Volcanogenic sulfide deposits in the southernmost Appalachians

Abstract

Volcanogenic massive sulfide deposits in the southernmost Appalachians of east-central Alabama and west-central Georgia are associated with metamorphosed submarine basalts and felsic rocks of the Ashland, Wedowee, and Talladega lithotectonic terranes. These three terranes lie between the Brevard fault on the south and the Talladega-Cartersville and Hayesville faults on the north. The oldest sulfide deposits occur in a regional setting characterized by a thick sequence of metamorphosed Eocambrian to lower Paleozoic continentally derived clastic and intercalated submarine metavolcanic rock. The metamorphosed elastic rocks represent the basal section of a rifted margin prism, whereas the metavolcanic rocks represent rhyolites, andesites, and basalts which were probably erupted along rift zones of a spreading back-arc basin. Most of the volcanogenie massive sulfide deposits are localized within metavolcanic rocks and are rare or absent in the enclosing or interbedded metasedimentary rock. The youngest sulfide deposits occur in the distal part of a volcanic arc sequence of the Talladega terrane, which terminated sediment deposition and volcanic activity in the region. Talladega terrane sulfide deposits appear anomalously young (Devonian) respective to other deposits in the eastern United States.Three types of massive sulfide host rock associations have been recognized in the southernmost Appalachians; Kuroko-type deposits associated with predominantly felsic volcanic assemblages, Anyox-type deposits associated with predominantly mafic volcanic assemblages, and Besshi-type deposits associated with interbedded assemblages of elastic sedimentary and marie volcanic rocks.

Hydrothermal alteration of mafic metavolcanic rocks and genesis of Fe-Zn-Cu sulfide deposits, Stone Hill District, Alabama

“…The amphibolite which encloses the deposits has been interpreted as a metamorphosed tholeiitic basalt (Whittington, 1982;Stow et al, 1984;Schafer and Coolen, 1986) and the enclosing pelitic metasedimentary rocks have been interpreted as metamorphosed fiysch-type sediments (Neathery and Hollister, 1984 rocks and the oxide facies iron-formations have been interpreted as altered basalts and exhalites, respectively (Whittington, 1982;Schafer and Coolen, 1986). On the basis of the above-lithological associations, their stratigraphic conformability, and the presence of hydrothermally altered rocks and exhalites, the FeZn-Cu deposits in the Stone Hill district have been interpreted by previous investigators as proximal volcanic-associated massive sulfide deposits (cf.…”

“…Whittington (1982) and Stow et al (1985) interpreted the felsic schists as metasedimentary rocks and concluded that the Stone Hill deposits formed along a spreading margin. Neathery and Hollister (1984) also interpreted the felsic schists as metasedimentary rocks but concluded that all of the deposits in the northern Piedmont formed in a backarc basin. Although Schafer and Coolen (1986) mentioned the possibility that the felsic schists may have formed by alteration, they interpreted them as rhyolitic metavolcanic-pyroclastic rocks.…”