Tectonostratigraphic implications of Late Proterozoic U-Pb zircon ages in the Avalon Zone of southeastern New England

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U-Pb zircon ages have been determined for several Late Proterozoic igneous units near Boston, Massachusetts, in the Avalon Zone of southeastern New England. Crystallization ages are 599 ± 1 Ma for the Westwood Granite, 596 ± 2 Ma for rhyodacite from the Mattapan Volcanic Complex and 589 ± 2 Ma for quartz diorite, which intrudes the Westwood Granite. These results together with published ages from granites of the Dedham Granite, the Esmond-Milford plutonic suite, and granitic gneisses in Massachusetts and Rhode Island fix Avalonian arc magmatism in southeastern New England between ca. 625 and 589 Ma, an interval diachronous with respect to sub-duction-related plutonism and volcanism in other northern Appalachian Avalonian terranes.

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Special Paper of the Geological Society of America