# Experimental investigations of mineral-organic chondritic analogs under hydrothermal conditions: implications for carbonaceous asteroids

Coline Serra, Olivier Grauby, Daniel Ferry, Fabrice Duvernay, Grégoire Danger, Johanna Marin-Carbonne, Vassilissa Vinogradoff

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## To cite this version:

Coline Serra, Olivier Grauby, Daniel Ferry, Fabrice Duvernay, Grégoire Danger, et al., Experimental investigations of mineral-organic chondritic analogs under hydrothermal conditions: implications for carbonaceous asteroids. Geochimica et Cosmochimica Acta, 2025, 398, pp.29 - 43. 10.1016/j.gca.2025.04.018. hal-05121158

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Submitted on 19 Jun 2025

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# Experimental investigations of mineral-organic chondritic analogs under hydrothermal conditions: implications for carbonaceous asteroids

Coline Serra<sup>a, b</sup>, Olivier Grauby<sup>b</sup>, Daniel Ferry<sup>b, d</sup>, Fabrice Duvernay<sup>a</sup>, Grégoire Danger<sup>a, c</sup>, Johanna Marin-Carbonne<sup>d, e</sup>, Vassilissa Vinogradoff<sup>a, * f</sup>

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## ARTICLE INFO

Associate editor: Hikaru Yabuta

**Keywords:**

Experimental meteorites

Carbonaceous chondrites

Organic-mineral interactions

Aqueous alteration

## ABSTRACT

The occurrence of hydroxylated minerals in carbonaceous chondrites provides valuable insights of water–rocks interactions in hydrous asteroids. Yet, the evolution of water-organic-rock type experiments, applied to carbonaceous chondrites, remains understudied. Here, we present experimental studies of chondritic analogs containing a mixture of minerals and 4 wt% of OM under hydrothermal anoxic conditions at low temperature. The mineral composition is a mixture of anhydrous minerals (peridot, feldspar and troilite), combined with hexamethylenetetramine ($C_6H_{12}N_4$), a model organic molecule derived from interstellar grains. After being exposed to water at 80 °C for different duration time (up to 100 days) simulating early-stage alteration, a combination of analytical techniques (X-ray diffraction, transmission electron microscopy, infrared spectroscopy and elemental analyses) revealed significant changes in the mineral part of the chondritic analogs. The secondary minerals formed are diverse, consisting of hydroxylated phases such as phyllosilicates, but also iron oxides, which become more abundant with time. Amorphous silicate phases are also observed in abundance. The formation of these secondary minerals is strongly influenced by the presence of soluble organic matter, which can impact the nature of the formed hydroxylated phases and reduce the formation of iron oxides. The secondary phase assemblage obtained in our experiments exhibits similarities with carbonaceous chondrites that have undergone a low degree of aqueous alteration (CM-type). The results indicate that the presence of organic matter, even accounting for 4 wt%, is an important driver in the formation of secondary mineral phases during the initial stage of aqueous alteration. They highlight the importance of understanding the complex interactions between organic and inorganic materials in the context of hydrous asteroids.

## 1. Introduction

Asteroids are considered the remnants of our protoplanetary disk, providing valuable information about the initial composition and formation of the Solar System. Carbonaceous chondrites (CC) are fragments of primitive asteroids that exhibit evidence of secondary alteration in their parent body, such as aqueous alteration (can be hydrothermal), that have occurred during brief period, shortly after asteroid formation. This alteration, characterized by the local circulation of fluids through the rock, has altered the initial organic and mineral composition and produced secondary minerals (Brearley, 2006). Various secondary mineral compositions are found in CC, such as phyllosilicates with

variable Fe/Mg ratios, but also carbonates, sulfates, oxides, sulfides, halides, and oxyhydroxides (Brearley, 2006; Le Guillou and Brearley, 2014; Howard et al., 2015). Such variations demonstrate the diversity and complexity of the physicochemical conditions of aqueous alteration, in addition to the starting composition (organics and minerals), as reflected by the different classes of CC (Brearley, 2006; Abreu et al., 2020; Suttle et al., 2021). The mineral fraction found in these CC, or from recent sample returns such as the Ryugu asteroid (Nakamura et al., 2022), may thus contain a summary of the history, including the formation and evolution of their parent body. The Mighei-subtype CC group (CM) are the most abundant hydrated meteorites, representing 25 % of CC with a water content ranging from 4.8 to 13.9 %wt (Garenne

<footnote><sup>a</sup> Aix-Marseille University, UMR CNRS 7345, PIIM, Institut Origines, Marseille, France</footnote>

<footnote><sup>b</sup> Aix-Marseille University, UMR CNRS 7325 CINAM, Marseille, France</footnote>

<footnote><sup>c</sup> Institut Universitaire de France, France</footnote>

<footnote><sup>d</sup> Institut des Sciences de la Terre, Université de Lausanne, Switzerland</footnote>

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: Vassilissa.vinogradoff@univ-amu.fr (V. Vinogradoff).</footnote>
et al., 2014; Alexander et al., 2015). These CC could contain up to 4 wt% of organic matter (OM) (Pearson et al., 2006; Alexander et al., 2007, 2013). From an analytical perspective, this OM can be divided into two fractions: a soluble fraction in common solvents (methanol, dichloro-methane, hexane, water) (called SOM) representing 10 to 30 % and an insoluble fraction (IOM) obtained after various acidic treatments, accounting for 70–90 % of the total organic carbon of CC (Remusat, 2015; Alexander et al., 2017). The SOM is mainly composed of small organic molecules (carboxylic acids, amines, aliphatic and polycyclic aromatic hydrocarbons, sugars, etc.) (Sephton, 2002; Pizzarello et al., 2006; Glavin et al., 2018), while the IOM consists of macromolecules containing heteroatoms (N, O, S) (Remusat et al., 2005; Derenne and Robert, 2010).

In situ observations of the OM reveal at least two distinct populations: submicron-sized OM particles and diffuse OM finely interspersed among the secondary phyllosilicates (Le Guillou and Brearley, 2014; Le Guillou et al., 2014) or incorporated within calcites (Chan et al., 2017). Such close association between OM and mineral matter likely means that certain chemical and morphological characteristics can be attributed to secondary alteration processes. As known in terrestrial environments, the interaction between organic and mineral compounds may influence reaction pathways in a selective manner (Schoonen et al., 2004). The impact between organic and mineral matters can occur in various ways, such as chelation, physi- or chemisorption, potentially impacting mineral nucleation, growth, and transformation (Kleber et al., 2021). Organic material can act as catalysts, can regulate the chemical environment of the mineral, influence the dissolution process or the recrystallization of secondary minerals (Ganor et al., 2009; Le Guillou et al., 2014; Kleber et al., 2015, 2021). For example, carboxylic acids can catalytically enhance the dissolution rate of silicates (Ganor et al., 2009). The presence of organic matter can also interfere with iron oxide formation, potentially inhibiting their formation entirely, due to the formation of organic complexes or the generation of new molecules (Fischer and Schwertmann, 1975; Schwertmann et al., 1986). The evolution of the organo-mineral system is thus a complex process. In light of the multitude of soluble organic molecules present in CC (Schmitt-Kopplin et al., 2010), it is evident that a vast array of interactions can be achieved during aqueous alteration.

The physical conditions of alteration in CM are estimated with an initial water to rock ratio ranging between 0.2–0.7(W/R), with early alteration occurring at low temperatures (<70 °C) while later alteration proceeded at higher temperatures (100–250 °C) and under unconstrained redox conditions (Suttle et al., 2021).

Previous studies have investigated the effect of an advanced aqueous alteration on natural chondritic samples, retrieving the conditions and formation of some secondary phases and still showing some evolution of secondary minerals (Jones and Brearley, 2006; Suttle et al., 2022). Other studies, using different primitive minerals like magnesio-silica smokes (Rietmeijer et al., 2004); enstatite (Ohnishi and Tomeoka, 2007); amorphous silicates phases (Le Guillou et al., 2015); mixture of olivine, pyrite, GEMS-like materials and alpha iron (Fabre et al., 2024); mixture of olivine, iron metal and GEMS-like materials, (Vacher et al., 2019); mixture of olivine, enstatite, silicate glass, troilite and iron metal (Kikuchi et al., 2022); have studied the effect of pH, temperature and time under hydrothermal alterations. These different studies have highlighted the fast and efficient transformation of primary minerals under aqueous alteration, typical of CC, and revealed some mechanisms of mineral formation found in low or high altered CCs. All of these experiments were conducted without OM, although OM could play a significant role in the transformation of primary minerals and the formation of secondary minerals.

Few previous studies have investigated the evolution of abiotic matter on hydrous minerals under asteroidal hydrothermal conditions, considering the effects of both water, nature of organic and hydrous mineral compounds (Jacquemot et al., 2019; Vinogradoff et al., 2020a; Viennet et al., 2022). The effects on mineral evolution (phyllosilicates or

silica gel) were contingent upon the nature of the organic compounds and pH. By controlling the crystallization process, or accelerating the maturation of the phyllosilicate, it was possible to influence the evolution of the mineral considered (Jacquemot et al., 2019; Viennet et al., 2022; Criouet et al., 2023).

The impact of OM on the aqueous alteration of non-hydrated minerals remains not understood. Two related investigations explored the co-alteration of primary silicate minerals (olivine) and OM (a mixture of carboxylic acids, aromatic compounds and fatty acids, (Nakano et al., 2020)) under simulated thermal metamorphism conditions (up to 400 °C) within the parent bodies of chondrites (Hirakawa et al., 2021a, b). These studies revealed that minerals can catalyze the decarboxylation of oxygenated organic matter at such temperatures (Hirakawa et al., 2021b). Moreover, it was demonstrated that hydrated silicates could form in situ from water produced by the degradation of OM, even in the absence of initial water, under heating conditions of 400 °C (Nakano et al., 2020; Hirakawa et al., 2021a).

In this present study, we present alteration experiments involving organic matter and non-hydrated minerals as chondritic analogs submitted to early-stage aqueous alteration conditions. The experiments were performed using simple initial materials (a single N-rich organic molecule and three different minerals) to investigate the transformation of the two phases at 80 °C under reducing conditions. These conditions were chosen to simulate the low-temperature environment proposed for less altered CC (Brearley, 2006; Howard et al., 2015; Suttle et al., 2021). This work is part of a broader issue concerning the co-evolution of organic and mineral matters under low-temperature hydrothermal conditions. Here, the objective was to investigate the composition of the new minerals, and the specific role of OM on the alteration of primary mineral phases during water-organic-rock interactions in the context of early-stage alteration in asteroids. A previous study examined the soluble organic fraction and its evolution due to the effect of primary minerals on samples containing the same composition (Serra et al., 2024). This present study shifts focus to the solid mineral fraction formed with and without OM, addressing several key questions: Does the presence of OM influence the types of hydrated minerals formed? Is a small quantity of OM, like the 4 wt% used here (similar to that observed in CC), sufficient to induce these effects? Does it catalyze or inhibit the formation of secondary minerals? The comparison of chondritic analogs with or without N-rich OM over time allowed drawing a chemical scenario of interactions between the matters, which can contribute to a better understanding of the mineral-OM assemblage found in CC. These results will help improve our understanding of the conditions that may have shaped the mineralogical evolution on hydrated C-type asteroids and their impact on mineralogical evolution. Out study shed light on the potential role of organic chemistry in such environments.

## 2. Material and methods

### 2.1. *Composition of the chondritic analogs, experimental design*

The chondritic analogs were prepared using a simple initial mixture of organic and mineral materials. Regarding the selection of organic matter, a fraction of the OM accreted in carbonaceous chondrites may originate from the evolution of interstellar ices in the interstellar medium. Laboratory experiments mimicking these ices have demonstrated a predominant organic product, hexamethylenetetramine ($C_6H_{12}N_4$, HMT) (Bernstein et al., 1995; Munoz Caro and Schutte, 2003). This molecule has also been detected in carbonaceous chondrites (Oba et al., 2020). Furthermore, HMT's cage-like structure facilitates its degradation under hydrothermal conditions, and numerous studies have demonstrated its significant reactive potential in such environments (Vinogradoff et al., 2018; Kebukawa et al., 2020) and produce amino acids (Vinogradoff et al., 2020b) highlighting an astrobiological interest. These properties make HMT a particularly valuable molecule model for mimicking a primitive chondritic analogue.
For minerals, we selected two silicates capable of forming secondary minerals during aqueous alteration, such as those observed in altered CC (Brearley, 2006; Suttle et al., 2021). We chose a Mg-rich olivine, specifically the peridot variety ((Mg, Fe) SiO₄), resembling the silicate observed in interstellar grains (Welsch et al., 2023) and highly suspected as precursors of serpines in CCs (Oyanagi et al., 2017). We then selected an alkali-rich plagioclase specifically oligoclase ((Ca,Na) AlSi₃O₈), observed in the minimally altered chondrite CM3 Asuka 12169 (Kimura et al., 2020), which provides alkali ions that can contribute to the formation of secondary minerals such as smectites, chlorite, and micas observed in CC (Brearley, 2006). In addition, an iron sulfide: troilite (FeS), commonly found in weakly altered chondrites, was also introduced as model primary iron minerals (Herndon et al., 1975; Brearley, 2006).

