Journal of Iberian Geology

The granite-hosted Variscan gold deposit from Santo António in the Iberian Massif (Penedono, NW Portugal): constraints from mineral chemistry, fluid inclusions, sulfur and noble gases isotopes --Manuscript Draft--

Manuscript Number: JIBG-D-18-00058R1 Full Title: The granite-hosted Variscan gold deposit from Santo António in the Iberian Massif (Penedono, NW Portugal): constraints from mineral chemistry, fluid inclusions, sulfur and noble gases isotopes Article Type: Research Paper

Funding Information: Fundação para a Ciência e a Tecnologia Prof. Antonio Moura (UID/GEO/04035/2013) Fundação para a Ciência e a Tecnologia Prof. Ana Neiva (PTDC/GEO-GEO/2446/2012) Prof. Antonio Moura Prof. Manuel Francisco Pereira

Abstract: A B S T R A C T The study area is located in the Central Iberian Zone, a major tectonic unit of the Iberian Massif (Variscan belt). In this region the basement is composed of Cambrian- Ordovician sedimentary and minor volcanic rocks that underwent deformation and metamorphism during the Carboniferous. These metamorphic rocks host ca. 331 to 308 Ma granitic plutons emplaced during the D2 extensional and D3-D4 contractional deformation phases. The gold-bearing quartz veins from the Santo António mine (Penedono region) occur in granite formed at 310.1 1.1 Ma and post-dated the peak of metamorphism. Gold-silver alloy is included in quartz, but mainly occurs in spaces between grains or micro-fractures within arsenopyrite of all three generations and less in pyrite. Late sulphides and sulphosalts were deposited along fractures mainly in arsenopyrite, and locally surrounding the gold-silver alloy grains. Ferberite, scheelite and stolzite replace arsenopyrite. The abundant aqueous carbonic fluids and the occurrence of a low-salinity fluid and their minimum possible entrapment temperature of 360-380ºC suggest that this gold-forming event began during the waning stages of the Variscan orogeny. The mean 34S values of arsenopyrite and pyrite are -4.7 ‰ and -3.8 ‰, respectively. He-Ar-Ne isotopic data suggest a crustal origin. The ascent of the granite magma has provided the heat for remobilization of gold, other metals and metalloids from the metamorphic rocks. This gold-arsenopyrite deposit has thus similar characteristics as other selected gold-arsenopyrite deposits from the Iberian Massif, but it contains tungstates. Corresponding Author: Antonio Moura, PhD Universidade do Porto Faculdade de Ciencias Porto, PORTUGAL Corresponding Author Secondary Information: Corresponding Author's Institution: Universidade do Porto Faculdade de Ciencias Corresponding Author's Secondary Institution: First Author: Ana Neiva First Author Secondary Information: Order of Authors: Ana Neiva Antonio Moura Carlos Leal Gomes Manuel Francisco Pereira Fernando Corfu

Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation Order of Authors Secondary Information: Author Comments: Good evening,

We sent the modified text plus figures and tables, according to the suggestions of the two reviewers.

A. Moura

Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation Manuscript Click here to access/download;Manuscript;TEXT- PENEDONO.docx Click here to view linked References

1 A.M.R. Neiva *a, A. Moura b, C.A. Leal Gomes c, M.F. Pereira d, F. Corfu e 1

2 2 3 4 3 The granite-hosted Variscan gold deposit from Santo António in the Iberian Massif (Penedono, NW 5 6 4 Portugal): constraints from mineral chemistry, fluid inclusions, sulfur and noble gases isotopes 7 8 5 9 10 6 a Geobiotec, Departamento de Geociências, Universidade de Aveiro, 3810-193 Aveiro, Portugal; Departamento 11 12 7 de Ciências da Terra, Universidade de Coimbra, 3030-780 Coimbra, Portugal 13 14 8 b Instituto de Ciências da Terra (ICT), Departamento de Geociências, Ambiente e Ordenamento do Território, 15 16 9 Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 687, 4099-007 Porto, Portugal 17 18 10 c Departamento de Ciências da Terra, Universidade do Minho, Gualtar, 4710-057 Braga, Portugal 19 20 11 d Instituto de Ciências da Terra (ICT), Departamento de Geociências, ECT, Universidade de Évora, 7000-671 21 22 12 Évora, Portugal 23 24 13 e Department of Geosciences, University of Oslo, PB1047 Blindern, N-0316 Oslo, Norway 25 26 14 27 28 15 * Corresponding author: Antonio Moura E-mail address: [email protected] 29 30 16 31 32 17 ORCID numbers: Ana Neiva- 0000-0001-7808-9461; António Moura- 0000-0002-2906-3078; Carlos Leal 33 34 18 Gomes- 0000-0001-6854-5398; Manuel Francisco-0000-0001-9032-2318; Fernando Corfu-0000 0002 9370 35 36 19 4239 37 38 20 39 40 21 41 42 22 Acknowledgments 43 44 23 This research was financially supported by Fundação para a Ciência e Tecnologia through the projects 45 46 24 GOLD-Granites, Orogenesis, Long-term strain/stress and Deposition of ore metals – PTDC/GEO- 47 48 25 GEO/2446/2012: COMPETE: FCOMP-01-0124-FEDER-029192 and UID/GEO/04035/2013. Thanks are due to 49 50 26 Colt Resources for having allowed sampling in the Santo António gold mine and Dr. Pedro Keil for having 51 52 27 helped in this field work, Profs. Martim Chichorro, José Brandão Silva and Rubén Díez-Fernández for 53 54 28 constructive discussions in the field, Dr. J.M. Farinha Ramos for helpful information, Prof. R. Machado Leite for 55 56 29 the use of electron microprobe at LNEG, Eng. Fernanda Guimarães for having helped to obtain analyses with 57 58 30 this equipment, Dr. Manuel Moreira for the He-Ne-Ar isotopic data, Prof. R.A. Creaser for the Re content of 59 60

61 62 1 63 64 65 31 pyrite and Dr. Armanda Dória for having helped with the Raman analysis. Thanks are also due to the editor and 1 2 32 reviewers for their comments to help improve this manuscript. 3 4 33 5 6 34 A B S T R A C T 7 8 35 The study area is located in the Central Iberian Zone, a major tectonic unit of the Iberian Massif (Variscan belt). 9 10 36 In this region the basement is composed of Cambrian-Ordovician sedimentary and minor volcanic rocks that 11 12 37 underwent deformation and metamorphism during the Carboniferous. These metamorphic rocks host ca. 331 to 13 14 38 308 Ma granitic plutons emplaced during the D2 extensional and D3-D4 contractional deformation phases. The 15 16 39 gold-bearing quartz veins from the Santo António mine (Penedono region) occur in granite formed at 310.1 1.1 17 18 40 Ma and post-dated the peak of metamorphism. Gold-silver alloy is included in quartz, but mainly occurs in 19 20 41 spaces between grains or micro-fractures within arsenopyrite of all three generations and less in pyrite. Late 21 22 42 sulphides and sulphosalts were deposited along fractures mainly in arsenopyrite, and locally surrounding the 23 24 43 gold-silver alloy grains. Ferberite, scheelite and stolzite replace arsenopyrite. The abundant aqueous carbonic 25 26 44 fluids and the occurrence of a low-salinity fluid and their minimum possible entrapment temperature of 360- 27 28 45 380ºC suggest that this gold-forming event began during the waning stages of the Variscan orogeny. The mean 29 30 46 34S values of arsenopyrite and pyrite are -4.7 ‰ and -3.8 ‰, respectively. He-Ar-Ne isotopic data suggest a 31 32 47 crustal origin. The ascent of the granite magma has provided the heat for remobilization of gold, other metals 33 34 48 and metalloids from the metamorphic rocks. This gold-arsenopyrite deposit has thus similar characteristics as 35 36 49 other selected gold-arsenopyrite deposits from the Iberian Massif, but it contains tungstates. 37 38 50 39 40 Keywords: Gold, Mineralogy, Geochemistry, Fluid inclusions, S, He, Ar, Ne isotopes, Variscan orogen 41 51 42 43 52 44 45 53 1. Introduction 46 47 54 Gold-only hydrothermal deposits include orogenic gold, intrusion-related gold systems (which may include 48 49 55 veins, stockworks, skarns, disseminations, epithermal and replacement types) and Carlin-type gold deposits. In 50 51 56 gold-only hydrothermal deposits, gold is very effectively fractionated from other metals (e.g. Garofalo and 52 53 57 Ridley 2014). Orogenic gold deposits are shear-hosted deposits developed along strike-slip fault systems linked 54 55 58 to late-stage orogenic events (e.g. Groves et al. 2000). Intrusion related gold deposits are developed in 56 57 59 magmatic-hydrothermal environments (e.g. Langard and Baker, 2001). Variscan gold deposits occur in western- 58 59 60 central Europe, e.g. in the Iberian Massif (e.g. Cotelo Neiva and Neiva 1990; Neiva 1994; Vallance et al. 2003; 60 61 62 2 63 64 65 61 Couto et al. 2007; Neiva et al. 2008; Gómez-Fernández et al. 2012; D’Angelico et al. 2016; Fuertes-Fuente et al. 1 2 62 2016), Massif Central and Bohemian Massif (Martínez Catalán et al., 1997; Goldfarb et al. 2001). The fluid 3 4 63 origin of gold deposits has been debated for a long time (e.g. Burrows and Spooner 1989; Lang and Baker 2001); 5 6 64 Pitcairn et al. 2006; Lawrence et al. 2013a, b; Rauchenstein-Martinak et al. 2014; Goldfarb and Groves 2015). 7 8 65 Some of the postulated mechanisms involve both magmatic and metamorphic, gold-bearing hydrothermal fluids, 9 10 66 but others are associated with regional metamorphic fluids, indicating that gold deposits can form from a variety 11 12 67 of fluid and metal sources (Lawrence et al. 2013b). Efforts have been directed at understanding the fluid origin 13 14 68 of gold deposits particularly from the standpoint of isotopic information including He-Ar isotopic data of fluid 15 16 69 inclusions in pyrite (e.g. Kim et al. 2012) and 34S of sulphides (e.g. Liu et al. 2016). 17 18 70 The Penedono area, northern Portugal, is located in the Central Iberian Zone (Iberian Massif; Fig. 1A,B) 19 20 71 where Carboniferous granitic plutons (ca. 330-307 Ma; Dias et al. 1998; Valle Aguado et al. 2005; Díez- 21 22 72 Fernandez and Pereira 2016, 2017; López Moro et al. 2017; Pereira et al. 2018) are hosted by Cambrian- 23 24 73 Ordovician metamorphic rocks. The tectonic evolution of this zone began in the Early Carboniferous (ca. 360- 25 26 74 340 Ma; Dallmeyer et al. 1997) with the thrusting of allochthonous units over the Iberian parautochthon and 27 28 75 autochthon (Martínez Catalán et al. 2009; Díez Fernández et al. 2013; Díez Fernández and Arenas 2015). The 29

30 76 nappe emplacement produced fold-and-thrust shortening in the Central Iberian Zone (D1). This crustal 31 32 77 thickening (D1 contractional deformation), considered responsible for creating a thermally and gravitationally 33 34 78 imbalanced crust (Escuder Viruete et al. 1994; Martinez Catalán et al. 2014; Alcock et al. 2015), was followed 35 36 79 by D2 extension with the development of D2 extensional shear zones (Diez Balda et al. 1995) and extensive high- 37 38 80 temperature and low-pressure metamorphism reaching anatexis (Escuder Viruete et al. 1998; Díez-Fernández 39 40 81 and Pereira 2016). In the Penedono area, the Pinhel shear zone, with maximum tectonomagmatic activity at ca. 41 42 82 321-317 Ma, represents a shallow-dipping D2 shear zone formed during the extensional collapse (Díez 43 44 83 Fernández and Pereira 2016). Later, the Central Iberian Zone experienced several pulses of subhorizontal 45 46 84 shortening with the development of upright folds and strike-slip shearing as identified by the superimposition of 47 48 85 D3, D4 and D5 structures (Díez-Fernández and Pereira 2016, 2017). 49 50 In the Penedono mining camp the deformed granite of the Tabuaço Massif hosts several gold-bearing quartz 51 86 52 53 87 veins formed during the D3 contractional event (Sousa and Ramos 1991). Some of these gold veins were already 54 55 88 exploited by the Romans and also between 1939 and 1957, producing a total of 100,816 t of ore with an average 56 57 89 grade of about 7.0 g/t Au. Remaining reserves are estimated at about 1200,000 tons (t) with an average grade of 58 59 90 about 11.5 g/t Au. There are about 105,000 t of ore with about 3.8 g/t Au in the waste dump from past mining 60 61 62 3 63 64 65 91 (Cathelineau et al. 1993). The Santo António project has an Experimental Mining License and prospecting tests 1 2 92 have been undertaken to evaluate the possibility of reopening the mine. Only few papers have been published 3 4 93 about the gold mineralization of the Penedono mining camp. Geology, mineralogy, paragenetic sequence and a 5 6 94 few chemical analyses of some sulphides, gold and electrum of different gold-bearing quartz veins from the 7 8 95 Penedono area are given by Sousa and Ramos (1991). However, different compositions of arsenopyrite and also 9 10 96 the minerals gustavite, cannizarite and rooseveltite were not considered. A comparison of the paragenetic 11 12 97 sequence of some gold-bearing quartz veins from the Penedono area is presented by Leal Gomes (2000 a). A 13 14 98 paragenetic sequence and a detailed study of gold-silver alloy grains from gold-bearing quartz veins of Santo 15 16 99 António and the relationship to late Variscan deformation effects are given by Leal Gomes (2000 b). But he does 17 18 100 not include ferberite, gustavite, cannizarite, covellite, rooseveltite and scorodite. Gold grains from several 19 20 101 Penedono prospects and evidence of mineralization episodes are described by Leal Gomes and Castelo Branco 21 22 102 (2003). Fluid inclusion studies of gold quartz veins from the Penedono area were published by Boiron et al. 23 24 103 (1996), Nogueira and Noronha (1993) and Noronha et al. (2000). 25 26 104 This paper presents a review of the geology of the Penedono mining camp, with the main focus on 27 28 105 paragenetic sequence, chemical compositions of minerals, fluid inclusions studies, S isotopic data of sulphides 29 30 106 and He, Ne and Ar isotopic data of fluids from pyrite of Santo António gold-bearing quartz veins to identify the 31 32 107 fluid origin of this gold deposit and to discuss the origin. It also reports a new U-Pb age for the granite hosting 33 34 108 the deposit. It is a contribution to understand a gold hydrothermal deposit hosted by a S-type granite deformed 35 36 109 by Variscan strike-slip systems. 37 38 110 39 40 111 2. Geology 41 42 112 In this section we present a summary of the geological setting of the study area of Penedono located in the 43 44 113 Central Iberian Zone and, in particular, of the Santo Antonio shear zone-related gold mineralization developed in 45 46 114 granite (Tabuaço Massif). 47 48 115 2.1. Geology of the Penedono area 49 50 116 In the study area, the metasedimentary rocks that host the Variscan granitic rocks (Tabuaço and Penedono- 51 52 117 Mêda-Escalhão massifs; Figs. 1C and 2) include Cambrian greywackes, siltstones, pelites and limestones (Douro 53 54 118 Group) unconformably overlain by Ordovician felsic volcaniclastic rocks (São Gabriel Formation), which are 55 56 119 overlain by Ordovician sandstones, siltstones and mudstones (Armorican Quartzite Formation) (Regêncio 57 58 Macedo 1988; Sousa and Sequeira 1989; Silva and Ribeiro 1991, 1994; Oliveira 1992; Ferreira and Sousa 1994). 59 120 60 61 62 4 63 64 65 121 These Cambrian-Ordovician rocks were transformed into slate, quartzite, phyllite, schist, gneiss and migmatite 1 2 122 as a result of variable metamorphic conditions attained during Variscan deformation. 3 4 123 Traditionally, the structure of the Penedono area has been described as the result of two main stages of 5 6 124 contractional deformation D1 and D3 without recognizing the existence of extensional structures and 7 8 125 metamorphism associated with a second deformation stage (D2). Recently, D2 structures related to a kilometer- 9 10 126 scale extensional shear zone were recognized in the host rocks surrounding the Penedono-Mêda-Escalhão massif 11 12 127 and further south (e.g. Pinhel shear zone; Díez-Fernández and Pereira 2016) (Fig. 2). The metamorphic 13 14 128 conditions related to the development of this shallow-dipping D2 shear zone reached partial melting and anatexis 15 16 129 (D2 granites). In the higher-grade metamorphic assemblages S2 is defined by the growth of sillimanite (fibrolite) 17 18 130 and andalusite, garnet and cordierite porphyroblasts and produced an intense overprinting of D1 structures (Díez- 19 20 131 Fernández and Pereira 2016). The D2 extensional Pinhel shear zone was folded during D3 contraction, and then 21 22 132 deformed by D3, D4 and D5 strike-slip shear zones under lower grade metamorphic conditions (Huebra, Lamego- 23 24 133 Malpica, Juzbado-Penalva do Castelo and Porto-Tomar shear zones; Díez-Fernández and Pereira 2016; 2017) 25 26 134 (Fig. 1B). 27 28 135 Accordingly, the Variscan intrusions can be classified in three age groups, including strongly and variably 29 30 136 deformed granitic rocks: syn-D2 (ca. 331-321 Ma), late D2-early D3 (ca. 319-315 Ma) and syn-D3 (ca. 311-310 31 32 137 Ma) (Fig. 1D; Díez Fernández and Pereira 2016; Pereira et al. 2018). The Penedono-Mêda-Escalhão and 33

34 138 Tabuaço massifs intruded the D2 extensional Pinhel shear zone (Figs. 1C and 2). Both plutons were deformed 35

36 139 later by the D3 strike-slip motions along the curved N130-140ºE to N80-90ºE trending Huebra shear zone (Fig. 37

