关键词: 前寒武纪, 三大地史阶段, 地质事件

Abstract:

The major geological events during the three Precambrian Eons of the Earth history, i.e., the Hadean, the Archean and the Proterozoic, are summarily described and the Precambrian evolution nature of China continent is roughly depicted. It is desirable to understand the similarity and difference between China and the global, and it is a further highlight of China continent Neoarchean super geological event, and response to the formation and breakup of the Proterozoic Colombia and Rodinia Supercontinents. The Hadean Eon for the earliest period of the Earth history extends from the age of formation of the solar system at 4567 Ma, to the age of Earths oldest dated rock from the Acasta Gneiss Complex, at 4030 Ma. The Hadean detrital zircon has been well preserved from Mt. Narryer and the Jack Hills greenstone belt of Western Australia. Meanwhile at present, rare detrital zircons of Hadean age were analyzed from 7 places in China, those are located at the Neoproterozoic to Paleozoic orogens, not in the cratons. The Archean Eon can be defined as the time of Precambrian history from the first appearance of preserved rocks at the Earths surface (4030 Ma Acasta Gneiss), to the first appearance of widespread glacial rocks, cooler Earth conditions. The oldest dated rock on Earth is a tonalitic gneiss that forms part of the 4.033.94 Ga Acasta gneiss of the northwestern Canada Slave Craton. Supracrustal rocks are locally well preserved in the Isua supracrustal belt in southwestern Greenland. It is worth to point out that the most important event of Archean is the super geological event between 2780 Ma to 2420 Ma. The oldest rocks of the North China Craton (NCC) and also of China are exposed at the Anshan region of Liaoning Province, where about 3.8 Ga tonalitetrondhjemite gneiss and 3.3 Ga supracrustal rocks are recognized. Archean evolution and nature of NCC are quite similar to that of cratons in the world, such as the granitegreenstone belt and highgrade gneiss, tonalitetrondhjemitegranadiritesuite (TTG), older continent crust (a little more than 3.8 Ga) and banded iron formation (BIF) and so on. It is noticed that Archean granitegreenstone belt is widely spreaded at the NCC, but differences with the classical ones in South Africa, Greenland, Canada and western Australia. For example, the age of granitegreenstone belt in NCC is dominantly of the Neoarchean, with smaller size of the belts, less komatiites and higher metamorphism up to amphibolitegranulite facies. Proterozoic Earth is a mature, cooler planet with large, rigid, emergent continental land masses, modernstyle plate tectonics, a supercontinent cycle, and more complex life (eukaryotes). This combination of geological and biological changes took place at about 2420 Ma, near to the time of disappearance of the Hamersleytype BIF and occurrence of the first global glacial event. It is noticed that the Huronian glacial beds and the red strata of the Great Oxidation Event are not recognized in China. The age of Paleoproterozoic Guanmenshan Formation, related to the LomagundieJatuli carbon isotopic excursion, is still uncertain. In addition, Paleoproterozoic phosphorites and the worldwide Shunga event dated to 2.01 Ga, being the source rocks for giant petroleum deposits, are not discovered. However, the assemblybreakup of supercontinentsrelated geological records are well developed in the North China, Yangtze and Tarim Cratons, respectively. The ultrahigh temperature metamorphic rocks, high pressure granulite and Columbia Supercontinet assemblyrelated magmatic association, as well as the arcrelated sedimentary and volcanic strata are exposed. And after 1780 Ma the Mesoproterozoic rifting basins and magmatic activity with disperse of Columbia Supercontinet are widespreaded in the NCC. Meanwhile the Early Neoproterozoic ophiolite, mélange, oceanic arc, subductionrelated accretion complex and continental marginal arcs occurred at the Yangtze and Tarim Cratons, which reflects the Rodinia formationrelated geological events. The rifting basins and a series of magmatism with Rodinia breakup took place since ca. 800 Ma. All of above mentioned provide an objective field laboratory and an outstanding example in studying Precambrian Earth system and mineralization to China and world geoscientists.

Key words: Precambrian, three eons of the Earth history, geological events