Widespread occurrences of variably crystalline C-13-depleted graphitic carbon in banded iron formations

Matthew S. Dodd, Dominic Papineau, Zhen-Bing She, Chakravadhanula Manikyamba, Yu-Sheng Wan, Jonathan O'Neil, Juha A. Karhu, Hanika Rizo, Franco Pirajno

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Almost all evidence for the oldest traces of life on Earth rely on particles of graphitic carbon preserved in rocks of sedimentary protolith. Yet, the source of carbon in such ancient graphite is debated, as it could possibly be non-biological and/or non-indigenous in origin. Here we describe the co-occurrence of poorly crystalline and crystalline varieties of graphitic carbon with apatite in ten different and variably metamorphosed banded iron formations (BIF) ranging in age from 1,800 to >3,800 Myr. In Neoarchean to Palaeoproterozoic BIF subjected to low-grade metamorphism, C-13-depleted graphitic carbon occurs as inclusions in apatite, and carbonate and arguably represents the remineralisation of syngenetic biomass. In BIF subjected to high-grade metamorphism, C-13-depleted graphite co-occurs with poorly crystalline graphite (PCG), as well as apatite, carbonate, pyrite, amphibole and greenalite. Retrograde minerals such as greenalite, and veins cross-cutting magnetite layers contain PCG. Crystalline graphite can occur with apatite and orthopyroxene, and sometimes it has PCG coatings. Crystalline graphite is interpreted to represent the metamorphosed product of syngenetic organic carbon deposited in BIF, while poorly crystalline graphite was precipitated from C-O-H fluids partially sourced from the syngenetic carbon, along with fluid-deposited apatite and carbonate. The isotopic signature of the graphitic carbon and the distribution of fluid-deposited graphite in highly metamorphosed BIF is consistent with carbon in the fluids being derived from the thermal cracking of syngenetic biomass deposited in BIF, but, extraneous sources of carbon cannot be ruled out as a source for PCG. The results here show that apatite + graphite is a common mineral assemblage in metamorphosed BIF. The mode of formation of this assemblage is, however, variable, which has important implications for the timing of life's emergence on Earth. (C) 2019 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)163-174
Number of pages12
JournalEarth and Planetary Science Letters
Volume512
DOIs
Publication statusPublished - 15 Apr 2019

Cite this

Dodd, Matthew S. ; Papineau, Dominic ; She, Zhen-Bing ; Manikyamba, Chakravadhanula ; Wan, Yu-Sheng ; O'Neil, Jonathan ; Karhu, Juha A. ; Rizo, Hanika ; Pirajno, Franco. / Widespread occurrences of variably crystalline C-13-depleted graphitic carbon in banded iron formations. In: Earth and Planetary Science Letters. 2019 ; Vol. 512. pp. 163-174.
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abstract = "Almost all evidence for the oldest traces of life on Earth rely on particles of graphitic carbon preserved in rocks of sedimentary protolith. Yet, the source of carbon in such ancient graphite is debated, as it could possibly be non-biological and/or non-indigenous in origin. Here we describe the co-occurrence of poorly crystalline and crystalline varieties of graphitic carbon with apatite in ten different and variably metamorphosed banded iron formations (BIF) ranging in age from 1,800 to >3,800 Myr. In Neoarchean to Palaeoproterozoic BIF subjected to low-grade metamorphism, C-13-depleted graphitic carbon occurs as inclusions in apatite, and carbonate and arguably represents the remineralisation of syngenetic biomass. In BIF subjected to high-grade metamorphism, C-13-depleted graphite co-occurs with poorly crystalline graphite (PCG), as well as apatite, carbonate, pyrite, amphibole and greenalite. Retrograde minerals such as greenalite, and veins cross-cutting magnetite layers contain PCG. Crystalline graphite can occur with apatite and orthopyroxene, and sometimes it has PCG coatings. Crystalline graphite is interpreted to represent the metamorphosed product of syngenetic organic carbon deposited in BIF, while poorly crystalline graphite was precipitated from C-O-H fluids partially sourced from the syngenetic carbon, along with fluid-deposited apatite and carbonate. The isotopic signature of the graphitic carbon and the distribution of fluid-deposited graphite in highly metamorphosed BIF is consistent with carbon in the fluids being derived from the thermal cracking of syngenetic biomass deposited in BIF, but, extraneous sources of carbon cannot be ruled out as a source for PCG. The results here show that apatite + graphite is a common mineral assemblage in metamorphosed BIF. The mode of formation of this assemblage is, however, variable, which has important implications for the timing of life's emergence on Earth. (C) 2019 Elsevier B.V. All rights reserved.",
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Widespread occurrences of variably crystalline C-13-depleted graphitic carbon in banded iron formations. / Dodd, Matthew S.; Papineau, Dominic; She, Zhen-Bing; Manikyamba, Chakravadhanula; Wan, Yu-Sheng; O'Neil, Jonathan; Karhu, Juha A.; Rizo, Hanika; Pirajno, Franco.

