The epsilon Nd (\(\epsilon_{Nd}\)) is a widely used parameter to understand the processes of rock forming, i.e. petrogenetic processes from both geochemical and geochronological approach. By definition, \(\epsilon_{Nd}\) is the difference of \(^{143}Nd/^{144}Nd\) of rock sample and ‘chondritic uniform reservoir’ at the time in the past T. For a rock of age T, \(\epsilon_{Nd}(T)\) is the ‘initial’ value of \(\epsilon_{Nd}\); the value at the time of crystallization of the rock, and \(\epsilon_{Nd}(0)\) is the measured value (dePaolo, 1981). We use the same form as in (dePaolo, 1981) as we will the author’s propose of \(\epsilon_{Nd}\) curve, therefore, the value of \(\epsilon_{Nd}\) is :
\[\epsilon_{Nd}(T)=10^4 \left[ \frac{(^{143}Nd/^{144}Nd)_{rock}(T)}{(^{143}Nd/^{144}Nd)_{CHUR}(T)} -1 \right]\]