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| SCIENCES ET TECHNIQUES [ S.T. ] |
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BIOTERRE |
| Auteurs de l'article |
| M.E. Allialy , S.C. Djro , Y. Coulibaly , A.N. Kouamelan , D.
Yao . A. Pouclet
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| Mots Clés |
| Seguela Kimberlite, Geochemistry, Petrogenesis,
Diamond Potential, Côte d’Ivoire, West Africa
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Num ISSN : 1817-5554 [ Bimestrielle ] |
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Parution N° 1 du 07-07-2010 |
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Volume : 10 de l'année 2010 |
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 Telecharger |
| Comparative geochemistry of seguela cretaceous
kimberlites, south africa group ii kimberlites and
other worldwide kimberlites.
pp. 51-83. |
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| Several altered diamond-bearing kimberlites from Seguela kimberlites complex in Côte d’Ivoire (West Africa) have been investigated to determine their geochemical affinity relative to group II (micaceous) kimberlites of Southern Africa. Comparison is made with other kimberlite occurrences in West Africa and worldwide. Based on major and trace element contents, the Seguela kimberlites show a geochemical signature similar to group II (micaceous) kimberlites of southern Africa and olivine lamproites from Australia. This signature includes high Nb/U (most
samples > 51), moderate Ce/Sr (0.5 - 0.6), Nb/Zr (0.2 - 0.4), P2O5 (22- 37), Ba/Rb (20 - 80), U/Th* (0.1 - 0.6), Ti/K (1- 4), and Nb/La of 0.7 – 5. Compatible elements such as Ni and Cr are somewhat enriched over the average in kimberlite presumably as a result of volume decrease
of the rock caused by leaching of mobile components. Incompatible elements such as Rb, Sr, Ba, La and Ce are strongly depleted relative to the least altered Seguela kimberlite. The degree of alteration varies widely for the studied samples. High La/Yb ratios and high Rb, Sr, Ba,
Nb, indicate that Seguela kimberlites are formed by lower degrees of partial melting. Similarly to Yakutian kimberlites, K2O, Na2O and MgO contents increase while TiO2 and CaO contents decrease as diamond grade increases in Seguela kimberlites. The strongly silica-undersatured
nature, extreme enrichment in compatible elements, fractionated REE patterns and high volatile content of the Seguela kimberlites point toward a metasomatised upper mantle source.
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