MAGMA MIXING, THE PETROGENETIC LINK BETWEEN ANORTHOSITIC SUITES AND RAPAKIVI GRANITES, ALAND, SW FINLAND

Structural, textural and geochemical features suggest that magma mixing was an important petrogenetic process in the formation of the earliest rapakivi granite intrusions in the Aland rapakivi batholith. Petrographic evidence of magma mixing can also be found in the major intrusion of the batholith, the wiborgite rapakivi granites. Chemically the mixing is difficult to specify in these rocks because of a high proportion of felsic component. Zircon and apatite fractionation trends, however, indicate that the wiborgite rapakivis also contain components from a mixed source.