38 140 1B). This D3 shear zone was displaced along the N70-80ºE trending D4 Juzbado-Penalva do Castelo shear zone 39 40 141 (Fig. 1B). 41 42 142 The Tabuaço Massif is located at the eastern end of the of the N130-140ºE trending D3 Malpica-Lamego 43 44 143 shear zone (Llana-Fúnez and Marcos 2001). Mapping suggests that the shear zone merges with the Huebra shear 45 46 144 zone (Fig. 1B) and both run parallel to the axial planes of major D3 folds. The D3 contractional deformation is 47 48 145 responsible for the foliation (S3) seen in N130-140ºE trending sinistral strike-slip shear zones aligned with the 49 50 146 strike of the Tabuaço massif. These D3 strike-slip shear zones control the opening of N50E trending dilatational 51 52 147 surfaces that host mineralized quartz veins. The D4 Juzbado-Penalva do Castelo shear zone drags D3 folds and 53 54 148 continues into the N130-140ºE trending Douro-Beira and Tamames shear zones (Díez-Fernández and Pereira 55 56 149 2016; 2017). Subsidiary shear zones of this D4 strike-slip shear zone reworked the preexisting N50E trending 57 58 mineralized quartz veins (Fig. 2). 59 150 60 61 62 5 63 64 65 151 The Penedono-Mêda-Escalhão massif (Fig. 2) shows a dominant subvertical magmatic fabric parallel to S3 1 2 152 and rarely shows a penetrative foliation except for its northern contact locally deformed by the Huebra shear 3 4 153 zone. This massif cuts S2 and occupies the core of a macro-D3 antiform and so can be considered a late-D2 to 5 6 154 early-D3 intrusion (ca. 319-318 Ma; Díez-Fernández and Pereira 2016; Pereira et al. 2018). 7 8 155 The Penedono mining camp includes several gold prospects, distributed in a 12 km-long and 4 km-wide 9 10 156 N100-110ºE-trending elongated band within the Tabuaço and Penedono-Mêda-Escalhão granitic massifs (Fig. 11 12 157 2). Important geological features of the camp include: gold-bearing quartz veins hosted by two-mica granites 13 14 158 locally hydrothermally altered in the vicinity of vein contacts; vein emplacement controlled by the motion along 15 16 159 strike-slip shear zones; in gold bearing mineral assemblages, quartz and arsenopyrite are generally the dominant 17 18 160 modal constituents; in peripheral gold-bearing quartz vein walls of 1m thickness disseminated arsenopyrite and 19 20 161 pyrite may also carry gold-silver alloy.. 21 22 162 23 24 163 2.2. Geology and gold setting at the Santo António mine 25 26 164 In the Santo António mine, a system of nearly vertical N40-80ºE to N10ºE trending quartz veins with less 27 28 165 than 3 m width (13 of which have been mined out) intruded a foliated coarse-grained, locally porphyritic, 29 30 166 muscovite>biotite granite belonging to the Tabuaço Massif (Fig. 2). Representative gold grades, obtained from 31 32 167 analysis of channel samples traversing these veins and related cataclastic gauge structures, as well as some 33 34 168 telescoped infillings and hydrothermally altered wallrocks, are located in Fig. 3 and represent the main sector of 35 36 169 ancient underground mine works in the Santo António mining camp. The observed results suggest an absence of 37 38 170 correlation between the total width of each vein and its gold content and also between the quartz proportion in 39 40 171 the veins and adjacent breccia gauges and gold grades. On the contrary there seems to be a more definitive 41 42 172 relationship between sulphides presence and gold. 43 44 173 One of the most complex inner vein structures, from a paragenetic and polyphasic deformation point of view, 45 46 174 outcrops at the Quarry sector (Fig. 3). It includes most of the major stages of sulphide and gold deposition and 47 48 175 thus reflects the progressive and interrelated evolution of deformation and mineralization (Fig. 4). 49 50 176 The inner structural characteristics of the veins may be synthesized by a massive milky quartz that is sheared 51 52 177 and recrystallized, and usually does not contain sulphides or gold, but may contain tourmaline. This 53 54 178 quartz±tourmaline assemblage is the main constituent of barren veins. In general, gold-bearing veins show a 55 56 57 179 similar type of quartz  tourmaline assemblage, forming a barren core surrounded, by vein walls containing 58 59 180 sulphides and gold, where arsenopyrite dominates. The arsenopyrite nucleation may eventually propagate into 60 61 62 6 63 64 65 181 winding fractures affecting inner sub-granulated quartz and corrosion and miarolitic cavities related to 1 2 182 hydrothermal alteration or multipulse dilation and deposition in tension voids. Recrystallization and annealed- 3 4 183 recovered arsenopyrite correspond to an event that is accompanied by the first expression of free gold (Au-Ag1). 5 6 184 Barren veins and gold-bearing veins occur in the same series. 7 8 185 From a broader point of view, shearing reflects a ductile to ductile-brittle behavior and is responsible for a set 9 10 186 of fractures that follow the model of Gamond and Giraud (1982). The deduced local deformation and 11 12 187 mineralization is polyphasic. As was observed by Leal Gomes and Gaspar (1992) and Leal Gomes (1994, 1997), 13 14 188 a coherent model consisting of three main stages of deformation (Sd1, Sd2 and Sd3) and gold mineralization (Au1, 15 16 189 Au2 and Au3) accommodated the successive reactivations of the sinistral strike-slip shearing motion following 17 18 190 the original opening of earlier tension gashes and formation of major fractures (Figs. 3 and 4). During the more 19 20 191 brittle deformation conditions (Sd2-Sd3) cataclastic zones with brecciation or the acquisition of crack-seal 21 22 192 layered textures were produced in the primary quartz gauges. 23 24 193 The last episodes of brittle deformation (Sd3) caused reactivation of earlier veins and mineral assemblages 25 26 194 and multistage late Pb-Bi-Ag mineralizations, expressed in the crystallization of sulphides, sulphosalts and 27 28 195 tellurides, some of which are located in minor transtensive openings (Fig. 4). It also led to remobilization of gold 29 30 196 and deposition of electrum, as gold diluted / depleted particles, associated with galena or with 31 32 197 chlorite±carbonates±fluorite, also recognized in other gold mining sites of NW Portugal (Leal Gomes and 33 34 198 Gaspar, 1992). 35 36 199 37 38 200 3. Analytical methods 39 40 201 Our studies include U-Pb monazite and zircon geochronology to obtain the age of the granite from Santo 41 42 202 António, and transmitted and reflected light microscopy, electron microprobe analyses, fluid inclusions, 43 44 203 microthermometry and Raman spectroscopy, 34S data of arsenopyrite and pyrite and isotopic He-Ne-Ar data to 45 46 204 characterize the composition of fluids from pyrite of gold-bearing quartz veins. 47 48 205 Monazite and zircon grains for U-Pb dating were separated, using a Frantz magnetic separator and heavy 49 50 liquids. Afterwards they were handpicked under a binocular microscope and abraded (Davis et al. 1982; Krogh 51 206 52 53 207 1982). Uranium and lead isotopic data were measured on a Finnigan MAT 262 multicollector mass spectrometer 54 55 208 at the Department of Geosciences, University of Oslo, Norway (Krogh 1973; Corfu 2004). Initial Pb was 56 57 209 corrected using Stacey and Kramers (1975) model compositions. The decay constants are from Jaffey et al. 58 59 210 (1971). The ISOPLOT 3 Microsoft Excel add-in (Ludwig 2003) was used for the calculation of the U-Pb age. 60 61 62 7 63 64 65 211 Channel samples from the Santo António ore deposit were prepared with aqua regia. Gold was determined by 1 2 212 induced coupled plasma emission mass spectrometry. The data source is from Rio Narcea Gold Minning 3 4 213 Company. 5 6 214 Attempts have been made to date the mineralization through isotopic pyrite analyses by Re-Os at the 7 8 215 Department of Earth and Atmospheric Sciences, University of Alberta (Canada), but as the rhenium content is 9 10 216 very low (coincident and below the detection limit of 0.03 ppb) it was not possible to date by this method. 11 12 217 The mineral compositions and backscattered images (BSE) were obtained in 55 polished sections using a 13 14 218 Hyperbole Jeol JXA-8500 electron microprobe at the National Laboratory of Energy and Geology, S. Mamede 15 16 219 de Infesta, Portugal. Sulphides, sulphosalts, gold-silver alloy, native bismuth and arsenates were analysed at an 17 18 220 accelaring voltage of 20 kV and a beam current of 20 nA, but tungstates at 15 kV and 10 nA. XPP corrections 19 20 221 were applied for sulphides, sulphosalts, gold, electrum, native bismuth, tungstates and arsenates. Standards used 21 22 222 include metallic Ni (Ni K), metallic Co (Co K); synthetic cuprite Cu2O (Cu K); metallic Ag (Ag L); 23

24 223 metallic Au (Au M); sphalerite (Zn K); pyrite (Fe K, S K); MnTiO3 (Mn K); CdS (Cd L); AsGa (As 25 26 224 L); galena (Pb M); Bi2Se3 (Bi M); Sb2S3 (Sb L); metallic pure Nb (Nb L); metallic pure Ta (Ta L); 27 28 scheelite (W L). 29 225 30 34 31 226 Sulphide grains for the isotope study were hand-picked under binocular microscope. The  S was 32 33 227 determined at Actlabs, Canada. Pure pyrite samples and arsenopyrite samples were combusted to SO2 gas under 34 -3 35 228 ~10 torr vacuum. The SO2 was inlet directly from the vacuum line to the ion source of a VG 602 Isotope Ratio 36 37 229 Mass Spectrometer (Ueda 1986). Quantitative combustion to SO2 was achieved by mixing 5 mg of sample with 38 39 230 100 mg of a V2O5 and SiO2 mixture (1:1). The reaction was carried out at 950º C for 7 minutes in quartz glass 40 41 231 reaction tube. Pure copper turnings were used as a catalyst to ensure conversion of SO3 to SO2. Internal 42

43 232 laboratory standards (SeaWaterBaSO4 and FisherBaSO4 were run at the beginning and end of each set of samples 44 45 233 (typically 25) and were used to normalize the data as well as correct for any instrument drift. All results are 46 47 234 reported in the permil notation relative to the international CDT standard. 48 49 235 Seven pyrite samples were crushed under vacuum for He-Ne-Ar elemental and isotopic compositions. The 50 51 236 gas was then purified using hot titanium (750º C) for 10 minutes. Noble gases were adsorbed on charcoal at ~10 52 53 237 k before being successively desorbed at 32 k, 75 k and 300 k for introduction in the mass spectrometer (Noblesse 54 55 238 © from Nu-instruments). Isotopes 4He and 40Ar were collected on a Faraday cup and measured on a voltmeter 56 57 239 using a resistance of 1011 ohms. The other isotopes (3He, 20Ne, 21Ne, 22Ne, 36Ar, 38Ar) were measured using 3 58 59 240 electron multipliers equipped in a pulse counting mode (the noblesse having 3 electron multipliers in order to 60 61 62 8 63 64 65 241 perform multi-collection). Air standards were analyzed routinely in order to determine the sensitivity and the 1 2 242 mass discrimination of the instrument. Blanks were measured before each sample but were negligible compared 3 4 243 to the relatively high noble gas abundances of the samples. The results presented are the concentrations 5 3 6 244 expressed in ccSTP/g (cm of gas at standard T and P). The isotopic ratios are corrected for blank and mass 7 8 245 discrimination. The data were obtained in the Institut de Physique du Globe de Paris by the Equipe Geochimie & 9 10 246 Cosmochimie. 11 12 247 Petrography, microthermometry and Raman analyses of fluid inclusions have been carried out at DGAOT 13 14 248 laboratories (Science Faculty, Porto University), in doubly-polished wafers of about 150-200 μm thickness. 15 16 249 Microthermometric characterization of the fluids was performed using a Chaixmeca heating-freezing stage (Poty 17 18 250 et al. 1976) for cooling experiments, and a Linkam THMSG 600 stage (Shepherd 1981) for the heating 19 20 251 experiments. Calibration was carried out with natural and synthetic fluid inclusion standards at T≤0ºC and with 21 22 252 melting-point standards at T>25ºC. The accuracy was 0.1°C during cryometric measurements and 1°C during 23 24 253 heating. Volumetric proportions between volatile and aqueous phases were estimated optically at room 25

26 254 temperature by reference to Roedder (1984) and Shepherd et al. (1985) charts. Molar fractions of CO2, CH4 and 27

28 255 N2 were determined by Raman microspectroscopy analyses in selected individual inclusions using a Labram 29 30 256 Dilor-Jobin Yvon Spectrometer attached to an Olympus microscope. The excitation source was a He–Ne laser 31 32 257 with 632.8 nm wavelength operated at 20 mW. Measurement of the N2 signal from the air was done immediately 33 34 258 after each fluid inclusion analysis. The quantification of the different gas species in the inclusions was obtained 35 36 259 using a computer program that follows routine procedures described by Prieto et al. (2012). Salinity (expressed 37 38 260 as equivalent wt% of NaCl) of the aqueous inclusions was calculated from microthermometric data using the 39 40 261 revised equation of Bodnar (1993). Bulk compositions of both types of fluids were calculated using Bakker 41 42 262 (2003) codes. Isochores for the aqueous carbonic fluids were calculated using Bakker (2003) software based on 43 44 263 Bakker (1999) and Bowers and Helgeson (1983) equations of state. The isochors for the H2O-NaCl inclusions 45 46 264 were calculated from the equation of state of Knight and Bodnar (1989). 47 48

49 265 50 51 266 4. Paragenetic sequence of Santo António gold quartz veins 52 53 267 The paragenetic sequence (Table 1) was determined with microscopic mineralogy and electron microprobe 54 55 268 analyses by us (Tables 2 and 3; Appendices A and B) in combination with earlier publications (Sousa and 56 57 269 Ramos, 1991; Leal Gomes and Castelo Branco 2003) and two unpublished reports (Cathelineau et al. 1993; Leal 58 59 270 Gomes 2000b). Three main stages (1, 2 and 3) of ore deposition and a late hydrothermal remobilization stage are 60 61 62 9 63 64 65 271 distinguished (Table 1). Chemical analyses of sulphides, sulphosalts and native bismuth from Santo António 1 2 272 gold-bearing quartz veins are given in Table 2. Those of gold-silver alloy are presented in Table 3. Chemical 3 4 273 analyses of tungstate minerals and arsenates are given in Appendix A, B, respectively. The gold-silver alloy 5 6 274 grains range from < 10 m to 30 x 20 m and rarely are > 100 m. 7 8 275 4.1. Stage 1 9 10 276 Schorl is rare, subhedral, brown in colour and intergrown with muscovite. The muscovite is frequent, fine- 11 12 277 grained, subhedral and radial and has rare monazite inclusions. Quartz (Qz1) dominates, is anhedral, dark grey 13 14 278 with undulatory extinction and deformation bands. Pyrrhotite (Fe0.90S1.01) is monocline, rare, euhedral, but 15 16 279 mainly anhedral. Arsenopyrite (Apy1) (Fig. 5a) is As-rich and S-deficient (Fig. 6a, b) frequent, euhedral, 17 18 280 subhedral and fractured. It has monazite and pyrrhotite inclusions. Pyrite (Py1) (Fig. 6a, c) is rare, anhedral and 19 20 281 has pyrrhotite inclusions. Anhedral gold-silver alloy (Au-Ag1) grains occur associated with micro-fractures and 21 22 282 between grains of arsenopyrite (Apy1) (Fig. 5a). Rare ferberite is anhedral, occurs as inclusions in quartz (Qz1) 23 24 283 and partially replaces arsenopyrite (Apy1) and quartz (Qz1) (Fig. 5b). It contains 8.4 mol.% MnO4 (Appendix 25 26 284 A). 27 28 285 29 30 286 4.2. Stage 2 31 32 287 Quartz (Qz2) is grey, clearer than quartz (Qz1), microgranular and rarely deformed. It contains rare 33 34 288 inclusions of monazite. It penetrates along micro-fractures of quartz (Qz1) and surrounds stage 1 sulphides. 35 36 289 Arsenopyrite (Apy2) is As-deficient and S-rich, abundant, anhedral, surrounds ferberite and is fractured. Pyrite 37 38 290 (Py2) is frequent and anhedral. Gold-silver alloy (Au-Ag2) grains are anhedral and occur filling micro-fractures 39 40 291 and in spaces between grains of arsenopyrite (Apy2) (Fig. 5c), but are rarely zoned and included in quartz (Qz2) 41 42 292 (Fig. 5d). Sphalerite is rare, anhedral and occurs filling micro-fractures of arsenopyrite (Apy2) and contains up to 43 44 293 2.59 wt.% Fe. Rare chalcopyrite is anhedral and partially surrounds pyrite (Py2) and sphalerite. Native bismuth 45 46 294 contains up to 0.36 wt.% Fe, is rare, anhedral, associated with micro-fractures in arsenopyrite, partially 47 48 295 surrounds gold-silver alloy (Au-Ag2) and occurs included in quartz (Qz2) (Fig. 5d). Galenobismutite 49 50 (Pb Bi S ) is anhedral, rare and occurs associated with micro-fractures of arsenopyrite, where is partially 51 296 1.09 1.95 4 52 53 297 surrounded by quartz (Qz2) (Fig. 5e). Bismuthinite (Bi1.94S3) is rare, anhedral, partially penetrated and 54 55 298 surrounded gold-silver alloy (Au-Ag2) grains, some associated with micro-fractures and filling spaces between 56 57 299 arsenopyrite grains and others included in quartz (Qz2) (Figs. 5c, d) but of similar composition. It has native 58 59 300 bismuth inclusions (Fig. 5d). Galena is anhedral, not frequent, has inclusions of quartz (Qz2), native bismuth 60 61 62 10 63 64 65 301 (Fig. 5f) and bismuthinite. It occurs included in arsenopyrite (Apy2) and associated with micro-fractures of 1 2 302 arsenopyrite (Apy2). Gustavite (Ag0.95Pb1.21Bi2.97S6) and cannizzarite (Pb7.93Bi10.10S23) are anhedral, very rare and 3 4 303 occur filling spaces between arsenopyrite (Apy2) grains (Figs. 5g, h). Gustavite also partially surrounds galena 5 6 304 (Gn) (Fig. 5i). 7 8 305 4.3. Stage 3 9 10 306 It has very clear light grey quartz (Qz3) which fills cavities. Arsenopyrite (Apy3) is frequent, anhedral and is 11 12 307 fractured. It is As-deficient and S-rich. Very rare crystals of arsenopyrite are zoned with a darker core of Apy2 13 14 308 and a lighter rim of Apy3, showing increase in Fe and S contents and a decrease in the As content from core to 15 16 309 rim (Table 2). An increase in the S content and a decrease in the As content of arsenopyrite is observed from the 17 18 310 stage 1 to the stage 2 and the stage 3 (Fig. 6b). Pyrite (Py3) is rare, anhedral and occurs as veinlets. Pyrite from 19 20 311 the three stages has a similar composition (Table 2, Fig. 6c), but a few compositions of the stage 1 have the 21 22 312 lowest S content and the highest Fe+Ni+Co content. Subhedral and anhedral gold-silver alloy (Au-Ag3) occurs 23 24 313 associated with micro-fractures and between grains of arsenopyrite (Apy3) (Fig. 5j) and rarely also fills micro- 25 26 314 fractures of pyrite (Py3). There is not a distinct chemical composition of gold-silver alloy from the three stages 27 28 315 (Fig. 7). Scheelite (Ca0.87W1.04O4) is very rare, anhedral and occurs included in quartz (Qz3). Chalcopyrite, 29 30 316 galena and marcasite (FeS2) are rare, anhedral and surround pyrite (Py3). No distinction was found in the 31 32 317 composition of galena (Fig. 6d). It contains up to 2.11 wt.% Ag (Table 2) and 5.46 wt.% Bi. The Ag is quite 33 34 318 insoluble in PbS if Sb or Bi are absent at significant temperatures (Amcoff 1976). This galena does not contain 35 36 319 Sb. The coupled substitution of Bi3++Ag+ for 2Pb2+ is suggested by Fig. 6d and is stable (Amcoff, 1976). 37 38 320 39 40 321 4.4. Late hydrothermal remobilization stage 41 42 322 The late hydrothermal remobilization stage consists mainly of clear quartz (Qz4) which resulted from 43 44 323 remobilization of previous quartz, gold-silver alloy (Au-Ag4) (Fig. 5l) with a composition similar to that of the 45 46 324 richest Au-Ag2 in Au (Fig. 7) and the occurrence of supergene covellite (Cu0.93S). Covellite is rare and partially 47 48 325 surrounds arsenopyrite (Apy3) and bismuthinite. All minerals are anhedral. 49 50 326 51 52 327 4.5. Weathering products 53 54 328 Stolzite (Pb1.00W1.00O4) is anhedral, replaces scheelite (Fig. 5k). Rooseveltite (Bi1.09As0.95O4) is anhedral, very 55 56 3+ 57 329 rare and partially surrounds arsenopyrite (Apy3), bismuthinite and covellite. Scorodite (Fe1.2As1.2O4.2H2O) is 58 59 60 61 62 11 63 64 65 330 subhedral, not frequent and occurs associated with micro-fractures of arsenopyrite (Apy2), gold-silver alloy (Au- 1 2 331 Ag4) (Fig. 5l) and bismuthinite. 3 4 332 5 6 333 5. Fluid inclusions 7 8 334 Studies of the types and petrography of fluid inclusions were carried out on wafers from representative 9 10 335 samples of three outcropping mineralized quartz veins and one vein underground at the former mine, all in the 11 12 336 Santo António mine. The succession of fluids and possible mineralization events has been studied by interpreting 13 14 337 the relationships between fluid inclusions and the different quartz types recognized during the petrographic 15 16 338 study. We have observed four types of quartz: the older (Q1) from the hypogene stage 1 is dark with very small 17 18 339 fluid inclusions and very often deformed and partly recrystallized. Quartz from the hypogene stages 2 and 3 (Q2 19 20 340 and Q3 respectively), are much more clear than Q1, practically undeformed and the fluid inclusions are much 21 22 341 bigger. The last type of quartz (Q4) from the late hydrothermal remobilization stage is undeformed, very clear, 23 24 342 practically without fluid inclusions and often in contact with the main sulphides (Fig. 8). The fluid inclusion 25 26 343 studies were performed in quartz Q2 and Q3 (Q2-3) without distinction because both quartz has identical 27 28 344 characteristics when observed on tick sections proper for the fluid inclusion study and also because both has the 29 30 345 same fluid inclusion assemblages. They focused on fluid inclusion assemblages composed of groups of 31 32 346 inclusions, isolated inclusions or inclusions in trails, all with identical characteristics concerning the vapor/liquid 33 34 347 ratio, composition, heating and freezing behavior. The lack of growth zones in the quartz precludes an 35 36 348 unambiguous classification as primary inclusions, but according to Roedder’s (1984) criteria those in 37 38 349 intracrystalline trails and at least some of the isolated inclusions should be pseudosecondary and primary, 39 40 350 respectively, coeval with quartz crystallization. 41 42 351 43 44 352 5.1. Fluid characterization 45 46 353 All the studied fluid inclusions are between 5 and 30 μm. We have estimated a density of around 1,500 fluid 47 48 3 354 inclusions bigger than 5 μm in 1mm of quartz Q2-3. From petrographic, microthermometric and Raman 49 50 355 characteristics different types of fluids (nomenclature according to Boiron et al., 1992) were recognized (Fig. 9): 51 52 356 (i) Lc-w type: aqueous carbonic fluids (H2O–CO2–CH4-N2–NaCl) triphasic in the range 10-25ºC. The volume 53 54 357 fraction of the aqueous phase (Flw) is in the range of 0.4-0.6. These are the most obvious fluids in all samples. 55 56 358 They could represent more than 50 % of the fluid inclusion population. (ii) Vc-w type: identical to Lc-w, but 57 58 with Th in vapor as the only difference (iii) Lw-c type: aqueous carbonic fluids (H O–CO –CH -N –NaCl) 59 359 tot 2 2 4 2 60 61 62 12 63 64 65 360 always biphasic at room temperature and with the Flw ranging between 0.6 and 0.7. This type of fluids is 1 2 361 scattered in the samples. (iv) Lw type: low salinity aqueous fluids (H2O–NaCl), with the Flw around 0.9. This 3 4 362 type of fluid can be observed in every sample although they represent probably less than 20 % of the fluid 5 6 363 inclusions. 7 8 364 Locally all types can be seen in trails traversing quartz (Q1), which attest a secondary origin in relation to this 9 10 365 quartz generation. The aqueous carbonic fluids were observed in clusters, occasionally isolated and in 11 12 366 intragranular trails only in quartz Q2 associated with sulphides and often placed less than 1 mm from these 13 14 367 phases. The Lw fluid type occurs mostly in trails but some are associated with clusters of the aqueous carbonic 15 16 368 Lw-c fluids. A summary of the microthermometric characteristics, micro-Raman data and bulk composition, for 17 18 369 selected fluid inclusions, is given in Table 4. 19 20 370 21 22 371 5.1.1. Microthermometry and Raman characteristics of the aqueous carbonic fluids 23 24 372 In the Lc-w fluids we could measure the melting temperature of the CO2-rich phase (TmCO2), the melting of 25 26 373 clathrates (TmCl), occasionally the temperature of ice melting (Tmice) and the temperature of gas homogenization 27 28 374 (ThCO2). In the Lw-c fluid inclusions, we could only measure TmCl and Tmice (Fig. 11). Many of the Lc-w and 29 30 375 Lw-c inclusions decrepitated, and some leaked, during the heating experiments, even at a temperature gradient as 31 32 376 low as 1ºC/min due to the high internal pressure. Rarely, we could measure temperatures of total 33

