Over 80 in situ zircon crystals from three jadeitites and two mica-albite rocks from the North Motagua M¨¦lange and one phengite jadeitite from the South Motagua M¨¦lange of the GSZ were studied for age and trace-element determination. Most of these zircons are characterized by low Th/U ratios, depleted chondrite-normalized REE patterns relative to zircons from oceanic gabbros, and contain fluid and mineral inclusions that reflect the primary mineralogy (i.e., jadeite) and context (i.e., crystallization from an aqueous fluid) of the host rock, and thus formed during jadeitite crystallization. The SHRIMP-RG and LAM-ICP-MS U-Pb dates from zircon indicate that jadeitites and mica-albite rocks from the GSZ were formed through vein precipitation at ~98?80 and ~154-158 Ma, respectively. These data show (a) older ages that indicate jadeitite crystallization occurred ~10-30 Ma before the preserved subduction-zone peak metamorphism (e.g., exhumed eclogite), and (b) a second group of ages slightly younger than, or similar to, exhumation ages given by Ar-Ar dates from micas. Similar relationships occur at other jadeitite occurrences, such as the Syum-Keu ultramafic complex in the Polar Urals (Russia) and the serpentinite m¨¦langes of the R¨ªo San Juan complex (Dominican Republic). The data argue for formation of jadeitite within the mantle wedge during active subduction. Thus, jadeitite provides a record of fluid introduction into the mantle wedge during subduction rather than during exhumation.