【摘要】 羌塘盆地至今没有片麻岩系基岩点位的报道,长期以来关于该盆地是否具有前古生代的结晶基底分歧较大。最近在羌塘盆地中央隆起带北缘兰新岭附近的俄久卖一带找到了具有中—深变质特征的片麻岩,追索确定片麻岩系沿逆冲断裂带出露,基岩出露宽度为50～200m,断续延伸长约4km。岩相学研究结果显示,片麻岩中含有典型的区域变质矿物矽线石和蓝晶石,结合附近发现的奥陶系仅经历了浅变质作用和新近的地球物理资料揭示盆地内可能有结晶基底,初步认为俄久卖片麻岩系为羌塘盆地的前奥陶系结晶基底岩片,羌塘盆地深部具有稳定的结晶基底。更多还原

【Abstract】 Up to now, no gneiss has been reported in the Qiangtang basin. Divergent views have long existed as to whether the pre-Paleozoic crystalline basement occurs in the basin. Recently gneiss with the medium- and high-grade metamorphic features has been found in the vicinity of Ejiumai near Lanxin Mountain on the northern margin the Central uplift zone in the Qiangtang basin. Through tracing, the authors found a gneiss outcrop, which is 50-200 m wide and 4 km long, extending discontinuously along a thrust. Petrographic study shows that the gneiss contains the typical regional metamorphic minerals sillimanite and kyanite, and in addition, it has been found that the nearby Ordovician only undergone low-grade metamorphism and recent geophysical data have revealed that there might be crystalline basement in the Qiangtang basin. Based on these findings, the authors preliminarily conclude that the Ejiumai gneiss is a slice of pre-Ordovician crystalline basement in the Qiangtang basin and that a stable crystalline basement might occur at the depth of the Qiangtang basin.更多还原