Altermann, W.

Ernst, Richard E.

Kingsbury, C. G.

Söderlund, Ulf

English

Tomsk State University Repository

МИНИСТЕРСТВО НАУКИ И ВЫСШЕГО ОБРАЗОВАНИЯ РОССИЙСКОЙ ФЕДЕРАЦИИНАЦИОНАЛЬНЫЙ ИССЛЕДОВАТЕЛЬСКИЙ ТОМСКИЙ ГОСУДАРСТВЕННЫЙ УНИВЕРСИТЕТ                LARGE IGNEOUS PROVINCES THROUGH EARTH HISTORY: MANTLE PLUMES, SUPERCONTINENTS, CLIMATE CHANGE,  METALLOGENY AND OIL-GAS, PLANETARY ANALOGUES  (LIP – 2019)Abstract volume of the 7 International ConferenceTomsk, Russia, 28 August – 8 September 2019КРУПНЫЕ ИЗВЕРЖЕННЫЕ ПРОВИНЦИИ В ИСТОРИИ ЗЕМЛИ: МАНТИЙНЫЕ ПЛЮМЫ, СУПЕРКОНТИНЕНТЫ, КЛИМАТИЧЕСКИЕ  ИЗМЕНЕНИЯ, МЕТАЛЛОГЕНИЯ, ФОРМИРОВАНИЕ НЕФТИ И ГАЗА,  ПЛАНЕТЫ ЗЕМНОЙ ГРУППЫ (КИП – 2019)Тезисы VII Международной конференцииТомск, Россия 28 августа – 8 сентября 2019644. Khubanov VB, Buyantuev MD, Tsygankov AA. (2016) U–Pb dating of zircons from PZ3 –MZ igneous com-plexes of Transbaikalia by sector-field mass spectrom-etry with laser sampling: technique and comparison with SHRIMP. Russian Geology and Geophysics 57:190-205.5. Litvinovsky B.A., Zanvilevich A.N., Alakshin A.M., Podladchikov Yu.Yu. (1993) The Angara–Vitim Batho-lith, the Largest Granitoid Pluton. Izdatelstvo OIGGM SO RAN, Novosibirsk:143 (in Russian).6. Litvinovsky BA, Tsygankov AA, Jahn BM, Katzir Y, Be’eri-Shlevin Y. (2011) Origin and evolution of over-lapping calc-alkaline and alkaline magmas: The Late Palaeozoic post-collisional igneous province of Trans-baikalia (Russia). Lithos 125:845-8747. Salop L.I. (1967) Geologiya Baikal’skoi gornoi oblasti (Geology of the Baikal Mountain Area). Moscow: Ne-dra. V 2:700 p. (in Russian).8. Tsygankov AA, Burmakina GN, Khubanov VB, Buy-antuev MD. (2017) Geodynamics of Late Paleozoic Batholith-Forming Processes in Western Transbaikalia. Petrology 25:396-418.9. Yarmolyuk V.V., Budnikov S.V., Kovalenko V.I., Anti-pin V.S., Goreglyad A.V., Sal’nikova E.B., Kotov A.B., Kozakov I.A., Kovach V.P., Yakovleva Z.S., Berezhnaya N.G. (1997) Geochronology and geodynamic setting of the Angara-Vitim batholith. Petrology 5(5):401-414.AN IDENTITY CRISIS SOLVED BY U-PB DATING: THE CASE OF THE CEDERBERG DYKE SWARM, WESTERN AND NORTHERN CAPES, SOUTH AFRICA Kingsbury C. G.1, Altermann W. 2, Ernst R. E.3,4, Söderlund U. 51University of Pretoria, Pretoria, South Africa2University of Johannesburg, Johannesburg, South Africa3Carleton University, Ottawa, Canada4Tomsk State University, Tomsk, Russia5University of Lund, Lund, SwedenKeywords: large igneous province, U-Pb baddeleyite, Karoo-Ferrar, Parana-Etendeka.IntroductionThe geologic evolution of South Africa during the Me-sozoic was heavily imprinted with dyke swarms and sill networks representing the plumbing systems of the 183 Ma Karoo-Ferrar Large Igneous Province (“Karoo LIP”) and the c. 50 Myr younger Parana-Etendeka LIP (134 Ma).  These LIPs are thought to be the products of mantle plume heads that were, at the time of their formation, under present-day extreme NE South Africa (Karoo) and the central Namibian coast (Parana-Etendeka). Each of these two magmatic prov-inces are associated in time with the breakup of the supercon-tinent Pangaea (White and McKenzie, 1989).The Cederberg dyke swarm predominantly consists of two parallel, NW-striking mafic dykes in western South Af-rica that are separated by ~50 km (Figs. 1 & 2).  The NW-trend of these dykes extends towards the plume centre of the 134 Ma Parana-Etendeka LIP and therefore could represent the plumbing system of the Parana-Etendeka LIP (Fig. 2). However, the eastern extent of the Cederberg dykes extends into the Karoo Basin, thereby clouding certainty over their origin; they could alternatively represent a western extent of the 183 Ma Karoo LIP in the Namaqualand and Cederberg region.  