Research status and prospect of Precambrian stratified iron formation
Stratified iron ore is mainly distributed in the Precambrian period,most of which are stratified.The most typical stratified iron ore is the banded iron formation,BIF,in the Precambrian period and the Paleoproterozoic Xuanlong type iron ore in Northwest Hebei Province.BIF is the most important type of stratified iron ore in the world,and their origin has been the focus of research.Two main viewpoints of their origin are present:abiogenic and biogenic.In recent decades,there is increasing evidence showing that microbes have involved in the formation of BIF,and may played important role in the formation of BIF.In this paper a few main biogenic hypotheses of BIF are reviewed,such as cyanobacteria may produce oxygen and promote BIF formation;the metabolism of iron bacteria played the key role in the formation of BIF;the magnetic particles in magnetotaxis bacteria can preserved to form ore deposits;and some unknown microorganisms have involved in the formation of BIF.The Xuanlong type iron ore is a famous iron ore type in our country.According to the microbial fossils in the ore and the similarity of the fabrics of the ore to those of biogenic carbonates,the ore it is generally interpreted to have a biogenic origin.Based on the research of the formation mechanism of the Xuanlong type iron ore,it is proposed here that the research of BIF can learn from the study of the Xuanlong type iron ore and microbial carbonates,and nanoscopic tools can be used in the recognition of microscopic fabrics of BIF to establish the standards to recognize biogenic BIF.
BIFXuanlong type iron oreMicrobialiteBiogenic carbonateBiogenic iron ore
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