前寒武纪地球动力学(Ⅷ):华北克拉通太古宙末期地壳生长方式  

Precambrian geodynamics(Ⅷ):Late Archean crustal growth models recorded in the North China Craton

作　　者：王伟[1,2] 刘树文[3,4] 白翔[5] 郭荣荣[6] 

机构地区：[1]地质过程与矿产资源国家重点实验室 [2]中国地质大学(北京)地球科学与资源学院,北京100083 [3]造山带与地壳演化教育部重点实验室 [4]北京大学地球与空间科学学院,北京100871 [5]中国地震局地质研究所,北京100029 [6]东北大学资源与土木工程学院,辽宁沈阳110819

出　　处：《地学前缘》2015年第6期109-124,共16页Earth Science Frontiers

基　　金：国家自然科学基金项目(41502179;41530207;41472165;41272209)

摘　　要：地球早期大陆地壳的生长方式和壳幔动力学机制一直是国际前寒武纪研究的热点问题。尽管太古宙是大陆地壳生长的主要时期已基本获得共识,但是对于太古宙时期地壳生长的具体方式和壳幔动力学过程仍然存在很大的争议。部分学者提出地幔柱或者与拆沉相关的垂向构造体制,而其他学者主张与俯冲相关的侧向增生模式或者地幔柱-岛弧的联合作用体制。研究表明,太古宙末期科马提岩明显减少、富钾花岗质岩石普遍发育、地壳再循环速度显著增强,反映地壳演化的壳幔动力学机制发生了明显的转变。华北克拉通以发育大规模2.5-2.6Ga构造岩浆活动为特征,是探讨太古宙末期地壳生长方式和壳幔动力学机制转变的关键地区。本文系统总结了近些年来华北克拉通东部陆块西北缘早前寒武纪研究的最新进展,特别是对辽西、冀东、辽北和五台地区的新太古代晚期（约2.5-2.6Ga）表壳岩变质火山岩系进行了系统的岩石成因和壳幔作用探讨。研究表明,上述地区的变质铁镁质岩石可以划分为3个岩石成因系列：MORB型、IAT（岛弧拉斑玄武岩）型和CAB（岛弧钙碱性玄武岩）型,它们的原岩分别起源于洋中脊软流圈地幔以及受到不同程度俯冲流体交代的地幔楔的部分熔融。变质安山质-英安质火山岩分别具有类似高镁安山岩和埃达克岩的地球化学特征,它们的原岩形成过程可能与俯冲板片的部分熔融以及板片熔体与地幔楔的相互作用有关。结合整个东部陆块早前寒武纪的研究进展,我们提出华北克拉通在太古宙末期（约2.5和约2.7Ga）经历了强烈的地壳生长过程,其中新太古代早期（约2.7Ga）地壳生长以地幔柱-岛弧联合作用体制为主,而新太古代末期（约2.5-2.6Ga）以洋内俯冲和弧陆增生作用体制占主导地位。新太古代末期与俯冲增生相关的构造岩浆活动在Tarim克拉通The early Precambrian crustal growth models and related crust-mantle geodynamics have always been the research focus of international Precambrian community.Although it is generally accepted that the continental crust was dominantly formed during the Archean period,the definite crustal growth models and crust-mantle geodynamic regimes remain largely controversial.Some researchers advocate the vertical tectonic regimes,e.g.,plume or lower crust delamination models,whereas others favor the lateral subductionaccretion processes or plume-arc interaction models.Recent studies reveal that several essential changes occurred during the late Archean crustal evolution history of the earth,i.e.,rapid decrease in the ratio of komatiites within metavolcanic sequences;the wide emplacement of potassium-rich granitoid gneisses;and the apparent increase of the crustal recycling processes.All the above lines of evidence indicate that the crustmantle geodynamic regimes may have significantly changed during the late Archean.The North China Craton（NCC）is characterized by intense-2.5-2.6Ga tectonothermal events,which offers valuable opportunities for us to investigate the transitional regimes of early Precambrian crust-mantle geodynamic evolution.In this study,we provide a timely review of recent early Precambrian studies along the northwestern margin of the Eastern Block（EB）,especially focusing on the petrogenesis and crust-mantle interaction processes recorded by the late Neoarchean（-2.5-2.6Ga）metavolcanic rocks in the Western-and Northern Liaoning Provinces,Eastern Hebei Province,and the Wutai granite-greenstone belt.It is suggested that the metamorphosed mafic rocks in these areas can be subdivided into three petrogenetic types of MORB（Mid-ocean ridge basalt）-type,IAT（Island arc tholeiite）-type and the CAB（calc-alkaline basalt）-type.These Neoarchean metavolcanic rocks are considered to be formed by the partial melting of the asthenospheric mantle underneath an Archean spreading ridge and of the mantle wedge

关 键 词：早前寒武纪地壳生长 壳幔动力学机制 华北克拉通 表壳岩变质火山岩系 太古宙末期弧陆增生 

分 类 号：P534[天文地球—古生物学与地层学] P311.2[天文地球—地质学]