Geochemistry International最新文献

{"title":"Underwater Discharge of Fluids at the Bottom of Lake Baikal: Composition, Sources, and Migration Peculiarities within the MSU Structure","authors":"T. V. Pogodaeva,&nbsp;G. G. Akhmanov,&nbsp;N. A. Onishchuk,&nbsp;O. V. Shubenkova,&nbsp;A. V. Khabuev,&nbsp;O. M. Khlystov","doi":"10.1134/S0016702924700447","DOIUrl":"10.1134/S0016702924700447","url":null,"abstract":"<p>The paper presents geochemical study of bottom sediments from the MSU structure located on the large Gydratny Fault in the Central Basin of Lake Baikal at a depth of 1380 m. The first detailed data on the spatial variations in the qualitative and quantitative composition of the pore waters are presented. Pioneering data were obtained on Li, B, and Sr contents in the pore water of the sediments. It has been established that fluids are actively discharged within the MSU structure, and the main pathways of their near-surface migration are confined to the tops of hills of this structure on the downthrown fault block. The fluids are highly mineralized (up to 2900 mg/L), showing the highest mineralization ever found in Lake Baikal sediments. The waters are significantly enriched in Mg, Li, B, and Sr but depleted in K. The waters are thought to be generated by the processes of authigenic formation and illitization of smectite at depths of 1 to 2.5 km in the sedimentary sequence. The maximum values of concentration gradients are recorded in the pore waters of the sediments of the western hill, which may indicate a gradual westward shift of the center of the fluid seepage activity along the fault.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"62 8","pages":"864 - 877"},"PeriodicalIF":0.7,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142414238","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":"Dissolution of Ta–Nb and Nb Minerals in Granitoid Melts","authors":"V. Yu. Chevychelov,&nbsp;A. A. Viryus","doi":"10.1134/S001670292470040X","DOIUrl":"10.1134/S001670292470040X","url":null,"abstract":"<p>The effective solubilities (maximum contents) of Ta and Nb in model felsic lithium-fluoride melts of variable alkalinity and alumina content were experimentally determined at the dissolution of Ta–Nb and Nb minerals: pyrochlore, microlite, ilmenorutile, and ferrotapiolite at <i>T</i> = 650–850°C and <i>P</i> = 100 and 400 MPa. The Ta and Nb partitioning in the mineral-melt systems was also studied. When pyrochlore is dissolved in granitoid melts at <i>P</i> = 100 MPa and <i>T</i> = 650–850°C, the highest effective solubilities of Nb (0.7–1.8 wt %) are obtained in alkaline melt, and they significantly decrease (to 0.03–0.5 wt %) in subaluminous and peraluminous melts. A temperature increase increases the solubility (content) of Nb in the melt. Similar dependences were obtained for Ta solubility by dissolving microlite. In peraluminous granitoid melt, microlite remains stable, while pyrochlore becomes unstable. A pressure decrease from 400 to 100 MPa in alkaline and subaluminous melts was found out to not significantly affect on the dissolution of microlite and pyrochlore, whereas Ta and Nb contents in the peraluminous melt noticeably decrease. The dependences of Nb solubility and its partitioning between granitoid melts and ilmenorutile on the alkalinity–alumina content of the melt are similar to those for the dissolution of columbite and tantalite. The dependences obtained by dissolving ferrotapiolite, pyrochlore, and microlite differ from them.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"62 8","pages":"805 - 823"},"PeriodicalIF":0.7,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142413886","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":"Organic Matter in Hydrotherms of the Pauzhetka Field: Composition and Comparative Analysis with Other Sites","authors":"V. N. Kompanichenko,&nbsp;V. A. Poturay","doi":"10.1134/S0016702924700423","DOIUrl":"10.1134/S0016702924700423","url":null,"abstract":"<p>The composition of medium-volatile organic matter (OM) was studied in the steam–water mixture condensate (<b>SWC</b>) from deep production wells of the Pauzhetka geothermal field. Using solid-phase extraction and chromatography–mass spectrometry, 17 organic compounds, including 14 aliphatic and aromatic hydrocarbon (HC), were identified in the studied SWC. These components