著者

Kenta Yoshida Rustam Orozbaev Takao Hirajima Akira Miyake Akira Tsuchiyama Apas Bakirov Akira Takasu Kadyrbek Sakiev

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.52, no.1, pp.59-67, 2018 (Released:2018-02-02)

参考文献数

42

被引用文献数

5 5

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Direct chemical analysis of a single fluid inclusion was conducted by micro-excavation at cryo-temperatures. A scanning electron microscope (SEM) equipped with a focused ion beam (FIB), an energy dispersive X-ray spectrometer (EDS), and a cold stage, were used to analyze the chemical composition of the sample fluid inclusion, which was trapped in the ultrahigh-pressure (UHP) talc-garnet-chloritoid schist obtained from the Makbal metamorphic complex, Kyrgyz. Conventional techniques such as microthermometry and cryo-temperature and room-temperature Raman spectroscopy enabled the detection of NaCl and CaCl2 as solute species in the fluid inclusions, as well as high salinity of 20.5 mass% CaCl2 and 1.7 mass% NaCl with the assumption of a NaCl-CaCl2-H2O ternary system. However, additional chemical analysis using the present cryo-FIB-SEM-EDS system further revealed the presence of K as a solute element, which is hardly identified by conventional techniques. Petrographic examination of the fluid inclusions indicated that they had been trapped during the exhumation stage of the UHP talc-garnet-chloritoid schist, possibly originating from the decompression breakdown of lawsonite. The data acquired from the present study challenges previous reports of the existence of simple chemical system of aqueous fluids in high-pressure and UHP metamorphic terrane in eastern Asia. This is imperative because misidentification of solute species introduces errors into salinity estimation, resulting in inaccuracy propagation in quantitative analytical processes such as LA-ICP-MS. A detailed fluid inclusion petrography would thus require accurate quantitative analysis involving FIB-based sample-preparation and SEM-EDS analysis.

著者

Masaya Takabayashi Yuta Hirakawa Takeshi Kakegawa Yoshihiro Furukawa

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

pp.GJ23012, (Released:2023-08-01)

被引用文献数

2

---

The spontaneous formation of ribonucleotides on prebiotic Earth is considered an essential step in the origin of life. Phosphorylation of ribose to form ribose 5′-phosphate with boric acid has been reported as a key step in ribonucleotide synthesis. However, the probability of phosphorylation of ribose with mineral phosphate, which is the most abundant form of phosphate on Earth, remains unclear. Carbonate and formate were both widely available compounds on prebiotic Earth and are known to increase the solubility of mineral phosphates. Therefore, the present study investigates the phosphorylation of ribose with apatite in the presence of carbonate or formate. Ribose was phosphorylated preferentially at 5′-hydroxyl when slightly alkaline ribose solution was dried down with hydroxyapatite, urea, boric acid, and formate or carbonate at 80 °C for 24 h. Conversely, the yield was limited to less than 10% in the absence of formate and carbonate at the same pH. Dissolution of apatite was substantially increased in the presence of carbonate and formate, allowing the phosphorylation of ribose. These results suggest that ribose 5′-phosphate may have been spontaneously formed in boron-rich evaporative environments on prebiotic earth, expanding the availability of ribonucleotides on prebiotic Earth in addition to the conventional process through ribonucleosides.

著者

Takashi Miyazaki Kazutaka Yasukawa Erika Tanaka Bogdan Stefanov Vaglarov Kenta Yoshida

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

pp.GJ23011, (Released:2023-06-27)

