Diverse monogenetic volcanism across the main arc of the central Andes, northern Chile

This work presents several small-volume eruptions of lava which provide new constraints on different compositions of mantle-derived magmas delivered to the base of the crust of the Andes. Melting is generated deep in the mantle beneath northern Chile as the tectonic Nazca plate beneath the Pacific Ocean sinks beneath the west coast of the South American continent. As this melt propagates upwards, it forms magmas of a wide range of compositions as separate batches experience variable amounts of crystallization, assimilation of surrounding rock, mixing with other magma(s), density fractionation, and/or prolonged storage in the crust of the Earth. The style and magnitude of volcanic eruptions at the surface is highly dependent on the composition(s) of the magma which are erupted as lava or ash. The thick (> 55 km) and complex lithosphere beneath the Andes of the Altiplano and Puna plateaus of northern Chile exerts a heavy influence on ascending mantle-derived magmas. Volcanism in the region dominantly erupts lava with compositions reflecting lithospheric alteration processes. The monogenetic (single eruption) volcanos presented in this study represent instances where fault systems reaching to the base of the crust have delivered magma to the surface with relatively minimal degrees of alteration since their genesis in the mantle. The origins of these volcanoes include melting of the mantle under the influence of fluids derived from the subducted Nazca plate, decompression melting of the mantle as it upwelled to fill space created at the base of the lithosphere by foundering of dense material, and melts derived directly from the lithospheric material sinking into the mantle.