Lead isotopic compositions in olivine-hosted melt inclusions from HIMU basalts and possible link to sulfide components

Lead isotope variability in olivine-hosted melt inclusions from Iceland

“…Typical 208 Pb count rates were 15 CPS nA À1 ppm À1 of Pb. These count rates are a factor of 2 lower than those reported for studies of basaltic melt inclusions from intraplate ocean islands (Saal et al, 1998(Saal et al, , 2005Kobayashi et al, 2004;Yurimoto et al, 2004). The reason for this discrepancy is not clear, but may be related to the absence of sulphide phases in the Icelandic glasses: count rates recovered from such phases are known to be higher than those from pure glasses.…”

Lead isotope analysis of melt inclusions by LA-MC-ICP-MS

“…[3][4][5][6] So far, the Pb composition measurement of melt inclusions has been mainly performed using Secondary Ion Mass Spectrometry (SIMS). 3,[6][7][8][9] However, this approach is hampered by very high instrument cost (thus SIMS is not as widespread as LA-ICP-MS), limited analytical machine time for users, and high analysis cost. In recent years, laser ablation multiple-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) has become a powerful alternative method, as it can conduct in situ isotope analyses rapidly and at lower cost than SIMS.…”

Origin of hotspots in the South Pacific: Recent advances in seismological and geochemical models

“…In comparison with the Hawaiian case, this may be explained by a radially zoned mantle plume with a central zone consisting of material from the EM2 reservoir in the deep mantle and an outer rim containing entrained depleted asthenospheric material. The early and main shield stage lavas were derived from the hot central zone, whereas the late stage lavas were derived from the beyond the Pb isotopic range of the host lavas, extending from HIMU-like composition toward a composition more similar to a depleted mantle source (Saal et al, 1998(Saal et al, , 2005Yurimoto et al, 2004). Saal et al (2005) preferred a model in which the depleted melt is derived from oceanic lithosphere.…”

“…However, it must be noted that there are other possible interpretations. Yurimoto et al (2004) proposed an alternative scenario based on their findings that sulfiderich inclusions always exhibit the most radiogenic Pb isotopes, whereas silicate inclusions show wide isotopic variation. Because sulfide fractionation must occur continuously and simultaneously with olivine fractionation in HIMU magmas, lack of sulfide-rich inclusions with less-radiogenic Pb isotopes is not indicative of the incorporation of lithospheric melt into the magmas.…”

“…Because sulfide fractionation must occur continuously and simultaneously with olivine fractionation in HIMU magmas, lack of sulfide-rich inclusions with less-radiogenic Pb isotopes is not indicative of the incorporation of lithospheric melt into the magmas. Yurimoto et al (2004) suggested that the depleted melt trapped in melt inclusions can be derived from the mantle plume along with the HIMU melt. In fact, such Pb isotopic heterogeneity recorded in melt inclusions has been recently contested by Paul et al (2011); thus, further studies are required to assess possible small-scale geochemical heterogeneity in OIB.…”