Banded iron formations also known as banded ironstone formations or bifs are distinctive units of sedimentary rock that are almost always of precambrian age a typical banded iron formation consists of repeated, thin layers a few millimeters to a few centimeters in thickness of silver to black iron oxides, either magnetite fe 3 o 4 or hematite fe 2 o 3, alternating with bands of iron. Ages of precambrian banded iron formations samuel s. Banded iron formations bifs are marine chemical precipitates that contain 15 wt. Their individual sediment layers can be as thin as 0. Chapter 14 role of microorganisms in banded iron formations. Banded iron formations or bifs are a distinctive type of rock often found in precambrian sedimentary rocks they consist of repeated thin layers of iron oxides, either magnetite fe 3 o 4 or hematite fe 2 o 3, alternating with bands of ironpoor shale and chert some of the oldest known rock formations, formed over 3,700 million years ago mya, include banded iron layers. Banded iron formations bifs are chemically precipitated sedimentary rocks. Mineralogy and geochemistry of banded iron formation and iron. Bifs are characterised by their compositional banding with thicknesses on the scales of metres, centimetres, and millimetres to micrometres, termed macrobands, mesobands. Anomalous isotopic composition has been reported for the carbon in carbonate minerals of banded iron formations. Pdf banded iron formations bifs and associated sediments do. Banded iron formations bifs are different they were all formed at a time where the earth was a decidedly different environment than it is today. The huge ironformation of the hamersley range in australia is dated between 2,200 and 2,000 m. Banded iron formation bif is a lithological term for a chemical sediment consisting of a thinly layered or laminated rock composed of alternating layers bands.
They consist of extensive ironrich and ironpoor layers within siliceous sedimentary rocks1,2. Iron formation band iron formation transvaal supergroup paleoenvironmental significance precambrian. It is found in minor amounts in the early archean and in large amounts in the late archean, appears again around 1. Banded iron formation bif is the principal source of iron. Eldorado gold corp gold mineralisation at lucky strike is hosted within multiple north.
Carbon isotopic evidence for the origin of a banded ironformation in western australia. It is found in minor amounts in the early archean and in large amounts in the late archean. A typical bif consists of repeated, thin layers a few millimeters to a few centimeters in thickness of silver to black iron oxides, either magnetite fe3o4 or hematite fe2o3, alternating with bands of iron poor shales and cherts. Historical geologybanded iron formations wikibooks, open. Many specific varieties of iron formation are known, and. Banded iron formations article about banded iron formations. Photoferrotrophy, deposition of banded iron formations. See more ideas about geology, iron and rocks and minerals.
Banded iron formations bifs are among the earliest possible indicators for oxidation of the archean biosphere. Banded iron formation at fortescue falls, karijini national park. Banded iron formations bifs host the worlds largest iron ore deposits, and they formed predominantly through the deposition of ferric iron feiii from ferruginous oceans during the archean eon 1, 2. The origin of banding in banded iron formations bif. Bif has a very distinct distribution with time figure 8. Wellpreserved bif contain iron rich bands consisting of iron oxides e. Such formations occur on all the continents and usually are older than 1. Banded iron formations bifs are made up of thin, iron rich layers alternating with layers of chert the oldest supercontinent that is known with some certainty is. Banded iron formation with icerafted debris and redeposited diamictite from the older cryogenian sturtian glaciation sayunei formation, rapitan group in the mackenzie. Each layer is relatively thin, varying in thickness from a millimeter or so up to several centimeters. Banded iron formations bifs are iron ores defined as layered, bedded, or laminated stratigraphic units composed of. Banded iron formation bif banded iron formation bif chemical sediments fe rich 20 40 wt. Banded iron formations are critical to our current economy as they are by far the biggest source of economic iron deposits. The spark to put together this volume on banded iron formation bifrelated highgrade iron ore was born in 2005 during a steamy night in carajas where the iron research group from the universidade federal minas gerais, vale geologists, carlos rosiere and steffen hagemann, were hotly debating the hypogene alteration genesis for the highgrade, jaspilitehosted serra norte iron ore deposits.
