A model is presented whereby the calc-alkaline series of igneous rocks is derived by partial melting of quartz eclogite at depths of approximately 100-140 km, leaving a residuum of clinopyroxene and garnet. Investigations of the fractional melting and crystallization of synthetic quartz tholeiite, basaltic andesite, andesite, dacite and rhyodacite at high pressures show that under dry conditions the low melting fraction of the eclogite at 25-40 kb is of andesitic composition, whereas under wet conditions it is probably granodioritic. At these pressures under dry conditions the andesite liquidus lies in a marked low temperature trough between the more basic and more acid compositions. Garnet and clinopyroxene are the liquidus or near-liquidus phases in dry tholeiite, basaltic andesite and andesite, while quartz is the liquidus phase in dry dacite and rhyodacite. Under wet conditions at high pressure garnet, not quartz, is the liquidus phase in the dacite.
|Number of pages||10|
|Journal||Earth and Planetary Science Letters|
|Publication status||Published - Sep 1966|