# The possible role of anoxic alkaline high subcritical water in the construction of the BIFs: the case of the 3.4 Ga Buck Reef Chert, Sth Africa

Marie-Paule Bassez

► To cite this version:

Marie-Paule Bassez. The possible role of anoxic alkaline high subcritical water in the construction of the BIFs: the case of the 3.4 Ga Buck Reef Chert, Sth Africa. Goldschmidt 2023: Workshop ExTerra 2023: Understanding subduction., Jul 2024, Lyon (Fr), France., 2023. hal-04531002

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Submitted on 9 Apr 2024

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# The possible role of anoxic alkaline high subcritical water in the construction of the BIFs: the case of the 3.4 Ga Buck Reef Chert, Sth Africa

Marie-Paule Bassez

► To cite this version:

Marie-Paule Bassez. The possible role of anoxic alkaline high subcritical water in the construction of the BIFs: the case of the 3.4 Ga Buck Reef Chert, Sth Africa. Goldschmidt 2023: Workshop ExTerra 2023: Understanding subduction., Jul 2024, Lyon (Fr), France., 2023. hal-04531002

HAL Id: hal-04531002

https://hal.science/hal-04531002v1

Submitted on 9 Apr 2024

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>
<figure><img src="image_2.png" /></figure>

# The possible role of anoxic alkaline high subcritical water in the construction of the BIFs: the case of the 3.4 Ga Buck Reef Chert, Sth Africa

Marie-Paule Bassez, [marie-paule.bassez@unistra.fr](mailto:marie-paule.bassez@unistra.fr)

[https://www.chemphys.fr/mpb](https://www.chemphys.fr/mpb)

ORCID 0000-0002-7548-8894

## Oxidation of Fe²⁺ into Fe³⁺

**1. An alternate hypothesis:** oxidation by water at 300°-350°C, 10-25 MPa, pH 9.5-14, density 600-700 kg/m³, µ 2.30 debyes
µT,P from Matubayasi et al. J.Chem.Phys. 1999: 2.35 D for liq. wat (1 g/cm³-25°C), 2.30 D (0.7 g/cm³ -300°C), 2.25 D (0.6 g/cm³ 400°C

<figure><img src="image_3.png" /><figcaption>**Fig.1** The inverse water dimer (µ 0 D) Bassez J. Phys. Cond. Matter 2003 lowers the dipole moment</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>**Fig.2** Fig.7a in Cook and Olive, Corr. Sci. 2012; Pourbaix diagram at 350°C, 25 MPa, 10⁻⁶ mol/kg
From this part of the diagram, I conclude that Fe²⁺ is oxidized by water with emission of H₂ :
**Fe(OH)₃⁻ + hsubcwater → Fe(OH)₄⁻ + H₂ at strongly basic pH** (Bassez EGU2013- OLEB 2023)</figcaption></figure>

<figure><img src="image_5.png" /></figure>

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /><figcaption>**Fig.3** red: predicted; violet: observed; Raman spectrum: Q, Hematite
The interaction of fayalite with hscwater explains the formation of ferric minerals, methane, carbon and H₂.</figcaption></figure>

## Construction of the Banded Iron Formations

<figure><img src="image_8.png" /><figcaption>**Fig.4** BIFs and NIFs</figcaption></figure>

The Back Reef Chert was emplaced between volcanic events. The two non-homogeneously mixed viscous (high SiO₂) fluids might have been ejected in flow-banding.

<figure><img src="image_9.png" /><figcaption>**Fig.5** 10 MPa reached at 1 to 5 km depth</figcaption></figure>

<figure><img src="image_10.png" /><figcaption>Flow-banded rhyolite
Mozambique,
Manninnen+ 2008</figcaption></figure>

<figure><img src="image_11.png" /><figcaption>Flow-banded dacite from a viscous lava flow; dacite, andesite: above subduction zones; black: amphibole, pyroxene; light: plagioclase feldspar
HHGeolSurvey</figcaption></figure>

<figure><img src="image_12.png" /><figcaption>Banded pumice,
Chistiansen, USGS</figcaption></figure>

**2. The currently accepted hypothesis:** oxidation by O₂-producing or FeII-oxidizing microorganisms :

$$H_2O + \text{light} \rightarrow 4H^+ + O_2 + 4e^- \quad (H_2O = 4H^+ + 2O^{--}; 2O^{--} \rightarrow O_2 + 4e^-)$$

