Origin of the Precambrian Banded Iron-Formations

Eichler, J.

doi:10.1016/b978-0-444-41407-6.50007-6

Cited by 11 publications

(2 citation statements)

References 71 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Goodwin 1956;Ayres 1972;Klein 1973;French 1973;Eichler 1976;Gole and Klein 1981;and Kimberley 1989b) or through diagenetic transformation of precipitated ferric hydroxide (Morris 1985 and1987) include hematite, magnetite, siderite, greenalite, and stilpnomelane. Goodwin 1956;Ayres 1972;Klein 1973;French 1973;Eichler 1976;Gole and Klein 1981;and Kimberley 1989b) or through diagenetic transformation of precipitated ferric hydroxide (Morris 1985 and1987) include hematite, magnetite, siderite, greenalite, and stilpnomelane.…”

Section: Origin and Paragenetic Position Of Carbonates Oxides And Smentioning

confidence: 99%

Examples and genetic significance of the formation of iron oxides in the Nigerian banded iron-formations

Mücke¹,

Annor

1993

Mineral. Deposita

View full text Add to dashboard Cite

Ore microscopic studies reveal two main parageneses in the banded iron-formations of Nigeria. In the low-grade metamorphic schist belts of northern Nigeria, a magnetitic paragenesis comprising magnetite, silicates (grunerite and garnet), and quartz is developed. Magnetite which sometimes contains carbonate inclusions is markedly martitized. In contrast, the higher-grade metamorphic terrains of central Nigeria exhibit a different paragenesis consisting of hematite (including specularite) and quartz. Here, minerals of the magnetitic paragenesis only occur as relics. The protolith of these banded ironformation occurrences envisioned as carbonate-containing sediments, with high concentrations of Fe and Si, and lower contents of Ca, Mg, A1 (and also Mn where they are associated with gondite) underwent both submarine weathering and metamorphic changes in their evolution. During submarine weathering, sheet silicates and porphyroblasts of Fe-Mn-(Mg-Ca)-carbonate solid solutions, were formed. At the outset of a regional metamorphic episode, grunerite, garnet and porphyroblastic magnetite were developed. Magnetite formed at the expense of carbonate and sheetsilicates but was later martitized under post-metamorphic conditions. In the course of a later heterogeneous tectono-metamorphic event, martitized magnetite was transformed as follows: under low-grade metamorphism, as observed in the northern Nigerian schist belts, recrystallization into coarse-grained martite occurred, while at the higher grades of metamorphism in central Nigeria, recrystallization into hematite and, ultimately, specularite, took place. This relationship between magnetite and hematite has also been observed in many other banded iron-formations from different parts of the world, thus underscoring its widespread significance. Magnetite crystallizes first at the expense of carbonate and silicate minerals and hematite is subsequently derived from it directly or generally through martitization. This metamorphic phenomenon contradicts the common assumption that magnetite and hematite in banded ironformations are invariably the products of direct precipitation from solution, in response to changes in environmental Eh/pH or different (reducing/oxidizing) diagenetic alterations of precipitated ferric hydroxide.

show abstract

Section: Origin and Paragenetic Position Of Carbonates Oxides And Smentioning

confidence: 99%

Examples and genetic significance of the formation of iron oxides in the Nigerian banded iron-formations

Mücke¹,

Annor

1993

Mineral. Deposita

View full text Add to dashboard Cite

show abstract

“…However, the origin of calcsilicate rocks associated with iron formations is uncertain. Eichler (1976) notes that amphibole and pyroxene-bearing rocks are metamorphosed iron silicate facies in the James (1954) classification. Stanton & Vaughan (1979) interpreted the amphibole-pyroxene assemblages at Pegmont, Queensland, in this manner.…”

Section: The Mineralization Environmentmentioning

confidence: 99%

Early Proterozoic Subaerial Volcanism and Its Relationship to Broken Hill-type Mineralization in Central Sweden

Parr

Rickard

1987

View full text Add to dashboard Cite

S U M M A RY:Broken Hill-type mineralization is characterized by abundant exhalites in a sulphur-poor, felsic volcanic environment. It is typically Proterozoic. The Ljusnarsberg area in central Sweden is a microcosm of this mineralization type. One part of the amphibolitegrade, supracrustal succession is characterized by a thick sequence of subaerial volcaniclastics which grade into diverse chemical sediments interpreted as exhalities containing sulphide, iron oxide and manganese mineralization. The environment is interpreted as terrestrial with frequent lakes which are fed by volcanic exhalations. Evaporites may also have been present. The non-marine environment may not only have helped determine the nature of the mineralization in the area but also affected the chemistry of the volcanic host rocks. Thus, the occurrence of potassic and sodic metavolcanics may be related to the effects on hydrothermal solution chemistry and water-rock ratios of non-marine surface conditions, as well as alteration temperature and primary volcanic chemistry.Broken Hill-type mineralization is a typically Proterozoic mineralization style characterized by the occurrence of diverse exhalitive deposits in a sulphur-poor environment (cf. Plimer 1984). The exhalites include sulphide, oxide and silicate facies and occur within sequences dominated by felsic volcanism and its pyroclastic derivatives. The oxide facies include banded iron formations sensu law of the small-scale Algoma-type in the Gross (1966) classification. The carbonate facies include calcium and magnesium carbonates, magnetite carbonates and manganese-magnetitecarbonates. End-member silicate facies are represented by cherts, calcsilicate rocks, magnetitecalcsilicates, W-calcsilicates, garnet-quartz rocks, Ba-calcsilicates and gahnite-quartz rocks. Associated sulphide facies include Zn-Pb sulphide and Cu-Pb-Zn sulphide rocks, and magnetite-sulphide-calcsilicates.

show abstract

Facies Analysis

Miall¹

2015

Stratigraphy: A Modern Synthesis

View full text Add to dashboard Cite

Origin of the Precambrian Banded Iron-Formations

Cited by 11 publications

References 71 publications

Examples and genetic significance of the formation of iron oxides in the Nigerian banded iron-formations

Examples and genetic significance of the formation of iron oxides in the Nigerian banded iron-formations

Early Proterozoic Subaerial Volcanism and Its Relationship to Broken Hill-type Mineralization in Central Sweden

Facies Analysis

Contact Info

Product

Resources

About