# The BARB3_23B disordered graphitic carbon

Marie-Paule Bassez

► To cite this version:

Marie-Paule Bassez. The BARB3_23B disordered graphitic carbon. Origins of Life and Evolution of Biospheres, 2023, Origins of Life and Evolution of Biospheres, 53 (1-2), 1-41 Supplementary Information. 10.1007/s11084-023-09638-x. http://dx.doi.org/10.1007/s11084-023-09638-x

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Submitted on 3 Apr 2024

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<figure><img src="image_1.png" /></figure>
# The BARB3_23B disordered graphitic carbon

Marie-Paule Bassez

► To cite this version:

Marie-Paule Bassez. The BARB3_23B disordered graphitic carbon. Origins of Life and Evolution of Biospheres, 2023, Origins of Life and Evolution of Biospheres, 53 (1-2), 1-41 Supplementary Information. 10.1007/s11084-023-09638-x. http://dx.doi.org/10.1007/s11084-023-09638-x

HAL Id: hal-04530251

https://hal.science/hal-04530251v1

Submitted on 3 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>

Open licence - etalab
# The BARB3_23B disordered graphitic carbon

Geological setting of the Buck Reef Chert and the BARB3_23B sample

Raman and HRTEM profiles of disordered graphitic carbon

The Raman profile of the BARB3_23B carbon matter

The BARB3_23B carbon matter and temperature

The BARB3_23B carbon matter and Archean graphitic carbon

The BARB3_23B carbon matter and oxygen content

The BARB3_23B carbon and amorphous carbon

The BARB3_23B carbon matter and curvature of the graphene layers

The BARB3_23B carbon and meteorite carbon

Conclusion on the BARB3_23B carbon matter

In this section the Raman profile of the carbon matter contained in the BARB3_23B sample drilled in the Buck Reef chert is compared with spectra reported by other authors for samples of various origins. The term carbon matter, used in the present article, represents the matter that contains disordered graphite associated with organic functional groups and is usually named carbonaceous matter and kerogen in some other articles.

## Geological setting of the Buck Reef Chert and the BARB3_23B sample

The Earth's continental crust contains approximately 35 large Archean fragments and smaller slivers, 4 to 2.5 Ga in age, which have undergone little internal deformation. These coherent domains are named Archean continental cratons and their exposed sections are named shields. The crustal geologies of the Archean cratons are related to their underlying lithospheric mantle keels and are linked to the much larger crust-mantle systems called supercratons. They are described in (Bleeker 2003, Bleeker and Davis 2004, Condie 2019 Fig.11.1 and Table 11.1). The Dharwar craton of India, the Zimbabwe craton of South Africa and the Wyoming craton of North America show similarities to the Slave craton exposed in the northwestern Canadian Shield. In contrast, the Kaapvaal craton of South Africa and the Superior craton of northeastern America and Canada are very different from the Slave craton. Widely studied cratons are the North Atlantic craton that hosts the Isua greenstone belt of West Greenland, the Superior craton that hosts the Abitibi greenstone belt, the Amazonian craton of Brazil, the Dharwar craton of India, the Kaapvaal craton of South Africa that hosts the Barberton greenstone belt, the Pilbara craton of Australia that hosts the Pilbara supergroup of greenstone belts (de Wit and Ashwal 1997, de Wit and Furnes 2013, Ledevin 2013, Anhaeusser 2014, Carlson et al. 2019). Greenstone belts are belt-like areas of the shields that host volcano-sedimentary rocks named greenstones. They are embedded within granitic domes called plutons. The Barberton greenstone belt is thus described as granite-greenstone terrain. "Granite is used as a broad term that includes the whole TTG compositional spectrum, and greenstone is a general term for the metamorphosed mafic/ultramafic rocks" (Carlson 2019). "It has been known since the mid-1800s that the mafic-ultramafic rocks of greenstone belts comprise a variety of green secondary minerals: serpentine, chlorite, epidote, actinolite, and hornblende constitute more than 80% (and commonly much more) of these rocks. The very name greenstone, therefore implies metamorphism.." (de Wit and Ashwal 1995 p.514). In (Anhaeusser 2014), terrestrial and satellite photographs of Archean greenstone belts and associated granitic rocks are shown.

It has been observed that the Kaapvaal craton "is bordered by rifted and collisional margins of different ages"...and proposed that it "was formerly connected to the Pilbara of Western Australia in a 'Vaalbara' supercraton" (Bleeker 2003 and refs therein). The Kaapvaal Craton shows resemblance in geological structure to the Pilbara Craton in Western Australia.
# The BARB3_23B disordered graphitic carbon

## Geological setting of the Buck Reef Chert and the BARB3_23B sample

### Raman and HRTEM profiles of disordered graphitic carbon

* The Raman profile of the BARB3_23B carbon matter

* The BARB3_23B carbon matter and temperature

* The BARB3_23B carbon matter and Archean graphitic carbon

* The BARB3_23B carbon matter and oxygen content

* The BARB3_23B carbon and amorphous carbon

* The BARB3_23B carbon matter and curvature of the graphene layers

* The BARB3_23B carbon and meteorite carbon

### Conclusion on the BARB3_23B carbon matter

In this section the Raman profile of the carbon matter contained in the BARB3_23B sample drilled in the Buck Reef chert is compared with spectra reported by other authors for samples of various origins. The term carbon matter, used in the present article, represents the matter that contains disordered graphite associated with organic functional groups and is usually named carbonaceous matter and kerogen in some other articles.

## Geological setting of the Buck Reef Chert and the BARB3_23B sample

The Earth's continental crust contains approximately 35 large Archean fragments and smaller slivers, 4 to 2.5 Ga in age, which have undergone little internal deformation. These coherent domains are named Archean continental cratons and their exposed sections are named shields. The crustal geologies of the Archean cratons are related to their underlying lithospheric mantle keels and are linked to the much larger crust-mantle systems called supercratons. They are described in (Bleeker 2003, Bleeker and Davis 2004, Condie 2019 Fig.11.1 and Table 11.1). The Dharwar craton of India, the Zimbabwe craton of South Africa and the Wyoming craton of North America show similarities to the Slave craton exposed in the northwestern Canadian Shield. In contrast, the Kaapvaal craton of South Africa and the Superior craton of northeastern America and Canada are very different from the Slave craton. Widely studied cratons are the North Atlantic craton that hosts the Isua greenstone belt of West Greenland, the Superior craton that hosts the Abitibi greenstone belt, the Amazonian craton of Brazil, the Dharwar craton of India, the Kaapvaal craton of South Africa that hosts the Barberton greenstone belt, the Pilbara craton of Australia that hosts the Pilbara supergroup of greenstone belts (de Wit and Ashwal 1997, de Wit and Furnes 2013, Ledevin 2013, Anhaeusser 2014, Carlson et al. 2019). Greenstone belts are belt-like areas of the shields that host volcano-sedimentary rocks named greenstones. They are embedded within granitic domes called plutons. The Barberton greenstone belt is thus described as granite-greenstone terrain. "Granite is used as a broad term that includes the whole TTG compositional spectrum, and greenstone is a general term for the metamorphosed mafic/ultramafic rocks" (Carlson 2019). "It has been known since the mid-1800s that the mafic-ultramafic rocks of greenstone belts comprise a variety of green secondary minerals: serpentine, chlorite, epidote, actinolite, and hornblende constitute more than 80% (and commonly much more) of these rocks. The very name greenstone, therefore implies metamorphism.." (de Wit and Ashwal 1995 p.514). In (Anhaeusser 2014), terrestrial and satellite photographs of Archean greenstone belts and associated granitic rocks are shown.

It has been observed that the Kaapvaal craton "is bordered by rifted and collisional margins of different ages"...and proposed that it "was formerly connected to the Pilbara of Western Australia in a 'Vaalbara' supercraton" (Bleeker 2003 and refs therein). The Kaapvaal Craton shows resemblance in geological structure to the Pilbara Craton in Western Australia.
A stratigraphic comparison of the Kaapvaal and Pilbara successions between 3.550 Ga and 2.450 Ga is described in (Hickman et al. 2021 Fig.4) and shows the sedimentary synchronous deposition of the 3.426-3.350 Ga Strelley Pool Formation and the 3.416-3.350 Ga Buck Reef Chert during a ~70 Ma break in volcanic activity. Below are presented the localities of the samples which are cited in the article.

The Kaapvaal Craton comprises dense greenstone belts that are infolded between plutons and domes made of granitic gneisses (Kröner and Hofmann 2019 p.vi Fig.1, Brandl 2006 Figs.1, 2). The contact between the greenstones and the gneisses is described as either tectonic or intrusive. The oldest granitic-greenstone rocks are located in the eastern part of the craton. The Kaapvaal Craton is divided into four blocks, the Swaziland, Witwatersrand, Pietersburg and Kimberley blocks (Kröner and Hofmann 2019 p.vi Fig.1). The northeastern part of the Swaziland block contains the Barberton Granite-Greenstone Terrain (BGGT) with its supracrustal succession, the Barberton Greenstone Belt (BGB) which extends in a southwest-northeast direction, on ~120 km in length, ~20 to 50 km in width and ~12 km in depth or thickness. The geology, stratigraphy, lithofacies and carbon content of the BGGT have been described by many authors, including (de Wit and Ashwal 1995; de Wit et al. 1997, 2011, 2018; Lowe and Byerly 1999 p.1, 2020; Lowe and Worrell 1999 p.167; Westall et al. 2001; Poujol et al. 2003 Fig.1; Hofmann 2005 Fig.1; Brandl et al. 2006 Figs.1-3; Tice and Lowe 2006; Hofmann and Harris 2008; Hofmann et al. 2013; Ledevin 2013; Artal 2014; Molekwa 2017; van Kranendonk et al. 2019; Kröner and Hofmann 2019; Byerly et al. 2019 p.569 Fig.24.1; Kröner et al. 2019 p.1 Fig.1.1, Hofmann et al. 2019 Fig.2.1, Anhaeusser 2019 Fig.1; Agangi et al. 2019 p.171 Fig.7.1; Drabon et al. 2022; and refs therein).

The BGB includes the 3.55-3.23 Ga Paleoarchean volcano-sedimentary Barberton Supergroup (formerly Swaziland Supergroup) which is composed of three stratigraphic units: the 3.55-3.30 Ga Onverwacht, the 3.26-3.226 Ga Fig Tree and the 3.227 Ga Moodies groups. "These rock units are tightly folded into a number of synclines that are separated by narrow anticlines or shear zones." (Hofmann 2005). They form a mountain, the Barberton Makhonjwa Mountain Land, which is in contact with intrusive igneous granitic plutons, ~3.45 Ga in age in the southern part and ~3.22 Ga in age in the western part. "Both the Theespruit and Stolzburg (south) plutons are intrusive into adjacent greenstone belt (Onverwacht Group) lithology...The 3.45 Ga plutons are mostly high-silica trondhjemites" (Moyen et al. 2019 p.630 §3.3.1, 2007 §5.6-3.4). Both series of plutons are of the TTG group (trondhjemite-tonalite-granodiorite) with predominance of plagioclase over alkali feldspar. The BGB and the 3.6 to 3.3 Ga TTG plutons are surrounded by large sheeted potassic granitic batholiths of the GMS group (granite-monzonite-syenite), 3.25 to 3.1 Ga in age, with lower plagioclase than alkali feldspar (Kisters et al. 2003 Fig.1, Hofmann 2005 Fig.1, Agangi et al. 2015 Fig.1, 2018 Fig.1, Hofmann et al. 2019 p.34 Fig.2.1). "TTGs are sodic (Na₂O/K₂O ratios >1.5-2), quartz-bearing granitic (plutonic) rocks with plagioclase as the most common feldspar, and K-feldspar ranging from subordinate to nearly absent" (Moyen et al. 2019 p.616 and Fig.25.2). The TTG and GMS rocks overlap in age with the mafic-ultramafic to felsic metavolcanic assemblages of the greenstone belt. "The origin of both the TTGs and the greenstone units is still debated...this is due to an extensive tectono-magmato-metamorphic event at ca 3.2 Ga...(which) led to intracrystal melting" (Kröner et al. 2019 p.1). The Barberton belt consists of "a keel of tightly folded supracrustal greenstone rocks between granitic domes" (Hofmann et al. 2019 p.33).

The Onverwacht Group contains the Mendon, Kromberg, Hooggenoeg, Komati and Theespruit Formations as shown on the stratigraphic figures in (de Wit et al. 2011, Lowe and Byerly 2020) and in (Hofmann 2005, Brandl et al. 2006, Hofmann et al. 2013). All formations are observed south of the Inkoya fault. The 3.33 Ga Josefsdal chert is located in the 3.416-3.334 Ga Kromberg Formation, the 3.416 Ga Buck Reef Chert between the base of the Kromberg and
A stratigraphic comparison of the Kaapvaal and Pilbara successions between 3.550 Ga and 2.450 Ga is described in (Hickman et al. 2021 Fig.4) and shows the sedimentary synchronous deposition of the 3.426-3.350 Ga Strelley Pool Formation and the 3.416-3.350 Ga Buck Reef Chert during a ~70 Ma break in volcanic activity. Below are presented the localities of the samples which are cited in the article.

The Kaapvaal Craton comprises dense greenstone belts that are infolded between plutons and domes made of granitic gneisses (Kröner and Hofmann 2019 p.vi Fig.1, Brandl 2006 Figs.1, 2). The contact between the greenstones and the gneisses is described as either tectonic or intrusive. The oldest granitic-greenstone rocks are located in the eastern part of the craton. The Kaapvaal Craton is divided into four blocks, the Swaziland, Witwatersrand, Pietersburg and Kimberley blocks (Kröner and Hofmann 2019 p.vi Fig.1). The northeastern part of the Swaziland block contains the Barberton Granite-Greenstone Terrain (BGGT) with its supracrustal succession, the Barberton Greenstone Belt (BGB) which extends in a southwest-northeast direction, on ~120 km in length, ~20 to 50 km in width and ~12 km in depth or thickness. The geology, stratigraphy, lithofacies and carbon content of the BGGT have been described by many authors, including (de Wit and Ashwal 1995; de Wit et al. 1997, 2011, 2018; Lowe and Byerly 1999 p.1, 2020; Lowe and Worrell 1999 p.167; Westall et al. 2001; Poujol et al. 2003 Fig.1; Hofmann 2005 Fig.1; Brandl et al. 2006 Figs.1-3; Tice and Lowe 2006; Hofmann and Harris 2008; Hofmann et al. 2013; Ledevin 2013; Artal 2014; Molekwa 2017; van Kranendonk et al. 2019; Kröner and Hofmann 2019; Byerly et al. 2019 p.569 Fig.24.1; Kröner et al. 2019 p.1 Fig.1.1, Hofmann et al. 2019 Fig.2.1, Anhaeusser 2019 Fig.1; Agangi et al. 2019 p.171 Fig.7.1; Drabon et al. 2022; and refs therein).

The BGB includes the 3.55-3.23 Ga Paleoarchean volcano-sedimentary Barberton Supergroup (formerly Swaziland Supergroup) which is composed of three stratigraphic units: the 3.55-3.30 Ga Onverwacht, the 3.26-3.226 Ga Fig Tree and the 3.227 Ga Moodies groups. "These rock units are tightly folded into a number of synclines that are separated by narrow anticlines or shear zones." (Hofmann 2005). They form a mountain, the Barberton Makhonjwa Mountain Land, which is in contact with intrusive igneous granitic plutons, ~3.45 Ga in age in the southern part and ~3.22 Ga in age in the western part. "Both the Theespruit and Stolzburg (south) plutons are intrusive into adjacent greenstone belt (Onverwacht Group) lithology...The 3.45 Ga plutons are mostly high-silica trondhjemites" (Moyen et al. 2019 p.630 §3.3.1, 2007 §5.6-3.4). Both series of plutons are of the TTG group (trondhjemite-tonalite-granodiorite) with predominance of plagioclase over alkali feldspar. The BGB and the 3.6 to 3.3 Ga TTG plutons are surrounded by large sheeted potassic granitic batholiths of the GMS group (granite-monzonite-syenite), 3.25 to 3.1 Ga in age, with lower plagioclase than alkali feldspar (Kisters et al. 2003 Fig.1, Hofmann 2005 Fig.1, Agangi et al. 2015 Fig.1, 2018 Fig.1, Hofmann et al. 2019 p.34 Fig.2.1). "TTGs are sodic (Na₂O/K₂O ratios >1.5-2), quartz-bearing granitic (plutonic) rocks with plagioclase as the most common feldspar, and K-feldspar ranging from subordinate to nearly absent" (Moyen et al. 2019 p.616 and Fig.25.2). The TTG and GMS rocks overlap in age with the mafic-ultramafic to felsic metavolcanic assemblages of the greenstone belt. "The origin of both the TTGs and the greenstone units is still debated...this is due to an extensive tectono-magmato-metamorphic event at ca 3.2 Ga...(which) led to intracrystal melting" (Kröner et al. 2019 p.1). The Barberton belt consists of "a keel of tightly folded supracrustal greenstone rocks between granitic domes" (Hofmann et al. 2019 p.33).

The Onverwacht Group contains the Mendon, Kromberg, Hooggenoeg, Komati and Theespruit Formations as shown on the stratigraphic figures in (de Wit et al. 2011, Lowe and Byerly 2020) and in (Hofmann 2005, Brandl et al. 2006, Hofmann et al. 2013). All formations are observed south of the Inkoya fault. The 3.33 Ga Josefsdal chert is located in the 3.416-3.334 Ga Kromberg Formation, the 3.416 Ga Buck Reef Chert between the base of the Kromberg and
the top of the Hooggenoeg Formations, and the 3.472 Ga Middle Marker between the base of
the Hooggenoeg and the top of the Komati Formations.

The present article concerns one section of the 3.4 Ga Buck Reef Chert, located in the Onverwacht group of the Barberton greenstone belt in the Kaapvaal craton, South Africa. Its local geological setting is described in the main text.

The Pilbara Craton is described as geologically equivalent to the Kaapvaal Craton. Detailed lithostratigraphic descriptions of the North Pilbara Terrain are published in (van Kranendonk et al. 2002) and revised in (van Kranendonk et al. 2006, 2007, 2012, 2019) with a presentation of 20 greenstone belts in (van Kranendonk et al. 2006 Fig.4, Hickman et al. 2021 Fig.8). The exposed 530 km x 230 km northern part of the craton consists of the oldest 3.53-3.17 Ga East Pilbara Terrane, EPT. The proposed 3.53-3.42 Ga mantle plume activity resulted in a volcanic plateau and a lithospheric keel.

A recent report describes the East Pilbara Craton (Hickman 2021 table 1 p.10, p.15, Fig.6). It is composed of eight tectonic units including **1:** the 3.8-3.53 Ga Early Crust, which forms a basement for the Pilbara Supergroup. **2:** the Paleoarchean 3.530-3.223 Ga granite-greenstone terrane of the Pilbara Supergroup, which includes the 3.53-3.427 Ga Warrawoona Group, also named the Warrawoona large igneous province, LIP. The Warrawoona Group is composed of the Talga-Talga Subgroup with the 3.481-3.477 Ga Dresser/McPhee Formation, the Coongan Subgroup with the 3.474-3.449 Ga Duffer Formation and its 3.46 Ga Marble Bar Chert member, the Salgash Subgroup with the 3.459-3.440 Ga Apex Basalt Formation and the 3.448-3.427 Ga Panorama Formation. The 3.426-3.350 Ga Strelley Pool Formation, SPF, "overlies a regional unconformity between the two large igneous provinces represented by the Warrawoona and the Kelly Groups" (Hickman et al. 2021 p.72). The ~100 m thick Strelley Pool Formation outcrops in approximately 9 greenstone belts, as imaged within the stratigraphy of the Pilbara Supergroup in (Hickman et al. 2021 Fig.31 p.74). The "3426-3350 Ma, sedimentary deposition of the Strelley Pool Formation and Buck Reef Chert during a contemporaneous c.75 Ma break in volcanic activity" is drawn in (Hickman et al. 2021 Fig.4). **3:** The 3.066-2.930 Ga De Grey Supergroup which includes the Gorge Creek Group with the 3.066-3.022 Ga Farrel Quartzite. The Farrel Quartzite is composed of mafic to ultramafic volcanoclastic layers, evaporite beds and black chert layers (Sugitani et al. 2007).

The Dresser Formation is exposed in the granite-greenstone belt North Pole Dome, located at the center of the EPT. It is detailed in (Djokic 2015 thesis, Djokic et al. 2017). In some places, the EPT is unconformably overlain by the Neoarchean 2.775-2.629 Ga Fortescue Group and the 2.629-2.445 Ga Neoarchean to early Paleoproterozoic Hamersley Group. "The Fortescue Group is a succession of flood basalt and sedimentary rocks deposited on the southern margin of the Pilbara Craton from ~2.78 Ga to ~2.63 Ga, during one or more periods of rifting associated with extensive volcanism" (Flannery et al. 2014 Fig.1 and refs therein). It unconformably overlies the granite-greenstone rocks and includes the Jeerinah Formation.

Subgroups and Formations are visualized in the geological maps drawn in (Hickman 2021 Fig.5 and p.189, van Kranendonk et al. 2008 Fig.1) together with the dome and keel structure of the East Pilbara Terrane which is distributed in eleven granitic domes separated by fault, tectonic and shear zones and a corridor. The domes are composed of ovoid granitic cores surrounded by greenstone belts (Hickman 2021 Fig.8 and cover image). The "granitoid complexes are nearly vertical cylinders extending to depths of 14 km" (van Kranendonk et al. 2002 p.697, van Kranendonk et al. 2004 p.184). They have been divided into suites and supersuites that were emplaced 3.5-3.165 Ga ago during the period of mantle plume activities. The greenstones are older volcanic and sedimentary rocks that were emplaced before 3.5 Ga ago and subsequently strongly affected by deformation and faulting (van Kranendonk et al. 2006, 2012).
the top of the Hooggenoeg Formations, and the 3.472 Ga Middle Marker between the base of
the Hooggenoeg and the top of the Komati Formations.

The present article concerns one section of the 3.4 Ga Buck Reef Chert, located in the Onverwacht group of the Barberton greenstone belt in the Kaapvaal craton, South Africa. Its local geological setting is described in the main text.

The Pilbara Craton is described as geologically equivalent to the Kaapvaal Craton. Detailed lithostratigraphic descriptions of the North Pilbara Terrain are published in (van Kranendonk et al. 2002) and revised in (van Kranendonk et al. 2006, 2007, 2012, 2019) with a presentation of 20 greenstone belts in (van Kranendonk et al. 2006 Fig.4, Hickman et al. 2021 Fig.8). The exposed 530 km x 230 km northern part of the craton consists of the oldest 3.53-3.17 Ga East Pilbara Terrane, EPT. The proposed 3.53-3.42 Ga mantle plume activity resulted in a volcanic plateau and a lithospheric keel.

