Confirmation and global significance of a large-scale early Neoproterozoic banded iron formation on Hainan Island, China

摘要

The Shilu iron ore deposit on Hainan Island, China, contains 460 Mt of Fe ore reserves and formed during the early Neoproterozoic (1.0-0.8 Ga). However, the genesis of the deposit and whether the deposit actually represents a banded iron formation remain controversial. Here, we present new petrographic, whole-rock geochemical, and Fe isotopic data for Fe ores from the Shilu deposit. These samples have variable but strongly positive Fe isotopic compositions (-0.29%o to 1.62%o for delta Fe-56(IRMM-014)), contain alternating Si-rich and Fe-rich bands at millimetre to centimetre scales that are identical to those typically found in banded iron formations, and contain widespread fine-grained jasper. They have whole-rock compositions that contain elevated concentrations of Fe and Si, and have post-Archean Australian shale (PAAS)-normalised rare earth element (REE) patterns that are similar to the compositions of chemical sediments. These observations strongly suggest that the Shilu Fe ores were originally a banded iron formation.