Triassic alkaline intrusives in the Yanliao-Yinshan area: their chronology, Sr, Nd and Ph isotopic characteristics and their implication

Dated isotopic ages for 15 alkaline intrusives in the Yanliao-Yinshan area, ranging from 268 to 190 Ma, ten of which are from 250 to 208 Ma, indicate that most of them were formed in the Triassic Epoch. All the epsilon(Nd) (t ) ratios from -17.19 to - 3.21 averaging - 7.09, the epsilon(Sr) (t) ratios from 11.7 to 71.5 averaging 36.63, and the I-Sr(t) ratios from 0.705 a to 0.709 3 averaging 0.706 8, show their characteristics of enrichment. On the epsilon(Nd)(t) virus epsilon(Sr)(t) correlation diagram, the samples from these intrusives were plotted within the enriched mantle trend lines and ju st outside, demonstrating their close connection to materials from the enri ched mantle reservoir, taking into account the same Ph isotopic composition as that of the mantle.