U-Pb geochronology and petrography of Neoproterozoic to early Cambrian volcanic rocks in basement crustal terranes beneath the deep-water Gulf of Mexico

Though the Gulf of Mexico has been studied for more than a century, the lithology, age, and origin of the basement crustal terranes remain poorly understood. New U-Pb zircon ages of a volcanic sample in the DeSoto Canyon 535 #1 Raptor well were obtained by in situ laser-ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) and resulted in a crystallization age of 509 ± 23 Ma, indicating the crustal terrane beneath the northeastern Gulf of Mexico is likely of peri-Gondwanan affinity. This basement may be associated with the felsic volcanism related to Neoproterozoic to Cambrian subduction along the supercontinent’s western margin. This subduction-related volcanism likely represents the last pulses of magmatic activity before the west coast of Gondwana transitioned into a passive margin ca. 500 Ma. The data presented here for the DeSoto Canyon 535 #1 Raptor trachyte represent the oldest radiometrically dated evidence of volcanism in the present-day deep-water Gulf of Mexico.