sgr ms thesis - University of Maine

characteristic length and it refers to the clast’s radius in this study. Because is
normalized time with respect to the diffusivity and clast radius ratio, migration of a
phase change through any size clast would show similar results. This allows
easy comparison in a breccia with clast sizes spanning more than three orders of
magnitude.
7.3. Clast Melt Results
Figure 7.2 displays phase boundary migration for the three-dimensional
ideal model. The additional curve is formulated from Turcotte and Schubert
(1982), and defines phase migration in a semi-infinite slab from an infinite heat
source. The time it takes for the ideal clast to completely reach its solidus is =
0.2 (about 15 seconds for a 1 cm radius clast, 150,000 seconds or almost 2 days
for a 1m radius clast). Results (Figure 7.3) from the outcrop model show trends
for 800°C (ΔT = 150°C) and 900°C (ΔT = 250°C) intruding magma. For the ΔT =
250°C model, clasts with radii below 1cm completely reach solidus within 4
seconds, and all clasts with radii below 5cm reach solidus before 300 seconds.
The partially melted area at 300 seconds is equal to 35% of the initial bulk clast
area. Approximately 50% of clast area achieves solidus by 900 seconds, and all
clast area achieves solidus by 5800 seconds. For the ΔT = 150°C model, solidus
temperatures are achieved later and all clast area achieves solidus by 9000
seconds. Both models achieve equilibrium temperature within approximately 2
days.
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