北京房山岩体的磁组构特征及其对岩体侵位的约束  

Magnetic fabrics of the Fangshan pluton in Beijing and constraints on its emplacement

作　　者：纪新林[1,2] 王磊[1] 潘永信[1] 

机构地区：[1]中国科学院地质与地球物理研究所地球深部研究重点实验室,北京100029 [2]中国科学院研究生院,北京100049

出　　处：《地球物理学报》2010年第7期1671-1680,共10页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(40634024和40821091)资助

摘　　要：岩浆岩的磁组构与岩浆流动、侵位时应力和冷凝后遭受后期构造改造作用有关.本文分析了北京房山岩体东山口凤凰亭剖面岩石磁化率各向异(AMS)变化.热磁曲线和磁滞回线分析显示,岩石的主要载磁矿物为多畴磁铁矿颗粒.AMS磁化率椭球体呈压扁状,磁面理发育且产状陡倾,磁化率各向异性度P值平均值高达1.189.自边缘相(东山口)到中心相(凤凰亭),岩石磁化率椭球的扁率E值和形状因子T值逐渐减小,说明磁组构主要反映岩浆流动和岩体侵位时近NNE-SSW方向的挤压作用,在侵位冷凝后并没有遭受到明显的构造改造.Magnetic fabrics of magmatic rocks is usually controlled by magmatic flow and stresses during emplacement and later tectonic alteration. In order to understand the emplacement history of the Fangshan pluton in Beijing, we studied the anisotropy of magnetic susceptibility （AMS） along Dongshankou-Fenghuangting section of the pluton. Thermomagnetic curves and hysteresis loops showed that primary multi-domain （MD） magnetite was dominant. The AMS ellipsoids were characterized as oblate with a high P value （mean 1. 189）. From the pluton rim phase at Dongshankou to the central phase at Fenghuangting, the susceptibility ellipsoid E and shape factor T values gradually decreased, suggesting that the magnetic fabrics were formed by magmatic flow and a contemporaneous NNE-SSW direction stress during its emplacement, rather than a post-emplacement tectonic influence.

关 键 词：房山岩体 磁化率各向异性 构造应力 侵位 

分 类 号：P318[天文地球—固体地球物理学]