【摘要】 中缅边界那邦麻粒岩相变质基性岩地球化学特征研究表明其原岩是岩浆岩 ,并具有 MORB的特性 ,其岩石化学具有以下特征 :岩石的 TFe O/ Mg O值低 (1.10～ 2 .17) ,AFM图解上显示拉斑玄武岩演化趋势 ;Ti O2 含量 (1.14%～ 1.81% )高于岛弧拉斑玄武岩。多数微量元素与大洋中脊拉斑玄武岩含量相当 ,Nd、Ta值高于岛弧拉斑玄武岩。稀土元素配分图显示轻稀土亏损、重稀土较有富集的配分型式 ,稀土元素和总量 (ΣREE)值十倍于球粒陨石 (2 4～ 5 0μg/ g) ,(L a/ Sm ) N=0 .43～ 0 .75 ,(L a/ Yb) N=0 .45～ 0 .74,87Sr/ 86 Sr=0 .70 4～ 0 .70 5 ,1 4 3Nd/ 1 4 4 Nd=0 .5 12 9～ 0 .5 132 ,εNd=+4 .85～ +9.6 7。大地构造背景和年代学研究显示 ,那邦变质基性岩是先前密支那新特提斯洋壳的上部组成 ,是俯冲板片裂离作用折返地表的麻粒岩相岩石 ,对探讨特提斯洋俯冲时限、俯冲洋壳的变质变形作用、俯冲物质的深部运动等都有重要的意义更多还原

【Abstract】 The Nabang metamorphic basalt is discovered recently on the border of China and Burma. The majoy, trace and rare earth element characteristics of Nabang metamorphic basalt have been investigated. All studied rocks are depleted in light rare earth elements(LREE) with REE=24-50g/g, (La/Sm)N=0.43~0.75 the same and (La/Yb)N=0.45-0.74. Ti2O, Nb and Ta show that the Nabang metamorphic rocks are different from islandarc basalt as shown by the geochemical diagrams. The NdSr isotope data show a clear signature of a depleted mantle source similar to NMORB with 87Sr860.704-0.705,143Nd144Nd= 0.5129~0.5132, Nd=+4.85~+9.67. Combining with its geochronological results and geological background, it can be concluded that the Nabang metamorphic basalt is related to Myitkyina suture, east Burma. The Nabang metamorphic basalt may be an evidence of slabbreakoff of NeoTethys subducted upper oceanic crust.更多还原