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Petrology and Geochemistry of Early Cretaceous Bimodal Continental Flood Volcanism of the NW Etendeka, Namibia. Part 1: Introduction, Mafic Lavas and Re-evaluation of Mantle Source Components |
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| Authors: | EWART A; MARSH J S; MILNER S C; DUNCAN A R; KAMBER B S; ARMSTRONG R A |
| Institution: | 1 ADVANCED CENTER FOR QUEENSLAND UNIVERSITY ISOTOPE RESEARCH EXCELLENCE (ACQUIRE), THE UNIVERSITY OF QUEENSLAND, ST. LUCIA, QLD. 4072, AUSTRALIA 2 DEPARTMENT OF GEOLOGY, RHODES UNIVERSITY, GRAHAMSTOWN 6140, SOUTH AFRICA 3 PANALYTICAL, LELYWEG 1, 7602EA ALMELO, THE NETHERLANDS 4 DEPARTMENT OF GEOLOGICAL SCIENCES, UNIVERSITY OF CAPE TOWN, RONDEBOSCH 7700, SOUTH AFRICA 5 RESEARCH SCHOOL OF EARTH SCIENCES, THE AUSTRALIAN NATIONAL UNIVERSITY, CANBERRA, A.C.T. 0200, AUSTRALIA |
| Abstract: | The bimodal NW Etendeka province is located at the continentalend of the Tristan plume trace in coastal Namibia. It comprisesa high-Ti (Khumib type) and three low-Ti basalt (Tafelberg,Kuidas and Esmeralda types) suites, with, at stratigraphicallyhigher level, interstratified high-Ti latites (three units)and quartz latites (five units), and one low-Ti quartz latite.Khumib basalts are enriched in high field strength elementsand light rare earth elements relative to low-Ti types and exhibittrace element affinities with Tristan da Cunha lavas. The unradiogenic206Pb/204Pb ratios of Khumib basalts are distinctive, most plottingto the left of the 132 Ma Geochron, together with elevated 207Pb/204Pbratios, and Sr–Nd isotopic compositions plotting in thelower 143Nd/144Nd part of mantle array (EM1-like). The low-Tibasalts have less coherent trace element patterns and variable,radiogenic initial Sr ( |
| Keywords: | : Etendeka flood basalts LOMU– EM1 Pb isotope signatures recycled crust three-component magma mixing Tristan plume |
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