Geochemical Constraints from Volcanic Glasses drilled along the Louisville Seamount Trail
Abstract
The geochemical changes observed in long-lived seamount chains can be used to test models on the origin of oceanic intraplate volcanism and the evolution of magmas within a single seamount. Major and trace elements for volcanic glasses along the westernmost 1500 km of the Louisville Seamount trail show that volcanism was geochemically extremely uniform over a period from ~85 Ma to 50 Ma both along-chain and within a single seamount. Here, we present major (including F, S, and Cl), trace and volatile element data measured by electron microprobe, laser ablation inductively coupled mass spectrometry (LA-ICP-MS) and Fourier-transform infrared (FTIR) spectroscopy, respectively, from four guyots that were drilled during IODP Expedition 330. All 55 glass samples analysed are alkalic; most are basalts to tephrites, with a few trachybasalts, and their MgO and SiO2 contents range from 3.5 to 7.3 wt.% and 44.46 to 50.17 wt.%, respectively. The glasses provide no evidence for a tholeiitic shield building stage in the Lousiville guyots, contrary to what is generally observed in the Hawaiian volcanoes. Incompatible element ratios (e.g., Nb/U, Ce/Pb) imply that the glasses are fresh and, unlike published whole rock data (Cheng et al., 1987, Beier et al., revised), display no evidence for significant alteration despite the relatively large age range covered. Rare earth element (REE) ratios (e.g., Ce/Yb, Sm/Yb) from the deepest site drilled during IODP Expedition 330, U1374 at Rigil Guyot, imply that older glasses from deeper than 245 meters below seafloor may have been derived from smaller degrees of partial melting than the younger lavas. However, these changes are small (<1-2% difference in degree of partial melting). Immobile, source sensitive trace element ratios, e.g. La/Yb, Nb/Zr imply an extremely homogenous source over this ~35 Myr period of volcanism. H2O and CO2 concentrations in a subset of the same glass samples are currently being measured to complement the major, particularly F, S and Cl, and trace element data. Beier, C., L. Vanderkluysen, M. Regelous, J. J. Mahoney, and D. Garbe-Schönberg (revised), Lithospheric control on geochemical composition along the Louisville Seamount Chain, Geochem. Geophys. Geosyst., Cheng, Q., K. H. Park, J. D. Macdougall, A. Zindler, G. W. Lugmair, H. Staudigel, J. W. Hawkins, and P. F. Lonsdale (1987), Isotopic evidence for a hotspot origin of the Louisville seamount chain, in Seamounts, islands, and atolls, edited, pp. 283-296, American Geophysical Union, Washington, DC, United States.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.V51E2550B
- Keywords:
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- 1038 GEOCHEMISTRY / Mantle processes;
- 1065 GEOCHEMISTRY / Major and trace element geochemistry;
- 8410 VOLCANOLOGY / Geochemical modeling;
- 8415 VOLCANOLOGY / Intra-plate processes