scholarly journals Tsunami Deposits on a Paleoproterozoic Unconformity? The 2.2 Ga Yerrida Marine Transgression on the Northern Margin of the Yilgarn Craton, Western Australia

2021 ◽  
Vol 9 (2) ◽  
pp. 213
Author(s):  
Desmond F. Lascelles ◽  
Ryan J. Lowe
Keyword(s):  
Broad Band ◽  
Iron Formation ◽  
Banded Iron Formations ◽  
Banded Iron Formation ◽  
Marine Transgression ◽  
Sea Floor ◽  
Northern Margin ◽  
Fine Grained ◽  
Western Side ◽  
Cut Surface

Large blocks and boulders of banded iron formations and massive hematite up to 40 × 27 × 6 m3 and in excess of 10,000 metric tonnes were detached from an outcrop of the Wilgie Mia Formation during the ca 2.20 Ga marine transgression at the base of the Paleoproterozoic Windplain Group and deposited in a broad band on the wave-cut surface 900 to 1200 m to the east. At the same time, sand and shingle were scoured from the sea floor, leaving remnants only on the western side of the Wilgie Mia Formation and on the eastern sides of the boulders. Evidence suggesting that the blocks were detached and transported and the sea floor scoured by a tsunami bore with a height of at least 40 m is provided by the following: (1) the deposition of the blocks indicates transportation by a unidirectional sub-horizontal force, whereas the smaller boulders are randomly oriented; (2) 900–1200 m separates the banded iron formation (BIF) outcrop and the blocks (3) there is an absence of the basal conglomerate between the blocks; (4) the blocks and boulders rest directly on the wave-cut surface of deeply weathered amphibolites; (5) the blocks and boulders are surrounded and overlain by fine-grained sandstone of the Windplain Group.

scholarly journals Tsunami Deposits on a Paleoproterozoic Unconformity? The 2.2 Ga Yerrida Marine Transgression on the Northern Margin of the Yilgarn Craton, Western Australia

2021 ◽  
Author(s):  
Desmond Lascelles ◽  
Ryan J. Lowe
Keyword(s):  
Broad Band ◽  
Iron Formation ◽  
Yilgarn Craton ◽  
Banded Iron Formation ◽  
Marine Transgression ◽  
Sea Floor ◽  
Northern Margin ◽  
Fine Grained ◽  
Western Side ◽  
Cut Surface

Large blocks and boulders of banded iron formation and massive hematite up to 40 x 27 x 6 m and in excess of 10,000 metric tonnes were detached from outcrop of the Wilgie Mia Formation during the ca 2.20 Ga marine transgression at the base of the Paleoproterozoic Windplain Group, and deposited in a broad band on the wave-cut surface 900 to 1200 m to the east. At the same time sand and shingle was scoured from the sea floor, leaving remnants only on the western side of the Wilgie Mia Formation and on the eastern sides of the boulders. Evidence suggesting that the blocks were detached and transported and the sea floor scoured by a tsunami bore with a height of at least 40 m is provided by (1) the deposition of the blocks indicates transportation by a unidirectional sub-horizontal force, whereas the smaller boulders are randomly oriented (2) 900 -1200m separating the BIF outcrop and the blocks (3) the absence of the basal conglomerate between the blocks (4) the blocks and boulders rest directly on the wave-cut surface of deeply weathered amphibolites (5) the blocks and boulders are surrounded and overlain by fine-grained sandstone of the Windplain Group.

Auriferous chert, banded iron formation, and related volcanogenic hydrothermal alteration, Atik Lake, Manitoba

1989 ◽  
Vol 26 (12) ◽  
pp. 2676-2690 ◽  
Author(s):  
Louis R. Bernier ◽  
Wallace H. MacLean
Keyword(s):  
Hydrothermal Alteration ◽  
Earth Element ◽  
Massive Sulfide ◽  
Iron Formation ◽  
Small Scale ◽  
Banded Iron Formation ◽  
Sulfide Deposits ◽  
Sea Floor ◽  
Facies Metamorphism ◽  
Altered Basalt

