sgr ms thesis - University of Maine

thermal model ignores advection of heat due to flow of the matrix magma relative
to the clasts, there had to be an advective component at least during magma
intrusion. Flow of magma around the partially melting clasts would have
facilitated dissagregation, though “ghosting” of some clast margins suggests that
diffusion, or local mixing of the two magmas, may have occurred without marked
flow of the matrix magma. Flow is the physical component for complete
disaggregation to occur. Without it, clast melting and local mixing would still
occur, but flow is more effective at mixing the melted material into the magma,
essentially removing that clast. Small clasts reach melt temperatures within
seconds after emplacement, when there is a greater potential for magmatic flow.
This could lead to small clast disaggregation well before the cores of large clasts
reach solidus. There is no constraint on magma flow because there is no
evidence for its existence except at the local scale. Regardless of this, Bar
Harbor Formation clasts with the average bulk chemistry eventually achieve
supersolidus temperatures and given any magmatic flow, they have the potential
to disaggregate.
The degree of melt in Bar Harbor Formation clasts is dependent on the
melt temperature, the matrix to clast volume ratio, and the initial temperatures of
clast and intruding magma. As mentioned in sections (2.3) and (6.1), The Bar
Harbor Formation is heterogeneous with layers consisting of pelites, sandstone,
volcanic tuff, detrital quartzite, calc-silicates, and volcanic tuff. It should not be
expected that all Bar Harbor Formation clasts within the Shatter Zone should
have the same solidus temperature, and it is possible that some units did not
104