Geochronology, geochemistry and Nd, Sr and Pb isotopes of syn-orogenic granodiorites and granites (Damara orogen, Namibia) — Arc-related plutonism or melting of mafic crustal sources?

Osterhus, Lennart; Jung, Stefan; Berndt, Jasper; Hauff, Folkmar

doi:10.1016/j.lithos.2014.05.002

Cited by 23 publications

(15 citation statements)

References 76 publications

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“…2.0 and 1.1 Ga (Jacob, Kröner, & Burger, ; Kröner, Retief, Compston, Jacob, & Burger, ), and a single zircon from a granodiorite gave an Archean date of c . 2.8 Ga (Osterhus, Jung, Berndt, & Hauff, ). In the Central Damara orogen, the metamorphic grade generally increases southwestward and locally reaches high‐grade conditions close to the coastal area.…”

Section: Geological Settingmentioning

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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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: Geological Settingmentioning

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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“…The 555 Ma age is interpreted to reflect the age of intrusion and falls in the same age range as other intrusive rocks of the OLZ, as for instance the Gawib granodiorites (Osterhus et al, 2014) and the quartz diorites at Goas-Okongava (Jung et al, 2002) and Palmental (Jung et al, 2015). the Gd N /Yb N ratios (0.9-2.8) are high (Fig.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…Temperature and pressure estimates on the Bloedkoppie granite and other early-to syn-orogenic granites indicate that the lower crust was already hot at the time of the inferred onset of the first metamorphic peak (e.g. Ostendorf et al, 2014;Osterhus et al, 2014;Jung et al, 2015). Temperature-pressure estimates on high-grade metamorphic rocks from the Central Zone and temperature estimates on early syn-orogenic granites imply a geothermal gradient of ca.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…Fields represent isotope data of basement-derived intrusive rocks from the Central Zone (Jung et al, 2003;Osterhus et al, 2014;Ostendorf et al, 2014), metasedimentary rocks (McDermott et al, 1990;Jung, 2005), and quartz diorites (Jung et al, 2002;Jung et al, 2015). , 1981).…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…, 1981). Fields represent isotope data of basementderived intrusive rocks (Jung et al, 2003;Osterhus et al, 2014;Ostendorf et al, 2014), metasedimentary rocks (Jung, 2005), and quartz diorites (Jung et al, 2002) from the Central Zone. (Watson and Harrison, 1983) and Al-Ti thermometry (Jung and Pfänder, 2007).…”

Section: Accepted Manuscriptmentioning

confidence: 99%

See 2 more Smart Citations

Petrology of ferroan alkali-calcic granites: Synorogenic high-temperature melting of undepleted felsic lower crust (Damara orogen, Namibia)

Stammeier

Jung

Romer

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Geochemical and isotopic constraints on the role of juvenile crust and magma mixing in the UDMA magmatism, Iran: evidence from mafic microgranular enclaves and cogenetic granitoids in the Zafarghand igneous complex

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et al. 2017

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Geochronology, geochemistry and Nd, Sr and Pb isotopes of syn-orogenic granodiorites and granites (Damara orogen, Namibia) — Arc-related plutonism or melting of mafic crustal sources?

Cited by 23 publications

References 76 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

Petrology of ferroan alkali-calcic granites: Synorogenic high-temperature melting of undepleted felsic lower crust (Damara orogen, Namibia)

Geochemical and isotopic constraints on the role of juvenile crust and magma mixing in the UDMA magmatism, Iran: evidence from mafic microgranular enclaves and cogenetic granitoids in the Zafarghand igneous complex

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