Samples from the Cardigan pluton preserve magmatic gamet-biotite temperatures and record an intrusive cooling history. Cardigan garnets do not seem to have formed in situ nor to have been reset by regional metamorphism. The interiors of Cardigan garnets are compositionally homogeneous, reflecting high-temperature, rapid volume diffusion. Garnet core-matrix biotite temperatures range from 750 to 900°C, with samples from the margins of the Cardigan pluton recording higher temperatures than those from the interior of the pluton. On the other hand, garnets from metapelites surrounding the Cardigan pluton have different compositions and preserve lower temperatures (500-700°C) than Cardigan garnets. The rims of Cardigan garnets are steeply zoned, reflecting incomplete re-equilibration at lower temperatures. Temperatures calculated from garnet rim and adjacent biotite compositions are approximately 400°C, reflecting the last temperature of equilibration.
These relationships provide constraints on the relative timing of emplacement of the Cardigan pluton and regional metamorphism. K-feldspar-cordierite zone metamorphism preserved in metapelites surrounding the Cardigan pluton could not have been a regional event that postdated the intrusion of the Cardigan pluton. These data contrast with previous work that suggested that high-grade Acadian isograds crosscut the Cardigan pluton.