A likely reason for the appearance of the Daly Gap in magmatic series of large igneous provinces: Geological and petrological evidence

Аннотация

The problem of the Daly Gap is considered for the example of bimodal basalt–trachyte series and their intrusive analogs (layered syenite–gabbro intrusions). It is shown that the gap is not controlled by the processes of crystallization differentiation or liquid immiscibility in intermediate chambers of igneous systems (intrusive chambers) and has a primary nature. We interpret its origin as from the existence of two independent types of melts from the materials of head parts of the same mantle plumes. These are mid-alkali Fe–Ti basalt, products of its adiabatic melting, and trachyte, which is the result of incongruent melting of the material of the upper cool rims of plumes under the influence of fluids percolating from the underlying zone of adiabatic melting.