Abstract
This study investigates the presence of rare earth element (REE)-bearing minerals in placer deposits from modern beaches along the West Coast of the South Island of New Zealand. The demand for REE is increasing, as these elements are associated with the “clean or green” technology sector. Sand from the strandline of thirteen beaches between Camerons and Karamea on the west coast of the South Island were sampled and the contents of their REE concentrates analysed. Three major rare earth minerals were identified: allanite, a REE-bearing end-member of the epidote family that is enriched in light REE; monazite, a phosphate mineral enriched in LREE; and xenotime, a phosphate mineral that is enriched in yttrium (Y) and heavy REE. Of these three minerals, mineral modal abundances calculated by mineral maps and scanning electron microscope electron dispersal X-ray spectroscopy show allanite to be the most abundant and found in all the beach sand separates. Monazite was also found at all the beaches with the exception of Westport. Xenotime was only found along the Karamea Coast, north of Waimangaroa. Four minor REE-bearing minerals were also identified that contain REE in the range of 1000s of ppm: apatite, zircon, epidote and titanite. The provenance of the minerals was analysed using in-situ trace element analysis (LA-ICP-MS), grain morphology and in-situ Sr isotope analysis. Allanite and monazite are likely to be sourced from the Westland granites, with possible minor amounts from the Alpine Schist. Xenotime is probably sourced from Foulwind Granite. Apatite comes from the Karamea Batholith and Greenland Group, and possibly from Separation Point Suite, Foulwind Granite, Hohonu Batholith and Alpine Schist. The Sr isotope composition for the different source rocks overlap and further analysis of sand and potential source rocks would be required to better isolate the source of individual allanite, epidote, apatite, titanite and scheelite grains. The total concentration of extractable REE from the adjacent stranded Holocene shoreline deposits shows that Waimangaroa contains the highest concentration of REE at ~1900 t, followed by Little Wanganui (1600 t) and Barrytown (1400 t).