The H₂SO₄–CrO₃ method has been widely used in Re‐Os isotope dating of organic‐rich sedimentary rocks. However, the high Re blank of this method inhibits the collection of high‐precision Re‐Os data, especially for organic‐rich sedimentary rocks with low Re and Os mass fractions. Here, we report a new H₂SO₄–Na₂CrO₄ method in which the Re blank of the Na₂CrO₄ reagent can be greatly reduced after efficient purification by acetone. A proportion of 0.6 g Na₂CrO₄/8 ml H₂SO₄ was selected as the best digestion combination based on tests of black shales with different organic carbon contents in three digestion media (inverse aqua regia, H₂SO₄–CrO₃, and H₂SO₄–Na₂CrO₄). The H₂SO₄–Na₂CrO₄ method has an ultra‐low total procedural blank of 1–2 pg for Re and 0.6–1 pg for Os, respectively, which is one order of magnitude lower than the H₂SO₄–CrO₃ method and is comparable with to inverse aqua regia method. The new method was applied to reference material SBC‐1 and two series of black shale samples, and the results were consistent with those obtained via the inverse aqua regia method. These findings confirm the accuracy and feasibility of the H₂SO₄–Na₂CrO₄ method, and demonstrate its ability to accurately determine the depositional age of organic‐rich sedimentary rocks with low Re and Os mass fractions.

中文翻译：

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纯化的Na2CrO4-H2SO4：一种用于黑页岩Re-Os约会的新型低空白培养基

H ₂ SO ₄ -CrO ₃方法已被广泛用于富含有机物的沉积岩的Re-Os同位素测年。但是，这种方法的高Re空白值阻碍了高精度Re-Os数据的收集，特别是对于具有低Re和Os质量分数的富含有机物的沉积岩。在这里，我们报告了一种新的H ₂ SO ₄ -Na ₂ CrO ₄方法，其中通过丙酮有效纯化后，可以大大减少Na ₂ CrO ₄试剂的Re空白。0.6克Na甲比例₂的CrO ₄ /8毫升ħ ₂ SO ₄根据三种消解介质（逆王水，H ₂ SO ₄ -CrO ₃和H ₂ SO ₄ -Na ₂ CrO ₄）中不同有机碳含量的黑色页岩的测试，选择最佳的消解组合。H ₂ SO ₄ -Na ₂ CrO ₄方法的超低程序空白分别为：Re为1-2 pg，Os为0.6-1 pg，比H ₂ SO _4-低了一个数量级。 CrO ₃方法，可与逆王水相媲美方法。将该新方法应用于参考材料SBC-1和两个系列的黑色页岩样品，结果与通过反向王水法获得的结果一致。这些发现证实了H ₂ SO ₄ -Na ₂ CrO ₄方法的准确性和可行性，并证明了其能够准确确定具有低Re和Os质量分数的富含有机物的沉积岩的沉积年龄的能力。