北京西山房山岩体岩浆底辟构造及其地质意义

运用底辟构造的理论和模型, 通过对北京西山房山岩体边缘围岩构造、变形和应变的研究, 厘定出岩体边缘的高温剪切带、周缘向斜、呈穹状分布陡倾的线理和面理, 并结合对西山区域构造事件分析后提出房山岩体为典型的岩浆底辟构造(HotStokesDiapir).这项研究成果不仅在世界上首次证实了岩浆底辟的存在, 而且对理清北京西山地区的地质构造格架和演化序列具有十分重要的意义.研究认为房山地区可能不存在变质核杂岩; 房山岩体边缘的关坻太古宙杂岩是基底岩石随岩体底辟流动上升带到地壳上部的; 原先确定的一些印支期“剥离断层”是房山岩体岩浆底辟的刺穿构造或围岩高温剪切作用造成的地层缺失; 太平山和凤凰山等向斜是岩体底辟过程中在围岩拖曳下形成的周缘向斜. 

Magmatic Diapir of Fangshan Pluton in the Western Hills, Beijing and Its Geological Significance

A study of structures, deformation and strain of country rocks around Fangshan pluton in the western Hills, Beijing, reveals a high-temperature shear aureole, domal distribution of steep lineations and foliations in the thermodynamic aureole, and ring synclines around the pluton. Combining with the analysis of the regional tectonic events, it is concluded that Fangshan pluton is a real magmatic diapir (hot-stokes diapir). To our knowledge, this is the first reported magmatic diapir in the world. As such, this research result argues for a reconsideration of the structural frame and deformational series of the Zhoukoudian area. It is suggested that the Fangshan metamorphic core complex did not exist; the Guandi Archean complex in the margins of the pluton was outcropped by ductile flow of the diapiric ascent; previously proposed Indosinian denudational faults were piercing structures and/or the absence of the strata in the high temperature shear aureole; Taipingshan and Fenghuangshan synclines are ring synclines around the pluton formed by drag of country rocks due to the diapiric ascent.