Jean-Pierre Lorand
email: jean-pierre.lorand@univ-nantes.fr

Jabrane Labidi
email: jlabidi@carnegiescience.edu

Claire Rollion-Bard

Emilie Thomassot
email: emilie@crpg.cnrs-nancy.fr

Jeremy Bellucci
email: jeremy.belluci@gmail.com

Martin Whitehouse
email: martin.whitehouse@nrm.se

Alexander Nemchin
email: nemchin@curtin.edu.au

Munir Humayun
email: humayun@magnet.fsu.edu

James Farquhar

Roger Hewins
email: hewins@rci.rutgers.edu

The sulfur

Jean-Pierre LORAND1 , Jabrane LABIDI2,3,4 , Claire ROLLION-BARD 4 , Emilie THOMASSOT 5 , Jeremy J. 12 BELLUCCI 6 , Martin WHITEHOUSE 7 , Alexander NEMCHIN 6 , Munir HUMAYUN 8 , James FARQUHAR 3 , Roger 13 H. HEWINS 9,10 , Brigitte ZANDA 9 , Sylvain PONT 9 In the absence of ozone, terrestrial sulfur of Archean age exhibits prominent mass 56 independent isotope fractionation (MIF) effects due to UV irradiation of atmospheric SO 2 to 57 form a variety of reduced and oxidized sulfur species (Farquhar et al., 1998 grains, sometimes of very small size (down to 1 m across), especially when disseminated inside 191 ICM (Fig. 1B). Some anhedral pyrite grains replace low-Ca pyroxene clasts. Whether euhedral 192 or anhedral, many pyrite grains are poikiloblastic and enclose relict micron-sized Fe-(Ti) oxides 193 identified as being the same composition and habit as the magnetite-maghemite that is so 194 abundant in NWA 7533 (Fig. 1B). Pyrite-producing reactions thus involved sulfidation, either impactor debris of the pre-Noachian meteoritic bombardment [START_REF] Lorand | 869 Nickeliferous pyrite tracks pervasive hydrothermal alteration in martian regolith breccia : a 870 study in NWA 7533[END_REF](Lorand et al., , 2018b)). It rich pyroxene, silica, and Fe-oxide [START_REF] Leroux | Exsolution and shock microstructures of igneous pyroxene clasts in the NWA 854 7533 Martian meteorite[END_REF]. Hydrothermal alteration under 207 oxidizing conditions appears to have given rise to fine-grained Fe-rich phases 208 influencing the magnetic properties of the breccia (Gattaceca et al., 2014).

209

Pyrite, a very fragile mineral, shows planar fractures (Fig. 1) resembling planar 210 deformation features (PDF). The shock creating such planar fractures was a very late event, 211 because pyrite was one of the last phases to crystallize in the breccia on Mars (Lorand et al., 212 2015). The fractures were possibly related to the excavation event that liberated the meteorite 213 from the martian subsurface crust, yet its shock intensity could not be determined due to the lack 214 of olivine and quartz [START_REF] Hewins | Regolith breccia Northwest Africa 7533: 821 mineralogy and petrology with impli-cations for early Mars[END_REF]. These fractures acted as preferential pathways for 215 partial replacement of pyrite by iron oxyhydroxides of terrestrial origin according to their D/H 216 values and their distribution defining an alteration gradient throughout the meteorite (Lorand et 217 al., 2015). Electron Microprobe analyses (EMP) of altered and hydrated regions in pyrite show 218 compositions similar to that of goethite, but containing ~4% SiO 2 while electron diffraction data [START_REF] Lorand | 869 Nickeliferous pyrite tracks pervasive hydrothermal alteration in martian regolith breccia : a 870 study in NWA 7533[END_REF]. Indeed, S-MIFs are 360 generated by UV-induced photochemical processes in an atmosphere poor in O 2 like the martian 361 atmosphere since the earliest times (e.g. [START_REF] Farquhar | Evidence of atmospheric 755 sulfur in the martian regolith from sulfur isotopes in meteorites[END_REF][START_REF] Farquhar | Observation of wavelength-752 sensitive mass-independent sulfur isotope effects during SO 2 photolysis: Implications for 753 the early atmosphere[END_REF]Pavlov and Kasting, 2002). Young et al., 2002). This latter process should produce a regression line characterized by a 373 slope of -7±1 whereas our data set does not align on any correlation at all. However, it is worth 374 noting that all but three analyses of NWA 7533 sulfides plot within the scattergram of nakhlites 375 in the  36 S vs.  33 S plot of Fig. 4. This may be more than a coincidence because NWA 7533 376 sulfides were dated at 1.4 Ga, like nakhlites that recorded sulfate contamination at each stage of 377 their petrogenetic history (e.g. [START_REF] Franz | Isotopic links between atmospheric chemistry 764 and the deep sulfur cycle on Mars[END_REF][START_REF] Dottin | Evidence for 747 oxidation at the base of the nakhlite pile by reduction of sulfate salts at the time of lava 748 emplacement[END_REF]Lindsay et al., submitted).

378

This could reflect the S isotopic composition of surficial sulfur at that time on the martian crust, 379 or a specific S reservoir sampled by both martian breccias and nakhlites.

380

The presence of sulfur isotopic variations that are both mass-independent and 381 mass-dependent compared to the inferred composition of martian mantle-derived 382 sulfur, argues in favor of a crustal origin of NWA 7533 pyrite consistent with its 383 hydrothermal origin [START_REF] Lorand | 869 Nickeliferous pyrite tracks pervasive hydrothermal alteration in martian regolith breccia : a 870 study in NWA 7533[END_REF]. Even taking into account only the bulk-rock 384 data, the small but significant negative  33 S values overlap with the isotopic S compositions 385 reported for some shergottites that are now considered to have assimilated crustal sulfur (NWA 386 11300; NWA 7635; Franz et al., 2019). Before further discussion, it is necessary to address any 387 bias in the database. Hence, the following three points will be addressed 1) how can the slight 388 discrepancy between in-situ analyses and bulk-rock determination of  33 S be explained, 2) how 389 was anomalous S transferred to impact breccias, and 3) what was the ultimate process that 390 triggered hydrothermal cycling of S in these martian regolith breccias. the 8 polished pieces studied so far [START_REF] Lorand | 869 Nickeliferous pyrite tracks pervasive hydrothermal alteration in martian regolith breccia : a 870 study in NWA 7533[END_REF][START_REF] Hewins | Regolith breccia Northwest Africa 7533: 821 mineralogy and petrology with impli-cations for early Mars[END_REF]. There are no pyrrhotite by sulfur-bearing fluid influx into the nakhlite unit (Greenwood et al., 2000; Fig. 7).

