A CHARACTERIZATION OF METAMORPHOSED ULTRAMAFIC LENSES IN CARROLLTON, GEORGIA

Ultramafic metavolcanics of the Dog River Formation in the Carrollton, Georgia 7.5-minute quadrangle occur in a northeast-trending chain of lenticular bodies. Granitic gneiss and mica schist are the predominant lithologies in the quadrangle, which makes these ultramafic lenses that lie within them distinct. Some of these lenses appear to be weathering differently despite their common origin. The most striking difference is the presence of fibrous minerals in one location versus acicular minerals at another. Previous research indicates that these metamorphic outcrops contain talc, serpentine, and possibly asbestiform amphibole, yet few known geochemical analyses and petrographic inspections have been conducted on this group of rocks. Powder x-ray diffraction confirmed the presence of chlorite and amphibole, although in differing proportions between outcrops. Why do these rocks appear to have different weathering histories? Furthermore, do the chlorites from separate outcrops have different compositions, possibly indicating differing degrees of hydrothermal alteration? These questions are addressed by using polarized light and scanning electron microscopy to constrain the composition of the chlorites, confirm the identity of the amphibole, and observe alteration textures and morphologies of the minerals. In addition, this project fills in gaps in our understanding of the regional geology of West Georgia.