Title:

Magmatic Brecciation in the Pawtuckaway Ring Dike

The Pawtuckaway ring dike is part of the White Mountain Magma Series and formed 121Ma, and was mapped in 1990 as a masters thesis by Peter Richards. He proposes a model for the formation of the dike using geophysical data, and states that the pyroxenite and gabbro units intruded at or near the same time, followed by hornblende diorite, and monzonite intruding most recently. To see if the intrusive breccia support his model, four breccia localities were examined and three samples were taken. These samples were then cut and shipped to be made professionally into thin sections to be examined by a microscope. The field and sample observations show angular xenoliths of pyroxenite or gabbro completely enclosed by fine or coarse-grained monzonite and none of the breccia localities have pyroxenite within gabbro or vice versa in the same identified sample. The breccia locailites support Richard's model, as the lack of pyroxenite or gabbro xenoliths within the other means they formed at or around the same time. Finally, with both areas having xenoliths completely enclosed in monzonite, so the monzonite must have come after the pyroxenite or gabbro.

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