Sm–Nd evidence for the age and origin of a Mississippi Valley Type ore deposit

MISSISSIPPI Valley Type (MVT) ore deposits represent the relatively common product of large-scale fluid transport in the continental lithosphere, yet the models for their genesis have been more controversial and unconstrained than those of any other class of giant ore deposit1,2. Here we show that Sm–Nd isotope data can be used to determine the age and origin of an MVT deposit. Sm–Nd data for fluorites from the North Pennine orefield are difficult to explain unless some of the mineralization is of Mesozoic rather than the traditionally accepted Palaeozoic age. Furthermore, the Nd and Sr isotopie compositions of the fluorites do not support a variety of recent models that include derivation of the components from the mantle, the Lower Palaeozoic basement or the underlying buried granite which served to focus the flow of hydrothermal fluids.