TY - JOUR
T1 - Zircon U-Pb and Lu-Hf isotopes reveal the crustal evolution of the SW Angolan Shield (Congo Craton)
AU - Ferreira, Ezequiel
AU - Lehmann, Jérémie
AU - Feliciano Rodrigues, José
AU - Hayes, Ben
AU - Merino-Martínez, Enrique
AU - Milani, Lorenzo
AU - Bybee, Grant M.
AU - Owen‑Smith, Trishya M.
AU - Luis García-Lobón, José
AU - C. G. Tassinari, Colombo
AU - Ueckermann, Henriette
AU - Sato, Kei
AU - Bravo Silva, Paulo
AU - Correia, João
AU - Labaredas, José
AU - Duarte, Laurent
AU - Molekwa, Mmasetena Anna
AU - Manuel, José
AU - da Mata Lourenço Victorino, Américo
N1 - Publisher Copyright:
© 2024 The Author(s)
PY - 2024/7
Y1 - 2024/7
N2 - 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 εHf(i) and εNd(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 εHf(i) values indicating significant juvenile addition. The Kunene Complex (KC: ∼1.50–1.36 Ga) anorthosite-mangerite-charnockite-granite magmatism displays variable εHf(i) and εNd(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.
AB - 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 εHf(i) and εNd(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 εHf(i) values indicating significant juvenile addition. The Kunene Complex (KC: ∼1.50–1.36 Ga) anorthosite-mangerite-charnockite-granite magmatism displays variable εHf(i) and εNd(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.
KW - Archean to Mesoproterozoic
KW - Crustal evolution
KW - Detrital and igneous zircon
KW - SW Angolan Shield
KW - U-Pb and Lu-Hf isotopes
UR - http://www.scopus.com/inward/record.url?scp=85189808152&partnerID=8YFLogxK
U2 - 10.1016/j.gr.2024.03.010
DO - 10.1016/j.gr.2024.03.010
M3 - Article
AN - SCOPUS:85189808152
SN - 1342-937X
VL - 131
SP - 317
EP - 342
JO - Gondwana Research
JF - Gondwana Research
ER -