Age and Petrogenesis of the Doros Complex, Namibia, and Implications for Early Plume-derived Melts in the Paraná–Etendeka LIP

Owen-Smith, T.; Ashwal, Lewis D.; Sudo, Masafumi; Trumbull, Robert B.

doi:10.1093/petrology/egx021

Cited by 25 publications

(21 citation statements)

References 113 publications

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“…Only three of our low-Ti lavas plot within/near the mantle array in Figure 4a and are therefore considered to be minimally contaminated by continental crustal. These samples have N-MORB and E-MORB-type trace element compositions, similar to the Doros and Horingbaai magma-types (Owen-Smith et al, 2017;Thompson et al, 2001; Figure 5). A slight effect of continental contamination, however, cannot be ruled out for NAM59 (elevated 87 Sr/ 86 Sr and low 143 Nd/ 144 Nd), but is considered to be insignificant compared to all other low-Ti samples.…”

Section: Source Composition Of the Low-ti Basaltsmentioning

confidence: 66%

“…Mixing of a (hypothetically already present) Tristan plume component with depleted upper mantle ± crust also cannot explain the composition of the minimally contaminated low-Ti samples. Such a low-Ti end member is found in the Doros intrusion (130Ma; Owen-Smith et al, 2017) and related Tafelkop lava flows (Ewart et al, 1998;Gibson et al, 2000), which are believed to originate from the Doros igneous center (Marsh et al, 2001), and the Horingbaai dikes (131-132Ma; Thompson et al, 2001). (Jennings et al, 2019 and references therein), confirming that the Horingbaai magmas were generated within a hot mantle plume from the lower mantle (Thompson et al, 2001).…”

Section: Source Composition Of the Low-ti Basaltsmentioning

confidence: 84%

“…The low-Ti Tafelkop basalt type, characterized by low Ti and Zr and high Ti/Zr, is believed to contain the highest proportion of plume-derived material in its magma source (Ewart et al, 2004a;Ewart et al, 1998). The Tafelkop basalts occur near the base of the volcanic succesion in central southern Etendeka and there is compelling geochemical evidence that they are related to the nearby Doros intrusive complex (Marsh et al, 2001;Owen-Smith et al, 2017). Magmas with Tafelberg, Khumib and other compositions also form dikes and intrusions.…”

Section: Geological Background and Previous Researchmentioning

confidence: 99%

“…Hoernle et al (2015) argued that the large range in chemical composition of both flood basalt provinces could largely be explained by plume melts with a Gough-type composition assimilating continental lithosphere (upper and lower crust and lithospheric mantle). Isotopically enriched lavas with elevated delta 7/4Pb but low delta 8/4Pb ratios have been recognized in southern Etendeka (Ewart et al, 1998;Gibson et al, 2000;Owen-Smith et al, 2017;Thompson et al, 2001), but their origin and relationship to the main phase of the plateau has remained unclear thus far. This study presents new major and trace element and Sr-Nd-Hf-Pb (double spike) isotope data from mafic Etendeka flood basalts and feeder dikes sampled at a variety of locations in northwestern Namibia to evaluate their compositional relationship to the marine parts of the Tristan-Gough hotspot track.…”

Section: Introductionmentioning

confidence: 99%

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Geochemistry of Etendeka magmatism: Spatial heterogeneity in the Tristan-Gough plume head

Zhou

Hoernle

Geldmacher

et al. 2020

Earth and Planetary Science Letters

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Section: Source Composition Of the Low-ti Basaltsmentioning

confidence: 66%

Section: Source Composition Of the Low-ti Basaltsmentioning

confidence: 84%

Section: Geological Background and Previous Researchmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Geochemistry of Etendeka magmatism: Spatial heterogeneity in the Tristan-Gough plume head

Zhou

Hoernle

Geldmacher

et al. 2020

Earth and Planetary Science Letters

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“…Our palaeomagnetic work in the Etendeka LIP provides a refined South America -Africa reconstruction for the Early Cretaceous, and also places the Paraná/Etendeka plume above the plume-generation zone at the margin of the sub-African LLSVP (Owen-Smith et al, 2019). Our petrology, geochemistry and isotope work on a small 130 ± 1 Ma layered intrusion, the Doros Complex, demonstrate its emplacement as successive pulses of magmatic mushes (Owen-Smith and Ashwal, 2015a and b), and its derivation from depleted asthenospheric, rather than lithospheric mantle sources (Owen-Smith et al, 2017).…”

