Abstract:

During the 4.560.543 Ga Precambrian period, it has a lot of unique geological features of sedimentation, magmatism, metamorphism, deformation, mantle and lithospheric geodynamics. In order to understand the Precambrian geodynamics, this paper introduces some scientific advances on the composition and properties of the Precambrian crust and lithosphere, and their episodic growth, variation of Archean mantle temperature and viscosity, thickness, strength and rheological structure evolution of crust and lithosphere. The heat flow value of the Earth during 3.82.5 Ga is 2.54 times tham the presentday heat flow value. During the heat early Earth period, lower mantle heat accumulation is larger than the upper mantle heat loss, resulting in cyclic mantle overturn. Coevally the rising lower mantle went through the dry peridotite solidus, resulting in largescale melting at more than 150 km depth. This is the formation mechanism and energy background of Archean continental lithospheric mantle, but due to the Earths longterm cooling, this mechanism terminated after the Archean. The Archean high heat flow values caused the heat Archean mantle difficult to support the large terrain elevation; the Archean lithospheric strength is small, and fast terrain responses happened under the action of gravity. However, the giant mafic dyke swarms first appeared (at about 2.75 and 2.45 Ga), and supracrustal rocks occurred; the late Archean crust had gradually enough rigidity to allow melts ascending through the crust which is cooled and solidified. The fundamental cause of the major geological events in the Precambrian period is the result of the attenuation and oscillations of the Earths heat；all the Precambrian crustal growth (accretion), the formation of the supercontinent, the magmatism and the mineralization are characterized by different periods and nonlinear evolution. The formation of largescale TTG in a short time implies that they were possibly derived from vertical accretion. Finally this paper discusses the Hadean characteristics, origin, growth and preservation mechanisms of the continental crust, supercontinent reconstruction and mechanism, and coevolution of early life and environment, and other key scientific problems.

Key words: Precmabrian, continental crsut growth, TTG, greenstone belt, mafic dyke swarm, snowball Earth