34 377 homogenization (Thtot), but often these temperatures could not be observed accurately due to the darkening of 35

36 378 the inclusion during heating. TmCO2 was registered between -57.4 and -59.2°C (average of -58.5ºC), the melting 37 38 379 temperature of clathrate was in the range 8.6-10.5ºC (average of 9.6ºC) and the homogenization temperature of 39 40 380 CO2 was observed in the range of 13.0 to 25.5°C (to the liquid, average of 20.1ºC) and 11.6 to 20.0°C (to the 41 42 381 vapour, average of 16.5ºC). Flc (liquid CO2/total CO2) near TmCO2 was around 0.50. Thtot in these Lc-w fluid 43 44 382 inclusions was between 350 and 386ºC (average of 372ºC) to the liquid phase. The temperature of melting 45 46 383 clathrates in the Lw-c fluids were between 8.2 and 11.2ºC (average of 9.5ºC), and the melting of the last ice 47 48 384 crystal was in the range -2.0º to -3.0ºC (average of -2.3ºC). Thtot in these Lw-c fluid inclusions ranges between 49 50 385 290º and 320°C (average of 303ºC) for the liquid phase. A representative set of these inclusions was selected for 51 52 386 Raman spectroscopy analyses. Carbon dioxide (CO2), methane (CH4) and nitrogen (N2) were the only gaseous 53 54 387 species found. The molar content of the gases is dominated by CO2 which ranged from 82.35 to 100%; CH4 55 56 388 ranged from 0 to 17.65 %; N2 was detected only in one third of the inclusion and the highest content was 0.90 %. 57 58 These fluids had the following bulk compositions (%): Lc-w: 74.8-82.9 mol% H O, 14.3-17.4 mol% CO , up to 59 389 2 2 60 61 62 13 63 64 65 + − 390 1 mol% CH4, up to 0.06 mol% N2, and 0.3-3.8 mol% Na and the same for Cl . The densities were between 0.52 1 −3 2 391 and 0.85 g cm . The Lw-c fluids had the following average composition: 92.2 mol% H2O, 4.9 mol% CO2, 0.5 3 + − 4 392 mol% CH4, no N2, and 1.2 mol% of both Na and Cl (Table 4). Figure 11 shows the CO2 and CH4 Raman main 5 6 393 peaks for a typical aqueous Lc-w fluid inclusion. 7 8 394 9 10 395 5.1.2. Microthermometry of the aqueous fluids 11 12 396 Ice melting temperatures (Tmice) of Lw fluid inclusions measured in quartz l are between -7.4 and -0.1°C 13 14 397 (average of -3.4°C) corresponding to salinities lower than or equal to 9.7 eq. wt.% NaCl (average of 3.6 eq. wt.% 15 16 398 NaCl). Lw inclusions displayed Thtot values in the interval 150-250°C (average of 195°C). The densities were 17 18 399 between 0.84 and 0.99 g cm−3. 19 20 400 21 22 401 6. Isotopic data 23 24 402 6.1. Sulfur, Helium, Neon and Argon isotopes 25 26 403 It was not possible to separate pyrite or arsenopyrite grains according with their stage in the ore deposition 27 28 404 because of the intricate nature of ore textures. The 34S values of pyrite and arsenopyrite of four gold quartz 29 30 405 veins are presented in Table 5 and Figure 12. They range between -4.0 and -3.7 ‰ for pyrite, with a mean value 31 32 406 of -3.8 ‰, and between -5.3 and -4.3 ‰ for arsenopyrite, with a mean value of -4.7 ‰. 33 34 407 Isotopic data of He, Ne and Ar from fluid inclusions in pyrite of the gold quartz veins are given in Table 6. 35 36 408 The concentrations of 4He range from 0.53x10-7 to 1.40x10-7 cm3 STP/g. Those of 22Ne are of (0.693-4.31) x10-11 37 38 409 cm3 STP/g and those of 36Ar are of (0.191-1.01)x10-9 cm3 STP/g. Noble gas ratios are R/Ra of 0.126-0.201 (for 39 40 410 He, where R = sample 3He/4He, Ra = air 3He/4He), 20Ne/22Ne of 9.80-9.87, 21Ne/22Ne of 0.0294-0.0302, 41 42 411 38Ar/36Ar of 0.1864-0.1884 and 40Ar/36Ar of 298.1-324.8. 43 44 412 45 46 413 6.2. U-Pb Geochronology of the Tabuaço Massif 47 48 414 The Tabuaço Massif hosting the Santo António deposit has now been dated for the first time. Monazite in the 49

50 207 235 51 415 granite sample yields a Pb/ U age of 310.1 1.1 Ma (Table 7, Fig. 13). Coexisting zircon is extremely rich in 52 53 416 U (1000-10000 ppm) and three analyses yield variously discordant data defining an upper intercept age of 306.3 54 55 417 ± 1.8 Ma, which is broadly consistent with the monazite age. 56 57 418 58 59 419 7. Discussion 60 61 62 14 63 64 65 420 7.1. Mineralogy 1 2 421 The mineral paragenesis for gold-bearing quartz veins from Santo António (Table 1) differs from that of 3 4 422 Sousa and Ramos (1991) and Leal Gomes (2000b), because it includes more minerals. 5 6 423 In the gold-bearing quartz veins from Santo António, arsenopyrite is the most abundant sulphide and the only 7 8 424 one that shows distinct compositions. There is a progressive increase in the S content and decrease in the As 9 10 425 content from the first generation (Apy1) to the second generation (Apy2) and third generation (Apy3) due to 11 12 426 later growths (Fig. 6b). A few crystals of arsenopyrite are zoned with a darker core of Apy2 and a lighter rim of 13 14 427 Apy3. Some authors (e.g. Morey et al. 2008; Cook et al. 2013) consider that the zoned crystals of arsenopyrite 15 16 428 have alteration rims. Fuertes-Fuente et al. (2016) accept that idea for some crystals, but also admit the growth of 17 18 429 a later arsenopyrite for other rims. The preserved zoned crystals suggest that there was no significant sulphide 19 20 430 recrystallization (Craig et al. 1993). 21 22 431 As Ni and Co are only up to 0.06 wt.% and Sb was not detected in arsenopyrite (Sundlab et al, 1984) from 23 24 432 gold-bearing quartz veins of Santo António, the arsenopyrite geothermometer of Kretschmar and Scott (1976) 25 26 433 and Sharp et al. (1985) can be applied. Temperatures are estimated for arsenopyrite in equilibrium with pyrite. 27 28 434 No arsenopyrite standard was used, and the AsGa standard used may have increased the As content of our data 29 30 435 as As is bonded differently than in arsenopyrite. Therefore, the mean and minimum values of at.% As of the 31 32 436 three generations of unzoned arsenopyrite and of a selected rare zoned crystal were used avoiding rare values 33 34 437 above 34.3 at.% As of the first generation of arsenopyrite as indicated by Kretschmar and Scott (1976). The 35 36 438 temperature of unzoned arsenopyrite decreases progressively from Apy1 (444-433ºC) to Apy2 (395-369ºC) and 37 38 439 Apy3 (364-300ºC). The zoned arsenopyrite presents a decrease in temperature from core (383-376ºC) to rim 39 40 440 (363-329ºC). The temperatures of core and rim are within the ranges of temperatures for Apy2 and Apy3, 41 42 441 respectively. The composition of arsenopyrite shows an increase in the S content and decrease in the As content 43 44 442 (Fig. 6b) as the temperature drops. 45 46 443 Experimental data suggest that galenobismutite has a lower stability limit between 390 and 375ºC (Chang 47 48 444 and Hoda 1977). Galenobismutite and bismuthinite from the gold-bearing quartz veins of Santo António belong 49 50 445 to the stage 2 (Table 1) and the estimated temperatures of 395-369ºC obtained from the Apy2 are in accordance 51 52 446 with the experimental temperatures for galenobismutite and bismuthinite. 53 54 447 In the gold-bearing quartz veins from Santo António, three generations of gold-silver alloy (Au-Ag) were 55 56 448 distinguished associated with micro-fractures and filling spaces between grains of Apy1, Apy2 and Apy3, 57 58 59 60 61 62 15 63 64 65 449 respectively (Table 1, Figs. 5a, c, j). Rare Au-Ag2, also occurs included in quartz Qz2 (Fig. 5d). In general, there 1 2 450 is no significant distinction in the composition of deposited gold-silver alloy of the three generations (Fig. 7). 3 4 451 5 6 452 7.2. Fluid inclusion studies 7 8 453 The densest aqueous carbonic fluids are H2O-CO2 low salinity dominant fluids with only up to 1 % mol CH4 9 10 454 and occasional traces of N2 (Table 4). Their relatively uniform Flw ratio suggests that the fluid was 11 12 455 homogeneous during the entrapment (Fig. 14). This happened at a minimum temperature around 360-380ºC and 13 14 456 a pressure ≥ 170 MPa (minimum PT values of the highest isochore at Thtot), and most probably in a lithostatic 15 16 457 pressure gradient, which means that the crystallization of quartz from this fluid was at about 7 km depth. The 17 18 458 difficulty in obtaining homogenization temperatures in this type of fluid is a common problem (Bodnar et al. 19 20 459 2014). Marcoux et al. (2015) studied very similar fluids and could only measure six Thtot, all homogenized in 21 22 460 vapor. The next abundant aqueous carbonic fluid is much more water-rich and although the CH4/CO2 ratio is 23 24 461 higher than in the previous fluid, it has much less CO2 and CH4. This fluid has slightly lower Thtot than the 25 26 462 previous fluid, but the most striking characteristic is the much lower pressure around Thtot. The last fluid is 27 28 463 aqueous and low salinity, most probably meteoric water that percolated the lithologies above the deposition site. 29 30 464 The fact that this Lw-c fluid has a higher ratio of CH4/CO2 than the Lc-w fluid could indicate that the fluid 31 32 465 percolated through C-rich metasedimentary rocks, lithologies that are relatively abundant in the area. The 33 34 466 existence of aqueous carbonic fluids of different densities (Lc-w, Vc-w and Lw-c fluid types) very close (some 35 36 467 micra) each other suggest that one of the causes for ore deposition was probably pressure drop possibly triggered 37 38 468 by seismic events, a mechanism first proposed by Sibson (1973, 1983, 1987, 1990) and Sibson et al. (1975). 39 40 469 Destabilization of the ore forming-fluid due to mixing between aqueous carbonic and water-rich fluids could also 41 42 470 have contributed to metallic phase deposition. 43 44 471 In multidisciplinary studies of various gold deposits from the Iberian Peninsula Cathelineau et al. (1993) and 45 46 472 Boiron et al. (1996) presented the first data on fluid inclusions from the Penedono area. They describe only three 47 48 473 types of H2O-CO2-CH4-N2-NaCl±H2S fluids for this deposit, which they distinguished according to the degree of 49 50 474 filling (not quantified), microthermometric and Raman results and accordingly bulk compositions and densities. 51 52 475 All the fluids are of low salinity. These authors and also Nogueira and Noronha (1993) do not describe water- 53 54 476 (salt) inclusions in this deposit. The aqueous carbonic characteristics are broadly similar to those observed in the 55 56 477 present study. These authors considered that the mineralization has evolved from P-T conditions around 370ºC / 57 58 59 60 61 62 16 63 64 65 478 1-1.5 kbar to 200º±20ºC and 0.5 kbar, with gold precipitation occurring during or after this last stage of fluid 1 2 479 circulation. 3 4 480 The types of fluids, fluid compositions (gas content and low salinity), densities and temperatures and 5 6 481 pressures (and depths) of entrapment are in accordance with an orogenic type deposit. According to Goldfarb et 7 8 482 al. (2005) fluids that form orogenic gold deposits could have been extracted at depths of up to 20 km and 9 10 483 percolated through crustal fault zones. 11 12 484 13 14 485 7.3. Isotopic studies 15 16 486 7.3.1. Pyrite and arsenopyrite sulphide data 17 18 487 The Santo António fluid was not dominated by H2S, which has not been detected by Raman 19 20 488 spectroscopic analysis of the studied fluid in quartz. Given the reducing environment in the deposit, sulphur 21 22 489 should most probably have been present mainly as HS- and S2-. Sulphur isotope compositions of hydrothermal S- 23 24 490 bearing minerals is controlled by the total sulphur isotope composition of the fluids, temperature, pH and fO2. 25 26 491 The first parameter is a characteristic of the source, but the latter parameter is related to the environment of 27 28 492 deposition (Arias et al. 1997). The 34S from sulphides should be equivalent to 34S of the ore-forming fluids. 29 30 493 The arsenopyrite shows lower 34S values than pyrite, as found in orogenic gold deposits of Mali, West Africa 31 32 494 (Lawrence et al. 2013b). The 34S mean values of -3.8 ‰ for pyrite and -4.7 ‰ for the arsenopyrite of the Santo 33 34 35 495 António deposit can be compared to the total range of published data extending for -0.1 to -8.5 of arsenopyrite 36 37 496 (Fig. 12; Cathelineau et al. 1993) for orogenic gold veins of Penedono in Portugal and Corcoesto, Tomino and 38 39 497 Pino in Spain. The sulphur isotopic composition of arsenopyrite and pyrite from the Au Limarinho deposit are 40 41 498 only slightly negative then the average S isotopic composition from Penedono main sulphides. Values close to 0 42 34 43 499 ‰ for S have been interpreted as being indicative of a magmatic fluid (Ohmoto and Goldhaber 1997), 44 45 500 although according to a compilation of European granites 34S in magmatic systems could range from +9 ‰ to - 46 47 501 4‰ (Gunter 1986). The 34S values obtained in the Santo António mining area are within the range for those 48 49 502 found in orogenic gold deposits from the Juneau gold belt of southeastern Alaska (-17.8 ‰ to 1.2 ‰; Goldfarb et 50 51 503 al. 1991), but they are constrained to a much more narrow range of -3.7 ‰ to -5.3 ‰ (Fig. 15) suggesting that 52 53 504 most of the fluid acquired its sulphur signature from a country rock of relatively homogeneous chemistry. 54 55 505 However, some orogenic gold deposits from NW Spain hosted by Cambrian-Ordovician or Ordovician rocks 56 57 506 present positive 34S values of sulphides from + 9.7 to + 20.6 ‰ in the Navia Belt (Arias et al. 1997), from + 58 59 507 3.2 to + 18.0 ‰ in the Southern West Asturian Leonese zone (Tornos et al. 1997) and from + 6.8 to + 19.5 ‰ in 60 61 62 17 63 64 65 508 the Llamas de Cabrera area (Gómez-Fernández et al. 2012), which are similar to those in the respective host 1 2 509 metasedimentary rocks. 3 4 510 5 6 511 7.3.2. Helium-Argon-Neon isotopic data from fluids in pyrite 7 8 512 Helium and argon isotopic data are important for tracing ore-forming fluids, namely to distinguish those 9 10 513 coming from the mantle and also to separate meteoric from crustal generated fluids. 11 12 514 Since Simmons et al. (1987), it is accepted that hydrothermal minerals can preserve mantle derived 3He. The 13 14 515 other helium isotope (4He) is considered always radiogenic (produced by the alpha decay of U and Th) and so 15 16 516 the atmospheric contribution of 4He is negligible. These authors also concluded that the 3He/4He ratio (R) in the 17 18 517 crust is < 10 % the atmospheric 3He/4He ratio (Ra) and mantle R/Ra is ~8-9, although subcontinental mantle has 19 20 518 R~6. Further studies concluded that in many circumstances the R/Ra of mantle fluids is 1000 higher than in 21 22 519 crustal fluids. Many studies (e.g. Simmons et al. 1987; Kendrick et al. 2011) have established that pyrite traps 23 24 520 helium over geological time scales (up to 109 years). Sample contaminations from cosmogenic 3He (and 21Ne) 25 26 521 are only significant if they have been exposed to the surface for periods of more than a few thousand years 27 28 522 (Ozima and Podosek 2002); this problem does not apply to our study because samples used in noble gas analysis 29 30 523 have been collected underground in the mine. The noble gas data seem valid, because although there are 31 32 524 different fluid generations in the samples, the aqueous carbonic fluids (the deeper fluids) are much more 33 34 525 abundant than the aqueous fluid. 35 36 526 Helium as a geological resource is obtained from He-rich natural gas fields (although He and methane have 37 38 527 different genesis) and so the source area is probably the same for both gases. However, He isotopes are used to 39 40 528 determine if mantle fluid has contributed (in some extent) to the fluid. 41 42 529 The recent determination of 40Ar/36Ar in modern air is 299 (Lee et al. 2006; Valkiert et al. 2010). Meteoric 43 44 530 water is characterized by atmospheric noble gas signatures of 20Ne/22Ne <9.8 and 21Ne/22Ne >0.029, but 45 46 531 40Ar/36Ar can range from 299 to 100,000 (Kendrick and Burnard 2013). Radiogenic noble gas isotopes have 47 48 532 predictable ratios (e.g. 4He/40Ar*, 21Ne*/40Ar*) controlled by the (U + Th)/K ratio of the host rock (asterix 49 50 533 denote radiogenic noble gas isotopes corrected for atmospheric contributions). 20Ne/36Ar is 0.524 in air and 0.122 51 52 534 in meteoric waters, but can vary between 0.05 and 6 in shales and between 0.2 and 6.5 in crystalline basement. 53 54 535 Smaller components of mantle derived noble gas can be identified from 3He/4He > 0.1 Ra and elevated 3He/36Ar 55 56 536 (Kendrick and Burnard 2013). Several orogenic-gold deposits from many parts of the world have maximum fluid 57 58 inclusion 3He/4He ratios of less than 0.4 Ra (e.g. Pettke et al. 1997; Graupner et al. 2006, 2010). Kendrick et al. 59 537 60 61 62 18 63 64 65 538 (2001) proposed the following expression to estimate the amount of fluid from the mantle: He mantle (%) = [Ra 1 2 539 sample-Ra crust] / [Ra mantle-Ra crust] x 100. Assuming Ra mantle = 6 and Ra crust = 0.02 (Stuart et al. 1995; Zhai et al. 3 4 540 2012), the highest mantle contribution to the ore-forming fluids at the Santo António mine is 2.8%. The well- 5 3 4 6 541 known natural CO2 gas field at McElmo Dome (USA) has a He/ He ratio of 0.13-0.17 which was interpreted by 7 8 542 Gilfillan et al. (2008) as a demonstration of a potential small mantle helium component in the gas field. The 9 10 543 maximum value of 40Ar/36Ar = 324.8 could imply that 10 % of the fluid probably is of meteoric origin. The 11 12 544 contribution of a low temperature meteoric fluid is also suggested by the shift to the left in the diagram of Fig. 13 14 545 16. A small fluid amount escaped from the sub continental lithospheric mantle and incorporated in the ore- 15 16 546 forming fluid is consistent with our He-Ar isotopic data and also bulk fluid compositions obtained in the fluid 17 18 547 inclusion study. The amount of meteoric water percolation is consistent with the noble gas results and agrees 19 20 548 very well with the fluid inclusion data. Neon isotopic ratios also suggest that a fluid contribution from the mantle 21 22 549 is absent or very small (Fig. 16). Therefore, the fluids have a dominant crustal origin. 23 24 550 25 26 551 7.4. Mineralizing environment and source of ore metals and metalloids 27 28 552 Gold-bearing quartz veins from the Santo António mine are hosted by the Tabuaço Massif (Fig. 2), which 29 30 553 consists of a syn-D3 muscovite>biotite S-type granite dated at 310.11.1 Ma (Fig. 13). This granite intruded 31 32 554 Cambrian metamorphic rocks and the D2 extensional shear zone (Figs. 1c and 2) that reached amphibolite-facies 33 34 555 metamorphic conditions. The gold-bearing quartz veins fill dilatation surfaces of this granite formed in relation 35 36 556 to the motion of D3 strike-slip shear zones. Therefore, the Tabuaço granite and associated gold-bearing quartz 37 38 557 veins are post- M2 high-grade metamorphism (Fig. 1d). The peak of M2 metamorphism probably occurred 39 40 558 between ca. 320 and 314 Ma (Fig. 1d). The metamorphic conditions estimated on calc-silicate rocks interlayered 41 42 559 with the metapelites of the anatectic complex provided minimum metamorphic peak conditions of T = 76150ºC 43 44 45 560 and P = 5.01.0 kbar, but petrological modelling results show that temperature conditions may have exceeded 46 47 561 800ºC (Pereira et al. 2017). Therefore, the studied gold-bearing quartz veins are post- M2 metamorphic peak like 48 49 562 many other occurrences in western Europe (e.g. Boiron et al. 1996, 2001; Noronha et al. 2000; Gómez- 50 51 563 Fernández et al. 2012; Fuertes-Fuente et al. 2016). 52 53 564 In the Penedono mining area, an earlier major heat sink with steep metamorphic gradients was probably 54 55 565 related to development of the D2 extensional Pinhel shear zone (Diez-Fernández and Pereira 2016). The Tabuaço 56 57 566 granite hosting the gold-bearing quartz veins from Santo António is younger than the M2 metamorphic peak 58 59 567 between ca. 320 and 314 Ma (Fig. 1D). Therefore, the ascent of the granitic magma would have provided much 60 61 62 19 63 64 65 568 heat and remobilized gold and other metals and metalloids from the metamorphic rocks in a similar way as 1 2 569 recognized in other gold deposits in northwest Europe (e.g. Noronha et al. 2000; Boiron et al. 2003; Vallance et 3 4 570 al. 2003). There were two main reservoirs for the mineralized fluids that generated this type of gold deposits. 5 6 571 One reservoir consisted of waters percolated into the basement through faults enhanced by shear zones and 7 8 572 decompression, equilibrated with metamorphic rocks, transporting dissolved gold, other metals and metalloids 9 10 573 which later flowed upwards along the faults. Gold precipitation was probably linked to dilution by fluid mixing 11 12 574 during the basement uplift as temperature and pressure drop, as proposed to explain several gold quartz veins 13 14 575 from northwest Europe (e.g. Boiron 1996, 2001, 2003; Noronha et al. 2000; Vallance et al. 2003; Gómez- 15 16 576 Fernández et al. 2012). Sudden pressure drops caused by seismic events, a mechanism first proposed by Sibson 17 18 577 (1973, 1983, 1987, 1990) and Sibson et al. (1975) could also contribute to gold precipitation. The presence of 19 20 578 microfractured sulphides could have enhanced gold precipitation through electrochemical processes (Boiron et 21 22 579 al. 2003). Tungsten may have been leached from the country rocks in a manner similar to that documented by 23 24 580 Cave et al. (2017). 25 26 581 In hydrothermal systems, gold transport and deposition depends on fluid composition, temperature, pressure, 27 28 582 pH, oxygen and sulphur fugacity, and type and amount of dissolved sulphur and other species (e.g. Mikucki 29 30 583 1998). The occurrences of several sulphides and sulphosalts, gold-silver alloy from gold-bearing quartz veins of 31 32 584 the Santo António mining camp suggest that Au and Ag were carried as bisulphide complexes. The host Tabuaço 33 34 585 granite was hydrothermally altered at quartz vein walls and contains secondary muscovite. Neutral to slightly 35 36 586 alkaline solutions originating in the field of maximum gold solubility as a bisulphide complex produce sericite as 37 38 587 the most common potassium aluminosilicate in alteration assemblages (Romberger 1986). Gold and silver were 39 40   41 588 probably transported as Au(HS) 2 and Ag(HS) 2 , respectively, under neutral pH conditions (Stefánson and 42 43 589 Seward 2003, 2004; Pokrovski et al. 2014). The decrease in temperature from 444ºC to 300ºC estimated through 44 45 590 the evolution of arsenopyrite composition, including the range of 380-360ºC recorded in fluid inclusions, and the 46 47 591 decrease in pressure provided favorable conditions for the gold deposition. 48 49 592 50 51 593 7.5. Comparison with some other gold deposits in the Iberian Massif 52 53 594 In order to compare the Variscan gold deposit from Santo António, Penedono, NW Portugal, with some 54 55 595 Variscan gold deposits in the Iberian Massif, we selected data from the literature from northwest to central Iberia 56 57 596 (Table 8). All gold deposits occur in shear zones and most of them consist of arsenopyrite-gold quartz veins. 58 59 597 However, antimony-gold quartz veins occur in the Central Iberian Zone, and in central Portugal and central 60 61 62 20 63 64 65 598 Spain. Arsenopyrite-gold quartz veins are mainly hosted by granite, as in the Santo António mine and also the 1 2 599 Limarinho deposit, or by granites and metasedimentary rocks, or less commonly by metasedimentary rocks. 3 4 600 Antimony-gold quartz veins are hosted by metasedimentary rocks as in the Dúrico-Beirão Mining District. All 5 6 601 gold deposits contain sulphides and most of them, as in the Santo António mine, also have sulphosalts. However, 7 8 602 rare ferberite occurs in gold-bearing quartz veins from Santo António, but it does not occur in the other selected 9 10 603 gold deposits from the Iberian Massif (Table 8). In all selected arsenopyrite-gold quartz veins there were at least 11 12 604 two types of fluids, an aqueous-carbonic fluid and an aqueous fluid. Both fluids mixed inside the faults with 13 14 605 decrease in temperature and pressure during the basement uplift. This probably caused deposition of gold-silver 15 16 606 alloy in these gold-bearing quartz veins (Table 8). 17 18 607 The 34S presents negative values in arsenopyrite-gold quartz veins from Santo António and Limarinho 19 20 608 deposits, in N Portugal, and positive values in similar veins from Llamas de Cabrera, in NW Spain (Table 8). 21 22 609 The 34S values will depend on those of metasedimentary rocks from the respective area, as suggested by values 23 24 610 in the Llamas de Cabrera deposit. Isotopic He, Ar and Ne values are only available for arsenopyrite-gold-bearing 25 26 611 quartz veins from the Santo António mine and suggest a crustal origin. These veins were formed at a depth of 7 27 28 612 km, which is within the range of 6 to 12 km for most of the selected arsenopyrite-gold quartz veins (e.g. Gómez- 29 30 613 Fernández et al. 2012). Considering the three most important reservoirs for sulphur [magmatic, marine and 31 32 614 (meta)sedimentary] the d34S values for the studied sulphides at Santo António are compatible only with a 33 34 615 metasedimentary source, which in turn strongly suggests that the sulphides belong to an orogenic gold deposit. 35 36 37 616 The arsenopyrite-gold bearing quartz veins from the Santo António mine compare well with other similar 38 39 617 Variscan arsenopyrite-gold quartz veins from the Iberian Massif (Table 8), but these deposits do not contain 40 41 618 ferberite. However, there are some differences when compared with the antimony-gold quartz veins: they do not 42 43 619 contain antimony minerals, but have rare ferberite and are formed at higher pressure. 44 45 620 46 47 8. Conclusions 48 621 49 1) The gold-bearing quartz veins from the Santo António mine (Penedono, Portugal) cut a deformed Variscan 50 622 51 52 623 S-type muscovite>biotite granite dated at 310.1 1.1 Ma and are structurally controlled by sinistral sense of 53 54 624 motion of N130-140E trending D3 and N50E trending D4 strike-slip shear zones. These gold mineralizations are 55 56 625 post- M2 metamorphic peak. 57 58 626 2) Pyrrhotite, arsenopyrite and pyrite are the earliest sulphides. From the first generation to the second and 59 60 627 third generations of arsenopyrite, due to later growths, there is a progressive increase in the S content and 61 62 21 63 64 65 628 decrease in the As content and temperature from 444-433ºC to 395-369ºC and 364-300ºC, respectively. In a few 1 2 629 single crystals, the S content increases and As content and temperature decrease from core (383-376ºC) to rim 3 4 630 (363-329ºC). 5 6 631 3) Galenobismutite and bismuthinite occur associated with fractures of the second generation of arsenopyrite. 7 8 632 The lower experimental temperatures for these Bi minerals are within the temperature range for the second 9 10 633 generation of arsenopyrite. 11 12 634 4) There are no significant distinctions in compositions of gold-silver alloy associated with fractures and 13 14 635 filling spaces between grains of different arsenopyrite generations and included in quartz. 15 16 636 5) 34S mean values of arsenopyrite (-4.7‰) and pyrite (-3.8‰) are compatible with an ore-forming fluid of 17 18 637 metamorphic and meteoric origin. 19 20 638 6) He-Ar isotopic data indicate that fluids have a dominant crustal origin and Ne and Ar isotopic ratios are 21 22 639 atmospheric. 23 24 640 7) The ascent of the granite magma has provided the heat source for convective water circulation to remove 25 26 641 gold-silver alloy, other metals and metalloids from the metamorphic rocks. 27 28 642 8) The abundance of aqueous carbonic fluids, the existence of aqueous low-salinity fluids and their minimum 29

