Jean-Christophe Viennet
email: j.c.viennet@geo.uio.no

Benjamin Bultel
email: benjamin.bultel@geo.uio.no

Lucie Riu

Stephanie C Werner

Dioctahedral phyllosilicates versus zeolites and carbonates versus zeolites competitions as constraints to understanding early Mars alteration conditions

Keywords: 46 Mars, clay minerals, carbonates, zeolites, experiments, geochemical modeling 47

Dioctahedral phyllosilicates versus zeolites and carbonates versus zeolites competitions as constraints to understanding early Mars alteration conditions

Introduction

Among the various hydrated minerals detected by remote sensing instruments (such as: smectites (mainly Fe,Mg octahedral-rich), chlorites, kaolins, talc, serpentines and zeolites, in decreasing order of occurrence [START_REF] Carter | Hydrous minerals on Mars as seen by the CRISM and OMEGA imaging spectrometers: Updated global view[END_REF]), a particular interest has been devoted to the study of Fe,Mg-smectites. Indeed, their discovery on the Martian surface is a crucial observation because they could be an indicator for circum-neutral pH water activity, where a prebiotic chemistry could have been developed during the early Noachian [START_REF] Bibring | Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data[END_REF].

Hence, laboratory experiments [START_REF] Dehouck | Mineralogical record of the redox conditions on early Mars[END_REF][START_REF] Dehouck | Weathering of olivine under CO2 atmosphere: A martian perspective[END_REF][START_REF] Peretyazhko | Fe/Mg smectite formation under acidic conditions on early Mars[END_REF] and/or geochemical simulation [START_REF] Catalano | Thermodynamic and mass balance constraints on iron-bearing phyllosilicate formation and alteration pathways on early Mars[END_REF][START_REF] Chevrier | Early geochemical environment of Mars as determined from thermodynamics of phyllosilicates[END_REF][START_REF] Fernández-Remolar | The environment of early Mars and the missing carbonates[END_REF][START_REF] Griffith | A geochemical model for the formation of hydrothermal carbonates on Mars[END_REF][START_REF] Liu | Implications for the aqueous history of southwest Melas Chasma, Mars as revealed by interbedded hydrated sulfate and Fe/Mg-smectite deposits[END_REF] have been devoted to better understanding their formation. In particular, due to the Fe-rich Martian crust (compared to the Earth's) and the current oxidizing conditions, redox effects on the formation of Fe,Mgsmectites have been studied under conceivable early Martian environmental conditions. By using geochemical modeling, [START_REF] Chevrier | Early geochemical environment of Mars as determined from thermodynamics of phyllosilicates[END_REF] suggest that the presence of nontronite (Fe 3+ -rich smectite) could be the result of highly oxidizing conditions; while, [START_REF] Catalano | Thermodynamic and mass balance constraints on iron-bearing phyllosilicate formation and alteration pathways on early Mars[END_REF] argues for a primary alteration period under reducing conditions followed by an oxidizing period, leading to Fe 3+ -smectite formation. However, laboratory experiments [START_REF] Dehouck | Mineralogical record of the redox conditions on early Mars[END_REF] have shown that if early Mars had a dense CO2 atmosphere, highly oxidizing conditions would have strongly inhibited the formation of Fe,Mg-smectites and reducing conditions would have led to their formation. Moreover, a circum-neutral pH is sufficient to obtain Fe,Mg-phyllosilicates from volcanic rocks (especially basalt, Gysi and Stefánsson [2012a;2012c]), but not necessarily. Indeed, [START_REF] Peretyazhko | Fe/Mg smectite formation under acidic conditions on early Mars[END_REF] have experimentally demonstrated that the weathering of a chemically representative Martian basaltic glass, with a water at pH 4 under oxic or anoxic N2 atmosphere, leads to the formation of Fe,Mg-smectites. Finally, while our understanding of the early Martian atmosphere is dependent on our understanding of Fe,Mg-phyllosilicates (especially Fe,Mg-smectites), their formation conditions are too wide to provide enough constraints for a better understanding of the early history of Mars.

To a lesser extent, non-clay minerals associated with the Fe,Mg-phyllosilicates were observed on the Noachian Martian surface, such as carbonates [START_REF] Ehlmann | Orbital identification of carbonate-bearing rocks on Mars[END_REF][START_REF] Niles | Geochemistry of Carbonates on Mars: Implications for Climate History and Nature of Aqueous Environments[END_REF][START_REF] Wray | Orbital evidence for more widespread carbonate-bearing rocks on Mars[END_REF] and zeolites [START_REF] Carter | Hydrous minerals on Mars as seen by the CRISM and OMEGA imaging spectrometers: Updated global view[END_REF], see also section 2 of this paper). The presence of carbonates could be linked to an early thicker CO2-rich atmosphere [START_REF] Morse | The role of carbonates in the evolution of early Martian oceans[END_REF], which allows for the presence of liquid water (e.g., [START_REF] Pollack | The case for a wet, warm climate on early Mars[END_REF]). [START_REF] Brown | Hydrothermal formation of Clay-Carbonate alteration assemblages in the Nili Fossae region of Mars[END_REF] propose that the formation of carbonates results from hydrothermal alteration of basaltic rocks. The limits of carbonate formation in basaltic rocks on Earth has been investigated in both experimental and modelling studies (e.g., CO2 sequestration, [START_REF] Gysi | CO2-water-basalt interaction. Numerical simulation of low temperature CO2 sequestration into basalts[END_REF]2012a;b;[START_REF] Agee | Unique Meteorite from Early Amazonian Mars: Water-Rich Basaltic Breccia Northwest Africa 7034[END_REF][START_REF] Matter | Rapid carbon mineralization for permanent disposal of anthropogenic carbon dioxide emissions[END_REF]), but in Martian environments this is yet to be fully explored.

Indeed, geochemical simulation based on observations from altered Icelandic rocks Icelandic observations showed that hydrothermal alteration could be a source for carbonate formation and that at least one bar 1 bar of pCO2 could have been stored in the subsurface [START_REF] Griffith | A geochemical model for the formation of hydrothermal carbonates on Mars[END_REF]. The geochemical simulation of [START_REF] Chevrier | Early geochemical environment of Mars as determined from thermodynamics of phyllosilicates[END_REF] concluded that 1 bar of partial pressure of CO2 in oxidizing conditions could inhibit the formation of carbonates (while Fe,Mgsmectites will be formed). On the other hand, the experimental work of [START_REF] Dehouck | Mineralogical record of the redox conditions on early Mars[END_REF] showed that the formation of carbonates is possibly enhanced by highly oxidizing conditions under a dense CO2 atmosphere (from 0.8 up to 1.5 bars). Therefore, it is suggested that atmospheric conditions could have a strong influence on the formation of carbonates and/or Fe,Mg-phyllosilicates, and could be used as a probe to better understand the early Martian environment. In addition to carbonates, zeolite formation and stability are strongly dependent on the geochemical conditions (such as alkaline pH solution, [START_REF] Dyer | Natural Zeolites: Occurrences, Properties, Applications[END_REF]), and are therefore a good probe to investigate the Martian environmental conditions [START_REF] Ming | Zeolites on Mars: Possible environmental indicators in soils and sediments[END_REF]. Like clay minerals, zeolites are of prime importance, because they have a high potential for being major sinks of atmospheric gas [START_REF] Ming | Zeolites on Mars: Possible environmental indicators in soils and sediments[END_REF][START_REF] Mousis | Martian zeolites as a source of atmospheric methane[END_REF]., Tthey can sorb and protect organic compounds and act as a catalyst for organic-based reactions [START_REF] Ming | Zeolites on Mars: Possible environmental indicators in soils and sediments[END_REF][START_REF] Van Bekkum | The use of zeolites in organic reactions[END_REF][START_REF] Venuto | Organic catalysis over zeolites: A perspective on reaction paths within micropores[END_REF]. Although, zeolite formation in Martian environments has not been widely studied, links between carbonation and clay formation (mainly smectite) from basaltic rocks has already been observed in hydrothermal (natural and laboratory simulated) systems on Earth [START_REF] Dyer | Natural Zeolites: Occurrences, Properties, Applications[END_REF]Gysi and Stefánsson, 2012a;[START_REF] Agee | Unique Meteorite from Early Amazonian Mars: Water-Rich Basaltic Breccia Northwest Africa 7034[END_REF][START_REF] Kralj | Zeolites in volcanic-igneous hydrothermal systems: a case study of Pauzhetka geothermal field (Kamchatka) and Oligocene Smrekovec volcanic complex (Slovenia)[END_REF][START_REF] Stefánsson | Chemical Weathering of Basalts, Southwest Iceland: Effect of Rock Crystallinity and Secondary Minerals on Chemical Fluxes to the Ocean[END_REF][START_REF] Utada | Hydrothermal alteration envelope relating to Kuroko-type mineralization: a review[END_REF].