A recent report describes the East Pilbara Craton (Hickman 2021 table 1 p.10, p.15, Fig.6). It is composed of eight tectonic units including **1:** the 3.8-3.53 Ga Early Crust, which forms a basement for the Pilbara Supergroup. **2:** the Paleoarchean 3.530-3.223 Ga granite-greenstone terrane of the Pilbara Supergroup, which includes the 3.53-3.427 Ga Warrawoona Group, also named the Warrawoona large igneous province, LIP. The Warrawoona Group is composed of the Talga-Talga Subgroup with the 3.481-3.477 Ga Dresser/McPhee Formation, the Coongan Subgroup with the 3.474-3.449 Ga Duffer Formation and its 3.46 Ga Marble Bar Chert member, the Salgash Subgroup with the 3.459-3.440 Ga Apex Basalt Formation and the 3.448-3.427 Ga Panorama Formation. The 3.426-3.350 Ga Strelley Pool Formation, SPF, "overlies a regional unconformity between the two large igneous provinces represented by the Warrawoona and the Kelly Groups" (Hickman et al. 2021 p.72). The ~100 m thick Strelley Pool Formation outcrops in approximately 9 greenstone belts, as imaged within the stratigraphy of the Pilbara Supergroup in (Hickman et al. 2021 Fig.31 p.74). The "3426-3350 Ma, sedimentary deposition of the Strelley Pool Formation and Buck Reef Chert during a contemporaneous c.75 Ma break in volcanic activity" is drawn in (Hickman et al. 2021 Fig.4). **3:** The 3.066-2.930 Ga De Grey Supergroup which includes the Gorge Creek Group with the 3.066-3.022 Ga Farrel Quartzite. The Farrel Quartzite is composed of mafic to ultramafic volcanoclastic layers, evaporite beds and black chert layers (Sugitani et al. 2007).

The Dresser Formation is exposed in the granite-greenstone belt North Pole Dome, located at the center of the EPT. It is detailed in (Djokic 2015 thesis, Djokic et al. 2017). In some places, the EPT is unconformably overlain by the Neoarchean 2.775-2.629 Ga Fortescue Group and the 2.629-2.445 Ga Neoarchean to early Paleoproterozoic Hamersley Group. "The Fortescue Group is a succession of flood basalt and sedimentary rocks deposited on the southern margin of the Pilbara Craton from ~2.78 Ga to ~2.63 Ga, during one or more periods of rifting associated with extensive volcanism" (Flannery et al. 2014 Fig.1 and refs therein). It unconformably overlies the granite-greenstone rocks and includes the Jeerinah Formation.

Subgroups and Formations are visualized in the geological maps drawn in (Hickman 2021 Fig.5 and p.189, van Kranendonk et al. 2008 Fig.1) together with the dome and keel structure of the East Pilbara Terrane which is distributed in eleven granitic domes separated by fault, tectonic and shear zones and a corridor. The domes are composed of ovoid granitic cores surrounded by greenstone belts (Hickman 2021 Fig.8 and cover image). The "granitoid complexes are nearly vertical cylinders extending to depths of 14 km" (van Kranendonk et al. 2002 p.697, van Kranendonk et al. 2004 p.184). They have been divided into suites and supersuites that were emplaced 3.5-3.165 Ga ago during the period of mantle plume activities. The greenstones are older volcanic and sedimentary rocks that were emplaced before 3.5 Ga ago and subsequently strongly affected by deformation and faulting (van Kranendonk et al. 2006, 2012).
The Gunflint Formation, which is discussed below for comparison is dated to 1.88 Ga in age. The flint, in other words, the chert, outcrops in several localities of the USA and Canada, on the northern-western shore of Lake Superior (Fralik et al. 2002). It was unconformably deposited on granite-greenstone Neoarchean basement rocks. Centimeter stromatolitic columns with interspersed oncoids and ooids are observed in the black chert of large stromatolitic domes, up to 1 m in diameter. They appear likewise, a few hundred meters away, in stromatolitic layers or horizons located at the base of granular ironstone (Wacey et al. 2021).

# Raman and HRTEM profiles of disordered graphitic carbon

## *The Raman profile of the BARB3_23B carbon matter*

Since the Tuinstra and Koenig (1970) Raman report, at 488 nm laser wavelength, many authors have recorded Raman spectra of disordered graphite in various objects. Nemanich and Solin (1977, 1979) described that the second-order spectrum at 488 nm broadens noticeably with a decrease in crystal size. A strong feature appears at 2710 cm⁻¹ (S2 peak) weaker features appear at 2450 cm⁻¹ (S1 peak) and 3250 cm⁻¹ (S4 peak) for crystalline graphite, and a fourth peak appears at 2950 cm⁻¹ (S3 peak) with medium intensity for glassy carbon. Beny-Bassez and Rouzaud (1985, Fig.14) showed that the G and D band intensities increase with the rank of the coal, which is the amount of carbon contained in the coal and the amount of heat that the coal can produce. Wopenka and Pasteris (1993) reported the structural order of carbon matter from kerogens to granulite-facies graphite. They described the additional disorder-induced bands that appear in the Raman spectra as a strong disorder D peak at ~1355 cm⁻¹, associated with a shoulder at ~1622cm⁻¹ on the ordered peak that was named the "O" peak in 1993. They also show the direct relation between the decrease in the degree of ordering in graphite and the broadening of the second-order peaks.

Graphitic carbon is characterized by several peaks. "*The three most important features in the Raman spectrum of graphite are the G peak at ~1580 cm⁻¹, the D peak at ~1350 cm⁻¹ and the 2D peak at ~2700 cm⁻¹*" (Beyssac and Lazzeri 2012 Fig.1). With a 514.5 nm laser, the D₂ band at ~1620 cm⁻¹, also named D', appears as a shoulder on the G band or smooths the G peak to make it appear at ~1600 cm⁻¹ instead of 1582 cm⁻¹, D₃ appears at ~1500 cm⁻¹, D₄ at ~1200 cm⁻¹, D + D'' at 2450 cm⁻¹, 2D (or G') at ~2700 cm⁻¹, D + D' (earlier assigned to D+G) at ~2970 cm⁻¹, 2D' at 3240 cm⁻¹, and 2D + G at 4300 cm⁻¹. The D₄ peak is composed of three components with intensities that are a function of the carbon allotropy and of the energy of the excitation laser: the dispersive D'' band appearing between 1050 and 1150 cm⁻¹ as the excitation energy decreases, the nondispersive D* at 1200 cm⁻¹ and the D** exhibiting a weak dispersion between 1220 and 1260 cm⁻¹ (Couzi et al. 2016). The spectrum of a graphite monocrystal, presented in (Beyssac and Lazzeri 2012 Fig.1), displays the G band and an intense 2D band but not the D or D' bands.

Raman profiles are described using phonon modes, which are the crystal lattice vibrations consecutive to atom displacements and which correspond to the irreducible representation of the crystal symmetry group. "*Phonons and electrons (are) coupled by the double resonance mechanism*" (Merlen et al. 2017). The above cited peaks are detailed and illustrated in (Tan et al. 2001 Table II, Beyssac et al. 2002 Fig. 5, Lahfid et al. 2010 Fig. 2 (D₁ to D₄), Beyssac and Lazzeri 2012 Table 1, Couzi et al. 2016 Fig. 1, Merlen et al. 2017, Wu et al. 2018 Fig. 3, Kane 2021 Fig.3.10 p.126). The G band is associated with the vibration of the sp² carbon atoms located in the plane of the hexagonal lattice of the graphene layers in the graphite structure, and the D band is associated with the disorder caused by defects in the sp² structure and the presence of heteroatoms.
The Gunflint Formation, which is discussed below for comparison is dated to 1.88 Ga in age. The flint, in other words, the chert, outcrops in several localities of the USA and Canada, on the northern-western shore of Lake Superior (Fralik et al. 2002). It was unconformably deposited on granite-greenstone Neoarchean basement rocks. Centimeter stromatolitic columns with interspersed oncoids and ooids are observed in the black chert of large stromatolitic domes, up to 1 m in diameter. They appear likewise, a few hundred meters away, in stromatolitic layers or horizons located at the base of granular ironstone (Wacey et al. 2021).

# Raman and HRTEM profiles of disordered graphitic carbon

## *The Raman profile of the BARB3_23B carbon matter*

Since the Tuinstra and Koenig (1970) Raman report, at 488 nm laser wavelength, many authors have recorded Raman spectra of disordered graphite in various objects. Nemanich and Solin (1977, 1979) described that the second-order spectrum at 488 nm broadens noticeably with a decrease in crystal size. A strong feature appears at 2710 cm⁻¹ (S2 peak) weaker features appear at 2450 cm⁻¹ (S1 peak) and 3250 cm⁻¹ (S4 peak) for crystalline graphite, and a fourth peak appears at 2950 cm⁻¹ (S3 peak) with medium intensity for glassy carbon. Beny-Bassez and Rouzaud (1985, Fig.14) showed that the G and D band intensities increase with the rank of the coal, which is the amount of carbon contained in the coal and the amount of heat that the coal can produce. Wopenka and Pasteris (1993) reported the structural order of carbon matter from kerogens to granulite-facies graphite. They described the additional disorder-induced bands that appear in the Raman spectra as a strong disorder D peak at ~1355 cm⁻¹, associated with a shoulder at ~1622cm⁻¹ on the ordered peak that was named the "O" peak in 1993. They also show the direct relation between the decrease in the degree of ordering in graphite and the broadening of the second-order peaks.

Graphitic carbon is characterized by several peaks. "*The three most important features in the Raman spectrum of graphite are the G peak at ~1580 cm⁻¹, the D peak at ~1350 cm⁻¹ and the 2D peak at ~2700 cm⁻¹*" (Beyssac and Lazzeri 2012 Fig.1). With a 514.5 nm laser, the D₂ band at ~1620 cm⁻¹, also named D', appears as a shoulder on the G band or smooths the G peak to make it appear at ~1600 cm⁻¹ instead of 1582 cm⁻¹, D₃ appears at ~1500 cm⁻¹, D₄ at ~1200 cm⁻¹, D + D'' at 2450 cm⁻¹, 2D (or G') at ~2700 cm⁻¹, D + D' (earlier assigned to D+G) at ~2970 cm⁻¹, 2D' at 3240 cm⁻¹, and 2D + G at 4300 cm⁻¹. The D₄ peak is composed of three components with intensities that are a function of the carbon allotropy and of the energy of the excitation laser: the dispersive D'' band appearing between 1050 and 1150 cm⁻¹ as the excitation energy decreases, the nondispersive D* at 1200 cm⁻¹ and the D** exhibiting a weak dispersion between 1220 and 1260 cm⁻¹ (Couzi et al. 2016). The spectrum of a graphite monocrystal, presented in (Beyssac and Lazzeri 2012 Fig.1), displays the G band and an intense 2D band but not the D or D' bands.

Raman profiles are described using phonon modes, which are the crystal lattice vibrations consecutive to atom displacements and which correspond to the irreducible representation of the crystal symmetry group. "*Phonons and electrons (are) coupled by the double resonance mechanism*" (Merlen et al. 2017). The above cited peaks are detailed and illustrated in (Tan et al. 2001 Table II, Beyssac et al. 2002 Fig. 5, Lahfid et al. 2010 Fig. 2 (D₁ to D₄), Beyssac and Lazzeri 2012 Table 1, Couzi et al. 2016 Fig. 1, Merlen et al. 2017, Wu et al. 2018 Fig. 3, Kane 2021 Fig.3.10 p.126). The G band is associated with the vibration of the sp² carbon atoms located in the plane of the hexagonal lattice of the graphene layers in the graphite structure, and the D band is associated with the disorder caused by defects in the sp² structure and the presence of heteroatoms.
The descriptions of the Raman profiles of graphitic carbon are usually specified with values of Raman shifts for the peaks, of D and G peak intensity ratios I<sub>D</sub>/I<sub>G</sub> also named R1, of FWHMs, of D/G FWHMs ratios, of peak area ratios A<sub>D</sub>/A<sub>(D+G+D')</sub> also named R2 and A<sub>D1</sub>/A<sub>(D1+G+D2)</sub>.

In the present study, as described in the main text, all Raman spectra of the BARB3_23B carbon matter were recorded with a 532 nm laser on single points, along individual lines and along lines forming maps. They all display two well-resolved intense peaks at 1348 ± 5 cm<sup>-1</sup> and 1601 ± 5 cm<sup>-1</sup> and three second order peaks at ~2677 cm<sup>-1</sup>, 2923 cm<sup>-1</sup> and 3200 cm<sup>-1</sup>, which are assigned to the D and G bands, and the 2D, (D+D<sub>2</sub>), 2D<sub>2</sub> bands of disordered graphitic carbon, respectively. The D<sub>4</sub> band at ~1200 cm<sup>-1</sup> is absent. The D<sub>2</sub> (or D') band at 1620 cm<sup>-1</sup> appears connected to the 1582 cm<sup>-1</sup> G band leading to a peak at 1601 cm<sup>-1</sup>. The D<sub>3</sub> band at ~1500 cm<sup>-1</sup> may or may not be present. The Raman specific parameters that I calculate graphically by hand are ~1.3 ± 0.1 for I<sub>D</sub>/I<sub>G</sub>, ~70 ± 4 cm<sup>-1</sup> for the D band FWHM, ~50 ± 2 cm<sup>-1</sup> for the G band FWHM, and ~0.67 for the D/(D+G+D') ratio, also named the R2 area ratio.

In the following sections, the Raman spectra of the Buck Reef BARB3_23B carbon matter are
compared with spectra that display the same line profiles and that were recorded mainly with
532 nm or 514 nm laser beams, on samples from outcrops and drilled cores.

The BARB3_23B carbon matter and temperature

By comparison with metasediments, the Raman profile of the disordered graphitic carbon contained in the Buck Reef BARB3_23B sample approaches the profile of the metasediment which was submitted to temperatures of ~335°C.

The concept of metamorphic facies was developed by P. Eskola in 1915 (Winter 2010 chapter 25) to represent the mineral assemblages of a rock at specific temperature and pressure. Metamorphic facies are assigned to rocks after observation of their mineral assemblages. Various metamorphic facies are described in (Notre Dame University 2017), and their most common minerals are listed in (Klein and Philpotts 2017, Table 15.1 p.479).

Yui et al (1996) studied the carbon matter of pelitic samples from the metamorphic belt of Taiwan with Raman spectroscopy and a 514.5 nm laser. I calculate, from their Table 1, the average Raman parameters of the two samples S-114 and S-120, which are of greenschist facies (chlorite zone) and which display no 2450 cm⁻¹ peak in their Fig.2. The D line appears at 1349 ± 2 cm⁻¹, G at 1593 cm⁻¹, S2 at ~2697 ± 3 cm⁻¹, S3 at 2941 ± 3 cm⁻¹, and S4 at 3202 ± 4 cm⁻¹. The D FWHM is 79 ± 8 cm⁻¹, G FWHM 65 cm⁻¹, D/G FWHM ratio ~1.21 ± 0.12, I<sub>D</sub>/I<sub>G</sub> intensity ratio ~1.29 ± 0.08, area ratio ~1.50 ± 0.05, and the S2/G area ratio 0.93 ± 0.06. The spectrum is very distinct from those of the zeolite facies and greenschist facies in the biotite zone. The greenschist biotite facies shows a more intense G peak with an I<sub>D</sub>/I<sub>G</sub> of ~0.52, a very strong peak at 2700 cm⁻¹ and a very weak peak at 2450 cm⁻¹. The prehnite-pumpellyite facies shows an I<sub>D</sub>/I<sub>G</sub> of ~0.68, a foot on the D peak that I calculate at ~1215 cm⁻¹, and second-order peaks at 2688, 2939 and 3195 cm⁻¹. The three second-order peaks are not well resolved; however, their profile approaches the BARB3_23B profile, which appears to be between the greenschist metamorphic facies in the chlorite zone and the prehnite-pumpellyite facies. Chlorite is stable in the temperature range of ~150-350°C, and biotite is stable in the range of 425-625°C (Earle 2019, p244, Fig.7.4.1). At pressures up to 100 MPa, the prehnite-pumpellyite facies is represented in the range ~210-270°C and the greenschist facies in the range ~270-330°C
The descriptions of the Raman profiles of graphitic carbon are usually specified with values of Raman shifts for the peaks, of D and G peak intensity ratios I<sub>D</sub>/I<sub>G</sub> also named R1, of FWHMs, of D/G FWHMs ratios, of peak area ratios A<sub>D</sub>/A<sub>(D+G+D')</sub> also named R2 and A<sub>D1</sub>/A<sub>(D1+G+D2)</sub>.

In the present study, as described in the main text, all Raman spectra of the BARB3_23B carbon matter were recorded with a 532 nm laser on single points, along individual lines and along lines forming maps. They all display two well-resolved intense peaks at 1348 ± 5 cm<sup>-1</sup> and 1601 ± 5 cm<sup>-1</sup> and three second order peaks at ~2677 cm<sup>-1</sup>, 2923 cm<sup>-1</sup> and 3200 cm<sup>-1</sup>, which are assigned to the D and G bands, and the 2D, (D+D<sub>2</sub>), 2D<sub>2</sub> bands of disordered graphitic carbon, respectively. The D<sub>4</sub> band at ~1200 cm<sup>-1</sup> is absent. The D<sub>2</sub> (or D') band at 1620 cm<sup>-1</sup> appears connected to the 1582 cm<sup>-1</sup> G band leading to a peak at 1601 cm<sup>-1</sup>. The D<sub>3</sub> band at ~1500 cm<sup>-1</sup> may or may not be present. The Raman specific parameters that I calculate graphically by hand are ~1.3 ± 0.1 for I<sub>D</sub>/I<sub>G</sub>, ~70 ± 4 cm<sup>-1</sup> for the D band FWHM, ~50 ± 2 cm<sup>-1</sup> for the G band FWHM, and ~0.67 for the D/(D+G+D') ratio, also named the R2 area ratio.

In the following sections, the Raman spectra of the Buck Reef BARB3_23B carbon matter are
compared with spectra that display the same line profiles and that were recorded mainly with
532 nm or 514 nm laser beams, on samples from outcrops and drilled cores.

The BARB3_23B carbon matter and temperature

By comparison with metasediments, the Raman profile of the disordered graphitic carbon contained in the Buck Reef BARB3_23B sample approaches the profile of the metasediment which was submitted to temperatures of ~335°C.

The concept of metamorphic facies was developed by P. Eskola in 1915 (Winter 2010 chapter 25) to represent the mineral assemblages of a rock at specific temperature and pressure. Metamorphic facies are assigned to rocks after observation of their mineral assemblages. Various metamorphic facies are described in (Notre Dame University 2017), and their most common minerals are listed in (Klein and Philpotts 2017, Table 15.1 p.479).

Yui et al (1996) studied the carbon matter of pelitic samples from the metamorphic belt of Taiwan with Raman spectroscopy and a 514.5 nm laser. I calculate, from their Table 1, the average Raman parameters of the two samples S-114 and S-120, which are of greenschist facies (chlorite zone) and which display no 2450 cm⁻¹ peak in their Fig.2. The D line appears at 1349 ± 2 cm⁻¹, G at 1593 cm⁻¹, S2 at ~2697 ± 3 cm⁻¹, S3 at 2941 ± 3 cm⁻¹, and S4 at 3202 ± 4 cm⁻¹. The D FWHM is 79 ± 8 cm⁻¹, G FWHM 65 cm⁻¹, D/G FWHM ratio ~1.21 ± 0.12, I<sub>D</sub>/I<sub>G</sub> intensity ratio ~1.29 ± 0.08, area ratio ~1.50 ± 0.05, and the S2/G area ratio 0.93 ± 0.06. The spectrum is very distinct from those of the zeolite facies and greenschist facies in the biotite zone. The greenschist biotite facies shows a more intense G peak with an I<sub>D</sub>/I<sub>G</sub> of ~0.52, a very strong peak at 2700 cm⁻¹ and a very weak peak at 2450 cm⁻¹. The prehnite-pumpellyite facies shows an I<sub>D</sub>/I<sub>G</sub> of ~0.68, a foot on the D peak that I calculate at ~1215 cm⁻¹, and second-order peaks at 2688, 2939 and 3195 cm⁻¹. The three second-order peaks are not well resolved; however, their profile approaches the BARB3_23B profile, which appears to be between the greenschist metamorphic facies in the chlorite zone and the prehnite-pumpellyite facies. Chlorite is stable in the temperature range of ~150-350°C, and biotite is stable in the range of 425-625°C (Earle 2019, p244, Fig.7.4.1). At pressures up to 100 MPa, the prehnite-pumpellyite facies is represented in the range ~210-270°C and the greenschist facies in the range ~270-330°C
(Winter 2010). The processed temperature of the Buck Reef BARB3_23B carbon matter can therefore be described as ~300 °C.

Changes in Raman profiles of carbon matter at 514.5 nm, were shown to be sensitive to variations in metamorphic grade and usable as a geothermometer of the maximum temperature reached during metamorphism, from low-grade metamorphism, (~330°C) to high-grade metamorphism (~650°C) (Beyssac et al. 2002). The lowest metamorphic grade samples A1 to A6, from the pumpellyite-bearing chlorite zone along the Asemi River, Japan, (Beyssac et al. 2002 Fig.3, Table 2, A4 in Fig.6), show symmetrical peaks with a D band at ~1350 cm⁻¹, G band at ~1594 ± 3 cm⁻¹, R1 (ID/IG) of ~1.7 ± 4, G FWHM of ~51 ± 2 cm⁻¹, and R2 (D1/D1+G+D2) area ratio of ~0.70. The second-order region displays peaks at ~2700 cm⁻¹ and ~2900 cm⁻¹ with a higher intensity for the ~2700 cm⁻¹ peak. The first-order values are in accordance with those of the Buck Reef BARB3_23B and correspond to a metamorphic temperature of 343°C, that I calculate for the Buck Reef R2 ratio of 0.67 (cf above BARB3_23B Raman profile), according to the linear correlation established by (Beyssac et al. 2002 eq.1 p.868) between R2 and T. A calculation with R2 0.70 (the R2 of the A4 sample) produces a temperature of 329°C. However, the second-order region for Buck Reef displays a higher intensity for the 2900 cm⁻¹ than for the 2700 cm⁻¹ peak. Applying the Beyssac observation "*With increasing metamorphic grade, the relative intensity of the S2 (2900 cm⁻¹) band decreases*" (Beyssac et al. 2002 p.864), leads to the conclusion that the Buck Reef BARB3_23B carbon matter has experienced temperatures lower than for the A4 sample, 329°C. The two modes of calculations lead to a processed temperature for the BRC BARB3_23B of either 343°C or below 329°C.