Bif is a rock type composed of alternating silica and ironrich bands. Lake superiortype bandediron formation deposit britannica. Purchase precambrian bandedironformations, volume 5 1st edition. Chapter 1 precambrian banded ironformations, their distribution. Sixth, the reappearance of banded iron formations in the late neoproterozoic has been genetically linked to global glaciation. Banded iron formation synonyms, banded iron formation pronunciation, banded iron formation translation, english dictionary definition of banded iron formation. They are composed of alternating layers of iron rich material commonly magnetite and silica chert.
It is estimated that after they were originally deposited, about 2470 to 2450 million years ago, they covered some 150 000 km2 and contained about 300 trillion tonnes of iron. Ironformations of the hamersley group of western australia. Most models for bif deposition invoke photosynthesis in the oxidation of ferrous iron from seawater to induce its subsequent precipitation and deposition as mixed valence. Banded iron formation simple english wikipedia, the free. Lake superior and are called lake superiortype deposits.
The origin of iron ore associated with banded iron formation has long been the subject of. Depositional setting of algomatype banded iron formation pdf. A carbonatebanded iron formation transition in the early. All structured data from the file and property namespaces is available under the creative commons cc0 license. Banded iron formations bifs are major rock units having hematite layers intermittent with silica rich layers and formed. A textural and mineralogical study of the relationship of. Contrasting behavior of oxygen and iron isotopes in banded. They are composed of alternating thin millimeter to centimeter scale red, yellow, or cream colored layers of chert or jasper and black to dark gray iron oxides predominantly magnetite. Little is known about this early period in earths history, in particular about. Banded iron formation is economically among the most important rock types as our society is heavily reliant on iron, which is mostly extracted from this rock. Spectral characteristics of banded iron formations in singhbhum. Banded iron formation or bif is a chemical sediment, typically thinbedded or laminated with 15% iron of sedimentary origin figure 8. Banded iron formation core analysis using raman imaging.
Banded iron formation article about banded iron formation. The banded iron formations of the hamersley province in the pilbara region of western australia, are the thickest and most extensive rocks of this type in the world. View banded iron formation research papers on academia. Banded iron formations, figure 2 bif outcrop, gamohaan hill, south africa a, and white mfolozi gorge, kwazulu natal, south africa, jasper and magnetite, 3. Banded iron formations, or bifs, are unusual, dense sedimentary rocks consisting of alternating layers of ironrich oxides and ironrich silicates. Precambrian bandedironformations, volume 5 1st edition. Banded iron formations bifs banded iron formations, or bifs, are unusual, dense sedimentary rocks consisting of alternating layers of iron rich oxides and iron rich silicates. Banded iron formations bifs are chemical sedimentary rocks that originated in precambrian marine settings. Banded iron formation bif deposition was the likely result of oxidation of ferrous iron in seawater by either oxygenic photosynthesis or irondependent anoxygenic photosynthesisphotoferrotrophy. Banded iron formation department of earth and environmental.
Due to the information they offer regarding earths early evolution, and as they constitute the worlds richest source of commercial iron ore, banded iron formations bifs are pivotal to geological science. Bif deposition, however, remains enigmatic because the photosynthetic biomass produced during iron oxidation is conspicuously absent from bifs. Based on the organic carbon content and balance estimations it was established that these banded iron formations were deposited in environments rich in. The depositional environments of precambrian banded iron. Langalata iron ore deposits, singhbhumnorth orissa craton.
These pieces were broken off from the main formation by an unknown event and left to weather on the wyoming plains. The geological complexities of banded iron formation bif and associated iron ores of jilling. Condie, in earth as an evolving planetary system third edition, 2016. Home of the 2 billion year old banded iron formation. On the precambrian banded ironformations and the manganese ores or the singhbhum region, eastern india economic geology ironformation as an end member in carbonate sedimentary cycles in the transvaal supergroup, south africa. Banded iron formation bif, chemically precipitated sediment, typically thin bedded or laminated, consisting of 15 percent or more iron of sedimentary origin and layers of chert, chalcedony, jasper, or quartz. Banded iron formations occur in proterozoic rocks, ranging in age from 1. Eldorado gold corp gold mineralisation at lucky strike is hosted within multiple north west trending banded iron formation bif units. Banded iron formations bifs the banded iron formations were laid down in the early days, when the planet was almost devoid of oxygen. They formed throughout the precambrian, and today are globally distributed on the remnants of the ancient cratons. They are composed of alternating layers of ironrich material commonly magnetite and silica chert. Banded iron formations bif represent the largest source of iron in the world. This page was last edited on 24 november 2014, at 19. The coloured patterns in banded iron formations reveal a dramatic increase in atmospheric oxygen, a critical moment for the evolution of life on earth.