546

The same is true for Chassigny pyrite that replaced pyrrhotite (-4.6‰< 34 S<-1.5‰; Greenwood 547 et al., 2000). According to [START_REF] Shearer | Sulfur isotopic systematics in 975 alteration assemblages in martian meteorite Allan Hills 84001[END_REF] and Greenwood et al. (2000), igneous pyrrhotite 548 in ALH 84001 was largely converted to pyrite by a secondary alteration process, such as an 549 impact-driven hydrothermal system. A low-temperature (200°C) hydrothermal influx of volatile 550 components (S, C, H) was postulated for this reaction in Chassigny, too [START_REF] Floran | The Chassigny 757 meteorite: A cumulate dunite with hydrous amphibole-bearing melt inclusions[END_REF] 551 Peslier et al., 2019;Lorand et al., 2018a [START_REF] Machel | Products and distinguishing criteria of bacterial 882 and thermochemical sulfate reduction[END_REF]Seal, 2006). A crude estimate for initial martian sulfate source enriched in 567 34 S is suggested by  34 S as high as 4.7 ± 0.2‰ in sulfate extracted from Nakhla (Farquhar et al., 568 2007). Shergottite sulfates show  34 S of 6.68 ± 0.15‰ [START_REF] Farquhar | Implications from sulfur isotopes of the Nakhla 750 meteorite for the origin of sulfate on Mars[END_REF]. Higher values 569 recorded by sulfate of Antarctic nakhlites MIL 03346 and its pairs (up to 12.39 ‰) may reflect 570 input of terrestrial sulfates [START_REF] Franz | Isotopic links between atmospheric chemistry 764 and the deep sulfur cycle on Mars[END_REF], but are not unrealistic for martian sulfates as 571 suggested by analyses of sulfate in fluvio-lacustrine sediments of Gale crater (Franz et al., 2017)

585

(see detailed calculation in [START_REF] Dottin | Evidence for 747 oxidation at the base of the nakhlite pile by reduction of sulfate salts at the time of lava 748 emplacement[END_REF]. Our scenario of precursor sulfates is also 586 supported by the S/Se ratio of NWA 7533 pyrite (3,500-54,000;Lorand et al. 2018b;Fig. 5).

587

Selenium chemistry is strongly tied to S chemistry: both elements can substitute as anions into 588 sulfides while forming oxycompounds hosted in sulfates (Howard, 1977;Huston et al., 1995; 589 [START_REF] Lorand | S/Se systematics of the subcontinental 863 lithospheric mantle beneath the Massif Central[END_REF]Ziemkievics et al., 2011 and references therein). Although Se concentration 590 data (and hence S/Se ratio) are not available for martian sulfates, one nakhlite (MIL 03346) that 591 bears multiple evidence of martian sulfate contamination shows a bulk-rock S/Se ratio of up to 592 13,385 whereas it is only 3566 ± 798 for the shergottites that have incorporated juvenile (mantle-593 derived) martian sulfur (Wang and Becker, 2017). Owing to its S/Se ratio up to 54,000, there can 594 be little doubt that NWA 7533 pyrite formed from precursor sulfates (Fig. 6).

595

The Eh-pH redox conditions deduced for NWA 7533 from the Fe-S-O system, and the 596 lack of any firmly identified sulfate, imply that sulfate reduction products were recycled by 597 hydrothermal fluids in the martian breccia as reduced to near-neutral H 2 S/HS --rich aqueous 598 fluids [START_REF] Lorand | 869 Nickeliferous pyrite tracks pervasive hydrothermal alteration in martian regolith breccia : a 870 study in NWA 7533[END_REF]. Reduction of sulfate during the hydrothermal process would 599 generate H 2 S and potentially H 2 Se that are likely to precipitate as pyrite in the presence of Fe 2+ 600 [START_REF] Auclair | Distribution of selenium in high-temperature 720 hydrothermal sulfide deposits at 13° North, East Pacific Rise[END_REF]. Experimental studies on terrestrial hydrothermal vent systems demonstrate 601 that at 300 and 350 °C (a temperature range corresponding to that deduced from the Ni content 602 of NWA 7533 pyrite; [START_REF] Lorand | 869 Nickeliferous pyrite tracks pervasive hydrothermal alteration in martian regolith breccia : a 870 study in NWA 7533[END_REF]Lorand et al., , 2018b)), pyrite is expected to be depleted in the heavy 603 isotopes of S relative to H 2 S at equilibrium (Seal, 2006;[START_REF] Wu | Evaluating the S-isotope 1006 fractionation associated with Phanerozoic pyrite burial[END_REF][START_REF] Gregory | A degree of sulfate reduction in an open system to produce negative  34 S. 798[END_REF] 604 [START_REF] Magnall | Open 884 system sulfate reduction in a diagenetic environment -Isotopic analysis of barite ( 34 S and 885  18 O) and pyrite ( 34 S) from the Tom and Jason Late Devonian Zn-Pb-Ba deposits, Selwyn 886 Basin, Canada[END_REF]. [START_REF] Lorand | 869 Nickeliferous pyrite tracks pervasive hydrothermal alteration in martian regolith breccia : a 870 study in NWA 7533[END_REF]Lorand et al. ( , 2018b) ) suggested that NWA 7533 pyrite precipitated 605 by direct nucleation or sulfidation reactions between H 2 S/HS -rich aqueous fluids and Fe from 606 different sources (dissolved ions in the fluid, pyroxene clast, matrix oxides (magnetite, 607 maghemite)). Like pyrite, the negative ∆ 33 S coupled with negative  34 S values makes the few 608 fine-grained spongy anhedral pyrrhotite grains identified in the interclast matrix (ICM) of NWA 609 7533 crystallization products from fluids that reduced crustal sulfates (Fig. 2). However, the 610 highly resorbed and denticulated shape of these pyrrhotite blebs and their spongy textures 611 compared to euhedral pyrite crystals are noteworthy. Such sulfide textures were reported in SNC 612 meteorites that experienced shock-induced sulfur degassing (Lorand et al., 2012, Gattaceca et According to a detailed analysis of pyrite textures and its relationships with silicate 626 lithologies of NWA 7533, hydrothermal alteration took place at a very late stage of the history of 627 the meteorite during and after a lithification and annealing event that made the regolith breccia 628 very cohesive. This annealing event responsible for the lithification of the meteorite likely 629 occurred at ~1.4 Ga from the apatite U-Pb ages [START_REF] Bellucci | 727 Pb-isotopic evidence for an early, enriched crust on Mars[END_REF], the zircon lower intercept 630 ages and the K-Ar ages (Humayun et al., 2013;[START_REF] Lindsay | 40 Ar/ 39 Ar Ages of Martian Meteorite NWA 7533[END_REF][START_REF] Mccubbin | Geologic history of 901 Martian regolith breccia Northwest Africa 7034: evidence for hydrothermal activity and 902 lithologic diversity in the Martian crust[END_REF] 631 [START_REF] Cassata | Chronology of martian breccia NWA 7034 and the formation of the 738 martian crustal dichotomy[END_REF] and the whole-rock 187 Re/ 187 Os model ages [START_REF] Goderis | Ancient impactor components 786 preserved and reworked in martian regolith breccia Northwest Africa 7034[END_REF] (ii) a substantial heat source is generated (e.g. melt sheet, nearby pluton, raised geothermal 649 gradient) [START_REF] Newsom | Hydrothermal alteration of impact melt sheets with implications for Mars[END_REF]Abramov and Kring, 2004;[START_REF] Naumov | Principal features of impact-generated hydrothermal circulation systems: 928 mineralogical and geochemical evidence[END_REF]Osinski et [START_REF] Lorand | 869 Nickeliferous pyrite tracks pervasive hydrothermal alteration in martian regolith breccia : a 870 study in NWA 7533[END_REF] ; IS = Internal Standard.