In: Earth and Planetary Science Letters, Vol. 512, 15.04.2019, p. 163-174.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Widespread occurrences of variably crystalline C-13-depleted graphitic carbon in banded iron formations

AU - Dodd, Matthew S.

AU - Papineau, Dominic

AU - She, Zhen-Bing

AU - Manikyamba, Chakravadhanula

AU - Wan, Yu-Sheng

AU - O'Neil, Jonathan

AU - Karhu, Juha A.

AU - Rizo, Hanika

AU - Pirajno, Franco

PY - 2019/4/15

Y1 - 2019/4/15

N2 - Almost all evidence for the oldest traces of life on Earth rely on particles of graphitic carbon preserved in rocks of sedimentary protolith. Yet, the source of carbon in such ancient graphite is debated, as it could possibly be non-biological and/or non-indigenous in origin. Here we describe the co-occurrence of poorly crystalline and crystalline varieties of graphitic carbon with apatite in ten different and variably metamorphosed banded iron formations (BIF) ranging in age from 1,800 to >3,800 Myr. In Neoarchean to Palaeoproterozoic BIF subjected to low-grade metamorphism, C-13-depleted graphitic carbon occurs as inclusions in apatite, and carbonate and arguably represents the remineralisation of syngenetic biomass. In BIF subjected to high-grade metamorphism, C-13-depleted graphite co-occurs with poorly crystalline graphite (PCG), as well as apatite, carbonate, pyrite, amphibole and greenalite. Retrograde minerals such as greenalite, and veins cross-cutting magnetite layers contain PCG. Crystalline graphite can occur with apatite and orthopyroxene, and sometimes it has PCG coatings. Crystalline graphite is interpreted to represent the metamorphosed product of syngenetic organic carbon deposited in BIF, while poorly crystalline graphite was precipitated from C-O-H fluids partially sourced from the syngenetic carbon, along with fluid-deposited apatite and carbonate. The isotopic signature of the graphitic carbon and the distribution of fluid-deposited graphite in highly metamorphosed BIF is consistent with carbon in the fluids being derived from the thermal cracking of syngenetic biomass deposited in BIF, but, extraneous sources of carbon cannot be ruled out as a source for PCG. The results here show that apatite + graphite is a common mineral assemblage in metamorphosed BIF. The mode of formation of this assemblage is, however, variable, which has important implications for the timing of life's emergence on Earth. (C) 2019 Elsevier B.V. All rights reserved.

AB - Almost all evidence for the oldest traces of life on Earth rely on particles of graphitic carbon preserved in rocks of sedimentary protolith. Yet, the source of carbon in such ancient graphite is debated, as it could possibly be non-biological and/or non-indigenous in origin. Here we describe the co-occurrence of poorly crystalline and crystalline varieties of graphitic carbon with apatite in ten different and variably metamorphosed banded iron formations (BIF) ranging in age from 1,800 to >3,800 Myr. In Neoarchean to Palaeoproterozoic BIF subjected to low-grade metamorphism, C-13-depleted graphitic carbon occurs as inclusions in apatite, and carbonate and arguably represents the remineralisation of syngenetic biomass. In BIF subjected to high-grade metamorphism, C-13-depleted graphite co-occurs with poorly crystalline graphite (PCG), as well as apatite, carbonate, pyrite, amphibole and greenalite. Retrograde minerals such as greenalite, and veins cross-cutting magnetite layers contain PCG. Crystalline graphite can occur with apatite and orthopyroxene, and sometimes it has PCG coatings. Crystalline graphite is interpreted to represent the metamorphosed product of syngenetic organic carbon deposited in BIF, while poorly crystalline graphite was precipitated from C-O-H fluids partially sourced from the syngenetic carbon, along with fluid-deposited apatite and carbonate. The isotopic signature of the graphitic carbon and the distribution of fluid-deposited graphite in highly metamorphosed BIF is consistent with carbon in the fluids being derived from the thermal cracking of syngenetic biomass deposited in BIF, but, extraneous sources of carbon cannot be ruled out as a source for PCG. The results here show that apatite + graphite is a common mineral assemblage in metamorphosed BIF. The mode of formation of this assemblage is, however, variable, which has important implications for the timing of life's emergence on Earth. (C) 2019 Elsevier B.V. All rights reserved.

KW - early life

KW - banded iron formation

KW - carbon isotopes

KW - Raman

KW - graphite

KW - biosignatures

KW - FLUID-DEPOSITED GRAPHITE

KW - SUPRACRUSTAL ROCKS

KW - GREENSTONE-BELT

KW - LIFE

KW - ORIGIN

KW - RAMAN

KW - AKILIA

KW - APATITE

KW - ISOTOPE

KW - METASEDIMENTS

U2 - 10.1016/j.epsl.2019.01.054

DO - 10.1016/j.epsl.2019.01.054

M3 - Article

VL - 512

SP - 163

EP - 174

JO - Earth & Planetary Science Letters

JF - Earth & Planetary Science Letters

SN - 0012-821X

ER -