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A plutonic porphyry gold deposit model is proposed that is similar to the plutonic porphyry copper deposit model. However, unlike the plutonic porphyry copper deposit model, the proposed model is deficient in copper and contains less than 1 percent total sulfides. In the proposed model, gold is accompanied by scheelite, molybdenite, arsenopyrite, a variety of bismuth sulfides, tellurides, and native bismuth. The host rock varies from granite to granodiorite stock. Most of the ore is in the pluton. Deposits cited as examples of the proposed model are the Mokrsko deposit in Czechoslovakia, the Fort Knox deposit in the United States, and the Dublin Gulch deposit in Canada. In each of these deposits, pervasive potassic or phyllic alteration zones accompany the gold ore, which is disseminated in quartz-rich stockworks, veinlet swarms, and veins. Tonnages of gold-bearing material are large, but grades are low in the cited deposits. The proposed model is distinct from other gold deposit models because of the low Cu to Au ratio and the association of Au, Bi, W, and Mo.

The Fairbanks, Alaska, area became an important producer of placer gold in 1902, and since then it has produced an estimated 7.5 million oz of placer and 250,000 oz of lode gold. The U.S. Geological Survey and the Alaska State Division of Geological and Geophysical Surveys have published numerous reports on placer and lode gold deposits and detailed geology of the district. Many of these have speculated on the lode origin of placer gold in the Fairbanks area, and a number of small or very low grade bed rock discoveries have been proposed as the most important source of the placers. This scientific communication proposes that newly discovered, pervasively disseminated gold mineralization in the Fort Knox stock located on the north flank of Gilmore dome is the source for most gold in the placers.

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.

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