|dc.description.abstract||One purpose for studying banded meta-iron formations is to determine the chemical composition of
seawater in the Archean ocean and the oxygen content of the Archean oceanic-atmospheric system.
Geologists use the geochemistry of meta-iron formations to make interpretations on the chemical
conditions in the Archean. However, post-depositional alteration can affect the element geochemistry
preserved in the meta-iron formations. This thesis explores the role of post-depositional mechanisms
and determines element provenance in four Archean banded meta-iron formations.
The four different locations hosting Archean metamorphosed meta-iron formations chosen for this
study are: meta-iron formations from the Beardmore/Geraldton greenstone belt of the Eastern
Wabigoon Domain, Lake St. Joseph greenstone belt of the Uchi Domain, North Caribou greenstone belt
of the North Caribou Terrane and Shebandowan greenstone belt of the Wawa Subprovince. The metairon
formations from the Beardmore/Geraldton and Lake St. Joseph greenstone belts are interpreted to
have been deposited in a shallow water setting, while meta-iron formations from the North Caribou and
Shebandowan greenstone belts are interpreted to be deposited in deeper water environments. This
thesis also investigated element and oxygen ocean stratification by comparing the geochemistry of
shallow and deep meta-iron formations.
The main source of iron and silica to the oceans was hydrothermal venting fluids. Iron and silica
precipitated out of seawater as iron oxyhydroxides and amorphous silica. Elements dissolved in the
Archean ocean were adsorbed onto iron oxyhydroxides and silica during deposition. Crystallization of
quartz, magnetite and hematite occurred during diagenesis and magnetite continued to grow during
The lack of cerium anomalies, absence of significant Y/Ho anomalies and deficiency of authigenic
chromium supplied to the ancient suggests that the oceans were anoxic. Therefore, oxygen stratification
did not occur between shallow and deeper water environments in the Archean.
Significantly most of the elements were derived from multiple sources, including the siliciclastic phase,
seawater or hydrothermal venting fluids, at various proportions. Al2O3, TiO2, Th, V, Nb, U, REEs and Y
were determined immobile during post-depositional alteration.
Mobility during diagenesis is clearly exhibited by sodium and potassium in the meta-iron formation
samples from the Beardmore/Geraldton, Lake St. Joseph and North Caribou greenstone belts.
Diagenetic modification mobilized sodium in the hematite-, jasper- and chert-dominated samples, while
potassium was mobilized in the magnetite-dominated samples.
Element stratification occurred in the Archean due to the source provenance. Deeper oceans were more
enriched in Cs, Na2O, CaO, MnO, Cr and HREEs relative to shallow waters. Shallow oceans were more
enriched in K2O, Rb and LREEs relative to deeper waters. This indicates that the Archean oceans were