# A modified Rock-Eval approach to track organics in (bio)carbonates

A. Perron, B. Ménez, F. Baudin, F. Stalport

► To cite this version:

A. Perron, B. Ménez, F. Baudin, F. Stalport. A modified Rock-Eval approach to track organics in (bio)carbonates. Chemical Geology, 2025, 690, pp.122815. 10.1016/j.chemgeo.2025.122815. hal-05099134

HAL Id: hal-05099134

https://hal.science/hal-05099134v1

Submitted on 5 Jun 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
Research paper

# A modified Rock-Eval approach to track organics in (bio)carbonates

A. Perron<sup>a,b ID*</sup>, B. Ménez<sup>a ID</sup>, F. Baudin<sup>c ID</sup>, F. Stalport<sup>b ID</sup>

## ARTICLE INFO

Communicated by Oleg Pokrovsky

Keywords:

Rock-Eval combustion and pyrolysis

Carbonates

Biogenicity

Organic matter

Space missions

## ABSTRACT

Biominerals, notably carbonates, serve as valuable biosignatures for identifying past or present life in terrestrial environments. However, distinguishing between biogenic and abiotic minerals usually required multiple high-resolution techniques, challenging their application for the *in situ* search for extraterrestrial life in space missions with limited analytical capabilities. This study investigated the potential of gas profiles (i.e., carbon dioxide CO₂, carbon monoxide CO, and sulfur dioxide SO₂) generated by Rock-Eval purified air combustion (in the range 50–700 °C) and dinitrogen pyrolysis (in the range 700–1000 °C) of 66 natural and laboratory carbonates to detect organics associated with these carbonate minerals that could hold clues to their origin (either abiotic or biogenic) and formation process. For bio-related and organo-carbonates containing Ca and Ca/Mg, CO and SO₂ emissions detected below 700 °C were the product of combustion and associated thermal cracking of organic compounds initially coating mineral grain surfaces, while those detected above 700 °C, during and after the thermal decomposition of Ca- and Ca/Mg-carbonates, were derived from the thermal cracking of organic compounds trapped within carbonate crystals, suggesting the carbonates formed in the presence of organic compounds of biological or abiotic origin. For hydrated Mg-carbonates, the interpretation is more challenging due to multiple phase transitions that overlap with the combustion and thermal cracking of surface and trapped organic compounds in the same temperature range. Overall, this study highlights the potential of our modified Rock-Eval approach as a valuable technique for rapidly identifying and characterizing potential biosignatures in Ca- and Ca/Mg-carbonate at the bulk sample scale, an approach that can be reasonably implemented on *in situ* space instruments for the search for present or past extraterrestrial life.

## 1. Introduction

More than 80% of the history of life on Earth is microbial, primarily characterized by microscopic unicellular life (Reid et al., 2003; Amaral-Zettler et al., 2010; Knoll et al., 2016; Madigan et al., 2019). It is also in this form that we are most likely to find remnants of primitive life on Earth, or extraterrestrial life. However, microbial life preservation in the rock record is challenging because of the fragility of its organic components and the harshness of environmental conditions that may be or have been highly oxidizing (Sumner, 2004; Davila et al., 2008; Lasne et al., 2016) or irradiative (Cockell et al., 2000; Patel et al., 2002; Dartnell et al., 2007; Poch et al., 2013, 2014; Stalport et al., 2019), especially in extraterrestrial environments if we consider the Mars planet for example. Most of the time, it is only the traces left by microbial activity that provide evidence of its existence, past or present (Lepland et al., 2013; Javaux, 2019), among which are minerals. Minerals

derived from micro-organisms are particularly promising as proxies of microbial life in the rock record due to their greater resistance to harsh environmental conditions compared to organic material, as well as their potential to facilitate fossilization and preserve organic remnants inside crystals (as inclusions or impurities) and at grain boundaries (Benzerara and Menguy, 2009; Benzerara et al., 2011).

Minerals of microbial origin can form as a result of local environmental changes caused by the metabolic activity of microorganisms. Their nucleation can be facilitated by the presence of cell surfaces and extracellular polymeric substances (EPS) secreted by microbial organisms that also passively adsorb and accumulate mineral precursors and provide effective organic nucleation templates for mineral precipitation (Dupraz et al., 2009; Dupraz et al., 2011; Zhu and Dittrich, 2016). Moreover, the presence of organic compounds and/or living organisms influences the nature and texture of the mineral formed (Braissant

<footnote><sup>a</sup> Institut de physique du globe de Paris (IPGP), Université Paris Cité, CNRS UMR 7154, 1 rue Jussieu, Paris, 75005, France</footnote>

<footnote><sup>b</sup> Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), CNRS UMR 7583, Université Paris Cité and Université Paris Est Créteil, 61 avenue du Général de Gaulle, Créteil, 94010, France</footnote>

<footnote><sup>c</sup> Institut des Sciences de la Terre de Paris (ISTeP), CNRS UMR 7193, Sorbonne Université, 4 place Jussieu, Paris, 75005, France</footnote>

<footnote>* Correspondence to: Physique des Interactions Ioniques et Moléculaires (PIIM), CNRS UMR 7345, Université Aix-Marseille, 52 avenue Escadrille Normandie-Niémen, Marseille, 13013, France.</footnote>

<footnote>E-mail address: alexandra.perron@univ-amu.fr (A. Perron).</footnote>
et al., 2003), sometimes out of the equilibrium predicted by thermo-dynamics, as exemplified for ancient carbonates (Lepot et al., 2008). Classification used to distinguish mineralization processes (including biologically-induced or -influenced mineralization and organomineralization) has been extensively debated (e.g., Dupraz et al., 2009) without reaching any consensus, especially regarding the notions of biomineral and organomineral and the nature of the organic compounds involved in their formation (e.g., living or dead microbial cells, organic metabolites or abiotic organic compounds of geogenic origin; Perry et al., 2007; Défarge et al., 2009; Dupraz et al., 2009; Dupraz et al., 2011; Hoffmann et al., 2021). Identifying abiotic organic compounds on Earth is a challenge due to the omnipresence of biological activity. However, abiotic organic synthesis has been recognized as an efficient process, driven by water-rock interactions in the lithosphere, leading to the formation of alkanes, organic acids, polycyclic aromatic hydrocarbons, and amino acids (e.g., Ménez et al., 2018; Andreani and Ménez, 2019). In extraterrestrial environments, such compounds may result from the chemical processes in the interstellar medium or from the hydrothermal weathering of meteorites and/or their parent bodies (e.g., Burton et al., 2012; Meinert et al., 2016; Vinogradoff et al., 2017; Oba et al., 2019; Garcia et al., 2024). Therefore, in the present study, carbonate samples related to biological activities and components are hereafter referred to as “bio-related minerals” while laboratory samples involving organic compounds in a non-biological system are referred to as “organo-minerals”.

Minerals have been extensively used as biosignatures in modern and ancient terrestrial environments. As detailed by Westall et al. (2015), it can relate to particular structures and morphologies induced by living organisms (e.g., laminations formed by alternating microbial mats and minerals, where relics of cells and EPS can be found), organic compounds trapped in minerals (e.g., degraded biological polymers) or metabolic signatures (e.g., isotopic fractionations linked to microbial metabolisms recorded in minerals). Distinguishing biogenic carbonates from abiotic ones often requires a combination of imaging techniques with high spatial resolution such as scanning transmission X-ray microscopy (STXM) and transmission electron microscopy (TEM), including electron energy loss spectroscopy (EELS) (Cosmidis and Benzerara, 2014). While powerful, these approaches provide very local information, the representativeness of which is sometimes difficult to assess, and are hardly implemented on a large number of rock samples due to sophisticated preparation, as well as time-consuming analysis and data processing. It therefore limits their application to large-scale studies or those in situ on extraterrestrial bodies that could host or have hosted life (e.g., Mars, Europa, Enceladus). In addition, no space vehicles currently has the capacity to implement them.

This points to the need for complementary bulk approaches for the detection of bio-related carbonates, with the capability to rapidly screen a wide range of samples at a larger spatial resolution with the aim to explore life back in time on Earth but also implement them for space exploration. Among these approaches, thermogravimetry and differential thermal analyses (TG/DTA), which share similarities with analytical techniques and sample preparation used on space instruments such as Sample Analysis at Mars (SAM) from the Mars Science Laboratory (MSL) space mission (Mahaffy et al., 2012) and Mars Organic Molecule Analyzer (MOMA) from the ExoMars space mission (Goesmann et al., 2017), has revealed a difference in decomposition temperatures of 28 °C between bio-related carbonates (i.e., natural and laboratory calcium carbonates produced by various (micro)organisms) and abiotic carbonates (Stalport et al., 2005, 2007; Perron et al., 2023). This difference can be explained by the lower crystallinity of bio-related carbonates compared to their abiotic counterparts. This could relate to a larger amount of chemical impurities and the entrapment of organic compounds (e.g., microbial cells and their remnants, metabolites and EPS) in bio-related carbonates (Dupraz et al., 2009b, 2011; Zhu and Dittrich, 2016; Hoffmann et al., 2021;

Jarwar et al., 2022). Nevertheless, this has not been confirmed as TG/DTA does not allow the organic fraction to be characterized.

Another approach would be to investigate organic and inorganic fractions by thermal analysis as carried out by the TEGA (Thermal Evolved Gas Analyzer) instrument on the Mars Phoenix Scout Lander mission (Boynton et al., 2001). The TEGA instrument performed in situ thermal analysis (up to 1000 °C) and measured gas emissions (e.g., CO₂, O₂, H₂O) to detect and quantify volatile-bearing phases (Boynton et al., 2009; Hecht et al., 2009; Sutter et al., 2012). It was recently able to jointly highlight organic carbon and Ca-rich carbonates in Martian soils (Sutter et al., 2024). Similarly, laboratory Rock-Eval analysis, widely used in oil and gas exploration, allows to characterize, by pyrolysis under inert atmosphere, the petroleum potential of sedimentary rocks (i.e., the quantity of free hydrocarbons and of those potentially generated by their thermal maturation) while then assessing, by combustion under air, its solid carbonate fraction, overall leading to total organic and inorganic carbon content estimates (Espitalié et al., 1977; Lafargue et al., 1998; Behar et al., 2001). Its use recently extended to organic matter in soils and recent sediments (Di-Giovanni et al., 1998; Disnar et al., 2003; Sebag et al., 2006; Boussafir et al., 2012; Hare et al., 2014; Hetényi and Nyilas, 2014; Baudin et al., 2015, 2017; Hazera et al., 2023), as well as black carbon and pure organic compounds (Copard et al., 2006; Poot et al., 2009).

Here we assessed the potential of a modified Rock-Eval approach involving purified air combustion (in the range 50–700 °C) followed by dinitrogen pyrolysis (in the range 700–1000 °C), and of the associated carbon dioxide (CO₂), carbon monoxide (CO) and sulfur dioxide (SO₂) gas profiles to investigate organic and inorganic fractions in carbonated samples. For that purpose, a wide variety of carbonate samples has been studied including Ca-, Ca/Mg- and (hydrated) Mg-carbonates produced in environments where microbial life was acknowledged to have largely impacted the formation of solid carbonates, i.e., shallow water lakes hosting microbialites and stromatolites of various ages described in Gérard et al. (2013, 2018), Mlewski et al. (2018), Roche et al. (2018), Shirokova et al. (2013), and Wattinne (2004), chimneys from alkaline hydrothermal vents described in Pisapia et al. (2017) and Lecoeuvre et al. (2021), cold seep environments described in Pierre et al. (2002, 2012, 2015), Pierre and Rouchy (2004), and Gontharet et al. (2007), and involves metabolisms likely present on early Earth such as hydrogenotrophy, methanogenesis/methanotrophy, including anaerobic oxidation of methane coupled with sulfate reduction, in addition to anoxygenic photosynthesis that preceded oxygenic photosynthesis on Earth (Madigan et al., 2019). They are compared with samples of carbonates formed without any biological contribution or presence of organic compounds.

## 2. Materials and methods

### 2.1. Sample description

As detailed in Table A.1, a total of 66 diverse natural and laboratory carbonate samples were studied. Natural and laboratory samples have been classified *a priori* into six main categories according to their presumed formation processes: (1) abiotic (i.e., 6 natural samples from deposits worldwide and one laboratory sample), (2) organo (i.e., 4 laboratory samples formed by organo-mineralization experiments under sterile conditions following the protocol of Braissant et al., 2003 and using simple amino acids, including L-glutamine, L-glutamic acid, and L-aspartic acid), (3) natural bio-related (i.e., 5 ancient and modern lake microbialite and stromatolite samples described in Gérard et al., 2013, 2018, Mlewski et al., 2018, Roche et al., 2018, Shirokova et al., 2013, Vennin et al., 2021, and Wattinne, 2004; 15 carbonated chimney samples from alkaline hydrothermal vents described in Pisapia et al., 2017 and Lecoeuvre et al., 2021; 6 authigenic carbonate samples from ancient and active cold seeps described in Gontharet et al., 2007, Pierre
<figure><img src="image_2.png" /><figcaption>**Fig. 1.** Modified Rock-Eval approach used in this study with heating rate, temperature ranges and associated atmospheres. It consists firstly of a purified air combustion step in the range 50–700 °C, to maximize the combustion and the thermal cracking of surface organic compounds while minimizing the formation of solid carbon residue, followed by a N₂ pyrolysis step in the range 700–1000 °C, to thermally decompose Ca- and Ca/Mg-carbonates and crack trapped organic compounds.</figcaption></figure>

and Rouchy, 2004; Pierre et al., 2002, 2012, 2015), (4) laboratory bio-related composed of calcium (Ca-) carbonates (i.e., 12 samples derived from the carbonatogen bacteria *Sporosarcina pasteurii* using aqueous solutions containing Ca (±Ba or Sr) and following the protocol of Ferris et al., 2004 and Dupraz et al., 2009a,b), (5) laboratory bio-related composed of magnesium (Mg-) carbonates (i.e., 11 samples from Shirokova et al., 2013 and Mavromatis et al., 2015 derived from two carbonatogen cyanobacteria (*Gloeocapsa* sp. or *Synechococcus* sp.) using aqueous solutions of varying chemical composition) and (6) mixed origin (i.e., 6 limestone samples of undetermined or combined biological and chemical origin from modern and subactual travertines Baer and Rigby, 1978; Burnside, 2010; Kele and Bódai, 2022; Blanc and Monteau, 1988, as well as calcareous reservoir rocks from an established petroleum system that have accumulated hydrocarbons Wattinne, 2004; Roche et al., 2018; Vennin et al., 2021).