Small-scale alteration pipes and stratiform alteration in Archean glomeroporphyritic tholeiitic basalts at Atik Lake, Manitoba, stratigraphically underlie silicate-oxide banded iron formation (BIF) and auriferous sulfide-bearing chert. The auriferous chert is locally interbedded with graphitic argillite, indicating euxinic conditions during deposition. Cordierite–gedrite rocks formed by recrystallization of alteration assemblages during the lower amphibolite-facies metamorphism (T = 550 °C, P = 2.5 kbar). Al2O3, TiO2, Zr, and Nb, which were relatively immobile during alteration, have been used to monitor igneous differentiation and alteration. Volcanogenic hydrothermal alteration resulted in depletion of Ca, Si, Mg, Na, and Sr in the altered basalt and the addition of K, Fe, Rb, and Ba. This was accompanied by mass and volume losses of up to 25%. The mineralizing fluid was reducing and somewhat acidic. Rare-earth-element (REE) profiles of BIF and graphitic argillite, normalized to Archean shale, are less steep ((La/Lu)N = 0.51 and 0.49 respectively), than those of both mineralized chert ((La/Lu)N = 0.04) and recent sea-floor, siliceous, gold-enriched massive sulfides ((La/Lu)N = 0.11). REE profiles and Boström's plot suggest that the auriferous, sulfide-bearing chert formed by mixing of hydrothermal and detrital components. The overall chemical changes in the Atik Lake alteration system are comparable to those in Noranda-type massive-sulfide deposits. The trace-metal association in the auriferous chert is similar to that at some modern sea-floor hydrothermal sites.

scholarly journals Photoferrotrophy, deposition of banded iron formations, and methane production in Archean oceans

2019 ◽  
Vol 5 (11) ◽  
pp. eaav2869 ◽  
Author(s):  
Katharine J. Thompson ◽  
Paul A. Kenward ◽  
Kohen W. Bauer ◽  
Tyler Warchola ◽  
Tina Gauger ◽  
...  
Keyword(s):  
Large Scale ◽  
Iron Oxidation ◽  
Coastal Sediments ◽  
Oxygenic Photosynthesis ◽  
Iron Formation ◽  
Banded Iron Formations ◽  
Banded Iron Formation ◽  
Earth’S Climate ◽  
Iron Formations ◽  
Scale Deposition

Banded iron formation (BIF) deposition was the likely result of oxidation of ferrous iron in seawater by either oxygenic photosynthesis or iron-dependent anoxygenic photosynthesis—photoferrotrophy. BIF deposition, however, remains enigmatic because the photosynthetic biomass produced during iron oxidation is conspicuously absent from BIFs. We have addressed this enigma through experiments with photosynthetic bacteria and modeling of biogeochemical cycling in the Archean oceans. Our experiments reveal that, in the presence of silica, photoferrotroph cell surfaces repel iron (oxyhydr)oxides. In silica-rich Precambrian seawater, this repulsion would separate biomass from ferric iron and would lead to large-scale deposition of BIFs lean in organic matter. Excess biomass not deposited with BIF would have deposited in coastal sediments, formed organic-rich shales, and fueled microbial methanogenesis. As a result, the deposition of BIFs by photoferrotrophs would have contributed fluxes of methane to the atmosphere and thus helped to stabilize Earth’s climate under a dim early Sun.

scholarly journals A Fonte dos Metais da Mina de Ouro do Schramm, Santa Catarina: Evidências de Dados de Isótopos de Pb e Elementos Terras Raras

2005 ◽  
Vol 32 (1) ◽  
pp. 51
Author(s):  
FLÁVIO FRANÇA NUNES DA ROCHA ◽  
ARTUR CEZAR BASTOS NETO ◽  
MARCUS VINÍCIUS DORNELLES REMUS ◽  
VITOR PAULO PEREIRA
Keyword(s):  
Gold Mineralization ◽  
Isotope Composition ◽  
Shear Zones ◽  
Iron Formation ◽  
Gold Mine ◽  
Banded Iron Formations ◽  
Banded Iron Formation ◽  
Santa Catarina ◽  
Lead Isotope Composition ◽  
Ree Patterns