30 643 possible entrapment temperature (Thtot) suggest that the gold-forming event initiated during the waning stages of 31 32 644 the Variscan orogeny and happened at the transition from a lithostatic to an hydrostatic pressure gradient. 33 34 645 9) The depositions of gold-silver alloy took place during the decrease of temperature and pressure and in the 35 36 646 remobilization stage. 37 38 647 10) This quartz arsenopyrite-gold deposit compares well with other quartz arsenopyrite-gold deposits from the 39 40 648 Iberian Massif, but contains tungstates. 41 42 649 11) The Santo António mine is a gold deposit, younger than ca. 310 Ma, controlled by ductile to brittle-ductile 43 44 650 deformation due to Variscan shearing and brittle deformation. 45 46 651 12) This deposit it has several characteristics that contradict a genetic assignment to the “intrusion-related” 47 48 652 type, namely: 1) location in a large pluton (> 50 km2 in area), 2) location in an elongated pluton, 3) no regional 49 50 mineralogical zonation is observed with As-Au at the center of the pluton, followed by As-Sb-Au and Ag-Pb-Zn 51 653 52 53 654 associations further, 4) the deposit has a gold content that cannot be considered low, 5) pyrrhotite is not the 54 55 655 dominate sulphide, 6) very negative sulfur isotopes are not characteristic of a magmatic derivation, 7) there are 56 57 656 no characteristically magmatic fluids with boiling indications, 8) initial fluids, typical of metamorphism are 58 59 657 followed by meteoric fluids. 60 61 62 22 63 64 65 658 1 2 659 Compliance with ethical standards 3 4 660 Conflict of interest 5 6 661 There is no conflict of interest. 7 8 662 9 10 663 References 11 12 664 Alcock, J.E., Martínez Catalán, J.R., Rubio Pascual, F.J., Montes, A.D., Díez Fernández, R., Gómez Barreiro, J., 13 14 665 Arenas, R., Dias da Silva, Í. & González Clavijo, E. (2015). 2-D thermal modeling of HT-LP metamorphism 15 16 666 in NW and Central Iberia: Implications for Variscan magmatism, rheology of the lithosphere and orogenic 17 18 667 evolution. Tectonophysics 657, 21-37. 19 20 668 Amcoff, O. (1976). The solubility of silver and antimony in galena. Neues Jahrb. Mineral. Monat. 6, 247-261. 21 22 669 Arias, D., Corretgé, L.G., Villa, L., Gallastegui, G., Suárez, O., Cuesta, A., 1997. A sulphur isotopic study of the 23 24 670 Navia gold belt (Spain). J. Geochem. Explor. 59, 1-10. 25 26 671 Bakker, R.J. (1999). Adaptation of the Bowers and Helgeson (1983) equation of state to the H2O–CO2–CH4–N2– 27 28 672 NaCl system. Chem. Geol. 154, 225-236. 29 30 673 Bakker, R.J.(2003). Package FLUIDS 1. Computer programs for analysis of fluid inclusion data and for 31 32 674 modeling bulk fluid properties. Chem. Geol. 194, 3-23. 33

34 675 Bodnar, R.J. (1993). Revised equation and table for determining the freezing point depression of H2O–NaCl 35 36 676 solutions. Geochim. Cosmochim. Acta 57, 683-684. 37 38 677 Bodnar, R.J., Lecumberri-Sanchez, P., Moncada, D. & Steele-MacInnis, M. (2014). Fluid Inclusions in 39 40 678 Hydrothermal Ore Deposits. In: Holland, H.D., Turekian, K.K. (Eds.) Treatise on Geochemistry (2nd edition, 41 42 679 vol. 13) Elsevier, Oxford, pp. 119-142. 43 44 680 Boiron, M.-C., Cathelineau, M., Banks, D.A., Yardley, B.W.D., Noronha, F. & Miller, M.F. (1996). P-T-X 45 46 681 conditions of late Hercynian fluid penetration and the origin of granite-hosted gold quartz veins in 47 48 682 northwestern Iberia: A multidisciplinary study of fluid inclusions and their chemistry. Geochim. Cosmochim. 49 50 683 Acta 60, 43-57. 51 52 684 Boiron, M.C., Barakat, A., Cathekineau, M., Banks, D.A., Durivosa, J. & Moravek, P. (2001). Geometry and P- 53 54 685 V-T-X conditions of microfissural ore fluid migration: the Mokrsko gold deposit (Bohemia). Chem. Geol. 55 56 686 173, 207-225. 57 58 59 60 61 62 23 63 64 65 687 Boiron, M.C., Cathelineau, M., Banks, D.A., Fourcade, S. & Vallance, J. (2003). Mixing of metamorphic and 1 2 688 surficial fluids during the uplift of the Hercynian upper crust: consequences of gold deposition. Chem. Geol. 3 4 689 194, 119-141. 5 6 690 Boiron, M.C., Essaraj, S., Sellier, E., Cathelineau, M., Lespinasse, M. &Poty, B., (1992). Identification of fluid 7 8 691 inclusions in relation to their host microstructural domains in quartz by cathodoluminescence. Geochim. 9 10 692 Cosmochim. Acta 56, 175-185. 11 12 693 Bowers, T.S. & Helgeson, H.C. (1983). Calculation of the thermodynamic and geochemical consequences of 13 14 694 nonideal mixing in the system H2O–CO2–NaCl on phase relations in geological systems: equation of state for 15 16 695 H2O–CO2–NaCl fluids at high pressures and temperatures. Geochim. Cosmochim. Acta 47, 1247–1275. 17 18 696 Burrows, D.R. & Spooner, E.T.C. (1989). Relationships between Archean gold vein-shear zone mineralisation 19 20 697 and igneous intrusions in the Val d’Or and Timmins area, Abitibi Subprovince, Canada. Econ. Geol. Mon. 6, 21 22 698 424-444. 23 24 699 Cathelineau, M., Boiron, M.C., Palomero, F.G., Urbano, R., Florido, P., Pereira, E.S., Noronha, F., Barriga, F., 25 26 700 Mateus, A., Yardley B. & Banks, D. (1993). Multidisciplinary studies of Au-vein formation. Application to 27 28 701 the western part of the Hesperian massif (Spain-Portugal). Final report, EEC project MA2M-CT90-0033, 391 29 30 702 p. 31 32 703 Cave, B.J., Pitcairn, I.K., Craw, D., Large, R.R., Thompson, J.M. & Johnson, S.C. (2017). A metamorphic 33 34 704 mineral source for tungsten in the turbidite-hosted orogenic gold deposits of the Otago Schist, New Zealand. 35 36 705 Miner. Deposita 52, 515-537. 37

