华北克拉通早前寒武纪基性火山作用与地壳增生

大量的年代学资料表明,华北克拉通在早前寒武纪阶段有两个主要的基性火山活动时期,一期发生在2.7Ga左右,另一期发生在2.5Ga左右,代表了两期强烈的地壳增生事件。太古宙末期基性火山岩的分布、地球化学特征、基性火山岩与其他岩石的关系和组合特征表明,华北克拉通在新太古代时期,在陆块之间基性火山岩的喷溢使地壳面积增大并把原本分离的小陆块拼合到一起,造成地壳的增生。在陆块内部,地壳的增生主要通过地幔柱的方式进行,在较均匀的地壳部分主要通过基性岩浆的垫托方式使地壳增厚,部分岩浆侵位到地壳较浅部位,甚至溢出地表。这两种地壳增生方式是相辅相成的,它们的联合作用形成了太古宙末的华北古大陆。

Early Precambrian Basic Volcanism and Crustal Growth in the North China Craton

Chronological data show that two phases of basic volcanic activity appeared at about 2. 7 Ga and 2. 5 Ga in the North China craton in the Early Precambrian and represented two extensive crustal growth events respec-tively. Distribution and geochemical feature of basic volcanic rocks, and relationship and associations between basic volcanic rocks and other rocks suggest that the outpouring of basic volcanic rocks between landmasses in the Neoarchean increased crystal area, pieced the previously isolate mini - landmass together and caused the crustal growth. Within a landmass crust grew dominantly in the way of mantle plume. In the homogeneous part of the crust, where some magma intruded into the shallower crust and even spilt over the earth's surface, crust was mainly thickened in the way of underplating of basic magma. These two patterns of crustal growth, which supplemented each other, jointly resulted in the North China Paleocontinent of the end Archean.