We made mixtures that only contained one variety of mineral and a mixture containing all minerals with or without the HMT (Table 1). The mixtures were subjected to aqueous condition at 80 °C, using a water/rock (W/R) ratio of 10 with a total solution volume of 1 mL to increase material interaction (Fig SI1, Table 1). Although this ratio exceeds typical ratios in CC (usually around 1 (Brearley, 2006)), it can be justified in specific locations during the initial stages of alteration reactions (Howard et al., 2015). Experimentally, this higher ratio also offers the advantage of providing 1 mL of solution, which facilitates subsequent analyses, and enhances reactivity, allowing for rapid transformation of organic and mineral matters. The concentration of HMT was chosen so that we have a mass ratio of OM/mineral of 4 wt%, which is close to the actual quantity of OM found in CC (Pearson et al., 2006; Alexander et al., 2007, 2013).

## 2.2. Samples preparation, experimental protocol

HMT (Sigma Aldrich > 99%-30 mM) was mixed with minerals at 80 °C for diverse durations, ranging from 1 to 100 days (Table 1). Natural silicates (peridot from San Carlos Arizona and feldspar from Madras, India) were obtained from Minerals Unlimited (USA) in grain form (centimeters). Following successive cleaning with a mixture of methanol and dichloromethene (MeOH/DCM) to eliminate external contamination, centimeter-sized grains were oven-dried at 60 °C. Then, they were ground into a fine powder of micrometer size using a Speccam pebble mill in agate cells. The resulting fine powder underwent further washing with MeOH/DCM. Synthetic troilite (Iron (II) sulfide, Sigma Aldrich) was already in powder form (less than 150 µm grain size). 100 mg of silicate mineral were introduced, as 100% when it is alone and with a ratio of 2:1:2 Peridot: Troilite: Feldspar: when they are all together. The feldspar to olivine ratio used in our study was chosen to maximize cation availability for interaction with organic matter, even though it may not be representative of natural chondritic compositions. We used milli-Q water (Merck, conductivity < 18.2MΩ cm⁻¹), degassed

<caption>**Table 1**</caption>

Summary of the manipulations performed with their names and composition, abbreviations are: H = HMT, P = Peridot, F = Feldspar, T = Troilite.

<table><thead><tr><th rowspan="2">Composition</th><th rowspan="2">Organic (4.2 mg)</th><th rowspan="2">Minerals (100 mg)</th><th colspan="4">Time (days)</th></tr><tr><th>1</th><th>10</th><th>45</th><th>100</th></tr></thead><tbody><tr><td>HMT</td><td>Peridot</td><td></td><td>HP1</td><td>HP10</td><td>HP45</td><td>HP100</td></tr><tr><td>HMT</td><td>Feldspar</td><td></td><td>HF1</td><td>HF10</td><td>HF45</td><td>HF100</td></tr><tr><td>HMT</td><td>Troilite</td><td></td><td>HT1</td><td>HT10</td><td>HT45</td><td>HT100</td></tr><tr><td>HMT</td><td>Peridot (40 mg)</td><td></td><td>HPTF1</td><td>HPTF10</td><td>HPTF45</td><td>HPTF100</td></tr><tr><td></td><td>Feldspar (40 mg)</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td></td><td>Troilite (20 mg)</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>/</td><td>Peridot</td><td></td><td>P1</td><td>P10</td><td>P45</td><td>P100</td></tr><tr><td>/</td><td>Feldspar</td><td></td><td>F1</td><td>F10</td><td>F45</td><td>F100</td></tr><tr><td>/</td><td>Troilite</td><td></td><td>T1</td><td>T10</td><td>T45</td><td>T100</td></tr><tr><td>/</td><td>Peridot (40 mg)</td><td></td><td>PTF1</td><td>PTF10</td><td>PTF45</td><td>PTF100</td></tr><tr><td></td><td>Feldspar (40 mg)</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td></td><td>Troilite (20 mg)</td><td></td><td></td><td></td><td></td><td></td></tr></tbody></table>

by nitrogen to eliminate dissolved oxygen. The mixtures were prepared under argon atmosphere (>99.999%; Air Liquide; ALPHAGAZ 1) in a glove box (<0.5 ppm O₂). Solutions with or without solids were placed in quartz inserts, then in Teflon pots, inserted in ToptionLab autoclaves, which can be considered as a closed system (Fig. SI1). The reactors were subjected to different times at 80 °C in an oven. Once the time has elapsed, the samples were cooled to room temperature overnight before centrifugation, resulting in their separation into a liquid fraction (supernatant) and a solid fraction (precipitate) (Fig. SI1). The pH was not buffered, and measurements were conducted using universal indicator paper on the liquid fraction. Due to the inherent inaccuracies of pH paper, the measurements should be interpreted as relative values rather than absolute. The liquid fraction of the samples were preserved for other analysis and the result are presented in a previous publication (Serra et al., 2024). The solid fraction was dried for 24 h at 50 °C (without further washing steps) and then analyzed using elemental analysis, electronic microscopy (in transmission and scanning modes), infrared spectroscopy and X-ray diffraction analysis (Fig. SI1).

## 2.3. Analytical techniques

### 2.3.1. X-ray diffraction

The XRD measurements were carried out at the CINAM laboratory (Marseille, France) using a RigaKu RU6200BH instrument equipped with a high-gloss rotating Cu Kα anode (λ = 1.5418Å) and a 2D flat image type detector, model Mar345. For these measurements, the working power was 50 kV and the intensity was 50 mA with a beam size of 0.5 × 0.5 mm². XRD patterns were collected in a quartz capillary containing crushed samples. The data processing and comparison with reference minerals were performed using the Highscore Plus software database.

### 2.3.2. Electron microscopy

Transmission electron microscopy coupled to energy dispersive X-Ray (TEM-EDX) microanalyses were conducted at the CINAM laboratory on individual particles using a JEOL JEM 2011 TEM fitted with a Bruker X-Flash Silicon Drift Detector 5030. Data collection parameters for EDX analyses were set as follows: magnification of 50,000, 4L spot size, angular tilt of 20° toward the detector, time constant of 60 kcp.s⁻¹, energy range of 40 keV, and corrected counting time of 30 s. The beam diameter was set to ~20 nm (200 Å) in order to reach the smallest particles. The constant beam density was ~63.5 pA.cm⁻². Atoms O, Na, Mg, Al, Si, K, Ca, and Fe were quantified by applying the Bruker AXS MET line mark data quantification procedure (Cliff and Lorimer, 1975). Microphotographs of sample were also acquired with a scanning electron microscope (SEM) JEOL JSM 7900F at 5 kV intensity.

### 2.3.3. Infrared spectroscopy

Attenuated total reflectance (ATR) analyses were performed in the PIIM laboratory (Marseille, France) using a Bruker Vertex 70 FTIR spectrometer equipped with an attenuated total resonance instrument, ATR-Quest (Specac). Spectra were acquired from 400 to 4000 cm⁻¹ with a spectral resolution of 4 cm⁻¹. Background spectra were acquired with 62 scans and 32 scans for the samples. The spectra shown in the figures are raw. Deconvolution were performed using the OPUS software after baseline correction. For the IR spectra presented in this study, the best fitting results were obtained by assuming a symmetric Gaussian peak shape for each band.

### 2.3.4. Elemental analysis

The amount of hydrogen, nitrogen, and carbon in the solid part was measured using a Thermo Finnigan EA 1112 analyzer (Spectropole of the Fédération des Sciences Chimiques in Marseille, France). In order to ensure the accuracy of the results, two separate analyses were conducted on approximately 2 mg of powder each. Analytical errors were estimated on soil reference samples, 0.2 wt% for C, 0.02 wt% for N, 0.02 for S.
# 3. Results

## 3.1. Feldspar samples evolution (samples F and HF)

We observed a clear increased of pH in the solutions of these feldspar samples after reactions (+2 units), likely due to the presence of HMT and the feldspar dissolution releasing metallic cations ($Ca^{2+}$, $Na^+$ and $Al^{3+}$), leading to more alkaline solutions (Table SI1.).

X-ray diffraction analyses did not exhibited significant changes over time under hydrothermal conditions in presence of OM or without, and remained consistent with the initial mineral composition (mainly albite -ab) (Fig. SI2).

Nevertheless, the observation of these samples with TEM revealed the existence of spheres in both samples with or without OM that were destroyed by the beam (see the yellow arrows in images for F1, HF1, F45 Fig. 1). EDX analysis of these morphologies highlighted a silica composition.

The small bands observed at 1429, 1466, and 1688 $cm^{-1}$ in the IR spectrum (Fig. 2) in the sample containing OM (HF) suggested the presence of an organic fraction associated with the mineral. These observed bands could correspond to various vibrations, such as C=O stretching (1688), C-N/C-O stretching (1466–1429), and N–H bending (1466–1429) in amines. (Fig. 2). Consistently, the mineral fraction exhibited some sorbed nitrogen and carbon, with up to 15 % of the initial nitrogen (from the HMT) remaining after 45 days in the mineral fraction (Table SI2).

## 3.2. Troilite samples evolution (samples T and HT)

The presence of HMT in the mineral mixture under hydrothermal condition has increased the pH (5 to 7 after 45 days, Table SI1). On the other hand, troilite may have caused acidification of the environment, as it can result into the formation of polysulfides and the release of $H_2S$. The presence of $H_2S$ was confirmed by degassing on opening the reactors, with a characteristic rotten egg smell. With the OM (HT samples), the rust-like precipitate, likely reflecting the presence of $Fe^{3+}$ was not observed, it was only seen in samples without OM (T) suggesting the oxidation of troilite (Fig. 3).

The diffraction pattern between initial troilite (T crude) and hydrothermal samples revealed the mineral transformation under hydrothermal conditions with new peaks of diffraction (Fig. 4). After one day of aqueous alteration, XRD analysis of the sample with organic matter (HT1) showed peaks of troilite that remain discernible, although they were barely perceptible in the sample without OM (Fig. 4). In both samples after 1 day of reaction (HT1 and T1), pyrrhotite ($Fe_{1-x}S$) was identified by XRD (Fig. 4), supporting the notion of troilite transformation under hydrothermal conditions (Taylor et al., 1979; Kikuchi et al., 2022).

After 100 days of hydrothermal alteration, troilite remained predominant in the presence of OM as demonstrated by XRD analyses (Fig. 4). Conversely, in the absence of OM, the pyrrhotite fraction was oxidized (rust like precipitate, Fig. 3) into hematite ($Fe_2O_3$), $szo-molnokite ($FeSO_4·H_2O$) and goethite ($FeO(OH)$) becoming evident as early as 45 days of alteration (Fig. 4).

Regardless of the presence of OM, transmission microscopy with EDX analysis showed that troilite is rapidly forming new phases. For example, the formation of elemental sulfur growing at the surface of the grain (Image c, Fig. 5) or in filament form (Image g, Fig. 5) were observed, however not seen by XRD analysis (Fig. 4) (Chevrier et al., 2006). Iron platelets were also identified with EDX analysis from time 1 onwards for all composition (HT or T) (Images g and i, Fig. 5).

In agreement with the XRD results, SEM observations revealed a variety of morphological phases, including grain aggregates, platelets, needles, and spherules (Fig. 4 and Fig. 5). The characteristic morphology of troilite grains was observed across all samples at all times, confirming only partial transformation (Fig. 5). Pyrrhotite formation was confirmed with the presence of platelets in SEM images, as seen in HT1 and T1 (images d and f, Fig. 5) (Spiess et al., 1980). In T45 and T100, the needle-like morphology could indicate goethite, in agreement with XRD results (Image l, Fig. 5) (Strauss, 2016). In presence of OM (HT45) some goethite was also tentatively identified by SEM but the quantities seemed too small for X-ray detection (Image j, Fig. 5 and Fig. 4). $Szo-molnokite$ was observed in the platelet morphology only in T45 and T100 as observed in the X-ray analysis (Image h in Fig. 5, Fig. 4) (Wiese et al., 1987). Finally, the spherules observed at time 100 days, both in presence or absence of OM (HT100 and T100) indicated the presence of magnetite ($Fe_3O_4$) (Images k and n, Fig. 5) (Jeon et al., 2018). In HT100, some pyrrhotite was still observed (Image m, Fig. 5). The pyrrhotite and magnetite spherules were likely not detected by XRD due to their low quantities (Fig. 4).

Elemental analysis revealed that after 45 days, around 11 % of the initial nitrogen (from HMT) remained in the HT mixture. Furthermore, a difference in sulphur content was observed between the samples with and without OM, with the HT samples having a higher S content (~31 wt % for HT45 versus ~ 20 wt% for T45), which may suggest a lower loss of $H_2S$ without OM (Table SI2).

## 3.3. Peridot samples evolution (samples P and HP)

The presence of HMT did not result in a significant change of pH in samples containing peridot since the pH (around 8) were measured similar for all samples (Table SI1). By itself, the presence of peridot increased the pH (up to 8) due to the release of metallic cations ($Fe^{2+}$ and $Mg^{2+}$) and the consumption of $H^+$ for the formation of secondary phases.