## 2.2. Carbonate sample preparation

Natural and laboratory samples were ground by hand using an agate mortar and pestle and then sieved using stainless steel sieves with mesh sizes of 100 and 63 µm. Between each sample, the sieves were ultrasonically cleaned in an ultrapure water bath for 30 min, then washed with ethanol 70% (diluted with ultrapure water). The sieves were dried in a dry oven at 80 °C for 30 min. For each sample, the particle size fraction between 63 and 100 µm was stored in small glass containers, protected from light and humidity until use. Only the laboratory abiotic sample and all laboratory bio-related Mg-carbonates were not ground due to their small initial size below 63 µm.

## 2.3. Analytical techniques

Carbonate samples were analyzed by powder X-ray diffraction (XRD) using a Malvern Panalytical Empyrean X-ray diffractometer (The

X-rays facility, ITODYS, Université Paris Cité, Paris, France) operated at 45 keV and 40 mA. Analyses (theta-theta scans with step of 0.007° 2θ) were performed in Bragg-Brentano focusing geometry with monochromatized Cu Kα1 radiation (λ = 1.5406 Å) and a PIXcel multi-channel detector (Malvern Panalytical) in continuous scanning line (1D) mode with an active length of 3.34727° 2θ. To estimate semi-quantitatively the sample mineralogical composition, diffractograms were analyzed using the HighScore Plus (Degen et al., 2014) and MAUD (Lutterotti et al., 1999) softwares by comparing, based on known crystalline material diffractograms from the (NIST Inorganic Crystal Structure Database), the positions and intensities of the diffraction peaks. Mineralogical relative abundances are provided with an uncertainty of ±1 weight percent (wt%).

Scanning electron microscopy (SEM) observations were carried out on Au-coated mineral powder (coating thickness between 7 and 10 nm) using a Zeiss AURIGA 40 field-emission scanning electron microscope located at IPGP (Plateforme PARI, Paris, France). Images were acquired using secondary electron detectors (SESI detector for high and low current and InLens for low current) under high vacuum conditions (10⁻⁶ mbar). Only laboratory organo- and bio-related Ca-carbonates were cleaned with ultrapure water and absolute ethanol before Au-coating.

Thermal analyses were performed using a Rock-Eval®7S apparatus (Vinci Technologies) located at ISTEp (Sorbonne Université, Paris, France) (e.g., Cohen-Sadon et al., 2022; Baudin, 2023). The instrument is an open pyrolysis system operating under non-isothermal conditions (Espitalié et al., 1977). A modified heating program was used starting at 50 °C and finishing at 1000 °C with an heating rate of 10 °C min⁻¹, first under purified ambient air (≤ 1 ppm CO, CO₂) that allowed combustion (i.e., from 50 °C up to 700 °C), and then under dinitrogen N₂ atmosphere (≥ 99.999%, Azote ALPHAGAZ™ 1, Air Liq-uide) for pyrolysis (i.e., from 700 °C up to 1000 °C) (Fig. 1). The carrier gas pressure was 2 bar for all gases. For each analysis, 60.05 ±0.05 mg of powdered samples were heated. Simultaneous detection of effluents
during combustion and pyrolysis generated gas profiles describing, as a function of temperature T, the evolution of CO and CO₂ measured by infrared (IR) spectrophotometry (lowest ranges of 0–50 ppm and 0–300 ppm for CO and CO₂, respectively) and SO₂ measured by ultraviolet (UV) spectrophotometry (lowest range of 0–130 ppm) using a nondispersive infrared (NDIR)/UV/visible (VIS) spectrophotometer allowing detection in the spectral range 250–390 nm (Rosemount X-STREAM X2GP, Intrinx technology). To ensure that only SO₂ is detected by the UV spectrophotometer, an oxidative furnace (temperature of 850 °C; incoming air flow of 50 ml min⁻¹) is located at the outlet of the furnace containing the sample.

## 2.4. Rock-Eval data processing and statistical analysis

Four area ratios were derived from the Rock-Eval gas profiles collected using the IR and UV signals, based on the integration of the area f of the CO and SO₂ peaks found either at low temperatures (LT) in the range 50–700 °C (Eqs. (1) and (2), respectively) and high temperatures (HT) in the range 700–1000 °C (Eqs. (3) and (4), respectively), all normalized by the area of the CO₂ peak between 50 °C and 1000 °C. The trapezoidal rule for computing the definite integral between two temperatures was used. Area ratio values were multiplied by 100 to facilitate comparison.

$$CO.LT = \frac{\int_{50}^{700} f_{CO}(T)dt}{\int_{50}^{1000} f_{CO_2}(T)dt} \times 100 \quad (1)$$

$$SO_2.LT = \frac{\int_{50}^{700} f_{SO_2}(T)dt}{\int_{50}^{1000} f_{CO_2}(T)dt} \times 100 \quad (2)$$

$$CO.HT = \frac{\int_{700}^{1000} f_{CO}(T)dt}{\int_{50}^{1000} f_{CO_2}(T)dt} \times 100 \quad (3)$$

$$SO_2.HT = \frac{\int_{700}^{1000} f_{SO_2}(T)dt}{\int_{50}^{1000} f_{CO_2}(T)dt} \times 100 \quad (4)$$

Of the 66 samples studied (see Section 2.1 and Table A.1), 50 were analyzed in duplicate to assess the repeatability of the gas profiles obtained and the reliability of the calculated area ratios. Not all Rock-Eval analysis could be duplicated due to the very low quantities available for some samples. Three statistical approaches were used: (1) linear regression parameters (i.e., slope and y-intercept value) between duplicated area ratios, (2) mean standard error (i.e., standard deviation to the mean) of duplicated area ratios to assess the standard error of all samples for one area ratio, and (3) Kendall rank correlation coefficients to compare area ratio values determined for the first replicate with area ratio values determined for the second one.

# 3. Results

## 3.1. Physico-chemical characterization of the sample set

As illustrated in Fig. 2, XRD analyses show that, of all samples, 37 samples (latter referred to as “Ca(Mg)CO₃” subset) are dominated by Ca-carbonates (i.e., CaCO₃ polymorphs namely calcite, aragonite, vaterite) or Ca/Mg-carbonates (i.e., magnesian calcite (Ca,Mg)CO₃, dolomite CaMg(CO₃)₂) while other mineral phases represent less than 5 wt%, 14 samples (latter referred to as “MgCO₃·nH₂O” subset) are dominated by hydrated Mg-carbonates (i.e., hydromagnesite Mg₅(CO₃)₄(OH)₂·4H₂O, nesquehonite MgCO₃·3H₂O and dypingite Mg₅(CO₃)₄(OH)₂·5H₂O) with other mineral phases ≤ 5 wt%, 6 samples (latter referred to as “Mix Ca(Mg)CO₃/others” subset) are composed of both Ca-carbonates (ranging from 40 to 85 wt%) and other crystalline phases (mainly quartz, SiO₂ and brucite, Mg(OH)₂) and finally, 9 samples (latter referred to as “Mix Ca-,Mg-CO₃/others” subset) are composed of both Ca- and hydrated Mg-carbonates (ranging from 2 to 55 wt% and 2 to 25 wt%, respectively) and other mineral phases (mainly brucite).

SEM images of bio-related samples highlight the presence of EPS intertwined with carbonates (e.g., microbialite sample; Fig. 3a) or microbial cells and their EPS-filaments (e.g., laboratory bio-related sample; Fig. 3b). For calcareous reservoir rocks, in which hydrocarbons have accumulated (Wattinne, 2004; Vennin et al., 2021; Roche et al., 2018), calcite grains are coated with organic material filling the porosity of the rock (e.g., stromatolitic reservoir rock sample; Fig. 3c). Abiotic organo-carbonates having precipitated from amino acid-rich solutions are also strongly associated to organic compounds. In those samples, carbonate grains are coated with agglomerates of condensed amino acids as observed on a sample precipitated in 1% w/v L-aspartic acid aqueous solution (Fig. 3d).

## 3.2. Gas profiles of carbonate samples and associated repeatability

As illustrated in Fig. 4, Rock-Eval gas profiles obtained for all samples show CO₂ peaks either below 650–700 °C for hydrated Mg-carbonates (Fig. 4e–f) or above 650–700 °C for Ca-carbonates (Fig. 4a–e). Although some gas profiles show no or weak SO₂ and CO peaks between 50 °C and 1000 °C (Fig. 4a), several gas profiles highlight SO₂ and CO peaks from 50 °C to 650–700 °C (Fig. 4f) or from 650–700 °C up to 1000 °C (Fig. 4d) or even for both temperature ranges (Fig. 4a–c,e). For all samples, CO and SO₂ profiles return close to baseline around 700 °C (Fig. 4a–e) except the SO₂ profile of all laboratory bio-related Mg-carbonates (Fig. 4f).

For the entire temperature range studied, the duplicated ratios are all close to the 1:1 agreement line (see linear regressions in Fig. A.1). The mean standard error is ±0.009 and ±0.008, for CO.LT and CO.HT area ratios, respectively, and ±0.014 for SO₂.LT and SO₂.HT area ratios (Table A.2). All mean standard errors are rather low, with lower values, hence lower variability, between duplicates for CO area ratios than for those of SO₂. Kendall rank correlation coefficients are 0.92 for CO.LT and CO.HT and 0.85 and 0.74 for SO₂.LT and SO₂.HT, respectively. All coefficients are heading towards 1, meaning that data are sufficiently reproducible, with especially high repeatability for the CO area ratios and slightly lower repeatability for the SO₂ area ratios, probably due to the many significantly low SO₂ peak area values associated with high noise level (e.g., Fig. 4a,e), as also observed for mean standard errors.

## 3.3. CO.LT and SO₂.LT area ratios at low temperatures [50–700 °C]

Boxplots in Fig. 5 show CO.LT and SO₂.LT values obtained for the six sample categories. Both ratios follow the same pattern, with significantly higher area ratio values for laboratory bio-related Mg-carbonates compared to any other sample category (median: 7.686 and 2.352 for CO.LT and SO₂.LT, respectively; Table A.3), followed by natural bio-related carbonate samples (median: 0.368 and 0.229 for CO.LT and SO₂.LT, respectively) showing, however, a large dispersion of their area ratio values (IQR: 0.259 and 0.225 for CO.LT and SO₂.LT, respectively; Table A.3). Laboratory bio-related Ca-carbonate samples show lower area ratio values (median: 0.147 and 0.138 for CO.LT and SO₂.LT, respectively) nonetheless higher than those obtained for abiotic, organo- and mixed origin carbonate samples (median: 0.026–0.054 and 0.009–0.043 for CO.LT and SO₂.LT, respectively), all showing IQR values below 0.095 and 0.153 for CO.LT and SO₂.LT, respectively.

## 3.4. CO.HT and SO₂.HT area ratios at high temperatures [700–1000 °C]

Considering CO.HT area ratios among all sample categories (Fig. 6 a–b), organo-carbonate samples display the largest dispersion (IQR: 3.260; Table A.4) and the highest values (median: 3.870; Table A.4). Natural bio-related carbonate samples also exhibit high dispersion (IQR: 0.248) with half of low area ratio values (down to 0.005) and half of high area ratio values (up to 0.762). In this category, most low CO.HT values are associated with samples mainly composed of
<figure><img src="image_3.png" /><figcaption>**Fig. 2.** Carbonate sample bulk mineralogy as shown by powder X-ray diffraction (in weight percent relative abundance). Mineral phases: Cal = Calcite, Arg = Aragonite, Vtr = Vaterite, Mg-Cal = Magnesian calcite, Dol = Dolomite, Hmgs = Hydromagnesite, Dyp = Dypingite, Nes = Nesquehonite, Others = Quartz, Brucite, Halite, Analcime, Iowaite, Tremolite, Jamborite, Quintinite, Zeolite, Oxides and Hydroxides (see Table A.6 for empirical mineral formula listed above).</figcaption></figure>

hydrated Mg-carbonates or combining carbonates and other mineral phases (Fig. 2). Laboratory bio-related Ca-carbonate samples also display high and dispersed CO.HT values (median: 0.258; IQR: 0.181). Finally, CO.HT area ratios of laboratory bio-related Mg-, abiotic and mixed origin carbonate samples exhibit mainly clustered values (IQR: 0.015, 0.050 and 0.141, respectively) and the lowest CO.HT values (median: 0.028, 0.019 and 0.020, respectively).

