Aleutian lead isotopic data: additional evidence for the evolution of lithospheric plumbing systems
Lead isotopic ratios and concentrations have been measured in lavas from the Aleutian volcanic centers of Adak (12) and Atka (12). Lead contents in lavas from Atka increase four-fold over the compositional range of the volcanic suite. In contrast, Adak lavas have concentration levels of 0.6-13 ppm and display no simple correlation with SiO/sub 2/. The lead isotopic data alone can be explained by three different processes. Model 1 assigns lead isotopic differences to original magma source heterogeneity. According to Model 2, the isotopic ratios of a primary, non-radiogenic component from the mantle are elevated by the addition of an isotopically enriched slab-derived component. In contrast, Model 3 assumes a primary radiogenic magma produced by melting of the slab is contaminated by a non-radiogenic lithospheric component during conduit formation. Because these models all adequately explain the lead isotopic data, supplementary geologic, petrographic, geochemical and isotopic data must be used to select the most likely model. Careful consideration of the evidence suggests Model 3 best explains their extensive lead isotopic data as well as other characteristics of Aleutian lavas. The authors study suggests detailed isotopic studies of individual volcanic centers can be extremely useful in understanding the complex processes of magma generation, extraction, ascent and evolution.
- Research Organization:
- Univ. of Wyoming, Laramie (USA)
- OSTI ID:
- 7252263
- Journal Information:
- Geochim. Cosmochim. Acta; (United States), Vol. 51:7
- Country of Publication:
- United States
- Language:
- English
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