A research article in the August issue of Earth & Planetary Science Letters offers a new view on the origin of giant porphyry ore deposits in the western US. Thomas Pettke and co-authors "propose that Cenozoic melting of subcontinental lithospheric mantle metasomatized by subduction fluids during early Proterozoic amalgamation of terranes to the Wyoming Craton provides the metal endowment and subduction flavour to the giant magmatic-hydrothermal Cu–Mo–Au ore deposits in western North America, which together constitute the world's major molybdenum ore province." [right, porphyry deposit model. Credit, USGS]
The abstract is available online.
Ref: "The magma and metal source of giant porphyry-type ore deposits, based on lead isotope microanalysis of individual fluid inclusions," Thomas Pettke, Felix Oberlia, and Christoph A. Heinricha, Earth and Planetary Science Letters, Volume 296, Issues 3-4, 1 August 2010, Pages 267-277, doi:10.1016/j.epsl.2010.05.007