Ta'u and Ofu/Olosega volcanoes : the “Twin Sisters” of Samoa, their P, T, X melting regime, and global implications
MetadataShow full item record
The Samoan islands of Ta'u and Ofu/Olosega (Ofol hereafter) are single shield volcanoes that have erupted alkali basalt for the past 70 and 440 kyr, respectively. They are 20 km apart, and are the easternmost subaerial expressions of the Samoan plume. The isotopic data for these islands are published; we report here the first major and trace element data for Ofol. The two islands are similar isotopically and in trace elements. Their high 3He/4He marks them as being a FOZO mantle end-member. By comparing data from both volcanoes, we test the efficacy of melting models in constraining the mantle compositions and their P-T of melting. We show that the mantle sources are similar, with spidergrams that peak at Ta (4× BSE), and Lu ∼0.5× BSE. Melts and mantle sources both have Lu/Hf ratios that are too low to support measured 176Hf/177Hf ratios, pointing to a young enrichment event in the mantle source. Degrees of melting are 6.5% for Ta'u and 5.2% for Ofol. P-T of melting show a wide, overlapping range, but define a precise array; average values are 1475°C—77 km for Ta'u and 1550°C—110 km for Ofol. The deepest P-T estimate is 4.2 GPa and 1550°C. The P-T array is either a melting adiabat, or a mixing line of melts equilibrated at various depths. Kinetic modeling shows melt re-equilibration will be likely for ascent velocities (m/yr) less than 40/(conduit radius in cm)2. P-T estimates for melting may typically be minimum values.
Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 15 (2014): 2301–2318, doi:10.1002/2013GC005221.
Showing items related by title, author, creator and subject.
Volatile and trace elements in basaltic glasses from Samoa : implications for water distribution in the mantle Workman, Rhea K.; Hauri, Erik H.; Hart, Stanley R.; Wang, Jianhua; Blusztajn, Jerzy S. (2005-10-24)We report volatile (H2O, CO2, F, S, Cl) and trace element data for submarine alkalic basalt glasses from the three youngest Samoan volcanoes, Ta’u, Malumalu and Vailulu’u. Most samples are visibly sulfide saturated, so ...
Volatile cycling of H2O, CO2, F, and Cl in the HIMU mantle : a new window provided by melt inclusions from oceanic hot spot lavas at Mangaia, Cook Islands Cabral, Rita A.; Jackson, Matthew G.; Koga, Kenneth T.; Rose-Koga, Estelle F.; Hauri, Erik H.; Whitehouse, Martin J.; Price, Allison A.; Day, James M. D.; Shimizu, Nobumichi; Kelley, Katherine A. (John Wiley & Sons, 2014-11-28)Mangaia hosts the most radiogenic Pb-isotopic compositions observed in ocean island basalts and represents the HIMU (high µ = 238U/204Pb) mantle end-member, thought to result from recycled oceanic crust. Complete geochemical ...
Distribution of recycled crust within the upper mantle : insights from the oxygen isotope composition of MORB from the Australian-Antarctic Discordance Cooper, Kari M.; Eiler, John M.; Sims, Kenneth W. W.; Langmuir, Charles H. (American Geophysical Union, 2009-12-03)Geochemical heterogeneity within the mantle has long been recognized through the diversity of trace element and radiogenic isotopic compositions of mantle-derived rocks, yet the specific origin, abundance, and distribution ...