USING ICELANDIC APATITES TO INVESTIGATE ELEVATED CONTENTS OF RARE EARTH ELEMENTS WITHIN ICELAND

Iceland is an island located in the North Atlantic near the Arctic Circle, sitting at the intersection of the Icelandic mantle plume and the Mid Atlantic Ridge. The crust of Iceland is diverse, containing all varieties of volcanic products, including rhyolites. Apatite is a ubiquitous accessory mineral in Icelandic rhyolites. Apatite is able to withstand a large amount of structural distortion (Pan & Fleet, 2002), which allows for the incorporation of Light Rare Earth Elements (LREEs) into its structure. Recent data suggests that Icelandic apatite is capable of accommodating particularly high levels of LREEs (up to 18.9% by weight; Connors et al. in press). The study found elevated concentrations of each LREE investigated (La, Ce, Nd) within several volcanic units of Torfajökull. The lowest concentrations of LREEs in apatites at Torfajokull were 0.5-2.5 wt%, compared to a more typical REE value of 0.5% (Connors et al. in press; Pan & Fleet, 2002) with units of higher concentrations containing 14 combined wt % on average). The purposes of this study are to: (1) determine if elevated concentrations of REEs within apatites are pervasive in Iceland beyond Torfajökull; and (2) understand the economic implications of having elevated REE abundances in accessory minerals. Samples were collected downstream of Vatnajökull due to potential liberation and concentration of REE-enriched apatite as Vatnajökull is a glacier and massive generator of loose sediment in southeastern Iceland. This study functions as a survey of glacially derived sediments collected in multiple river systems downstream of Vatnajökull (Lagarfljót-Fljótsdal to the northeast, Jökulsá á Fjöllum to the north, Jökulsá i Loni to the southeast). Electron Probe Microanalysis (EPMA), Scanning Electron Microscope (SEM), and Cathodoluminescence (CL) analyses are used to characterize the compositions of Icelandic apatite. Regardless of whether or not REE concentrations within Icelandic apatite are found to be uniformly high, this study will contribute to a greater understanding of Icelandic apatite compositions, which will be useful for future petrologic research.