中国东部地幔岩中的钨含量及其意义

Tungsten content of mantle-derived rocks from eastern China and its implications

分析了56件中国东部地幔岩包体及其寄主岩石中的钨含量。结果表明,地幔岩包体和寄主玄武岩中的钨含量分别在0.1～1.0μg/g和0.1～2.5μg/g之间。后者一般高于前者且明显不均一,反映钨是不相容元素,在部分熔融过程中倾向于富集在熔体中,而主要源于软流圈地幔低程度熔融的熔体在上升过程中发生了不同程度的岩石圈-软流圈或地壳-地幔相互作用。地幔岩包体钨平均含量接近或仅略高于上地幔钨的丰度,而寄主玄武岩钨平均含量与世界基性岩钨的丰度非常一致,说明我国地幔中钨的丰度与世界其他地区相比并无明显不同,反映钨矿集中区的形成和分布与地幔中钨的原始分布关系不大,我国钨矿集中区的形成可能主要与地壳演化有关。

Tungsten contents in 56 samples of mantle derived xenoliths and their host rocks from eastern China are analyzed. The W contents of the mantle derived rocks from eastern China is in the ranges of 0.1～1.0 μg/g (averaging 0.4 μg/g) and 0.1～2.5 μg/g (averaging 0.7 μg/g) in the mantle derived xenoliths and the host basalts, respectively. The mantle derived xenoliths have lower tungsten content than the host rocks, suggesting that tungsten tended to be concentrated into the melt during the partial melting, and there may be interaction between asthenosphere and lithosphere or between crust and mantle in the formation and rising of the basalts. Our data indicate that the average tungsten content of the mantle derived xenoliths in eastern China is approximately equal to or only slightly higher than the average tungsten abundance of the upper mantle, and the average tungsten content of the host basalts shows no difference with the average tungsten abundance of the basites in the world, indicating that the formation and distribution of tungsten deposits and tungsten ore concentrated districts may be not related to the primitive distribution of tungsten in mantle, and the formation of the tungsten deposit concentrated districts in China may be the products of the crust evolution.