38 706 Chang, L.L.Y. & Hoda, S.H. (1977). Phase relations in the system PbS-Cu2S-Bi2S3 and the stability of 39 40 707 galenobismutite. Am. Mineral. 62, 346-350. 41 42 708 Cook, N.J., Ciobanu, C.L., Meria, D., Silcock, D. & Wade, B. (2013). Arasenopyrite-pyrite association in an 43 44 709 orogenic gold ore: tracing mineralization history from textures and trace elements. Econ. Geol. 108, 1273- 45 46 710 1283. 47 48 711 Corfu, F. (2004). U-Pb age, setting and tectonic significance of the anorthosite-mangerite-charnockite-granite 49 50 712 suite, Lofoten-Vesterälen, Norway. J. Petrol. 56, 2081-2097. 51 52 713 Cotelo Neiva, J.M. & Neiva, A.M.R (1990). The gold area of Jales (northern Portugal). Terra Nova 2, 243-254. 53 54 714 Couto, H., Roger, G., Moëlo, Y. & Bril, H. (1990). Le district à antimoine-or Dúrico Beirão (Portugal): 55 56 715 évolution paragénétique et géochimique: implications métallogéniques. Miner. Deposita 25, Suppl. 569-581. 57 58 59 60 61 62 24 63 64 65 716 Couto, H., Roger, G. & Borges, F.S. (2007). Late Paleozoic orogenic gold-antimony deposits from the Dúrico- 1 2 717 Beirã area (North Portugal): relation with hidden granite apexes. Proc. Ninth Biennal Meeting of the Society 3 4 718 for Geology Applied to Mineral Deposits, Ireland. Edited by Colin J. Andrew et al. Cambridge Mineral 5 6 719 Resources 1, 609-615. 7 8 720 Craig, J.R., Vokes, F.M. & Solberg, T.N. (1993). Pyrite: physical and chemical textures. Miner. Deposita 34, 82- 9 10 721 101. 11 12 722 Dallmeyer, R.D., Martínez Catalán, J.R., Arenas, R., Gil Ibarguchi, J.J., Gutiérrez-Alonso, G., Farias, P., 13 14 723 Bastida, F. & Aller, J. (1997). Diachronous Variscan tectonothermal activity in the NW Iberian Massif: 15 16 724 evidence from 40Ar/39Ar dating of regional fabrics. Tectonophysics 277, 307-337. 17 18 725 D’Angelico, A.J., Jenkin, G.R.T. & James, D. (2016). Orogenic gold mineralization in northwest Iberia, 19 20 726 Portugal: role of meta-sediment source as a control on location, geochemistry and mineralogy. Ap. Earth Sc. 21 22 727 125, 73-74. 23 24 728 Davis, D.W., Blackburn, C.E. & Krogh, T.E. (1982). Zircon U-Pb ages from Wabigoon, Manitou Lakes Region, 25 26 729 Wabigoon Subprovince, northwest Ontario. Can. J. Earth Sci. 19, 254-266. 27 28 730 Dee, S.J. & Roberts, S. (1993). Late-Kinematic gold mineralization during regional uplift and the role of 29 30 731 nitrogen: an example from the La Codosera area, W. Spain. Mineral. Mag. 57, 437-450. 31 32 732 Dias, G., Leterrier, J., Mendes, A., Simões, P.P. & Bertrand, J.M. (1998). U-Pb zircon and monazite 33 34 733 geochronology of post-collisional Hercynian granitoids from the Central Iberian Zone (Northern Portugal). 35 36 734 Díez Balda, M.A., Martínez Catalán, J.R. & Ayarza, P. (1995). Syn-collisional extensional collapse parallel to 37 38 735 the orogenic trend in a domain of steep tectonics - The Salamanca detachment zone (Central Iberian Zone, 39 40 736 Spain). J. Str. Geol. 17, 163-182. 41 42 737 Díez Fernández, R. & Arenas, R. (2015). The Late Devonian Variscan suture of the Iberian Massif: A correlation 43 44 738 of high-pressure belts in NW and SW Iberia. Tectonophysics 654, 96-100. 45 46 739 Díez Fernández, R. & Pereira, M.F. (2016). Extensional orogenic collapse captured by strike-slip tectonics: 47 48 740 constrains from structural geology and U-Pb geochronology of the Pinhel shear zone (Variscan orogen, 49 50 741 Iberian Massif). Tectonophysics 691, 290-310. 51 52 742 Díez Fernández, R. & Pereira, M.F. (2017). Strike-slip shear zones of the Iberian Massif: are they 53 54 743 coeval? Lithosphere, 9, 726-744, doi:10.1130/L648.1. 55 56 57 58 59 60 61 62 25 63 64 65 744 Díez Fernández, R., Gómez Barreiro, J., Martínez Catalán, J.R. & Ayarza, P. (2013). Crustal thickening and 1 2 745 attenuation as revealed by regional fold interference patterns: Ciudad Rodrigo basement area (Salamanca, 3 4 746 Spain). J. Str. Geol. 46, 115-128. 5 6 747 Escuder Viruete, J.E., Arenas, R. & Martínez Catalán, J.R. (1994). Tectonothermal evolution associated with 7 8 748 Variscan crustal extension in the Tormes gneiss dome (NW Salamanca, Iberian massif, Spain). 9 10 749 Tectonophysics 23, 117-138. 11 12 750 Escuder Viruete, J., Hernáiz Huerta, P.P., Valverde-Vaquero, P., Rodríguez Fernández, R. & Dunning, G. 13 14 751 (1998). Variscan syncollisional extension in the Iberian Massif: structural, metamorphic and 15 16 752 geochronological evidence from the Somosierra sector of the Sierra de Guadarrama (Central Iberian Zone, 17 18 753 Spain). Tectonophysics 290, 87-109. 19 20 754 Ferreira, N. & Sousa, M.B. (1994). Notícia explicativa da folha 14-B da Carta Geológica de Portugal (scale 21 22 755 1/50000; Moimenta da Beira). Serv. Geol. Portugal, 53p. 23 24 756 Fischer, N.H. (1945). The fineness of gold with special reference to the Morobe goldfield, New Guinea. Econ. 25 26 757 Geol. 40, 449-495. 27 28 758 Fuertes-Fuente, M., Cepedal, A., Lima, A., Dória, A., Ribeiro, M.J. & Guedes, A. (2016). The Au-bearing vein 29 30 759 system of the Limarinho deposit (northern Portugal): Genetic constraints from Bi-chalcogenides and Bi-Pb- 31 32 760 Ag sulfosalts, fluid inclusions and stable isotopes. Ore Geol. Rev. 72, 213-231. 33 34 761 Gamond, J.F. & Giraud, A. (1982). Identification des zones de faille á l’aide des associations de fractures de 35 36 762 second ordre. Bull., Soc., Geol., France 24, 755-762. 37 38 763 Garofalo, P.S. & Ridley, J.R. (2014). Gold-transporting hydrothermal fluids in the Earth’s crust: an introduction. 39 40 764 In: Garofalo, P.S., Riddley, J.R. (Eds.). Gold-Transportation Hydrothermal Fluids in the Earth’s Crust. The 41 42 765 Geol. Soc. Spec. Pub., London, 402, 1-7. 43 44 766 Gilfillan, S., Ballentine, C., Holland, G., Blagburn, D., Sherwood, B., Lollar, B., Scott Stevens, S., Schoell, M. & 45 46 767 Cassidy, M. (2008). The noble gas geochemistry of natural CO2 gas reservoirs from the Colorado Plateau and 47 48 768 Rocky Mountain provinces, USA. Geochim. Cosmochim. Acta 72, 1174-1198. 49 50 769 Goldfarb, R.J., Baker, T., Dube, B. Gorves, D.L., Hart, C.J.R. & Gosselin, P. (2005). Distribution, character, and 51 52 770 genesis of gold deposits in metamorphic terranes. Econ. Geol. 100th Anniversary Volume, 407-450. 53 54 771 Goldfarb, R.J. & Groves, D.I. (2015). Orogenic gold: Common or evolving fluid and neutral sources through 55 56 772 time. Lithos 233, 2-26. 57 58 59 60 61 62 26 63 64 65 773 Goldfarb, R.J., Groves, D.I. & Gardoll, S. (2001). Orogenic gold and geologic time: a global synthesis. Ore 1 2 774 Geol. Rev. 18, 1-75. 3 4 775 Goldfarb, R.J., Newberry, R.J., Pickthorn, W.J. & Gent, C.A. (1991). Oxygen, hydrogen, and sulfur isotope 5 6 776 studies in the Juneau gold belt, southeastern Alaska: constraints on the origin of hydrothermal fluids. Econ. 7 8 777 Geol. 86, 66-80. 9 10 778 Gómez-Fernández, F., Vindel, E., Martín-Crespo, T., Sánchez, V., González Clavijo, E. & Matías, R. (2012). 11 12 779 The Llamas de Cabrera gold district, a new discovery in the Variscan basement of northwest Spain: A fluid 13 14 780 inclusion and stable isotope study. Ore Geol. Rev. 46, 68-82. 15 16 781 Graupner, T., Niedermann, S., Kempe, U., Klemd, R. & Bechtel, A. (2006). Origin of ore fluids in the Muruntau 17 18 782 gold system: constraints from noble gas, carbon isotope and halogen data. Geochim. Cosmochim. Acta 70, 19 20 783 21, 5356–5370. 21 22 784 Graupner, T., Niedermann, S., Rhede, D., Kempe, U., Seltmann, R., Williams, C.T. & Klemd, R. (2010). 23 24 785 Multiple sources for mineralizing fluids in the Charmitan gold (-tungsten) mineralization (Uzbekistan). 25 26 786 Miner. Deposita 45, 667–682. 27 28 787 Groves, D.I., Gordfarb, R.J., Knox-Robinson, C.M., Ojala, J., Gardoll, S., Yun, G.Y. & Holyland, P. (2000). 29 30 788 Late-kinematic timing of orogenic gold deposits and significance for computer-based exploration techniques 31 32 789 with emphasis on the Yilgarn Block, Western Australia. Ore Geol. Rev. 17, 1-38. 33 34 790 Gunter, F. (1986). Principles of Isotope Geology. Second Edition. John Wiley & Sons. 35 36 791 Jaffey, A.H., Flynn, K.F., Glendenin, L.E., Bentley, W.C. & Essling, A.M. (1971). Precision measurement of 37 38 792 half-lives and specific activities of 235U and 238U. Phys. Rev., Sec. C, Nucl. Phys. 4, 1889-1906. 39 40 793 Kendrick, M.A., Burgess, R., Pattrick, R.A.D. & Turner, G. (2001). Fluid inclusion noble gas and halogen 41 42 794 evidence on the origin of Cu-porphyry mineralizing fluids. Geochim. Cosmochim. Acta 65, 2651–2668. 43 44 795 Kendrick, M.A. & Burnard, P. (2013). Noble Gases and Halogens in Fluid Inclusions: A Journey Through the 45 46 796 Earth’s Crust. In: P. Burnard (Ed.). The Noble Gases as Geochemical Tracers, Advances in Isotope 47 48 797 Geochemistry. Springer-Verlag Berlin Heidelberg. 49 50 798 Kendrick, M.A., Honda, M., Walshe, J. & Petersen, K. (2011). Fluid sources and the role of abiogenic-CH4 in 51 52 799 Archean gold mineralization: constraints from noble gases and halogens. Precam. Res. 189, 313–327. 53 54 800 Kim, K.H., Lee, S., Nagao, K., Sumino, H., Yang, K. & Lee, J.I. (2012). He-Ar-H-O isotopic signatures in Au- 55 56 801 Ag bearing ore fluids of the Sunshin epithermal gold-silver ore deposits, South Korea. Chem. Geol. 320-321, 57 58 128-139. 59 802 60 61 62 27 63 64 65 803 Knight, C.L. & Bodnar, R.J. (1989). Synthetic fluid inclusions: IX. Critical PVTX properties of NaCl–H2O 1 2 804 solutions. Geochim. Cosmochim. Acta 53, 3-8. 3 4 805 Kretschmar, U. & Scott, S.D. (1976). Phase relations involving arsenopyrite in the system Fe-As-S and their 5 6 806 application. Can. Mineral. 14, 364-386. 7 8 807 Krogh, T.E. (1973). A low contamination method for hydrothermal decomposition of zircon and extraction of U 9 10 808 and Pb for isotopic age determinations. Geochim. Cosmochim. Acta 37, 485-494. 11 12 809 Krogh, T.E. (1982). Improve accuracy of U-Pb zircon ages by creation of more concordant systems using an air 13 14 810 abrasion technique. Geochim. Cosmochim. Acta 46, 637-649. 15 16 811 Lang, J.R. & Baker, T. (2001). Intrusion-related gold systems: the present level of understanding. Miner. 17 18 812 Deposita 36, 477-489. 19 20 813 Lawrence, D.M., Treloar, P.J., Rankin, A.H., Harbidge, P. & Holliday, J. (2013a). The geology and mineralogy 21 22 814 of the Loulo Mining District, Mali, West Africa: evidence for two distinct styles of orogenic gold 23 24 815 mineralization. Econ. Geol. 108, 199-227. 25 26 816 Lawrence, D.M., Treloar, P.J., Rankin, A., Boyce, A. & Harbidge, P. (2013b). A fluid inclusion and stable 27 28 817 isotope study at the Loulo Mining District, Mali, West Africa: implications for multifluid sources in the 29 30 818 generation of orogenic gold deposits. Econ. Geol. 108, 229-257. 31 32 819 Leal Gomes, C. (1994). Estudo estrutural e paragenético de um sistema pegmatoide granítico. – O campo aplito- 33 34 820 pegmatítico de Arga – Minho (Portugal). Unpublished PhD thesis, Univ. Minho, Portugal, 695 p. 35 36 821 Leal Gomes, C. (1997). Estruturas de deformação Hercínica tardia na transição D3-D4 – evidência e 37 38 822 interpretação de marcadores mineralógicos, marcadores litológicos, objectos geométricos simples e critérios 39 40 823 cinemáticos – discussão da viabilidade de isolamento de um episódio deformacional D’3 (D3-tardio) na 41 42 824 vertente oriental da Serra de Arga – Minho – N de Portugal. “Livro guia da excursão pós-reunião” – Coke, C. 43 44 825 (ed.) – PICG 376 – XIV Reunião de Geologia do Oeste Peninsular, 97-118. 45 46 826 Leal Gomes, C. (2000a). Análise comparativa das paragéneses auríferas nos índices, Dacotim, Fonte do Coxo, 47 48 827 Bouções e Turgueira – área de Penedono – relatório inédito para Rio Narcea Gold Mines – filial portuguesa, 49 50 828 Penedono, 35 p. 51 52 829 Leal Gomes, C. (2000b). Análise paragenética e tipologia das expressões auríferas do depósito de Santo 53 54 830 António-Vieiros (Penedono) – relatório inédito para Rio Narcea Gold Mines – filial portuguesa, Penedono, 55 56 831 20 p. 57 58 59 60 61 62 28 63 64 65 832 Leal Gomes, C. & Castelo Branco, J.M. (2003). Tipologia do particulado aurífero tardio nas mineralizações de 1 2 833 Penedono (Viseu, Portugal). IV Congresso Ibérico de Geoquímica e XIII Semana de Geoquímica, Livro de 3 4 834 Resumos, 190-192. 5 6 835 Leal Gomes, C. & Gaspar, O.C. (1992). Mineralizações filonianas associadas a cisalhamentos pós-pegmatóides 7 8 836 do campo aplito-pegmatítico de Arga – Minho. Comun. Serv. Geol. Portugal 78, 31-47. 9 10 837 Lee, J.Y., Marti, K., Severinghaus, J.P., Kawamura, K., Yoo, H.S., Lee, J.B. & Kim, J.S. (2006). A 11 12 838 redetermination of the isotopic abundances of atmospheric Ar. Geochim. Cosmochim. Acta 70, 4507-4512. 13 14 839 Liu, C., Liu, J., Carranza, E.J.M., Yang, L., Wang, J., Zhai, D., Wang, Y., Wu, J. & Dai, H. (2016). Geological 15 16 840 and geochemical constraints on the genesis of the Huachanggou gold deposit, western Qinling region, central 17 18 841 China. Ore Geol. Rev. 73, 354-373. 19 20 842 Llana-Fúnez, S. & Marcos, A. (2001). The Malpica-Lamego Line: a major crustal scale shear zone in the 21 22 843 Variscan belt of Iberian. J. Str. Geol. 23, 1015-1030. 23 24 844 López-Moro, F.J., López-Plaza, M., Gutíerrez-Alonso, G., Fernández-Suárez, J., López-Carmona, A., Hofmann, 25 26 845 M. & Romer, R.L. (2017). Crustal melting and recycling: geochronology and sources of Variscan 27 28 846 syn‑ kinematic anatectic granitoids of the Tormes Dome (Central Iberian Zone). A U–Pb LA‑ ICP‑ MS 29 30 847 study. Int. J. Earth Sc., DOI 10.1007/s00531-017-1483-8. 31 32 848 Ludwig, K.R. (2003). Users manual for Isoplot 3.00. Berkeley Geochr. Cent. Spec. Publ. 4, 70 pp. 33 34 849 Marcoux, E, Nerci, K., Branquet Y., Ramboz, C., Ruffet, G., Peucat, J.-J., Stevenson, R. & Jébrak, M. (2015). 35 36 850 Late-Hercynian intrusion-related gold deposits: An integrated model on the Tighza polymetallic district, 37 38 851 central Morocco. J. Afric. Earth Sci. 107, 65-88. 39 40 852 Martínez Catalán, J.R., Arenas, R., Abati, J., Sánchez Martínez, S., Díaz García, F., Fernández-Suárez, J., 41 42 853 González Cuadra, P., Castineiras, P., Gómez Barreiro, J., Díez Montes, A., González Clavijo, E., Rubio 43 44 854 Pascual, F.J., Andonaegui, P., Jeffries, T.E., Alcock, J.E., Díez Fernández, R. & López Carmona, A. (2009). 45 46 855 A rootless suture and the loss of the roots of a mountain chain: The 1159 Variscan belt of NW Iberia. Compt. 47 48 856 Rend. Geos. 341, 114-126. 49 50 857 Martínez Catalán, J.R., Arenas, R., Díaz Garcia, F. & Abati, J. (1997). Variscan accretionary complex of 51 52 858 northwest Iberia: terrane correlation and succession of tectonothermal events. Geology 25, 1103-1106. 53 54 859 Martínez Catalán J.R., Rubio Pascual F.J., Díez Montes A., Díez Fernández R., Gómez Barreiro J., Dias da Silva 55 56 860 Í., González Clavijo E., Ayarza P. & Alcock J.E. (2014). The late Variscan HT/LP metamorphic event in NW 57 58 59 60 61 62 29 63 64 65 861 and Central Iberia: relationships to crustal thickening, extension, orocline development and crustal evolution. 1 2 862 Geol. Soc., London, Spec. Pub. 405, 225-247. 3 4 863 Mikucki, E.J. (1998). Hydrothermal transport and depositional processes in Archean lode-gold systems: a 5 6 864 review. Ore Geol. Rev. 13, 307-321. 7 8 865 Morey, A.A., Tomkins, A.G., Bierlein, F.G., Weinberg, R.F. & Davidson, G.J. (2008). Bimodal distribution of 9 10 866 gold in pyrite and arsenopyrite: example from the Archean Boorara and Bardoc shear zones, Yilgarn craton, 11 12 867 Western Australia. Econ. Geol. 103, 599-614. 13 14 868 Murphy, P.J. & Roberts, S. (1997). Evolution of a metamorphic fluid and its role in lode gold mineralization in 15 16 869 the Central Iberian Zone. Miner. Deposita 32, 459-474. 17 18 870 Neiva, A.M.R. (1994). Gold-quartz veins at Gralheira, northern Portugal: mineralogical and geochemical 19 20 871 characteristics. Trans. Inst. Min. Metall., Sct. B: Appl. Earth Sci. 103, B188-B196. 21 22 872 Neiva, A.M.R., András, P. & Ramos, J.M.F. (2008). Antimony quartz and antimony-gold quartz veins from 23 24 873 northern Portugal. Ore Geol. Rev. 34, 533-546. 25 26 874 Nogueira, P. & Noronha, F. (1993). A evolução de fluidos hidrotermais associados a mineralizações de (Au-Ag- 27 28 875 As) em contexto granítico. Os exemplos de Grovelas e Penedono, norte de Portugal. Mem. nº 3, Univ. Porto, 29 30 876 Fac. Ciênc., Mus. Lab. Mineral. Geol., p. 275-278. IX Semana de Geoquímica e II Cong. Geoquímica dos 31 32 877 países de língua portuguesa. Noronha, F., Marques, M. and Nogueira, P. (eds). 33 34 878 Noronha, F., Cathelineau, M., Boiron, M.-C., Banks, D.A., Dória, A., Ribeiro, M.A., Nogueira, P. & Guedes, A. 35 36 879 (2000). A three stage fluid flow model for Variscan gold metallogenesis in northern Portugal. J. Geochem. 37 38 880 Expl. 71, 209-224. 39 40 881 Ohmoto, H. & Goldhaber, M.B. (1997). Sulfur and carbon isotopes. In: Barnes, H.I. (Ed.). Geochemistry of 41 42 882 hydrothermal ore deposits, 3rd Edition, New York, Wiley, 517-612. 43 44 883 Oliveira, J.T. (1992). Carta Geológica de Portugal, Folha Norte, scale 1/500000. Serv. Geol. Portugal. 45 46 884 Ortega, L., Oyarzun, R., Gallego, M., (1996). The Maria Rosa late Hercynian Sb-Au deposit (western Spain): 47 48 885 geology and geochemistry of mineralizing processes. Miner. Deposita 31, 172-187. 49 50 886 Ortega, L. & Vindel, E. (1995). Evolution of ore forming fluids associated with late Hercynian antimony 51 52 887 deposits in central/western Spain: case study of Maria Rosa and El Juncalón. Eur. J. Mineral. 7, 655-673. 53 54 888 Ozima, M. & Podosek, F.A. (2002). Noble Gas Geochemistry, Cambridge University Press. 55 56 57 58 59 60 61 62 30 63 64 65 889 Pereira, I., Dias, R., Santos, T.B. & Mata, J. (2017). Exhumation of a migmatite complex along a transpessive 1 2 890 shear zone: inferences from the Variscan Juzbado-Penalva do Castelo Shear Zone (Central Iberian Zone). J. 3 4 891 Geol. Soc., http://doi.org/10.1144/pgs2016-159. 5 6 892 Pereira, M.F., Díez Fernández, R., Gama, C., Hofmann, M., Gärtner, A. & Linnemann, U. (2018). S-type granite 7 8 893 generation and emplacement during a regional switch from extensional to contractional deformation (Central 9 10 894 Iberian Zone, Iberian autochthonous domain, Variscan Orogeny). Int. J. Earth Sc., 107, 251-267; DOI 11 12 895 10.1007/s00531-017-1488-3. 13 14 896 Pettke, T., Frei, R., Kramers, J.D. & Villa, I.M. (1997). Isotope systematics in vein gold from Brusson, Val 15 16 897 d’Ayas (NW Italy). 2. (U+Th)/He and K/Ar in native Au and its fluid inclusions. Chem. Geol. 135, 173–187. 17 18 898 Pitcairn, I.R., Teagle, D.A., Craw, G.R., Olivo, G.R., Kerrich, R. & Brewer, T.S. (2006). Sources of metals and 19 20 899 fluids in orogenic gold deposits: Insights from the Otageo and Alpine Schists, New Zealand. Econ. Geol. 21 22 900 101, 1525-1546. 23 24 901 Pokrovski, G.S., Akinfiev, N.N., Borisova, A.Y., Zotov, A.V. & Kouzmanov, K. (2014). Gold speciation and 25 26 902 transport in geological fluids: insights from experiments and physical-chemical modelling. In: Garofalo, P.S., 27 28 903 Ridley, J.R. (Eds.). Gold-Transporting Hydrothermal Fluids in the Earth’s Crust, The Geol. Soc., Spec. Pub., 29 30 904 London, 42, 9-70. 31 32 905 Poty, B., Leroy, J. & Jachimowicz, L. (1976). Un novel appareil pour la mesure des températures sous le 33 34 906 microscope: L'installation de microthermométrie Chaixmeca. Bull. Minér. 99, 182-186. 35 36 907 Prieto, A.C., Guedes, A., Dória, A., Noronha, F. & Jiménez, J. (2012). Quantitative determination of gaseous 37 38 908 phase compositions in fluid inclusions by Raman microspectrometry. Spectrosc. Lett. 45, 156-160. 39 40 909 Rauchenstein-Martinek, K., Wagner, T., Wälle, M. & Heinrich, C.A. (2014). Gold concentrations in 41 42 910 metamorphic fluids: A LA-ICPMS study of fluid inclusions from the Alpine orogenic belt. Chem. Geol. 385, 43 44 911 70-83. 45 46 912 Regêncio Macedo, C.A. (1988). Granitoids, Complexo Xisto-Grauváquico e Ordovícico na região entre 47 48 913 Trancoso e Pinhel (Portugal Central): Geologia, Petrologia, Geocronologia. Unpublished PhD thesis, Univ. 49 50 914 Coimbra, Coimbra, Portugal, p. 430. 51 52 915 Roedder, E. (1984). Fluid inclusions. In: Ribbe, Paul H. (Ed.), Reviews in Mineralogy, vol. 12. Mineral. Soc. 53 54 916 Amer. 55 56 917 Romberger, S.B. (1986). The solution chemistry of gold applied to the origin of hydrothermal deposits. In: 57 58 Clark, L.A. (Ed). Gold in the Western Shield, Spec. Vol. Can. Inst. Min. Mettal., pp. 168-186. 59 918 60 61 62 31 63 64 65 919 Sharp, Z.D., Essene, E.J. & Kelly, W.C. (1985). A re-examination of the arsenopyrite geothermometer: pressure 1 2 920 considerations and applications to natural assemblages. Can. Mineral. 23, 517-534. 3 4 921 Shepherd, T. (1981). Temperature-programmable heating-freezing stage for microthermometric analysis of fluid 5 6 922 inclusions. Econ. Geol. 76, 1244-1247. 7 8 923 Sibson, R. (1973). Interactions between temperature and pore-fluid pressure during earthquake faulting and a 9 10 924 mechanism for partial or total stress relief. Nature 243, 66-68. 11 12 925 Sibson, R. (1983). Continental fault structure and the shallow earthquake source. J. Geol. Soc. London 140, 741- 13 14 926 767. 15 16 927 Sibson, R. (1987). Earthquake rupturing as a mineralizing agent in hydrothermal systems. Geology 15, 701-704. 17 18 928 Sibson, R. (1990). Faulting and fluid flow. In: B.E. Nesbitt (Ed.), Fluids in Tectonically Active Regimes of the 19 20 929 Continental Crust. Short Course Handbook, 18. Mineral. As. Canada, Vancouver, B.C., pp. 93-132. 21 22 930 Sibson, R., McM, Moore & Rankin, A. (1975). Seismic pumping - a hydrothermal fluid transport mechanism. J. 23 24 931 Geol. Soc. London 131, 653-659. 25 26 932 Silva, A.F. & Ribeiro, M.L. (1991). Carta Geológica de Portugal, scale 1:500000, Notícia explicativa da Folha 27 28 933 15-A Vila Nova de Foz Côa. Instituto Geológico e Mineiro, 52 p. 29 30 934 Silva, A.F. & Ribeiro, M.L. (1994). Carta Geológica de Portugal, scale 1:500000, Notícia explicativa da Folha 31 32 935 15-B Freixo de Espada à Cinta. Instituto Geológico e Mineiro, 48 p. 33 34 936 Simmons, S.F., Sawkins, F.J. & Schlutter, D.J. (1987). Mantle derived helium in two Peruvian hydrothermal ore 35 36 937 deposits. Nature 329, 429-432. 37 38 938 Sousa, M.B. & Ramos, J.M.F. (1991). Características geológico-estruturais e químico-mineralógicas das jazidas 39 40 939 auríferas da região de Penedono-Tabuaço (Viseu, Portugal). Est. Not. Trab., D.G.G.M. 33, 71-96. 41 42 940 Sousa, M.B. & Sequeira, A.J.D. (1989). Notícia explicativa da folha 10-D da Carta Geológica de Portugal (scale 43 44 941 1/50000; Alijó). Serv. Geol. Portugal, 59p. 45 46 942 Stacey, J.S. & Kramers, J.D. (1975). Approximation of terrestrial lead isotope evolution by a low-stage model. 47 48 943 Earth Plan. Sci. Let. 34, 207-226. 49 50 944 Stefánsson, A. & Seward, T.M. (2003). Experimental determination of the stability and stoichiometry of 51 52 945 sulphide complexes of silver (I) in hydrothermal solutions to 400º C. Geochim. Cosmochim. Acta 67, 1395- 53 54 946 1413. 55 56 947 Stefánsson, A. & Seward, T.M. (2004). Gold (I) complexing in aqueous sulphide solutions to 500º C at 500 bar. 57 58 Geochim. Cosmochim. Acta 68, 4121-4143. 59 948 60 61 62 32 63 64 65 949 Stuart, F.M., Burnard, P., Taylor, R.P. & Turner, G. (1995). Resolving mantle and crustal contributions to 1 2 950 ancient hydrothermal fluid: He-Ar isotopes in fluid inclusions from Dae Hwa W-Mo mineralization, South 3 4 951 Korea. Geochim. Cosmochim Acta 59, 4663-4673. 5 6 952 Sundlab, K., Zachrisson, E., Smeds, S.A., Berglund, S. & Alinder, C. (1984). Sphalerite geobarometry and 7 8 953 arsenopyrite geothermometry applied to metamorphosed sulfide ores in the Swedish Caledonides. Econ. 9 10 954 Geol. 79, 1660-1668. 11 12 955 Tornos, F., Spiro, B.F., Shepherd, T.Y. & Ribera, F. (1997). Sandstone-hosted lodes of the southern West 13 14 956 Asturian Leonese Zone (NW Spain). Chron. Rech. Min. 528, 71-86. 15 16 957 Ueda, A.H.R.K. (1986). Direct conversion of sulphide and sulphate minerals to SO2 for isotope analysis. 17 18 958 Geochem. J. 20, 209-212. 19 20 959 Valkiers, S., Vendelbo, D., Berglund, M., Podesta & M. (2010). Preparation of argon primary measurement 21 22 960 standards for the calibration of ion current ratios measured in argon. Int. J. Mass Spectrom. 291, 41-47. 23 24 961 Vallance, J., Cathelineau, M., Boiron, M.C., Fourcade, S., Shepherd, T.J. & Naden, J. (2003). Fluid-rock 25 26 962 interactions and the role of late Hercynian aplite intrusion in the genesis of the Castromil gold deposit, 27 28 963 northern Portugal. Chem. Geol. 194, 201-224. 29 30 964 Valle Aguado, B., Azevedo, M.R., Schaltegger, U., Martínez Catalán, J.R. & Nolan, J. (2005). U–Pb zircon and 31 32 965 monazite geochronology of Variscan magmatism related to syn-convergence extension in Central Northern 33 34 966 Portugal. Lithos 82, 169-184. 35 36 967 Zhai W., Sun X., Wu Y., Sun Y., Hua R., Y. & X. (2012). He-Ar isotope geochemistry of the Yaoling-Meiziwo 37 38 968 tungsten deposit, North Guangdong Province: Constraints on Yanshanian crust-mantle interaction and 39 40 969 metallogenesis in SE China. Chinese Sc. Bul. 57, 10, 1150-1159. 41 42 970 43 44 971 Figure captions 45 46 972 Figure 1. Geology of the Penedono area, northern Portugal: a) Location of the study area in the Iberian Massif; 47 48 973 a) shows the location of (b); b) Schematic representation of the Variscan granitic rocks and main strike-slip shear 49 50 974 zones in the Central Iberian zone with location of the Penedono area; b) shows the location of figure 2; c) Cross- 51 52 975 sections through the Penedono area (K1-K2) and its southern adjacent area (K3-K4) showing the shallow- 53 54 976 dipping D2 extensional Pinhel shear zone captured and folded by D3 and D4 strike-slip shear zones; b) and c) 55 56 977 Adapted from Díez-Fernández and Pereira, 2016; 2017; Pereira et al., 2018; d) Diagram showing the age 57 58 59 60 61 62 33 63 64 65 978 variation and time relations of Variscan deformation events, high-grade metamorphism and granitic rocks 1 2 979 generation in Central Iberia Zone (Adapted from Pereira et al., 2018 and references therein). 3 4 980 5 6 981 Figure 2. Simplified geological map of the Penedono area (Adapted from Sousa and Ramos 1991; Sousa and 7 8 982 Sequeira 1989; Ferreira and Sousa 1994) with reinterpretation of the main Variscan structures. 9 10 983 11 12 984 Figure 3. Geometry of the Santo António quartz vein system and some selected gold contents obtained for 13 14 985 channel sampling from early works of Rio Narcea Gold Mines Ltd. (Leal Gomes 2000a). 15 16 986 17 18 987 Figure 4. Diagram of the multistage ore deposition in gold quartz veins, considering the Variscan and post- 19 20 988 Variscan deformation (Adapted from Leal Gomes 1997, 2000b; Leal Gomes and Castelo Branco 2003). Ars1, 21 22 989 Ars2 and Ars3 are the three generations of arsenopyrite presented now. 23 24 990 25 26 991 Figure 5. Backscattered electron images of ore minerals from gold-bearing quartz veins of the Santo António 27 28 992 mine. a. Gold-silver alloy (Au-Ag1) grain penetrated a space between grains of arsenopyrite Apy1 grains. b. 29 30 993 Ferberite (Fer) associated with micro-fractures of arsenopyrite (Apy1) partially replaced this sulphide and quartz 31 32 994 (Qz1). c. Gold-silver alloy (Au-Ag2) grains partially penetrated and surrounded by bismuthinite (Bis) are 33 34 995 associated with micro-fractures of arsenopyrite (Apy2). d. Gold-silver alloy (Au-Ag2) grains mainly surrounded 35 36 996 by bismuthinite, which has native bismuth (Bi) inclusions and all are included in quartz (Qz2). e. 37 38 997 Galenobismutite (Glb) partially surrounded by quartz are both associated with micro-fractures of arsenopyrite 39 40 998 (Apy2). f. Galena (Gn) containing inclusions of native bismuth and quartz (Qz2) is in contact with arsenopyrite 41 42 999 (Apy2). g. Gustavite (Gus) filling a space between crystals of arsenopyrite (Apy2). h. Cannizzarite (Can) fillings 43 44 1000 a space between crystals of arsenopyrite (Apy2). i. Galena containing a small inclusion of native bismuth is 45 46 1001 surrounded by gustavite and they replace arsenopyrite (Apy2). j. Gold-silver alloy (Au-Ag3) grain penetrated 47 48 1002 along a micro-fracture of arsenopyrite (Apy3). k. Stolzite (Stl) with inclusions of scheelite (Schl) associated with 49 50 1003 quartz (Qz3) and arsenopyrite (Apy3). l. Gold-silver alloy (Au-Ag4) grain associated with micro-fractures in 51 52 1004 arsenopyrite (Apy2) and mainly surrounded by scorodite (Scor). 53 54 1005 55 56 1006 Figure 6. Compositions of some sulphides from gold-bearing quartz veins of the Santo António mine. a) S- 57 58 (Fe+Ni+Co)-As diagram showing the positions of diagrams (b) and (c); b) three generations of arsenopyrite are 59 1007 60 61 62 34 63 64 65 1008 distinguished in the gold-bearing quartz veins; c) the three pyrite compositions are similar; d) Ag+Bi versus Pb 1 2 1009 diagram of galena, suggesting that these metals substitute for Pb in galena. 3 4 1010 5 6 1011 Figure 7. Compositions of gold and electrum grains from gold-bearing quartz veins of the Santo António mine 7 8 1012 showing that generally different generations of gold and electrum are not distinct. 9 10 1013 11 12 1014 Figure 8. Spatial relationship between quartz associated with hypogenic stages (2-3) and remobilized quartz 13 14 1015 (stage 4) and arsenopyrite, from a gold-bearing quartz vein of the Santo António mine. 15 16 1016 17 18 1017 Figure 9. Fluid inclusion images of the fluid types: Lc-w, Vc-w, Lw-c and Lw from gold-bearing quartz veins of 19 20 1018 the Santo António mine. See 5.1 in the text for fluid type characteristics. Inclusions are in the range 15-30 m. 21 22 1019 23 24 1020 Figure 10. Microthermometric measurements on fluid inclusions in quartz from Santo António Au-As quartz 25 26 1021 veins. See text for significance of abbreviations. 27 28 1022 29

