Origin and evolution of the ∼1.9 Ga Richtersveld Magmatic Arc, SW Africa

Macey, P.H.; Thomas, Robert J.; Minnaar, H.; Gresse, P. G.; Lambert, Christopher W.; Groenewald, C.A.; Miller, Jodie; Indongo, J.; Angombe, M.; Shifotoka, G.; Frei, Dirk; Diener, J. F. A.; Kisters, Alexander F. M.; Dhansay, Taufeeq; Smith, Hilary; Doggart, S.; Roux, Petrus le; Hartnady, Michael I.H.; Tinguely, C.

doi:10.1016/j.precamres.2017.01.013

Cited by 58 publications

(28 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Geological setting. The Haib deposit is hosted mainly by the high-K calc-alkaline intrusions of the Vioolsdrif Suite and subaerial volcanic rocks of the Orange River Group along the western part of the Paleoproterozoic Richtersveld Magmatic Arc (RMA) of southern Namibia [15][16][17][18] (Fig. 1, Supplementary Note 1 and Supplementary Figs.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Oxidized sulfur-rich arc magmas formed porphyry Cu deposits by 1.88 Ga

et al. 2021

View full text Add to dashboard Cite

Most known porphyry Cu deposits formed in the Phanerozoic and are exclusively associated with moderately oxidized, sulfur-rich, hydrous arc-related magmas derived from partial melting of the asthenospheric mantle metasomatized by slab-derived fluids. Yet, whether similar metallogenic processes also operated in the Precambrian remains obscure. Here we address the issue by investigating the origin, fO2, and S contents of calc-alkaline plutonic rocks associated with the Haib porphyry Cu deposit in the Paleoproterozoic Richtersveld Magmatic Arc (southern Namibia), an interpreted mature island-arc setting. We show that the ca. 1886–1881 Ma ore-forming magmas, originated from a mantle-dominated source with minor crustal contributions, were relatively oxidized (1‒2 log units above the fayalite-magnetite-quartz redox buffer) and sulfur-rich. These results indicate that moderately oxidized, sulfur-rich arc magma associated with porphyry Cu mineralization already existed in the late Paleoproterozoic, probably as a result of recycling of sulfate-rich seawater or sediments from the subducted oceanic lithosphere at that time.

show abstract

Section: Resultsmentioning

confidence: 99%

“…1, Supplementary Note 1 and Supplementary Figs. 1, 2), which formed in a mature island-arc setting at 1.85-1.91 Ga 15,18 . The pre-mineralization Orange River Group mainly contains plagioclase-phyric andesite porphyry and interleaved rhyolitic tuff (Fig.…”

Section: Resultsmentioning

confidence: 99%

Oxidized sulfur-rich arc magmas formed porphyry Cu deposits by 1.88 Ga

et al. 2021

View full text Add to dashboard Cite

show abstract

“…8). Zircon ages of 1.9 Ga can be assigned to the Richtersveld Magmatic Arc, which is part of the Namaqua Sector (Hofmann et al 2014;Macey et al 2017). In addition, the Orange River Group (also part of the Namaqua Sector) can also provide zircon grains of that age, as these strata feature zircon ages ranging from 1.8 to 2.1 Ga (Minnaar 2011;Pettersson et al 2007;Van Niekerk 2006).…”

Section: Protosources Of the Sedimentsmentioning

confidence: 99%

Mesozoic deposits of SW Gondwana (Namibia): unravelling Gondwanan sedimentary dispersion drivers by detrital zircon

Zieger

Harazim

Hofmann

et al. 2020

Int J Earth Sci (Geol Rundsch)

View full text Add to dashboard Cite

The Namibian Mesozoic successions may be remnant of a high dynamic sedimentary system that is characterized by multiple stages of sediment accumulation and erosion with contemporaneous homogenization starting with the deposition of the Permo-Carboniferous Dwyka Group strata and continues at least until the Lower Cretaceous. The Lower Cretaceous sedimentary system is interpreted to have involved at least an area covering the whole SW Gondwana, documenting the sedimentary history during the evolution from an ice house environment to an arid desert. To test the sediment homogenization hypothesis, we applied a combination of isotopic and morphometric data on detrital zircon grains, as well as whole-rock geochemical data of selected Mesozoic sandstones from Namibia. As a base for the interpretation of the detrital zircon age data we compiled a zircon age dataset with c. 44,000 analyses for the southern African region. All samples reveal a major detrital pan-African zircon age peak of c. 0.5-0.7 Ga sourced from the pan-African magmatic events occurring around the Kalahari Craton margin. The lowermost Triassic is characterized by the occurrence of additional Mesoproterozoic and Paleoproterozoic age peaks of c. 1.0-1.2 Ga and 1.8-2.0 Ga with a majority of zircon grains showing angular shapes. The protosource of these grains is interpreted to possibly be the Namaqua Metamorphic Complex and other Paleoproterozoic structural units deformed in course of the Namaqua orogeny. In contrast, other samples show a prominent Permo-Triassic age peak and completely rounded zircon grains, putatively derived from within the Gondwanides volcanic arc. The disparity in the zircon age pattern may point towards a change in provenance and also a change in the whole system of zircon recycling during the Mesozoic southern Gondwana. The Lower Triassic Neu Loore fm. are constrained to more local bedrock sources and short zircon transport distance. In contrast, zircon grains of the Middle Triassic Omingonde, the Jurassic Etjo und the Cretaceous Twyfelfontein formations are an expression for a major recycling and sediment homogenization system. The system was facilitated by an interplay between fluvial and eolian sedimentary transport systems.

