# Effect of out-of-equilibrium crystallization and fluid-assisted dynamic recrystallization on Ti-in-quartz thermometry in porphyry-epithermal deposits: Insights from Pagoni Rachi (NE Greece)

Baptiste Abiven, Alexandre Tarantola, Antonin Richard, Manuel Keith, Vasilios Melfos, Panagiotis Voudouris

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Baptiste Abiven, Alexandre Tarantola, Antonin Richard, Manuel Keith, Vasilios Melfos, et al.. Effect of out-of-equilibrium crystallization and fluid-assisted dynamic recrystallization on Ti-in-quartz thermometry in porphyry-epithermal deposits: Insights from Pagoni Rachi (NE Greece). Lithos, 2025, 512-513, pp.108314. 10.1016/j.lithos.2025.108134. hal-05117646

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# Effect of out-of-equilibrium crystallization and fluid-assisted dynamic recrystallization on Ti-in-quartz thermometry in porphyry-epithermal deposits: Insights from Pagoni Rachi (NE Greece)

Baptiste Abiven<sup>a,*</sup>, Alexandre Tarantola<sup>a</sup>, Antonin Richard<sup>a</sup>, Manuel Keith<sup>b</sup>, Vasilios Melfos<sup>c</sup>, Panagiotis Voudouris<sup>d</sup>

## ARTICLE INFO

### Keywords:

Porphyry-epithermal

Ti-in-quartz

Thermometry

Out-of-equilibrium crystallization

Fluid-assisted dynamic recrystallization

Fluid inclusions

## ABSTRACT

Understanding the temperature evolution of magmatic-hydrothermal systems is key to unraveling fluid-rock-deformation reactions and related ore-forming processes. Ti-in-quartz thermometry has been widely used to determine the quartz crystallization temperatures in these systems. However, out-of-equilibrium crystallization and fluid-assisted recrystallization of hydrothermal quartz may significantly influence the temperature estimates; a process that has not sufficiently been studied to date despite its broad implications.

Here, we use the Pagoni Rachi Cu-Mo-(Re-Au) deposit (NE Greece) to provide insights into these processes. Typical A-type (ductile, 460–510 °C), B-type (ductile/brittle, 420–440 °C) and E-type (brittle, 220–330 °C) veins are developed in a continuum of deformation, forming from phase-separated fluids followed by cooling and dilution with surface waters. In A-type veins, fluid-assisted recrystallization modified the Ti concentrations (10–60 ppm), yielding Ti-in-quartz temperatures (330–500 °C) lower than the fluid inclusion trapping temperatures, likely due to Ti loss. In later B-type veins, rapid growth under out-of-equilibrium conditions resulted in overestimated Ti-in-quartz temperatures (440–750 °C), i.e., higher than fluid inclusion trapping temperatures. By contrast, effects of recrystallisation are lacking in the late-stage E-type veins, leading to a better agreement between Ti-in-quartz (160–360 °C) and fluid inclusion trapping temperatures.

Our results show that out-of-equilibrium crystallization and fluid-assisted dynamic recrystallization processes can shift the Ti concentration in quartz leading to potential misinterpretation of the cooling path of magmatic-hydrothermal systems. This has also important implications on the common classification of vein types in porphyry-epithermal systems based on the Al/Ti and Ge/Ti ratios in quartz. More generally, careful micro-textural examinations of quartz veins are crucial for a reliable use of Ti concentrations in quartz as a petrogenetic indicator.

## 1. Introduction

Understanding the temperature evolution of porphyry-epithermal systems is essential for elucidating ore-forming processes, including fluid-phase separation, metal solubility and the associated alteration and deformation history (e.g. Kouzmanov and Pokrovski, 2012; Monecke et al., 2018; Rottier et al., 2021; Acosta et al., 2022). Quartz, one of the most abundant minerals in the Earth's crust (Götze, 2009), is particularly prevalent in hydrothermal ore deposits, including

porphyry-epithermal mineralization (Seedorff et al., 2005; Sillitoe, 2010). Due to its widespread presence and complex growth textures, which record multiple fluid and deformation events, quartz provides critical insights into the evolution and history of ore deposit formation (e.g., (Wilkinson, 2001; Stipp et al., 2002a,b; Rusk and Reed, 2002; Redmond et al., 2004; Landtwing et al., 2005; Rusk et al., 2006; Landtwing et al., 2010; Redmond and Einaudi, 2010; Huang and Audôtat, 2012; Kouzmanov and Pokrovski, 2012; Reed et al., 2013; Bennett, 2014; Monecke et al., 2018; Pan et al., 2019; Rottier and Casanova,

<footnote><sup>a</sup> GeoRessources, UMR 7359, Université de Lorraine, CNRS, Nancy 54000, France</footnote>

<footnote><sup>b</sup> GeoZentrum Nordbayern, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Schlossgarten 5, Erlangen 91054, Germany</footnote>

<footnote><sup>c</sup> Department of Mineralogy, Petrology, Economic Geology, School of Geology, Aristotle University of Thessaloniki, GR-54124, Greece</footnote>

<footnote><sup>d</sup> Department of Mineralogy and Petrology, Faculty of Geology and Geoenvironment, National and Kapodistrian University of Athens, 15784 Athens, Greece</footnote>

<footnote>* Corresponding author.
E-mail address: baptiste.abiven@univ-lorraine.fr (B. Abiven).</footnote>
2021; Acosta et al., 2022; Cernuschi et al., 2023; Hong et al., 2023). Quartz is also a robust host for fluid inclusions, making it a useful mineral for reconstructing fluid histories (e.g. Bodnar, 1993; Kouzmanov and Pokrovski, 2012; Bodnar et al., 2014; Monecke et al., 2018).

Hydrothermal quartz is commonly investigated by cathodoluminescence (CL) imaging, trace element analysis and fluid inclusion microthermometry. This combined approach aims to discriminate fluid provenance and to constrain various physico-chemical fluid parameters that are crucial for the genetic interpretation and classification of different mineralizing events (e.g., Schrön et al., 1988; Götze, 2009; Tanner et al., 2013; Maydagán et al., 2015; Breiter et al., 2017; Mao et al., 2017; Mao et al., 2018; Rottier and Casanova, 2021; Falkenberg et al., 2024). Aluminum and Li are considered as CL-inhibitors (Phelps et al., 2020), while Ti is the most important CL active element in quartz. Increasing CL intensity commonly correlates with increasing Ti contents, which is a typical sign of increasing fluid temperature (Götze, 2009, Götze and Möckel, 2012; Rusk, 2012). Consequently, fluid temperature constraints are commonly based on fluid inclusions (Bodnar et al., 1985; Wilkinson, 2001; Kouzmanov and Pokrovski, 2012; Moncke et al., 2018) and Ti-in-quartz thermometry (e.g., Grujic et al., 2011; Zhang et al., 2020; Rottier et al., 2021; Rottier and Casanova, 2021; Hong et al., 2023; Falkenberg et al., 2024), which can both be applied to the same quartz grain.

It is important to note there has generally been no consensus between Ti-in-quartz thermometry at hydrothermal conditions and the temperature constraints of independent methods, such as mineral paragenetic association or fluid inclusion data (e.g., Rottier and Casanova, 2021). This discrepancy has been explained by several factors, including uncertainty in the evaluation of *PT* conditions, inaccurate assessment of Ti activity, or out-of-equilibrium quartz precipitation during rapid crystal growth (e.g., Rottier and Casanova, 2021; Acosta et al., 2022). However, ultimate processes that cause this discrepancy remain unclear. The best correlations between calculated temperatures and those expected from fluid inclusions were observed with the Zhang et al. (2020) calibration for temperatures below 400 °C, and with the Huang and Audétat (2012) calibration for temperatures above 550 °C (Rottier and Casanova, 2021).

In addition, trace elements in quartz, notably Al, Ge, and Ti, are commonly used for retracing fluid evolution in hydrothermal systems and for vein classification, based on their proposed systematic variation with pressure, temperature and pH (e.g. Götze and Möckel, 2012; Rottier and Casanova, 2021; Raimbourg et al., 2022). This allows for the interpretation of ore-forming conditions through the geochemistry of quartz. However, it remains unclear how the concentration and distribution of these elements in quartz are affected by out-of-equilibrium crystallization and dynamic recrystallization.

The incorporation of Ti in quartz during out-of-equilibrium crystallization is significantly influenced by the growth rate of the crystal, leading to higher Ti concentrations, more than an order of magnitude than expected (e.g. Huang and Audétat, 2012; Nachlas and Hirth, 2015; Cernuschi et al., 2018; Acosta et al., 2022; Liu et al., 2023). Huang and Audétat (2012) demonstrated that fast crystal growth, as evidenced by euhedral oscillatory growth zoning in quartz, leads to higher than equilibrium levels of incorporation in quartz crystals, specifically Ti. This emphasizes that Ti-in-quartz thermometry must be applied with caution and only following microtextural examinations, in order to avoid misinterpretation of inferred formation conditions (Huang and Audétat, 2012).

The state of intragranular deformation provides key information on the strain rate at a given temperature (Stipp et al., 2002a, 2002b). In general, three major parameters control the dynamic recrystallization of quartz: the temperature, the deformation rate and the influence of circulating fluids (Stipp et al., 2002a, 2002b; Passchier and Trouw, 2005; Grujic et al., 2011; Nachlas et al., 2014; Nachlas and Hirth, 2015; Bromiley and Hiscock, 2016). Thus, a high-temperature (500–600 °C) or low-strain rate system will result in dynamic recrystallization by grain boundary migration (GBM) (Passchier and Trouw, 2005). By contrast, a

low-temperature (250–400 °C) or high-strain rate system will result in dynamic recrystallization by bulging (BLG) (Stipp et al., 2002a, 2002b; Passchier and Trouw, 2005). Structures, such as subgrain rotation (SGR) are developed at moderate temperature of 400–500 °C. The recrystallization of quartz also influences the equilibrium of contained fluid inclusions, i.e., their structure and physico-chemical composition (Kerrich, 1976; Audétat and Günther, 1999; Tarantola et al., 2010, 2012; Lecumberri-Sanchez et al., 2012; Eglinger et al., 2014; Diamond and Tarantola, 2015; Audétat, 2023). Recrystallisation may stretch fluid inclusions, generate volume modification (increase of homogenization temperature), water loss, and increase in salinity. In addition, extreme recrystallization can erase fluid inclusions from the host mineral (Kerrich, 1976; Audétat and Günther, 1999; Tarantola et al., 2010; Audétat, 2023). Similarly, recrystallization of quartz may also affect the element distribution by diffusion, potentially leading to a loss of elements into the surrounding matrix. Titanium can diffuse within quartz crystals especially during such processes (Cherniak et al., 2007; Ashley et al., 2014; Bromiley and Hiscock, 2016; Nachlas and Hirth, 2015, Nachlas et al., 2018; Cavalcante et al., 2022). The diffusion of Ti through quartz is very slow (Jollands et al., 2020), but grain boundary migration in fluid-rich systems (i.e. fluid-assisted recrystallization) induces Ti homogenization in quartz and allows it to reset to the equilibrium value at a rate that is much faster (Nachlas and Hirth, 2015; Van den Kerkhof et al., 2004). Additionally, Nachlas and Hirth (2015, 2018) concluded that dislocation creep enhanced by GBM in a fluid-rich system, enables the resetting of Ti in quartz. Titanium partitioning into dislocations can accelerate overall diffusivity. This allows mineral compositions to reequilibrate more rapidly than through static volume diffusion. Grujic et al. (2011) proposed that GBM conditions reset the quartz Ti signal, whereas weaker deformation associated with SGR or BLG does not. Accordingly, Ti diffusion may also influence the temperatures obtained by Ti-in-quartz thermometry and the CL intensity of quartz (Huang and Audétat, 2012; Acosta, 2020). The CL textures of quartz are thus not only indicative of fluid circulation and quartz growth but also point to potential disequilibrium conditions (Götze and Möckel, 2012; Monecke et al., 2018; Acosta, 2020; Acosta et al., 2022). When well crystallized, quartz shows marked oscillatory growth zoning, while recrystallized quartz may present specific CL textures like ghost bands, mosaic, or mottled patterns characterized by erased or darkened CL signals (Landtwing et al., 2005; Rusk, 2014; Monecke et al., 2018; Acosta et al., 2022). CL variations linked to partial recrystallization of fluid inclusions might cause a geochemical marking of the host quartz, as indicated by CL trails with low Ti concentration (Lambrecht and Diamond, 2014).

