Structure of the plumbing system at Tungurahua volcano, Ecuador: Insights from phase equilibrium experiments on July-August 2006 eruption products

摘要: Understanding the plumbing system structure below volcanoes and storage conditions (temperature, pressure, volatile content oxygen fugacity) of erupted magmas is paramount importance for eruption forecasting understanding factors controlling eruptive dynamics. Phase equilibria experiments have been performed on a Tungurahua andesite (Ecuador) to shed light magmatic that lead July-August 2006 eruptions parameters controlled Crystallization were representative August mafic product between 950-1025oC, at 100, 200 400 MPa NNO+1 +2, water mole fractions in fluid (XH2O) from 0.3 1 (water-saturation). Comparison natural phenocryst assemblage, proportions compositions with our experimental data indicates experienced two levels ponding prior eruption. During first step, magma was stored (15-16 km), 1000oC, contained ca. 6 wt % dissolved H2O. In second rose confining pressure 200 MPa (8-10 km), where subsequent cooling (down 975oC) water-degassing led crystallization reversely zoned rims pre-existing phenocrysts. The combination these processes induced oxidation overpressure reservoir, triggering July injection new, hot, volatile-rich andesitic 15-16 km into reservoir shortly before eruption, responsible explosive event. Our results highlight complexity which different reservoirs can co-exist interact time are main