pyrite ores consisting predominantly of sulfurous (sulfide) ore minerals. The composition of pyrites is dominated by iron sulfides (pyrite, pyrrhotite, marcasite). Also present are the sulfides of copper (chalcopyrite, bornite), zinc (sphalerite), and lead (galenite) and barium sulfate (barite). Pyrite deposits consist of massive as well as disseminated ores. These deposits have the shape of beds, lenses, stocks, and veins measuring up to 5,000 m long and 250 m thick; they occur at depths of as much as 2,000 m.
In terms of formation and occurrence, pyrites are closely linked to the basic and alkaline igneous rocks that issued onto the floor of ancient seas and formed extended ophiolite zones characteristic of the early stage of geosynclinal development. In the volcanic zones, pyrites form discontinuous chains measuring up to several thousand kilometers long. Pyrites arise in the late stage of volcanic cycles, when the eruption of the primary magma has been replaced by alkaline and acidic lavas, which are accompanied by the heavy venting of volcanic gaseous and liquid solutions. The solutions carry a large amount of metals that combine with the sulfurous sublimates and are deposited in the form of sulfides, creating the pyrites. That portion of the pyrites that arises along the seepage paths of the solutions through the volcanic rock forms hydrothermal metasomatic deposits. The other part of the mineral matter carried by the volcanic solutions reaches the floor of the sea and, in being deposited here, creates the volcanogenic sedimentary deposits of pyrites.
The accumulation of pyrites occurs over a long period of time, and in the early stages, predominantly the sulfurous iron compounds form, which are of limited practical interest. The pyrite deposits of copper, zinc, and lead arise in the later stages.
In the USSR the following pyrite deposits are known: Proterozoic (Karelia), Lower Paleozoic (Buriatia and Tuva), Middle and Upper Paleozoic (Urals and Caucasus), and Mesozoic and Cenozoic (Caucasus) deposits. Abroad, there are Proterozoic (Canada), Lower Paleozoic (Norway and Australia), Middle and Upper Paleozoic (Spain, Portugal), Mesozoic (Yugoslavia), and Cenozoic (Japan, Turkey, Greece, Cuba) deposits.
Pyrite deposits are an important source for obtaining copper, zinc, and lead and, in part, gold, silver, bismuth, cadmium, indium, barium, selenium, sulfur, and sulfuric acid.
V. I. SMIRNOV