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The Main Geological Events of the Chinese Archaean and Proterozoic Eons

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The Main Geological Events of the Chinese Archaean and Proterozoic Eons Open Journal of Geology, 2012, 2, 111-120 http://dx.doi.org/10.4236/ojg.2012.23012 Published Online July 2012 (http://www.SciRP.org/journal/ojg) The Main Geological Events of the Chinese Archaean and Proterozoic Eons Keqiang He1, Rulin Du2 1Geological Environment Center, Qingdao Technological University, Qingdao, China 2School of Economics Shijiazhuang, The Precambrian Institute of Shijiazhuang, Shijiazhuang, China Email: [email protected] Received January 17, 2012; revised February 20, 2012; accepted March 22, 2012 ABSTRACT A systematic review and comparison of the time, sequence, nature, and characteristics of the major geological events of worldwide Archean and Chinese Precambrian and their interrelationships reveals that these events reveals the spa- tial-temporal pattern of the events and their significance in geological evolution. The study also touches upon rela- tionship between Early Precambrian Era and plate tectonics. A comparison between the Precambrian major geological events and those elsewhere on the earth proves that the crustal evolution is characterized by striking irreversibility, gradualism, and synchronism. The geological events in China have their unique features, which show that China has a relatively complete record of formation and evolution of rocks, strata, structures, and organisms spanning 3800 Ma to 540 Ma. The Archean underwent multiple-stage complex metamorphism and deformation; metamorphism is on the higher end; komatiite is absent in the greenstone belts; cratonization occurred rather late and varied between the north and the south. The research results above provide main theoretical basis for deeply systematic researching the early dy- namic evolution laws of the earth and the dynamic evolution characteristics of the tectonic plates. Keywords: China; Archaean; Proterozoic; Precambrian; Geological Events 1. Introduction This study synthesizes the author’s own and other re- searchers’ publications, systematically examines and com- The Precambrian Era, which spans roughly over eighty- pares the time, sequence, nature, and features of the Ar- five percent of the earth’s recorded history out of it entire chean worldwide and Chinese Precambrian major geo- history, is a critical stage in the earth’s evolution history, logical events and their interrelationships, and identifies captivating geologists all over the world for its complex a spatial pattern of consistency, differentiation, and im- experience, rich mineral resources it produced, and it’s balance along with a temporal pattern of periodicity and relevance to the research on the origin and evolution of cycles. These findings may provide a useful basis for the the earth and life. investigation of the evolution trend and for the division More than seventy percent of the land on the pre- of the evolution stages of the earth in its early days, and sent-day earth is composed of Archean terrains and their offer significant clues to the relations between early-day metamorphosed equivalents. Therefore, that the evolu- structural framework and plate tectonics of the crust. tion of the Archaean or Early Precambrian crust has in recent years become one of the biggest hotspots and 2. Main Geological Events of the Chinese challenges in geological research, which, in turn, has Archaean Eon (Tables 1 and 2) become an important source of inspiration for new re- search. 2.1. The Time Sequence and Features of Main China is one of the countries which are bestowed with Geological Events in Archaean Eon the most widespread Precambrian strata, facilitating re- Since 1980s four pieces of detrital zircon were separated search in this subject and nurturing a tradition of such from metamorphic quartz sandstone deposited about research. The country has a relatively complete historical 2800 Ma at Mount Narryer in West Australia. The U-Pb record (dating from 3800 Ma to 543 Ma) of formation age tested by ionic probe mass spectrum was 4200 Ma, and evolution of rocks, strata, structures, and organisms, and it represents the oldest known mineral age in the which hosts a wide variety of minerals and displays an Earth [1,2]. Subsequently, the history of original crust assortment of unique geological conditions. could be pushed forward ca. 4300 Ma (see Table 1). Copyright © 2012 SciRes. OJG 112 K. Q. HE, R. L. DU Ancient crustal rocks older than 3800 Ma globally are Middle Archean Era are represented globally by the very rare. They have only been discovered in SW Swaziland greenstone of Barberton, South Africa in Af- Greenland, NW Canada, and Enderby Land, South Pole rican shield [7], and Warawoona greenstone of Yilgarn [3,4]. The Isua Belt of Godthab district in SW Greenland shield, West Australia [8]. The amphibolites of Xiaolaihe was the earliest layered series which qualified as crustal greenstone belt in Liaoning, NE China which have a rocks. They comprise mainly metamorphic volcanic 3000 Ma Sm-Nd isochron age belong to this early green- rocks and sedimentary rocks >3000 m in