Mesoproterozoic-trans-Laurentian magmatism: A synthesis of continent-wide age distributions, new SIMS U-Pb ages, zircon saturation temperatures, and Hf and Nd isotopic compositions

摘要

The origin and tectonic setting of the Mesoproterozoic (1.50-1.34 Ga) granite-rhyolite Provinces of the midcontinent region of the United States, and the coeval A-type granite plutons of the southwestern United States, have been an enigma for decades. In this paper we review the history of this problem, examine the significance of a wealth of previously published U-Pb zircon and whole-rock Sm-Nd data, and present new U-Pb zircon age and Lu-Hf isotopic data from selected zircon samples. Our data show that the initiation of this magmatism spans the interval 1.50-1.40 Ga across the continent, but there is a general younging westward. Younger, 1.39-1.34 Ga magmatism also occurred across the continent, but forms a major magmatic event only in the south-central mid-continent.