Raman spectra of graphitic carbon sampled in metamorphic rocks of the Glarus Alps, central Swiss, from low-greenschist grade (~200°C peak temperature) to UHP eclogite (~700°C peak temperature) are shown in (Lahfid et al. 2010 Fig.3, Beyssac and Lazzeri 2012 Fig.8, Buseck and Beyssac 2014 Fig.5). Considering the increase in metamorphic temperature, the Raman shift of the (G+D') peak decreases from ~1600 to 1580 cm⁻¹, and the width narrows down to ~20 cm⁻¹. Fitting procedures on the D and G bands including the shoulders, lead to five peaks, D₁ ~1350 cm⁻¹, D₂ ~1620 cm⁻¹, D₃ ~1500 cm⁻¹, D₄ ~1170 cm⁻¹ and G ~1580 cm⁻¹. The intensities of these five peaks vary regularly. When metamorphic temperature increases, the G peak residing at ~1600 cm⁻¹ for what is described as low-greenschist ~200°C facies moves towards 1580 cm⁻¹ at low-blueschist ~360°C facies, and the D₂ peak starts to appear. The D₂ peak disappears in the eclogite ~540°C facies, leaving a narrow G peak at 1580 cm⁻¹. The D₁ peak narrows and weakens continuously. The D₃ peak decreases from the low-greenschist ~200°C facies and disappears entirely at blueschist ~380°C. The D₄ peak widely broadens the D₁ peak at low-greenschist ~200°C and ~250°C facies, starts to weaken at greenschist ~300°C, becomes very weak at low-blueschist ~330°C, extremely weak at low-blueschist ~360°C and disappears entirely at blueschist ~380°C facies. The Buck Reef BARB3_23B spectra resemble those described as low-blueschist facies with a peak temperature of ~330°C, apart from the very weak foot peak at ~1170 cm⁻¹ which is absent in the Buck Reef. The low-blueschist facies with a peak temperature of ~360°C can also correspond to Buck Reef apart from the very weak shoulder peak at ~1620 cm⁻¹. Both 330°C and 360°C low-blueschist facies show second-order spectra with very weak broad peaks. The low-blueschist ~330°C facies displays one ~2900 cm⁻¹ peak slightly more intense than the ~2700 cm⁻¹ and the ~3200 cm⁻¹ peaks, which is a profile coherent with the Raman spectrum of the Buck Reef carbon matter, while the low-blueschist ~360°C facies displays a decrease in intensity from ~2700 cm⁻¹ to ~2900 cm⁻¹ to ~3200 cm⁻¹. By comparison, the BARB3_23B graphitic carbon appears to have been submitted to temperatures of ~335°C or ~340°C, corresponding to the metamorphic grade described as low-blueschist facies.
(Winter 2010). The processed temperature of the Buck Reef BARB3_23B carbon matter can therefore be described as ~300 °C.

Changes in Raman profiles of carbon matter at 514.5 nm, were shown to be sensitive to variations in metamorphic grade and usable as a geothermometer of the maximum temperature reached during metamorphism, from low-grade metamorphism, (~330°C) to high-grade metamorphism (~650°C) (Beyssac et al. 2002). The lowest metamorphic grade samples A1 to A6, from the pumpellyite-bearing chlorite zone along the Asemi River, Japan, (Beyssac et al. 2002 Fig.3, Table 2, A4 in Fig.6), show symmetrical peaks with a D band at ~1350 cm⁻¹, G band at ~1594 ± 3 cm⁻¹, R1 (ID/IG) of ~1.7 ± 4, G FWHM of ~51 ± 2 cm⁻¹, and R2 (D1/D1+G+D2) area ratio of ~0.70. The second-order region displays peaks at ~2700 cm⁻¹ and ~2900 cm⁻¹ with a higher intensity for the ~2700 cm⁻¹ peak. The first-order values are in accordance with those of the Buck Reef BARB3_23B and correspond to a metamorphic temperature of 343°C, that I calculate for the Buck Reef R2 ratio of 0.67 (cf above BARB3_23B Raman profile), according to the linear correlation established by (Beyssac et al. 2002 eq.1 p.868) between R2 and T. A calculation with R2 0.70 (the R2 of the A4 sample) produces a temperature of 329°C. However, the second-order region for Buck Reef displays a higher intensity for the 2900 cm⁻¹ than for the 2700 cm⁻¹ peak. Applying the Beyssac observation "*With increasing metamorphic grade, the relative intensity of the S2 (2900 cm⁻¹) band decreases*" (Beyssac et al. 2002 p.864), leads to the conclusion that the Buck Reef BARB3_23B carbon matter has experienced temperatures lower than for the A4 sample, 329°C. The two modes of calculations lead to a processed temperature for the BRC BARB3_23B of either 343°C or below 329°C.

Raman spectra of graphitic carbon sampled in metamorphic rocks of the Glarus Alps, central Swiss, from low-greenschist grade (~200°C peak temperature) to UHP eclogite (~700°C peak temperature) are shown in (Lahfid et al. 2010 Fig.3, Beyssac and Lazzeri 2012 Fig.8, Buseck and Beyssac 2014 Fig.5). Considering the increase in metamorphic temperature, the Raman shift of the (G+D') peak decreases from ~1600 to 1580 cm⁻¹, and the width narrows down to ~20 cm⁻¹. Fitting procedures on the D and G bands including the shoulders, lead to five peaks, D₁ ~1350 cm⁻¹, D₂ ~1620 cm⁻¹, D₃ ~1500 cm⁻¹, D₄ ~1170 cm⁻¹ and G 1580 cm⁻¹. The intensities of these five peaks vary regularly. When metamorphic temperature increases, the G peak residing at ~1600 cm⁻¹ for what is described as low-greenschist ~200°C facies moves towards 1580 cm⁻¹ at low-blueschist ~360°C facies, and the D₂ peak starts to appear. The D₂ peak disappears in the eclogite ~540°C facies, leaving a narrow G peak at 1580 cm⁻¹. The D₁ peak narrows and weakens continuously. The D₃ peak decreases from the low-greenschist ~200°C facies and disappears entirely at blueschist ~380°C. The D₄ peak widely broadens the D₁ peak at low-greenschist ~200°C and ~250°C facies, starts to weaken at greenschist ~300°C, becomes very weak at low-blueschist ~330°C, extremely weak at low-blueschist ~360°C and disappears entirely at blueschist ~380°C facies. The Buck Reef BARB3_23B spectra resemble those described as low-blueschist facies with a peak temperature of ~330°C, apart from the very weak foot peak at ~1170 cm⁻¹ which is absent in the Buck Reef. The low-blueschist facies with a peak temperature of ~360°C can also correspond to Buck Reef apart from the very weak shoulder peak at ~1620 cm⁻¹. Both 330°C and 360°C low-blueschist facies show second-order spectra with very weak broad peaks. The low-blueschist ~330°C facies displays one ~2900 cm⁻¹ peak slightly more intense than the ~2700 cm⁻¹ and the ~3200 cm⁻¹ peaks, which is a profile coherent with the Raman spectrum of the Buck Reef carbon matter, while the low-blueschist ~360°C facies displays a decrease in intensity from ~2700 cm⁻¹ to ~2900 cm⁻¹ to ~3200 cm⁻¹. By comparison, the BARB3_23B graphitic carbon appears to have been submitted to temperatures of ~335°C or ~340°C, corresponding to the metamorphic grade described as low-blueschist facies.
Raman spectra of carbonaceous material, CM, from Southwest Japan show metamorphic temperatures that are classified into four types: low grade (150°-280°C), medium grade (280°-400°C), high grade (400°-650°C) and well-crystallized graphite (>650°C). "*The Raman spectra of low-grade CM exhibit features typical of amorphous carbon...* CM starts to *transform from amorphous carbon to crystallized graphite at around 280°C*" (Kouketsu et al. 2014). Raman FWHMs at 532 nm, are shown inversely correlated to metamorphic temperatures and usable as a geothermometer of the maximum temperature reached during metamorphism, from low-grade metamorphism, ~150°C, up to ~400°C. Their Fig. 2 shows that the Raman profile of the Buck Reef BARB3_23B carbon matter lies between the samples with metamorphic temperatures of 301° and 340°C, and their $I_G/I_D$ varies from 1.8 to 0.5. With an $I_G/I_D$ of 0.77, the inverse of the above reported value for $I_D/I_G$ of 1.3, the BARB3_23B carbon matter has a profile at ~20% of the 340°C sample. It can be deduced that the BARB3_23B sample can have been submitted to a temperature of ~332°C. The FWHMs of the Kouketsu 301° and 340°C G peaks vary from 35 to 55 cm⁻¹. With a G-FWHM of 50 cm⁻¹, the BARB3_23B carbon matter has a profile at ~25% of the 340°C sample. It can be deduced that the BARB3_23B sample can have been submitted to a temperature of ~330°C.

Compared with the Raman spectra of carbon matter submitted to various metamorphic temperatures, the Buck Reef BARB3_23B sample can be described as submitted to temperatures of ~335°C, temperature in the domain of high subcritical water, where the anoxic strongly basic oxidation of ferrous iron can proceed.

*The BARB3_23B carbon matter and Archean graphitic carbon*

The carbon matter from the 3.4 Ga Buck Reef BARB3_23B sample produces Raman spectra that resemble those from 3.5 to 2.7 Ga Archean BIFs in the Kaapvaal and Pilbara cratons.

South Africa and Western Australia contain well-preserved Archean segments of granite-greenstone crust that have been studied for their carbon matter. The Raman spectra presented below were recorded by other authors on samples of rocks from geological sites described in the above geological setting section. Raman first-order spectra recorded at 532 nm on single points of the carbon matter observed either on the mineral matrix or on the chemically extracted kerogen from black chert of the 3.0 Ga Farrel Quartzite at Mount Grant locality in the Goldsworthy greenstone belt were shown to be identical (Bekaert et al. 2018), and they both resemble the BARB3_23B carbon matter profile. Consequently, both methods of carbon matter observation, on thin sections and from chemically extracted kerogen, will be considered in the next paragraphs.

Raman 514.5 nm spectra of kerogen chemically isolated with the HF/HCl method from the 3.4 Ga Strelley Pool chert outcropping in the North Pole area of the Pilbara craton profiles (Marshall et al. 2007 Fig.6, Marshall et al. 2010 Fig.3) shows resemblance both in the first- and second-order regions with the BARB3_23B Buck Reef carbon matter, except for the D band foot at low wavenumber that I calculate at the position ~1179 cm⁻¹, suggesting the $D_4$ peak.

Kerogen chemically isolated with the HF/HCl method from outcropping cherts of the BGB 3.472 Ga Middle Marker and 3.416 Ga Buck Reef and of the Pilbara 3.48 Ga Dresser Formation in the Talga-Talga subgroup, and the 2.7 Ga Jeerinah Formation in the Fortescue group show carbon Raman profiles at 514 nm that are similar to those of the BARB3_23B Buck Reef, considering D and G peak positions, intensity ratios, and FWHMs. The Raman profiles of the samples that are dated between 3.5 and 2.7 Ga, form a group that appears different from the group dated between 1.9 and 0.4 Ga, the width of the 1.9 Ga Gunflint D band, as well as
Raman spectra of carbonaceous material, CM, from Southwest Japan show metamorphic temperatures that are classified into four types: low grade (150°-280°C), medium grade (280°-400°C), high grade (400°-650°C) and well-crystallized graphite (>650°C). "*The Raman spectra of low-grade CM exhibit features typical of amorphous carbon...* CM starts to *transform from amorphous carbon to crystallized graphite at around 280°C" (Kouketsu et al. 2014). Raman FWHMs at 532 nm, are shown inversely correlated to metamorphic temperatures and usable as a geothermometer of the maximum temperature reached during metamorphism, from low-grade metamorphism, ~150°C, up to ~400°C. Their Fig. 2 shows that the Raman profile of the Buck Reef BARB3_23B carbon matter lies between the samples with metamorphic temperatures of 301° and 340°C, and their $I_G/I_D$ varies from 1.8 to 0.5. With an $I_G/I_D$ of 0.77, the inverse of the above reported value for $I_D/I_G$ of 1.3, the BARB3_23B carbon matter has a profile at ~20% of the 340°C sample. It can be deduced that the BARB3_23B sample can have been submitted to a temperature of ~332°C. The FWHMs of the Kouketsu 301° and 340°C G peaks vary from 35 to 55 cm⁻¹. With a G-FWHM of 50 cm⁻¹, the BARB3_23B carbon matter has a profile at ~25% of the 340°C sample. It can be deduced that the BARB3_23B sample can have been submitted to a temperature of ~330°C.

Compared with the Raman spectra of carbon matter submitted to various metamorphic temperatures, the Buck Reef BARB3_23B sample can be described as submitted to temperatures of ~335°C, temperature in the domain of high subcritical water, where the anoxic strongly basic oxidation of ferrous iron can proceed.

*The BARB3_23B carbon matter and Archean graphitic carbon*

The carbon matter from the 3.4 Ga Buck Reef BARB3_23B sample produces Raman spectra that resemble those from 3.5 to 2.7 Ga Archean BIFs in the Kaapvaal and Pilbara cratons.

South Africa and Western Australia contain well-preserved Archean segments of granite-greenstone crust that have been studied for their carbon matter. The Raman spectra presented below were recorded by other authors on samples of rocks from geological sites described in the above geological setting section. Raman first-order spectra recorded at 532 nm on single points of the carbon matter observed either on the mineral matrix or on the chemically extracted kerogen from black chert of the 3.0 Ga Farrel Quartzite at Mount Grant locality in the Goldsworthy greenstone belt were shown to be identical (Bekaert et al. 2018), and they both resemble the BARB3_23B carbon matter profile. Consequently, both methods of carbon matter observation, on thin sections and from chemically extracted kerogen, will be considered in the next paragraphs.

Raman 514.5 nm spectra of kerogen chemically isolated with the HF/HCl method from the 3.4 Ga Strelley Pool chert outcropping in the North Pole area of the Pilbara craton profiles (Marshall et al. 2007 Fig.6, Marshall et al. 2010 Fig.3) shows resemblance both in the first- and second-order regions with the BARB3_23B Buck Reef carbon matter, except for the D band foot at low wavenumber that I calculate at the position ~1179 cm⁻¹, suggesting the $D_4$ peak.

Kerogen chemically isolated with the HF/HCl method from outcropping cherts of the BGB 3.472 Ga Middle Marker and 3.416 Ga Buck Reef and of the Pilbara 3.48 Ga Dresser Formation in the Talga-Talga subgroup, and the 2.7 Ga Jeerinah Formation in the Fortescue group show carbon Raman profiles at 514 nm that are similar to those of the BARB3_23B Buck Reef, considering D and G peak positions, intensity ratios, and FWHMs. The Raman profiles of the samples that are dated between 3.5 and 2.7 Ga, form a group that appears different from the group dated between 1.9 and 0.4 Ga, the width of the 1.9 Ga Gunflint D band, as well as
those of younger cherts, being more than twice those of the 3.5-2.7 Ga range (Bourbin et al. 2012 Fig.7, Table 4). The observation of their Fig. 6, which shows the EPR electron paramagnetic resonance linewidth as a function of chert ages, leads to the conclusion that Middle Marker, Buck Reef, Dresser and Jeerinah kerogen are likewise grouped together, with Gunflint being located slightly apart from the group. The BARB3_23B Buck Reef carbon spectra resemble those of the Paleoarchean-Mesoarchean 3.5 to 2.7 Ga group.

Raman profiles were recorded with a 532 nm laser for terrestrial cherts of various ages, including the 3.5 Ga Apex, the 3.4 Ga Strelley Pool, the 2.7 Ga Tumbiana carbonate and several 1.9 Ga to 0.4 Ga cherts (Bower et al. 2013). Two groups of Raman profiles can likewise be observed: the 3.5 to 2.7 Ga group and a younger one. The BARB3_23B Buck Reef profiles correspond to those of the Archean group except for the ~1200 cm⁻¹ foot, which corresponds most likely to the D₄ peak, and which may suggest that Apex, Strelley Pool and Tumbiana were submitted to lower peak temperatures than the ~335°C of Buck Reef.

Raman single spectra at 514.5 nm on kerogen isolated from 17 outcropping cherts likewise show two groups of profiles, considering the D FWHMs, *ID*/*IG*, and D FWHMs versus *ID*/*IG*: the 3.5 to 2.65 Ga group composed of cherts from the 3.48 Ga Dresser, 3.472 Ga Middle Marker, 3.33 Ga Josefsdal, 3.0 Ga Farrel Quartzite, 2.65 Ga Rietgat-Ventersdorp Supergroup, and the 1.9 to 0.05 Ga group (Delarue et al. 2016, Table 2). The BARB3_23B Buck Reef carbon spectra again resemble those of the Archean 3.5 to 2.65 Ga group.

Hofmann et al. (2013) investigated bedded and vein cherts in outcropping samples from the Onverwacht Group, including the Buck Reef Chert, as described in the main text.

Filamentous and spheroidal microstructures usually assigned to biological microfossils or putative microorganisms are observed in some Archean sites. Their carbonaceous material also shows some resemblance in Raman profile with the BARB3_23B. For instance, four different morphologies of carbon matter are presented for the 3.47 Ga BGB Middle Marker in (Hickman-Lewis et al. 2018 Fig.16). I observe 532 nm second-order peaks which vary in intensity, a D₄ peak at ~1200 cm⁻¹ which seems present and a ratio *ID*/*IG* which I calculate as 2.1, 2.1, 2.5 and 1.8, values much higher than for the Buck Reef BARB3_23B.

Raman spectra of the carbon matter recorded at 514.5 nm on thin sections of the black chert from the 3.066-3.022 Ga Farrel Quartzite outcropping on Mount Grant and Mount Goldsworthy (Sugitani et al. 2007 Fig. 8a) resemble those observed on the BARB3_23B BIF. Except for the ~1170 cm⁻¹ foot appearing on the Farrel D band, which can be assigned to the D₄ peak, the Raman values are the same, considering the G and D peak positions, the *ID*/*IG*, and the FWHMs that I calculate to be 61 cm⁻¹ for Farrel G and 77 cm⁻¹ for D. The second-order profiles are also equivalent in peak positions and relative intensities. The Farrel microstructures are described as "thread-like, film-like, spheroidal and lenticular to spindle like". The same morphological shapes are observed in black cherts assigned to the 3.426-3.350 Ga Strelley Pool formation outcropping in the Panorama, Warralong and Goldsworthy greenstone belts, and associated with stromatolites and/or evaporites (Sugitani et al. 2010). These three belts are drawn in (Hickman et al. 2021 Fig.8) and in (van Kranendonk 2006 Fig.4) with Panorama located at n°8, Warralong at n°19 and Goldsworthy at n°20. The Raman spectra of the Strelley Pool microstructures likewise display a very weak foot on the D peak, at a wavenumber that I calculate to be ~1173 cm⁻¹, nonetheless less intense than in Farrel. The ~1620 cm⁻¹ peak appears included in the G peak for the Panorama locality and separated from the G peak for the Goldsworthy locality. By comparison with spectra in (Beyssac and Lazzeri 2012 Fig.8) the Strelley Pool Formation and the Farrel Quartzite appear to have been submitted to peak temperatures slightly lower than those of Buck Reef, with metamorphic grades of low blueschist ~330°C, greenschist ~300°C facies instead of low blueschist ~335°C for the Buck Reef BIF. The thread-like, spheroidal and lenticular to spindle-like microstructures, with carbon
those of younger cherts, being more than twice those of the 3.5-2.7 Ga range (Bourbin et al. 2012 Fig.7, Table 4). The observation of their Fig. 6, which shows the EPR electron paramagnetic resonance linewidth as a function of chert ages, leads to the conclusion that Middle Marker, Buck Reef, Dresser and Jeerinah kerogen are likewise grouped together, with Gunflint being located slightly apart from the group. The BARB3_23B Buck Reef carbon spectra resemble those of the Paleoarchean-Mesoarchean 3.5 to 2.7 Ga group.

Raman profiles were recorded with a 532 nm laser for terrestrial cherts of various ages, including the 3.5 Ga Apex, the 3.4 Ga Strelley Pool, the 2.7 Ga Tumbiana carbonate and several 1.9 Ga to 0.4 Ga cherts (Bower et al. 2013). Two groups of Raman profiles can likewise be observed: the 3.5 to 2.7 Ga group and a younger one. The BARB3_23B Buck Reef profiles correspond to those of the Archean group except for the ~1200 cm⁻¹ foot, which corresponds most likely to the D₄ peak, and which may suggest that Apex, Strelley Pool and Tumbiana were submitted to lower peak temperatures than the ~335°C of Buck Reef.

Raman single spectra at 514.5 nm on kerogen isolated from 17 outcropping cherts likewise show two groups of profiles, considering the D FWHMs, *ID*/*IG*, and D FWHMs versus *ID*/*IG*: the 3.5 to 2.65 Ga group composed of cherts from the 3.48 Ga Dresser, 3.472 Ga Middle Marker, 3.33 Ga Josefsdal, 3.0 Ga Farrel Quartzite, 2.65 Ga Rietgat-Ventersdorp Supergroup, and the 1.9 to 0.05 Ga group (Delarue et al. 2016, Table 2). The BARB3_23B Buck Reef carbon spectra again resemble those of the Archean 3.5 to 2.65 Ga group.

Hofmann et al. (2013) investigated bedded and vein cherts in outcropping samples from the Onverwacht Group, including the Buck Reef Chert, as described in the main text.

Filamentous and spheroidal microstructures usually assigned to biological microfossils or putative microorganisms are observed in some Archean sites. Their carbonaceous material also shows some resemblance in Raman profile with the BARB3_23B. For instance, four different morphologies of carbon matter are presented for the 3.47 Ga BGB Middle Marker in (Hickman-Lewis et al. 2018 Fig.16). I observe 532 nm second-order peaks which vary in intensity, a D₄ peak at ~1200 cm⁻¹ which seems present and a ratio *ID*/*IG* which I calculate as 2.1, 2.1, 2.5 and 1.8, values much higher than for the Buck Reef BARB3_23B.

Raman spectra of the carbon matter recorded at 514.5 nm on thin sections of the black chert from the 3.066-3.022 Ga Farrel Quartzite outcropping on Mount Grant and Mount Goldsworthy (Sugitani et al. 2007 Fig. 8a) resemble those observed on the BARB3_23B BIF. Except for the ~1170 cm⁻¹ foot appearing on the Farrel D band, which can be assigned to the D₄ peak, the Raman values are the same, considering the G and D peak positions, the *ID*/*IG*, and the FWHMs that I calculate to be 61 cm⁻¹ for Farrel G and 77 cm⁻¹ for D. The second-order profiles are also equivalent in peak positions and relative intensities. The Farrel microstructures are described as "thread-like, film-like, spheroidal and lenticular to spindle like". The same morphological shapes are observed in black cherts assigned to the 3.426-3.350 Ga Strelley Pool formation outcropping in the Panorama, Warralong and Goldsworthy greenstone belts, and associated with stromatolites and/or evaporites (Sugitani et al. 2010). These three belts are drawn in (Hickman et al. 2021 Fig.8) and in (van Kranendonk 2006 Fig.4) with Panorama located at n°8, Warralong at n°19 and Goldsworthy at n°20. The Raman spectra of the Strelley Pool microstructures likewise display a very weak foot on the D peak, at a wavenumber that I calculate to be ~1173 cm⁻¹, nonetheless less intense than in Farrel. The ~1620 cm⁻¹ peak appears included in the G peak for the Panorama locality and separated from the G peak for the Goldsworthy locality. By comparison with spectra in (Beyssac and Lazzeri 2012 Fig.8) the Strelley Pool Formation and the Farrel Quartzite appear to have been submitted to peak temperatures slightly lower than those of Buck Reef, with metamorphic grades of low blueschist ~330°C, greenschist ~300°C facies instead of low blueschist ~335°C for the Buck Reef BIF. The thread-like, spheroidal and lenticular to spindle-like microstructures, with carbon
walls, ~50 µm in diameter or length, which are observed in the Archean Farrel Quartzite and the Strelley Pool Formation, resemble morphologically those observed in the Paleoproterozoic 1.88 Ga Gunflint Formation (Lepot et al. 2017), except they are approximately five to ten times larger. Their carbon Raman spectra, as the BARB3_23B Buck Reef spectrum, are different from that of Gunflint, which shows a much wider D peak. Greenalite and siderite are observed inside the quartz matrices of the Gunflint ~5 µm spherical structures with carbon walls (Lepot et al. 2017 Suppl. Figs.). Greenalite is identified inside a cell-like segmented structure (Lepot et al. 2017 Fig.2g-i, position circled in Suppl. Fig. 7c and SAED in Fig.15a). The lattice spacing value of 0.72 nm is determined with selected area electron diffraction, SAED. The cell-like structure is composed of attached spheres, 2 to 5 µm in size, forming a chain. The spheres are rimmed with carbon, which shows open spaces. Greenalite is also identified inside a ~600 nm elongated structure, with the EDXS spectrum shown in Suppl. Fig. 15c and with the Si L<sub>2,3</sub> edge EELS (Electron Energy Loss Spectroscopy) spectrum 1 shown in Suppl. Fig. 15d. Both figures correspond to position 1 in the STEM images of Fig. 3 and Suppl. Fig. 15b in (Lepot et al. 2017). Position 2 of the STEM image shows the same Si L<sub>2,3</sub> edge EELS spectrum, with the addition of a peak at ~106 eV. Fe<sup>II</sup>Fe<sup>III</sup>-greenalite is likewise identified with the Fe L<sub>2,3</sub> edge EELS spectrum of (Lepot et al. 2017 Suppl. Figs.15e, 8g), displaying the Fe<sup>2+</sup> and Fe<sup>3+</sup> peaks at 708.9 eV and 710.5 eV, respectively, with the amount of Fe<sup>3+</sup> being 4.5% of Fe<sub>total</sub>.