  195 from magnetite/maghemite, from the low-Ca pyroxene, or from dissolved divalent iron in a fluid. 196 Regardless of their mode of formation, NWA 7533 pyrite grains show nickel-rich areas (up to 197 4.5 wt.%; EMPA and SEM data) representing former Fe-Ni metal particles, as well as highly 198 siderophile element-rich micro-inclusions (Os, Ir, Ru, Pt, Pd, Re, Mo) interpreted as altered 199

  200 was inferred from this maximum Ni content (positively correlated with Se) that pyrite started 201 crystallizing at 400-500°C. Compared to pyrite, hydrothermal pyrrhotite is very scarce, always 202 anhedral, and highly spongy (see Fig 1C). The assemblage pyrite-pyrrhotite-magnetite and 203 maghemite defines Eh-pH conditions of hydrothermal fluids as near neutral H 2 S-HS-rich 204 (6<pH<10) oxidizing fluids (minimum log fO 2 of > FMQ + 2 log units; Lorand et al., 2015) in 205 agreement with the redox conditions deduced from pyroxene clast decomposition into Mg-206

362

  In oxygen isotopes, MIF effects also affect the bulk-rock composition of NWA 7034(Agee et 363 al., 2013), phosphates (Belluci et al., 2020) and are largest in NWA 7533 zircons(Nemchin et 364 al., 2014). Moreover, the variation in ∆ 33 S with an absence of significant anomalies in ∆ 36 S (Fig. 3654) is considered to be diagnostic of S-MIF production on Mars, by different pathways from those 366 that operated on the early Earth and in Earth's stratosphere today (see e.g.Masterson et al., 367 2011). The calculated mean  36 S value from both the bulk-rock and SIMS analyses is close to 368 0 ‰, a characteristic feature of S multi-isotope systematics of martian meteorites compared to 369 Archean terrestrial samples showing mass independent signatures(Franz et al., 2014, 370 2019a,b)(Fig.4). The plot in Fig.4also rules out alternative fractionation processes, such as, for 371 example, mass-dependent fractionation during Rayleigh distillation with alternative mass laws

  442 coupled Ba+S spikes that could correspond to barite micro-inclusions in the time-resolved 443 diagram of the LA-ICP-MS analyses of Fe oxyhydroxides (Fig. 5). Barium was systematically 444 detected along with S (in agreement with EMP and TEM data for Ca, S and Si). The Sr and Ba 445 ion signals are highly correlated and the 34 S signal follows the Ba and Sr signals very closely in 446 the first portion of the scan in Fig. 5, while the Ca signal is independent of the Ba-Sr-S signals. 447 The high Sr might indicate that a Sr-Ba sulfate is the only sulfate present and that it is 448 sufficiently widely distributed at a nanometric scale in the Fe-oxyhydroxides not to form discrete 449 spikes. However, the trend of strongly decreasing S/Se ratio in NWA 7533 Fe oxyhydroxides 450 (137<S/Se<1,193) compared to their pyrite precursors (3,500<S/Se<54,000) supports the 451 hypothesis of extensive leaching of sulfates from the breccia during terrestrial weathering (Fig. 452 6). Such a drop in the S/Se ratios is consistent with the well documented differences in the 453 behaviour of S and Se in terrestrial weathering (e.g.

Figure caption 1014 1015 Figure 1 :Figure 2 : 1028 Figure 3 :Figure 4 : 1034 Figure 5 .Figure 6 :

 101512102834103456 Figure caption

F

  36 S values. We additionally report our δ 34 S values on the V-CDT scale to allow 252 comparisons with other datasets that also reported δ 34 S values relative to V-CDT (e.g., terrestrial 253 mantle-derived rocks, Labidi et al. 2012). We obtained 2 uncertainties of 0.10, 0.012 and 254 0.25‰ for  34 S,  33 S and  36 S values, respectively, for all measurements with a SF 6 amount > 1  33 S values and 0.24‰ for  36 S. Several pyrite in-house reference materials (Maine, Philippot et 283 al., 2012, Balmat pyrite, courtesy of M. Whitehouse, and Spain-CR,[START_REF] Muller | Multiple sulfur-isotope signatures 913 in Archean sulfates and their implications for the chemistry and dynamics of the early 914 atmosphere[END_REF] were

