Geochemical variations in the Central Southern Volcanic Zone, Chile (38-43°S): The role of fluids in generating arc magmas

We present new major and trace element, volatile and Sr-Nd-Pb-Hf-O isotope data from the Central Southern Volcanic Zone in Chile (CSVZ; 38-43°S). The satellitic and between stratovolcano cinder cones display different geochemical characteristics from the stratovolcanoes. The cinder cone samples have lower HREEs contents and U/Th, Pb/Ce and Ba/Nb ratios, but higher LREE, Nb and Ta abundances, and La/Yb and Nb/Yb ratios. As in the Transitional (T) SVZ (34.5-38°S), S and Cl contents are elevated in some small cinder cones of the CSVZ relative to the stratovolcanoes. They also extend to less radiogenic Pb and Sr isotopic compositions and higher "18Oolivine compared to the stratovolcano samples, but almost completely overlap in Nd and Hf isotopic composition. These variations are consistent with the lower-volume cinder cones forming through lower degrees of melting as a result of a lower fluid flux from the subducting slab than at the stratovolcanoes. When compared to the TSVZ ([1]Jacques et al.., in press), the magmas feeding the CSVZ stratovolcanoes have experienced higher fluid flux released from the subducting slab, resulting in higher degrees of melting and larger magma production