A review of zeolites detected on Noachian terrains is given in section 2, highlighting the associated minerals and probable geological processes. The aim of the present study is to investigate the formation of phyllosilicates/carbonates/zeolites by experimental work, in closed systems with various aqueous CO2 levels (100% N2, 10% CO2 / 90% N2, 100% CO2). Note that due to the use of closed systems, the purpose of this study is not an attempt at determining pCO2 level(s) of the Martian atmosphere. The cause and source of various aqueous CO2 levels could be driven by either atmospheric and/or magmatic interaction [as explained [START_REF] Brown | Hydrothermal formation of Clay-Carbonate alteration assemblages in the Nili Fossae region of Mars[END_REF][START_REF] Bultel | Deep alteration between Hellas and Isidis Basins[END_REF]. The various CO2 % are chosen to reflect 1 order of magnitude of CO2 content between each experiment. To better define this behaviour, we report on geochemical simulations constrained by the experimental results. Finally, the results obtained are used to evaluatebetter determine the environmental conditions during the early Noachian epoch. Compared to the sole investigation of clay minerals, shed new light on the importance of di/tri-Formatted: Subscript phyllosilicate/carbonate/zeolite formationdioctahedral clay minerals versus zeolites and carbonates versus zeolites competitions is used during the early Noachian epoch and to highlight the pH conditions during the alterationwill help to better determine the environmental conditions for such alteration products.

Martian Zeolites

Remote sensing detection of zeolites

In the near-infrared domain, sampled by instruments in orbit around Mars, zeolites have specific absorption bands near 1.20, 1.40, 1.90, 2.70-3.10 µm and one centered at 2.40-2.50 µm.

The latter is attributed to the cation-OH liaison while the others are attributed to structural water or absorbed water on its surface zeolites have specific absorption bands near 1.20, 1.40, 1.90, 2.70-3.10 µm, attributed to structural water or absorbed water on its surface, and at 2.40-2.50 µm, attributed to the cation-OH liaison [START_REF] Cloutis | Spectral reflectance properties of zeolites and remote sensing implications[END_REF]. The detection of zeolites on the Martian surface is usually confirmed by a combination of absorptions near 1.40 and 1.90 µm due to hydration, and reduced reflectance from 2.30 µm due to a large absorption centered near 2.50 µm. Except for analcime identified by its specific NIR feature, a ( band near 1.79 µm),, identification of other types of zeolites is challenging when mixed with hydrated minerals such as phyllosilicates. Indeed, the absorptions near 1.40 and 1.90 µm are common spectral bands among hydrated minerals. Therefore, no specific absorption can be attributed to zeolite if mixed with other hydrated minerals. However, the "zeolite background" spectrum is specific and, hence, zeolite detection is possible from the inflexion band after 2.30 µm. In addition to phyllosilicates, sulfates have a similar spectral shape with (bands near 1.90 and 2.50 µm). In this particular case, the geological context could be used as criteria to characterize the mineralogy. For example, the detection by proximity of monohydrated sulfates, kaolin, opal and nontronite suggest acidic environment, which is more favorable for sulfate than zeolite formation, as explained in [START_REF] Pajola | Eridania Basin: An ancient paleolake floor as the next landing site for the Mars 2020 rover[END_REF].

Formatted: English (United States)

Absence and controversial detection of zeolites

Unlike the main alteration products observed on the Martian surface such as(i.e. Fe,Mg clay minerals, carbonates, etc…), zeolites have not been reported in Martian meteorites [START_REF] Gooding | Soil mineralogy and chemistry on Mars: Possible clues from salts and clays in SNC meteorites[END_REF]; [START_REF] Tomkinson | Sequestration of Martian CO2 by mineral carbonation[END_REF]). Nevertheless, Martian meteorites may not be representatives of the main Martian alteration features [START_REF] Mcsween | What we have learned about Mars from SNC meteorites[END_REF]; therefore, the zeolite formation process cannot be understood from meteorites. [START_REF] Ruff | Spectral evidence for zeolite in the dust on Mars[END_REF] suggests that zeolite is a component of the dust on Mars from thermal infrared data. It could be an indication of a widespread zeolite presence on the Martian surface. Nevertheless, the zeolite presence in Martian dust is uncertain and disputed [START_REF] Bandfield | Spectroscopic identification of carbonate minerals in the Martian dust[END_REF]. Zeolites mixed with hydrated silica, opaline have also been suggested in the faulted region of Nili Fossae [START_REF] Ehlmann | Identification of hydrated silicate minerals on Mars using MRO-CRISM: Geologic context near Nili Fossae and implications for aqueous alteration[END_REF][START_REF] Viviano | Implications for early hydrothermal environments on Mars through the spectral evidence for carbonation and chloritization reactions in the Nili Fossae region[END_REF]), and at the bottom of stratigraphic profiles in Terby crater and Eridania Basin, with a sequence (from top to bottom: of Al-phyllosilicates, Fe,Mg-phyllosilicates and possibly zeolite with hydrated silica (opaline); [START_REF] Ansan | Stratigraphy, mineralogy, and origin of layered deposits inside Terby crater[END_REF]; [START_REF] Carter | Widespread surface weathering on early Mars: A case for a warmer and wetter climate[END_REF]; [START_REF] Carter | Mineralogy of Layered Deposits in Terby Crater, N. Hellas Planitia[END_REF]; [START_REF] Carter | Hydrous minerals on Mars as seen by the CRISM and OMEGA imaging spectrometers: Updated global view[END_REF]; [START_REF] Pajola | Eridania Basin: An ancient paleolake floor as the next landing site for the Mars 2020 rover[END_REF]). However, these detections remain uncertain because identification is based on the shape of spectra near 2.5 µm observed by the CRISM (Compact Reconnaissance Infrared Spectrometer for Mars (CRISM) spectra near 2.5 µm.

Reliable zeolite detections

Zeolites have been detected on crustal outcrops via CRISM Compact Reconnaissance Imaging Spectrometer for Mars (CRISM)CRISM data [START_REF] Ehlmann | Subsurface water and clay mineral formation during the early history of Mars[END_REF][START_REF] Sun | Ancient and recent clay formation on Mars as revealed from a global survey of hydrous minerals in crater central peaks[END_REF][START_REF] Viviano-Beck | Compositional and structural constraints on the geologic history of eastern Tharsis Rise[END_REF][START_REF] Wray | Diverse aqueous environments on ancient Mars revealed in the southern highlands[END_REF] together with Fe,Mg-rich phyllosilicates, hydrated silica or carbonates. We can now classify the different detections of zeolite by mineral associations. It is possible to distinguish three classes of zeolites based on their association with (i) Fe,Mg-phyllosilicates (Fe,Mg-smectites and/or chlorites) and hydrated silica; (ii) Fe,Mg-Formatted: English (United Kingdom)

Formatted: French (France)
phyllosilicates (Fe,Mg-smectites and/or chlorites) and carbonates; and (iii) only Fe,Mg-phyllosilicates (Fe,Mg-smectites and/or chlorites).

Near Nili Fossae, few craters excavated an association of zeolite (analcime), Fe,Mgphyllosilicates (mainly chlorite and possible prehnite) and hydrated silica [START_REF] Ehlmann | Subsurface water and clay mineral formation during the early history of Mars[END_REF].

The association of zeolites with Fe,Mg-phyllosilicates and carbonates is found in Valles Marineris (see [START_REF] Viviano-Beck | Compositional and structural constraints on the geologic history of eastern Tharsis Rise[END_REF]). Zeolites in association with only Fe,Mg-smectites and/or chlorite are found in impact craters or in valleys formed by tectonic activity [START_REF] Viviano-Beck | Compositional and structural constraints on the geologic history of eastern Tharsis Rise[END_REF]. No particular stratigraphy is related to these detections. Moreover, detections are concentrated on the spurs (lateral ridge on the wall of a valley) or on the re-entrant (terrain between two spurs) of the canyon [START_REF] Ehlmann | Identification of hydrated silicate minerals on Mars using MRO-CRISM: Geologic context near Nili Fossae and implications for aqueous alteration[END_REF][START_REF] Loizeau | Characterization of hydrated silicate-bearing outcrops in Tyrrhena Terra, Mars: Implications to the alteration history of Mars[END_REF][START_REF] Sun | Ancient and recent clay formation on Mars as revealed from a global survey of hydrous minerals in crater central peaks[END_REF][START_REF] Viviano-Beck | Compositional and structural constraints on the geologic history of eastern Tharsis Rise[END_REF][START_REF] Viviano | Implications for early hydrothermal environments on Mars through the spectral evidence for carbonation and chloritization reactions in the Nili Fossae region[END_REF]. In at least three craters where zeolite is found with Fe,Mg-phyllosilicates, few authors suggest that a possible prehnite detection could be present [START_REF] Ehlmann | Identification of hydrated silicate minerals on Mars using MRO-CRISM: Geologic context near Nili Fossae and implications for aqueous alteration[END_REF][START_REF] Sun | Ancient and recent clay formation on Mars as revealed from a global survey of hydrous minerals in crater central peaks[END_REF][START_REF] Viviano | Implications for early hydrothermal environments on Mars through the spectral evidence for carbonation and chloritization reactions in the Nili Fossae region[END_REF].

The detection of zeolites on Mars on crustal outcrops is therefore always associated with Fe,Mg-phyllosilicates (smectite and/or chlorite) and, in a few instances, with carbonates or hydrated silica. Note that, when analcime has been detected, no other zeolite types have been found nearby.

