中央アジア造山帯の多重脈捕獲岩が示す沈み込みマントル交代作用の同位体的証拠

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Trace element composition (SIMS and ID-TIMS) and isotopic ratios of Sr and Nd (ID-TIMS) were determined for four gabbro intrusions, three veined mantle xenoliths, and host lamprophyre from the Sangilen Highland. Mineralogical and geochemical study of veined xenoliths shows existence of infiltration and diffusion zoning near the amphibole-phlogopite-clinopyroxene-vein and absence of any zoning near the amphibole-veins. The presence of metasomatic profile near the amphibole-phlogopite-clinopyroxene-vein indicates on their recent formation (shortly before entrainment into the host camptonites). The alignment of metasomatic profile in the host peridotite near the amphibole-vein requires a more prolonged period of time. Initial isotopic 87Sr/86Sr and 143Nd/144Nd ratios for the phlogopite-clinopyroxene-vein (0.70274±2 and 0.51243±14, respectively) calculated by isochrone method and host camptonite 87Sr/86Sr (0.702715±3) and 143Nd/144Nd (0.512399±1) calculated at 444 Ma indicate similar isotopic sources for both melts. Initial isotopic 87Sr/86Sr and 143Nd/144Nd ratios of the Pravotarlashkin gabbro massif (494.6 Ma; 0.703706±10 and 0.512257±2, respectively) and Rb-Sr and Sm-Nd isotope evolution lines for the amphibole-vein (0.703705±7 and 0.512324±1, respectively) indicate that Pravotarlashkin gabbro massif has primary melt related to amphibole-vein.