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Geochronology and sources of late Neoproterozoic to Cambrian granites of the Saldania Belt |
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| Authors: | F Chemale Jr R Scheepers P G Gresse W R Van Schmus |
| Institution: | 1. Instituto de Geoci??ncias - UnB, Bras??lia, DF, 70910-900, Brazil 2. Department of Geology, University of Stellenbosch, Private Bag X1, Matieland, 7602, South Africa 3. Trans Hex, P.O. Box 572, Parow, South Africa 4. Department of Geology, University of Kansas, Lawrence, KS, 66045, USA |
| Abstract: | The Saldania Belt (SB), located in the southernmost part of South Africa, contains S-, I-, and A-type granites. Whole-rock Sm?CNd data for the Saldania granites indicate the presence of a juvenile as well as inherited crustal signature. The earlier S-type granites have ??Nd(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 ??Nd 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?CPb 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 ??Nd(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. |
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