VU Research Portal Isotope analysis of fluid inclusions de Graaf, S. 2018 document version Publisher's PDF, also known as Version of record Link to publication in VU Research Portal citation for published version (APA) de Graaf, S. (2018). Isotope analysis of fluid inclusions: Into subsurface fluid flow and coral calcification. General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. E-mail address: [email protected] Download date: 01. Oct. 2021 Chapter Fluid flow evolution in the Albanide fold- 3 and-thrust belt ectonic forces generated during thrust emplacement along active margins may drive complex fluid flow patterns in fold-and-thrust belts and foreland basins. In the Albanide fold-and-thrust belt, fracture-controlled fluid flow Tled to the development of calcite vein networks in a sequence of naturally fractured Cretaceous to Eocene carbonate rocks. Fluid inclusion isotope data of these calcite veins demonstrate that fluids circulating in the carbonates were derived from an underlying reservoir that consisted of a mixture of meteoric water and evolved marine fluids, probably sourced from deep-seated evaporites. The meteoric fluids infiltrated in the hinterland before being driven outward into the foreland basin and ascended as soon as fracturing induced a sufficient increase in permeability. The contribution of fluids derived from evaporites increases towards the thrust front in association with elevated deformation, which is expected to be the main driver of expulsing connate waters from the evaporites. Structural and petrographic observations provide time constraints for the various phases of fracture infilling and reveal an increasing dominance of meteoric water in the system through time as migration pathways shortened and marine formation fluids were progressively flushed out. Similar fluid flow evolutions have previously been recorded in various fold-and-thrust belt settings elsewhere in the world. Based on: De Graaf, S., Nooitgedacht, C. W., Le Goff, J., Van der Lubbe, H. J. L., Vonhof, H. B., and Reijmer, J. J. G. (accepted for publication in AAPG Bulletin) Fluid flow evolution in the Albanide fold-and-thrust belt: Insights from δ2H and δ18O isotope ratios of fluid inclusions Nooitgedacht, C. W., De Graaf, S., Van der Lubbe, H. J. L., Vonhof, H. B., Le Goff, J., and Reijmer, J. J. G. (in prep.) Tracking fluid migration in the external Albanides using hydrogen and oxygen isotopes of fluid inclusions in calcite veins 46 Chapter 3 3.1 Introduction Fold-and-thrust tectonics is commonplace along convergent plate margins and is associated with the development of intricate fracture and fault networks (Roure and Sassi, 1995). The structural complexity of fold-and-thrust belts opens up a wide array of conceivable fluid flow patterns (Travéet al., 2007; Morley et al., 2011; Lacroix et al., 2014). Tectonic loading due to thrust emplacement, for instance, may instigate basin-ward expulsion of fluids along large-scale migration pathways like faults or basement detachments (Oliver, 1986; Ge and Garven, 1992). The timing of fluid flow and circulating fluid types may differ considerably between foreland fold-and-thrust belts depending on their stratigraphic architecture and structural evolution (Ferket et al., 2003; Schneider et al., 2004; Barbier et al., 2012; Crognier et al., 2018). Predicting the evolution and interplay of deformation and fluid flow in foreland fold-and-thrust belts remains complicated, while it is of key importance when assessing the potential existence of aquifers or petroleum-bearing reservoirs (Agosta et al., 2010; Morley et al., 2011). Carbonate rock formations are of particular interest since the permeability of lithified limestone is generally governed by brittle deformation structures (i.e., fracture and faults) due to limited matrix porosities (Nelson, 2001). In this Chapter, fluid inclusion isotope data of calcite veins are used to delineate the fluid flow system of the Albanide foreland fold-and-thrust belt. Prominent calcite veining in the Albanide fold-and-thrust belt exists in fracture networks in Cretaceous to Eocene Ionian Basin carbonates, which are the main reservoir rocks in the area (Velaj et al., 1999) and an analogue to producing reservoirs in the Adriatic Sea and onshore Italy (Cazzola and Soudet, 1993; Zappaterra, 1994). The carbonate rocks are mainly composed of calciclastic gravity flows and mass transport deposits (Rubertet al., 2012; Le Goffet al., 2015). Events of fracturing provided discrete pathways facilitating the episodic migration of fluids and governing the emplacement of abundant hydrocarbon accumulations in the area (Graham Wall et al., 2006). Previous vein-based fluid flow reconstructions in the Ionian Zone