2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 14-2
Presentation Time: 8:20 AM

LAST 27 MILLION YEARS OF HAWAIIAN PLUME EVOLUTION: HE, SR, ND, PB– ISOTOPES AND TRACE ELEMENT EVIDENCE IN BASALTS FROM NEARLY ONE QUARTER OF THE HOTSPOT TRACK


BASU, Asish R., Department of Earth and Environmental Science, University of Texas at Arlington, 500 Yates St, 107 Geoscience Building, Arlington, TX 76019, FAGGART Jr, Billy E., US Environment Protection Agency, Headquarters, 1200 Pennsylvania Avenue, N.W, William Jefferson Clinton Building, Washington D.C, 20460 and GHOSH, Nilotpal, Department of Earth and Environmental Sciences, University of Rochester, 227, Hutchison Hall, Rochester, NY 14627

We honor Fred Frey for his numerous contributions to igneous petrology and Hawaiian volcanism. We also posthumously recall the contributions of H.Craig and M.Tatsumoto, particularly, for providing the He-isotope and U-Th-Pb systematics data, respectively, for this study.

We report trace elements, Nd, Sr, Pb isotopes in volcanics from Lanai, Molokai, Nihoa, La Perouse, Necker, Kaula Rock, Gardner Seamount and Northampton Bank, and in addition, He-isotopes in Lanai, Molokai, Nihoa, Kaula Rock, Gardner Seamount and Northampton Bank. He-isotopes (R/Ra) range from 8 (mostly in Molokai), through (8.6-17.5) in Nihoa, (12-15.8) in Lanai to (8.6) in Kaula Rock, (12.9) in Gardner Seamount, to (17.0) in Northampton Bank. This data establishes the ubiquity of the high 3He nature of the Hawaiian plume source for the past 27 million years.

Our combined data demonstrate correlated temporal and spatial variations in all the isotopic ratios that also correlate with trace element abundance ratios. Some noteworthy correlations and variations of the He isotope ratios against the Pb, Nd and Sr–isotopes, individually, are as follows: Lanai 206Pb/204Pb is the least radiogenic of all the groups studied, although all Lanai basalts maintain high R/Ra of ~14. The Molokai basalts are MORB like in R/Ra of ~8 and their 206Pb/204Pb ratios range between 18.4-18.6, East Pacific MORB-like, however, their Sr and Nd isotopes are unlike MORB. Nihoa basalts show wide variations in 206Pb/204Pb and restricted ranges in Nd and Sr isotopes. Gardner and Northampton rocks are clearly plume- like in He, Nd and Sr–isotopes, that is unlike MORB, whereas Kaula Rock shows characteristically lower R/Ra of 8.6. In general, although our data are indicative of some spatial and temporal geochemical trend in the plume source, there is no indication of recycled sediment or oceanic crust in the 27 million year history of Hawaiian plume volcanism, for nearly one quarter of its hotspot track.

Session No. 14

T117. Magmas and Their Sources I: A Tribute to the Distinguished Career of Fred Frey
Sunday, 19 October 2014: 8:00 AM-12:00 PM
205/206 (Vancouver Convention Centre-West)
Geological Society of America Abstracts with Programs. Vol. 46, No. 6, p.56
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