Dating disequilibrium

Pyle D, Ivanovich M, Sparks RSJ (1988) Magma-cumulate mixing identified by U-Th disequilibrium dating. Nature 331 157-159... 

Rubin KH, Macdougall JD (1990) Dating of neovolcanic MORE using ( Ra/ °Th) disequilibrium. Earth Planet Sci Lett 101 313-322... 

Poll S, Schmidt MW (1995) H2O transport and release in subduction zones experimental constraints on basaltic and andesitic systems. J Geophys Res 100 22,299-22,314 Pyle DM, Ivanovich M, Sparks RSJ (1988) Magma-cumulate mixing identified by U-Th disequilibrium dating. Nature 331 157-159... 

Uranium-series dating is by far the most widely-used dating technique applied to speleothems, and is only applicable to material that is currently in a state of disequilibrium. Given the rates of ingrowth of daughter isotopes of Pa and °Th, conditions of uranium-series disequilibrium in systems which have remained isotopically-closed are generally restricted to materials < 500 ka... 

Schwarcz HP, Bietti A, Buhay WM, Stiner M, Griin R, Segre E (1991) On the reexamination of Grotta Guattari Uranium series and ESR dates. Current Anthro 32 313-316 Schwarcz HP, Blackwell BA (1992) Archaeological applications. In Uranium Series Disequilibrium Applications to Earth, Marine and Enviromnental Sciences. Ivanovich M, Harmon RS (eds) Clarendon, Oxford, p. 513-552... 

Blackwell B. A. and H. P. Schwarcz (1995), The uranium series disequilibrium dating methods, in Rutter, N. W. and N. R. Catto (eds.), Dating Methods for Quaternary Deposits, Geotext 2, Geological Association of Canada. 

Figure 5-4 Dating sediment using U-disequilibrium series.

The a-particle counting method has been widely used in U-Th disequilibrium series studies (Vdovenko and Dubasov, 1974 Ivanovich and Harmon, 1992). However, recent developments in TIMS have greatly improved the analytical precision and sample size requirements (Chen et al., 1986 Edwards et al., 1987). Certain samples that could not be dated with a counting can now be measured precisely. The use of electrostatic filters or deceleration lenses has greatly improved the abundance sensitivity of TIMS (Cohen et al., 1992), so that ratios of 10 5-10-6 for 230Th/232Th can now be accurately measured. 

Racemization Dating of Shell from Interglacial Marine Terraces in San Diego County. Numerous fossiliferous terrace deposits occur along the coast of San Diego County. Only one reliable date has been reported for these terraces a uranium-disequilibrium age of 120,000 10,000 years on coral for a locality on Point Loma in San Diego (50). This and... 

Ages deduced by using as a calibration the mean alleu/iso ratio (0363) and a uranium disequilibrium date of 120,000 10,000 years 50) at SDSU 2577 to calculate /ciso = 3.0 X 10-6 yr-i. 

Condomines M. (1997) Dating recent volcanic rocks through disequilibrium in accessory minerals example of the Puy de Dome (French Massif Central). Geology 25, 375-378. 

Any disturbance from secular equilibrium decays back toward secular equilibrium through the decay of the shorter-lived supported chains. If the chains have significantly different decay rates, they are reasonably well decoupled and can be used to date processes comparable to the lifetimes of each chain (e.g., Condomines et al., 1988 Rubin et al., 1994 Thompson et al., 2003). As a useful rule of thumb, the time taken for a parent-daughter pair to return to approximate secular equilibrium, is about five half-lives of the shorter lived nuclide. In five half-lives, —97% of initial disequilibrium has decayed. Whether any detectable disequilibrium actually remains depends on the precision of measurements and degree of initial disequilibrium. 

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