---

During the early Paleogene (59–50 Ma), several short-term global warming events, known as hyperthermal events, occurred. Negative carbon isotope (δ13C) excursions are a typical proxy for detecting hyperthermal events. During the recovery from hyperthermal events, δ13C values returned toward pre-event levels via scavenging lighter C isotopes from the ocean and sequestrating them within sediments. The biological pump plays a key role in this process. Barium (Ba) is a nutrient-type element primarily transported in the water column by barite formed in microenvironments associated with the decomposition of organic matter, and the Ba-stable isotope ratio is a proxy of biological productivity. In this study, the δ138/134Ba values of bulk sediment samples from Ocean Drilling Program Site 738C in the southern part of the Kerguelen–Heard Plateau were analyzed. Although the samples predominantly comprised calcareous chalk corresponding to the latest Paleocene to early Eocene (56–52 Ma), the Ba isotope ratios of the bulk samples reflected a mixture of carbonate and barite. Three negative δ138/134Ba shifts were detected, corresponding to the global super-warming event “Paleocene–Eocene Thermal Maximum” at 56 Ma and to two hyperthermal events, known as ETM2 and I1. The changes in δ138/134Ba and δ13C values during PETM were comparable to those reported from the South Atlantic Ocean. Although commonly recognized, the scale of δ138/134Ba changes was smaller in the modest hyperthermal events (ETM2 and I1). Ba stable isotope ratios are a highly effective and powerful tool to reveal the response of the surficial system of Earth during hyperthermal events.

著者

UTA KONNO KEN TAKAI SHINSUKE KAWAGUCCI

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.47, no.4, pp.469-473, 2013-08-20 (Released:2013-11-26)

参考文献数

10

被引用文献数

1 2

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An analytical system using continuous-flow isotope ratio mass spectrometry (CF-IRMS) was developed to determine the stable chlorine isotope ratios (δ37Cl) for CH3Cl. By using appropriate devices for sample processing prior to introduction into the spectrometer, the newly developed system successfully reduces sample requirements (>0.6 nmol-CH3Cl) to less than one hundredth of that required by the previous CF-IRMS systems while maintaining comparable precision in the δ37Cl determination (±0.1‰, 1σ). This system is also able to determine carbon isotope ratio for CH3Cl with comparable precision (±0.3‰, 1σ, >0.3 nmol-CH3Cl) to the previous study. δ37ClSMOC and δ13CVPDB values of CH3Cl in commercial tank were determined to be -6.8 ± 0.1‰ and -46.9 ± 0.3‰, respectively.

著者

Asfie Meshesha Nigussie Dereje Ayalew Gezahegn Yirgu

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

pp.GJ23009, (Released:2023-05-25)

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Major and trace element data are presented for Quaternary basalts from Butajira-Kibet area, close to the western escarpment of the Central Main Ethiopian Rift to investigate the petrogenetic processes involved and the nature of mantle source compositions. The data indicate that the basalts are mildly alkaline characterized by moderate to high contents of MgO (6.85-9.00 wt. %) and TiO2 (2.40-2.92 wt. %). In the primitive mantle-normalized multi-element diagram, they exhibit troughs at Th, U, Rb and K and peaks at Ba, Nb, Ta, La, Pb and Sr with positive Eu/Eu*(1.01-1.17). Incompatible element ratios e.g., Ba/Nb (8.92-16.25), Rb/Nb (0.42-0.70), K/Nb (233.00-340.00) and Nb/U (47.97-61.05) suggest that the basalts are unaffected by crustal contamination. The acquired data do not evidence fractionation of plagioclase and clinopyroxene. On the other hand, relationships between major elements and their ratios (e.g., Na2O and Ca2O/Al2O3) and trace element ratios (e.g., Zr/Y and (La/Sm)N) indicate partial melting of a clinopyroxene - rich mantle at medium pressure. Chondrite - normalized REE diagram is characterized by relatively flat HREE (TbN/YbN=1.73-2.13) and significantly enriched HREE (higher than 10-times chondritic values) patterns. LREE/MREE versus MREE/HREE modelling of non-modal batch melting indicates that the basalts are formed by 1.5-3% partial melting of spinel peridotite mantle source with minor contribution from garnet-bearing peridotite. Primitive mantle-normalized multi-element diagram and trace element ratios, such as Nb/Zr, Nb/U, Ba/La, Rb/Zr and Ba/Nb, suggest that the studied basalts are not affected by carbonatite and/or hydrous phase metasomatism. Rather, they are closely similar to the OIB source (mainly EM-I) and the SCLM. They are most likely the result of significant interaction of melts from a mantle plume and the SCLM.

