Geochemistry of the volcanic rocks from Bioko Island(“Cameroon Hot Line”)： Evidence for plume-lithosphere interaction  

作　　者：Fadimatou Ngounouno Yamgouot Bernard Déruelle Isaac Bertrand Gbambié Mbowou Ismaila Ngounouno Daniel Demaiffe 

机构地区：[1]Departement des Sciences de la Terre, Faculte des Sciences, Universite de Ngaoundere, B.P. 454, Ngaoundere, Cameroon [2]Laboratoire de Magmatologie et Ceochimie lnorganique et Experimentale (MAGIE), Institut de Physique du Globe de Paris, UMR 7154, Universite Pierre et Marie Curie, 4, place Jussieu, 75252, Paris cedex 05, France [3]Departement des Mines et de la Geologie, Ecole de Geologie et d'Exploitation Miniere (EGEM), Universite de Ngaoundere, B.R 115, Meiganga, Cameroon [4]Laboratoire de Geochimie lsotopique et Geodynamique Chimique, DSTE, (CP 160/02) Universite Libre de Bruxelles 50, av. Roosevelt, 1050, Bruxelles,Belgium

出　　处：《Geoscience Frontiers》2016年第5期743-757,共15页地学前缘（英文版）

基　　金：financially supported by the Ministère des Affaires Economiques (Project SGB/ NAT 91-98)

摘　　要：Bioko Island（3008 m a.s.l） is located in the presently more active volcanic zone of the Cameroon Line and composed essentially of alkaline basalts and hawaiites, and lesser mugearites. The rocks show microlitic porphyritic texture with phenocrysts of olivine（83% 〈 Fo 〈 87%） and clinopyroxene in a matrix of plagioclase, clinopyroxene and oxides. Hawaiites and mugearites also include phenocrysts of plagioclase（An62-67Ab35-32Or3-1）. Major element variation diagrams show an increase in Si O2, Al2O3, Na2 O and K2 O with increasing Mg O for the studied rock groups. The rocks are characterized by low（^86Sr/^87Sr）i ratios（0.70320e0.70406）, high 3Nd（t） values（2.56e4.33） and high（^206Pb/^204Pb）i ratios（20.032e20.035） values.Basalts are enriched in LILE and LREE, and have（Hf/Sm）N= 0.57e1.16. These geochemical signatures are similar to those of the Mount Cameroon rocks, and might be attributed to low degrees of partial melting from a garnet-amphibole-bearing mantle source. The trace elements and isotopic compositions suggest that the parental magma source might have involved HIMU- and EM1-components.Bioko Island（3008 m a.s.l） is located in the presently more active volcanic zone of the Cameroon Line and composed essentially of alkaline basalts and hawaiites, and lesser mugearites. The rocks show microlitic porphyritic texture with phenocrysts of olivine（83% 〈 Fo 〈 87%） and clinopyroxene in a matrix of plagioclase, clinopyroxene and oxides. Hawaiites and mugearites also include phenocrysts of plagioclase（An62-67Ab35-32Or3-1）. Major element variation diagrams show an increase in Si O2, Al2O3, Na2 O and K2 O with increasing Mg O for the studied rock groups. The rocks are characterized by low（^86Sr/^87Sr）i ratios（0.70320e0.70406）, high 3Nd（t） values（2.56e4.33） and high（^206Pb/^204Pb）i ratios（20.032e20.035） values.Basalts are enriched in LILE and LREE, and have（Hf/Sm）N= 0.57e1.16. These geochemical signatures are similar to those of the Mount Cameroon rocks, and might be attributed to low degrees of partial melting from a garnet-amphibole-bearing mantle source. The trace elements and isotopic compositions suggest that the parental magma source might have involved HIMU- and EM1-components.

关 键 词：GEOCHEMISTRY HIMU-EM1 Volcanic rocks BIOKO Cameroon Hot Line 

分 类 号：P588.14[天文地球—岩石学] P542.5[天文地球—地质学]