Preliminary Characterization of Rock Units to Determine Layer Divisions in a High-Pressure Metamorphic Rock Package of the Goshen Dome, Western Massachusetts, USA

In Western Massachusetts a package of rocks, known as the Damon Pond section, has been the focus of ongoing study due to characteristics signifying it may have formed under suspected ultra-high pressure (UHP) conditions. Currently there are no confirmed UHP terranes in North America causing research surrounding this package of rocks to be of particular significance. In order to better understand the Damon Pond section and a mechanism of emplacement for this potential UHP terrane, more must be known about its size and the surrounding strata. Field observations, structural measurements, and samples were collected from in-situ outcrops surrounding the Damon Pond section where it is exposed at the edge of the Goshen Dome in order to determine the lithologic units present and if they show signs of disruption indicating the Damon Pond section is more extensive than currently mapped. Petrographic analyses were conducted on 11 representative samples from the surrounding area focusing on the metamorphic mineral assemblage, relative abundance of minerals, notable structural characteristics, distribution of mineral grains, size variance of mineral grain populations, and the spatial association of metamorphic minerals. The Damon Pond section was found to be different from the surrounding lithology. Three rock type divisions were made in the surrounding lithology from analysis of hand samples and thin sections. Spatial location of the samples showed these lithologic divisions to be consistent along strike with no repeating sections or disruptions. The units present were determined to be Amphibole Gneiss, Amphibole Quartz Garnet Gneiss, and Garnet Schist