著者

Hui Lan Urumu Tsunogai Fumiko Nakagawa Masanori Ito Ryo Shingubara Yuko Miyoshi Shuichi Hara

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

pp.GJ23005, (Released:2023-02-10)

被引用文献数

1

---

To clarify the sources and fate of CH4 enriched in coastal seawaters, we determined the distribution of both the concentrations and dual stable isotope compositions (δ13C and δ2H) of dissolved CH4 in the bays of Ise and Mikawa in Japan during five sampling campaigns from 2013 to 2020, together with those in the major inflows of the Kiso, Nagara, and Yahagi Rivers. Excess CH4 were found in the surface layer of Ise Bay, and their δ13C and δ2H values were close to those of CH4 enriched in the major inflows, but deviated from those of CH4 in the sedimentary layer at the bottom of Ise Bay. The oxidation rates of CH4 in the water columns were negligibly small during the incubation experiments. In conclusion, the excess CH4 in the surface layer of Ise Bay was derived from the inflows. The CH4 enrichment in the freshwater sediments of the inflows showing up to four orders of magnitude higher CH4 concentrations than those in the sediments of Ise Bay supported this conclusion. Similar results were obtained in Mikawa Bay. The total emission flux of CH4 from the estuary area of Ise Bay was larger than the influx of CH4 into Ise Bay via the inflows, suggesting that the CH4 dissolved in the inflows was emitted into the atmosphere immediately after inflowing into the bay water.

著者

Amalendra Nath Chowdhury Baldev Krishna Handa Ajit Kumar Das

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.8, no.2, pp.61-65, 1974 (Released:2008-04-08)

参考文献数

11

被引用文献数

13 20

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High values for lithium, rubidium and cesium contents have been observed by the authors in some samples from thermal spring area in Puga valley, Kashmir, India. Samples studied are (1) water from thermal springs, (2) sediments deposited at the thermal springs, (3) samples from borax deposits from the near vicinity of the thermal springs. Estimation of Li, Rb and Cs was carried out by atomic absorption method. In the borax samples separate determinations were carried out by complete decomposition of the samples as also by extraction with water. In the thermal spring water, the average rare alkali content was 5.9 ppm Li, 0.9 ppm Rb and 10.5 ppm Cs. In the spring deposits the maximum contents of rare alkalies observed were 565 ppm Li, 240ppm Rb, 3, 530ppm Cs. There are variations from sample to sample. In the borax deposits the maximum values are 4, 500ppm Li, 350ppm Rb, 2, 150ppm Cs. Difference between the total and water soluble alkali metals shows increased absorption of Rb and Cs in the argillaceous impurities. Geochemical aspects leading to the strong enrichment of rare alkalies, specially Cs, have been discussed. Association of late stage magmatic activity has been suggested for the origin of thermal springs and associated deposits.

著者

Aiko Nakato Shiori Inada Shizuho Furuya Masahiro Nishimura Toru Yada Masanao Abe Tomohiro Usui Hideto Yoshida Takashi Mikouchi Kanako Sakamoto Hajime Yano Yayoi N. Miura Yoshinori Takano Shinji Yamanouchi Ryuji Okazaki Hirotaka Sawada Shogo Tachibana

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.56, no.6, pp.197-222, 2022 (Released:2022-12-16)

