sgr ms thesis - University of Maine

The final breccia classified in this study, Type 4, is found within the
Cadillac Mountain Granite and consists of large, meter scale xenoliths of Bar
Harbor Formation, diorite, and felsic volcanics. The matrix is nearly as coarse
grained as the Cadillac Mountain Granite, and there are schlieren textures
surrounding some of the xenoliths. No more will be said of the Type 4 xenoliths.
There is significant change in clast morphology of Bar Harbor Formation
clasts between Type 2 and Type 3. This implies an additional modification
process that altered the original size and shape of Type 3 Bar Harbor clasts.
Additionally, outcrop observations suggest that Type 3 diorite clasts exhibit
additional size and shape modification by late stage fracturing (Figure 6.8). I use
clast size distribution (CSD), clast boundary shape (CBS), and clast circularity
analysis (CCA) methods to identify the primary developmental mechanisms and
to determine possible secondary progressions that could lead to clast
modification. The results lead to a discussion involving the use of thermalmechanical
modeling to explain the modification of clast size and shape, and in
doing so explain the transition from explosive to magmatic breccia.
6.2. Methods
Data from 12,732 clasts have been used to identify the brecciation
mechanism and quantify the physical modifications to clast size and shape. Clast
data were calculated from image mosaics collected from outcrops representative
of Types 1, 2, and 3 of the Shatter Zone (blue dots on Figure 2.1, Figure 6.1).
Grids were overlain on flat outcrops with individual boxes of 30x25cm. High
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