DOI:10.19762/j.cnki.dizhixuebao.2021109
 
Effect of 2. 56~2. 52 Ga oxidation event on mineralization and life evolution in the North China block
Author NameAffiliationE-mail
SHEN Baofeng 1) Tianjin Center, China Geological Survey, Tianjin, 300170 2) North China Center for Geoscience Innovation, China Geological Survey, Tianjin, 300170 sbaofeng.2009@163.com 
BI Junhui 1) Tianjin Center, China Geological Survey, Tianjin, 300170 2) North China Center for Geoscience Innovation, China Geological Survey, Tianjin, 300170  
ZHANG Kuo 1) Tianjin Center, China Geological Survey, Tianjin, 300170 2) North China Center for Geoscience Innovation, China Geological Survey, Tianjin, 300170  
Abstract:The significant increase in atmospheric oxygen concentration on the earth’s surface is one of the most important geological events in the earth’s history. It not only changed the earth’s surface environment and promoted the evolution of life, but also accelerated the supergene geological process, forming a series of rocks and important ore deposits adapted to the abrupt change of environment. During the Precambrian, the earth experienced two rapid atmospheric oxygen enrichment events, namely the Great Oxidation Event (GOE) and the Neoproterozoic Oxidation Event (NOE). This paper mainly discusses the time limit of the late Neoarcheanoxidation eventin the North China block and its influence on mineralization and biological evolution. In the late Neoarchean period, more than thousand oxide phase BIF type iron deposits and occurrences belonging to the Algoma type were formed in the North China block. The total identified reserves are about 33. 536 billion tons, accounting for 46% of the total iron ore reserves in China. These deposits and mineralised pit occurrences were formed in a weakly alkaline oxidation environment, and their metallogenic ages are mainly between 2. 56 Ga and 2. 52 Ga, and underwent metamorphism at 2. 51~2. 50 Ga. The characteristics of Ce anomaly, iron isotopic composition and Mass Independent Fractionation effect of sulfur isotope (MIF- S) in BIF type iron ore deposits show that the oxygen concentration in the atmosphere increased greatly during 2. 56~2. 52 Ga, and changed from anoxic reduction environment to oxidation environment with oxygen concentration (1%~10% PAL), implying that a significant oxygenation event occurred in the North China block during this period. The oxidation event has an important impact on the mineralization of the North China landmass, mainly in the following three aspects: (1) the formation of a large number of oxide phase BIF type iron ore deposits, which are the most important iron deposit typesmined in China, but lack carbonate BIF type iron ore deposits; (2) restricting the development of VMS type Cu, Zn massive sulfide deposits in the late Neoarchean, which is only reported in the Hongtoushan area, Northern Liaoning Province; (3) there is no Rand type gold uranium conglomerate deposit as in South Africa. In addition, the oxidation event accelerated the evolution of life on the North China block. Generally, it takes about 1. 6~1. 7 billion years to evolve from single cell eukaryotes to macro multicellular eukaryotes. However, from the late Neoarchean (2. 56~2. 52 Ga) oxidation event to the discovery of macro fossils from the Gaoyuzhuang Formation of Jixian period in the North China block, the evolution from single cell eukaryotes to macro multicellular eukaryotes only took about 1 billion years. The results show that the time limit of the first oxidation event is 2. 56~2. 52 Ga in the North China block, which is not only about 100 million years earlier than the other regions of the world (~2. 4 Ga), but also the life evolution is 600~700 million years earlier than other regions.
keywords:Great Oxygenation Event  North China block  oxide phase BIF type iron deposit  2. 56~2. 52 Ga  mineralization  life evolution
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