Abstract

Low-Ti iron-oxide deposits in exposed Grenville-age rocks of New York and New Jersey belong to a distinct class of iron-oxide (Cu-U-Au–rare earth element [REE]) deposits that includes similar iron deposits in southeastern Missouri and the Kiruna district of Sweden, the giant Olympic Dam U-Cu-Au-Ag deposit (Australia), and the Bayan Obo REE-Nb deposit (China). Most of the New York–New Jersey deposits exhibit features consistent with a hydrothermal origin and define a regionally significant metallogenic event that provides important clues to the evolution of this part of the Grenville orogen. In the Adirondacks, the tectonic setting of these deposits is consistent with postorogenic uplift and extensive crustal melting at 1070–1050 Ma that was accompanied by late tectonic to posttectonic deposition of iron.

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