Zircon U-Pb Geochronological Constraints on Long-Lived and Localized Post-Orogenic Magmatism on the Eastern North American Margin

An Earth and Planetary Sciences Colloquium

Contact Vadim Levin for access to this Webinar.

Speaker: Sean Kinney, Lamont-Doherty Earth Observatory, Columbia University

Abstract:

The Jurassic White Mountain Magma Series (WMMS) and Cretaceous New England Quebec (NEQ) igneous provinces are two episodes of enigmatic post-orogenic magmatism on the Eastern North American Margin (ENAM). In order to precisely and accurately assess the variety of hypothesized causal mechanisms for both initiating and sustaining magmatism in each province, we conducted CA-ID-TIMS and LA-ICP-MS zircon U-Pb measurements on nearly every igneous center within the WMMS province and on several key units within the NEQ provinces. Our results constrain the timing of the onset of the WMMS to be no younger than ~199 Ma, and that the main phase of magmatism lasted ~ 20 Myr, significantly shorter in duration than published ages suggest. The spatial and temporal proximity of the WMMS to the Central Atlantic Magmatic Province (CAMP) should motivate future examination of a geodynamic link between the two. However, given the prolonged duration of WMMS magmatism well beyond the punctuated timing of the CAMP, a variety of processes are likely responsible for the generation, transport, and emplacement of these melts. Our age constraints for the NEQ province suggest a relatively brief episode of magmatism across the entire region during the Cretaceous and provide the first zircon U-Pb chronological test of the Great Meteor Hotspot on land. Our work provides the necessary chronological boundary conditions for integrating high-precision geochronology, geochemistry, and geophysics to understand the tectono-magmatic history of the ENAM and evaluate to what extent these processes had in producing geophysical anomalies (e.g, the Northern Appalachian Anomaly) observed today.