Making plutons a bit at a time and the rarity of large magma chambers
Prof. Allen Glazner
UNC Chapel Hill
Abstract:
Plutons are commonly thought to be the frozen remains of large, mobile blobs of magma--in essence, frozen magma chambers. However, a large and growing body of field, geochronological, and geochemical evidence indicates that many plutons were assembled incrementally over millions of years, and that the final pluton was never a magma chamber of comparable size.?If so, then many widely accepted magma ascent and emplacement processes (e.g., diapirism and stoping) may be uncommon in nature, and many aspects of the petrochemical evolution of magmatic systems (e.g., crystal fractionation and magma mixing) need to be reconsidered. It is likely that many textural features, such as "magmatic" fabric and layering, were imposed after incremental emplacement and reflect the death of the magmatic system rather than its growth.