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GEOREF RECORD

Geochemical provinciality in the Cretaceous basaltic magmatism of northern Madagascar; mantle source implications

L. Melluso, V. Morra, P. Brotzu, L. Franciosi, A. M. Petteruti Lieberknecht and L. Bennio
Geochemical provinciality in the Cretaceous basaltic magmatism of northern Madagascar; mantle source implications
Journal of the Geological Society of London (May 2003) 160 (3): 477-488

Abstract

The northern part of the Late Cretaceous flood-basalt province of Madagascar is formed by lava flows, dykes and intrusive complexes. These range from tholeiitic to weakly alkaline and have composition from basalts to basaltic andesites (with rare, more evolved, rocks). The magmatic evolution is dominated by low-pressure crystal fractionation of olivine, Cr-spinel, plagioclase and clinopyroxene. The erupted rocks form two subprovinces, in terms of incompatible element concentrations or ratios and geographical position. The mafic and intermediate samples from the western subprovince have low abundances of high field strength elements (e.g. Nb 2-9 ppm; Zr 50-230 ppm), negative Nb anomalies on mantle-normalized diagrams, and a wide range of initial (88 Ma) (super 143) Nd/ (super 144) Nd (0.51293-0.51197; epsilon Nd +7.9 to -10.9). These elemental and isotopic variations are compatible with melting of predominantly N-MORB-like mantle and variable low-pressure crustal contamination. The mafic samples of the eastern subprovince are mildly enriched in incompatible elements (e.g. Nb 6-25 ppm; Zr 109-330 ppm), with the highest values found in tholeiites from the east Mahajanga basin, Tampoketsa Kamoreen and Tamatave. They also have a comparatively narrow range of initial (super 143) Nd/ (super 144) Nd (0.51276-0.51258; epsilon Nd +5.1 to +1.0), consistent with derivation from incompatible element enriched mantle sources and minor subsequent crustal contamination. The marked differences in the chemical and isotopic characteristics of the samples imply variable degrees of partial melting of hotter than normal, chemically heterogeneous, mantle sources at pressures where spinel to garnet are residual phases. No clear evidence is seen for a chemical component similar to that represented at present by the Marion hotspot lavas.


ISSN: 0016-7649
EISSN: 2041-479X
Coden: JGSLAS
Serial Title: Journal of the Geological Society of London
Serial Volume: 160
Serial Issue: 3
Title: Geochemical provinciality in the Cretaceous basaltic magmatism of northern Madagascar; mantle source implications
Affiliation: Universita di Napoli Federico II, Dipartimento di Scienze della Terra, Naples, Italy
Pages: 477-488
Published: 200305
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 34
Accession Number: 2003-042100
Categories: Geochemistry of rocks, soils, and sedimentsIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 plate, 2 tables, geol. sketch map
S19°00'00" - S14°00'00", E44°00'00" - E51°00'00"
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 200313
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