The carbon isotope ratios of bog peat in the Ozegahara peatland, Japan, were measured. The vertical variation of the bulk peat featured: 1) rapid decrease of the carbon isotope ratio (δ¹³C) near the surface, 2) broad rises in the ratio around depths corresponding to 3000, 5500, 7500 years BP with a period of approximately 2500 years, and 3) a further decrease toward the bottom. In order to understand the reasons for the changes, peat components were separated and their isotopic composition measured along with modern peat-forming vegetation. The selective decay of holocellulose is responsible for the rapid decrease of δ¹³C in the surface layers, and the transition from earlier vegetation caused the further decrease of δ¹³C near the bottom. The decay constant for holocellulose was estimated to be as small as 0.001 yr^–1. The variation of δ¹³C seemed to be synchronized with sea level change, but showed poor correlation with solar activity and the temperature change estimated from pollen analysis. The δ¹³C of peat mosses lacking in stomata would increase with the rise in atmospheric CO₂. The increase in the atmospheric CO₂ occurring synchronously with sea level rise could be the reason for the periodical change. Some climatic information of the Holocene period may have been recorded in the Ozegahara bog peat.

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Ductile shear zone hosted mesothermal gold mineralization of the Okote area is located in southern Ethiopia. Three N-S striking ductile shear zones, with different intensity of shearing and hydrothermal alteration, cut the mafic rocks. The gold-mineralized parts of these shear zones reveal zonings: slightly altered but not sheared protolith at shear boundaries, transitional zone, and mylonite zones. Auriferous quartz-carbonate-tourmaline veins occur mainly in the mylonite zone. The ore minerals of the veins and their wall rocks are pyrite, chalcopyrite, pyrrhotite, gold, and accessory chalcocite, covellite, galena, and melonite (NiTe₂). The textural relationships among minerals in these alteration zones indicate that epidote, ferroamphiboles, and magnetite were formed first, followed by chlorite, ankerite, pyrrhotite, chalcopyrite I, and K-feldspar, and, finally, calcite, chlorite, biotite, tourmaline, gold, and galena. Primary fluid inclusion data from auriferous type 2 quartz veins (qv₂) indicate aqueous-carbonic inclusions with low salinity (<6.59 wt % NaCl equivalent), 0.38 to 0.90 g/cm³ in density that homogenized at 218°C to 345°C. Most of the inclusions decrepitate at 220°C to 388°C before or immediately after homogenization. Chlorite geothermometry gives temperatures of formation that range from 230°C to 410°C with modes at 250°C and 380°C, in good agreement with fluid inclusion data. Chemical mass balance studies, using samples from meta-gabbro and alteration products, reveal addition of K₂O, P₂O₅, volatile, Ba, Sr, V, and Cu into wall rock and loss of MgO, CaO, and SiO₂ from the wall rock to the veins accompanying gold mineralization. Chondrite-normalized REE patterns of samples show HREE enrichments in meta-gabbro, a flat pattern with a positive Eu anomaly in the epidote-amphibole-magnetite rich transitional zone, and HREE enrichment with a negative Cc anomaly in the mylonite zone. Stable isotope ratios of sulfur, carbon, and oxygen indicate a predominance of deep-seated fluids of metamorphic and magmatic signatures. Considering the combined structural and spatial association of gold with greenschist facies, the mineral and wall rock chemistry, fluid inclusion data, and isotopic data presented here, we conclude that the Okote gold mineralization formed by interaction of structurally focused hydrothermal fluids with mafic rocks.

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The precise concentrations of rare earth elements (REEs) in Japanese Ashibetsu and Taiheiyo coals, in Indonesian Ambalut coal, and in Australian boghead coal have been determined, in order to compare the REE contents of the coals with those of plants and also to obtain further knowledge of the original plants from which these coals were formed. By leaching the coals after ashing using a 10% acetic acid solution, each coal sample was separated into two fractions: an acetic acid soluble fraction, and an acetic acid insoluble fraction. Our results show that three different types of chondrite-normalized REE patterns are observed in the acetic acid soluble fraction of these coals. The acetic acid soluble fractions of the Ashibetsu, the Taiheiyo, and some of the Ambalut coals showed REE patterns identical to those of peat vegetation. Those of other Ambalut coals showed an REE pattern that was similar to that of tree trunks. The boghead coal showed a different REE pattern that was similar to algae, an origin that is also suggested from a maceral study. The REE patterns of the acetic acid soluble fraction can therefore be a useful proxy for determining the original plants that formed the coals.

