Geochemistry International最新文献

{"title":"Bitumens in the Mir Kimberlite Pipe (Yakutia)","authors":"F. V. Kaminsky,&nbsp;I. V. Konopleva,&nbsp;V. L. Skvortsova,&nbsp;O. V. Kuznetsova","doi":"10.1134/S0016702924601694","DOIUrl":"10.1134/S0016702924601694","url":null,"abstract":"<p>Solid bitumens in the Mir kimberlite pipe form vein-like segregations several centimeters in size. They are distributed irregularly in the pipe body, regardless of the kimberlite breccia varieties distribution. The bitumen content in the kimberlites ranges from 0.001 to 0.12 wt %. Bitumen-rich areas are confined to the pipe contacts and faults. The question of the origin of bitumens in kimberlites is hotly debated. Therefore, this work is aimed at determining their origin in the Mir pipe. The studied bitumen-bearing kimberlite samples were collected in the Mir pipe, from depths of 100 and 130 m. The chloroform bitumoid was extracted from bitumen. The carbon isotope compositions of bitumoids were determined, and biomarker analysis was carried out by gas chromatography mass spectrometry. Biomarker hydrocarbons were detected in the bitumoid, indicating a biogenic origin of the organic matter. The following biomarkers were identified: <i>n</i>-alkanes, isoprenoids Pr and Ph, tri- and pentacyclic terpanes–hopanes, and steranes. The pristane to phytane ratio Pr/Ph = 0.8 indicates reducing conditions of formation corresponding to marine environment. The oddness ratio of <i>n</i>-alkanes, sterane and hopane maturity indices show that the thermal maturity of organic matter (OM) corresponds to the initial stage of the oil formation. The low content of long-chain alkanes and the predominance of C29 over C27 among regular steranes (C29/C27 = 2.2) allow us to assume that the initial biota for the OM of the bitumen sample under study could be phytoplankton. The δ¹³C_VPDB values of the studied bitumoid (from –29.4 to –31.6‰) correspond to the isotopic compositions of bitumoids in the Paleozoic and Mesozoic sediments of the Siberian Platform (from –25.8 to –33.8‰) and differ significantly from the isotopic composition of endogenous carbon (from –2 to –10‰). According to these features, the investigated bitumen from the Mir pipe is of marine origin.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"63 8","pages":"665 - 674"},"PeriodicalIF":0.8,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145062290","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Erratum to: Evaporation Features of the Melts of Ca–Al–Inclusions in Chondrites: Experimental Data and Their Implications","authors":"S. I. Shornikov,&nbsp;O. I. Yakovlev","doi":"10.1134/S0016702925240048","DOIUrl":"10.1134/S0016702925240048","url":null,"abstract":"","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"63 8","pages":"762 - 762"},"PeriodicalIF":0.8,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0016702925240048.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145062295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ti Ferriallanite-(Ce), Ti and Ti–V Allanite-(Ce), Allanite-(Ce), Allanite-(Y), and REE Epidote in Biotite-Bearing Quartz Gabbroids and Plagiogranitoids within the Island-Arc Pervomaysk-Ayudag Complex of the Mountain Crimea","authors":"E. M. Spiridonov,&nbsp;G. N. Ovsyannikov,&nbsp;S. V. Filimonov,&nbsp;E. S. Koybagarova,&nbsp;N. N. Korotaeva","doi":"10.1134/S001670292560021X","DOIUrl":"10.1134/S001670292560021X","url":null,"abstract":"<p>The unique association of the epidote-group REE minerals, as well as the evolution of lanthanides and actinides, titanium and vanadium in their composition are described. Allanite-(Ce), often with a ferriallanite-(Ce) core, allanite-(Y) in an outer zone, and a rim of REE epidote forms pseudomorphs after chevkinite-(Ce) and perrierite-(Ce), as well as isolated crystals. They form intergrowths with biotite and are developed near it in quartz gabbronorite-dolerites and gabbronorite-diorites of the island-arc hypabyssal mafic Pervomaysk–Ayudag complex of the Middle Jurassic–Early Bajocian age in the Mountain Crimea. Zonal allanite-(Ce) of similar composition with REE epidote rims is widespread in the quartz diorites and plagiogranites of the same complex, where it is often developed in granophyric quartz–oligoclase intergrowths. Brown ferriallanite-(Ce) enriched in Ti (±Th) forms cores in brown allanite-(Ce) crystals enriched in Ti (±V) (up to 4.9 wt % TiO₂). The Ti-rich (up to 3.5 wt % TiO₂) allanite-(Ce) developed after ilmenite is extremely rich in vanadium (up to 4.5 wt % V₂O₃). Light colored low-titanium allanite-(Ce) has grown on the titanium-enriched allanite-(Ce). The distribution of REE and yttrium in the allanite-(Ce) and ferriallanite-(Ce) is as follows: Ce &gt; La &gt; Nd &gt; Y &gt; Pr &gt; Sm ∼ Dy ∼ Gd &gt; Er ∼ Tb. The outer zones of allanite-(Ce) crystals and REE epidote are relatively enriched in Nd, with Nd &gt; La in some of them. The yttrium and REE show peculiar relations in allanite-(Y): Y <span>( gg )</span> Ce ∼ Nd ∼ Dy ∼ Er &gt; La ∼ Gd ∼ Yb. Allanite-(Ce) in the Crimean gabbroids is noticeably richer in La, Ti, V and poorer in Y, Sm, Gd in comparison with allanite-(Ce) in Crimean plagiogranitoids. The distribution of REE and yttrium in allanite-(Ce) of Crimean plagiogranitoids is close to that of common granites, differing in an increased proportion of Gd. The coloration reasons and sources of Crimean magmatic allanite are considered. Allanite was partially replaced by monazite-(Ce) during regional metamorphism under the prehnite-pumpellyite facies conditions.