The Sr, Nd isotopic composition of lamprophyres in Laowangzhai gold orefield, Yunnan Province

Lamprophyres are widely spread over the Laowangzhai gold orefield in northern Mt. Ailao structure zone, Yunnan Province. Lampmphyres in the orefield are temporally and spatially related to gold mineralization. Lampmphyren in the orefield have anomalous Sr and Nd isotopic compositions, e.g. the87Sr/86Sr ratios (0.706 665–0.707 960, the87Sr/86Sr ratio of sample YLW-44 is 0.709 041) are higher than the modern value of the original mantle (0.704 5), the143Nd/144Nd ration (0.512 463–0.512 551) are lower than the modern value of the original mantle (0.512 638), and the calculated values εSr > 0 (28.1–63.7) and εNd< 0 (- 1.34- -3.07). The results of investigation inete that lampmphyres in the Laowangzhai gold orefield with anomalous Sr and Nd isotopic compositions would not be produced as a result of contamination of the primary magma with the isotopic features of MORB by the crust materials high87Sr/86Sr ratios and low143Nd/144Nd ratios in the ploeaws of rising or in the magma chamber, but the result of metasomatism of source mantle.