Along-strike variations in synrift magmatism on the Eastern North American Margin

Columbia University, New York NY

Investigators

Abstract

Continental breakup to form new oceans is often accompanied by extensive outpouring of magmatism. Magmas may make continental breakup possibly by heating up and weakening continental tectonic plates. Volcanism associated with these events has also been associated with major extinction events on Earth. Despite the importance of magmatism during continental breakup, very little is known about the total volume of magmatism involved during rifting and how the volume varies between rift systems. The continental margin off the coast of the eastern U.S. is one of the best examples in the world of a continental breakup event associated with extensive magmatism. One of the biggest magmatic events in history occurred during the breakup of the supercontinent of Pangea and opening of the Atlantic Ocean. This project will involve the analysis of existing marine seismic data collected across the margin offshore North Carolina in 2014 to quantify the volume and distribution of magma frozen in the crust and how it relates to the structures that allowed breakup to occur. The project supports the training of an undergraduate student. Magmatic intrusions contribute to the growth and modification of the crust of the Earth and strongly influence strain localization in a variety of tectonic settings. Despite this, very few constraints exist on the 3-D distribution of magmatic intrusions throughout the crust in a tectonic setting that can be used to understand the controls on their distribution and the consequences for crustal modification and deformation. This project focuses on magmatism in rifts, but the scientific questions apply across many tectonic settings. Do intrusions exploit pre-existing structures and/or are they focused in the areas of greatest crustal/lithospheric thinning? Does the volume of intrusions in magmatic rifts vary along strike and relate to segmentation at the mid-ocean ridge, or does voluminous magmatism overwhelm focusing mechanisms and result in a more uniform distribution of intrusions along the margin? A 3D seismic velocity model of the crust and uppermost mantle will be built in one of the type examples of magma-rich continental rifting: The Eastern North American Margin (ENAM). The NSF-GeoPRISMS Program supported the collection of active/passive, onshore/offshore seismic data across the ENAM in 2014. As a part of this experiment, data were also collected along and across the East Coast Magnetic Anomaly, which is thought to mark the location of significant synrift magmatism. The data provide excellent 3-D ray coverage of the ENAM area and will be used for 3-D travel time tomography. The resulting velocity model will be used to map the 3-D distribution of magmatic intrusions. This part of the margin is an excellent place to test competing ideas for controls on synrift magmatic addition to the crust.