【摘要】 俯冲带沉积物(岩)的变质脱水作用对俯冲带流体组成、矿物和同位素组成及岛弧岩浆演化具有深远影响。以天然泥质岩为研究对象,通过高温高压实验,确定了1.5~3.5 GPa、746~930℃条件下,俯冲带沉积物中绿泥石、绢云母及其脱水后产物角闪石和黑云母在俯冲带的稳定范围,绘制了高温高压条件下泥质岩体系相图。研究结果表明,在泥质岩体系中,绿泥石是最早发生变质脱水的矿物,在俯冲带50 km深度以上全部分解,其分解产物———角闪石可携带流体进入到俯冲带85 km处,黑云母则可俯冲至120 km或更深的深度,据此可知,在俯冲带深部,沉积物完全脱水的深度范围(≥120 km)要大于蚀变洋壳(90~100 km)。更多还原

【Abstract】 Metamorphic dehydration of subducted sediments is of importance in understanding the composition of slab-derived fluids,the mineral and isotope composition in subduction zone,which is also important for understanding the evolution of arc magmas.The stability of chlorite,sericite,amphibole and biotite has been identified in natural pelitic system at pressures 1.5~3.5GPa,and at temperatures 746~930℃ by high pressure experiments on natural pelite.The systematic diagram suggests that with the increasing of pressure and temperature chlorite completely decomposes at lower depth(<50km.)The run production of this process-amphibole can be subducted to 85km,and biotite devolatilizes at the depth ≥120km in subduction zone.This leads to the conclusion that subducted sediments can be subducted into more deep depth(≥120km) than basaltic oceanic crust.更多还原