Banded iron formation definition is a sedimentary deposit that consists of alternating thin layers of iron oxides such as magnetite or hematite and ironpoor minerals such as shale or chert abbreviation bif. Banded ironstone formation theory challenges current. The greatest development of banded ironformations occurred between 2,600 and 1,800 m. A uwa geologist has proposed a hypothesis which threatens to overturn conventional notions of the way banded ironstone formations bif first evolved. Files are available under licenses specified on their description page. They consist of repeated thin layers of iron oxides, either magnetite fe 3 o 4 or hematite fe 2 o 3, alternating with bands of iron poor shale and chert. Banded iron formation bif lower middleback ironformation, paleoproterozoic, 1. Crossreferences banded iron formations synonyms definition. Well studied examples show an enrichment in the light isotope of carbon, 12c.
Pdf role of microorganisms in banded iron formations. Global paleogeography at 750 ma, after powell et al. Other articles where lake superiortype bandediron formation deposit is discussed. Banded iron formations are distinctive units of sedimentary rock that are almost always of. Most bifs are proterozoic in age although some are late archean, and do not form today theyre extinct. Banded iron formations, figure 1 appearance of bifs in geological time and marked as algoma and superior types. The possible photochemical origins of banded iron formations. Iron deposits banded iron formations bif geology for. Pdf ringinring structures in australian early precambrian banded iron formation bif were identified as bubbling mud wavelets, which lithified. Each layer is relatively thin, varying in thickness from a. Banded iron formations also known as banded ironstone formations or bifs are distinctive units of sedimentary rock that are almost always of precambrian age. On the precambrian banded iron formations and the manganese ores or the singhbhum region, eastern india economic geology iron formation as an end member in carbonate sedimentary cycles in the transvaal supergroup, south africa.
Banded ironformations bifs, which provide the worlds main source of iron, accumulated during a restricted lower. The origin of iron ore associated with banded iron formation has long been the subject of speculation and controversy. Banded iron formation an overview sciencedirect topics. A sedimentary mineral deposit consisting of alternate silicarich and ironrich layers formed 2. The precambrian banded iron formations bifs are the major iron ore sources on the earth. In situ o and fe isotope measurements of magnetite and hematite in banded iron formations bifs from the 2. Photoferrotrophy, deposition of banded iron formations, and. Genesis stone banded iron genesis stone banded iron is a sedimentary stone made of alternating layers of jasper and hematite or magnetite. A typical bif consists of repeated, thin layers a few millimeters to a few centimeters in thickness of silver to black iron oxides, either magnetite fe3o4 or hematite fe2o3, alternating with bands of ironpoor shales and cherts. They are composed of alternating thin millimeter to centimeter scale red, yellow, or cream colored layers of chert or jasper and black to dark gray iron oxides predominantly magnetite and hematite, andor iron carbonate siderite layers. The banded iron formation bif orebodies in this district have great vertical continuity and have been mined to depths of 2,500 m along a down dip length of up to 4,800 m. Pdf banded iron formations bif are the protolith to most of the worlds largest iron ore deposits.
Early precambrian or archean deposits, older than 2,600 m. Mining iron ore technical 3d animation ir pr presentation kostanay. The precambrian ironformations, of which banded ferruginous or iron cherts and jaspilites are the most important component, are known in all continents. Proposed formation mechanisms include oxidation of feii by o2 cloud, 1973, photoferrotrophy konhauser et al. They consist of extensive iron rich and iron poor layers within siliceous sedimentary rocks1,2. Bandediron formation bif, chemically precipitated sediment, typically thin bedded or laminated, consisting of 15 percent or more iron of sedimentary origin and layers of chert, chalcedony, jasper, or quartz. Goldich abstract considerable progress has been made in the radiometric dating of precambrian iron formations, but the age of relatively few is known precisely. Many specific varieties of iron formation are known, and some are given special rock names. Wellpreserved bif contain ironrich bands consisting of iron oxides e. Colloidal origin of microbands in banded iron formations.