REINVESTIGATING OLD IRON MINES OF THE NEW JERSEY HIGHLANDS

The Highland mines of New York and New Jersey were active iron oxide (predominantly magnetite) mines until the 1900s and provided a large percentage of the iron needed for steel manufacturing in nineteenth century America. The New Jersey Highlands are primarily made up by the Mesoproterozoic Losee Metamorphic Suite, the Mount Eve Granite, the Vernon Supersuite (the plutonic Byram and Lake Hopatcong Intrusive Suites), sequences of Mesoproterozoic amphibolites and carbonate-rich rocks, and Neoproterozoic Chestnut Hill Formations. The magnetite deposits can be found within several different units of the Highlands and are slightly different depending on the rock formation. Different mechanisms have been proposed for iron ores hosted by the Losee, Vernon Supersuite, amphibolite, carbonate, and Chestnut Hill bodies (Puffer, 2001). However, most models are predominantly based on magnetite and host rock major element chemistry without consideration of trace element composition. Additionally, small concentrations of uranium and rare earth elements (REE) have been associated with several Fe deposits in the area, particularly the Chestnut Hill Formations (Puffer, 2001; Volkert, 2001; Volkert, 2010). The origin and extent of these REE deposits are unclear due to the lack of research in the area. Our study aims to see the extent to which REE may be found in deposits from magnetite mines in the New Jersey Highlands. Magnetite ore samples were collected from several locations throughout northern New Jersey from different abandoned mines including the Edison Mines, Sulfur Hill, Andover, and others. The geochemistry of the bulk rocks will be determined by x-ray fluorescence/ inductively coupled plasma mass spectrometry, while electron microprobe and cathodoluminescence analyses will examine the magnetite and apatite geochemistry in particular. The geochemical analyses of these samples will lead to a better understanding of the formation of the Fe- and REE-deposits. The increased use of REE has led to a greater demand for REE deposits and, as such, understanding potential sources of REE deposits within magnetite mines may have positive economic impacts within current iron mines and more crucially in old mining districts throughout the world.