Exhalative origins of iron formations

Kimberley, Michael M.

doi:10.1016/0169-1368(89)90003-6

Cited by 116 publications

(58 citation statements)

References 372 publications

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“…Exhalites also occur with some sediment-hosted, stratiform ZnPb deposits. Based on abundant lithological and geochemical data, exhalites are widely interpreted as precipitates from seafloor hydrothermal vents and plumes (Kimberley, 1989;Isley, 1995;Peter, 2003;Grenne and Slack, 2005). Exhalites vary greatly in mineralogy and composition, mostly consisting of silica in the form of chert or microcrystalline quartz and iron oxides (e.g., hematite, magnetite), silicates (e.g., greenalite, stilpnomelane, grunerite), carbonates (e.g., siderite, ankerite), or sulfides (e.g., pyrite, pyrrhotite); other exhalites may contain abundant Ba (barite), Mn (spessartine), P (apatite), or F (fluorite).…”

Section: Secular Patterns In Precambrian Vms-related Exhalitesmentioning

confidence: 99%

Iron Formation: The Sedimentary Product of a Complex Interplay among Mantle, Tectonic, Oceanic, and Biospheric Processes

Bekker¹,

Krapež²,

Slack³

et al. 2010

Economic Geology

854

494

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Iron formations are economically important sedimentary rocks that are most common in Precambrian sedimentary successions. Although many aspects of their origin remain unresolved, it is widely accepted that secular changes in the style of their deposition are linked to environmental and geochemical evolution of Earth. Two types of Precambrian iron formations have been recognized with respect to their depositional setting. Algoma-type iron formations are interlayered with or stratigraphically linked to submarine-emplaced volcanic rocks in greenstone belts and, in some cases, with volcanogenic massive sulfide (VMS) deposits. In contrast, larger Superior-type iron formations are developed in passive-margin sedimentary rock successions and generally lack direct relationships with volcanic rocks. The early distinction made between these two iron-formation types, although mimimized by later studies, remains a valid first approximation. 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. 2.6 Ga, when construction of large continents changed the heat flux at the core-mantle boundary. From ca. 2.6 to ca. 2.4 Ga, global mafic magmatism culminated in the deposition of giant Superior-type BIF in South Africa, Australia, Brazil, Russia, and Ukraine. 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 2.50 to 2.45 Ga may have triggered atmospheric oxidation. After the rise of atmospheric oxygen during the GOE at ca. 2.4 Ga, GIF became abundant in the rock record, compared to the predominance of BIF prior to the Great Oxidation Event (GOE). Iron formations generally disappeared at ca. 1.85 Ga, reappearing at the end of the Neoproterozoic, again tied to periods of intense magmatic activity and also, in this case, to global glaciations, the so-called Snowball Earth events. By the Phanerozoic, marine iron deposition was restricted to local areas of closed to semiclosed basins, where volcanic and hydrothermal activity was extensive (e.g., backarc basins), with ironstones additionally being linked to periods of intense magmatic activity and ocean anoxia.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 oxid...

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Section: Secular Patterns In Precambrian Vms-related Exhalitesmentioning

confidence: 99%

Iron Formation: The Sedimentary Product of a Complex Interplay among Mantle, Tectonic, Oceanic, and Biospheric Processes

Bekker¹,

Krapež²,

Slack³

et al. 2010

Economic Geology

854

494

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“…The Kremikovtsi deposit is a large zonal carbonatehosted SEDEX-type deposit consisting of stratiform pyrite and barite orebodies (intermediate facies), and MECS-IF-type (Metazoan-poor, extensive, chemicalsediment-rich shelf-sea iron formation) (Kimberley, 1989) siderite and hematite iron formations with lowgrade stratabound sulfide mineralization (distal facies) as well as their respective stockwork and vein iron carbonate-barite-sulfide occurrences in the underlying rocks and ores (Damyanov, 1996(Damyanov, , 1998. It was a product of polystage Middle Triassic metallogenesis located in the marginal parts of a second-order grabenshaped structure adjacent to the West Balkan early Paleozoic accretud block and related to an incipient rift setting.…”

Section: Geological Settingmentioning

confidence: 99%

Authigenic Phyllosilicates in the Middle Triassic Kremikovtsi Sedimentary Exhalative Siderite Iron Formation, Western Balkan, Bulgaria

Damyanov

Vassileva

2001

Clays and clay miner.