	251 284 285 313 314 315 316 343 344 345 346 and  255 used to determine (i) the instrumental mass fractionation, and (ii) the reference mass discrimination line, from which  33 S and  36 S values were calculated. The values of the in-house RESULTS The two bulk-rock analyses yield quite reproducible bulk S concentrations (805-920 ppm). These bulk chemistry values are very close to the mean value calculated from LA-ICP-MS The six pyrite crystals analysed with the NORDSIMS ion microprobe show a very similar range of negative  33 S values (-0.05‰< 33 S <-0.36‰) to the 12 Nancy SIMS pyrite analyses, however with no positive values. Both data sets also yield consistent results with regard to the negative  34 S value of NWA 7533 sulfides (-3.3 ‰< 34 S<-1.5 ‰). Duplicate mol. 286 reference materials can be found in Muller et al. (2017). The bulk isotopic compositions of these 317 raster analyses of Humayun et al. (2013) although the latter method detected huge variations 347 analyses generated variable reproducibility that reflected the different degrees of sulfide
	256 287 318 348	The in-situ analyses of S multi-isotopes were done with ion probes on two polished thin materials were measured by conventional gas source mass spectrometer at IPGP following (100 to 1500 ppm) between each of the breccia components (CLIMR, ICM, microbasalts, melt alteration from one section to another (e.g. site 16a,b; Table 1), and the grain size of the
	257 288 319 349	sections (7533-4 and 7533-5) over the 8 available. These two polished thin sections show Labidi et al. (2012). spherules; see section 2), reflecting small scale variations in modal abundances and weathering preserved pyrite. Pyrite and the three highly spongy pyrrhotite grains of hydrothermal origin
	258 259 289 290 291 320 321 322 350 351 352	F o r F o r unaltered pyrite crystal cores large enough to be analysed. The dimensions and localisation of the final ion microprobe spots were checked with a scanning electron microscope (Tescan VEGA II F o r Quadruple S-isotopes were measured in-situ on section 7533-4 at a ca. 10 m scale using a CAMECA ims1280 SIMS instrument (NordSIMS facility, Stockholm), closely following analytical protocols outlined by Whitehouse (2013). The sulfur isotopes 32 S, 33 S and 34 S were F o r degrees of pyrite (Lorand et al., 2015; 2018b). The samples yield an average  33 S of -0.029±0.010 ‰ reflecting a small but resolvable non-zero signal in  33 S at the 2 level. This non-zero  33 S is coupled with negative  34 S (-2.54 ± 0.10 ‰). The NWA 7533 meteorite S analysed here carry similar isotopic compositions at the 2-sigma level (Table 1; Fig. 2). Due to F their lower count rate the NordSIMS analyses of pyrrhotite are less precise compared to the o r analyses of pyrite, as shown by the two sigma values of the three S isotope ratios. This lower
	323 324 325 326 353	P e e r P e e r P e e r P e e r isotopic composition is distinct from that of the juvenile martian S isotopic composition calculated by Franz et al. (2019) from 47 shergottite analyses ( 34 S = -0.24 ± 0.05 ‰,  33 S = In addition to bulk isotope measurements, 29 spot analyses were performed on 18 pyrite r e 0.0015 ± 0.0016 ‰,  36 S = 0.039 ± 0.054 ‰). e P precision may result from the highly spongy nature of that pyrrhotite, showing pore sizes much
	327 328	R e R e R e R e and 3 pyrrhotite grains of sufficient size (>20 m) that were not significantly altered to Fe-oxyhydroxides. Ion microprobe measurements yielded more negative  33 S values (-0.05< 33 S <-R e
	329 330	v i e v i e v i e v i e v 0.38‰,) compared to the bulk-rock analyses, and a wider range of negative  34 S signatures (-1.5< 34 S<-3.1‰; with outliers up to -5.5 and +0.6 ‰) (Fig. 2). The Nancy SIMS analyses show i e
	274 304 331 332 333 334 305 335	w O n l y w O n l y beam focused to a spot of about 15 μm, with secondary intensities from 8.2 x10 8 to 10.2 x 10 8 w O n l y w O n l a larger scatter in the  34 S and  33 S values than the bulk analyses and include two positive values w for  33 S (0.24-0.35 ‰ corresponding to Site 16-1 and Site F-4 pyrites; Table 1). The ranges of O  36 S are similar: -0.55 to +0.49 ‰ (NORDSIMS) vs. -0.9 to +0.49 ‰ (Nancy SIMS), excluding one outlier at -2.2 ‰ (Site B-1 Pyrite). Correlation between  33 S and  34 S is lacking (Fig. 2). n l and 20x demagnification, resulting in low fluences on the sample (<4 J/m 2 ). Spot sizes for standards and samples were set to 25-50 µm depending on the size of the mineral grains. Six Fe y There are no correlations between sulfur isotopic compositions and pyrite Ni contents (<0.1-3 y
	275 306 336	cps for 32 S, depending on the mineralogy. Gains and backgrounds of the Faraday cups were oxyhydroxide grains replacing pyrite were analysed in section 7533-5 with a spot size of 25 µm, wt.%; Table 1)(Fig. 3), suggesting that the correction procedure of SIMS analyses was not
	276 277 307 337 308 338	regularly measured during the entire session. Measurements were performed with an automatic centering process and consist of 30 cycles of 4 seconds each after a pre-sputtering time of 300 affected by the small deviation of NWA 7533 pyrite compared to pure FeS 2 . The spread in the NIST 610 glass as calibration standard and SiO 2 content as internal standard, based on the values published by Lorand et al. (2015) and Hewins et al. (2017). Eight apatite crystals from NWA  34 S values seems to be due to beam overlap over polymineralic aggregates (pyrite-Fe oxides or
	278 309 339 310 340	7533 -5 were analysed with a laser spot size of 50 µm, NIST 612 glass as calibration standard Fe oxyhydroxides), matrix silicates or vein-filling terrestrial products (calcite). The analyses seconds. The background of the detectors was measured during the pre-sputtering and was then and Ca as internal standard based on the apatite analyses reported by Hewins et al. (2017). having incorporated some calcite seem to shift  34 S toward more positive values (7533-5-19;
	311 341	Concentrations in both cases were determined using Glitter™ software (Table 2). 7533-5-17; 7533-5-F-2; 7533-5-1a) (Fig. 1). No systematic trend can be seen for those analyses
	342	overlapping Fe oxyhydroxides or matrix silicates ( 34 S down to -5.58 ‰ for NWA7533-5-G).

