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Volume 16 (1982)
- Issue 6 Pages 263-
- Issue 5 Pages 213-
- Issue 4 Pages 149-
- Issue 3 Pages 99-
- Issue 2 Pages 51-
- Issue 1 Pages 1-
Volume 16, Issue 3
Displaying 1-4 of 4 articles from this issue
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Hans-W. Hubberten1982 Volume 16 Issue 3 Pages 99-105
Published: June 20, 1982
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSOceanic basalts are often altered by circulating seawater. During this process carbonates are formed frequently as veinlets and crystal aggregates. Additionally hydrothermal carbonate is found occasionally. The isotopic composition of secondary and possibly primary carbonates has been investigated for 75 samples from Hole 418 A, a 550m long basalt sequence drilled during DSDP Legs 52 and 53 to the south of the Bermuda Rise, in the Atlantic Ocean. Isotope ratios of secondary carbonates, carbonate rich basalts and some of the so called “fresh” basalts have values typical for marine carbonates, i.e., δ13C +2.8 to -2.3‰ vs. PDB. Isotope ratios of samples with small carbonate content fall in the range of primary magmatic carbon, i.e., δ13C -4 to -8‰. The carbon isotope composition of carbonates in oceanic basalts is therefore constituted by an overprinting of seawater-derived secondary carbonates on traces of primary carbonate carbon.View full abstractDownload PDF (1831K) -
Hiroshi Shimizu, Kazuyoshi Sangen, Akimasa Masuda1982 Volume 16 Issue 3 Pages 107-117
Published: June 20, 1982
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSPartition coefficients of rare-earth elements (REE), Ba and Sr were precisely determined for crystal glass pairs prepared by partial melting and partial solidification of alkali olivine basalt at 10kb and of picrite basalt at 10 and 20kb. Mutually unfractionated REE partition patterns were observed for olivine-glass pairs prepared by partial melting and partial solidification experiments on alkali olivine basalt. A similar unfractionated REE pattern was observed for (clinopyroxene + olivine)/glass formed by 10kb partial melting of picrite basalt. On the other hand, clinopyroxene was produced in 10kb partial solidification of the same picrite basalt and the clinopyroxene showed fractionated, terrace-shaped REE partition pattern. Partial solidification experiments on picrite basalt produced only clinopyroxene as a mineral coexisting with melt, and the resultant REE partition pattern was a guyot-shaped one. It should be noted that the REE partition pattern (terrace-shaped or guyot-shaped) of clinopyroxene bears on the mutual relationship concerning the relative magnitudes of partition values of Fe and heavy REE. Finally, it is worth while to note that clinopyroxene is prevailingly formed in partial solidification process.View full abstractDownload PDF (3016K) -
Naoki Isshiki, Naoki Onuma, Masataka Hirano1982 Volume 16 Issue 3 Pages 119-127
Published: June 20, 1982
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSCa, Sr and Ba contents in various volcanic rocks (basalts, andesites, rhyolites and their cognate inclusions) from Quaternary volcanoes in Toshima, Udonejima, Niijima and Kozushima, the Izu Islands, Japan, have been determined by an ICP-OES method. Basalts and andesites from Toshima and Niijima make two different series of Sr/Ca-Ba/Ca systematics (SB systematics), indicating that there exist two different primary magmas derived from a common mantle peridotite with different degrees of partial melting. The various series of SB systematics of volcanoes in the Izu Islands so far obtained, suggest that the common mantle peridotite has a chondritic composition in terms of Sr/Ca and Ba/Ca ratios. The various series of SB systematics defined by basalt-andesite-dacite series in the Izu Islands converge into a rhyolitic composition of Jinaijima type. The silicic rock may be an end product of a crystal fractionation process, and might have formed a thin crust under the Niijima and Kozushima region. The majority of rhyolites which characterize the volcanoes of Niijima and Kozushima display quite different SB systematics, suggesting that the rhyolites are formed by remelting of a thin crust, and substraction of Na-rich plagioclase from the silicic magma. The rhyolite volcanism may be triggered by the heat of basaltic magma intruded under the thin crust, as indicated by the presence of cognate inclusions with basaltic composition in the rhyolites.View full abstractDownload PDF (2488K) -
S. Tsunogai, M. Uematsu, S. Noriki, N. Tanaka, M. Yamada1982 Volume 16 Issue 3 Pages 129-147
Published: June 20, 1982
Released on J-STAGE: April 08, 2008
JOURNAL FREE ACCESSSediment traps were deployed at five depths for about one month during summer in the northern North Pacific. The samples were physically and chemically divided into four subsamples and analyzed for Al, Fe, Mn, Cu, Ni, Co, Cd, Ca, Mg, K, Na, Si, P, 234Th, 232Th, 230Th, 228Th, 210Po, 210Pb and 7Be. The concentrations of major components, silica and calcium carbonate, in the settling particles varied greatly with depth. Ca was more concentrated in large particles. The Al concentration in settling particles, which was somewhat smaller than that in suspended particles, increased with depth. The same tendency was observed for 210Pb and 210Po, whereas the concentration of 234Th showed a minimum value at 2.16km depth. Al fluxes were found to increase linearly with depth in deep water. These results suggest that there are two kinds of particles transporting the chemical components. One is the large biogenic particles produced near the surface. The other is the aggregates of suspended matter, which is important for the downward transport of some elements such as Al, Fe, Mn and 230Th. The observed fluxes are much larger than the net fluxes. This fact may be explained by the undulation of settling particles. Bottom sources of transition metals are also confirmed.View full abstractDownload PDF (4338K)
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