Regarding SO₂.HT area ratios (Fig. 6c-d), laboratory bio-related Mg-carbonate samples are those exhibiting the highest values (median: 0.477; Table A.4) and highest dispersion (IQR: 0.149; Table A.4). Natural bio-related carbonate samples also exhibit a large dispersion of their SO₂.HT values (IQR: 0.139) with low area ratios (down to 0.012) and several high ones (up to 2.792), most of them being nonethe-less considered as outliers. Similarly to CO.HT area ratios, most of these low SO₂.HT values are associated with samples composed of hydrated Mg-carbonates and other mineral phases while most of the high SO₂.HT values derive from Ca- and Ca/Mg-carbonates (Fig. 2). Organo-carbonate samples also show large dispersion and high SO₂.HT

values (IQR: 0.142; median: 0.212) in contrast with laboratory bio-related Ca-carbonate samples (IQR: 0.023; median: 0.054). Finally, all abiotic carbonate samples have clustered and significantly low SO₂.HT values (IQR: 0.018; median: 0.005) and most mixed origin carbonate samples also exhibit low SO₂.HT values (median: 0.020), but with larger dispersion (IQR: 0.105).

### 3.5. CO.HT and SO₂.HT area ratios of natural bio-related carbonates

The mineralogical and chemical variability of the natural bio-related carbonate samples considerably biased the statistical analysis leading to largely dispersed and significantly low and high CO.HT and SO₂.HT values (Fig. 7 and Table A.5). Natural bio-related carbonate samples primarily consist of three distinct types: (1) modern microbialites and an ancient stromatolite, (2) authigenic carbonates from active and ancient cold seeps and (3) modern hydrothermal chimneys from alkaline vents.
<figure><img src="image_4.png" /><figcaption>**Fig. 3.** Scanning electron microscopy images (secondary electrons) of (a) a microbialite sample from Salda lake (Turkey; \*Mg-\*Ca_N_SL; Shirokova et al., 2013), with hydromagnesite platelets (blue star) agglomerated by an exopolymer-like organic material (white arrows), (b) a laboratory bio-related Ca-carbonate sample precipitated by the bacterial strain S. pasteurii (\*Ca_L_Ca2), with a calcite grain (red star) covered with 1 µm-sized rod-shaped cells and extracellular polymeric substance (white arrows) secreted by bacteria, (c) a stromatolite sample from Grand Gandaillat quarry (Limagne basin, France; \*Ca_N_GG) in which hydrocarbons have accumulated, with calcite grains (red star) coated with organic material (white dotted circle) described as bitumen by Roche et al. (2018) and Vennin et al. (2021), and (d) a laboratory organo-carbonate sample precipitated with L-aspartic acid (Ca_L_Aspx), with a calcite grain (red star) embedded by a large quantity of condensed aspartic acid molecules (white dashed arrow). See Table A.1 for details on samples.</figcaption></figure>

Microbialite samples display the largest dispersion of their CO.HT and SO₂.HT values (IQR: 0.307 and 2.454, respectively). Those composed of hydrated Mg-carbonates have low values (down to 0.005 and 0.012, respectively) while those composed of Ca- and Ca/Mg-carbonates show higher values (up to 0.762 and 2.792, respectively).

Authigenic carbonate samples also display a large dispersion of their CO.HT and SO₂.HT values (IQR: 0.236 and 0.932, respectively), though smaller than that of stromatolite and microbialite samples. Those samples have some of the highest values (median: 0.386 and 0.487, respectively).

Hydrothermal chimney samples exhibit narrow dispersion of their CO.HT and SO₂.HT values (IQR: 0.016 and 0.055, respectively) and significantly low values (median: 0.030 and 0.095, respectively) compared to authigenic carbonates, as well as stromatolites and microbialites. These samples are all mineral mixtures with Ca-carbonates, some hydrated Mg-carbonates along with various amounts of brucite (20–90 wt%; Fig. 2). The large sample size of the hydrothermal chimneys subset (15 samples; Table A.1) significantly skews towards lower values the median area ratio values for the natural bio-related carbonate category and, as a result, most of the area ratio values for stromatolites/microbialites and authigenic carbonates samples are regarded as outliers.

## 4. Discussion

CO₂ emissions in Rock-Eval analyses arise significantly from the thermal decomposition of carbonate minerals into CO₂ and Ca-/Mg-oxides. Hydrated Mg-carbonates (e.g., hydromagnesite, nesquehonite, and dypingite) decompose at low temperatures (100 °C to 600 °C) (Suzuki and Ito, 1974; Sawada et al., 1978, 1979; Hales et al., 2008;

Hollingbery and Hull, 2012; Ren et al., 2014; Unluer and Al-Tabbaa, 2014; Jauffret et al., 2015; Glasser et al., 2016; Lin et al., 2018; Yamamoto et al., 2021; Baudin et al., 2023). In contrast, Ca- and Ca/Mg-carbonates (e.g., calcite, aragonite, vaterite, magnesian calcite and dolomite) decompose at higher temperatures (600 °C to 900 °C) (Stern and Weise, 1969; Rao, 1973; Rao and Mehrotra, 1979; McIntosh et al., 1990; L'vov, 1997, 2002; Galwey and Brown, 1999; Stalport et al., 2005, 2007; Rodriguez-Navarro et al., 2012; Olszak-Humienik and Jablonski, 2015; Blue and Dove, 2015; Dobrego et al., 2021; Ptáček et al., 2021; Perron et al., 2023; Baudin et al., 2023). Accordingly, only CO and SO₂ emissions will be discussed in greater detail in the 50–700 °C and 700–1100 °C temperature ranges.

### 4.1. Origin of CO and SO₂ emissions at low temperatures [50–700 °C]

Thermolabile organic compounds desorb in the 100–200 °C range, while others crack thermally between 200 and 650 °C (Leinweber and Schulten, 1999; Disnar et al., 2003; Mehrabanian, 2013; Derenne and Quéné, 2015; Picó and Barceló, 2020). Therefore, the IR CO and CO₂ signals and the UV SO₂ signal detected from 50 to 700 °C during Rock-Eval analysis under oxidative conditions (Fig. 1) should highlight, among others, the purified air combustion and thermal cracking of organic compounds in powdered carbonate samples. Note that, although sulfide thermal decomposition can be expected below 700 °C (Fig. 1), no sulfide minerals were detected using XRD (Fig. 2) and therefore made little or no contribution to the SO₂ signal detected. For Ca and Ca/Mg-carbonates, which remain intact in this temperature range (Fig. 1), the detected organics likely correspond to compounds present at carbonate grain surfaces, including remnants of microbial cells and EPS for natural and laboratory bio-related carbonates (Fig. 3a–b), organic materials like bitumen for carbonated reservoir rocks (Fig. 3c),
<figure><img src="image_5.png" /><figcaption>**Fig. 4.** Typical gas profiles detected by Rock-Eval (with CO, CO₂ and SO₂ signal in orange, blue and green, respectively) and obtained on (a) a natural abiotic Ca-carbonate sample (Ca_N_Cal3), (b) a natural bio-related Ca-carbonate sample (*Ca_N_DZ), (c) a laboratory bio-related Ca-carbonate sample (*Ca_L_Sr), (d) a laboratory organo- Ca-carbonate sample (Ca_L_Glu1), (e) a natural bio-related Ca-Mg carbonate sample (*Ca_Nmers), and (f) a laboratory bio-related Mg-carbonate sample (*Mg_L_S2). See Table A.1 for details on samples.</figcaption></figure>

and condensed organic molecules such as amino acids for laboratory
organo-carbonates (Fig. 3d), overall leading to high CO.LT, and to
a lesser extend SO₂.LT, values (Figs. 4b-c,e and 5 and Tables A.2
and A.3). Both reservoir rock samples with the highest CO.LT and
SO₂.LT values represent unique cases of Ca- and Ca/Mg-carbonates
with significant amounts of organic compounds trapped within the
rock porosity at the carbonate grain boundary (Figs. 3c and 5 and
Table A.3). SO₂ emissions suggest organo-sulfur compounds, common
in bitumen (Fig. 4b-c,e). Conversely, low CO.LT and SO₂.LT area ratios
of Ca and Ca/Mg-carbonates indicate minimal or no organic compounds
present at carbonate grain surfaces. This applies to most abiotic and
mixed-origin carbonate samples, as well as some natural bio-related
and organo-carbonate samples (Figs. 4a,d and 5 and Tables A.2 and
A.3).

As for Ca- and Ca/Mg-carbonates, low-temperature emissions of
CO and SO₂ observed for hydrated Mg-carbonates result from the
combustion and the thermal cracking of organic compounds. However,
distinguishing the CO₂ signal from the thermodesorption, purified air
combustion and thermal cracking of organic compounds from the one
resulting from the thermal decomposition of hydrated Mg-carbonates
is challenging in the 50-700 °C range. CO₂ emissions at low temper-
ature mainly result from decarbonation of hydrated Mg-carbonates
occurring between 350 °C and 500 °C (Fig. 4e-f), with occasionally
the neoformation of magnesite at 500 °C, which thermally decomposes
at 550-600 °C, as observed in Fig. 4f (Suzuki and Ito, 1974; Sawada
et al., 1978, 1979; Unluer and Al-Tabbaa, 2014; Jauffret et al., 2015;
Glasser et al., 2016; Lin et al., 2018; Yamamoto et al., 2021; Baudin
et al., 2023). Conversely, as hydrated Mg-carbonates do not release CO

and SO₂ from their thermal degradation, these gaseous emissions are
expected to result solely from the combustion and thermal cracking
of organic compounds. Samples with hydrated Mg-carbonates, such
as most laboratory bio-related Mg-carbonate samples, can exhibit CO
±SO₂ peaks correlating with the CO₂ ones: one below 400 °C (Fig. 4f),
likely resulting from the purified air combustion and thermal cracking
of surface organic compounds and another, sometimes intense, between
400-700 °C (Fig. 4e-f), possibly resulting from the purified air combus-
tion and thermal cracking of remaining surface organic compounds and
organic compounds trapped within hydrated Mg-carbonate grains. In
contrast, low CO.LT and SO₂.LT area ratios indicate, for hydrated Mg-
carbonates, no or only few organic compounds associated to carbonate
minerals, neither at their surfaces, nor trapped inside grains.

Among the analyzed natural bio-related carbonate samples, some
contain Ca-, Ca/Mg-, and hydrated Mg-carbonates, along with other
minerals like brucite, jamborite, and Iowaite (Fig. 2). In these cases,
deciphering the origin of the gaseous emissions resulting from our
modified Rock-Eval approach is made even more challenging by the
overlapping thermal decomposition temperatures of all these phases.
Brucite decomposes near 400 °C through dehydration (MacKenzie and
Meinhold, 1993; Bai and Koster Van Groos, 1998), while Iowaite un-
dergoes thermal decomposition through dehydration reactions between
50 °C and 350 °C followed by dehydration and dechlorination (and in
some cases decarbonation due to the replacement of Cl⁻ by CO₃²⁻ ions)
(Frost and Erickson, 2004; Bouzaid et al., 2007; Zhitova et al., 2020).
Jamborite fully decomposes between 300-350 °C (Morales, 2017).
The thermal decomposition of brucite releases only water molecules
(MacKenzie and Meinhold, 1993; Bai and Koster Van Groos, 1998),
<figure><img src="image_6.png" /><figcaption>**Fig. 5.** Boxplots derived from Rock-Eval analysis (see Section 2.4) in the low temperature range [50–700 °C], grouped by sample categories (see Section 2.1). Panels (a) and (c) show all data for CO.LT and SO₂.LT area ratios, respectively. Panels (b) and (d) are respectively magnified views of the dashed boxed area in (a) and (c), excluding outliers (circles) to provide a clearer view of the central tendency and distribution within the interquartile range (IQR, framed by boxes; Table A.3). Black lines are minimum and maximum area ratio values, endpoints of boxes are first (Q1) and third quartiles (Q3), green lines are median values. Sample subset shown in (b) and (d) derives from XRD analysis (see Section 3.1).</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>**Fig. 6.** Boxplots derived from Rock-Eval analysis (see Section 2.4) in the high temperature range [700–1000 °C], grouped by sample categories (see Section 2.1). Panels (a) and (c) show all data for CO.HT and SO₂.HT area ratios, respectively. Panels (b) and (d) are respectively magnified views of the dashed boxed area in (a) and (c), excluding outliers (circles) to provide a clearer view of the central tendency and distribution within the interquartile range (IQR, framed by boxes; Table A.4). Black lines are minimum and maximum area ratio values, endpoints of boxes are first (Q1) and third quartiles (Q3), green lines are median values. Sample subset shown in (b) and (d) derives from XRD analysis (see Section 3.1).</figcaption></figure>
<figure><img src="image_8.png" /><figcaption>Fig. 7. Boxplots derived from Rock-Eval analysis (see Section 2.4) in the high temperature range [700–1000 °C] for natural bio-related carbonate samples considered as a whole or subdivided into three categories according to their nature and origin. Panels (a) and (b) show CO.HT and SO₂.HT area ratios, respectively. Black lines are minimum and maximum area ratio values, endpoints of boxes are first (Q1) and third quartiles (Q3), boxes are interquartile ranges (IQR), green lines are median values and circles are outliers (Table A.5). Sample subset derives from XRD analysis (see Section 3.1).</figcaption></figure>

while Iowaite releases water, hydrogen chloride (and in some cases CO₂)(Frost and Erickson, 2004; Bouzaid et al., 2007; Zhitova et al., 2020), and jamborite likely releases water and SO₂ (Morales, 2017). Thus, CO₂ and SO₂ emitted by the thermal decomposition of these minerals below 700 °C add up to CO₂ and SO₂ emissions coming from the purified air combustion and thermal cracking of organic compounds present at the mineral grain surface and from organic compounds potentially trapped within each of these mineral phases (i.e., hydrated Mg-carbonates, brucite, Iowaite, jamborite). CO.LT and SO₂.LT area ratios of such samples (e.g., Fig. 4e) are generally high compared to other natural bio-related carbonate samples (Fig. 5b,d and Table A.3). However, these ratios are not easily comparable with those obtained for other carbonate-dominated samples. Their lower relative percentage of carbonates artificially decreases the amount of CO₂ released during Rock-Eval analysis, consequently increasing the associated CO.LT and SO₂.LT area ratios, which are normalized by the area of the CO₂ peak (see Section 2.4). Therefore, alternative methods should be developed to accurately compare samples entirely composed of Ca/Mg-carbonates with those combining hydrated Mg-carbonates and other mineral phases.

