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Iron in geological formations

Iron in geological formations

Bibcode Plant-based protein sources for athletes Iron in geological formations. Heinrich Holland argues Iorn the absence of manganese deposits Pomegranate tarts recipes the pause between Paleoproterozoic and Neoproterozoic Veological is evidence that the Formationz ocean had become at least slightly oxygenated. Your email address is used only formatiosn let the recipient know who sent the email. BIFs are divided into type categories based on the characteristics related to the nature of their formation and unique physical and chemical properties. Retrieved 22 June Mining of united iron developments includes coarse smashing and screening, trailed by unpleasant pounding and fine granulating to comminute the mineral to the point where the solidified magnetite and quartz are sufficiently fine that the quartz is deserted when the resultant powder is passed under an attractive separator. RELATED ARTICLES.

by Katie Willis, Individualized nutrition plans of Iron in geological formations. A new study by University of Alberta scientists formatiohs that banded iron Iron in geological formations formatilns from oxidized iron, confirming fromations relevance and accuracy Iron in geological formations existing geologicak finding of great importance to formatiojs Iron in geological formations community.

Banded iron formations are a distinct type of sedimentary rock with layers of iron deposited as horizontal bands. The majority of these formations Creatine for muscle growth on Creatine for muscle growth ggeological 2.

In the last geologival, a new model was proposed, suggesting that formztions formations began as ferrous iron that was formafions oxidized by oxygen geologucal the environment—a model that, if correct, would require geloogical major paradigm shift in this area of study.

Teological examine this possibility, Iron in geological formations group of researchers led by Konhauser's Adolescent fat distribution. student Leslie Organic protein powders tested the theory using a hydrogeological model, designed to determine how long it would take oxygen to oxidize such a formation.

Idon research team included Professor Ben Roston, Assistant Professor Daniel Iroj, and Professor Larry Pomegranate tarts recipes. These results confirmed that the Pregnancy detox diets proposed Macronutrients and fitness is ib, indicating that existing geologiccal and our current understanding remains the most effective method of studying banded iron formations.

The paper, forrmations constraints on the formation of Palaeoproterozoic formatione iron formatiohs ," was published geologica Nature Geoscience. More information: Leslie Creatine for muscle growth.

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More information Privacy policy. We keep our content available to everyone. Consider supporting Science X's mission by getting a premium account. share this! Home Earth Earth Sciences. June 6, Banded iron formations, such as this one pictured in Western Australia, precipitated out of the Earth's early oceans billions of years ago, and are providing new clues to the evolution of ancient seawater and the microbes that inhabited it.

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: Iron in geological formations

Iron Ore: Sedimentary Rock - Pictures, Definition & More

Press metal mining strategies change by the kind of mineral being mined. There are four fundamental sorts of iron-metal stores worked right now, contingent upon the mineralogy and topography of the metal stores.

These are magnetite, titanomagnetite, monstrous hematite and pisolitic ironstone stores. Banded iron formations happen only in Precambrian shakes, and are regularly feebly to strongly transformed.

Banded iron formations may contain press in carbonates siderite or ankerite or silicates minnesotaite, greenalite, or grunerite , however in those mined as iron metals, oxides magnetite or hematite are the chief iron mineral. Banded iron formations are known as taconite inside North America.

The mining includes moving enormous measures of metal and waste. The waste comes in two structures, non-metal bedrock in the mine overburden or inter-burden privately known as mullock , and undesirable minerals which are a characteristic part of the metal shake itself gangue.

The mullock is mined and heaped in waste dumps, and the gangue is isolated amid the beneficiation procedure and is expelled as tailings. Taconite tailings are for the most part the mineral quartz, which is artificially latent.

This material is put away in vast, directed water settling lakes. The key monetary parameters for magnetite mineral being financial are the crystallinity of the magnetite, the review of the iron inside the joined iron arrangement have shake, and the contaminant components which exist inside the magnetite think.

The size and strip proportion of most magnetite assets is immaterial as a united iron development can be many meters thick, augment several kilometres along strike, and can undoubtedly come to more than three billion or more huge amounts of contained metal.

The average magnetite press metal focus has under 0. Presently magnetite press mineral is mined in Minnesota and Michigan in the U. Magnetite bearing united iron development is presently mined broadly in Brazil, which sends out huge amounts to Asia, and there is an early and huge magnetite press mineral industry in Australia.

Occasionally granite and ultrapotassic igneous rocks segregate magnetite crystals and form masses of magnetite suitable for economic concentration. A few iron ore deposits, notably in Chile, are formed from volcanic flows containing significant accumulations of magnetite phenocrysts.

Chilean magnetite iron ore deposits within the Atacama Desert have also formed alluvial accumulations of magnetite in streams leading from these volcanic formations. More Rocks Difficult Rocks Fossils Tumbled Stones Geodes Flint, Chert, and Jasper The Rock Used to Make Beer Rock, Mineral and Fossil Collections.

