【摘要】 南祁连党河南山地区发育一些小规模的煌斑岩脉,岩脉穿插于前泥盆纪地层及岩体中,岩石w（SiO₂）=46.93%⁵6.82%,w（K₂O）=0.64%⁴.12%,属钙碱性系列煌斑岩.稀土元素总量较低(1.534 5×10^-42.744 9×10^-4),轻稀土富集,重稀土相对亏损.强烈富集大离子亲石元素（Rb、Ba、La、Ce、Sr）和U、Pb,亏损高场强元素（Nb、Ta、Zr、Hf）.岩石w(⁸⁷Sr)/w(⁸⁶Sr)=0.713 716⁰.716 950,εNd（t）=-6.713 9^-8.3986,w(¹⁴³Nd)/w(¹⁴⁴Nd)=0.512 036⁰.512 117,具有高Sr低Nd的特征.煌斑岩源岩具岛弧钙碱性玄武岩的性质,源区可能为EMⅠ型富集地幔.煌斑岩的形成指示党河南山地区在海西早期已经处于碰撞后的伸展阶段.更多还原

【Abstract】 There are some small- scale lamprophyre dykes in the Danghe’nanshan area of the south Qilian Mountains,which have intruded into the pre-Devonian strata and plutons.The content of SiO₂ and K₂O of lamprophyre ranges respectively from 46.93%to 56.82%and 0.64%to 4.12%,indicating that the dykes belong to calc-alkaline series.The rocks have relatively low ∑REE(1.534 5×10^-4-2.744 9×10^-4),are strongly enriched in LREE and relatively depleted in HREE.The trace elements are characterized by being rich in large ion lithophile elements（Rb,Ba,La,Ce,Sr） and U,Pb,and poor in high field strength elements（Nb,Ta,Zr and Hf）.The isotope w(⁸⁷Sr)/w(⁸⁶Sr)=0.713 716-0.716 950,εNd（t）=-6.713 9-—8.398 6,w(¹⁴³Nd)/w(¹⁴⁴Nd)=0.512 036-0.512 117,showing that the lamprophyre rocks are geochemistrially featured by high Sr and low Nd.All these suggested that the lamprophyre rocks originated from the calc-alkaline basalts of the island-arc type,with a source area of the EM I type enrichment mantle.The occurrence of these lamprophyre dykes reveals that the Danghe’nanshan area had undergone the post-collisional extension during the early Hercynian.更多还原