This paper analyzes the lamprophyres from the Laowangzhai gold deposits in Yunnan Province, China, which have close temporal-spatial relations with gold mineralization, for their major elements, trace elements and rare earth elements (REE), as well as their Sr, Nd isotopic compositions and the contents of fixed ammonia (NH₄⁺). The analytical results of major elements indicate that the lamprophyres in this region are potassic, calc-alkaline lamprophyres. Their M [Mg/(Mg + Fe²⁺)] and the contents of the transition elements reflect that the rocks possess the characteristics of primary magmas. As compared with the mid-ocean ridge basalts (MORB), the lamprophyres in this region are enriched in large ion lithophile elements (LILE) and high field strength elements (HFSE). Their REE distribution patterns are of the LREE-enrichment type and their trace element distribution patterns are of the strong incompatible element enrichment type, indicating that the rocks originated from a fertile mantle. As compared with the modern values of the primitive mantle, the lamprophyres in this region have relatively high ⁸⁷Sr/⁸⁶Sr (0.70644∼0.70895) and relatively low ¹⁴³Nd/¹⁴⁴Nd (0.512436∼0.512524). The contents of NH₄⁺ in the rocks (74.34 ppm∼468.7 ppm) are obviously higher than those of other types of mantle-source rocks (1 ppm∼27 ppm), but lower than those of the carbonaceous country rocks (799.6 ppm∼1742 ppm) in the ore field. Various lines of evidence demonstrate that the lamprophyres which possess the above Sr, Nd isotopic signatures and the contents NH₄⁺ of could not be derived from the magma with MORB characteristics during its ascending, or derived from the magma chamber, which had both been contaminated by crustal materials with high ⁸⁷Sr/⁸⁶Sr, low ¹⁴³Nd/¹⁴⁴Nd and high contents of NH₄⁺, instead, the rocks are the results of partial melting of the fertile mantle. It is the main mechanism of formation of the fertile mantle in this region that metasomatism of the mantle mixed with crustal materials by fluids resultant from dewatering of crustal materials brought into the mantle during subduction and LREE-, LILE- and HFSE-rich fluids from the deep mantle (including the astrosphere).

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The rare earth elements (REEs) of the two major vegetation of the Ozegahara peatland, peat moss (Sphagnum sp.) and peat grass (Carex sp.), were determined. The overall variation of the chondrite-normalized REE patterns was almost identical to that of soil-grown plants except for cerium. Peat moss and peat grass showed no cerium anomaly, while all the soil-grown plants we have surveyed showed negative cerium anomaly. The E_H and pH condition to produce the cerium anomaly was discussed and the peatland was found to be too low in E_H or in pH to the appearance of the cerium anomaly. The E_H-pH condition of the peat water in the Ozegahara peatland seems to be determined largely by FeOOH-Fe²⁺ system.

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Schwertmannite, 2-line ferrihydrite, and 6-line ferrihydrite were synthesized at 25°C in the laboratory to determine their solubilities. Chemical and thermal analyses of the synthesized minerals show that schwertmannite has the chemical formula Fe₂O_3-x(SO₄)_x·nH₂O (0.41 ≤ x ≤ 0.49, 1.51 ≤ n ≤ 2.81) and ferrihydrite Fe₂O_3-0.5y(OH)_y·nH₂O (0 ≤ y ≤ 1.96, 0.82 ≤ n ≤ 1.14). The solubility products (K) of the minerals were estimated from the activities of the corresponding species calculated with the computer program PHREEQC. The estimated log K values are 2.01 ± 0.30 for schwertmannite, 8.46 ± 1.40 for 2-line ferrihydrite, and 10.12 ± 0.74 for 6-line ferrihydrite. The solubility of schwertmannite seems to vary depending on the sulfate content, but more investigation is needed to quantify the relationship. The solubility of ferrihydrite does not show any significant correlation with the water content. The stability boundary between schwertmannite and ferrihydrite predicted in this study is biased to higher pH than that observed in nature, which also need further investigation.

