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Banded Iron Formation

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Lianchang Zhang – 1st expert on this subject based on the ideXlab platform

  • earth s youngest Banded Iron Formation implies ferruginous conditions in the early cambrian ocean
    Scientific Reports, 2018
    Co-Authors: Zhiquan Li, Lianchang Zhang, Mengtian Zheng, Leslie J Robbins, John F Slack, Noah J Planavsky, Kurt O Konhauser

    Abstract:

    It has been proposed that anoxic and Iron-rich (ferruginous) marine conditions were common through most of Earth history. This view represents a major shift in our understanding of the evolution of marine chemistry. However, thus far, evidence for ferruginous conditions comes predominantly from Fe-speciation data. Given debate over these records, new evidence for Fe-rich marine conditions is a requisite if we are to shift our view regarding evolution of the marine redox landscape. Here we present strong evidence for ferruginous conditions by describing a suite of Fe-rich chemical sedimentary rocks-Banded Iron Formation (BIF)–deposited during the Early Cambrian in western China. Specifically, we provide new U-Pb geochronological data that confirm a depositional age of ca. 527 Ma for this unit, as well as rare earth element (REE) data are consistent with anoxic deposition. Similar to many Algoma-type Precambrian Iron Formations, these Early Cambrian sediments precipitated in a back-arc rift basin setting, where hydrothermally sourced Iron drove the deposition of a BIF-like protolith, the youngest ever reported of regional extent without direct links to volcanogenic massive sulphide (VMS) deposits. Their presence indicates that marine envIronments were still characterized by chemical- and redox-stratification, thus supporting the view that-despite a dearth of modern marine analogues-ferruginous conditions continued to locally be a feature of early Phanerozoic seawater.

  • changing provenance of late neoarchean metasedimentary rocks in the anshan benxi area north china craton implications for the tectonic setting of the world class dataigou Banded Iron Formation
    Gondwana Research, 2016
    Co-Authors: Changle Wang, Lianchang Zhang, Mengtian Zheng, Hua Huang, Xiaoxue Tong, Zidong Peng, Mingguo Zhai

    Abstract:

    Abstract The Anshan-Benxi (AnBen) area is situated in the northeastern part of the North China Craton and is considered to be the most important Iron metallogenic province in China. The giant Dataigou Banded Iron Formation (BIF) has the potential to be the largest Iron deposit in this area, even in Asia. Here, we present in situ zircon U–Pb-Hf-O isotopic and whole-rock geochemical data for metasedimentary rocks (metapelites and metaarenites) and trondhjemitic gneiss associated with this BIF, in order to provide constraints on the setting of the deposit, with implications for geological and exploration models. SIMS zircon U–Pb dating results indicate that the trondhjemitic gneiss crystallized at 3450 ± 19 Ma, and thus it is the oldest rock so far indentified in the Benxi area. The youngest group of detrital zircons from the metaarenite samples constrains their maximum depositional age at ~ 2.54 Ga. In combination with the earlier metamorphic age of ~ 2.51 Ga for the metaarenites, the deposition age of the Dataigou BIF can be constrained between 2.54 and 2.51 Ga. The metasediments have undergone varying degrees of source weathering. Source rocks of the metapelites have undergone moderate to severe chemical weathering, whereas those of the metaarenites have subjected to relatively weak chemical weathering. Diagnostic geochemical features such as the Al2O3/TiO2 values, trace element ratios, and REE patterns suggest that the metaarenites were predominantly derived from felsic igneous sources, whereas the metapelites were sourced mainly from mafic tholeiitic rocks. The dominant late Neoarchean detrital zircons further indicate that they were most likely sourced from almost synchronous volcanic rocks in the AnBen area. Taking into account the lithostratigraphic, geochemical, and geochronological data, the Dataigou BIF is interpreted as having been deposited in a back-arc basin, most probably on the margin of an ancient continental crust. Continuous provenance variations of these metasediments during highstand times and transgression can be ascribed to changes in natures of nearby volcanisms. Integrated with previous zircon Hf isotopic data from other supracrustal rocks in the AnBen area, our Hf-O data reveal major juvenile crustal growth stages at 3.0 Ga and during 2.8–2.7 Ga, and a crustal reworking event with minor juvenile addition at ~ 2.5 Ga in the studied area.