Possible process of formation

In cases of co-detection of zeolites, Fe,Mg-phyllosilicates and hydrated silica, the latter is found only on crater floors, while zeolites and phyllosilicates are found in both crater floors and the central structure. Their location could suggest post-impact hydrothermalism. Moreover, their detection in the ejecta layer, which would imply an alteration before the impact, is missing. In the case of zeolite detections exposed in the walls of Valles Marineris (assemblages ii and iii, see section 2.4), they do not represent a particular stratigraphy [START_REF] Viviano-Beck | Compositional and structural constraints on the geologic history of eastern Tharsis Rise[END_REF]. The authors suggest hydrothermal alteration of layers in the subsurface prior to the opening of the canyon. The presence of zeolites in impact craters together with Fe,Mg-phyllosilicates (with or without carbonates), are attributed to either hydrothermalism before or after the impact, or diagenesis [START_REF] Viviano-Beck | Compositional and structural constraints on the geologic history of eastern Tharsis Rise[END_REF][START_REF] Ehlmann | Identification of hydrated silicate minerals on Mars using MRO-CRISM: Geologic context near Nili Fossae and implications for aqueous alteration[END_REF][START_REF] Sun | Ancient and recent clay formation on Mars as revealed from a global survey of hydrous minerals in crater central peaks[END_REF]. However, the possibility of burial diagenesis seems unlikely since detection of the zeolite zonation (i.e. analcime to mordenite/clinoptilolite transformation) in the stratigraphy is lacking [START_REF] Hay | Occurrence of zeolites in sedimentary rocks: An overview[END_REF]. On the other hand, the zonation could also be below the resolution and the detectability of the instrument. Without a clear stratigraphic sequence unambiguously revealing zeolites, diagenesis, as well as surface weathering, are unlikely the source of zeolite formation on Mars. The most probable geological process resulting in the majority of zeolite detections could be hydrothermal systems, from ambient temperature to <200°C when prehnite is not present. This is in good agreement with the preferred alteration processes proposed for the alteration of the Noachian crust [START_REF] Carter | Hydrous minerals on Mars as seen by the CRISM and OMEGA imaging spectrometers: Updated global view[END_REF]].

Based on these surveys dedicated to zeolites and to the processes of formation of phyllosilicates and/or carbonates on Martian surfaces (see introduction), hydrothermal experiments have been set up to reproduce the main mineralogical assemblages described above (Fe,Mg-phyllosilicates/carbonates, Fe,Mg-phyllosilicates/zeolites). To do so, we set up closed system laboratory experiments for 3 weeks at 120°C with different percentages of CO2 to study the aqueous alteration of basaltic glass., and use gGeochemical simulations are used to decipher the pH conditions, especially water pH, controlling the minerals formation of minerals..

Materials & Methods

Starting material and sample preparation

The raw material used for this study is a volcanic basaltic glass of tholeiitic composition from Iceland (Stapafell, Reykjanes Peninsula). The pristine rocks were manually crushed and the fraction between 0.5 to 1 mm was collected by using sieves. The 0.5-1 mm size fraction was cleaned by washing the particles with deionized water in an ultrasonic bath. Then, the particles were immersed in hydrochloric solution at pH 3 for 1 hour to remove any possible carbonates and washed three times in distilled water. The millimetric particles were manually crushed in a mortar to decrease the particle size to sizes between 100 and 500 µm. Finally, the particle size (of less than 10 µm) used for the experiments was obtained by crushing the 100-500 µm size fractions using a micro-mill to obtain particles < 10 µm. The total chemistry of the final product was obtained by fusion and XRF analysis (Actlabs, Canada, Table 1). The chemical composition of the basaltic glass is in the range of the chemical composition range of Noachian Martian meteorites [START_REF] Agee | Unique Meteorite from Early Amazonian Mars: Water-Rich Basaltic Breccia Northwest Africa 7034[END_REF][START_REF] Lodders | A survey of shergottite, nakhlite and chassigny meteorites whole-rock compositions[END_REF], orbital [START_REF] Boynton | Concentration of H, Si, Cl, K, Fe, and Th in the low-and mid-latitude regions of Mars[END_REF] and in-situ analysis [START_REF] Gellert | Alpha Particle X-Ray Spectrometer (APXS): Results from Gusev crater and calibration report[END_REF][START_REF] Mcsween | Elemental composition of the Martian crust[END_REF][START_REF] Mcsween | Characterization and petrologic interpretation of olivine-rich basalts at Gusev Crater, Mars[END_REF][START_REF] Ming | Geochemical properties of rocks and soils in Gusev Crater, Mars: Results of the Alpha Particle X-Ray Spectrometer from Cumberland Ridge to Home Plate[END_REF] performed on the Martian surfaces.

Experimental set-up and procedure

The hydrothermal experiments were performed in closed systems at 120°C for a duration of 3 weeks in a 600 mL Parr Reactor ©. 4.0 g of the <10 µm size fraction was mixed with 80 ml of pure water and filled to the Parr reactor container leading to a gas head space of 520 ml at room temperature. The pure-water and head space were flushed for 10 minutes by injection of the desired gas into the reactors through two valves. Then the reactors were sealed and heated to 120°C. Three different high purity gases were used for the experiments: Nitrogen (100% N2), Carbon Dioxide (100% CO2) and a mixture of 10% CO2 and 90% N2, referred to as 10% CO2 / 90% N2 (with a CO2 content uncertainty of less than ±1%). Note that, the experiments are referred to by the percentage of the initial content of CO2 and/or N2.

Solid phase analysis

X-Ray diffraction analysis

On the bulk and altered rocks, X-Ray diffraction (XRD) patterns were recorded with a D8 Advance Bruker (CuKα1 + 2 radiations) from 2 to 55°2θ using a step interval of 0.25°2θ and a counting time per step of 2.5 s. The size of the divergence slit, the two Ssoller slits and the antiscatter slit were 0.25°, 2.5°, 2.5° and 0.5°, respectively. The bulk initial and final materials were analyzed on powder preparation. The clay minerals were analyzed by performing Ca-and K-saturation using four saturation cycles with 0.5 mol.L -1 of CaCl2 and 1 mol.L -1 of KCl, respectively. Then the solutions were washed in distilled water and dried at 50°C. The XRD patterns for clay minerals were recorded from oriented samples, prepared by pipetting slurries of the particles dispersed in distilled water on glass slides and drying these at room temperature. The Ca-preparations were analyzed after air-dried preparation (the associated acronym is Ca-AD).

Thereafter, the glass slides were exposed to ethylene-glycol vapor at 50°C overnight to obtain ethylene-glycol solvation; the subsequent XRD patterns recorded are referred to as Ca-EG. Heat treatments at 110°C, 330°C and 550°C were performed on the K-saturated glass slide preparations and the respective XRD patterns were recorded (referred to as K-110, K-330 and K-550, respectively). To obtain these XRD patterns for the different treatments, the slides were progressively heated over 4 hours stopping at each specific temperature to allow the slides to cool down to ambient temperature before XRD analysis was acquired.

Near Infra-red analysis

The near-infrared reflectance spectra were obtained with a PerkinElmer FTIR spectrometer. The wavelength range explored is from 1 to 4 µm with a spectral resolution of 1 cm -1 and a spectral sampling of 0.4 nm. On the bulk and altered rocks, the reflectance spectra were acquired on rock powder preparation under ambient temperature and pressure conditions.

Additionally, a calibration was carried out prior to the analysis to derive the samples reflectance spectra, using an Infragold and a Spectralon 99% sample from Labsphere.

Geochemical simulation

The aim of the geochemical simulation exercise is to reproduce the mineralogical association obtained during the experiments as a function of the initial gas composition for the same rock composition, temperature and water/rock ratio. The thermodynamic simulations were performed by using the EQ3/6, software version 8.0 [Wolery, 1992a;b;[START_REF] Wolery | Current Status of the EQ3/6 Software Package for Geochemical Modeling[END_REF].

Backward reactions are authorized (e.g. which means that the dissolution of the product is authorized). The thermoddem data base (http://thermoddem.brgm.fr/) was used to account for updated clay minerals and zeolite thermodynamic values compared to the data0.cmp database (see Table 2).(e.g., Fe-rich saponite (1 Fe atom in substitution of 1 Mg atom in the octahedral sheet), sudoite, sudoite(Fe), vermiculite, illite, phillipsite, clinoptilolite, heulandite, chabazite, mordenite and stellerite). Ideal solid-solutions were used during the geochemical exercise i n c l u d i n g t r i o c t a h e d r a l s m e c t i t e s ( s a p o n i t e C a -, N a -, K-, M g -s a t u r a t e d , F e -s a p o n i t e C a -, N a -, K-, M g -s a t u r a t e d ) ; d i o c t a h e d r a l s m e c t i t e s ( b e i d e l l i t e C a -, N a -, K-, M g -s a t u r a t e d , m o n t m o r i l l o n i t e C a -, N a -, K-, M g -s a t u r a t e d a n d n o n t r o n i t e C a -, N a -, K-, M g -s a t u r a t e d ) ; t a l c s ( M g -t a l c , m i n n e s o t a i t e ) ; p h i l l i p s i t e s ( p h i l l i p s i t e C a -, K-, N a -s a t u r a t e d ) ; The basaltic glass used during the experiments was also implemented in the database. The following structural formula of the basaltic glass Si1Al0.35Fe0.23Mg0.29Ca0.26K0.07Na0.01O3.345 was calculated from the total chemistry (Table 1) and it is similar to in accordance with previous studies using similar volcanic glass [START_REF] Aradóttir | Development and evaluation of a thermodynamic dataset for phases of interest in CO2 mineral sequestration in basaltic rocks[END_REF][START_REF] Gysi | CO2-water-basalt interaction. Numerical simulation of low temperature CO2 sequestration into basalts[END_REF]. The estimation of the log(K) values for the dissolution of the basaltic glass were based on a theoretical approach [START_REF] Paul | Chemical durability of glasses; a thermodynamic approach[END_REF], which considers the glass as oxide mixtures. Then, the solubility of the volcanic glass corresponds to the sum of the solubility products of the oxides weighted by the mole fractions. The values obtained (Table 1) are in good agreement with previous data on similar Icelandic volcanic glass [START_REF] Aradóttir | Development and evaluation of a thermodynamic dataset for phases of interest in CO2 mineral sequestration in basaltic rocks[END_REF].

