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摘要
Multiple sulfur isotope ratios (S-14/S-33/S-32) of Archean bedded sulfides deposits were measured in the Yanlingguan Formation of the Taishan Group in Xintai, Shandong Province, East of China; delta S-33 = -0.7 parts per thousand to 3.8 parts per thousand, delta S-34 = 0.1 parts per thousand-8.8 parts per thousand, Delta S-33 = -2.3 parts per thousand, to -0.7 parts per thousand. The sulfur isotope compositions show obvious mass-independent fractionation (MIF) signatures. The presence of MIF of sulfur isotope in Archean sulfides indicates that the sulfur was from products of photochemical reactions of volcanic SO2 induced by solar UV radiation, implying that the ozone shield was not formed in atmosphere at that time, and the oxygen level was less than 10(-5) PAL (the present atmosphere level). The sulfate produced by photolysis of SO2 with negative Delta S-33 precipitated near the volcanic activity center; and the product of element S with positive Delta S-33 precipitated far away from the volcanic activity center. The lower Delta S-33 values of sulfide (-2.30 parts per thousand to -0.25 parts per thousand) show that Shihezhuang was near the volcanic center, and sulfur was mostly from sulfate produced by photolysis. The higher Delta S-33 values (4.5 parts per thousand to -2 parts per thousand) indicate that Yanlingguan was far away from the volcanic center and that some of sulfur were from sulfate, another from element S produced by photolysis. The data points of sulfur isotope from Yanlingguan are in a line parallel to MFL (mass dependent fractionation line) on the plot of delta S-34-delta S-33, showing that the volcanic sulfur species went through the atmospheric cycle into the ocean, and then mass dependent fractionation occurred during deposition of sulfide. The data points of sulfur isotope from Shihezhuang represent a mix of different sulfur source.
- 出版日期2008-4
- 单位中国地质科学院; 中国地质科学院矿产资源研究所