  • decoupled sources of the 2 3 2 2ga yuanjiacun Banded Iron Formation implications for the nd cycle in earth s early oceans
    Precambrian Research, 2016
    Co-Authors: Changle Wang, Kurt O Konhauser, Lianchang Zhang, Mingguo Zhai, Wenjun Li

    Abstract:

    Abstract The recognized worldwide gap in BIF deposition between 2.4 and 2.0 billion years ago has long been considered as an obstacle to fully determining the geochemical composition of seawater at that time. However, the recently dated 2.3–2.2 Ga Yuanjiacun Banded Iron Formation (BIF) in the North China Craton (NCC) offers a possibility to redress these uncertainties. Shale-normalized rare earth element-yttrium (REE + Y) patterns of the BIF and interlayered meta-chert samples show features characteristic of other Archean and Paleoproterozoic BIFs, with HREE enrichment relative to LREE, positive La and Eu anomalies, and superchondritic Y/Ho ratios comparable to modern seawater. Very low Al 2 O 3 ( e Nd ( t ) ∼ +3.5) derived from interaction with a depleted mantle source and associated with high Fe fluxes. The second is ambient surface seawater ( e Nd ( t ) ∼ −2.4), which obtained its signature through weathering of the nearby landmasses and associated with high Si fluxes. Our findings suggest that the REE budget of the oceans prior to 2.3 Ga was generally dominated by hydrothermal circulation of seawater through depleted mantle-derived source rocks. However, where evolved local continental crust and/or an enriched mantle source were present, this positive mantle Nd signal became discernible in the BIFs. By comparing the Nd isotopic features of similar aged BIFs and marine carbonates, it is concluded that similar to modern oceans, the early Precambrian ocean was not well-mixed with respect to its Nd isotopic composition.

Mathias S Egglseder – 2nd expert on this subject based on the ideXlab platform

  • Tiny particles building huge ore deposits – Particle-based crystallisation in Banded Iron Formation-hosted Iron ore deposits (Hamersley Province, Australia)
    Ore Geology Reviews, 2020
    Co-Authors: Mathias S Egglseder, Alexander R Cruden, Hilke J Dalstra, Jens Baumgartner, Andrew G Tomkins, Siobhan A Wilson, Andrea Rielli, Chenghao Li, Damien Faivre

    Abstract:

    Abstract The world’s major source of Iron ore is hosted in Precambrian Banded Iron Formations. These chemical (meta-) sedimentary rocks are composed of alternating laminae of Iron oxide minerals and chert. Despite the economic significance of high-grade Iron ore deposits, controversy persists after decades of research on how Banded Iron Formations became upgraded to form Iron ore. The fundamental requirement for Iron ore Formation is the removal of vast amounts of chert coupled with an increased concentration of Iron oxide minerals. Here, we assess the fate of colloidal hematite inclusions encapsulated in chert after quartz dissolution and examine their role in the Formation of hematite ore. We have analysed hematite ores from the Hamersley Province (Australia) using a combination of petrography, high-resolution electron microscopy and X-ray diffraction. These techniques reveal the presence of abundant nano and microscale hematite particles that we suggest form the building blocks of larger hematite crystals within the Iron ore. Our textural observations indicate that hematite colloids that were previously encapsulated inside the microcrystalline quartz grains in chert layers are released during quartz dissolution, and subsequently reassemble in a self-similar fashion to from new microplaty hematite crystals via non-classical crystallisation pathways. Progressive growth and fusion leads to the transFormation of hematite microplates into hematite bands, which resemble pre-existing Iron oxide laminae of Banded Iron Formations. In contrast to previous models, we observe the direct transFormation of Banded Iron Formations to microplaty hematite and have not found evidence that significant amounts of hematite formed through metamorphism of goethite or that intermediate carbonate minerals were involved during the upgrading of Banded Iron Formations to pure hematite ore. Given the strong evidence for hypogene fluids found in many deposits, we have also assessed the role that such warm, highly saline fluids may have played during the evolution of Iron ore. Using insights from crystal chemistry we conclude that fluid infiltration impacts many aspects of Iron ore Formation by controlling hematite colloid liberation and aggregation, and finally controlling the transFormation of the colloids into macroscopic crystals of hematite via non-classical crystallisation mechanisms. Our study underlines the significance of hypogene fluids in the upgrading of Banded Iron Formation to Iron ore, however, we suggest that their influence was mainly passive as hematite was not precipitated directly from these fluids.