To mimic the experimental procedure, we first saturate the water with the desired atmosphere. Therefore, wWe put in contact 80 grams (80 mlL) of pure water with the desired gas at 25°C and at atmospheric pressure. (The number of mol of gas was calculated by considering the volume of the head space in the reactor). Then, the aqueous solution and the atmosphere are heated in a closed system model until the experiment's nominal temperature (120°C) is reached.

ThereforeHence, , the total content of C (for the experiments involving CO2(g)) in the system is constant and similar to the experimental value. The last step of the geochemical simulation consists of mixing the 4 grams of basalt with the gas/water components and then letting the simulation reach equilibrium as a function of the mol of basalt destroyed (% of dissolution).

The numerical setup is slightly different compared with the experimental procedure. The original basalt is put in contact with the aqueous solution at 120°C during the simulation while For the experduring the experiments the original basalt is mixed with pure water at 25°C and then heated toat 120°C. However, this difference does not alter the simulated results compare to the experimental ones,. tThe slow reaction of basalt at this temperature, compared with the 1hour heating time (less than 1 hour) required to reach 120°C during the experiments, likely prevents alteration and minerals formation formation and no stable thermodynamical state can be reached during this period. The geochemical simulations take in account all the minerals present in the data base even if they are not in equilibrium in such pressure and temperature conditions. Hence,

In comparison, preliminary during the geochemical simulationsimulations were performed. Then, , minerals whichminerals, which are not assumed to form in such systems/environmentsconditions, are suppressed (see table 2). The final geochemical simulations corresponds to minerals formation possible in such temperature and pressure range.. Thus, although given in the database, minerals are suppressed if formed in much higher temperature and/or pressure ranges (e.g., prehnite, olivine, magnetite, biotite, graphite, wollastonite, amphibole and epidote) and in metamorphosed sediments (e.g., akermanite, monticellite and merwinite), as well as in lower temperature ranges (e.g., chabazite [START_REF] Blanc | Thermochimie -Sélection de constantes thermodynamiques pour les zéolites : version 2[END_REF]). In addition, the minerals which are already taken into account in the solid solution products are also suppressed, such as, dolomite, dolomite-ordered and disordered (carbonates solid-solution from calcite, magnesite to siderite) and mesolite (scolecite-natrolite solid-solution). Finally, the serpentines have not been considered because they are usually formed from olivine alteration.

Results

Experimental results

The To assess the rate of dissolution % of the volcanic glass, the full pattern fitting method [START_REF] Chipera | Fitting Full X-Ray Diffraction Patterns for Quantitative Analysis: A Method for Readily Quantifying Crystalline and Disordered Phases[END_REF] was applied. This method consists of determining the difference in area between the XRD peaks corresponding to both the original glass and the weathered sample. The results obtained show that 19, 23 and 25% of volcanic glass (±2%, uncertainty on laboratory mixture between basaltic glass and zinc) was dissolved during the experiments under 100% N2, 10% CO2 / 90% N2 and 100% CO2 initial gas mixtures, respectively. The intensities of the XRD peaks corresponding to forsterite, pyroxene and quartz do not display any differences between the unreacted basalt and all the weathered products. This means that they have not been weathered dissolved completely completely during the experiments.

For non-clay minerals, the XRD peaks at 3.02, 2.48 and 1.87 Å (Figure 1 [START_REF] Gaffey | Reflectance spectroscopy in the visible and near-infrared (0.35-2.55 µm)[END_REF][START_REF] Hunt | Spectral signatures of particulate minerals in the visible and near infrared[END_REF]). Note that, during the 100% N2 experiment no carbonate mineral was formed.

The XRD peaks at 7. 13, 4.94, 4.14, 4.06, 3.25, 3.13 phyllosilicates, such as, smectites and/or chlorites [START_REF] Bishop | Infrared spectroscopic analyses on the nature of water in montmorillonite[END_REF][START_REF] Clark | Material Absorption Band Depth Mapping of Imaging Spectrometer Data Using a Complete Band Shape Least-Squares Fit with Library Reference Spectra[END_REF][START_REF] Hunt | Visible and near-infrared spectra of minerals and rocks, I. Silicate minerals[END_REF].

The Brown, [1985]. In fact, the d(060) peak position is also dependent on the amount of Fe 3+ /Al 3+ substitution in the octahedral and/or tetrahedral sheets [START_REF] Baron | Influence of aqueous Si and Fe speciation on thetrahedral Fe(III) substitutions on nontronites: a clay synthesis approach[END_REF][START_REF] Iriartre | Synthesis of Kaolinite with a High Level of Fe3+ for Al substitution[END_REF][START_REF] Petit | Hydrothermal (200°C) synthesis and crystal chemistry of iron-rich kaolinites[END_REF][START_REF] Petit | Hydrothermal synthesis of dioctahedral smectites: The Al-Fe3+ chemical series[END_REF]. Depending on the Fe 3+ /Al 3+ content (both octahedral and/or tetrahedral), the d(060) could reflect the position of trioctahedral clay minerals (~1.54 Å, Brindley and Brown, [1985]), while only dioctahedral clay minerals are present [START_REF] Petit | Hydrothermal synthesis of dioctahedral smectites: The Al-Fe3+ chemical series[END_REF]. NIR analysis is also less affected by the difference in crystallinity of the clay minerals formed than XRD analysis. Additionally, non-clay minerals calcite, forsterite and quartz present XRD peaks in the range of the 060 peaks analysis, complicating interpretation.

For the 100% N2 experiment ( layer of Fe(II) rich chlorite below 550°C; Barnishel and Bertsch, [1989]). However, the infra-red spectra do not exhibit the characteristic bands of kaolinite (at 2.16 and 2.2µm, [START_REF] Bishop | Reflectance and emission spectroscopy study of four groups of phyllosilicates: smectites, kaolinite-serpentines, chlorites and micas[END_REF]);. In addition, therefore, no kaolinite layers are present in these samples. Tthe absorption bands at 2.35 µm are more pronounced with the CO2 % increase and disappear after heating at 550°C (sSee supplementary Figure S2). This band could be linked to (Fe,Mg)3-OH liaisons of Fe-rich trioctahedral chlorite [START_REF] King | Spectral characteristics of chlorites and Mgserpentines using high-resolution reflectance spectroscopy[END_REF]. Note that, this XRD and NIR behavior could not be attributed to serpentine (while the XRD peak position could correspond to serpentine) because its dehydration temperature is at 600°C [START_REF] Dlugogorski | Dehydroxylation of serpentine minerals: Implications for mineral carbonation[END_REF].

Therefore, from the XRD behavior and the 2.35 µm NIR bandanalysis, this clay mineral constitutes is mainly a Fe-rich chl ori t e/ smect i t e MLM wi t h a l ow amount of smect i t e l ayers. l ayers. Fi nal l y, t hi s mi neral i s an Fe-ri ch t ri oct ahedral chl ori t e/ smect i t e MLM wi t h mi nor smect i t e l ayersThe, and i t s rel at i ve amount cont ent of such MLM, compared to the trioctahedral smectite, content for the 100% N2 experiment, increases with the CO2 %. In addition with the CO2 % increase, the dioctahedral character of the clay minerals is increasingly pronounced and can be assessed by the NIR analysis. The due to the intensity intensities increase of the 2.19 and 2.25 µm spectral band (Figures Table 32 presents the summary of minerals formed during the experiments. The results obtained show that zeolites formed without carbonate formation for the 100% N2 experiment, while carbonates without zeolites are formed under experiments involving CO2. Moreover, with the increase in CO2 levels, the trioctahedral smectite/chlorite MLM content decreases, while the dioctahedral MLM increases. In addition with the increasing CO2 levels, the relative content of trioctahedral smectite layers decreases relative toin favor of the Fe-rich trioctahedral chlorite, with increasing CO2 levels. Note that, zeolite mineral formation during the 100% N2 experiment cannot be observed by NIR analysis, but XRD analyses confirms its presence.

2.III

Geochemical model results

To better understand the mechanism leading to mineral formation as a function of gas composition, geochemical modeling was performed and constrained by the experimental results

(for more details see section 3.4, materials and methods).

At firstIn a first time, the geochemical simulations are run until the given dissolution basaltic glass % estimated by XRD is reached. This solution has been chosen rather than a Formatted: Subscript kinetics method in order to avoid any limitation due to clay minerals, carbonates and zeolites formation, which lead to a decrease of the dissolution rate of the basaltic glass (sSee for example, [START_REF] Stockmann | Dissolution of diopside and basaltic glass: the effect of carbonate coating[END_REF]). Then, Tthe results obtained from the geochemical modeling are presented at the corresponding percentage of glass dissolution determined by XRD for each experiment (see section 4.1)results and are compared to the mineral identification results (Table 32). The aim is to compare mineral formation between the experimental results and the geochemical simulation, in order to confirm that the results obtained by the geochemical simulations are coherent with the experiments. The clay minerals identification has shown that their crystal structure constitutes sa stacking of layers with different natures (mixed-layerminerals). Nevertheless, the geochemical simulation does not take into account the formation of these MLMs. Indeed, even if solid-solution products ((same layer nature but different interlayer cations)) are authorized, it does not simulate mixed-layer minerals. Therefore, clay mineral identification (Table 2 and32) is split into two families, the di-and tri-octahedral phyllosilicates.

