9508104 Spear This study involves a systematic analysis of nucleation and growth processes of metamorphic porphyroblasts in regionally metamorphosed rocks with a wide variety of P-T histories. The primary goal is to examine the processes of garnet nucleation, growth and breakdown with increasing metamorphic grade from the first occurrence of garnet within the garnet zone to the occurrence of coexisting garnet and staurolite within the lower staurolite zone. Research will focus on a suite of samples collected from western New Hampshire, eastern Vermont, and the Taconic Mountains near the NY- MA-CT tri-state area. For each sample, data on the 3-dimensional spatial distribution, size distribution and compositional zoning will be determined for every garnet within the chosen volume of rock. The proposed study will be among the first systematic studies to test the idea that garnet nucleation and growth processes may vary with metamorphic grade and P-T history.
