Petrochronology of monazite and xenotime from emerald deposits in the Eastern Cordillera of Colombia: constraints on the hydrothermal evolution of the Cretaceous basin

Abstract Lower Cretaceous strata of the Eastern Cordillera of Colombia host some of the world’s premier emerald deposits, yet the timing of mineralization—and its relationship to the tectonic evolution of the Cordillera—remains poorly constrained. We present high-resolution in situ U–Th–Pb petrochronology of monazite and xenotime from both the Eastern and Western Emerald Belts, revealing at least three stages of mineral growth: (1) authigenic crystallization during early burial and diagenesis (~ 140–120 Ma, Eastern Belt; ~125–100 Ma, Western Belt) (2) metamorphic recrystallization at ~ 120 Ma (Eastern Belt) and ~ 99 Ma (both belts) associated with peak basin temperatures; and (3) prolonged hydrothermal overprinting initiated by a major fluid pulse at ~ 85 Ma and persisting until ~ 37 Ma. Emeralds (± euclase) and associated REE minerals formed during this final stage in at least two distinct episodes. Our results document a multistage, episodic history of emerald mineralization, with REE redistribution closely linked to polyphase tectonothermal processes rather than a single mineralizing event. These findings refine the temporal framework for Colombian emerald formation, highlight the potential for REE recovery as a by-product of emerald mining, and underscore the importance of non-magmatic hydrothermal systems in sedimentary basins as potential sources of critical minerals.