Extended Data Figure 4: EDS images showing the heterogeneous concentration of various elements in the melt filaments.

a, BSE image showing the area mapped by EDS. EDS maps show the distribution of Fe (b, in green), Ti (c, in blue), and Al (d, in red). Colour-scale values represent X-ray counts per pixel for each energy band in the line type Ka1. During frictional melting of andesite and dacite, selective melting tends to affect the iron-titanium oxides more readily than silicate mineral phases owing to their lower fusion temperature30.