Role of crustal contribution in the early stage of the Damara Orogen, Namibia: New constraints from combined U–Pb and Lu–Hf isotopes from the Goas Magmatic Complex

Milani, Lorenzo; Kinnaird, Judith A.; Lehmann, J.; Naydenov, Kalin; Saalmann, Kerstin; Frei, Dirk; Gerdes, Axel

doi:10.1016/j.gr.2014.08.007

Cited by 39 publications

(20 citation statements)

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“…545 Ma (Jung, Hoernes, & Mezger, ; Jung, Kröner, Hauff, & Masberg, ) although some of them may be slightly older (up to c . 575 Ma; Milani et al., ). The absence of coeval basaltic rocks with a clear asthenospheric signature in the central Damara orogen suggests that the emplacement of asthenosphere‐derived magmas at or near the base of the crust did not play a significant role in the development of high‐ T metamorphism and crustal magmatism.…”

Section: Discussionmentioning

confidence: 99%

“…The age of the syenites has been determined at c. 545 Ma (Jung, Hoernes, & Hoffer, 2005;Schmitt, Trouw, Passchier, Medeiros, & Armstrong, 2012;S. Jung, unpublished data) and the quartz diorites have been dated also at c. 545 Ma (Jung, Hoernes, & Mezger, 2002;Jung, Kröner, Hauff, & Masberg, 2015) although some of them may be slightly older (up to c. 575 Ma;Milani et al, 2015). The absence of coeval basaltic rocks with a clear asthenospheric signature in the central Damara orogen suggests that the emplacement of asthenosphere-derived magmas at or near the base of the crust did not play a significant role in the development of high-T metamorphism and crustal magmatism.…”

Section: How the Crust Gets Hot In The Damaramentioning

confidence: 99%

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Metamorphic petrology of a high‐T/low‐P granulite terrane (Damara belt, Namibia) – Constraints from pseudosection modelling and high‐precision Lu–Hf garnet‐whole rock dating

Jung

Brandt

Bast

et al. 2018

Journal Metamorphic Geology

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Migmatites comprise a minor volume of the high‐grade part of the Damara orogen of Namibia that is dominated by granite complexes and intercalated metasedimentary units. Migmatites of the Southern Central Zone of the Damara orogen consist of melanosomes with garnet+cordierite+biotite+K‐feldspar, and leucosomes, which are sometimes garnet‐ and cordierite‐bearing. Field evidence, petrographic observations, and pseudosection modelling suggest that, in contrast to other areas where intrusion of granitic magmas is more important, in situ partial melting of metasedimentary units was the main migmatite generation processes. Pseudosection modelling and thermobarometric calculations consistently indicate that the peak‐metamorphic grade throughout the area is in the granulite facies (~5 kbar at ~800°C). Cordierite coronas around garnet suggest some decompression from peak‐metamorphic conditions and rare andalusite records late, near‐isobaric cooling to <650°C at low pressures of ~3 kbar. The inferred clockwise P–T path is consistent with minor crustal thickening through continent–continent collision followed by limited post‐collisional exhumation and suggests that the granulite facies terrane of the Southern Central Zone of the Damara orogen formed initially in a metamorphic field gradient of ~35–40°C/km at medium pressures. New high‐precision Lu–Hf garnet‐whole rock dates are 530 ± 13 Ma, 522.0 ± 0.8 Ma, 520.8 ± 3.6 Ma, and 500.3 ± 4.3 Ma for the migmatites that record temperatures of ~800°C. This indicates that high‐grade metamorphism lasted for c. 20–30 Ma, which is compatible with previous estimates using Sm–Nd garnet‐whole rock systematics. In previous studies on Damara orogen migmatites where both Sm–Nd and Lu–Hf chronometers have been applied, the dates (c. 520–510 Ma) agree within their small uncertainties (0.6–0.8% for Sm–Nd and 0.1–0.2% for Lu–Hf). This implies rapid cooling after high‐grade conditions and, by implication, rapid exhumation at that time. The cause of the high geothermal gradient inferred from the metamorphic conditions is unknown but likely requires some extra heat that was probably added by intrusion of magmas from the lithospheric mantle, i.e., syenites that have been recently re‐dated at c. 545 Ma. Some granites derived from the lower crust at c. 545 Ma are the outcome rather than the cause of high‐T metamorphism. In addition, high contents of heat‐producing elements K, Th, and U may have raised peak temperatures by 150–200°C at the base of the crust, resulting in the widespread melting of fertile crustal rocks. The continuous gradation from centimetre‐scale leucosomes to decametre‐scale leucogranite sheets within the high‐grade metamorphic zone suggests that leucosome lenses coalesced to form larger bodies of anatectic leucogranites, thereby documenting a link between high‐grade regional metamorphism and Pan‐African magmatism. In view of the close association of the studied high‐T migmatites with hundreds of synmetamorphic high‐T granites that invaded the terrane as metre‐ to decametre...