30 1023 Figure 11. Raman spectrum on CO2 lines from a Lc-w fluid inclusion (image inside) of gold-bearing quartz 31 32 1024 veins from the Santo António mine. 33 34 1025 35 36 1026 Figure 12. Sulphur isotopic data (34S) from pyrite and arsenopyrite from four gold-bearing quartz veins from 37 38 1027 the Santo António mine, Penedono, and literature. 39 40

41 1028 42 Figure 13. U-Pb Concordia diagram for monazite and zircon from granite hosting the Santo António 43 1029 44 45 1030 mineralization. Ellipse represents 2 uncertainty. 46 47 1031 48 49 1032 Figure 14. Isochores for the fluids entrapped in quartz from the Santo António mine orebody and probable PT 50 51 1033 path for the ore-forming hydrothermal fluid. Yellow area: PT domain constrained by Boiron et al. (1996) for 52 53 1034 highest PT conditions in the beginning of fluid trapping in mineralized quartz at Penedono and other areas in 54 55 1035 northwestern Iberia. Red dot: PT point for the aqueous carbonic fluid represented by the isochore (P1-2, see 56 57 1036 Table 4) fluid at Thtot=378ºC, which is the lowest temperature (and pressure) for the Lc-w fluid entrapment. This 58 59 1037 corresponds to ~7 km depth, assuming a lithostatic pressure gradient and rock density of 2.7. Blue area: PT 60 61 62 35 63 64 65 1038 domain for the entrapment of water low salinity fluids without measurable gas, considering the lower and the 1 2 1039 higher isochores (represented also the average isochore) and 7 km at hydrostatic as maximum depth. (Vc-w fluid 3 4 1040 is an aqueous carbonic fluid with gas homogenization in vapour). Green arrows: probable PT path for the 5 6 1041 mineralizing fluid at the Santo António mine. 7 8 1042 9 10 1043 Figure 15. 40Ar*/4He vs. 3He/4He (R/Ra) diagram for fluids liberated from pyrites from gold-bearing quartz 11 12 1044 veins of the Santo António mine. Small rectangle delimits lithospheric subcontinental mantle values. 40Ar* is 13 14 1045 non-atmospheric argon, i.e. 40Ar* = 40Ar − 295.5 36Ar. 15 16 1046 17 18 1047 Figure 16. Neon isotopic data for fluids trapped in pyrites from gold-bearing quartz veins from the Santo 19 20 1048 António mine, Penedono. Radiogenic 21Ne and 22Ne are produced by alpha particles interacting with 18O or 19F, 21 22 1049 respectively. The displacement of 21Ne/22Ne from AIR neon ratio probably reflects mixing of the distinct 23 24 1050 basement signature with atmospheric noble gases present either in ground water or metasediments (Kendrick and 25 26 1051 Burnard 2013). 27 28 1052 29 30 1053 Appendix A. Electron-microprobe chemical analyses in wt.% of tungsten minerals of gold-bearing quartz veins 31 32 1054 from the Santo António mine, Penedono, northern Portugal. 33 34 1055 35 36 1056 Appendix B. Electron-microprobe analyses in wt.% of rooseveltite and scorodite of gold-bearing quartz veins 37 38 1057 from the Santo António mine, Penedono, northern Portugal. 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 36 63 64 65 Table Click here to access/download;Table;Table 1.tif Table Click here to access/download;Table;Table 2_6 fev 2019.docx

Table 2 Selected electron-microprobe chemical analyses in wt.% of sulphides, sulphosalts and native bismuth of gold-bearing quartz veins from the Santo António mine, Penedono, northern Portugal

Ni Co Cu Ag Zn Fe Mn Cd As Pb Bi S Total Pyrrhotite — — — — — 60.85 — — — — 0.09 38.98 99.92 Arsenopyrite (1st generation Apy1) with pyrrhotite inclusions 0.02 0.05 — — — 33.27 — — 47.07 — 0.02 19.62 100.05 with gold-silver alloy Au-Ag1 — 0.05 — — — 33.81 — — 47.25 — 0.05 19.14 100.30 replaced by ferberite 0.03 0.06 — 0.01 — 34.00 — — 46.16 — 0.06 19.21 99.53 Arsenopyrite (2nd generation Apy2) surrounding by ferberite — 0.06 — 0.02 — 34.08 — — 45.45 — 0.03 20.60 100.24 with gold-silver alloy Au-Ag2 — 0.02 — — — 34.00 — — 45.93 — 0.04 20.24 100.23 with sulphides and sulphosalts2 — 0.06 — — — 33.75 — — 46.08 — 0.06 20.05 100.00 Arsenopyrite (3rd generation Apy3) — — 0.01 0.01 0.04 35.28 — — 42.36 — 0.13 22.14 99.97 Zoned arsenopyrite darker core (2nd generation Apy2) — — — — — 34.08 — — 45.65 — — 20.60 100.33 lighter rim (3rd generation Apy3) — — 0.01 — — 34.68 — — 43.28 — 0.09 22.32 100.38 Pyrite (1st generation) — — — — — 46.57 — — — — 0.14 53.06 99.77 Pyrite (2nd generation) — — — — — 46.19 — — 0.01 — 0.16 53.47 99.83 Pyrite (3rd generation) — — — 0.02 — 46.46 — — 0.01 — 0.17 53.28 99.94 Sphalerite — — — — 63.46 2.59 0.02 0.54 — — — 33.30 99.91 Chalcopyrite — — 33.96 — — 30.25 — — — — 0.13 35.50 99.84 Native bismuth — — — — — 0.36 — — — — 99.74 — 100.10 Galenobismutite — — — — — — — — — 29.50 53.30 16.75 99.55 Bismuthinite — — — — — — — — — — 80.86 19.13 99.99 Galena — — — 2.11 — — — — — 79.29 4.93 13.73 100.06 Gustavite — — — 8.73 — — — — — 21.47 53.01 16.44 99.65 Cannizzarite — — — — — — — — — 36.57 47.00 16.42 99.99 Marcasite — — — — — 46.50 — — — — — 53.25 99.75 Covellite — — 64.68 — — — — — — — — 35.10 99.78

Gold-silver alloy associated with micro-fractures and filling spaces between grains of arsenopyrite; Au and Sb were not detected in sulphides and sulphosalts; — not detected. Table Click here to access/download;Table;Table 3_6 fev 2019.xlsx

Table 3 Representative electron-microprobe analyses in wt.% of gold-silver alloy grains of gold-bearing quartz veins from Santo António, Penedono, northern Portugal Associated with fractures in arsenopyrite Included in quartz 2 Remobilized Gold-silver alloy 1 Gold-silver alloy 2 Gold-silver alloy 3 Gold-silver alloy 2 Gold-silver alloy 4 Au 83.39 72.96 83.54 94.50 64.70 80.96 64.46 80.05 52.86 94.78 Ag 16.08 26.45 15.55 4.89 34.57 18.84 34.80 18.81 47.14 4.65 Bi 0.53 0.56 0.63 0.63 0.59 0.30 0.52 0.64 0.35 0.59 Total 100.00 99.97 99.72 100.02 99.86 100.10 99.78 99.50 100.35 100.02

Fineness 838 734 843 951 652 811 649 810 529 953 Gold-silver alloy 1 is within fractures and between grains of arsenopyrite Apy1. Gold-silver alloy 2 and gold-silver alloy 3 are within fractures and between grains of arsenopyrites Apy2 and Apy3, respectively. Fineness [1000 wt.% Au/(wt.% Au + wt.% Ag)] (Fischer, 1945).

