A good example of an application of the Re-Os isochron method is a study on the dating of a gold deposit in the Witwatersrand mining camp, South Africa. Re tends to enter the melt phase incompatible while Os remains in the solid residue compatible. In this regard, the Re—Os system to study the geochemical evolution of mantle rocks and in defining the chronology of mantle differentiation is extremely helpful. Peridotite xenoliths which are thought to sample the upper mantle sometimes contain supra-chondritic Os-isotopic ratios. This combination of radiogenic Os that was created by decay of Re and nonradiogenic melts helps to support the theory of at least two Os-isotopic reservoirs in the mantle. The second reservoir is chondritic in composition.
SHARE Although studying creativity is considered a legitimate scientific discipline nowadays, it is still a very young one. In the early s, a psychologist named J. Guilford was one of the first academic researchers who dared to conduct a study of creativity. He challenged research subjects to connect all nine dots using just four straight lines without lifting their pencils from the page. Today many people are familiar with this puzzle and its solution. In the s, however, very few were even aware of its existence, even though it had been around for almost a century. If you have tried solving this puzzle, you can confirm that your first attempts usually involve sketching lines inside the imaginary square. The correct solution, however, requires you to draw lines that extend beyond the area defined by the dots.