The Geology of the Arabian-Nubian Shield
| dc.contributor.author | Ibnoof, M.A. | |
| dc.contributor.author | Bumby, A.J. | |
| dc.contributor.author | Liégeois, J.P. | |
| dc.contributor.author | Grantham, G.H. | |
| dc.contributor.author | Armstrong, R. | |
| dc.contributor.author | Le Roux, P. | |
| dc.contributor.editor | Hamimi, Z., Fowler, A, Liégeois, J.P., Collins, A., Abdelsalam, M.G., Abd El Wahed, M. | |
| dc.coverage.spatial | Sudan | |
| dc.date | 2021 | |
| dc.date.accessioned | 2025-03-05T14:24:05Z | |
| dc.date.available | 2025-03-05T14:24:05Z | |
| dc.identifier.uri | https://orfeo.belnet.be/handle/internal/13681 | |
| dc.description | The Saharan Metacraton (SmC) is a fascinating continental-scale entity. However, its boundaries are not all well defined, which is the case to the SE in the Nuba Mountains, Sudan, here studied. Shoshonitic granites, a class of A-type granites, anhydrous and of high temperature, are good probes for determining the composition of the crust or mantle and the geodynamical process at work at their time of crystallization. Here, we provide time (U Pb on zircon ages), compositional (geochemistry) and source characteristics (Sr Nd isotopes) of shoshonitic A-type granites from the Nuba Mountains (southern Sudan), located at the extreme south-eastern tip of the SmC. Their lithology is dominated by medium-grained biotite granite grading into coarse-grained varieties. Mostly undeformed, they are locally affected by E W oriented shears; the exhumation of these late-kinematic intrusions was facilitated by a N S extension as evidenced from the geometry and the shear sense indicators of the E W shear system. U Pb SHRIMP zircon dating indicates that the granitic plutons crystallized at 602 ± 5 Ma and 592 ± 4 Ma with some Tonian inherited zircons but no older pre-Neoproterozoic xenocrystic zircons. These granites are slightly peraluminous, rich in silica and alkalis, with high Fe/Mg ratios and are depleted in CaO, MgO and TiO2, all features consistent with A-type granite chemistry. By contrast, the high field strength elements are enriched in Th, U and Zr and show depletion in Ta and Nb, which is typical of magmas with a source generated in a subduction-related environment. Globally, their geochemistry is that of post-collisional shoshonitic granites. Cou pled with positive eNd,600Ma (+3.5 to +3.8) and low-initial Sr600Ma ratios (0.7023 0.7032), these characteristics are attributed to derivation of the Nuba shoshonitic granites from a mostly juvenile lower crustal source formed during an earlier but not much older subduction period that could correspond to the deep equivalent of the nearby late Tonian volcanic rocks. All the traits of these granitic probes indicate that the Nuba Mountains are located just outside the SmC. So, while the western part of the Nuba Mts has been considered till now to belong to the Saharan metacraton, we propose that the south-eastern boundary of the Saharan metacraton is actually located along the continental-scale Central African shear zone that passes just north of the Nuba Mountains, excluding the latter from the Saharan metacraton. This newly defined southern boundary of the SmC was regularly reactivated during the Phanerozoic. | |
| dc.language | eng | |
| dc.publisher | Springer Nature | |
| dc.relation.ispartofseries | Regional Geology Reviews | |
| dc.title | The Geology of the Arabian-Nubian Shield | |
| dc.type | Book chapter | |
| dc.subject.frascati | Earth and related Environmental sciences | |
| dc.audience | Scientific | |
| dc.subject.free | Geodynamics and mineral resources | |
| dc.source.title | The Geology of the Arabian-Nubian Shield | |
| dc.source.page | 39-62 | |
| Orfeo.peerreviewed | Yes | |
| dc.identifier.doi | 10.1007/978-3-030-72995-0_2 | |
| dc.identifier.url | 10.1007/978-3-030-72995-0_2 | |
| dc.identifier.rmca | 6779 |
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