Northeastern Section - 54th Annual Meeting - 2019

Paper No. 39-4
Presentation Time: 1:30 PM-5:30 PM


BENIMOFF, Alan and KOMINOSKI, Sara, Department of Engineering and Environmental Science, College of Staten Island, Staten Island, NY 10314

The Staten Island Serpentinite was mapped by Lyttle and Epstein (1987) as a lens shaped body whose long axis trends NE-SW. This is one of the many discontinuous ultramafic bodies that extend from Quebec, Canada into the southern Appalachians. Samples for this study were collected from an excavation for a shopping center in the Staten Island Serpentinite (N 40.58° and W 74.11°). The average composition of the serpentinite at this location is SiO2 34.96, Al2O3 0.21, CaO 0.04, MgO 41.41, Na2O<0.01, K2O 0.03, Fe2O3 7.66, MnO 0.01, TiO2 0.02, Cr2O3 0.44, and LOI 15.57 sum 100.36 wt %. Benimoff and Lupulescu (2008) reported on zoned accessory Cr-Spinel in this serpentinite body. They plotted the Cr-spinel analyses in the Cr/(Cr+Al)sp vs. Mg/(Mg+Fe)sp of Coish and Gardner (2004) where the analyses plot in the forearc peridotite field. In this preliminary study we have added two new olivine analyses to the Coish and Gardner (2004) plot. Electron microprobe analyses were used to compute the following empirical formula: Mg1.87FeO0.16Ni0.015(Si0.98O4). These olivine compositions average Fo92. The olivine of this study plots in the ophiolitic harzburgite field in the Olivine Spinel Mantle Array (OSMA) of Coish and Gardner (2004). According to Coish and Gardner (2004) this could be interpreted as evidence for the residual origin of the peridotite represented as refractory mantle residues. This could be further evidence in support of a suprasubduction zone (SSZ) ophiolite.