Copper is an extremely important metal for the development of human civilization. From the Bronze Age to the Electronic Age, copper has been an integral part of human civilization for over 6,000 years. Especially today, from mobile phones to computers, from generators to motors, from airplanes to cars, trains, and ships, from high-precision and advanced instruments to household appliances, from factories to homes, and from cities to rural areas, copper contributes to nearly everything that represents modernization. Some even believe that the per capita copper consumption represents the level of civilization of a country in today's society.
At present, the globally proven copper reserves are about 1 billion tons, but they are unevenly distributed. Chile, located in South America, is the country with the most abundant copper mines in the world, with proven copper reserves accounting for more than one-third of the global total. It is estimated that the global copper resource volume is around 3 billion tons, of which 60% is distributed along the western edge of the American continent. Chile is located in the southwest of South America, with the world-famous Andes Mountains to the east and the Pacific Ocean to the west. Although its land area is only 750,000 square kilometers, less than 8% of China's territory, its proven copper reserves are more than four times that of China. Chile's copper mines are mainly in the form of low-grade and large-scale porphyry copper deposits. Porphyry copper deposits are the most important type of copper deposits, accounting for more than 70% of the globally proven copper reserves. Among the top 10 largest porphyry copper deposits in the world, five are located in Chile, including the three largest copper mines.
Why is Chile so "lucky"? Scientists have found that this is mainly related to the subduction of ocean ridges and young ocean crust. Because the average copper content in ocean crust is more than three times higher than that in the mantle and continental crust, coupled with the high oxygen fugacity of subduction zones, sulfides in source areas are easily destroyed, so the copper content in magma formed by partial melting of subducted ocean crust is much higher than that of other magmas. Chile's western side is the East Pacific subduction zone, where the Pacific ocean crust subducts under the South American continent along the East Pacific trench, penetrating hundreds of kilometers into the interior of South America. Unlike other subduction zones, the Pacific ocean crust off the coast of Chile is one of the youngest subduction zones in the world, with many crusts less than 25 million years old, making partial melting more likely during subduction. More importantly, along the 4,000-kilometer-long subduction zone, four young ocean ridges are subducting. It is these ocean ridges and the surrounding young ocean crust that have formed Chile's unique super-large porphyry copper deposits.
The Andes Mountains also play a significant role in the distribution of porphyry copper deposits. Porphyry copper deposits are mainly formed at a depth of 2-4 kilometers below the ground. Without significant crustal uplift or erosion, porphyry copper deposits are difficult to be discovered, and even if they are discovered, they often lack economic value. However, the subduction of the Pacific plate caused the rapid uplift and erosion of the Andes Mountains, allowing a large number of porphyry copper deposits formed in Chile between 5 million and 30 million years ago to emerge above ground and be successively discovered.
China has also been subject to the subduction of young plates and ocean ridges in geological history, and should have formed a large number of porphyry copper deposits. However, many deposits have been destroyed due to excessive erosion, such as the famous suture line formed by the closure of the Paleoasian Ocean in northern Inner Mongolia. The vast Paleoasian Ocean subducted and disappeared around 500 million to 400 million years ago, and should have undergone the final subduction of ocean ridges and other processes. However, the erosion degree of Inner Mongolia is very severe, and it was named the Inner Mongolia Axis by the older generation of seismologists. Most areas in Inner Mongolia have an erosion depth of more than 10 kilometers. While the formation depth of porphyry copper deposits is 2-4 kilometers, it is difficult to be preserved, so large-scale porphyry copper deposits have not been found. On the Mongolian side dozens of kilometers away from the Sino-Mongolian border, located in the ancient island arc zone, the erosion degree is much lower than that of the Inner Mongolia Axis. The famous Oyutolgoi super-large porphyry copper deposit is located less than 50 kilometers away from the Mongolian side of the Sino-Mongolian border. There are also some places where porphyry copper deposits have not undergone sufficient erosion after subduction of ocean ridges and remain buried more than 2 kilometers below the ground.It cannot be exploited.