Hydrothermal fluid flow associated to the extensional evolution of the Adriatic rifted margin: Insights from the pre‐ to post‐rift sedimentary sequence (SE Switzerland, N ITALY)

Abstract

This paper investigates the hydrothermal fluid circulation that was linked to the extensional evolution of the Adriatic rifted margin during the Jurassic opening of the Alpine Tethys. Remnants of this rifted margin are spectacularly preserved in SE Switzerland and N Italy. Five study areas were chosen ranging from the former proximal to the most distal part of the margin. We demonstrate an intimate link between Jurassic extensional tectonics and fluid activity affecting the pre-to early post-rift sedimentary sequences. Nature, composition and origin of fluids are constrained by a multidisciplinary approach based on field observations and including geochemical (O-C, Sr, He isotopes, U-Pb datings, fluid inclusion microthermometry) and petrological methods. Several fluid-related diagenetic products and processes such as dolomitization, veining, hydraulic brecciation, and silicification can be recognized. It appears that different paleogeographic settings and different stratigraphic levels document distinct phases of fluid activity. The fluids reached temperatures of up to 150°C near paleo-seafloor. They were enriched in 18 O, had high 87 Sr/ 86 Sr and low 3 He/ 4 He ratios, documenting a strong interaction between seawater and a granitic basement. Many lines of evidence point to the occurrence of over-pressured fluids and long-lasting fluid circulation due to fault-valve mechanisms and high thermal gradients. Two main stages with different fluid chemistry can be recognized: (1) a carbonate-rich stage that developed during the stretching phases and was linked to high-angle normal faulting, and (2) a silica-rich stage occurring during late rift exhumation of crustal and mantle rocks in the distal domains in the presence of detachment faults and high thermal gradients. This paper provides, for the first time, a large and robust characterization of fluid-rock interactions occurring during rifting along an almost complete section across a magma-poor rifted margin. K E Y W O R D S Adriatic rifted margin, Alpine Tethys, diagenetic evolution, hydrothermal fluids, Jurassic rifting 92 | EAGE INCERPI Et al.

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb carbonate geochronology: strategies, progress, and limitations

“…To date, LA-ICP-MS U-Pb carbonate geochronology has been utilised for a wide range of applications. These include the dating of speleothem deposition (Hopley et al, 2019;Scardia et al, 2019;Nicholson et al, 2020), brittle deformation (Roberts and Walker, 2016;Ring and Gerdes, 2016;Goodfellow et al, 2017;Hansman et al, 2018;Parrish et al, 2018;Beaudoin et al, 2018;Nuriel et al, 2017Nuriel et al, , 2019; Smeraglia et al, 2019), hydrocarbon migration (Holdsworth et al, , 2020, hydrothermal ore mineralisation (Burisch et al, 2017(Burisch et al, , 2019Kreissl et al, 2018), hydrothermal and deep-crustal fluid flow (Drake et al, 2017(Drake et al, , 2019(Drake et al, , 2020Mazurek et al, 2018;Walter et al, 2018;Incerpi et al, 2020;MacDonald et al, 2019), pedogenesis (Methner et al, 2016;Liivamägi et al, 2019), ocean crust alteration (Coogan et al, 2016), diagenesis in sedimentary deposits (Li et al, 2014;Pagel et al, 2018;Mangenot et al, 2018;Godeau et al, 2018;Lawson et al, 2018), and sedimentary deposition (Drost et al, 2018). Published dates range in age from 0.6 to 548 Ma (see Fig.…”

Impact of crust–mantle mechanical coupling on the topographic and thermal evolutions during the necking phase of ‘magma-poor’ and ‘sediment-starved’ rift systems: A numerical modeling study

“…As in natural rift systems faults are regions of increased permeability, and thus o f efficient fluid circulation and heat transport (e.g. Pinto et al, 2015;Incerpi et al, 2019), we suggest that integrating major faults into basin modeling is necessary to obtain a reliable understanding of the thermal evolution of a rift system.…”

Fluid–rock interactions along detachment faults during continental rifting and mantle exhumation: the case of the Urdach lherzolite body (North Pyrenees)

“…Fluid circulations in magma--poor passive margins are still poorly investigated since they develop in deep seafloor environments and at various levels of the stretched lithosphere. Recent studies focused on fluid--rock interactions in fossil passive margin systems of orogenic belts such as those preserved in the Alps and Pyrenees (Fallourd et al, 2014;Pinto et al, 2015;Corre et al, 2018;Quesnel et al, 2019, Incerpi et al, 2019. Along the northern flank of the Pyrenean belt, the North Pyrenean Zone (NPZ) hosts well--preserved remnants of inverted mid--Late Cretaceous basins including exhumed lherzolitic mantle fragments (Lagabrielle and Bodinier, 2008;Jammes et al, 2009;Lagabrielle et al, 2010;Clerc and Lagabrielle, 2014;Corre et al, 2016).…”