## 4.2. Origin of CO emissions at high temperatures [700–1000 °C]

CO₂ emissions detected from 700 to 1000 °C during dinitrogen pyrolysis (Fig. 4) result firstly from the thermal decomposition of Ca- and Ca/Mg carbonates. They may be related to CO emissions in the same temperature range due to the production of CO through Boudouard reactions (Lafargue et al., 1998; Behar et al., 2001; Baudin et al., 2015). High temperature Boudouard reactions under dinitrogen atmosphere produce two CO molecules, one with a carbon atom of organic origin and the other with a carbon atom of mineral origin (Eq. (5)).

$$CO_{2(g)} + C_{(s)} \rightarrow 2CO_{(g)} \quad (5)$$

The efficiency of this reaction highly depends on the analytical conditions, the nature of the thermally-degrading minerals and organic compounds, as well as the nature and amount of the solid carbon-rich residue produced from the thermal cracking of organic compounds at lower temperatures. It is therefore highly difficult to predict the amount of CO formed from Boudouard reactions according to samples.

CO.LT and SO₂.LT area ratios could allow to assess the quantity of solid carbon residue produced below 700 °C: a high CO.LT value may indicate a high amount of thermally-degraded organic compounds potentially leading to substantial solid carbon residue and hence, high CO production rates through Boudouard reactions. However, most samples associated with high CO.HT values exhibit low CO.LT ones (Table A.2), which do not appear to be linked to the quantity of organic compounds initially present in the sample, as illustrated by

organo-carbonate samples (e.g., Ca_L_Glu1). Their low CO.LT area ratios compared to other sample categories (Fig. 5b,d and Table A.3) suggest a limited production of solid carbon residue, i.e., no more than ~20 wt% of the initial organic content (Sharma et al., 2006), considering, moreover, that an oxidizing atmosphere would produce even less than an inert atmosphere. Consequently, even if Boudouard reactions occurred from solid carbon residue during our Rock-Eval analysis, these reactions alone cannot explain the variability in CO emissions observed for these samples above 700 °C (Table A.2).

High-temperature CO release may also result from the presence of organic compounds trapped within Ca- and Ca/Mg-carbonate grains during their formation (as e.g., dead microbial cells, EPS, degraded biological polymers, metabolites or abiotic organic compounds). Thermally cracked compounds only released when carbonate minerals are thermally decomposed could explain the synchronicity observed for CO₂ and CO emissions (e.g., Fig. 4d). For organo-carbonate samples showing correlated and significant CO₂ and CO emissions (Fig. 4d and Table A.2), this is highly plausible since these samples have precipitated in organic-rich solutions (Fig. 3d), hence favoring organic molecules entrapment during crystal growth. High CO.HT area ratios obtained for reservoir rock and natural bio-related samples, also support this hypothesis (Table A.2). Nevertheless, on the basis of CO emission alone, it is impossible to specify the nature and origin of the entrapped organic material and no distinction can therefore be made between bio- and organo-carbonates. Conversely, most of the mixed origin carbonate samples show low CO.HT area ratios, suggesting that no organic compounds were trapped within carbonate crystals during growth, in favor of precipitation in an organic-free environment and thus, of a potential abiotic origin (Fig. 6b and Table A.4).

## 4.3. Origin of SO₂ emissions at high temperatures [700–1000 °C]

SO₂.HT and CO.HT area ratios differ significantly in their behavior and distribution among samples (Fig. 6). Notably, the presence of multiple SO₂ peaks (Fig. 4) prompt a search for various SO₂ producing reactions and potential UV signal interferences.

### 4.3.1. Sulfate and sulfite neoformation

Rock-Eval analysis generally uses the UV signal at high temperatures to investigate the sulfur content of either rocks or kerogens and oils (e.g. Aboussou, 2018; Cohen-Sadon et al., 2022). Since, no sulfate, sulfite or sulfide minerals were detected using XRD in any of the studied samples (within the instrument's detection limit), only SO₂ emissions from the thermal cracking of trapped organic sulfur compounds are expected. However, thermal cracking of Ca- and/or Mg-carbonate samples associated with organic sulfur can lead to the neoformation of Ca and/or Mg-sulfates and -sulfites during Rock-Eval analysis (Espitalié et al., 2024). Two neoformation mechanisms have
been suggested, including direct sulfation (Eqs. (6) and (7)) or indirect sulfation (with CaO or MgO derived from the thermal decomposition of Ca- or Mg-carbonates) (Eqs. (8) and (9)) (Wang et al., 2009; Yan et al., 2015), both potentially leading here to the formation of Mg-sulfates and -sulfites from hydrated Mg-carbonates under oxidizing conditions below 700 °C. For Ca-carbonates, Ca-sulfates and -sulfites could form below 700 °C by direct sulfation under oxidizing conditions and only Ca-sulfates could form above 700 °C by indirect sulfation under dinitrogen atmosphere.

$$ (\text{Ca}-\text{Mg})\text{CO}_{3(\text{s})} + \text{SO}_{2(\text{g})} \rightarrow (\text{Ca}-\text{Mg})\text{SO}_{3(\text{s})} + \text{CO}_{2(\text{g})} \quad (6) $$

$$ (\text{Ca}-\text{Mg})\text{CO}_{3(\text{s})} + \text{SO}_{2(\text{g})} + \frac{1}{2}\text{O}_{2(\text{g})} \rightarrow (\text{Ca}-\text{Mg})\text{SO}_{4(\text{s})} + \text{CO}_{2(\text{g})} \quad (7) $$

$$ (\text{Ca}-\text{Mg})\text{O}_{4(\text{s})} + \text{SO}_{2(\text{g})} \rightarrow (\text{Ca}-\text{Mg})\text{SO}_{3(\text{s})} \quad (8) $$

$$ (\text{Ca}-\text{Mg})\text{O}_{4(\text{s})} + \text{SO}_{2(\text{g})} + \frac{1}{2}\text{O}_{2(\text{g})} \rightarrow (\text{Ca}-\text{Mg})\text{SO}_{4(\text{s})} \quad (9) $$

For both sulfation mechanisms, a release of SO₂ above 700 °C can be attributed to the thermal decomposition of these neoformed minerals. As shown in Fig. 1, Ca-sulfites and -sulfates thermally decompose above 600 °C and 1200 °C, respectively (Swift et al., 1976; Matsuzaki et al., 1978; Kuusik et al., 1985; Popescu et al., 1985; Han et al., 2022) and Mg-sulfites and -sulfates thermally decompose slightly above 600 °C and 1000 °C, respectively (Lau et al., 1977; Ishihara et al., 1992; Scheidema and Taskinen, 2011; Yan et al., 2014). However, neoformed sulfates/sulfites with low crystallinity or as amorphous phases would thermally decompose at lower temperatures (Ishihara et al., 1992).

### 4.3.2. UV interferences

The UV spectrophotometer used to detect SO₂ has a spectral range of 250–390 nm, allowing it to also detect nitrogen oxide, aromatic hydrocarbons (e.g., benzene C₆H₆, toluene C₆H₄CH₃; Khan et al., 2019), ketones, ozone and halogens. Conventional Rock-Eval analysis, which usually involves a air combustion step above 700 °C (Behar et al., 2001), theoretically prevents the formation and emission of most of these compounds at high temperatures, therefore ensuring that the UV detected signal corresponds solely to SO₂. Conversely, our modified Rock-Eval approach (Fig. 1) involved dinitrogen atmosphere above 700 °C, which prevents the combustion of organic compounds entrapped within carbonates and cracked at high temperatures (see Section 4.2). Cyclization and aromatization reactions are therefore expected to occur, promoting the formation of polycyclic aromatic hydrocarbons (PAHs) and ketones, which can contribute to the detected UV signal. Similarly, high-temperature dinitrogen pyrolysis of the solid carbon residue derived from the thermal cracking of organic compounds at low temperatures can also lead to the release of PAHs (McGrath et al., 2001, 2003; Sharma and Hajaligol, 2003; Zhou et al., 2014, 2016; Wang et al., 2017; Buss et al., 2016; Sekimoto et al., 2018). Specifically, xylene (C₈H₁₀), toluene, and styrene (C₈H₈) absorb radiation within the spectral range used by the Rock-Eval UV spectrophotometer and may interfere with the SO₂ signal (Vinci Technologies, personal communication).

### 4.3.3. UV signal interpretation in carbonates

Gas emission profiles of each carbonate sample reveal different patterns for the UV signal above 700 °C (Fig. 4). First, most samples entirely composed of Ca-carbonates were associated with a UV signal returning close to the baseline value observed at 700 °C. While some Ca-carbonate samples lacked a UV signal above 700 °C, others exhibited a UV signal that correlated with CO and CO₂ peaks (e.g., Fig. 4b–d). Because the CO peak likely indicates thermal cracking of organic compounds trapped within Ca-carbonates, this suggests that the UV signal may similarly correspond to sulfur-bearing organic compounds released in the form of reduced sulfur effluents (e.g. Aboussou, 2018; Cohen-Sadon et al., 2022; Xian et al., 2023) (oxidized to SO₂ in the oxidative

furnace, see Section 2.3) during the thermal decomposition of Ca-carbonates but also to PAH or ketone compounds (see Section 4.3.2). Few samples also showed significant UV signal at higher temperatures (i.e., 900–1000 °C; Fig. 4b–e). This UV signal, not correlated to CO and CO₂ peaks, may correspond to SO₂ resulting from the thermal decomposition of neoformed Ca-sulfates and -sulfites (see Section 4.3.1) and/or to aromatic hydrocarbons formed from the solid carbon residue (see Section 4.3.2). This significant SO₂ peak generates high SO₂-HT area ratios, especially for natural bio-related carbonate samples (Fig. 6c). Similarly, the slight increase in the UV signal towards the highest temperatures without joint CO and CO₂ emissions, as observed for hydrated Mg-carbonate samples (Fig. 4f), may correspond to PAHs since none of these minerals thermally decompose above 700 °C. Regarding hydrated Mg-carbonates, combined or not with other mineral phases, the UV signal does not return to the baseline value observed at 700 °C (Fig. 4e–f). The most extreme cases are laboratory bio-related Mg-carbonate samples with significant high UV signals below 700 °C that gradually decrease towards higher temperatures (Fig. 4f), overall resulting in high SO₂-HT values which appear aberrant compared to other samples because no gas emissions are expected above 700 °C. Since no tangible hypothesis can be proposed, this might suggest a potential experimental bias notably instrument clogging preventing complete evacuation of compounds derived from the analysis for these samples. A systematic study of the gas emission profiles, sample by sample, is required to better understand the distribution and significance of the obtained SO₂-HT values.

## 5. Conclusion and perspectives

The Rock-Eval analysis was adapted to be used in carbonate combustion and pyrolysis in the 50–700 °C and 700–1000 °C ranges, respectively, and studied associated CO, CO₂, SO₂ gas profiles as indicators of the presence of organic compounds associated with solid carbonates that may hold clues to their formation process. Results could in the future be used to characterize the origin of carbonates in terrestrial or extraterrestrial environments, by examining the gas profiles obtained using IR and UV spectroscopy, notably developed for in situ space instrumentation. However, we also demonstrated that the identification of organics trapped within carbonates is challenging for specific carbonate chemistry (e.g., Ca- vs. hydrated Mg-carbonates).

The decomposition temperature of these minerals, monitored via CO₂ emissions, plays a crucial role in interpreting results. For minerals that thermally decompose above 700 °C, such as Ca- and Ca/Mg-carbonates, SO₂.LT and CO.LT area ratios obtained below 700 °C indicate purified air combustion and thermal cracking of surface organic compounds, while CO.HT area ratio obtained above 700 °C primarily relate to the thermal cracking of organic compounds trapped within carbonate crystals. Identifying trapped organic compounds could help distinguish organic-rich carbonates, produced by organo- and bio-related mineralization, from organic-free carbonates resulting from chemical precipitation.

The use of SO₂.HT area ratio is more challenging: although it is mainly related to the thermal cracking of organic sulfur compounds, apparent SO₂ emissions can also relate to aromatic hydrocarbons derived from the pyrolysis of organic compounds released during the thermal decomposition of Ca-carbonates, of solid carbon residue, and from the thermal decomposition of neoformed sulfates/sulfites. These multiple reaction pathways complicate the interpretation of SO₂.HT ratios. For mineral phases that thermally decompose below 700 °C, such as hydrated Mg-carbonates or other mineral phases like brucite, Iowaite, and jamborite, CO.LT and SO₂.LT area ratios could indicate the purified air combustion and thermal cracking of either surface organic compounds or organic compounds trapped within these minerals. These area ratios alone cannot differentiate between these two origins.