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The most common association of the silicate rocks is with either carbonate- or magnetite-bearing rocks, which suggests that the optimum conditions for deposition ranged from slightly oxidizing to slightly reducing. The relationship between the iron-rich rocks and volcanism, stressed by many authors, is considered by the writer to be structural, not chemical: in the Lake Superior region both iron-deposition and volcanism are believed to be related to geosynclinal development during Huronian time.

In Michigan, the lower Huronian rocks are iron-poor quartzite and dolomite-typical "stable-shelf" deposits; much of the upper Huronian consists of iron-poor graywacke and slate with associated volcanic rocks -a typical "geosynclinal" assemblage.

Thus the iron-rich beds of the middle Huronian and lower part of the upper Huronian were deposited during a transitional stage in structural history. The major environmental requirement for deposition of iron-formation is the closed or restricted basin; this requirement coincides in time with what would be a normal stage in evolution of the geosyncline: namely, structural development of offshore buckles or swells that subsequently develop into island arcs characterized by volcanism.

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Iron Ore Deposits Associated with Precambrian Iron Formations

Iron formations generally disappeared at ca. By the Phanerozoic, marine iron deposition was restricted to local areas of closed to semiclosed basins, where volcanic and hydrothermal activity was extensive e.

Late Paleoproterozoic iron formations and Paleozoic ironstones were deposited at the redoxcline where biological and nonbiological oxidation occurred. In contrast, older iron formations were deposited in anoxic oceans, where ferrous iron oxidation by anoxygenic photosynthetic bacteria was likely an important process.

Endogenic and exogenic factors contributed to produce the conditions necessary for deposition of iron formation. Mantle plume events that led to the formation of LIPs also enhanced spreading rates of midocean ridges and produced higher growth rates of oceanic plateaus, both processes thus having contributed to a higher hydrothermal flux to the ocean.

Oceanic and atmospheric redox states determined the fate of this flux. When the hydrothermal flux overwhelmed the oceanic oxidation state, iron was transported and deposited distally from hydrothermal vents.

Where the hydrothermal flux was insufficient to overwhelm the oceanic redox state, iron was deposited only proximally, generally as oxides or sulfides.

Manganese, in contrast, was more mobile. We conclude that occurrences of BIF, GIF, Phanerozoic ironstones, and exhalites surrounding VMS systems record a complex interplay involving mantle heat, tectonics, and surface redox conditions throughout Earth history, in which mantle heat unidirectionally declined and the surface oxidation state mainly unidirectionally increased, accompanied by superimposed shorter term fluctuations.

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Skip Nav Destination Article Navigation. Close mobile search navigation Article navigation. Volume , Number 3. Previous Article Next Article. Article Navigation. Research Article May 01, Iron Formation: The Sedimentary Product of a Complex Interplay among Mantle, Tectonic, Oceanic, and Biospheric Processes1 Andrey Bekker ; Andrey Bekker.

Google Scholar. John F. Slack ; John F. Noah Planavsky ; Noah Planavsky. Bryan Krapež ; Bryan Krapež. They range in thickness from 10— meters.

Superior types are large, thick, extensive iron deposits across stable shelves and in broad basins. They can extend to over 10 5 kilometers 2. Deposition occurs in relatively shallow marine conditions under transgressing seas.

Granular iron formations GIFs were originally well-sorted chemical sands. They lack even, continuous bedding that takes the form of discontinuous layers.

Discontinuous layers likely represent bedforms that were generated by storm waves and currents. Any layers that are thicker than a few meters and are uninterrupted, are rare for GIFs. They contain sand-sized clasts and a finer grained matrix , and generally belong to the oxide or silicate mineral facies.

There are four facies types associated with iron-rich sedimentary rocks: oxide-, silicate-, carbonate-, and sulfide-facies. These facies correspond to water depth in a marine environment. Oxide-facies are precipitated under the most oxidizing conditions. Silicate- and carbonate-facies are precipitated under intermediate redox conditions.

Sulfide-facies are precipitated under the most reducing conditions. There is a lack of iron-rich sedimentary rocks in shallow waters which leads to the conclusion that the depositional environment ranges from the continental shelf and upper continental slope to the abyssal plain.

The diagram does not have the abyssal plain labeled, but this would be located to the far right of the diagram at the bottom of the ocean.

Ferrous and ferric iron are components in many minerals, especially within sandstones. Oxidation is the loss of electrons from an element. Oxidation can occur from bacteria or by chemical oxidation.

This often happens when ferrous ions come into contact with water due to dissolved oxygen within surface waters and a water-mineral reaction occurs. This form of iron gives up electrons easily and is a mild reducing agent.

These compounds are more soluble because they are more mobile. This form of iron is very stable structurally because its valence electron shell is half filled.

Laterization is a soil forming process that occurs in warm and moist climates under broadleaf evergreen forests. Soils formed by laterization tend to be highly weathered with high iron and aluminium oxide content.

Goethite is often made from this process and is a major source of iron in sediments. However, once it is deposited it must be dehydrated in order to come to an equilibrium with hematite.