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Metagranites (granitic orthogneisses) constitute one of the important lithologic units in the Dabie ultrahigh pressure metamorphic belt. They often display direct contact with paragneisses and eclogites. TIMS zircon U-Pb dating on the metagranites reveal that their protolith was crystallized as granitoids in Neoproterozoic ages of 755 to 611 Ma and thus correspond to rift magmatism associated with breakup of the Rodinia supercontinent in the northern margin of the Yangtze Block. Zircon U-Pb age and Ar-Ar ages of amphibole and biotite indicate that the granitoids experienced eclogite-facies metamorphism in Early Mesozoic with rapid exhumation at cooling rates of 8.7 to 10.2°C/Ma from 225 ± 6 to 181 ± 3 Ma in response to amphibolite-facies retrogression. Fission track ages of sphene, zircon and apatite indicate that the metagranites experienced slow exhumation with cooling rates of 0.88 to 1.25°C/Ma in Late Mesozoic. It is possible that in the first period of exhumation, the metagranites were uplifted from the mantle depth to lower crustal level at ca. 225 Ma, then rapidly reached middle to upper crustal levels between 204 Ma and 180 Ma. After the intensive magmatism in Early Cretaceous, the Dabie terrane was uplifted at the slow rate in response to unroofing. Either the rapid exhumation in the Early Mesozoic or the slow uplift in the Late Mesozoic in the Dabie terrane were contemporaneous with two rapid subsidence and sedimentation of the Hefei Basin in Early Jurassic and Paleogene, respectively. This suggests that the orogeny and basin-forming events were closely related to each other rather than independently separated.

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The sedimentary rock-hosted disseminated gold (SRHDG) deposits in southwest Guizhou Province, China, are located near the buried edge of the Yangtze Craton. Three deposits, Lannigou, Getang and Zimudang, were chosen for this study. The deposits are hosted by fine-grained clastic and calcareous sedimentary rocks and formed at low temperatures from low salinity solutions of low to intermediate pH and low f_O2 . Chemical analyses of the ores and host rocks show that high field strength elements, such as Nb, Ta, Zr and Hf, were immobile during hydrothermal alteration. However, rare earth elements (REE) were mobile. Light rare earth elements (LREE) were depleted, whereas heavy rare earth elements (HREE) were enriched. A differentiation of platinum group elements (PGE) concentrations was documented. The ores are enriched in Pd and Pt, consistent with the higher solubility of these two elements in ore fluids. The Pd/Ir ratios of the ores are lower than those of the ultramafic rocks and the Emeishan basalts in the region. Thus, the ultramafic intrusives and basalts could not have been the main source of the PGEs and gold in the SRHDG deposits. Rather, these metals were derived mainly from the sedimentary host rocks as evidenced by the trace element and stable isotopic characteristics of the ores. Our data suggest that the SRHDG deposits in southwest Guizhou are most likely of amagmatic origin, which is consistent with the lack of igneous intrusives in the vicinity of the deposits, the very weak metamorphic grade of the rocks, the lack of metamorphic effects within the time range of the SRHDG deposits, and coincidence in time of gold mineralization with regional extension.

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We detected the formation of formate (HCOOH/HCOO^–) in solutions containing hydrated formaldehyde (CH₂(OH)₂), HOOH, and Fe(III) or Cu(II). Formate formation increased significantly (ca. 5 times) when the solution underwent freezing and thawing. Although the reaction mechanisms are not clearly understood, we believe that the concentration effect of freezing enhanced the catalytic reactions between HOOH and Fe(III) or Cu(II) and the reduction of transition metals, i.e., Fe(III) to Fe(II) and Cu(II) to Cu(I). The concentration effect also enhanced reactions between Fe(II) and HOOH or Cu(I) and HOOH, which generated OH radical (“freeze-Fenton reaction”). We suspect that hydroxyl radical formed by the freeze-Fenton reaction probably oxidized CH₂(OH)₂ and resulted in the formation of formate. Samples of identical compositions kept in the refrigerator did not form any formate except for the CH₂(OH)₂-Fe(III)-HOOH solution that formed a small amount of formate. Our study of the effects of pH on the CH₂(OH)₂-Fe(III)-HOOH solution (pHs between 1.5–5.0) showed that formate formation was the highest at pH = 4.0, indicating that the speciation of Fe(III) affected the formation of formate. Concentration-dependent experiments demonstrated that Fe is probably the limiting agent under typical environmental conditions.

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Nakajima and Terakado (2003) measured rare earth elements in stream waters from eleven locations in the Rokko granite area. The present paper examines their data in the light of a model in which each sample arises from mixing two sources, followed by concentration or dilution. The concentrations of rare earth elements in the specimens will then follow particular equations, and a straight line will be seen if the data are plotted in a certain way. It is concluded that data from some, perhaps all, of the locations is compatible with this model.

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