Molecular mechanism of metamorphic alteration on traces of early life in banded iron formations

Nan, Jingbo; Peng, Zidong; Wang, Chao; Papineau, Dominic; She, Zhenbing; Guo, Zhaopei; Peng, Xiaotong; Zhou, Junlie; Hu, Yuling; Yao, Weiqi; Zhang, R. Y.; Wang, Changle; Tao, Renbiao

doi:10.1016/j.epsl.2023.118226

Cited by 4 publications

(4 citation statements)

References 56 publications

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“…The co-occurrence of multiple crystallinities of graphite has been documented in early Phanerozoic S-type granite from the Lusatian block of eastern central Europe 40 , Proterozoic gneiss and quartzite from the Iberian metamorphic belt of Spain 41 , Archean and Paleoproterozoic metamorphosed BIF from Nuvvuagittuq (Canada), Anshan (China), Wutai (China), and Michigamme (USA) 27 , 42 , as well as in chert from the Apex Formation in Western Australia 43 . The degree of graphitic order has been widely used to calculate the crystallisation temperature of graphite under peak metamorphic conditions 12 , 15 , 28 . Based on the geothermometer using Raman spectroscopy of organic matter calibrated for temperatures between 330 °C and 641 °C 44 , we calculate the crystallisation temperatures with a precision of about ±50 °C for the Gra I , Gra II , Gra III and Gra IV to be between 425 °C and 627 °C, between 415 °C and 610 °C, between 336 °C and 498 °C, and between 368 °C and 583 °C, respectively (Supplementary Data 2 ).…”

Section: Resultsmentioning

confidence: 99%

“…The carbon isotope values of graphite (δ 13 C gra ) in the Saglek-Hebron metasedimentary rocks range from −27.0‰ to −22.7‰ (average = −25.5‰, n = 8), while the carbon isotope values of carbonate (δ 13 C carb ) show an overall range of 9.8‰ (−11.2‰ to −1.4‰, average = −6.3‰, n = 8; Table 1 ). The low and large variable δ 13 C carb values indicate that these carbonates formed from the 12 C-enriched CO 2 produced by the oxidation of organic matter in rocks 15 , 42 , 45 , as suggested by our observation on the petrographic mode of occurrence with more Gra I and Gra II near the central zone of quartz-rich band and more graphite-free calcite grains near the Fe-silicate + magnetite portions of the Saglek-Hebron BIF (Fig. 1g ).…”

Section: Resultsmentioning

confidence: 99%

“…Observations show high-grade metamorphism results in biomass losing heteroatoms such as H, N, O and S 13 as well as 12 C and 14 N isotopes, thereby leaving isotopically heavy residual graphitic carbons 14 . To determine the precursor carbon in such graphitic carbon requires consideration of the effects of metamorphism and various abiotic processes that could potentially explain their composition and crystallinity in metamorphosed sedimentary rocks 1 , 15 .…”

Section: Introductionmentioning

confidence: 99%

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Abiotic synthesis of graphitic carbons in the Eoarchean Saglek-Hebron metasedimentary rocks

Guo,

Papineau,

O’Neil

et al. 2024

Nat Commun

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Graphite in metasedimentary rocks of the Eoarchean Saglek-Hebron Gneiss Complex (Canada) is depleted in 13C and has been interpreted as one of the oldest traces of life on Earth. The variation in crystallinity of this oldest graphitic carbon could possibly confirm the effect of metamorphism on original biomass, but this is still unexplored. Here, we report specific mineral associations with graphitic carbons that also have a range of crystallinity in the Saglek-Hebron metasedimentary rocks. Petrographic, geochemical and spectroscopic analyses in the Saglek-Hebron banded iron formations suggest that poorly crystalline graphite is likely deposited from C-H-O fluids derived from thermal decomposition of syngenetic organic matter, which is preserved as crystalline graphite during prograde metamorphism. In comparison, in the Saglek-Hebron marble, disseminations of graphite co-occur with carbonate and magnetite disseminations, pointing to abiotic synthesis of graphitic carbons via decarbonation. Our results thus highlight that variably crystalline graphitic carbons in the Saglek-Hebron metasedimentary rocks are potential abiotic products on early Earth, which lay the groundwork for identifying the preservation of prebiotic organic matter through metamorphism on Earth and beyond.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Abiotic synthesis of graphitic carbons in the Eoarchean Saglek-Hebron metasedimentary rocks

Guo,

Papineau,

O’Neil

et al. 2024

Nat Commun

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“…Predominantly, graphite deposits in Madagascar are believed to have originated from sediment metamorphism, as indicated by their light carbon isotopic compositions [18][19][20]. While some researchers propose the transformation of organic matter into graphite occurs via prograde metamorphism (graphitization) [21,22], others argue for the derivation of graphite from inorganic sources such as carbonates [23,24]. Yang et al [25] reported the existence of inorganic carbon in the Antanisoa graphite deposit (ANG) and suggested that carbon isotope exchange between organic and inorganic carbon occurred during the formation process.…”

Section: Introductionmentioning

confidence: 99%

A New Insight into the Genesis of Graphite Deposits in Madagascar Using U–Pb Zircon Dating and Electron Microprobe Analysis

Yang,

Di,

Zhang

et al. 2024

Minerals

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Madagascar is globally recognized as an important producer of high-quality flaky graphite. However, current research on graphite deposits in Madagascar remains insufficient. Previous studies have linked the genesis of Madagascan graphite deposits to the metamorphism of sedimentary organic matter. Here, we provide a case study of graphite deposits in Madagascar, combining new data from the Ambahita graphite deposit (AMG) in southern Madagascar with data from the Antanisoa graphite deposit (ANG) in central Madagascar and the Vohitasara graphite deposit (VOG) on the east coast of Madagascar. We note that the mineral assemblages of graphite-bearing rocks in the AMG, ANG, and VOG are not typical of metamorphic mineral assemblages but rather the results of filling and metasomatism by mantle-derived fluids that occurred after peak metamorphism. Electron microprobe analysis indicates that the graphite of the AMG, VOG, and ANG is usually associated with phlogopite or Mg-biotite; the phlogopite shares a common genesis with other widespread phlogopite deposits across Madagascar. We reveal that the distribution of graphite deposits in Madagascar is primarily controlled by ductile shear zones between blocks. Ductile shear zones that extend deep into the mantle can provide an ideal migration channel and architecture for the emplacement of mantle-derived fluids. The graphite mineralization formed no earlier than the peak metamorphism (490 Ma) and no later than the intrusion of pegmatite veins (389 ± 5 Ma). The distribution of graphite deposits, graphite orebody morphologies, mineral associations, and geochemical data suggest that the genesis of graphite deposits in Madagascar is linked to mantle-derived fluid filling rather than the metamorphism of sediments, as previously suggested. These findings have important implications for similar deposits in Madagascar and potentially globally.

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Assessing micrometer-scale contamination from organic materials in serpentinite analysis

Nan,

Zhu,

Ren

et al. 2023

Science of The Total Environment

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Molecular mechanism of metamorphic alteration on traces of early life in banded iron formations

Cited by 4 publications

References 56 publications

Abiotic synthesis of graphitic carbons in the Eoarchean Saglek-Hebron metasedimentary rocks

Abiotic synthesis of graphitic carbons in the Eoarchean Saglek-Hebron metasedimentary rocks

A New Insight into the Genesis of Graphite Deposits in Madagascar Using U–Pb Zircon Dating and Electron Microprobe Analysis

Assessing micrometer-scale contamination from organic materials in serpentinite analysis

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