REMAPPING AND GEOCHEMICAL ANALYSIS OF THE CROTON FALLS AND PEACH LAKE PLUTONS IN SOUTHERN NEW YORK AND PLACING THEM IN THE CONTEXT OF THE BEEMERVILLE-CORTLANDT TREND

The two plutonic bodies of Croton Falls and Peach Lake in southeast New York are sparsely documented intrusions laying to the northeast of the Cortlandt Complex. The two plutons are thought to be the easternmost end of the Beemerville-Cortlandt trend of intrusions through Northern New Jersey and Southern New York. The western Beemerville complex consists of alkaline silica-undersaturated rocks and then become dominated by slightly alkaline mafic-ultramafic rocks in the Rosetown and Cortlandt complex. Preliminary research and mapping was done by Brock and Mose (1979), but their main focus was on the metamorphic effects in the surrounding Reading Prong. The plutons were simplistically field identified as mafic to ultramafic bodies with additional unrelated felsic pegmatite dikes. However, precise mineralogical and textural analyses of the plutons was not completed. More importantly, there are currently no geochemical data for the Croton Falls and Peach Lake plutons. The purpose of this research is to remap the plutons, determine the petrography of the plutons and conduct geochemical analysis to precisely understand the genetic relationship of these plutons within the Beemerville-Cortlandt trend. Additionally, the data will be compared with geochemical data on lamprophyres within the Beemerville-Cortlandt trend from Shamus et al., 2018, Langschultz et al., 2019, and Castle et al., 2020 to observe any potential relationships between the Peach Lake-Croton Falls plutons and the lamprophyres. During preliminary analysis in the field, the plutons consist of mostly amphibole-rich diorites and gabbros to ultramafic hornblendites. There is evidence for multiple intrusive events, which is more prominent in the Croton Falls pluton, as indicated by cross-cutting relationships of coarser and finer grained mafic units. The Peach Lake pluton had some units that appeared to have minor preferred foliations and possible evidence of magma mixing with xenoliths of gabbro found within dioritic bodies. The samples were analyzed by inductively coupled plasma–optical emission/mass spectrometry for bulk rock geochemistry. Preliminary results suggest a definitive similarity with the composition of the Cortlandt Complex and extends the eastern terminus to the Peach Lake and Croton Falls plutons.