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"63 8","pages":"686 - 719"},"PeriodicalIF":0.8,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145062296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Erratum to: Different Types of CaSiO3 in the Earth’s Mantle and Its Geochemical Heterogeneity: the Juina Area in Brazil as an Example","authors":"F. V. Kaminsky,&nbsp;Yu. A. Kostitsyn","doi":"10.1134/S0016702925240036","DOIUrl":"10.1134/S0016702925240036","url":null,"abstract":"","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"63 8","pages":"761 - 761"},"PeriodicalIF":0.8,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0016702925240036.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145062257","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Recalibration of the Equation for Calculating Water Content in Silicate Melt Equilibrated with Aqueous Fluid","authors":"Ya. Yu. Gnuchev,&nbsp;D. A. Bychkov,&nbsp;E. V. Koptev-Dvornikov","doi":"10.1134/S0016702925600312","DOIUrl":"10.1134/S0016702925600312","url":null,"abstract":"<p>Experience in using our previous equation for the prediction of water solubility in silicate melt revealed that the calculated water contents for some experiments at pressures of 5–20 kbar are unrealistically high compared with the experimental measurements. The sample containing the results of 412 experiments used in the previous study was significantly expanded by adding experiments from the MELT database. Using the new total sample containing 1241 experiments, the set of variables describing the effect of melt composition on water solubility was revised. The newly calibrated equation predicts water solubility in silicate melts with an uncertainty of no higher than ±0.01 mole fraction or ±0.25 wt % at pressures from one atmosphere to 20 kbar and temperatures from 825 to 1550 K. The sample size used for the optimization allows the equation to be applied over a wide range of silicate melt composition from komatiitic basalt to rhyolite.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"63 8","pages":"720 - 729"},"PeriodicalIF":0.8,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145062293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Erratum to: Kinetics of Hydrocarbon Formation in the Sedimentary Cover of a Subducting Plate","authors":"D. A. Bushnev","doi":"10.1134/S0016702925240024","DOIUrl":"10.1134/S0016702925240024","url":null,"abstract":"","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"63 8","pages":"760 - 760"},"PeriodicalIF":0.8,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0016702925240024.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145062291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Conditions during the Formation of Carbon-Bearing Rocks, Transonega Region","authors":"Z. A. Kotelnikova,&nbsp;A. R. Kotelnikov,&nbsp;N. I. Suk,&nbsp;G. M. Akhmedzhanova,&nbsp;K. V. Martynov,&nbsp;V. M. Chubarov,&nbsp;V. V. Ananiev,&nbsp;Yu. B. Shapovalov","doi":"10.1134/S0016702924601785","DOIUrl":"10.1134/S0016702924601785","url":null,"abstract":"<p>In order to determine the physico-chemical conditions for the formation of Precambrian сarbon-bearing rocks (CBR) of the Trans-Onega region, the compositions of their minerals and fluid inclusions (FI) in quartz were studied in samples collected at different mine workings of the Zazhogino ore field. The obtained FI density values in the rocks fluctuate in a sufficiently wide range. This indicates the existence of several stages of changes in the temperature regime of fluids during epigenesis. The densities and concentrations of FI solutions from the host silicified lydites are close to those of the highest-density varieties from quartz veinlets in the CBR. Some FI are partially decrepitated, which indicates superimposed processes in the post-capture period. Based on the studies of eutectic temperatures, it is suggested that mineral-forming solutions in the inclusions throughout the entire ore field contain magnesium chloride. The study of the chemical composition of the minerals of the CBR and host rocks allowed us to identify various sulfides, oxides, carbonates, phosphates, silicates, and aluminosilicates. Among them, mineral assemblages suitable for calculating the temperatures and pressures of mineral formation were selected and the corresponding calculations were carried out. Comparison of the results of the FI study and mineral thermobarometry allowed us to estimate the <i>PT</i> conditions that existed during the CBR epigenesis. The maximum values of the greenschist-facies temperatures and pressures during CBR formation correspond to <i>T</i> = 410–400°C and <i>P</i> = 2.4–2.1 kbar. Chlorites were formed at <i>T</i> = 240–200°C and <i>P</i> = 0.5–0.4.