Recent studies demonstrated that quartz exhibits the same types of recrystallization patterns within hydrothermal systems (e.g. Acosta et al., 2022), which may also help to explain potential discrepancies in geochemical interpretation and classification of vein types in porphyry-epithermal systems (e.g. Rottier and Casanova, 2021). Most research on CL textures and trace element chemistry in porphyry deposits has focused on common Cu—Mo sub-types (e.g., Redmond et al., 2004; Landtwing et al., 2005; Rusk et al., 2006; Rusk et al., 2008a,b, 2011; Müller et al., 2010; Rusk, 2012; Tanner et al., 2013; Maydagán et al., 2015; Mao et al., 2017; Mao et al., 2018; Monecke et al., 2018; Rottier and Casanova, 2021; Rottier et al., 2021; Gao et al., 2022; Falkenberg et al., 2024). However, the effects of fluid-assisted dynamic recrystallization on Ti concentration in quartz under the temperature conditions of typical porphyry-epithermal systems (150–600 °C) are not well understood and remain debated. The Pagoni Rachi porphyry-epithermal Cu-Mo-(Re-Au) mineralization in NE Greece provides a compelling case study on how the intricate interactions between deformation, fluid chemistry, and thermal conditions influence the development of quartz veins in porphyry-epithermal environments. As the system evolved from ductile to brittle deformation and transitioned from lithostatic to hydrostatic conditions, key processes such as rate of quartz crystals growth, and fluid-assisted dynamic recrystallization affected the incorporation and conservation of geochemical signature of quartz crystals.
This study aims to compare the incorporation and preservation of trace elements in quartz across different stages of growth and deformation, by integrating Ti-in-quartz thermometry, trace element analysis, and fluid inclusion data. Special attention is given to the effects of out-of-equilibrium crystallization and fluid-assisted dynamic recrystallization, which can significantly alter the original trace element signature and lead to discrepancies in temperature estimates derived from Ti-in-quartz. By linking quartz microstructures with geochemical variations, this work highlights how deformation history, fluid-rock interaction, and recrystallization processes influence Ti distribution and trace element behavior in quartz. These insights not only improve the interpretation of Ti-in-quartz thermometry but also contribute to a more robust understanding of the physicochemical conditions that govern quartz formation in hydrothermal and mineralizing systems.

## 2. Geological and metallogenic context

The Tethyan Metallogenic Belt (TMB) stretches from the Alps to the Himalayas and hosts numerous hydrothermal deposits, rich in metals like Au, Cu, and Mo. These deposits formed during the subduction of the Neo-Tethys Ocean and collisions between tectonic plates. In the South-east Balkan-Rhodope region (NE Greece, SE Bulgaria, NW Turkey), magmatic-hydrothermal deposits are notable for their rare and precious metal contents (e.g., Marchev et al., 2005; Melfou et al., 2023; Voudouris et al., 2019, 2022). Post-orogenic processes and slab rollback also contributed to Cu-Mo deposit formation in the Balkans during the Eocene. The Pagoni Rachi porphyry-epithermal system is part of the Sapes-Kirki ore district in Western Thrace, NE Greece. The mineralization is centered in a high-K calc-alkaline biotite-amphibole granodiorite

porphyry (Fig. 1). The Cu-Mo-(Re-Au) mineralization occurs in the form of a succession of mineralized veins, organized in a stockwork pattern, with typical successive hydrothermal stages (Voudouris et al., 2013a) (Fig. 2, Table 1). The nomenclature of vein- and alteration-types, based on structural criteria (vein shapes, orientation) and mineralogical composition (mineral assemblage of vein or alteration), is consistent with previous studies of porphyry and epithermal systems (Sillitoe, 2010; Voudouris et al., 2013a, 2013b; Monecke et al., 2018)

(i) The earliest stage is represented by A- and M-type veins, which are dominated by quartz and magnetite, respectively, with only little sulfides occurrence. A-type veins are either continuous or discontinuous, undulating with irregular edges, lack any symmetry and show a variable thickness (mm to cm) (Figs. 2A). They are dominated by quartz (90–95 %), but also host minor magnetite-hematite, pyrite, chalcopyrite, molybdenite and bornite (5–10 %). Oxides and sulfides are disseminated and occur along the vein salvage or form discontinuous lines. The veins are associated with proximal sodic-calcic to potassic alteration with quartz, biotite, orthoclase/albite, actinolite, magnetite, epidote and chlorite, where the two latter minerals are possibly the result of a proximal propylitic overprint (Fig. 2A–C). (ii) These are followed by continuous quartz-bearing B-type veins with constant thickness, a sinuous to straight shape and sharp boundaries. Sulfides occur at the vein margins, disseminated in quartz or along the center of the vein. The B-type veins contain quartz (anhedral to euhedral) (90–95 %), and minor pyrite, chalcopyrite, bornite, covellite, digenite, molybdenite associated with rheniite (ReS₂), biotite, hematite, magnetite, albite, chlorite, fluorite, sericite and calcite (Voudouris et al., 2009, 2013a, 2013b). The host-rock alteration assemblage is composed of quartz, albite/orthoclase, chlorite and calcite, corresponding to a sodic-potassic

<figure><img src="image_3.png" /><figcaption>**Fig. 1.** Geographical and geological context of the study area and sampling zones. A. Geographic location (red rectangle) of the Sapes-Kirki district in Thrace, NE Greece – AL = Albania, BG = Bulgaria, MK = Macedonia, TR = Turkey. B. Geological and alteration map of the Sapes-Kirki district. The porphyry-epithermal mineralization at Pagoni Rachi is found within a granodioritic body at the Southeastern part of the map. Early potassic to sodic-calcic alteration are frequently overprinted by other alterations, such as propylitic, sericitic or advanced argillic alteration (based on Mavrogonatos et al., 2020).</figcaption></figure>
<figure><img src="image_4.png" /><figcaption>**Fig. 2.** Petrography of A-, B- and E-type veins (outcrops and hand specimens) from Pagoni Rachi. A. Outcrop of a stockwork of A- and B-type veins enclosed within a potassic-altered granodiorite. B. Granodiorite with propylitic alteration overprinting potassic alteration hosting a stockwork of A-, M-, and B-type veins (quartz-chalcopyrite-molybdenite). C. Potassic-altered granodiorite with propylitic overprint enclosing a B-type vein (quartz-chalcopyrite-pyrite-bornite-molybdenite-rheniite) and E-type vein (calcite). D. Granodiorite with sericitic/argillic alteration cut by an E-type vein with comb quartz filling, containing base metal sulfides (pyrite, sphalerite, galena) and calcite. Red dashed lines = A-type veins, black = M-type veins, blue = B-type veins, pink = E-type veins. Abbreviations: bor = bornite, cal = calcite, cpy = chalcopyrite, fl = fluorite, gal = galena, moly = molybdenite, py = pyrite, qz = quartz, rhn = rheniite, ser = sericite, sph = sphalerite.</figcaption></figure>

alteration that locally show signs of propylitic overprinting (Fig. 2A–C). (iii) The third stage consists of massive straight continuous pyrite-chalcopyrite-molybdenite veins (D-type) cross-cutting previous veins, especially the B-type veins. They are associated with pervasive sericitic alteration, consisting of pyrite, quartz, sericite and calcite. This marks the transition from the porphyry to the epithermal environment (Richards, 2015), where the latter is reflected by (iv) straight continuous quartz-carbonate veins (E-type) with sharp boundaries, showing a geodic texture. Geodic cavities, formed by comb quartz, are infilled by carbonates. Base metal sulfides, such as sphalerite, galena, pyrite and chalcopyrite, are associated with the gangue quartz, which contain elevated concentrations of critical and precious (semi-) metals (e.g., Te, Bi, Au, Ag, Se; Voudouris et al., 2009, 2013a, 2013b) (Fig. 2C, D). The E-type veins are associated with sericitic to advanced argillic alteration assemblages characterized by kaolinite, sericite, calcite, quartz and disseminated pyrite. Major NNW-SSE trending faults crosscut the magmatic body, which are linked to the E-type veins and to some late-stage veins associated with silicified breccias, which have a regional control on the mineralization in this area (Fig. 1).

This consecutive vein sequence was the basis for previous fluid inclusion and micro-analytical studies of the vein stockwork at Pagoni Rachi (Voudouris et al., 2009, 2013a; Mavrogonatos et al., 2019, 2020). In these studies, three types of fluid inclusions were described, including: (i) Type 1 two-phase (at room temperature) liquid + vapor (LV) inclusions with low salinity (1.4 to 2.9 wt% equiv. NaCl),

homogenizing to the liquid phase at ~250 °C. (ii) Type 2 three-phase (at room temperature) liquid + vapor + halite (LVH) inclusions with high-salinity (36 to 74 wt% equiv. NaCl), homogenizing to the liquid phase at temperatures from 400 to 500 °C. Post-entrapment modification was suggested for some Type 2 inclusions that homogenize by dissolution of halite. (iii) Type 3 two-phase (at room temperature) vapor dominated vapor + liquid (VL) inclusions of low to intermediate salinity (1.7 to 10.7 wt% equiv. NaCl), homogenizing at temperatures in the range from 400 to 500 °C to the vapor phase. The type 2 and 3 fluid inclusions were only observed within quartz of the A- and B-type veins, whereas the Type 1 inclusions were found in all vein types, but particularly in the E-type veins. Voudouris et al. (2013a) proposed that phase separation due to boiling occurred during the PT evolution of the fluids at 400 to 500 °C, which is accompanied by the A- and B-type vein formation. This was followed by a progressive dilution of magma-derived fluids by surface waters causing cooling to 250 °C and decreasing fluid salinity (Voudouris et al., 2013a).

## 3. Sampling and methods

### 3.1. *Sampling selection*

The sample selection for this study aimed at covering the deformational history and magmatic-hydrothermal evolution of Pagoni Rachi, with a focus on quartz-bearing vein types. The samples were chosen
<table><caption>**Table 1**
Table of the petrological characteristics of the different vein types, part of the mineralized stockwork of Pagoni Rachi.</caption><thead><tr><th>Ore<br>mineralization<br>style</th><th>Vein<br>type</th><th>Vein<br>assemblage</th><th>Alteration<br>assemblage<br>(type)</th><th>Vein textures</th><th>Quartz structures</th><th>CL textures</th><th>Deformation<br> textures<br>(temperatures from<br>Stipp et al., 2002a,<br>2002b)</th><th>Sample (GPS<br>coordinates)</th></tr></thead><tbody><tr><td rowspan="2">Porphyry</td><td>A</td><td>Qz + Mag +<br>Hem + Py +<br>Bt + Or/Ab +<br>Act + Ep +<br>Cpy + Bor +<br>Moly + Chl +<br>Ser</td><td>Qz + Bt + Or/<br>Ab + Act + Ep<br>+ Mag + Hem<br>+ Chl (potassic<br>- propylitic<br>overprint)</td><td>Irregular and sharp<br>borders, variable<br>thickness,<br>asymmetric,<br>discontinuous to<br>continuous,<br>undulating</td><td>Anhedral, granular,<br>with subgrains and<br>lobate margins - 10 to<br>100 µm size, seriate<br>distribution, no<br>preferential crystal<br>orientation</td><td>Dark to medium<br>bright CL from dark<br>red to blue, with<br>mosaic texture, rare<br>ghost bands, and rare<br>oscillatory growth<br>zoning relict</td><td>Widespread SGR;<br>Widespread GBM<br>(400–600 °C)</td><td>MB02<br>(N40°59,744′<br>E25°50,144′)</td></tr><tr><td>B</td><td>Qz + Py +<br>Cpy + Mol +<br>Rhn + Hem +<br>Bt + Chl + Ep<br>+ Ab + Fl +<br>Cal + Ser</td><td>Qz + Bt + Ab/<br>Or + Chl + Cal<br>+ Ep (potassic -<br>propylitic<br>overprint)</td><td>Regular and sharp<br>borders, constant<br>thickness, central<br>axial symmetry,<br>continuous,<br>planar, syntaxial</td><td>Anhedral to<br>subhedral, at margins<br>or near fractures,<br>elongated in central<br>parts, growing stripes<br>of opaque minerals,<br>preferential<br>orientation of crystal<br>elongation<br>orthogonal to the<br>walls - dozen to<br>hundred microns in<br>size</td><td>Dark to medium<br>bright CL from dark<br>red to blue,<br>oscillatory growth<br>zoning showing<br>syntaxial opening,<br>with frequent ghost<br>bands at elongate<br>quartz margins,<br>mosaic textures near<br>fracture and<br>deformation zones</td><td>SGR at vein<br>margins or at<br>fractures contacts,<br>local GBM at<br>elongate quartz<br>margins, rare local<br>BLG (250–400 °C)</td><td>MB02<br>(N40°59,744′<br>E25°50,144′)<br>AB120.01<br>(N40°59'46";<br>E25°49'56")</td></tr><tr><td rowspan="2">Epithermal</td><td>E1</td><td>Qz + Fl + Py<br>+ Gal + Sph +<br>Cpy + Ser +<br>Kln + Tnt +<br>Ttr + Eng</td><td>Qz + Cal + Ser<br>+ Kln<br>(advanced<br>argillic)</td><td>Straight veins,<br>regular and sharp<br>borders, constant<br>thickness,<br>continuous,<br>frequent<br>branching, comb<br>quartz</td><td>Undeformed<br>elongated euhedral<br>quartz, orthogonally<br>oriented to the vein<br>walls, comb quartz -<br>hundred microns in<br>size</td><td>Oscillatory growth<br>zoning from center to<br>margins of quartz<br>crystals</td><td>Fractures (<br>250 °C?)</td><td>AB.122.03<br>(N40°58'29";<br>E25°49'56")</td></tr><tr><td>E2</td><td>Cal + Fl + Py<br>+ Gal + Sph +<br>Ser + Kln</td><td>Qz + Cal + Ser<br>+ Kln<br>(advanced<br>argillic)</td><td>Straight veins,<br>irregular and sharp<br>borders, constant<br>thickness,<br>continuous with<br>frequent<br>branching</td><td>Calcite: Subhedral to<br>euhedral, frequent<br>twins when<br>crosscutting older<br>veins</td><td>Calcite: Oscillatory<br>growth zoning from<br>center to margins</td><td>Twins when<br>crosscutting older<br>veins</td><td>AB.122.03<br>(N40°58'29";<br>E25°49'56")</td></tr></tbody></table>

Abbreviations: Act = actinolite, Ab = albite, Bt = biotite, Bn = bornite, Cal = calcite, Cpy = chalcopyrite, Chl = chlorite, Eng = enargite, Ep = epidote, Fl = fluorite, Gn = galena, Hem = hematite, Kln = kaolinite, Mag = magnetite, Mol = molybdenite, Or = orthoclase, Py = pyrite, Qz = quartz, Rhn = rheniite, Ser = sericite, Sp = sphalerite, Tnt = tennantite, Ttr = tetrahedrite.

because they show typical macroscopic characteristics of porphyry-epithermal A-, B- and E-type veins (Table 1) (Voudouris et al., 2013a, b; Mavrogonatos et al., 2019, 2020). A set of five samples, hosting A-, B- and E-type veins that crosscut altered granodiorite, were prepared for thin and doubly-polished thick (150 µm) sections at GeoRessources (Fig. 2): MB0201 (A- and B-types), MB0202 (A- and B-types), AB120.01 (B-type), AB.122.03 (E-type) and MB11.02.01 (E-type).

