Abstract
Lamellae of clinoenstatite are common in enstatite grains in the high-grade ultramafic hornfelses around the Mount Stuart Batholith in the Central Cascades of Washington. Laboratory deformation experiments on enstatite have shown that shear stress on (100) planes parallel to [001] drastically promotes the formation of clinoenstatite. Petrofabric studies of a sample of the hornfels reveal a strong preferred orientation of clinoenstatite-bearing enstatite grains that is unrelated to the fabric of the complete set of enstatite grains. This preferred orientation is well explained by supposing that the clinoenstatite was produced by shearing due to N-S compression. Local and regional geological features are also consistent with N-S compression. These results suggest that there is considerable potential for the application of stress-induced clinoenstatite as a geopiezometer in rocks.
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Now with: Department of Geology, University of Wyoming, Laramie, WY 80271, USA
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Frost, B.R., Coe, R.S. & Okamura, F.P. Principal stress directions from a natural occurrence of stress-induced clinoenstatite. Contr. Mineral. and Petrol. 67, 119–126 (1978). https://doi.org/10.1007/BF01046570
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DOI: https://doi.org/10.1007/BF01046570