are strongly dominant in the Pauzhetka hydrothermal system and a number of other geothermal fields in Kamchatka, with their average contents amounting to higher than 60%. According to the specifics of the molecular weight distribution of the saturated HC, the high temperature of the steam–water mixture condensate (more than 108°C at the wellhead), and the absence of obviously biogenic components, these HC are thought to be produced by thermogenic processes: the transformation of organic remnants under the effect of high temperatures and pressures. The contents of the other compounds are much lower, and these components are mostly oxygen-containing compounds (ketones, aldehydes, and alcohols). Similarities between the spectra of organic compounds in the Pauzhetka and Uzon SWC may be at least partly explained by their extraction from volcanogenic–sedimentary layers containing buried organic matter.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"62 8","pages":"832 - 843"},"PeriodicalIF":0.7,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142413913","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":"Biogeochemistry of Peat Deposits of the Holocene Section of the Vydrino Bog (Southern Baikal Region)","authors":"A. E. Maltsev,&nbsp;V. A. Bobrov,&nbsp;G. A. Leonova,&nbsp;Y. I. Preis,&nbsp;M. A. Klimin,&nbsp;V. A. Bychinsky","doi":"10.1134/S0016702924700435","DOIUrl":"10.1134/S0016702924700435","url":null,"abstract":"<p>The paper reports the detailed studies of drilling cores from peat deposits of the Vydrino bog with a thickness of 4.4 m and an age of 13 100 cal. years. The peat is composed of fen, transitional, and raised types. The early-diagenetic transformations of peat sediments are considered, and the distribution of elements, the formation of authigenic minerals, and the chemical composition of bog waters are studied. The destruction of organic matter begins from the upper intervals of peat at the early diagenetics stage. Pyrograms do not have clearly defined high-temperature peaks, “rudiments” of the macromolecular structure of kerogen, which indicates a low degree of transformation of peat organic matter. The high abundance of organotrophic, ammonifying, nitrifying, and phosphate-mobilizing microorganisms, and the low abundance of Fe- and Mn-oxidizing microorganisms, and sulfate-reducing bacteria are revealed. The presence of organotrophic microorganisms throughout the section indicates that the biogeochemical processes of the carbon cycle span the entire peat sequence. The low S(II) content indicates the low intensity of sulfate reduction. The fen peat is characterized by the high contents of Si, Al, Fe, Ca, Sr, Ba, Zr, La and anomalous contents of Cu, Zn, which is caused by the peatland formation under conditions of rich mineral nutrition. The ash part of the transitional peat demonstrates a decrease in the contents of Si, Fe, Sr, Br, K Si, Ca, Ba, Cu, Zn and La, which reflects the gradual weakening of the connection of the peat deposit with the underlying rocks. The near-surface horizon of raised peat is characterized by an increase in the contents of K, Mn, Zn, Hg, Pb and As, which is accompanied by an increase in atmospheric dust and anthropogenic impact on the bog ecosystem in the 20th and 21st centuries. The bog waters of the fen peat are characterized by the high contents of the main ions, Al, Fe, Mn, Sr, while the transitional peat shows a decrease in DOC, <span>({text{SO}}_{4}^{{2 - }})</span>, <span>({text{HCO}}_{3}^{ - })</span>, Al, Fe, Ni, Ca, Mg. The oligotrophic stage peat deposit layer is characterized by the development of Fe oxides and hydroxides, the presence of vivianite is noted for transitional peats, and the eutrophic stage layer includes rhodochrosite and sulfides of Fe, Cu, and Zn.