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After 11·5 ka of quiescence (24·513 ka),the Nevado de Toluca volcano started a 2500 year period of activity.This period was characterized by a dome destruction event at13 ka, a small Plinian event at 12·1 ka, and a largePlinian eruption at 10·5 ka. About 10 km3 of magma waserupted that was homogeneous in composition (63·365·7SiO2 wt % whole-rock) and in mineralogy. Pumice consists ofplagioclase (An3059) > orthopyroxene (En5659)> hornblende >> FeTi oxides + rare apatite (inopx) + biotite, set in a rhyolitic matrix (7276 SiO2wt %). 40Ar/39Ar analysis of single biotite crystals yieldedages (0·814·7 Ma), that do not correspondto eruption ages. The biotite represents partially assimilatedxenocrysts, which could have resided in the magma for only ashort period of time. Mineral chemical data, coupled with hydrothermalexperiments, indicate that prior to eruption the dacitic magmastagnated at a depth of 4·56 km below the summitat water pressures of 160210 MPa and a temperature of824 ± 12°C on the basis of FeTi oxide thermometry,and under water-saturated conditions. To stabilize a homogeneousmagma body of >10 km3 at 824°C in the upper crust, wepropose that reheating of the dacitic reservoir by hotter magmabatches was able to maintain the equilibrium between the temperatureof the magma and the assimilation of wall-rock over a periodof 2500 years. Based on similarities among the juvenile products,we suggest that the three eruptions were fed from the same magmabody. KEY WORDS: explosive volcanism; xenocrystic contamination; Nevado de Toluca, Mexico 相似文献
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