sgr ms thesis - University of Maine

Figure 7.4 displays model results from the transient temperature path for
points within the spherical clast model with ΔT = 150°C and ΔT = 250°C runs.
The ΔT = 250°C results show that, for a magmatic breccia with 75% matrix,
homogenization temperature is reached by = 1.6. For this model, clast centers
achieve supersolidus temperatures by = 0.2 for T i = 900°C and = 0.3 for T i =
800°C. Equilibrium temperature is 840°C (θ = 0.76) and 770°C (θ = 0.48)
respectively. Results from the 34% magma by volume model show a constant
intrusion temperature of 900°C for T c = 650°C with
= 0.24 and 450°C, which
does not reach the solidus temperature at the clast center. Results from the 16%
magma by volume model show a constant intrusion temperature of 900°C for T c
= 650°C and 400°C, both of which do not reach the solidus temperature at the
clast center.
7.3.1. Discussion
Based on thermal modeling results and the calculated solidus temperature
of 720°C, All Bar Harbor Formation clasts with the average bulk chemistry
(Metzger, 1959) achieved supersolidus temperatures with 75% magma matrix by
volume, allowing partial melt to occur. Small, noncircular clasts melt first, and
because there is such a large population of small clasts, there is a rapid increase
in percent partial melt seen in Figure 7.3. The melt percent by area slope
decreases when only larger clasts remain. An order of magnitude change in clast
radius will cause two orders of magnitude change in the amount of time for the
clast to achieve supersolidus temperatures (Okaya et al., in press). Although the
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