MINERALOGIC, TEXTURAL, AND GEOCHEMICAL EVALUATION OF METAGABBROIC ROCKS FROM THE GLADESVILLE COMPLEX, CENTRAL GEORGIA

The Southern Appalachians are the result of a complex series of terrane accretion and collisional events that span the Paleozoic. A suite of samples collected from lens-shaped gabbroic bodies within the Gladesville Complex of Central Georgia exhibit a range of styles and intensities of metamorphic overprints, ranging from near-complete replacement of the original igneous mineral assemblage with fine-grained amphibole- and epidote-bearing assemblages, to the complex symplectitic growth of amphibole- and spinel-bearing rims on relict orthopyroxene/olivine phenocrysts adjacent to anorthitic plagioclase. Recent undergraduate-led research projects characterized the development of these textures within the northernmost exposure near Juliette, Georgia. In this presentation data from microfabric, mineralogic, and geochemical analyses from two additional lens-shaped bodies are presented for comparison with the previous work. The construction of equilibrium assemblage diagrams is considered in conjunction with major- and trace-element geochemical data; careful consideration of bulk composition is necessary to isolate portions of the rocks that are in chemical equilibrium. Interpretation of models can place potential constraints on the thermobarometric evolution and the relative timing of development of these textures to relate them to regional-scale tectonic processes. The intensity of the development of the metamorphic overprints is proposed to result from the availability of intergranular fluid; samples that demonstrate more complete replacement textures had sufficient fluid present to drive reaction, while samples that preserve a high proportion of the original igneous assemblage with only minor overprinting by amphibole + spinel symplectite were fluid-poor.