Bani Hamid Quartzites 16/09—05/10/2013

These granulite-facies quartzites, formed at depth beneath the Oman Ophiolite, show a remarkable sequence of quartz microstructures representing overprinting of the original very coarse high-T fabrics by progressively lower-temperature microstructures as the Bani Hamid rock unit was emplaced to high crustal levels by thrusting within the ophiolite. Since the microstructures reflect the deformation mechanisms and therefore also the temperature regime under which deformation took place, while the mineral assemblages also help to constrain pressure and temperature, a P-T-deformation path can be reconstructed.
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Overview
Overview
Granulite-facies microstructure JC107, crossed-polars slide scan 1.5 x 1 cm. Granulite-facies microstructure of very coarse-grained quartz. Other minerals are enstatite (high relief,...
Granulite-facies microstructure
GBM microstructure JC68, crossed-polars slide scan 1.5 x 1 cm. This quartzite has wholly recrystallized to a grain size of about 1 mm. These grains now have wavy, sutured grain...
GBM microstructure
SGR microstructure JC73, crossed-polars slide scan 1.5 x 1 cm. Much of the matrix is made up of recrystallized grains about 100 ┬Ám in diameter, and deformed larger relics have...
SGR microstructure
Mylonite, BLG microstructure JC84, crossed-polars slide scan 1.5 x 1 cm. A quartz mylonite with scattered diopside porphyroclasts from near the thrust contact against peridotite. Most of...
Mylonite, BLG microstructure
Microstructure detail
Microstructure detail
Granulite, chessboard Qtz JC66, crossed-polars slide scan 1.5 x 1 cm. Granulite-facies microstructure: very coarse-grained quartz strained into roughly square subgrains (chessboard...
Granulite, chessboard Qtz
Granulite microstructure JC61, crossed-polars slide scan 1.5 x 1 cm. Banded quartz-diopside calc-silicate rock with fresh granulite-facies assemblage, coarse-grained quartz, and very...
Granulite microstructure
Granulite, chessboard Qtz JC66, crossed polars, field width 2 mm. High-tempeature chessboard subgrain microstructure in quartz. Horizontal subgrain boundaries are aligned roughly...
Granulite, chessboard Qtz
GBM microstructure JC68, crossed polars, field width 4 mm. Medium-grained quartz with wavy boundaries is attributable to a high-temperature recrystallization of the...
GBM microstructure