XRD analysis shows the rapid transformation of peridot under

<figure><img src="image_5.png" /><figcaption>**Fig. 1.** Representative TEM and SEM images showing the surface texture of mineral before (initial feldspar (F0)) and after different time (1 and 45 days) with or without OM under hydrothermal conditions. No significant changes in morphology were observed over time or with/without OM, except for the formation of silica spheres (indicated by yellow arrows).</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>**Fig. 2.** Infrared Spectra of the insoluble/mineral fraction from F and HF samples over time (1, 10, 45 and 100 days) under hydrothermal conditions. A comparison is made using the initial feldspar spectrum (in gray). On the right a zoom in the [1200–1800 cm⁻¹] range of the spectrum. Arrows indicated new vibrational bands possibly linked to organic matter in samples HF. These bands could correspond to various vibrations, such as C=O stretching (1688), C-N/C-O stretching (1466–1429), and N-H bending (1466–1429) in amines.</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>**Fig. 3.** Photographs showing the hydrothermal product of samples T and HT after 1, 45 and 100 days at 80 °C under hydrothermal condition. The rust precipitate, characteristic of ferrous to ferric oxidation from troilite, is observed only in the absence of OM.</figcaption></figure>

hydrothermal conditions in the samples with and without OM, with the appearance of a peak that evolve over time between 7.77 Å<d-spacing < 8.13 Å (compared to the initial signal of standard forsterite, -Fo) (Fig. SI3). This contribution corresponds to the 001 reflection of phyllosilicates poorly crystallized. Our samples showed that the band continued to grow and move towards smaller d-spacing over time. In addition, two new peaks had also appeared (with or without OM) after 1 day of alteration, at 1.55 Å and 1.53 Å, likely corresponding to diffraction of trioctahedral clay structure (Grauby et al., 1993, 1994; Steudel et al., 2017) (Fig. SI3). XRD also highlighted the presence of amorphous phases with an increase of the baseline (Fig. SI3).

Microscopic analysis validated the presence of secondary phases from day 1 of alteration, regardless of the presence of organic matter. A fibrous morphology surrounding peridot grains was observed in all samples and has grown over time corresponding to the phyllosilicates identified through XRD (Fig. 6). Additionally, amorphous SiO₂-rich morphologies were detected, which may correlate with the increased baseline observed in XRD (Fig. 6, sample P45, dotted area).

To ensure representability of the chemical composition of phyllosilicate formed, EDX analysis was conducted on approximately 15 different phyllosilicate grains for each sample (Fig. 7). In presence of OM (HP samples), we noted, from day 1 of hydrothermal alteration, a phyllosilicate composition richer in magnesium compared to P samples, in agreement with serpentine-like composition. The discrepancy in chemical composition between samples with and without OM gradually diminished over time, as the chemical composition evolved. Regardless

of the presence of OM, EDX analysis revealed the highest concentration of iron in the first phyllosilicates formed (between 1 and 45 days) from peridot. After 100 days of alteration, chemical analysis of phyllosilicate samples with or without OM displayed chemical composition in between talc or saponite and lizardite (Fig. 7).

The IR analyses validated the formation of phyllosilicates phases with the emergence of a band at 3693 cm⁻¹ from day 1 of aqueous alteration with or without OM (HP and P samples), which intensifies over time (Fig. 8). Such band is assigned to Metal-O-H stretching vibrations characteristic of Mg-phyllosilicate hydroxyls (Beck et al., 2010), and probably corresponding to a serpentine-like composition in our samples (Chukanov, 2013). The presence of phyllosilicates in the solid residue was also confirmed by the additional band observed at approximately 1630 cm⁻¹. This band is attributed to O-H bending vibrations of absorbed/interlayer water within the phyllosilicate sheets formed. Additionally, the change observed in the bands at approximately 1005 and 886 cm⁻¹ (Si-O-Si stretching vibrations) is indicative of an evolution in the silicate structure across time. Indeed, the olivine mineral has a main Si-O-Si band at 886 cm⁻¹, which decreases with alteration time in favor of the increase in the Si-O-Si band at 1005 cm⁻¹, matching the IR signature of these phyllosilicates and amorphous phases (Beck et al., 2010) identified by XRD and microscopy in our samples. With alteration time, two other new bands appeared, one at 667 cm⁻¹, which can correspond to Mg-OH bending vibrations (Grauby et al., 1993), and one at 3676 cm⁻¹, indicating hydroxyl vibrations from a new component (Fig. 8). These two additional bands are consistent with a
<figure><img src="image_8.png" /><figcaption>**Fig. 4.** XRD pattern of initial troilite (T crude) and altered troilite with or without OM at 80 °C for 1, 45 and 100 days. The dashed line highlights the peak position of Troilite (Tro). New peaks are observed especially from troilite under hydrothermal condition without organic matter and are indexed with the following abbreviations: Po, pyrrhotite; He, Hematite; Sz, Szomolnokite; Go, Goethite.</figcaption></figure>

<figure><img src="image_9.png" /><figcaption>**Fig. 5.** Representative TEM (images a, c, e, g and i) and SEM images (b, d, f, h, j, k, l, m, and n) showing the surface texture of mineral before (initial troilite, a and b) and after different time with or without OM under hydrothermal conditions. New morphologies resulting from troilite alteration over time are observed and highlighted in yellow, with the following abbreviations.: Po, pyrrhotite; Sz, Szomolnokite; Go, Goethite; Mag: magnetite and S⁰ for elemental sulfur.</figcaption></figure>
<figure><img src="image_10.png" /><figcaption>**Fig. 6.** Representative TEM and SEM images showing the surface texture of mineral before (initial peridot (P0)) and after different time (1, 45 and 100 days) with or without OM under hydrothermal conditions. Phyllosilicate morphologies are clearly observed since day 1 of alteration both with and without OM. In sample P45, the area outlined with white dotted lines likely corresponds to an amorphous silicate gel.</figcaption></figure>

<figure><img src="image_11.png" /><figcaption>**Fig. 7.** Si-Fe-Mg ternary diagram (atomic %) showing the composition of phyllosilicates obtained from samples containing peridot with or without OM altered for 1, 45 and 100 days at 80 °C. The reference presented in this figure are from the RUFF database. For shorter alteration times, a clear difference in mineral composition is observed between samples with and without OM, whereas this difference becomes less pronounced with longer alteration times.</figcaption></figure>

saponite and/or talc-like phyllosilicate formation (OH from saponite at 3676 cm⁻¹ (Grauby et al., 1993; Criouet et al., 2023)) and Mg-OH of talc at 667 cm⁻¹ (Steudel et al., 2017)) in agreement with the composition obtained with EDX analysis (Fig. 7).

Elemental analysis of the solid residues showed that less than 5 % of the initial nitrogen (from the HMT) is with the mineral fraction, but since no carbon has been clearly quantified, it is likely under inorganic form (like $NH_4^+$) (Table SI2).

### 3.4. Mix-mineral samples evolution (samples PTF and HPTF)

The co-presence of the three minerals (2:1:2 peridot:troilite:feldspar) along with the HMT enabled an alkalization of the pH during aqueous alteration, shifting from 6 to 8–9 (Table SI1).

It is likely that the initial composition of three mineral phases (PTF: peridot, feldspar, troilite) resulted in heterogeneity being observed after alteration, which was visible under optical microscopy (Fig. SI4). Therefore, we did sorted and unsorted analysis. We sorted the grains based on their color appearance (gray, white and yellow) and subsequently analyzed these different fractions separately.

For the unsorted samples, XRD analysis revealed the co-presence of the three initial phases (peridot, feldspar, and troilite), even after 100 days of alteration (Fig. SI5). However, they also show the appearance of new large peaks at 7.77 Å and 1.54 Å after 100 days, corresponding to the formation of phyllosilicate-type phases, as previously observed in the samples containing only peridot (Fig. SI3). These peaks were particularly evident in the sorted samples, specifically in the yellow grains (Fig. SI4). Additionally, a noticeable increase in the baseline was
<figure><img src="image_12.png" /><figcaption>**Fig. 8.** Infrared spectrum of the insoluble fraction from P and HP samples. Deconvolution was carried out in the 2900–3800 cm⁻¹ range using OPUS software. To note, the deconvolution procedure was consistent for both 1 and 10 days, as well as for 45 and 100 days. Therefore, only the results for the 1 and 100 days of alteration are presented. The bands in the 3660–3690 cm⁻¹ regions correspond to the O–H stretching vibrations of phyllosilicates, while the band at 1600 cm⁻¹ is attributed to O–H bending within the phyllosilicates sheets. A change is observed in the 886 cm⁻¹ region, corresponding to Si–O–Si stretching vibrations of olivine, indicating the consumption of olivine towards phyllosilicates and amorphous phases with the increase of the band at 1000 cm⁻¹.</figcaption></figure>

observed in the PTF45 yellow grains, similar to the P samples, indicating the formation of amorphous materials (Fig. SI3 and Fig. SI4). In contrast, the white grains displayed a diffraction pattern dominated by feldspar, closely resembling that of pure feldspar samples (Fig. SI2 and Fig. SI4), consistent with the albite standard. The gray grains exhibited an X-ray diffractogram spectrum primarily composed of troilite, with additional peaks of pyrrhotite (Fig. 4 and Fig. SI4) (Taylor et al., 1979; Kikuchi et al., 2022) and unaltered olivine and feldspar, corresponding to forsterite and albite composition, respectively (Fig. SI4).

Overall, we have observed such different color grains in all samples, including samples with HMT. The resulting XRD pattern of HPTF100 (unsorted grains) showed the presence of unaltered troilite, feldspar, peridot and new characteristic phyllosilicates bands similarly to the sample without OM (PTF100) (Fig.SI5).

Microscopic SEM and TEM analyses of unsorted samples revealed similar morphologies in HPTF and PTF samples than HP and P, characteristic of phyllosilicates structures (Fig. 9) and an amorphous SiO₂-rich morphology (see the dotted area in HPTF100) in agreement with the XRD analysis.

For each sample, about 15 location on phyllosilicates morphologies (from different grains) were targeted for EDX analyses and their atomic composition in Fe, Mg, Si, Ca and Na are reported in the ternary graph (Fig. 10). This M⁺–4SI⁻–3R²⁺ diagrams are most commonly employed for clay minerals to highlight differences in di-and trioctahedral species and composition of mixed-layered minerals (Meunier and Velde, 1989; Meunier, 2005). EDX analysis revealed significant differences in the nature of the formed phyllosilicates after a short alteration time (1 day) between samples with and without organic matter. The presence of OM depleted the phyllosilicate in Fe and/or Mg, while enriching it in alkali cations (Na and Ca) tending towards a beidelite-like composition for longer time. For more longer alteration periods (100 days), the difference between samples with and without organic matter seemed to be fading and are likely mixed-layered smectites from saponite to montmorillonite composition (Fig. 10).

The IR analysis (unsorted samples) confirmed the formation of these secondary phases with the appearance of shoulder bands beyond 3500 cm⁻¹, indicative of the O–H bond in phyllosilicates hydroxyls (Fig. SI6) and the OH bending vibrations of adsorbed water (1630 cm⁻¹). After

<figure><img src="image_13.png" /><figcaption>**Fig. 9.** Representative TEM and SEM images showing the surface textures of samples PTF containing a mix of minerals (peridot/troilite/feldspar, ratio 2:1:2) after different time (1, 45 and 100 days) with or without OM under hydrothermal conditions. Phyllosilicates morphologies were observed in all images. The area outlined with white dotted lines in the sample HPTF100 likely corresponds to an amorphous silicate gel.</figcaption></figure>
<figure><img src="image_14.png" /><figcaption>**Fig. 10.** Projection in the $M^+ - 4Si - 3R^{2+}$ system of the chemical composition of the phyllosilicates from samples containing the mixture of minerals (2:1:2, PTF) with or without OM altered for 1, 45 and 100 days at 80 °C. In this representation, $M^+$ represent the sum of electrical charges from alkalines cations, here $Na^+ + 2Ca^{2+}$. The term $4Si$ indicates the tetrahedral layer saturation rate within the structural formula ($Si_4O_{10}(OH)_8$), representing the number of silicium in the formula divided by 4. Finally, $3R^{2+}$ corresponds to the cumulative charge of other cations, here $Fe^{2+}$ and $Mg^{2+}$ divided by 3 (Meunier, 2005). The references presented in this figure are from the RUFF database. With increased alteration time, the samples containing organics resemble those without, whereas a clear dichotomy was observed after one day of alteration.</figcaption></figure>

deconvolution, two distinct bands were observed in HPTF and PTF (at 3598 cm$^{-1}$ and ~ 3460 cm$^{-1}$), which could both correspond to smectite-like compositions (Chukanov, 2013)(Fig. SI6).

The elemental analysis showed that approximately 11 % of the nitrogen from the HMT remained after 45 days of aqueous alteration, however with a very low carbon quantity, which likely indicated inorganic nitrogen (Table SI2).

# 4. Discussion

## 4.1. Evolution of the chondritic analogs without OM

The chondritic analog was made by mixing several minerals under hydrothermal conditions that are comparable to those experienced by the parent bodies of carbonaceous chondrites. The experiments conducted on each mineral phase separately allow for a more precise determination of their transformations and mutual interactions under the specified conditions.