In the context of the search for evidence of life in extraterrestrial environments, space instruments such as SAM and MOMA could adapt
a two-step thermal analysis procedure similar to our modified Rock-Eval approach. Below 700 °C, molecular fragments resulting from the thermal cracking of organic compounds present at the surface of carbonate grains can be distinguished from those detected above 700 °C, which result from the thermal cracking of organic compounds trapped within carbonates. By distinguishing bio-related carbonates and organo-carbonates from abiotic ones, this would aid in the detection of organics involved in carbonate formation possibly representing traces of past and present extraterrestrial life. Further investigations will be necessary to refine this two-step analytical procedure, particularly regarding the impact of Boudouard reactions on CO production, and the formation of aromatic compounds during analysis.

### CRediT authorship contribution statement

**A. Perron:** Writing – review & editing, Writing – original draft, Visualization, Software, Methodology, Investigation, Formal analysis, Conceptualization.
**B. Ménez:** Writing – review & editing, Writing – original draft, Visualization, Supervision, Resources, Project administration, Methodology, Funding acquisition, Data curation, Conceptualization.
**F. Baudin:** Writing – review & editing, Resources, Methodology, Investigation.
**F. Stalport:** Writing – review & editing, Writing – original draft, Visualization, Supervision, Resources, Project administration, Methodology, Investigation, Funding acquisition, Data curation, Conceptualization.

### 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

We would like to express our gratitude to S. Nowak (The X-rays facility, ITODYS-LISA, Université Paris Cité, Paris, France) for her technical assistance in XRD data analysis, as well as to S. Borensztajn (Scanning electron microscopy, plateforme d'analyze haute-résolution (PARI), IPGP, France) for SEM images. We are also grateful to N. Bouton and J. Ammouial (Rock-Eval division of Vinci Technologies, France) for the exchange of data and information concerning the Rock-Eval instrument. We gratefully thank E. Gérard, C. Pisapia and F. Moynier (IPGP, Université Paris Cité, Paris, France), K. Benzerara and E. Muller (IMPMC, Sorbonne Université, Paris, France), O. Pokrovsky (GET, Toulouse, France), C. Pierre, S. Gontharet, and J.-M. Rouchy (LOCEAN, Sorbonne Université, Paris, France), J. Cosmidis (Oxford University, UK), as well as the Galerie de Minéralogie (Sorbonne Université, Paris, France) for providing samples. We also gratefully thank Brad Sutter, Yoav Oved Rosenberg and one anonymous Reviewer for insightful review of the manuscript. Special thanks to Clara Caurant for creating the carbonate drawing for the graphical abstract. This study was funded by the DIM ACAV+ Région Île-de-France and supported by the IPGP multidisciplinary program PARI (Région Île-de-France SESAME grant No. 12015908), as well as the Canadian CIFAR funded project Earth4D. It contributes to the IdEx Université Paris Cité ANR-18-IDEX-0001.

## Appendix A. Supplementary data

Supplementary material related to this article can be found online at https://doi.org/10.1016/j.chemgeo.2025.122815.

### Data availability

All data used for this study are included in the manuscript and in the supplementary data. Raw data are available on reasonable request from the corresponding author.

### References

Aboussou, A., 2018. New Rock-Eval Method for Pyritic and Organic Sulphur Quantification: Application to Study Organic Matter Preservation in Jurassic Sediments (Ph.D. thesis). Sorbonne Université, URL: https://theses.hal.science/tel-02947050.

Amaral-Zettler, L., Artigas, L.F., Baross, J., Bharathi, L., Boetius, A., Chandramohan, D., Herndl, G., Kogure, K., Neal, P., Pedrós-Alió, C., Ramette, A., Schouten, S., Stal, L., Thessen, A., Leeuw, J.D., Sogin, M., 2010. A global census of marine microbes. In: McIntyre, A.D. (Ed.), Life in the World's Oceans: Diversity, Distribution and Abundance. Wiley-Blackwell, Oxford, UK, pp. 221–245. http://dx.doi.org/10.1002/9781444325508.ch12.

Andreani, M., Ménez, B., 2019. New perspectives on abiotic organic synthesis and processing during hydrothermal alteration of the oceanic lithosphere. Cambridge University Press, pp. 447–479. http://dx.doi.org/10.1017/9781108677950.015.

Baer, J.L., Rigby, J.K., 1978. Geology of the crystal geyser and environmental implications of its effluent, Grand County, Utah. In: Utah Geology, vol. 5, pp. 125–130, URL: http://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetail&id=PASCALGEODEBRGM7920409317.

Bai, T.B., Koster Van Groos, A.F., 1998. Phase relations in the system MgO-NaCl-H₂O: The dehydroxylation of brucite in the presence of NaCl-H₂O fluids. Am. Mineral. 83 (3–4), 205–212. http://dx.doi.org/10.2138/am-1998-3-402.

Baudin, F. (Ed.), 2023. The Rock-Eval Method: Principles and Application. Wiley-ISTE, London, UK, p. 336, URL: https://www.wiley.com/en-nl/The+Rock-Eval+Method%3A+Principles+and+Application-p-9781394256228.

Baudin, F., Bouton, N., Wattripont, A., Carrier, X., 2023. Carbonates thermal decomposition kinetics and their implications in using Rock-Eval® analysis for carbonates identification and quantification. Sci. Technol. Energy Transit. 78 (38), 13. http://dx.doi.org/10.2516/stet/2023038.

Baudin, F., Disnaï, J.R., Aboussou, A., Savignac, F., 2015. Guidelines for Rock-Eval analysis of recent marine sediments. Org. Geochem. 86, 71–80. http://dx.doi.org/10.1016/j.orggeochem.2015.06.009.

Baudin, F., Stetten, E., Schnyder, J., Charlier, K., Martinez, P., Dennielou, B., Droz, L., 2017. Origin and distribution of the organic matter in the distal lobe of the Congo deep-sea fan – A Rock-Eval survey. Deep-Sea Res. Part II: Top. Stud. Ocean. 142 (January), 75–90. http://dx.doi.org/10.1016/j.dsr2.2017.01.008.

Behar, F., Beaumont, V., De B. Penteado, H.L., 2001. Rock-Eval 6 technology: Performances and developments. Oil & Gas Sci. Technol. 56 (2), 111–134. http://dx.doi.org/10.2516/ogst:2001013.

Benzerara, K., Menguay, N., 2009. Looking for traces of life in minerals. Comptes Rendus Palevol 8 (7), 617–628. http://dx.doi.org/10.1016/j.crpv.2009.03.006.

Benzerara, K., Miot, J., Morin, G., Ona-Nguema, G., Skouri-Panet, F., Férard, C., 2011. Significance, mechanisms and environmental implications of microbial biomineralization. Comptes Rendus Geosci. 343 (2–3), 160–167. http://dx.doi.org/10.1016/j.carte.2010.09.002.

Blanc, J.J., Monteau, R., 1988. Le karst du massif des Calanques (Marseille - Cassis). Karstologia 11 (1), 17–24. http://dx.doi.org/10.3406/karst.1988.2186.

Blue, C.R., Dove, P.M., 2015. Chemical controls on the magnesium content of amorphous calcium carbonate. Geochim. Cosmochim. Acta 148, 23–33. http://dx.doi.org/10.1016/j.gca.2014.08.003.

Boussafir, M., Sifeddine, A., Jacob, J., Foudi, M., Cordeiro, R.C., Albuquerque, A.L., Abrao, J.J., Turcq, B., 2012. Petrographical and geochemical study of modern lacustrine sedimentary organic matter (Lagoa do Caçô, Maranão, Brazil): Relationship between early diagenesis, organic sedimentation and lacustrine filling. Org. Geochem. 47, 88–98. http://dx.doi.org/10.1016/j.orggeochem.2012.03.013.

Bouzaid, J., Frost, R., Martens, W., 2007. Thermal decomposition of the composite hydrotalcites of Iowaite and woodallite. J. Therm. Anal. Calorim. 89 (2), 511–519. http://dx.doi.org/10.1007/s10973-006-7562-x.

Boynton, W.V., Bailey, S.H., Hamara, D.K., Williams, M.S., Bode, R.C., Fitzgibbon, M.R., Ko, W., Ward, M.G., Sridhar, K.R., Blanchard, J.A., Lorenz, R.D., May, R.D., Paige, D.A., Pathare, A.V., Kring, D.A., Leshin, L.A., Ming, D.W., Zent, A.P., Golden, D.C., Kerry, K.E., Lauer Jr., H.V., Quinn, R.C., 2001. Thermal and evolved gas analyzer: Part of the Mars volatile and climate surveyor integrated payload. J. Geophys. Res.: Planets 106 (E8), 17683–17698. http://dx.doi.org/10.1029/1999JE001153.

Boynton, W.V., Ming, D.W., Kounaves, S.P., Young, S.M.M., Arvidson, R.E., Hecht, M.H., Hoffman, J., Niles, P.B., Hamara, D.K., Quinn, R.C., Smith, P.H., Sutter, B., Catling, D.C., Morris, R.V., 2009. Evidence for calcium carbonate at the Mars Phoenix landing site. Science 325 (5936), 61–64. http://dx.doi.org/10.1126/science.1172768.

Braissant, O., Cailleau, G., Dupraz, C., Verrecchia, E.P., 2003. Bacterially induced mineralization of calcium carbonate in terrestrial environments: The role of exopolysaccharides and amino acids. J. Sediment. Res. 73 (3), 485–490. http://dx.doi.org/10.1306/111302730485.

Burnside, N.M., 2010. U-Th dating of travertine on the Colorado Plateau: Implications for the leakage of geologically stored CO₂ (Ph.D. thesis). University of Glasgow, UK, URL: http://theses.gla.ac.uk/1988/.

Burton, A.S., Stern, J.C., Elsila, J.E., Glavin, D.P., Dworkin, J.P., 2012. Understanding prebiotic chemistry through the analysis of extraterrestrial amino acids and nucleobases in meteorites. Chem. Soc. Rev. 41, 5459–5472. http://dx.doi.org/10.1039/C2CS35109A.
Buss, W., Graham, M.C., MacKinnon, G., Mašek, O., 2016. Strategies for producing biochars with minimum PAH contamination. J. Anal. Appl. Pyrolysis 119, 24–30. http://dx.doi.org/10.1016/j.jaap.2016.04.001.

Cockell, C.S., Catling, D.C., Davis, W.L., Snook, K., Kepner, R.L., Lee, P., McKay, C.P., 2000. The ultraviolet environment of Mars: Biological implications past, present, and future. Icarus 146 (2), 343–359. http://dx.doi.org/10.1006/icar.2000.6393.

Cohen-Sadon, H., Amrani, A., Feinstein, S., Rosenberg, Y.O., 2022. A new empirical approach for rapid quantification of organic and pyritic sulfur in sedimentary rocks using the Rock-Eval 7S. Org. Geochem. 166 (August 2021), 104350. http://dx.doi.org/10.1016/j.orggeochem.2021.104350.

Copard, Y., Di-Giovanni, C., Martaud, T., Albéric, P., Olivier, J.E., 2006. Using Rock-Eval 6 pyrolysis for tracking fossil organic carbon in modern environments: Implications for the roles of erosion and weathering. Earth Surf. Process. Landf. 31 (2), 135–153. http://dx.doi.org/10.1002/esp.1319.

Cosmidis, J., Benzerara, K., 2014. Soft X-ray scanning transmission spectromicroscopy. In: DiMasi, E., Gower, L.B. (Eds.), Biomineralization Sourcebook, first ed. CRC Press, New York, USA, pp. 115–133. http://dx.doi.org/10.1201/b16621-11.

Dartnell, L.R., Desorgher, L., Ward, J.M., Coates, A.J., 2007. Modelling the surface and subsurface Martian radiation environment: Implications for astrophysics. Geophys. Res. Lett. 34 (2), L02207. http://dx.doi.org/10.1029/2006GL027494.

Davila, A.F., Fairén, A.G., Gago-Duport, L., Stoker, C., Amils, R., Bonaccorsi, R., Zavaleta, J., Lim, D., Schulze-Makuch, D., McKay, C.P., 2008. Subsurface formation of oxidants on Mars and implications for the preservation of organic biosignatures. Earth Planet. Sci. Lett. 272 (1–2), 456–463. http://dx.doi.org/10.1016/j.epsl.2008.05.015.

Défarge, C., Gautret, P., Reitner, J., Trichet, J., 2009. Defining organominerals: Comment on 'Defining biominerals and organominerals: Direct and indirect indicators of life' by Perry et al.. Sediment. Geol. 213 (3–4), 152–155. http://dx.doi.org/10.1016/j.sedgeo.2008.04.002.

Degen, T., Sadki, M., Bron, E., König, U., Nénert, G., 2014. The HighScore suite. Powder Diffr. 29 (S2), S13–S18. http://dx.doi.org/10.1017/S0885715614000840.

Derené, S., Quéné, K., 2015. Analytical pyrolysis as a tool to probe soil organic matter. J. Anal. Appl. Pyrolysis 111, 108–120. http://dx.doi.org/10.1016/j.jaap.2014.12.001.

