Chronological application of Re-Os system to sulfide ores

对于硫化物矿床的研究，其年代学研究具有十分重要的意义。然而，由于Re-Os测年仍存在一些问题，这类硫化物形成年龄的研究一直受到阻碍，Re-Os测年有望成为一种有前途的地质计时仪。在本工作中，我们试图从技术改进的基本观点出发，研究Re-Os时钟在硫化矿石矿物中的实际应用和广泛应用中存在的问题，其中包括采用电感耦合等离子体离子源质谱计。主要研究结果如下：(1)提出了一种对电感耦合等离子体质谱仪中的质量分辨效应进行校正的新方法。将这种校正方法与高丰度Os-192的同位素稀释相结合，成功地同时测定了(Os-187)/(Os-186)比值和Os丰度。在这方面，设计了一种将OS视为…设备更多的四氧化物，具有很高的挥发性。(2)我们还成功地提高了Os和Re的灵敏度。在这种方法中，由特殊设计的小炉子产生的OSO4“或Re_2O_7蒸气合并成由传统雾化器产生的”纯“雾。因此，Os或Re被引入到等离子体炬中，而不会有实质性的损失或丢弃。在使用传统的简单雾化元素水溶液(S)的方法时，需要50-100ngOs，而根据我们的系统，-10ngOs是足够的。(3)我们认识到辉钼矿中的Re含量是不同的。这个问题是通过仔细粉碎来解决的。此外，我们还发现，我们很难在放射性成因的Os和添加的Os尖峰之间达到同位素平衡。这个同位素问题可以通过蒸馏5小时来解决，在蒸馏过程中，每小时分别收集馏分，并对每个馏分进行蒸馏出的Os的同位素测量。因此，我们可以得到正确的年龄。较少

For the studies of sulfide ore deposits, chronological studies of them are of much significance. However, such studies of formation ages of sulfides have been retarded, since there remain some problems concerning Re-Os dating which has been expected to be a promising geochronometer. In the present work, we tried to examine the problems underlying the practical and wide application of Re-Os clock to the sulfide ore minerals, from basic points of view involving the technical improvement, where the mass spectrometer with inductively coupled plasma (ICP) ion source was employed. Our results are summarized below:(1) A new method has been developed to make a correction about the effect of mass discrimination which takes place in ICP mass spectrometer. By combination of this correction method with isotope dilution employing highly enriched Os-192, we succeeded in simultaneous determination of (Os-187)/(Os-186) ratio and Os abundance. In this connection, an apparatus was devise to treat Os as … More tetroxide which has very high volatility.(2) Also we succeeded in enhancing the sensitivities of Os and Re. In this method, the vapor of OsO_4"or Re_2O_7 generated from a specially designed small furnace merges into the "pure" mist produced by a conventional nebulizer. Thus, Os or Re is introduced into the plasma torch without substantial loss or discard. In use of the customary introduction employing the simple nebulization of aqueous solution of element(s), 50-100 ng Os was required, whereas -10 ng Os is sufficient amount according to our system.(3) We recognized that the Re content in molybdenite is different from portion to portion. This problem is solved by careful pulverization. Besides, it was found out that it is difficult for us to attain the isotopic equilibrium between the radiogenic Os and the Os spike added. This isotopic problem can be solved by distillation for 5 hours, in which the distillate is collected separately for each hour and isotopic measurement of Os distilled is made for each fraction. As a result, we could obtain the correct age. Less