The purpose  of this study is to test our hypothesis that the Cederberg dykes represent the plumbing system of the 134 Ma Parana-Etendeka LIP and to do so by applying high-precision U-Pb age determinations on baddeleyite. ResultsSample 18CK003 was collected from a dolerite dyke that measures ~90 m in width and strikes 305° (towards the NW). The dyke is exposed as a roadcut along R363, 26 km southwest from Nuwerus in the Western Cape (coordinates 31.356°S, 18.235°E; Figure 1).  Baddeleyite extraction of sample 18CK003 was successful.  U-Pb TIMS dating gave a 206Pb/238U age of 131.4±4.5 Ma  MSWD  of 0.1; Fig. 3), based on two concordant fractions.  Figure 1. Google Earth® map showing (A) the location of where sample 18CK003 was collected. Thin red, NW-trending lines represent mapped dykes of the Cederberg dyke swarm in the vicinity of the sample collection site. (B) Inset map showing the location of sample 18CK003 (white box) relative to South Africa. Key to abbreviations: CT = Cape Town and PTA = Pretoria. 65Figure 2: Distribution of dykes (in red) of the 183 Karoo LIP (after Hastie et al. 2014) and the Cederberg dyke swarm (in green after Figs. 7 and 8 in Ernst and Buchan 1997).    Note that based on their trend, the Cederberg dyke swarm is proposed to be linked to the 134 Ma Parana-Etendeka LIP. Key to select abbreviations and designations: NLDS = Northern Lebombo dyke swarm;  RRDS = Rooi Rand dyke swarm; SLDS = Save-Limpopo dyke swarm; KC = Kaapvaal Craton; ZC = Zimbabwe Craton; 1 = Southern Botswana dyke swarm; 2 = Southern Lesotho dyke swarm.References1. Almeida, V. V, V.A. Janasi, L.M. Heaman, B.J. Shaulis, M.H. Hollanda & P.R. Renne. 2017. Contemporaneous alkaline and tholeiitic magmatism in the Ponta Grossa Arch, Paraná-Etendeka Magmatic Province: Constraints from U–Pb zircon/baddeleyite and 40Ar/ 39Ar phlogo-pite dating of the José Fernandes Gabbro and mafic dykes. J. Volcanol. Geotherm. Res.2. Ernst, R.E. & K.L. Buchan. 1997. Giant radiating dyke swarms: their use in identifying pre-Mesozoic large ig-neous provinces and mantle plumes. AGU Geophysical Monograph, 100: 297–3333. Florisbal, L.M., L.M. Heaman, V.A. Janasi & M.F. Bi-tencourt. 2014. Tectonic significance of the Florianópolis Dyke Swarm, Paraná- Etendeka Magmatic Province: A reappraisal based on precise U – Pb dating. J. Volcanol. Geotherm. Res. 289: 140–150.4. Hastie, W.W., M.K. Watkeys & C. Aubourg. 2014. Magma flow in dyke swarms of the Karoo LIP: Implications for the mantle plume hypothesis. Gondwana Res. 25: 736–755.5. Janasi, V.A., V.A. Freitas & L.H. Heaman. 2011. The onset of flood basalt volcanism, Northern Paraná Basin, Brazil: A precise U – Pb baddeleyite/zircon age for a Chapecó-type dacite. Earth Planet. Sci. Lett. 302: 147–153.6. Pinto, V.M., L.A. Hartmann, J.O.S. Santos, N.J. McNaugh-ton & W. Wildner. 2011. Zircon U – Pb geochronology from the Paraná bimodal volcanic province support a brief eruptive cycle at ~135 Ma. Chem. Geol. 281: 93–102.7. White, R. & D. McKenzie. 1989. Magmatism at Rift Zones : The Generation of Volcanic Continental Mar-gins. J. Geophys. Res. 94: 7685–7729.Figure 3: U-Pb concordia diagram of Sample 18CK003AcknowledgementsThe first author acknowledges the financial support of the DST-NRF Centre of Excellence for Integrated Mineral and Energy Resource Analyses (DST-NRF CIMERA) through a postdoctoral research grant. Opinions expressed and conclu-sions arrived at, are those of the author and are not necessarily to be attributed to the CoE. Additional funding for this study is provided through a NSERC-CRD research grant to R. Ernst # CRDPJ 523131-17. 

An identity crisis solved by U-Pb dating: the case of the Cederberg dyke swarm, Western and Northern Capes, South Africa

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An identity crisis solved by U-Pb dating: the case of the Cederberg dyke swarm, Western and Northern Capes, South Africa

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