Discontinuously zoned or two-stage garnet has been observed in numerous locations and geologic settings worldwide. These garnets are characterized by sharp breaks in inclusion density and compositional zoning, and often, these sharp breaks are interpreted as a hiatus in growth, change in growth rate, change in bulk rock composition, chemical diffusion, or absorption and new growth of garnet. During accretion of terranes and microplates, thermal pulses and thrust fault movements occur, which drive metamorphism and therefore the growth of garnet. Multiple garnet growth events could produce a discontinuously zoned garnet and each growth stage could be interpreted to represent a separate metamorphic event. Two-stage garnet is common in the Salmon River suture zone (SRSZ) and multiple tectonic models have been proposed based on the two-stage garnet. Getty et al. (1993) and Selverstone et al. (1992) proposed multiple accretion and metamorphic events based on the estimates for pressure, temperature, and age of these garnets. Recently, McKay (2011) proposed that heating after several major fault displacements caused the growth of two-stage garnet. This study uses compositions of garnet cores and rims on isochemical phase diagrams to construct new garnet growth P-T paths. Core and rim P-T estimates combined with observed mineral assemblages indicate an initial garnet growth reaction, followed by a reaction consuming and then growing garnet, e.g., chlorite + garnet = amphibole + H2O and amphibole = garnet + Al2SiO5 (kyanite) + H2O. Isochemical P-T modeling of garnet modal percentages, mineral compositions, and petrologic observations supports the occurrence of these reactions in the SRSZ garnet. The proposed reaction history would produce two-stage garnet along a single prograde path, which does not require multiple thermal and tectonic events. This interpretation supports the single terrane accretion hypothesis proposed by McKay (2011).