参考文献数

60

被引用文献数

13

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The Hayabusa2 spacecraft explored C-type near-Earth asteroid (162173) Ryugu and returned asteroidal materials, collected during two touchdown operations, to the Earth as the first sample from carbonaceous-type asteroid. The sample container, in which ~5 g of Ryugu sample was enclosed, was safely opened in the clean chamber system with no severe exposure to the terrestrial atmosphere. In the course of preparation operation of the sample container, two dark-colored millimeter- to sub-millimeter-sized particles were found outside the sealing part of the sample container. Because they look similar to the Ryugu particles inside the sample container, the particles were named as Q particles (Q from questionable). In this study, we investigated Q particles (Q001 and Q002) mineralogically and petrographically to compare them with potential contaminants (the ablator material of the reentry capsule and fine sand particles at the capsule landing site), Ryugu sample, and CI chondrites. The Q particles show close resemblance to Ryugu sample and CI chondrites, but have no evidence of terrestrial weathering that CI chondrites experienced. We therefore conclude that the Q particles are originated from Ryugu and were expelled from the sample catcher (sample storage canister) in space prior to the enclosure operation of the sample catcher in the sample container. The most likely scenario is that the Q particles escaped from the sample catcher during the retrieval of the sample collection reflector, which was the necessary operation for the sample container closing.

著者

Kenji Shimizu Takayuki Ushikubo Takeshi Kuritani Naoto Hirano Shigeru Yamashita

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

pp.GJ22019, (Released:2022-11-22)

被引用文献数

1

---

Analyses of elemental abundances by secondary ion mass spectrometry (SIMS) require matrix-matched standard samples to account for the matrix effect on correction factors. This requirement makes it difficult to obtain accurate results for geological samples of variable chemistry. In this study, we prepared 39 volcanic glasses of foiditic, basaltic, basaltic andesitic, rhyolitic and pure SiO2 compositions, including synthetic samples and natural samples collected from the deep seafloor. The measured H2O contents of these samples were in the range 0.02–4.8 wt%. We showed that calibration curves (H2O content vs. 16OH−/30Si−SIMS ratio) differed according to the composition of the volcanic glasses. Our results demonstrated that for a particular 16OH/30SiSIMS ratio, water content could differ by up to a factor of five, depending on the composition of the volcanic glass. Although the correction factor (the slope of the calibration curve for water [H2O/(16OH−/30Si−)SIMS]) was weakly correlated with SiO2 content, we identified a stronger correlation with the molar weight (g mol−1, on a one-oxygen mole basis) of the silicate glasses. Our results suggest that modification of the correction factor for the matrix effect on SIMS-based H2O content of volcanic glasses according to their molar weights provides more accurate water contents of silicate glasses, regardless of their chemical composition and water content and without the need for a series of standard glasses of known water contents.

著者

Rofiqul Umam Masaharu Tanimizu Hitomi Nakamura Yoshiro Nishio Ryo Nakai Naoto Sugimoto Yasunori Mori Yuuki Kobayashi Akane Ito Shigeyuki Wakaki Kazuya Nagaishi Tsuyoshi Ishikawa

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.56, no.5, pp.e8-e17, 2022 (Released:2022-10-18)

参考文献数

28

被引用文献数

3

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Slab-dehydrated fluid is considered to be involved in island arc magmatism. In this study, Li isotope ratios were determined for deep groundwater samples from the non-volcanic forearc region of SW Japan. The contribution of the slab-dehydrated fluid from the Philippine Sea Plate (PHS) was investigated in the Arima area and the eastern Kii Peninsula area, corresponding to the slab depths of ~60 km and 20–30 km, respectively. In the Arima area, the high-temperature thermal waters with high salinity called the Arima-type fluid were clarified to have low δ7Li values of +1–+3‰. The low δ7Li values with high Li concentrations are thought to be the result of fluid-rock interactions at high temperatures, which is consistent with the characteristics of the slab-dehydrated fluid. On the other hand, the δ7Li values of deep groundwaters in the eastern Kii Peninsula showed a wide range of +2 to +29‰. Several groundwater samples had a similar chemical property to the Arima-type fluid: low δ7Li values, low Cl/Li ratios, and 87Sr/86Sr ratios around 0.708–0.710. They are distributed along the Median Tectonic Line (MTL) and within about 20 km south of the MTL. These results indicate a common supply of slab-dehydrated fluids to the non-volcanic forearc region in SW Japan from PHS along the large faults, and Li isotope ratios will be a useful indicator to detect their contribution.

