Ann E. Isley and Dallas H. Abbott
Plume-related mafic volcanism and the deposition of banded iron formation
Journal of Geophysical Research(July 1999), 104(B7):15,461-15,477
Index Terms/Descriptors: banded iron formations; chemically precipitated rocks; cratons; depositional environment; geochronology; igneous rocks; iron formations; komatiite; mantle; mantle plumes; marine environment; Precambrian; sedimentary rocks; ultramafic composition; volcanic rocks; volcanism
We have compiled a record of the geochronology of mantle plume activity between 3.8 and 1.6 Ga. Over this time period, the ages of komatiites, and those of global plumes, correlate strongly, at the 99% confidence level, with the ages of banded iron formations (BIFs). The ages of continental plumes correlate more weakly, at an overall 85% confidence level. Using the geochronological records of these events, we can define four periods characterized by mantle superplume activity. Three of these periods are also times of enhanced BIF deposition. The fourth mantle plume period may similarly be coeval with increased BIF accumulation, but the BIF chronostratigraphic resolution is not accurate enough to test this rigorously. Mantle superplume volcanism may promote BIF deposition by increasing the Fe flux to the global oceans through continental weathering and/or through submarine hydrothermal processes. It may also be enhanced by increasing the number of paleotectonic environments appropriate for BIF deposition (particularly plume-induced ocean plateaus, seamounts, and intracratonic rifts) and by promoting global anoxic, Fe-rich hydrothermal plumes in the shallow to intermediate marine water column.