The Si L<sub>2,3</sub> edge EELS spectrum 2 of (Lepot et al. 2017 Suppl. Fig.15d) displays four peaks that I calculate by hand at ~106.3, ~108.7, ~115.4 and ~130 eV. I observe that these four peaks correspond to those observed in (Garvie and Craven 1994 Fig. 9) where the Si L<sub>2,3</sub> edges from quartz SiO<sub>2</sub>, talc Mg<sub>3</sub>Si<sub>4</sub>O<sub>10</sub>(OH)<sub>2</sub> and nontronite Na<sub>0.3</sub>Fe<sub>2</sub>((Si,Al)<sub>4</sub>O<sub>10</sub>)(OH)<sub>2</sub>.nH<sub>2</sub>O, "exhibit very similar edge shapes, characterized by the two initial sharp peaks, peaks A (106.3) and B (108.4eV), followed by a sharp peak C (115.0) and a broad peak D (ca 133 eV)". Peak A at 106.3 eV seems to disappear for the three glasses forsterite Mg<sub>2</sub>SiO<sub>4</sub>, fayalite Fe<sub>2</sub>SiO<sub>4</sub> and basaltic glass, as shown in (Garvie and Craven 1999 Fig.4). Like glasses, greenalite, as described by (Guggenheim and Eggleton 1998, Tosca et al. 2016), does not show a structure with long length order. This is probably the reason why peak A at 106.3 eV is absent in the greenalite spectrum of (Lepot et al. 2017 Fig. 15d-1). As noted in the text by Lepot et al "Fe-bearing minerals (siderite and greenalite) occur inside the cells, but not outside". The cells contain quartz matrices. Neither hematite nor magnetite were observed. The cells are rimmed with carbon and the rims show discontinuities and openings.

Another nanoscale analysis of the filamentous structures observed in the 3.46 Ga Apex chert, Western Australia, show that the microstructures are carbon-coated stacks of phyllosilicate crystals. "Each filament is made of multiple plate- or sheet-like grains of phyllosilicate within a matrix of microcrystalline quartz" (Wacey et al. 2016 §3.2). Dark field scanning of an ultrathin (100 nm) slice through a filament shows that "the phyllosilicate mineral contains the elements K, Al, Si, O, Ba and minor Mg" (Wacey et al. 2016 Fig.9). This observation confirms the conclusion of Brasier et al that "the 'microfossils' were in fact carbonaceous mineral rims that formed around recrystallizing grain margins during a complex series of hydrothermal events." (Wacey et al. 2016, Brasier et al. 2002, 2004).

From the comparison of the Raman profile of the carbon matter observed in the BARB3_23B sample drilled in Buck Reef, with those of the carbon matter from outcropping samples of the same area, the conclusion is that the BARB3_23B carbon matter resembles the ~3.48 to ~3.26 Ga group of the Komati, Hooggenoeg, Kromberg and Mendon Formations of the Onverwacht group in the Barberton Greenstone Belt to which it belongs. All these BGB formations show no D<sub>4</sub> band at ~1200 cm<sup>-1</sup>, suggesting that they were submitted to a temperature of ~335°C. A difference is observed in the I<sub>D</sub>/I<sub>G</sub> which is ~70% higher for the outcropping samples, in the grain sizes of the carbon matter, which appear approximately ten times larger for the
walls, ~50 µm in diameter or length, which are observed in the Archean Farrel Quartzite and the Strelley Pool Formation, resemble morphologically those observed in the Paleoproterozoic 1.88 Ga Gunflint Formation (Lepot et al. 2017), except they are approximately five to ten times larger. Their carbon Raman spectra, as the BARB3_23B Buck Reef spectrum, are different from that of Gunflint, which shows a much wider D peak. Greenalite and siderite are observed inside the quartz matrices of the Gunflint ~5 µm spherical structures with carbon walls (Lepot et al. 2017 Suppl. Figs.). Greenalite is identified inside a cell-like segmented structure (Lepot et al. 2017 Fig.2g-i, position circled in Suppl. Fig. 7c and SAED in Fig.15a). The lattice spacing value of 0.72 nm is determined with selected area electron diffraction, SAED. The cell-like structure is composed of attached spheres, 2 to 5 µm in size, forming a chain. The spheres are rimmed with carbon, which shows open spaces. Greenalite is also identified inside a ~600 nm elongated structure, with the EDXS spectrum shown in Suppl. Fig. 15c and with the Si L<sub>2,3</sub> edge EELS (Electron Energy Loss Spectroscopy) spectrum 1 shown in Suppl. Fig. 15d. Both figures correspond to position 1 in the STEM images of Fig. 3 and Suppl. Fig. 15b in (Lepot et al. 2017). Position 2 of the STEM image shows the same Si L<sub>2,3</sub> edge EELS spectrum, with the addition of a peak at ~106 eV. Fe<sup>II</sup>Fe<sup>III</sup>-greenalite is likewise identified with the Fe L<sub>2,3</sub> edge EELS spectrum of (Lepot et al. 2017 Suppl. Figs.15e, 8g), displaying the Fe<sup>2+</sup> and Fe<sup>3+</sup> peaks at 708.9 eV and 710.5 eV, respectively, with the amount of Fe<sup>3+</sup> being 4.5% of Fe<sub>total</sub>.

The Si L<sub>2,3</sub> edge EELS spectrum 2 of (Lepot et al. 2017 Suppl. Fig.15d) displays four peaks that I calculate by hand at ~106.3, ~108.7, ~115.4 and ~130 eV. I observe that these four peaks correspond to those observed in (Garvie and Craven 1994 Fig. 9) where the Si L<sub>2,3</sub> edges from quartz SiO<sub>2</sub>, talc Mg<sub>3</sub>Si<sub>4</sub>O<sub>10</sub>(OH)<sub>2</sub> and nontronite Na<sub>0.3</sub>Fe<sub>2</sub>((Si,Al)<sub>4</sub>O<sub>10</sub>)(OH)<sub>2</sub>.nH<sub>2</sub>O, "exhibit very similar edge shapes, characterized by the two initial sharp peaks, peaks A (106.3) and B (108.4eV), followed by a sharp peak C (115.0) and a broad peak D (ca 133 eV)". Peak A at 106.3 eV seems to disappear for the three glasses forsterite Mg<sub>2</sub>SiO<sub>4</sub>, fayalite Fe<sub>2</sub>SiO<sub>4</sub> and basaltic glass, as shown in (Garvie and Craven 1999 Fig.4). Like glasses, greenalite, as described by (Guggenheim and Eggleton 1998, Tosca et al. 2016), does not show a structure with long length order. This is probably the reason why peak A at 106.3 eV is absent in the greenalite spectrum of (Lepot et al. 2017 Fig. 15d-1). As noted in the text by Lepot et al "Fe-bearing minerals (siderite and greenalite) occur inside the cells, but not outside". The cells contain quartz matrices. Neither hematite nor magnetite were observed. The cells are rimmed with carbon and the rims show discontinuities and openings.

Another nanoscale analysis of the filamentous structures observed in the 3.46 Ga Apex chert, Western Australia, show that the microstructures are carbon-coated stacks of phyllosilicate crystals. "Each filament is made of multiple plate- or sheet-like grains of phyllosilicate within a matrix of microcrystalline quartz" (Wacey et al. 2016 §3.2). Dark field scanning of an ultrathin (100 nm) slice through a filament shows that "the phyllosilicate mineral contains the elements K, Al, Si, O, Ba and minor Mg" (Wacey et al. 2016 Fig.9). This observation confirms the conclusion of Brasier et al that "the 'microfossils' were in fact carbonaceous mineral rims that formed around recrystallizing grain margins during a complex series of hydrothermal events." (Wacey et al. 2016, Brasier et al. 2002, 2004).

From the comparison of the Raman profile of the carbon matter observed in the BARB3_23B sample drilled in Buck Reef, with those of the carbon matter from outcropping samples of the same area, the conclusion is that the BARB3_23B carbon matter resembles the ~3.48 to ~3.26 Ga group of the Komati, Hooggenoeg, Kromberg and Mendon Formations of the Onverwacht group in the Barberton Greenstone Belt to which it belongs. All these BGB formations show no D<sub>4</sub> band at ~1200 cm<sup>-1</sup>, suggesting that they were submitted to a temperature of ~335°C. A difference is observed in the I<sub>D</sub>/I<sub>G</sub> which is ~70% higher for the outcropping samples, in the grain sizes of the carbon matter, which appear approximately ten times larger for the
outcropping samples, and in the mineral content, which, observed by Raman spectroscopy, seems much simpler for BARB3_23B. The BARB3_23B carbon matter appears to belong to the 3.5 to 2.65 Ga group, except for the D₄ band, which is present in other Archean formations, such as the 3.4 Ga Strelley Pool in the Pilbara craton. The morphologies of the carbon microstructures observed in the outcrops of the ~3.4-3.0 Ga Archean Farrel Quartzite, Strelley Pool Formation, Apex Chert and of the Paleoproterozoic 1.88 Ga Gunflint Formation, are different than those of the BARB3_23B dispersed carbon. Nonetheless, the Raman spectra appear equivalent for all Archean formations except for the D₄ peak at ~1200 cm⁻¹, which is absent for BARB3_23B. The Raman profiles suggest a temperature of 300°-330°C for Farrel Quartzite, Strelley Pool Formation and Apex Chert, and 335°C for the BARB3_23B BIF. The same individual or chained spheres morphologies are observed in the Archean and Gunflint formations. They are approximately ten times smaller in Gunflint, ~5 µm instead of ~50 µm. The Gunflint Raman spectrum shows a much wider D peak. The spheres have carbon rims with discontinuities and openings, and interiors with quartz, greenalite, siderite, no hematite or magnetite.

## *The BARB3_23B carbon matter and oxygen content*

The Raman spectrum of the BARB3_23B sample drilled in the Buck Reef Chert seems characteristic of very low oxygen content.

Raman spectra of graphene oxide and reduced graphene oxides are shown in (Moon et al. 2010 Fig.1e). They were recorded with a 514,5 nm (2.41 eV) excitation energy. Graphene oxide (GO) leads to wide G and D peaks and a very broad peak between 2600 cm⁻¹ and 3000 cm⁻¹ which includes the 2D and D + D' bands. The D band is at 1358 cm⁻¹, the G band is at 1594 cm⁻¹, and the $I_D/I_G$ is ~0,77. One reduced graphene oxide, rGO, contains much less oxygen than GO. Elemental analysis indicates 45% C and 46% O for GO and 83% C and 7% O for rGO. The Fourier Transform-Infra Red, FT-IR, spectra display the OH and C=O vibrations for GO and not for rGO (Moon et al. 2010 Table. S1, Fig.S8). The Raman spectrum of rGO displays four well-resolved peaks: the D band at 1350 cm⁻¹, G at 1581 cm⁻¹, 2D at 2680 cm⁻¹, and D + D' at 2910 cm⁻¹, with an $I_D/I_G$ of 1.10, D FWHM that I calculate to be ~70 cm⁻¹, and G FWHM ~77 cm⁻¹. The $D_2$ band at 1620 cm⁻¹ appears to slightly broaden the G band width. The Raman profile of rGO shows the $D_3$ peak intensity at ~1500 cm⁻¹, which is ~ half that of the GO profile, with no $D_4$-foot at the low wavelength of ~1200 cm⁻¹ or a separate peak at ~1620 cm⁻¹.

The Moon et al. 2010 second-order profile appears resolved for the above described rGO and unresolved for the GO. This appearance is also noticed by (Xu and Cheng 2013 Fig.2a), who studied the 532 nm Raman spectrum of a graphene oxide with an O:C atomic ratio of 1:2, which is an intermediate ratio between those of the rGO and GO. The second-order peaks of the graphene oxide with an O:C of 1:2 are not as well resolved as those of rGO. They follow the trend described in (Xu and Cheng 2013 §3): "*the intensity of 2D and 2D' bands is inversely proportional to the concentration of defects because both are activated by two-phonon (with opposite momentum) assisted double resonant processes...graphene with perfect sp² carbon network presents very strong 2D and 2D' bands*". This observation is also graphically represented in (Sheka et al. 2020 Figs.8f, 8g) for the two chemically produced amorphous graphene, Ak-rGO and TE-rGO, as described in the following section on "The BARB3_23B carbon and amorphous carbon". The Raman spectrum of the graphene Ak-rGO, which contains no hydroxyl groups, shows second-order peaks that are well resolved.

The carbon profile of the BARB3_23B BIF approximates the rGO profile. The carbon of the BARB3_23B BIF from Buck Reef resembles the reduced graphene oxide, which contains a very low amount of oxygen.
outcropping samples, and in the mineral content, which, observed by Raman spectroscopy, seems much simpler for BARB3_23B. The BARB3_23B carbon matter appears to belong to the 3.5 to 2.65 Ga group, except for the D₄ band, which is present in other Archean formations, such as the 3.4 Ga Strelley Pool in the Pilbara craton. The morphologies of the carbon microstructures observed in the outcrops of the ~3.4-3.0 Ga Archean Farrel Quartzite, Strelley Pool Formation, Apex Chert and of the Paleoproterozoic 1.88 Ga Gunflint Formation, are different than those of the BARB3_23B dispersed carbon. Nonetheless, the Raman spectra appear equivalent for all Archean formations except for the D₄ peak at ~1200 cm⁻¹, which is absent for BARB3_23B. The Raman profiles suggest a temperature of 300°-330°C for Farrel Quartzite, Strelley Pool Formation and Apex Chert, and 335°C for the BARB3_23B BIF. The same individual or chained spheres morphologies are observed in the Archean and Gunflint formations. They are approximately ten times smaller in Gunflint, ~5 µm instead of ~50 µm. The Gunflint Raman spectrum shows a much wider D peak. The spheres have carbon rims with discontinuities and openings, and interiors with quartz, greenalite, siderite, no hematite or magnetite.

## *The BARB3_23B carbon matter and oxygen content*

The Raman spectrum of the BARB3_23B sample drilled in the Buck Reef Chert seems characteristic of very low oxygen content.

Raman spectra of graphene oxide and reduced graphene oxides are shown in (Moon et al. 2010 Fig.1e). They were recorded with a 514,5 nm (2.41 eV) excitation energy. Graphene oxide (GO) leads to wide G and D peaks and a very broad peak between 2600 cm⁻¹ and 3000 cm⁻¹ which includes the 2D and D + D' bands. The D band is at 1358 cm⁻¹, the G band is at 1594 cm⁻¹, and the $I_D/I_G$ is ~0,77. One reduced graphene oxide, rGO, contains much less oxygen than GO. Elemental analysis indicates 45% C and 46% O for GO and 83% C and 7% O for rGO. The Fourier Transform-Infra Red, FT-IR, spectra display the OH and C=O vibrations for GO and not for rGO (Moon et al. 2010 Table. S1, Fig.S8). The Raman spectrum of rGO displays four well-resolved peaks: the D band at 1350 cm⁻¹, G at 1581 cm⁻¹, 2D at 2680 cm⁻¹, and D + D' at 2910 cm⁻¹, with an $I_D/I_G$ of 1.10, D FWHM that I calculate to be ~70 cm⁻¹, and G FWHM ~77 cm⁻¹. The $D_2$ band at 1620 cm⁻¹ appears to slightly broaden the G band width. The Raman profile of rGO shows the $D_3$ peak intensity at ~1500 cm⁻¹, which is ~ half that of the GO profile, with no $D_4$-foot at the low wavelength of ~1200 cm⁻¹ or a separate peak at ~1620 cm⁻¹.

The Moon et al. 2010 second-order profile appears resolved for the above described rGO and unresolved for the GO. This appearance is also noticed by (Xu and Cheng 2013 Fig.2a), who studied the 532 nm Raman spectrum of a graphene oxide with an O:C atomic ratio of 1:2, which is an intermediate ratio between those of the rGO and GO. The second-order peaks of the graphene oxide with an O:C of 1:2 are not as well resolved as those of rGO. They follow the trend described in (Xu and Cheng 2013 §3): "*the intensity of 2D and 2D' bands is inversely proportional to the concentration of defects because both are activated by two-phonon (with opposite momentum) assisted double resonant processes...graphene with perfect sp² carbon network presents very strong 2D and 2D' bands*". This observation is also graphically represented in (Sheka et al. 2020 Figs.8f, 8g) for the two chemically produced amorphous graphene, Ak-rGO and TE-rGO, as described in the following section on "The BARB3_23B carbon and amorphous carbon". The Raman spectrum of the graphene Ak-rGO, which contains no hydroxyl groups, shows second-order peaks that are well resolved.

The carbon profile of the BARB3_23B BIF approximates the rGO profile. The carbon of the BARB3_23B BIF from Buck Reef resembles the reduced graphene oxide, which contains a very low amount of oxygen.
Carbon dots are quasi-spherical carbon nanoparticles that are 2-10 nm in diameter. "They consist of combination of graphitic and turbostratic carbon in various volumetric ratios" (Georgakilas et al. 2015). The structure of carbon objects is defined as turbostratic or graphitic depending on the stacking of the graphene layers. The turbostratic structure corresponds to "random rotational stacking", while the graphitic structure corresponds to the "ABA stacking sequence of graphite" (Monthiou et al. 2017). Cançado et al. (2008) showed that "Raman spectroscopy can be used as a tool for measuring the degree of stacking order of graphite systems". They studied the variation of the second harmonic of the D band, the G' band, of nanographites at 514.5 nm, and they showed that a single peak appears at ~2700 cm⁻¹ for a turbostratic structure and two peaks at ~2687 cm⁻¹ and ~2727 cm⁻¹ for more crystalline graphites. The first-order Raman spectrum at 633 nm displays peaks that are almost equivalent to those of the BARB3_23B BIF from Buck Reef with the D band at ~1350 cm⁻¹ and G band at ~1600 cm⁻¹ (Georgakilas et al. 2015 Fig.4).

Carbon dots are classified as graphene quantum dots (GQDs), carbon quantum dots (CQDs), and carbonized polymer dots (CPDs) (Liu et al. 2020 Fig.1). Raman spectra were recorded at 532 nm on graphene quantum dots, also named nanofragments of graphene and nanographene, with fully benzenoid structures, armchair edges, lateral dimensions from 0.97 nm to 1.62 nm and chemical compositions of C₆₀H₂₃(COOH), C₁₃₂H₃₆(COOH)₂, and C₂₀₄H₄₈(COOH)₂. "Interestingly, although the GQDs studied here approach molecular sizes, all three systems yielded spectra highly characteristic of extended graphene structures" (Dervishi et al. 2019 p.16573). The characteristic D and G peaks of graphitic carbon are present. With a Lorentzian fit, a D₃ peak is observed at ~1500 cm⁻¹. From their Fig. 2b, I calculate the D* peak at ~1220 cm⁻¹. It corresponds to the D** band appellation that is described in the above section on the "Raman profile of the carbon observed in the BARB3_23B drilled sample". I calculate the D FWHM to be ~69 cm⁻¹ (measured on the D peak only, without the D**), the G FWHM ~33 cm⁻¹ for the C₂₀₄ assemblage, and the I<sub>D</sub>/I<sub>G</sub> ~1. The 2D, the D + G (also named earlier D + D'), and the 2G (also named above 2D') peaks are described at 2614, 2905 and 3187 cm⁻¹, respectively. These peaks are better resolved for an increasing number of carbon atoms. The G peak is narrow and does not seem to integrate the D' (or D₂) peak at 1620 cm⁻¹, even if the position is at 1595 cm⁻¹. The D' peak has been observed for graphene structures with armchair edges (Dervishi et al. 2019 p.16577 and refs therein). Edge structures may be at the origin of the D' mode. The D mode is activated by symmetry breaking at defects and edges and appears to be a function of the nature of the edge structure. The D band scattering is not activated by the zigzag edge structure, and the D band intensity is weaker for zigzag than for armchair edge structures (Dervishi et al. 2019 p.16576, Jia et al. 2011). The presence of heptagon-pentagon pairs or pentagon-octagon-pentagon trios, replacing hexagons as shown in (Jia et al. 2011) and in (Bourrat et al. 2001 for pyrocarbons), can induce curvature of the graphene layers. From these studies on graphene quantum dots, it can be inferred that at the nanoscale, the presence of the D' peak at 1620 cm⁻¹, and of a high D peak intensity may suggest structures with armchair edges. It can also be inferred that for GQDs and disordered graphitic carbon, the second-order spectrum is better resolved with an increasing number of carbon atoms, and that the presence of heptagon-pentagon pairs and pentagon-octagon-pentagon trios can induce curvature of the graphene layers.

It is worth noting that the C₆₀, C₁₃₂ and C₂₀₄ GQDs are in fact polycyclic aromatic hydrocarbons (PAHs) with carboxyl groups (-COOH) containing one carbonyl (-C=O) and one hydroxyl (-OH) functional groups, replacing hydrogen atoms. PAHs and graphite were previously studied with Raman spectroscopy by (Castiglioni et al. 2001). The structures of branched, intermediate and armchair PAHs are shown in (Ricca et al. 2019), and connections between PAHs and graphene are presented in (Wang et al. 2019). PAHs with heteroatoms such
Carbon dots are quasi-spherical carbon nanoparticles that are 2-10 nm in diameter. "They consist of combination of graphitic and turbostratic carbon in various volumetric ratios" (Georgakilas et al. 2015). The structure of carbon objects is defined as turbostratic or graphitic depending on the stacking of the graphene layers. The turbostratic structure corresponds to "random rotational stacking", while the graphitic structure corresponds to the "ABA stacking sequence of graphite" (Monthiou et al. 2017). Cançado et al. (2008) showed that "Raman spectroscopy can be used as a tool for measuring the degree of stacking order of graphite systems". They studied the variation of the second harmonic of the D band, the G' band, of nanographites at 514.5 nm, and they showed that a single peak appears at ~2700 cm⁻¹ for a turbostratic structure and two peaks at ~2687 cm⁻¹ and ~2727 cm⁻¹ for more crystalline graphites. The first-order Raman spectrum at 633 nm displays peaks that are almost equivalent to those of the BARB3_23B BIF from Buck Reef with the D band at ~1350 cm⁻¹ and G band at ~1600 cm⁻¹ (Georgakilas et al. 2015 Fig.4).

