A Seafloor Volcano in the Desert
The semi-arid landscape of Cabo de Gata-Níjar Natural Park is one of Europe's geological sites. It is the continent's driest region, a landscape of sharp volcanic peaks and jagged cliffs that meet the Mediterranean. This terrain is the exposed remnant of a massive volcanic complex that was active during the Miocene epoch, between 7.5 and 15 million years ago. The volcanic activity resulted from the complex collision between the African and Eurasian tectonic plates.
The gold deposits in the park's Rodalquilar area formed within an 8-kilometer-wide volcanic caldera that collapsed around 11 million years ago. After the collapse, magma deep below the surface continued to heat the surrounding rock to between 400 and 500 degrees Celsius. This heat created a hydrothermal system, where seawater and groundwater percolated through fractures, became superheated, and dissolved metals from the volcanic rocks. These hot, acidic, metal-rich fluids then rose toward the seafloor. When they mixed with the cold seawater, the abrupt change in temperature and chemistry caused the dissolved minerals, including gold, to rapidly precipitate out of the solution, forming veins of ore. This type of mineral deposit is a low-sulfidation epithermal deposit.