SILICON ISOTOPIC COMPOSITIONS OF ARCHEAN BANDED SI-FE FORMATION (BIF)IN THE GONGCHANGLING ORE DEPOSIT, LIAONING-PROVINCE, CHINA

The results of silicon isotope analyses of Precambrian BIF are reporte d for the first time. The deltaSi-30 values of magnetite-quartzite in the Gongchangling ore deposit are between -0.9 and -2.2 parts per thou sand, which are obviously different from those in host rocks (0.2--0.6 parts per thousand). It is suggested that the BIF may be a product of chemical precipitation in Archean submarine hydrothermal environment. There is a possibility of using silicon isotopes to distinguish the p rotolith of metamorphic rocks and trace the origin of silicon of alter ed minerals.