U-series disequilibrium

Wood BJ, Blundy JD, Robinson JAC (1999) The role of clinopyroxene in generating U-series disequilibrium during mantle melting. Geochim Cosmochim Acta 63 1613-1620 Zou H, Zindler A, Niu Y (2002) Constraints on melt movement beneath the East Pacific Rise from °Th- U disequilibrium. Science 295 107-110... 

Villemant B, Boudon G, Komorowski JC (1996) U-series disequilibrium in arc magmas induced by water-magma interaction. Earth Planet Sci Lett 140 259-267 Volpe AM, Hammond PE (1991) U- °Th- Ra disequilibrium in young Mt. St. Helens rocks time constraint for magma formation and crystallization. Earth Planet Sci Lett 107 475-486 Volpe A M (1992) U- °Th- Ra disequilibrium in young Mt. Shasta andesites and dacites. J Volcanol Geotherm Res 53 227-238... 

Alley RB, Mayewski PA, Sowers T, Stuiver M, Taylor KC, Clark PU (1997) Holocene climatic instability A prominent, widespread event 8200 yr ago. Geology 25 483-486 Amelin Y, Zaitsev AN (2002) Precise geochronology of phoscorites and carbonatites The critical role of U-series disequilibrium in age interpretations. Geochim Cosmochim Acta 66 2399-2419 Amundson RG, Chadwick OA, Sowers JM, Doner HE (1988) Relationship between climate and vegetation and the stable carbon isotope chemistry of soils in the eastern Mojave Desert, Nevada. Ouat Res 29 245-254... 

Other conditions being equal, the intermediate species with longer half-lives in a decay series have more opportunities to be fractionated from their parents. Hence, in the decay series of two nuclides °Th and Ra have a greater chance to be fractionated. In the decay series, Pa (half-life 32.8 has the greatest chance to be fractionated. In the Th decay series, all the intermediate species have short half-lives (the longest half-life of Intermediates is 5.75 3T for Ra (A, = 0.1205 3 ) and the disturbance of this decay system does not have much utility. That is, the U-series (including U and U series) disequilibrium is much more often applied. Some examples of disturbed decay chain (i.e., fractionation of the intermediate species) are given below ... 

Feineman M. D. and DePaolo D. J. (2002) A diffusion-decay model for steady-state U-series disequilibrium in the mantle with implications for island arc lavas. EOS, Trans., AGU 83(47) Fall Meet. Suppl. 

Lundstrom CC, Sampson DE, Perfit MR, Gill J, and Williams Q (1999) Insight, into mid-ocean ridge basalt petrogenesis U-series disequilibrium from the Siqueiro, Transform, lamont seamounts, and East Pacific Rise Journal of Geophysical Research 104 13035-13048. 

Fig. 17.49 Tephra from layers of dusty ice adjacent to the Allan Hills have a wide range of chemical compositions. Sites 1 and 2 contain tephra that range from trachyte to dacite in Fig. 17.50, whereas tephra at sites 3 and 4 in the Cul de Sac are composed of basanite and basalt. The ice at sites 3 and 4 in the Cul de Sac yielded U-series disequilibrium dates of 195,000 years (site 3) and 295,(XX) years (site 4). The ice at sites 1 and 2 is distinctly younger at 95,(X)0 years (1) and 85,000 years (2) (Data from Marvin 1990)...

---