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GENETIC MECHANISM AND TECTONIC SETTING OF PROTEROZOIC MAFIC DYKE SWARM: ITS IMPLICATION FOR PALEOPLATE RECONSTRUCTION

Li Jiang-hai, He Wen-yuan, Qian Xiang-lin   

  1. Department of Geology, Peking University
  • Received:1997-09-20 Revised:1997-09-20 Online:1997-09-20 Published:1997-09-20

Abstract: Preterozoic mafic dyke swarms occur in nearly every Archean continental craton, and recorded significant geological events of continental evolution.It is generally recognized that the generation and emplacement time of dyke swarm is relatively short, while its genetic mechanism is complex. At different conditions, dyke swarms have different propagation mechanism. Commonly, each dyke fracture initially fills vertically, then propagates laterally and not always intrudes perpendicularly to the lowest normal stress axis. Dykes Can intrude in different crustal levels, but distinct with each other. Although there are different magma sources, the major source: of dyke swarm is continental asthenosphere or lithospheric mantle. The evidence of crystallization differentiation or crustal contamination is tardy documented. Dykes’ bulk geochemical feature is enriched and shows some small changes which could be used to detect the evolution of mantle process. Because extension can occur in different tectonic settings, where dykes actually generated still needs careful study. The plate tectonics had been operating at least from Neoarchean to Paleoproterozoic, and in the Proterozoic, the earth lithosphere was characterized by assembly and breakup of continental cratonic blocks. The occurrence of mafic dyke swarms marked the initial breakup of the supercontinents. A wide range of Preterozoic mafic dyke swarm, occurred in North China Craton, which will provide important constraints on reconstructing North China Craton and its position in the Mid-Proterozoic supercontinent.