| Summary: | Melange and phacoidal or scaly cleavage have been observed in both ancient and modern day accretionary tectonic environments throughout the world. This unique structural fabric reflects common structural elements from microscopic to macroscopic scales of observation and from one region to another. Structures include: distinct individual polyhedral phacoids, phacoidal shear-aparts, rootless dismembered bedlets of silt, isolated rootless near isoclinal fold noses, seams of preferentially oriented phyllosilicates that generally parallel the foliation, abundant pyrite that ranges in form from large globular masses to small euhedral framboids, and calcite present as foliation-parallel veins and as intergranular precipitates. The characteristic phacoid shape is defined by an anastomosing network of regularly intersecting curviplanar slip surfaces whose average orientation defines a macroscopic and microscopic foliation. In three dimensions these intersections form individual phacoidal forms. The relationship of these lensoid shapes to their internal geometry and the overall stress environment in which they form is the least understood aspect of this fabric. By comparing structural data from Taconic melange in western Newfoundland, Canada and eastern New York State insight into the nature of the fabric has been gained. Three primary analytical techniques were used to obtain data for this study: microstructural analysis of thin-sections, analysis of individual phacoid specimens, and manual dissection of large hand samples. Because of the friable nature of phacoidally cleaved material, a method of dissection was developed to measure structural data such as phacoidal surface orientations and associated slickenline orientations. Data collected from these techniques was analyzed using standard stereographic methods using the computer program Orient. In addition, a stress analysis of the foliation and lineation data was done. The results of these analyses suggest that the lensoid shape of individual phacoids is significant ...
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