The source of the ore elements in the Schramm gold mine, localized in central part of Santa Catarina shield, has been constrained based on lead isotope composition of galena and sulfosalts, and the rare earth element (REE) patterns of the ore. The Pb207/ Pb206 model age obtained in galena and lillianite-gustavite series from the mineralization yields an age of 1.88 Ga. It is higher than the estimated age of the deposit (» 534 Ma). The Pb isotopic composition obtained in these minerals indicates that the age of Schramm mine source is similar to that of the galena of the Ribeirão da Prata mine (Pb-Zn-Cu-Ag). This mine is located 25 Km southwest of the Schramm gold mine witch is hosted in the tension fracture zone conjugated with the first order shear zone that contains the Ribeirão da Prata deposit. The similarities between Pb-isotope compositions of both deposits could indicate that they were contemporaneous and derived from the same regional lead source. The REE patterns of the ore samples of Schramm mine are similar to that of the pyroxenites and banded iron formations from the Archean Santa Catarina Granulitic Complex that host the Schramm gold mine. They present low REE contents with flat patterns and lack Eu anomalies. The comparison among the isotopic data from this mine with those from other places indicates that the banded iron formation and mafic-ultramafic granulitic gneisses are the source of the gold mineralization. This evidence agreed with the hypothesis that the ore fluids were derived from retrogressive metamorphism reactions of Santa Catarina Granulitic Complex in the shear zones during the final stage of Brasiliano orogenic cycle.

Petro-Mineralogical and Geochemical Characterization of the Banded Irons Formations BIFs of the Nimba Range and its Western Extension (Nimba Region)

2019 ◽  
Vol 44 ◽  
pp. 99-134
Author(s):  
Mohamed Samuel Moriah Conté ◽  
Abdellah Boushaba ◽  
Ali Moukadiri
Keyword(s):  
Regional Metamorphism ◽  
Major Elements ◽  
Iron Formation ◽  
Banded Iron Formations ◽  
Banded Iron Formation ◽  
Metasedimentary Rocks ◽  
Republic Of Guinea ◽  
Metavolcanic Rocks ◽  
The Republic ◽  
Iron Formations

The Nimba Range and its western extension are located in the Nimba region on the borders of the Republic of Guinea, Liberia and Côte d'Ivoire. It is a mountainous region made up of metavolcanic and metasedimentary rocks. Metavolcanic rocks are gneisses, granites, amphibolites and quartzites, which constitute the lower part of Archean age. The upper part consists of Proterozoic rocks of metasedimentary origin. It contains important deposits of itabirites which occupy the top of the mountains and hills of the region. The petrographic study of the banded iron formations reveals the existence of silicate banded iron formations (SIF) and oxidized banded iron formations (OIF). The results of the scanning electron microscope (SEM) and metallogenic analyzes show the presence of iron minerals (magnetites, hematites, pyrites, goethites, martites and siderites). These analyzes also reveal the presence of the metamorphic index minerals associated with the banded iron formations, hence the existence of several types of ferriferous formations (silicate (SIF) and oxidized (OIF) banded iron formations). Overall, there is an increase in the degree of regional metamorphism from east to west of the Nimba region. The geochemical analysis of the banded iron formations reveals that with the exception of Na2O, all the major elements have a negative linear correlation although dispersed with Fe2O3. This correlation is explained by a decrease in quartz, garnet, micas (muscovite and biotite), amphibole, pyroxene, plagioclase, titanium and phosphorus contents. Conversely, there is an increase in iron ore content: magnetites, pyrites, hematites, goethite. But the alkali content remains constant in these banded iron formations. Then, the lower the Fe2O3content, the higher the FeO content, while those of SiO2and Al2O3are constant in all of these formations in the Nimba region except in the chlorite banded iron formation where both are anticorelated. Finally, the ratio SiO2/ Fe2O3vs MgO + CaO + MnO / Fe2O3of the banded iron formations of the Nimba region compared to the same formations of the whole world allows to give them Proterozoic age. Some itabirites have high levels of magnetite, hematite, and goethite (same feature as itabirites of Lac supérieur and Pic de fon) and only chlorite itabirite has a low to medium Mg-Si-BIF content.

