Journal ArticleDOI
Depositional Environment of the Paleoproterozoic Yuanjiacun Banded Iron Formation in Shanxi Province, China
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TLDR
The Yuanjiacun banded iron formation (BIF) as discussed by the authors is a Superior-type BIF in the North China craton, which has undergone lower greenschist-facies metamor phism.Abstract:
The Paleoproterozoic (~2.38–2.21 Ga) Yuanjiacun banded iron formation (BIF), located in Shanxi Province, is a Superior-type BIF in the North China craton. This BIF is within a metasedimentary rock succession of the Yuanjiacun Formation, in the lower Luliang Group, which has undergone lower greenschist-facies metamor phism. Iron oxide (magnetite and hematite), carbonate, and silicate facies are all present within the iron-rich layers. The eastward transition from carbonate- into oxide-facies iron formations is accompanied by a change in mineralogical composition from siderite in the west through magnetite-ankerite and magnetite-stilpnomelane assemblages in the transition zone to magnetite and then hematite in the east. These distinct lateral facies are also observed vertically within the BIF, i.e., the iron mineral assemblage changes upsection from sider ite through magnetite into hematite-rich iron formation. The oxide-facies BIF formed near shore, whereas carbonate (siderite)- and silicate-facies assemblages formed in deeper waters. Based on detailed analyses of these variations on a basinal scale, the BIF precipitated during a transgressive event within an environment that ranged from deep waters below storm wave base to relatively shallow waters. The BIF samples display distinctively seawater-like REEs + Y profiles that are characterized by positive La and Y anomalies and HREEs enrichment relative to LREEs in Post-Archean Australian shale-normalized diagrams. Consistently positive Eu anomalies are also observed, which are typical of reduced, high-temperature hydrothermal fluids. In addition, slightly negative to positive Ce anomalies, and a large range in ratios of light to heavy REEs, are present in the oxide-facies BIF. These characteristics, in combination with consistently positive δ 56Fe values, suggest that deposition of the BIF took place along the chemocline where upwelling of deep, anoxic, iron- and silicarich hydrothermal fluids mixed with shallower and slightly oxygenated seawater. The ankerite displays highly depleted δ13C values and the carbonate-rich BIF has a high content of organic carbon, suggesting dissimilatory Fe(III) reduction of a ferric oxyhydroxide precursor during burial of biomass deposited from the water column; that same biomass was likely tied to the original oxidation of dissolved Fe(II). The fact that the more ferric BIF facies formed in shallower waters suggests that river-sourced nutrients would have been minimal, thus limiting primary productivity in the shallow waters and minimizing the organic carbon source necessary for reducing the hematite via dissimilatory Fe(III) reduction. By contrast, in deeper waters more proximal to the hydrothermal vents, nutrients were abundant, and high biomass productivity was coupled to increased carbon burial, leading to the deposition of iron-rich carbonates. The deposition of the Yuanjiacun BIF during the onset of the Great Oxidation Event (GOE; ca. 2.4–2.2 Ga) confirms that deep marine waters during this time period were still episodically ferruginous, but that shallow waters were sufficiently oxygenated that Fe(II) oxidation no longer needed to be tied directly to proximal cyanobacterial activity.read more
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Journal ArticleDOI
Iron formations: A global record of Neoarchaean to Palaeoproterozoic environmental history
Kurt O. Konhauser,Noah J. Planavsky,Noah J. Planavsky,Dalton S. Hardisty,Leslie J. Robbins,Tyler J. Warchola,Rasmus Haugaard,Rasmus Haugaard,Stefan V. Lalonde,Camille A. Partin,Paul B.H. Oonk,Harilaos Tsikos,Timothy W. Lyons,Timothy W. Lyons,Andrey Bekker,Clark M. Johnson,Clark M. Johnson +16 more
TL;DR: A review of the defining features of iron formations and their distribution through the Neo-archaean and Palaeoproterozoic is presented in this article, along with an update of previous reviews by Bekker et al. (2010, 2014).
Iron and Carbon Isotope Evidence for Microbial Iron Respiration Throughout the Archean
Paul R. Craddock,Nicolas Dauphas +1 more
TL;DR: In this article, the authors reported the results of a study of the early Archean BIFs from the Hamersley Basin, Australia and the early Isua Supracrustal Belt (ISB), Greenland.
Journal ArticleDOI
Depositional age and tectonic environment of the Gouap banded iron formations from the Nyong group, SW Cameroon: Insights from isotopic, geochemical and geochronological studies of drillcore samples
Landry Soh Tamehe,Landry Soh Tamehe,Chongtao Wei,Sylvestre Ganno,Carlos Alberto Rosière,Jean Paul Nzenti,Chesther Gatsé Ebotehouna,Guanwen Lu +7 more
TL;DR: The discovery of the Gouap banded iron formations (BIFs)-hosted iron mineralization in the northwestern of the Nyong Group (Ntem Complex) in southwestern Cameroon provides unique insights into the geology of this region.
Journal ArticleDOI
Changes of Ge/Si, REE + Y and SmNd isotopes in alternating Fe- and Si-rich mesobands reveal source heterogeneity of the ~ 2.54 Ga Sijiaying banded iron formation in Eastern Hebei, China
TL;DR: In this paper, major and trace element and Sm Nd isotopic analyses of individual mesobands of a Sijiaying BIF specimen were conducted to characterize the source and depositional environment over a transient period.
Journal ArticleDOI
Geochemistry and origin of the Neoproterozoic Dahongliutan banded iron formation (BIF) in the Western Kunlun orogenic belt, Xinjiang (NW China)
TL;DR: The Tianshuihai Group is a dominantly submarine siliciclastic and carbonate sedimentary succession that generally has been metamorphosed to greenschist facies as mentioned in this paper.
References
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Book
Principles of isotope geology
TL;DR: The roots of isotope geology can be found in this paper, where a geology of Neodymium and Strontium in meteorites and Igneous rocks is described.
Book ChapterDOI
Rare earth elements in sedimentary rocks; influence of provenance and sedimentary processes
Journal ArticleDOI
Late Archean to Paleoproterozoic evolution of the North China Craton: key issues revisited
TL;DR: In this paper, the authors proposed a model for the evolution of the North China Craton that envisages discrete Eastern and Western Blocks that developed independently during the Archean and collided along the Trans-North China Orogen during a Paleoproterozoic orogenic event.
Journal ArticleDOI
Dating the rise of atmospheric oxygen
Andrey Bekker,Heinrich D. Holland,Pei-Ling Wang,D. Rumble,Holly J. Stein,Judith L. Hannah,Louis Coetzee,Nicolas J. Beukes +7 more
TL;DR: It is found that syngenetic pyrite is present in organic-rich shales of the 2.32-Gyr-old Rooihoogte and Timeball Hill formations, South Africa, indicating that atmospheric oxygen was present at significant levels during the deposition of these units.
Journal ArticleDOI
Distribution of yttrium and rare-earth elements in the Penge and Kuruman iron-formations, Transvaal Supergroup, South Africa
Michael Bau,Peter Dulski +1 more
TL;DR: In this article, a sequence of eleven adjacent samples (each comprising less than ten microbands) from the Kuruman and Penge Iron-Formations (IFs) in the Late-Archaean to Early-Palaeoproterozoic Transvaal Supergroup display pronounced heavy rare-earth element enrichment, and positive anomalies of LaSN, EuSN, GdSN, YSN, ErSN, but neither positive nor negative CeSN anomalies.