Section: (Right Panel) Tectonic/magmatic Model Explaining Recurrent Amentioning

confidence: 66%

Wandering continents of the Indian Ocean

Ashwal

2019

South African Journal of Geology

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On the last page of his 1937 book “Our Wandering Continents” Alex Du Toit advised the geological community to develop the field of “comparative geology”, which he defined as “the study of continental fragments”. This is precisely the theme of this paper, which outlines my research activities for the past 28 years, on the continental fragments of the Indian Ocean. In the early 1990s, my colleagues and I were working in Madagascar, and we recognized the need to appreciate the excellent geological mapping (pioneered in the 1950s by Henri Besairie) in a more modern geodynamic context, by applying new ideas and analytical techniques, to a large and understudied piece of continental crust. One result of this work was the identification of a 700 to 800 Ma belt of plutons and volcanic equivalents, about 450 km long, which we suggested might represent an Andean-type arc, produced by Neoproterozoic subduction. We wondered if similar examples of this magmatic belt might be present elsewhere, and we began working in the Seychelles, where late Precambrian granites are exposed on about 40 of the >100 islands in the archipelago. Based on our new petrological, geochemical and geochronological measurements, we built a case that these ~750 Ma rocks also represent an Andean-type arc, coeval with and equivalent to the one present in Madagascar. By using similar types of approaches, we tracked this arc even further, into the Malani Igneous Province of Rajasthan, in northwest India. Our paleomagnetic data place these three entities adjacent to each other at ~750 Ma, and were positioned at the margins, rather than in the central parts of the Rodinia supercontinent, further supporting their formation in a subduction-related continental arc. A widespread view is that in the Neoproterozoic, Rodinia began to break apart, and the more familiar Gondwana supercontinent was assembled by Pan-African (~500 to 600 Ma) continental collisions, marked by the highly deformed and metamorphosed rocks of the East African Orogen. It was my mentor, Kevin Burke, who suggested that the present-day locations of Alkaline Rocks and Carbonatites (called “ARCs”) and their Deformed equivalents (called “DARCs”), might mark the outlines of two well-defined parts of the Wilson cycle. We can be confident that ARCs formed originally in intracontinental rift settings, and we postulated that DARCs represent suture zones, where vanished oceans have closed. We also found that the isotopic record of these events can be preserved in DARC minerals. In a nepheline syenite gneiss from Malawi, the U-Pb age of zircons is 730 Ma (marking the rifting of Rodinia), and that of monazites is 522 Ma (marking the collisional construction of Gondwana). A general outline of how and when Gondwana broke apart into the current configuration of continental entities, starting at about 165 Ma, has been known for some time, because this record is preserved in the magnetic properties of ocean-floor basalts, which can be precisely dated. A current topic of active research is the role that deep mantle plumes may have played in initiating, or assisting, continental fragmentation. I am part of a group of colleagues and students who are applying complementary datasets to understand how the Karoo (182 Ma), Etendeka (132 Ma), Marion (90 Ma) and Réunion (65 Ma) plumes influenced the break-up of Gondwana and the development of the Indian Ocean. Shortly after the impingement of the Karoo plume at 182 Ma, Gondwana fragmentation began as Madagascar + India + Antarctica separated from Africa, and drifted southward. Only after 90 Ma, when Madagascar was blanketed by lavas of the Marion plume, did India begin to rift, and rapidly drifted northward, assisted by the Marion and Deccan (65 Ma) plumes, eventually colliding with Asia to produce the Himalayas. It is interesting that a record of these plate kinematics is preserved in the large Permian – Eocene sedimentary basins of western Madagascar: transtensional pull-apart structures are dextral in Jurassic rocks (recording initial southward drift with respect to Africa), but change to sinistral in the Eocene, recording India’s northward drift. Our latest work has begun to reveal that small continental fragments are present in unexpected places. In the young (max. 9 Ma) plume-related, volcanic island of Mauritius, we found Precambrian zircons with ages between 660 and 3000 Ma, in beach sands and trachytic lavas. This can only mean that a fragment of ancient continent must exist beneath the young volcanoes there, and that the old zircons were picked up by ascending magmas on their way to surface eruption sites. We speculate, based on gravity inversion modelling, that continental fragments may also be present beneath the Nazareth, Saya de Malha and Chagos Banks, as well as the Maldives and Laccadives. These were once joined together in a microcontinent we called “Mauritia”, and became scattered across the Indian Ocean during Gondwana break-up, probably by mid-ocean ridge “jumps”. This work, widely reported in international news media, allows a more refined reconstruction of Gondwana, suggests that continental break-up is far more complex than previously perceived, and has important implications for regional geological correlations and exploration models. Our results, as interesting as they may be, are merely follow-ups that build upon the prescient and pioneering ideas of Alex Du Toit, whose legacy I appreciatively acknowledge.

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Viscosity of Palmas-type magmas of the Paraná Magmatic Province (Rio Grande do Sul State, Brazil): Implications for high-temperature silicic volcanism

et al. 2021

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Age and Petrogenesis of the Doros Complex, Namibia, and Implications for Early Plume-derived Melts in the Paraná–Etendeka LIP

Cited by 25 publications

References 113 publications

Geochemistry of Etendeka magmatism: Spatial heterogeneity in the Tristan-Gough plume head

Geochemistry of Etendeka magmatism: Spatial heterogeneity in the Tristan-Gough plume head

Wandering continents of the Indian Ocean

Viscosity of Palmas-type magmas of the Paraná Magmatic Province (Rio Grande do Sul State, Brazil): Implications for high-temperature silicic volcanism

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