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Apatite nanoparticles in 3.46–2.46 Ga iron formations: Evidence for phosphorus-rich hydrothermal plumes on early Earth

Rasmussen, Birger and Muhling, Janet R. and Suvorova, Alexandra and Fischer, Woodward W. (2021) Apatite nanoparticles in 3.46–2.46 Ga iron formations: Evidence for phosphorus-rich hydrothermal plumes on early Earth. Geology, 49 (6). pp. 647-651. ISSN 0091-7613. doi:10.1130/g48374.1.

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Phosphorus is an essential nutrient that is thought to have regulated primary productivity in global oceans after the advent of oxygenic photosynthesis. The prime source of seawater phosphorus is regarded to be continental weathering of phosphate minerals. Ancient seawater phosphorus concentrations have been constrained using the phosphorus content of iron-rich chemical sediments—banded iron formations (BIFs); however, the removal processes and depositional phases remain unclear. Here we report that nanometer-sized apatite crystals (<500 nm) are ubiquitous in 3.46–2.46 Ga BIFs and cherts from the Kaapvaal (South Africa) and Yilgarn and Pilbara (Western Australia) cratons. The apatite is uniformly dispersed in a chemical sediment comprising greenalite nanoparticles, which were encased in very early diagenetic silica cement that limited compaction and chemical reactions. The lack of organic carbon (below detection; <0.3 wt%) and absence of primary iron oxides implies that the phosphorus was not derived from the degradation of organic matter or seawater scavenging by oxide particles. Instead, the occurrence of apatite in sediments derived from hydrothermally sourced Fe²⁺ and SiO₂ (aq) suggests that phosphorus too was derived from vent plumes. Today, seawater P is rapidly removed from vent fluids due to scavenging by oxidized Fe²⁺. However, prior to the Great Oxidation Event (2.45–2.32 Ga), dissolved phosphorus released during anoxic alteration of seafloor basalts escaped the iron-oxidation trap. Our results point to the existence of a submarine hydrothermal flux of dissolved phosphorus that supplied nutrients to the early anoxic oceans. High amounts of seawater P may help to explain why phosphorus is ubiquitous in cell biology—it was not limiting during the origin and early evolution of life.

Item Type:Article
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URLURL TypeDescription
Rasmussen, Birger0000-0001-5052-6797
Fischer, Woodward W.0000-0002-8836-3054
Additional Information:© 2021 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Manuscript received 8 September 2020; Revised manuscript received 30 November 2020; Manuscript accepted 2 December 2020. This work was supported by Australian Research Council grants DP140100512 (to Rasmussen) and DP190102237 (to Rasmussen and Muhling). Support for Fischer was provided by the Simons Foundation Collaboration on the Origins of Life (New York, USA). Focused ion beam and TEM analyses were performed at the Centre for Microscopy, Characterisation and Analysis at The University of Western Australia, a node of Microscopy Australia funded from university and government sources. The manuscript benefitted from comments by Huan Cui and two anonymous journal reviewers.
Funding AgencyGrant Number
Australian Research CouncilDP140100512
Australian Research CouncilDP190102237
Simons FoundationUNSPECIFIED
Issue or Number:6
Record Number:CaltechAUTHORS:20210209-143705993
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Official Citation:Rasmussen, B., et al., 2021, Apatite nanoparticles in 3.46–2.46 Ga iron formations: Evidence for phosphorus-rich hydrothermal plumes on early Earth: Geology, v. 49, p. 647–651,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107970
Deposited By: Tony Diaz
Deposited On:09 Feb 2021 22:48
Last Modified:03 Jun 2021 18:59

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