- abstract:
We present major and trace element concentrations and Sr-Nd-Hf-Pb isotope data for the c. 13-2 Ma Tertiary lavas from eastern Iceland. Our new geochemical results, together with published geological, geochronological, geochemical and geophysical data, are used to evaluate temporal changes in mantle sources contributing to the Tertiary Icelandic magmatism and the relative roles of these sources in magma productivity. The trace element and radiogenic isotopic compositions clearly distinguish three distinct end-member components in the Tertiary magmatism. Temporal variations in lava geochemistry can be attributed to changes in the relative contributions of these three end-member components to the erupted magmas and correlated with temporal variations in magma productivity. The extrusion of lavas with geochemically and isotopically enriched compositions was particularly pronounced at ~13-12 and 8-7 Ma, coincident in time with higher magma productivity. However, the geochemical characteristics of the lavas are different during these two periods: the 13-12 Ma lavas have more radiogenic 176Hf/177Hf and less radiogenic 206Pb/204Pb than those erupted from 8 to 7 Ma. The eruption of relatively depleted lavas, at around 10 Ma and younger than 6.5 Ma, is coincident with lower magma productivity. The correlation between the composition and productivity of the Tertiary lavas from eastern Iceland is probably due to periodic changes in the involvement of the enriched end-member component, followed by a gradation to periods dominated by the signature of the depleted end-member component and lower magma productivity, at an approximate frequency of 5 Myr.
- summary:
The data presented in this study provide an 11 Myr record of temporal geochemical variations in Icelandic magmatism from 13 to 2 Ma, and yield constraints on the characteristics of the mantle end-member components involved in this magmatism. Temporal variations in the lava geochemistry can be explained by changes in the relative contributions from three mantle end-member components (E-1, E-2 and D), each with distinct geochemical characteristics. The temporal geochemical variations in the Tertiary lavas are well correlated with magma productivity: higher magma productivity is associated with the eruption of geochemically more enriched lavas, whereas lower magma productivity is coincident with the emplacement of less enriched lavas. Correspondence between productivity and the compositions of the Tertiary Icelandic lavas could be due to the periodic entrainment of recycled crustal lithologies into the Iceland plume at its source.
- doi: 10.1093/petrology/egn029
- modified at 9 h ago
@article{20081202172326.hkitagawa,
author = "Kitagawa, H. and Kobayashi, K. and Makishima, A. and Nakamura, E.",
title = "Multiple pulses of the mantle plume: Evidence from Tertiary Icelandic lavas",
journal = "Journal of Petrology",
year = "2008",
number = "7",
month = "July",
volume = "49",
pages = "1365-1396",
note = "ISI:000257414700005",
doi = "10.1093/petrology/egn029",
}