Abstract
During the partial melting of the mantle, due to the compatibility difference, Re tends to enter the melt and concentrate in the earth crust, while Os tends to remain in the residual phase, thereby enriching in the mantle. This isotope fractionation caused differences in the distribution of Re and Os isotopes between the crust and the mantle, which lead to the change in the isotopic composition of 187Os/188Os in the ocean. The change is recorded in the growing of the hydrogenetic marine authigenic mineral such as polymetallic crusts, and by comparing the layered Os isotope composition curve of crusts with the seawater standard curve, the dating can be realized. K/T (Cretaceous/Tertiary) boundary low values, E/O (Eocene/Oligocene) boundary low values and Miocene “deflection” are the only three “anchor points” for curve comparison before, which causes the uncertainty of the dating result. In this study, by comparing the Os isotopic composition curves of six polymetallic crust samples from the central and western Pacific, four new curve characteristics were recognized, providing reference for the accurate chronology work. Meanwhile, the regional and periodic difference of the curve are studied. It can be preliminarily explained as the regional earth-mantle derived materials supply events but it didn’t break the overall pattern of the Pacific system.
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