AbstractsEarth & Environmental Science

The quartz microstructures and microfabrics in tectonites representing greenschist to granulite facies conditions are examined to assess the factors influencing their development. The c-axis patterns range from random distributions to small, great, and crossed circle girdles, and to c-axes maxima. The small circle girdles, the most common fabrics at all metamorphic grades, are oriented at 30(DEGREES)-40(DEGREES) and 50(DEGREES)-70(DEGREES) about the axes of shortening and extension, respectively. The c-axis orientations of the recrystallized grains bear no relationship to those of the host grains suggesting that host control, though important initially, is commonly overridden by strain controls. The style and magnitude of strain, and the metamorphic grade are the significant controlling factors in the microfabric development. Intracrystalline slip mechanisms are favoured for the origin of the c-axis preferred orientations. Apparent discrepancies between experimental and natural fabrics can be reconciled when symmetries of strain are considered.