著者

Akihiro Tamura Takuya Sagawa Kyoko Okino Tomoaki Morishita

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

pp.GJ22020, (Released:2022-11-29)

被引用文献数

1

---

The whole-rock trace-element compositions of igneous rocks provide primary geochemical information about their petrogenesis. Such compositions can be determined by LA–ICP–MS analysis of fused-glass samples as well as the conventional solution ICP–MS method. However, in contrast to basalt and andesite, the fused-glass method is not suitable for Si-rich rocks (granite and rhyolite) due to the difficulty of making homogeneous glasses. To extend the method to Si-rich rocks, we adopted an MgO dilution process to prepare fused glasses and evaluated the technique by analysis of granite and rhyolite reference materials. Dilution of 30 mg of powdered samples with 10 mg MgO facilitated the preparation of homogeneous fused-glass samples of felsic rocks. LA–ICP–MS analyses indicate that the fused glass is homogeneous in the contents of most incompatible elements considered in igneous petrology. The glass enables the analysis of these elements in felsic rocks within 20% deviation from reference data. The sample data are consistent with reference values for rhyolite although Zr and Hf data deviate significantly (by ~40%) from reference values for granitic rocks.

著者

Yoshiaki Endo Sebastian O. Danielache Moeko Ogawa Yuichiro Ueno

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.56, no.1, pp.40-56, 2022 (Released:2022-02-28)

参考文献数

80

被引用文献数

4

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The sulfur isotope fractionation that occurs during SO2 photolysis is key to explaining the isotope signatures stored in ancient sedimentary rocks and understanding the atmospheric compositions of the early Earth and early Mars. Here, we report the photoabsorption cross-sections of 32SO2, 33SO2, 34SO2, and 36SO2 measured from 206 to 220 nm at 296 K. The wavelength resolution was set to 1 cm–1, 25 times higher than that of previous SO2 isotopologue absorption spectra measurements. The precision of ~10% is in agreement with previously reported SO2 absorption spectra. In comparison with previously reported high-resolution spectra of natural abundance, SO2 measurements demonstrate smaller cross-sectional magnitudes at absorption peaks and an offset wavelength by ~0.016 nm. Using the newly recorded isotopologue spectra, we calculated the sulfur isotope fractionation for self-shielding during SO2 photolysis. The calculated 34S fractionation (34ε) roughly reproduces the observed relationship between 34ε and the SO2 column density in previous photolysis experiments. Thus, the cross-section is useful for predicting 34S/32S isotope fractionation in an optically thick SO2 atmosphere. In contrast, for mass-independent fractionation (MIF-S, i.e., non-zero Δ33S), the measured spectra predicted a weakly negative Δ33S/δ34S slope of about –0.1. The small Δ33S/δ34S slope is consistent with the slopes of SO2 photolysis experiments under high-pressure atmospheres (i.e., the pressure broadened absorption line width will be comparable to the spectral resolution). Therefore, MIF-S during photolysis experiments was linked to spectroscopic measurements for the first time. We conclude that reasonable precision and high-resolution spectroscopic measurements are key to explaining the origin of MIF-S at column densities below 1018 cm–2. However, MIF-S production in chamber experiments or atmospheric conditions may require understanding pressure or temperature effects, such as linewidth broadening on the UV-absorption spectra, and how these effects manifest themselves on isotopologues.

