According to scientific determination and inference, about 2.6 billion years ago, in Archean, volcanic eruption brought a large amount of gold from the core to the mantle and crust along cracks, and then formed the original gold source through marine deposition and regional metamorphism. About 1 100 million years ago, due to the strong force, the crust was deformed and folded out of the sea, and the gold material was activated and migrated to form a gold field, which is what we call rock gold.
In rock gold-rich areas, a large amount of natural gold is often left after rock oxidation. After tens of millions of years of weathering and denudation, the shallow rock gold on the surface has turned into sand. Because of its stable nature, it dissociates into monomers, which are deposited in the stable water of the river due to its heavy specific gravity during river transportation, thus forming placer gold deposits. At the same time, due to the affinity of placer gold, it rolls from small to large in the process of river transportation, forming granular gold of different sizes.
Gold deposits formed in the process of natural change can be roughly divided into three categories: rock gold deposits, placer gold deposits and associated gold deposits. The reserve ratio of rock gold, associated gold and placer gold in the world is about 70: 15: 15. Among them, rock gold deposits can be divided into several genetic types: magmatic hydrothermal type, metamorphic hydrothermal type, volcanic hydrothermal type, sedimentary metamorphic type, hot water leaching type and metamorphic conglomerate type.
The proportion of all kinds of gold deposits in the world's total reserves is: metamorphic conglomerate type 56.2%, metamorphic hydrothermal type 12.4%, associated gold 9.5%, placer gold 8.9%, magmatic hydrothermal type and volcanic hydrothermal type 7.0%, hot water leaching type 0.9%.
From a global perspective, according to the structural units of gold deposits, they can be divided into four types: shield metallogenic areas, platform and edge metallogenic areas, geosyncline folded belt metallogenic areas and Pacific Rim metallogenic areas. Among them, the gold reserves produced in the shield account for 25.6-27.8% of the world's total reserves; Paleozoic platform caprock was partially activated in Mesozoic, accounting for 1. 1- 1.3%, and excellent geosyncline accounted for 12.9- 15.6%. Underground trough area, accounting for1.1-1.2%; However, the structural area of paleoplatform caprock accounts for 47. 1-47.7%.