## 3.2. Cathodoluminescence (CL) imaging

The CL imaging of quartz from the different vein types was performed on thin sections at GeoRessources by (i) an OPEA Cathodyne using the following parameters: *P* = 50–60 mTorr, *T* = 11.0–14.0 mV, *I* = 250–480 µA and a 5–10 s obturation duration and (ii) a SEM TScan was used with the following parameters: *T* = 15 kV, *I* = 2–3 nA, x300 magnification and 4 min obturation. The former provided CL imagery at the section scale, while higher resolution imaging was performed by the latter. Combining the two approaches is particularly suitable for investigating zoned quartz next to carbonates, exhibiting strong yellow-red luminescence. It is noteworthy that the CL intensity of different images with varying acquisition parameters (voltage tension, intensity and pressure) can usually not be compared. However, the presence of different vein types in the same sample with varying CL intensity allowed such a comparison to some extent.

## 3.3. Fluid inclusion analysis

Fluid inclusions hosted in quartz of the different vein types were studied on thick sections at GeoRessources. After a detailed petrographic study, primary fluid inclusions were analyzed by a Linkam THMS600 cooling-heating stage, designed to work in the temperature range –180 to +600 °C, linked to an Olympus BX50 microscope equipped with several objectives (x10 to x100) and a camera for image caption.

The stage was calibrated prior to each analytical session by measuring the phase transition temperatures of natural and synthetic standard fluid inclusions: the triple point of CO₂ at –56.6 °C, the melting point of pure water at 0.0 °C (synthetic sample) and the homogenization temperature of natural fluid inclusions at +165 °C. A heating rate of 10 °C/min was first adopted and then reduced to 2.0–0.1 °C/min approaching the phase transitions of interest, with stabilization steps of 30 sec. The temperature accuracy was 0.1 °C for temperatures <31.0 °C and 1 °C for higher temperatures. The samples were first cooled to –100 °C, then gradually heated. The following phase transition temperatures were reported: *T*<sub>m</sub>(ice) the ice melting temperature; *T*<sub>h</sub> (L + V → L), *T*<sub>h</sub> (L + V → V) the temperature of total homogenization by disappearance of the vapor or liquid phase, respectively; *T*<sub>m</sub>(hal) the dissolution temperature of halite. All data are presented in Supplementary S1.

Although fluid inclusions along growth zones were noticed, they were too small to be analyzed. Fluid inclusions were identified due to similarities in size and shape and phase ratios based on petrographic
observations and were interpreted accordingly as primary, pseudo-secondary or secondary fluid inclusion assemblages (FIAs) (Bodnar et al., 2014; Goldstein and Reynolds, 1994). Only fluid inclusions found either isolated, evenly clustered or forming quartz intragrain trails, and which were interpreted to be of primary or pseudo-secondary origin were measured. Fluid inclusion petrography was supplemented by CL-imaging to determine more accurately the geometric relationships between fluid inclusions and the host quartz growth zoning.

The salinity was calculated from $T_m(\text{hal})$ using the Sterner et al. (1988) equation for Type 1 (LV) and Type 3 (VL) fluid inclusions and the Bodnar (1993) equation for Type 2 (LVH) fluid inclusions. The presence of both Type 2 and Type 3 fluid inclusions in the same assemblage suggests a heterogeneous entrapment due to fluid boiling. In that specific case, $T_h$ represents the true trapping temperature, and $P_h$ (homogenization pressure) represents the true trapping pressure ($P_{\text{trapping}}$) without any correction (e.g., Diamond, 2001). The trapping pressure was graphically determined using the PTX diagram from Bodnar (1993, 2003), showing the isotherm curves (Supplementary S2). As an example, we show our approach to calculate the pressure by considering heterogeneous entrapment below the H$_2$O-NaCl solvus of hypersaline Type 2 (blue dot) and vapor-rich Type 3 (green dot) fluid inclusions at 500 °C. In that case, the homogenization temperatures of both coexisting fluid inclusions are the same and correspond to the true trapping conditions Diamond (2001). The $T_h$ and salinity of each fluid inclusion are shown as an example in Supplementary S2, i.e. a Type 2 LVH fluid inclusion with $T_h = 500$ °C and a salinity of 35.0 wt% equiv. NaCl, and a Type 3 VL fluid inclusion with $T_h = 500$ °C and a salinity of 0.5 wt%. The salinity of the fluid inclusion is projected on the isothermal curves of 500 °C. Then, the pressure value is the horizontal projection on the P scale (~500 bars in that example). In addition, the pressure of H$_2$O-NaCl fluid inclusions was estimated using the Atkinson, 2002 equation in the HokieFlincs_H$_2$O-NaCl spreadsheet (Steele-MacInnis et al., 2012), which yielded similar pressure estimates (within 5 % difference) compared to the method described above (Supplementary S1).

### 3.4. Selection of previous fluid inclusion data

Fluid inclusion data from Voudouris et al. (2013a) were used to supplement the measurements from this study. This is possible because the measurements were made on the same or similar samples. The selected data correspond to fluid inclusions for which $T_m(\text{ice})$, $T_m(\text{hal})$, $T_h$ and the salinity values were available, allowing to calculate the trapping pressure using the method described above.

The main observation of the dataset from Voudouris et al. (2013a) was that cogenetic Type 2 and Type 3 fluid inclusions, from A-type veins display a bimodal $T_h$ dispersion, i.e., one population in the range 457–510 °C and a second population in the range 360–412 °C. In the B-type vein, the $T_h$, of Types 2 and 3 fluid inclusions, show a unimodal dispersion, overlapping the second population of A-type veins, in the 366–436 °C range (Table 2). E-type veins present a unimodal population of Type 1 fluid inclusions (named E), with $T_h$ ranging from 219 to 334 °C. However, dozens of their measurements, on A- and B-type veins,

display evidence of post-entrapment reequilibration and obvious modification of initial VX properties. These data were therefore not considered in the present study. Secondary Type 1 fluid inclusions in A and B-type veins were also not considered here, as they formed late, associated to cooling of the system and mixing with surface fluids, which is out of scope of this study that focuses on the primary fluids that formed the A- and B-type veins. All data of Voudouris et al. (2013a) are available in Supplementary S1. Data derived from reequilibrated fluid inclusions is indicated by a grey background colour.

Voudouris et al. (2013a) described Type 2 fluid inclusions that homogenize by halite dissolution ($T_m(\text{hal}) > T_h$) in quartz of the A- and B-type veins. According to Lecumberri-Sanchez et al. (2012) and Audétat (2023) this either suggests (i) the modification of original fluid inclusions by stretching and H$_2$O loss during host-quartz recrystallization, or (ii) the incorporation of halite crystals during trapping of a heterogeneous fluid. Most of the fluid inclusions show typical textures that suggest post-entrapment modification within deformed or recrystallized quartz crystals (Kerrich, 1976; Tarantola et al., 2010; Eglinger et al., 2014). Due to potential post-entrapment effects (e.g., water loss, density change) (Audétat and Günther, 1999; Audétat, 2023), we thus assert that the fluid inclusions showing homogenization by halite dissolution were reequilibrated by stretching, likely during the recrystallization of the host quartz crystals and do not represent the VX properties of the original mineralizing fluid. Because of the non-representative information of the trapping condition, these data are also discarded from this paper.

### 3.5. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS)

The strategy for defining LA-ICP-MS spots was to select different microtextural domains of quartz (i.e. growth zoning, microstructures linked to deformation, undeformed grains) within the different vein types based on optical microscopy and CL imaging. Only spots with low variability in CL intensity were chosen, so that the data does not reflect a mixture of the composition of different CL domains. Cathodoluminescence variations linked to partial recrystallization of fluid inclusions were also avoided. As far as reasonably possible, areas with visible fluid and solid inclusions were not ablated.

The LA-ICP-MS setup operated at GeoRessources consists of Agilent 7900 quadrupole ICP-MS coupled with a 193 nm ArF excimer laser (GEOLAS Pro). Laser ablation was performed with a constant frequency of 5 Hz and a fluence of 12 J.cm$^{-2}$, focused on the thick section surface. The ablation diameter was 50 µm. Helium was used as the carrier gas to transport the ablation-generated particles from the ablation cell to the ICP-MS. Argon was added as an auxiliary gas through a flow adapter before the ICP-MS torch. The reference materials NIST SRM 610 (primary) and NIST SRM 612 (secondary) were used for the external standardization (Pearce et al., 1997; Jochum et al., 2011) (see Supplementary S3). The standards were analyzed twice before and after each sample or every 20–30 measurements. The acquisition time included 30 s of background measurement, 60–90 s of ablation and 30 s of

<caption>**Table 2**</caption>

Synthesis of fluid inclusion data (this study and from Voudouris et al., 2013a), showing different fluid events. Bold = retained trapping condition for the different fluid event, italic = trapping condition for fluid overlap.

<table><thead><tr><th rowspan="2">Vein type</th><th rowspan="2">Fluid inclusion</th><th colspan="2">T<sub>h</sub> (°C)</th><th colspan="2">T<sub>m</sub> (°C)</th><th colspan="2">Sal. (wt% equiv. NaCl)</th><th colspan="2">P<sub>trapping</sub> (bar)</th><th rowspan="2">n</th></tr><tr><th>Range</th><th>Mean ± 1σ</th><th>Range</th><th>Mean ± 1σ</th><th>Range</th><th>Mean ± 1σ</th><th>Range</th><th>Mean ± 1σ</th></tr></thead><tbody><tr><td rowspan="5">A</td><td>Type 2</td><td>457–510</td><td>486 ± 12</td><td>394–502</td><td>440 ± 40</td><td>46.5–60.0</td><td>52.0 ± 5.0</td><td>273–339</td><td>333 ± 55</td><td>10</td></tr><tr><td>Type 3</td><td>470–490</td><td>483 ± 11</td><td>−5.7–−4.4</td><td>−4.8 ± 0.7</td><td>7.0–8.8</td><td>7.6 ± 1.1</td><td>495–605</td><td>564 ± 60</td><td>3</td></tr><tr><td>Type 2</td><td>360–391</td><td>379 ± 16</td><td>315–347</td><td>327 ± 17</td><td>39.3–42.1</td><td>40.4 ± 1.5</td><td>120–173</td><td>152 ± 29</td><td>3</td></tr><tr><td>Type 3</td><td>371–419</td><td>391 ± 15</td><td>−7.0–−0.4</td><td>−5.2 ± 3.0</td><td>0.8–10.4</td><td>8.0 ± 2.6</td><td>201–319</td><td>239 ± 40</td><td>14</td></tr><tr><td>Type 2</td><td>418–436</td><td>420 ± 13</td><td>274–323</td><td>293 ± 18</td><td>36.2–39.9</td><td>37.6 ± 1.4</td><td>190–260</td><td>228 ± 44</td><td>8</td></tr><tr><td rowspan="2">B</td><td>Type 3</td><td>366–428</td><td>394 ± 15</td><td>−6.3–−2.8</td><td>−4.5 ± 0.9</td><td>4.6–9.6</td><td>7.2 ± 1.3</td><td>191–357</td><td>259 ± 40</td><td>47</td></tr><tr><td>E - event</td><td>219–334</td><td>264 ± 35</td><td>−1.7–−0.6</td><td>−1.2 ± 0.3</td><td>1.1–2.9</td><td>2.0 ± 0.5</td><td>22–134</td><td>55 ± 34</td><td>29</td></tr></tbody></table>
of wash-out time. Due to the generally low trace element contents of quartz, the stoichiometric Si content of quartz was used for the internal standardization (e.g., Müller et al., 2003; Monnier et al., 2018).

