Anoxygenic photosynthesis linked to Neoarchean iron formations in Carajas (Brazil)

Autor(es)

Rego, Eric Siciliano ^{[1, 2, 3]} ; Busigny, Vincent ^[2] ; Lalonde, Stefan V. ^[4] ; Philippot, Pascal ^{[5, 2, 3]} ; Bouyon, Amaury ^[3] ; Rossignol, Camille ^{[5, 2]} ; Babinski, Marly ^[1] ; de Cassia Zapparoli, Adriana ^[6]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Geociencias, Rua Lago 562, BR-05508080 Sao Paulo - Brazil

^[2] Univ Paris, CNRS, Inst Phys Globe Paris, Paris 05 - France

^[3] Univ Antilles, Univ Montpellier, CNRS, Geosci Montpellier, F-34095 Montpellier - France

^[4] Univ Bretagne Occidentale, CNRS, Inst Univ Europeen Mer, Plouzane - France

^[5] Univ Sao Paulo, Dept Geofis, Inst Astron Geofis & Ciencias Atmosfer, Sao Paulo - Brazil

^[6] Vale SA, CTF, Nova Lima - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Geobiology; v. 19, n. 4, p. 326-341, JUL 2021.
• Citações Web of Science: 0

Resumo

Microbial activity is often invoked as a direct or indirect contributor to the precipitation of ancient chemical sedimentary rocks such as Precambrian iron formations (IFs). Determining a specific metabolic pathway from the geological record remains a challenge, however, due to a lack of constraints on the initial conditions and microbially induced redox reactions involved in the formation of iron oxides. Thus, there is ongoing debate concerning the role of photoferrotrophy, that is the process by which inorganic carbon is fixed into organic matter using light as an energy source and Fe(II) as an electron donor, in the deposition of IFs. Here, we examine similar to 2.74-Ga-old Neoarchean IFs and associated carbonates from the Carajas Mineral Province, Brazil, to reconstruct redox conditions and to infer the oxidizing mechanism that allowed one of the world's largest iron deposits to form. The absence of cerium (Ce) anomalies reveals that conditions were pervasively anoxic during IF deposition, while unprecedented europium (Eu) anomalies imply that Fe was supplied by intense hydrothermal activity. A positive and homogeneous Fe isotopic signal in space and time in these IFs indicates a low degree of partial oxidation of Fe(II), which, combined with the presence of C-13-depleted organic matter, points to a photoautotrophic metabolic driver. Collectively, our results argue in favor of reducing conditions during IF deposition and suggest anoxygenic photosynthesis as the most plausible mechanism responsible for Fe oxidation in the Carajas Basin. (AU)

• Processo FAPESP: 18/02645-2 - Cronestratigrafia e rastreamento isotópico do Supergrupo Minas, Paleoproterozóico
• Beneficiário: Camille Yann Rossignol
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 19/16271-0 - Geoquímica elementar e isotópica de formações ferríticas, carbonatos e folhelhos negros: condições paleoredox durante o Neoarqueano, Paleo- e Neoproterozóico no Brasil
• Beneficiário: Eric Siciliano Rego
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Doutorado
• Processo FAPESP: 15/16235-2 - Evolução da vida e oxigenação da Terra primitiva: uma perspectiva a partir da América do Sul
• Beneficiário: Pascal Andre Marie Philippot
• Modalidade de apoio: Auxílio à Pesquisa - Programa SPEC