The formation of secondary phases is indeed influenced by the presence of other mineral phases present (peridot: troilite: feldspar in a ratio 2:1:2). Phyllosilicates formation in presence of troilite and feldspar

resulted in the formation of phyllosilicates enriched in alkali cations, as well as with a lower content in Fe and/or Mg close to smectite-type phases. These phyllosilicates formed in PTF samples differ from the serpentine-like phases obtained from peridot only after 100 days (Fig. 7 and Fig. 10). This is likely due to the releases of ions in the solution by feldspar dissolution in our experiments (Chirită and Descostes, 2006; Kikuchi et al., 2022). Although feldspar does not form alone new phases, it dissolves in the aqueous phase, releasing $Na^+$, $Ca^{2+}$, $Al^{3+}$, and $K^+$, as well as $SiO_2$ (Okamoto et al., 2021) (observed in spherical forms, Fig. 1). To note, since this silica spheres were also observed in presence of OM, they did not provide evidence of the impact of OM on the dissolution of feldspar alone (Fig. 1). Anyway, Al-enriched phases are expected to be present in altered mixtures with peridot (Oyanagi et al., 2017), as observed in our experiments with the formation of Al-enriched smectite phases (Fig. 10).

Phyllosilicate formations were also observed in a previous study conducted by Kikuchi et al. (2022) on a chondrite analog composed of olivine, enstatite, silicate glass, troilite and iron metal at 80 °C. The formation of phyllosilicates was proposed to occur through a two-step process. Firstly, an intermediate amorphous gel phase was formed, followed by the formation of phyllosilicates with a random orientation. The
literature describes this process of formation by dissolution/re-
crystallisation for temperatures below 150 °C (Jones and Brearley,
2006; Besselink et al., 2020). In our experiments, conducted at 80 °C, we
have observed by TEM and XRD amorphous gel (area outlined with
white dotted lines in Fig. 6 and Fig. 9; shift in the baseline Fig. SI3),
suggesting that a two-step formation process could be also plausible in
our experiments. This intermediate phase could enable the incorpora-
tion of all the elements dissolved in the fluid from the other minerals into
the new secondary structure that crystallizes with time. This observation
corroborate the hypothesis that the composition of the secondary phases
is particularly controlled by the fluid composition (Velbel, 2012; Velbel
et al., 2015).

In order to question the effect of iron sulfide in the formation of
secondary phases, we have added 20 wt% of troilite in our chondritic
analog, as some previous studies (pyrite, GEMS-like materials and alpha
iron (Fabre et al., 2024); GEMS-like materials and iron metal (Vacher
et al., 2019); and troilite and iron metal (Kikuchi et al., 2022)). In these
previous studies, a substantial impact of iron was observed with the
formation of iron-rich phyllosilicates (Vacher et al., 2019) and iron
oxides on the surface of olivine grains (Fabre et al., 2024). However, in
our conditions, we did not observe such iron-enrichments in minerals
formed after alteration. The low concentration of troilite in our study
and the oxidation state of iron may have contributed to this outcome.
Our study only used an iron sulfide, troilite (Fe(II)S), while other studies
have included at least a percentage of iron metal (Fe(0)) known to be
more reactive and commonly found in accretionary assemblages.
Indeed, the troilite remain relatively stable under these conditions and
even more with OM as shown in our study. Also, the observed trans-
formation of troilite to pyrrhotite in our experiments reflects a loss of
sulfur without a corresponding mobilization of Fe. Hence, the formation
of iron-rich phyllosilicates could be directly related to the availability
and reactivity, linked to the oxidation state, of the iron during aqueous
alteration. Further experiments starting with iron sulfide could test the
incorporation of sulfur into secondary minerals with different alteration
conditions and the possibility of organic sulfur formation.

Another parameter affecting mineral transformation is likely the
grain size (Kleber et al., 2015; Han et al., 2016). Our phyllosilicate
formation from peridot is notably rapid, with a visible alteration by day
1, possibly facilitated by the very small grain size of peridot in our ex-
periments (~1µm). This correlation is supported by experimental
studies of cometary dust alteration, which revealed a proportional
relationship between grain size and silicate alteration reaction rate
(Nakamura-Messenger et al., 2011). It has been postulated that over
short alteration periods in meteorite parent bodies, fine-grained amor-
phous materials converted to hydrated phyllosilicates more rapidly than
coarser mineral grains (Nelson et al., 1987).

In addition to previous studies, we have shown here that the nature
of dissolved ions in the fluid, initial mineralogical diversity, and iron
oxidation state will influence the obtained paragenesis (Vacher et al.,
2019; Kikuchi et al., 2022; Fabre et al., 2024). These findings underscore
the importance of considering diverse experimental conditions and
mineralogical compositions to better comprehend the hydrothermal
alteration processes of minerals in chondrites.

## 4.2. Effect of OM on iron sulfide under hydrothermal condition

In our study, we observed the conversion of troilite into pyrrhotite
within one day, both in the presence and absence of organic matter (HT
and T samples), in agreement with the rapid transformation of FeS under
hydrothermal alteration (Herndon et al., 1975; Berger et al., 2015;
Kikuchi et al., 2022). Pyrrhotite formation is proposed to proceed
through incongruent dissolution, resulting in the formation of Fe²⁺ in
the solution, which further can be oxidized (Taylor et al., 1979; Kikuchi
et al., 2022). Indeed, the formation of szomolnokite (Nikiforov et al.,
2012), magnetite (Herndon et al., 1975), goethite (Chevrier et al.,
2006), and hematite in our experiments without OM attest of the

oxidation of pyrrhotite. Chevrier et al. (2006) have demonstrated that
this oxidation could occur under anoxic conditions through equilibrium
displacement facilitated by the release of hydrogen (redox couples:
Fe³⁺/Fe²⁺, H₂O/H₂, Fig. SI7).

However, in the presence of organic matter, a fraction of unaltered
troilite was still observed after 100 days of alteration (Fig. 4) and very
low oxidation of pyrrhotite was found. The main visible indication of no
oxidation was the absence of the rusty precipitates in all OM-troilite
samples confirmed by the lack of iron oxide from XRD and micro-
scopic observations (Fig. 3 and Fig. 5). The Fe²⁺ ions have likely inter-
acted with the organic matter leading to the formation of only minor
oxidized phase, tentatively observed in electronic microscopy in HT
/goethite and magnetite) (Fig. 5). Since this oxidation is not observed in
the presence of OM, we wondered whether it might be linked to the
effect of the OM on the pH (Table SI1). Additional tests have been
conducted by submitted troilite in a concentrated sodium hydroxide
solution (initial pH of 9) under the same aqueous alteration conditions
(80 °C). After 1 and 10 days, the rust precipitate was observed. We can
therefore propose that the oxidation of troilite is not solely a result of pH
changes caused by the HMT transformation. The presence of organic
matter may prevent the oxidation of troilite simply through reactions
with the Fe²⁺ released. The Fe²⁺ could indeed interact with OM through
the formation of chelates (Kleber et al., 2015; Jilling et al., 2018) as
previously observed in the liquid part of the same samples (Serra et al.,
2024). Also, because the initial OM in our sample consists of reduced
carbon, it may interact with the Fe²⁺/Fe³⁺ couple through redox re-
actions, helping to maintain iron in its reduced state by consuming Fe³⁺.
This is consistent with previous observations and experiments on natural
organic matter in which, Fe(II) oxidation is slower. The natural organic
matter has been shown to preserve the Fe(II) by functioning as both
redox buffer and complexant (Daugherty et al., 2017). These in-
teractions were proposed in our previous study, where we found a high
abundance of amides in the soluble organic matter from HMT, likely
formed through a catalytic cycle involving radical chemistry in the
presence of troilite (Serra et al., 2024).

The OM has also an impact on the sulfur sequestration (Table SI2). In
the presence of OM, more sulfur was observed to remain in the mineral
fraction as elemental sulfur or polysulfides, than without OM (Fig. 5-
Table S2). This was found to occur in conditions of excess of reduced
sulfur species and limited iron reactivity (Jørgensen et al., 2019).
Without organic matter, sulfur appeared to be possibly more released as
H₂S during the oxidation of troilite. In the presence of OM, some sulfur
could have been more incorporated into OM and/or stay reduced,
forming sulfur compounds that influences the formation of the second-
ary mineral phases (Heinen and Lauwers, 1996; ThomasArrigo et al.,
2020).

Therefore, the formation of iron oxides is influenced by various
factors, including pH (see Pourbaix diagram, Fig. SI7), oxidation rate,
temperature, Fe²⁺ concentration, and the presence or absence of
external compounds (Cornell and Schwertmann, 1997) including OM as
shown here.

## 4.3. Effect of the OM on the paragenesis of chondritic analogs

Previous studies have focused on the formation of secondary phases
in a carbon-free chondritic analog (Vacher et al., 2019; Kikuchi et al.,
2022; Fabre et al., 2024). This study highlights that the formation of
secondary mineral phases is influenced by the presence of organic
matter (Fig. 11), despite its low abundance (4 wt%/mineral). Especially
the phyllosilicates formed in our study in the presence of OM exhibit
distinct compositions compared to carbon-free chondritic analogs
(Fig. 11). It should be noted, that the OM used in this study, produced
mainly soluble compounds such as amines or carboxylic acids (Serra
et al., 2024), which we assume have a greater impact on the paragenesis
than refractory compounds (like the IOM) (Le Guillou et al., 2014).

The presence of organic matter does not inhibit the formation of
<figure><img src="image_15.png" /><figcaption>**Fig. 11.** Schematic representation of the alteration process performed in our experiments, based on a mixture of three minerals exposed to 80 °C with organic matter (HMT) or without. During the alteration process, the fluid is loaded with dissolved minerals and organic matter. Salt type interactions are also observed along with adsorbed OM at the mineral surfaces. During the alteration process, the primary minerals evolve and give way to the formation of phyllosilicates, iron oxides and amorphous silica.</figcaption></figure>

phyllosilicates but in counterpart has influenced their composition. We have observed large formation of Mg-rich serpentine-type (like lizardite in HP samples, Fig. 7) and/or Al-rich smectite-type (beidelite type in HPTF samples, Fig. 10) depending on the mineral mixtures and the presence of OM. One of the impact of OM can be on the reactivity of silicates and their dissolutions (Wogelius and Walther, 1991, 1992; Kleber et al., 2015, 2021), especially for shorter time reaction as shown here. The experiments performed in this study used hexamethylenetetramine (HMT), a molecule, which decomposes into ammonia and formaldehyde during hydrothermal alteration (Hulet t et al., 1971; Vinogradoff et al., 2018). This decomposition under hydrothermal condition leads to an increase in pH, as observed in the different samples resulting in a more alkaline solution. The chemical reactivity of formaldehyde and ammonia in aqueous systems is producing a wide range of molecules, including, ketones, aldehydes, acids, amides, nitrogen aromatic compounds, as observed in the liquid fraction of the samples and previous studies (Serra et al., 2024; Vinogradoff et al., 2018; Kebukawa et al., 2020; Vinogradoff et al., 2020b). Therefore, we suspect here that the organic molecules produced from HMT decomposition could interfere with the reactivity and dissolution of silicates, but due to the large diversity produced, it is difficult to identify the main responsible. For instance, it has been shown that the presence of carboxylic acids catalyzes the rate of silicate dissolution (Welch and Ullman, 1993; Ganor et al., 2009; Le Guillou et al., 2014) but in contrast, alkaline pH decreases the rate and changes the ratio of cations dissolved (Oelkers, 2001; Gudbrandsson et al., 2014; Oelkers et al., 2018). This raises an interesting question: if we were to start with degradation products of HMT, such as formaldehyde and ammonia, or each chemical family separately (acids, ketones, amides, amines), would we observe similar effects on the transformation of mineral phases under hydrothermal conditions?

In addition, the interactions between this OM produced from HMT and the mineral fractions can occur in various ways (McCollom, 2013; Kleber et al., 2021) and at different time of alterations because of the production of diverse organic molecules with time (Serra et al., 2024). With the silicates, OM-sorption can occur through physisorption with van der Waals-type bonds and organic chelates can be formed on the

surface (Vinogradoff et al., 2020a; Serra et al., 2024). In the aqueous fraction extracted from our samples containing phyllosilicates (HP and HPTF), the presence of organic salts/chelates from day 1, more particularly complexes with Fe²⁺, Mg²⁺ and SO₄²⁻ were indeed detected by IR analysis (Serra et al., 2024). The observation of salts (mainly organosulfur -bearing) in natural samples such as the Ryugu asteroid (Yoshimura et al., 2023) has also been reported, and proposed as resulting from aqueous alteration process. These interactions are likely to occur during dissolution, forming chelates with dissolved elements and limiting their availability for secondary mineral formation. As a result, depending on alteration duration and especially at short time, the final product may differ from the one obtained without OM (Fig. 7 and Fig. 10). In our experiments, we indeed observed a greater impact of OM at short time of alteration. For longer time, this impact is less significant and a similar phyllosilicates composition is observed with and without OM (Fig. 10). Another question arises regarding the concentration of OM that can alter the paragenesis. As shown here, the low OM content (4 wt % / minerals) affects the early stages of alteration, would a higher OM concentration extend this effect?

