How the geochemistry of syn-kinematic calcite cement depicts past fluid flow and assists structural interpretations: a review of concepts and applications in orogenic forelands

Abstract

Orogenic forelands host interactions between deformation and static or migrating fluids. Given their accessibility and dimensions, these areas are not only historic landmarks for structural geology, but they are also areas of prime interest for georesource exploration and geological storage, and loci of potential geohazards. Geochemical techniques applied on cements filling tectonic structures and associated trapped fluids can constrain the temperature, pressure, origin and pathways of fluids during deformation and allow the characterization of the past fluid system. In this review focused on calcite cements, we first present and critically discuss the most used geochemical techniques to appraise specific parameters of the fluid system. Second, we summarize the outcomes of selected case studies where the past fluid system was reconstructed with consideration of tectonics, either at the scale of the individual fold/thrust or at the scale of the fold-and-thrust belt. At first order, the past fluid system evolves in a similar way with respect to the considered stage of deformation, being rather closed to external fluids when deformation is bounded to mesoscale structure development, and opening to vertical flow when thrust and folds develop. In a more detailed view, it seems that the past fluid system evolves and distributes under the influence of the structural style, of the geometry of the major faults and of the lithology of the sedimentary succession. Through this review, we illustrate the concept of geochemistry-assisted structural geology through case studies where the geochemistry of calcite veins constrained subsurface geometries and structural developments in orogenic forelands.

Regional Scale, Fault‐Related Fluid Circulation in the Ionian Zone of the External Hellenides Fold‐And‐Thrust Belt, Western Greece: Clues for Fluid Flow in Fractured Carbonate Reservoirs

“…On the contrary, in the uplifted hinterland zones, fluid circulation occurred in an open‐system characterized by the downward infiltration of meteoric‐derived fluids through fault conduits, such as the NE‐SW‐striking strike‐slip faults (Figure 11b). Increasing dominance of meteoric‐derived fluids during increasing contractional deformation was observed in the Albanides fold‐and‐thrust belt (De Graaf et al., 2019; Vilasi et al., 2009), as well in other fold‐and‐thrust belts worldwide (Beaudoin et al., 2022; Fitz‐Diaz et al., 2011; Smeraglia et al., 2022). In the Albanides fold‐and‐thrust belt, faults associated with folding also recorded the mixing between meteoric fluids and evaporite‐derived deep fluids (Swennen et al., 2000).…”

“…Therefore, those veins precipitated from warm fluids, probably brines, partly buffered by the carbonate rocks (Figure 11a). Warm brines were thought to circulate also during foreland flexuring in the Albanides fold‐and‐thrust belt (Swennen et al., 2000) and in many other fold‐and‐thrust belts (Beaudoin et al., 2022).…”

“…During post-orogenic extension, fluid circulation was characterized by an open system as veins and breccia cements along normal faults precipitated from meteoric-derived fluids (Figure 11a) that infiltrated in groundwater aquifers and laterally moved due to high topographic reliefs developed in the internal part of the Hellenides fold-and-thrust belt. Meteoric-derived fluid circulation was extensively documented during post-orogenic extension and normal faulting in the Apennines (Agosta & Kirschner, 2003;Agosta, 2008;Curzi et al, 2020Curzi et al, , 2021Ghisetti et al, 2001;Lucca et al, 2019;Smeraglia et al, 2016Smeraglia et al, , 2018 and in other fold-and-thrust belts (Beaudoin et al, 2022).…”

“…In the past decades, several studies focused on fault‐fluid interactions through the structural, geochemical, and geochronological characterization of syn‐tectonic mineralization in specific fault zones pertaining to fold‐and‐thrust belts (Agosta & Kirschner, 2003; Agosta, 2008; Beaudoin et al., 2011; Dennis et al., 2019; Dewever et al., 2013; Huntington & Lechler, 2015; Lacombe & Beaudoin, 2024 for review; Lacroix et al., 2011; Lucca et al., 2019; Marchesini et al., 2022 Smeraglia et al., 2016, 2018). However, a few studies attempted to characterize the spatio‐temporal fluid paleo‐circulation along transects tens to hundreds of kilometers long (Callot et al., 2010; Crognier et al., 2018; Fitz‐Diaz et al., 2011; Kirschner & Kennedy, 2001; Knoop et al., 2002; Vandeginste et al., 2012), and rarely at scales covering entire fold‐and‐thrust belts (Beaudoin et al., 2014, 2022 for review; Cruset et al., 2023; Ghisetti et al., 2001; Smeraglia et al., 2022; Travé et al., 2007).…”

Depicting past stress history at passive margins: A combination of calcite twinning and stylolite roughness paleopiezometry in supra-salt Sendji deep carbonates, Lower Congo Basin, west Africa

“…Note however that constraining the origin and migration pathways of the cementing fluids would require more geochemical proxies (e.g. Beaudoin et al, 2022), which is beyond the scope of this study.…”