福建岱前山辉长岩体的地球化学特征与成因探讨

岱前山辉长岩体沿福建长乐一南澳大断裂带分布，侵位于沿海的绿片岩相和角闪岩相的变质岩中及内陆的中生代火山岩中，对其成因存在较多分歧。该岩体表现为与俯冲有关的岛弧地球化学特点，但在时间上又与古太平洋板块低角度歪斜俯冲、晚中生代的变质事件、平潭一东山变质带抬升和长乐一南澳剪切带运动在时间上基本一致。对于其成因不能简单的用拉张或碰撞加以解释，是受俯冲流体交代的上地幔，经部分熔融沿长乐一南澳断裂．应力转换带侵入。它与中国东南部出露的其它基性岩同源，但并未受到地壳的混染作用。计算结果表明，岱前山岩体经7％的部分熔融形成，其Sm、Nd含量高于原始地幔。

GEOCHEMISTRY AND GENESIS OF DAIQIANSHAN GABBRO, FUJIAN PROVINCE

The Daiqianshan mafic intrusion is situated along the Changle-Nanao fault zone in the Fujian coastal area. The rock body intruded the metamorphic rocks which are composed of biotite gneiss, amphibole schist, sillmanite schist and Mesozoic volcanic rocks. This paper shows that the rock body possesses subduction-related signatures with island-arc affinity. However, the age of the rock is close to the timing of low-angle oblique subduction of the ancient Pacific plate, high-pressure metamorphic event, uplift of the Pingtan-Dongshan metamorphic belt and movement along the Changle-Nanao shear zone. So the genesis of the rock shouldn't be interpreted merely as lithospheric extension or collision events, it might be derived from the upper mantle and intruded along the Changle-Nanao fault zone, and also had experienced metasomatism prior to intrusion. The rock body has the same source like other mafic rocks exposed in southeastern China, but the Daiqianshan intrusion has not experienced much crustal assimilation. The degree of partial melting is estimated at about 7.4%, and the Sm, Nd concentrations of the source rocks are slightly higher than those of the pre-mantle source.