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Section: Discussionmentioning

confidence: 99%

Section: How the Crust Gets Hot In The Damaramentioning

confidence: 99%

Metamorphic petrology of a high‐T/low‐P granulite terrane (Damara belt, Namibia) – Constraints from pseudosection modelling and high‐precision Lu–Hf garnet‐whole rock dating

Jung

Brandt

Bast

et al. 2018

Journal Metamorphic Geology

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“…Recent studies on paleomagnetic data [ Li et al ., ] and on Hf‐systematics on dated detrital zircon populations [ Foster et al ., ] have suggested that the present‐day southern margin of the Congo and northern margin of the Kalahari cratons were not proximal in Rodinia. These pre‐Gondwana distal relationships are further supported by patterns of U‐Pb ages in the Congo basement of the Damara Belt that reveal (i) absence of ~1.1 Ga Umkondo Large Igneous Province magmatism [ Milani et al ., . and references therein] and (ii) very rare indications of Mesoproterozoic magmatism (see review in Lehmann et al .…”

Section: Discussionmentioning

confidence: 99%

“…The oldest indication of convergence between the Congo and Kalahari cratons is given by eclogite facies metamorphism of subducted oceanic crust at ~675–590 Ma in the Zambezi Belt [ John and Schenk , ; John et al ., ; John et al ., ]. In the Damara Belt, the Goas Magmatic Complex was interpreted to reflect convergence between the Congo and Kalahari cratons that was active as early as 580 Ma [ Milani et al ., ].…”

Section: Geological Settingsmentioning

confidence: 99%

Structural and geochronological constraints on the Pan‐African tectonic evolution of the northern Damara Belt, Namibia

et al. 2016

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The Pan-African Orogen formed by convergence of numerous continental blocks during the Neoproterozoic to early Cambrian. This convergence eventually led to amalgamation of Gondwana, a supercontinent crosscut by a network of highly oblique linear orogenic belts that locally intersect each other, as in NW Namibia, where the NNW trending Kaoko Belt joins the NE trending Damara Belt. The northern Damara Belt has preserved well three regional Pan-African tectonic events due to the dominance of weak Neoproterozoic marine sediments (Damara Supergroup) that have been affected by low-grade metamorphism. A newly discovered early N-S horizontal contraction, dated by 40 Ar/ 39 Ar at~590 Ma, is tentatively linked to convergence between the Congo and Kalahari cratons. This was superseded by collision between the Congo and Rio de la Plata cratons between 580 and 530 Ma that thickened and exhumed the orogenic crust of the Kaoko Belt and produced upper crustal N-S oriented folds of earlier fold trains and associated axial planar schistosities in the northern Damara Belt. A switch from E-W to NW-SE horizontal shortening occurred at 530 Ma as a result of collision with the Kalahari Craton, triggering extensive syn-orogenic magmatism in the entire Damara Belt. During this last event, southward indentation and underthrusting of the Congo Craton promontory below the Neoproterozoic cover sequences produced a deformation front in the northern Damara Belt. Our results show that highly oblique convergent processes competed over a period of~120 Ma to build Gondwana in Namibia during the late Neoproterozoic to early Cambrian.The Damara Orogen is composed of three highly oblique branches, the NNW trending Kaoko and Gariep belts and the NE trending Damara Belt [Martin and Porada, 1977;Coward, 1981;Miller, 1983;Gray et al., 2008] that were at least partly active at the same time [e.g., Miller et al., 2009] during mutual convergence of three cratonic blocks, the Rio de la Plata, Congo, and Kalahari cratons (Figure 1). Despite the Damara Orogen being extensively LEHMANN ET AL.TECTONIC EVOLUTION NORTHERN DAMARA BELT 103

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“…The youngest age is confirmed by 40 Ar-39 Ar metamorphic ages of 590 Ma obtained in the Kuiseb Formation (Lehmann et al, 2016). A minimum deposition age for the top of the Swakop Group in Northern Zone of Namibia, intruding the Karibib and Kuiseb formations, is constrained by granite and metamorphic age determinations of ~585-F. Delpomdor, S. Schröder, A. Préat, P. Lapointe, C. Blanpied 570 Ma (Bergemann et al, 2014;Milani et al, 2014;Forster et al, 2015). In the CAC, the oldest metamorphic ages are 592 ± 22 Ma (U-Pb monazite) and 585.8 ± 0.8 Ma Ar-Ar plateau age for biotite (Rainaud et al, 2005).…”

Section: Stratigraphic Correlationsmentioning

confidence: 91%

Sedimentology and chemostratigraphy of the late Neoproterozoic carbonate ramp sequences of the Hüttenberg Formation (northwestern Namibia) and the C5 Formation (western central Democratic Republic of Congo): Record of the late post-Marinoan marine transgression on the margin of the Congo Craton

Delpomdor

Schröder

Préat

et al. 2018

South African Journal of Geology

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Role of crustal contribution in the early stage of the Damara Orogen, Namibia: New constraints from combined U–Pb and Lu–Hf isotopes from the Goas Magmatic Complex

Cited by 39 publications

References 100 publications

Metamorphic petrology of a high‐T/low‐P granulite terrane (Damara belt, Namibia) – Constraints from pseudosection modelling and high‐precision Lu–Hf garnet‐whole rock dating

Metamorphic petrology of a high‐T/low‐P granulite terrane (Damara belt, Namibia) – Constraints from pseudosection modelling and high‐precision Lu–Hf garnet‐whole rock dating

Structural and geochronological constraints on the Pan‐African tectonic evolution of the northern Damara Belt, Namibia

Sedimentology and chemostratigraphy of the late Neoproterozoic carbonate ramp sequences of the Hüttenberg Formation (northwestern Namibia) and the C5 Formation (western central Democratic Republic of Congo): Record of the late post-Marinoan marine transgression on the margin of the Congo Craton

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