show abstract

“…Here, we focus on the amphibolite to granulite facies Namaqua Sector, consisting of polydeformed and polymetamorphosed orthogneisses and minor metasedimentary and metamafic lithologies that formed during two main tectonometamorphic cycles in the Palaeoproterozoic (~2,050–1,800 Ma) and the Mesoproterozoic (1,300–1080 Ma; Clifford, Barton, & Stern, ; Cornell & Pettersson, ; Cornell, Pettersson, Whitehouse, & Schersten, ; Cornell et al, ; Eglington, ; Macey et al, ; Thomas et al, ). The Namaqua Sector is interpreted as a stack of thin, but laterally extensive fault‐bounded thrust sheets that constitute several tectonostratigraphic domains (e.g.…”

Section: Regional Geologymentioning

confidence: 99%

“…We investigate the energy of reaction involved in partial melting of a number of lithologies and demonstrate that each records a different apparent peak temperature, despite all rock types having received the same heat budget. | 1051 SCHORN aNd dIENER Eglington, 2006;Macey et al, 2017;Thomas et al, 2016). The Namaqua Sector is interpreted as a stack of thin, but laterally extensive fault-bounded thrust sheets that constitute several tectonostratigraphic domains (e.g.…”

Section: Introductionmentioning

confidence: 99%

Seemingly disparate temperatures recorded in coexisting granulite facies lithologies

Schorn

Diener

2019

Journal Metamorphic Geology

View full text Add to dashboard Cite

Phase equilibrium modelling of a conformable sequence of supracristal lithologies from the Bushmanland Subprovince of the Namaqua–Natal Metamorphic Complex (South Africa) reveals a disparity of some 60–70°C in estimated peak metamorphic temperature. Aluminous metapelites were equilibrated at ~770–790°C, whereas two‐pyroxene granulite and garnet–orthopyroxene–biotite gneiss record distinctly higher conditions of ~830–850°C. Semi‐pelite and Mg–Al‐rich gneisses yield poorly constrained estimates that span the range derived from other lithologies. All samples record peak pressure of ~5–6 kbar, and followed a roughly isobaric heating path from andalusite‐bearing greenschist/lower amphibolite facies conditions through a tight clockwise loop at near‐peak conditions, followed by near‐isobaric cooling. The disparity in peak temperatures appears to be robust, as the low‐variance assemblages in all samples reflect well‐known melting reactions that only occur over narrow temperature intervals. The stable coexistence of both products and reactants of these melting reactions indicates that they did not go to completion before metamorphism waned. Calculated pressure–enthalpy diagrams show that the melting reactions are strongly endothermic and therefore buffer temperature while heat is consumed by melting. Because the respective reactions occur at distinct P–T conditions and have different reactant assemblages, individual lithologies are thermally buffered at different temperatures and to different degrees, depending on the occurrence and abundance of reactant minerals. Our calculations show that all lithologies received essentially the same suprasolidus heat budget of 19 ± 1 kJ/mol, which led to the manifestation of lower peak temperatures in the more fertile and strongly buffered aluminous metapelites compared with more refractory rock types. If little to no thermal communication is assumed, this implies that lithology exerts a first‐order control over the heating path and the peak temperature that can be attained for a specific heat budget. Our results caution that the metamorphic conditions derived from pelitic granulites should not be assumed or extrapolated to larger sections of an orogenic crust that consist of other, more refractory lithologies.

show abstract

Origin and evolution of the ∼1.9 Ga Richtersveld Magmatic Arc, SW Africa

Cited by 58 publications

References 29 publications

Oxidized sulfur-rich arc magmas formed porphyry Cu deposits by 1.88 Ga

Oxidized sulfur-rich arc magmas formed porphyry Cu deposits by 1.88 Ga

Mesozoic deposits of SW Gondwana (Namibia): unravelling Gondwanan sedimentary dispersion drivers by detrital zircon

Seemingly disparate temperatures recorded in coexisting granulite facies lithologies

Contact Info

Product

Resources

About