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Holocene volcanoes in the Jingpohu region are situated in the “Crater Forest” and “Frog Pool” areas along the northwest side of Jingpohu Lake, northeastern China. Dating of three charcoal samples from the first and second volcanic cycles shows that the ages of the first and second cycles are 3430∼3490 and 2470 years respectively. The lavas from the Jingpohu area consist of basanites (BSN), alkali olivine basalts (AOB) and tephrites (TP). Crystal fractionation models are consistent with the generation of AOB and TP from a basanitic parent. Minor fractionation of olivine, augite, magnetite and Cr-spinel is required to produce AOB compositions whereas the generation of TP requires extensive fractionation of kaersutite, phlogopite and anorthoclase with minor olivine, augite, magnetite and leucite. The presence of kaersutite, phlogopite and anorthoclase megacrysts and mantle xenoliths suggest a fractionation history occurring at high pressure in the mantle. Although all basaltic rocks contain many granitic xenoliths, their geochemical characteristics show that they have not undergone any contamination of upper crust en route to the surface, but some alkali basalts were suffered from the contamination of lower crust. Relatively unradiogenic isotope ratio (compared with Bulk Earth), steep chondrite-normalized REE patterns and strong incompatible element enriched patterns suggest that the magmas are derived from a mixture of an incompatible element depleted anhydrous lherzolite asthenospheric mantle source and an enriched, amphibole-phologite-(apatite-)bearing lherzolite continental lithospheric mantle source. We propose that the basanites are the products of very low degree partial melts (<1%) of this source under high extension strength.

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Mesothermal gold-quartz veins of the Youngbogari deposit in the Youngdong area, South Korea, are hosted in faulted shear zones in Precambrian gneiss of the Sobaegsan massif. The Youngbogari deposit shares many features with other metamorphic rock-hosted gold deposits in the area, including a massive single-stage nature of veins and a simple vein mineralogy. However, its ore mineralogy is unique in that (1) arsenopyrite and pyrite occur dominantly with only minor pyrrhotite and (2) electrum grains are very poor in gold content (<40 atom. % Au). A variety of geochemical data indicate that deposition of the mesothermal gold–silver ores of the Youngbogari deposit resulted mainly from cooling of ore fluids accompanying decreasing sulfur fugacity. Fluid inclusion evidence indicates that gold deposition was not related to an early history of CO₂ phase separation (at temperatures of 300° to 420°C), but rather was tied to a later history of cooling and dilution of H₂O–NaCl ore fluids at temperatures of <300°C. These temperature estimates for gold deposition agree with those based on chlorite thermometry (270° to 320°C) and sulfide mineral assemblages (<290°C). Measured and/or calculated, stable isotope compositions of hydrothermal fluids (δ¹⁸O_Water = 5.8 to 8.0‰, δD_Water = −75 to −54‰) indicate an important role of rock-dominated (possibly magmatic) fluids in the mesothermal gold–silver system. The unusual arsenopyrite pyrite-rich nature of the Youngbogari ores and their anomalously negative δ³⁴S values (−2.9 to −5.1‰), compared to other mesothermal gold deposits of the Youngdong area, are interpreted to reflect a more oxidizing nature of the Youngbogari ore fluids, likely due to less reaction with graphite in wallrock gneiss.

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Sixty-two mono- and 4 bicyclic alkanes, and 11 diamondoid hydrocarbons were detected in the Cretaceous-Tertiary (K/T) boundary sediments at Kawaruppu, Hokkaido, Japan. The monocyclic alkanes included series of n-alkylcyclohexanes, methyl-n-alkylcyclohexanes and n-alkylcyclopentanes, and other alkylcyclohexanes. The bicyclic alkanes included bicyclo[3.3.1]nonane, trans-decalin, and methyldecalins. The diamondoid hydrocarbons included adamantane, and methyl- and dimethyladamantanes, and diamantane and methyldiamantanes. These mono- and bicyclic alkanes were detected at a level of 0.001–0.1 nmol g^-1 and the diamondoid hydrocarbons were at the same or one order magnitude less than those of the cyclic alkanes. Concentrations of all cyclic alkanes within the K/T boundary claystone were markedly small compared to those in the sediments above and below the claystone. The molecular distributions of n-alkylcyclohexanes, methyl-n-alkylcyclohexanes and n-alkylcyclopentanes were relatively smooth within the claystone. On the other hand, those of n-alkylcyclohexanes and methyl-n-alkylcyclohexanes showed predominances from C₁₅ to C₁₈ and those of n-alkylcyclopentanes showed even carbon number predominances from C₁₆ to C₂₂ in the sediments above and below the boundary claystone. These characteristic features in concentration and molecular distribution within the boundary claystone are likely related to the large biomass extinction event at the end of the Cretaceous. Compositions of compounds among trimethylcyclohexanes, methylethylcyclohexanes, decalins, methyladamantanes, and methyldiamantanes were roughly constant over sedimentary sequence. This indicated that diagenetic effect to these compounds had been nearly constant over the sedimentary sequence.

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We have prepared an artificial mixture of ³He and ⁴He to be used as an internal standard for precise ³He/⁴He measurements of terrestrial mantle-derived samples. The mixture is named HESJ (He Standard of Japan). The ³He/⁴He ratio of HESJ was determined by obtaining the weighted average of repeated analyses from five machines in four laboratories in Japan. The recommended value of the ³He/⁴He ratio of HESJ relative to the air value (R/Ra) is 20.63 ± 0.10. HESJ is available to all researchers.

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