A Study On Fluid Geochemistry Of The Hubin Strong Gas-Emission Zone In The Tianchi Caldera, Changbaishan

Volcano is a geological landform where magma erupts through the crust and deposits on the surface of the Earth. The volcanic activity is an important geological phenomenon. The study on volcano has a great significance for people to enjoy benefits, to reduce hazards and to realize the forecasting of the eruption, and harmonic co-existing for the people and volcanoes. The magma degassing is one of the most common phenomena of a volcanic eruption. Different degassing processes may result varied hazards around the volcano and can be taken as an indicator for the magma activity beneath the volcano.Based on the field work of ground fluid, especially on the Hubin strong gas release zone in Tianchi, this thesis uses some new theories and methods, such as geochemistry, including hydrogen chemistry, gas geochemistry, isotopic geochemistry of the rare gases, volcanology, seismology, petrology, and tectonics, to solve several existing problems. They are the structural background, distributions and characters of ground fluids, chemical compositions and the origin of released gases, the distribution character of He isotopic composition and the significance in geology. In a point of view of monitoring,this thesis discusses the recent periodic gas geochemical anomalies happened in the Changbai Tianchi Volcano and states that the strong gas emission zone by the edge of the Tianchi caldera lake possesses a highest significance for the understanding of gas geochemistry.Here the Changbai Tianchi volcano refers to the center of the Changbaishan volcanoes with decreasing elevation outward in an area of more than 13000 km~2 of the system. The Tianchi volcano (Baitoushan volcano) is the top of the Changbai Mountains. The Tianchi lake lies near the top of the cone and is a caldera lake formed by the water accumulation after many eruptions happened almost in a same place. Besides the Giant Millennium Eruption, there have been several different recent eruptions of middle or small scales.The circular and radial fault system related to the centralized eruptions of the Tianchi Volcano controls the hydrothermal activity of the Tianchi Volcano. The...