Geochemical reconnaissance of the Carroll County Gold Belt and southwestern part of the Dahlonega Gold Belt, western Georgia

Abstract

The gold deposits in the Carroll County gold belt and the southwestern part of the Dahlonega gold belt are in interlayered metasedimentary and metavolcanic rocks of Late Proterozoic to early Paleozoic age. These rocks are in several thrust sheets that form the southwest continuation of the Blue Ridge thrust stack. The rocks are now mostly mica gneiss and schist, graphitic schist and phyllite, quartzite, amphibolite, and granite gneiss. A sample suite of 788 rock and saprolite samples was collected; the suite represents most of the rock types exposed in the southwest extension of the Dahlonega gold belt in Cherokee, Cobb, Bartow, Paulding, and Haralson Counties, Ga., and in the Carroll County gold belt in Carroll and Douglas Counties, Ga. The samples were analyzed semiquantitatively for 30 elements and quantitatively for gold, copper, lead, and zinc; some samples were also analyzed quantitatively for arsenic, mercury, and molybdenum. Whole-rock analyses were made on 27 samples of relatively fresh mafic rock. More than two-thirds of the samples are saprolite derived from mica schist and gneiss, graphitic schist, amphibolite, and quartzite, or vein quartz in saprolite. The samples were collected from roadcuts, surface and underground mine workings, and mine dumps. Of the samples collected, 78 percent of those from old mine areas and 13 percent of those from roadcuts contain gold at or above a limit of determination of 0.02 parts per million (ppm). Of those samples that contain detectable gold, 36 percent of the mine samples and 92 percent of the roadcut samples have less than 0.2 ppm gold. Gold is present in detectable amounts in some samples from all the major rock types that were sampled. Gold does not correlate consistently with the other elements in the data set. The few positive correlation coefficients greater than 0.50 are restricted to the smaller subsets of a few samples. Most of the old mine areas contain small resources of .gold in saprolite and probably larger amounts of lower grade material in unweathered rock. The mineralized zones are generally about 5 to 100ft wide, but may be as much as 250ft wide. Many deposits are only 100 to 800ft long, but a few mineralized zones are longer; one is as much as 0. 75 mi long.