Remarkable advances in age dating Mississippi Valley-type (MVT) lead–zinc deposits provide a new opportunity to understand how and where these deposits form in the Earth's crust.
This broad agreement between paleomagnetic and radiometric dates provides added confidence in the dating techniques used.
The new dates confirm the direct connection between the genesis of MVT lead–zinc ores with global-scale tectonic events.
The dates show that MVT deposits formed mainly during large contractional tectonic events at restricted times in the history of the Earth.
Only the deposits in the Lennard Shelf of Australia and Nanisivik in Canada have dates that correspond to extensional tectonic events.
The most important period for MVT genesis was the Devonian to Permian time, which corresponds to a series of intense tectonic events during the assimilation of Pangea.
The second most important period for MVT genesis was Cretaceous to Tertiary time when microplate assimilation affected the western margin of North America and Africa–Eurasia.
There is a notable paucity of MVT lead–zinc ore formation following the breakup of Rodinia and Pangea.
Of the five MVT deposits hosted in Proterozoic rocks, only the Nanisivik deposit has been dated as Proterozoic.
The contrast in abundance between SEDEX and MVT lead–zinc deposits in the Proterozoic questions the frequently suggested notion that the two types of ores share similar genetic paths.
The ages of MVT deposits, when viewed with respect to the orogenic cycle in the adjacent orogen suggest that no single hydrologic model can be universally applied to the migration of the ore fluids.
However, topographically driven models best explain most MVT districts.