Abstract

Three localities of metamorphosed and cleaved, laminated mudstone and siltstone show complex intrusive clastic dikes that have been attributed to a precleavage liquefaction mechanism of formation soon after deposition. When the first tectonic surface (S1) is parallel to the compositional layers, the clastic dikes are not unlike chose described from undisturbed sequences. In regions where S1 is at an angle to bedding (S0), the dikes are dominantly planar and subparallel to the cleavage. Some cross-cutting relations are preserved and are particularly striking in examples of deformed compaction folds. In two localities, a crenulation cleavage becomes an important feature of the pelitic layers and there is some alignment of the sedimentary structures in the tectonic direction.

The examples of planar dikes are similar to those used to support the theory of tectonic dewatering (Maxwell, 1962). In this work, there is sufficient evidence to suggest that penecontemporaneous clastic dikes and first cleavages have converged during deformation, thus requiring a re-examination of the data used to support Maxwell's proposal.

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