A total of 38 isotopes were measured with an integration time of 10 ms: ⁷Li, ⁹Be, ¹¹B, ²³Na, ²⁴Mg, ²⁷Al, ²⁹Si, ³⁵Cl, ³⁹K, ⁴⁴Ca, ⁴⁷Ti, ⁵⁵Mn, ⁵⁶Fe, ⁵⁹Co, ⁶³Cu, ⁶⁶Zn, ⁷¹Ga, ⁷²Ge, ⁷⁵As, ⁸⁵Rb, ⁸⁸Sr, ⁹⁰Zr, ⁹³Nb, ⁹⁵Mo, ¹⁰⁷Ag, ¹¹⁵In, ¹¹⁸Sn, ¹²¹Sb, ¹²⁵Te, ¹³³Cs, ¹³⁷Ba, ¹⁸¹Ta, ¹⁸²W, ¹⁸⁵Re, ¹⁹⁷Au, ²⁰⁸Pb, ²⁰⁹Bi and ²³⁸U. The different isotopes were selected for the following reasons: (i) they represent the most abundant isotope of a given element in order to maximize the obtained signal, (ii) they were selected to avoid interferences, such as between ⁴⁰Ca and ⁴⁰Ar as well as ⁵⁶Fe and ⁴⁰Ar¹⁶O, (iii) they represent metals and semi-metals that are known to be important constituents of porphyry-epithermal mineralization (Voudouris et al., 2013a), (iv) they represent elements that allow to discriminate the ablation of quartz from possible fluid/solid inclusions, such as K, Na, Cl, Fe and Ca, and (v) they commonly substitute into quartz (Al, Li, Ti, Ge) and may serve as markers for temperature, pressure, pH and growth rate (e.g., Götze et al., 2021; Götze and Möckel, 2012; Rottier and Casanova, 2021; Raimbourg et al., 2022).

A total of 211 measurements were carried out, which were subsequently processed using the Iolite software (https://iolite-software.com) for data reduction. The limits of detection (LOD) of each element were calculated according to Longerich et al. (1987) using the 3σ criterion. Initially, the retained spectra showed a stable signal over time. Signals showing intensity spikes of elements potentially representing fluid inclusions (K, Na, Cl) or solid inclusions such as silicates and oxides (Al, Ca, Fe, Mg, etc.) or sulfides (Cu, Re, Mo), were excluded from further data processing. The background signal for Ti and Ge during LA-ICP-MS is extremely low. According to the used LOD calculation from Longerich et al. (1987), this returns to a LOD of 0 ppm (see Supplementary S4). Analytical precision monitored by the repeated analysis of the primary and secondary standards (NIST 610, NIST 612), was <6.0 % RSD for all elements except for B (11.4 %), Cl (7.3 %), K (11.2 %), and Fe (20.1 %). Analytical accuracy of the secondary standard was better than 12.5 % for all elements, except for Mg (17.9 %) and Fe (14.6 %) (Supplementary 3).

### 3.6. Ti-in-quartz thermometry

Several calibrations of Ti-in quartz thermometers are available from the literature Wark and Watson, 2006; Thomas et al., 2010; Huang and Audétat, 2012; Zhang et al., 2020; Osborne et al., 2022). Recent studies have favored the calibration of Zhang et al. (2020) (e.g. Cernuschi et al., 2018; Rottier and Casanova, 2021; Hong et al., 2023), as this calibration minimizes the temperature difference relative to genetically related fluid inclusions (Rottier and Casanova, 2021). The Ti-in-quartz thermometer also depends on the pressure conditions, since the Ti⁴⁺ substitution into quartz increases with decreasing pressure. Even though the calibration of Zhang et al. (2020) was initially valid for temperatures between 700 and 900 °C and pressures between 0.5 and 4.0 kbars, it was suggested to be also the best calibration for hydrothermal systems at lower PT conditions, as it yielded comparable results as fluid inclusions in this temperature range (Rottier and Casanova, 2021).

The temperature of quartz crystallization was thus obtained using Eq. (1) (Zhang et al., 2020).

$$T[\text{Ti}] = \frac{1948.4 + 981.4 \times P^{0.2}}{5.3226 - \log_{10}([\text{Ti}]_{\text{Qz}})} - 273.15 \quad (1)$$

where T[Ti] is the temperature (in °C) and P the pressure (in kbar) of quartz crystallization, and [Ti]Qz is the Ti concentration (in ppm) in quartz. The pressure was estimated from primary fluid inclusions. All Ti-in-quartz thermometers are PX dependent. Here, we used the maximum and minimum Ti contents in quartz (i.e., [Ti]min and [Ti]max) and pressure values calculated from primary fluid inclusion (as Pmin and Pmax) of each vein type (e.g. Tanner et al., 2013). For this purpose, we

combined the fluid inclusion datasets of this study and Voudouris et al. (2013a), to constrain a range of T[Ti] for each vein type. Consequently, the T[Ti] domains are bounded by the minimum and maximum Ti concentration and pressure values for each vein type, i.e., [Ti]min and Pmin giving T[Ti]min, and [Ti]max and Pmax giving T[Ti]max.

## 4. Results

### 4.1. Petrography – Quartz microstructures and cathodoluminescence (CL) imaging

The Pagoni Rachi deposit forms a mineralized stockwork associated with an altered and fine-grained granodioritic intrusion (Fig. 2B). The fresh granodiorite consists of hornblende, biotite, plagioclase, quartz and disseminated magnetite. The succession of mineralized quartz veins and the associated alteration style of the host-rock allow defining a relative chronological sequence of the hydrothermal evolution (Fig. 2, Table 1).

Quartz crystals, from A-type veins, range in size from a few microns to tens of microns with a seriate distribution (Fig. 3A-D). They are granular, xenomorphic and do not exhibit any preferential orientation. The edges of the quartz grains are straight to curvy. In cross-polarized light, several domains with distinct extinction are visible in individual quartz crystals (Fig. 3C), with well-developed to diffuse and polygonal grain boundaries forming subgrains. These structures can be observed throughout the vein. Locally, the quartz shows interlobate edges with other quartz grains and sinuous edges (Fig. 3D). The CL imaging of quartz crystals in A-type veins exhibits different colour hues (reddish to blue) and intensities (dark to bright) (Fig. 3E-G). Luminescence and associated quartz structures are heterogeneous within the A-type veins. Several zones can be distinguished by microtextural domains in quartz: (i) mottled and mosaic CL patterns with dark red colors and some bluish streaks, where zones with chaotic red zoning are spatially associated with the location of subgrains and interlobate features, (ii) ghost bands textures mostly at grain boundaries, near domains with interlobate textures (Fig. 3D-F) and (iii) rare remnants of chevron zoning related to oscillatory growth textured quartz, with shades of blue luminescence. They are spatially associated with subhedral quartz (Fig. 3B, G).

The B-type veins are continuous, planar, with sharp edges and show syntaxial textures (Fig. 4A). In addition, the B-type veins exhibit an axial symmetry and have a banded texture, emphasized by the presence of oxides and sulfides in the center of the veins or by a central quartz suture (Fig. 4A). Multiple structural and microtextural domains can be observed in quartz within the B-type veins, based on CL imaging: (i) xenomorphic to granular quartz without preferred crystallographic orientation at the vein edges or in contact with fractures. Their size ranges from a few tens microns up to hundred microns with a seriate distribution. The granular quartz sometimes shows subgrain boundaries with diffuse to clear edges forming contiguous subgrains. Small grains show CL-ghost bands or mottled red colors of low intensity and some rare oscillatory growth zoning in discontinuous bluish chevrons. These chevrons are highlighted by discontinuous lines of magnetite/hematite. (ii) Sub-euhedral to euhedral quartz crystals in the central part of the B-type veins have interlobate borders and are oriented orthogonal to the vein selvage with a homogeneous size distribution ranging from a few hundred microns to some millimeters. These elongated quartz grains may host discontinuous oxide chevron lines, linked to a syntaxial growth of the vein. The CL imaging of this quartz-type supports oscillatory growth zoning in a chevron pattern with variations in hues and the intensity of blue, suggesting an oriented quartz growth towards the center of the vein, where the opaque mineral linings are developed. The boundaries of grains with oscillatory growth zoning show CL textures in ghost bands, which are spatially associated with interlobate quartz crystals (Fig. 4D, E). (iii) Reopening of B-type were commonly observed by CL imaging (Fig. 4D), with two distinct types of later infills. The first one shows minerals, such as chlorite, sericite, K-feldspar, calcite, pyrite,
<figure><img src="image_5.png" /><figcaption>**Fig. 3.** Cross-polarized (XPL) views of quartz petrography and microstructures and cathodoluminescence (CL) images of A-type veins. Ti concentration in ppm associated with the ablation spot location (white circles) are shown in E and F. A. Wavy A-type vein consisting of recrystallized quartz crystals crosscutting the granodiorite host rock. B. Quartz porphyroclast showing typical relicts of primary oscillatory growth zoning in contact with recrystallized quartz crystals with misorientation and a seriate size distribution (see details E and G). C. Dynamically-recrystallized quartz crystals showing sub-grain rotation (SGR). D. Dynamically-recrystallized quartz crystals showing typical interlobate margins due to grain boundary migration (GBM). E. CL imaging showing relicts of primary oscillatory growth zoning of quartz crystals in contact with mosaic and mottled CL texture linked to SGR- to GBM-type dynamic recrystallization of quartz crystals. F. CL imaging of quartz crystal showing a mosaic texture linked to dynamically-recrystallized quartz crystals. G. Relicts of primary oscillatory growth zoning domain in contact with a B-type vein, and a domain of quartz crystals with a mottled texture.</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>**Fig. 4.** Cross-polarized (XPL) views of quartz petrography and microstructures and cathodoluminescence (CL) images of B-type veins. Ti concentration in ppm associated with the ablation spot location (white circles) are shown in D. A. Continuous and planar B-type vein with parallel walls and sharp margins, crosscutting a wavy A-type vein. The B-type vein shows a late reopening in the center of the vein (green dotted line) visible in CL (see details in B). Quartz grains show different types of dynamic recrystallization textures detailed in B and C. B. Dynamically-recrystallized quartz crystals with SGR and GBM textures, typical of B-type vein margins. C. Dynamically-recrystallized quartz crystals with GBM textures at margins, typical of the center of B-type vein. D. CL imaging of a half B-type vein showing oscillatory growth zoning orientated perpendicular to the wall, with a growth direction from the vein wall to the center of the vein, and with a late reopening with dark red CL. Few bright homogeneous domains show a mottled texture especially at vein margins. E. CL(-SEM) imaging of an euhedral quartz, from a B-type vein, showing primary oscillatory growth zoning and ghost bands at contact with another grain and quartz-filled fracture.</figcaption></figure>

molybdenite and magnetite, while the second one consists of quartz and small fluorite crystals mainly at the contact with the B-type vein quartz. The quartz present in this reopened part of the B-type veins is faintly luminescent in red tones, distinguishing them from the quartz crystals of the earlier B-type vein stage (Fig. 4A, D). Some growth zoning is observable associated with oriented quartz growth towards the center of the reopening. No alteration has been identified and linked to this

reopening event, but it can be suggested as a transition from potassic to sericite-chlorite and sericitic alteration.

Quartz crystals, in the E-type veins, are elongated, euhedral, oriented orthogonally to the vein selvages and precipitated on host-rock fragments that are enclosed in the veins (Figs. 2D; Fig. 5B). The quartz exhibits oscillatory growth zoning, as revealed by CL imaging in reddish to bluish tones. It is difficult to discern the zoning due to the presence of
<figure><img src="image_7.png" /><figcaption>**Fig. 5.** Transmitted light, cross-polarized (XPL) views of quartz petrography and microstructures and cathodoluminescence (CL) images of E-type veins. Ti concentration in ppm associated with the ablation spot location (white circles) are shown in C. A. Thick section (for better contrasts compared to a thin section) of E-type vein with comb quartz at vein margins and calcite filling. B. Comb quartz at vein margins, with preferential orientation (white arrow) of growth, from the vein wall to the center. C. CL imaging of euhedral comb quartz with oscillatory growth zoning from the center to the boundaries of the quartz crystal with surrounding calcite (yellow/orange/red). D. CL-SEM imaging of euhedral comb quartz crystals (± fractured) with oscillatory growth zoning (and internal reflections) cut by and surrounded with calcite cement. Abbreviations: cal = calcite, qz = quartz. Pink dotted line = E-type vein margins, red dashed line = fractured quartz surface, white dotted line = CL zoning, yellow arrow = growth direction.</figcaption></figure>

calcite in contact with the quartz, which results in high-intensity luminescence artifacts that blur the quartz signal (Fig. 5C, D). The quartz can be fractured, but no other deformation features are observable, as supported by the lack of undulous extinction (Fig. 5A-D).

In A- and B-type veins, the CL intensity seems to vary with the microtextural quartz domain, which is also recorded by a shift from blue to red CL colors and from well preserved growth zoning to ghost bands, mottled or mosaic textures. In contrast, E-type veins display quartz crystals showing well preserved growth zoning.

## 4.2. Fluid inclusion petrography and microthermometry

The A-, B- and E-type veins contain clear and translucent quartz. Primary fluid inclusions that are isolated or arranged in clusters or trails along quartz growth zoning (Van den Kerkhof and Hein, 2001) can reach 20 µm in size, but are mostly between 5 and 15 µm. Recrystallized quartz grains in A- and B-type veins are devoid of primary inclusions or show textures suggesting partial post-entrapment reequilibration (Kerrich, 1976; Tarantola et al., 2010). Numerous stretched hypersaline Type 2 and vapor-dominated Type 3 fluid inclusions located in dynamically-recrystallized quartz showed high $T_h$ or $T_m$(hal) with no phase evolution upper than 550 °C) and were discarded as in Voudouris et al. (2013a).

