Geochemistry of Hawaiian volcanics

The "Ko'olau" component of the Hawaiian mantle plume represents an extreme (EM1-type) end member of Hawaiian shield lavas in radiogenic isotope space, and was defined on the basis of the composition of subaerial lavas exposed in the Makapu'u section of Ko'olau Volcano. The 679 m-deep Ko'olau Scientific Drilling Project (KSDP) allows the long-term evolution of Ko'olau Volcano to be reconstructed and the longevity of the "Ko'olau" component in the Hawaiian plume to be tested. Here, we report triple spike Pb isotope and Sr and Nd isotope data on KSDP core samples, and rejuvenation stage Honolulu Volcanics (HV) (together spanning ~2.8 m.y.), and from ~110 Ma basalts from ODP Site 843, thought to be representative of the Pacific lithosphere under Hawai'i. Despite overlapping ranges in Pb isotope ratios, KSDP and HV lavas form two distinct linear arrays in 208Pb/204Pb-206Pb/204Pb isotope space. These arrays intersect at the radiogenic end indicating they share a common component. This "Kalihi" component has more radiogenic Pb, Nd, Hf, but less radiogenic Sr isotope ratios than the "Makapu'u" component. The mixing proportions of these two components in the lavas oscillated through time with a net increase in the "Makapu'u" component upsection. Thus, the "Makapu'u" enriched component is a long-lived feature of the Hawaiian plume, since it is present in the main shield-building stage KSDP lavas. We interpret the changes in mixing proportions of the Makapu'u and Kalihi components as related to changes in both the extent of melting as well as the lithology (eclogite vs. peridotite) of the material melting as the volcano moves away from the plume center. The long-term Nd isotope trend and short-term Pb isotope fluctuations seen in the KSDP record cannot be ascribed to a radial zonation of the Hawaiian plume: rather, they reflect the short length-scale heterogeneities in the Hawaiian mantle plume. Linear Pb isotope regressions through the HV, recent East Pacific Rise MORB and ODP Site 843 datasets are clearly distinct, implying that no simple genetic relationship exists between the HV and the Pacific lithosphere. This observation provides strong evidence against generation of HV as melts derived from the Pacific lithosphere, whether this be recent or old (100 Ma). The depleted component present in the HV is unlike any MORB-type mantle and most likely represents material thermally entrained by the upwelling Hawaiian plume and sampled only during the rejuvenated stage. The "Kalihi" component is predominant in the main shield building stage lavas but is also present in the rejuvenated HV. Thus this material is sampled throughout the evolution of the volcano as it moves from the center (main shield-building stage) to the periphery (rejuvenated stage) of the plume. The presence of a plume-derived material in the rejuvenated stage has significant implications for Hawaiian mantle plume melting models.

(Table 4) Concentrations of radionuclides in waters of the Barents and Kara Seas in August 2003

A methodology of experimental simulation of state of spent nuclear fuel that occurs on the sea floor due to some catastrophes or dumping is developed. Data on long-term (more than 2000 days) experiments on estimation of 85Kr and 137Cs release rate from spent nuclear fuel (fragments of irradiated UO2 pellets) were firstly obtained; these estimates prove correctness of a hypothesis offered by us in early 1990s concerning to earlier 85Kr release (by one order of magnitude higher than that of 137Cs) as compared to other fission fragments in case of loss of integrity of fuel containment as a result of corrosion on the sea floor. A method and technique of onboard 85Kr and 137Cs sampling and extraction (as well as sampling of tritium, product of triple 235U fission) and their radiometric analysis at coastal laboratories are developed. Priority data on 85Kr background in bottom layers of the Barents and Kara Seas and 137Cs and 3H in these seas (state of 2003) are presented. Models necessary for estimation of dilution of fission products of spent nuclear fuel and their transport on the floor in accident and dumping regions are developed. An experimental method for examination of state of spent nuclear fuel on the sea floor (one expedition each 2-3 years) by 85Kr release into environment (a leak tracer) is proposed; this release is an indicator of destruction of fuel containment and release of products of spent nuclear fuel in case of 235UO2 corrosion in sea water.