MINERALOGICAL AND GEOCHEMICAL EVALUATION OF RARE-EARTH ELEMENT POTENTIAL IN THE SPARTA GRANITE COMPLEX

Rare earth elements (REEs) are important resources with applications in the electronics, renewable energy, and automotive industries. REEs may be concentrated in the residual weathered portion of igneous parent rocks, typically granites. These residual deposits are mined in southeast Asia, but analogous climatic and geologic conditions suggest the existence of economically viable REE residual deposits in the southeastern United States (U.S.). The Sparta Granite Complex in east-central Georgia is a granitoid complex emplaced at the end of the Alleghanian orogeny, forming a suture between the Savannah River and Milledgeville terranes. Petrologic and geochemical assessments of the Sparta Granite and overlying in situ residual deposits elucidate its intrusive history and explore the potential to produce economically significant residual REE deposits. Fresh rock and saprolite were obtained from two aggregate quarries near Sparta, Georgia and one aggregate quarry near Warrenton, Georgia. Field observations of flow banding and multiple granitic phases including pegmatitic and aplite dikes indicate significant fractionation. Thin section modal analysis showed primarily monzogranite composition in main phases, with higher proportions of plagioclase in the aplites. Accessory minerals biotite, Fe-Ti oxides, epidote, zircon, titanite, apatite and allanite are present in each quarry; however, amphibole, garnet, and fluorite are restricted to quarries near Sparta. Allanite crystals are partially to fully metamict, and locally attain lengths of 1-2 cm. Geochemical data of representative rock samples were acquired with inductively coupled plasma mass spectrometry (IC-PMS) and indicate significant REE content. Major REE sources are garnet and zircon for HREE and allanite, titanite, and apatite for LREE.