A suggested volcanigenic origin for certain gold deposits in the slate belt of the North Carolina piedmont

Abstract

Geological studies in the Piedmont of central North Carolina have suggested several lines of evidence that certain gold deposits may be related to volcanism in genesis. The area considered here, in south-central North Carolina, is underlain by rocks of the Carolina slate belt and is bounded on the west by the Charlotte belt plutonic complex, and on the east by the Deep River Triassic basin. Rocks of the Carolina slate belt include a basal sequence of felsic pyroclastics overlain by argillite, tuffaceous argillites, and one or more later volcanic sequences. The region has been gently folded, weakly metamorphosed, and intruded by minor mafic sills and dikes.Lode gold deposits in this part of the Piedmont commonly are zones of silicified and weakly pyritic strata bearing low-grade gold ore. The deposits are largely conformable and are almost entirely within the basal volcanic unit or a short distance stratigraphically above it. In as much as the area has no prominent granite intrusives, is only weakly metamorphosed and has only minor evidences of subsequent hydrothermal mineralization; the strata-bound gold lodes seemingly must be referred to their enclosing volcanic strata for their origin. A volcanigenic origin for the gold deposits in the waning exhalations of the basal felsic volcanic pile seems to best account for the form, composition, and areal distribution of these deposits. Such an origin has certain similarities to many epithermal precious-metal deposits located in more recent volcanic fields in the western United States.