Carbon dots are classified as graphene quantum dots (GQDs), carbon quantum dots (CQDs), and carbonized polymer dots (CPDs) (Liu et al. 2020 Fig.1). Raman spectra were recorded at 532 nm on graphene quantum dots, also named nanofragments of graphene and nanographene, with fully benzenoid structures, armchair edges, lateral dimensions from 0.97 nm to 1.62 nm and chemical compositions of C₆₀H₂₃(COOH), C₁₃₂H₃₆(COOH)₂, and C₂₀₄H₄₈(COOH)₂. "Interestingly, although the GQDs studied here approach molecular sizes, all three systems yielded spectra highly characteristic of extended graphene structures" (Dervishi et al. 2019 p.16573). The characteristic D and G peaks of graphitic carbon are present. With a Lorentzian fit, a D₃ peak is observed at ~1500 cm⁻¹. From their Fig. 2b, I calculate the D* peak at ~1220 cm⁻¹. It corresponds to the D** band appellation that is described in the above section on the "Raman profile of the carbon observed in the BARB3_23B drilled sample". I calculate the D FWHM to be ~69 cm⁻¹ (measured on the D peak only, without the D**), the G FWHM ~33 cm⁻¹ for the C₂₀₄ assemblage, and the I<sub>D</sub>/I<sub>G</sub> ~1. The 2D, the D + G (also named earlier D + D'), and the 2G (also named above 2D') peaks are described at 2614, 2905 and 3187 cm⁻¹, respectively. These peaks are better resolved for an increasing number of carbon atoms. The G peak is narrow and does not seem to integrate the D' (or D₂) peak at 1620 cm⁻¹, even if the position is at 1595 cm⁻¹. The D' peak has been observed for graphene structures with armchair edges (Dervishi et al. 2019 p.16577 and refs therein). Edge structures may be at the origin of the D' mode. The D mode is activated by symmetry breaking at defects and edges and appears to be a function of the nature of the edge structure. The D band scattering is not activated by the zigzag edge structure, and the D band intensity is weaker for zigzag than for armchair edge structures (Dervishi et al. 2019 p.16576, Jia et al. 2011). The presence of heptagon-pentagon pairs or pentagon-octagon-pentagon trios, replacing hexagons as shown in (Jia et al. 2011) and in (Bourrat et al. 2001 for pyrocarbons), can induce curvature of the graphene layers. From these studies on graphene quantum dots, it can be inferred that at the nanoscale, the presence of the D' peak at 1620 cm⁻¹, and of a high D peak intensity may suggest structures with armchair edges. It can also be inferred that for GQDs and disordered graphitic carbon, the second-order spectrum is better resolved with an increasing number of carbon atoms, and that the presence of heptagon-pentagon pairs and pentagon-octagon-pentagon trios can induce curvature of the graphene layers.

It is worth noting that the C₆₀, C₁₃₂ and C₂₀₄ GQDs are in fact polycyclic aromatic hydrocarbons (PAHs) with carboxyl groups (-COOH) containing one carbonyl (-C=O) and one hydroxyl (-OH) functional groups, replacing hydrogen atoms. PAHs and graphite were previously studied with Raman spectroscopy by (Castiglioni et al. 2001). The structures of branched, intermediate and armchair PAHs are shown in (Ricca et al. 2019), and connections between PAHs and graphene are presented in (Wang et al. 2019). PAHs with heteroatoms such
as O, N, and S are usually named kerogen, the term used for the description of Archean graphitic carbon.

The Raman spectra of the graphene quantum dots $C_{132}H_{36}(COOH)_2$ and $C_{204}H_{48}(COOH)_2$, synthesized at the nanoscale level, on the surface of nanocrystalline $TiO_2$ films, resemble the carbon observed in the BARB3_23B BIF from Buck Reef, and thus, as shown in the section on Archean carbon matter, with Archean kerogen. Both GQDs and BARB3_23B carbon show a narrow G peak, suggesting the absence of the D' peak at $1620 \text{ cm}^{-1}$. However, the $1220 \text{ cm}^{-1}$ peak, a component of the $D_4$ band, which appears present in the GQDs profiles, is absent in Buck Reef, and the D peak appears at $\sim1335 - \sim1315 \text{ cm}^{-1}$ for the GQDs, and at $\sim1348 \text{ cm}^{-1}$ for Buck Reef (Dervishi et al. 2019 Figs.2, 3a). The Raman profile of the $C_{60}$ GQD, with a higher O/C content, resembles the Gunflint profile, with a broad D peak at $\sim1335 \text{ cm}^{-1}$ and a FWHM that I calculate to be $\sim106 \text{ cm}^{-1}$ on their Lorentzian component without the $D_4 \sim1200 \text{ cm}^{-1}$ peak.

From this section on carbon and oxygen content, it can be concluded that Raman profiles depend on the amount of oxygen, as deduced above from the graphene oxide and the reduced graphene oxide study, and from the study on graphene quantum dots, which are nanoscale assemblages identical to the polycyclic aromatic hydrocarbons that form the so-called geological kerogen. The Raman D peak is observed to be much broader in the case of higher oxygen content. Chemical functional groups containing oxygen, such as the carboxylic function, may prevent the alignment of the graphene layers. They induce curvature of the layers, as do pentagons, heptagons and octagons replacing the aromatic hexagons. A random rotational stacking named the turbostratic structure may be constructed instead of the AB stacking of graphite named the graphite structure. A relation appears to exist between the width of the D peak and the oxygen content.

## *The BARB3_23B carbon and amorphous carbon*

The Raman spectrum of the BARB3_23B sample drilled in the Buck Reef Chert shows a profile characteristic of amorphous carbon with no hydroxyl functional groups.

The first- and second-order Raman peaks, recorded at 514.5 nm, of a chemically produced amorphous graphene, Ak-rGO, appear similar to the carbon profile of the BARB3_23B considering the D and G peak positions, $I_D/I_G$, D and G FWHMs, relative intensities of the second-order peaks, and $D_3$ peak at $\sim1500 \text{ cm}^{-1}$. The D' (or D2) at $\sim1620 \text{ cm}^{-1}$ and the $D_4$ at $\sim1200 \text{ cm}^{-1}$ appear absent (Sheka et al. 2020a Figs. 4, 7 and 8). The structure of this amorphous graphene differs from the structure of another synthesized amorphous graphene, named TE-rGO, by the presence of hydroxyl groups in the TE-rGO (Sheka et al. 2020a Fig.6, Sheka et al. 2020b Fig.10), which broadly enlarge the second-order peaks and the D peak, and highly increase the intensity of the $D_3$ peak, making the profile of this second amorphous synthesized carbon, much more similar to that of the Gunflint carbon. Both synthesized amorphous carbons contain no nitrogen (Sheka et al. 2020a Table 2).

From this comparison of Raman profiles, the Buck Reef BARB3_23B carbon matter can be described as containing no hydroxyl groups. Again, the profile of the Raman spectrum seems to be related to the amount of oxygen, as proposed in the above section on "the BARB3_23B carbon matter and the oxygen content".

## *The BARB3_23B carbon matter and curvature of the graphene layers*
as O, N, and S are usually named kerogen, the term used for the description of Archean graphitic carbon.

The Raman spectra of the graphene quantum dots $C_{132}H_{36}(COOH)_2$ and $C_{204}H_{48}(COOH)_2$, synthesized at the nanoscale level, on the surface of nanocrystalline $TiO_2$ films, resemble the carbon observed in the BARB3_23B BIF from Buck Reef, and thus, as shown in the section on Archean carbon matter, with Archean kerogen. Both GQDs and BARB3_23B carbon show a narrow G peak, suggesting the absence of the D' peak at $1620 \text{ cm}^{-1}$. However, the $1220 \text{ cm}^{-1}$ peak, a component of the $D_4$ band, which appears present in the GQDs profiles, is absent in Buck Reef, and the D peak appears at $\sim1335 - \sim1315 \text{ cm}^{-1}$ for the GQDs, and at $\sim1348 \text{ cm}^{-1}$ for Buck Reef (Dervishi et al. 2019 Figs.2, 3a). The Raman profile of the $C_{60}$ GQD, with a higher O/C content, resembles the Gunflint profile, with a broad D peak at $\sim1335 \text{ cm}^{-1}$ and a FWHM that I calculate to be $\sim106 \text{ cm}^{-1}$ on their Lorentzian component without the $D_4 \sim1200 \text{ cm}^{-1}$ peak.

From this section on carbon and oxygen content, it can be concluded that Raman profiles depend on the amount of oxygen, as deduced above from the graphene oxide and the reduced graphene oxide study, and from the study on graphene quantum dots, which are nanoscale assemblages identical to the polycyclic aromatic hydrocarbons that form the so-called geological kerogen. The Raman D peak is observed to be much broader in the case of higher oxygen content. Chemical functional groups containing oxygen, such as the carboxylic function, may prevent the alignment of the graphene layers. They induce curvature of the layers, as do pentagons, heptagons and octagons replacing the aromatic hexagons. A random rotational stacking named the turbostratic structure may be constructed instead of the AB stacking of graphite named the graphite structure. A relation appears to exist between the width of the D peak and the oxygen content.

## *The BARB3_23B carbon and amorphous carbon*

The Raman spectrum of the BARB3_23B sample drilled in the Buck Reef Chert shows a profile characteristic of amorphous carbon with no hydroxyl functional groups.

The first- and second-order Raman peaks, recorded at 514.5 nm, of a chemically produced amorphous graphene, Ak-rGO, appear similar to the carbon profile of the BARB3_23B considering the D and G peak positions, $I_D/I_G$, D and G FWHMs, relative intensities of the second-order peaks, and $D_3$ peak at $\sim1500 \text{ cm}^{-1}$. The D' (or D2) at $\sim1620 \text{ cm}^{-1}$ and the $D_4$ at $\sim1200 \text{ cm}^{-1}$ appear absent (Sheka et al. 2020a Figs. 4, 7 and 8). The structure of this amorphous graphene differs from the structure of another synthesized amorphous graphene, named TE-rGO, by the presence of hydroxyl groups in the TE-rGO (Sheka et al. 2020a Fig.6, Sheka et al. 2020b Fig.10), which broadly enlarge the second-order peaks and the D peak, and highly increase the intensity of the $D_3$ peak, making the profile of this second amorphous synthesized carbon, much more similar to that of the Gunflint carbon. Both synthesized amorphous carbons contain no nitrogen (Sheka et al. 2020a Table 2).

From this comparison of Raman profiles, the Buck Reef BARB3_23B carbon matter can be described as containing no hydroxyl groups. Again, the profile of the Raman spectrum seems to be related to the amount of oxygen, as proposed in the above section on "the BARB3_23B carbon matter and the oxygen content".

## *The BARB3_23B carbon matter and curvature of the graphene layers*
The HRTEM images of kerogen appear more graphite-like with increasing metamorphic grade of rocks and with increasing ages of rocks in the case of Precambrian rocks.

HRTEM, High-Resolution Transmission Electron Microscopy, images of kerogen from several metamorphic rocks are displayed in (Buseck and Huang 1985). Their Figs. 2 to 10 are presented in order of increasing Barrovian metamorphism, which follows the sequence shale, slate, phyllite, schist and gneiss (Jmu 2000). The studied rocks belong to the metamorphic zones, classified as chlorite, chlorite/biotite, garnet, staurolite, and sillimanite, associated with increasing metamorphic temperature and pressure. I observe that the two images of the shungite rocks from the chlorite zone show groups of approximately 10-15 curved distorted and discontinuous layers, 5 to 10 nm long, which intersect. A group of approximately 35 curved parallel layers is much longer (~85 nm). The phyllite rock of the chlorite zone shows a group of approximately 10 curved parallel discontinuous layers of ~70 nm long. The black slate from the chlorite zone shows sets of ~15-20 curved parallel discontinuous layers approximately ~60 nm long with intercrossing and a set of parallel ~50 discontinuous layers constructed in onion-shaped circles approximately ~60 nm long at the periphery. The image of a black slate from the garnet zone shows a set of ~35 well-aligned parallel layers and a set of ~100 well-aligned parallel layers slightly locally curved, with a graphite structure. The image of a phyllite from the chlorite/biotite zone shows a set of ~70 well-aligned parallel curved layers characteristic of graphite. The image of calc-silicate granofels from the garnet zone shows a graphite-like set of ~20 well-aligned parallel layers rimming a rectangle with curved corners, filled with a mineral and a set of ~170 well-aligned parallel layers of a large graphite crystal. The image of a black slate in the staurolite zone likewise shows a graphite set of ~45 well-aligned parallel layers rimming a crystal. The image of a graphite schist of the sillimanite zone shows a set of ~80 still more perfectly aligned parallel layers. All the graphitic layers of the chlorite zone appear in discontinuous curves, while the alignment is enhanced with increasing metamorphic grade. As expressed in the conclusion of (Buseck and Huang 1985), "increasing crystallinity of carbons is roughly proportional to metamorphic grade", and as expressed in the section on Kerogen in (Buseck et al. 1988), "the degree of graphitization reflects the mobility of the heteroatoms...and the subsequent ability of the carbon layers to align themselves into parallel planes".

HRTEM ~30 x 43 nm images of kerogen from several Precambrian rocks are displayed in (Buseck et al. 1988 Figs.1-8). They are presented in order of increasing age, between 0.9 and 3.8 Ga. Buseck et al. observed an "apparent trend of increasing structural order with age". I observe well-defined graphite parallel layers only in the 3.8 Ga Isua kerogen which displays 38 distinguishable parallel fringes. This assemblage disappears entirely for the 1.6 Ga kerogen and younger. The parallelism in the layers is pronounced in the 3.5 Ga kerogen from Onverwacht, which shows ~12 layers curved at 180°, a geometry usually called hairpin turn (Buseck et al. 1988 Fig.5E). The Onverwacht image also displays a set of ~15-20 layers in rims and a series of ~15 parallel locally curved and discontinuous layers, more than 35 nm long (Buseck et al. 1988 Fig.8B). The kerogen from the 2.8 Ga Fortescue Group displays a set of short and intercrossing 2-4 nm long filaments that appear identical to the kerogen 0.9, 1.4 and 1.6 Ga in age, and a small group of ~15 very discontinuous layers that seem parallel. The kerogen of the 2.6 Ga Ventersdorp Supergroup shows several sets of 10-15 layers that are well-aligned and parallel, although showing discontinuities. The 2.6 Ga Manjeri formation of Zimbabwe, shows very well-aligned parallel layers, ~15 in number, rimming a kind of distorted rectangle. The kerogen of the 2.5 Ga Hamersley Group displays several groups of ~15 discontinuous curved parallel layers, ~25 nm long, that intersect. The Hamersley kerogen resembles more the 2.2 Ga Transvaal kerogen than the 2.8 Ga Fortescue. The kerogen of the 2.2 Ga Transvaal Supergroup
The HRTEM images of kerogen appear more graphite-like with increasing metamorphic grade of rocks and with increasing ages of rocks in the case of Precambrian rocks.

HRTEM, High-Resolution Transmission Electron Microscopy, images of kerogen from several metamorphic rocks are displayed in (Buseck and Huang 1985). Their Figs. 2 to 10 are presented in order of increasing Barrovian metamorphism, which follows the sequence shale, slate, phyllite, schist and gneiss (Jmu 2000). The studied rocks belong to the metamorphic zones, classified as chlorite, chlorite/biotite, garnet, staurolite, and sillimanite, associated with increasing metamorphic temperature and pressure. I observe that the two images of the shungite rocks from the chlorite zone show groups of approximately 10-15 curved distorted and discontinuous layers, 5 to 10 nm long, which intersect. A group of approximately 35 curved parallel layers is much longer (~85 nm). The phyllite rock of the chlorite zone shows a group of approximately 10 curved parallel discontinuous layers of ~70 nm long. The black slate from the chlorite zone shows sets of ~15-20 curved parallel discontinuous layers approximately ~60 nm long with intercrossing and a set of parallel ~50 discontinuous layers constructed in onion-shaped circles approximately ~60 nm long at the periphery. The image of a black slate from the garnet zone shows a set of ~35 well-aligned parallel layers and a set of ~100 well-aligned parallel layers slightly locally curved, with a graphite structure. The image of a phyllite from the chlorite/biotite zone shows a set of ~70 well-aligned parallel curved layers characteristic of graphite. The image of calc-silicate granofels from the garnet zone shows a graphite-like set of ~20 well-aligned parallel layers rimming a rectangle with curved corners, filled with a mineral and a set of ~170 well-aligned parallel layers of a large graphite crystal. The image of a black slate in the staurolite zone likewise shows a graphite set of ~45 well-aligned parallel layers rimming a crystal. The image of a graphite schist of the sillimanite zone shows a set of ~80 still more perfectly aligned parallel layers. All the graphitic layers of the chlorite zone appear in discontinuous curves, while the alignment is enhanced with increasing metamorphic grade. As expressed in the conclusion of (Buseck and Huang 1985), "increasing crystallinity of carbons is roughly proportional to metamorphic grade", and as expressed in the section on Kerogen in (Buseck et al. 1988), "the degree of graphitization reflects the mobility of the heteroatoms...and the subsequent ability of the carbon layers to align themselves into parallel planes".

HRTEM ~30 x 43 nm images of kerogen from several Precambrian rocks are displayed in (Buseck et al. 1988 Figs.1-8). They are presented in order of increasing age, between 0.9 and 3.8 Ga. Buseck et al. observed an "apparent trend of increasing structural order with age". I observe well-defined graphite parallel layers only in the 3.8 Ga Isua kerogen which displays 38 distinguishable parallel fringes. This assemblage disappears entirely for the 1.6 Ga kerogen and younger. The parallelism in the layers is pronounced in the 3.5 Ga kerogen from Onverwacht, which shows ~12 layers curved at 180°, a geometry usually called hairpin turn (Buseck et al. 1988 Fig.5E). The Onverwacht image also displays a set of ~15-20 layers in rims and a series of ~15 parallel locally curved and discontinuous layers, more than 35 nm long (Buseck et al. 1988 Fig.8B). The kerogen from the 2.8 Ga Fortescue Group displays a set of short and intercrossing 2-4 nm long filaments that appear identical to the kerogen 0.9, 1.4 and 1.6 Ga in age, and a small group of ~15 very discontinuous layers that seem parallel. The kerogen of the 2.6 Ga Ventersdorp Supergroup shows several sets of 10-15 layers that are well-aligned and parallel, although showing discontinuities. The 2.6 Ga Manjeri formation of Zimbabwe, shows very well-aligned parallel layers, ~15 in number, rimming a kind of distorted rectangle. The kerogen of the 2.5 Ga Hamersley Group displays several groups of ~15 discontinuous curved parallel layers, ~25 nm long, that intersect. The Hamersley kerogen resembles more the 2.2 Ga Transvaal kerogen than the 2.8 Ga Fortescue. The kerogen of the 2.2 Ga Transvaal Supergroup
displays intercrossing groups of approximately 5-15 curved parallel and discontinuous layers, ~25 nm long.

HRTEM images of the kerogen from the 3.47 Ga Middle Marker, South Africa and ~3.48 Ga Dresser formations, Australia, are displayed with sizes of 15 x 15 nm and 30 x 30 nm, respectively, in (Delarue et al. 2016) together with the associated Raman spectra. I observe that the Middle Marker kerogen displays sets of 5 to 10 curved distorted parallel layers, 5 to 10 nm long, which intercross. A set of parallel curved features seems recognizable at the bottom of the poorly resolved and double-scaled image of the Dresser kerogen. They are absent from the 0.42 Ga and 0.05 Ga Phanerozoic kerogens.

The HRTEM image of the 2.0 Ga shungite carbon of the chlorite zone shown in (Buseck and Huang 1985 Fig. 3) is presented with improved contrast in (Buseck and Beyssac 2014 Fig.4) and described as "contorted fringes showing low degree of structural order, surrounded by longer, straighter, more parallel fringes on the grain exteriors. These rims have distinctly more graphite-like structures than the grain interiors". The contorted graphitic layers of the grain interior appear parallel, discontinuous and curved at the intercross with the more aligned layers of the grain exterior. Such a structure can be recognized in the upper right part of the 2.8 Ga Fortescue and the center of the 3.5 Ga Onverwacht images of kerogen in (Buseck et al. 1988 Figs. 5B and 8B) while being more locally curved and not as well-aligned in Fortescue. In 2001, it was confirmed for shungite carbon, a structure in curved graphene layers "that is similar to natural and synthetic cokes", with turbostratic stacking disorder of the graphene layers and that is a variety of nongraphitizable carbon (Kovalevski et al. 2001 Fig.5 and refs therein). An image of turbostratic graphitic carbon obtained from a nongraphitizable carbon is shown in (Buseck and Beyssac 2014 Fig. 1). The shungite rocks form the black sedimentary-volcanic rocks, 2.0 Ga Paleoproterozoic in age, from the Shunga village in Karelia, Russia, were widely studied for their large carbon content. Since 1937, shungite carbon was described as dispersed graphite, then as Ceylan graphite, poorly ordered carbon, containing graphitic layers but nongraphitizable even at 2800°C, associated with aromatic layers forming stacks with no graphite, and as globular units consisting of curved layers that surround pores. The 532 nm Raman spectrum of the unaltered 2.0 Ga shungite carbon shows similar 1st- and 2nd-order profiles to the 3.4 Ga BARB3_23B Buck Reef (Chazhengina and Kovalevski 2017, Figs.1-2a, Table 1). Peaks appear at ~1350 cm⁻¹ for the D band, ~1580 cm⁻¹ for the G band, and at ~2700 cm⁻¹, ~2900 cm⁻¹ and ~3200 cm⁻¹. The G peak is not broadened by the D₂ peak at ~1620 cm⁻¹, the D FWHMs are narrower (56 cm⁻¹ for shungite and 70 cm⁻¹ for Buck Reef) and the ID/IG is slightly higher (1.45/shungite, 1.30/Buck Reef).

From this section on carbon matter and the curvature of the graphene layers, it can be concluded that the alignment and the length of the graphene layers increase with increasing metamorphic grade. For Precambrian rocks, which, for most of them may be processed at the same temperature, the 3.8 Ga Isua kerogen displays very well-aligned graphite layers that disappear entirely at 1.6 Ga and younger. The trend between 2.8 Ga and 2.2 Ga is a mixture of two kinds of graphitic carbon, while the 2.0 Ga shungite carbon seems more graphitized. Although not definitively identified, a transition seems to occur around the time of the Great Oxidation Event (GOE). Systematic HRTEM observations of samples from 3.8 Ga to present time, including the Buck Reef BARB3_23B, may be envisioned with the purpose of concluding in a continuous graphitization through time or in a possible transition at the GOE following the rise in atmospheric oxygen.

*The BARB3_23B carbon and meteorite carbon*
displays intercrossing groups of approximately 5-15 curved parallel and discontinuous layers,
~25 nm long.

HRTEM images of the kerogen from the 3.47 Ga Middle Marker, South Africa and
~3.48 Ga Dresser formations, Australia, are displayed with sizes of 15 x 15 nm and 30 x 30 nm,
respectively, in (Delarue et al. 2016) together with the associated Raman spectra. I observe that
the Middle Marker kerogen displays sets of 5 to 10 curved distorted parallel layers, 5 to 10 nm
long, which intercross. A set of parallel curved features seems recognizable at the bottom of
the poorly resolved and double-scaled image of the Dresser kerogen. They are absent from the
0.42 Ga and 0.05 Ga Phanerozoic kerogens.