Between the formed phyllosilicates and the OM, more interactions are also possible such as chemisorption (covalent bond with O-R), or sorption within the interlayer space as observed in previous chondritic analogs (Jacquemot et al., 2019; Vinogradoff et al., 2020a; Viennet et al., 2022). Despite the low initial OM concentration in our samples, small amounts of organic molecules were still detected in the solid residues (Table S1), with nitrogen present in higher quantities than carbon. The N-rich compounds could be in the form of ammonium (NH₄) as indicated by the band present in the HF samples at 1466 cm⁻¹ and 1429 cm⁻¹ (Fig. 2) (Petit et al., 2006) but not seen for the complex mixture (HPTF samples). By comparing the HP and HPTF samples, we observed a lower quantity of adsorbed OM in HP (Table S1). This could be explained by the nature of the phyllosilicates formed: in HP, serpentine-like phyllosilicates, which are non-expandable, are predominantly formed, unlike the smectites observed in HPTF samples, which are more prone to adsorb OM (Table S1) (Petit et al., 2006; Vinogradoff et al., 2020a). Previous studies modeling chondritic analogs used high OM concentrations (33–100 wt%/ minerals), which could explain the
significant OM adsorption observed with phyllosilicates (Jacquemot et al., 2019; Vinogradoff et al., 2020a; Viennet et al., 2022). Overall, the nature of the phyllosilicates formed (which depends on the initial alteration conditions) is a crucial parameter for assessing the absorption of OM in CC but also the concentration and nature of the OM.

## 4.4. Implications for carbonaceous chondrites

The parent bodies of carbonaceous chondrites accreted both organic matter and minerals, but secondary processes such as aqueous alteration blurred this initial composition. The organic matter found in these objects, for up to 4–5 wt% (Pearson et al., 2006; Remusat, 2015) or more (20 wt% proposed for Ceres (Marchi et al., 2019; Vinogradoff et al., 2021)), are closely associated with the secondary minerals produced during this aqueous alteration (Brearley, 2006; Rubin et al., 2007; Le Guillou et al., 2014).

In our study, instead of starting from already formed phyllosilicates (Vinogradoff et al., 2020a, b) or gel phases (Jacquemot et al., 2019; Viennet et al., 2022), we have chosen to start from primary minerals (likely accreted in the asteroid parent body) and induced interaction with an organic-rich fluid. Both phases have in our experiments evolved, been transformed and have affected each other, as discussed previously for the organic soluble part (Serra et al., 2024) and in this paper for the mineral part. Our initial mineral mixture differed also from previous studies that experimented with chondritic analogs (Vacher et al., 2019; Kikuchi et al., 2022; Fabre et al., 2024). It contained feldspar as a source of cations (Al²⁺, Na⁺, Ca²⁺) and troilite (FeS) as a source of iron, in addition to olivine. Our experiments highlighted that the initial composition has several implications on the phyllosilicates produced. Although the earliest phyllosilicates formed solely from peridot (within 1 to 45 days) exhibit the highest iron concentration—consistent with the preferential release of iron, followed by magnesium, during olivine dissolution (Stopar et al., 2006; Velbel et al., 2015)—the presence of other minerals reduces iron availability. This favors the formation of Mg-rich serpentines and smectites, while aluminum efficiently promotes the development of Al-rich smectites. *A fortiori*, the paragenesis obtained when all three minerals are present with or without OM (PTF and HPTF samples), closely resembles the one of altered CM chondrites with a majority of Mg-rich-smectites (Herndon et al., 1975; Brearley, 2006) but also an improbable enrichment in Al derived from the excess feldspar integrated in our initial conditions (Fig. 10).

In carbonaceous chondrites, Mg-rich phyllosilicates are proposed to be the main minerals associated with OM in chondrites (Changela et al., 2018; Aléon-Toppani et al., 2024), which suggest the necessity of different mineral mixtures and a lower abundance of aluminium than in our experiments. Further clarification is nonetheless required regarding the nature of these phyllosilicates (serpentine or smectite), which are fundamental to assessing the interaction with organic matter in terms of adsorption and reactivity (Lagaly et al., 2013; Vinogradoff et al., 2020b; Kleber et al., 2021; Viennet et al., 2022). As shown in our experiments, the structures and compositions of these secondary minerals can reflect those of the precursor silicate grains, the interacting fluids, and the environmental conditions that accompany aqueous alteration (Browning et al., 1996) but this is not fully straightforward and need more experimental works.

The formation of phyllosilicates phases in our chondritic analogs, occurred through the formation of intermediate amorphous gel phase, along with the study by Kikuchi et al. (2022). Such gel phases are also observed in some altered CC, such as the Paris meteorite, Asuka 12,236 and the Ryugu asteroid (Leroux et al., 2015; Kimura et al., 2020; Aléon-Toppani et al., 2024) or in alteration experiments of natural CC (Jones et al. (2006)). Therefore, our experiment appears to replicate the processes that have occurred in the parent bodies of meteorites during aqueous alteration leading to the formation of phyllosilicates phases. In fact, the heterogeneity in terms of secondary phase composition observed in chondrites at the sub-micrometer scale is well reproduced in

our experiments. Our results show partial consistency with the chemical compositions of minerals found in CCs, likely due to differences in starting materials, but adding organic molecules in the material is also enriching the diversity of minerals. These findings provide valuable insights into the interactions between water, organics matter, and minerals under conditions analogous to those of CC parent bodies.

The evidence presented here demonstrates that the presence of soluble organic compounds even at low concentration could modify the paragenesis of our chondritic analogs in the early stage of aqueous alteration by inhibiting or altering the composition of the secondary phases formed. The chemical complexity and variability of soluble organic matter found nowadays in carbonaceous chondrites (Schmitt-Kopplin et al., 2010; Remusat, 2015; Alexander et al., 2017), raises intriguing interrogations regarding its potential impact on the mineral fraction during aqueous alteration, and in spatially localized scale (µm²) (Le Guillou et al., 2014; Changela et al., 2018). In CC, OM can be found in the form of grains or diffused in phyllosilicates (Le Guillou et al., 2014, 2022; Yabuta et al., 2023), which likely result from the aqueous alteration. The alteration fluid may have driven the most polar compounds with the minerals, such as carboxylic acids or amides, identified in the diffuse OM (Le Guillou and Brearley, 2014) and in these samples from the degradation of HMT (Serra et al., 2024). The hydrothermal fluid will carry the altered OM and diffuse it within the mineral matrix, where it will interact closely with the forming minerals, as shown here. Hence, soluble organic compounds, a third of the OM in CC, can have a non-negligible impact on the mineral transformation that remain to be further investigated. Specific questions have arisen directly as a result of this work, and request additional investigations. For instance, what are the atomic-scale mechanisms by which HMT influences mineral dissolution? Does the impact occur specifically during the formation of the amorphous gel? Would a nitrogen-free organic molecule produce similar effects? Would a higher concentration of organic molecules lead to a comparable outcome?

While our system appears to reproduce the basic processes occurring between organic and mineral matter during aqueous alteration, other parameters remain to be tested (Zolotov, 2012). Such parameters could be the presence of few percent of CO₂, temperature variations, and water to rock ratio. More research is required to fully comprehend the organo-mineral interaction in chondrites, which is crucial for understanding the phenomena that occurred in carbonaceous chondrites and for explaining the diversity of secondary mineral phases observed.

## 5. Conclusion

In this work, we have attempted to study the interaction between organic and minerals under conditions defined for aqueous alteration in the parent bodies of CC. We demonstrated the influence of HMT, introduced at 4 wt% as a precursor primarily forming soluble organic molecules, on the primary mineral phases (peridot, troilite, and feldspar) and their subsequent transformation under hydrothermal conditions at 80 °C. We observed that serpentine-like phyllosilicate formed exclusively when single-phase olivine was altered, whereas smectites was produced in the presence of additional minerals, likely due to increased Si activity from feldspar dissolution. Furthermore, we showed that the presence of HMT significantly influenced the composition and speciation of secondary mineral phases, particularly during the early stages of aqueous alteration. In particular, HMT altered the dissolution rates of primary minerals, modifying the fluid composition and leading to reduced Fe/Mg cation incorporation into phyllosilicates while enriching them with alkali cations such as Na and Ca. Additionally, HMT inhibited the oxidation of troilite into iron oxides (such as goethite, hematite, magnetite, szomolnokite), likely through the formation of organic chelates, or via red-ox reactions toward more oxidized organic molecules. Studying the formation of these secondary phases, all together, with and without OM have provided new insights into the formation processes during hydrothermal alteration. We have
demonstrated that organic matter in low concentration can significantly influence the transformation of chondritic analogs under hydrothermal conditions. This prompts the question of how OM affects the mineral transformation in the context of the molecular diversity observed in a carbonaceous chondrite.

### CRediT authorship contribution statement

**Coline Serra:** Writing – original draft, Visualization, Validation, Methodology, Investigation, Formal analysis, Conceptualization. **Olivier Grauby:** Writing – review & editing, Validation, Resources, Investigation. **Daniel Ferry:** Writing – review & editing, Validation, Resources. **Fabrice Duvernay:** Writing – review & editing. **Grégoire Danger:** Writing – review & editing. **Johanna Marin-Carbonne:** Writing – review & editing, Validation. **Vassilissa Vinogradoff:** Writing – original draft, Validation, Supervision, Resources, Methodology, Investigation, Funding acquisition, Conceptualization.

### Data availability

Data are available through Mendeley data at: https://doi.org/10.17632/2z3ydnwzpk1.

### Declaration of competing interest

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

### Acknowledgments

The authors thank Gregory Excoffier (Spectropole of the Fédération des Sciences Chimiques Marseille, Aix Marseille University) for his help with elemental analysis and Vasile Heresanu for X-ray diffraction measurements. We gratefully acknowledge support from the Agence Nationale de la Recherche (ANR 22-CE49-0007 ORGAMISS - PI V. Vinogradoff). C. S. is grateful to Aix-Marseille University for doctoral grant. We thank Vincent Chevrier and Martin Suttle for their reviews, suggestions and critical questions that help us to improve our paper.

### Appendix A. Supplementary material

This manuscript contain supplementary material with figures and tables that support the work and main results: the method protocol, additional XRD data and IR data and the Pourbaix diagram. Supplementary material to this article can be found online at https://doi.org/10.1016/j.gca.2025.04.018.

### References

* Abreu, N.M., Aponte, J.C., Cloutis, E.A., Nguyen, A.N., 2020. The Renazzo-like carbonaceous chondrites as resources to understand the origin, evolution, and exploration of the solar system. *Geochemistry* 80, 125631.

* Aléon-Toppani, A., Brunetto, R., Dionnet, Z., Rubino, S., Baklouti, D., Brisset, F., Vallet, M., Heripre, E., Nakamura, T., Lantz, C., Djouadi, Z., Borondics, F., Sandt, C., Troadec, D., Mivumbi, O., Matsumoto, M., Amano, K., Morita, T., Yurimoto, H., Noguchi, T., Okazaki, R., Yabuta, H., Naraoka, H., Sakamoto, K., Tachibana, S., Yada, T., Nishimura, M., Nakato, A., Miyazaki, A., Yogata, K., Abe, M., Okada, T., Usui, T., Yoshikawa, M., Saiki, T., Tanaka, S., Terui, F., Nakazawa, S., Watanabe, S., Tsuda, Y., 2024. Correlated IR-SEM-TEM studies of three different grains from Ryugu: From the initial material to post-accretional processes. *Geochimica et Cosmochimica Acta*.

* Alexander, C.M.O., Bowden, R., Fogel, M.L., Howard, K.T., 2015. Carbonate abundances and isotopic compositions in chondrites. *Meteorit. Planet. Sci.* 50, 810–833.

* Alexander, C.M.O., Cody, G.D., De Gregorio, B.T., Nittler, L.R., Stroud, R.M., 2017. The nature, origin and modification of insoluble organic matter in chondrites, the major source of Earth's C and N. *Geochemistry* 77, 227–256.

* Alexander, C.M.O., Fogel, M., Yabuta, H., Cody, G.D., 2007. The origin and evolution of chondrites recorded in the elemental and isotopic compositions of their macromolecular organic matter. *Geochim. Cosmochim. Acta* 71, 4380–4403.

* Alexander, C.M.O., Howard, K.T., Bowden, R., Fogel, M.L., 2013. The classification of CM and CR chondrites using bulk H, C and N abundances and isotopic compositions. *Geochim. Cosmochim. Acta* 123, 244–260.

* Beck, P., Quirico, E., Montes-Hernandez, G., Bonal, L., Bollard, J., Orthous-Daunay, F.-R., Howard, K.T., Schmitt, B., Brissaud, O., Deschamps, F., Wunder, B., Guillot, S., 2010. Hydrous mineralogy of CM and CI chondrites from infrared spectroscopy and their relationship with low albedo asteroids. *Geochim. Cosmochim. Acta* 74, 4881–4892.

* Berger, E.L., Keller, L.P., Lauretta, D.S., 2015. An experimental study of the formation of cubanite (CuFe2S3) in primitive meteorites. *Meteorit. Planet. Sci.* 50, 1–14.

