Co-eruption of carbonate and silicate magmas during volcanism in the Limagne graben (French Massif Central)

Chazot, Gilles; Mergoil-Daniel, Juliette

doi:10.1016/j.lithos.2012.06.032

Cited by 16 publications

(9 citation statements)

References 59 publications

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“…Experimentally shocked dolomite (Sk ala et al 2002), however, shows a comparable though more fractured microstructure than observed in the UNAM-7 sample. A formation from melt is also indicated, as comparable microstructures were described in volcanic carbonatites or alvikite xenoliths (Rosatelli et al 2003), immiscible dolomite globules (Chazot et al 2003), and dolomite clasts (Chazot and Mergoil-Daniel 2012). An alternative scenario may be that elevated temperatures induced a solid-state recrystallization as described by Deutsch and Langenhorst (2007).…”

Section: The Polymict Silicate Melt-poor Brecciamentioning

confidence: 59%

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Evidence for shock‐induced anhydrite recrystallization and decomposition at the UNAM‐7 drill core from the Chicxulub impact structure

Salge

Stosnach

Rosatelli

et al. 2019

Meteorit & Planetary Scien

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Drill core UNAM‐7, obtained 126 km from the center of the Chicxulub impact structure, outside the crater rim, contains a sequence of 126.2 m suevitic, silicate melt‐rich breccia on top of a silicate melt‐poor breccia with anhydrite megablocks. Total reflection X‐ray fluorescence analysis of altered silicate melt particles of the suevitic breccia shows high concentrations of Br, Sr, Cl, and Cu, which may indicate hydrothermal reaction with sea water. Scanning electron microscopy and energy‐dispersive spectrometry reveal recrystallization of silicate components during annealing by superheated impact melt. At anhydrite clasts, recrystallization is represented by a sequence of comparatively large columnar, euhedral to subhedral anhydrite grains and smaller, polygonal to interlobate grains that progressively annealed deformation features. The presence of voids in anhydrite grains indicates SOx gas release during anhydrite decomposition. The silicate melt‐poor breccia contains carbonate and sulfate particles cemented in a microcrystalline matrix. The matrix is dominated by anhydrite, dolomite, and calcite, with minor celestine and feldspars. Calcite‐dominated inclusions in silicate melt with flow textures between recrystallized anhydrite and silicate melt suggest a former liquid state of these components. Vesicular and spherulitic calcite particles may indicate quenching of carbonate melts in the atmosphere at high cooling rates, and partial decomposition during decompression at postshock conditions. Dolomite particles with a recrystallization sequence of interlobate, polygonal, subhedral to euhedral microstructures may have been formed at a low cooling rate. We conclude that UNAM‐7 provides evidence for solid‐state recrystallization or melting and dissociation of sulfates during the Chicxulub impact event. The lack of anhydrite in the K‐Pg ejecta deposits and rare presence of anhydrite in crater suevites may indicate that sulfates were completely dissociated at high temperature (T > 1465 °C)—whereas ejecta deposited near the outer crater rim experienced postshock conditions that were less effective at dissociation.

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Section: The Polymict Silicate Melt-poor Brecciamentioning

confidence: 59%

“…), immiscible dolomite globules (Chazot et al. ), and dolomite clasts (Chazot and Mergoil‐Daniel ). An alternative scenario may be that elevated temperatures induced a solid‐state recrystallization as described by Deutsch and Langenhorst ().…”

Section: Discussionmentioning

confidence: 99%

Evidence for shock‐induced anhydrite recrystallization and decomposition at the UNAM‐7 drill core from the Chicxulub impact structure

Salge

Stosnach

Rosatelli

et al. 2019

Meteorit & Planetary Scien

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“…Rather, the intermediate initial (Hf) values ranging from +7.0 to +14.8 suggest a metasomatized sub-continental lithospheric mantle. Subsequent enrichment of the mantle in incompatible trace elements such as HFSE, Th and U (Aulbach et al, 2008;Kalfoun et al, 2002;Pfänder et al, 2012) by carbonatite metasomatism can be considered beneath the French Massif Central (Chazot et al, 2003;Paquette and Mergoil-Daniel, 2009;Chazot and Mergoil-Daniel, 2012). This is probably responsible for some variability of the (Hf) values, as well as the possibility of a weak continental crust assimilation.…”

Section: Discussion: Origin and Formation Of The Zirconsmentioning

confidence: 99%

Origin of zircon megacrysts in alkaline lavas (French Massif Central): Petrology and in situ U-Pb-Hf isotopes

