辽北西丰地区晚侏罗世营厂岩体LA-ICP-MS锆石U-Pb年龄及岩石地球化学特征

营厂岩体分布于辽北西丰县和隆镇境内,研究结果表明,该岩体主要为似斑状二长花岗岩,锆石²⁰⁶Pb/²³⁸U年龄加权平均值为156.1 Ma±1.5 Ma,形成时代为晚侏罗世。营厂岩体w（Na₂O）/w（K₂O）平均值为1.07,属高钾钙碱性系列;里特曼指数σ平均值为2.15,属钙碱系列;铝饱和指数A/CNK平均值为1.16,A/CN平均值为1.99,属过铝型;Rb、Sr、Ba、Th、Hf含量偏高,Cr、Ni、Co、V、Rb、Zr、Nb等元素含量低,为"S"型花岗岩特征。稀土元素总量平均值为w（ΣREE）＝82.80×10^-6,w（LREE）/w（HREE）=15.76,w（La）_N/w（Yb）_N=24.32,表明其轻稀土相对富集,重稀土相对亏损,稀土配分曲线右倾。δEu=0.80,铕弱负异常,说明成因与板块运动有关,w（Sm）/w（Nd）=0.20,w（Ba）/w（Sr）=1.60,w（K）/w（Rb）=249.15,表明具有壳源性质。营厂岩体具有埃达克岩的特点,其属于受太平洋板块向欧亚板块俯冲作用的影响,在挤压环境下加厚下地壳部分熔融,从而形成活动陆缘型花岗岩。

LA-ICS-MS zircon U-Pb dating and geochemical characteristics of Yingchang pluton in Xifeng area of the North Liaoning province

The Yingchang pluton occurs at Helong town, Xifeng county, the North Liaoning province. Lithologically it is dominated by porphyritic mozonitic granit. The weighted ²⁰⁶Pb/²³⁸U age is 156.1 Ma±1.5 Ma corresponding to Late Jurassic Epoch. w(NaO₂) of the pluton is averagely 1.07 suggesting that it belongs to high K calc-alkaline series; Rittman index, averagely 2.15, calc-alkaline series; A/CNK,averagely 1.16 and A/CN 1.99, pera- luminous type; high Rb, Sr, Ba, Th, Hf and low Cr, Ni, Co, V, Rb, Zr, Nb, "S" type of granite. The average w(REE) is 82.80×10^-6, w(LREE)/w(HREE) 15.76 and w(La)/w(Yb) 24.32 indicating that it is relatively rich in LREE, relatively depleted in HREE with right- leaning REE distribution curve and weak negative Eu (Eu=0.80) anomaly. Thus it is a plate-movement- related pluton and w(Sm)/w(Nd)=0.20, w(Ba)/w(Sr)=1.60 and w(K)/w(Rb)=249.15 are the characteristic of crustal material. The mentioned above show that the pluton is of characteristics of adakite formed as active continental marginal granite by partial melting of lower crustal material under thickening crust condition due to compression during subduction of Pacific ocean plate under Eurasian plate.