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"63 7","pages":"601 - 613"},"PeriodicalIF":0.8,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144832166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaporation Features of the Melts of Ca–Al–Inclusions in Chondrites: Experimental Data and Their Implications","authors":"S. I. Shornikov,&nbsp;O. I. Yakovlev","doi":"10.1134/S0016702925600178","DOIUrl":"10.1134/S0016702925600178","url":null,"abstract":"<p>The paper presents experimental results on the evaporation of the main types (A and B) of Ca–Al inclusions of chondrites in a Knudsen tungsten cell in the temperature range of 1000–2400°C. A peculiarity of the evaporation of the inclusions is that the silicon component is preserved in the residual melt to high temperatures exceeding 2200°C. At the same time, magnesium oxide completely evaporates from the melt, which leads to a decrease in the spinel content and even its disappearance during the crystallization of the residual melt at 2000°C. Magnesium evaporation leads, in turn, to an increase in the Al₂O₃ content in the melt and, accordingly, to an increase in the content of gehlenite in melilite during its crystallization, as is observed in the high-temperature rims of subtype B1 inclusions. Experiments have also shown that the high-temperature evaporation of Ca–Al inclusions occurs in an oxygen-rich atmosphere compared to carbonaceous chondrite matter. In this regard, it is assumed that the condensation of the first mineral products of the inclusions occurred in the oxygen-rich atmosphere of the star (O-rich AGB) outside the protosolar system.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"63 7","pages":"551 - 561"},"PeriodicalIF":0.8,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0016702925600178.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144832021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"History of Iron Accumulation in the Precambrian and Phanerozoic","authors":"A. D. Savko","doi":"10.1134/S0016702924601670","DOIUrl":"10.1134/S0016702924601670","url":null,"abstract":"<p>Iron ores are mostly typical supergene mineralized rocks whose origins were controlled by various tectonic, paleogeographic, and biochemical factors. Mineralogical and petrographic analysis of iron ore types shows that the most widely spread and abundant Precambrian and Phanerozoic types are banded iron formations (BIF), oolitic hydrogoethite–chamosite–siderite (Lorraine type), and hematite and goethite–hydrogoethite weathering crusts (WC). The other types of the ores do not play any significant role in the resources, and their amount is at the level of the statistical error. The Earth’s history was associated with a clearly discernible evolution in the character of iron accumulation. The trend was pulsating, with several stages of ore accumulation. The accumulation of iron ores was confined to greenstone belts in the Archean, to protoplatforms in the Paleoproterozoic, to rift basins in the Neoproterozoic, and to platforms in the Phanerozoic. The Archean and Paleoproterozoic ores are BIF, the Neoproterozoic ones belong to the granular iron formation, and the Phanerozoic are the WC and oolitic formations. The mineralogical–petrographic types of ores also evolved with time. While hematite–magnetite ores are typical of the Archean and Paleoproterozoic; hematite ores are typical of the Neoproterozoic; and hematite, hydrohematite, goethite WC, and oolitic hematite–chamosite–siderite ores are characteristic of the Phanerozoic. The change in ore types was controlled by changes in the facies conditions and by metamorphic processes in the Precambrian.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"63 7","pages":"579 - 600"},"PeriodicalIF":0.8,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144832102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessment of Kinetic Conditions of Quartz Geothermometer Application: Experiment and Modeling","authors":"V. A. Alekseyev","doi":"10.1134/S0016702925600117","DOIUrl":"10.1134/S0016702925600117","url":null,"abstract":"<p>A quartz geothermometer (<i>QG</i>) makes it possible to determine the temperature of a deep geothermal reservoir (<i>GR</i>) using SiO₂ concentration (<i>m</i>) in a solution outflowing from this reservoir on the surface. An error made in the initial <i>QG</i> modeling led to the underestimation of the quartz precipitation rate and thus expanded the region of <i>QG</i> application. Another disadvantage of this modeling was that it ignored the possibility of precipitation of metastable silica modifications. To eliminate these shortcomings, a new numerical <i>QG</i> modeling was performed by the finite-difference method using new kinetic data. The reliability of data was assessed by their involvement in modeling the slow cooling of the quartz–water system and comparison of the obtained results with the experimental results of this process. The best agreement between the experiments and calculations was obtained using two-stage SiO₂ precipitation when different kinetic constants were applied above and below the amorphous silica (<i>AS</i>) solubility for the description of deposition of <i>AS</i> and other metastable silica modifications, respectively. The results of the new <i>QG</i> simulation using new kinetic data were similar at the same ratio of the two initial parameters that characterize the deposition surface area normalized to the water mass in the system (<i>S</i>/<i>M</i>) and the rate of solution rise (<i>v</i>). The real boundary values of this ratio, <i>S</i>/<i>M</i> and <i>v</i>, were determined, at which the model predicts the correct <i>QG</i> values for different temperatures of the solution in <i>GR</i> and at the surface. Kinetic equations used in the simulation ignore many peculiarities of the silica precipitation mechanism. An experimental study of these peculiarities will provide a more realistic <i>QG</i> model close to the real natural processes.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"63 7","pages":"614 - 622"},"PeriodicalIF":0.8,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1134/S0016702925600117.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144832165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}