GEOCHEMICAL JOURNAL

Major elements and REE in tektites and three probable shock-metamorphic rock series of the Baltic shield

Tapio Koljonen, R. J. Rosenberg

1976 Volume 10 Issue 1 Pages 1-11
Published: March 20, 1976
Released on J-STAGE: April 08, 2008

DOIhttps://doi.org/10.2343/geochemj.10.1

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REE contents of four tektites from separate strewn-fields have been determined and the REE and major elements in ten shock-metamorphic rocks from lakes Lappajärvi, Sääksjärvi (Finland), and Jänisjärvi (Soviet Karelia). Neither the impact of meteorite or comet nor secondary weathering seems to change the REE content or distribution pattern in rocks. Therefore, where the texture and major element composition in country rock has changed through impact and after it, REE can be used as indicators of the original rock or sediment type. The surfaces of the Moon and each planet, including the earth, probably have unique REE distribution patterns as a result of the prevailing endogenic and exogenic processes. The distribution patterns of REE in tektites, are quite similar to those found in sediments, sedimentary rocks and shock-melted rocks. Accordingly, the origin of tektites from silica-rich clayey sediments or silicic rocks through impact is strongly indicated.

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Granitization and U-Pb studies of zircons in the Lauterbrunnen Crystalline Complex

Brian L. Gulson, Heinz Rutishauser

1976 Volume 10 Issue 1 Pages 13-23
Published: March 20, 1976
Released on J-STAGE: April 08, 2008

DOIhttps://doi.org/10.2343/geochemj.10.13

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Zircons from the granitic part of the Lauterbrunnen Crystalline Complex are a mixture of detrital zircons and predominantly clear euhedral types which occasionally have detrital cores. The clear euhedral crystals contain old radiogenic lead which has probably been generated over approximately 2b.y. The zircons from gneissic xenoliths, which are inherent parts of the Lauterbrunnen Crystalline Complex, are all detrital rounded types and their upper projection with ‘concordia’ is also approximately 2b.y. Uranium lead data for zircons from the granitic and transition rocks define a curve rather than a straight line. The ‘reverse’ discordancy pattern (a feature observed in other possible anatectic granites) and incompatibility of the data to any event as defined by Rb-Sr mica ages are consistent with the conclusions drawn from detailed mapping, petrography and geochemistry that the Lauterbrunnen Crystalline Complex was formed in situ from former sediments rather than intrusion from depth. Fission track registration shows the uranium to be evenly distributed throughout the zircons from the gneiss, transition rock and final granitic product, although some crystals from the transition granitic rock have uranium-rich rims.

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Xenon isotope anomalies and extinct superheavy elements in carbonaceous chondrites

P. K. Kuroda

1976 Volume 10 Issue 1 Pages 25-31
Published: March 20, 1976
Released on J-STAGE: April 08, 2008

DOIhttps://doi.org/10.2343/geochemj.10.25

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And in this also (pursues Eleutherius) methinks both you and the chymists may easily agree, that the surest way is to learn by particular experiments, what differing parts particular bodies do consist of, and by what wayes (either actual or potential fire) they may best and most conveniently be separated, as without relying too much upon the fire alone, for the resolving of bodies, so without fruitlessly contending to force them into more elements than nature made them up of, or strip the severed principles so naked, as by making them exquisitely elementary to make them almost useless. ROBERT BOYLE (1661) The Sceptical Chymist Carbonaceous chondrites contain approximately 10^-11cc per gram of excess fission xenon, most of which is released from the meteorites at temperatures 1, 200 to 1, 400°C. It appears to be the xenon from the decay of ²⁴⁴Pu, but its concentration is at least several times the amount calculated from the uranium content of the meteorites. The so-called Renazzo-type fission xenon, which is released at temperatures 600 to 1, 000°C, can be shown to be non-fissiogenic. While the Renazzo-type fission xenon can be enriched by treating the meteorites with acids, the ²⁴⁴Pu fission xenon component becomes depleted in the residual mineral fractions.

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Partition of Al, Mg and Si between coexisting Ca-rich, and Ca-poor pyroxenes

Hideo Hirano, Takashi Matsumoto

1976 Volume 10 Issue 1 Pages 33-41
Published: March 20, 1976
Released on J-STAGE: April 08, 2008

DOIhttps://doi.org/10.2343/geochemj.10.33

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Partition of Al, Mg and Si in coexisting Ca-rich and Ca-poor pyroxenes is expressed by the equation: Mg₂Si₂O₆^Opx + CaAl₂SiO₆^Cpx = MgAl₂SiO₆^Opx + CaMgSi₂O₆^Cpx. Enthalpy- and volume differences in the reaction have been estimated on the basis of available high-temperature experimental data and unitcell parameters of the pyroxene solid solutions as follows: ΔH (at 0kb) = -11.2 (kcal/mol), ΔV = 7.52 X_Al^M1-1.72 (ml/mol) where X_Al^M1 is the mole fraction of MgAl₂SiO₆ in Ca-poor pyroxene in Mg₂Si₂O₆-MgAl₂SiO₆ join. From the thermodynamic data and the calculation of the apparent distribution coefficient, K_D', = (X_{MgAl₂SiO₆}/X_{Mg₂Si₂O₆})^Opx·(X_{CaMgSi₂O₆}/X_{CaAl₂SiO₆})^Cpx for natural pyroxene pairs of various modes of occurrence, the following conclusions have been obtained: (1) The apparent distribution coefficient, K_D' depends on the Fe/Mg ratio of pyroxene as well as equilibration temperature. (2) The normalized apparent distribution coefficient, K_D* can be used as a geothermometer. (3) The distribution coefficient, K_Al (=(^ZAl/Si)^Cpx/(^ZAl/Si)^Opx) defined by GREEN (1964)) may not be an appropriate geobarometer.

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Relations of the earth's metallogenetic history to possible chemical evolution of oceans

Yoshimichi Kajiwara

1976 Volume 10 Issue 1 Pages 43-46
Published: March 20, 1976
Released on J-STAGE: April 08, 2008

DOIhttps://doi.org/10.2343/geochemj.10.43

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The mineralization of iron (“iron formations”) seems to have been replaced in apparent production by those of other metals such as copper, zinc, and lead (stratiform massive sulfide ores, limestone-lead-zinc ores, “porphyry coppers”, and other vein type sulfide ores) about 1.9 × 10⁹ years ago, which corresponds to the time when oxidized sediments are believed to have begun to appear globaly on the earth's surface. This would strongly suggest that the evolution of ore types also is closely related with the development of oceanic and atmospheric oxygen during geologic time. The model for the evolution of metallic abundances in the oceans proposed in this paper can give a reasonable account of the evolution of ore types. The author's idea of ocean water origin of “ore solutions” may be acceptable throughout the geologic history.

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Thermodynamic interpretation of Na-K-Ca geothermometer in the natural water system

Naotatsu Shikazono

1976 Volume 10 Issue 1 Pages 47-50
Published: March 20, 1976
Released on J-STAGE: April 08, 2008

DOIhttps://doi.org/10.2343/geochemj.10.47

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A cation-chloride concentration diagram showing the stability of minerals in natural water system at elevated temperatures is constructed. The curves on this diagram showing the equilibrium between aqueous solution and minerals commonly occurring in nature generally satisfy the empirical Na-K-Ca relationship obtained by FOURNIER and TRUESDELL (1973). This indicates that the chemical composition of natural waters is largely controlled by minerals commonly occurring in nature.

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