We summarized practical shipboard methods for analyzing major chemical components (Cl, Ca, Mg, pH, alkalinity, Si, PO₄, NH₄, SO₄, Na, K, Li and Sr) in interstitial water samples. These methods, which have been developed through DSDP (Deep Sea Drilling Project) and ODP shipboard routine works, were favorably applied for the samples retrieved from the Nankai Trough accretionary prism during the ODP Leg 131.

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Cadmium contents of limestone samles were determined by flame atomic absorption spectrometry combined with ammonium pyrrolidinedithiocarbamate (APDC)-4-methyl-2-pentanone (MIBK) solvent extraction system. The Cd contents of Quaternary limestones occurring in the Nansei Islands are independent of the amount of impurities such as silicates or oxides, the fact suggesting that Cd²⁺ may be directly incorporated into calcite by replacing Ca²⁺ in the lattice. The geometric mean and the median of Cd in the present samples (n =94) are both 0.07_1ppm, which is quite similar to Mason and Moore's value (0.09ppm) of this element in carbonate rocks. The Cd contents of Quaternary limestones may be largely controlled by the concentration of this element in aragonite, high-Mg calcite and low-Mg calcite in unconsolidated carbonate sediments which are the precursor of these limestones. During the formation of pure Quaternary limestones, Cd seems to behave together with Zn. However, the observed enrichment of Cd relative to Zn in these limestones might be caused through the above replacement mechanism.

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The purpose of this report is to compile the most recent data of trace element concentrations and distributions in seawater as of 1991. The geochemical and oceanographical factors controlling their oceanic distributions are not described in detail here, so that the readers, if necessary, should refer to the original references. Since the excellent articles of Bruland (1983), Broecker and Peng (1982) and Quinby-Hunt and Turekian (1983) have appeared in the early 1980's, there has been a continued quantum leap in our knowledge of trace element concentrations in the ocean, and we are now approaching to the final stage in the game of filling up the periodic table of oceanic distribution. Summarizing the results, (1) there is no data for Rh and Os, and the only upper limits can be placed for Ta, Rh and In, (2) data for Y, Zr, Hf, Nb, Re, In, and Sn are so few that further confirmation is needed for their oceanographic consistency, (3) the distributions of Al, Pb, Bi, Te, Mn, Co, Ti, Cu, and Ga are strongly influenced by scavenging, and some evidences are available for bottom regeneration of trace metals like Al, Cu, Ti, Ga etc., and (4) more than 30 elements are correlated with nutrients such as reactive phosphate, nitrate and silicate. It is hoped that within the 20th century, all the elements in the periodic table may be accurately determined by improved techiques, and thereby the new field of chemical tracer oceanography will be opened up for the next century.

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The origin of p-isotopes (proton rich isotopes) and their isotopic anomalies are reviewed in this article. The p-isotopes (⁸⁴Sr,¹²⁴Xe, ¹³⁰Ba, ¹⁴⁴Sm, ¹⁹⁶Hg, etc.) are heavy isotopes (A≧74) which cannot be synthesized by s-process or r-process. The p-isotopes are considered to be produced by the transmutation of heavy elements into lighter p-isotopes via a series of (γ, n), (γ, p) and (γ, α) reactions in supernovae. We can constrain the site and the condition of nucleosynthesis in supernovae from abundances of the p-isotopes. The isotopic anomalies of the p-isotopes of Xe, Cd and Sn are found in acid residues of the Allende carbonaceous chondrite. The anomalies of ⁸⁴Sr and ¹⁴⁴Sm are also found in the Allende FUN inclusions. They are considered to be presolar origin. The anomalies of ¹⁹⁶Hg are found, however, their origin still remains enigmatic. The anomaly of Mo isotopic abundances is found in the Sikhote-Alin iron meteorite. The anomaly can be explained by (γ, n) reaction chains of Mo. The further study of the Mo anomaly will give us interesting informations not only about the p-process, but also about the r-process effect on ⁹³Nb, the double β^--decay of ⁹⁶Zr, and the (γ, n) reaction chain of ⁹⁹Tc.

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Recent developments in dating two types of deposits, Mississippi Valley-type (MVT) deposits which are related to crustal fluid flow and rare-earth deposits, are reviewed here. The MVT deposits are epigenetic carbonate-hosted Pb-Zn deposits. They have concealed their precise ages in spite of many attempts using variety of techniques. The Rb-Sr method has been sucessfully applied to sphalerites from MVT deposis. The result indicated that mineralization in East Tennessee took place at 350-380Ma, which denies genetic linkage of the deposits to the late Paleozoic crustal fluid flow during the Alleghanian orogeny (320-250Ma). The application of this dating method will put reliable geochronological constraints on the formation of the MVT deposits and shed light on the genesis of the deposits. A new geochronometer using electron capture decay of ¹³⁸La has been applied to rare-earth rich minerals such as monazite, allanite and bastnaesite. The method allowed to determine an age of otherwise undatable bastnaesite in Gakara, Burundi.

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