Basaltic flows and sills occur in the Gedo region and in the Shebelle valley (Buulobarde area) of the western-central part of Somalia. These basalts have a subalkaline-transitional tholeiitic character but, on the basis of geochemical and isotope data, three different types can be evidenced. The basalts of Gedo region along the Juba river, from Luuq to Baardheere, are different from those of the Laaf Maakada plateau due to their slightly higher SiO2 and lower FeOt and TiO2 contents, alkalis and Mg values being almost equivalent. The Webe Shebelle basalts, as indicated by their lower Mg values, can be classified as more evolved rocks; they also exhibit slightly higher TiO2 content. The different groups cannot have been derived by simple fractionation processes, as indicated by the87Sr/86Sr isotope composition which ranges from 0.70388 to 0.70530. These variations are correlated with Rb and K2O values, suggesting a crustal contamination process. The Laaf Maakada basalts, characterized by the lowest SiO2, Rb, K2O contents and minimum87Sr/86Sr value, may represent the less contaminated products.
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|Titolo:||Flood basalts in the Gedo region (Southern Somalia): geology, petrology and isotopic geochemistry|
|Citazione:||Carmignani, L., ALI KASSIM, M., Fantozzi, P., Ferrara, G., Tonarini, S., Bellieni, G., et al. (1992). Flood basalts in the Gedo region (Southern Somalia): geology, petrology and isotopic geochemistry. ATTI DELLA ACCADEMIA NAZIONALE DEI LINCEI. RENDICONTI LINCEI. SCIENZE FISICHE E NATURALI, 3(4), 311-334.|
|Appare nelle tipologie:||1.1 Articolo in rivista|