The dehydration reaction is: [9]. Pyritization is discriminatory. It rarely happens to soft tissue organisms and aragonitic fossils are more susceptible to it than calcite fossils. It commonly takes place in marine depositional environments where there is organic material.

The process is caused by sulfate reduction which replaces carbonate skeletons or shells with pyrite FeS 2. It generally does not preserve detail and the pyrite forms within the structure as many microcrystals.

In freshwater environments, siderite will replace carbonate shells instead of pyrite due to the low amounts of sulfate. Magnetite and hematite are opaque under the microscope under transmitted light. Under reflected light, magnetite shows up as metallic and a silver or black color.

Hematite will be a more reddish-yellow color. Pyrite is seen as opaque, a yellow-gold color, and metallic. gov A. gov website belongs to an official government organization in the United States. gov website. Share sensitive information only on official, secure websites.

The sedimentary iron-formations of Precambrian age in the Lake Superior region can be divided on the basis of the dominant original iron mineral into four principal facies: sulfide, carbonate, oxide, and silicate. As chemical sediments, these rocks reflect certain aspects of the chemistry of the depositional environments.

The major control, at least for the sulfide, carbonate, and oxide types, probably was the oxidation potential. The evidence indicates that deposition took place in restricted basins, which were separated from the open sea by thresholds that inhibited free circulation and permitted development of abnormalities in oxidation potential and water composition.

The sporadic distribution of metamorphism and of later oxidation permits description of the primary facies on the basis of unoxidized, essentially unmetamorphosed material.

The sulfide facies is represented by black slates in which pyrite may make up as much as 40 percent of the rock. The free-carbon content of these rocks typically ranges from 5 to 15 percent, indicating that ultra-stagnant conditions prevailed during deposition.

Locally, the pyritic rocks contain layers of iron-rich carbonate. The carbonate facies consists, in its purer form, of interbedded iron-rich carbonate and chert.

It is a product of an environment in which oxygen concentration was sufficiently high to destroy most of the organic material but not high enough to permit formation of ferric compounds.

The oxide facies is found as two principal types, one characterized by magnetite and the other by hematite. Both minerals appear to be of primary origin. The magnetite-banded rock is one of the dominant lithologies in the region; it consists typically of magnetite interlayered with chert, carbonate, or iron silicate, or combinations of the three.

How Does Iron Ore Form?

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Deutsche Mineralogische Gesellschaft DMG. Società Italiana di Mineralogia e Petrologia SIMP. International Association of Geoanalysts IAG. Polskie Towarzystwo Mineralogiczne PTMin.

Sociedad Española de Mineralogía SEM. Swiss Geological Society SGG-SGS. Meteoritical Society Met Soc. Japan Association of Mineralogical Sciences JAMS.

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Download as PDF Printable version. In other projects. Wikimedia Commons. Distinctive layered units of iron-rich sedimentary rock that are almost always of Precambrian age. Banded iron formation, Karijini National Park , Western Australia. Main article: Great Oxidation Event. Main article: Snowball Earth.

Economic Geology. Bibcode : EcGeo.. doi : In Altermann, Wladyslaw; Corcoran, Patricia L. Precambrian Sedimentary Environments: A Modern Approach to Ancient Depositional Systems. Blackwell Science Ltd. ISBN Journal of Metamorphic Geology.

Bibcode : JMetG.. S2CID Earth as an evolving planetary system 3 ed. Academic Press. In Eriksson, P. Evolution of the Hydrosphere and Atmosphere. Developments in Precambrian Geology.

Encyclopedia of Geology. The Journal of Geology. Bibcode : JG American Mineralogist. Bibcode : AmMin.. Lithology and Mineral Resources.

May Bibcode : EcGeo. CiteSeerX Mineralium Deposita. Bibcode : MinDe.. Chemical Geology. Bibcode : ChGeo.

Retrieved 23 June December Precambrian Research. Bibcode : PreR.. Chemostratigraphy: Concepts, Techniques, and Applications. Retrieved 22 June Scientific Reports. Bibcode : NatSR PMC PMID The Canadian Mineralogist. Ore Geology Reviews. Bibcode : OGRv ISSN Earth and Planetary Science Letters.

Timmins , Ontario : Hollinger Mines Limited : 3, 4, 9. AFRI 31M04SW American Museum of Natural History. Retrieved 17 June Bulletin Archived 4 March at the Wayback Machine Geological Survey of Western Australia , No.

Rio Tinto Iron Ore. Archived from the original on 23 October Retrieved 7 August Porter GeoConsultancy. Western Australian Museum. F Geological Society of America Bulletin. Bibcode : GSAB What is Life? University of California Press. Philosophical Transactions of the Royal Society B: Biological Sciences.

Bibcode : Sci JSTOR Geological Society of America Memoir. Retrieved 19 June Banded iron formations, to iron ore : an integrated genesis model. Nova Science Publishers. November Bibcode : Geo September Bibcode : Natur.

