Based on composition of chemical analyses of rocks in Padong Area ,Sumatra (Indonesia) comparing with the data of the typical adakitic rocks ,this paper discusses the geochemical characteristics and their significance of tectonic setting .The comparative results shows that the trace element composition of the adakite-like rocks have the characteristics of low Sr contents (general 3 .88 × 10-6 ~83 .6 × 10-6 ) ,low Y contents(≤20 × 10-6 ) ,low Yb contents(≤1 .9 × 10-6 )of HREE ,and lower Sr/Y ratio (1 .09~18 .55) .On the chondrite-normalized spider diagram of trace element ,there are positive peak of Th ,Ba and strongly negative anomaly of Nb、Ta、Ti elements .The La/Yb ratio of REE are within the range of 1 .28~35 .46 ,and there are two types of chondrite-nomalized rare earth elements pattern:enriched and no enriched model , belonging to C-and O-type adakite respectively .The tectonic setting of theses adakite-like rocks are located at the volcano-arc of active continental margin near ocean-continent collision zone .The igneous magma derived from the areas of partly melting of seduction ocean slab plus partly molting and assimilation o f mantle wedge(MASH) .The distribution of adakite-like rocks in this area is in perfect accord with Cu-Au deposits of skarn type and iron deposits as well as hypothermal hot-spring Au zone .That meams the adakite-like rocks have a big significance in exploration .%根据苏门答腊岛巴东地区的岩石化学分析数据与典型埃达克岩进行对比，本文讨论其地球化学特征及其大地构造环境意义。对比结果表明：该地区的埃达克质岩微量元素特征为低Sr含量（一般为3．88×10－6～83．6×10－6），低重稀土元素Y含量（≤20×10－6）和低Yb含量（≤1．9×10－6），低Sr／Y比值（1．09～18．55）。在微量元素蛛网图上有 Th、Ba正异常峰和强烈的 Nb、Ta、Ti等元素负异常。稀土元素La／Yb比值为1．28～35．46，在REE元素配分曲线模式图上显示LREE富集和不富集两种模式，属于C-型和O-型埃达克岩。该地区埃达克质岩的大地构造环境位于洋-陆碰撞带附近的活动大陆边缘火山弧带中，岩浆来源于俯冲板片局部熔融叠加地幔楔的局部熔融和混染（MASH）区。埃达克岩的分布区域与矽卡岩型铜-金矿、铁矿和浅成热泉型金矿成矿带分布相一致，具有重要的指示意义。
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