Noble gases in submarine pillow volcanic glasses

Fifteen submarine glasses from the East Pacific Rise (CYAMEX), the Kyushu-Palau Ridge (DSDP Leg 59) and the Nauru Basin (DSDP Leg 61) were analysed for noble gas contents and isotopic ratios. Both the East Pacific Rise and Kyushu-Palau Ridge samples showed Ne excess relative to Ar and a monotonic decrease from Xe to Ar when compared with air noble gas abundance. This characteristic noble gas abundance pattern (type 2, classified by Ozima and Alexander) is interpreted to be due to a two-stage degassing from a noble gas reservoir with originally atmospheric abundance. In the Kyushu-Palau Ridge sample, noble gases are nearly ten times more abundant than in the East Pacific Rise samples. This may be attributed to an oceanic crust contamination in the former mantle source. There is no correlation between the He content and that of the other noble gas in the CYAMEX samples. This suggests that He was derived from a larger region, independent from the other noble gases. Except where radiogenic isotopes are involved, all other noble gas isotopic ratios were indistinguishable from air noble gas isotopic ratios. The 3He/4He in the East Pacific Rise shows a remarkably uniform ratio of (1.21 +/- 0.07)*10**-5, while the40Ar/36Ar ranges from 700 to 5600.

Composition of marine phosphorites and phosphate-bearing sediments

The book deals with behavior of phosphorus and its concentration in oceanic phosphorites. The major stages of marine geochemical cycle of phosphorus including its supply to sedimentary basins, precipitation from sea water, distribution and speciation in bottom sediments, diagenetic redistribution, and relation to other elements are under consideration. Formation of recent phosphorites as a culmination of phosphate accumulation in marine and oceanic sediments is examined. Distribution, structure, mineral and chemical compositions of major phosphorite deposits of various age on continental margins, as well as on submarine plateaus, uplifts and seamounts and some islands are described. A summary of trace element abundances in oceanic phosphorites is presented. Problems of phosphorite origin are discussed.