冀北水泉沟偏碱性杂岩体的地质—地球化学特征及其构造环境
FORMATION MECHANISM OF DETACHMENT IN THE XUZHOU-SUZHOU AREA
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摘要: 冀北崇礼—赤城地区水泉沟岩体是一个钾质—高钾质的钙碱性、弱碱性和碱性岩石共存的杂岩体。总体上以富碱、准铝、低钙、低钛为特征。稀土、微量元素和同位素特征表明该岩体源于上地幔与下地壳的边界附近,在各类地球化学构造判别图解中大多落于火山弧区。侵位机制分析表明该岩体是拉张作用下的产物。结合同位素年龄,认为水泉沟杂岩体形成于西伯利亚板块和中朝板块碰撞后的应力松弛阶段。Abstract: There are three nappe belts in plan and two detachment zones in the section in the Xuzhou Suzhou. The nappe structures underwent two tectonic movements. The earlier detachment formed by the thrusting from the back and gravity gliding of the front. The later detachment formed by the S W thrusting. The deformational mechanism of tectonite is marked by simple compresso shear at edges and pure compresso shear in the inner parts.