The HRTEM image of the 2.0 Ga shungite carbon of the chlorite zone shown in (Buseck and Huang 1985 Fig. 3) is presented with improved contrast in (Buseck and Beyssac 2014 Fig.4) and described as "contorted fringes showing low degree of structural order, surrounded by longer, straighter, more parallel fringes on the grain exteriors. These rims have distinctly more graphite-like structures than the grain interiors". The contorted graphitic layers of the grain interior appear parallel, discontinuous and curved at the intercross with the more aligned layers of the grain exterior. Such a structure can be recognized in the upper right part of the 2.8 Ga Fortescue and the center of the 3.5 Ga Onverwacht images of kerogen in (Buseck et al. 1988 Figs. 5B and 8B) while being more locally curved and not as well-aligned in Fortescue. In 2001, it was confirmed for shungite carbon, a structure in curved graphene layers "that is similar to natural and synthetic cokes", with turbostratic stacking disorder of the graphene layers and that is a variety of nongraphitizable carbon (Kovalevski et al. 2001 Fig.5 and refs therein). An image of turbostratic graphitic carbon obtained from a nongraphitizable carbon is shown in (Buseck and Beyssac 2014 Fig. 1). The shungite rocks form the black sedimentary-volcanic rocks, 2.0 Ga Paleoproterozoic in age, from the Shunga village in Karelia, Russia, were widely studied for their large carbon content. Since 1937, shungite carbon was described as dispersed graphite, then as Ceylan graphite, poorly ordered carbon, containing graphitic layers but nongraphitizable even at 2800°C, associated with aromatic layers forming stacks with no graphite, and as globular units consisting of curved layers that surround pores. The 532 nm Raman spectrum of the unaltered 2.0 Ga shungite carbon shows similar 1st- and 2nd-order profiles to the 3.4 Ga BARB3_23B Buck Reef (Chazhengina and Kovalevski 2017, Figs.1-2a, Table 1). Peaks appear at ~1350 cm⁻¹ for the D band, ~1580 cm⁻¹ for the G band, and at ~2700 cm⁻¹, ~2900 cm⁻¹ and ~3200 cm⁻¹. The G peak is not broadened by the D₂ peak at ~1620 cm⁻¹, the D FWHMs are narrower (56 cm⁻¹ for shungite and 70 cm⁻¹ for Buck Reef) and the ID/IG is slightly higher (1.45/shungite, 1.30/Buck Reef).

From this section on carbon matter and the curvature of the graphene layers, it can be concluded
that the alignment and the length of the graphene layers increase with increasing metamorphic
grade. For Precambrian rocks, which, for most of them may be processed at the same
temperature, the 3.8 Ga Isua kerogen displays very well-aligned graphite layers that disappear
entirely at 1.6 Ga and younger. The trend between 2.8 Ga and 2.2 Ga is a mixture of two kinds
of graphitic carbon, while the 2.0 Ga shungite carbon seems more graphitized. Although not
definitively identified, a transition seems to occur around the time of the Great Oxidation Event
(GOE). Systematic HRTEM observations of samples from 3.8 Ga to present time, including the
Buck Reef BARB3_23B, may be envisioned with the purpose of concluding in a continuous
graphitization through time or in a possible transition at the GOE following the rise in
atmospheric oxygen.

The *BARB3_23B* carbon and meteorite carbon
The Buck Reef BARB3_23B carbon matter shows identical Raman profiles to the CV<sub>oxA</sub> chondrites.

A 514.5 nm Raman study of meteorites from the NASA Antarctic collection shows that the carbonaceous matter of four CV3 chondrites has similar spectra to the Buck Reef: ALHA 81003, GRA 06101, MIL 091010, and QUE 94688 (Bonal et al. 2016 Table 2). The D Raman shift is positioned at 1349.5 cm⁻¹, G at 1600.6 cm⁻¹. The FWHM<sub>D</sub> is 73.2 cm⁻¹, FWHM<sub>G</sub> 67.9 cm⁻¹, and I<sub>D</sub>/I<sub>G</sub> 1.46. These values approach those of the Allende Insoluble Organic Matter (IOM) (Bose et al. 2017, Table 2 and Fig.4). As drawn in their Fig. 5, which represents FWHM<sub>D</sub> versus I<sub>D</sub>/I<sub>G</sub>, the CV3 chondrites form a group together with the Allende reference meteorite. They can be classified in the same way as Allende in the oxidized group of chondrites, CV<sub>ox</sub>. Based on (Yesiltas et al. 2021, Bonal et al. 2020, Krot et al. 1998, Weisberg et al. 1997), the oxidized group of chondrites is divided into two subgroups: Allende-like CV<sub>oxA</sub> and Bali-like CV<sub>oxB</sub>. I propose that the four cited above CV3 chondrites can be classified as CV<sub>oxA</sub> Allende-like chondrites. The peak metamorphic temperature of Allende has been estimated to be between 330° and 600°C (Bonal et al. 2016 and refs therein, Huss et al. 2006, Busemann et al. 2007, Bose et al. 2017). This range of temperatures includes the temperature submitted to the BARB3_23B sample of Buck Reef, which has been calculated above, to be ~335°C. "Phyllosilicates are only minor in Allende" (Krot et al. 1995, p.771 and refs therein). "The CV<sub>oxA</sub> subtypes lack pure fayalite (Fa>95 composition)" (Yesiltas et al 2021 and refs. therein). "The oxidized/reduced classification is based on magnetite and metal contents only, other iron phases are not taken into account" (Garenne et al. 2019). As described in (Bonal et al. 2020 Table 6), eleven CV<sub>oxA</sub> chondrites, including Allende and the four above cited CV3 chondrites, are depleted in magnetite: "Their average saturation magnetization Ms = 0.69 ± 0.37 Am² kg⁻¹ (Amp m² kg⁻¹) indicates maximum magnetite and metal content well below 1 wt.%. In contrast, CV<sub>oxB</sub> contain abundant magnetite and CV<sub>red</sub> abundant magnetite and metal". Fig. 7 in (Bonal et al. 2020) shows a plot of the saturation magnetization Ms vs FWHM<sub>D</sub>. The CV<sub>oxA</sub> chondrites with the narrowest FWHM<sub>D</sub>, between 50 cm⁻¹ and 80 cm⁻¹, form the group located at very low Ms, 0 Amp m² kg⁻¹ to 2 Amp m² kg⁻¹, and thus have no magnetite content. The absence of magnetite is confirmed by the Mrs, remnant magnetization at saturation, which is the remnant magnetization after application of a strong field to reach saturation and subsequent removal of this field. The CV<sub>oxA</sub> chondrites have a very low Mrs, 0.05 ± 0.02 Amp m² kg⁻¹, which is a consequence of the absence of magnetite. In contrast, Fig. 7 in (Bonal et al. 2020) shows that the CV<sub>red</sub> chondrites have broad FWHM<sub>D</sub>, 130 cm⁻¹-175 cm⁻¹, and high saturation magnetization, 6 Amp m² kg⁻¹ to 11 Amp m² kg⁻¹, thus containing high amounts of magnetite. They have a much higher Mrs, 0.60 ± 0.25 Amp m² kg⁻¹.

The above resemblance of the BARB3_23B carbon with the carbon of CV3 meteorites is confirmed in a Raman study at 532 nm of Antarctica carbon chondrites of type CV3 (Yesiltas et al. 2021 Fig.2). Peaks appear at 1343, 1600, 2690 and 2930 cm⁻¹. Raman data for the (Bonal et al. 2016) GRA 06101 chondrite are confirmed in their Table S1, with D at 1348.9 cm⁻¹, G at 1598.5 cm⁻¹, FWHM<sub>D</sub> of 65.3, FWHM<sub>G</sub> of 59.6 cm⁻¹, and I<sub>D</sub>/I<sub>G</sub> 1.5. They resemble the BARB3_23B Buck Reef carbon, while the CO3-type chondrites display much wider D peaks.

The Raman profile of the Buck Reef BARB3_23B carbon matter resembles the profiles displayed by the group of CV<sub>oxA</sub> Allende-like chondrites, ALHA 81003, GRA 06101, MIL 091010, QUE 94688. The metamorphic temperature of the Buck Reef BARB3_23B sample was calculated above to be 335°C, a value that is included in the range of metamorphic temperatures associated with the Allende meteorite. The Buck Reef BARB3_23B sample, as the CV<sub>oxA</sub> chondrites, contains minor phyllosilicates and no magnetite, while the CV<sub>red</sub> chondrites show broad FWHM<sub>D</sub> and contain abundant magnetite.
The Buck Reef BARB3_23B carbon matter shows identical Raman profiles to the CV<sub>oxA</sub> chondrites.

A 514.5 nm Raman study of meteorites from the NASA Antarctic collection shows that the carbonaceous matter of four CV3 chondrites has similar spectra to the Buck Reef: ALHA 81003, GRA 06101, MIL 091010, and QUE 94688 (Bonal et al. 2016 Table 2). The D Raman shift is positioned at 1349.5 cm⁻¹, G at 1600.6 cm⁻¹. The FWHM<sub>D</sub> is 73.2 cm⁻¹, FWHM<sub>G</sub> 67.9 cm⁻¹, and I<sub>D</sub>/I<sub>G</sub> 1.46. These values approach those of the Allende Insoluble Organic Matter (IOM) (Bose et al. 2017, Table 2 and Fig.4). As drawn in their Fig. 5, which represents FWHM<sub>D</sub> versus I<sub>D</sub>/I<sub>G</sub>, the CV3 chondrites form a group together with the Allende reference meteorite. They can be classified in the same way as Allende in the oxidized group of chondrites, CV<sub>ox</sub>. Based on (Yesiltas et al. 2021, Bonal et al. 2020, Krot et al. 1998, Weisberg et al. 1997), the oxidized group of chondrites is divided into two subgroups: Allende-like CV<sub>oxA</sub> and Bali-like CV<sub>oxB</sub>. I propose that the four cited above CV3 chondrites can be classified as CV<sub>oxA</sub> Allende-like chondrites. The peak metamorphic temperature of Allende has been estimated to be between 330° and 600°C (Bonal et al. 2016 and refs therein, Huss et al. 2006, Busemann et al. 2007, Bose et al. 2017). This range of temperatures includes the temperature submitted to the BARB3_23B sample of Buck Reef, which has been calculated above, to be ~335°C. "Phyllosilicates are only minor in Allende" (Krot et al. 1995, p.771 and refs therein). "The CV<sub>oxA</sub> subtypes lack pure fayalite (Fa>95 composition)" (Yesiltas et al 2021 and refs. therein). "The oxidized/reduced classification is based on magnetite and metal contents only, other iron phases are not taken into account" (Garenne et al. 2019). As described in (Bonal et al. 2020 Table 6), eleven CV<sub>oxA</sub> chondrites, including Allende and the four above cited CV3 chondrites, are depleted in magnetite: "Their average saturation magnetization Ms = 0.69 ± 0.37 Am² kg⁻¹ (Amp m² kg⁻¹) indicates maximum magnetite and metal content well below 1 wt.%. In contrast, CV<sub>oxB</sub> contain abundant magnetite and CV<sub>red</sub> abundant magnetite and metal". Fig. 7 in (Bonal et al. 2020) shows a plot of the saturation magnetization Ms vs FWHM<sub>D</sub>. The CV<sub>oxA</sub> chondrites with the narrowest FWHM<sub>D</sub>, between 50 cm⁻¹ and 80 cm⁻¹, form the group located at very low Ms, 0 Amp m² kg⁻¹ to 2 Amp m² kg⁻¹, and thus have no magnetite content. The absence of magnetite is confirmed by the Mrs, remnant magnetization at saturation, which is the remnant magnetization after application of a strong field to reach saturation and subsequent removal of this field. The CV<sub>oxA</sub> chondrites have a very low Mrs, 0.05 ± 0.02 Amp m² kg⁻¹, which is a consequence of the absence of magnetite. In contrast, Fig. 7 in (Bonal et al. 2020) shows that the CV<sub>red</sub> chondrites have broad FWHM<sub>D</sub>, 130 cm⁻¹-175 cm⁻¹, and high saturation magnetization, 6 Amp m² kg⁻¹ to 11 Amp m² kg⁻¹, thus containing high amounts of magnetite. They have a much higher Mrs, 0.60 ± 0.25 Amp m² kg⁻¹.

The above resemblance of the BARB3_23B carbon with the carbon of CV3 meteorites is confirmed in a Raman study at 532 nm of Antarctica carbon chondrites of type CV3 (Yesiltas et al. 2021 Fig.2). Peaks appear at 1343, 1600, 2690 and 2930 cm⁻¹. Raman data for the (Bonal et al. 2016) GRA 06101 chondrite are confirmed in their Table S1, with D at 1348.9 cm⁻¹, G at 1598.5 cm⁻¹, FWHM<sub>D</sub> of 65.3, FWHM<sub>G</sub> of 59.6 cm⁻¹, and I<sub>D</sub>/I<sub>G</sub> 1.5. They resemble the BARB3_23B Buck Reef carbon, while the CO3-type chondrites display much wider D peaks.

The Raman profile of the Buck Reef BARB3_23B carbon matter resembles the profiles displayed by the group of CV<sub>oxA</sub> Allende-like chondrites, ALHA 81003, GRA 06101, MIL 091010, QUE 94688. The metamorphic temperature of the Buck Reef BARB3_23B sample was calculated above to be 335°C, a value that is included in the range of metamorphic temperatures associated with the Allende meteorite. The Buck Reef BARB3_23B sample, as the CV<sub>oxA</sub> chondrites, contains minor phyllosilicates and no magnetite, while the CV<sub>red</sub> chondrites show broad FWHM<sub>D</sub> and contain abundant magnetite.
## Conclusion on the BARB3_23B carbon matter

The section leads to the conclusion that the disordered graphitic carbon observed in the BARB3_23B sample of the Buck Reef Chert has been submitted to a temperature of ~335°C, contains very low amounts of oxygen and no hydroxyl functional groups. It resembles the carbon matter observed in the group of Archean cherts, 3.5 Ga to 2.7 Ga in age. The broadening of the D peak as a function of the oxygen content appears to characterize the 1.9 to 0.4 Ga group. This conclusion is coherent with the fact that there was no atmospheric oxygen in Archean times. The carbon matter contained in the CVoxA Allende-like chondrites also shows Raman profiles similar to those of BARB3_23B. They both contain minor phyllosilicates, no fayalite, and no magnetite.

The appearance of the Raman spectrum of the BARB3_23B seems related more to the amount of oxygen creating defects and curvature of the graphene layers, than to the classification of kerogen / non-kerogen. The Raman profile relation between the carbon matter and the amount of oxygen, would explain why spectra of kerogen resemble spectra of non-kerogen as described in (Beyssac and Lazzeri 2012 Fig.10) "Raman spectra of carbonaceous phases generated in purely abiotic processes can be very similar to Raman spectra of real kerogens... i.e. bio-derived graphitic carbons". In the present study, emphasis is placed on the presence of oxygen instead of the usual biotic-abiotic origin of carbon matter. HRTEM images are envisioned for the observation of the curvature of the graphene layers in the BARB3_23B of Buck Reef Chert and for conclusions with respect to the Great Oxidation Event.

## References

* Agangi A, Hofmann A, Kamenetsky VS, Vroon PZ (2015) Paleoarchaean felsic magmatism: A melt inclusion study of 3.45 Ga old rhyolites from the Barberton Greenstone Belt, South Africa. Chemical Geology 414:69-83. //doi.org/10.1016/j.chemgeo.2015.09.002

* Agangi A, Hofmann A, Elburg MA (2018) A review of Palaeoarchaean felsic volcanism in the eastern Kaapvaal craton: Linking plutonic and volcanic records. Geoscience Frontiers 9:667-688. //doi.org/10.1016/j.gsf.2017.08.003

* Agangi A, Hofmann A, Eickmann B, Marin-Carbonne J (2019) Mesoarchean gold mineralisation in the Barberton greenstone belt: a review. In: Kröner A and Hofmann A (eds) The Archean Geology of the Kaapvaal Craton, South Africa, Springer Nature Switzerland, pp 171-184. //doi.org/10.1007/978-3-319-78652-0

* Anhaeusser CR (2014) Archean greenstone belts and associated granitic rocks – A review. Journal of African Earth Sciences 100: 684-732. //doi.org/10.1016/j.jafrearsci.2014.07.019

* Anhaeusser CR (2019) The geology and tectonic evolution of the northwest part of the Barberton Greenstone Belt, South Africa: A review. South African Journal of Geology 122(4): 1-33. //doi.org/10.25131/sajg.122.0033

* Artal LR (2014) A Palaeomagnetic study of 3.5 to 3.2 billion years old rocks from the Barberton Greenstone Belt, South Africa. Thesis, University of Liverpool, U.K.

* Bekaert DV, Broadley MW, Delarue F, Avice G, Robert F, Marty B (2018) Archean kerogen as a new tracer of atmospheric evolution: implications for dating the widespread nature of early life. Science Advances 4: eaar2091. //doi.org/10.1126/sciadv.aar2091

* Beny-Bassez C, Rouzaud JN (1985) Characterization of carbonaceous materials by correlated electron and optical microscopy and Raman microspectroscopy. Scanning Electron Microscopy 1: 112-132
## Conclusion on the BARB3_23B carbon matter

The section leads to the conclusion that the disordered graphitic carbon observed in the BARB3_23B sample of the Buck Reef Chert has been submitted to a temperature of ~335°C, contains very low amounts of oxygen and no hydroxyl functional groups. It resembles the carbon matter observed in the group of Archean cherts, 3.5 Ga to 2.7 Ga in age. The broadening of the D peak as a function of the oxygen content appears to characterize the 1.9 to 0.4 Ga group. This conclusion is coherent with the fact that there was no atmospheric oxygen in Archean times. The carbon matter contained in the CVoxA Allende-like chondrites also shows Raman profiles similar to those of BARB3_23B. They both contain minor phyllosilicates, no fayalite, and no magnetite.

The appearance of the Raman spectrum of the BARB3_23B seems related more to the amount of oxygen creating defects and curvature of the graphene layers, than to the classification of kerogen / non-kerogen. The Raman profile relation between the carbon matter and the amount of oxygen, would explain why spectra of kerogen resemble spectra of non-kerogen as described in (Beyssac and Lazzeri 2012 Fig.10) "Raman spectra of carbonaceous phases generated in purely abiotic processes can be very similar to Raman spectra of real kerogens... i.e. bio-derived graphitic carbons". In the present study, emphasis is placed on the presence of oxygen instead of the usual biotic-abiotic origin of carbon matter. HRTEM images are envisioned for the observation of the curvature of the graphene layers in the BARB3_23B of Buck Reef Chert and for conclusions with respect to the Great Oxidation Event.

## References

* Agangi A, Hofmann A, Kamenetsky VS, Vroon PZ (2015) Paleoarchaean felsic magmatism: A melt inclusion study of 3.45 Ga old rhyolites from the Barberton Greenstone Belt, South Africa. Chemical Geology 414:69-83. //doi.org/10.1016/j.chemgeo.2015.09.002

* Agangi A, Hofmann A, Elburg MA (2018) A review of Palaeoarchaean felsic volcanism in the eastern Kaapvaal craton: Linking plutonic and volcanic records. Geoscience Frontiers 9:667-688. //doi.org/10.1016/j.gsf.2017.08.003

* Agangi A, Hofmann A, Eickmann B, Marin-Carbonne J (2019) Mesoarchean gold mineralisation in the Barberton greenstone belt: a review. In: Kröner A and Hofmann A (eds) The Archean Geology of the Kaapvaal Craton, South Africa, Springer Nature Switzerland, pp 171-184. //doi.org/10.1007/978-3-319-78652-0

* Anhaeusser CR (2014) Archean greenstone belts and associated granitic rocks – A review. Journal of African Earth Sciences 100: 684-732. //doi.org/10.1016/j.jafrearsci.2014.07.019

* Anhaeusser CR (2019) The geology and tectonic evolution of the northwest part of the Barberton Greenstone Belt, South Africa: A review. South African Journal of Geology 122(4): 1-33. //doi.org/10.25131/sajg.122.0033

* Artal LR (2014) A Palaeomagnetic study of 3.5 to 3.2 billion years old rocks from the Barberton Greenstone Belt, South Africa. Thesis, University of Liverpool, U.K.

* Bekaert DV, Broadley MW, Delarue F, Avice G, Robert F, Marty B (2018) Archean kerogen as a new tracer of atmospheric evolution: implications for dating the widespread nature of early life. Science Advances 4: eaar2091. //doi.org/10.1126/sciadv.aar2091

* Beny-Bassez C, Rouzaud JN (1985) Characterization of carbonaceous materials by correlated electron and optical microscopy and Raman microspectroscopy. Scanning Electron Microscopy 1: 112-132
Beyssac O, Goffé B, Chopin C, Rouzaud JN (2002) Raman spectra of carbonaceous material in metasediments: a new geothermometer. J. of Metamorphic Geology 20(9): 859-871

Beyssac O, Lazzeri M (2012) Application of Raman spectroscopy to the study of graphitic carbons in the Earth Sciences. In: Dubessy J, Caumon MC, Rull F (eds) Raman Spectroscopy Applied to Earth Sciences and Cultural Heritage, EMU Notes in Mineralogy, vol.12, chp.12: pp 415-454. //doi.org/10.1180/EMU-notes.12.12

Bleeker W (2003) The late Archean record: a puzzle in ca. 35 pieces. Lithos 71:99-134.
//doi.org/10.1016/j.lithos.2003.07.003

Bleeker W, Davis BW (2004) What is a craton? How many are there? How do they relate? And how did they form? American Geophysical Union, Spring meeting 2004, Abstract T41C-01

Bonal L, Quirico E, Flandinet L, Montagnac G (2016) Thermal history of type 3 chondrites from the Antarctic meteorite collection determined by Raman spectroscopy of their polyaromatic carbonaceous matter. Geochimica et Cosmochimica Acta 189: 312-337.
//doi.org/10.1016/j.gca.2016.06.017

Bonal L, Gattacceca J, Garenne A, Eschrig J, Rochette P, Ruggiu LK (2020) Water and heat: new constraints on the evolution of the CV chondrite parent body. Geochimica et Cosmochimica Acta 276: 363-383. //doi.org/10.1016/j.gca.2020.03.009

Bose M, Root RA, Pizzarello S (2017) A XANES and Raman investigation of sulfur speciation and structural order in Murchison and Allende meteorites. Meteoritics & Planetary Science 52(3): 546-559. //doi.org/10.1111/maps.12811

Bourbin M, Derenne S, Gourier D, Rouzaud JN, Gautret P, Westall F (2012) Electron Paramagnetic Resonance study of a photosynthetic microbial mat and comparison with Archean cherts. Origins of Life Evolution of Biospheres 42: 569-585
//doi.org/10.1007/s11084-012-9320-3

Bourrat X, Lavenac J, Langlais F, Naslain R (2001) The role of pentagons in the growth of laminar pyrocarbon. Carbon 39: 2376-2380

Bower DM, Steele A, Fries MD, Kater L (2013) Micro Raman spectroscopy of carbonaceous material in microfossils and meteorites: improving a method for life detection. Astrobiology 13(1): 103-113. //doi.org/10.1089/ast.2012.0865

Brandl G, Cloete M, Anhaeusser CR (2006) Archean greenstone belts, p. 9-56 in: The Geology of South Africa, MR Johnson, CR Anhaeusser, RJ Thomas, eds. Johannesburg, Council for Geoscience, Pretoria 691 pp.

