Contents of Re, Cd, Ag and platinum-group elements in specimens from four sub-zones of a 3cm-thick bed of a K-T boundary layer from Stevns Klint in Denmark, were determined by stable isotope dilution using ICP mass spectrometer. The chondrite-normalized Re value linearly decreases in the upper zone. Also the content of Ag linearly diminishes upward. These relations lead us to a conclusion that, at the earliest stage of the formation of this bed, the marine site studied was hi ghlyreducing, and at the final stage of the bed formation, the sea recovered to the “normal” oxidation-reduction potential. That is, it is reasoned that the anomalously reducing condition at the site persisted for a relatively short period. Some discussions are given to effect of chemical valency state on distributional features and to fractionation in the dust fallout.
Processes of melt generation in subduction zones are discussed, based on numerical calculations taking account of the flow pattern, energy balance and phase equilibrium constraints for H2O-bearing peridotites. A significant amount of melt is newly found to be produced in the downward flow along the plate by compression melting, corresponding to a gentle or negative dT/dP slope of the solidus curve. The amount of melt produced is comparable to the eruption rate of magmas on volcanic arcs (i.e., 100 to 102km3/million year per 1km of the arc length). Although further studies on the distribution of H2O and melt segregation processes are required for accurate estimates, compression melting in subduction zones is probably inevitable.
Lurlenicacid[(4E, 8E, 12E)-14-[2'-hydroxy-3', 4'-dimethyl-5'-(1"-β-D-xylopyranosyloxy) phenyl]-4, 8, 12-trimethyltetradeca-4, 8, 12-trienoic acid, 1] and lurlenol (2), the sex pheromones produced by the female gametes of the green flagellate Chlamydomonas, were synthesized stereoselectively.