Melting plume

The previous chapter described the consequences of a nuclear reactor accident. Chemical process accidents are more varied and do not usually have the energy to melt thick pressure vessels and concrete basemats. The consequences of a chemical process accident that releases a toxic plume, like Bhopal did, are calculated similarly to calculating the dose from inhalation from a radioactive plume but usually calculating chemical process accidents differ from nuclear accidents for which explosions do not occur. 

Bourdon B, Joron J-L, Claude-lvanaj C, Allegre CJ (1998) U-Th-Pa-Ra systematics for the Grande Comore volcanics melting processes in an upwelling plume. Earth Planet Sci Lett 164 119-133... 

Richardson C, McKenzie D (1994) Radioactive diseqtrilibria from 2D models of melt generation by plumes and ridges. Earth Planet Sei Lett 128 425-437... 

MELTING PROCESSES AND RELATION TO CONVECTIVE STRUCTURE OF PLUME... 

Bercovici D, Lin J (1996) A gravity current model of cooling mantle plume heads with temperature dependent buoyancy and viscosity. J Geophys Res 101 3291-3309 Blundy J, Wood B (1994) Prediction of crystal-melt partition coefficients from elastic moduh. Nature 372 452-454... 

Minster JF, Allegre CJ (1978) Systemahc use of trace elements in igneous processes. Part III Inverse problem of batch melting in volcanic suites. Contrib Mineral Pehol 68 37-52 Morgan JW (1971) Convechon plumes in the lower manhe. Nature 230 42-43... 

Ribe NM Smooke MD (1987) A stagnation point flow model for melt extraction from a mantle plume. J Geophys Res 92 6437-6443... 

Vigier N, Bourdon B, Joron J-L, Allegre CJ (1999) U-Th-Ra disequilibria in Ardoukoba tholeiitic basalts (Asal rift) timescales of ciystallization. Earth Planet Sci Lett 174 81-98 Watson S, McKenzie D (1991) Melt generation by plumes a study of Hawaiian volcanism. J Petrol 32 501-537... 

Wendt Jl, Regelous M, Collerson KD, Ewart A (1997) Evidence for a contribution from two mantle plumes to island arc lavas from northern Tonga. Geology 25 611-614 Williams RW, Gill JB (1989) Effects of partial melting on the uranium decay series. Geochim Cosmochim Acta 53 1607-1619... 

A second example is shown in excerpt 13Q. Harpp s proposed work initially involves the collection of held data in two sampling campaigns. Following collection, the samples will be analyzed for trace and major element concentrations and isotopic ratios. In her case, the order in which she conducts these analyses is less important than how she will use the data to answer questions about plume-ridge interaction mechanisms. Thus, she organizes her proposed work (titled Proposed Plan ) not by the tests she will perform, but rather by the types of information the analyzed data will provide (i.e., information about formation mechanisms, melting dynamics, and spatial distributions). 

Year Five Complete analysis of trace elements by ICP-MS at Lawrence University analysis of major elements by XRF at Macalester College (up to 100 samples) determination of Sr, Nd, and Pb isotopic ratios of a selection of Wolf and Darwin samples by TIMS at Cornell (up to 30 samples). Interpretation of geochemical data, modeling of melting parameters. Presentation of results at Fall AGU meeting by undergraduate student(s). Preparation of final plume-ridge interaction synthesis paper for publication with student authors. 

The variable isotopic compositions (especially for Pb) reveal geochemi-cally heterogeneous sources. The origin of this heterogeneity is debated and may derive either from shallow mantle processes, such as variable me-tasomatic modifications of the lithosphere by asthenospheric melts, or from mixing between a deep-mantle plume and asthenosphere-lithosphere material. Etna and Ustica show some trace element and isotopic characteristics (e.g. Rb/Nb, Ce/Pb, and boron isotopes), indicative of a contribution from subduction-derived components. 

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