The Role of Continental Crust and Lithospheric Mantle in the Genesis of Cameroon Volcanic Line Lavas: Constraints from Isotopic Variations in Lavas and Megacrysts from the Biu and Jos Plateaux |
| |
| Authors: | RANKENBURG K; LASSITER J C; BREY G |
| |
| Institution: | 1 MAX-PLANCK-INSTITUT FÜR CHEMIE, ABT. GEOCHEMIE, POSTFACH 3060, 55020 MAINZ, GERMANY
2 INSTITUT FÜR MINERALOGIE, SENCKENBERGANLAGE 28, 60054 FRANKFURT/MAIN, GERMANY |
| |
| Abstract: | We present a combined Sr, Nd, Pb and Os isotope study of lavasand associated genetically related megacrysts from the Biu andJos Plateaux, northern Cameroon Volcanic Line (CVL). Comparisonof lavas and megacrysts allows us to distinguish between twocontamination paths of the primary magmas. The first is characterizedby both increasing 206Pb/204Pb (19·82–20·33)and 87Sr/86Sr (0·70290–0·70310), and decreasing Nd (7·0–6·0), and involves addition of anenriched sub-continental lithospheric mantle-derived melt. Thesecond contamination path is characterized by decreasing 206Pb/204Pb(19·82–19·03), but also increasing 87Sr/86Sr(0·70290–0·70359), increasing 187Os/188Os( 0·130–0·245) and decreasing Nd (7·0–4·6),and involves addition of up to 8% bulk continental crust. Isotopicsystematics of some lavas from the oceanic sector of the CVLalso imply the involvement of a continental crustal component.Assuming that the line as a whole shares a common source, wepropose that the continental signature seen in the oceanic sectorof the CVL is caused by shallow contamination, either by continent-derivedsediments or by rafted crustal blocks that became trapped inthe oceanic lithosphere during continental breakup in the Mesozoic. KEY WORDS: crustal contamination; CVL; megacrysts; ocean floor; osmium isotopes |
| |
| Keywords: | : crustal contamination CVL megacrysts ocean floor osmium isotopes |
| 本文献已被 Oxford 等数据库收录！ |
|
