sgr ms thesis - University of Maine

Somesville granite suite to the west, both of which are inferred to be underlain by
composite gabbro-diorite sheets (Hodge et al., 1982; Wiebe, 1994). The entire
complex dips slightly to the east, exposing the intrusive layers and their relative
contact relationships. The Cranberry Island volcanic series, located in the south,
features a bimodal geochemistry that correlates well with the intrusive complex,
leading some authors to consider it as genetically related to the Cadillac
Mountain intrusive complex (e.g. Seaman et al., 1995, 1999; Wiebe et al.,
1997a). The complex was emplaced into the Ellsworth Schist, Bar Harbor
Formation, and the Cranberry Island volcanic series. The Southwest Harbor
Granite is a poorly studied, older unit cross-cut by the main intrusion.
Several factors indicate shallow crustal emplacement of the intrusive
complex, including evidence for plutonic intrusion within its own eruptive
products, miarolitic textures in the upper section of the Cadillac Mountain
Granite, and relatively low pressure metamorphic mineral assemblages in
surrounding wall rock (Metzger, 1959; Chapman, 1962; Berry and Osberg, 1989;
Seaman et al., 1995; Wiebe et al., 1997a; Seaman et al., 1999). Cadillac
Mountain Granite compositions in the Quartz-Orthoclase-Albite-H 2 O system plot
between 0.5-1kbar, and presence of edenitic hornblende indicates low pressure
crystallization. Emplacement likely occurred at approximately 2-5km depth
(Wiebe et al., 1997a; Nichols and Wiebe, 1998). Gravity data from Hodge et al.
(1982) indicate a saucer-shaped floor geometry for the Cadillac Mountain Granite
with a thickness of approximately 2.5km, underlain by gabbro-diorite sheets of a
potentially similar thickness. Wiebe et al. (1997a) have suggested that the
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