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RESEARCH PRODUCT

Formation Ages and Environments of Early Precambrian Banded Iron Formation in the North China Craton

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The North China Craton (NCC) has had a long geological history back to ca. 3.8 Ga ago, but the most important tectonothermal event occurred at the end of the Neoarchean, the most important period of BIF formation. There are three ancient terranes (>2.6 Ga) in the NCC. Most BIFs are distributed along the western margin of the Eastern Ancient Terrane, accounting for about 89 % of the total identified BIF iron ore resources in the NCC. They are considered to have formed on a continental basement in terms of rock association of the BIF-bearing supracrustal sequences which were intruded by slightly younger crustally derived granites. Most BIFs in the NCC show positive Y anomalies, implying that Fe in the BIFs had an affinity to seawater; however, positive Eu anomalies in the BIFs may suggest that high-temperature fluids also played a role in their formation. It seems that the BIFs were deposited on a continental margin, or more likely a back-arc basin environment, and a stable environment was one of the key factors for the formation of large-scale BIFs. In this paper, we provide new BIF metallogenic prospects for the NCC, namely in the northeast of Anben, between Anben and eastern Hebei, and between eastern Hebei and western Shandong.