Cinder cone distributions around stratovolcanoes in the Trans-Mexican volcanic belt: Testing models of andesite genesis

Recent studies support that magma mixing between basaltic and rhyolitic magma is the most common origin of andesite in subduction zones. Although much research about magma mixing has been done, few of them, if any, have focused on the surface expressions resulting from magma mixing. As cinder cones are a common surface expression of basaltic magmatism, a stratovolcano generally represents andesite volcanism. I mapped out the stratovolcanoes and cinder cones in the Trans-Mexican Volcanic Belt (TMVB) in central Mexico based on 1-arc second (~30m) Digital Elevation Models (DEMs). The cinder cones in the west TMVB shows NW-SE tend while those in the east shows E---W trend. Cinder cones overall are not evenly distributed; they tend to be concentrated along rifting zones and around a central stratovolcano. In the vicinity of a central stratovolcano, however, there are few, if any, cinder cones. The maximum density of cinder cones is reached just out of the footprint of the central stratovolcano. This is consistent with recent "filter" models that suggest that basaltic magmas ultimately drive the andesitic magmatism and magma mixing is the main resource for the andesite generation. The endmember rhyolitic magma rarely erupts due to a viscosity barrier and the basaltic magma cannot erupt through the main magma chamber beneath the stratovolcano because of a density barrier. The hybrid andesite has the required an appropriate viscosity and density to erupt. The cinder cone distributions observed here support this model for the generation of andesite at stratovolcanoes in the TMVB.