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Patterns of Total Strain in the Walls of Two Greenstone Assemblage Boundaries, Western Birch-Uchi (Confederation Lake) Belt, NW Ontario

出版	University of Toronto, 1999
URL	http://books.google.com.hk/books?id=zDBPzwEACAAJ&hl=&source=gbs_api

註釋The boundaries between the Balmer-Woman and Woman-Confederation assemblages are well exposed in western central parts of the Birch-Uchi belt. Based on zircon dates for the felsic metavolcanics, age gaps of 'ca'. 100 Ma between the assemblages were recognized by others. The results of the present structural analysis suggest that boundary slip was kinematically insignificant during regional ductile deformation, and did not lead to omission of rock strata or production of large age gaps. Nothing can be said, however, about the possible effects of (i) brittle faulting at early stages of tectonism or (ii) discomformable deposition of the basal strata of the assemblages. Detailed study of effects of total strain finishes structural data that permit qualitative and quantitative assessments of the displacement field associated with ductile deformation. Applying the stretching-fault concept to the study area, distributed tangential-shear strain at the Balmer-Woman assemblage boundary proves to have the sense of thrust faults (hanging wall of Woman assemblage rocks to the NW). By contrast, the distributed tangential-shear strain at the Woman-Confederation assemblage boundary has the sense of sinistral faults (hanging wall of Confederation rocks to the north). This result is compatible with elements of the northward transportation hypothesis for the Birch-Uchi belt.