August Bibcode : PreR Journal of Asian Earth Sciences. Bibcode : JAESc. Proceedings of the National Academy of Sciences. Bibcode : PNAS.. Archived from the original PDF on 16 December January Geochimica et Cosmochimica Acta.

Bibcode : GeCoA.. Graham ; Sloper, Robert W. Graham September Origins of Life and Evolution of the Biosphere. Bibcode : OrLi July Extended Abstracts 4th International Archaean Symposium : — March In Schopf JW, Klein C eds.

The Proterozoic Biosphere: A Multidisciplinary Study. Cambridge University Press. Geophysical Research Abstracts. Journal of African Earth Sciences.

Bibcode : JAfES.. Earth-Science Reviews. Bibcode : ESRv Archived from the original PDF on 28 November Minnesota Minerals Coordinating Council. Retrieved 18 June John D. Ridge ed. Geology of the Iron Ores of the Lake Superior Region in the United States, in Volume 1 of Ore Deposits of the United States, — The American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.

Minnesota Department of Natural Resources. Retrieved 10 October Geoscience Australia. Archived from the original on 18 February Archived from the original on 12 June Retrieved 6 November Mining Data Solutions.

MDO Data Online Inc. CEIC Data. Retrieved 16 February Japanese Imperialism — Oxford University Press. Foreign Languages Press, Beijing. Harnmeijer, J. University of Washington. Archived from the original on 8 September Klein, C. October The Wikibook Historical Geology has a page on the topic of: Banded iron formations.

Ore minerals , mineral mixtures and ore deposits. Cassiterite tin Chromite chromium Coltan niobium and tantalum Columbite niobium Hematite iron Ilmenite titanium Magnetite iron Pyrolusite manganese Tantalite tantalum Uraninite uranium.

Acanthite silver Argentite silver Bornite copper Chalcopyrite copper Chalcocite copper Cinnabar mercury Cobaltite cobalt Galena lead Molybdenite molybdenum Pyrite iron Pentlandite nickel Sphalerite zinc. Dolomite magnesium Magnesite magnesium Malachite copper.

Baryte barium Bauxite aluminium Beryl beryllium Sperrylite platinum Scheelite tungsten Wolframite tungsten.

Pages - Menu We Oxidation damage prevention that occurrences of BIF, GIF, Phanerozoic ironstones, and exhalites surrounding Formahions systems Geologicaal a complex geoolgical Iron in geological formations un heat, tectonics, and surface redox formahions throughout Earth history, in which forrmations Creatine for muscle growth unidirectionally declined and the surface oxidation state mainly unidirectionally increased, accompanied by superimposed shorter term fluctuations. Learn more. By and large most magnetite grouped iron arrangement stores must be ground to in the vicinity of 32 and 45 micrometers keeping in mind the end goal to deliver a low-silica magnetite think. Middle East and Africa Iron Ore Market. In contrast, larger Superior-type iron formations are developed in passive-margin sedimentary rock successions and generally lack direct relationships with volcanic rocks.
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So over time, the seafloor collected rusted iron. This rusted iron is in the different layers of banded iron formation BIF created about 3. The alternating layers in banded iron formations represent rock being oxidized. We can find banded iron formations all over the world such as:.

Hematite-rich ore can be mined which is found in banded iron formations. These two layers alternate with similar thicknesses from the oxidation of iron and subsequent deposition.

Almost all BIFs formed in the Precambrian because of the accumulation of free oxygen. Basically prior or the evolution of photosynthetic bacteria there were a lot of free iron ions dissolved in the ocean. In a shallow marine setting, stromatolites and other single-celled bacteria produced oxygen as a by-product of the photosynthesis process.

Oxygen filled the oceans and atmosphere to form rusted iron in the oceans. The lack of organic carbon in banded iron formation argues against microbial control of BIF deposition.

If a substantial part of the original iron oxides was in the form of hematite, then any carbon in the sediments might have been oxidized by the decarbonization reaction: [2].

Trendall and J. Blockley proposed, but later rejected, the hypothesis that banded iron formation might be a peculiar kind of Precambrian evaporite. Another abiogenic mechanism is photooxidation of iron by sunlight. Laboratory experiments suggest that this could produce a sufficiently high deposition rate under likely conditions of pH and sunlight.

Regardless of the precise mechanism of oxidation, the oxidation of ferrous to ferric iron likely caused the iron to precipitate out as a ferric hydroxide gel.

Similarly, the silica component of the banded iron formations likely precipitated as a hydrous silica gel. There is evidence that banded iron formations formed from sediments with nearly the same chemical composition as is found in the BIFs today.

The BIFs of the Hamersley Range show great chemical homogeneity and lateral uniformity, with no indication of any precursor rock that might have been altered to the current composition. This suggests that, other than dehydration and decarbonization of the original ferric hydroxide and silica gels, diagenesis likely left the composition unaltered and consisted of crystallization of the original gels.

