College

Buchtel College of Arts and Sciences

Date of Last Revision

2021-05-06 08:54:57

Major

Geology

Honors Course

3370 497-003

Number of Credits

6

Degree Name

Bachelor of Science

Date of Expected Graduation

Summer 2021

Abstract

In nature, the segregation of granitic melts at the source may be controlled by fabric and compositional heterogeneities in the source rock, such as foliation and lineation. To investigate the influence of foliation/lineation orientation and composition on rock strength and melt interconnectivity, I performed a series of experiments on cores of a fine-grained gneiss (Gneiss Minuti) and a fine-grained muscovite-bearing quartzite (Moine Thrust quartzite). These rocks were cored at six primary orientations parallel, 45 degrees, and perpendicular to the foliation and lineation and were deformed at a constant temperature of 900°C, pressure of ~2 GPa, and strain rate of ~10-6/s using the D-DIA apparatus at Beamline 6-BMB at the Advanced Photon Source at Argonne National Laboratory.

Strengths of the Gneiss Minuti cores varied from 1.02 to 1.17 GPa, and strengths of the Moine Thrust quartzite ranged from 1.28 to 1.61 GPa. The strength anisotropy of the cores relative to the core with the foliation oriented 45 degrees to the compression direction varied from 0.87 to 1.99 in the Gneiss Minuti cores and ranged from 0.59 to 2.13 in the Moine Thrust quartzite cores. Melt was present in all cores, and concentrations varied from 1 to 4 vol% for the Gneiss Minuti and from 0.6 to 1.2 vol% for the Moine Thrust quartzite. The Gneiss Minuti and Moine Thrust quartzite cores had similar melt topology in all foliation orientations with small melt channels/pockets parallel to the compression direction, and the only significant melt interconnectivity was observed in the Gneiss Minuti foliation/lineation parallel to the compression direction sample, which also had the largest melt fraction (3.74 vol%). These results indicate that when above a low melt content (~1 to 2 vol%), the presence of melt has a greater effect than the orientation of foliation and lineation on the strength of foliated rocks and melt migration.

Research Sponsor

Dr. Caleb Holyoke III

First Reader

Dr. Molly Witter

Second Reader

Dr. John Peck

Honors Faculty Advisor

Dr. John Peck

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