Most primary global gold resources are associated with deformed metamorphic belts or shallow oceanic and continental arcs. In mainly greenschist environments of the metamorphic belts, orogenic gold deposits form provinces with numerous economic deposits in areas of structural complexity. These deposits are products of aqueous-carbonic metamorphic fluid migration along first-order deep-crustal structures, form at variable depths as shallow as 3 km or as deep as 15–20 km, and are well preserved in exhumed rocks as old as Archean and as young as Eocene. In contrast, most intrusion-related gold deposits are associated with oxidized intrusions and form at depths from the near surface down to 3 km. These include gold-bearing porphyries and high-sulfidation epithermal deposits that form from magmatic fluids, as well as low-sulfidation epithermal deposits in which convecting meteoric water mixes with the exsolved magmatic aqueous fluid. Most of these gold deposits are younger than 100 Ma given their low preservation potential. Gold-bearing skarn and more distal carbonate-replacement deposits may host some of the gold resource surrounding a causative magmatic system. Gold-bearing volcanogenic massive sulfide deposits (VMS) typically have been accreted along active continental margins, metamorphosed and deformed during subsequent orogenesis, and preserved in many of the same belts as orogenic gold. The iron oxide-copper gold (IOCG), reduced intrusion-related gold, and Carlin-type gold deposits are economically important each in a few locations globally, but are not recognized to be widespread and, in many cases, are misclassified orogenic or oxidized intrusion-related gold deposits. The Central and South Eastern Desert of the Nubian Shield is highly prospective for ca. 600 Ma orogenic gold given its tectonic, metamorphic, and structural setting. A few areas in these parts of the Eastern Desert are also favorable for ca. 750 Ma gold resources in VMS systems. In addition, areas of Ediacaran Dokhan volcanism in the North Eastern Desert and adjacent southern Sinai are permissive for gold ores in Cu porphyry occurrences, particularly where there is well-developed secondary enrichment zones.

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Gold Deposit Types and Settings

  • Richard J. Goldfarb

摘要

Most primary global gold resources are associated with deformed metamorphic belts or shallow oceanic and continental arcs. In mainly greenschist environments of the metamorphic belts, orogenic gold deposits form provinces with numerous economic deposits in areas of structural complexity. These deposits are products of aqueous-carbonic metamorphic fluid migration along first-order deep-crustal structures, form at variable depths as shallow as 3 km or as deep as 15–20 km, and are well preserved in exhumed rocks as old as Archean and as young as Eocene. In contrast, most intrusion-related gold deposits are associated with oxidized intrusions and form at depths from the near surface down to 3 km. These include gold-bearing porphyries and high-sulfidation epithermal deposits that form from magmatic fluids, as well as low-sulfidation epithermal deposits in which convecting meteoric water mixes with the exsolved magmatic aqueous fluid. Most of these gold deposits are younger than 100 Ma given their low preservation potential. Gold-bearing skarn and more distal carbonate-replacement deposits may host some of the gold resource surrounding a causative magmatic system. Gold-bearing volcanogenic massive sulfide deposits (VMS) typically have been accreted along active continental margins, metamorphosed and deformed during subsequent orogenesis, and preserved in many of the same belts as orogenic gold. The iron oxide-copper gold (IOCG), reduced intrusion-related gold, and Carlin-type gold deposits are economically important each in a few locations globally, but are not recognized to be widespread and, in many cases, are misclassified orogenic or oxidized intrusion-related gold deposits. The Central and South Eastern Desert of the Nubian Shield is highly prospective for ca. 600 Ma orogenic gold given its tectonic, metamorphic, and structural setting. A few areas in these parts of the Eastern Desert are also favorable for ca. 750 Ma gold resources in VMS systems. In addition, areas of Ediacaran Dokhan volcanism in the North Eastern Desert and adjacent southern Sinai are permissive for gold ores in Cu porphyry occurrences, particularly where there is well-developed secondary enrichment zones.