260 LSU Scanning Electron Microscope (SEM) operating in conventional (high-vacuum) mode, and 261 equipped with an SD3 (Bruker) EDS detector (Muséum National d'Histoire Naturelle Paris, 262 France = MNHN) operating in the backscattered mode (BSE) (see Lorand et al., 2015 for more 263 details). Major element compositions of pyrite (Fe, Ni, S) were determined with the same 264 standard-less Energy Dispersive procedure as in

[START_REF] Lorand | 869 Nickeliferous pyrite tracks pervasive hydrothermal alteration in martian regolith breccia : a 870 study in NWA 7533[END_REF]

inside the ion beam craters 265 of SIMS analysis; these latter analyses agree quite well with pyrite compositions reported in 266

[START_REF] Lorand | 869 Nickeliferous pyrite tracks pervasive hydrothermal alteration in martian regolith breccia : a 870 study in NWA 7533[END_REF] 2018b)

267 Two Cameca IMS 1280 facilities (CRPG, Nancy, France; NordSIMS facility, Stockholm, 268 Sweden) (Table

1

) were used. The analytical method for the CRPG Cameca IMS 1280 HR2 is 269 described in detail in

[START_REF] Thomassot | Metasomatic diamond growth: A multi-isotope study ( 13 C, 15 N, 33 S, 34 S) of sulfide 994 inclusions and their host diamonds from Jwaneng (Botswana)[END_REF]

and in

[START_REF] Muller | Multiple sulfur-isotope signatures 913 in Archean sulfates and their implications for the chemistry and dynamics of the early 914 atmosphere[END_REF]

. Sulfur isotope 270 compositions of sulfides from thick section 7533-5 were measured by simultaneous 271 measurements of 32 S -, 33 S -, 34 S -, and 36 S -in multicollection mode with three off-axis Faraday 272 cups (L'2, C and H1) that were intercalibrated before each session of analyses, and one electron 273 multiplier (H2) for the most rare isotope ( 36 S). The analytical settings were: 5 nA, Cs + -primary 279 used to correct each analysis. The internal precision achieved under these conditions was better 280 than 0.05‰ for δ 34 S and 0.03‰ for δ 33 S values (2σ). The external precision, determined from 281 repeated measurements on various reference materials, was 0.40‰ (2σ) for δ 34 S, 0.09‰ (2σ) for 292 measured on Faraday detectors, while 36 S was measured on an ion counting electron multiplier, 293 corrected for drift using interspersed reference materials (Balmat and Ruttan pyrites), which 294 were also used to correct for instrumental mass bias. Isua pyrite was used to monitor the mass 295 independent values. 296 Sulfur contents of Fe oxyhydroxides and apatite that may be potential S reservoirs (e.g. 297

[START_REF] Parat | Sulfur-bearing magmatic accessory minerals[END_REF]

were analysed in-situ using a Laser Ablation Inductively Coupled Plasma 298 Mass Spectrometer -LA-ICP-MS) at the «Laboratoire de Planétologie et Géodynamique" in 299 Nantes (France) following the procedure described in detail by

Lorand et al (2018b)

. The 300 samples were ablated and analysed for 34 S using a Bruker 880 quadrupole ICP-MS coupled with 301 a Photon Machine Analyte™ G2 equipped with an excimer laser (193 nm laser wavelength) and 302 a dual volume sample cell that keeps the sample volume small and constant. The laser was 303 operated with a repetition rate of 10 Hz and a laser output energy of 90 mJ with a 50% attenuator 354 smaller (<1 m) than the ion beam diameter (> 10 m). 355 356 DISCUSSION 357 At first sight, the occurrence of Mass Independent Fractionation of sulfur (S-MIFs) 358 supports a martian origin for sulfur in NWA 7533 as deduced from microtextural and 359 compositional characteristics of NWA 7533 pyrite

391 392 The balance of the bulk-rock S multi-isotope budget of NWA 7533

  402than the bulk analyses. Another possible source of analytical bias is that S-bearing phases other 403 than the two Fe-sulfides, pyrrhotite and pyrite, were overlooked by petrographic studies.

	431	represent c.a. 40 ppm S (5% of the bulk-rock S concentration) at best taking into account the
	432	highest in-situ measured S content (≈4,000 ppm) and modal abundances of ca. 1 wt.% (implying
	433	a total oxidation of pyrite, which is an over-estimate). Some of the sulfur of Fe oxyhydroxides
	404 434	Sulfur in NWA 7533 was identified as residing in both magmatic sulfide assemblages, may come from both oxidized pyrites and terrestrial sources with near-zero  33 S values, which
	405 406 435 407 436 408 437	apatite and Fe-oxyhydroxides (Lorand et al., 2015; this study). As said before, the impact breccia would explain the shift in the bulk-rock  33 S values compared to ion microprobe data. From the is almost devoid of magmatic sulfides, which is interpreted to result from repeated impact and mass balance calculations, Fe oxyhydroxides would have to have unrealistically positive  33 S of shock melting. It is well known that shock melts are strongly degassed (Pierazzo and Artemieva, 2012; Righter et al., 2015). Nickel, a strongly chalcophile element was demonstrated to behave about +6 to +9 ‰ to explain the shift of  33 S from -0.2 ± 0.1 ‰ (SIMS data) relative to the
	409 410 411 438 439 440	F o r as a lithophile element in impact-melt derived noritic and monzonitic clasts that crystallized without evolving sulfide melts (Hewins et al., 2017 and references therein). The paucity of magmatic sulfides in NWA 7533 clearly reflects the repeated heavy bombardment of the martian bulk value of -0.03±0.01 ‰. F Sulfates, also major S-bearing phases on Mars (Franz et al., 2017, 2019 and reference o r therein), have not been detected in martian breccia NWA 7533 despite careful SEM scanning of
	441	P e e P
		e r e r
		R e R e
		v v
		i e i e
		w w
		O O
		n l n l
		y y
	426	magmatic sulfides nor apatite could account for the dilution of the pre-existing non-zero  33 S at
	427	near constant  34 S between in-situ SIMS analyses and the two bulk-rock data.

393

Anomalous  33 S for pyrite was observed with two different ion microprobes in two 394 different laboratories. This argues for a significant negative  33 S anomaly as measured by SIMS, 395 which seems to conflict with the near-zero  33 S value of -0.029±0.010‰ measured with precise 396 bulk S isotope measurements. It is not the first time that in-situ analyses and bulk-rock 397 determination of S isotopes do not match.

[START_REF] Franz | Isotopic links between atmospheric chemistry 764 and the deep sulfur cycle on Mars[END_REF]

documented quite a large 398 discrepancy between SIMS analyses and chemical extractions of MIL 03346 pyrrhotite ( 33 S = -399 0.73 ± 0.13 vs. -0.43‰) but did not propose a reason for the discrepancy.