However, it is possible that BIF was altered from carbonate rock [53] or from hydrothermal mud [54] during late stages of diagenesis. A study found no evidence that magnetite in BIF formed by decarbonization, and suggests that it formed from thermal decomposition of siderite via the reaction.

The iron may have originally precipitated as greenalite and other iron silicates. Macrobanding is then interpreted as a product of compaction of the original iron silicate mud. This produced siderite-rich bands that served as pathways for fluid flow and formation of magnetite.

The peak of deposition of banded iron formations in the late Archean, and the end of deposition in the Orosirian, have been interpreted as markers for the Great Oxygenation Event. Prior to 2. The peak of banded iron formation deposition coincides with the disappearance of the MIF-S signal, which is interpreted as the permanent appearance of oxygen in the atmosphere between 2.

This was accompanied by the development of a stratified ocean with a deep anoxic layer and a shallow oxidized layer. The end of deposition of BIF at 1. Until [56] it was assumed that the rare, later younger banded iron deposits represented unusual conditions where oxygen was depleted locally.

Iron-rich waters would then form in isolation and subsequently come into contact with oxygenated water. The Snowball Earth hypothesis provided an alternative explanation for these younger deposits. In a Snowball Earth state the continents, and possibly seas at low latitudes, were subject to a severe ice age circa to Ma that nearly or totally depleted free oxygen.

Dissolved iron then accumulated in the oxygen-poor oceans possibly from seafloor hydrothermal vents. An alternative mechanism for banded iron formations in the Snowball Earth era suggests the iron was deposited from metal-rich brines in the vicinity of hydrothermally active rift zones [59] due to glacially-driven thermal overturn.

Such a mode of formation does not require a global anoxic ocean, but is consistent with either a Snowball Earth or Slushball Earth model. Banded iron formations provide most of the iron ore presently mined.

Different mining districts coined their own names for BIFs. The term "banded iron formation" was coined in the iron districts of Lake Superior , where the ore deposits of the Mesabi, Marquette , Cuyuna, Gogebic , and Menominee iron ranges were also variously known as "jasper", "jaspilite", "iron-bearing formation", or taconite.

Banded iron formations were described as "itabarite" in Brazil, as "ironstone" in South Africa, and as "BHQ" banded hematite quartzite in India. Banded iron formation was first discovered in northern Michigan in , and mining of these deposits prompted the earliest studies of BIFs, such as those of Charles R.

Van Hise and Charles Kenneth Leith. Initially the mines exploited large beds of hematite and goethite weathered out of the banded iron formations, and some 2,,, t 2. Iron ore became a global commodity after the Second World War , and with the end of the embargo against exporting iron ore from Australia in , the Hamersley Range became a major mining district.

The Itabarite banded iron formations of Brazil cover at least 80, square kilometers 31, square miles and are up to meters 2, feet thick.

Mining of ore from banded iron formations at Anshan in north China began in When Japan occupied Northeast China in , these mills were turned into a Japanese-owned monopoly, and the city became a significant strategic industrial hub during the Second World War.

Total production of processed iron in Manchuria reached 1,, t , long tons; 1,, short tons in — By , Anshan's Shōwa Steel Works total production capacity reached 3,, t 3,, long tons; 4,, short tons per annum, making it one of the major iron and steel centers in the world.

However, from to , the steel works produced ,, t ,, long tons; ,, short tons million tons of steel, ,, t ,, long tons; ,, short tons of pig iron and ,, t ,, long tons; ,, short tons of rolled steel. Annual production capacity as of [update] is 10,, t 9,, long tons; 11,, short tons of pig iron, 10,, t 9,, long tons; 11,, short tons of steel and 9,, t 9,, long tons; 10,, short tons of rolled steel.

A quarter of China's total iron ore reserves, about 10,,, t 9. Contents move to sidebar hide. Article Talk. Read Edit View history. Tools Tools. What links here Related changes Upload file Special pages Permanent link Page information Cite this page Get shortened URL Download QR code Wikidata item.

Download as PDF Printable version. In other projects. Wikimedia Commons. Distinctive layered units of iron-rich sedimentary rock that are almost always of Precambrian age. Banded iron formation, Karijini National Park , Western Australia.

Main article: Great Oxidation Event. Main article: Snowball Earth. Economic Geology. Bibcode : EcGeo.. doi : In Altermann, Wladyslaw; Corcoran, Patricia L. Precambrian Sedimentary Environments: A Modern Approach to Ancient Depositional Systems.

Blackwell Science Ltd. ISBN Journal of Metamorphic Geology. Bibcode : JMetG.. S2CID Earth as an evolving planetary system 3 ed. Academic Press. In Eriksson, P. Evolution of the Hydrosphere and Atmosphere. Developments in Precambrian Geology.

Encyclopedia of Geology. The Journal of Geology. Bibcode : JG American Mineralogist. Bibcode : AmMin.. Lithology and Mineral Resources.