Phylogeographic analyses of Acacia karina (Fabaceae) support long term persistence of populations both on and off banded iron formations

2019 ◽  
Vol 67 (3) ◽  
pp. 194 ◽  
Author(s):  
Anna V. Funnekotter ◽  
Melissa Millar ◽  
Siegfried L. Krauss ◽  
Paul G. Nevill
Keyword(s):  
Genetic Diversity ◽  
Nuclear Data ◽  
Iron Formation ◽  
Banded Iron Formations ◽  
Banded Iron Formation ◽  
Chloroplast Haplotype ◽  
Historical Processes ◽  
Midwest Region ◽  
Associated Species

Understanding the response of species to past climatic changes and whether particular areas acted as refugia is critical both to our understanding of the distribution of genetic variation, and for the conservation and/or restoration of species. We used phylogeographical analyses of Acacia karina, a Banded Iron Formation (BIF) associated species, to better understand historical processes in the semiarid midwest region of Western Australia. We specifically examined whether BIF acted as refugia for the species during the colder, dryer periods of the Quaternary. The genetic structure over the entire range of A. karina was assessed using seven nuclear microsatellites (19 populations; n=371) and 3196bp of chloroplast sequence (19 populations; n=190). We found high levels of nuclear and chloroplast genetic diversity and high levels of chloroplast haplotype differentiation. Genetic diversity was higher than expected for such a geographically restricted species, and similarly high levels of nuclear and chloroplast diversity were observed in BIF and non-BIF populations. The chloroplast and nuclear data suggest that BIFs have not acted as climate refugia for A. karina. Instead, long-term persistence of both BIF and non-BIF populations is supported.

Using In Situ Monazite and Xenotime U-Pb Geochronology to Resolve the Fate of the “Missing” Banded Iron Formation-Hosted High-Grade Hematite Ores of the North China Craton

2020 ◽  
Vol 115 (1) ◽  
pp. 189-204
Author(s):  
Li-Xing Li ◽  
Jian-Wei Zi ◽  
Jie Meng ◽  
Hou-Min Li ◽  
Birger Rasmussen ◽  
...  
Keyword(s):  
North China Craton ◽  
North China ◽  
Greenschist Facies ◽  
Iron Formation ◽  
High Grade ◽  
Banded Iron Formations ◽  
Banded Iron Formation ◽  
The North ◽  
Proposed Model

Abstract High-grade hematite mineralization is widely developed in banded iron formations (BIFs) worldwide. However, in the North China craton where Neoarchean-Paleoproterozoic BIFs are abundant, economic high-grade hematite ores are scarce. High-grade hematite ores hosted in the Paleoproterozoic Yuanjiacun BIFs represent the largest occurrence of this type of ore in the North China craton. The orebodies are fault controlled and show sharp contacts with lower greenschist facies metamorphic BIFs. In situ U-Pb geochronology of monazite and xenotime intergrown with microplaty hematite and martite in high-grade ore established two episodes of metamorphic-hydrothermal monazite/xenotime growth after deposition of the BIFs. The earlier episode at ca. 1.94 Ga is interpreted as the timing of lower greenschist-facies metamorphism, and the later episode at 1.41 to 1.34 Ga represents the timing of high-grade hematite mineralization. Petrography and microthermometry of primary fluid inclusion assemblages indicate that the high-grade hematite ore formed from hot (313°–370°C), CO2-rich, and highly saline (~20 wt % NaCl equiv) hydrothermal fluids. These fluids channeled along faults, which concentrated iron through interaction with the BIFs—a process similar to typical hematite mineralization elsewhere. The deposition of hematite was probably related to tectonic extension in the North China craton related to the breakup of the Columbia/Nuna supercontinent. Our results challenge a previously proposed model ascribing the scarcity of high-grade hematite ores in the North China craton to the lack of prolonged weathering conditions. Rather, we argue that the high-grade ore formed in lower metamorphic-grade BIFs at shallower depths than magnetite mineralization and was largely eroded during later exhumation and uplift of the craton.

scholarly journals The Proterozoic Guanhães banded iron formations, Southeastern border of the São Francisco Craton, Brazil: evidence of detrital contamination

2017 ◽  
Vol 17 (2) ◽  
pp. 303 ◽  
Author(s):  
Vitor Rodrigues Barrote ◽  
Carlos Alberto Rosiere ◽  
Vassily Khoury Rolim ◽  
João Orestes Schneider Santos ◽  
Neal Jesse Mcnaughton
Keyword(s):  
Detrital Zircons ◽  
Iron Formation ◽  
Geochemical Data ◽  
Banded Iron Formations ◽  
Banded Iron Formation ◽  
Zircon Age ◽  
Shallow Marine ◽  
Eu Anomaly ◽  
Depositional Age ◽  
Iron Formations