The dioctahedral phyllosilicates formed during the simulations consist of the sum of montmorillonite (mainly (Mg,Ca)0.165Mg0.33Al1.67Si4O10(OH)2), nontronite (mainly (Mg,Ca)0.165Fe2Al0.33Si3.67O10(OH)2), dioctahedral chlorite (Fe,Mg)2Al4Si3O10(OH)8 and kaolinite (Al2Si2O5(OH)4). The trioctahedral phyllosilicates formed during the simulations correspond to the sum of saponite (mainly (Mg,Ca)0.165Mg3Al0.33Si3.67O10(OH)2), trioctahedral chlorite (Fe,Mg)5Al2Si3O10(OH)8 and talc (Fe3Si4O10(OH)2). Due to the lack of garronite in the geochemical database, the zeolites considered and that appear during the geochemical simulation are mainly gismondine (Ca2Al4Si4O16:9H2O) and, to a lesser extent, phillipsite ((Na,Ca0. 5)1AlSi3O8:3H2O). Gismondine, phillipsite and garronite belong to the group of zeolites with chains of edge-sharing four-membered rings [START_REF] Dyer | Natural Zeolites: Occurrences, Properties, Applications[END_REF]. In particular the gismondine, which is the zeolite mainly formed during the geochemical simulation, has the same subgroup structure type as the garronite: the GIS group. Moreover, the structural formula of garronite Formatted: Font: Italic (Ca2.5NaAl6Si10O32:13H2O) is similar to that of gismondine and phillipsite zeolites (in terms of cation content). In addition, the Si/Al ratio of garronite is comprised between the Si/Al ratio for gismondine and phillipsite zeolites (1 for gismondine, 3 for phillipsite and ~1.7 for garronite).

Therefore, even if the garronite zeolite is not thermodynamically documented, the choice of simulating its formation with gismondine and phillipsite is coherent.

The geochemical simulation results show that the same minerals formed during the experiments were simulated during the geochemical exercise (Table 23). The characterization of the carbonates formed is the same (e.g., calcite under 10% CO2 / 90% N2 and solid-solution of Ca/Mg/Fe carbonate under 100% CO2). Note that at the end of the experiment, the final pCO2 obtained by the geochemical simulation in the experiments with initial gas mixture of 100% CO2 and 10% CO2 / 90% N2 (calculated from the geochemical modeling results) are equal to 0.79 and 0, for initial gas mixture of 100% CO2 and 10% CO2 / 90% N2 respectively. Zeolite is formed for the 100% N2 experiment in both the geochemical simulation and the experiments. ; while fFor the 10% CO2 / 90% N2 experiment, a minor amount is estimated during the geochemical simulation while, no zeolite is observed during the experimentthis is not the case for the experimental part.

Nevertheless, the amount estimated is low relative to the other minerals (1%). If zeolite was formed duri ng t he experi ment s, i t coul d expl ai n why i t has not been det ect ed by XRD and NIR. The geochemi cal si mul at i on coul d overest i mat e t he zeol i t es format i on and a l onger experi ment time will have led to their formation. Concerning geochemical simulation of the clay minerals, as for the experimental results mainly trioctahedral clay minerals are predicted (as for the experimental results) for the 100% N2, experiment while mainly dioctahedral phyllosilicates are predicted and observed in the experiments during the experiments involving CO2. More generally, the same overall trends are obtained between the experiments and the geochemical simulation. Indeed, with the CO2 % increase, the amount of trioctahedral phyllosilicates decreases and the inverse trend is observed for the dioctahedral minerals. In the same manner, the CO2 % increase leads to a decrease in zeolite content and an increase in carbonates formation. The pH values at the end of the experiments obtained by geochemical simulation are 6.3, 7.8 and 10.1

for the 100% CO2, 10%CO2 / 90% N2 and 100% N2 experiments, respectively. The final pH values decrease with the increase of initial CO2 %. To conclude, while there are noticeable differences between the geochemical simulation and the experimental results, the same general trends are observed with CO2 % increase, which confirms the constraints, used and validates the geochemical simulation.

Discussion

pH, a key to understanding mineral formation competition

The hydrothermal alteration of the tholeiitic volcanic glass, performed in this work, produced phyllosilicatesclay minerals (di-and/or tri-octahedral, depending on the experimental conditions), carbonates (with CO2) and zeolites (initially CO2-free). The minerals formed are in line with previous experiments performed on tholeiitic basalt. Reaction products obtained from experiments with various pCO2 (from 1 to 35 bars) at various temperatures (from ambient to 250°C) on volcanic glass, contain trioctahedral smectites, chlorites, talc, carbonates and zeolites [START_REF] Declercq | Experimental alteration of artificial and natural impact melt rock from the Chesapeake Bay impact structure[END_REF][START_REF] Gysi | CO2-water-basalt interaction. Numerical simulation of low temperature CO2 sequestration into basalts[END_REF]2012a;b;[START_REF] Agee | Unique Meteorite from Early Amazonian Mars: Water-Rich Basaltic Breccia Northwest Africa 7034[END_REF][START_REF] Hellevang | Can alteration experiments on impact melts from El'gygytgyn and volcanic glasses shed new light on the formation of the Martian surface?[END_REF][START_REF] Stefánsson | Chemical Weathering of Basalts, Southwest Iceland: Effect of Rock Crystallinity and Secondary Minerals on Chemical Fluxes to the Ocean[END_REF]. The experimental conditions have been chosen to better understand the key parameters driving zeolite and/or carbonate formation with trioctahedral minerals as observed on Mars [START_REF] Viviano-Beck | Compositional and structural constraints on the geologic history of eastern Tharsis Rise[END_REF]; [START_REF] Wray | Orbital evidence for more widespread carbonate-bearing rocks on Mars[END_REF] and section 2 of this study). The initial experimental conditions have a strong influence on whether such minerals form and the relative amounts produced (Table 23). In order to grasp the factors involved in these mechanisms of formation, geochemical modeling has been applied in this work.

Figure 3 presents the results of the geochemical modeling. The, predicted mineral formed (in mol) by the simulation (mineral in equilibrium with the aqueous solution during the dissolution of the basaltic glass) and the percentage of dissolution (mol of basaltic glass dissolved divided by the initial mol of basaltic glass) are plotted as a function of pH. We consider As,,pH which is a key parameter to understand the formation of these minerals from the weathering of tholeiitic volcanic rock [Gysi and Stefánsson, 2012a;[START_REF] Stefánsson | Chemical Weathering of Basalts, Southwest Iceland: Effect of Rock Crystallinity and Secondary Minerals on Chemical Fluxes to the Ocean[END_REF]. Figure 3 represents the evolution of the minerals formed (solid lines) as a function of pH for closed systems (atmosphere and aqueous solution are not renewed during the simulation). The mineral predicted and dissolutionse evolutions vary between the experiments. This is driven by and the % of dissolution (dashed grey lines) due to the decrease of the CO2 content in the available headspace gases (carbonation) and due to the release of the chemical elements from the dissolution of the basaltic glass. The presence of CO2 in the aqueous solution and in the head space controls the pH of the aqueous solution, due to the dissociation of aqueous CO2 into HCO3 -+ H + . Therefore, the increase of the initial CO2 % leads to a decrease of the initial pH (Figure 3), with pH (6, 4.8, 4.3 for the 100% N2, 10% CO2 / 90% N2 and 100% CO2 simulations, respectively). During the basaltic glass dissolution (represented by the % of dissolution, dotted grey lines, Figure 3), the CO2 present in the aqueous solution and in the head space are consumed by the carbonation as a consequence the aqueous pH increase. The ( final pCO2 calculated from the geochemical modelling results are equal at 0.32 and 0 for the 100% CO2 and 10% CO2 / 90% N2, respectively; the pCO2 were calculated from the geochemical modelling results).

During carbonation (Fig. 3.I and II), di-and tri-octahedral phyllosilicates are formed with a pH <~7.2, while when pH >~7.2 (after 12% of dissolution for 10% CO2 / 90% N2 and 100% N2 simulation Figures 3.II Indeed, tThe increase in zeolite formation is due to both the availability of Ca 2+ and due to the decrease in formation of carbonates, which is accompanied by a pH increase (due to carbonation) until pH ~7.2. That pH dependency has already been suggested as a key factor to understand zeolite formation. In fact, [START_REF] Burriesci | Factors affecting formation of zeolite a from alumino-silicate gels[END_REF] argue that pH is a more important factor than time and temperature. Moreover, as observed on soil on Earth, zeolite minerals are generally described in neutral to basic soils [START_REF] Ming | Zeolites in soil environments[END_REF][START_REF] Ming | Zeolites in Soils[END_REF]]. Reciprocally, zeolites can be dissolved from soil samples by using acid treatments [START_REF] Ming | Zeolites in soil environments[END_REF]. Moreover, it is also described during the weathering process of basaltic glass by geochemical modeling: a pH above 6.5 at 45°C leads to the formation of zeolite [Gysi and Stefánsson, 2012a]. Indeed, the pH increase leads to the deprotonation of H4SiO4(aq) into H4SiO3 -and H4SiO2 2-and to high cation/H + ratios that are needed for the formation of zeolite minerals [START_REF] Chipera | Geochemical Stability of Natural Zeolites[END_REF][START_REF] Ming | Zeolites in soil environments[END_REF][START_REF] Mora-Fonz | Modeling Aqueous silica Chemistry in Alkali Media[END_REF].

