Limited and localized magmatism in the Central Atlantic Magmatic Province

Abstract

The Central Atlantic Magmatic Province (CAMP) is the most aerially extensive magmatic event in Earth's history, but many questions remain about its origin, volume, and distribution. Despite many observations of CAMP magmatism near Earth's surface, few constraints exist on CAMP intrusions at depth. Here we present detailed constraints on crustal and upper mantle structure from wide-angle seismic data across the Triassic South Georgia Rift that formed shortly before CAMP. Lower crustal magmatism is concentrated where synrift sedimentary fill is thickest and the crust is thinnest, suggesting that lithospheric thinning influenced the locus and volume of magmatism. The limited distribution of lower crustal intrusions implies modest total CAMP volumes of 85,000 to 169,000 km 3 beneath the South Georgia Rift, consistent with moderately elevated mantle potential temperatures (<1500°C). These results suggest that CAMP magmatism in the South Georgia Rift is caused by syn-rift decompression melting of a warm, enriched mantle.

Modification of Crust and Mantle Lithosphere Beneath the Southern Part of the Eastern North American Passive Margin

“…The ∼4–8% velocity reduction of anomaly 1 beneath the oceanic‐continental transitional crust suggests that the mantle lithosphere, at least to some degree, had been chemically modified during the rifting process. Many active‐source seismic surveys (e.g., Holbrook et al., 1994; Klitgord et al., 1988; Marzen et al., 2020) have suggested underplating of rifting‐induced basaltic magmas beneath the transitional crust in the southern ENAM. Such underplating can refertilize the mantle lithosphere by enriching the basaltic components (e.g., Muntener et al., 2004; Picazo et al., 2016), which would contribute to ∼2–3% reduction of shear‐wave velocity within the upper mantle (e.g., Connolly, 2009; Xu et al., 2008).…”

“…A variety of geophysical studies has been conducted to investigate the modification of the crust and mantle lithosphere in the southern ENAM. Strong seaward‐dipping reflectors have been detected near the Moho beneath the continental shelf, suggesting modification of the lower crust by rifting and rifting‐related magmatism (e.g., Guo et al., 2019; Hales et al., 1968; Holbrook et al., 1994; Klitgord et al., 1988; Marzen et al., 2020). Rifting eventually led to the creation of new Atlantic Ocean lithosphere, whose present‐day thickness is estimated to be ∼120–150 km (Savage et al., 2017).…”

The Impact of Complex Volcanic Plumbing on the Nature of Seismicity in the Developing Magmatic Natron Rift, Tanzania

“…A key question is how strain accommodation is partitioned between faulting and magmatism (e.g., Ebinger and Casey, 2001;Thybo and Nielsen, 2009;Marzen et al, 2020). Tectonic thinning is commonly accompanied by decompression melting and the rise of volatiles and magma through the lithosphere (White and McKenzie, 1989;Weinlich et al, 1999;Rooney, 2010;Lee et al, 2016).…”

Mantle Structure and Flow Across the Continent‐Ocean Transition of the Eastern North American Margin: Anisotropic S‐Wave Tomography

“…This distinctly follows the Brunswick positive magnetic anomaly (BMA) and more subtly follows positive gravity anomalies. Wide‐angle seismic results suggest that across the failed Georgia rift, high velocity material intruded the lower crust as part of the Central Atlantic Magmatic Province (CAMP) (Marzen et al., 2020). The imaged fast velocity feature is potentially crustal CAMP underplating, with recovery smeared vertically through the lithosphere according to synthetic tests (Figures S9 and S14 in Supporting Information ).…”