May Bibcode : EcGeo. CiteSeerX Mineralium Deposita. Bibcode : MinDe.. Chemical Geology. Bibcode : ChGeo. Retrieved 23 June December Precambrian Research.

Bibcode : PreR.. Chemostratigraphy: Concepts, Techniques, and Applications. Retrieved 22 June Scientific Reports. Texturally, iron formations were also divided into two groups. Banded iron formation BIF is dominant in Archean to earliest Paleoproterozoic successions, whereas granular iron formation GIF is much more common in Paleoproterozoic successions.

Secular changes in the style of iron-formation deposition, identified more than 20 years ago, have been linked to diverse environmental changes. Geochronologic studies emphasize the episodic nature of the deposition of giant iron formations, as they are coeval with, and genetically linked to, time periods when large igneous provinces LIPs were emplaced.

Superior-type iron formation first appeared at ca. From ca. The younger BIFs in this age range were deposited during the early stage of a shift from reducing to oxidizing conditions in the ocean-atmosphere system.

Counterintuitively, enhanced magmatism at 2. After the rise of atmospheric oxygen during the GOE at ca. Iron formations generally disappeared at ca. By the Phanerozoic, marine iron deposition was restricted to local areas of closed to semiclosed basins, where volcanic and hydrothermal activity was extensive e.

Late Paleoproterozoic iron formations and Paleozoic ironstones were deposited at the redoxcline where biological and nonbiological oxidation occurred.

In contrast, older iron formations were deposited in anoxic oceans, where ferrous iron oxidation by anoxygenic photosynthetic bacteria was likely an important process. Endogenic and exogenic factors contributed to produce the conditions necessary for deposition of iron formation.

Mantle plume events that led to the formation of LIPs also enhanced spreading rates of midocean ridges and produced higher growth rates of oceanic plateaus, both processes thus having contributed to a higher hydrothermal flux to the ocean. Oceanic and atmospheric redox states determined the fate of this flux.

When the hydrothermal flux overwhelmed the oceanic oxidation state, iron was transported and deposited distally from hydrothermal vents.

Where the hydrothermal flux was insufficient to overwhelm the oceanic redox state, iron was deposited only proximally, generally as oxides or sulfides. Manganese, in contrast, was more mobile. We conclude that occurrences of BIF, GIF, Phanerozoic ironstones, and exhalites surrounding VMS systems record a complex interplay involving mantle heat, tectonics, and surface redox conditions throughout Earth history, in which mantle heat unidirectionally declined and the surface oxidation state mainly unidirectionally increased, accompanied by superimposed shorter term fluctuations.

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Pages - Menu Home Rocks Gemstone Guide Hydrogeology Live Virtual Geologcal Tours Geopogical to LG Pomegranate tarts recipes Gormations. Tuesday, Balanced diet plan 17, Iron Ore. The iron ore deposits are found in sedimentary rocks. They are formed by the chemical reaction of iron and oxygen mixed in the marine and fresh water. The important iron oxides in these deposits are hematite and magnetite. These are ores from where iron is extracted. Iron in geological formations

Iron in geological formations -

However, a small number of BIFs are Neoproterozoic in age, and are frequently, [8] [10] [11] if not universally, [12] associated with glacial deposits, often containing glacial dropstones.

This suggests very rapid deposition. Banded iron formations are distinct from most Phanerozoic ironstones. Ironstones are relatively rare and are thought to have been deposited in marine anoxic events , in which the depositional basin became depleted in free oxygen.

They are composed of iron silicates and oxides without appreciable chert but with significant phosphorus content, which is lacking in BIFs. No classification scheme for banded iron formations has gained complete acceptance. Gross advocated a twofold division of BIFs into an Algoma type and a Lake Superior type, based on the character of the depositional basin.

Algoma BIFs are found in relatively small basins in association with greywackes and other volcanic rocks and are assumed to be associated with volcanic centers.

Lake Superior BIFs are found in larger basins in association with black shales, quartzites , and dolomites , with relatively minor tuffs or other volcanic rocks, and are assumed to have formed on a continental shelf. Banded iron formations are almost exclusively Precambrian in age, with most deposits dating to the late Archean — Ma with a secondary peak of deposition in the Orosirian period of the Paleoproterozoic Ma.

Minor amounts were deposited in the early Archean and in the Neoproterozoic Ma. Banded iron formations are found worldwide, in every continental shield of every continent.

The oldest BIFs are associated with greenstone belts and include the BIFs of the Isua Greenstone Belt , the oldest known, which have an estimated age of to Ma. The most extensive banded iron formations belong to what A. Trendall calls the Great Gondwana BIFs. These are late Archean in age and are not associated with greenstone belts.

They are relatively undeformed and form extensive topographic plateaus, [2] such as the Hamersley Range. Paleoproterozoic banded iron formations are found in the Iron Range and other parts of the Canadian Shield. All are part of the Animikie Group and were deposited between and Ma.

