GEOCHEMICAL ANALYSIS OF RARE EARTH ELEMENTS IN PROTEROZOIC IRON MINES IN THE NEW JERSEY AND NEW YORK HIGHLANDS REGION

The New Jersey Highlands and Hudson Highlands region features Proterozoic aged iron deposits hosted within Grenvillian aged granitic gneiss including the Byram Granite, Pochuck Gneiss, and the Losee Gneiss. The iron deposits within this region often exhibit similar characteristics to other low titanium iron-oxide deposits around the world including the Kiruna district of Sweden and more importantly, the iron deposits in the Adirondacks, which show elevated concentrations of rare earth elements (REE; Foose and McLelland, 1995). It has been suggested that the iron deposits in the Adirondacks were formed by similar hydrothermal fluids to those that formed the ore in the Kiruna district as evidenced by potassic and sodic metasomatism in both regions (Foose and McLelland, 1995). Although the origin of the Highlands deposits has been debated, it is now recognized that the ore-forming fluids are hydrothermal in nature, with the precise mechanism uncertain. The iron ore deposits are found in a variety of different host rocks and may have different formation mechanisms. Some authors favor an original “depositional” type environment similar to a sedimentary exhalative deposit (e.g., Gunderson, 2004) while others favor a metamorphic replacement origin of these deposits (e.g., Puffer, 2001). This study aims to determine whether there are potentially economically viable concentrations of REE from various abandoned iron mines from the Highlands region. The sampling technique is similar to that used by Taylor et al., (2019) that collected multiple samples in a grid-like manner from tailings pile(s) and the host rock. This was done largely because in some cases REE-bearing minerals could be present within both the ore material itself and within the host rock. Geochemistry of the bulk rock was determined using inductively coupled plasma-optical emission spectrometry and mass spectrometry (ICP-OES/MS). In addition, radiation measurements were taken for each sample using a handheld Laurus RadEye B20 as Shah et al., (2019) found a positive correlation between the radiation of the rocks with the total REE. The presence of REE in these deposits in the Highlands could provide us with a better understanding of how REE get deposited so that economically viable deposits may be located in the future.