focused on the areas of Kremenara (Van Geet et al., 2002; Swennen et al., 2003), Shpiragu (Graham Wall et al., 2006), Kelçyrë (Vilasi et al., 2009) and Saranda (Lacombe et al., 2009). These previous researches inferred multiple fluid flow episodes throughout the evolution of the foreland fold-and- thrust belt. Although the sequence of fluid flow and vein cementation events has quite elaborately been studied, the precise origin and migration pathways of fluids requires further constraints, especially for the early-stage fluid system. Excellent outcrops of Cretaceous to Eocene carbonate rocks are present in the Mali Gjere mountain ridge, which is a topographic expression of the Kurveleshi thrust sheet in the Ionian Zone of south Albania (Figure 3.1). In addition to studying veins from the Mali Gjere, calcite veins from a set of outcrops from the two other main thrust units in the Ionian Zone – the Çika and the Berati belt – were analyzed Fluid flow evolution in the Albanide fold-and-thrust belt 47 A B Berati BeltB Montenegro Albanian alps Kosovo Mirdita Zone Mashkullorë Korabi 15 N Tirana Macedonia Pre-Adriatic Depression Pre-Adriatic Gjirokastër Mali Gjere Korça Basin Kurveleshi Belt Kruja Zone 20 Krasta Zone Vanister 40˚ Ionian 00’ Berati belt 18 Çika belt Sazani Zone Zone Terihat Kurveleshi belt 20 Frashtan Research area Greece Muzinë Çika Belt 22 Jorgucat Greece 41 Legend Quaternary Bodrishtë A Sarandë 14 Neogene Paleocene Ionian Sea Cretaceous 39˚ 50’ Jurassic 10 km Triassic 20˚ 00’ 20˚ 15’ C SW Çika belt Kurveleshi belt Berati belt NE A Mali Gjere B Jura Flysch ssic-Cr and m etace olass ous c e cove arbon r Delvina oil field ates an Triassic evaporites d shales 1 km 4 km Figure 3.1 (A) Map showing the main structural units of Albania (Moisiu and Gurabardhi, 2004) with the research area indicated by the black square. (B) Geological map of southern Albania after Moisiu and Gurabardhi (2004). Seven outcrop locations (Mashkullorë, Vanister, Terihat, Frashtan, Muzinë, Jorgucat and Bodrishtë) were studied along the Mali Gjere mountain ridge, which exposes Cretaceous to Eocene carbonate rocks within the Kurveleshi thrust sheet. Red lines depict faults. (C) Simplified geological cross-section through southern Albania after Velaj (2015), indicated by the line A-B in the geological map. to assess spatial variations in the fluid flow evolution throughout the entire fold-and- thrust belt. Besides fluid inclusion isotope analysis, complementary petrographic and δ18O and δ13C isotope analyses of the calcite vein cements were carried out. An analysis of the arrangement and cross-cutting relations of distinct structural sets was performed to acquire a chronological framework for the various generations of fracture-infilling calcite. 48 Chapter 3 3.2 Background 3.2.1 Geological evolution of the Ionian Zone The Ionian Zone is one of the structural domains that makes up the Al- banides (Figure 3.1) and refers to an assembly of folds and thrusts of Ionian Basin deposits situated in the southwest of Albania (Meço and Aliaj, 2000; Robertson and Shallo, 2000). Deposition in the Ionian Basin was closely linked to the structural evolution of the Adriatic plate (Channell et al., 1979). In Triassic times, at least 2000 m of evaporites and shallow-water carbonates were deposited in an epicontinental marine environment (Vlahović et al., 2005; Karakitsios, 2013). Subsequent exten- sional tectonics within the Adriatic plate from the Late Triassic onward led to the development of rift basins in a horst and graben system. The Ionian Basin was such an intracontinental rift basin and formed between the Apulian and Kruja carbonate platforms (Robertson and Shallo, 2000; Heba and Prichonnet, 2009). The syn-rift sequence in the Ionian Basin from the Jurassic until the Oligocene is characterized by sediment input from the bordering carbonate platforms (Hairabian et al., 2015; Le Goffet al., 2015). The sequence of Cretaceous to Eocene carbonate gravity flows that is presently exposed along the Mali Gjere mountain ridge exhibits a thickness of 900-1350 m (Velaj, 2015) and is mainly composed of decimeter to meter-scale strata of fine-grained mud- to wackestones with minor amounts (< 2%) of planktic foraminifera. Uplift of the hinterland provoked by the Alpine Orogeny led to an increasing input of terrigenous material into the basin and the deposition of up to 2000 m of Oligocene flysch, Neogene molasse, and Quaternary sand- and siltstones on top of the Ionian Basin carbonates (Meço and Aliaj, 2000). The position of the Ionian Zone in the southern extremity of the Alpine orogenic belt was crucial for its structural development from the Oligocene onward (Robertson and Shallo, 2000; Nieuwland et al., 2001).