Metallogenic Epochs

the epochs during which ore deposits formed; these epochs correspond to the principal stages in the geological development of the earth’s crust.

The Archean metallogenic epoch was distinguished by deeply metamorphosed deposits of ferruginous quartzites and ceramic pegmatites that were comparatively limited in distribution. The early Proterozoic metallogenic epoch was distinguished by widespread distribution of meta-morphogenic iron ores (jaspilites, itabirites), uranium-containing auriferous conglomerates, cuprous sandstones, and magmatic deposits of chromium, titanium, copper, and nickel. The middle Proterozoic metallogenic epoch was also characterized by metamorphogenic deposits of iron and metal-bearing conglomerates; moreover, it was at this time that the most ancient pyrite copper, lead-zinc, and hydrothermal uranium deposits were formed. The early Riphean metallogenic epoch was characterized by the formation of metamorphogenic deposits of iron and manganese and magmatic deposits of sulfide copper-nickel ores and rare-metal pegmatites. The late Riphean metallogenic epoch was distinguished by massive development of deposits of cuprous sandstones and the appearance of hydrothermal deposits of gold, copper, tin, and tungsten. The Caledonian metallogenic epoch was characterized by a prevalence of deposits associated with basaltoid magma, and the deposits were represented by magmatic deposits of iron, titanium, chromium, and platinoids; hydrothermal deposits of gold were also formed. The Hercynian metallogenic epoch was distinguished by varied minerals. Among them were magmatic deposits of iron, titanium, chromium, and platinoids; skarn deposits of iron and copper; pyrite deposits of copper, lead, and zinc; pegmatite and greisen deposits of tungsten, tin, lithium, and beryllium; and hydrothermal deposits of copper, lead, zinc, molybdenum, gold, and uranium. The Alpine metallogenic epoch was characterized by the development of various plutonogenic and volcanogenic hydrothermal deposits of copper, zinc, lead, gold, tungsten, tin, molybdenum, and, especially, antimony and mercury.