Di-Giovanni, C., Disnar, J.R., Bichet, V., Campy, M., Guillet, B., 1998. Geochemical characterization of soil organic matter and variability of a postglacial detrital organic supply (Chaillexon Lake, France). Earth Surf. Process. Landf. 23 (12), 1057–1069. http://dx.doi.org/10.1002/(SICI)1096-9837(199812)23:12<1057::AID-ESP921>3.0.C0-2:H.

Disnar, J.R., Guillet, B., Keravis, D., Di-Giovanni, C., Sebag, D., 2003. Soil organic matter (SOM) characterization by Rock-Eval pyrolysis: Scope and limitations. Org. Geochem. 34 (3), 327–343. http://dx.doi.org/10.1016/S0146-6380(02)00239-5.

Dobrego, K.V., Koznacheev, I.A., Shmelev, E.S., Mal'ko, M.V., Vasilevich, S.V., 2021. Macrokinetic models of thermal decomposition of dolomite for engineering calculations. J. Eng. Phys. Thermophys. 94 (4), 899–909. http://dx.doi.org/10.1007/s10891-021-02366-x.

Dupraz, S., Ménez, B., Gouze, P., Leprovost, R., Bénézeth, P., Pokrovsky, O.S., Guyot, F., 2009a. Experimental approach of CO₂ biomineralization in deep saline aquifers. Chem. Geol. 265 (1–2), 54–62. http://dx.doi.org/10.1016/j.chemgeo.2008.12.012.

Dupraz, S., Parmentier, M., Ménez, B., Guyot, F., 2009b. Experimental and numerical modeling of bacterially induced pH increase and calcite precipitation in saline aquifers. Chem. Geol. 265 (1–2), 44–53. http://dx.doi.org/10.1016/j.chemgeo.2009.05.003, arXiv:arXiv:1011.1669v3.

Dupraz, C., Reid, R.P., Braissant, O., Decho, A.W., Norman, R.S., Visscher, P.T., 2009. Processes of carbonate precipitation in modern microbial mats. Earth-Sci. Rev. 96 (3), 141–162. http://dx.doi.org/10.1016/j.earscirev.2008.10.005.

Dupraz, C., Reid, R.P., Visscher, P.T., 2011. Microbialites, modern. In: Reitner, J., Thiel, V. (Eds.), Encyclopedia of Geobiology. In: Encyclopedia of Earth Sciences Series, Springer, Cham, Switzerland, pp. 617–635. http://dx.doi.org/10.1007/978-1-4020-9212-1_195.

Espitalié, J., Lamoureux-Var, V., Bouton, N., 2024. Characterization of sulfur compounds. In: Baudin, F. (Ed.), The Rock-Eval Method: Principles and Application. Wiley-ISTE, London, UK, pp. 125–152. http://dx.doi.org/10.5192/ISTE.9153.ch8.

Espitalié, J., Laporte, J.L., Madec, M., Marquis, F., Leplat, P., Paulet, J., Boutefeu, A., 1977. Méthode rapide de caractérisation des roches mères, de leur potentiel pétrolier et de leur degré d'évolution. Rev. de l' Inst. Français Du Pétrole 32 (1), 23–42. http://dx.doi.org/10.2516/ogst:1977002.

Ferris, F., Phoenix, V., Fujita, Y., Smith, R., 2004. Kinetics of calcite precipitation induced by ureolytic bacteria at 10 to 20°C in artificial groundwater. Geochim. Cosmochim. Acta 68 (8), 1701–1710. http://dx.doi.org/10.1016/S0016-7037(03)00503-9.

Frost, R.L., Erickson, K.L., 2004. Thermal decomposition of natural Iowaite. J. Therm. Anal. Calorim. 78 (2), 367–373. http://dx.doi.org/10.1023/B:JTN.0000046103.00586.61.

Galwey, A.K., Brown, M.E., 1999. Decomposition of carbonates. In: Galwey, A.K., Brown, M.E. (Eds.), Thermal Decomposition of Ionic Solids. In: Studies in Physical and Theoretical Chemistry, vol. 86, Elsevier, Amsterdam, The Netherlands, pp. 345–364. http://dx.doi.org/10.1016/S0167-6881(99)80014-7.

Garcia, A., Yan, Y., Meinert, C., Schmitt-Kopplin, P., Vinogradoff, V., Viennet, J.C., Remusat, L., Bernard, S., Righezza, M., Le Sergeant d'Hendecourt, L., et al., 2024. Molecular diversity and amino acid evolution in simulated carbonaceous chondrite parent bodies. ACS Earth Space Chem. 8 (3), 606–615. http://dx.doi.org/10.1021/acsearthspacechem.3c00366.

Gérard, E., De Goeyse, S.D., Hugoni, M., Agogué, H., Richard, L., Milesi, V., Guyot, F., Lecourt, L., Borensztajn, S., Joseph, M.B., Leclerc, T., Sarazin, G., Jézéquel, D., Leboulanger, C., Ader, M., 2018. Key role of alphaproteobacteria and cyanobacteria in the formation of stromatolites of Lake Dziani Dzaha (Mayotte, Western Indian Ocean). Front. Microbiol. 9 (796), 796. http://dx.doi.org/10.3389/fmicb.2018.00796.

Gérard, E., Ménez, B., Couradeau, E., Moreira, D., Benzerara, K., Tavera, R., López-García, P., 2013. Specific carbonate-microbe interactions in the modern microbialites of Lake Alchichica (Mexico). ISME J. 7 (10), 1997–2009. http://dx.doi.org/10.1038/ismej.2013.81.

Glasser, F.P., Jauffret, G., Morrison, J., Galvez-Martos, J.L., Patterson, N., Imbabi, M.S.E., 2016. Sequestering CO₂ by mineralization into useful nesquehonite-based products. Front. Energy Res. 4, 3. http://dx.doi.org/10.3389/fenrg.2016.00003.

Goesmann, F., Brinckerhoff, W.B., Raulin, F., Goetz, W., Danell, R.M., Getty, S.A., Siljeström, S., Mißbach, H., Steininger, H., Arevalo, R.D., Buch, A., Freissinet, C., Grubisic, A., Meierhenrich, U.J., Pinnick, V.T., Stalport, F., Szopa, C., Vago, J.L., Lindner, R., Schulte, M.D., Brucato, J.R., Glavin, D.P., Grand, N., Li, X., van Amerom, F.H.W., the MOMA Science Team, 2017. The Mars Organic Molecule Analyzer (MOMA) instrument: Characterization of organic material in martian sediments. Astrobiology 17 (6–7), 655–685. http://dx.doi.org/10.1089/ast.2016.1551.

Gontharet, S., Pierre, C., Blanc-Valleron, M.M., Rouchy, J.M., Fouquet, Y., Bayon, G., Foucher, J.P., Woodside, J., Mascle, J., 2007. Nature and origin of diagenetic carbonate crusts and concretions from mud volcanoes and pockmarks of the Nile deep-sea fan (eastern Mediterranean Sea). Deep Sea Res. Part II: Top. Stud. Ocean. 54 (11–13), 1292–1311. http://dx.doi.org/10.1016/j.dsr2.2007.04.007.

Hales, M.C., Frost, R.L., Martens, W.N., 2008. Thermo-Raman spectroscopy of synthetic nesquehonite—implication for the geosequestration of greenhouse gases. J. Raman Spectrosc. 39 (9), 1141–1149. http://dx.doi.org/10.1002/jrs, arXiv:arXiv:1011.1669v3.

Han, Y.Q., Yang, R.M., Dong, Y., Tong, H.L., 2022. Experimental study of the pyrolysis path of CaSO₃·1/2H₂O. J. Therm. Anal. Calorim. 147 (22), 12431–12436. http://dx.doi.org/10.1007/s10973-022-11477-3.

Hare, A.A., Kuzyk, Z.Z.A., Macdonald, R.W., Sanei, H., Barber, D., Stern, G.A., Wang, F., 2014. Characterization of sedimentary organic matter in recent marine sediments from Hudson Bay, Canada, by Rock-Eval pyrolysis. Org. Geochem. 68, 52–60. http://dx.doi.org/10.1016/j.orggeochem.2014.01.007.

Hazera, J., Sebag, D., Kowalewski, I., Verrecchia, E., Ravelojaona, H., Chevallier, T., 2023. Adjustments to the Rock-Eval® thermal analysis for soil organic and inorganic carbon quantification. Biogeosciences 20 (24), 5229–5242. http://dx.doi.org/10.5194/bg-20-5229-2023.

Hecht, M.H., Kounaves, S.P., Quinn, R.C., West, S.J., Young, S.M.M., Ming, D.W., Catling, D.C., Clark, B.C., Boynton, W.V., Hoffman, J., DeFlores, L.P., Gospodinova, K., Kapit, J., Smith, P.H., 2009. Detection of perchlorate and the soluble chemistry of Martian soil at the Phoenix lander site. Science 325 (5936), 64–67. http://dx.doi.org/10.1126/science.1172466.

Hetényi, M., Nyilas, T., 2014. Soil organic matter characterization using S3 and S4 signals from Rock-Eval pyrolysis. Pedosphere 24 (5), 563–574. http://dx.doi.org/10.1016/S1002-0160(14)60042-4.

Hoffmann, T.D., Reeksting, B.J., Gebhard, S., 2021. Bacteria-induced mineral precipitation: A mechanistic review. Microbiology 167 (4), 001049. http://dx.doi.org/10.1099/mic.001049.

Hollingbery, L.A., Hull, T.R., 2012. The thermal decomposition of natural mixtures of huntite and hydromagnesite. Thermochim. Acta 528, 45–52. http://dx.doi.org/10.1016/j.tca.2011.11.002.

Ishihara, M., Matsui, H., Hashizume, G., 1992. Thermal behaviour and S-O bonding state of alkaline-earth metal sulfites. J. Therm. Anal. 38 (8), 1801–1815. http://dx.doi.org/10.1007/bf01974675.

Jarwar, M.A., Dumontet, S., Pasquale, V., Chen, C., 2022. Microbial induced carbonate precipitation: Environments, applications, and mechanisms. Geomicrobiol. J. 39 (10), 833–851. http://dx.doi.org/10.1080/01490451.2022.2097343.

Jauffret, G., Morrison, J., Glasser, F.P., 2015. On the thermal decomposition of nesquehonite. J. Therm. Anal. Calorim. 122 (2), 601–609. http://dx.doi.org/10.1007/s10973-015-4756-0.

Javaux, E.J., 2019. Challenges in evidencing the earliest traces of life. Nature 572 (7770), 451–460. http://dx.doi.org/10.1038/s41586-019-1436-4.

Kele, S., Bódai, B., 2022. Age, depositional environment, and geochemistry of freshwater carbonates (travertine, tufa) from Hungary. In: Veress, M., Leél-Őssy, S. (Eds.), Cave and Karst Systems of Hungary. In: Cave and Karst Systems of the World (CAKASYWO), Springer, Cham, Switzerland, pp. 513–533. http://dx.doi.org/10.1007/978-3-030-92960-2_18.

Khan, S., Newport, D., Le Calvé, S., 2019. Gas detection using portable deep-UV absorption spectrophotometry: A review. Sensors 19 (23), 5210. http://dx.doi.org/10.3390/s19235210.
Knoll, A.H., Bergmann, K.D., Strauss, J.V., 2016. Life: The first two billion years. Philos. Trans. R. Soc. B 371 (1707), 20150493. http://dx.doi.org/10.1098/rstb.2015.0493.

Kuusik, R., Salkkonen, P., Niinistö, L., 1985. Thermal decomposition of calcium sulphate in carbon monoxide. J. Therm. Anal. 30 (1), 187–193. http://dx.doi.org/10.1007/BF02128129.

Lafargue, E., Marquis, F., Pillot, D., 1998. Rock-Eval 6 applications in hydrocarbon exploration, production, and soil contamination studies. Rev. de L' Inst. Français Du Pétrole 53 (4), 421–437. http://dx.doi.org/10.2516/ogst:1998036.

Lasne, J., Noblet, A., Szopa, C., Navarro-González, R., Cabane, M., Poch, O., Stalport, F., François, P., Atreya, S.K., Coll, P., 2016. Oxidants at the surface of Mars: A review in light of recent exploration results. Astrobiology 16 (12), 977–996. http://dx.doi.org/10.1089/ast.2016.1502.

Lau, K.H., Cubiciotti, D., Hildenbrand, D.L., 1977. Effusion studies of the thermal decomposition of magnesium and calcium sulfates. J. Chem. Phys. 66 (10), 4532–4539. http://dx.doi.org/10.1063/1.433707.

Lecoeuvre, A., Ménez, B., Cannat, M., Chavagnac, V., Gérard, E., 2021. Microbial ecology of the newly discovered serpentine-hosted Old City hydrothermal field (southwest Indian ridge). ISME J. 15 (3), 818–832. http://dx.doi.org/10.1038/s41396-020-00816-7.

Leinweber, P., Schulten, H.R., 1999. Advances in analytical pyrolysis of soil organic matter. J. Anal. Appl. Pyrolysis 49 (1), 359–383. http://dx.doi.org/10.1016/S0165-2370(98)00082-5.

