The axial-plane foliation of early-phase folds in metagreywacke is commonly obliterated by a secondary, regional, crenulation cleavage or schistosity and quartz segregation layering. Nevertheless, remnants are preserved as quartz inclusion trails in biotite porphyroblasts. The trails deviate little in strike for over 20 km across traces of the early folds curving around a granodiorite pluton. Evidently the trails reflect trends existing before emplacement of the pluton. Later regional compression across the secondary cleavage apparently deflected folds around the pluton and thus displaced the porphyroblasts. These, however, were "locked" in orientation by the cleavage forming by a process of quartz diffusion.In a 10 km2 area near the pluton, the secondary cleavage is less pronounced and dips at shallower angles than elsewhere. This suggests a modification to the regional strain such as expected above a satellite pluton rising during formation of the cleavage.

You do not currently have access to this article.