Percorrer por autor "Ueckermann, Henriette"
A mostrar 1 - 3 de 3
Resultados por página
Opções de ordenação
- Namibe Group detrital zircon U-Pb and Lu-Hf isotopes: a testimony of late-Orosirian (1.9–1.8 Ga) crustal growth in the Angolan Shield (Congo Craton)Publication . Ferreira, Ezequiel; Lehmann, Jeremie; Rodrigues, José Feliciano; Silva, Paulo Bravo; Smith, Trishya M. Owen; García-Lobón, J. L.; Correia, João; Ueckermann, Henriette; Molekwa, Mmasetena Anna; Manuel, José; Victorino, Américo da MataABSTRACT: The Namibe Group represents the largest package of immature supracrustal rocks of the Angola Shield (Congo Craton), occupying an area of nearly 10,000 km2 in the Namibe Zone (NZ). It is a folded, steeply dipping, meta-volcanosedimentary sequence essentially comprising immature micaschists and greywackes, felsic metavolcaniclastites, along with intercalated marbles and amphibolites. The metavolcanosedimentary sequence is intruded by ca. 1810–1790 Ma ultramafic to felsic plutonic rocks with magmatic arc geochemical signatures. Despite its importance, key aspects such as its maximum depositional age (MDA), sedimentary provenance, and the detrital zircon (DZ) record of crustal evolution remain unresolved. This study presents LA-ICP-MS U-Pb and Lu-Hf DZ analyses from nine NG samples.
- Zircon U-Pb and Lu-Hf Constraints on the Paleo- to Mesoproterozoic Evolution of the Southwest Angolan Shield (Congo Craton) [Resumo]Publication . Ferreira, Ezequiel; Lehmann, Jeremie; Rodrigues, José Feliciano; Hayes, Ben; Merino-Martinez, Enrique; Milani, Lorenzo; Bybee, Grant M.; Smith, Trishya M. Owen; García-Lobón, J. L.; Tassinari, Colombo C. G.; Ueckermann, Henriette; Sato, Kei; Silva, Paulo Bravo; Correia, João; Labaredas, José; Duarte, Laurent; Molekwa, Mmasetena Anna; Manuel, José; Victorino, Américo da MataABSTRACT: The crustal evolution of the Angolan Shield (AS) remains poorly constrained. To address this, we analysed U-Pb and Lu-Hf isotopes in detrital and igneous zircons to determine the age and provenance of extensive sedimentary strata in southwest Angola, and use them as a proxy for the Paleoproterozoic to Mesoproterozoic evolution of the southwest AS. Mesoproterozoic maximum depositional ages between 1334 ± 8 Ma and 1184 ± 23 Ma for the Iona, Cahama, and Ompupa siliciclastic rocks refute previous correlations with the Paleoproterozoic Chela Group. Detrital zircon U-Pb and Lu-Hf isotopes closely match those of magmatic rocks from the southwest AS, indicating that Mesoproterozoic siliciclastic rocks were primarily derived from the AS.
- Zircon U-Pb and Lu-Hf isotopes reveal the crustal evolution of the SW Angolan Shield (Congo Craton)Publication . Ferreira, Ezequiel; Lehmann, Jeremie; Rodrigues, José Feliciano; Hayes, Ben; Merino-Martinez, Enrique; Milani, Lorenzo; Bybee, Grant M.; Smith, Trishya M. Owen; García-Lobón, J. L.; Tassinari, Colombo C. G.; Ueckermann, Henriette; Sato, Kei; Silva, Paulo Bravo; Correia, João; Labaredas, José; Duarte, Laurent; Molekwa, Mmasetena Anna; Manuel, José; Victorino, Américo da MataABSTRACT: The crustal evolution of the Angolan Shield (AS) remains poorly constrained. To address this, we analysed U-Pb and Lu-Hf isotopes in detrital and igneous zircons to investigate the age and provenance of extensive sedimentary strata in southwestern Angola and use it as a proxy to gain insight into the Archean to Mesoproterozoic evolution of the region. Mesoproterozoic maximum depositional ages for the Iona (<1323 +/- 13 Ma), Ompupa (<1215 +/- 13 Ma), and Cahama (<1184 +/- 23 Ma) siliciclastics challenge previous correlations with the Paleoproterozoic Chela Group. Provenance analysis reveals that the Mesoproterozoic strata were derived internally from the AS. Our combined dataset indicates that the widespread Eburnean magmatism (-2.05-1.93 Ga) resulted from reworking of Archean crust, possibly in collision orogens. A major increase in the eHf(i) and eNd(i) values at - 1.87-1.73 Ga indicates a change in geodynamics, with magmatism of the Epupa-Namibe Metamorphic Complex (ENMC) generated in an extensional accretionary orogen at the southern margin of the Eburnean-Archean crustal block. Magmatism resumed in the Mesoproterozoic (-1.56-1.50 Ga), with suprachondritic eHf(i) values indicating significant juvenile addition. The Kunene Complex (KC: -1.50-1.36 Ga) anorthosite-mangerite-charnockite-granite magmatism displays variable eHf(i) and eNd(i) values, consistent with mixing between reworked ENMC-crust and juvenile melts in a long-lived accretionary orogen back-arc region. Post-KC (-1.36-1.30 Ga) magmatism shows an increased juvenile contribution, potentially linked to partial melting of ENMC and - 1.56-1.50 Ga juvenile crust during an orogenic event, or alternatively, related to renewed slab retreat and back-arc extension. The Hf isotopic compositions of - 1.29-1.18 Ga zircons are compatible with a renewed input from the depleted mantle and/or reworking of the earlier - 1.56-1.50 Ga juvenile crust. Emplacement of - 1.13-1.10 Ga mafic dikes/sills marks the end of Mesoproterozoic magmatism in the AS. Our new data enhance our understanding of the Archean to Mesoproterozoic crustal evolution of the AS.