著者

Meraj Alam Mukesh-Kumar Mishra Tatiana-Vladimirovna Kaulina Talat Ahmad Ashwini-Kumar Choudhary

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

pp.GJ22016, (Released:2022-09-27)

被引用文献数

5

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The Central Indian Tectonic Zone (CITZ) is major E-W trending suture zone between Northern and Southern Indian crustal blocks. The southern portion of the CITZ comprises three litho-tectonic units: Tirodi Gneissic Complex (TGC), Sausar Mobile Belt (SMB) and Bhandara-Balaghat Granulite Belt (BBGB). Elemental and isotopic data are used to constrain the genesis of granitoids and their protoliths, which may help us to understand the Proterozoic crustal evolution in CITZ. Geochemical and isotopic results are consistent with previous studies that these granitoid plutons are linked to the felsic magmatism of the Columbian crustal assembly in India, North America and North China. Granitoids varies from tonalite to granite, alkalic to calcic, metaluminous to peraluminous composition. Normalized elemental ratios of La/Sm, La/Yb, La/Lu, and Gd/Yb depict variable LREE enrichments and varying degrees of partial melting of heterogeneous crustal/lithospheric sources. The studied rocks are characterized by positive anomalies for Pb and negative anomalies for Nb, Sr, P, Ti, which indicate the influence of subduction-zone fluids in the source regions. Negative anomalies for K, Sr, and Ti for SMB and BBGB granitoids may also be attributed to K-feldspar, plagioclase, and Fe-Ti oxide fractionation. However, TGC porphyritic leucogranites display K, Ba and Eu positive anomalies, probably related to the accumulation of K-feldspar phenocrysts. Nd-Sr data presents initial ratios of 143Nd/144Nd t=1.6 Ga ranges between 0.509961 and 0.510300; εNd t=1.6 Ga ranges from -5.3 to -11.9 with TDM ages ranging from 2.20 to 2.78Ga for TGC granitoid. The ratios of 143Nd/144Nd t=1.6 Ga ranges between 0.510232 and 0.510985; εNd t=1.6 Ga ranges from +0.2 to +8.2 and TDM ages varies from 1.5 to 3.0 Ga. The initial 87Sr/86Sr t=1.6 Ga ratios ranges between 0.699834 and 0.797151 for SMB granitoid. However, BBGB granitoids show the ratios of 143Nd/144Nd t=1.6 Ga ranges between 0.509752- and 0.510910; εNd t=1.6 Ga ranges from +6.7 to -16, and TDM ages range from 1.51 to 3.29 Ga. The initial 87Sr/86Sr (t=1.6 Ga) ratios varies between 0.705096 and 0.717440. These ranges of εNd (t) and TDM values possibly indicate their derivation from enriched and heterogeneous crustal/lithospheric sources, and minor components from depleted lithospheric sources.

著者

Takeru Yanagi Yuji Ichimaru Shogo Hirahara

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.25, no.1, pp.17-30, 1991 (Released:2008-04-08)

参考文献数

39

被引用文献数

15 19

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We report systematic petrochemical changes of historical lava flows from the Sakurajima volcano. The lavas are all calc-alkalic in composition. They change in composition from dacitic to andesitic at an increasing rate with time, and show a straight-linear correlation in chemical composition. Plagioclase phenocrysts show a bimodal compositional distribution with peaks at about An58 and An85, regardless of variation in bulk rock composition. The intensity of An85 peak increases, while that of the An58 peak decreases with eruption stage. Orthopyroxene phenocrysts also show a bimodal compositional distribution. K2O content of the lavas progressively drops at almost the same rate with every gigantic eruption. These chemical and petrological aspects with other lines of evidence support binary mixing of dacitic and basaltic magmas, and a progressive increase in proportion of basaltic magma in the mixed magmas. The mixing has progressively proceeded for 475 years at least. The magma chamber model proposed in this paper consists of upper and lower chambers and a set of a huge cylinder and a mobile plug between the chambers. Both the cylinder and the plug have same frustum form. The plug subsiding into the lower chamber drives the basaltic magma upward through an opening between the cylinder-wall and the plug, and mixes it with dacitic magma in the upper chamber. Continuous influx of volatile-rich basaltic magma into the upper chamber may result in repetitive volcanic eruptions, and causes a continuous change in magma composition in the upper chamber, which erupts as lavas with discrete compositions.

