Black and Secondary Gold Mines
Black mines and secondary gold mines are geological ages and are objects of geological surveys and geological prospecting. When the thickness of gold-bearing ore bodies is more than a certain thickness, or when the ore bodies are well developed or covered, black or secondary gold deposits should be considered for exploration.
In nature, black or secondary gold usually appears as gold-bearing quartz veins and veins in hydrothermal fractures. There are also more secondary gold deposits in the form of gold-bearing quartzose limestone beds and iron-quartzite beds. Some secondary gold deposits may be polymetallic deposits.
Geologically, black and secondary gold mines are composed of gold-bearing quartz veins in quartz gangue rocks, such as calcareous and acid metamorphic rocks, or some sedimentary rocks, such as sandstones and shales. The rock formations hosting the black or secondary gold deposits are usually massive, hard, strong and uniform in structure, no obvious cracks and weathering, well-developed strata, rarely affected by regional metamorphism, and generally have strong lateral and vertical continuity.
The exploration of black or secondary gold ore requires a very clear geological understanding of the distribution of black or secondary gold ore bodies. According to the geological characteristics of black or secondary gold ore bodies, the following exploration methods may be used: geological observation and geological mapping, magnetic survey (because the occurrences of black or secondary gold ore bodies are generally related to the tectonic dislocation and fracture of rocks); geochemical survey (Including stream sediment survey and soil survey); underground prospecting and so on.
Geological observation and mapping is the basis of exploration work, and geophysical exploration methods such as seismic and electromagnetic exploration can be used in gold-bearing areas to identify hidden deposits and supplement local geological information. Through geochemical prospecting, more specific areas of heavy mineral deposits can be identified. Trenching and outcrop sampling can be used to determine the grade and mineralized area. Underground prospecting can develop and test the ore, obtain sample data of various structures, and obtain basic information for determining the mining method and mining, mineral processing and ore dressing methods.
With the advent of modern high-tech exploration, modern geophysical methods such as gravity and magnetic exploration have been developed. Also, data analysis methods such as remote sensing, computer analysis, and miniaturization have been developed to provide powerful help for the exploration of black or secondary gold deposits.