The Guanhães banded iron formation (BIF) bearing succession occurs as tectonic slices, juxtaposed to Archean TTG granite-gneissic basement rock, developed during the Neoproterozoic-Cambrian Brasiliano collage. The succession has a maximum depositional age of ~2.18 Ga, from detrital zircons in quartzite, and consists of quartzites, schists, BIFs, gneiss and amphibolite, all metamorphosed under amphibolite facies conditions. The Guanhães BIF shows HREE enrichment and consistent positive Eu anomaly (PAAS-normalized REE+Y). Two types of contamination were observed in the samples. The first is contamination by an exotic detrital component, which resulted in low Y/Ho (<30) and Pr/Yb (SN) ratios. Evidence of such contamination, combined with inferred stratigraphic stacking data, indicates that the Guanhães BIFs were deposited on a shallow marine environment. The second type of contamination resulted in higher Eu-anomalies, positive Ce-anomalies, and higher REE+Y concentrations, possibly due to the interaction between later magmatic fluids and the Guanhães BIF. A strong Cambrian event is recorded in zircon age data. The uncontaminated samples display REE+Y distribution similar to other Precambrian BIFs, particularly those from the Morro-Escuro Sequence and the Serra da Serpentina Group, without true Ce-anomalies and Y/Ho close to seawater values (45). Geochronological and geochemical data presented in this paper strongly suggest a correlation between the Guanhães supracrustal succession and the Serra da Serpentina and Serra de São José Groups.

scholarly journals Using modern ferruginous habitats to interpret Precambrian banded iron formation deposition

2015 ◽  
Vol 15 (3) ◽  
pp. 205-217 ◽  
Author(s):  
Elif Koeksoy ◽  
Maximilian Halama ◽  
Kurt O. Konhauser ◽  
Andreas Kappler
Keyword(s):  
Depositional Environments ◽  
Iron Formation ◽  
Biogeochemical Processes ◽  
Banded Iron Formations ◽  
Banded Iron Formation ◽  
Depositional Processes ◽  
Microbiological Characteristics ◽  
Rock Record ◽  
Alternative Approaches ◽  
Iron Formations

AbstractEarly Earth processes are typically identified through the study of mineralogical, elemental and isotopic features in the rock record, including Precambrian banded iron formations (BIF). However, post-depositional processes often obscure the primary geochemical signals, making the use of BIF as proxies for paleo-seawater and the paleo-biosphere potentially imprecise. Thus, alternative approaches are required to complement the information gained from the rock record in order to fully understand the distinctive biogeochemical processes on ancient Earth. Simulating these conditions in the laboratory is one approach, but this approach can never fully replicate the complexity of a natural environment. Therefore, finding modern environments with a unique set of geochemical and microbiological characteristics to use as analogues for BIF depositional environments can provide invaluable information. In this review, we provide an overview of the chemical, physical and biological parameters of modern, ferruginous lakes that have been used as analogue BIF environments.

Earth’s Middle Ages: What Came after the GOE

2017 ◽  
Author(s):  
Donald Eugene Canfield
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Middle Ages ◽  
Atmospheric Oxygen ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Dissolved Iron ◽  
Great Oxidation Event ◽  
Low Levels ◽  
Substantial Rise

This chapter considers the aftermath of the great oxidation event (GOE). It suggests that there was a substantial rise in oxygen defining the GOE, which may, in turn have led to the Lomagundi isotope excursion, which was associated with high rates of organic matter burial and perhaps even higher concentrations of oxygen. This excursion was soon followed by a crash in oxygen to very low levels and a return to banded iron formation deposition. When the massive amounts of organic carbon buried during the excursion were brought into the weathering environment, they would have represented a huge oxygen sink, drawing down levels of atmospheric oxygen. There appeared to be a veritable seesaw in oxygen concentrations, apparently triggered initially by the GOE. The GOE did not produce enough oxygen to oxygenate the oceans. Dissolved iron was removed from the oceans not by reaction with oxygen but rather by reaction with sulfide. Thus, the deep oceans remained anoxic and became rich in sulfide, instead of becoming well oxygenated.

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