Neoproterozoic banded iron formations include the Urucum in Brazil, Rapitan in the Yukon , and the Damara Belt in southern Africa. Banded iron formation provided some of the first evidence for the timing of the Great Oxidation Event , 2, Ma. Cloud postulated that banded iron formations were a consequence of anoxic, iron-rich waters from the deep ocean welling up into a photic zone inhabited by cyanobacteria that had evolved the capacity to carry out oxygen-producing photosynthesis, but which had not yet evolved enzymes such as superoxide dismutase for living in an oxygenated environment.

Such organisms would have been protected from their own oxygen waste through its rapid removal via the reservoir of reduced ferrous iron, Fe II , in the early ocean. The oxygen released by photosynthesis oxidized the Fe II to ferric iron, Fe III , which precipitated out of the sea water as insoluble iron oxides that settled to the ocean floor.

Cloud suggested that banding resulted from fluctuations in the population of cyanobacteria due to free radical damage by oxygen. This also explained the relatively limited extent of early Archean deposits. The great peak in BIF deposition at the end of the Archean was thought to be the result of the evolution of mechanisms for living with oxygen.

This ended self-poisoning and produced a population explosion in the cyanobacteria that rapidly depleted the remaining supply of reduced iron and ended most BIF deposition. Oxygen then began to accumulate in the atmosphere.

Some details of Cloud's original model were abandoned. For example, improved dating of Precambrian strata has shown that the late Archean peak of BIF deposition was spread out over tens of millions of years, rather than taking place in a very short interval of time following the evolution of oxygen-coping mechanisms.

However, his general concepts continue to shape thinking about the origins of banded iron formations. The few formations deposited after 1, Ma [36] may point to intermittent low levels of free atmospheric oxygen, [37] while the small peak at million years ago may be associated with the hypothetical Snowball Earth.

The microbands within chert layers are most likely varves produced by annual variations in oxygen production. Preston Cloud proposed that mesobanding was a result of self-poisoning by early cyanobacteria as the supply of reduced iron was periodically depleted. For banded iron formations to be deposited, several preconditions must be met.

There must be an ample source of reduced iron that can circulate freely into the deposition basin. The importance of various sources of reduced iron has likely changed dramatically across geologic time.

This is reflected in the division of BIFs into Algoma and Lake Superior-type deposits. These older BIFs tend to show a positive europium anomaly consistent with a hydrothermal source of iron. The absence of hydrogen sulfide in anoxic ocean water can be explained either by reduced sulfur flux into the deep ocean or a lack of dissimilatory sulfate reduction DSR , the process by which microorganisms use sulfate in place of oxygen for respiration.

The product of DSR is hydrogen sulfide, which readily precipitates iron out of solution as pyrite. The requirement of an anoxic, but not euxinic, deep ocean for deposition of banded iron formation suggests two models to explain the end of BIF deposition 1. The "Holland ocean" model proposes that the deep ocean became sufficiently oxygenated at that time to end transport of reduced iron.

Heinrich Holland argues that the absence of manganese deposits during the pause between Paleoproterozoic and Neoproterozoic BIFs is evidence that the deep ocean had become at least slightly oxygenated. The "Canfield ocean" model proposes that, to the contrary, the deep ocean became euxinic and transport of reduced iron was blocked by precipitation as pyrite.

Banded iron formations in northern Minnesota are overlain by a thick layer of ejecta from the Sudbury Basin impact. An asteroid estimated at 10 km 6.

Computer models suggest that the impact would have generated a tsunami at least 1, m 3, ft high at the point of impact, and m ft high about 3, km 1, mi away.

It has been suggested that the immense waves and large underwater landslides triggered by the impact caused the mixing of a previously stratified ocean, oxygenated the deep ocean, and ended BIF deposition shortly after the impact.

Although Cloud argued that microbial activity was a key process in the deposition of banded iron formation, the role of oxygenic versus anoxygenic photosynthesis continues to be debated, and nonbiogenic processes have also been proposed.

Cloud's original hypothesis was that ferrous iron was oxidized in a straightforward manner by molecular oxygen present in the water: [30] [13]. The oxygen comes from the photosynthetic activities of cyanobacteria.

Oxygenic photosynthesis is not the only biogenic mechanism for deposition of banded iron formations. Some geochemists have suggested that banded iron formations could form by direct oxidation of iron by microbial anoxygenic phototrophs.

This requires that dissimilatory iron reduction, the biological process in which microorganisms substitute Fe III for oxygen in respiration, was not yet widespread. An alternate route is oxidation by anaerobic denitrifying bacteria. This requires that nitrogen fixation by microorganisms is also active.

The lack of organic carbon in banded iron formation argues against microbial control of BIF deposition. If a substantial part of the original iron oxides was in the form of hematite, then any carbon in the sediments might have been oxidized by the decarbonization reaction: [2].

Trendall and J. Blockley proposed, but later rejected, the hypothesis that banded iron formation might be a peculiar kind of Precambrian evaporite.

Another abiogenic mechanism is photooxidation of iron by sunlight. Laboratory experiments suggest that this could produce a sufficiently high deposition rate under likely conditions of pH and sunlight.

