MECHANICAL BEHAVIOR OF MID-CRUSTAL SHEAR ZONES, CARTHAGE COLTON SHEAR ZONE, ADIRONDACKS, NEW YORK STATE

The Carthage Colton Shear Zone (CCSZ) is a NE-SW trending shear zone located on the western edge of the Adirondacks, New York. The CCSZ is a 100 km mid-crustal exposure of a major tectonic boundary between two distinct parts of the Grenville Province. The Adirondack Lowlands to the NW are part of the central metasedimentary belt and the Adirondack Highlands to the SE part of the central granulite terrane. Foliations in the CCSZ strike SW with dips of 30-50^o to the NW, lineations plunge to the NW at 30-50^o. The CCSZ has a long and complex kinematic history with several phases of movement from 1060-920 Ma.

The goal of this project is to understand the architecture of the CCSZ in regards to the distribution of deformation characteristics. Data and orientated rock samples were collected along nine transects across the CCSZ. Preliminary data suggest that the CCSZ is characterized by a broad area of deformation with meter-scale component shear zones within it. These component shear zones usually exist along contacts between different rock types and show much higher degrees of shearing and mylonitization than is seen in the surrounding rocks. This suggests that the shears zones developed along contacts due to mechanical differences between the rock types. There are distinct textural differences between the rock inside and outside these component shear zones, the foliation is much stronger, and the size of mineral grains reduced within the zones compared to the surround rocks. An analysis of one of the transects showed a change in average grain size from 0.6mm outside to 0.3mm within a component shear zone. This data, along with sources from the literature, will be used to correlate rock type with the magnitude and style of deformation, ultimately leading to how the shear zone networks began and developed. Better knowing the kinematic history of the CCSZ will help in understanding the mechanical behavior of mid-crustal shear zone networks and related structures.