Table Click here to access/download;Table;Table 4_6 fev 2019.xlsx

Table 4 Microthermometry, gas composition, global composition and densities for selected fluid inclusions of gold-bearing quartz veins from the Santo António mine, Penedono, northern Portugal Microthermometry (ºC) Gas composition (%) Global composition (moles %) + - F.I. Flw FI type TmCO2 TmCl Tmice ThCO2 TH CO2 CH4 N2 H2O CO2 CH4 N2 Na Cl density P1-1 60 Lc-w -58.8 9.8 23.8 L 375 97.87 1.75 0.38 75.62 17.30 0.28 0.06 3.35 3.35 0.85 P1-2 60 Lc-w -58.8 9.7 -2.0 23.3 L 378 97.58 2.42 nd 75.32 17.36 0.39 0.00 3.46 3.46 0.85 P1-3 60 Lc-w -59.2 10.0 22.7 L 360 96.84 2.90 0.25 75.82 17.23 0.46 0.04 3.22 3.22 0.85 P2-1 70 Lw-c 11.2 -2.4 >330 82.35 17.65 nd 92.19 4.94 0.54 0.00 1.17 1.17 0.76 P2-2 70 Lw-c 11.0 -2.0 >300 83.58 16.42 nd 92.23 4.91 0.49 0.00 1.18 1.18 0.76 P2-3 60 Lc-w -59.7 10.5 11.6 V 93.24 6.76 nd 81.93 16.50 1.04 0.00 0.25 0.25 0.85 P6-1 40 Lc-w -58.9 22.0 L 96.46 2.64 0.90 P6-2 60 Lc-w -59.2 9.1 23.6 L 96.22 3.78 nd 74.83 16.97 0.60 0.00 3.80 3.80 0.84 P6-3 40 Lc-w -58.0 8.6 22.1 V 100 nd nd 82.88 14.34 0.00 0.00 1.39 1.39 0.52

F.I. - fluid inclusion; Flw - filling water; TmCO2 - temperature of melting of the gas phase; TmCl - temperature of melting of clathrates; Tmice - ice melting temperature;

ThCO2 - temperature of gas homogenization; TH - homogenization temperature.

Table Click here to access/download;Table;Table 5_6 fev 2019.docx

Table 5 34S sulphide data of pyrite and arsenopyrite of gold- bearing quartz veins from the Santo António mine, Penedono, northern Portugal

Sample 34S ‰ Sample 34S ‰ reference pyrite number arsenopyrite P1 -3.9 A1 -4.6 P2 -4.0 A2 -4.3 P3 -3.8 A3 -4.8 P4 -3.6 A4 -4.3 P5 -3.8 A5 -5.0 P6 -3.7 A6 -5.3 Precision and reproducibility 34S were better than 0.2 ‰.

Table Click here to access/download;Table;Table 6_6 fev 2019.xlsx

Table 6 He-Ar-Ne isotopic compositions of inclusion-trapped fluid in pyrite of gold-bearing quartz veins from the Santo António mine, Penedono, northern Portugal Pyrite Weight (g) 4He R/Ra 1s 40Ar/36Ar 1s 36Ar 38Ar/36Ar 1s 22Ne 20Ne/22Ne 1s 21Ne/22Ne 1s 3 1.02 5.26E-08 0.126 0.008 306.6 4.10 2.26E-10 0.1881 0.0006 6.98E-10 9.80 0.06 0.0294 0.0004 5 1.00 8.01E-08 0.136 0.007 324.8 4.40 1.91E-10 0.1884 0.0005 6.93E-10 9.81 0.06 0.0300 0.0004 4 1.00 1.05E-07 0.177 0.007 298.7 4.00 5.78E-10 0.1878 0.0006 2.10E-11 9.80 0.06 0.0296 0.0004 6 1.02 1.40E-07 0.201 0.005 303.3 4.10 1.01E-09 0.1875 0.0005 4.31E-11 9.87 0.06 0.0296 0.0004 1 1.02 7.35E-08 0.142 0.007 311.6 4.20 2.90E-10 0.1864 0.0005 1.10E-11 9.83 0.06 0.0301 0.0004 2 1.02 8.02E-08 0.142 0.007 313.4 4.20 2.18E-10 0.1878 0.0006 7.21E-12 9.81 0.06 0.0302 0.0005 7 1.01 5.89E-08 0.131 0.007 298.1 4.00 5.42E-10 0.1740 0.0007 1.91E-11 9.81 0.06 0.0295 0.0004 Air 1.000 295.5 0.1880 9.80 0.0290 Units of concentrations are cm3STP/g

Table Click here to access/download;Table;Table 7_6 fev 2019.xls

Table 7. U-Pb data for zircon and monazite in granite from Santo António 2) 2) 3) 4) 5) 206 207 206 207 206 207 207 Mineral Weight U Th/U Pbi Pbc Pb/ Pb/ ± 2s Pb/ ± 2s rho Pb/ ± 2s Pb/ ± 2s Pb/ ± 2s Pb/ ± 2s Disc characteristics1) 204Pb6) 235U7) 238U7) 206Pb7) 238U7) 235U7) 206Pb7) [mg] [ppm] [ppm] [pg] [abs] [abs] [Ma] [%] P3.7 - granite Penedono area M NA [1] 1 2437 6.26 4.84 6.8 1127 0.3575 0.0015 0.04951 0.00010 0.62 ###### 0.00017 311.5 0.6 310.4 1.1 301.9 7.3 -3.3 Z lp AA [1] 1 8822 0.01 0.01 2.0 12425 0.3292 0.0010 0.04546 0.00011 0.92 ###### 0.00006 286.6 0.7 288.9 0.7 307.7 2.6 7.0 Z AA [1] 1 9082 0.01 0.00 2.0 13076 0.3287 0.0009 0.04543 0.00010 0.92 ###### 0.00006 286.4 0.6 288.5 0.7 305.8 2.5 6.5 Z fr AA [1] 1 1125 0.13 0.00 1.3 362 0.0451 0.0009 0.00614 0.00002 0.46 ###### 0.00103 39 0 45 1 340 43 89

1) Z = zircon; M = monazite; fr = fragment; lp = long prismtic (l/w>5); AA = treated with air abrasion; NA = not abraded; [1] = number of grains. 3) Th/U model ratio inferred from 208/206 ratio and age of sample. 4) Pbi = initial common Pb (corrected for blank). 5) Pbc = total common Pb in sample (initial + blank). 6) raw data corrected for fractionation. 7) corrected for fractionation, spike, blank, and initial common Pb; error calculated by propagating the main sources of uncertainty. Initial common Pb corrected with compositions calculated with Stacey and Kramers (1975) model. Decay constants are from Jaffey et al. (1971). Table Click here to access/download;Table;Table 8_6 fev 2019.xlsx

Table 8 Selected Variscan orogenic gold deposits in the Iberian Massif

Fluid composition and P-T Deposit / Au District Main type of ore Host rock Paragenesis d34S per mil Other Characteristics References conditions

Santo António, Penedono Arsenopyrite-gold- Granite Arsenopyrite-pyrite- H2O-CO2-CH4-N2-NaCl -5.3 to -4.3 ‰ Gold precipitated due to mixing between This study (Portugal) -quartz veins -gold-sulphides- 360-380ºC, >170 MPa (arsenopyrite) aqueous carbonic and water-rich fluids

-sulphosalts H2O-NaCl -4.0 to -3.7 ‰ during transition of a lithostatic pressure (pyrite) gradient to an hydrostatic one He-Ar-Ne data *

Grovelas, Penedono, Arsenopyrite-gold- Granites Arsenopyrite-pyrite- H2O-CO2-CH4-NaCl-(H2S) No data Gold precipitated from meteoric waters, Noronha et al. 2000 Vila Pouca, Três Minas -quartz veins Metasedimentary -gold-sulphides 300-550ºC, 100-350 MPa after being remobilized from metas-

(Portugal) rocks H2O-NaCl < 300ºC, sediments by aqueous-carbonic fluids < 100 MPa

Penedono (Portugal), Arsenopyrite-gold- Granites Arsenopyrite-pyrite- CO2-CH4-H2O-(N2-H2S)- -8.5 to -0.1 ‰ Gold precipitation linked to extended Boiron et al. 1996; Corcoesto, Tomino, Pino -quartz veins Granites and -gold-sulphides- NaCl, 450ºC, 150-300 MPa (arsenopyrite) fluid penetration downward in the crust. Cathelineau et al. 1993

(Spain) metamorphic rocks -sulphosalts H2O-NaCl* 260-310ºC, Crush-leach data < 75 MPa

Castromil, Paredes Arsenopyrite-gold- Granite, contact Arsenopyrite-pyrite- H2O-CO2-CH4-NaCl No data Gold precipitation linked to mixing Vallence et al. 2003 (Portugal) -quartz veins metasedimentary -gold-sulphides 400-500ºC, 100-200 MPa between two distinct aqueous fluids of

rocks and aplite H2O-NaCl, 150-180ºC contrasting salinity d18O data

Limarinho (Portugal) Arsenopyrite-gold- Granite Arsenopyrite-pyrite- H2O-CO2(CH4-N2)-NaCl -9.2 to-7.1 ‰ Evolution from aqueous carbonic fluids Fuertes-Fuente et al. -quartz veins -gold-sulphides- 300-330ºC, 130-200 MPa (arsenopyrite) - towards water-richer volatile poorer 2016

-sulphosalts H2O-NaCl 285-330ºC, +1.6 ‰ (pyrite) fluids, that mixed 24-29 MPa d18O dD data

Lamas de Cabrera (Spain) Arsenopyrite-gold- Granites and Arsenopyrite-pyrite- CO2-(CH4) +6.8 to + 19.5 ‰ Gold precipitation linked to decreasing of Gómez-Fernández

-quartz veins metasedimentary -gold-sulphides H2O-CO2-CH4-N2-NaCl Au solubility due to mixing between two et al. 2012 rocks 300-390ºC, 200-220 MPa distinct aqueous fluids 18 H2O-NaCl d O data 180-310ºC, < 200 MPa

Dúrico-Beirã region Antimony-gold- Metasedimentary Arsenopyrite-pyrite- H2O-NaCl-CO2(-CH4) No data Stibnite precipitation due to mixing of an Couto et al. 1990 (Portugal) -quartz veins rocks -berthierite-stibnite- 290-340ºC, No P data aqueous carbonic fluid with a meteoric Neiva et al. 2008

-gold-sulphides- H2O-NaCl one. Pb isotope data indicate a -sulphosalts 128-225ºC, No P data homogeneous lead source of crustal origin

Central Portugal and Antimony-gold- Metasedimentary Arsenopyrite-pyrite- H2O(-NaCl)-CO2-CH4(-N2) No data Gold precipitated in structural setting from Dee and Roberts 1993; Central Iberian regions -quartz veins rocks -stibnite-gold- 300ºC, 150 MPa unmixing due to pressure release Ortega and Vindel 1995;

-sulphides-sulphosalts H2O-NaCl Murphy and Roberts 1997 128-225ºC, No P data * At Penedono authors do not describe this type of fluid

Figure Click here to access/download;Figure;Fig 01.tif Figure Click here to access/download;Figure;Fig 02.tif Figure Click here to access/download;Figure;Fig 03.tif Figure Click here to access/download;Figure;Fig 04.tif Figure Click here to access/download;Figure;Fig 05.tif Figure Click here to access/download;Figure;Fig 06.tif Figure Click here to access/download;Figure;Fig 07.tif Figure Click here to access/download;Figure;Fig 8 new.tif Figure Click here to access/download;Figure;Fig 9 - new.tif Figure Click here to access/download;Figure;Fig 10.tif Figure Click here to access/download;Figure;Fig 11.tif Figure Click here to access/download;Figure;Fig 12.tif Figure Click here to access/download;Figure;Fig 13.tif Figure Click here to access/download;Figure;Fig 14.tif Figure Click here to access/download;Figure;Fig 15.tif Figure Click here to access/download;Figure;Fig 16.tif Supplementary Material

Click here to access/download Supplementary Material Appendix A_6 fev 2019.docx Supplementary Material

Click here to access/download Supplementary Material Appendix B_6 fev 2019.docx Author’s Response to Reviewers‘ Comments Click here to access/download;Author’s Response to Reviewers‘ Comments;ANSWERS TO REVIEWER # 1.docx

Answers to the reviewer 1

Thank you very much for the comments.

Lines of the reviewer

Line 54. Inaccurate, gold-only hydrothermal deposits also include High Sulfidation Epithermal deposits and gold skarn deposits.

Reply. They were added.

Line 56. The correct terminology for this type of deposit is Orogenic Gold Deposit, the term hydrothermal is unnecessary (authors should change it in the whole text).

Reply. The term Hydrothermal was removed.

Lines 57-58-59. The sentence "Magma….Laurussia" is not related to what is being described before and after. I cannot understand why this sentence is included here.

Reply. This statement was deleted.

Line 89. I guess it is Fig. 2 instead of Fig.1

Reply. Figures were removed from the Introduction.

Line 92. I suggest gold-bearing quartz veins (for the whole manuscript) instead of gold quartz veins

Reply. gold-bearing quartz veins was used.

From line 100 to 103. This sentence is too long (4 lines), I suggest to divide it in smaller sentences.

Reply. It was divided.

Moreover, in the previous paragraph, the authors point out that the paragenetic sequence, the mineralizing episodes and the fluid inclusions have already been presented in previous publications. These are the main issues of the current work. So, authors should specify the new contributions of this work to the previous ones.

Reply. The data obtained enable to improve the knowledge about this ore deposit.

From line 135 to 137. Is it the first dating of this granite? If so, authors should present it in a separate section to emphasize it instead of presenting the results in Appendices. In addition, this new dating should be mentioned in the last paragraph of the introduction section.

Reply. It is the first time that the granite is dated. It is presented separately in Table 7 and Fig. 13 and a text was written.

From line 152 to 155. The photographs of figure 3a & b do not show "strongly hydrothermally altered in the vicinity of the vein contacts". Same happens with figure 3c, it does not show "vein emplacement controlled by motion along strike-slip shear zones". It only shows a vein deformed by shear. Same happens with figure 3d, it does not show "...in peripheral gold quartz vein walls of 1m thickness disseminated arsenopyrite and pyrite may also carry gold". Finally, Figure 3e is not mentioned in the text and does not show anything of interest.

Reply. Figure 3 was removed.

From line 156 to 158. This description is confused, some photographs and/or drawings should be included. The sentence "... repositioning of sulphides and metals such as Ag, Bi, Pb and Te" is difficult to understand what the authors want to say: reorientation/reorganization..... of native metals???

1

Reply. This statement was deleted.

Line 220. Were sulfide samples for the isotope study hand-picked under binocular microscope? If so, authors should specify it in the text.

Reply. Sulfide samples for the isotope study was hand-picked under binocular microscope.

Line 243. I suggest cooling experiments instead of "cryometric analyses" and heating experiments instead of "thermometric studies". My suggestions are more usual nomenclature in microthermotry studies.

Reply. AGREED: new phrase incorporate the suggested changes

Line 247. Authors should add references of the volumetric charts, Roedder (1984)? or Shepherd et al. (1985)? or?

Reply. AGREED: new phrase is now : Volumetric proportions between volatile and aqueous phases were estimated optically at room temperature by reference to Roedder (1984) and Shepherd et al. (1985) charts.

Lines 266 to 288. The texture descriptions of the ore minerals are very poor and repetitive.

Reply. Sections 4 and 5 were merged.

Moreover, the presence of wolframates is poorly (if any) discussed in the current manuscript. I think that the presence of wolframates is important because these are not described in any of the other variscan orogenic deposits used form comparison in Table 7.

Reply. Ferberite is now in the discussion.

In addition, in this section and in the whole text (tables, figures and figure captions), authors must use the abbreviations for minerals from Kretz (1983) and Whitney & Evans (2010), e.g.: Arsenopyrite symbol is Apy instead of Ars.

Reply. The symbols given by Whitney and Evans (2010) were used.

What about of gold 4 from tables and figures? It does not appear in figure 5, neither in figure 6. In fact, gold only appears as gold 2 in BSE images from figure 6. It must be clarified in the manuscript.

Reply. Gold 4 is clarified in the figure, table and text.

- Stage I. Authors do not include tourmaline in this stage but they point out this mineral in the previous subsection 2.2.

Reply. Tourmaline was included in the stage 1.

- I think that the Au-Ag alloy grain of figure 6d is an only grain that shows a compositional zonation. I suggest to the authors that think in this possibility instead of using electrum and gold as if they were two different grains. In fact, the use of both terms complicate the understanding of the text. I suggest to use gold-silver alloy or electrum (as you prefer). For example, stage II is characterized by Au-Ag alloy/electrum that sometimes reaches Au contents as high as to be gold, or other possibility, to give the values like a solid solution i.e. Au90Ag10. In that way, the reader could notice easier the differences in gold fineness between stages.

Reply. The zonation of the Au-Ag alloy is used. The composition Au-Ag alloy is not distinct in the different stages as shown by Fig. 7.

2

- the stage II description needs to improve the organization, for instance, the description of bismuthinite and bismuth (lines 283-285) should be after the description of native bismuth in lines 280-281. In the present way, the same things are repeated several times making the text tedious and obscure.

Reply. In stage II the description of bismuthinite is after the description of native bismuth.

Line 291-295: In figure 6j, Ars3 is not fracture and does not show corroded borders supporting Py2 replaces Asr3. It is sub-euhedral arsenopyrite surrounded by pyrite, that´s all. Authors should select a better image to support their statement. Same happens with Py3, authors should show a photograph of the Py3 veinlets crosscutting the previous sulfides.

Reply. The Fig. 6j was replaced.

In figure 6k, stolzite seems to replace previous scheelite. Stolzite is usually a secondary mineral occurring in the oxidized zones of tungsten-bearing hydrothermal base metal deposits. So, authors should explain why they consider that this stolzite has a hydrothermal origin instead of being a secondary mineral.

Reply. Stolzite was removed as goes as a weathering product.

In figure 6k, stolzite is associated with Q2 but in the text authors point out that stolzite is associated with Q3. It must be clarified because in the present way it is confusing.

Reply. Q2 was changed to Q3 in Fig. 5k now.

Section 5. As I comment before, this section should be joined to section 4. The imprecise differences described between arsenopyrite, pyrite, and gold/electrum of each stage of section 4 would be more evident adding the chemical differences. Furthermore, there are many descriptions of the sulfides from section 4 that are repeated in this section 5 and vice versa. So, the join of both sections would improve the manuscript that would be easier to read & understand.

Reply. It was joined to the section 4.

Regarding the Pb-Bi-Ag sulfosalts, e.g.: authors give a structural formula of galenobismutite that does not fit well with the atomic proportion of this mineral (too must lead). Authors should be cautious with this complex group of minerals (the Pb-Bi-Ag sulfosalts). I suggest authors to revise carefully all the Pb-Bi-Ag sulfosalts found in this work taking into account this reference (a references therein): - Moëlo et al (2008) Sulfosalt systematics: a review. Report of the sulfosalt sub-committee of the IMA Commission on Ore Mineralogy. Eur. J. Mineral. 2008, 20, 7-46

Reply. Pb-Bi-Ag sulfosalts were revised carefully, using the reference received.

Lines 326-327: I cannot understand what authors want to highlight with this observation, I mean what is the point of it? Authors should explain it: ."Some galena grains associated with micro-fractures of arsenopyrite have a similar composition to that of galena included in arsenopyrite"

Reply. They were removed.

