Chemie Der Erde-Geochemistry最新文献

{"title":"Multistage evolution of the Aladağ mantle peridotites (S-Türkiye): Processes of partial melting and melt-peridotite interaction in Mid-Ocean Ridge and Subduction Zones","authors":"Samet Saka ,&nbsp;Ibrahim Uysal ,&nbsp;Hans-Michael Seitz ,&nbsp;Dirk Müller","doi":"10.1016/j.chemer.2023.126074","DOIUrl":"10.1016/j.chemer.2023.126074","url":null,"abstract":"<div><div><span>The Aladağ ophiolite<span><span> is located in the eastern Taurides, north of the city of Adana, southern Türkiye and, from bottom to top, is composed of mantle peridotites<span>, ultramafic-mafic cumulates, isotropic (massive) gabbro and diabase<span> dykes. Mantle peridotites are represented by varying degrees of serpentinized dunite, </span></span></span>harzburgite<span> and lherzolite. We studied 100 lherzolite, harzburgite and dunite samples representing the entire Aladağ ophiolite mantle. Whole rock major and trace element analysis were performed for all samples, and </span></span></span>mineral chemistry analysis were carried out on selected mineral phases.</div><div><span>According to geochemical characteristics, mantle peridotites are divided into two sub-groups: abyssal (Group-1) and suprasubduction zone peridotites (Group-2). Group-1 mantle peridotites are represented by high clinopyroxene<span> modal abundances, whole-rock and clinopyroxene heavy Rare Earth Element (REE) contents and low spinel Cr# values (13–47). Whole-rock heavy REE patterns indicate that these rocks are 5–18 % unhydrous partial melting residues. In contrast, Group-2 mantle peridotites are represented by lower clinopyroxene modal abundances, whole-rock and clinopyroxene heavy REE contents, and higher spinel Cr# values (44–74) than Group-1 samples, reflecting higher partial melting degrees of up to 33 %. Light REE and LILE enriched whole-rock and clinopyroxene contents of Group-2 samples reflect that, in addition to depletion, they were enriched with fluids/melts and underwent both cryptic and modal </span></span>metasomatism<span> in the subduction zone.</span></div><div>Aladağ peridotites have formed originally by low degree partial melting at mid-ocean spreading ridge (MOR) and later re-melted and metasomatized/refertilized in a suprasubduction zone (SSZ) environment.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"84 4","pages":"Article 126074"},"PeriodicalIF":2.6,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139507429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fluid evolution and genesis of the Shipenggou gold deposit in Central Jilin Province, China: Constraints from C–H–O and in–situ sulphur isotopes of pyrite and fluid inclusions","authors":"Jun-chi Chen ,&nbsp;Ke-yong Wang ,&nbsp;Xiang-jin Yan ,&nbsp;Qing-ying Zhao ,&nbsp;Li-Xue Sun","doi":"10.1016/j.chemer.2024.126203","DOIUrl":"10.1016/j.chemer.2024.126203","url":null,"abstract":"<div><div>The origin and evolution of the Shipenggou gold deposit in the Shipenggou–Jiapigou–Jinchengdong (SJJ) gold belt in Jilin Province, Northeast China, remain poorly understood. In this study, fluid inclusion and C–H–O–S isotopes from the Shipenggou deposit were investigated to clarify the fluid evolution and mineralisation process. The gold mineralisation is hosted in the biotite plagiogneiss of the Archaean Sandaogou Formation and is dominated by gold–bearing quartz veins. The orebodies are controlled by NNE– and NEE–striking brittle–ductile structures. Four stages of mineralisation have been identified: (I) milky quartz–minor pyrite, (II) quartz–pyrite–minor gold, (III) gold–quartz–polymetallic sulphide, and (IV) quartz–carbonate. Fluid inclusions were identified as four types: aqueous (VL–type), CO₂–bearing (CL–type), CO₂–rich (LC–type), and carbonic (PC–type). VL–, CL–, LC–, and PC–type FIs were developed within quartz from Stages I–II. Stage III quartz contains both CL– and VL–type FIs. Only VL–type FIs were observed in calcite from Stage IV. The total homogenisation temperatures (Tht) of FIs in Stages I, II, III, and IV are of 281.5–324.8, 215.5–269.1, 151.2–198.3, and 125.4–149.5 °C with salinities of 2.8–13.2, 2.8–9.6, 3.2–8.4, and 3.0–5.9 wt% NaCl eqv. Laser Raman spectroscopy analysis indicated the CL– and PC–type FIs from Stages I and II contain CO₂ and minor quantities of CH₄. The ore–forming fluids have developed from a medium temperature, low–medium salinity immiscible NaCl–H₂O–CO₂ ± CH₄ system to a low temperature, low salinity homogeneous NaCl–H₂O system. The H<img>O isotopic compositions indicate that the initial ore–forming fluids were mantle–derived magmatic water. Subsequently, the ore–forming fluids were gradually joined by meteoric water. δ¹³C values indicate C in the fluids have originated from organic matter. Organic matter may have originated from the mantle, which mixed crust materials influenced by the subduction of the Palaeo–Pacific slab. In–situ, S isotope data of pyrite indicate that the origin of sulphur at the Shipenggou deposit is the mantle containing a crust component. Based on the above analysis results, the Shipenggou gold deposit is a mesothermal magma-hydrothermal vein–type gold deposit.