The present study deals with peridotites found in the paleo-proterozoic domain of the Leo Man Shield, Séguéla region, west-central of Côte d’Ivoire. Results show that Séguéla peridotites ...The present study deals with peridotites found in the paleo-proterozoic domain of the Leo Man Shield, Séguéla region, west-central of Côte d’Ivoire. Results show that Séguéla peridotites are composed of lherzolites, dunites and harzburgites. However, iherzolites are the most abundant. The phenocrysts in these rocks are olivine most often serpentinised, and pyroxenes, represented by diopside and enstatite. Amphiboles are divided into two groups: magmatic amphiboles and those from the destabilization of clinopyroxene. Spinels have CrO<sub>3</sub> content which varies between 28% and 37%, Al<sub>2</sub>O<sub>3</sub> between 33% - 41% and MgO is equal to 18%;they are poor in TiO<sub>2</sub> and do not contain zinc oxide. Séguéla peridotites are characterised by a negative anomaly in Nb-Ta, associated with an enrichment of lithophilic elements and light rare earth elements with a fractionation rate (La/Yb) which varies between 46.22 and 150.72 and heavy rare earth elements, and HFSE depletion, which may suggest that were formed in an art context, that is, a mantle enriched by fluids from a subduction zone. However, another hypothesis could be considered, that of the interaction between the mantle and magmas in a subduction zone context.展开更多
文摘The present study deals with peridotites found in the paleo-proterozoic domain of the Leo Man Shield, Séguéla region, west-central of Côte d’Ivoire. Results show that Séguéla peridotites are composed of lherzolites, dunites and harzburgites. However, iherzolites are the most abundant. The phenocrysts in these rocks are olivine most often serpentinised, and pyroxenes, represented by diopside and enstatite. Amphiboles are divided into two groups: magmatic amphiboles and those from the destabilization of clinopyroxene. Spinels have CrO<sub>3</sub> content which varies between 28% and 37%, Al<sub>2</sub>O<sub>3</sub> between 33% - 41% and MgO is equal to 18%;they are poor in TiO<sub>2</sub> and do not contain zinc oxide. Séguéla peridotites are characterised by a negative anomaly in Nb-Ta, associated with an enrichment of lithophilic elements and light rare earth elements with a fractionation rate (La/Yb) which varies between 46.22 and 150.72 and heavy rare earth elements, and HFSE depletion, which may suggest that were formed in an art context, that is, a mantle enriched by fluids from a subduction zone. However, another hypothesis could be considered, that of the interaction between the mantle and magmas in a subduction zone context.