[START_REF] Dottin | Evidence for 747 oxidation at the base of the nakhlite pile by reduction of sulfate salts at the time of lava 748 emplacement[END_REF]

400 also reported SIMS analyses of nakhlites paired with MIL 00336 yielding lower  33 S compared 401 to bulk rocks, and argued that the SIMS measurements captured a different population of sulfides 412 regolith. Another potential S carrier in igneous rocks is apatite

(Parrat et al., 2011)

which is a late 413 magmatic mineral in lithic clasts and microbasalts of the breccia

[START_REF] Hewins | Regolith breccia Northwest Africa 7533: 821 mineralogy and petrology with impli-cations for early Mars[END_REF]

. NWA 414 7533 apatite S content determined by LA-ICP-MS is quite homogeneous (200-300 ppm; Table

415

2). However, apatite is a minor mineral (<6 vol% in NWA 7034, paired with NWA 7533; Agee 416 et al., 2013) and its contribution to the whole rock S budget is expected to be negligible (< 15 417 ppm vs. 865 ppm). Its effect on the S isotopic composition is difficult to predict without a 418 reliable apatite standard for SIMS isotope analyses. However, we can speculate that magmatic 419 sulfides or apatite containing juvenile martian sulfur would drive the S multi-isotope 420 composition of NWA 7533 toward 0 ‰ in the  34 S vs.  33 S diagram of Fig. 2. Alternatively, 421 Humayun et al. (

2014

) suggested that NWA 7533 lithic clasts crystallized from impact 422 melts that incorporated already weathered clay-rich martian soils. In that case, evidence 423 from SNC meteorites and analyses of Gale crater sulfates

(Greenwood et al., 2000;

424

[START_REF] Farquhar | Implications from sulfur isotopes of the Nakhla 750 meteorite for the origin of sulfate on Mars[END_REF][START_REF] Franz | Isotopic links between atmospheric chemistry 764 and the deep sulfur cycle on Mars[END_REF], 2017, 2019[START_REF] Dottin | Evidence for 747 oxidation at the base of the nakhlite pile by reduction of sulfate salts at the time of lava 748 emplacement[END_REF][START_REF] Mari | Syneruptive incorporation of martian surface sulphur in the nakhlite lava flows 889 revealed by S and Os isotopes and highly siderophile elements : implication for mantle 890 sources in Mars[END_REF]

425 predict deviation of  34 S toward strongly positive values in Fig.

2

. Clearly, neither 428 Fe oxyhydroxides contain ten times more S than does apatite (3000±1000 ppm; now 429 measured in-situ with both EMP and LA-ICP-MS, Table

2

). However, simple mass balance 430 calculations suggest that Fe oxyhydroxides are a negligible S reservoir, too. They would

  Lorand et al., 2003 and ref. therein). Under uncertainty data on the average triple S compositions reported Table1as the 484 simple 2x standard deviation on the values, and the weighted average uncertainty on the data, 485 along with its MSWD value. Both the NORDSIMS and Nancy data set yield similar results :  33 S values define statistically single low MSWD (1.1 vs. 1.5 for the Nancy and NORDSIMS 493 data set, respectively) populations that are very slightly negative. In fact, combining both data 494 sets gives a weighted average of -0.165 ± 0.032 permil, not overlapping the bulk value. OfFranz et al., 2019; Bridges et al., 2019 and reference therein). These rocks produce 524 trends of positive  34 S values coupled with negative  33 S values with water soluble (Ca sulfates)

	461 462 463 464 492 523 et al., 2018; 525 The discussion above casts serious doubt on whether another S reservoir with a significant effect on bulk S isotopic composition is present in these breccias. Another possible source of discrepancy between the bulk-rock analyses and in-situ measurements is analytical bias generated by one or both of the two techniques. The bulk-rock analysis involved an extraction and acid soluble sulfates (jarosite) in Antarctic nakhlites (McCubbin et al., 2009) defining the -495 course, the fact that  34 S shows variation means that our analyses may have sampled two (or 526 highest  34 S endmembers (Fig. 7). Likewise ALH 84001 (a proxy of NWA 7533 orthopyroxene
	465 496 527	procedure of S using a Cr(II) solution (c.f. Labidi et al., 2012) which has been shown to be very more) reservoirs that are very slightly different in  33 S. Testing that interpretation from a  33 S crystal clasts with similar ages of formation; Hewins et al., 2017) incorporated crustal sulfate
	466 497 528	inefficient for sulfates. (Gröger et al., 2009). However, this analytical bias was likely negligible vs.  34 S plot would demand many more analyses with much better individual data uncertainties enriched in 34 S along with anomalous 33 S ( 34 S = 7.20 ± 0.15‰,  33 S = -0.072 ± 0.008‰,  36 S =
	467 498 529	because as shown above, NWA 7533 meteorite lacks detectable amounts of sulfates. A than we have. In that case, the calculation with standard deviations may apply, which would give 0.02 ± 0.15‰; Franz et al., 2014). We note here that the MIF observed in NWA 7533 (this
	468 469 470 499 500 501 530 531 532	F o r systematic analytical bias from both the Nancy and Stockholm SIMS can be ruled out because multiple sulfur analyses were processed in both places the same way using the same reference materials and both were mass resolved from 32 S 1 H. One may speculate that hydride generation F o r a mean  33 S value of -0.2 ± 0.18 (2SD) for the Stockholm data, -0.12 ± 0.22 (2SD) for the Nancy data and a -0.16 ± 0.11 (2SD) for the combined dataset. Taken individually, both mean  33 S values overlap the bulk rock data, but when study) and in the nakhlites (Franz et al., 2014; Dottin et al., 2018) are an order of magnitude F smaller than the effects observed in terrestrial Archean pyrites (Farquhar et al., 2000). During the o r photolysis of SO 2 , the magnitude of the S-MIF effect is dependent on the formation of at least
	502 533	P e P e e P two distinct species, an oxidized sulfate (or gaseous SO 3 ) and a reduced sulfur polymer (S 2 or S 8 ) combined, they do not.
		e r e r e r
		R e R e R e
		v v v
		i e i e i e
	541	w w w (2000) documented a wide range of  34 S (-9.69 ± 0.22‰ to 7.8 ± 0.7‰), as well as anomalous
	542	O O O ∆ 33 S signals (-0.74 ± 0.39‰ and -0.51 ± 0.38‰) in two pyrite grains located in "crushed zones"
		n l n l n l
	454 515	Clearly, resolving both issues will demand better spatial resolution and analytical precision than acidic conditions that characterize terrestrial weathering, both Se 4+ and Se 6+ tend to adsorb onto y y y
	455 516	naturally occurring Fe oxides and oxyhydroxides while S is leached as SO 4 2-(e.g. Ziemkievics et those of present-day SIMS techniques.
	456 486 517	al., 2011). From pyrite modal abundance (up to 1 wt.%; Lorand et al., 2015), NWA 7533 should  large spread of data for  34 S (MSWD of 42 for the NORDSIMS analyses and 132 for the
	457 487 518	show a bulk-rock S content of 5,400 ppm S instead of 865±80 ppm measured in the present Nancy analyses), beyond what can be explained by analytical uncertainties. This scatter could Hydrothermal cycling of MIF-bearing S in NWA 7533
	458 488 519	study. This suggests a loss of 80% S as dissolved sulfates during terrestrial weathering, which is represent a real Mass Dependent Fractionation (MDF) trend or a subtle analytical issue. Hence, As recalled in the introduction, SNC meteorites that have sampled sub-effusive igneous

