Early History of the Carthage‐Colton Shear Zone, Grenville Province, Northwest Adirondacks, New York (U.S.A.)

Abstract

Abstract The Adirondack Mountains expose two distinct tectonic elements of the Proterozoic Grenville Province of northeastern North America: the Adirondack Lowlands and Highlands. The Lowlands are located along the eastern edge of the Metasedimentary Belt, and the Highlands form the western portion of the Granulite Terrane. The two are separated by the Carthage‐Colton Shear Zone (CCSZ). U/Pb titanite and 40Ar‐39Ar hornblende ages in the Lowlands are ca. 100 m.yr. older than in the Highlands, across the CCSZ. While both the Lowlands and the Highlands record a history of metamorphism during the Elzevirian Orogeny (ca. 1150 Ma), only the Highlands record evidence of a major phase of Grenvillian thermotectonic activity (Ottawan Orogeny) at ca. 1090–1030 Ma. Proposed tectonic models require that the Lowlands were either laterally separated from the Highlands or were at structurally higher levels during this metamorphism. New U/Pb and 40Ar‐39Ar ages from titanite and hornblende‐bearing mylonites in the Dana Hil...