RB/SR AND SM/ND SYSTEMATICS OF TWO MIXED MAGMA SYSTEMS FROM THE COASTAL MAINE MAGMATIC PROVINCE
21 samples from the Deer Isle pluton and 15 from the Mt. Waldo pluton were analyzed for Nd, Sm, Rb, and Sr concentrations and isotopic compositions. As the age of each pluton is known, data were plotted on Rb/Sr isochron diagrams to test for linearity relative to a 371 Ma reference isochron. Samples that deviate significantly from the reference isochron were excluded from further consideration because of apparent open system behavior, and εNd and (87Sr/86Sr)i ratios were calculated for the remaining samples. Samples from the Deer Isle pluton show a limited range in both εNd and (87Sr/86Sr)i values, whereas the Mt. Waldo samples show a significant range in (87Sr/86Sr)i but a limited range in εNd.
The relatively large variation in (87Sr/86Sr)i but homogeneous εNd for samples of the Mt. Waldo pluton, suggest that mixing was important in the evolution of the Mt. Waldo pluton, and that end-members with variable (87Sr/86Sr)i but relatively homogeneous εNd mixed incompletely. Because petrographic, chemical and textural data from the Deer Isle pluton indicate that magma mixing was important in its petrogenesis, the more homogeneous εNd and (87Sr/86Sr)i data suggest that the mixing process was thorough. Low 87Sr/86Sri values and young TDM ages are consistent with derivation from a relatively young volcanic source material.