Three types of primary fluid inclusions were identified: Type 1, two-phase (LV) aqueous inclusions, are characterized by a vapor bubble occupying 10 to 50 vol%, that disappears upon homogenization to

liquid. They are secondary in A- and B-type veins, since they intersect the oscillatory growth zoning of quartz, but are of primary origin in E-type veins. Type 2 inclusions are three-phase (LVH) and contain a vapor phase occupying 5 to 50 vol% of the inclusion and a halite crystal (Fig. 6A). They homogenize by bubble disappearance to the liquid phase or by dissolution of halite after bubble disappearance. Type 3 inclusions are two-phase (VL) vapor-dominated (70–90 vol%) inclusions, that homogenize to the vapor phase (Fig. 6B). Locally, they can contain daughter or accidentally-trapped opaque crystals, possibly chalcopyrite or hematite.

The inclusions in A-type veins are more generally found isolated or in clusters. Rare pseudo-secondary planes, without any preferential orientation, were observed (Fig. 6C). Three main types of fluid inclusions were distinguished (Supplementary S1): (i) secondary Type 1 liquid-rich inclusions showed a $T_m$(ice) of −1.7 ± 0.4 °C corresponding to a low-salinity fluid (1.4 to 3.3 wt% equiv. NaCl) that homogenized in the 320–425 °C range, (ii) high-salinity Type 2 inclusions where $T_h$ or $T_m$(hal) could not be determined due to lack of phase transitions during heating (Fig. 6D), (iii) vapor-rich inclusions that show two distinct populations, one characterized by high $T_h$ at 470–490 °C and $T_m$(ice) at −4.8 ± 0.7 °C (medium salinity of 7.0–8.8 wt% equiv. NaCl), as well as a second population with lower $T_h$ at 376–419 °C and $T_m$(ice) at −3.3 ± 2.9 °C (medium salinity of 0.8–9.1 wt% equiv. NaCl).

In the B-type veins, fluid inclusion planes were observed in quartz, including secondary Type 1 and primary and pseudo-secondary Type 2 and Type 3 inclusions (Fig. 6E, F). Microthermometric measurements
<figure><img src="image_8.png" /><figcaption>**Fig. 6.** Fluid inclusion petrography from A and B-type veins. A. Isolated Type 2 fluid inclusion (VLH) in B-type vein. B. Isolated Type 3 fluid inclusion (VL) in A-type vein. C. Intragrain plane of Type 3 and Type 2 fluid inclusions ending at a contact of a quartz subgrain margin in A-type vein. D. Type 2 and Type 3 fluid inclusions in A-type vein. E. Intragrain plane of Type 3 and Type 2 fluid inclusions in B-type vein. F. Intragrain planes of Type 3 fluid inclusions in B-type vein. G. Primary plane of Type 1 fluid inclusion in E-type vein. H. Primary plane of Type 1 fluid inclusion in E-type vein. V = vapor phase, L = aqueous liquid phase, H = halite crystal, op = opaque mineral. Yellow (intragrain), blue (secondary), lines indicate the strikes of the fluid inclusion planes, white dotted lines = quartz grain/subgrain margins.</figcaption></figure>
provided the following results: (i) Type 1 inclusions with a $T_m$(ice) at -3.3 ± 2.3 °C corresponding to a low salinity (1.1–7.4 wt% equiv. NaCl) fluid with a $T_h$ of 125 to 301 °C, (ii) primary Type 2 inclusions with a $T_m$(hal) of 282 ± 7 °C and hypersaline conditions (36.2–37.2 wt% equiv. NaCl). During heating they homogenized by vapor disappearance at 418–436 °C. (iii) primary Type 3 inclusions with a $T_m$(ice) of -4.8 ± 1.3 °C and moderately saline liquid phase (6.3–9.6 wt% equiv. NaCl), which homogenized by disappearance of the liquid phase at 386 to 398 °C.

E-type quartz veins showed only primary Type 1 liquid-rich inclusions occurring along trails following the growth zoning of the host quartz (Fig. 6G, H). Fluid inclusion measurement data for the E-type veins are issued from Voudouris et al. (2013a).

### 4.3. Trace elements in quartz

Hydrothermal quartz from the different vein types showed distinct trace element compositions. The most prominent elements are Al, Fe,

<figure><img src="image_9.png" /></figure>

**Fig. 7.** Histograms of Ti content in quartz analyzed by LA-ICP-MS, for A. A-type veins, B. B-type veins, C. E-type veins and the expected Ti concentration (colored dotted line) in quartz obtained using the (1) calculation and typical fluid inclusion data with $T_{mean}$ and $P_{mean}$ trapping from respective vein type (see Table 4).

Mg, Ti, Cl, Ca with concentrations between 50 and 100 ppm for A-type veins, 100–200 ppm for B-type veins and 10–400 ppm for E-type veins. Other elements, such as B, Na, Li, K, Mn, Cu, Zn, Ge, Mo, Sn and Ba, generally showed concentrations close to the respective detection limits (see Supplementary S4).

In the A-type veins, the Ti concentrations in quartz showed two populations: (i) [Ti]$_{A-1}$ ranging from 83.6 to 114 ppm ($n$ = 6) mainly linked to light blueish CL domains, and (ii) [Ti]$_{A-2}$ ranging from 9.7 to

<figure><img src="image_10.png" /></figure>

**Fig. 8.** Concentration of Ti, Al and Ge in quartz from A-, B- and E-type veins, measured by LA-ICP-MS, A. Ge vs Al. B. Ge vs Ti. C. Ti vs Al.
<table><caption>**Table 3**
Ti, Al, and Ge concentrations in quartz from A-, B- and E-type veins.</caption><thead><tr><th rowspan="2">Vein type</th><th colspan="4">[Ti] (ppm)</th><th colspan="4">[Al] (ppm)</th><th colspan="4">[Ge] (ppm)</th></tr><tr><th>Range</th><th>Median</th><th>Mean ± 1σ</th><th>n</th><th>Range</th><th>Median</th><th>Mean ± 1σ</th><th>n</th><th>Range</th><th>Median</th><th>Mean ± 1σ</th><th>n</th></tr></thead><tbody><tr><td>A</td><td>83.6–115<br>9.7–56.4</td><td>99.4<br>24.0</td><td>99.7 ± 11.5<br>28.3 ± 12.2</td><td>6<br>27</td><td>63.9–372<br>77.8–677</td><td>104<br>205</td><td>131 ± 75<br>273 ± 175</td><td>18<br>55</td><td>1.5–8.7<br>0.7–3.3</td><td>2.3<br>1.4</td><td>2.8 ± 1.6<br>1.6 ± 0.5</td><td>18<br>53</td></tr><tr><td>B</td><td>44.6–416</td><td>170.5</td><td>201 ± 111</td><td>65</td><td>172–3458</td><td>790</td><td>1073 ± 793</td><td>62</td><td>0.7–1.7</td><td>1.3</td><td>1.3 ± 0.3</td><td>16</td></tr><tr><td>E</td><td>0.2–8.7</td><td>1.3</td><td>2.0 ± 1.9</td><td>63</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr></tbody></table>

56.4 ppm (n = 27) mainly linked to dark reddish CL domains (Fig. 7A). The [Ti]A-1 population is spatially linked to well-preserved growth zoning showing no obvious evidence of recrystallization processes, while the [Ti]A-2 population is spatially linked to low-intensity CL with mottled, mosaic and to dynamic recrystallization textures as GBM to SGR (Fig. 3E, F). In the A-type vein quartz, the Ge concentration ranges from 1.5 to 4.5 ppm (n = 18) with one outlier at 8.7 ppm and Al ranges from 63.9 to 372 ppm (n = 18). In the B-type veins the Ti content values ([Ti]B) range from 44.6 to 416 ppm (n = 65) (Fig. 7B), but no link was observed with CL intensities (e.g. growth zoning, mottled) or quartz micro textures (SGR to well-crystallized) (Fig. 4D, E). The Ge data ranged from 0.7 to 3.3 ppm (n = 53) and the Al data ranged from 77.7 to 677 ppm (n = 55). In E-type veins Ti content values ([Ti]E) ranged from 0.2 to 8.7 ppm (n = 57) ppm and were variable (less than 10 ppm) (Fig. 7C) within the veins but not along the growth zoning (Fig. 5C, D). The Ge data ranged from 0.7 to 1.7 ppm (n = 17), Al ranged from 77.7 to 677 ppm (n = 59) with three outliers at concentrations >3100 ppm (Fig. 8) (Table 3).

Regarding the different vein types, Ge concentrations in quartz are very similar and show only slight variations and small concentration ranges (Fig. 8A, B). Quartz from A- and B-type veins have similar Al concentrations (Fig. 8A, C) and show only slight variations within each vein type. By contrast, quartz in E-type veins shows higher Al concentrations than A- and B-type vein quartz (Fig. 8). The B-type vein quartz shows higher Ti concentrations than the A-type vein quartz, which in turn shows higher Ti concentrations than the E-type veins quartz (Figs. 7 and 8). In E-type veins, the CL-intensity of quartz is low and corresponds to low Ti concentration and high Al concentrations. The trace elements considered as CL activators (e.g. Ti) do not show any clear correlation even within a specific vein. In A- and B-type vein quartz, Al and Ge values do not display any relation regarding the CL intensity or micro-textural quartz domains. Accordingly, Ti is interpreted here as the main element responsible for quartz luminescence signal.

# 5. Discussion

## 5.1. Evidence for fluid-assisted dynamic recrystallisation processes

Quartz crystals, from A and B-type veins, display well-developed to diffuse polygonal grain boundaries forming sub-grains which suggest a deformation of quartz by dynamic recrystallization of SGR type (Stipp et al., 2002a, 2002b; Passchier and Trouw, 2005) (Fig. 4B, C). Such textures are indicative of recrystallization occurring at 400–500 °C and moderate deformation rate (Stipp et al., 2002a, 2002b; Passchier and Trouw, 2005). In A-type veins, quartz crystals show widespread interlobate and sinuous edges that suggest dynamic GBM recrystallization (Fig. 3D) (Stipp et al., 2002a, 2002b; Passchier and Trouw, 2005). These quartz micro textures are interpreted as markers of quartz deformation by dynamic recrystallization at elevated temperatures (500–600 °C) or relatively low deformation rates (Stipp et al., 2002a, 2002b; Passchier and Trouw, 2005). The CL imaging of quartz crystals in A-type veins exhibits different colour hues (reddish to blue) and intensities (dark to bright) (Fig. 3E-G). Luminescence and associated quartz structures are heterogeneous within the A-type veins. Several zones can be distinguished by microtextural domains in quartz, where different dynamic recrystallization types are spatially associated to different CL domains:

(i) The presence of mosaic textures—commonly associated with mottled CL patterns (Fig. 3F)—is consistent with the action of fluids that promote dynamic recrystallization of quartz during early vein formation. Such micro textures are also interpreted as evidence of late-stage fluid circulation (Rusk, 2012; Acosta et al., 2022). These fluids may have circulated via microfractures or healing sutures, thereby enhancing recrystallization processes. The A-type veins provide compelling evidence for one or more fluid-assisted recrystallization episodes, which may have continued during the development of later-stage B- and E-type hydrothermal veins.

(ii) Ghost bands textures mostly at grain boundaries, near domains with dynamic recrystallization of GBM type (Fig. 3D-F) which are mostly interpreted as partial recrystallization of the quartz crystals (e.g. Acosta et al., 2022). However, in B-type veins, such textures, mostly localized at subhedral quartz crystal margins in the central part of the veins (Fig. 4A, D), can be interpreted as euhedral crystals that underwent partially recrystallization during the initial precipitation stage due to growing competition among different adjacent quartz crystals (e.g., Acosta et al., 2022).

(iii) In A-type veins, rare remnants of chevron zoning related to oscillatory growth textured quartz, with shades of blue luminescence (Fig. 3B, G), are suggesting a conserved primary zoning structure of quartz crystals.

Overall, at Pagoni Rachi, fluid-rich conditions appear facilitating various deformation-related processes, including fracture healing and dynamic recrystallization, significantly accelerating microstructural transformations in quartz. All our observations point to an evolution of conditions from hot ductile conditions associated to widespread fluid-assisted dynamic recrystallization with GBM textures in the early A-type to cold brittle conditions with quartz crystals fracturing in the late E-type veins.

## 5.2. Vein and fluid chronology

The undulating and discontinuous characteristics of the A-type veins together with the highly recrystallized quartz are evidence for plastic deformation supported by the development of GBM features. By contrast, the B-type veins, which are planar and continuous only show weak and localized signs of quartz recrystallization (SGR to none). Finally, the continuous and planar E-type veins contain fractured quartz (Figs. 2, 3, 4 and 5), suggesting an evolution of the deformation from ductile to brittle conditions. This is highlighted by the fluid inclusion temperatures in quartz of the A- and B-type (420–495 °C) veins, which corresponds to the ductile-to-brittle transition (375–500 °C, Monecke et al. (2018)) and then the fluid inclusion temperature in quartz of E-type veins (160–360 °C) which correspond to brittle domain (<375 °C, Monecke et al., 2018).

