MINERALOGY OF REE-BEARING NYF-TYPE PEGMATITES FROM THE KIN PROPERTY, NEAR REVELSTOKE, BC, CANADA

Deformed REE, Nb, Mo-bearing pegmatites were discovered in 2011 on the Trident and KIN properties ca. 95 kilometers northeast Revelstoke British Columbia. The pegmatites are hosted in amphibolite grade meta-sedimentary rocks of the Neoproterozoic Horsethief Creek group and underwent metamorphic overprinting at approximately 60 Ma.

The pegmatites are composed of four main zones, each with its own mineralogical signature and characteristics. From center outwards, these four zones are the core, the intermediate zone, the wall zone, and the border zone. The core is the most simple of the zones and is composed primarily of quartz with actinolite, pyrite, and spessartine. The intermediate zone contains feldspar with coarse grains of ferrocolumbite and allanite-(Ce) with monazite-(Ce), nioboaeschynite, fluorapatite, phlogopite, almandine, Nb-rich rutile, epidote, and molybdenite. The wall zone is composed of feldspar, phlogopite, and almandine with allanite-(Ce), monazite-(Ce), nioboaeschynite-(Ce) euxenite-(Y), Nb-rich rutile, ilmenite, thorite, and zircon. Finally, the border zone is primarily magnesiohornblende with allanite-(Ce), monazite-(Ce), chevkinite, ferrocolumbite, almandine, ilmenite, thorite, and zircon. Monazite is of particular interest in this locality, as there are visible alteration coronas of monazite breakdown to allanite + apatite present.

The KIN property pegmatites have a strong NYF-type signature of elevated Nb, Ti, Y, F, and REE. This is shown through the presence of minerals such as ferrocolumbite, ilmenite, Nb-rich rutile, fluorapatite and an abundance of REE-rich minerals, such as allanite and monazite, and elevated geochemical analyses values of Nb (2402 ppm) and TREE+Y (17160 ppm).

A finer grained syenite body was also found in the area and is primarily composed of plagioclase, K-feldspar, and amphibole with minor amounts of nepheline, biotite, and titanite. It also contains the REE-bearing mineral allanite. Geochemical analyses of the syenite show elevated LREE values, with La and Ce values of up to 209 ppm and 328 ppm respectively. This signature supports the argument that the syenite is the parental source of the pegmatite.