摘要
俯冲带是地壳与地幔之间物质交换的主要场所.前人对大洋俯冲带壳幔相互作用进行了大量研究,但是对俯冲带壳幔相互作用的物理化学过程和机理仍缺乏明确认识.在大陆俯冲带出露有造山带橄榄岩,它们来自俯冲板片之上的地幔楔,是解决这个问题的理想样品.通过对大别-苏鲁和柴北缘造山带橄榄岩进行系统的岩石学和地球化学研究,发现地幔楔橄榄岩由于俯冲地壳的交代作用而含有新生锆石和残留锆石,它们能为地壳交代作用时间、交代介质来源、性质和组成提供制约.地幔楔橄榄岩在大陆碰撞过程的不同阶段受到了俯冲大陆地壳衍生的多期不同性质流体的交代作用.地幔楔橄榄岩还受到了陆壳俯冲之前古俯冲洋壳衍生流体的交代作用.深俯冲陆壳衍生熔体与橄榄岩反应形成的石榴辉石岩具有高的水含量,能提供高水含量的地幔源区.
Subduction zones are the major sites for mass exchange between crust and mantle.Although a great deal of studies have devoted to the crust-mantle interaction in oceanic subduction zones,it is still not clear what are physicochemical processes and mechanisms for the crust-mantle interactions in subduction zones.Orogenic peridotites are widely exposed in collisional subduction zones and they were originally located in the mantle wedge above the subducting continental slab,providing us excellent samples to resolve this issue.Through a systematic study of petrology and geochemistry for orogenic peridotites from the Dabie-Sulu and North Qaidam orogens,it is found that crustal metasomatism results in the occurrence of both newly grown zircon and relict zircon.The two types of zircons provide important constraints on not only the timing of crustal metasomatism but also the origin,property and composition of metasomatic agents in the mantle wedge.The mantle wedge peridotites in the continental subduction zones underwent multiple episodes of crustal metasomatism by different properties of fluids derived from the deeply subducted continental crust during continental collision.They were also metasomatized by fluids derived from precedingly subducted oceanic crust.They reacted with subducted continental crust-derived melts to generate garnet pyroxenites,which have high water contents and thus can serve as the mantle source of mafic igneous rocks with high water contents.
作者
陈仁旭
郑永飞
Chen Renxu;Zheng Yongfei(CAS Key Laboratory of Crust-Mantle Materials and Environments,School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China;Center of Excellence for Comparative Planetology,Chinese Academy of Sciences,Hefei 230026,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2019年第12期4095-4101,共7页
Earth Science
基金
国家“973”计划项目(No.2015CB856106)
国家自然科学基金项目(Nos.41590624,41873033)
中科院先导项目(No.XDB18020303)
关键词
造山带橄榄岩
超高压变质作用
壳幔相互作用
流体活动
俯冲带
orogenic peridotite
ultrahigh-pressure metamorphism
crust-mantle interaction
fluid action
subduction zone