Brasier MD, Green OR, Jephcoat AP, Kleppe AK, van Kranendonk MJ, Lindsay JF, Steele A, Grassineau NV (2002) Questioning the evidence for Earth's oldest fossils. Nature 416: 76-81

Brasier M, Green O, Lindsay J, Steele A (2004) Earth's oldest (~3.5 Ga) fossils and the 'Early Eden Hypothesis': questioning the evidence. Origins of Life and Evolution of the Biosphere 34: 257-269

Buseck PR, Huang BJ (1985) Conversion of carbonaceous material to graphite during metamorphism. Geochimica et Cosmochimica Acta 49: 2003-2016

Buseck PR, Huang BJ, Miner B (1988) Structural order and disorder in Precambrian kerogens. Organic Geochemistry 12(3): 221-234

Buseck PR, Beyssac O (2014) From organic matter to graphite: graphitization. Elements 10: 421-426. //doi.org/10.2113/gselements.10.6.421

Busemann H, Alexander CMO'D, Nittler LR (2007) Characterization of insoluble organic matter in primitive meteorites by microRaman spectroscopy. Meteoritics & Planetary Science 42(7/8): 1387-1416

Byerly GR, Lowe DR, Heubeck C (2019) Geologic Evolution of the Barberton Greenstone Belt - A Unique Record of Crustal Development, Surface Processes, and Early Life
Beyssac O, Goffé B, Chopin C, Rouzaud JN (2002) Raman spectra of carbonaceous material in metasediments: a new geothermometer. J. of Metamorphic Geology 20(9): 859-871

Beyssac O, Lazzeri M (2012) Application of Raman spectroscopy to the study of graphitic carbons in the Earth Sciences. In: Dubessy J, Caumon MC, Rull F (eds) Raman Spectroscopy Applied to Earth Sciences and Cultural Heritage, EMU Notes in Mineralogy, vol.12, chp.12: pp 415-454. //doi.org/10.1180/EMU-notes.12.12

Bleeker W (2003) The late Archean record: a puzzle in ca. 35 pieces. Lithos 71:99-134.
//doi.org/10.1016/j.lithos.2003.07.003

Bleeker W, Davis BW (2004) What is a craton? How many are there? How do they relate? And how did they form? American Geophysical Union, Spring meeting 2004, Abstract T41C-01

Bonal L, Quirico E, Flandinet L, Montagnac G (2016) Thermal history of type 3 chondrites from the Antarctic meteorite collection determined by Raman spectroscopy of their polyaromatic carbonaceous matter. Geochimica et Cosmochimica Acta 189: 312-337.
//doi.org/10.1016/j.gca.2016.06.017

Bonal L, Gattacceca J, Garenne A, Eschrig J, Rochette P, Ruggiu LK (2020) Water and heat: new constraints on the evolution of the CV chondrite parent body. Geochimica et Cosmochimica Acta 276: 363-383. //doi.org/10.1016/j.gca.2020.03.009

Bose M, Root RA, Pizzarello S (2017) A XANES and Raman investigation of sulfur speciation and structural order in Murchison and Allende meteorites. Meteoritics & Planetary Science 52(3): 546-559. //doi.org/10.1111/maps.12811

Bourbin M, Derenne S, Gourier D, Rouzaud JN, Gautret P, Westall F (2012) Electron Paramagnetic Resonance study of a photosynthetic microbial mat and comparison with Archean cherts. Origins of Life Evolution of Biospheres 42: 569-585
//doi.org/10.1007/s11084-012-9320-3

Bourrat X, Lavenac J, Langlais F, Naslain R (2001) The role of pentagons in the growth of laminar pyrocarbon. Carbon 39: 2376-2380

Bower DM, Steele A, Fries MD, Kater L (2013) Micro Raman spectroscopy of carbonaceous material in microfossils and meteorites: improving a method for life detection. Astrobiology 13(1): 103-113. //doi.org/10.1089/ast.2012.0865

Brandl G, Cloete M, Anhaeusser CR (2006) Archean greenstone belts, p. 9-56 in: The Geology of South Africa, MR Johnson, CR Anhaeusser, RJ Thomas, eds. Johannesburg, Council for Geoscience, Pretoria 691 pp.

Brasier MD, Green OR, Jephcoat AP, Kleppe AK, van Kranendonk MJ, Lindsay JF, Steele A, Grassineau NV (2002) Questioning the evidence for Earth's oldest fossils. Nature 416: 76-81

Brasier M, Green O, Lindsay J, Steele A (2004) Earth's oldest (~3.5 Ga) fossils and the 'Early Eden Hypothesis': questioning the evidence. Origins of Life and Evolution of the Biosphere 34: 257-269

Buseck PR, Huang BJ (1985) Conversion of carbonaceous material to graphite during metamorphism. Geochimica et Cosmochimica Acta 49: 2003-2016

Buseck PR, Huang BJ, Miner B (1988) Structural order and disorder in Precambrian kerogens. Organic Geochemistry 12(3): 221-234

Buseck PR, Beyssac O (2014) From organic matter to graphite: graphitization. Elements 10: 421-426. //doi.org/10.2113/gselements.10.6.421

Busemann H, Alexander CMO'D, Nittler LR (2007) Characterization of insoluble organic matter in primitive meteorites by microRaman spectroscopy. Meteoritics & Planetary Science 42(7/8): 1387-1416

Byerly GR, Lowe DR, Heubeck C (2019) Geologic Evolution of the Barberton Greenstone Belt - A Unique Record of Crustal Development, Surface Processes, and Early Life
3.55-3.20 Ga. In: van Kranendonk MJ, Bennett VC, Hoffmann JE (eds), Earth's Oldest Rocks, Elsevier Amsterdam NI, pp 569-606. ISBN: 978-0-444-63901-1

Cançado LG, Jorio A, Pimenta MA (2007) Measuring the absolute Raman cross section of nanographites as a function of laser energy and crystallite size. Physical review B 76: 064304-1, 7pp. //doi.org/10.1103/PhysRevB.76.064304

Cançado LG, Takai K, Enoki T, Endo M, Kim YA, Mizusaki H, Speziali NL, Jorio A, Pimenta MA (2008) Measuring the degree of stacking order in graphite by Raman spectroscopy. Carbon 46: 272-275. //doi.org/10.1016/j.carbon.2007.11.015

Carlson RW, Garçon M, O'Neil J, Reimink J, Rizo H (2019) The nature of Earth's first crust. Chemical Geology 530: 119321 (25pp). //doi.org/10.1016/j.chemgeo.2019.119321

Castiglioni C, Mapelli C, Negri F, Zerbi G (2001) Origin of the D line in the Raman spectrum of graphite: a study based on Raman frequencies and intensities of polycyclic aromatic hydrocarbon molecules. Journal of Chemical Physics 114(2): 963-974. //doi.org/10.1063/1.1329670

Chazhengina SY, Kovalevski VV (2017) Raman spectroscopy of weathered shungites. Journal of Raman spectroscopy 48: 1590-1596. //doi.org/10.1002/jrs.5188

Condie KC (2019) Earth's oldest rocks and minerals. chapt.11 In: van Kranendonk JM, Bennett CV, Hoffmann JE (eds) Earth's oldest rocks, Elsevier, Amsterdam, Netherlands, pp 239-253. ISBN: 978-0-444-63901-1

Couzi M, Bruneel JL, Talaga D, Bokobza L (2016) A multi wavelength Raman scattering study of defective graphitic carbon materials: The first order Raman spectra revisited. Carbon 107: 388-394. //doi.org/10.1016/j.carbon.2016.06.017

Delarue F, Rouzaud JN, Derenne S, Bourbin M, Westall F, Kremer B, Sugitani K, Deldicque D, Robert F (2016) The Raman-derived carbonization continuum: a tool to select the best preserved molecular structures in Archean kerogens. Astrobiology 16(6): 1-11. //doi.org/10.1089/ast.2015.1392

Dervishi E, Ji Z, Htoon H, Sykora M, Doorn S (2019) Raman spectroscopy of bottom-up synthesized graphene quantum dots: size and structure dependence. Nanoscale 11/16571-16581. //doi.org/10.1039/c9nr05345j

Djokic T (2015) Assessing the link between Earth's oldest stromatolites and hydrothermal fluids: the c. 3.5 Ga Dresser Formation, North Pole Dome, Pilbara Craton, Western Australia. MPhil in Geoscience, University of New South Wales, Australia

Djokic T, van Kranendonk MJ, Campbell KA, Walter MR, Ward CR (2017) Earliest signs of life on land preserved in ca. 3.5 Ga hot spring deposits. Nature Comm 8: 15263. //doi.org/10.1038/ncomms15263

de Wit M, Ashwal LD (1995) Greenstone belts: what are they? South African Journal of Geology 98(4): 505-520

de Wit MJ, Ashwal LD (1997) Greenstone Belts. Oxford Monographs on Geology and Geophysics, Oxford: Clarendon Press, 35 (XXVII) 809 pp
//doi.org/10.1017/S0016756898228883

de Wit MJ, Furnes H, Robins B (2011) Geology and tectonostratigraphy of the Onverwacht Suite, Barberton Greenstone Belt, South Africa. Precambrian Research 186: 1-27. //doi.org/10.1016/j.precamres.2010.12.007

de Wit MJ, Furnes H (2013) Earth's oldest preserved unconformity - Prospect of a beginning in the tectono-sedimentary continental cycle? Gondwana Research 23: 429-435. //doi.org/10.1016/j.gr.2012.03.002

de Wit M, Furnes H, MacLennan S, Doucouré M, Schoene B, Weckmann U, Martinez U, Bowring S (2018) Paleoarchean bedrock lithologies across the Makhonjwa Mountains of South Africa and Swaziland linked to geochemical, magnetic and tectonic data
3.55-3.20 Ga. In: van Kranendonk MJ, Bennett VC, Hoffmann JE (eds), Earth's Oldest Rocks, Elsevier Amsterdam NI, pp 569-606. ISBN: 978-0-444-63901-1

Cançado LG, Jorio A, Pimenta MA (2007) Measuring the absolute Raman cross section of nanographites as a function of laser energy and crystallite size. Physical review B 76: 064304-1, 7pp. //doi.org/10.1103/PhysRevB.76.064304

Cançado LG, Takai K, Enoki T, Endo M, Kim YA, Mizusaki H, Speziali NL, Jorio A, Pimenta MA (2008) Measuring the degree of stacking order in graphite by Raman spectroscopy. Carbon 46: 272-275. //doi.org/10.1016/j.carbon.2007.11.015

Carlson RW, Garçon M, O'Neil J, Reimink J, Rizo H (2019) The nature of Earth's first crust. Chemical Geology 530: 119321 (25pp). //doi.org/10.1016/j.chemgeo.2019.119321

Castiglioni C, Mapelli C, Negri F, Zerbi G (2001) Origin of the D line in the Raman spectrum of graphite: a study based on Raman frequencies and intensities of polycyclic aromatic hydrocarbon molecules. Journal of Chemical Physics 114(2): 963-974. //doi.org/10.1063/1.1329670

Chazhengina SY, Kovalevski VV (2017) Raman spectroscopy of weathered shungites. Journal of Raman spectroscopy 48: 1590-1596. //doi.org/10.1002/jrs.5188

Condie KC (2019) Earth's oldest rocks and minerals. chapt.11 In: van Kranendonk JM, Bennett CV, Hoffmann JE (eds) Earth's oldest rocks, Elsevier, Amsterdam, Netherlands, pp 239-253. ISBN: 978-0-444-63901-1

Couzi M, Bruneel JL, Talaga D, Bokobza L (2016) A multi wavelength Raman scattering study of defective graphitic carbon materials: The first order Raman spectra revisited. Carbon 107: 388-394. //doi.org/10.1016/j.carbon.2016.06.017

Delarue F, Rouzaud JN, Derenne S, Bourbin M, Westall F, Kremer B, Sugitani K, Deldicque D, Robert F (2016) The Raman-derived carbonization continuum: a tool to select the best preserved molecular structures in Archean kerogens. Astrobiology 16(6): 1-11. //doi.org/10.1089/ast.2015.1392

Dervishi E, Ji Z, Htoon H, Sykora M, Doorn S (2019) Raman spectroscopy of bottom-up synthesized graphene quantum dots: size and structure dependence. Nanoscale 11/16571-16581. //doi.org/10.1039/c9nr05345j

Djokic T (2015) Assessing the link between Earth's oldest stromatolites and hydrothermal fluids: the c. 3.5 Ga Dresser Formation, North Pole Dome, Pilbara Craton, Western Australia. MPhil in Geoscience, University of New South Wales, Australia

Djokic T, van Kranendonk MJ, Campbell KA, Walter MR, Ward CR (2017) Earliest signs of life on land preserved in ca. 3.5 Ga hot spring deposits. Nature Comm 8: 15263. //doi.org/10.1038/ncomms15263

de Wit M, Ashwal LD (1995) Greenstone belts: what are they? South African Journal of Geology 98(4): 505-520

de Wit MJ, Ashwal LD (1997) Greenstone Belts. Oxford Monographs on Geology and Geophysics, Oxford: Clarendon Press, 35 (XXVII) 809 pp
//doi.org/10.1017/S0016756898228883

de Wit MJ, Furnes H, Robins B (2011) Geology and tectonostratigraphy of the Onverwacht Suite, Barberton Greenstone Belt, South Africa. Precambrian Research 186: 1-27. //doi.org/10.1016/j.precamres.2010.12.007

de Wit MJ, Furnes H (2013) Earth's oldest preserved unconformity - Prospect of a beginning in the tectono-sedimentary continental cycle? Gondwana Research 23: 429-435. //doi.org/10.1016/j.gr.2012.03.002

de Wit M, Furnes H, MacLennan S, Doucouré M, Schoene B, Weckmann U, Martinez U, Bowring S (2018) Paleoarchean bedrock lithologies across the Makhonjwa Mountains of South Africa and Swaziland linked to geochemical, magnetic and tectonic data
reveal early plate tectonic genes flanking subduction margins. Geoscience Frontiers 9: 603-665. //doi.org/10.1016/j.gsf.2017.10.005

Drabon N, Byerly BL, Byerly GR, Wooden JL, Wiedenbeck M, Valley JW, Kitajima K, Bauer AM, Lowe DR (2022) Destabilization of long-lived Hadean protocrust and the onset of pervasive hydrous melting at 3.8 Ga. AGU Advances 3: e2021AV000520. 17pp. //doi.org/10.1029/2021AV000520

Earle S (2019) Physical Geology - 2nd edition. Victoria B.C.: BCcampus. //opentextbc.ca/physicalgeology2ed

Flannery DT, van Kranendonk MJ, Mazumder R, Walter M (2014) The *ca* 2.74 Ga Mopoke Member, Kylena Formation: a marine incursion into the northern Fortescue Group? Australian Journal of Earth Sciences 61: 1095-1108. //doi.org/10.1080/08120099.2014.960898

Fralik P, Davis DW, Kissin SA (2002) The age of the Gunflint Formation, Ontario, Canada: single zircon U-Pb age determinations from reworked volcanic ash. Canadian Journal of Earth Sciences 39: 1085-1091. //doi.org/10.1139/E02-028

Garenne A, Beck P, Montes-Hernandez G, Bonal L, Quirico E, Proux O, Hazemann JL (2019) The iron record of asteroidal processes in carbonaceous chondrites. Meteoritics & Planetary Science 54(11): 2652-2665. //doi.org/10.1111/maps.13377

Garvie LAJ, Craven AJ, Brydson R (1994) Use of electron-energy loss near-edge fine structure in the study of minerals. American Mineralogist 79: 411-425.

Garvie LAJ, Buseck PR (1999) Bonding in silicates: Investigation of the Si L<sub>2,3</sub> edge by parallel electron energy-loss spectroscopy. American Mineralogist 84: 946-964.

Georgakilas V, Perman JA, Tucek J, Zboril R (2015) Broad family of carbon nanoallotropes: classification, chemistry, and applications of fullerenes, carbon dots, nanotubes, graphene, nanodiamonds, and combined superstructures. Chemical Reviews 115: 4744-4822. //doi.org/10.1021/cr500304f

Guggenheim S, Eggleton RA (1998) Modulated crystal structures of greenalite and caryopilite: a system with long-range, in-plane structural disorder in the tetrahedral sheet. Can Mineral 36: 163-179

Hickman AH (2021) East Pilbara Craton: a record of one billion years in the growth of Archean continental crust. Government of western Australia, Dept. Mines, Industrial regulation and safety; Geological Survey of W. Australia, Perth, report 143

Hickman-Lewis K, Cavalazzi B, Foucher F, Westall F (2018) Most ancient evidence for life in the Barberton greenstone belt: Microbial mats and biofabrics of the ~3.47 Ga Middle Marker horizon. Precambrian Research 312:45-67 //doi.org/10.1016/j.precamres.2018.04.007

Hofmann A (2005) The geochemistry of sedimentary rocks from the Fig Tree Group, Barberton greenstone belt: Implications for tectonic, hydrothermal and surface processes during mid-Archaean times. Precambrian Research 143: 23-49. //doi.org/10.1016/j.precamres.2005.09.005

Hofmann A, Harris C (2008) Silica alteration zones in the Barberton Greenstone Belt: A window into subseafloor processes 3.5-3.3 Ga ago. Chemical Geology 257: 221-239. //doi.org/10.1016/j.chemgeo.2008.09.015

Hofmann A, Bolhar R, Orberger B, Foucher F (2013) Cherts of the Barberton Greenstone Belt, South Africa: petrology and trace-element geochemistry of the 3.5 to 3.3 Ga old silicified volcaniclastic sediments. South African Journal of Geology 116(2): 297-322. //doi.org/10.2113/gssajg.116.2.297

Hofmann A, Anhaeusser RC, Dixon J, Kröner A, Saha L, Wilson A, Xie H (2019) Archaean granitoid-greenstone geology of the southeastern part of the Kaapvaal Craton. In:
reveal early plate tectonic genes flanking subduction margins. Geoscience Frontiers 9: 603-665. //doi.org/10.1016/j.gsf.2017.10.005

Drabon N, Byerly BL, Byerly GR, Wooden JL, Wiedenbeck M, Valley JW, Kitajima K, Bauer AM, Lowe DR (2022) Destabilization of long-lived Hadean protocrust and the onset of pervasive hydrous melting at 3.8 Ga. AGU Advances 3: e2021AV000520. 17pp. //doi.org/10.1029/2021AV000520

Earle S (2019) Physical Geology - 2nd edition. Victoria B.C.: BCcampus. //opentextbc.ca/physicalgeology2ed

Flannery DT, van Kranendonk MJ, Mazumder R, Walter M (2014) The *ca* 2.74 Ga Mopoke Member, Kylena Formation: a marine incursion into the northern Fortescue Group? Australian Journal of Earth Sciences 61: 1095-1108. //doi.org/10.1080/08120099.2014.960898

Fralik P, Davis DW, Kissin SA (2002) The age of the Gunflint Formation, Ontario, Canada: single zircon U-Pb age determinations from reworked volcanic ash. Canadian Journal of Earth Sciences 39: 1085-1091. //doi.org/10.1139/E02-028

Garenne A, Beck P, Montes-Hernandez G, Bonal L, Quirico E, Proux O, Hazemann JL (2019) The iron record of asteroidal processes in carbonaceous chondrites. Meteoritics & Planetary Science 54(11): 2652-2665. //doi.org/10.1111/maps.13377

Garvie LAJ, Craven AJ, Brydson R (1994) Use of electron-energy loss near-edge fine structure in the study of minerals. American Mineralogist 79: 411-425.

Garvie LAJ, Buseck PR (1999) Bonding in silicates: Investigation of the Si L<sub>2,3</sub> edge by parallel electron energy-loss spectroscopy. American Mineralogist 84: 946-964.

Georgakilas V, Perman JA, Tucek J, Zboril R (2015) Broad family of carbon nanoallotropes: classification, chemistry, and applications of fullerenes, carbon dots, nanotubes, graphene, nanodiamonds, and combined superstructures. Chemical Reviews 115: 4744-4822. //doi.org/10.1021/cr500304f

Guggenheim S, Eggleton RA (1998) Modulated crystal structures of greenalite and caryopilite: a system with long-range, in-plane structural disorder in the tetrahedral sheet. Can Mineral 36: 163-179

Hickman AH (2021) East Pilbara Craton: a record of one billion years in the growth of Archean continental crust. Government of western Australia, Dept. Mines, Industrial regulation and safety; Geological Survey of W. Australia, Perth, report 143

Hickman-Lewis K, Cavalazzi B, Foucher F, Westall F (2018) Most ancient evidence for life in the Barberton greenstone belt: Microbial mats and biofabrics of the ~3.47 Ga Middle Marker horizon. Precambrian Research 312:45-67 //doi.org/10.1016/j.precamres.2018.04.007

Hofmann A (2005) The geochemistry of sedimentary rocks from the Fig Tree Group, Barberton greenstone belt: Implications for tectonic, hydrothermal and surface processes during mid-Archaean times. Precambrian Research 143: 23-49. //doi.org/10.1016/j.precamres.2005.09.005

Hofmann A, Harris C (2008) Silica alteration zones in the Barberton Greenstone Belt: A window into subseafloor processes 3.5-3.3 Ga ago. Chemical Geology 257: 221-239. //doi.org/10.1016/j.chemgeo.2008.09.015

Hofmann A, Bolhar R, Orberger B, Foucher F (2013) Cherts of the Barberton Greenstone Belt, South Africa: petrology and trace-element geochemistry of the 3.5 to 3.3 Ga old silicified volcaniclastic sediments. South African Journal of Geology 116(2): 297-322. //doi.org/10.2113/gssajg.116.2.297

Hofmann A, Anhaeusser RC, Dixon J, Kröner A, Saha L, Wilson A, Xie H (2019) Archaean granitoid-greenstone geology of the southeastern part of the Kaapvaal Craton. In:
Kröner A, Hofmann A (eds) The Archean Geology of the Kaapvaal Craton, South Africa, Springer Nature Switzerland, pp 33-54.
[doi.org/10.1007/978-3-319-78652-0](doi.org/10.1007/978-3-319-78652-0)

Huss GR, Rubin AE, Grossman JN (2006) Thermal metamorphism in chondrites. In: Lauretta DS, McSween HY (eds) Meteorites and the Early Solar System II, Space Science Series, Univ. of Arizona Press, pp 567-586. [doi.org/10.2307/j.ctv1v7zdmm.34](doi.org/10.2307/j.ctv1v7zdmm.34)

Jia X, Campos-Delgado J, Terrones M, Meunier V, Dresselhaus MS (2011) Graphene edges: a review of their fabrication and characterization. Nanoscale 3: 86-95.
[doi.org/10.1039/c0nr00600a](doi.org/10.1039/c0nr00600a)

Jmu (2000) Barrovian Metamorphism. Lectures on-line, James Madison University.
[csmgeo.csm.jmu.edu/geollab/fichter/metarx/barrovian.html](csmgeo.csm.jmu.edu/geollab/fichter/metarx/barrovian.html)

Kane A (2021) Synthèse de nanotubes, graphène et hybrides par PECVD et arc électrique. Ph.D. Thesis, Univ. Nouakchott Al-Aasriya, Mauritanie et Sorbonne Paris-Nord, France

Kisters AFM, Stevens G, Dziggel A, Armstrong RA (2003) Extensional detachment faulting and core-complex formation in the southern Barberton granite-greenstone terrain, South Africa: evidence for a 3.2 Ga orogenic collapse. Precambrian Research 127: 355-378. [doi.org/10.1016/j.precamres.2003.08.002](doi.org/10.1016/j.precamres.2003.08.002)

