New materials on the western Ladoga area provide evidence for a revision of preexisting concepts of the prograde metamorphic zonation, suggest its retrograde nature, and, taking into account its temporal relationships with plutonic rocks, make it possible to recognize the principal stages in the evolution of the complex. There are only very scarce data on the prograde preculmination metamorphic stage. The stage (1.88-1.87 Ga) included the origin of a norite-enderbite plutonic complex, metamorphism, and migmatization under granulite-facies conditions. The peak metamorphic conditions, calculated using the cotes of zoned garnet grains in assemblage with cordierite and hypersthene, attained 880-945 degrees C and 5.6-6.5 kbar at a geothermal gradient of approximately 40 degrees C/km. The early retrograde stage (1.87-1.86 Ga) comprised the emplacement of a gabbronorite-tonalite intrusive complex, high-temperature retrograde metamorphism, and migmatization, which continued under these conditions. The metamorphic parameters, determined by the compositions of garnet and cordierite occurring in physical contact, compose a continuous Linear trend, which terminates at 600 degrees C and 4 kbar. This trend suggests a slow uplift at a nearly constant geothermal gradient of about 40 degrees C/km. The late retrograde stage was marked by the intrusion of late-synorogenic granite and a further decrease in the metamorphic parameters, which were estimated at 500-460 degrees C and 1.0-1.4 kbar by contacting garnet-biotite pairs. The P-T path of this stage implies a rapid uplift and a simultaneous rapid decrease in the gradient to 25, possibly 10-15 degrees C/km. The evolution of the complex was generally controlled by a continuous but uneven crustal growth at a nearly constant and relatively high heat flow.
