Geochemical Data of Major and Trace Elements of the BIF of ZD Fm of the RGB

Whole rock geochemical data (wt.%) of the 20 selected samples of Banded Iron Formation (BIF) of the Zandrivierspoort Formation (Fm) of the Rhenosterkoppies Greenstone Belt (RGB) in a descending order are: SiO2 > FeO > MgO > CaO > MnO > Al2O3 > P2O5 > K2O > Na2O > BaO > Cr2O3 > ZrO2 > TiO2 > SrO > V2O5. The trace elements data (ppm) are highest for Ba (476.13), Co (21), and V (129.34), Ni (56,79), and lowest for U (0.20), Sb (0.28), and Cd (0,10). No significant enrichment observed, nonetheless, some transition elements were enriched and their variations are: Ni (1.10 – 56.79), Cu (0.30 – 25.89), Pb (0.10 – 13.00), Ta (0.08 – 11.35), W (1.91 – 17.32). The RGB BIF Fe deposits are depleted in high field strength elements (HFSE) with averages of Ta (1.62), Th (1.34), Sc (4.01), Y (6.00), Zr (9.18). Large ion lithophile elements (LILE) and their average contents are relatively elevated, e.g. Rb (11.11), Sr (6.24), Ba (87.54).

The average concentrations (ppm) of the rare earth elements (REE) of BIF samples of the RGB in a descending order are: Ce (10.95), La (10.38), Nd (8.81), Y (6.00), Sm (1.94), Yb (0.67), Eu (0.71), Tb (0.29), and Lu (0.10). The enrichment of light rare earth elements (LREE) relative to heavy rare earth elements (HREE) is shown by the ratios of chondrite normalized (La/Sm)n, (La/Yb)n, and (Tb/Yb)n. Chondrite-normalised REE show strong LREE fractionation with (La/Yb)n 18.10 on average. The RGB BIF REE patterns show enrichment in LREE with (La/Sm)n = 3.52 relative to the HREE with (Tb/Yb)n = 2.75. Correspondingly, the RGB BIF samples show a very weak (+) Eu anomaly with Eu/Eu* = Eu(n)/(0.67Sm(n) + 0.33Tb(n)) = 0.09 when normalized against chondrite values by multiplying Anders and Grevesse (1989) values by the factor 1.36, following after (Boynton; 1985; Taylor and McClennan, 1985). In comparison, the REE data show a weak negative (-) Ce anomaly (Ce/Ce* = Ce/Ce* = log[Cen/(La(n) x Nd(n))1/2] = -0.82 (Ndema et al., 2020; Chombong et al., 2017; Akagi and Masuda, 1998).

Pearson’s correlation matrix and binary plots display negative correlations of FeO with La, Ce, Nd, Sm, Eu, Tb, Y, Yb, and Lu. Conversely, unlike FeO, SiO2 shows a positive correlation with La, Ce, Nd, Sm, Eu, Tb, Y, Yb, and Lu.