Conversely, dioctahedral phyllosilicates are formed with pH <~7.2 in disfavor of zeolites (Figure 3, Table 23). This pH dependency could be a consequence of the incorporation of aluminum and silica to build the framework of dioctahedral phyllosilicates and zeolites. The similarity between zeolites and dioctahedral minerals are their structural formulae, notably regarding the Formatted: Superscript predominance of Si and Al. Even if no further explanation can be drawn from our study, it seems that the silica and aluminum in solution plays a key role in mineral formation: pH <~7.2 lead to dioctahedral phyllosilicates, while pH >~7.2 conditions lead to zeolites.

Moreover, tThe formation of trioctahedral smectite clay minerals dedicated to Martian environments does not appear to have strong pH dependency.; They can be formnedit is possible to form these from both acidic and basic conditions (pH 4 in, [START_REF] Peretyazhko | Fe/Mg smectite formation under acidic conditions on early Mars[END_REF], basic)

and basic conditions [START_REF] Tosca | Smectite formation on early Mars: Experimental constraints[END_REF], both Gysi and Stefánsson [2012a]). Nevertheless, for the same temperature and alteration time, the content of Fe-rich trioctahedral chlorite increases relative to the content of trioctahedral smectite with the increase of CO2 % and /or acidity (source of acidity could come from other aqueous species in the solution). . The source of acidity could either come from atmospheric gases or aqueous solution. Finally, the ratio between di-to trioctahedral minerals decreases with the pH increase and is therefore a good indicator of alteration conditions.

The intrinsic parameter, which seems to govern the competition of formation between dioctahedral phyllosilicates/ versus zeolites and carbonates/ versus zeolites, is pH. When the pH is <~7.2, dioctahedral clay minerals are favored; while, when the pH is above 7.2, zeolites are formed in disfavor of dioctahedral clay minerals. The competition between di-and tri-octahedral phyllosilicates/carbonates/zeolites competition formation is a probe of the pH evolution of the weathered solution. The association of dioctahedral phyllosilicates with carbonates will be an indicator of acidic conditions, while the association of trioctahedral phyllosilicates with carbonates will be an indicator of a fluid that could be acidic to < ~7.2. The indicator of basic conditions is the association between trioctahedral phyllosilicates and zeolites. As consequence, Formatted: Font: Italic the association with trioctahedral phyllosilicates, carbonates and zeolites will indicate that the weathering fluid has passed through pH =~7.2.

Martian implications

The results of this study are likely more relevant to understanding alteration by hydrothermal fluids with different CO2 % content rather than the impact of total atmospheric CO2 levels. In closed system experiments, the CO2 in the gas-head space is consumed during the experiment. and tHence, the CO2 levels herefore do es not necessarily represent a CO2 partial pressure change, as suggested for the early Mars atmosphere evolution, because the real atmosphere would buffer this level. Nevertheless, cCo-occurrence of carbonates and/or zeolites with trioctahedral phyllosilicates has been observed on Martian Noachian crust [START_REF] Viviano-Beck | Compositional and structural constraints on the geologic history of eastern Tharsis Rise[END_REF]; J. J. [START_REF] Wray | Orbital evidence for more widespread carbonate-bearing rocks on Mars[END_REF] and section 2). The geological formation process for such mineral assemblages has putatively been assigned to hydrothermalism [START_REF] Brown | Hydrothermal formation of Clay-Carbonate alteration assemblages in the Nili Fossae region of Mars[END_REF][START_REF] Ehlmann | Subsurface water and clay mineral formation during the early history of Mars[END_REF][START_REF] Niles | Geochemistry of Carbonates on Mars: Implications for Climate History and Nature of Aqueous Environments[END_REF][START_REF] Viviano | Implications for early hydrothermal environments on Mars through the spectral evidence for carbonation and chloritization reactions in the Nili Fossae region[END_REF]. The hydrothermal experimental results obtained during this study are in line with previously discussed Martian observations (Figure 1 and 2 and Table 23). Indeed, these two mineralogical assemblages have been formed

during the experiments under 100% N2 and 10% CO2 / 90% N2.

The source of CO2 levels in the hydrothermal fluids cannot be determined from this study, but it could come from either the Martian atmosphere or magma [START_REF] Brown | Hydrothermal formation of Clay-Carbonate alteration assemblages in the Nili Fossae region of Mars[END_REF][START_REF] Bultel | Deep alteration between Hellas and Isidis Basins[END_REF]. The hydrothermal experiments and their geochemical modeling show the strong link between the formation of carbonates and zeolites during hydrothermal alteration in the presence of CO2. Due to the occurrence of trioctahedral phyllosilicates/carbonates and trioctahedral phyllosilicates/zeolites at different conditions, a counter relationship between these two assemblages (Al-phyllosilicates/zeolites and carbonates/zeolites) could certainly have existed during early Mars. Thus, these reaction products can be used as an indicator for environmental conditions due to the constraint given by their formation limits. Therefore, the observation of trioctahedral phyllosilicates and zeolites on the Martian crust [START_REF] Ehlmann | Identification of hydrated silicate minerals on Mars using MRO-CRISM: Geologic context near Nili Fossae and implications for aqueous alteration[END_REF][START_REF] Viviano-Beck | Compositional and structural constraints on the geologic history of eastern Tharsis Rise[END_REF] is an indicator of an alteration with an aqueous solution from a pH > ~7.2, while the occurrence of trioctahedral clay minerals and carbonates is an indicator of slightly acidic to ~7.2. Trioctahedral phyllosilicates associated with carbonates and zeolites were observed in Valles Marineris [START_REF] Viviano-Beck | Compositional and structural constraints on the geologic history of eastern Tharsis Rise[END_REF] and impact craters [i.e. [START_REF] Sun | Ancient and recent clay formation on Mars as revealed from a global survey of hydrous minerals in crater central peaks[END_REF]. This mineralogical association is an indicator that the aqueous solution has passed through a pH value of ~7.2 during the alteration process and perhaps in a closed hydrothermal system.

The formation of trioctahedral phyllosilicates characterizes the major part of the Martian weathered surface/outcrops formed in the Noachian by [START_REF] Bibring | Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data[END_REF]. However, here we demonstrated that, with the wide range of aqueous CO2 levels present during the experiments and used in the geochemical simulations, trioctahedral phyllosilicates have never been formed alone.

Different studies without CO2 involved have been able to produce trioctahedral minerals byfrom the hydrothermal alterationism of a volcanic glass and have pointed out that specific acidic conditions (experiments using rock of basaltic composition, constant pH equal to ~4, [START_REF] Peretyazhko | Fe/Mg smectite formation under acidic conditions on early Mars[END_REF]) are needed to form only trioctahedral minerals. Therefore, the widespread presence of trioctahedral phyllosilicates (mainly smectitic) on Martian crust could imply acidic conditions instead of a circum-neutral pH [START_REF] Bibring | Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data[END_REF][START_REF] Peretyazhko | Fe/Mg smectite formation under acidic conditions on early Mars[END_REF]. Nevertheless, the identification of zeolite when mixed with trioctahedral phyllosilicates (see section 2 of this study), is difficult by NIR analysis. Therefore, the confirmation of the presence/absence of zeolites (notably by lander/rover equipped with XRD, such as that on board the MSL mission)

with the widespread presence of trioctahedral phyllosilicates [START_REF] Bibring | Global mineralogical and aqueous mars history derived from OMEGA/Mars Express data[END_REF] Interestingly, when the percentage of aqueous CO2 increases and consequently the pH decreases, the content of trioctahedral chlorite increases in disfavor of the trioctahedral smectite content (Figure 1 and 2). The observation on the relative content of chlorite compared to smectite as a function of depth [START_REF] Bultel | Deep alteration between Hellas and Isidis Basins[END_REF]; [START_REF] Carter | Hydrous minerals on Mars as seen by the CRISM and OMEGA imaging spectrometers: Updated global view[END_REF]; [START_REF] Loizeau | Characterization of hydrated silicate-bearing outcrops in Tyrrhena Terra, Mars: Implications to the alteration history of Mars[END_REF]; [START_REF] Sun | Ancient and recent clay formation on Mars as revealed from a global survey of hydrous minerals in crater central peaks[END_REF]) could not only be related to burial diagenesis on Mars [START_REF] Sun | Ancient and recent clay formation on Mars as revealed from a global survey of hydrous minerals in crater central peaks[END_REF],

but also to fluid composition during hydrothermal alteration. Further experiments dedicated to this transformation using infrared and XRD characterization of the smectite/chlorite relative amounts in MLM will bring more constraints to the processes which led to this specific observation.

Conclusion and remarks

In the present study, we have investigated the di/tri-octahedral clay minerals/carbonates/zeolites relationship to better understand the early aqueous alteration in Martian history. IndeedOn Mars, widespread occurrence of Fe,Mg-phyllosilicates have been observed by remote sensing instruments on Noachian terrains. Experimental investigations had shown that their conditions formations could be widespread in terms of pH range, oxic/anoxic conditions, etc... Thus, the present study is dedicated to better constraint the formation conditions of clay minerals by using other minerals found in association with them on the Martian surface.

While Fe,Mg clay minerals are the main minerals observed, ccarbonates and zeolites were also Moreover,Finally, trioctahedral clay minerals and zeolites are formed with a pH >~7.2.

Moreover,In addition, the results obtained here show that the relative content of trioctahedral chlorite compares to trioctahedral /smectite increase with de decrease of acidity.

