TY - JOUR

T1 - A five million year record of compositional variations in mantle sources to magmatism on Santiago, southern Cape Verde archipelago

AU - Barker, Abigail K.

AU - Holm, Paul Martin

AU - Peate, David W.

AU - Baker, J.

PY - 2010

Y1 - 2010

N2 - High-precision Pb isotope data and Sr-Nd-Hf isotope data are presented together with major and trace element data for samples spanning the 4.6 Ma history of volcanism at Santiago, in the southern Cape Verde islands. Pb isotope data confirm the positive ¿8/4 signature of the southern islands indicating that the north-south compositional heterogeneity in the Cape Verde archipelago has persisted for at least 4.6 Ma. The Santiago volcanics show distinct compositional differences between the old, intermediate and young volcanics, and suggest greater involvement of an enriched mantle (EM1)-like source over time. Isotopic variations in the Santiago volcanics indicate convergence towards a homogeneous EM1-like end-member and distinct temporal variations in the FOZO-like end-member. Santiago and Santo Antão (a northern island, Holm et al. 2006), show a simultaneous decrease in 208Pb/204Pb of the high 206Pb/204Pb FOZO-like source with time. Such systematic archipelago-wide variations in the FOZO-like component suggest that this component is more likely to be present as a coherent package of recycled ocean crust rather than as multiple small heterogeneities dispersed in the upwelling mantle. The temporal variations in 208Pb/204Pb reflect minor lateral variations in Th/U of this recycled ocean crust package entering the melting zone beneath the islands. The location of the EM1-like component is more equivocal. A shallow lithospheric location is possible, but this would require a coincidence between spatial compositional variations in the lithosphere (EM1 is spatially restricted to the southern islands) and flow lines in the upwelling mantle revealed by seismic anisotropy. Therefore, we favour a deeper asthenospheric mantle source for the EM1-like source

AB - High-precision Pb isotope data and Sr-Nd-Hf isotope data are presented together with major and trace element data for samples spanning the 4.6 Ma history of volcanism at Santiago, in the southern Cape Verde islands. Pb isotope data confirm the positive ¿8/4 signature of the southern islands indicating that the north-south compositional heterogeneity in the Cape Verde archipelago has persisted for at least 4.6 Ma. The Santiago volcanics show distinct compositional differences between the old, intermediate and young volcanics, and suggest greater involvement of an enriched mantle (EM1)-like source over time. Isotopic variations in the Santiago volcanics indicate convergence towards a homogeneous EM1-like end-member and distinct temporal variations in the FOZO-like end-member. Santiago and Santo Antão (a northern island, Holm et al. 2006), show a simultaneous decrease in 208Pb/204Pb of the high 206Pb/204Pb FOZO-like source with time. Such systematic archipelago-wide variations in the FOZO-like component suggest that this component is more likely to be present as a coherent package of recycled ocean crust rather than as multiple small heterogeneities dispersed in the upwelling mantle. The temporal variations in 208Pb/204Pb reflect minor lateral variations in Th/U of this recycled ocean crust package entering the melting zone beneath the islands. The location of the EM1-like component is more equivocal. A shallow lithospheric location is possible, but this would require a coincidence between spatial compositional variations in the lithosphere (EM1 is spatially restricted to the southern islands) and flow lines in the upwelling mantle revealed by seismic anisotropy. Therefore, we favour a deeper asthenospheric mantle source for the EM1-like source

U2 - 10.1007/s00410-009-0470-x

DO - 10.1007/s00410-009-0470-x

M3 - Journal article

VL - 160

SP - 133

EP - 154

JO - Contributions to Mineralogy and Petrology

JF - Contributions to Mineralogy and Petrology

SN - 0010-7999

IS - 1

ER -