Identifying plutons associated with long-lived volcanism by thermal modeling of contact metamorphic aureoles

A compilation of the thicknesses of contact metamorphic aureoles (CMAs) developed around intermediate to felsic plutons shows many CMAs are far broader than expected by commonly used thermal models for pluton emplacement. Shortfalls in the amount of heat potentially provided based on pluton size, compared to that needed to form the observed CMA, can be accounted for if some hot magma has been lost by volcanic eruption after passing through the pluton domain and replaced by new hot magma. A high ambient temperature may also contribute to broad CMA formation. However, the presence of coeval pairs of both narrow and broad CMAs in the same area requires contrasting types of pluton growth history. Our thermal modeling, constrained by the peak metamorphic temperature, shows the broad CMA of a well-developed pair of CMAs in the Hongusan area of Japan is due to a magmatic history, including magma tapping and replenishment. A global compilation of CMAs suggests more than 30% of plutons are associated with broad CMAs and fed contemporaneous volcanic eruption.