  • tiny particles building huge ore deposits particle based crystallisation in Banded Iron Formation hosted Iron ore deposits hamersley province australia
    Ore Geology Reviews, 2019
    Co-Authors: Mathias S Egglseder, Alexander R Cruden, Hilke J Dalstra, Andrew G Tomkins, Siobhan A Wilson, Andrea Rielli, Chenghao Li, Jens Baumgartner

    Abstract:

    Abstract The world’s major source of Iron ore is hosted in Precambrian Banded Iron Formations. These chemical (meta-) sedimentary rocks are composed of alternating laminae of Iron oxide minerals and chert. Despite the economic significance of high-grade Iron ore deposits, controversy persists after decades of research on how Banded Iron Formations became upgraded to form Iron ore. The fundamental requirement for Iron ore Formation is the removal of vast amounts of chert coupled with an increased concentration of Iron oxide minerals. Here, we assess the fate of colloidal hematite inclusions encapsulated in chert after quartz dissolution and examine their role in the Formation of hematite ore. We have analysed hematite ores from the Hamersley Province (Australia) using a combination of petrography, high-resolution electron microscopy and X-ray diffraction. These techniques reveal the presence of abundant nano and microscale hematite particles that we suggest form the building blocks of larger hematite crystals within the Iron ore. Our textural observations indicate that hematite colloids that were previously encapsulated inside the microcrystalline quartz grains in chert layers are released during quartz dissolution, and subsequently reassemble in a self-similar fashion to from new microplaty hematite crystals via non-classical crystallisation pathways. Progressive growth and fusion leads to the transFormation of hematite microplates into hematite bands, which resemble pre-existing Iron oxide laminae of Banded Iron Formations. In contrast to previous models, we observe the direct transFormation of Banded Iron Formations to microplaty hematite and have not found evidence that significant amounts of hematite formed through metamorphism of goethite or that intermediate carbonate minerals were involved during the upgrading of Banded Iron Formations to pure hematite ore. Given the strong evidence for hypogene fluids found in many deposits, we have also assessed the role that such warm, highly saline fluids may have played during the evolution of Iron ore. Using insights from crystal chemistry we conclude that fluid infiltration impacts many aspects of Iron ore Formation by controlling hematite colloid liberation and aggregation, and finally controlling the transFormation of the colloids into macroscopic crystals of hematite via non-classical crystallisation mechanisms. Our study underlines the significance of hypogene fluids in the upgrading of Banded Iron Formation to Iron ore, however, we suggest that their influence was mainly passive as hematite was not precipitated directly from these fluids.

  • the role of deFormation in the Formation of Banded Iron Formation hosted high grade Iron ore deposits hamersley province australia
    Precambrian Research, 2017
    Co-Authors: Mathias S Egglseder, Alexander R Cruden, Hilke J Dalstra, Leigh Nicholas

    Abstract:

    Abstract The Hamersley Province (Western Australia) hosts some of the world’s largest Iron ore deposits but despite decades of research, their genesis is still extensively debated. Many Iron ore deposits are hosted in complexly deformed Archean to Paleoproterozoic Banded Iron Formations, comprising thin chert and Iron oxide bands interlayered with silicate-rich shales and carbonates. Current Iron ore genesis models have identified a strong structural control on ore Formation linked to extensive hypogene and supergene fluid circulation along fault structures. These fluid pathways facilitate the removal of vast amounts of gangue minerals, leading to enrichment of the Iron oxide residue to Iron ore. However, the evolution of the associated structures has not yet been considered as a key element in ore genesis. Here we show through multiscale structural analyses that deFormation not only forms suitable fluid channels, but that folding and shearing also result in significant synkinematic removal of gangue minerals. Our multidisciplinary investigation of the structural evolution of the Mount Tom Price deposit combines microtectonic, field geology and 3D implicit modelling techniques to establish a link between deFormation structures at various scales. Microscale shear bands and outcrop-scale asymmetric parasitic folds share striking similarities in their evolution and their controlling mechanisms. Both features record substantial non-coaxial deFormation accompanied by volume changes due to stress-induced silica remobilisation. The closely spaced layering of rheologically different lithologies within Hamersley Province strata plays a crucial role in complex multilayer deFormation, which resulted in extensive strain partitioning. Our study suggests that deFormation was of major significance in the upgrading of Banded Iron Formation to Iron ore and was active from the early stages of Banded Iron Formation during diagenesis. DeFormation structures also established a micro- to deposit-scale lateral and vertical fluid network, which enabled infiltration by hypogene and supergene fluids during or after deFormation. These new insights have important implications for Iron ore genesis models, structural applications in the mine envIronment, and for understanding complex multilayer deFormation with volume loss.

