A compare geochemistry study for Algoma- and Superior-type banded iron formations

作者：Li YanHe^*; Hou KeJun; Wan DeFang; Zhang ZengJie

来源：Acta Petrologica Sinica, 2012, 28(11): 3513-3519.

• Banded iron formations (BIFs)
• Silicon and iron isotope
• Sulfur isotope mass independent fractionation

The Precambrian banded iron formations (BIFs) are the most important type for iron resources in the world and extraordinary chemical marine sediments formation only occurred in the early Earth, which were concentrated during Archean to Early Proterozoic eras (3.2 similar to 1.8Ga) and recorded lithosphere, hydrosphere, atmosphere and biosphere status and evolvement then and there. The BIFs were classified into Algoma- and Superior-type on the basis of mineralogical composition and proposed tectonic setting. But contrastive studies about their geochemical characteristic, depositional environment and origin are little. So the silicon, oxygen, iron and multiple sulfur isotopic compositions of Algoma- and Superior-type BIFs were compared. The silicon isotopic compositions of BIFs of different types and ages are similar and strongly depleted in Si-30, the delta Si-30 values are lower. Their iron and multiple sulfur isotopic compositions are obvious different. Most Delta S-33 values of Algoma-type BIF are negative, whereas positive Delta S-33 values appear at Superior-type BIF. The heavy iron isotope are usually enriched in Algoma-type BIF, the delta Fe-56 are large positive values; whereas the light iron isotope are enriched in Superior-type BIF, the delta Fe-56 are negative or small positive values. The data imply that BIFs were formed by submarine exhalation, whatever the Algoma-type or the Superior-type, they belong to the same mineralize system. In contrast, Algoma-type BIF were closely related to volcanic activities and formed in depth marine basin and more reductive depositional environment.

• 出版日期2012-11
• 单位中国地质科学院矿产资源研究所