The relative fluid chronology derived from fluid inclusion petrography led to valuable insights. In the quartz of the A- and B-type veins, both Type 2 (LVH) and Type 3 (VL) inclusions may coexist within the same assemblage with similar $T_h$. The heterogeneous entrapment below the $H_2O-NaCl$ solvus suggests a phase separation, interpreted as a boiling event (Voudouris et al., 2013a; Fig. 6C-E). However, although
<figure><img src="image_11.png" /><figcaption>**Fig. 9.** A. TX (temperature, salinity) diagram showing fluid inclusion homogenization temperature and salinity (data from this study and Voudouris et al., 2013a). L, V, and H refer respectively to liquid, vapor and halite, which are the three phases present in fluid inclusions of the H₂O-NaCl system at room temperatures. Homogenization of Type 2 inclusions can be either by vapor or halite disappearance. In the latter case, the inclusions are considered as reequilibrated (see text for discussion) and appear in grey along the blue LVH equilibrium curve. Type 3 VL inclusions in grey show textures suggesting post-entrapment modification. B. PX (pressure, salinity) diagram showing homogenization pressure calculated from Lecumberri-Sanchez et al. (2012). For a given temperature, the red LV curves correspond to a solvus below which phase separation occurs with Type 3 VL inclusions on the left and hypersaline Type 2 LVH inclusions on the right. These red curves represent the conditions at homogenization for fluid inclusions homogenizing by liquid or vapor disappearance. The homogenization pressure of reequilibrated fluid inclusions homogenizing by halite disappearance display abnormal elevated pressure conditions. For those inclusions, the temperature of homogenization is shown by the yellow LH curves.</figcaption></figure>

the $T_h$ values are comparable (Fig. 9A), the salinity of VL inclusions is too high compared to what should be expected (see Fig. in Supplementary S2) and the pressure calculation thus result in overestimated values (Fig. 9B). This is likely attributed to bias in the observations and the inclusions which could be measured by microthermometry (i.e., only fluid inclusions with a large liquid phase showed primary textures and had a size that could be measured). This is likely due to some bias in the type of inclusions which could be measured, i.e., only fluid inclusions with a large liquid phase showed primary textures and had a size that could be measured. It is also well established that vapor-rich inclusions almost invariably entrap a minor amount of liquid in addition to the vapor phase (Bodnar et al., 1985). Therefore, the data presented for VL correspond to fluid inclusions with intermediate composition between the extremes (liquid and vapor phase, formed by boiling) on the liquid-vapor equilibrium curve at identical $T_h$ values (e.g., Diamond, 2001; Wilkinson, 2001; Bodnar, 2003) (Fig. 9). The hypersaline fluid inclusions appear to correspond to the most suitable end-member, to define the actual trapping conditions. Therefore, only these PT data will be retained in this paper.

The presence of primary and pseudo-secondary planes with the same fluid inclusion-types suggests a continuous trapping process during crystallization and recrystallisation. This is coherent with the dynamic recrystallization that commonly affects the quartz grains in the B-type veins, which is evidenced by GBM of at elongate quartz grain margins, and the associated CL-ghost band textures (Acosta et al., 2022).

In a shallow crustal environment, as for E-type veins, it is assumed that the pressure correction is <10 bars and hence the trapping pressure correction was negligigted (e.g. Bodnar et al., 1985). Our fluid inclusion observations and measurements are comparable to the ones of the A-, B- and E-type veins from Voudouris et al. (2013a). Merging of both datasets

allows us to distinguish and describe three major fluid events. These data will then be used in the rest of the discussion (Fig. 10, Table 4).

Different fluid events related to the different fluid inclusion populations for each vein type are distinguished. In A-type veins two populations are discernable: (i) higher temperatures and pressures with a $T_{trapping}$ ranging from 457 to 510 °C and a $P_{trapping}$ ranging from 273 to 339 bars, (ii) lower temperatures and pressures with a $T_{trapping}$ ranging from 360 to 391 °C and a $P_{trapping}$ ranging from 120 to 173 bars. In B-type veins only one population of fluid is discernable with a $T_{trapping}$ ranging from 418 to 436 °C and a $P_{trapping}$ ranging from 190 to 260 bars (Table 2). The low temperature and pressure population of the A-type veins are comparable to the ones found in the B-type veins. We therefore assume that they do not reflect the fluid conditions of the A-type veins but were entrapped during a later stage possibly during the B-type vein formation, which allow fracturing of quartz crystals and sealing of secondary fluid inclusions. Such overlapping supports the fluid-assisted recrystallization processes, evidenced in the A-type by the mosaic textures and dynamically-recrystallized quartz crystals. Only the high temperature and pressure population is thus considered to be representative of the fluid event that formed the A-type veins. The last fluid event is represented by Type 1 fluid inclusions related to the E-type vein formation, which yields $T_{trapping}$ ranging from 219 to 334 °C and a $P_{trapping}$ from 22 to 134 bars (Table 2).

The fluid inclusions show a clear temperature and pressure decrease from the A- via the B- and finally to the late E-type veins. Fluid inclusions show a pressure drop from the B- to E-type veins, and an overlap of low temperature and pressure fluid inclusion population of A- and B-type veins. Indeed, Type 1 fluid inclusions, related to the E-type vein formation, are also present in the A and B-type veins.

The shallow emplacement of the system between 3 and 0.2 km at
<figure><img src="image_12.png" /><figcaption>**Fig. 10.** PT diagram showing the fluid inclusion data retained for the calculation of Ti-in-quartz thermometry (this study and from Voudouris et al., 2013a). The obtained PT[Ti] domains for the A- (red), B- (blue) and E- (pink) type veins are represented. LVH, LV, LH equilibrium curves and critical curve are from Bodnar (1993), Ti isopleths are coming from Ti-in-quartz calculation (Zhang et al., 2020).</figcaption></figure>
<caption>**Table 4**</caption>

Synthesis of fluid events ($T_{trapping}$ and $P_{trapping}$), Ti concentration in quartz ([Ti]), Ti-in-quartz temperatures ($T[Ti]$), the differences between the Ti-in-quartz temperatures and fluid inclusion temperatures ($\Delta T(Ti-in-quartz–FI)$) and the involved process for the different vein types (A, B and E).

<table><thead><tr><th rowspan="2">Vein type</th><th colspan="2">$T_{trapping}$ (°C)</th><th colspan="2">$P_{trapping}$ (bar)</th><th colspan="2">[Ti] (ppm)</th><th rowspan="2">$T[Ti]$ range (°C)</th><th rowspan="2">$\Delta T(Ti-in-quartz–FI)$ (°C)</th><th rowspan="2">Involved process</th></tr><tr><th>Range</th><th>Mean ± 1σ</th><th>Range</th><th>Mean ± 1σ</th><th>Range</th><th>Mean ± 1σ</th></tr></thead><tbody><tr><td>A</td><td>457–510</td><td>486 ± 12</td><td>273–339</td><td>318 ± 21</td><td>83.6–115<br>9.7–56.4</td><td>99.7 ± 11.5<br>28.3 ± 12.2</td><td>492–567<br>327–496</td><td>Up to +66<br>Down to –130</td><td>Fast growth?<br>Dynamic recrystallization</td></tr><tr><td>B</td><td>418–436</td><td>420 ± 13</td><td>190–260</td><td>228 ± 44</td><td>44.6–416<br>0.2–8.7</td><td>201 ± 111<br>2.0 ± 1.9</td><td>435–751<br>159–359</td><td>Up to +315<br>Down to –60</td><td>Fast growth<br>/</td></tr><tr><td>E</td><td>219–334</td><td>264 ± 35</td><td>22–134</td><td>55 ± 34</td><td></td><td></td><td></td><td></td><td></td></tr></tbody></table>

temperatures ranging from ~485 °C (A-type) to ~260 °C (E-type) implies that fluid inclusion data mostly fall between hydrostatic and lithostatic domain. This is consistent with the phase separation phenomenon, involving a rapid pressure drop and intense hydrothermal fracturing, represented by stockwork veins (such as A-, B- and E-type veins), suggesting a shift in the pressure regime. The overall scheme is consistent with a telescoping process during which the quartz vein succession displays a clear evolution in the deformation style (i.e., dynamic recrystallization types, fractures) from hot ductile to cold brittle conditions, where an epithermal system superimposes the porphyry mineralization (Sillitoe, 2010).

### 5.3. Ti-in-quartz temperatures and comparison with fluid inclusion thermometry

The occurrence of rutile and titanite mineral inclusions in hydrothermal quartz and the host rocks (Voudouris et al., 2013a) suggest a $TiO_2$ activity of ~1. This allows the estimation of quartz formation temperatures by Ti-in-quartz thermometry (Zhang et al., 2020). The minimum and maximum values of the Ti contents in quartz of the A- and B-type veins were used for the Ti-in-quartz thermometry by using the trapping pressure of fluid inclusions from the respective vein types (Fig. 7A-C) (Tables 3 and 4). For the A-type veins, the extreme pressures (range of 273–339 bars) given by the high-temperature fluid inclusions. For the B-type veins the pressure range of 190–260 bars are used, from the fluid inclusion data of the B-type veins. For the E-type veins the extrema pressure range of 22–134 bars are used, from the fluid inclusion data of the E-type veins (Figs. 9, 10, Tables 3 and 4).

The here preferred Ti-in-quartz geothermometer after Zhang et al. (2020) gives the following temperatures for the quartz formation in the A-, B- and E-type veins: $T[Ti]_{A-1} = 492–567$ °C, $T[Ti]_{A-2} = 327–496$ °C, $T[Ti]_B = 435–751$ °C and $T[Ti]_E = 159–359$ °C (Table 4, Fig. 10). This results in an increase of the precipitation temperature of quartz in the A-type to the B-type veins following a decrease in the E-type veins. This agrees with the higher Ti contents in quartz in the B- compared to the A-type veins. The $T[Ti]_{A-2}$ temperatures partially overlap with the trapping temperature of the fluid inclusions in the A-type veins (457–510 °C) and extends to lower values, while the $T[Ti]_{A-1}$ temperatures are higher than that of the fluid inclusions. The $T[Ti]_B$ temperatures (435–751 °C) are generally higher than that of the respective fluid inclusions (418–436 °C) in the B-type veins, which may be due to a discrepancy on the Ti-in-quartz thermometer (i.e. Ti in excess). The $T[Ti]_E$ temperatures (159–359 °C) are within the range of the fluid inclusion trapping temperatures of the E-type veins (219–334 °C) (Table 4, Fig. 10).

Using the equation by Zhang et al. (2020), we can recalculate the expected quartz concentration based on the PT data of the fluid inclusions from the different types of veins. The maximum and minimum PT values are used to obtain [Ti] ranges for each type of quartz veins. As such, we obtain the following ranges: $[Ti]_A = 41.4–55.6$ ppm, $[Ti]_B = 29.1–30.5$ ppm, $[Ti]_E = 2.7–10.8$ ppm (Fig. 7A-C). For the A-type veins, the expected $[Ti]_A$ values are lower than that of the $[Ti]_{A-1}$ and higher than that of the population. For B-type veins, the expected $[Ti]_B$ values are lower than the analyzed $[Ti]_B$ values. For the E-type veins, the expected values mostly overlap with the measured concentrations and only small differences (< 1 ppm) were observed that may be attributed

to the low-pressure conditions, which could induce an error (Fig. 7A-C) (e.g., Thomas et al., 2010; Huang and Audôtat, 2012; Zhang et al., 2020).

Here, the calibration of Zhang et al. (2020), is compared with the results derived from Thomas et al. (2010), Huang and Audôtat (2012) and Osborne et al. (2022) (see Supplementary S5). In general, the temperature range calculated by Thomas et al. (2010) falls within the range established by Zhang et al. (2020), with a maximum difference of 70 °C for high [Ti] values. The temperatures derived from the Huang and Audôtat (2012) are consistently higher than that from Zhang et al. (2020), with a maximum difference of 98 °C. By contrast, the temperatures provided by Osborne et al. (2022) are generally lower than those from Zhang et al. (2020), with a maximum difference of 152 °C for high [Ti] values. In addition, the influence of different Ti activities was tested in the different calibrations, using an activity of 1 at rutile precipitation and 0.5 when Fe—Ti oxides (magnetite/hematite) are saturated in the fluid (Thomas et al., 2010; Reid et al., 2011; Huang and Audôtat, 2012). The use of a Ti activity of 0.5 could be justified by the ubiquitous presence of hematite and magnetite within the quartz veins. Thus, a decrease in Ti activity leads to a mean increase of 20 to 60 °C in the precipitation temperatures of quartz and of up to 94 °C at high [Ti]. However, irrespective of the applied Ti-in-quartz calibration and the suggested Ti activities the temperature difference regarding the fluid inclusion microthermometry could not be resolved. These findings demonstrate that the use of Ti-in-quartz thermometers (e.g., Thomas et al., 2010; Huang and Audôtat, 2012; Zhang et al., 2020; Osborne et al., 2022) should always be conducted with caution, particularly under hydrothermal conditions, where out-of-equilibrium processes, as discussed in the following may have a significant impact.

