摘要
对华北克拉通碱性岩等板内拉张背景岩浆岩进行了大量的同位素年代学及空间分布的研究,并结合前人的有关研究成果得出:华北克拉通板内拉张性岩浆作用主要集中在3个时段,即古元古代末—中元古代早期(1850~1600Ma)新元古代中–晚期(900~600Ma)、和古生代末—新生代(250Ma~现今)。这3个时段的拉张性岩浆作用,由老到新依次称之为第一拉张作用阶段、第二拉张作用阶段和第三拉张作用阶段岩浆作用,3个阶段拉张性岩浆作用出现的频率强度和空间分布的广度均有明显差别。第三阶段拉张性岩浆作用出现的频率强度最大,空间分布也最广;第一阶段拉张性岩浆作用次之;而第二阶段拉张性岩浆作用出现的频率强度最弱,并且空间分布也很局限。特别值得提出的是三个阶段拉张性岩浆作用在时间上分别与哥伦比亚(Columbia)、罗迪尼亚(Rodinia)及潘基亚(Pangaea)三个超级大陆的拉张裂解时间基本一致。这可能说明华北克拉通对三个超级大陆的拉张裂解都有不同程度的反映。对于导致超级大陆拉张裂解的深部地质过程地球动力学,一般认为是超级热地幔柱活动。推测华北克拉通距导致三个超级大陆拉张裂解的超级热地幔柱活动中心,在第三拉张阶段时可能最近,第一拉张阶段时也较近,但在第二拉张阶段时相对较远。
Based on authers'twenty years research on isotope geochronology and spatial distribution of intraplate extensional magmatic rocks(such as alkaline intrusives etc.)in North China Craton,as well as the existing references,this paper suggests that intraplate extensional magmatisms of North China Craton were concentrated in three stages:the latest Paleoproterozoic-early Mesoproterozoic era(1 850~1 600 Ma),the middle-late Neoproterozoic era(900~600 Ma)and the latest Palaeozoic-Cenozoic era(250 Ma~now),respectively,as named the first,the second and the third extensional stage.The appearance frequency and the spatial distribution of the threestages extensional magmatisms are distinctly different from each other.The third stage has the highest appearance frequency and widest distribution,and the first stage takes second place.It must be especially emphasized that the isochron ages of the threestages magmatic rocks are basically coincident with the break-up timings of Columbia,Rodinia and Pangaea supercontinents,respectively,showing different degrees of response of North China Craton to the break-up of related supercontinents.The activities of super mantle hot plumes are popularly considered as the deep geodynamics of dispersal of supercontinents.So it is speculated that the distance from North China Craton to the center of super mantle hot plume activities in the third extensional stage was the nearest,and that in the second stage was the farthest.