Lepland, A., McLoughlin, N., Melezhik, V.A., Brasier, A.T., Medvedev, P.V., Javaux, E.J., Lepot, K., van Zuilen, M., Furnes, H., Hanski, E.J., Staudigel, H., Summons, R.E., Illing, C.J., Strauss, H., 2013. Traces of life. In: Melezhik, V.A., Prave, A.R., Hanski, E.J., Fallick, A.E., Lepland, A., Kump, L.R., Strauss, H. (Eds.), Reading the Archive of Earth's Oxygenation. In: Global Events and the Fennoscandian Arctic Russia - Drilling Early Earth Project, vol. 3, Springer, Berlin Heidelberg, Germany, pp. 1297–1405. http://dx.doi.org/10.1007/978-3-642-29670-3_8.

Lepot, K., Benzerara, K., Brown, G.E., Philippot, P., 2008. Microbially influenced formation of 2,724-million-year-old stromatolites. Nat. Geosci. 1 (2), 118–121. http://dx.doi.org/10.1038/ngeo107.

Lin, Y., Zheng, M., Ye, C., Power, I.M., 2018. Thermogravimetric analysis-mass spectrometry (TGA-MS) of hydromagnesite from Dujiali Lake in Tibet, China. J. Therm. Anal. Calorim. 133 (3), 1429–1437. http://dx.doi.org/10.1007/s10973-018-7197-8.

Lutterotti, L., Matthies, S., Wenk, H.R., 1999. MAUD: A friendly java program for material analysis using diffraction. Newsl. Comm. Powder Diffr. 21, 14–15, URL: https://api semanticscholar.org/CorpusID:136186256.

L'vov, B.V., 1997. Mechanism of thermal decomposition of alkaline-earth carbonates. Thermochim. Acta 303 (2), 161–170. http://dx.doi.org/10.1016/S0040-6031(97)00261-X.

L'vov, B.V., 2002. Mechanism and kinetics of thermal decomposition of carbonates. Thermochim. Acta 386 (1), 1–16. http://dx.doi.org/10.1016/S0040-6031(01)00757-2.

MacKenzie, K.J., Meinhold, R.H., 1993. Thermal decomposition of brucite, Mg(OH)₂; a ²⁵Mg MAS NMR study. Thermochim. Acta 230 (C), 339–343. http://dx.doi.org/10.1016/0040-6031(93)80371-G.

Madigan, M.T., Bender, K.S., Buckley, D.H., Sattley, W.M., Stahl, D.A., Brock, T.D. (Eds.), 2019. Brock Biology of Microorganisms, fifteenth ed. Pearson Education limited, New York, Harlow (UK), URL: https://elibrary.pearson.de/book/99.150005/9781292405063.

Mahaffy, P.R., Webster, C.R., Cabane, M., Conrad, P.G., Coll, P., Atreya, S.K., Arvey, R., Barciniak, M., Benna, M., Bleacher, L., Brinckerhoff, W.B., Eigenbrode, J.L., Carignan, D., Cascia, M., Chalmers, R.A., Dworkin, J.P., Errigo, T., Everson, P., Franz, H., Farley, R., Feng, S., Frazier, G., Freissinet, C., Glavin, D.P., Harpold, D.N., Hawk, D., Holmes, V., Johnson, C.S., Jones, A., Jordan, P., Kellogg, J., Lewis, J., Lyness, E., Malespin, C.A., Martin, D.K., Maurer, J., McAdam, A.C., McLennan, D., Nolan, T.J., Noriega, M., Pavlov, A.A., Prats, B., Raaen, E., Sheinman, O., Sheppard, D., Smith, J., Stern, J.C., Tan, F., Trainer, M., Ming, D.W., Morris, R.V., Jones, J., Gundersen, C., Steele, A., Wray, J., Botta, O., Leshin, L.A., Owen, T., Battel, S., Jakosky, B.M., Manning, H., Squyres, S., Navarro-González, R., McKay, C.P., Raulin, F., Sternberg, R., Buch, A., Sorensen, P., Kline-Schoder, R., Coscia, D., Szopa, C., Teinturier, S., Baffes, C., Feldman, J., Flesch, G., Forouhar, S., Garcia, R., Keymeulen, D., Woodward, S., Block, B.P., Arnett, K., Miller, R., Edmonson, C., Gorevan, S., Mumm, E., 2012. The Sample Analysis at Mars investigation and instrument suite. Space Sci. Rev. 170 (1–4), 401–478. http://dx.doi.org/10.1007/s11214-012-9879-z.

Matsuzaki, R., Masumizu, H., Murakami, N., Saeki, Y., 1978. The thermal decomposition process of calcium sulfite. Bull. Chem. Soc. Japan 51 (1), 121–122. http://dx.doi.org/10.1246/bcsj.51.121.

Mavromatis, V., Bundeleva, I.A., Shirokova, L.S., Millo, C., Pokrovsky, O.S., Bénézeth, P., Ader, M., Oelkers, E.H., 2015. The continuous re-equilibration of carbon isotope compositions of hydrous Mg carbonates in the presence of cyanobacteria. Chem. Geol. 404, 41–51. http://dx.doi.org/10.1016/j.chemgeo.2015.03.016.

McGrath, T.E., Chan, W.G., Hajajigol, R., 2003. Low temperature mechanism for the formation of polycyclic aromatic hydrocarbons from the pyrolysis of cellulose. J. Anal. Appl. Pyrolysis 66, 51–70. http://dx.doi.org/10.1016/S0165-2370(02)00105-5.

McGrath, T.E., Sharma, R., Hajajigol, M., 2001. An experimental investigation into the formation of polycyclic-aromatic hydrocarbons (PAH) from pyrolysis of biomass materials. Fuel 80 (12), 1787–1797. http://dx.doi.org/10.1016/S0016-2361(01)00062-X.

McIntosh, R.M., Sharp, J.H., Wilburn, F.W., 1990. The thermal decomposition of dolomite. Thermochim. Acta 165 (2), 281–296. http://dx.doi.org/10.1016/0040-6031(90)80228-Q.

Mehrabanian, M., 2013. Molecular geochemistry of soil organic matter by pyrolysis gas chromatography/mass spectrometry (GC/MS) technique: A review. J. Soil Sci. Environ. Manag. 4 (2), 11–16. http://dx.doi.org/10.5897/jsem12.033.

Meinert, C., Myrgorodská, I., De Marcellus, P., Buhse, T., Nahon, L., Hoffmann, S.V., d'Hendecourt, L.L.S., Meierhenrich, U.J., 2016. Ribose and related sugars from ultraviolet irradiation of interstellar ice analogs. Science 352 (6282), 208–212. http://dx.doi.org/10.1126/science.aad8137.

Ménez, B., Pisapia, C., Andreani, M., Jamme, F., Vanbellingen, Q.P., Brunelle, A., Richard, L., Dumas, P., Réfrégiers, M., 2018. Abiotic synthesis of amino acids in the recesses of the oceanic lithosphere. Nature 564 (7734), 59–63. http://dx.doi.org/10.1038/s41586-018-0684-z.

Mlewski, E.C., Pisapia, C., Gomez, F., Lecourt, L., Rueda, E.S., Benzerara, K., Ménez, B., Borenztajn, S., Jamme, F., Réfrégiers, M., Gérard, E., 2018. Characterization of pustular mats and related *Rivularia*-rich laminations in oncoids from the Laguna Negra lake (Argentina). Front. Microbiol. 9, 996. http://dx.doi.org/10.3389/fmicb.2018.00996.

Morales, B.M., 2017. Effect of preparation method on catalytic activity of Ni/ γ-Al₂O₃ catalysts. Ingeniería 27 (1), 21–38. http://dx.doi.org/10.15517/jte.v27i1.23189.

NIST Inorganic Crystal Structure Database, NIST Standard Reference Database Number 3, National Institute of Standards and Technology, Gaithersburg MD, 20899, DOI: https://doi.org/10.18434/M32147, (retrieved [June 26, 2023]).

Oba, Y., Takano, Y., Naraoka, H., Watanabe, N., Kouchi, A., 2019. Nucleobase synthesis in interstellarices. Nat. Commun. 10 (1), 4413. http://dx.doi.org/10.1038/s41467-019-12404-1.

Olszak-Humienik, M., Jablonski, M., 2015. Thermal behavior of natural dolomite. J. Therm. Anal. Calorim. 119 (3), 2239–2248. http://dx.doi.org/10.1007/s10973-014-4301-6.

Patel, M.R., Zarnnecki, J.C., Catling, D.C., 2002. Ultraviolet radiation on the surface of Mars and the Beagle 2 UV sensor. Planet. Space Sci. 50 (9), 915–927. http://dx.doi.org/10.1016/S0032-0633(02)00067-3.

Perron, A., Stalport, F., Dupraz, S., Person, A., Coll, P., Szopa, C., Navarro-González, R., Glavin, D., Vaulay, M.J., Ménez, B., 2023. Thermal stability of (bio)carbonates: A potential signature for detecting life on Mars? Astrobiology 23 (4), 359–371. http://dx.doi.org/10.1089/ast.2021.0202.

Perry, R.S., McLoughlin, N., Lynne, B.Y., Sephton, M.A., Oliver, J.D., Perry, C.C., Campbell, K., Engel, M.H., Farmer, J.D., Brasier, M.D., Staley, J.T., 2007. Defining biominerals and organominerals: Direct and indirect indicators of life. Sediment. Geol. 201 (1–2), 157–179. http://dx.doi.org/10.1016/j.sedgeo.2007.05.014.

Picó, Y., Barceló, D., 2020. Pyrolysis gas chromatography-mass spectrometry in environmental analysis: Focus on organic matter and microplastics. TRAC Trends Anal. Chem. 130, 115964. http://dx.doi.org/10.1016/j.trac.2020.115964.

Pierre, C., Blanc-Valleron, M.M., Demange, J., Boudouma, O., Foucher, J.P., Pape, T., Himmler, T., Fekete, N., Spiess, V., 2012. Authigenic carbonates from active methane seeps offshore southwest Africa. Geo-Mar. Lett. 32 (5–6), 501–513. http://dx.doi.org/10.1007/s00367-012-0295-x.

Pierre, C., Rouchy, J.M., 2004. Isotopic compositions of diagenetic dolomites in the Tortonian marls of the western Mediterranean margins: Evidence of past gas hydrate formation and dissociation. Chem. Geol. 205 (3–4), 469–484. http://dx.doi.org/10.1016/j.chemgeo.2003.12.026.

Pierre, C., Rouchy, J.M., Blanc-Valleron, M.M., Pelletier, L., Lang, S.Q., Pelletier, B., Payri, C.E., Monnin, C., Guaotas, L., Postec, A., Quéméneur, M., Erauso, G., Ménez, B., 2017. Mineralizing filamentous bacteria from the Prony bay hydrothermal field give new insights into the functioning of serpentinization-based subseafloor ecosystems. Front. Microbiol. 8, 57. http://dx.doi.org/10.3389/fmicb.2017.00057.

Pierre, C., Rouchy, J.M., Blanc-Valleron, M.M., 2002. Gas hydrate dissociation in the Lora Basin (SE Spain) during the Mediterranean Messinian salinity crisis. Sediment. Geol. 147 (3–4), 247–252. http://dx.doi.org/10.1016/S0037-0738(01)00232-9.

Pierre, C., Rouchy, J.M., Blanc-Valleron, M.M., Etoubleau, J., Fouquet, Y., 2015. Methanogenesis and clay minerals diagenesis during the formation of dolomite nodules from the Tortonian marls of southern Spain. Mar. Pet. Geol. 66, 606–615. http://dx.doi.org/10.1016/j.marpetgeo.2015.04.017.

Pisapia, C., Gérard, E., Gérard, M., Lecourt, L., Lang, S.Q., Pelletier, B., Payri, C.E., Monnin, C., Guaotas, L., Postec, A., Quéméneur, M., Erauso, G., Ménez, B., 2017. Mineralizing filamentous bacteria from the Prony bay hydrothermal field give new insights into the functioning of serpentinization-based subseafloor ecosystems. Front. Microbiol. 8, 57. http://dx.doi.org/10.3389/fmicb.2017.00057.

Poch, O., Kaci, S., Stalport, F., Szopa, C., Coll, P., 2014. Laboratory insights into the chemical and kinetic evolution of several organic molecules under simulated Mars surface UV radiation conditions. Icarus 242, 50–63. http://dx.doi.org/10.1016/j.icarus.2014.07.014.

Poch, O., Noblet, A., Stalport, F., Correia, J.J., Grand, N., Szopa, C., Coll, P., 2013. Chemical evolution of organic molecules under Mars-like UV radiation conditions simulated in the laboratory with the “Mars organic molecule irradiation and evolution” (MOMIE) setup. Planet. Space Sci. 85, 188–197. http://dx.doi.org/10.1016/j.pss.2013.06.013.

Poot, A., Quik, J.T., Veld, H., Koelmans, A.A., 2009. Quantification methods of black carbon: Comparison of Rock-Eval analysis with traditional methods. J. Chromatogr. A 1216 (3), 613–622. http://dx.doi.org/10.1016/j.chroma.2008.08.011.
Popescu, M., Simion, A., Matei, V., 1985. Study of thermal behaviour up to 1550°C of materials containing calcium sulphate. J. Therm. Anal. 30 (2), 297-303. http://dx.doi.org/10.1007/BF02156495.

Ptáček, P., Šoukal, F., Opravil, T., 2021. Thermal decomposition of ferroan dolomite: A comparative study in nitrogen, carbon dioxide, air and oxygen. Solid State Sci. 122 (November), 106778. http://dx.doi.org/10.1016/j.solidstatesciences.2021.106778.

