ASSESSMENT OF GARNET-GRADE METAMORPHISM AT GARNET HILL, PAULDING COUNTY, GEORGIA
Comparison of the samples reveals several textural differences. The porphyroblastic garnets in GH-1 are much more idiomorphic and contain fewer inclusions than the garnets in GH-2. The matrix is coarser-grained in sample GH-2, and distinct quartz-rich and chlorite-rich layers in the matrix are much more common than they are in GH-1. The overgrowth of either chlorite-rich or quartz-rich layers appears to control the density of inclusions within GH-2 garnets, reflecting nutrient supply. Garnets in GH-2 contain obvious core and rim domains that are characterized by different populations and proportions of aligned mineral inclusions. The internal fabric defined by aligned ilmenite and quartz inclusions in the garnet cores is distinct from the matrix foliation; garnet rims are very inclusion-rich, the internal fabric wraps the garnet cores and is continuous with the matrix. Garnets in GH-1 do contain identifiable core and rim domains noted by patterns of aligned ilmenite inclusions. In both samples, there are complex garnet clusters in which individual garnet nuclei coalesced during growth of garnet rim domains.
Data from mineral and bulk chemical analyses will be used to constrain models for the P-T conditions during metamorphism of these samples. Insights gained from analyses of petrographic and geochemical processes active at the micron-scale can help refine our understanding of the kilometer-scale orogenic processes that formed the Southern Appalachians.