### 5.4. Evidence for Ti excess in quartz during out-of-equilibrium crystallization

A decrease of the Ti content ([Ti]) and associated calculated temperature ($T[Ti]$) in quartz from the A- to the B-type veins was expected, as suggested by the fluid inclusion temperatures. Instead, the estimated Ti-in-quartz temperatures of the B-type veins are higher than that of the A-type veins and which may thus indicate a primary enrichment or a post-crystallization modification, particularly in quartz of the B-type veins, where the measured $[Ti]_B$ is higher than the expected Ti content for these temperature and pressure of formation, up to one order of magnitude (Figs. 7A, B and 10). Huang and Audôtat (2012) suggested that the quartz crystallization rate influences the Ti incorporation. At slow crystallization rates, the Ti incorporation is typically in equilibrium with the fluid, while during high crystallization rates less time is available for a re-organization of the crystal lattice, resulting in out-of-equilibrium conditions and in excess Ti contents compared to equilibrium conditions. As a result, it is usually recommended to use the minimum [Ti] of a given quartz population, limiting the impact of a Ti in excess, to calculate the temperature of crystallization using Ti-in-quartz thermometry (Huang and Audôtat, 2012; Cernuschi et al., 2018, 2023; Hong et al., 2023).

Quartz crystals of the B-type veins at Pagoni Rachi are elongated and have a euhedral to subhedral shape (Fig. 4C) and most CL textures consist of alternating dark and bright growth zones revealing euhedral
<figure><img src="image_13.png" /><figcaption>**Fig. 11.** Synthetic sketch of the respective influence of rapid growth and dynamic recrystallization of quartz on the Ti content of quartz and on the Ti thermometer, with comparison of our Ti data and fluid inclusions. A. Out-of-equilibrium crystallization of quartz in A-type veins. The quartz shows a significant contrast in CL intensity with oscillatory growth zoning from the edge of the vein to the center. In some cases, dynamic recrystallization occurs simultaneously with crystallization, with the presence of GBM at the grain boundaries. Titanium is in excess due to the rapid growth of quartz, implying a ΔT(Ti-in-quartz – FI) of up to +60 °C. B. Out-of-equilibrium crystallization of quartz in B-type veins. The quartz shows a significant contrast in CL intensity with oscillatory growth zoning from the edge of the vein to the center. In some cases, dynamic recrystallization occurs simultaneously with crystallization, with the presence of GBM at the grain boundaries, associated with a ghost bands texture (see Fig. 4E). Titanium is in excess due to the rapid growth of quartz, implying a ΔT(Ti-in-quartz – FI) of up to +315 °C. C. Equilibrium crystallization of automorphic quartz in E-type veins. The quartz shows a low CL intensity contrast with oscillatory growth zoning from the center of the vein grains to the rim. Titanium is at equilibrium, implying a ΔT(Ti-in-quartz – FI) close to 0 °C within error. D. Ductile deformation of quartz in A-type veins with intense generalized dynamic recrystallization, with GBM and associated CL textures in ghost bands, mottled, of low intensity, and a Ti deficit, implying a ΔT (Ti-in-quartz – FI) down to –130 °C. In some cases, quartz porphyroclasts with little to no deformation can be observed, preserving their CL textures (oscillatory growth zoning with intensity contrast) and an excess Ti signal, implying a ΔT(Ti-in-quartz – FI) of up to +60 °C. E. Ductile deformation of quartz in B-type veins with low-intensity dynamic recrystallization, with SGR and an excess of Ti, implying a ΔT(Ti-in-quartz – FI) of up to +315 °C. F. Brittle deformation of quartz in E-type veins with quartz fracturing and cementation by calcite (orange). The quartz shows unmodified oscillatory growth zoning in CL with low-intensity CL. Their Ti signal is at equilibrium, implying a ΔT(Ti-in-quartz – FI) close to 0 °C. G. Expected (grey rectangle) and actual (red rectangles) Ti concentrations in quartz from A-type veins. The expected values are calculated from the *T*trapping of the fluid inclusions (FI), using the extreme pressure values (*P*min = 273 bars, *P*max = 339 bars). H. Expected (grey rectangle) and actual (blue rectangles) Ti concentration in quartz from B-type veins. The expected values are calculated from the *T*trapping of the fluid inclusions, using the extreme pressure values (*P*min = 190 bars, *P*max = 260 bars). I. Expected (grey rectangle) and actual (pink rectangles) Ti concentrations in quartz from E-type veins. The expected values are calculated from the *T*trapping of the fluid inclusions, using the extreme pressure values (*P*min = 22 bars, *P*max = 134 bars). ΔT(Ti-in-quartz – FI) = temperature difference between Ti-in-quartz thermometer and fluid inclusion data, FI = fluid inclusion.</figcaption></figure>

crystal faces (Fig. 4D, E), and thus reflecting primary crystal growth from a hydrothermal fluid. This observation is particularly evident in the central parts of the veins, which were not affected by dynamic recrystallization (Fig. 11B, H). One possibility is that CL-bright bands form during pressure fluctuations that are relatively short-lived, but which can cause fast growth rates (Acosta et al., 2022; Raimbourg et al., 2022). Moreover, the elongated habit of subhedral quartz was suggested to be controlled by particularly fast growth rates along the c-axis compared to the a-axis, which may be linked to oscillatory growth zoning with alternating high and low CL intensity domains (Swanson and Fenn, 1986; Yang et al., 2015) (Fig. 4D, E). Hence, fast crystal growth can likely explain the excess Ti contents in quartz from the B-type veins at

Pagoni Rachi. Such observations have been reported highlighting the potential involvement of similar processes during the formation of quartz in early-type veins. Comparable mechanisms may also be active in other porphyry and epithermal systems, such as Butte (Acosta et al., 2022), Bilihe (Hong et al., 2023), Maronia (Falkenberg et al., 2024), and Skouries (Höss et al., 2024), where elevated Ti concentrations in quartz (e.g., Ti contents up to 330 ppm, Falkenberg et al. (2024)) have been associated with rapid crystal growth.

If this Ti excess is due to fast crystallization of B-type veins, it is also possible that similar Ti excess is found in non-recrystallized parts of A-type veins. Indeed, the A-type veins show relics of primary oscillatory growth zoning (rarely), with high CL contrast (Fig. 3B, G). If a fast
crystallization process occurred during the A-type vein formation, this could imply an excess Ti incorporation, leading to a higher $[Ti]_{A-1}$ than expected by the fluid inclusion data, which is the case (Fig. 7 A, Fig. 11 A). These results for the A-type veins, suggest a link between high CL intensities and low to no dynamic recrystallization micro textures of quartz, and a $T[Ti]_{A-1}$ higher than the fluid inclusion temperatures (Fig. 11A, D, G). In contrast to such processes, the measured $[Ti]_E$ are within the expected Ti from fluid inclusion. Quartz of the E-type veins display low CL-intensities with well-developed growth zoning, suggesting equilibrium crystallization (Figs. 7C, 11C, I). Ti content and associated $T[Ti]$ is subsequently decreasing due to intense deformation allowing a process responsible for a decrease of the Ti content in quartz (e.g. as diffusion, see next section). Thus, even if fast quartz growth can cause a Ti excess in quartz, dynamic recrystallization may influence the preservation of this Ti enrichment, adding complexity of the interpretation of Ti-in-quartz temperatures in hydrothermal environments.

In addition to the clear influence of Ti enrichment at Pagoni Rachi—interpreted because of rapid quartz growth—this phenomenon appears to be relatively common in porphyry and hydrothermal systems more broadly (e.g., Cernuschi et al., 2018; Acosta et al., 2022; Hong et al., 2023; Höss et al., 2024; Falkenberg et al., 2024). Elevated Ti concentrations in quartz are particularly associated with the earliest and highest-temperature vein generations, suggesting that rapid crystallization under disequilibrium conditions is a recurring feature in these settings. This supports the interpretation that Ti uptake during quartz growth is sensitive not only to temperature but also to crystallization kinetics, with implications for the use of Ti-in-quartz as a geochemical and thermometric proxy in hydrothermal environments.

## 5.5. Evidence for Ti diffusion during fluid-assisted dynamic recrystallization

The presence of quartz domains in A-type veins with Ti concentrations near to 1 order of magnitude lower than expected (down to 9.7 ppm), and thus resulting in lower Ti-in-quartz temperatures (327–496 °C) compared to what is expected from fluid inclusion data (457–510 °C) suggests a phenomenon of post-crystallization Ti loss (Table 4, Figs. 7A, 10 and 11D, G). The microtextural domains of quartz, indicating high deformation intensity by the presence of GBM (to SGR) and CL texture with ghost bands and mottled textures of low CL intensity with low Ti content, suggest that this Ti deficit may be associated with dynamic recrystallization (Fig. 3C-F). Grain boundary migration textures are such an example, which were described as a possible factor of Ti diffusion during deformation and dynamic recrystallization (Nachlas and Hirth, 2015; Cavalcante et al., 2022). Even if volume diffusion of Ti through quartz is known to be very slow (Cherniak et al., 2007; Jollands et al., 2020), Ti in quartz can be reset by stress-induced GBM to a new equilibrium at a faster stress rate (Van den Kerkhof et al., 2004; Nachlas and Hirth, 2015; Bromiley and Hiscock, 2016), particularly in fluid-rich systems such as porphyry-epithermal systems. Then, A-type vein quartz underwent a Ti loss through deformation to highly deformed quartz showing widespread GBM and SGR textures, responsible for the lowering of the CL intensity due to a low $[Ti]_{A-2}$ (<56.4 ppm). The given $T[Ti]_{A-2}$ values are derived from Ti loss and therefore, may not reflect the expected temperatures based on fluid inclusions.

The volume diffusion of Ti through quartz is generally slow (Cherniak et al., 2007; Jollands et al., 2020). In areas where GBM occurs, even short periods of deformation at peak temperatures are sufficient to lead to the reequilibration of Ti concentration in quartz (e.g. Grujic et al., 2011). Volume diffusion alone cannot fully homogenize Ti concentration in larger grains at temperatures below 700 °C, even over extended periods (e.g., one million years) (Cherniak et al., 2007). However, GBM significantly accelerates the redistribution of Ti, particularly in fluid-rich environments (e.g. Grujic et al., 2011). Grain boundary migration allows Ti to reach a new equilibrium concentration much more quickly, which is especially evident in fluid-saturated

systems (e.g. Acosta et al., 2022). In these systems, the presence of fluids enhances the mobility of Ti within quartz, facilitating faster equilibration.

Under fluid-rich conditions, as is the case at Pagoni Rachi, fluids significantly accelerate several processes, including fracture healing and recrystallization. During this process, Ti redistribution and resetting occurred (e.g. A-type veins) within specific zones, further supporting the idea that fluid-induced recrystallization and Ti equilibration are closely linked to the development of these textures. This limitation highlights the critical role of GBM, coupled with fluid-assisted trace element diffusion along grain boundaries, as a key process in achieving the equilibration of Ti concentrations in quartz. The variations in Ti concentrations in quartz, associated with fluid-assisted dynamic recrystallization, are consistent with the values reported in the literature, a reduction of one order of magnitude, possibly reaching an intermediate value and a new equilibrium level. Indeed, Kidder et al. (2013) observed no variation in Ti concentration between recrystallized (with GBM) and undeformed quartz, with low values ranging from 0.2 to 2 ppm in their quartz veins. However, they present a significant decrease in Ti concentrations between recrystallized and undeformed quartz from a quartzite, ranging from 1–100 ppm to 1–10 ppm. They conclude that Ti diffused to an intermediate value, or to another equilibrium concentration. Bestmann et al. (2021) showed that Ti concentrations in quartz are variable and associated with the recrystallization texture of the quartz, with a decrease in Ti concentration from the core (2–50 ppm) to the recrystallized borders, which display a lower Ti content ranging from 40 to 60 % of the core content. Newly recrystallized quartz had even lower concentrations (2–10 ppm), showing nearly an order of magnitude difference. This reduction in Ti content induces a decrease in Ti-in-quartz temperature from the center of the quartz to the recrystallized borders.

Low temperature recrystallization (e.g. SGR and BLG) has been described as possible mechanisms to reset Ti to lower equilibrium values in certain PT conditions (Grujic et al., 2011; Bestmann et al., 2021; Cavalcante et al., 2022). Experimental studies (Nachlas and Hirth, 2015) proposed that Ti diffusion is possible during SGR deformation under metamorphic conditions. However, during the exhumation of synkinematic quartz veins that underwent retrograde BLG and SGR at temperatures less than 350 °C, the quartz preserved its Ti concentration (Haertel et al., 2013). At Pagoni Rachi, combining quartz micro- and CL-textures, as well as its trace element composition does not show any evidence of Ti diffusion in B-type vein quartz crystals (Fig. 4D). Indeed, quartz display heterogeneous spatial distribution of dynamic recrystallization within the vein with rare BLG and minor SGR indicators, as well as rare GBM structures in central parts of the vein, and present similar Ti concentrations through the veins irrespective of the presence, intensity and type (e.g., SGR) of deformation and CL domains (Fig. 4B-E). Thus, it can also be assumed that the CL-mottled texture occurred during low temperature BLG and SGR recrystallization must have occurred during vein cooling and exhumation, but did not further facilitate Ti loss and equilibration. The E-type vein quartz does not show any evidence of dynamic recrystallization, which is supported by its euhedral shape and well-preserved CL-oscillatory growth zoning, lacking also signs of disequilibrium reactions (Fig. 5A-D). This suggests that no intra-crystalline deformation was involved at a lower temperature (~ 250 °C).