* Bernstein, M.P., Sandford, S.A., Allamandola, L.J., Chang, S., Scharberg, M.A., 1995. Organic Compounds Produced by Photolysis of Realistic Interstellar and Cometary Ice Analogs Containing Methanol.

* Besselink, R., Stawski, T.M., Freeman, H.M., Hövelmann, J., Tobler, D.J., Benning, L.G., 2020. Mechanism of Saponite Crystallization from a Rapidly Formed Amorphous Intermediate. *Cryst. Growth Des.* 20, 3365–3373.

* Brearley, A.J., 2006. The action of water. *Meteorites and the Early Solar System II* 943, 587–624.

* Browning, L.B., McSween, H.Y., Zolensky, M.E., 1996. Correlated alteration effects in CM carbonaceous chondrites. *Geochim. Cosmochim. Acta* 60, 2621–2633.

* Chan, Q.H.S., Zolensky, M.E., Bodnar, R.J., Farley, C., Cheung, J.C.H., 2017. Investigation of organo-carbonate associations in carbonaceous chondrites by Raman spectroscopy. *Geochim. Cosmochim. Acta* 201, 392–409.

* Changela, H.G., Le Guillou, C., Bernard, S., Brearley, A.J., 2018. Hydrothermal evolution of the morphology, molecular composition, and distribution of organic matter in CR (Renazzo-type) chondrites. *Meteorit. Planet. Sci.* 53, 1006–1029.

* Chevrier, V., Mathé, P.-E., Rochette, P., Grauby, O., Bourrié, G., Trolard, F., 2006. Iron weathering products in a CO2+(H2O or H2O2) atmosphere: Implications for weathering processes on the surface of Mars. *Geochim. Cosmochim. Acta* 70, 4295–4317.

* Chiriță, P., Descostes, M., 2006. Anoxic dissolution of troilite in acidic media. *J. Colloid Interface Sci.* 294, 376–384.

* Chukanov, N.V., 2013. *Infrared spectra of mineral species: Extended library*. Springer Science & Business Media.

* Cliff, G., Lorimer, G.W., 1975. The quantitative analysis of thin specimens. *J. Microsc.* 103, 203–207.

* Cornell, R.M., Schwertmann, 1997. The iron oxides: structure, properties, reactions, occurrence and uses. *Corros. Rev.* 15, 533–559.

* Criouet, I., Viennet, J.C., Baron, F., Balan, E., Buch, A., Delbes, L., Guillaumet, M., Remusat, L., Bernard, S., 2023. Influence of pH on the Hydrothermal Synthesis of Al-Substituted Smectites (Saponite, Beidellite, and Nontronite). *Clay Clay Miner. Acta* 71, 539–558.

* Daugherty, E.E., Gilbert, B., Nico, P.S., Borch, T., 2017. Complexation and Redox Buffering of Iron(II) by Dissolved Organic Matter. *Environ. Sci. Technol.* 51, 11096–11104.

* Derenne, S., Robert, F., 2010. Model of molecular structure of the insoluble organic matter isolated from Murchison meteorite. *Meteorit. Planet. Sci.* 45, 1461–1475.

* Fabre, S., Béche, E., Eshan, J., Thébault, Y., Munsch, P., Quitté, G., 2024. Iron and Sulfur Secondary Phases as Proxies of Aqueous Alteration on Chondrite Parent Bodies. *ACS Earth Space Chem.*

* Fischer, W.R., Schwertmann, U., 1975. The Formation of Hematite from Amorphous Iron (III)Hydroxide. *Clays Clay Miner.* 23, 33–37.

* Ganor, J., Reznik, I.J., Rosenberg, Y.O., 2009. Organics in Water-Rock Interactions. *Rev. Mineral. Geochem.* 70, 259–369.

* Garenne, A., Beck, P., Montes-Hernandez, G., Chiriac, R., Toche, F., Quirico, E., Bonal, L., Schmitt, B., 2014. The abundance and stability of “water” in type 1 and 2 carbonaceous chondrites (CI, CM and CR). *Geochim. Cosmochim. Acta* 137, 93–112.

* Glavin, D.P., Alexander, C.M.O., Aponte, J.C., Dworkin, J.P., Elsila, J.E., Yabuta, H., 2018. Chapter 3 - The Origin and Evolution of Organic Matter in Carbonaceous Chondrites and Links to Their Parent Bodies. In: Abreu, N. (Ed.), *Primitived Meteorites and Asteroids*. Elsevier. pp. 205–271.

* Grauby, O., Petit, S., Decarreau, A., Baronnet, A., 1993. The beidellite-saponite series: an experimental approach. *Eur. J. Mineral.* 623–636.

* Grauby, O., Petit, S., Decarreau, A., Baronnet, A., 1994. The nontronite-saponite series: an experimental approach. *Eur. J. Mineral.* 99–112.

* Gudbrandsson, S., Wolff-Boenisch, D., Gislason, S.R., Oelkers, E.H., 2014. Experimental determination of plagioclase dissolution rates as a function of its composition and pH at 22°C. *Geochim. Cosmochim. Acta* 139, 154–172.

* Han, L., Sun, K., Jin, J., Xing, B., 2016. Some concepts of soil organic carbon characteristics and mineral interaction from a review of literature. *Soil Biol. Biochem.* 94, 107–121.

* Heinen, W., Lauwers, A.M., 1996. Organic sulfur compounds resulting from the interaction of iron sulfide, hydrogen sulfide and carbon dioxide in an anaerobic aqueous environment. *Origins Life Evol Biosphere* 26, 131–150.

* Herndon, J.M., Rowe, M.W., Larson, E.E., Watson, D.E., 1975. Origin of magnetite and pyrrhotite in carbonaceous chondrites. *Nature* 253, 516–518.

* Hirakawa, N., Kebukawa, Y., Furukawa, Y., Kondo, M., Nakano, H., Kobayashi, K., 2021a. Aqueous alteration without initial water: possibility of organic-induced hydration of anhydrous silicates in meteorite parent bodies. *Earth Planets Space* 73, 16.

* Hirakawa, N., Kebukawa, Y., Kobayashi, K., Nakano, H., 2021b. Effects of minerals on metamorphism of organic matter during thermal processes in meteorite parent bodies. *Icarus* 358, 114167.

* Howard, K.T., Alexander, C.M.O., Schrader, D.L., Dyl, K.A., 2015. Classification of hydrous meteorites (CR, CM and C2 ungrouped) by phyllosilicate fraction: PSD-XRD modal mineralogy and planetesimal environments. *Geochim. Cosmochim. Acta* 149, 206–222.
Hulett, H.R., Wolman, Y., Miller, S.L., Ibanez, J., Oró, J., Fox, S.W., Windsor, C.R., 1971. Formaldehyde and ammonia as precursors to prebiotic amino acids. *Science* **174**, 1038-1041.

Jacquemot, P., Viennet, J.-C., Bernard, S., Le Guillou, C., Rigaud, B., Delbes, L., Georgelin, T., Jaber, M., 2019. The degradation of organic matter impacts the crystallization of clay minerals and vice versa. *Sci Rep* **9**, 20251.

Jeon, S.-H., Son, Y.-H., Choi, W.-I., Song, G., Hur, D., 2018. Simulating Porous Magnetite Layer Deposited on Alloy 690TT Steam Generator Tubes. *Materials* **11**, 62.

Jilling, A., Keiluweit, M., Contosta, A.R., Frey, S., Schimel, J., Schnecker, J., Smith, R.G., Tiemann, L., Grandy, A.S., 2018. In the rhizosphere: overlooked mediators of soil nitrogen availability to plants and microbes. *Biogeochemistry* **139**, 103-122.

Jones, C.L., Brearley, A.J., 2006. Experimental aqueous alteration of the Allende meteorite under oxidizing conditions: constraints on asteroidal alteration. *Geochim. Cosmochim. Acta* **70**, 1040-1058.

Jørgensen, B.B., Findlay, A.J., Pellerin, A., 2019. The biogeochemical sulfur cycle of marine sediments. *Front. Microbiol.* **10**.

Kebukawa, Y., Nakashima, S., Mita, H., Muramatsu, Y., Kobayashi, K., 2020. Molecular evolution during hydrothermal reactions from formaldehyde and ammonia stimulating aqueous alteration in meteorite parent bodies. *Icarus* **347**, 113827.

Kikuchi, S., Shibuya, T., Abe, M., Uematsu, K., 2022. Experimental chondrite-water reactions under reducing and low-temperature hydrothermal conditions: Implications for incipient aqueous alteration in planetesimals. *Geochim. Cosmochim. Acta* **319**, 151-167.

Kimura, M., Imae, N., Komatsu, M., Barrat, J.A., Greenwood, R.C., Yamaguchi, A., Noguchi, T., 2020. The most primitive CM chondrites, Asuka 12085, 12169, and 12236, of subtypes 3.0-2.8: Their characteristic features and classification. *Polar Sci.* **26**, 100565.

Kleber, M., Bourg, I.C., Coward, E.K., Hansel, C.M., Myneni, S.C.B., Nunan, N., 2021. Dynamic interactions at the mineral-organic matter interface. *Nat. Rev. Earth Environ.* **2**, 402-421.

Kleber, M., Eusterhues, K., Keiluweit, M., Mikutta, C., Mikutta, R., Nico, P.S., 2015. Chapter One - Mineral-Organic Associations: Formation, Properties, and Relevance in Soil Environments. In *Advances in Agronomy* (ed. D. L. Sparks). Academic Press. pp. 1-140.

Lagaly, G., Ogawa, M., Dékány, I., 2013. Chapter 10.3 - Clay Mineral-Organic Interactions. In: *Bergaya, F.*, Gerhard Lagaly (Eds.). Developments in Clay Science, Handbook of Clay Science. Elsevier. pp. 435-505.

Le Guillou, C., Bernard, S., Brearley, A.J., Remusat, L., 2014. Evolution of organic matter in Orgueil, Murchison and Renazzo during parent body aqueous alteration: In situ investigations. *Geochim. Cosmochim. Acta* **131**, 368-392.

Le Guillou, C., Bernard, S., Leroux, H., Noguchi, T., Yurimoto, H., Nakamura, T., Ubuta, H., Naraoka, H., Okazaki, R., Sakamoto, K., 2022. Organics and Their Relationship to Phyllosilicates in Ryugu, Orgueil and Ivuna: In Situ TEM and XANES Study. *LPI Contributions* **2678**, 2999.

Le Guillou, C., Brearley, A., 2014. Relationships between organics, water and early stages of aqueous alteration in the pristine CR3.0 chondrite MET 00426. *Geochim. Cosmochim. Acta* **131**, 344-367.

Le Guillou, C., Dohmen, R., Rogalla, D., Müller, T., Vollmer, C., Becker, H.-W., 2015. New experimental approach to study aqueous alteration of amorphous silicates at low reaction rates. *Chem. Geol.* **412**, 179-192.

Leroux, H., Cuvillier, P., Zanda, B., Hewins, R.H., 2015. GEMS-like material in the matrix of the Paris meteorite and the early stages of alteration of CM chondrites. *Geochim. Cosmochim. Acta* **170**, 247-265.

Marchi, S., Raponi, A., Prettyman, T.H., De Sanctis, M.C., Castillo-Rogez, J., Raymond, C. A., Ammannito, E., Bowling, T., Ciarniello, M., Kaplan, H., Palomba, E., Russell, C.T., Vinogradoff, V., Yamashita, N., 2019. An aqueously altered carbon-rich Ceres. *Nat Astron* **3**, 140-145.

McCollom, T.M., 2013. The influence of minerals on decomposition of the n-alkyl-α-amino acid clays under hydrothermal conditions. *Geochim. Cosmochim. Acta* **104**, 330-357.

Meunier, A., 2005. Clays. Springer Science & Business Media.

Meunier, A., Velde, B., 1989. Solid solutions in I/S mixed-layer minerals and illite. *Am. Mineral.* **74**, 1106-1112.

Munoz Caro, C.M., Schutte, W.A., 2003. UV-photoprocessing of interstellar ice analogs: New infrared spectroscopic results. *A&A* **412**, 121-132.