459

consistent with previous estimates, either based on pyrite/Fe oxyhydroxide modal ratios

(Lorand 460 et al., 2015)

or in-situ analyses of pyrite S and Se contents

(Lorand et al., 2018b)

. 471 could be a bit higher on the sulfide standard mount block (in epoxy) (or if the standard sulfides 472 themselves are hydrated) than on the meteorite section, thus generating  33 S values biased 473 towards higher values that would in return make the unknowns lower in  33 S. Another effect that 474 could alter the  33 S values measured by SIMS is the Faraday amplifier background drift. Many 475 of the sulfides analysed in our paper are yielding somewhat lower 70-80% count rates than the 476 standards so a small drift would have a disproportionate effect in any drift correction, probably at 477 around the 0.1 permil level (around 1000 cps in 10 7 cps), and it would lower  33 S too. However, 478 there is no direct evidence that this putative drift might have operated during the analytical 479 session of NWA 7533 sulfides. Moreover the background was systematically measured during 480 the pre-sputtering time. 481 The question that arises now is whether the SIMS analyses sampled one or several S 482 populations from the same sulfides (pyrite/and or pyrrhotite). This issue can be addressed by 483 looking at the 489 the weighted average uncertainty is obviously not a useful measure of 490 the scatter for  34 S that integrates a component of geological scatter (MDF).

503 -Our  36 S averages are similar to each other and within error of the 504 bulk. However, the Nancy data display a greater spread (MSWD of 13) perhaps inconsistent with 505 sampling a single population. 506

To summarize, the fact that SIMS and bulk-rock data do not overlap at 95% confidence 507 suggests that the two techniques may have sampled different sulfur isotopic compositions from 508 the same Fe-sulfides, assuming that each data set (the UMD bulk-rock data, the NordSIMS data 509 and the Nancy data) are single populations. Thus, the case for multiple S populations could be 510 stronger than the case for analytical bias. Deciphering which parameter really played the major 511 role in our data set is made difficult by the fact that we are comparing data at the 0.1 permil level 512 which is very close to the limitations of the SIMS method. We also cannot exclude that the tiny 513 pyrite crystals that are well below the size of the SIMS beam (1 vs. 10 m, respectively) in 514 impact breccia NWA 7533 show less negative  33 S compared to the larger crystals measured. 520 rocks of the martian crust (i.e. nakhlites) have provided multiple evidence of crustal S 521 contamination that took place throughout the cooling history of these rocks, from the magma 522 crystallization stage to late exposure to hydrothermal fluids and evaporitic brines (see also Dottin 534 between which the sulfur isotopes are distributed in a mass-independent manner (Pavlov and 535 Kasting, 2002). The presence of oxidation on Mars' surface evidenced by oxychlorine 536 compounds would oxidize the reduced species, so that practically all sulfur ends up as sulfate at 537 the surface. This would prevent the formation of large MIF effects in surficial sulfate, contrary to 538 initial expectations. 539 As suggested by NWA 7533 pyrite, negative  34 S values seem to be a characteristic 540 feature of pyrite occurrences in SNC meteorites. Shearer et al. (1996) and Greenwood et al. 543 of ALH 84001 and associated with carbonates interpreted to have hydrothermal origin. Negative 544  34 S values were also published for Lafayette pyrite resulting from partial replacement of 545

  . , well above typical martian magmatic conditions. Reduction of one mole of S 6+ to S 2- 584 consumes eight moles of electrons and has the potential to oxidize eight moles of Fe 2+ to Fe 3+

	582	highly oxidized state of NWA 7533 of ~FMQ + 2 log units (Leroux et al., 2016; Hewins et al.,
	583	2017)
		F o r
		P e
		e r
		R e
		v
		i e
		w
	572	Hence, taking into account the extreme isotopic composition of martian sulfates, the isotopic O
	573 574	fractionation relationship between NWA 7533 pyrite and putative martian sulfates ( 34 S sulfate -n l pyrite ) is about 10 ‰. Such  34 S values require TSR temperatures in excess of 250 °C using the y
	575	experimentally derived equation of Kiyosu and Krouse (1990) (see also Machel et al. (1995)). To
	576	preserve negative  34 S values, this system must have been open with respect to the supply of
	577	sulfate (sulfate supply > sulfate consumption), otherwise pyrite would develop positive  34 S
	578	values upon completion of closed system fractionation effects (e.g. Magnall et al., 2016). Such
	579	an open system is consistent with the widespread distribution of pyrite inside porosity of each

580 lithogical component of martian breccias, including late veinlets. The TSR process may have 581 contributed along with other petrogenetic processes (magma degassing, weathering……) to the

igneous intrusion as source of NWA 7533 hydrothermal pyrite? 625

	613	2013). Lorand et al. (2012) concluded that pyrite in the strongly shocked chassignite NWA 2737
	614	was desulfurized into FeS due the high shock pressure (55 GPa) coupled with strong heating
	615	conditions (perhaps up to 800 °C) published for this meteorite. In NWA 7533, the shock event
	616	postdating pyrite crystallization generated only planar deformation features in pyrite. A
	617	desulfurization of pyrite into spongy pyrrhotite is thus considered to be very unlikely. For
	618	comparison, pyrite was preserved in Chassigny that experienced a shock pressure of much
	619	greater intensity (about 35 GPa with a post-shock temperature of about 300 °C; Lorand et al.,
	620	2018a). The NWA 7533 spongy pyrrhotite must be interpreted as a metastable hydrothermal
	621 622	F product of sulfate reduction reactions reflecting local, transient more reducing conditions during o r percolation by hydrothermal fluids (see Lorand et al., 2015).
	623 624	Meteorite impact vs.	P e
			e r
			R e
			v
			i e
			w
			O
			n l
			y
			al.,