著者

Atsuyuki Ohta Noboru Imai Takashi Okai Mitsuo Manaka Ran Kubota Atsunori Nakamura Yoshiko Tachibana

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.55, no.2, pp.59-88, 2021 (Released:2021-11-22)

被引用文献数

1

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Recent interest in geochemical maps produced for environmental assessment has led to multi-purpose applications of such maps in various other fields including provenance studies for agriculture and archaeology. Research subjects of these provenance studies closely relate to surficial rocks. Fine stream sediment samples used for Japanese geochemical mapping originate from parent rocks present in the corresponding drainage basins. Consequently, as well as the chemical composition of stream sediment samples, information regarding the parent lithology is imperative for the applications mentioned above. In this work, the exposed areas of different lithologies in river drainage basins were calculated using a digitalized geological map and watershed polygons obtained using a hydrologic model. Stream sediment samples were classified into 18 different types in a larger-scale classification and into 92 more specific types in a smaller-scale classification based on the following assumption: when a specific rock type crops out over more than 50% of the watershed area, it is the dominant rock type controlling the chemical composition of stream sediments. This assumption was confirmed to be reasonable using a one-way analysis of variance. Chemical Index Alteration values suggest that the chemical weathering process is not dominant in the formation of stream sediments from their source rocks. Accordingly, the chemical compositions of stream sediments are approximately comparable to that of their source rocks. Finally, the percentages of the different lithologies in the watershed areas were tabulated for all stream sediment samples (n = 3024). The median values of 53 elemental concentrations were calculated for samples classified according to the dominant lithology. This new database lists the chemical compositions and the dominant lithology in the watershed area for each sample and constitutes an extensive source of information relevant to understanding of the chemical, mineralogical, and petrological variety of surface materials in this island arc setting, which helps to respond to existing academic or industrial requests.

著者

Iwao Kawabe

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.26, no.6, pp.309-335, 1992-12-20 (Released:2008-04-08)

参考文献数

73

被引用文献数

51 70

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The refined spin-pairing energy theory (RSPET) has been improved in order to understand quantitatively the tetrad or double-double effects recognized in the Ln3+ ionic radii. Since the ionic radii have been determined from the lattice constants and structural parameters of LnO1.5 and LnF3, the lattice energies of the compounds and the enthalpy difference of ΔHfo(LnF3)-ΔHfo(LnO1.5) have been examined by the improved RSPET. The RSPET parameters for the lowest levels of 4fq electronic configurations strongly depend upon the effective nuclear charge (Z*). Such effects due to Z* have been taken into account. This made it possible to separate the variations in the lattice energies and the enthalpy difference across the Ln3+ series into the following two parts: (1) the large variation as a smooth function of q (the lanthanide contraction trend), and (2) the small zig-zag variation referred to the tetrad or double-double effect. The lattice energy of LnO1.5 and ΔHfo(LnF3) − ΔHfo(LnO1.5) exhibit upward concave tetrad curves in their plots against q of Ln3+. The tetrad effect in the lattice energy of LnF3 is less conspicuous. This means that the Racah parameters for Ln3+ decrease very slightly in going from the gaseous free Ln3+ to LnF3, and then decrease greatly to LnO1.5, in accordance with the nephelauxetic series. The differences in Racah parameters between LnF3 and LnO1.5 have been estimated from ΔHfo(LnF3) − ΔHfo(LnO1.5) by means of an inversion technique based on the improved RSPET. The RSPET results for the thermochemical data are consistent with the careful spectroscopic determinations of Racah parameters for NdF3 and NdO1.5. Both the tetrad effect and the smooth lanthanide contraction seen in the Ln3+ ionic radii can be interpreted in terms of the quantum mechanical energetics of 4f electrons.

