Skip Navigation

This Article
Right arrow Full Text Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrow Search for citing articles in:
ISI Web of Science (14)
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by TRUMBULL, R. B.
Right arrow Articles by VOLKER, F.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

Journal of Petrology | Volume 44 | Number 1 | Pages 93-112 | 2003
© Oxford University Press 2003

The Petrology of Basanite–Tephrite Intrusions in the Erongo Complex and Implications for a Plume Origin of Cretaceous Alkaline Complexes in Namibia

R. B. TRUMBULL1,*, B. BÜHN2,{dagger}, R. L. ROMER1 and F. VOLKER2

1GEOFORSCHUNGSZENTRUM POTSDAM, TELEGRAFENBERG, 14473 POTSDAM, GERMANY
2INSTITUT FÜR GEOWISSENSCHAFTEN UND LITHOSPHÄRENFORSCHUNG, UNIVERSITÄT GIESSEN, 35390 GIESSEN, GERMANY

Basanite intrusions from the Early Cretaceous Erongo complex, Namibia, have compositions consistent with near-primary mantle melts derived from a depth of at least 100 km. These rocks provide a key reference for the mantle component(s) involved in breakup-related magmatism in this region. Initial Sr–Nd–Pb isotope ratios of the Erongo basanites and associated tephrites and phonotephrites (87Sr/86Sr = 0·70425–0·70465; {epsilon}Nd = +1·8 to +2·7; 206Pb/204Pb = 18·63–18·91) are independent of the degree of differentiation and correspond closely to an estimated range for the Tristan plume at 130 Ma. Incompatible trace element ratios also overlap with ratios of ocean island basalt (OIB) from the South Atlantic islands of Tristan da Cunha, Gough and Inaccessible associated with the modern Tristan hotspot. The Tristan plume signature of Erongo basanite–tephrite intrusions is shared by at least six other Early Cretaceous mafic alkaline complexes in Namibia, whereas the associated flood basalts in general lack a plume signature. We attribute the contrast in mantle sources for the flood basalts and alkaline complexes to their relative timing with respect to lithospheric thinning. Thick lithosphere during the main flood basalt event prevented direct melting of the Tristan plume and magmas were generated mostly from the lithosphere. The alkaline complexes intruded later, when the lithosphere was sufficiently thinned to allow decompression melting of the underlying plume mantle.

KEY WORDS: Sr–Nd–Pb isotopes; Namibia; plume; basanite; petrogenesis


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?


This article has been cited by other articles:


Home page
 South African Journal of GeologyHome page
R. B. Trumbull, D. L. Reid, C. de Beer, D. van Acken, and R. L. Romer
Magmatism and continental breakup at the west margin of southern Africa: A geochemical comparison of dolerite dikes from northwestern Namibia and the Western Cape
South African Journal of Geology, September 1, 2007; 110(2-3): 477 - 502.
[Abstract] [Full Text] [PDF]


Disclaimer: Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.