HUDSON VOLCANO (SOUTHERN CHILE) - THE LAS T ERUPTION OF AUGUST 1991

Hudson strato-volcano (South Chile) lies on the large Deseado fault an d on the prolongation under the continent of the Taitao Fracture Zone. The 1971 and 1973 eruptions produced lahar deposits. The eruption of August 1991 produced voluminous scoriae and pumice block deposits sout heast of the volcano. The pumice is a hypersthene-free andesite with v ery scarce augite and plagioclase phenocrysts. Compared to other andes ites from Southern Andes, this andesite is abnormally rich in Na2O, K2 O, TiO2, niobium, incompatible and rare-earth elements. The magma gene sis is the result of low-rate partial melting in the deep lithospheric mantle followed by a limited crustal contamination and fast ascent th rough the deeply fractured continental crust.