Geochemistry and Tectonic Significance of Chlorite Amphibolite in Nanfen BIF, Benxi Area, Northeastern China

Benxi area, Northeastern China, is the main distribution area of Archean BIF-hosted iron deposits in China. In this area, Nanfen iron deposit is well known as the largest open-pit iron deposit not only in China but also in Asia. So far, the tectonic nature during Archean BIF formation period in Benxi area has been long disputed and the tectonic setting of Nanfen BIF had not been found. In this study, the geochemical characters of chlorite amphibolites closely associated with BIF have been investigated for the tectonic environment of Nanfen BIF. Chlortie amphibolites show the geochemical affinity to the back-arc basin basalt (BABB), indicating that the tectonic environment of Nanfen BIF is the back-arc basin. In conjunction with geological evidence of other BIFs at Benxi area, it is identified that BIF in Benxi area might be formed in the subduction-related back-arc basin, which provides a favorable sedimentary environment of Algoma-type BIF.