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

Ewart, A., Marsh, J.S., Milner, S.C., Duncan, A.R., Kamber, B.S. and Armstrong, R.A. (2004) 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. Journal of Petrology, 45 1: 59-105. doi:10.1093/petrology/egg083


Author Ewart, A.
Marsh, J.S.
Milner, S.C.
Duncan, A.R.
Kamber, B.S.
Armstrong, R.A.
Title 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
Journal name Journal of Petrology   Check publisher's open access policy
ISSN 0022-3530
1460-2415
Publication date 2004-01-01
Sub-type Critical review of research, literature review, critical commentary
DOI 10.1093/petrology/egg083
Volume 45
Issue 1
Start page 59
End page 105
Total pages 47
Place of publication Oxford, United Kingdom
Publisher Oxford University Press
Collection year 2004
Language eng
Subject C1
260300 Geochemistry
Abstract The bimodal NW Etendeka province is located at the continental end of the Tristan plume trace in coastal Namibia. It comprises a high-Ti (Khumib type) and three low-Ti basalt (Tafelberg, Kuidas and Esmeralda types) suites, with, at stratigraphically higher 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 elements and light rare earth elements relative to low-Ti types and exhibit trace element affinities with Tristan da Cunha lavas. The unradiogenic Pb-206/Pb-204 ratios of Khumib basalts are distinctive, most plotting to the left of the 132 Ma Geochron, together with elevated Pb-207/Pb-204 ratios, and Sr-Nd isotopic compositions plotting in the lower Nd-143/Nd-144 part of mantle array (EM1-like). The low-Ti basalts have less coherent trace element patterns and variable, radiogenic initial Sr (similar to0.707-0.717) and Pb isotope compositions, implying crustal contamination. Four samples, however, have less radiogenic Pb and Sr that we suggest approximate their uncontaminated source. All basalt types, but particularly the low-Ti types, contain samples with trace element characteristics (e.g. Nb/Nb-*) suggesting metasediment input, considered source-related. Radiogenic isotope compositions of these samples require long-term isolation of the source in the mantle and depletions (relative to unmodified sediment) in certain elements (e.g. Cs, Pb, U), which are possibly subduction-related. A geodynamic model is proposed in which the emerging Tristan plume entrained subducted material in the Transition Zone region, and further entrained asthenosphere during plume head expansion. Mixing calculations suggest that the main features of the Etendeka basalt types can be explained without sub-continental lithospheric mantle input. Crustal contamination is evident in most low-Ti basalts, but is distinct from the incorporation of a metasedimentary source component at mantle depths.
Keyword Geochemistry & Geophysics
Etendeka Flood Basalts
Lomu-em1 Pb Isotope Signatures
Recycled Crust
Three-component Magma Mixing
Tristan Plume
Plume-lithosphere Interactions
Trace-element Geochemistry
Messum Igneous Complex
Parana Plateau Brazil
Ocean Island Basalts
South-atlantic
Pb-isotope
Northwestern Namibia
Walvis Ridge
Ar-40-ar-39 Geochronology
Q-Index Code C1

Document type: Journal Article
Sub-type: Critical review of research, literature review, critical commentary
Collections: Excellence in Research Australia (ERA) - Collection
School of Earth Sciences Publications
2005 Higher Education Research Data Collection
 
Versions
Version Filter Type
Citation counts: TR Web of Science Citation Count  Cited 69 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 0 times in Scopus Article
Google Scholar Search Google Scholar
Created: Wed, 15 Aug 2007, 14:59:41 EST