Formatted: Indent: First line: 1.27 cm Hence, the relative content of chlorite and smectite could not only have been related to burial diagenesis, but may also be a result of differing acidic fluids. More experiments and geochemical modeling using different fluids or /atmosphere compositions (rich in SO2, for example) will help to better define the mineral competition behavior and, therefore, to grasp the aqueous and alteration processes of early Mars. Tables Table 1: Total chemistry in oxides, the related calculated structural formulae and the Log(K) values of the original basalt used in the present study.

Figure caption

Oxides

  t r i o c t a h e d r a l c h l o r i t e s ( d a p h n i t e , c l i n o c h l o r e ) ; d i o c t a h e d r a l c h l o r i t e s ( s u d o i t e , s u d o i t e ( F e ) ) ; n a t r o l i t e g r o u p o f z e o l i t e s ( s c o l e c i t e , n a t r o l i t e ) ; c l i n o p t i l o l i t e s ( c l i n o p t i l o l i t e C a -, N a -, K-s a t u r a t e d ) ; a n d h e u l a n d i t e s ( h e u l a n d i t e C a -, N a -s a t u r a t e d ) . T h e f o r m a t i o n o f c a r b o n a t e s w a s s i m u l a t e d b y u s i n g a s o l i d -s o l u t i o n o f m a g n e s i t e , c a l c i t e a n d s i d e r i t e .

  and 1.75 Å), the stars at 4.26 and 3.33 Å correspond to quartz (Figure 1.I.a, stars at 4.26 and 3.33 Å) and the diamonds at 3.20 and 2.99 Å correspond to a minor amount of pyroxene (Figure 1.I.a, diamonds at 3.20 and 2.99 Å). The volcanic glass and quartz minerals have no specific absorption bands in this NIR range, which lead to a high intensity band corresponding to olivine and low-calcium pyroxene (LCP) (Figure 1.II.a, at 1.07 and 1.85 µm, respectively) [Hunt and Salisbury, 1970]. The large spectral band at around 2.90 µm corresponds to H2O molecules present in the sample probably adsorbed on the edges of the basaltic particles (Figure 1.II.a). All XRD patterns obtained on the reacted materials show a decrease in the broad peak intensity (Figure 1.I.b, c and d) corresponding to the volcanic glass (Figures 1.I.a). These intensity decreases indicate that the initial glass was dissolved and that minerals were formed during the experiments (Figure 1.I). (corresponding to the appearance of XRD peaks indexed by their position in Å on the XRD patterns, figure 1.I, and the indexed spectral band in µm, figure 1.II).

  .I.b) indicate the presence of Ca-Mg-Fe carbonate for the 100% CO2 experiment while for the 10% CO2 / 90% N2 experiment, the XRD peaks at 3.85, 3.04, 2.49, 2.09, 1.93, 1.91 and 1.88 Å (Figure 1.I.c) correspond to calcite. The NIR spectra confirm the presence of carbonates, due to the spectral band at 3.85 and 3.98 µm corresponding to the C-O liaison (Figure 1.II.b and c,

  and 2.67 Å correspond to the formation of garronite zeolite for the experiment under 100% N2 (Figure 1.I.d), while no zeolite is formed in experiments involving CO2 gas (Figure 1.I.b and c). There is no evidence of a characteristic zeolite band from the NIR analysis. This could either be due to low proportions relative to the trioctahedral phyllosilicates, and/or due to overlapping of the characteristic spectral bands for phyllosilicates and zeolites. Indeed, the bands near 1.41 µm and at 1.91 µm correspond to the bending and stretching overtone of bound water, and between 2.19 -2.5 µm to cation-OH liaison (Figures 1.II.b, c and d). The combination of bands at 2.76, 2.90 and 3.07 µm (Figures 1.II.b, c and d) corresponds to OH fundamental stretching and H2O stretching in di/tri-octahedral

  presence of clay minerals can be confirmed by the bulk XRD patterns due to the presence of 00l reflections at 15.09 and 2.57 Å (Ffigures 1.I.d c and b), at 7.35 and 2.39Å under 10% CO2 / 90% N2 and 100% CO2 experiments (Ffigures 1.I.b and c, respectively); as well as 020 reflections at 4.57 Å (Figures 1.I.b, c and d). No evidence of rational series of 00l reflections (l×00l is constant for all the reflections) was seen; therefore, clay minerals present in the samples are mainly mixed layer minerals (MLM). More detailed identification of clay minerals present in the samples after the experiments, was performed using conventional XRD treatments (sSee section 3.3.1 and Ffigures 2.I and II) and by removing the continuum of the spectral data to highlight the absorption band intensities (Figure 2.III). The determination of the di/tri-octahedral characters of the minerals formed are based on the NIR analysis and not on the XRD patterns dedicated to the d(060) peaks (see supplementary FigureS1). Indeed, the XRD patterns dedicated to the measurement of the d(060) (FigureS1) exhibit only slight differences in peak position between the three experiments. Conversely, the NIR analysis (Figure2.II) exhibits more variation on the di/tri-octahedral character of the minerals formed. Different reasons can be evoked, as explained below. The NIR analysis is a direct probe to investigate the metal-OH bond in the octahedral sheet of clay minerals (see[START_REF] Petit | Handbook of Clay Science Part B[END_REF] and references therein).Therefore, NIR analysis is less affected by the difference in poorly compared to /well crystalline clay minerals formed than XRD analysis., and In addition NIR spectroscopy has already been largely used in the identification of di/tri-octahedral clay minerals on the Martian surface (sSee[START_REF] Carter | Widespread surface weathering on early Mars: A case for a warmer and wetter climate[END_REF] and references therein). Moreover, tThe investigation of the di/tri-octahedral clay minerals via the d(060) position could be more difficult than explained by Brindley and

  Figure2.I.c, 2.II.c), the reflection at 14.82 Å in the Ca-AD state shifts to 16.69 Å, and its 002 reflection at 8.35 Å appears in the Ca-EG state. Moreover, the reflection shifts to 11.55 Å in the K-110 state and then to 10.41 Å after heating at 330 and 550°C. This XRD behavior is attributed to smectite layers. NIR confirmed this analysis with V-shaped bands at 1.91 and 2.31 µm (Figure2.III.c), which correspond to H2O stretching and bending bands, and (Fe,Mg)3-OH stretching and bending bands of trioctahedral smectite, respectively.The absorption band at 2.35 µm could correspond to (Fe,Mg)3-OH liaisons of Fe-rich trioctahedral chlorite (Figures 2.III.a, b and c)[START_REF] Bishop | Reflectance and emission spectroscopy study of four groups of phyllosilicates: smectites, kaolinite-serpentines, chlorites and micas[END_REF][START_REF] King | Spectral characteristics of chlorites and Mgserpentines using high-resolution reflectance spectroscopy[END_REF]]. The band near 2.43 µm (Figures 2.III.b and c) could be due to the presence of Fe 2+ and/or Mg 2+ in the octahedral sheet of TOT phyllosilicates and its intensity is related to the relative amount of Fe and Mg[START_REF] Mustard | Chemical composition of actinolite from reflectance spectra[END_REF]. The position and the strength of this band would indicate a high Fe content in the smectite layers for the 100% N2 experiment. The slight band at 2.25 µm (Figures 2.III.a and b) corresponds to Al 3+ ,Fe 3+ -OH bending and stretching overtone in dioctahedral chlorite and/or smectite. Therefore, from the XRD behavior and NIR analysis, this sample constitutes is composed of a trioctahedral-rich smectite and toin a lesser extent ofa minor proportion of a dioctahedral smectite or /chlorite mixed-layer mineral (MLM). With CO2 % increase (Figures 2.I.b, 2.I.a, 2.II.b, 2.II.a, 2.III.b, 2.III.a), the XRD behavior of smectite layers corresponding to a (shift of the XRD peaks between Ca-AD and Ca-EG state to lower angles) becomes less pronounced and spectral band intensities of the smectite layers decreases. The ( absorption of the hydration band near 1.9 µm,, the absorption band of (Fe,Mg)3-OH liaison at 2.31 µm decrease and the band at 2.43 µm disappearance disappearsof the band at 2.43 µm, (Figures 2.III.a and b). While this phenomenon could be partly attributed to a decrease in the coherent scattering domain size of the clay minerals, it mainly indicates a decrease in trioctahedral smectite layers content with the CO2 % increase. Inversely, the XRD peak intensities at 7.35 Å in the Ca-AD state increase with the CO2 % (Figures 2.I.a, b). This XRD peaks shifts slightly to 7.60 Å in the Ca-EG state and hence shows the presence of smectite layers (Figures 2.I.a and b). Moreover, this XRD peak does not shift between 110 -330°C and disappears after 550°C (Figures 2.II.a and b). This XRD behavior is suggestive of kaolinite layers and/or of the 002 reflection of Fe-rich chlorite layers (dehydration of the octahedral sheet of 2:1

  .a, b and c), which are related to Al2-OH and (Al,Fe)2-OH liaison, increase with the CO2 %. These bands correspond to dioctahedral smectite/chlorite MLM. The presence of this MLM is confirmed by XRD due to the shift of the peak positions at 14.82 and 16.69 Å in the Ca-AD and CA-EG state, respectively (Figures 2.I.a, b and c).