  Pyrite is by far the major host of sulfur in the polymict NWA 7533 breccia and paired 677 meteorites. Apatite and Fe oxyhydroxides are negligible S carriers, as are the tiny magmatic

	675 1002 1013	Whitehouse M.J. 2013. Multiple Sulfur Isotope Determination by SIMS: Evaluation of
	676
	678	sulfide grains so far identified. Sulfates (barite or gypsum) have not been firmly identified in the
	679	breccia. The initial sulfur content of the breccia inferred from the modal abundance of pyrite and
	680	al., 2013; its pseudomorphous Fe-oxyhydroxides is estimated to be ~5,400 ppm. The two bulk-rock S
	650 681	Koeberl, 2014). Sulfides are common hydrothermal products in impact craters on Earth and analyses obtained here confirm previous estimates of 80% S loss resulting from terrestrial
	651 682	mineralisation dominated by pyrite is thought to occur during the latest stages of cooling (Parnell weathering of NWA 7533 pyrite.
	652 653 654 683 684 685 655 656 686 687 657	et al., 2010; Simpson et al., 2005; 2017). Geochemical modeling of impact-generated hydrothermal systems for Mars also frequently return pyrite among hydrothermal products (e.g. F o r The occurrence of S-MIF in the S multi-isotope composition supports a model of NWA F o r F o r F o r F o r F o r F o r F o r F o r F o r F o r F o r F o r 7533 pyrite formation from martian surficial sulfur that experienced photochemical reaction(s). Schwenzer and Kring, 2013). As shown by these authors, pyrite becomes a major mineral along with hematite for water/rock ratios exceeding 1,000. Such conditions are met inside veins, as P e The slight discrepancy between in-situ SIMS analyses ( 33 S = -0.2 ± 0.1 ‰; mean of 29 analyses) and the bulk IRMS analyses ( 33 S = -0.029 ± 0.010 ‰) is tentatively interpreted as a P e P e P e P e P e P e P e P e P e P e P e P e observed in NWA 7533 where some cracks are filled with pyrite + maghemite (Lorand et al., 2015). Cassata et al. (2018) proposed for NWA 7034 (paired with NWA 7533) a rather different e r e r e r e r e r e r e r e r e r e r e r e r e r
	658 659 660 661 662 663 691 692 693 694	interpretation linking the lithification and annealing event with a thermal dome above deeper intrusives because thermal metamorphism recorded by the K-Ar and U-Pb systems yield plateau age differences that were greater than durations (10's of Ma or less) required to cool shock-heated basement terrains following large (100 to 200 km) impact events that might have occurred at ~1,300 Ma. Magmatism is known to have occurred on Mars at 1.4-1.35 Ga from the nakhlite and chassignite meteorites (Nyquist et al., 2001; Cohen et al., 2017 and references R e v i e w R e R e R e R e R e R e R e R e R e R e R e R e reflective of authigenic sulfide precipitated from H 2 S produced via open-system reduction of v v v v v v v v v v v v sulfates. A transient more reducing stage likely produced the spongy pyrrhotite that carries i e i e i e i e i e i e i e i e i e i e i e i e similar S multi-isotope compositions as that of pyrite. It is concluded that sulfur was recycled by downward percolation of reduced S -bearing w w w w w w w w w w w w
	664 665 666 695 696 697 667 698 699	therein), while the impact cratering rate of the martian surface was already considerably reduced at that time (e.g., Moser et al., 2019). However, MacArthur et al. (2019) related the maximum O n l aqueous fluid produced by melting of permafrost. However, the driving force that recycled O O O O O O O O O O O O crustal S in NWA 7533 lithologies, underlying magmatic intrusions or impact-induced heating, is presently unclear. n l n l n l n l n l n l n l n l n l n l n l n l 40 Ar-39 Ar age of 1130 -1250 Ma in the NWA 8114 meteorite clast (paired with NWA 7533) analysed by them to an impact shock event and the subsequent high-temperature oxidative y y y y y y y y y y y y y
	668	breakdown of many of the pyroxenes (also documented in NWA 7533 by Leroux et al., 2016). A
	669	simple Fourier cooling model suggested that a burial depth of 5 m was enough to maintain
	670	sufficiently high temperatures (>600°C) for ~30 days (MacArthur et al., 2019). With this
	671	constraint in hand, one may assume that sulfates in martian breccias may have been reduced to
	672	sulfides almost in-situ, implying very little transport of aqueous fluids.
	673
	674	CONCLUSIONS

688 likely sampling bias since only grains > 20 µm in size were analyzed. 689 Negative  34 S values were previously reported for several occurrences of secondary 690 pyrite in SNC meteorites. Such negative values in the hydrothermal setting of NWA 7533 are

Table 2 .

 2 Comparison of NWA 7533 pyrite compositions with SNC meteorites in a   S vs  33 S Table 1. S isotopic compositions of sulfides in NWA 7533 (Canon Diablo-normalized) S (ppm)d 34 S (‰) 2s D 33 S (‰) 2s D 36 S (‰) 2s : exclude the positive values of D33S in Site F-4 Pyrite and Site 16-1 Pyrite2SD is the simple 2x standard deviation on the values (measures variation in a data set regardless of individual ru wtd.av. is the weighted average uncertainty on the data along its MSWD value (measures the spread) Laser Ablation inductively-coupled mass spectrometry (LA-ICPMS) analyses of pyrite alteration products.

	1042
	1043 Figure 7. 1044 diagram. A = ALH 84001; L = Lafayette; N = Nakhla; Y = Y000593 (nakhlite); M = Miller
	1045	Range nakhlites; NWA 998 and NWA 6148 : nakhlites; WSS : water-soluble sulfates; AVS :
	1046	acid-volatile sulfides; CRS : Chromium-reducible sulfides; Py : pyrite. Other data : bulk-rock
	1047	analyses. Note the overall negative   S values of NWA 7533 sulfides for slightly negative  33 S
	1048	values compared to nahklite sulfates. Arrow materializes possible thermochemical reduction of
	1049	sulfates	into	NWA	7533	hydrothermal	sulfides.
			o r
			P e
				e r
				R e
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					O
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						y

*

*Electron Microprobe analyses-EMPA

Laboratoire de Planétologie et Géodynamique à Nantes, CNRS UMR 6112,Université de Nantes,

Rue de la

Meteoritics & Planetary ScienceRunning Head

Acknowledgement

We are indebted to L. Labenne for the sample. We are grateful for funding