<figure><img src="image_13.png" /><figcaption>**Fig.8** Part of Fig.2 in Tschörtner et al. Frontiers in Microbiology 2019; Biophotovoltaics: Green power generation from sunlight and water; open doi: 10.3389/fmicb.2019.00866; BPV is a subcategory of photosynthetic microbial fuel cell. The figure shows the complex system of life, with membranes, pigments, proteins, emission of O₂, transferts of e⁻ from the thylakoid membrane.
Circled by **MPB**: the photosynthesis system: light, PSII system (pigment-protein photosystem), **emitted O₂** and e⁻.
Question: How these complicated systems formed 3.4 Ga ago?</figcaption></figure>
<figure><img src="image_2.png" /></figure>

# The possible role of anoxic alkaline high subcritical water in the construction of the BIFs: the case of the 3.4 Ga Buck Reef Chert, Sth Africa

Marie-Paule Bassez, [marie-paule.bassez@unistra.fr](mailto:marie-paule.bassez@unistra.fr)

[https://www.chemphys.fr/mpb](https://www.chemphys.fr/mpb)

ORCID 0000-0002-7548-8894

## Oxidation of Fe²⁺ into Fe³⁺

**1. An alternate hypothesis:** oxidation by water at 300°-350°C, 10-25 MPa, pH 9.5-14, density 600-700 kg/m³, µ 2.30 debyes
µT,P from Matubayasi et al. J.Chem.Phys. 1999: 2.35 D for liq. wat (1 g/cm³-25°C), 2.30 D (0.7 g/cm³ -300°C), 2.25 D (0.6 g/cm³ 400°C

<figure><img src="image_3.png" /><figcaption>**Fig.1** The inverse water dimer (µ 0 D) Bassez J. Phys. Cond. Matter 2003 lowers the dipole moment</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>**Fig.2** Fig.7a in Cook and Olive, Corr. Sci. 2012; Pourbaix diagram at 350°C, 25 MPa, 10⁻⁶ mol/kg
From this part of the diagram, I conclude that Fe²⁺ is oxidized by water with emission of H₂ :
**Fe(OH)₃⁻ + hsubcwater → Fe(OH)₄⁻ + H₂ at strongly basic pH** (Bassez EGU2013- OLEB 2023)</figcaption></figure>

<figure><img src="image_5.png" /></figure>

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /><figcaption>**Fig.3** red: predicted; violet: observed; Raman spectrum: Q, Hematite
The interaction of fayalite with hscwater explains the formation of ferric minerals, methane, carbon and H₂.</figcaption></figure>

## Construction of the Banded Iron Formations

<figure><img src="image_8.png" /><figcaption>**Fig.4** BIFs and NIFs</figcaption></figure>

The Back Reef Chert was emplaced between volcanic events. The two non-homogeneously mixed viscous (high SiO₂) fluids might have been ejected in flow-banding.

<figure><img src="image_9.png" /><figcaption>**Fig.5** 10 MPa reached at 1 to 5 km depth</figcaption></figure>

<figure><img src="image_10.png" /><figcaption>Flow-banded rhyolite
Mozambique,
Manninnen+ 2008</figcaption></figure>

<figure><img src="image_11.png" /><figcaption>Flow-banded dacite from a viscous lava flow; dacite, andesite: above subduction zones; black: amphibole, pyroxene; light: plagioclase feldspar
HHGeolSurvey</figcaption></figure>

<figure><img src="image_12.png" /><figcaption>Banded pumice,
Chistiansen, USGS</figcaption></figure>

**2. The currently accepted hypothesis:** oxidation by O₂-producing or FeII-oxidizing microorganisms :

$$H_2O + \text{light} \rightarrow 4H^+ + O_2 + 4e^- \quad (H_2O = 4H^+ + 2O^{--}; 2O^{--} \rightarrow O_2 + 4e^- )$$

<figure><img src="image_13.png" /><figcaption>**Fig.8** Part of Fig.2 in Tschörtner et al. Frontiers in Microbiology 2019; Biophotovoltaics: Green power generation from sunlight and water; open doi: 10.3389/fmicb.2019.00866; BPV is a subcategory of photosynthetic microbial fuel cell. The figure shows the complex system of life, with membranes, pigments, proteins, emission of O₂, transferts of e⁻ from the thylakoid membrane.
Circled by **MPB**: the photosynthesis system: light, PSII system (pigment-protein photosystem), **emitted O₂** and e⁻.
Question: How these complicated systems formed 3.4 Ga ago?</figcaption></figure>