> [!quote] [Failed eruptions are at the origin of copper deposits](https://www.sciencedaily.com/releases/2022/05/220509112044.htm) via [[ScienceDaily]] > Copper comes from hot fluids, mostly composed of water, released by cooling magmas. These magmas, which are also the basis of eruptions, come from the intermediate layer between the core and the crust of the Earth, known as the "mantle," and then rise to the surface of the Earth where they form a "magma chamber." This chamber is generally located between 5km and 15km depth. "If the volume and speed of magma injection into this reservoir is very large, a large quantity of fluids can be emitted catastrophically into the atmosphere with the magma during a volcanic eruption," explains Massimo Chiaradia, first author of the research. But these fluids can also develop in a quieter way under the earth's surface and give rise to a porphyry copper deposit at a depth varying between 1km and 6km. > > However, this phenomenon is much less frequent, which partly explains the rarity of copper deposits. "It takes tens to hundreds of thousands of years for a copper deposit to form, whereas volcanic eruptions are more frequent. A failed eruption depends on the combination of several parameters: the speed of magma injection, the speed of its cooling and the rigidity of the earth's crust that surrounds the magma chamber. The latter must be flexible to absorb the pressure exerted by the new magma arrivals, so that the eruption does not take place," explains Luca Caricchi, second author and associate professor at the Department of Earth and Environmental Sciences.