L. Edwards R. M. Mellors D. M. Pyle R. S. J. Sparks Marvin A. Lanphere M. Davies B. Barreirio T. H. Druitt 1999 <p><span>Disequilibria between the short-lived radioactive nuclides&nbsp;</span>²²⁶<span>Ra,&nbsp;</span>²³⁰<span>Th and&nbsp;</span>²³⁸<span>U in young volcanic rocks can be used both for dating the time of crystallisation of a rock, and as isotopic tracers of the sources of magmas and the chemical evolution of volcanic systems. The principles of these methods have been reviewed extensively elsewhere (Condomines&nbsp;</span><i>et al</i><span>. 1988; Gill&nbsp;</span><i>et al</i><span>. 1992; Gill &amp; Condomines 1992; Macdougall 1995). In this chapter, we present new&nbsp;</span>²³⁸<span>U-</span>²³⁰<span>Th-</span>²²⁶<span>Ra disequilibria data for the Thera pyroclastics and for selected lavas. These data complement the radiogenic isotopic data presented in Chapter 6 on the compositional evolution through time of the pyroclastic ejecta. In particular, we find that the (</span>²³⁰<span>Th/</span>²³²<span>Th) isotopic ratio corrected to the time of eruption varies in a systematic way with time through the second cycle of the Thera pyroclastics and variations in this ratio are correlated with the variations of&nbsp;</span>⁸⁷<span>Sr/</span>⁸⁶<span>Sr,&nbsp;</span>¹⁴³<span>Nd/</span>¹⁴⁴<span>Nd and Pb isotopes.</span></p> application/pdf 10.1144/GSL.MEM.1999.019.01.07 en Geological Society of London Chapter 7: Studies of short-lived radionuclides in Santorini volcanics article