GEOCHEMICAL ANALYSIS AND REGIONAL CORRELATIONS BETWEEN GRANITIC GNEISSES OF THE WESTERN HUDSON HIGHLANDS, NY

The Byram Intrusive Suite granite gneisses of the New Jersey Highlands are believed to be similar in chemical composition as well as age to the Storm King hornblende granite gneisses of the Hudson Highlands of New York (Drake et al., 1991; Ratcliffe and Aleinikoff, 2001; Volkert et al., 2010). The goal of this project is to determine the geochemical continuity between the Byram Intrusive Suite of the NJ Highlands and the Storm King granite gniesses, located near Bear Mountain, NY. Thirty-two samples of granitic gneisses with similar field relations and textures to the Byram and Storm King granite gneisses were collected in the western Hudson Highlands spanning the region between the New Jersey border and the Hudson River within Sterling Forest and Harriman State Parks, NY. The samples are all coarse-grained, hornblende-bearing monzogranites and syenogranites. Whole-rock elemental analysis was obtained via ICP-OES for major elements and ICP-MS for trace elements. The collected samples all have variably mild A-type granite chemical characteristics defined by high Fe/(Fe+Mg) (~0.9), K₂O/Na₂O (1.5-2), high Ba (500-1800 ppm), Nb (20-50 ppm), Y (60-180 ppm), total REE (300-800 ppm) and low MgO (<0.7%), CaO (<2%), and Sr (80-180 ppm). REE patterns are LREE-enriched (La/Yb_N = 5-15), but have flat MREE and HREE and relatively high HREE concentrations (~20-40x chondrite) with moderately deep negative europium anomalies (Eu/Eu* = 0.20-0.50). Compared to data from Volkert et al. (2004) and Verrengia (2004), the major and trace element geochemistry of granitic gneisses analyzed for this study are nearly identical to the Byram Intrusive Suite and the Storm King granite gneiss. Further geochemical modeling and analysis will be conducted to determine (1) the petrogenetic history and tectonic interpretation of the suites in connection to each other, and (2) their relation similar granitic gneisses associated with the Anorthosite-Mangerite-Charnockite-Granite (AMCG) suite in the Adirondacks of northeastern New York.