REE distribution and enrichment of drainage point sediments from Makran and Lasbela, Pakistan.

Rare Earth Elements (REEs) are mobile during weathering and their distribution is susceptible to both natural and anthropogenic influences. Four major drainage points in the Makran and Lasbela areas were selected for sampling to examine their REE geochemistry. The mean values of ∑REE are highest in Dasht River (DR: 109.4) and lowest in Shadi River (SR: 84.4). The mean values of Eu/Eu* are highest in Rakhshan River (RR:0.95) and lowest in DR (0.70); these values are higher as compared to the Upper Continental Crust (UCC: 0.23) and Post-Archean Australian shale (PAAS: 0.21) in all drainage points. The mean values of (Gd/Yb)_N are highest in RR (2.66) and lowest in DR (2.03), while the mean values of Ce/Ce*, (La/Sm)N, (La/Yb)_N, and (La/Lu)_N are highest in DR (1.01, 3.01, 9.86 and 9.66, respectively) and lowest in RR (0.93, 1.49, 5.75 and 5.93). DR and HR, covering the longest distances from headwater to mouth, pass through a variety of lithologies and convey a more diverse range of sediment compared to RR and SR. Noticeably depleted elemental concentrations relative to UCC (elemental ratios <1) are observed in the majority of sediments, implying the influence of weathered source rocks. Normalized chondrite distributions of the REEs exhibit consistent trends marked by an enrichment of LREEs and a depletion of HREEs, a characteristic pattern was found in upper crust materials exposed to weathering and erosion. The presence of a positive Eu anomaly in UCC and PAAS normalized patterns suggests the contribution of plagioclase minerals. However, leaching is insignificant for the studied sediments due to low average annual precipitation. [ABSTRACT FROM AUTHOR]