著者

Masayo Minami Akimasa Masuda

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.31, no.3, pp.125-133, 1997-06-20 (Released:2008-04-08)

参考文献数

20

被引用文献数

4 9

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Here is presented a mathematical method which enables us to evaluate the degrees of lanthanide tetrad effects from the data involving all of REE. Each of the four spans corresponding to four subgroups, La-Nd, Pm-Gd, Gd-Ho, and Er-Lu, is approximately fitted to a quadratic function and the resultant quadratic coefficient is employed as a numerical indicator for the tetrad effect. For the purpose of approximation by a quadratic function, the least-squares method is used under the constraint that the first and second quadratic curves intersect at the middle point between Pm and Sm, and that the third and fourth ones intersect at the middle point between Ho and Er. Since, mathematically, the subject is a problem on the conditional extremum, the method of Lagrange undetermined multipliers should be used. It is noted that the degrees of four tetrad effects can be evaluated simultaneously. This method can lead us to the mathematically well-defined estimation of the tetrad effect.

著者

Tasuku Akagi Shun'ichi Nakai Akimasa Masuda

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.32, no.2, pp.135-141, 1998-04-20 (Released:2008-04-08)

参考文献数

22

被引用文献数

1 1

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Rare earth elements in REE-rich minerals were determined accurately by isotope dilution mass spectrometry (IDMS). The chondrite normalized REE patterns of some specimens showed regular relative aberrations, which are similar to that of the “tetrad effect”. We have introduced a background curve passing normalized values of La, Nd, Gd, Er and Lu, to measure the aberrations. The relative differential variations of some of the minerals are not small, but have been overlooked due to large overall variations of the chondrite normalized values.

著者

Shinsuke Kawagucci Yohei Matsui Gretchen L. Früh-Green

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.54, no.3, pp.129-138, 2020 (Released:2020-06-22)

参考文献数

45

被引用文献数

1 5

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Here we quantify radiocarbon (14C) content in CO2 and CH4 from hydrothermal fluids collected at 5 vent sites in the Okinawa Trough. These data provide preliminary insights on how different carbon sources and circulation processes contribute to vent fluids and take into consideration all potential contaminations during sample processing and analysis with accelerator mass spectrometer. For CO2, 14C-dead values observed in fluids of most sites (Hatoma, Hitoshi, Noho) demonstrate the complete removal of the inorganic carbon in the recharged seawater. Conversely, the significantly positive 14CO2 are detected in fluids from the Daiyon-Yonaguni site, which implies the persistence of the recharged seawater-derived inorganic carbon and/or a contribution from thermal degradation of sedimentary 14C-containing carbon during fluid upwelling. The CH4 in these fluids were predominantly 14C-dead or nearly 14C-dead, suggesting a source of deep-buried, 14C-dead sedimentary carbon. The methods outlined in our study exemplify a useful way of elucidating radiocarbon contents of geofluids, and provide future studies with a means to improve our understanding of carbon circulation between hydrosphere and lithosphere.

著者

HIKARU IWAMORI HITOMI NAKAMURA

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.46, no.4, pp.e39-e46, 2012-08-20 (Released:2013-11-08)

参考文献数

37

被引用文献数

6 22

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In order to decipher the mantle geochemical heterogeneity that reflects material differentiation and circulation within the Earth, we examined mid-ocean ridge basalts (MORB), ocean island basalts (OIB) and arc basalts (AB), in terms of the radiogenic isotopic variability and its geographical distribution. It has been found that the Sr, Nd and Pb isotopic ratios of MORB, OIB and AB exhibit a two-dimensional structure, and are mostly distributed on the same compositional plane that is spanned by two independent components (IC1 and IC2). One of the two components (IC2) divides geochemically the mantle broadly into the Eastern and Western Hemispheres. Inspection of the geochemical nature of IC2 suggests that it may represent a fluid mobile component recycled through subduction zones. The mantle geochemical domain beneath the Eastern Hemisphere is enriched in the fluid mobile component, possibly by focused subduction towards the supercontinent Pangea which was surrounded by subduction zones. Although the present-day continents have been dispersed since then, the geochemical domain has seemingly been anchored to the asthenosphere without moving with the continents.