Line 340: It is unclear if the arsenates are hydrothermal or are weathering products in origin since authors state that they occur in the late hydrothermal remobilization stage. It is again very confusing. From this section 5, I have a doubt and/or misunderstanding, authors state that in stage III arsenopyrite replaces pyrite. This supports a decrease in sulfur fugacity. However, the sulfur content of arsenopyrite is constantly increasing from stage I to III. It implies an increase in sulfur fugacity. So, authors should discuss it in the text.

Reply. The arsenates are weathering products. The statement that arsenopyrite of the stage III replaces pyrite was removed and the Fig. 6j, was replaced by Fig. 5j. 3

Line 350: "quartz (Q3) from the late hydrothermal remobilization stage". Authors previously label it as Q4 (see page 10 section 4.4).

Reply. We have rewritten now …

Lines 347-352

We have observed four types of quartz: the older (Q1) from the hypogene stage 1 is dark with very small fluid inclusions and very often deformed and partly recrystallized. Quartz from the hypogene stages 2 and 3 (Q2 and Q3 respectively), are much more clear than Q1, practically undeformed and the fluid inclusions are much bigger. The last type of quartz (Q4) from the late hydrothermal remobilization stage is undeformed, very clear, practically without fluid inclusions and often in contact with the main sulphides (Fig. 9). The fluid inclusion studies were performed in quartz Q2 and Q3 (Q2-3) without distinction because both quartz has identical characteristics when observed on tick sections proper for the fluid inclusion study and also because both has the same fluid inclusion assemblages.

Lines 360-361. I do not see the point to the fluid inclusion density estimation, I suggest authors give the reason of including this data in the manuscript.

Reply. We would like to maintain the phrase

3 “We have estimated a density of around 1,500 fluid inclusions bigger than 5 μm in 1 mm of quartz Q2-3.” because it is informative about the quantity and concentration of fluid inclusion population on that quartz type. However we agreed that the phrase could be eliminated without harming the work.

For the whole fluid section: Relate to the fluid inclusions nomenclature, authors do not use correctly the nomenclature of Boiron et al. (1992) since the first capital letter indicates the way of total homogenization and, for instance, authors use Lc- w for fluids inclusions that homogenize in vapour. The Boiron et al. 1992 nomenclature is based on both micro-thermometric and Raman data. The type of total homogenization Th is indicated by V (to vapour phase), L (to liquid phase) and C (to critical state). The presence of C-H-O-(N) species is indicated by subscript c (only C-O-H-N volatile species are detected and H2O is absent), c-w (both water and C-O-H-N volatile species are present), w-c (water is largely dominant; in general >80% and CO2 has a low density, w-(c) (CO2 is only detected by clathrate melting or by Raman spectrometry), and w (no C-H-O-N volatile species are detected by any methods). So, authors should revise the nomenclature used in this manuscript.

Reply. We have observed occasionally some Vc-w inclusions. These are not easily distinguished from Lc-w type of inclusions because the majority of the Lc-w and Vc-W inclusions decrepitate before total homogenization.

We have rephrase and write the following:

Line 361-369 From petrographic, microthermometric and Raman characteristics different types of fluids (nomenclature according to Boiron et al., 1992) were recognized (Fig. 10): (i) Lc-w type: aqueous carbonic fluids (H2O–CO2– CH4-N2–NaCl) triphasic in the range 10-25ºC. The filling water ratio (Flw) is in the range of 0.4-0.6. These are the most obvious fluids in all samples. They could represent more than 50 % of the fluid inclusion population. (ii) Vc-w type: identical to Lc-w, but with Thtot in vapor as the only difference (iii) Lw-c type: aqueous carbonic fluids (H2O–CO2–CH4-N2–NaCl) always biphasic at room temperature and with the Flw ranging between 0.6 and 0.7. This type of fluids is scattered in the samples. (iv) Lw type: low salinity aqueous fluids (H2O–NaCl), with the Flw around 0.9. This type of fluid can be observed in every sample although they represent probably less than 20 % of the fluid inclusions.

Moreover, Flw is the volume fraction of the aqueous phase instead of "the filling water ratio".

Reply. AGREED: new phrase incorporate the suggested changes 4

Authors should use "to the vapour" or "to the liquid state" in the whole section instead of: into the../ for the…/.. liquid phase/ …into vapor/ in the..

Reply. AGREED: new phrase incorporate the suggested changes

Line 395: use concentration or content instead of grade. The term "grade" is usually used in an ore deposit context.

Reply. AGREED: new phrase incorporate “content” instead of grade

Lines 396 and 398: the salinity is usually expressed in mol% of NaCl. So, authors should add Na and Cl concentrations.

Reply. We describe salinity in terms of Na+ and Cl- concentrations because it is chemically more correct then NaCl.

Lines 398-399. it is figure 11 instead of figure 12, I guess. Nevertheless, I think that this figure of Raman peaks can be eliminated, it has not any interest.

Reply. We would like to maintain the image in order to document this point of the research

Section 7: isotopic data. Authors must specify from which stages are the pyrite and arsenopyrite (stages I, II, III) used in the isotope analyses. This is critical since if there is a variation in isotopic composition between stages you will obtain an average data of isotope compositions. This seems likely in the sulfur isotopic composition obtained in this work. The range of S isotopic compositions obtained in this work is close to an average range of the data given by previous authors, see figure 13. So, authors must discuss this possibility or point out from which stages are the sampled sulfides.

Reply. Due to the fact that the different stages of the mineralization are highly interrelated, it is not possible to separate pyrite or arsenopyrite according to the mineralizing stage, so the data can be considered as an average of the sulfur isotope characteristic of the entire stage of ore deposition.

Accordingly, Line 408 now begin with the phrase:

It was not possible to separate pyrite or arsenopyrite grains according with their stage in the ore deposition because of the intricate nature of ore textures.

Discussion it is too long, confusing and repetitive. I comment some points (as examples) below but it must be rewritten completely:

From line 418 to 424. This must be in the introduction section.

Reply. It was removed to the introduction.

From line 425 to 434. Authors should specify what they propose for Santo Antonio. I mean in Santo Antonio, the variation in arsenopyrite composition is due to alteration rims or to later growths.

Reply. To later growths.

From line 443 to 445. I do not understand what authors want to say with "…the ranges of temperatures for arsenopyrite from the second and third generations, respectively, which is supported by their respective chemical compositions."

5

Of course, temperatures are supported by chemical compositions since the arsenopyrite geothermometer is basis on arsenopyrite composition. I do not see the point of the above sentence.

Reply. They were removed. lines 468-469: "exsolution of Au from arsenopyrite and pyrite"??. The Au can be as nanoparticles in both sulfides instead of being structurally bound gold, so what do authors want to say with exsolution? I think that exsolution is not an appropriate term.

Reply. They were removed. line 470: the galena composition data should be present before the discussion (in section 5)

Reply. It is present before discussion.

- " orogenic formation for this deposit" it has no sense for me, it is clear that this deposit formed during the Variscan orogeny. "Orogenic formation for this deposit" is not the same as orogenic type deposit.

Reply. It was removed.

From 475 to 491: too much speculative, lacking of own data that support the statements, for example:

"One of the causes for ore deposition was probably pressure drop possibly triggered by seismic events…" - " orogenic formation for this deposit" it has no sense for me, it is clear that this deposit formed during the Variscan orogeny. "Orogenic formation for this deposit" is not the same as orogenic type deposit.

Reply. We have now write the following immediately before the first of this two quoted phrases:

The existence of aqueous carbonic fluids of different densities (Lc-w, Vc-w ad Lw-c fluid types) very close (some micra) each other suggest that…

Concerning the second quoted phrase we agreed to change Line 502 to

“… pressures (and depths) of entrapment are in accordance with an orogenic type deposit.”

From 508 to 511. H2S could be present in low contents in comparison with CO2, CH4 or N2, and not being detected by Raman. I think authors cannot state that S occurs as HS- y S2-

Reply. NOT AGREED because we put the statement very cautiously. We have written: “most probably have been present mainly as HS- and S2-.”

From 510 to 511: sulphur isotope compositions of hydrothermal S-bearing minerals is also controlled by PH and fO2.

Reply. AGREED: new phrase is (Lines 510-11) Sulphur isotope compositions of hydrothermal S-bearing minerals is controlled by the total sulphur isotope composition of the fluids, temperature, pH and fO2.

- I cannot understand this sentence: "However, the value for 34S for pyrite from Santo Antonio is lower than - 1.6‰ for this sulphide and that for arsenopyrite is higher than -9.2 to -7.1‰ for arsenopyrite from the Portuguese orogenic gold deposit of Limarinho…" It should be rewritten.

Reply. AGREED: new phrase is: 6

The sulphur isotopic composition of arsenopyrite and pyrite from the Au Limarinho deposit are only slightly negative then the average S isotopic composition from Penedono main sulphides.

- I think that this comparison (below) is inadequate, it can be omitted: "The 34S values obtained in the Santo Antonio mining area are within the range for those found in orogenic gold deposits from the Juneau gold belt of southeastern Alaska (-17.8 ‰ to 1.2 ‰; Goldfarb et al. 1991), but.."

Reply. NOT AGREED. Review does not refer why he/she thinks the phrase is inadequate.

We have established a comparison between two gold deposits, Juneau (considered an orogenic type Au deposit) with a wide range of 34S values, and Santo António where the range is much lower and we conclude suggesting that this may be due to a more homogeneous country rock chemistry, than in the case of Juneau.

Overall, in the discussion about S isotopic composition of the sulfides, the reader does not get a clear idea of which is the origin of the sulfur proposed by the authors in Santo Antonio.

Reply.

Add to Line 636 …

Considering the three most important reservoirs for sulphur [magmatic, marine and (meta)sedimentary] the 34S values for the studied sulphides at Santo António are compatible only with a metasedimentary source, which in turn strongly suggests that the sulphides belong to an orogenic gold deposit.

From line 585 to 587: it does not fit in this section, authors should move it to analytical methods.

Reply. It was removed to analytical methods.

From line 595 to 297. I cannot understand what authors want to say. I do not see the differences between the two main reservoirs: "surface water" and "of superficial origin".

Reply.

Line 594-595 we have eliminate the word “surface” One reservoir consisted of surface waters percolated into the basement through faults ……………

Line 597 the phrase is now: “The other reservoir was meteoric water.” instead of “The other reservoir was of superficial origin in the faults.”

From line 597 to 602: Authors should join what is said in this sentences with what is said before (from line 488 to 491) about causes of gold deposition.

Reply. Lines 597-602 :we have substitute the text by this :

Gold precipitation was probably linked to dilution by fluid mixing during the basement uplift as temperature and pressure drop, as proposed to explain several gold quartz veins from northwest Europe (e.g. Boiron 1996, 2001, 2003; Noronha et al. 2000; Vallance et al. 2003; Gómez-Fernández et al. 2012). Sudden pressure drops caused by seismic events, a mechanism first proposed by Sibson (1973, 1983, 1987, 1990) and Sibson et al. (1975) could also contribute to gold precipitation. The presence of microfractured sulphides could have enhanced gold precipitation through electrochemical processes (Boiron et al. 2003).

7

Section 8.5 The comparison to other deposits is poor, it is a repetition of what was said before and some sentences have no meaning, e.g.: "However, there are some differences when compared with the orogenic antimony-gold quartz veins: they do not contain antimony minerals…". Of course, this difference is obvious.

Reply. It was improved.

Line 657: Authors must explain what an orogenic source from fluids means. Fluids can have difference sources: meteoric, metamorphic, igneous, marine among others but I have never read anything about an orogenic source.

Reply. It was improved.

Lines 657 to 659

AGREED: new phrase is

“5) 34S mean values of arsenopyrite (-4.7‰) and pyrite (-3.8‰) are compatible with an ore-forming fluid of metamorphic and meteoric origin.”

8

Author’s Response to Reviewers‘ Comments Click here to access/download;Author’s Response to Reviewers‘ Comments;ANSWERS TO REVIEWER # 2.docx

1 Answers to the reviewer 2

2 Thank you very much for the comments.

3 1. Introduction – Does Ordovician outcrop in the area? You mention in the text but not in figures, only 4 Cambrian.

5 Reply. We maintain Cambrian-Ordovician metamorphic rocks, but removed the indication of figures from the 6 Introduction.

7 4. Paragenetic sequence of Santo António gold quartz veins – please see also in the text

8 What order you use to describe minerals? Is not clear

9 In each stage, indicating the minerals becomes more understandable

10 Reply. The order I used within each stage is from the oldest mineral to the youngest mineral. I do not like to 11 present first only some minerals.

12 4.1 Stage 1 (Ars1+..Au1+Elt1…

13 277 – you say “Arsenopyrite (Ars1) is frequent” Arseno 2 is also frequent so in paragenetic table the 14 distribution should be similar. Correct the length of bars; verify other minerals (see in text mod). You refer 15 minerals in micro-fractures but after we see in photos often they are in the space between grains.

16 Reply. I wrote that arsenopyrite 2 is abundant than is more than frequent.

17 4.2 Stage 2 (Ars2+Py2+Au2+Elt2……)

18 291 – you say “Bismuthinite is rare, anhedral, partially penetrated and surrounded gold (Au2) an electrum 19 (Elt2) grains” but than bismutinite should appear after Au2 and Elt2 in Table1.

20 Reply. Bismuthinite has inclusions of native bismuth. Therefore, it is after it in Table 1. The bismuthinite that 21 surrounds gold-silver alloy grains penetrated later and filled open spaces.

22 4.3 Stage 3 (quartz+Ars3+Py3+….)

23 300 – Colour of Q3? In line 361 you say very clear

24 300 – You say “Arsenopyrite (Ars3) is frequent, anhedral, replaces pyrite (Py2) (Fig. 6j) and is fractured” 25 Sure? In Fig. 6J arsenopyrite seems earlier as you refer in the paragene table 1. Is really a third generation?

26 Reply. Quartz is very clear light grey. Fig. 6j was replaced.

27 4.4 Late hydrothermal remobilization stage (Qu+Au4+covellite+…

28 309 – Here there is another generation of gold? Why you say is remobilization from Au2? Is it easy to 29 understand if is a remobilization of a certain early generation? Looking at the photo it can be Au2 and not a 30 remobilization. If you consider remobilization because it’s in scorodite why is Au2? Or you mean Au4? In 31 Table 1 your refer 4 generations of gold.

32 Reply. It is Au-Ag4 in Fig. 5l.

33 5. Chemical characteristics of minerals from the Santo António gold quartz veins

34 Appendixes C and D – Why not Tables 4 and 5?

1

35 “Arsenopyrites from the first generation (Ars1) are As-rich and S‐deficient. Arsenopyrite from thesecond (Ars2) 36 and third (Ars3) generations are As‐deficient and S‐rich. Very rare S‐rich and As‐deficient zoned….” Why not 37 to indicate the composition here? 38 342 – “Gold (Au1) and electrum (Elt1) occur within micro‐fractures of arsenopyrite (Ars1) (Fig. 6a)” occur in 39 space between grains.

40 Reply. Appendices C and D are now Appendices A and B. They contain mainly weathered products. 41 Furthermore, there are many tables. 42 I think that the compositions of arsenopyrite are not necessary as chemical analyses are given. 43 Spaces between grains was used for gold-silver alloy 1. 44 45 8. Discussion

46 8.1. Mineralogy and geothermometry

47 Did you apply the arsenopyrite geothermometer of Kretschmar and Scott (1976) and Sharp et al. (1985)? The 48 diagram should be insert as a figure. 49 Should mention Sundlab et al. 1984 for limits of Co, Ni and Sb. 50 You should compare the temperatures obtained from arsenopyrite geothermometer and from fluid inclusions.

51 Reply. The arsenopyrite geothermometer of Kretschmar and Scott (1976) and Sharp et al. (1985) was applied. 52 However, they are old diagrams that give only an estimation of temperature. Therefore, I think that the 53 diagram is not necessary. 54 The temperatures are compared with that from fluid inclusions later in the text. 55 56 538 –“…narrow range of -3.7‰ to -5.3 ‰ (Fig. 15)” Where are These data in Fig. 15? 57 Reply. You are wright; it is not Fig 15 but Fig. 13 58 59 8.4 Mineralizing environment and source of ore metals and metalloids

60 594 – “…peak of M2 metamorphism probably occurred between ca. 320 and 314 Ma. “- missing a reference, 61 no?

62 608 – “…way as recognized in other gold deposits in northwest Europe (e.g. Noronha et al. 2000; Boiron et al. 63 2003; Vallance et al. 2003)” – should add Couto et al. 2007

64 616 – “Gold precipitation was probably linked to dilution and fluid mixing during the basement uplift as 65 temperature and pressure drop, as proposed to explain several gold quartz veins from northwest Europe (e.g. 66 Boiron 1996, 2001, 2003; Noronha et al. 2000; Vallance et al. 2003….” should add Couto et al.1990

67 628 – “The decrease in temperature from 444ºC to 300ºC estimated through the evolution of arsenopyrite 68 composition, including the range of 380-360ºC recorded in fluid inclusions, and the decrease in pressure 69 provided favourable conditions for the gold deposition” – can you explain the difference?

70 Reply. The reference for the peak of metamorphism is Fig. 1D.

71 Couto et al. 2007 was added

72 Couto et al. 1990 was added

73 The difference in temperature is due to the fact that temperatures for arsenopyrite are estimated.

74 8.5. Comparison with other orogenic gold deposits in the Iberian Massif

75 637 – “Orogenic arsenopyrite-gold quartz veins are mainly hosted by granite, as in the Santo António mine 76 and also the Limarinho deposit, or by granites and metasedimentary rocks as in Jales and Gralheira, or less 2

77 commonly by metasedimentary rocks. Orogenic antimony-gold-quartz veins are hosted by 78 metasedimentary rocks as in Dúrico‐Beirão Mining District.” I would join Jales and Gralheira, and Dúrico 79 Beirão Mining District.

80 Reply. Jales and Gralheira were included.

81

82 9. Conclusions

83 672 - “However, a few gold grains filling fractures of the second arsenopyrite generation and late hydrothermal 84 remobilized gold present the highest Au content” can you explain this fact?

85 682 – “8) The depositions of gold and electrum took place during the decrease of temperature and pressure” 86 and remobilization gold?

87 Reply. I cannot explain it.

88 We have not information for temperature and pressure of remobilized gold-silver alloy.

89 Figures (some comments already mentioned above)

90 Missing the Kretschmar and Scott (1976) diagram.

91 Fig. 6 – 6a electrum seems to be more frequent in the grains contact than in microfractures; 6j – Ars3 seems 92 to be earlier than Py2. In photo it seems arseno crystals are involved by pyrite.

93 6g and h – Gus and Can also seems filling space between crystals of Ars2;

94 Fig. 7 – 7C write pyrite (as you have arsenopyrite and galena)

95 Table 1 – insert dashed lines to separate stages; rectify length of bars according the frequency of minerals.

96 Table 4 – 1, 2, 3 – stages of mineralization??

97 Table 7 – see suggestions

98 Reply.

99 Fig. 6a is now Fig. 5a. I agree.

100 Fig. 6j is now Fig. 5j. It was replaced.

101 Fig. 6g and h I agree.

102 Fig. 7 I agree

103 104 105 106 107 108 109 110 111

3

112 Figure 10. Fluid inclusion images of the three fluid types: Lc-w , Lw-c and Lw from gold quartz veins 113 of the Santo António mine. 114 Legend could be more complete - Lc-w type: aqueous carbonic fluids (H2O–CO2–CH4-N2–NaCl) 115 triphasic in the range 10-25ºC 116 117 Reply. New Fig.9 (former Fig. 10) captions is now: 118 119 Figure 9. Fluid inclusion images of the fluid types: Lc-w, Vc-w, Lw-c and Lw from gold-bearing quartz 120 veins of the Santo António mine. See 5.1 in the text for fluid type characteristics. Inclusions are in 121 the range 15-30 m. 122

123 124 125 126 127 Fig.14– 1062‐ Green arrows – you mean blue arrows? 128 129 Reply. Last phrase of Fig. 14 captions 130 131 “ Green arrows : probable PT path for the mineralizing fluid at the Santo António mine.” 132 133 Is now 134 “ Blue arrows : probable PT path for the mineralizing fluid at the Santo António mine.” 135 136 137 Table 1 The dashed line makes the figure with many lines

138 Table 7 was improved by Prof. Corfu.

4