The present investigation of the Pagoni Rachi deposit indicates that Ti reset during fluid-assisted dynamic recrystallization of quartz with GBM type induces a Ti deficit (to one order of magnitude) to a possible new equilibrium state. Such process has not been observed at dynamic recrystallization, as SGR or BLG, which in these case preserves the Ti signature of the quartz formation, even if Ti is in excess in the quartz (Figs. 7A, 10 and 11A, D, G). This hypothesis is interesting regarding the stability of the geochemical signature along the lifespan, deformation and fluid presence of the porphyry-epithermal system. Then a potential Ti sink, when Ti diffusion, could be the surrounding magnetite/hematite or biotite present in the host rock or directly included in the quartz.
## 5.6. Implication for Ti-in quartz thermometry in magmatic-hydrothermal systems

Out-of-equilibrium crystallization due to fast growth rate results in an excess of Ti in quartz, and thus higher inferred crystallization temperatures. Conversely, when quartz crystals are dynamically-recrystallized and may induce Ti diffusion (Cherniak et al., 2007; Ashley et al., 2014; Nachlas and Hirth, 2015; Bromiley and Hiscock, 2016; Cavalcante et al., 2022), a Ti deficiency and lower inferred temperatures can be expected. It is important to note that the calculated maximum $[Ti]_{A-1}$ values align with the measured Ti contents of the same quartz crystal, while the lowest $[Ti]_{A-2}$ values correspond to recrystallized quartz crystals, where Ti has been lost through diffusion. This is supported by Grujic et al. (2011), who found that deformation processes in metamorphic systems are recorded by quartz through grain boundary migration (GBM) textures. At Pagoni Rachi, this leads to an unusual evolution in quartz precipitation temperatures from $T[Ti]_{A-1} = 492–576$ °C and $T[Ti]_{A-2} = 327–496$ °C, to higher temperatures, $T[Ti]_B = 435–751$ °C and then lower temperatures $T[Ti]_E = 159–359$ °C (Table 4, Figs. 10, 11G-I).

For the B-type veins, the lowest temperature values have been used as recommended (e.g. Cernuschi et al., 2018), which suggests a possible temperature range based on Ti-in-quartz thermometry [435–461] °C (Fig. 8). This same reasoning can be applied to the $[Ti]_{A-1}$ quartz population by assuming that (i) the Ti has not diffused and (ii) considering rapid quartz growth with Ti excess, which would yield the interval [492–576] °C (Figs. 10, 11G). This analysis also underlines the pressure dependency of the thermometer, potentially leading to a broad range of temperature values, which is observable along Ti isopleths (Fig. 10), particularly at low pressures.

Furthermore, the use of the lowest Ti content (e.g. Huang and Audôtat, 2012; Cernuschi et al., 2018) is consistent with the fact that the temperatures for $[Ti]_{A-1}$, which retains the primary Ti signature of quartz, are higher than those for $[Ti]_{A-2}$, which exhibits partial Ti loss due to diffusion during dynamic recrystallization. Thus, the temperatures should decrease from $T[Ti]_{A-1}$ to $T[Ti]_{A-2}$. In this context, the evolution appears more consistent with a transition from (i) high temperature A-type veins, where quartz retains the primary crystallization signal, with low Ti temperatures when Ti has diffused during dynamic recrystallization, as GBM type, to (ii) intermediate temperature B-type veins, where the quartz is moderately deformed to undeformed, and to (iii) low temperature E-type veins that lack evidence of plastic deformation (Figs. 10 and 11A-I).

Moreover Nachlas and Hirth (2015) suggested that the Ti-in-quartz temperatures of highly recrystallized grains give the temperature of the deformation conditions. Noting that, it is interesting to look at the low temperatures due to Ti loss during deformation, which go from 327 to 496 °C in the A-type veins. They may represent the possible range of temperature of deformation, which are consistent with the deformation texture, as widespread GBM and SGR that give a range of theoretical deformation temperatures from 250 to 600 °C (Stipp et al., 2002a, 2002b). This is coherent with the circulation of fluid forming A-type veins quartz at around 500 °C and a later fluid forming B-type veins at around 420 °C. This may indicate a possible temperature of deformation ranging from 350 to 500 °C, consistent with fluid circulation conditions and thus with recrystallization during quartz crystallization. By contrast, an artificial underestimation of $T[Ti]_E$ is conceivable for E-type veins which appear lower than those expected from fluid inclusion data (Fig. 10I). At low pressures, the isopleth curves flatten (Fig. 10), so even slight variations in pressure can significantly alter the temperature yield.

However, the temperature ranges are mostly similar and are coherent with a deformation in brittle condition at temperature <250 °C (e.g. Passchier and Trouw, 2005), during cooling.

Therefore, the Ti-in-quartz thermometer is not suitable for calculating the temperature of Ti incorporation in quartz when recrystallized during deformation processes, or when the Ti incorporation in quartz is related to fast growth rates. In the first case, the given $T[Ti]$ may represent the temperature of deformation, and in the second case the use of the lowest Ti concentrations may help to reduce the effect of fast growth rates on Ti-in-quartz thermometry.

## 5.7. Implication for Al/Ti vs Ge/Ti-based vein typology in porphyry-epithermal systems

It is common to distinguish different vein types in porphyry-epithermal systems based on distinct Al/Ti and Ge/Ti ratios in quartz (e.g Schrön et al., 1988; Götze and Möckel, 2012; Rottier and Casanova, 2021; Falkenberg et al., 2024), which, however, can be disturbed by dynamic recrystallization and rapid crystal growth (Nachlas and Hirth, 2015; Cernuschi et al., 2018). For instance, the quartz data from Pagoni Rachi from the A-type veins fall within the range of B-type veins from other porphyry systems, while our data from the B-type veins overlaps with data from the A-type veins of other deposits (Fig. 12). This suggests that deformation and recrystallisation also influences this geochemical vein classification scheme. Germanium contents appear to be relatively constant in quartz within the veins and do not show any resetting due to dynamic recrystallization, as also observed for the Al content (Fig. 8). Some authors have already described Al as immobile or only slightly mobile at the micrometer scale (Tailby et al., 2018). Moreover, the variability of Al in quartz has been suggested to be closely linked to the pH evolution of the ore-forming fluid, with higher Al contents in quartz correlating with decreasing pH conditions (Rusk et al., 2008a, 2008b; Müller et al., 2018). Hence, the increasing Al contents in quartz from the A- to E-type veins, are indicative of decreasing pH conditions during the evolution of the system. The shift from sericitic to advanced argillic alteration assemblages in the host rocks further supports this acidification process, which is typical of the late stages of porphyry to epithermal transitions (Sillitoe, 2010; Raimbourg et al., 2022). Therefore, Ti appears to be the main factor in the Al/Ti an Ge/Ti ratios that is influenced by recrystallisation and growth rate, which leads to the observed geochemical overlap or quartz from A- and B-type veins in this classification scheme. This again indicates that the Ti contents in quartz from A- and B-type veins may not generally reflect the actual precipitation conditions at equilibrium, but rather the history of deformation, fluid-assisted recrystallization and out-of-equilibrium crystallization processes.

For quartz in the A-type veins, it is likely that Ti diffusion is controlled and possibly enhanced by deformation processes causing quartz recrystallization. This results in an underestimation of quartz precipitation temperatures by the Ti-in-quartz thermometer (Fig. 11G) and unexpectedly high Ge/Ti and Al/Ti ratios in quartz (Fig. 12). This is likely to explain why the Ge/Ti and Al/Ti ratios of A-type veins overlap with that of the B-type veins (Fig. 12). On the other hand, a fast precipitation rate, which implies an excess of Ti in quartz, leads to high Ti concentrations in quartz (Fig. 11H) and an underestimation of Ge/Ti and Al/Ti ratios. This can likely explain the low ratios of quartz in the B-type relative to that of the A-type vein. By contrast, the E-type veins that do not show any evidence of Ti in excess or a Ti loss, as evidenced by the distinct Ge/Ti and Al/Ti values relative to the other vein types (Fig. 12). We note that a similar overlap in the Ge/Ti and Al/Ti of quartz between
<figure><img src="image_14.png" /><figcaption>Fig. 12. Ge/Ti vs Al/Ti (mass ratios) diagram based on LA-ICP-MS analyses of quartz of A-type (red), B-type veins (blue), and E-type veins (pink). Compilation of data from the literature is shown by the grey shaded aeras (from Rottier and Casanova, 2021), by the colored circles for veins in Pagoni Rachi porphyry-epithermal system (this study) and by the shaded colored squares for similar veins in Maronia porphyry system (from Falkenberg et al., 2024).</figcaption></figure>

the A-type and B-type veins was described by Falkenberg et al. (2024) in the nearby Maronia porphyry mineralization. This suggests that quartz recrystallization processes may be a more common processes in porphyry environments than previously thought, which has important consequences on the geochemical vein classification and the reconstruction of the fluid history by quartz chemistry. Hence, the Al/Ti vs. Ge/Ti classification scheme by Rottier and Casanova (2021) may be valid only for quartz veins formed under equilibrium conditions which were not influenced by post-formation dynamic recrystallization.

## 6. Summary and conclusion

Overall, the Pagoni Rachi system serves as a case study illustrating how the interplay between deformation, fluid chemistry and thermal conditions can impact the development of quartz veins in porphyry-epithermal systems. The evolution from ductile to brittle deformation and from lithostatic to hydrostatic conditions (Fig. 10), associated with fluid boiling, Ti loss by diffusion, and Ti-in-excess due to rapid growth rate, suggest that careful attention must be paid to the petrographic textures and trace element compositions of quartz, when reconstructing the fluid evolution of such systems. This provides further important implications regarding the stability of the geochemical signatures in quartz along the lifespan and deformation history of porphyry-epithermal system.

This study highlights the profound impact of out-of-equilibrium rapid quartz growth and fluid-assisted dynamic recrystallization on the geochemical signatures of quartz in porphyry-epithermal systems. The varying degrees of recrystallization observed in A-, B-, and E-type quartz veins underscore the importance of considering deformation history and fluid interactions when interpreting quartz geochemistry, particularly for Ti-in-quartz thermometry.

A-type veins, characterized by fluid-assisted dynamic recrystallization and grain boundary migration, demonstrate how intense deformation under high-temperature conditions alters both the microstructure and Ti distribution in quartz. This deformation can lead to discrepancies in Ti-in-quartz temperature estimates, resulting in underestimations of up to 100 °C. Similarly, B-type veins, formed under lower-temperature conditions and exhibiting rapid quartz precipitation, show Ti excess, which further complicates temperature interpretation, leading to overestimations of up to 300 °C. These findings give emphasis the importance of understanding how fluid-assisted recrystallization processes influence the incorporation and redistribution of Ti within quartz and how they can significantly affect the reliability of geochemical thermometers. Conversely, E-type veins, which formed under brittle conditions at lower temperatures, show no such discrepancies, providing a clearer, more accurate reflection of the fluid inclusion temperatures. This comparison emphasizes the critical role that recrystallization and fluid-assisted processes play in altering the Ti contents of quartz, thus affecting temperature estimates derived from Ti-in-quartz thermometry.

A deeper understanding of the role of recrystallization in quartz, especially in relation to its geochemical signatures, could prove crucial for targeting areas of high-temperature fluid flow and potential mineralization. The related textures and geochemical changes can provide valuable clues regarding the distribution of mineralization, as fluids are often associated with metal-rich mineral deposits in porphyry-epithermal systems. Moreover, understanding the influence of fluid-rich conditions on quartz recrystallization can enhance exploration by identifying favorable sites for mineralization. Regions that show evidence of fluid infiltration and grain boundary migration may host concentrated mineralization in response to the physical and chemical changes induced by these fluids. Overall, the study highlights the need for careful petrographic analysis and CL imaging to discern the
deformation and recrystallization history of quartz veins in porphyry-
epithermal systems. Only through a comprehensive understanding of
these processes can we accurately interpret the geochemical signatures
in quartz, ensuring more reliable temperature estimates for fluid flow
and mineralization events. This research brings valuable insights into
the complexities of fluid-driven processes in ore-forming systems, which
will be critical for advancing exploration strategies and improving the
accuracy of geochemical thermometers in such settings. These insights
can be applied to more effectively map out prospective areas, refine
exploration models and emphasize all the processes that must be
considered to avoid errors in interpretation.

CRediT authorship contribution statement

**Baptiste Abiven:** Writing – original draft, Investigation. **Alexandre Tarantola:** Writing – review & editing, Supervision, Project administration, Conceptualization. **Antonin Richard:** Writing – review & editing, Supervision, Project administration, Funding acquisition, Conceptualization. **Manuel Keith:** Writing – review & editing. **Vasilios Melfos:** Writing – review & editing. **Panagiotis Voudouris:** Writing – review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.

Acknowledgements

We would like to acknowledge Chantal Peiffert for her assistance
during the LA-ICP-MS measurements and Alexandre Flammang for the
preparation of thin and thick sections. The ERASMUS+ ARTEMIS (Ac-
tion for Research and Teaching Mineral exploration Inclusive School)
project number KA220-HED-B1B19447, supported field trip to Northern
Greece and part of the analytical work. This work was supported by the
French National Research Agency through the national program
"Investissements d'avenir" with the reference ANR-10-LABX-
21-RESSOURCES21.

**Appendix A. Supplementary data**

Supplementary data to this article can be found online at https://doi.
org/10.1016/j.lithos.2025.108134.

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