{"title":"LATE ARCHEAN SHELF-TO-BASIN IRON SHUTTLE CONTRIBUTES TO THE FORMATION OF THE WORLD-CLASS DATAIGOU BANDED IRON FORMATION","authors":"Changle Wang, Mingguo Zhai, Leslie J. Robbins, Zidong Peng, Xin Zhang, Lianchang Zhang","doi":"10.5382/econgeo.5047","DOIUrl":null,"url":null,"abstract":"\n Banded iron formations (BIFs) are among the few chemical sedimentary archives that capture the biogeochemical evolution of Fe cycling and the redox evolution of the early Earth. Although biologically recycled continental Fe has been previously proposed to be a significant source of Fe in BIFs deposited from a stratified ocean at the onset of the Great Oxidation Event (GOE; ~2.5–2.2 Ga), constraining Fe sources and pathways in Archean BIFs remains challenging. Here we present major and trace element and Fe-Nd-Cr isotope data for the largest BIF (i.e., Dataigou) in China to test whether a benthic Fe shuttle was operative during deposition of pre-GOE BIFs. The absence of true, shale-normalized Ce anomalies, coupled with unfractionated Cr and positive Fe isotope compositions, suggests that BIF deposition occurred in an anoxic water column under reducing atmospheric conditions, whereas positive Eu anomalies indicate a significant input from a high-temperature hydrothermal source. Based on a significant correlation between initial Nd and Fe isotope data, we suggest that two Fe sources were periodically mixed and resulted in deposition of the Dataigou BIF. Here, we suggest the following sources: (1) hydrothermal fluids from sea-floor systems (low εNd(t) and high δ56Fe), derived from the interaction of fluids with underlying, older continental crust, and (2) a benthic Fe flux (high εNd(t) and low δ56Fe), generated by microbial Fe(III) reduction in coastal sediments during weathering of a nearby depleted landmass. Results presented here confirm, for the first time, that a microbially driven Fe shuttle was operational and supplied Fe on a basin-wide scale in the absence of atmospheric oxygen.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":null,"pages":null},"PeriodicalIF":5.5000,"publicationDate":"2024-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Economic Geology","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.5382/econgeo.5047","RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
引用次数: 0
Abstract
Banded iron formations (BIFs) are among the few chemical sedimentary archives that capture the biogeochemical evolution of Fe cycling and the redox evolution of the early Earth. Although biologically recycled continental Fe has been previously proposed to be a significant source of Fe in BIFs deposited from a stratified ocean at the onset of the Great Oxidation Event (GOE; ~2.5–2.2 Ga), constraining Fe sources and pathways in Archean BIFs remains challenging. Here we present major and trace element and Fe-Nd-Cr isotope data for the largest BIF (i.e., Dataigou) in China to test whether a benthic Fe shuttle was operative during deposition of pre-GOE BIFs. The absence of true, shale-normalized Ce anomalies, coupled with unfractionated Cr and positive Fe isotope compositions, suggests that BIF deposition occurred in an anoxic water column under reducing atmospheric conditions, whereas positive Eu anomalies indicate a significant input from a high-temperature hydrothermal source. Based on a significant correlation between initial Nd and Fe isotope data, we suggest that two Fe sources were periodically mixed and resulted in deposition of the Dataigou BIF. Here, we suggest the following sources: (1) hydrothermal fluids from sea-floor systems (low εNd(t) and high δ56Fe), derived from the interaction of fluids with underlying, older continental crust, and (2) a benthic Fe flux (high εNd(t) and low δ56Fe), generated by microbial Fe(III) reduction in coastal sediments during weathering of a nearby depleted landmass. Results presented here confirm, for the first time, that a microbially driven Fe shuttle was operational and supplied Fe on a basin-wide scale in the absence of atmospheric oxygen.
期刊介绍:
The journal, now published semi-quarterly, was first published in 1905 by the Economic Geology Publishing Company (PUBCO), a not-for-profit company established for the purpose of publishing a periodical devoted to economic geology. On the founding of SEG in 1920, a cooperative arrangement between PUBCO and SEG made the journal the official organ of the Society, and PUBCO agreed to carry the Society''s name on the front cover under the heading "Bulletin of the Society of Economic Geologists". PUBCO and SEG continued to operate as cooperating but separate entities until 2001, when the Board of Directors of PUBCO and the Council of SEG, by unanimous consent, approved a formal agreement of merger. The former activities of the PUBCO Board of Directors are now carried out by a Publications Board, a new self-governing unit within SEG.