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TitleOrigin of the Sokoman iron formation, Labrador Trough, Canada
AuthorZajac, I S; Peter, J MORCID logo
SourceCanadian Mineralogist vol. 60, 2022 p. 417-431,
Alt SeriesNatural Resources Canada, Contribution Series 20210149
PublisherMineralogical Association of Canada
Mediapaper; on-line; digital
File formatpdf
ProvinceQuebec; Newfoundland and Labrador
NTS23; 24
Lat/Long WENS -72.0000 -64.0000 60.0000 52.0000
Subjectsstratigraphy; mineralogy; iron; iron formations; history; silica; Sokoman Iron Formation; Labrador Trough; Proterozoic
Illustrationslocation maps; stratigraphic charts; photographs; schematic models
ProgramTargeted Geoscience Initiative (TGI-5) Volcanic and sedimentary systems - volcanogenic massive sulphide ore systems
Released2022 05 31
AbstractThe Lower Proterozoic, Lake Superior-type Sokoman Iron Formation of the Labrador Trough is one of the world's largest iron formations. It represents a unique, major event in the history of the Trough. Originally a largely irregularly bedded, intraclastic, granular, locally oolitic, conglomeratic iron formation, it is highly variable in its stratigraphy, mineralogy, and textures, which are the consequence of sedimentology, diagenesis, metamorphism, structural deformation, and magmatic overprint. Despite its complexity, the regional characteristics of the iron formation within the 1200 km length of the Labrador Trough indicate three main stratigraphic units, defined by their dominant iron minerals: the lower and upper parts of the formation are characterized by the abundance of iron silicates and carbonates (silicate-carbonate facies), and the middle part is characterized by the dominance of iron oxides (oxide facies). The origin of these lithostratigraphic units of the iron formation is attributed to three main sea-level changes which changed the chemistry (oxidation-reduction potential) and the physical energy (wave and current action) of the sedimentary environment. The vast amount of iron and some of the silica required for deposition of the Sokoman Formation is inferred to be the consequence of intense hydrothermal activity within a major rift created by the eastward extension of the Labrador Trough ca 1.88 Ga. The hydrothermal fluids venting within the rift saturated the deep and likely anoxic sea of the Trough with ferrous iron and some silica which then upwelled onto its oxygenated shallow waters to deposit the iron formation. The end of the processes involved in creating the iron formation ca. 1.82 Ga is attributed to the westward contraction of the Trough induced by the Hudsonian (Trans-Hudson) orogeny, which closed the iron- and silica-generating rift and at the same time ended all magmatic activities and related sedimentation coeval with the deposition of the iron formation.
Summary(Plain Language Summary, not published)
This journal paper presents the geological characteristics of the Sokoman iron formation, the principal source of Canada's iron ore production.

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