thickness, and stones event [9], and comprise komatiites, mafic rock have a U-Pb age of ca. 3820 Ma based on detrital zircons. and offshore marine sedimentary deposits as the main The granites that intrude the Isua Belt are some of the characteristics. Combined they form a complete vol- earliest known granites with a Rb-Sr age of 3780 Ma and canic-sedimentary cycle. The appearance of advanced have been transformed into the Amitsoq gneiss after me- metamorphic zone of late Palaeo-Middle Archean Era tamorphism [5]. The gneiss which is exposed in large (granulite facies) was part of the global granulite-facies areas can be divided into three rock groups: tonalite, metamorphic event that happened in the earliest phase of trondhjemite and granodiorite (TTG rock). These so- lithosphere formation. It is marked worldwide by strong called “grey gneiss” became the primitive palaeo-conti- tectogenesis (tectono-thermal event) and regional meta- nental nucleus. Between the continental nucleus and their morphism, and represents the first collision of ancient margins, there are many greenstone belts which became continental nucleus and land masses, and which made the hyperplasia body on the continental nucleus and the original lithosphere sink and was shaped into granulite welded belts of continental nucleus. facies after deep melting and into charnockite after Since 1990s, the trondhjemite found in the Anshan remelting. This “Movement” (event) can be recognized Mountain of China and dated ca. 3800 Ma could be di- in North America, Europe, West Australia, and Africa. In vided into two types: Baijiafen trondhjemite (also known Africa, it was called the Dahomey Movement. In China, as ortho-gneiss) and Dongshan trondhjemite migmatite. many scientists agreed to name this movement the In addition, Liu D. Y, Nutman A. P., Compston W. ob- Qianxi Movement. According to the tectogenesis and tained a U-Pb age between 3500 Ma - 3850 Ma from a intensity of magma activities and universality of regional single-grain zircon found in Huang Boyu, eastern Hebei metamorphism, the time period of 2900 - 3000 Ma can Province [6]. It was the earliest dated rock in China. be regarded as the demarcation age between the Palaeo- Caozhuang Rock represents the earliest super crustal Middle Archean Era and the Neo-Archean Era. The Rocks. These rocks show the evolution of an early con- trondhjemite event of early Neo-Archean Era is recorded tinental nucleus (craton) in China. in Southwest Finland, Norway, and West Greenland. The greenstones (early greenstone) of the Palaeo- Along with the grey gneiss, it has formed the bulk of Table 1. The time sequence of main geological events in Archean Eon. Event Crustal Geologic Chronology Main Geologic Events Isotopic Age Main Districts Sequence Movement Archean Eon ~Ken Nore Kali granite Intrusive and large-scale Movement~ 2500 Ma Canada, West Australia, China, 8 regional metamorphism 2600 - 2500 Ma Finland Late Archean Greenstone Terrane North America, South Neo-Archeozoic Eon 7 ~ ~ ~ ~ 2800 - 2700 Ma (Late Greenstone) Africa, West Australia, Russian 2800 - 2900 Ma West Finland, Greenland, 6 Trondhjemite Event ~ Dahomey China Movement ~ Early Archean Granulite Event 5 Covering globally (Global Regional Metamorphism) 3000 - 2900 Ma Ancient Archean Granite-Greenstone Terrance (Early Greenstone) South Africa, West Australia 4 ~ ~ ~ ~ 3400 - 3100 Ma (Some districts suffered high-grade India, and China Paleo-Middle regional metamorphism) Archaeozoic Eon The earliest granite intrusion and and Pre-Archean Eon 3 ~ ~ ~ ~ 3800 - 3700 Ma Greenland, Canada, China metamorphic event (Amitsoq Granite) The earliest layered rock system 2 3820 Ma Southwest Greenland (Greenland Isuah Group) The earliest geological record 1 4200 Ma West Australia (zircon age) Copyright © 2012 SciRes. OJG K. Q. HE, R. L. DU 113 Archean rocks or intruded into ancient greenstone belts. the granite evolved from the early tonalite and trond- In Qian’an of eastern Hebei Province, Qingyuan of hjemite, to the late kaligranite. From its components, we northern Liaoning Province, Anshan of Southern Liaon- also can conclude that it accords with the model of con- ing Province, and Taishan of western of Shandong Prov- tinental growth; in the early stage abundant in sodium, ince, there is a lot of charnockite exposed (see Table 2). later in calcium. Zhou et al. separated an apatite sample For example, in Qian’an of eastern Hebei Province an- from the 3.8 Ga (zircon SHRIMP U-Th-Pb age) meta- cient charnockite was found intruded in the grey gneiss quartz-diorite sample in Anshan area and using SHRIMP of Qianxi granulite facies. Cored with its rock mass, II. 32 analyses yielded a 207Pb/206Pb weighted mean Qingyuan charnockite featured within migmatite belt and age of 3007 ± 22 Ma. This is interpreted as the age of granulite (grey gneiss) to the outer zone [10]. Reference recrystallization of the apatite during the very intense [10] shows that charnockite was formed by remelting, thermo-tectonic events at ~3.0 Ga in the Anshan area. crystal fractionation and metasomatism. Its intrusion is In the late Archean Era, greenstones (late greenstone) dated as the same as that of granulite formation, ca.
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