Regional-scale paleofluid system across the Tuscan Nappe–Umbria–Marche Apennine Ridge (northern Apennines) as revealed by mesostructural and isotopic analyses of stylolite–vein networks

Beaudoin, N. et al. (2020) Regional-scale paleofluid system across the Tuscan Nappe–Umbria–Marche Apennine Ridge (northern Apennines) as revealed by mesostructural and isotopic analyses of stylolite–vein networks. Solid Earth, 11, pp. 1617-1641. (doi: 10.5194/se-11-1617-2020)

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We report the results of a multiproxy study that combines structural analysis of a fracture–stylolite network and isotopic characterization of calcite vein cements and/or fault coating. Together with new paleopiezometric and radiometric constraints on burial evolution and deformation timing, these results provide a first-order picture of the regional fluid systems and pathways that were present during the main stages of contraction in the Tuscan Nappe and Umbria–Marche Apennine Ridge (northern Apennines). We reconstruct four steps of deformation at the scale of the belt: burial-related stylolitization, Apenninic-related layer-parallel shortening with a contraction trending NE–SW, local extension related to folding, and late-stage fold tightening under a contraction still striking NE–SW. We combine the paleopiezometric inversion of the roughness of sedimentary stylolites – that constrains the range of burial depth of strata prior to layer-parallel shortening – with burial models and U–Pb absolute dating of fault coatings in order to determine the timing of development of mesostructures. In the western part of the ridge, layer-parallel shortening started in Langhian time (∼15 Ma), and then folding started at Tortonian time (∼8 Ma); late-stage fold tightening started by the early Pliocene (∼5 Ma) and likely lasted until recent/modern extension occurred (∼3 Ma onward). The textural and geochemical (δ18O, δ13C, Δ47CO2 and 87Sr∕86Sr) study of calcite vein cements and fault coatings reveals that most of the fluids involved in the belt during deformation either are local or flowed laterally from the same reservoir. However, the western edge of the ridge recorded pulses of eastward migration of hydrothermal fluids (>140 ∘C), driven by the tectonic contraction and by the difference in structural style of the subsurface between the eastern Tuscan Nappe and the Umbria–Marche Apennine Ridge.

Item Type:Articles
Additional Information:This research has been supported by the Natural Environmental Research Council (grant no. IP-1494-1114), the European Union’s Seventh Framework Programme (grant no. 316889), the Sorbonne Université (grant no. C14313), the Région Nouvelle- Aquitaine, and the Agence Nationale de la Recherche (Projet Investissement d’Avenir (programme E2S)).
Glasgow Author(s) Enlighten ID:Boyce, Professor Adrian and Beaudoin, Dr Nicolas and Koehn, Dr Daniel
Authors: Beaudoin, N., Labeur, A., Lacombe, O., Koehn, D., Billi, A., Hoareau, G., Boyce, A., John, C. M., Marchegiano, M., Roberts, N. M., Millar, I. L., Claverie, F., Pecheyran, C., and Callot, J.-P.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Solid Earth
Publisher:European Geosciences Union
ISSN (Online):1869-9529
Copyright Holders:Copyright © 2020 The Authors
First Published:First published in Solid Earth 11:1617–1641
Publisher Policy:Reproduced under a Creative Commons License

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