Carbon dioxide in ultrapotassic silicate melts: mechanisms and rates of magma degassing and their influence on the intensity and style of volcanic eruptions.

世界上一些最危险的活火山区的特征是位于碳酸盐岩基底内的岩浆管道系统：例如Mt.埃特纳山维苏威火山、Campi Flegrei和Colli Albani（意大利）; Popocatépetl和Colima（墨西哥）; Merapi（印度尼西亚）。接触变质反应过程中的岩浆-碳酸盐相互作用导致这些系统中存在大量的二氧化碳。到目前为止，有关CO2为主的岩浆性质的实验数据缺失。确定CO2在岩浆上升的动力学中的作用是理解和模拟脱气和碎裂过程的先决条件，不仅在CO2为主的火山系统，而且在深度，相对不溶性的CO2可能发挥重要作用旁边的水。此外，这些信息是至关重要的，明确界定的作用，在硅酸盐melts.This工作中发挥的不同挥发分将进行超钾岩浆套件（如foiditic和phonolitic熔体），火山系统的特点，侵位在富碳酸盐地壳。在高压高温装置上进行CO2-H2O溶解度实验和CO2扩散实验，研究近平衡条件下岩浆的性质。所获得的信息将有助于理解和描述深部（即岩浆房）的长期过程，如结晶、岩浆分异或围岩同化。此外，将在能够进行受控减压的高压-高温装置中进行减压实验，以研究短期至中期过程的动力学，例如CO2气泡成核和生长。相态关系和脱气作用对岩浆流变学性质有重要影响，从而影响火山的破碎作用和喷发方式。所获得的实验数据将与记录在纹理图案和化学的天然样品从科利Albani和山的信息进行比较。我们的实验数据将为高风险火山区的火山灾害评估提供有用的约束。

Some of the most dangerous active volcanic areas in the world are characterized by magmatic plumbing systems emplaced within carbonate substrata: e.g. Mt. Etna, Mt. Vesuvius, Campi Flegrei and Colli Albani (Italy); Popocatépetl and Colima (Mexico); Merapi (Indonesia). The magma-carbonate interaction during contact metamorphic reactions results in a significant presence of carbon dioxide in those systems. So far, experimental data on magma properties of CO2 dominated magmas are missing. Determining the role of CO2 in the dynamics of magma ascent is a pre-condition for understanding and modeling of degassing and fragmentation processes not only at CO2 dominated volcanic systems but also at depth, where the relatively insoluble CO2 may play an important role beside water. Furthermore, this information are crucial to unambiguously define the role played by different volatiles in the silicate melts.This work will be performed on ultrapotassic magma suites (e.g. foiditic and phonolitic melts), characteristic of volcanic systems emplaced in carbonate-rich crust. CO2-H2O solubility experiments and CO2 diffusion experiments will be carried out in high pressure-high temperature apparatus to investigate magma properties at near equilibrium conditions. The acquired information will be useful to understand and describe long-term processes at depth (i.e. in the magma chamber) such as crystallization, magma differentiation or wall rock assimilation. In addition, decompression experiments in high pressure-high temperature apparatus able to perform a controlled decompression will be performed to study the kinetics of short to intermediate term processes such as CO2 bubble nucleation and growth. Phase relation and degassing processes may significantly influence rheological magma properties and thus fragmentation and eruptive style of volcanoes. The obtained experimental data will be compared with the information recorded in the textural patterns and in the chemistry of the natural samples from Colli Albani and Mt. Vesuvius volcanoes.Our experimental data will provide useful constrain for volcanic hazard assessment at high risk volcanic areas.