Volcanoes and mineral resources
Volcanoes are geological formations that arise from the movement of tectonic plates, where intense pressure can lead to eruptions and the formation of new rock. This volcanic activity is often associated with various mineral resources, which are created and enriched through geological processes. The three primary types of volcanoes—basaltic, andesitic, and rhyolitic—each produce distinct types of magma that influence the minerals formed. Basaltic volcanoes are known for their low explosiveness and sulfur deposits, while andesitic volcanoes can be more explosive, often leading to nutrient-rich volcanic ash that revitalizes the surrounding environment post-eruption. Rhyolitic volcanoes, on the other hand, are rich in silica and can produce significant mineral deposits, including gold and silver, though these are often found in small quantities requiring extensive mining.
Additionally, volcanic activity can lead to the formation of diamond pipes, where diamonds crystallize under high-pressure conditions in the Earth's mantle and are transported to the surface by magma. These pipes often remain underground, with erosion eventually revealing the diamonds. Volcanic regions around the world, such as South Africa and Siberia, are noted for their unique mineral resources, highlighting the complex relationship between volcanic activity and resource formation. Understanding this relationship provides valuable insights into both geological processes and the economic significance of mineral resources derived from volcanic environments.
Volcanoes and mineral resources
Volcanoes or volcanic activity can be a valuable source of natural resources. Some of the economically important resources derived from volcanic activity are diamonds, precious metallic minerals, native sulfur, and a nutrient-rich soil produced by the weathering of volcanic rock.
Background
All volcanoes are related to the process of plate tectonics. Plate tectonics describes the continual movement of immense sections (plates) of the Earth’s crust relative to one another. Although this process is incredibly slow, geologic time is equally long. Both earthquakes and volcanoes most often occur along the boundaries of these plates. They result from the buildup of intense pressure as one plate collides with, or slides past, another. Here old crustal rock is melted as it plunges down into the upper mantle, or new rock forms as magma squeezes out from great fissures in the crust. In the process, old crustal rock is recycled to form new rock that is rich in mineral resources.
Major metallic mineral deposits from around the world are associated with plate boundaries past and present. The island of Cyprus is rich in copper that once formed on the seafloor of an ancient oceanic spreading center. The same process has been happening in the Red Sea, where copper-rich minerals are being extruded through volcanic activity.
The best evidence for submarine deposition of sulfide minerals by volcanic activity comes from structures called hydrothermal vents, also known as “black smokers.” In appearance, they resemble underwater geysers with cone-type vents emitting black smoke. They result from the seepage of seawater into the hot oceanic basalt crust. This heated seawater then interacts with the basalt by extracting iron, copper, sulfur, and other metals from it. Once this mixture erupts onto the seafloor, it mixes with the cold seawater and precipitates sulfide minerals into massive deposits. These become the resources for the future.
Volcanoes come in three basic types, based on their particular chemistry. They are named for the volcanic rock produced by each: basalt, andesite, and rhyolite. The most common type of volcano is the basaltic variety. Varieties of basaltic volcanoes can be found along plate boundaries as well as plate centers (such as the one where the Hawaiian Islands formed). The principal rock that underlies the world’s oceans is also basalt.
Basaltic Volcanoes
Basaltic volcanoes are usually low in silica (approximately 50 percent) and gas content. This type of volcano commonly produces fast-moving lava flows and is generally not explosive. The only mineral that is consistently associated with basaltic volcanoes is sulfur. It forms from sulfur-rich gases that escape from fissures in the cooling lava rock. As the hot gases escape, sulfur quickly crystallizes, with its distinctive yellow color present on the rock. Sulfur is mined at various volcanic locations. One is Mount Etna on the island of Sicily, where it is an important economic resource.
Andesitic Volcanoes
The second type of volcano results from andesitic magma. It is richer in silica (approximately 60 percent) and gas than basaltic volcanoes are. This results in a volcano that can be explosive and can produce a large quantity of lava, depending upon slight variations in its chemical composition. Volcanoes such as this can be extremely dangerous since no one is ever certain what will happen each time they erupt.
Mount St. Helens in the state of Washington and Mount Fuji in Japan are two examples of andesitic volcanoes, which can remain dormant for hundreds of years and then suddenly erupt. The 1980 eruption of Mount St. Helens devastated the area around it. In the aftermath, a rich volcanic ash covered the region. Despite the fact that considerable vegetation was destroyed by the eruption and associated flooding, vigorous plant life returned within a couple of years. This was possible because of the nutrient-rich ash that created a new soil.
Rhyolitic Volcanoes
A magma of rhyolitic composition produces the third volcanic type. Compared to the other two, rhyolitic magma is the richest in both its silica (approximately 70 percent) and its gas content. Both gases and fluids present are rich in dissolved metallic minerals. The magma, as it nears the Earth’s surface, first cracks crustal rock and then may erupt with a violent explosion.
Often, large hydrothermal mineral deposits are associated with rhyolitic volcanoes. These are deposits of various minerals such as malachite, chalcopyrite, and pyrite, where a metallic element like copper or iron is bonded with sulfur or bonded to a carbonate molecule. Such minerals tend to occur in veins where the mineral-rich fluids penetrate fissures in existing rock and then crystallize during cooling. Often gold and/or silver are deposited in this manner. Although such deposits are common, they do not usually occur in large quantities. Most often, huge amounts of rock must be mined in order to extract relatively small amounts of the valuable metals. The great Bingham copper mine in Utah is an excellent example of such a deposit.
Diamond Pipes
One important occurrence of a valuable mineral associated with volcanic activity is the diamond pipe. Diamond formation is typically associated with a high-pressure, high-temperature environment. Such conditions are present in the Earth’s upper mantle at depths of approximately 200 kilometers. Here diamonds slowly crystallize within magma. As a result of rapid upward movement, the diamonds are carried along with the magma column. Eventually, upon cooling, the magma will form a pipe structure. In shape it somewhat resembles a champagne glass.
Most volcanic pipes do not reach the surface and produce a volcano. The more probable situation is that they remain underground as a magma source for an erupting volcano. In those pipes which contain diamonds, the diamonds are disseminated throughout a rock called kimberlite. erosion may eventually destroy evidence of the volcano, exposing the diamond pipe. Erosion also acts as a natural means of extracting the diamonds and then depositing them as sediment in rivers or on beaches. The most important diamond pipes include those of South Africa, Siberia, and western Australia.
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