A few days ago, the famous journal "Nature Communications" published a research team of Professor Xia Qunke College of Earth Sciences Institute, Zhejiang University. It has fully defined and analyzed the causes and mechanisms of the formation of supervolcanoes. The key is that the researchers have mastered high quality and credible data on the content of magma water.

　　

The secret of the interior of the earth has become more of a cognizance. Xia Qunke said that the super volcano is not only a "demon" that has caused great changes in the earth, but it also brings rich mineral resources to human beings. The great igneous province is the remnant of the super volcano eruption, which includes large spillway spillway basalt and magmatic donor large radial rock wall groups. They are to a large extent related to the mantle plume activities from the deep, and are the direct products of the magmatic activity of the mantle plume. They are all rich in mineral resources, the famous Panzhihua iron ore, located in the region of the Mount Emei province. "The study of the formation mechanism of the igneous province will help people to find new mineral resources better."

　　

　　

Super volcano is the most violent motion of the earth. In front of the super volcano, known as Sicily volcano, Hawaii volcano and Philippines volcano is pale into insignificance by comparison, they can only be called "small volcano". The eruption of small volcanoes is about one cubic kilometre each time, while the super volcanoes erupt at least one thousand cubic kilometers. The scale is equivalent to 1000 small volcanoes erupting at the same time, and it will last for more than 1 million years.

　　

Today's earth is the remnants of the super volcano eruptions - large igneous provinces. Through the investigation of geological age of large igneous province, it is found that the extinction of organisms in the history of the earth has a precise correspondence with the age of the formation of the igneous provinces. Each time the super volcano erupts, it causes 30 - 40% species to disappear from the earth. The discomfort of human beings is that the outbreak of "demons" is carried out regularly, and "demons" will erupt once every 1000 to 20 million years.

　　

In order to predict the super volcano, we should first find out the formation mechanism of super volcano: How does a huge amount of magma come into being in a short period of time? At present, it is recognized by the scientific community that the formation of magma depends on four major factors: temperature, pressure, rock composition and water. The first three factors, the scientific community has a reliable way to determine. Only the water factor is the most difficult to be elusive, the previous method, the operation is difficult and the error is big.

　　

Many scientists have suggested that water is very important for the formation of magma. If we can't measure the content of water, we can't further evaluate and simulate the influence of water. Xia Qunke said.

　　

　　The secret of water in the magma, hidden in stone

　　

In the quiet laboratory, postdoc Liu Jia used tweezers to remove a thin slice of basalt and put it into the infrared spectrometer. This sample is a product of a massive magma eruption about 250 million years ago. On the dark grey surface, there are some white dots with blurred edges. It is these inconspicuous small spots that hide the "cipher" of the cause of the super volcano.

　　

The Xia group project group collected some basalt samples from the Mount Emei igneous province of the southwest of China. About 250 million years, a super volcano eruption occurred during the middle and Late Permian period. It affects the land and sea change, deposition and mineralization in Southwest China, and may also lead to Permian global climate change and biological mass extinction.

　　

Basalt is a magma formed by the melting of the material deep in the mantle, which is ejected from the surface through segregation and cooling. The sample of basalt, at first glance, is a deep gray, dense stone, carefully identified with some white glittering particles. This is the clinopyxene. Xia Qunke said that during the cooling of the magma, some atoms would be arranged in an orderly lattice to form minerals. In this process, water enters the mineral lattice in the form of OH hydroxyl.

　　

The team found a way to accurately reverse the water content of the original magma by measuring the water content in the clinopyxene. "We have found that the supervolcano's magma contains water, more than a hundred or hundreds times higher than the ordinary water content." Xia Qunke said. Where does a lot of water come from? A further study of the scientists found that this is the water that the ocean plate subducts into the mantle during the movement of the earth's plate. The water in the huge amount of magma comes from the fluid that the subduction plates carry through the dehydrated plates and into the mantle.

　　

With high - quality, reliable water content data, scientists have been able to fully consider the formation mechanism of super volcanoes. In this way, the scientific community can finally define and analyze the causes and mechanisms of the formation of super volcanoes in an all-round way. Xia Qunke research group published papers “Mantle hydration and the role of water in the generation of large igneous provinces” in “Natural Communications” comprehensively expounded the causes of the earth's igneous provinces: temperature, pressure, rock properties and water, the four factors must have at the same time, in order to form super volcanoes. "Only when all the conditions are available, the interior of the earth can produce huge amounts of magma in a short period of time. "Summer Qunke said. The Mount Emei large igneous province is the first case to confirm this theory.

　　

　　Global distribution of known igneous provinces

　　

　　

The supervolcano happens once every 1000 to 20 million years. The most "young" relic is a large igneous province located in the Columbia River area, which was formed about 16 million years ago, where today Yellowstone National Park is located.

　　

"Ordinary volcanoes and super volcanoes are different. Ordinary volcanoes can produce one or more of four factors, while super volcanoes must have four factors at the same time. This makes the prediction of the super volcano possible”, Xia Qunke said, “We know that the supervolcano's magma needs a lot of water, which is subducted from the earth's surface into the mantle. We can deduce that supervolcanoes are bound to occur in or near the subduction of the plate.”

　　

Xia Qunke said, next, the team will work with scientists from Europe and Japan to study the igneous provinces in different regions of the world, and further test and improve the research results. Super volcano is not only a "demon" that causes great changes in the earth, but it also brings rich mineral resources to human beings. The great igneous province is rich in mineral resources, and the famous Panzhihua iron mine is located in the region of the Mount Emei province. "The study of the formation mechanism of the igneous province will help people to find new mineral resources better."

　　

The study was funded by the strategic pilot project of the Chinese Academy of Sciences (B), the National Natural Science Foundation of China and the Finland Natural Science Foundation.