14 The Appalachians, from North to South, from Crust to Mantle II

Friday, 20 March 2020
1:30 PM - 5:30 PM
Regency Ballroom B

LONG-LIVED AND LOCALIZED POST-OROGENIC MAGMATISM ON THE EASTERN NORTH AMERICAN MARGIN: INSIGHTS FROM ZIRCON U-PB GEOCHRONOLOGY

Paper number: 14-9
Program: Symposia Sessions
Time: 4:10 PM – 4:30 PM

Authors

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 several units for both the WMMS and NEQ provinces, including: all major igneous centers associated with the WMMS; all igneous centers within the largest composite intrusion of this province, the White Mountain Batholith; and key units within the NEQ province.

Our results constrain the timing of the onset of the WMMS to be no younger than ~199 Ma, though we cannot rule out a potentially older initiation as some samples did not yield zircons. We also demonstrate that the main phase of WMMS magmatism lasted ~20 Myr, significantly shorter duration than published ages suggest.

The spatial and temporal proximity of the WMMS to the CAMP should motivate future examination of the 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 demonstrate a relatively brief duration between magmatism in the Monteregian Hills (Québec) and Cretaceous White Mountains (New Hampshire) and provide the first zircon U-Pb chronological test of the Great Meteor Hotspot on land.

Our work provides the necessary boundary conditions for integrating high-precision geochronology, geochemistry, and geophysics to understand the tectono-magmatic history of the ENAM and evaluate to what extent such process had in producing geophysical anomalies (e.g, the Northern Appalachian Anomaly1) observed today.

1Menke et al., GRL. (2016).

Geological Society of America Abstracts with Programs. Vol. 52, No. 2

doi: 10.1130/abs/2020SE-345449

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