Low Ti - Fe oxide – fluorapatite deposits from the Adirondacks and Hudson Highlands

This project utilizes field, geochemistry and textural evidence to explain: (1) The magnetite-fluorapatite – REE deposits of the eastern Adirondacks, including origin and subsequent long-lived, fluid-rock interaction; (2) The origin of the initial protolith of the metamorphosed high-aluminum (sillimanite) – magnetite ore, partial melt, and carbonates-fluorite-hydrocarbon hydrothermal veins from the Benson mines; and (3) The source of boron in the magnetite – vonsenite deposit from Jayville.

The project combines mapping and analytical work (SEM, EPMA, isotope geochemistry, and geochronology).

Hudson Highlands: The goal of this project is to explain the origin of the iron deposits from the Hudson Highlands. We found the following evidences:  (a) an ultramafic magma; (b) efficient settling of cumulus phases (e.g., Mgt) and xenocrysts (Grt) from assimilated gneiss; (c) assimilation of marble and meta-evaporite horizons to account for high Cl amphibole and primary carbonate; (d) a carbonate melt; (e) a sulfide ± oxide melt; (f) evolved derivative of a ferropicritic melt of possible asthenospheric origin.  

The juxtaposition of such multiple partial melts has been found in other granulite terranes after the cessation of contractional forces, e.g., in the Oaxacan terrane in southern Mexico (also of Grenville age). Our new research will be focused on the isotopic evidence for a mixture of crust and mantle components. 

Low Ti