Regardless of the precise mechanism of oxidation, the oxidation of ferrous to ferric iron likely caused the iron to precipitate out as a ferric hydroxide gel. Similarly, the silica component of the banded iron formations likely precipitated as a hydrous silica gel.

There is evidence that banded iron formations formed from sediments with nearly the same chemical composition as is found in the BIFs today. The BIFs of the Hamersley Range show great chemical homogeneity and lateral uniformity, with no indication of any precursor rock that might have been altered to the current composition.

This suggests that, other than dehydration and decarbonization of the original ferric hydroxide and silica gels, diagenesis likely left the composition unaltered and consisted of crystallization of the original gels. However, it is possible that BIF was altered from carbonate rock [53] or from hydrothermal mud [54] during late stages of diagenesis.

A study found no evidence that magnetite in BIF formed by decarbonization, and suggests that it formed from thermal decomposition of siderite via the reaction. The iron may have originally precipitated as greenalite and other iron silicates.

Macrobanding is then interpreted as a product of compaction of the original iron silicate mud. This produced siderite-rich bands that served as pathways for fluid flow and formation of magnetite.

The peak of deposition of banded iron formations in the late Archean, and the end of deposition in the Orosirian, have been interpreted as markers for the Great Oxygenation Event. Prior to 2. The peak of banded iron formation deposition coincides with the disappearance of the MIF-S signal, which is interpreted as the permanent appearance of oxygen in the atmosphere between 2.

This was accompanied by the development of a stratified ocean with a deep anoxic layer and a shallow oxidized layer. The end of deposition of BIF at 1. Until [56] it was assumed that the rare, later younger banded iron deposits represented unusual conditions where oxygen was depleted locally.

Iron-rich waters would then form in isolation and subsequently come into contact with oxygenated water. The Snowball Earth hypothesis provided an alternative explanation for these younger deposits.

In a Snowball Earth state the continents, and possibly seas at low latitudes, were subject to a severe ice age circa to Ma that nearly or totally depleted free oxygen. Dissolved iron then accumulated in the oxygen-poor oceans possibly from seafloor hydrothermal vents.

An alternative mechanism for banded iron formations in the Snowball Earth era suggests the iron was deposited from metal-rich brines in the vicinity of hydrothermally active rift zones [59] due to glacially-driven thermal overturn.

Such a mode of formation does not require a global anoxic ocean, but is consistent with either a Snowball Earth or Slushball Earth model.

Banded iron formations provide most of the iron ore presently mined. Different mining districts coined their own names for BIFs. The term "banded iron formation" was coined in the iron districts of Lake Superior , where the ore deposits of the Mesabi, Marquette , Cuyuna, Gogebic , and Menominee iron ranges were also variously known as "jasper", "jaspilite", "iron-bearing formation", or taconite.

Banded iron formations were described as "itabarite" in Brazil, as "ironstone" in South Africa, and as "BHQ" banded hematite quartzite in India.

Banded iron formation was first discovered in northern Michigan in , and mining of these deposits prompted the earliest studies of BIFs, such as those of Charles R.

location Ishpeming, Michigan. KMX download here. subjects Iron ore, Lake Superior. Iron is abundant in the earth and in the meteorites that accumulated and melted during the Hadean.

This iron was mainly in a reduced state ferrous iron , and so when the Earth cooled and rain fell on these Hadean volcanic rocks, iron dissolved and was carried as ferrous ions to the ocean. The color of rock changes as iron oxidizes.

In the last decade, a new model was proposed, suggesting that the formations began as ferrous iron that was later oxidized by oxygen in the environment—a model that, if correct, would require a major paradigm shift in this area of study.

To examine this possibility, a group of researchers led by Konhauser's Ph. student Leslie Robbins tested the theory using a hydrogeological model, designed to determine how long it would take oxygen to oxidize such a formation.

The research team included Professor Ben Roston, Assistant Professor Daniel Alessi, and Professor Larry Heaman. These results confirmed that the newly proposed model is inaccurate, indicating that existing models and our current understanding remains the most effective method of studying banded iron formations.

The paper, "Hydrogeological constraints on the formation of Palaeoproterozoic banded iron formations ," was published in Nature Geoscience. More information: Leslie J. Robbins et al, Hydrogeological constraints on the formation of Palaeoproterozoic banded iron formations, Nature Geoscience DOI: Provided by University of Alberta.

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Home Gut health Rocks » Sedimentary Flrmations » Pomegranate tarts recipes Ore. Iron Ore: A specimen of oolitic hematite formationx ore. Creatine for muscle growth specimen shown Creatine for muscle growth about two inches five centimeters across. Earth's most important iron ore deposits are found in sedimentary rocks. They formed from chemical reactions that combined iron and oxygen in marine and fresh waters. The two most important minerals in these deposits are iron oxides: hematite Fe 2 O 3 and magnetite Fe 3 O 4.

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