Geochemical Study of Collision Volcanism at the Plate Boundary in Turkey -Comparison With Subduction Volcanism in Japan-

这些地球化学资料表明，土耳其上地幔结构存在与板块构造有关的不均匀性。东部卡拉恰达格的Sr同位素比值较低，说明岩浆-地壳相互作用的贡献较小。货车湖地区火山的Sr同位素具有局部差异。Nemurut的Sr比值与SiO_2含量有相关性，表明受地壳污染。该区He同位素值高于空气，表明地幔He的存在。地幔He值与俯冲区相同，说明俯冲区和碰撞区的He同位素是相同的。在土耳其中部，Erciyes和Hasan的Sr同位素为0.7038-0.7058，处于俯冲带范围。He同位素显示地壳污染程度高于土耳其东部。在土耳其西部，爱琴海沿岸的地热区到处都能观测到放射成因的^4He。然而，库拉的^3He/^4He比值很高，碳同位素很低，Sr同位素也很低（0.7030-0.7035）。如果说库拉是爱琴海岛弧的延伸，那它就显得很特别了。将来有必要与本研究相比较，对爱琴海弧进行研究。

All these geochemical data show that there are inhomogeneity in the upper mantle structure related with the plate tectonics in Turkey. In the eastern part, Sr isotopic rations of Karacadag are low, suggesting the less contribution of magma-crust interaction. Sr isotopes for the volcanoes in the lake Van area vary locally. The Sr rations of Nemurut have a correlation with SiO_2 contents, indicating the crustal contamination. He isotopes in this area is higher than that of air, and suggest the presence of mantle He. The value of mantle He is the same as that in the subduction area, suggesting that the He isotopes are the same in both subduction and collision area. In the central part of Turkey, Sr isotopes of Erciyes and Hasan are 0.7038-0.7058 which are in the range of the subduction area. He isotopes show the higher degree of crustal contamination than that in the eastern Turkey. In the western Turkey, the radiogenic ^4He was observed in all over the geothermal area in the Aegean coast. However, the high high ^3He/^4He ratios and low carbon isotopes are obtained in Kula, where Sr isotopes are also very low (0.7030-0.7035). Kula seem to be very special if it is on the extension of Aegean island arc. It should be necessary to examine the Aegean arc in future in comparison with this study.