Geochronology and sources of late Neoproterozoic to Cambrian granites of the Saldania Belt
The Saldania Belt (SB), located in the southernmost part of South Africa, contains S-, I-, and A-type granites. Whole-rock Sm–Nd data for the Saldania granites indicate the presence of a juvenile as well as inherited crustal signature. The earlier S-type granites have εNd(t) values from −4.2 to −3.28 (for t = 550 Ma). In contrast, the intermediate I-type and youngest A-type and highly fractionated I-type granites display εNd values ranging from −1.44 to −3.68 (for t = 540 Ma) and from +3.66 to +5.1(for t = 530 Ma), respectively. The U–Pb single zircon data of A-type granites exposed in the Western Branch of the SB yielded dates from 524 ± 8 to 510 ± 4 Ma, whereas an S-type granite, situated in the Southern Branch of the SB and represented by the syn- to late-tectonic Rooiklip Granite, yielded an age of 527 ± 8 Ma. The volcano-sedimentary rocks intruded by these granites display Nd model ages from Ga to 1.67 Ga and εNd(t) values from −6.58 to +3.34 (for t = 560 Ma) with isotope signature similar to those of the granites. The S- and I-type granitic magmatism is mostly a product of melting of an earlier crust (Mesoproterozoic to Paleoproterozoic) with different degree of juvenile contribution. The obtained isotope data and field relationship support the hypothesis that the lithological units of the SB were affected by the late Neoproterozoic to Early Cambrian tectonism, related to compressive deformational processes at the southern margin of the Kalahari Plate and probably correlated with the Sierra La Ventana Belt basement.