Klein C, Philpotts AR (2017) Earth materials: Introduction to Mineralogy and Petrology. Cambridge University Press, United Kingdom [doi.org/10.1017/9781316652909](doi.org/10.1017/9781316652909)

Kouketsu Y, Mizukami T, Mori H, Endo S, Aoya M, Hara H, Nakamura D, Wallis S (2014) A new approach to develop the Raman carbonaceous material geothermometer for low-grade metamorphism using peak width. Island Arc 23:33-50.
[doi.org/10.1111/iar.12057](doi.org/10.1111/iar.12057)

Kovalevski VV, Buseck PR, Cowley JM (2001) Comparison of carbon in shungite rocks to other natural carbons: an X-ray and TEM study. Carbon 39: 243-256

Kröner A, Hofmann A (2019) The Archean Geology of the Kaapvaal Craton, South Africa, Springer Nature Switzerland. [doi.org/10.1007/978-3-319-78652-0](doi.org/10.1007/978-3-319-78652-0)

Kröner A, Hoffmann JE, Wong M J, Geng H-Y, Schneider PK, Xie H, Yang J-H, Nhleko N (2019) Archean crystalline rocks of the Eastern Kaapvaal Craton. In: Kröner A, Hofmann A (eds) The Archean Geology of the Kaapvaal Craton, South Africa, Springer Nature Switzerland, p 1. [doi.org/10.1007/978-3-319-78652-0](doi.org/10.1007/978-3-319-78652-0)

Krot AN, Scott ERD, Zolensky ME (1995) Mineralogical and chemical modification of components in CV3 chondrites: Nebular or asteroidal processing? Meteoritics 30: 748-775

Krot AN, Petaev MI, Scott ERD, Choi BG, Zolensky ME, Keil K (1998) Progressive alteration in CV3 chondrites: more evidence for asteroidal alteration. Meteoritics & Planetary Science 33: 1065-1085

Lahfid A, Beyssac O, Deville E, Negro F, Chopin C, Goffé B (2010) Evolution of the Raman spectrum of carbonaceous material in low-grade metasediments of the Glarus Alps (Switzerland). Terra Nova 22(5): 354-360
[doi.org/10.1111/j.1365-3121.2010.00956.x](doi.org/10.1111/j.1365-3121.2010.00956.x)

Ledevin M (2013) Les cherts Archéens de la ceinture de roches vertes de Barberton (3.5-3.2Ga), Afrique du Sud. Processus de formation et utilisation comme proxys paleo-environnementaux. Thesis-Earth Sciences, Université de Grenoble, France

Lepot K, Addad A, Knoll AH, Wang J, Troadec D, Béché A, Javaux EJ (2017) Iron minerals within specific microfossil morphospecies of the 1.88 Ga Gunflint Formation. Nature Communications 8: 14890. [doi.org/10.1038/ncomms14890](doi.org/10.1038/ncomms14890)

Liu J, Yang B (2020) Carbon dots: a new type of carbon-based nanomaterial with wide applications. ACS Central Science 6: 2179-2195.
Kröner A, Hofmann A (eds) The Archean Geology of the Kaapvaal Craton, South Africa, Springer Nature Switzerland, pp 33-54.
[doi.org/10.1007/978-3-319-78652-0](doi.org/10.1007/978-3-319-78652-0)

Huss GR, Rubin AE, Grossman JN (2006) Thermal metamorphism in chondrites. In: Lauretta DS, McSween HY (eds) Meteorites and the Early Solar System II, Space Science Series, Univ. of Arizona Press, pp 567-586. [doi.org/10.2307/j.ctv1v7zdmm.34](doi.org/10.2307/j.ctv1v7zdmm.34)

Jia X, Campos-Delgado J, Terrones M, Meunier V, Dresselhaus MS (2011) Graphene edges: a review of their fabrication and characterization. Nanoscale 3: 86-95.
[doi.org/10.1039/c0nr00600a](doi.org/10.1039/c0nr00600a)

Jmu (2000) Barrovian Metamorphism. Lectures on-line, James Madison University.
[csmgeo.csm.jmu.edu/geollab/fichter/metarx/barrovian.html](csmgeo.csm.jmu.edu/geollab/fichter/metarx/barrovian.html)

Kane A (2021) Synthèse de nanotubes, graphène et hybrides par PECVD et arc électrique. Ph.D. Thesis, Univ. Nouakchott Al-Aasriya, Mauritanie et Sorbonne Paris-Nord, France

Kisters AFM, Stevens G, Dziggel A, Armstrong RA (2003) Extensional detachment faulting and core-complex formation in the southern Barberton granite-greenstone terrain, South Africa: evidence for a 3.2 Ga orogenic collapse. Precambrian Research 127: 355-378. [doi.org/10.1016/j.precamres.2003.08.002](doi.org/10.1016/j.precamres.2003.08.002)

Klein C, Philpotts AR (2017) Earth materials: Introduction to Mineralogy and Petrology. Cambridge University Press, United Kingdom [doi.org/10.1017/9781316652909](doi.org/10.1017/9781316652909)

Kouketsu Y, Mizukami T, Mori H, Endo S, Aoya M, Hara H, Nakamura D, Wallis S (2014) A new approach to develop the Raman carbonaceous material geothermometer for low-grade metamorphism using peak width. Island Arc 23:33-50.
[doi.org/10.1111/iar.12057](doi.org/10.1111/iar.12057)

Kovalevski VV, Buseck PR, Cowley JM (2001) Comparison of carbon in shungite rocks to other natural carbons: an X-ray and TEM study. Carbon 39: 243-256

Kröner A, Hofmann A (2019) The Archean Geology of the Kaapvaal Craton, South Africa, Springer Nature Switzerland. [doi.org/10.1007/978-3-319-78652-0](doi.org/10.1007/978-3-319-78652-0)

Kröner A, Hoffmann JE, Wong M J, Geng H-Y, Schneider PK, Xie H, Yang J-H, Nhleko N (2019) Archean crystalline rocks of the Eastern Kaapvaal Craton. In: Kröner A, Hofmann A (eds) The Archean Geology of the Kaapvaal Craton, South Africa, Springer Nature Switzerland, p 1. [doi.org/10.1007/978-3-319-78652-0](doi.org/10.1007/978-3-319-78652-0)

Krot AN, Scott ERD, Zolensky ME (1995) Mineralogical and chemical modification of components in CV3 chondrites: Nebular or asteroidal processing? Meteoritics 30: 748-775

Krot AN, Petaev MI, Scott ERD, Choi BG, Zolensky ME, Keil K (1998) Progressive alteration in CV3 chondrites: more evidence for asteroidal alteration. Meteoritics & Planetary Science 33: 1065-1085

Lahfid A, Beyssac O, Deville E, Negro F, Chopin C, Goffé B (2010) Evolution of the Raman spectrum of carbonaceous material in low-grade metasediments of the Glarus Alps (Switzerland). Terra Nova 22(5): 354-360
[doi.org/10.1111/j.1365-3121.2010.00956.x](doi.org/10.1111/j.1365-3121.2010.00956.x)

Ledevin M (2013) Les cherts Archéens de la ceinture de roches vertes de Barberton (3.5-3.2Ga), Afrique du Sud. Processus de formation et utilisation comme proxys paleo-environnementaux. Thesis-Earth Sciences, Université de Grenoble, France

Lepot K, Addad A, Knoll AH, Wang J, Troadec D, Béché A, Javaux EJ (2017) Iron minerals within specific microfossil morphospecies of the 1.88 Ga Gunflint Formation. Nature Communications 8: 14890. [doi.org/10.1038/ncomms14890](doi.org/10.1038/ncomms14890)

Liu J, Yang B (2020) Carbon dots: a new type of carbon-based nanomaterial with wide applications. ACS Central Science 6: 2179-2195.
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Moyen JF, Stevens G, Kisters AFM, Belcher RW (2007) TTG plutons of the Barberton granitoid-greenstone terrain, South Africa. In: van Kranendonk MJ, Smithies RH, Bennett VC (eds) Precambrian ophiolites and related rocks, Elsevier, Amsterdam, Netherlands, chapt 5.6-3.4. //doi.org/10.1016/S0166-2635(07)15056-8

Moyen JF, Stevens G, Kisters AFM, Belcher RW, Lemirre B (2019) TTG plutons of the Barberton granitoid-greenstone terrain, South Africa. In: van Kranendonk MJ, Bennett VC, Hoffmann JE (eds) Earth's oldest rocks, Elsevier, Amsterdam, Netherlands, pp 615-654. ISBN: 978-0-444-63901-1

Nemanich RJ, Solin SA (1977) Observation of an anomalously sharp feature in the second-order Raman spectrum of graphite. Solid state communications 23: 417-420

Nemanich RJ, Solin SA (1979) First- and second-order Raman scattering from finite-size crystals of graphite. Physical Review B 20(2): 392-401

Notre Dame University (2017) Metamorphic Facies. https://www3.nd.edu/~asimonet/CE30540/SP2017/Lecture_21_new_Meta_Facies_2_SP2017_web_based.pdf

Poujol M, Robb LJ, Anhaeusser CR, Gericke B (2003) A review of the geochronological constraints on the evolution of the Kaapvaal Craton, South Africa. Precambrian Research 127: 181-213. //doi.org/10.1016/S0301-9268(03)00187-6
Ricca A, Roser JE, Peeters E, Boersma C (2019) Polycyclic aromatic hydrocarbons with armchair edges: potential emitters in class B sources. The astrophysical journal 882: 56 (28pp). //doi.org/10.3847/1538-4357/ab3124

Sheka EF, Golubev YA, Popova NA (2020a) Graphene domains signature of Raman spectra of sp² amorphous carbons. Nanomaterials 10: 2021 (22pp). //doi.org/10.3390/nano10102021

Sheka EF, Natkaniec I, Ipatova EU, Golubev YA, Kabachkov EN, Popova VA (2020b) Heteroatom necklaces of sp² amorphous carbons. XPS supported INS and DRIFT spectroscopy. Fullerenes, Nanotubes and Carbon Nanostructures 28(12): 1010-1029. //doi.org/10.1080/1536383X.2020.1794849

Sugitani K, Grey K, Allwood A, Nagaoka T, Mimura K, Minami M, Marshall CP, van Kranendonk MJ, Walter MR (2007) Diverse microstructures from Archaean chert from the Mount Goldsworthy-Mount Grant area, Pilbara Craton, Western Australia: Microfossils, dubiofossils, or pseudofossils? Precambrian Research 158: 228-262. //doi.org/10.1016/j.precamres.2007.03.006

Sugitani K, Lepot K, Nagaoka T, Mimura K, van Kranendonk M, Oehler DZ, Walter MR (2010) Biogenicity of morphologically diverse carbonaceous microstructures from the ca. 3400 Ma Strelley Pool Formation, in the Pilbara Craton, Western Australia. Astrobiology 10(9): 899-920. //doi.org/10.1089/ast.2010.0513

Tan PH, Hu CY, Dong J, Shen WC, Zhang BF (2001) Polarization properties, high-order Raman spectra, and frequency asymmetry between Sitokes and anti-Stokes scattering of Raman modes in a graphite whisker. Physical Review B, 64: 214301-1-214301-12 //doi.org/10.1103/PhysRevB.64.214301

Tice MM and Lowe DR (2006) The origin of carbonaceous matter in pre-3.0 Ga greenstone terrains: A review and new evidence from the 3.42 Ga Buck Reef Chert. Earth Science Reviews 76: 259-300. //doi.org/10.1016/j.earscirev.2006.03.003

Tosca NJ, Guggenheim S, Pufahl PK (2016) An authigenic origin for Precambrian greenalite: Implications for iron formation and the chemistry of ancient seawater. Geological Society of America Bulletin 128: 511-530. //doi.org/10.1130/B31339.1

Tuinstra F, Koenig JL (1970) Rama spectrum of graphite. The Journal of Chemical Physics 53(3): 1126-1130

van Kranendonk MJ, Hickman AH, Smithies RH, Nelson DR (2002) Geology and tectonic evolution of the Archean North Pilbara Terrain, Pilbara Craton, Western Australia. Economic Geology 97: 696-732

van Kranendonk MJ, Collins WJ, Hickman A, Pawley MJ (2004) Critical tests of vertical vs horizontal tectonic models for the Archaean East Pilbara Granite- Greenstone Terrane, Pilbara Craton, Western Australia. Precambrian Research 131: 173-211. //doi.org/10.1016/j.precamres.2003.12.015

van Kranendonk MJ, Hickman AH, Smithies RH, Williams IR, Bagas L, Farrell TR (2006) Revised lithostratigraphy of Archean supracrustal and intrusive rocks in the northern Pilbara craton, Western Australia. Western Australia Geological Survey, Perth, Record 2006/15, 57pp

van Kranendonk MJ, Smithies RH, Hickman AH, Champion DC (2007) Review: secular tectonic evolution of Archean continental crust: interplay between horizontal and vertical processes in the formation of the Pilbara Craton, Australia. Terra Nova 19: 1-38. //doi.org/10.1111/j.1365-3121.2006.00723.x

van Kranendonk MJ, Philippot P, Lepot K, Bodorkos S, Pirajno F (2008) Geological setting of Earth's oldest fossils in the ca. 3.5 Ga Dresser Formation, Pilbara Craton, Western
Ricca A, Roser JE, Peeters E, Boersma C (2019) Polycyclic aromatic hydrocarbons with armchair edges: potential emitters in class B sources. The astrophysical journal 882: 56 (28pp). //doi.org/10.3847/1538-4357/ab3124

Sheka EF, Golubev YA, Popova NA (2020a) Graphene domains signature of Raman spectra of sp² amorphous carbons. Nanomaterials 10: 2021 (22pp). //doi.org/10.3390/nano10102021

Sheka EF, Natkaniec I, Ipatova EU, Golubev YA, Kabachkov EN, Popova VA (2020b) Heteroatom necklaces of sp² amorphous carbons. XPS supported INS and DRIFT spectroscopy. Fullerenes, Nanotubes and Carbon Nanostructures 28(12): 1010-1029. //doi.org/10.1080/1536383X.2020.1794849

Sugitani K, Grey K, Allwood A, Nagaoka T, Mimura K, Minami M, Marshall CP, van Kranendonk MJ, Walter MR (2007) Diverse microstructures from Archaean chert from the Mount Goldsworthy-Mount Grant area, Pilbara Craton, Western Australia: Microfossils, dubiofossils, or pseudofossils? Precambrian Research 158: 228-262. //doi.org/10.1016/j.precamres.2007.03.006

Sugitani K, Lepot K, Nagaoka T, Mimura K, van Kranendonk M, Oehler DZ, Walter MR (2010) Biogenicity of morphologically diverse carbonaceous microstructures from the ca. 3400 Ma Strelley Pool Formation, in the Pilbara Craton, Western Australia. Astrobiology 10(9): 899-920. //doi.org/10.1089/ast.2010.0513

Tan PH, Hu CY, Dong J, Shen WC, Zhang BF (2001) Polarization properties, high-order Raman spectra, and frequency asymmetry between Sitokes and anti-Stokes scattering of Raman modes in a graphite whisker. Physical Review B, 64: 214301-1-214301-12 //doi.org/10.1103/PhysRevB.64.214301

Tice MM and Lowe DR (2006) The origin of carbonaceous matter in pre-3.0 Ga greenstone terrains: A review and new evidence from the 3.42 Ga Buck Reef Chert. Earth Science Reviews 76: 259-300. //doi.org/10.1016/j.earscirev.2006.03.003

Tosca NJ, Guggenheim S, Pufahl PK (2016) An authigenic origin for Precambrian greenalite: Implications for iron formation and the chemistry of ancient seawater. Geological Society of America Bulletin 128: 511-530. //doi.org/10.1130/B31339.1

Tuinstra F, Koenig JL (1970) Rama spectrum of graphite. The Journal of Chemical Physics 53(3): 1126-1130

van Kranendonk MJ, Hickman AH, Smithies RH, Nelson DR (2002) Geology and tectonic evolution of the Archean North Pilbara Terrain, Pilbara Craton, Western Australia. Economic Geology 97: 696-732

van Kranendonk MJ, Collins WJ, Hickman A, Pawley MJ (2004) Critical tests of vertical vs horizontal tectonic models for the Archaean East Pilbara Granite- Greenstone Terrane, Pilbara Craton, Western Australia. Precambrian Research 131: 173-211. //doi.org/10.1016/j.precamres.2003.12.015

van Kranendonk MJ, Hickman AH, Smithies RH, Williams IR, Bagas L, Farrell TR (2006) Revised lithostratigraphy of Archean supracrustal and intrusive rocks in the northern Pilbara craton, Western Australia. Western Australia Geological Survey, Perth, Record 2006/15, 57pp

van Kranendonk MJ, Smithies RH, Hickman AH, Champion DC (2007) Review: secular tectonic evolution of Archean continental crust: interplay between horizontal and vertical processes in the formation of the Pilbara Craton, Australia. Terra Nova 19: 1-38. //doi.org/10.1111/j.1365-3121.2006.00723.x

van Kranendonk MJ, Philippot P, Lepot K, Bodorkos S, Pirajno F (2008) Geological setting of Earth's oldest fossils in the ca. 3.5 Ga Dresser Formation, Pilbara Craton, Western
Australia. Precambrian Research 167: 93-124.
[doi.org/10.1016/j.precamres.2008.07.003]

van Kranendonk MJ, Smithies RH, Hickman AH, Wingate MTD, Bodorkos S (2012) Evidence for Mesoarchean (~3.2 Ga) rifting of the Pilbara Craton: The missing link in an early Precambrian Wilson cycle. Precambrian Research 177: 145-161.
[doi.org/10.1016/j.precamres.2009.11.007]

van Kranendonk JM, Bennett CV, Hoffmann JE (2019) (eds) Earth's oldest rocks, Elsevier, Amsterdam, Netherlands, 1078 pp. ISBN: 978-0-444-63901-1

Wacey D, Saunders M, Kong C, Brasier A, Brasier M (2016) 3.46 Ga Apex chert 'microfossils' reinterpreted as mineral artefacts produced during phyllosilicates exfoliation. Gondwana Research 36: 296-313 [doi.org/10.1016/j.gr.2015.07.010]

Wacey D, Eiloart K, Saunders M (2021) Pathways of microfossil mineralisation by hematite in the 1878 Ma Gunflint Formation. Chemical Geology 581: 120419
[doi.org/10.1016/j.chemgeo.2021.120419]

Wang XY, Yao X, Müllen K (2019) Polycyclic aromatic hydrocarbons in the graphene era. Science China Chemistry 62: 1099-1144. [doi.org/10.1007/s11426-019-9491-2]

Weisberg MK, Prinz M, Clayton RN, Mayeda TK (1997) CV3 chondrites: three subgroups, not two. Meteoritics & Planetary Science 32: A138-A139

Westall F, de Wit MJ, Dann J, van der Gaast S, de Ronde CEJ, Gerneke D (2001) Early Archean fossil bacteria and biofilms in hydrothermally-influenced sediments from the Barberton Greenstone Belt, South Africa. Precambrian Research 106: 93-116.

Wopenka B, Pasteris DD (1993) Structural characterization of kerogens to granulite-facies graphite: applicability of Raman microprobe spectroscopy. American Mineralogist 78:533-557

Winter JD (2010) An introduction to igneous and metamorphic petrology. Prentice Hall, Upper Saddle River, New-Jersey. ISBN 0-13-21*03142-0

Wu J-B, Lin M-L, Cong X, Liu H-N, Tan P-H (2018) Raman spectroscopy of graphene-based materials and its applications in related devices. Chemical Society Reviews 47: 1822-1873. [doi.org/10.1039/c6cs00915h]

Xu L, Cheng L (2013) Graphite oxide under high pressure: a Raman spectroscopic study. Journal of nanomaterials v2013: 731874, 5pp. [doi.org/10.1155/2013/731875]

Yesiltas M, Young J, Glotch T (2021) Thermal metamorphic history of Antarctic CV3 and CO3 chondrites inferred from the first- and second-order Raman peaks of polyaromatic organic carbon. American Mineralogist 106: 506-517.
[doi.org/10.2138/am-2021-7507]

Yui TF, Huang E, Xu J (1996) Raman spectrum of carbonaceous material: a possible metamorphic grade indicator for low-grade metamorphic rocks. J. Metamorphic Geology 14: 115-124
Australia. Precambrian Research 167: 93-124.

//doi.org/10.1016/j.precamres.2008.07.003

van Kranendonk MJ, Smithies RH, Hickman AH, Wingate MTD, Bodorkos S (2012) Evidence for Mesoarchean (~3.2 Ga) rifting of the Pilbara Craton: The missing link in an early Precambrian Wilson cycle. Precambrian Research 177: 145-161.
//doi.org/10.1016/j.precamres.2009.11.007

van Kranendonk JM, Bennett CV, Hoffmann JE (2019) (eds) Earth's oldest rocks, Elsevier, Amsterdam, Netherlands, 1078 pp. ISBN: 978-0-444-63901-1

Wacey D, Saunders M, Kong C, Brasier A, Brasier M (2016) 3.46 Ga Apex chert 'microfossils' reinterpreted as mineral artefacts produced during phyllosilicates exfoliation. Gondwana Research 36: 296-313 //doi.org/10.1016/j.gr.2015.07.010

Wacey D, Eiloart K, Saunders M (2021) Pathways of microfossil mineralisation by hematite in the 1878 Ma Gunflint Formation. Chemical Geology 581: 120419
//doi.org/10.1016/j.chemgeo.2021.120419

Wang XY, Yao X, Müllen K (2019) Polycyclic aromatic hydrocarbons in the graphene era. Science China Chemistry 62: 1099-1144. //doi.org/10.1007/s11426-019-9491-2

Weisberg MK, Prinz M, Clayton RN, Mayeda TK (1997) CV3 chondrites: three subgroups, not two. Meteoritics & Planetary Science 32: A138-A139

Westall F, de Wit MJ, Dann J, van der Gaast S, de Ronde CEJ, Gerneke D (2001) Early Archean fossil bacteria and biofilms in hydrothermally-influenced sediments from the Barberton Greenstone Belt, South Africa. Precambrian Research 106: 93-116.

Wopenka B, Pasteris DD (1993) Structural characterization of kerogens to granulite-facies graphite: applicability of Raman microprobe spectroscopy. American Mineralogist 78:533-557

Winter JD (2010) An introduction to igneous and metamorphic petrology. Prentice Hall, Upper Saddle River, New-Jersey. ISBN 0-13-21*03142-0

Wu J-B, Lin M-L, Cong X, Liu H-N, Tan P-H (2018) Raman spectroscopy of graphene-based materials and its applications in related devices. Chemical Society Reviews 47: 1822-1873. //doi.org/10.1039/c6cs00915h

Xu L, Cheng L (2013) Graphite oxide under high pressure: a Raman spectroscopic study. Journal of nanomaterials v2013: 731874, 5pp. //doi.org/10.1155/2013/731875

Yesiltas M, Young J, Glotch T (2021) Thermal metamorphic history of Antarctic CV3 and CO3 chondrites inferred from the first- and second-order Raman peaks of polyaromatic organic carbon. American Mineralogist 106: 506-517.
//doi.org/10.2138/am-2021-7507

Yui TF, Huang E, Xu J (1996) Raman spectrum of carbonaceous material: a possible metamorphic grade indicator for low-grade metamorphic rocks. J. Metamorphic Geology 14: 115-124