Kurt O Konhauser – 3rd expert on this subject based on the ideXlab platform

  • Using Ge/Si ratios to decouple Iron and silica fluxes in Precambrian Banded Iron Formations
    Geology, 2020
    Co-Authors: Tristan Hamade, Kurt O Konhauser, Robert Raiswell, Sarah Goldsmith, R.c. Morris

    Abstract:

    Banded Iron Formations are prominent sedimentary deposits of the Precambrian, yet the source of their silica remains unresolved. Here we show that Ge/Si ratios preserved in Banded Iron Formation chert layers are indicative of weathering of continental landmass. This conflicts with the accumulation of evidence suggesting that chemical components were sourced at mid-ocean-ridge hydrothermal systems. Instead, it implies that the sources of silica and Iron were decoupled during Banded Iron Formation deposition, silica being dominantly derived from weathering of continental landmass and Iron having a hydrothermal origin. Thus, the chemistry within Banded Iron Formation depositional basins underwent clear switching that varied on a periodic basis and is recorded in the alternation of Iron– to silica-rich layers.

  • earth s youngest Banded Iron Formation implies ferruginous conditions in the early cambrian ocean
    Scientific Reports, 2018
    Co-Authors: Zhiquan Li, Lianchang Zhang, Mengtian Zheng, Leslie J Robbins, John F Slack, Noah J Planavsky, Kurt O Konhauser

    Abstract:

    It has been proposed that anoxic and Iron-rich (ferruginous) marine conditions were common through most of Earth history. This view represents a major shift in our understanding of the evolution of marine chemistry. However, thus far, evidence for ferruginous conditions comes predominantly from Fe-speciation data. Given debate over these records, new evidence for Fe-rich marine conditions is a requisite if we are to shift our view regarding evolution of the marine redox landscape. Here we present strong evidence for ferruginous conditions by describing a suite of Fe-rich chemical sedimentary rocks-Banded Iron Formation (BIF)–deposited during the Early Cambrian in western China. Specifically, we provide new U-Pb geochronological data that confirm a depositional age of ca. 527 Ma for this unit, as well as rare earth element (REE) data are consistent with anoxic deposition. Similar to many Algoma-type Precambrian Iron Formations, these Early Cambrian sediments precipitated in a back-arc rift basin setting, where hydrothermally sourced Iron drove the deposition of a BIF-like protolith, the youngest ever reported of regional extent without direct links to volcanogenic massive sulphide (VMS) deposits. Their presence indicates that marine envIronments were still characterized by chemical- and redox-stratification, thus supporting the view that-despite a dearth of modern marine analogues-ferruginous conditions continued to locally be a feature of early Phanerozoic seawater.

  • decoupled sources of the 2 3 2 2ga yuanjiacun Banded Iron Formation implications for the nd cycle in earth s early oceans
    Precambrian Research, 2016
    Co-Authors: Changle Wang, Kurt O Konhauser, Lianchang Zhang, Mingguo Zhai, Wenjun Li

    Abstract:

    Abstract The recognized worldwide gap in BIF deposition between 2.4 and 2.0 billion years ago has long been considered as an obstacle to fully determining the geochemical composition of seawater at that time. However, the recently dated 2.3–2.2 Ga Yuanjiacun Banded Iron Formation (BIF) in the North China Craton (NCC) offers a possibility to redress these uncertainties. Shale-normalized rare earth element-yttrium (REE + Y) patterns of the BIF and interlayered meta-chert samples show features characteristic of other Archean and Paleoproterozoic BIFs, with HREE enrichment relative to LREE, positive La and Eu anomalies, and superchondritic Y/Ho ratios comparable to modern seawater. Very low Al 2 O 3 ( e Nd ( t ) ∼ +3.5) derived from interaction with a depleted mantle source and associated with high Fe fluxes. The second is ambient surface seawater ( e Nd ( t ) ∼ −2.4), which obtained its signature through weathering of the nearby landmasses and associated with high Si fluxes. Our findings suggest that the REE budget of the oceans prior to 2.3 Ga was generally dominated by hydrothermal circulation of seawater through depleted mantle-derived source rocks. However, where evolved local continental crust and/or an enriched mantle source were present, this positive mantle Nd signal became discernible in the BIFs. By comparing the Nd isotopic features of similar aged BIFs and marine carbonates, it is concluded that similar to modern oceans, the early Precambrian ocean was not well-mixed with respect to its Nd isotopic composition.