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"62 8","pages":"844 - 863"},"PeriodicalIF":0.7,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142414115","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":"Trace Element Composition of Discordant Zircon as a Reflection of the Fluid Regime of Paleoproterozoic Granulite Metamorphism (Khapchan Terrane, Anabar Shield)","authors":"S. G. Skublov,&nbsp;N. I. Gusev,&nbsp;L. I. Salimgaraeva,&nbsp;L. Yu. Romanova","doi":"10.1134/S0016702924700393","DOIUrl":"10.1134/S0016702924700393","url":null,"abstract":"<p>New data on the U–Pb age (SHRIMP-II) and trace element composition (SIMS) of zircon from gneisses of the Khapchan Group of the Khapchan terrane of the Anabar Shield are presented. Zircon grains contain relicts of magmatic zircon, the protolith and source areas of which are difficult to specify. The only zircon in this group with the least altered core preserved the ²⁰⁷Pb/²⁰⁶Pb protolith age of 1971 ± 19 Ma. During granulite metamorphism, the zircon was subjected to the impact of fluid enriched in incompatible elements. The disurbances affected both the U–Pb isotope system (zircon age was “reset” at metamorphic age of 1920–1930 Ma) and composition of zircon, magmatic cores of which were significantly recrystallized in a solid state or dissolved by fluid up to the practically complete disappearance of primary zircon. In both the cases, zircon was sharply enriched in incompatible elements (Ca, Ti, Pb, Sr, Ba, and some others) owing to fluid effect, while preserved cores seemed to be rimmed by a new zircon population (CL-black). The REE distribution patterns in the recrystallized cores acquired a “bird’s wing” profile atypical for zircon. When the fluid lost its reactivity, the main part of the zircon grain crystallized, typical of granulite zircon. This zircon population is less enriched in incompatible element than the cores are. The horizontal pattern of HREE distribution is consistently repeated, which indicates the co-crystallization of zircon and garnet. The estimated crystallization temperature of the main part of zircon varies in a narrow range of 800–830°C. All zircon domains in the Wetherill concordia diagram form a single trend with a zero lower intercept and an upper intercept confirmed by concordant cluster with an age around 1920–1930 Ma. This value corresponds to the age of regional Paleoproterozoic granulite metamorphism. A unique feature of zircon from the Khapchan gneisses is that its cores did not retain the age marks of the protolith, but were completely reset during metamorphism both in terms of the U-Pb system and the trace element composition, which can be explained by the extremely high intensity of fluid impact during the granulite facies metamorphism superimposed on the rocks of the Khapchan terrane of the Anabar Shield.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"62 8","pages":"793 - 804"},"PeriodicalIF":0.7,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142414242","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":"Cryolite as a Reference Mineral of Rare Metal Mineralization: An Experimental Study","authors":"A. A. Rusak,&nbsp;T. I. Shchekina,&nbsp;N. G. Zinovieva,&nbsp;A. Y. Bychkov,&nbsp;O. A. Lukanin","doi":"10.1134/S0016702924700332","DOIUrl":"10.1134/S0016702924700332","url":null,"abstract":"<p>Phase relations and the distributions of rare earth elements (REE), Sc, Y, and Li between aluminofluoride and aluminosilicate melts in the model granite system Si–Al–Na–K–Li–F–O–H were experimentally studied at 700°C, 1 and 2 kbar, and water contents of 3 to 50 wt %. Our original and available literature experimental data on phase relations in the granite system saturated with water and fluorine and containing trace elements are compared with the mineral assemblages of rare-metal cryolite-bearing granites from the Zashikhinsky, Katugin, and Ulug-Tanzek deposits in eastern Siberia. Liquid immiscibility between granite and salt aluminofluoride melts, which occurs at high contents of fluorine and lithium in the system, is proved to facilitate the accumulation of rare elements in salt cryolite-like melts. At a temperature of 700°C and pressures of 1 and 2 kbar, aluminofluoride melt in the granite system crystallizes and forms cryolite. Fluorine-bearing minerals of trace and rare earth elements, such as pyrochlore and gagarinite, occur at these deposits in association with cryolite and lithium micas. Comparison of experimental data and natural observations provides arguments in support of the hypothesis that liquid immiscibility should play an important role in the formation of cryolite. Cryolite is thought to be able to serve as a reference mineral for rare metal-rare earth mineralization in granites with high lithium and fluorine content.