Protracted intra- and inter-pluton magmatism during the Acadian orogeny: evidence from new LA-ICP-MS U-Pb zircon ages from northwestern Maine, USA

Devonian granitoid plutons comprise a major part of the bedrock northwestern Maine representing magmatic expression Acadian orogeny in this northern Appalachian orogen. They are petrographically diverse with minerals characteristic both I- and S-type granites, some cases within same intrusion, compositionally zoned. New LA-ICP-MS ages presented here elucidate timing duration magmatism. The earliest phase magmatism began around 410–405 Ma emplacement Flagstaff Lake Igneous Complex, presence contemporaneous mafic rocks suggests that mantle-derived magmas were also produced at time. Late ages, ca. 365 Ma, for many intrusions, such as Chain Ponds Songo plutons, reveal continued 45 million years during which produced. In addition, there is evidence intrusive activity was prolonged example Rome-Norridgewock pluton Mooselookmeguntic 10–15 myr between units. new suggest break 400 390 apparently separating into early late pulses. production lower crustal I-type appears to have been concentrated later, 380–365 although several granitoids emplaced period. These display abundant zircon inheritance 385 crust experiencing enhanced thermal perturbations extended timeframe. data consistent tectonic models other parts Ganderia propose initial flat slab subduction followed by breakoff delamination.