Seminar

Archean tonalite-trondhjemite-granodiorite (TTG) is an important constitute of continents. Its petrogenesis is crucial for understanding of the formation of early continents. Existing petrogenesis models of TTG can be roughly grouped into two groups: partial melting of subducted oceanic crust and partial melting of the base of an oceanic plateau. In this study, we sought to find primary mantle-derived melts whose differentiates can be melted to produce TTG-like melts. Thermal dynamic modeling software rhyolite-MELTS was used to model (1) the fractional crystallization of primary mantle-derived melts and (2) the partial melting of sources solidified from the differentiated mantle-derived melts. It is discovered that TTG-like melts are only produced when the sources melted are evolved from primary mantle-derived melts with relatively low concentrations of MgO. Primary mantle-derived melts of oceanic plateau are relatively enriched in MgO. Therefore, it is concluded that Archean TTG is more likely to be form by partial melting of subducted oceanic crust.

Additional information: Mr. Ruining YAO, geochem@connect.hku.hk