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"62 7","pages":"714 - 732"},"PeriodicalIF":0.7,"publicationDate":"2024-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208341","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":"EPR Spectroscopic and Calorimetric Study of Minerals of the Amblygonite–Montebrasite Series from Rare-Metal Pegmatite of the Voron’i Tundras (Kola Peninsula) and Sangilen Highlands (Tuva)","authors":"S. V. Vyatkin,&nbsp;Yu. D. Gritsenko,&nbsp;L. P. Ogorodova,&nbsp;M. F. Vigasina,&nbsp;D. A. Ksenofontov,&nbsp;L. V. Melchakova","doi":"10.1134/S0016702924700344","DOIUrl":"10.1134/S0016702924700344","url":null,"abstract":"<p>The paper reports the first comprehensive physicochemical study of minerals of the amblygonite LiAlPO₄F–montebrasite LiAlPO₄(OH) series. An EPR spectroscopic and calorimetric study of montebrasite LiAlPO₄(OH)_0.9F_0.1 from the Shuk-Byul rare-metal granite pegmatites (Sangilen Highlands, Tuva) and amblygonite LiAlPO₄F_0.5(OH)_0.5 from pegmatites of the Voron’i Tundras (Kola Peninsula) was carried out. Using the EPR method, the radiation-sensitive paramagnetic O^– centers were discovered. They were formed without participation of impurity elements in the regular sites of crystal lattice. The possibility use of minerals of the amblygonite–montebrasite series for EPR geochronometry has been demonstrated for the first time. Using the method of high-temperature melt dissolution calorimetry on a Tian-Calvét microcalorimeter, the enthalpies of formation from elements <span>({{Delta }_{f}}H_{{{text{el}}}}^{0})</span> (298.15 K) = –2326.3 ± 2.2 kJ/mol for montebrasite with the composition LiAl(PO₄)(OH)_0.9F_0.1 and for amblygonite with the composition LiAl(PO₄)F_0.5(OH)_0.5 (‒2347.9 ± 3.1 kJ/mol) are obtained; and the values of this parameter are calculated for the end members with an ideal composition of the series: for montebrasite (–2315.5 ± 2.2 kJ/mol) and for amblygonite (–2401.6 ± 3.1 kJ/mol). The values of the standard entropy <i>S</i>⁰ (298.15 K) and the Gibbs energy of formation <span>({{Delta }_{f}}G_{{{text{el}}}}^{0})</span> (298.15 K) for intermediate and end members of the amblygonite–montebrasite series are estimated.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"62 7","pages":"748 - 759"},"PeriodicalIF":0.7,"publicationDate":"2024-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208342","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":"Biogeochemical Aspects of Transformation of Humic Substances and Silicate Rocks during Freezing–Thawing","authors":"L. M. Kondratyeva,&nbsp;D. V. Andreeva,&nbsp;E. M. Golubeva,&nbsp;Z. N. Litvinenko","doi":"10.1134/S0016702924700356","DOIUrl":"10.1134/S0016702924700356","url":null,"abstract":"<p>In the northern regions, seasonal temperature fluctuations cause cyclic thawing and freezing of soils and rocks, which is accompanied by dangerous natural phenomena, including landslides. Special conditions arise on the mountain slopes of many reservoirs due to the fluctuations of water levels and the interaction of humified waters with rocks. The paper presents the results of an experimental study of the biotransformation of sodium humate (SH) and changes in the microstructure of the surface of silicate rock that is a part of the Bureya landslide body under various conditions of cyclic freezing–thawing (CFT). Freezing of samples was carried out at a temperature of –18°C, and thawing at different temperature ranges (+4 and +23°C). The role of biogenic factor was played by four strains of microorganisms isolated from the surface and bottom waters in the Bureya Reservoir above and below the landslide body. The nature of the SH biotransformation during CFT was studied by spectral methods at different wavelengths (254, 275, and 465 nm). Analysis of the composition of water-soluble forms of chemical elements in an aqueous environment during rock destruction was carried out by ICP-MS, and changes in the surface microstructure was studied using scanning electron microscopy. It was found that the aromatic component of SH was subjected to the most intense transformation. After CFT, the strain <i>Actinomyces</i> sp. 45VD isolated from bottom waters showed maximum activity at a thawing temperature of +4°C relative to SH and leaching of elements from rock (Al, Ca, Mg, Mn). Its activity was comparable to the intensity of element leaching by a natural microbial consortium of non-sterile rock. Rocks subjected to CFT in deionized water were used for comparison; in this case, the content of water-soluble forms of many chemical elements (Fe, Ni, Cu, Zn, As, Mo, Ag, Cd, Tl, Bi, As) was below the detection limits (&lt;0.001). The high biogeochemical activity of <i>Actinomyces</i> sp<i>.