A PETROLOGICAL STUDY OF THE SPARTA GRANITE AT WARRENTON QUARRY, GEORGIA

An aggregate quarry, operating in the northern extension of the Sparta Granite complex in the Kiokee belt near Warrenton, Georgia, is host to one of the more heterogenous Alleghanian granites of Georgia. Three main granitic phases within the quarry are peraluminous and include a coarse foliated granodiorite (CFG) that intrudes the gneissic country rock. A coarse to pegmatitic hypidiomorphic-granular granite (CPP) exhibits gradational to intrusive contacts with the CFG. A less fractionated foliated tonalite may represent a marginal phase between the CFG and the surrounding gneiss. Large bodies of country rock exposed in the upper levels of the quarry suggest exposure of the roof zone of the magmatic complex at Warrenton. A fine-medium grained hypidiomorphic-granular granite (MGG) phase intrudes the CFG and CPP units. Portions of the MGG are rich in macroscopic allanite with correspondingly high Th contents. Two suites of granitic pegmatites intrude the complex. The older phase intrudes CFG and may be related to the CPP; the youngest pegmatite unit crosscuts all earlier phases. Field relations and trace element plots from samples of uniform coarse-grained portions of the CPP unit suggest an origin by fractionation and melt separation from main phase magmas. Leucocratic dikes emplaced at multiple times have the most variable and fractionated compositions. Deformation features in most phases include grain size reduction, patchy microcline twinning, kinked feldspars, and local myrmekite development suggesting late-kinematic emplacement.