The dynamic evolution of the Iceland mantle plume: the lead isotope perspective

Details The dynamic evolution of the Iceland mantle plume: the lead isotope perspective The dynamic evolution of the Iceland mantle plume: the lead isotope perspective

Sep 1997

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997e%26psl.151...43h&link_type=abstract

Earth and Planetary Science Letters, Volume 151, Issue 1-2, p. 43-60.

Computer Science

22

Scientific paper

We report Pb isotope compositions of 42 Tertiary basalts from two widely separated paleo-rift zones from eastern and western Iceland spanning the age range 15.3-2.7 Ma. These samples have previously been well characterized in terms of major and trace element compositions, igneous and zeolite metamorphic petrography, K/Ar ages, and paleo-magnetostratigraphy. The Pb isotope temporal variation is smooth and cyclic. A maximum in radiogenic Pb is observed around 7-8 Ma, which is coincident in time with maxima in the volcanic production rates on Iceland and along the Reykjanes Ridge. In Pb isotope space the Iceland Tertiary basalts do not fit a binary mixing model between the depleted MORB source and a single radiogenic plume source, as previously suggested by La/Sm and 87Sr/86Sr variations. A third EM-I type component, apparently entrained by the 206Pb-rich plume, is suggested. We show that the discrepancy simply reflects that the La/Sm, 87Sr/86Sr (and 143Nd/144Nd) of the two enriched plume components proposed are too similar to be resolvable in ternary mixtures containing a significant fraction of the depleted MORB mantle source (i.e. a third component). We also show that the contribution of the radiogenic Pb-rich plume component positively correlates with the lava production rate. The cyclicity in Pb isotope composition is consistent with a pulsating or blob-like plume interacting with the asthenospheric flow related to the Mid-Atlantic ridge spreading plate boundary.

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