</i> 45VD is confirmed by the analysis of SEM-images of the microstructure of the silicate rock surface and the formation of a wide variety of isomorphic biominerals.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"62 7","pages":"760 - 771"},"PeriodicalIF":0.7,"publicationDate":"2024-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208343","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":"Geochemistry and Age of the Paleoproterozoic Metavolcanic and Metasedimentary Rocks of the Don Terrane of the Volga–Don Orogen","authors":"R. A. Terentiev,&nbsp;K. A. Savko,&nbsp;E. H. Korish,&nbsp;M. V. Chervyakovskaya","doi":"10.1134/S0016702924700368","DOIUrl":"10.1134/S0016702924700368","url":null,"abstract":"<p>The Don terrane, which is extensively reworked by metamorphism and granitoid intrusions, is part of the Volga–Don orogen stretching along the eastern margin of the Sarmatian segment of the East European Craton. The terrane consists of gneiss-granites of the Pavlovsk complex, metavolcanic rocks, ranging from basaltic andesites to dacites (amphibolites and gneisses), and metasedimentary rocks (marbles and calc-silicate rocks) of the Don Group. The volcanic rocks are typically enriched in LILE and LREE and show negative HFSE anomalies, indicating fluid-assisted melting of the mantle wedge in a subduction zone. The Nd isotopic composition (ε_Nd2200 = –1.2 to +3.4, model age 2180–2550 Ma) and Hf isotopic composition (ε_Hf = –4.3 to +3.3, model age 2290–2640 Ma) indicate an enriched mantle or a mixed crustal–mantle source of the parental melts of the volcanics and a juvenile source for sediments of the Don Group. The U–Pb zircon metamorphic age of the gneisses and amphibolites is 2047 ± 7 Ma, and that of the thermal effect of the granitoid batholith on the host rocks is 2060 ± 4 Ma. According to isotope geochemical and geochronological data, the Don Group is underlain by Archean rocks, contains Archean detrital zircons, but the age of this group is no older than 2300 Ma. A facies and age analogue of the Don Group is the Temryuk Formation of the Central Azov Group of the Ukrainian shield. In the Paleoproterozoic, the eastern margin of Sarmatia was likely a continental arc, which was nearly coeval with the island arc–backarc basin system of the Losevo Group.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"62 7","pages":"675 - 695"},"PeriodicalIF":0.7,"publicationDate":"2024-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208344","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":"Geochemistry of Alirajpur Granitoids (Gujarat, India) and Their Genetic Relationship to the Precambrian Basement Underlying the Deccan Traps","authors":"Sunit Mohanty,&nbsp;Vishal Nareda,&nbsp;Arundhuti Ghatak","doi":"10.1134/S0016702924700514","DOIUrl":"10.1134/S0016702924700514","url":null,"abstract":"<p>The granitic basement rocks of central and western India, which are overlain by the Deccan Traps, are important for understanding early Earth processes and crustal evolution. The Alirajpur region presents a unique opportunity to study the complete sequence of basement granites, overlain by the marine Turonian Bagh beds. These granitic basement rocks are mainly composed of orthoclase, quartz, plagioclase, and biotite as rock-forming minerals. Abundant zoned zircons are hosted within biotite and hornblende. The whole rock geochemistry is calc-alkaline with a prevalence of potassium over sodium. The Alirajpur granitoids exhibit low REE with positive Eu anomaly exhibiting typical lower crust signatures. A detailed petrological-geochemical comparison of the granitic basement rocks from the Koyna and Alirajpur basement, separated by ~500 km, indicates that they are genetically related and provide important clues about the extent of the Precambrian basement underlying the ~500 000 km² of Deccan Traps.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"62 13","pages":"1359 - 1377"},"PeriodicalIF":0.7,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141737637","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}