Volcanic eruptions of intermediary and silica-rich magmas (andesites, dacites and rhyolites) in convergent arcsettings generate voluminous and explosive eruptions that can strongly affect human activity and have signifi-cant environmental impacts. It is therefore crucial to understand how these magmas are generated in order toanticipate their potential impact. At convergent margins, primitive magmas (primitive basalts and/or andesites)are derived from the mantle wedge and they are progressively modified by physical and chemical processes op-erating between the melting zone and the surface to produce silica-rich magmas.In order to elucidate the relationship between andesites and dacites, we focus on Tungurahua volcano, located inthe Ecuadorian Andes. We collected a set of samples comprising such lithologies that were erupted during thelast 3000 year BP. This relatively short period of time allows us to assume that the geodynamic parameters re-main constant. Petrology and major-trace element compositions of these lavas have already been examined,and so we performed a complementary Pb-Sr isotope study in order to determine the nature and origin of thecomponents involved in andesite and dacite genesis. Sr isotopes range from 0.70417 to 0.70431, and Pb isotopecompositions range from 18.889 to 19.154 for206Pb/204Pb, from 15.658 to 15.696 for207Pb/204Pb, and from38.752 to 38.918 for208Pb/204Pb. Dacites display a remarkably homogeneous Pb isotopic composition, withhigher206Pb/204Pb values for a given207-208Pb/204Pb compared to andesites. Andesites show notable207Pb/206Pb variations for a given SiO2content, whereas dacites have lower and homogenous207Pb/206Pb values.Andesite and dacite altogether plot in a roughly triangular distribution, with dacitic magmas systematically plot-ting at the high SiO2and87Sr/86Sr and low207Pb/206Pbfields. Based on our new dataset, we show that at least 3different components are required to explain the Tungurahua compositional and isotope variation: one corre-sponds to the mantle, the second has a deep origin (slab component or lower crust), and a mixture betweenthese two components explains andesite heterogeneity. The third component is derived from the underlyingupper continental crust. While andesites are derived from deep components, dacites are derived from the andes-itic magmas that underwent an assimilation-fractional crystallization (AFC) process with incorporation of thelocal metamorphic basement. Finally, we used the geochemical and isotopic data to produce a model of the mag-matic plumbing system beneath Tungurahua, consistent with geophysical and experimental petrology con-straints. We conclude that melt migration and storage in the upper crust appears to be a key parameter forcontrolling volcanic behavior though time.