阿尔金北缘枕状玄武岩的地质特征及其锆石U-Pb年龄

Geology and Zircon U-Pb Age of Pillow Basalt at Qiashikansoy in Northern Altun Tagh, W China

阿尔金山北缘恰什坎萨依出露的玄武岩具枕状、气孔和杏仁状构造,镜下多为间隐结构,岩石化学成分特点及REE等微迹元素显示洋岛玄武岩特征;其颗粒锆石U-Pb年龄为448.6±3.3Ma。该区玄武岩与相伴产出的蛇纹石化橄榄岩、辉长岩及硅质岩、粉砂岩等呈断层接触关系,它们共同组成了较标准的蛇绿岩。这为探讨阿尔金山的大地构造演化提供了新的证据。

Basalt at Qiashikansoy on the northern margin of Altun Tagh, western China, occurred in pillow, gas holes and almonds structures, and usually had ophitic interstitial texture under microscope. It might be formed in an oceanic island environment, as shown by the features of petrochemical components, REE patterns and other trace elements of the basalt. Because the grains from the basalt are too small to be analyzed by SHRIMP, they can only be dated by the TIMS method. The zircon U-Pb age of 448.6±3.3 Ma may represent a compression setting of the Altun fault. The basalt, serpentinized periodtite, gahhro, silica rocks and silt rocks were separated by faults. These rocks appeared as slabs in cross section, and they constitute a substandard ophiolite. Both the geology and geochemistry and the age of zircon U-Pb dating of the ophiolite provided new evidence for the research of the tectonic evolution of Altun Tagh.