Rao, M.S., 1973. Kinetics and mechanism of the transformation of vaterite to calcite. Bull. Chem. Soc. Japan 46 (5), 1414-1417. http://dx.doi.org/10.1246/bcsj.46.1414.

Rao, C.R.M., Mehrotra, P.N., 1979. DTA studies on the effect of impurities on the phase transformations of barium carbonate. J. Therm. Anal. 17 (2), 539-542. http://dx.doi.org/10.1007/BF01914043.

Reid, R.P., Dupraz, C., Visscher, P.T., 2003. Microbial processes forming marine stromatolites. In: Krumbein, W.E., Paterson, D.M., Zavarzin, G.A. (Eds.), Fossil and Recent Biofilms, A Natural History of Life on Earth. Springer, Berlin Heidelberg, Germany, pp. 103-118. http://dx.doi.org/10.1007/978-94-017-0193-8.

Ren, H., Chen, Z., Wu, Y., Yang, M., Chen, J., Hu, H., Liu, J., 2014. Thermal characterization and kinetic analysis of nesquehonite, hydromagnesite, and brucite, using TG-DTG and DSC techniques. J. Therm. Anal. Calorim. 115 (2), 1949-1960. http://dx.doi.org/10.1007/s10973-013-3372-0.

Roche, A., Vennin, E., Bouton, A., Olivier, N., Wattinne, A., Bundeleva, I., Decon-ick, J.F., Virgone, A., Gaucher, E.C., Visscher, P.T., 2018. Oligo-Miocene lacustrine microbial and metazoan builds from the Limagne Basin (French Massif Central). Palaeogeogr. Palaeoclimatol. Palaeoecol. 504 (January), 34-59. http://dx.doi.org/10.1016/j.palaeo.2018.05.001.

Rodriguez-Navarro, C., Kudlacz, K., Ruiz-Agudo, E., 2012. The mechanism of thermal decomposition of dolomite: New insights from 2D-XRD and TEM analyses. Am. Mineral. 97 (1), 38-51. http://dx.doi.org/10.2138/am.2011.3813.

Sawada, Y., Uematsu, K., Mizutani, N., Kato, M., 1978. Thermal decomposition of hydromagnesite 4MgCO₃·Mg(OH)₂·4H₂O. J. Inorg. Nucl. Chem. 40 (6), 979-982. http://dx.doi.org/10.1016/0022-1902(78)80492-8.

Sawada, Y., Yamaguchi, J., Sakurai, O., Uematsu, K., Mizutani, N., Kato, M., 1979. Thermal decomposition of basic magnesium carbonates under high-pressure gas atmospheres. Thermochim. Acta 32 (1-2), 277-291. http://dx.doi.org/10.1016/0040-6031(79)85115-1.

Scheidema, M.N., Taskinen, P., 2011. Decomposition thermodynamics of magnesium sulfate. Ind. Eng. Chem. Res. 50 (16), 9550-9556. http://dx.doi.org/10.1021/ie102554f.

Sebag, D., Disnar, J.R., Guillet, B., Di Giovanni, C., Verrecchia, E.P., Durand, A., 2006. Monitoring organic matter dynamics in soil profiles by 'Rock-Eval pyrolysis': Bulk characterization and quantification of degradation. Eur. J. Soil Sci. 57 (3), 344-355. http://dx.doi.org/10.1111/j.1365-2389.2005.00745.x.

Sekimoto, K., Koss, A.R., Gilman, J.B., Selimovic, V., Coggon, M.M., Zarzana, K.J., Yuan, B., Lerner, B.M., Brown, S.S., Warneke, C., Yokelson, R.J., Roberts, J.M., De Gouw, J., 2018. High-and low-temperature pyrolysis profiles describe volatile organic compound emissions from western US wildfire fuels. Atmospheric Chem. Phys. 18 (13), 9263-9281. http://dx.doi.org/10.5194/acp-18-9263-2018.

Sharma, R.K., Chan, W.G., Hajaligol, M.R., 2006. Product compositions from pyrolysis of some aliphatic α-amino acids. J. Anal. Appl. Pyrolysis 75 (2), 69-81. http://dx.doi.org/10.1016/j.jaap.2005.03.010.

Sharma, R.K., Hajaligol, M.R., 2003. Effect of pyrolysis conditions on the formation of polycyclic aromatic hydrocarbons (PAHs) from polyphenolic compounds. J. Anal. Appl. Pyrolysis 66 (1), 123-144. http://dx.doi.org/10.1016/S0165-2370(02)00109-2.

Shirokova, L., Mavromatis, V., Bundeleva, I.A., Pokrovsky, O.S., Bénézeth, P., Gérard, E., Pearce, C.R., Oelkers, E.H., 2013. Using Mg isotopes to trace cyanobacterially mediated magnesium carbonate precipitation in alkaline lakes. Aquat. Geochem. 19 (1), 1-24. http://dx.doi.org/10.1007/s10498-012-9174-3.

Stalport, F., Coll, P., Cabane, M., Person, A., Navarro-González, R., Raulin, F., Vaulay, M.J., Ausset, P., McKay, C.P., Szopa, C., Zarnecki, J., 2005. Search for past life on Mars: Physical and chemical characterization of minerals of biotic and abiotic origin: Part 1 - Calcite. Geophys. Res. Lett. 32 (23), L23205. http://dx.doi.org/10.1029/2005GL023403.

Stalport, F., Coll, P., Szopa, C., Person, A., Navarro-González, R., Cabane, M., Ausset, P., Vaulay, M.J., 2007. Search for past life on Mars: Physical and chemical characterization of minerals of biotic and abiotic origin: 2. Aragonite. Geophys. Res. Lett. 34 (24), L24102. http://dx.doi.org/10.1029/2007GL031184.

Stalport, F., Rouquette, L., Poch, O., Dequaire, T., Chaouche-Mechidal, N., Payart, S., Szopa, C., Coll, P., Chaput, D., Jaber, M., Raulin, F., Cottin, H., 2019. The photochemistry on space station (PSS) experiment: Organic matter under Mars-like surface UV radiation conditions in low Earth orbit. Astrobiology 19 (8), 1037-1052. http://dx.doi.org/10.1089/ast.2018.2001.

Stern, K.H., Weise, E.L., 1969. High Temperature Properties and Decomposition of Inorganic Salts. Part 2. Carbonates. Technical Report NSRDS-NBS 30, National Bureau of Standards, United States Department of Commerce, National Bureau of Standards, Washington, D.C, U.S.A., pp. 1-27, URL: https://nvlpubs.nist.gov/nistpubs/Legacy/NSRDS/nbsnsrds30.pdf.

Sumner, D.Y., 2004. Poor preservation potential of organics in Meridiani Planum hematite-bearing sedimentary rocks. J. Geophys. Res.: Planets 109 (12), E12007. http://dx.doi.org/10.1029/2004JE002321.

Sutter, B., Archer, P., Niles, P., Ming, D., Hamara, D., Boynton, W., 2024. Organic carbon and Ca-rich carbonate detections in soils of the northern plates, Mars: Evaluation of unreported data from the Mars Phoenix Scout's Thermal Evolved Gas Analyzer (TEGA). J. Geophys. Res.: Planets 129 (10), e2024JE008335. http://dx.doi.org/10.1029/2024JE008335.

Sutter, B., Boynton, W., Ming, D., Niles, P., Morris, R., Golden, D., Lauer, H., Fellows, C., Hamara, D., Mertzman, S., 2012. The detection of carbonate in the martian soil at the Phoenix Landing site: A laboratory investigation and comparison with the Thermal and Evolved Gas Analyzer (TEGA) data. Icarus 218 (1), 290-296. http://dx.doi.org/10.1016/j.icarus.2011.12.002.

Suzuki, J., Ito, M., 1974. Nesquehonite from Yoshikawa, Aichi Prefecture, Japan: Occurrence and thermal behaviour. J. Jpn. Assoc. Miner. Pet. Econ. Geol. 69 (8), 275-284. http://dx.doi.org/10.2465/ganko1941.69.275.

Swift, W.M., Panek, A.F., Smith, G.W., Vogel, G.J., Jonke, A.A., 1976. Decomposition of calcium sulfate: A review of the literature. Technical Report OSTI ID: 7224692, Argonne National Laboratory, U.S. Department of Energy, Office of Scientific and Technical Information, pp. 1-64. http://dx.doi.org/10.2172/7224692.

Unluer, C., Al-Tabbaa, A., 2014. Characterization of light and heavy hydrated magnesium carbonates using thermal analysis. J. Therm. Anal. Calorim. 115 (1), 595-607. http://dx.doi.org/10.1007/s10973-013-3300-3.

Vennin, E., Bouton, A., Roche, A., Gérard, E., Bundeleva, I., Boussagol, P., Wattinne, A., Kolodka, C., Gaucher, E., Virgone, A., Visscher, P.T., 2021. The Limagne Basin: A journey through modern and fossil microbial deposits. Le bassin des Limagnes : Une excursion à travers les dépôts microbiens modernes et fossiles. Bull. de la Société Géologique de Fr. - Earth Sci. Bull. 192 (1), 41. http://dx.doi.org/10.1051/bsgf/2021030.

Vinogradoff, V., Le Guillou, C., Bernard, S., Binet, L., Cartigny, P., Brearley, A.J., Remusat, L., 2017. Paris vs. Murchison: Impact of hydrothermal alteration on organic matter in CM chondrites. Geochim. Cosmochim. Acta 212, 234-252. http://dx.doi.org/10.1016/j.gca.2017.06.009.

Wang, C., Wang, Y., Herath, H.M., 2017. Polycyclic aromatic hydrocarbons (PAHs) in biochar - Their formation, occurrence and analysis: A review. Org. Geochem. 114, 1-11. http://dx.doi.org/10.1016/j.orggeochem.2017.09.001.

Wang, H., Xu, H.B., Zheng, C.G., Qiu, J.R., 2009. Temperature dependence on reaction of CaCO₃ and SO₂ in O₂/CO₂ coal combustion. J. Central South Univ. Technol. 16 (5), 845-850. http://dx.doi.org/10.1007/s11771-009-0140-1.

Wattinne, A., 2004. Évolution d'un Environnement Carbonate Lacustre À Bioconstruc-tions, En Limagne Bourbonnaise (Oligo-Miocène, Massif Central, france) (Ph.D. thesis). Muséum National d'Histoire Naturelle, Paris, France, URL: http://www.sudoc.fr/08393247X.

Westall, F., Foucher, F., Bost, N., Bertrand, M., Loizeau, D., Vago, J.L., Kminek, G., Gaboyer, F., Campbell, K.A., Bréhéret, J.G., Gautret, P., Cockell, C.S., 2015. Biosignatures on Mars: What, where, and how? Implications for the search for Martian life. Astrobiology 15 (11), 998-1029. http://dx.doi.org/10.1089/ast.2015.1374.

Xian, S., Xu, Q., Li, H., 2023. Mechanism insight into the conversion between H₂S and thiophene during coal pyrolysis: A theoretical study. ACS Omega 8 (37), 33982-33996. http://dx.doi.org/10.1021/acsomega.3c04847.

Yamamoto, G.-i., Kyono, A., Sano, Y., Matsushita, Y., Yoneda, Y., 2021. In situ and ex situ studies on thermal decomposition process of hydromagnesite Mg₄(CO₃)₃(OH)₂·4H₂O. J. Therm. Anal. Calorim. 144 (3), 599-609. http://dx.doi.org/10.1007/s10973-020-09618-7.

Yan, L.Y., Lu, X.F., Guo, Q., Wang, Q.H., Ji, X.Y., 2014. Research on the thermal decomposition and kinetics of byproducts from MgO wet flue gas desulfurization. Adv. Powder Technol. 25 (6), 1709-1714. http://dx.doi.org/10.1016/j.apt.2014.06.018.

Yan, Z.Q., Wang, Z.A., Wang, X.F., Liu, H., Qiu, J.R., 2015. Kinetic model for calcium sulfate decomposition at high temperature. Trans. Nonferrous Met. Soc. China (Engl. Edition) 25 (10), 3490-3497. http://dx.doi.org/10.1016/S1003-6326(15)63986-3.

Zhitova, E.S., Greenwell, H.C., Krzhizhanovskaya, M.G., Apperley, D.C., Pekov, I.V., Yakovenchuk, V.N., 2020. Thermal evolution of natural layered double hydroxides: Insight from quintinite, hydrotalcite, stichtite, and Iowaite as reference samples for CO₃⁻ and Cl-members of the hydrotalcite supergroup. Minerals 10 (11), 961. http://dx.doi.org/10.3390/min10110961.

Zhou, H., Wu, C., Onwudili, J.A., Meng, A., Zhang, Y., Williams, P.T., 2014. Polycyclic aromatic hydrocarbon formation from the pyrolysis/gasification of lignin at different reaction conditions. Energy Fuels 28 (10), 6371-6379. http://dx.doi.org/10.1021/ef5013769.

Zhou, H., Wu, C., Onwudili, J.A., Meng, A., Zhang, Y., Williams, P.T., 2016. Influence of process conditions on the formation of 2-4 ring polycyclic aromatic hydrocarbons from the pyrolysis of polyvinyl chloride. Fuel Process. Technol. 144, 299-304. http://dx.doi.org/10.1016/j.fuproc.2016.01.013.

Zhu, T., Dittrich, M., 2016. Carbonate precipitation through microbial activities in natural environment, and their potential in biotechnology: A review. Front. Bioeng. Biotechnol. 4 (JAN), 4. http://dx.doi.org/10.3389/fbioe.2016.00004.