Paquette

Chazot

Gannoun

2020

Journal of Volcanology and Geothermal Research

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In the south eastern Devès volcanic domain of the French Massif Central, we sampled red zircon megacrysts in, both, alluvium from a small stream and neighbouring mugearite lava. LA-ICP-MS U-Pb dating results yield similar ages for both suites of zircons at about 2.6 Ma. Superchondritic signatures of the Hf isotopes clearly indicate a depleted mantle source for these zircons. The mugearite lava also contains xenoliths of mantle (lherzolites) and lower crustal rocks (granulites). The chemical compositions of the minerals within the mugearite lava are 2 similar to the mineral compositions found in these xenoliths (granulites) and granulite and peridotite xenoliths from other volcanic localities of the Massif Central. The mugearite lava also preserves Variscan zircon crystals dated at 285 Ma, originating from recycled lower continental crust. In spite of their mantle origin, as recorded by in situ Hf isotopes, the geochemistry suggests that these Pliocene zircons do not result from crystallization in the mantle or in mantle-derived mafic magmas. In order to explain this inconsistency, we propose that these zircon grains crystallized from felsic melts produced during the ultimate differentiation of mantle-derived mafic magmas in the mid or upper continental crust. Subsequently, a last basaltic batch forced its way to the surface, scavenging upper mantle and lower crust xenoliths as well as zircon xenocrysts formed in these felsic melts which partly dissolved during their ascent. Large amounts of Cenozoic zircon megacrysts are often associated with sapphires in alluvial deposits in many continental volcanic domains, not only in the French Massif Central but also worldwide. Consequently, a huge volume of felsic differentiates issued from mantlederived basaltic magmas might be suspected in many alkaline volcanic domains at the global scale.

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“…However, the effects of the magmatic framework are not limited to the hydrothermal flow; some phreato-magmatic events and associated deposits may have impacted the sedimentation. A phreato-magmatic activity that persisted from the Chattian to the Early Aquitanian has been recorded in the Grand Gandaillat area (Figure 13; Goër de Hervé, 2000;Michon, 2000;Chazot and Mergoil-Daniel, 2012). A phreato-magmatic activity that persisted from the Chattian up to the Early Aquitanian has been recorded in the Grand Gandaillat area (Figure 18; Goër de Hervé, 2000;Michon, 2000;Chazot and Mergoil-Daniel, 2012).…”

Section: Contrasting Buildup Composition Size and Distribution Through Timementioning

confidence: 99%

“…A phreato-magmatic activity that persisted from the Chattian to the Early Aquitanian has been recorded in the Grand Gandaillat area (Figure 13; Goër de Hervé, 2000;Michon, 2000;Chazot and Mergoil-Daniel, 2012). A phreato-magmatic activity that persisted from the Chattian up to the Early Aquitanian has been recorded in the Grand Gandaillat area (Figure 18; Goër de Hervé, 2000;Michon, 2000;Chazot and Mergoil-Daniel, 2012). The influence of volcanism on subaerial and lacustrine deposits in a rift setting has been extensively discussed (Cerling, 1994;Wright and Barnett, 2015;Szatmari and Milani, 2016) and contributes to the changes in the alkaline conditions and/or the modification of magnesium, calcium and silica concentrations in lakes (Cerling, 1994;Armienta et al, 2008) in lakes.…”

Section: Contrasting Buildup Composition Size and Distribution Through Timementioning

confidence: 99%

The Limagne Basin: a journey through modern and fossil microbial deposits

Vennin¹,

Bouton²,

Roche³

et al. 2021

BSGF - Earth Sci. Bull.

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The Limagne Basin (Massif Central, France) originated during a major, European-scale, extensive event (European Cenozoic Rift System), which led to the formation of several rift systems in the foreland of the Alps between the Upper Eocene and Pliocene. A fluvio-lacustrine system emplaced in the basin and resulted in a mixed carbonate-siliciclastic sedimentation in which microbial and metazoan buildups occupy an important place. However, microbial deposits are not exclusive to the Cenozoic history of the Limagne Basin; nowadays, in the basin, they still form in association with thermal spring systems. A fieldtrip was carried out in the Limagne Basin as part of the Microbialites: formation, evolution and diagenesis (M-Fed) meeting (October 2019). The objective of this excursion was to assess the diversity of modern and fossil (Chattian to Aquitanian) microbial sediments and structures in three prime locations (the Jussat and Chadrat outcrops and the Grand Gandaillat quarry). A detailed description of the morphologies and fabrics of the buildups and their associated biotic components can be used to discuss the spatio-temporal distribution pattern. Different margin models are proposed based on the changes in the distribution, morphology and size of the microbial and metazoan-rich deposits through time. The Jussat outcrop offers novel perspectives to unravel the evolution of the lacustrine/palustrine cycles over time and to establish a long-term paleoenvironmental history of the western margin of the basin during the Aquitanian. These cycles are composed of (i) lacustrine sedimentation comprising microbial and metazoan buildups and organic matter-rich marls reflecting a period of high accommodation, and (ii) palustrine deposits made of mudstones and clayey paleosoils, indicative of a period of low accommodation. It is suggested that climatic, tectonic, volcanic and local parameters (physiography, substrate) control the deposition of the buildups in each of the different cycles. In addition, the modern microbial mats of the Sainte-Marguerite and La Poix outcrops offer an opportunity to approach the controlling processes at the origin of the mineralization involved in the formation of the microbialites and their preservation in the fossil record.

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Co-eruption of carbonate and silicate magmas during volcanism in the Limagne graben (French Massif Central)

Cited by 16 publications

References 59 publications

Evidence for shock‐induced anhydrite recrystallization and decomposition at the UNAM‐7 drill core from the Chicxulub impact structure

Evidence for shock‐induced anhydrite recrystallization and decomposition at the UNAM‐7 drill core from the Chicxulub impact structure

Origin of zircon megacrysts in alkaline lavas (French Massif Central): Petrology and in situ U-Pb-Hf isotopes

The Limagne Basin: a journey through modern and fossil microbial deposits

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