Abstract

The preferred orientation of chlorite that defines a bedding-plane foliation, both in shales and adjacent slaty tectonites, Mt. Albert area, Gaspé Peninsula, has been quantitatively determined by X-ray diffraction. The resultant preferred orientation index indicates that in the shaly sedimentary rocks chlorite alignment is partly dependent on lithological variations. Nevertheless, the mean index is closely similar to that of chlorites in undeformed shaly rocks from elsewhere. In contrast, the slates with a tectonic foliation parallel to bedding exhibit, with few exceptions, distinctly higher preferred orientations.The method thus allows the quantitative separation of bedding-plane foliations of sedimentary and tectonic origin that are not otherwise readily distinguishable.

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