  and 3.III, respectively) the minerals formed are trioctahedral phyllosilicates and zeolites. Therefore, the CO2 % content has a strong influence on the mechanism leading to the dioctahedral clay minerals, carbonate or zeolite formation. As seen by the models dedicated to the 10% CO2 / 90% N2 experiments (Fig 3.II), the dioctahedral phyllosilicates content increases until pH ~7.2 and then decreases in favor of zeolite content. The increase of zeolite content is also accompanied by a decrease in the formation of carbonates. These minerals are competing and the formation of one inhibits the formation of the other, such as: dioctahedral clay minerals versus zeolites and carbonates versus zeolites (see figure 3.II).

  detected always associated with Fe/Mg phyllosilicatesare. Here, we report on the dioctahedral versus zeolites and carbonates versus zeolites formation to better define the early Mars alteration history. always associated with Fe/Mg phyllosilicates or can occur with both zeolites and Fe/Mg phyllosilicates. Hydrothermal Hydrothermal experiments on a tholeiitic volcanic glass were performed, in this study, in a closed system with a water-rock ratio of 20 and a head space of 520 ml. Three different initial gas mixtures with various CO2 contents were used in the experiments: 100% CO2, 10% CO2 / 90 % N2 and 100 % N2. The minerals formed during the experiments were characterized by XRD and NIR analyses. Complementary geochemical modeling was done to reproduce the different experiments to establish the parameter driving the mineralogical formation. The experimental results show that Wwith the decrease of CO2 percentage, the content of dioctahedral clay minerals decreases in favor of trioctahedral minerals and zeolites. Carbonates are formed during the experiments containing CO2 while zeolite is formed with a CO2-free fluid.The geochemical simulation provides insight into the aqueous alteration environment as a function of the mineral association. Three mineralogical associations could be used to follow the pH conditions during the alteration. Indeed, dDioctahedral clay minerals and carbonate minerals are formed under pH <~7.2 (at 120°C)acidic conditions. and trioctahedral Trioctahedral minerals are formed with carbonates from pH >6 (at 120°C)neutral pH aqueous solutions.

Figure 1 :

 1 Figure 1: Bulk XRD patterns between 2-55 °2θ and NIR spectra of the unreacted basalt (I.a and II.a, respectively), bulk XRD patterns and NIR spectra and of the weathered basalt under 100% CO2 (I.b and II.b, respectively), under 10% CO2 / 90% N2 (I.c and II.c, respectively) and under 100% N2 (I.d and II.d, respectively). The triangles, thediamonds and ,the stars represent the XRD peaks of forsterite, pyroxene and quartz respectively. From low to high angles, the peak position corresponding to: the triangles are at 5.12, 3.89, 3.50, 2.78, 2.52, 2.47, 2.36, 2.27, 2.56,

Figure 2 :

 2 Figure 2: Comparison of the XRD patterns recorded on oriented preparation obtained in Ca-AD (black line) and Ca-EG (grey line) states for the weathered basalt under 100% N2 (I.c), under 10% CO2/90% N2 (I.b) and under 100% CO2 (I.a). Comparison of the XRD patterns recorded on oriented preparations obtained in Ca-AD (black line), K-110 (grey line), K-330 (blue line) and K-550 (red line) states for the weathered basalt under 100% N2 (II.c), under 10% CO2/90% N2 (II.b) and under 100% CO2 (II.a). Comparison of the NIR spectra continuum removed for the weathered basalt under 100% N2 (III.c), under 10% CO2/90% N2 (III.b) and under 100% CO2 (III.a).

Figure 3 :

 3 Figure 3: Geochemical results obtained from the dissolution of the basaltic glass for the 100% N2 (I), 10% CO2 / 90% N2 (II) and 100% CO2 (III) simulation as a function of pH.

a

  The percentage of dissolution of the basaltic glass has been estimated by XRD with an uncertainty of ±2 % (for more details see section 4.1)b The trioctahedral minerals correspond to the sum of trioctahedral smectite, trioctahedral chlorite and talc.c The dioctahedral minerals correspond to the sum of dioctahedral smectite, kaolinite and illite.d The carbonates are expressed as a solid solution between the proportion of calcite (Ca), magnesite (Mg) and siderite (Fe).

eFormatted

  The zeolites correspond to garronite for the experiments and to the sum of gismondine and phillipsite for the geochemical modeling (for more details see section 4.1 and 4.2). ++, +++ represent the relative abundance of the minerals (based on peak intensities) between the different atmospheres from non-present to the highest relative proportion.

  figure 1.I and 1.II presents the XRD powder patterns and the NIR spectra obtained on

	the unreacted sample (a) and after the experiments as a function of the gas composition (b, c and
	d under 100% CO2, 10% CO2 / 90% N2 and 100% N2, respectively). The large and intense bump
	between 5 and 2.33 Å, centered at 3.23 Å of the unreacted sample (Figure 1.I.a and 1.II.b) defines
	is composed mainly of athe volcanic glass. The triangles at 5.12, 3.89, 3.50, 2.78, 2.52, 2.47,
	2.36, 2.27, 2.56, 2.17 and 1.75 Å (Figure 1.I.a, large and intense bump between 5 and 2.33 Å,
	centered at 3.23 Å) with a correspond to a small proportion of forsterite (Figure 1.I.a, triangles at
	5.12, 3.89, 3.50, 2.78, 2.52, 2.47, 2.36, 2.27, 2.56, 2.17

  is of prime interest. It could imply drastically different environmental conditions during early Mars: acidic and/or basic conditions. In addition, pH appears to be one of the most important parameters as a driver of mineralogical competitions (in addition to silica activity for the formation of zeolites).

	More experimental and geochemical modeling studies are required to investigate the clay
	minerals/carbonates/zeolites competition. Indeed, other gases such as SO2, which is considered
	one of the important gases released during Martian volcanism [Cradock and Greeley, 2009], will
	significantly modify the competitive behavior.

Table 2 :

 2 List of minerals and solid-solution added during the geochemical simulation to account of the lack of the original at the data0.cmp data base (from EQ3/6 software).

		SiO2 Al2O3 Fe2O3(T) MgO NaO K2O CaO
	%	48.2 14.2	12.0	9.4 1.9 0.3 11.7
	Elements	Si	Al	Fe	Mg Na K Ca O
	mol	1	0.35	0.23	0.29 0.01 0.07 0.26 3.345
	Temperature (°C)	0	25	60	100 150 200 250 300
	Log(K)	18.10 16.30 13.86 11.59 9.28 7.37 5.71 4.21

Table 2 :

 2 List of minerals, and solid-solution added and suppressed during the geochemical simulation to account of the lack of the original at the data0.cmp data base (from EQ3/6 software).

	Minerals / Solid-solutions	Structural formulae
	Trioctahedral clay minerals:
	Saponite	(Ca,Mg,Na2,K2)0.17(Mg3)(Al0.34Si3.66)O10(OH)2
	Fe-rich saponite	(Ca,Mg,Na2,K2)0.17(Fe,Mg2)(Al0.34Si3.66)O10(OH)2
	Tri-chlorite	(Fe,Mg)5Al2Si3O10(OH)8
	Talcs	(Mg,Fe)3Si4O10(OH)2
	Dioctahedral clay minerals:
	MontmorrilloniteMontmorrillonites	(Mg,Ca, Na2,K2)0.165(Mg0.33Al1.67)Si4O10(OH)2)
	Nontronites	(Mg,Ca, Na2,K2)0.165(Fe2)(Al0.33Si3.67)O10(OH)2)
	Beidellites	(Mg,Ca, Na2,K2)0.17Al2.34Si3.66O10(OH)2
	Kaolinite	Al2Si2O5(OH)4
	Di-chloritesFe-sudoite	(Fe,Mg)2Al4Si3O10(OH)8
	VermiculiteVermiculites	(Ca,Mg, Na2,K2)0.43(Mg3)(Al0.43,Si3.14)O10OH2
	IlliteIllites	K0.85(Mg,Fe)0.25Al2.35Si3.4O10(OH)2
	ZeolitesPhillipsite
	Phillipsites	(Ca,N2,K2)0.5AlSi3O8:3H2O
	Gismondine	Ca2Al4Si4O16:9H2O
	Clinoptilolites	(Ca, Na2,K2)0.55(Si4.9Al1.1)O12:3.9H2O
	Heulandites	(Ca,Na2)1Al2Si7O18:5H2O
	Mordenite	Ca0.2895Na0.361Al0.94Si5.06O12:3.468H2O
	Stellerite	Ca2Al4Si14O36:14H2O

Table 23 :

 23 Summary of the experimental results and mol of minerals predicted by the geochemical modeling at the same rate of dissolution as a function of the gas composition.

Acknowledgements

This work was partly supported by the Research Council of Norway through its Centre of Excellence funding scheme, project number 223272. This project has received funding from the European Union's Horizon 2020 (H2020-COMPET-2015) research and innovation programme under grant agreement No 687302 (PTAL). This study is supported by the Research Council of Norway (235058/F20 CRATER CLOCK). L. Riu acknowledges the IDEX Université Paris-Saclay for her PhD grant. The authors would like to thank Thanusha Naidoo for correcting the English, Christian Saetre, Mufak Said Naoroz, Rune Bjørnestøl Per-Olav Korsmo for laboratory help and Helge Hellevang, Henning Dypvik for providing the sample. Finally, the authors wish to acknowledge the editor Dr. D. Baratoux, as well as Dr. H. Newsom and two anonymous reviewers, for their constructive comments that greatly improved the quality of this work. All data used to characterize our initial and altered samples are included in the figures, tables, and supporting information of this manuscript.