Central. The results of this study show that subsolidus processes are more important in the development of migmatitic textures in the orthogneiss than anatectic leucosome development. Four textural stages are identified from the mylonitic non-anatectic orthogneiss, annealed, migmatitic orthogneiss to diatexite. The monomineralic K-feldspar and plagioclase-muscovite banding was transformed with increasing temperature to polymineralic plagioclase-quartz-muscovite and K-feldspar-quartz-muscovite layers by the wetting of feldspar boundaries during heterogeneous nucleation of quartz from a fluid phase at high surface energy triple points. A further increase of temperature led to the growth of K-feldspar probably related to production of small amounts of melt in plagioclase rich aggregates, controlled by muscovite abundance. Solid state annealing processes in conjunction with incipient anatexis resulted in the formation of apparent granitic-like textures in plagioclase dominated aggregates. By contrast, in K-feldspar dominated aggregates exclusively subsolidus processes prevail, leading to the development of coarse grained leucosome. With the onset of biotite dehydration melting the plagioclase-dominated aggregates are destroyed by the melt whereas the K-feldspar aggregates may be preserved.

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Ou sont les nappes dans le massif central francais?

Cited by 158 publications

References 0 publications

Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)

Multiple Generations of Wolframite Mineralization in the Echassieres District (Massif Central, France)

Permian‐Triassic high thermal regime in the Alps: Result of late Variscan collapse or continental rifting? Validation by numerical modeling

Textural evolution in the transition from subsolidus annealing to melting process, Velay Dome, French Massif Central

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