Nakamura, T., Matsumoto, M., Amano, K., Enokido, Y., Zolensky, M.E., Mikouchi, T., Genda, H., Tanaka, S., Zolotov, M.Y., Kurosawa, K., Wakita, S., Hyodo, R., Nagano, H., Nakashima, D., Takahashi, Y., Fujioka, Y., Kikui, M., Kagawa, E., Matsuoka, M., Brearley, A.J., Tsuchiya, A., Uesugi, M., Matsuno, J., Kimura, Y., Sato, M., Milliken, R.E., Tatsumi, E., Sugita, S., Hiroi, T., Kitazato, K., Brownlee, D., Joswiak, D.J., Takahashi, M., Ninomiya, K., Takahashi, T., Osawa, T., Terada, K., Brenker, F.E., Tkalcec, B.J., Vincze, L., Brunetto, R., Aléon-Toppani, A., Chan, Q.H. S., Roskosz, M., Viennet, J.-C., Beck, P., Alp, E.E., Michikami, T., Nagaashi, Y., Tsuji, T., Ino, Y., Martinez, J., Han, J., Dolocan, A., Bodnar, R.J., Tanaka, M., Yoshida, H., Sugiyama, K., King, A.J., Fukushi, K., Suga, H., Yamashita, S., Kawai, T., Inoue, K., Nakato, A., Noguchi, T., Vilas, F., Hendrix, A.R., Jaramillo-Correa, C., Domingue, D.L., Dominguez, G., Gainsforth, Z., Engrand, C., Duprat, J., Russell, S.S., Bonato, E., Ma, C., Kawamoto, T., Wada, T., Watanabe, S., Endo, R., Enju, S., Riu, L., Rubino, S., Tack, P., Takeshita, S., Takeuchi, Y., Takeuchi, A., Takigawa, A., Takir, D., Tanigaki, T., Taniguchi, A., Tsukamoto, K., Yagi, T., Yamada, S., Yamamoto, K., Yamashita, Y., Yasutake, M., Uesugi, M., Umegaki, I., Chiu, I., Ishizaki, T., Okumura, S., Palomba, E., Pilorget, C., Potin, S.M., Alasli, A., Anada, S., Araki, Y., Sakatani, N., Schultz, C., Sekizawa, O., Sitzman, S.D., Sugiya, K., Sun, M., Dartois, E., De Pauw, E., Dionnet, Z., Djouadi, Z., Falkenberg, G., Fujita, R., Fukuma, T., Gearba, I.R., Hagiya, K., Hu, M.Y., Kato, T., Kawamura, T., Kimura, M., Kubo, M.K., Langenhorst, F., Lantz, C., Lavina, B., Lindner, M., Zhao, J.,

Vekemans, B., Baklouti, D., Bazi, B., Borondics, F., Nagasawa, S., Nishiyama, G., Nitta, K., Mathurin, J., Matsumoto, T., Mitsukawa, I., Miura, H., Miyake, A., Miyake, Y., Yurimoto, H., Okazaki, R., Ubuta, H., Naraoka, H., Sakamoto, K., Tachibana, S., Connolly, H.C., Lauretta, D.S., Yoshitake, M., Yoshikawa, M., Yoshikawa, K., Yoshihara, K., Yokota, Y., Yogata, K., Yano, H., Yamamoto, Y., Yamamoto, D., Yamada, M., Yamada, T., Yada, T., Wada, K., Usui, T., Tsukizaki, R., Terui, F., Takeuchi, T., Takei, Y., Iwamae, A., Soejima, H., Shirai, K., Shimaki, Y., Senshu, H., Sawada, H., Saiki, T., Ozaki, M., Ono, G., Okada, T., Ogawa, N., Ogawa, T., Noguchi, R., Noda, H., Nishimura, M., Namiki, N., Nakazawa, S., Morota, T., Miyazaki, A., Miura, A., Mimasu, Y., Matsumoto, S., Kumagai, K., Kouyama, T., Kikuchi, S., Kawahara, K., Kameda, S., Iwata, T., Ishihara, Y., Ishiguro, M., Ikeda, H., Hosoda, S., Honda, R., Honda, C., Hitomi, Y., Hirata, N., Hirata, N., Hayashi, T., Hayakawa, M., Hatakeda, K., Furuya, S., Fukai, R., Fujii, A., Cho, Y., Arakawa, M., Abe, M., Watanabe, S., Tsuda, Y., 2022. Formation and evolution of carbonaceous asteroid Ryugu: Direct evidence from returned samples. *Science* **379**, eabn8671.

Nakamura-Messenger, K., Clemett, S.J., Messenger, S., Keller, L.P., 2011. Experimental aqueous alteration of cometary dust. *Meteorit. Planet. Sci.* **46**, 843-856.

Nakano, H., Hirakawa, N., Matsubara, Y., Yamashita, S., Okuchi, T., Asahina, K., Tanaka, R., Suzuki, N., Naraoka, H., Takano, Y., Tachibana, S., Hama, T., Oba, Y., Kimura, Y., Watanabe, N., Kouchi, A., 2020. Precometary organic matter: A hidden reservoir of water inside the snow line. *Sci Rep* **10**, 7755.

Nelson, R., Nuth, J.A., Donn, B., 1987. A kinetic study of the hydrous alteration of amorphous MgSiO smokes: Implications for cometary particles and chondrite matrix. *J. Geophys. Res. Solid Earth* **92**, E657-E662.

Nikiforov, A.G., Onufrienok, V.V., Sazonov, A.M., Terehova, A.V., 2012. Weathering of Pyrrhotite to Szolmunkite. In *Proceedings of the 10th International Congress for Applied Mineralogy (ICAM)* (ed. M. A. T. M. Broekmans). Springer, Berlin, Heidelberg. pp. 463-466.

Oba, Y., Takano, Y., Naraoka, H., Furukawa, Y., Glavin, D.P., Dworkin, J.P., Tachibana, S., 2020. Extraterrestrial hexamethylenetetramine in meteorites—a precursor of prebiotic chemistry in the inner solar system. *Nat Commun.* **11**, 6243.

Oelkers, E.H., 2001. An experimental study of forsterite dissolution rates as a function of temperature and aqueous Mg and Si concentrations. *Chem. Geol.* **175**, 485-494.

Oelkers, E.H., Declercq, J., Saldi, G.D., Gislason, S.R., Schott, J., 2018. Olivine dissolution rates: a critical review. *Chem. Geol.* **500**, 1-19.

Ohnishi, I., Tomeoka, K., 2007. Hydrothermal alteration experiments of enstatite: implications for aqueous alteration of carbonaceous chondrites. *Meteorit. Planet. Sci.* **42**, 49-61.

Okamoto, A., Ishii, H., Oyanagi, R., Tsuchiya, N., 2021. Albite-K-feldspar-quartz equilibria in hydrothermal fluids at 400, 420°C and 20-35 MPa: Experimental measurements and thermodynamic calculations. *Geodynamics* **94**, 102102.

Oyanagi, R., Okamoto, A., Tsuchiya, N., 2017. Mechanisms of Serpentinization Utilizing Olivine-Plagioclase-H2O System under Hydrothermal Conditions. *Procedia Earth Planet. Sci.* **17**, 686-689.

Pearson, V.K., Sephton, M.A., Franchi, I.A., Gibson, J.M., Gilmour, I., 2006. Carbon and nitrogen in carbonaceous chondrites: Elemental abundances and stable isotopic compositions. *Meteorit. Planet. Sci.* **41**, 1899-1918.

Petit, S., Righi, D., Madejová, J., 2006. Infrared spectroscopy of NH4⁺-bearing and saturated clay minerals: a review of the study of layer charge. *Appl. Clay Sci.* **34**, 22-30.

Pizzarello, S., Cooper, G., Flynn, G., 2006. The nature and distribution of the organic material in carbonaceous chondrites and interplanetary dust particles. *Meteorites and the Early Solar System II*.

Remusat, L., 2015. Organics in primitive meteorites. In *Planetary Mineralogy* (eds. M. R. Lee and H. Leroux). European Mineralogical Union. p. 0.

Remusat, L., Derenne, S., Robert, F., Knicker, H., 2005. New pyrolytic and spectroscopic data on Orgueil and Murchison insoluble organic matter: A different origin than soluble. *Geochim. Cosmochim. Acta* **69**, 3919-3932.

Rietmeijer, F.J.M., Nuth III, J.A., Nelson, R.N., 2004. Laboratory hydration of condensed magnesiosilica smokes with implications for hydrated silicates in IDPs and comets. *Meteorit. Planet. Sci.* **39**, 723-746.

Rubin, A.E., Trigo-Rodríguez, J.M., Huber, H., Wasson, J.T., 2007. Progressive aqueous alteration of CM carbonaceous chondrites. *Geochim. Cosmochim. Acta* **71**, 2361-2382.

Schmitt-Kopplin, P., Gabelica, Z., Gougeon, R.D., Fekete, A., Kanawati, B., Harir, M., Gefebuegi, I., Eckel, G., Hertkorn, N., 2010. High molecular diversity of extraterrestrial organic matter in Murchison meteorite revealed 40 years after its fall. *Proc. Natl. Acad. Sci.* **107**, 2763-2768.

Schoonen, M., Smirnov, A., Cohn, C., 2004. A perspective on the role of minerals in prebiotic synthesis. *ami* **33**, 539-551.

Schwertmann, U., Kodama, H., Fischer, W.r., 1986. Mutual Interactions Between Organics and Iron Oxides. In *Interactions of Soil Minerals with Natural Organics and Microbes* John Wiley & Sons, Ltd. pp. 223-250.

Septon, M.A., 2002. Organic compounds in carbonaceous meteorites. *Nat. Prod. Rep.* **19**, 292-311.

Serra, C., Vinogradoff, V., Danger, G., Coulet, M.-V., Duvernay, F., 2024. Unexpected mineral impact on organic evolution during simulated aqueous alteration in asteroids. *Icarus* **116273**.

Spies, F.N., Macdonald, K.C., Atwater, T., Ballard, R., Carranza, A., Cordoba, D., Cox, C., Garcia, V.M.D., Franchetteau, J., Guerrero, J., Hawkins, J., Haymon, R., Hessler, R., Juteau, T., Kastner, M., Larson, R., Luyendyk, B., Macdougall, J.D., Miller, S., Normark, W., Orcutt, J., Rangin, C., 1980. East pacific rise: hot springs and geophysical experiments. *Science* **207**, 1421-1433.
Steudel, A., Friedrich, F., Schuhmann, R., Ruf, F., Sohling, U., Emmerich, K., 2017. Characterization of a Fine-Grained Interstratification of Turbostratic Talc and Saponite. *Minerals* **7**, 5.

Stopar, J.D., Jeffrey, T.G., Hamilton, V.E., Browning, L., 2006. Kinetic model of olivine dissolution and extent of aqueous alteration on mars. *Geochim. Cosmochim. Acta* **70**, 6136–6152.

Strauss, B., 2016. Characterization and modeling of materials responsible for planetary crustal magnetism.

Suttle, M.D., King, A.J., Ramkissoon, N.K., Bonato, E., Franchi, I.A., Malley, J., Schofield, P.F., Najorka, J., Salge, T., Russell, S.S., 2022. Alteration conditions on the CM and CV parent bodies – insights from hydrothermal experiments with the CO chondrite Kainsaz. *Geochim. Cosmochim. Acta* **318**, 83–111.

Suttle, M.D., King, A.J., Schofield, P.F., Bates, H., Russell, S.S., 2021. The aqueous alteration of CM chondrites, a review. *Geochim. Cosmochim. Acta* **299**, 219–256.

Taylor, P., Rummery, T.E., Owen, D.G., 1979. Reactions of iron monosulfide solids with aqueous hydrogen sulfide up to 160°C. *J. Inorg. Nucl. Chem.* **41**, 1683–1687.

ThomasArrigo, L.K., Bouchet, S., Kaegi, R., Kretzschmar, R., 2020. Organic matter influences transformation products of ferrihydrite exposed to sulfide. *Environ. Sci. Nano* **7**, 3405–3418.

Vacher, L.G., Truche, L., Faure, F., Tissandier, L., Mosser-Ruck, R., Marrocchi, Y., 2019. Deciphering the conditions of tochilinite and cronstedtite formation in CM chondrites from low temperature hydrothermal experiments. *Meteorit. Planet. Sci.* **54**, 1870–1889.

Velbel, M.A., 2012. Aqueous Alteration in Martian Meteorites: Comparing Mineral Relations in Igneous-Rock Weathering of Martian Meteorites and in the Sedimentary Cycle of Mars. In: Grotzinger, J.P., Milliken, R.E. (Eds.), *Sedimentary Geology of Mars. SEPM Society for Sedimentary Geology*. p. 0.

Velbel, M.A., Tonui, E.K., Zolensky, M.E., 2015. Replacement of olivine by serpentine in the Queen Alexandra Range 93005 carbonaceous chondrite (CM2): Reactant-product compositional relations, and isovolumetric constraints on reaction stoichiometry and elemental mobility during aqueous alteration. *Geochim. Cosmochim. Acta* **148**, 402–425.

Viennet, J.-C., Le Guillou, C., Remusat, L., Baron, F., Delbes, L., Blanchenet, A.M., Laurent, B., Criouet, I., Bernard, S., 2022. Experimental investigation of Fe-clay/ organic interactions under asteroidal conditions. *Geochim. Cosmochim. Acta* **318**, 352–365.

Vinogradoff, V., Bernard, S., Le Guillou, C., Remusat, L., 2018. Evolution of interstellar organic compounds under asteroidal hydrothermal conditions. *Icarus* **305**, 358–370.

Vinogradoff, V., Le Guillou, C., Bernard, S., Viennet, J.C., Jaber, M., Remusat, L., 2020a. Influence of phyllosilicates on the hydrothermal alteration of organic matter in asteroids: experimental perspectives. *Geochim. Cosmochim. Acta* **269**, 150–166.

Vinogradoff, V., Poggiali, G., Raponi, A., Ciarniello, M., De Angelis, S., Ferrari, M., Castillo-Rogez, J.C., Brucato, J., De Sanctis, M.-C., 2021. Laboratory investigations coupled to VIR/dawn observations to quantify the large concentrations of organic matter on ceres. *Minerals* **11**, 719.