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Abstract--Two distinct assemblages of authigenic phyllosilicates were distinguished in the K.remikovtsi sedimentary exhalative (SEDEX) siderite iron formation (SIF) and noted as important tracers of two styles of mineralization characteristic of this type of ore deposit. Hydrothermal-sedimentary layer silicates are represented by rare occurrences of relict microcrystalline Mg-rich berthierine with a relatively low degree of structural ordering, associated closely with framboidal pyrite as an intergranular matrix cementing sparry siderite grains; the larger silicates are also represented by the diagenetic transformation product of berthierine, chamosite. Berthierine precipitated under anoxic conditions during advanced early diagenesis after chert deposition. Hydrothermal-epigenetic phyllosilicates (berthierine, chamosite, illite-smectite (I-S), and kaolinite) from the barite-sulfide assemblage are characterized by: crystalline and undeformed habits; relatively larger particle size, low-temperature polytypes, low to no mixed layering, and a high degree of crystallinity; absence of impurities and dominant monomineralic aggregates; affiliation to initial open spaces and deposition mainly as rug fillings and linings. They formed under pronounced control by the vuggy porosity of the siderite host caused by the invasion of acid (pH = 3-5), hot (200-230~ hydrothermal fluids probably at the stage of burial diagenesis of the SIF under relatively stable reducing conditions fluctuating near the sulfide/sulfate stability boundary (logPo2 ~ -30). The greater AI concentration in hydrothermal solution than in seawater determines the affiliation of phyllosilicates in the Phanerozoic SEDEX SIFs to aluminous species (berthierine, chamosite) unlike low to non aluminous ones (greenalite, stilpnomelane) in the Precambrian IFs. The berthierine compositions, expressed by the Mg/Fe vs. A1/Si ratios, are a sensitive indicator of the geological conditions under which they formed (maline, non-marine, hydrothermal ore and pre-ore), thus allowing the genetic discrimination of this mineral from various localities.

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“…Some are SEDEX in origin (Damyanov and Vassileva, 2001;Xu and Veblen, 1996;Kimberley, 1989;Curtis andSpears, 1968 Wiewiora et al, 1998), other sulfide massive volcanogenic (Slack et al, 1992), metamorphic origin (Wybrecht et al, 1985), and associated to bauxite and laterite (White et al, 1985;Toth and Fritz, 1997). These minerals also occur in Northampton ironstone (Hirt and Gehring, 1991), in paleosol near Waterval Onder, South Africa (Retallack, 1986), in the oolitic ironstone beds, Hazara, Lesser Himalayan Copyright c The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB.…”

Section: Introductionmentioning

confidence: 99%

Berthierine and chamosite hydrothermal: genetic guides in the Peña Colorada magnetite-bearing ore deposit, Mexico

et al. 2006

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We report the first finding of berthierine and chamosite in Mexico. They occur in the iron-ore deposit of Peña Colorada, Colima. Their genetic characteristics show two different mineralization events associated mainly to the magnetite ore. Berthierine is an Fe-rich and Mg-low 1:1 layer phyllosilicate of hydrothermal sedimentary origin. Its structure is 7Å, d hkl [1 0 0] basal spacing and low degree structural ordering. The phyllosilicate has been identified by a lack of 14Å basal reflection on X-ray diffraction (XRD) patterns. These data were supported by High Resolution Transmision Electron Microscopy (HRTEM) images that show thick packets of berthierine in well defined parallel plates. From the analysis of Fast Fourier Transform (FFT), we found around [1 0 0] reflections of berhierine 7.12Å and corresponding angles of hexagonal crystalline structure. Berthierine has a microcrystalline structure, dark green color, and high refraction index (1.64 to 1.65). Birefringence is low, near 0.007 to null and it is associated to nanoparticles (<15 nm) and microparticles of magnetite (<25 μm), fine grain siderite, and organic matter. Its texture is intergranular-interstratified with colloform banding. The chamosite Mg-rich is of hydrothermal epigenetic origin affected by low-degree metamorphism. It is an Fe-rich 2:1 layer silicate, with basal space of 14Å, d hkl [0 0 1]. The chamosite occurs as lamellar in sizes ranging from 50 to 150 μm. It has intense green color and refraction index from 1.64 to 1.65. The birefringence is near 0.008, with biaxial (-) orientation and a 2V small. It is associated mainly to sericite, epidote, clay, feldspar, and magnetite. Chamosite is emplaced in open spaces filling and linings. Mössbauer spectra of berthierine and chamosite are similar. They show the typical spectra of paramagnetic substances, with two well defined unfoldings corresponding to the oxidation state of Fe +2 and Fe +3 . Chemical composition of both minerals was obtained by an electron probe X-ray micro-analyzer (EPMA). The radio Fe+Mg+Mn vs Si and Al show similar chemical compositions and different XRD patterns in the crystalline structure provoked by the environmental conditions of emplacement. A hydrothermal environment was predominant, occurring before, during, and after the magnetite mineralization. The identification of magnetite nanoparticles supports the hypothesis of a marine environment, specifically exhalative sedimentary (SEDEX) for the berthierine.

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Exhalative origins of iron formations

Cited by 116 publications

References 372 publications

Iron Formation: The Sedimentary Product of a Complex Interplay among Mantle, Tectonic, Oceanic, and Biospheric Processes

Iron Formation: The Sedimentary Product of a Complex Interplay among Mantle, Tectonic, Oceanic, and Biospheric Processes

Authigenic Phyllosilicates in the Middle Triassic Kremikovtsi Sedimentary Exhalative Siderite Iron Formation, Western Balkan, Bulgaria

Berthierine and chamosite hydrothermal: genetic guides in the Peña Colorada magnetite-bearing ore deposit, Mexico

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