The rifted eastern North American margin (ENAM) provides important clues to the long-term evolution of continental margins. An Eocene volcanic swarm exposed in the Appalachian Valley and Ridge Province of Virginia and West Virginia (USA) contains the youngest known igneous rocks in the ENAM. These magmas provide the only window into the most recent deep processes contributing to the postrift evolution of this margin. Here we present new ⁴⁰Ar/³⁹Ar ages, geochemical data, and radiogenic isotopes that constrain the melting conditions and the timing of emplacement. Modeling of the melting conditions on primitive basalts yielded an average temperature and pressure of 1412 ± 25 °C and 2.32 ± 0.31 GPa, corresponding to a mantle potential temperature of ∼1410 °C, suggesting melting conditions slightly higher than average mantle temperatures beneath mid-ocean ridges. When compared with magmas from Atlantic hotspots, the Eocene ENAM samples share isotopic signatures with the Azores and Cape Verde. This similarity suggests the possibility of a large-scale dissemination of similar sources in the upper mantle left over from the opening of the Atlantic Ocean. Asthenosphere upwelling related to localized lithospheric delamination is a possible process that can explain the intraplate signature of these magmas that lack evidence of a thermal anomaly. This process can also explain the Cenozoic dynamic topography and evidence of rejuvenation of the central Appalachians.

The complex geodynamic evolution of Aeolian Arc in the southern Tyrrhenian Sea resulted in melts with some of the most pronounced along the arc geochemical variation in incompatible trace elements and radiogenic isotopes worldwide, likely reflecting variations in arc magma source components. Here we elucidate the effects of subducted components on magma sources along different sections of the Aeolian Arc by evaluating systematics of elements depleted in the upper mantle but enriched in the subducting slab, focusing on a new set of B, Be, As, and Li measurements. Based on our new results, we suggest that both hydrous fluids and silicate melts were involved in element transport from the subducting slab to the mantle wedge. Hydrous fluids strongly influence the chemical composition of lavas in the central arc (Salina) while a melt component from subducted sediments probably plays a key role in metasomatic reactions in the mantle wedge below the peripheral islands (Stromboli). We also noted similarities in subducting components between the Aeolian Archipelago, the Phlegrean Fields, and other volcanic arcs/arc segments around the world (e.g., Sunda, Cascades, Mexican Volcanic Belt). We suggest that the presence of melt components in all these locations resulted from an increase in the mantle wedge temperature by inflow of hot asthenospheric material from tears/windows in the slab or from around the edges of the sinking slab.

The eastern margin of North America has been shaped by a series of tectonic events including the Paleozoic Appalachian Orogeny and the breakup of Pangea during the Mesozoic. For the past ∼200 Ma, eastern North America has been a passive continental margin; however, there is evidence in the Central Appalachian Mountains for post‐rifting modification of lithospheric structure. This evidence includes two co‐located pulses of magmatism that post‐date the rifting event (at 152 and 47 Ma) along with low seismic velocities, high seismic attenuation, and high electrical conductivity in the upper mantle. Here, we synthesize and evaluate constraints on the lithospheric evolution of the Central Appalachian Mountains. These include tomographic imaging of seismic velocities, seismic and electrical conductivity imaging along the Mid‐Atlantic Geophysical Integrative Collaboration array, gravity and heat flow measurements, geochemical and petrological examination of Jurassic and Eocene magmatic rocks, and estimates of erosion rates from geomorphological data. We discuss and evaluate a set of possible mechanisms for lithospheric loss and intraplate volcanism beneath the region. Taken together, recent observations provide compelling evidence for lithospheric loss beneath the Central Appalachians; while they cannot uniquely identify the processes associated with this loss, they narrow the range of plausible models, with important implications for our understanding of intraplate volcanism and the evolution of continental lithosphere. Our preferred models invoke a combination of (perhaps episodic) lithospheric loss via Rayleigh‐Taylor instabilities and subsequent small‐scale mantle flow in combination with shear‐driven upwelling that maintains the region of thin lithosphere and causes partial melting in the asthenosphere.