Vinogradoff, V., Remusat, L., McLain, H.L., Aponte, J.C., Bernard, S., Danger, G., Dworkin, J.P., Elsila, J.E., Jaber, M., 2020b. Impact of phyllosilicates on amino acid formation under asteroidal conditions. *ACS Earth Space Chem.* **4**, 1398–1407.

Welch, S.A., Ullman, W.J., 1993. The effect of organic acids on plagioclase dissolution rates and stoichiometry. *Geochim. Cosmochim. Acta* **57**, 2725–2736.

Welsch, B., First, E.C., Ruprecht, P., Jollands, M.C., 2023. Olivine—the little green science machine. *Elements* **19**, 138–143.

Wiese, R.G., Powell, M.A., Fyfe, W.S., 1987. Spontaneous formation of hydrated iron sulfates on laboratory samples of pyrite- and marcasite-bearing coals. *Chem. Geol.* **63**, 29–38.

Wogelius, R.A., Walther, J.V., 1991. Olivine dissolution at 25°C: Effects of pH, CO2, and organic acids. *Geochim. Cosmochim. Acta* **55**, 943–954.

Wogelius, R.A., Walther, J.V., 1992. Olivine dissolution kinetics at near-surface conditions. *Chem. Geol.* **97**, 101–112.

Yabuta, H., Cody, G.D., Engrand, C., Kebukawa, Y., De Gregorio, B., Bonal, L., Remusat, L., Stroud, R., Quirico, E., Nittler, L., Hashiguchi, M., Komatsu, M., Okumura, T., Mathurin, J., Dartois, E., Duprat, J., Takahashi, Y., Takeichi, Y., Kilcoyne, D., Yamashita, S., Dazzi, A., Deniset-Besseau, A., Sandford, S., Martins, Z., Tamenori, Y., Ohigashi, T., Suga, H., Wakabayashi, D., Verdier-Paoletti, M., Mostefaoui, S., Montagnac, G., Barosch, J., Kamide, K., Shigenaka, M., Bejach, L., Matsumoto, M., Enokido, Y., Noguchi, T., Yurimoto, H., Nakamura, T., Okazaki, R., Naraoka, H., Sakamoto, K., Connolly, H.C., Lauretta, D.S., Abe, M., Okada, T., Yada, T., Nishimura, M., Yogata, K., Nakato, A., Yoshitake, M., Iwamae, A., Furuya, S., Hataakeda, K., Miyazaki, A., Soejima, H., Hitomi, Y., Kumagai, K., Usui, T., Hayashi, T., Yamamoto, D., Fukai, R., Sugita, S., Kitazato, K., Naru, H., Honda, R., Morota, T., Tatsumi, E., Sakatani, N., Namiki, N., Matsumoto, K., Noguchi, R., Wada, K., Senshu, H., Ogawa, K., Yokota, Y., Ishihara, Y., Shimaki, Y., Yamada, M., Honda, C., Michikami, T., Matsuoka, M., Naoyuki, H., Arakawa, M., Okamoto, C., Ishiguro, M., Jaumann, R., Bibring, J.-P., Grott, M., Schröder, S., Otto, K., Pilonget, C., Schmitz, N., Biele, J., Ho, T.-M., Moussi-Soffys, A., Miura, A., Noda, H., Yamada, T., Yoshihara, K., Kawahara, K., Ikeda, H., Yamamoto, Y., Shirai, K., Kikuchi, S., Ogawa, N., Takeuchi, H., Ono, G., Mimasu, Y., Yoshikawa, K., Takei, Y., Fujii, A., Iijima, Y., Nakazawa, S., Hosoda, S., Iwata, T., Hayakawa, M., Sawada, H., Yano, H., Tsukizaki, R., Ozaki, M., Terui, F., Tanakā, S., Fujimoto, M., Yoshikawa, M., Saiki, T., Tachibana, S., Watanabe, S., Tsuda, Y., 2023. Macromolecular organic matter in samples of the asteroid (162173) Ryugu. *Science* **379**, eabn9057.

Yoshimura, T., Takano, Y., Naraoka, H., Koga, T., Araoka, D., Ogawa, N.O., Schmitt-Kopplin, P., Hertkorn, N., Oba, Y., Dworkin, J.P., Aponte, J.C., Yoshikawa, T., Satoru, T., Ohkouchi, N., Hashiguchi, M., McLain, H., Parker, E.T., Sakai, S., Yamaguchi, M., Suzuki, T., Yokoyama, T., Yurimoto, H., Nakamura, T., Noguchi, T., Okazaki, R., Yabuta, H., Sakamoto, K., Yada, T., Nishimura, M., Nakato, A., Miyazaki, A., Yogata, K., Abe, M., Okada, T., Usui, T., Yoshikawa, M., Saiki, T., Satoshi, T., Terui, F., Nakazawa, S., Watanabe, S., Tsuda, Y., Tachibana, S., 2023. Chemical evolution of primordial salts and organic sulfur molecules in the asteroid 162173 Ryugu. *Nat. Commun.* **14**, 5284.

Zolotov, M.Y., 2012. Aqueous fluid composition in CI chondritic materials: Chemical equilibrium assessments in closed systems. *Icarus* **220**, 713–729.
**Supplementary Material:**

**Experimental investigations of mineral-organic chondritic analogs under
hydrothermal conditions: implications for carbonaceous asteroids**

Coline Serra¹, Olivier Grauby², Daniel Ferry², Fabrice Duvernay¹, Grégoire Danger¹,³, Johanna Marin-Carbonne⁴
and Vassilissa Vinogradoff ¹*.

¹Aix-Marseille University, UMR CNRS 7345, PIIM, Institut Origines, Marseille, France; ²Aix-Marseille University, UMR CNRS 7325 CINAM, Marseille, France; ³Institut Universitaire de France, ⁴Institut des Sciences de la Terre, Université de Lausanne, Switzerland.

* Corresponding author: [Vassilissa.vinogradoff@univ-amu.fr](mailto:Vassilissa.vinogradoff@univ-amu.fr)

<figure><img src="image_16.png" /><figcaption>Fig. S11. Experimental protocol for the formation and characterization of the chondritic analogs. The protocol comprises two parts: the first involves mixing the mineral and organic phases to form the analogues, while the second involves preparing the two fractions for further analysis.</figcaption></figure>
<table><caption>Table SI1. pH value of each samples. pH was measured with universal indicator paper, error bar is 1. Water milliQ pH was 6.</caption><thead><tr><th rowspan="2"></th><th colspan="2">1 day</th><th colspan="2">10 days</th><th colspan="2">45 days</th><th colspan="2">100 days</th></tr><tr><th>sample</th><th>pH</th><th>sample</th><th>pH</th><th>sample</th><th>pH</th><th>sample</th><th>pH</th></tr></thead><tbody><tr><td rowspan="2">With feldspar</td><td>F1</td><td>6</td><td>F10</td><td>8</td><td>F45</td><td>8</td><td>F100</td><td>8</td></tr><tr><td>HF1</td><td>7</td><td>HF10</td><td>8</td><td>HF45</td><td>8</td><td>HF100</td><td>8</td></tr><tr><td rowspan="2">With troilite</td><td>T1</td><td>5</td><td>T10</td><td>5</td><td>T45</td><td>5</td><td>T100</td><td>5</td></tr><tr><td>HT1</td><td>6</td><td>HT10</td><td>7</td><td>HT45</td><td>7</td><td>HT100</td><td>6</td></tr><tr><td rowspan="2">With peridot</td><td>P1</td><td>8</td><td>P10</td><td>8</td><td>P45</td><td>8</td><td>P100</td><td>8</td></tr><tr><td>HP1</td><td>8</td><td>HP10</td><td>8</td><td>HP45</td><td>8</td><td>HP100</td><td>8</td></tr><tr><td rowspan="2">With the mixture of minerals</td><td>PTF1</td><td>8</td><td>PTF10</td><td>8</td><td>PTF45</td><td>8</td><td>PTF100</td><td>9</td></tr><tr><td>HPTF1</td><td>9</td><td>HPTF10</td><td>9</td><td>HPTF45</td><td>9</td><td>HPTF100</td><td>9</td></tr></tbody></table>

<figure><img src="image_17.png" /><figcaption>Fig. SI2. XRD patterns of initial feldspar (F crude) and altered feldspar with or without OM at 80°C for 1, 45 and 100 days. The dashed lines indicate the peak position of albite.</figcaption></figure>
<table><caption>Table SI2. Bulk Hydrogen, Carbon and Nitrogen elemental composition of the inorganic fraction of the hydrothermal products after 45 days and 100days. For each composition 2 grains of about 2mg were measured except for HT45 (3 grains)</caption><thead><tr><th>Name of the sample</th><th>N (wt%)</th><th>C (wt%)</th><th>H (wt%)</th><th>S (wt%)</th><th>N yield (%)</th></tr></thead><tbody><tr><td>HMT#</td><td>1.61</td><td>2.07</td><td>0.35</td><td>/</td><td>/</td></tr><tr><td>P45 /P100</td><td>0</td><td>0.49</td><td>1.89±0.1</td><td>/</td><td>/</td></tr><tr><td>HP45</td><td>0.09±0.01</td><td>0*</td><td>1.92±0.05</td><td>/</td><td>5.3±0.3</td></tr><tr><td>HP100</td><td>0.03</td><td>0*</td><td>1.82±0.4</td><td>/</td><td>1.86</td></tr><tr><td>F45 / F100</td><td>0</td><td>0.16</td><td>0.94±0.01</td><td>/</td><td>/</td></tr><tr><td>HF45</td><td>0.25±0.01</td><td>0.21±0.05*</td><td>0.91±0.03</td><td>/</td><td>15.2±0.3</td></tr><tr><td>HF100</td><td>0.13±0.01</td><td>0.13±0.04*</td><td>0.97±0.05</td><td>/</td><td>8.07±0.7</td></tr><tr><td>T45</td><td>0</td><td>0.07</td><td>0.98±0.01</td><td>19.8±0.2</td><td>/</td></tr><tr><td>HT45</td><td>0.18±0.02</td><td>0.20±0.07*</td><td>0.44±0.03</td><td>30.8±0.7</td><td>11.4±1.5</td></tr><tr><td>T100</td><td>0</td><td>0.04±0.01</td><td>1.15±0.03</td><td>18.96±1.83</td><td>/</td></tr><tr><td>HT100</td><td>0.09±0.02</td><td>0.16±0.04*</td><td>0.56±0.02</td><td>29.1±0.1</td><td>5.3±0.1</td></tr><tr><td>PTF45</td><td>0</td><td>0.20</td><td>1.13±0.03</td><td>9.5±3</td><td>/</td></tr><tr><td>HPTF45</td><td>0.18±0.01</td><td>0.26±0.1*</td><td>1.40±0.03</td><td>5.11±0.6</td><td>10.6±0.6</td></tr><tr><td>HPTF100</td><td>0.07±0.001</td><td>0.31±0.06*</td><td>1.57±0.1</td><td>6.2±2.7</td><td>3.7±0.5</td></tr></tbody></table>

<footnote>* For these carbon contents, the average of the carbon contamination from the mineral alone has been subtracted. # theoretical % of HMT in the initial mixture.</footnote>
<figure><img src="image_18.png" /><figcaption>Fig. SI3. XRD patterns of initial peridot (P crude) and altered peridot with or without OM at 80°C for 1, 45 and 100 days. The dashed lines indicate the peak position of Forsterite. Arrows highlight the generation of new pics with the d-spacing indicated in Ångström.</figcaption></figure>
<figure><img src="image_19.png" /></figure>

Fig. SI4. Image in optical microscopy of the grains after alteration from PTF45 sample. For each of the three families of grains of different colors (gray, white, and yellow), scanning electron microscopy analysis and X-ray diffraction spectra are presented. For the yellow grain, the dashed lines indicate the peak position of Forsterite, arrows highlight the generation of new pics with the d indicated in Ångström. For the white grains, the dashed lines indicate the peak position of albite. For the gray grains, peaks are indexed with the following abbreviations: Tro, troilite; Po, Pyrrhotite; Ab, albite and Fo, Forsterite.
<figure><img src="image_20.png" /><figcaption>Fig. SI5. XRD patterns of the PTF samples altered with or without OM at 80°C for 1, 45 and 100 days. The dashed line highlights the peak position already present from days 1: Fo: Forsterite, Ab; Albite. Tro: Troilite. Arrows highlighted the generation of new pics with the d indicated in Ångström.</figcaption></figure>
<figure><img src="image_21.png" /><figcaption>Fig. SI6. Infrared spectrum of the insoluble fraction from PTF and HPTF samples. Deconvolution was carried out in the 2700-3800 cm⁻¹ range using OPUS software. To note, the deconvolution procedure was consistent for both 1 and 10 days, as well as for 45 and 100 days. Therefore, only the results for the 1 and 100 days of alteration are presented.</figcaption></figure>
<figure><img src="image_22.png" /></figure>

Fig. SI7. Pourbaix diagram for Fe-S and H₂O adapted for our study from Anderko and Shuler (1997), pH versus potential in relation to the standard hydrogen electrode (SHE).

## References

Anderko A. and Shuler P. J. (1997) A computational approach to predicting the formation of iron sulfide species using stability diagrams. *Computers & Geosciences* **23**, 647–658.