Rare earth element geochemistry of Kelantan and Pahang river fluvial sediments

Rare earth elements (REE) are a set of 17 chemically similar metallic elements including 15 lanthanides, scandium, and yttrium. The current status of REE as the global strategic commodity has encouraged the identification of REE ore deposits. This research is carried out to identify the mining feasibility of fluvial sediment REE; and to understand the sediment physical and chemical characteristics effects on geochemical behavior of REE in Kelantan and Pahang River sediments. Surface sediment samples were collected along Kelantan River (n=28) and Pahang River (n=44) in 10 km distance intervals. Eight sets of core sediments were also collected from Kelantan River in order to scope down the potential main sources of REE in Kelantan. The sediment samples were analyzed using XRD and XRF to determine the major oxide and mineral content, respectively. Meanwhile, REE content in the sediment samples were extracted using Total Digestion method and analysed using ICP-MS. The average values of ΣREE at surface sediments of Kelantan River (49.00±33.40ppm) and Pahang River (42.58±29.51ppm), even the Kelantan River core sediments with highest ΣREE (327.35±34.17ppm) were too low to be economically mined. Each area shows higher fractionation of light REE than heavy REE with negative europium anomalies, suggesting sediments in both areas are derived from felsic rocks. The geochemical behavior of REE in fluvial sediments was controlled by physical and geochemical characteristics and its sources. The concentration of REE in Pahang River surface sediments were controlled by the porosity and organic matter as showed by correlation of ΣREE with porosity (R2=0.65) and organic matter content (R2=0.71). In addition, REE in both Kelantan and Pahang River surface sediments might be controlled by titanium and aluminum as both are enriched by these minerals. Pahang River aluminum minerals have profound effects on REE occurrence (R2= 0.75). The sources of Kelantan River surface sediments were predicted using the model from the average of REE in rock formations in Kelantan. The finding shows that 50% of REE in Kelantan River surface sediment was originated from metasedimentary rocks (Taku-Schist) and another 50% from granite rocks which come from Pergau (20%), Dabong (15%), and Gua Musang (5%). As a conclusion, the findings of this research are thus generally useful for further REE mineral exploration and fluvial sediment environmental monitoring, specifically for studies in Kelantan and Pahang.