The Sr-Nd isotopic compositions of

The Sr-Nd isotopic compositions of the Tubagou basalts from the study area are presented in Table 3 and plotted in Fig. 7. Type I has a small range of age-corrected 87Sr/86Sr ratios of 0.70526 to 0.70554 and positive and uniform εNd(t) (t=257Ma) values between +2.4 and+2.9. On the other hand, εNd(t) (t=257Ma) values (+1.8 to +2.2) of Type II are slightly lower than those of Type I, and Type II displays a relatively larger variation and higher 87Sr/86Sr(i) ratios of 0.70545 to 0.70828.On the 87Sr/86Sr(i) vs. εNd(t) diagram(Fig. 7), with the exception of one sample (TBG11), the Tubagou basalts overlap the fields of the Emeishan basalts and Siberian Traps. Type I data lie within the field of OIB, whereas most of Type II display much higher 87Sr/86Sr(i) than OIBs. However, the Tubagou basalts apparently deviate fromthe high-εNd(t) and low-87Sr/86Sr(i) end of severalmodern Indian Ocean hotspots and some Pacific ‘C-type’ hotspots (Hanan and Graham, 1996).