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"84 4","pages":"Article 126203"},"PeriodicalIF":2.6,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemical and geochronological evidences from Cambrian to Ordovician protracted magmatism in the Istranca Massif, NW Türkiye","authors":"Sabah Yılmaz Şahin ,&nbsp;Özge Naycı ,&nbsp;Namık Aysal ,&nbsp;Zeynep Cansu ,&nbsp;Fatma Şişman Tükel","doi":"10.1016/j.chemer.2024.126196","DOIUrl":"10.1016/j.chemer.2024.126196","url":null,"abstract":"<div><div>Plutonic rocks in different ages are cropted out and form the basement rocks in the Istranca Massif. One of the plutons located at the basement is the Cambrian-Ordovician Vize pluton (Vize-Kırklareli) and is distinguished from other plutons by some of its characteristic features. This pluton intruded into the high-grade metamorphic sedimentary rocks, and is unconformably overlay by Triassic low-grade metamorphic rocks and Eocene aged coral reef limestones (Soğucak Formation). Based on new whole rock geochemical and zircon U<img>Pb data concentrated in two different ages, it can be said that the Vize pluton was affected by protracted magmatic activity. The igneous minerals and texture of Vize pluton are partly preserved, It has a mylonitic texture, a distinct foliation consisting of light and dark zones. In addition, metagranites contain mafic magmatic enclaves (MMEs) in some places.</div><div>The Vize pluton is an I-type pluton with predominantly peraluminous and slightly metaluminous character. It is also High-K, calc-alkaline, and reflecting volcanic arc and post-collisional tectonic settings. Mineral chemical analyses show that the mafic minerals in the Vize pluton consist of Fe-biotite and calcic amphibole (hornblende). Ti-in biotite thermometry shows that the temperature of the pluton in the final crystallization temperatures are between 834 and 850 °C (mean = 845 ± 4 °C), while the crystallization temperatures of amphiboles are between 876 and 910 °C (mean = 893 ± 22 °C). Crystallization depths are estimated to be a range of 6.5 to 7.9 km. It can be assumed that the oxygen fugacity of calcic amphiboles (logƒO₂) is stabilized between −10.7 and − 11.3 bar (mean = −11.05 ± 0.4 bar). ∆NNO values are between 0.72 and 1.11 (mean = 0.96 ± 0.12) and H₂O melt content is between 4.63 % and 5.43 % (mean = 5.04 ± 0.4 %). Oxygen fugacity values are among the typical values of calc-alkaline magma crystallization.</div><div>The Vize pluton was crystallized in Cambrian to Ordovician times according to zircon U<img>Pb dating is concentrated in two different populations as 526.16 ± 3.26 Ma and 452.93 ± 2.76 Ma. All data obtained are consistent with the ages of the magmatism that produced the Vize Pluton in the Balkanides and Istranca Massif of 420–470 Ma (mean 447.17 ± 3.24 Ma) and indicate that it probably formed in the northern Gondwana. It was affected by the magma-mixing processes of coeval felsic and mafic magmas, and anatexis processes. Geochronological and geochemical data indicate the existence of a protracted magmatic activity related to convergent setting (long-lived magmatic arc) that forced the Vize-Pluton to undergo multi-stage melting-crystallization processes.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"84 4","pages":"Article 126196"},"PeriodicalIF":2.6,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mineralogy, ore genesis and zircon UPb age characteristics of the Cerattepe CuAu (±Zn) deposit (Artvin, NE Turkey)","authors":"İbrahim Akpınar ,&nbsp;Yılmaz Demir ,&nbsp;Namık Aysal ,&nbsp;Nurullah Hanilçi ,&nbsp;Kıymet Deniz ,&nbsp;Yusuf Kaan Kadıoğlu ,&nbsp;Martin Yates ,&nbsp;Emin Çiftçi","doi":"10.1016/j.chemer.2024.126167","DOIUrl":"10.1016/j.chemer.2024.126167","url":null,"abstract":"<div><div>The Cerattepe deposit is associated with bimodal felsic volcanics of the Kızılkaya Formation, which hosts the majority of VMS deposits in the Eastern Pontide Orogenic Belt. Pyrite, chalcopyrite, sphalerite, and bornite are the main sulfides, with minor galena, fahlores, marcasite, idaite, covellite, and chalcocite. Barite and quartz are the primary gangue minerals, with minor calcite and gypsum. Hematite, limonite, goethite, jarosite, and lepidocrocite are common oxide minerals. The sulfide ore is shaped by rapid cooling, zone refinement, replacement, and local deformation processes, which affect textural relationships and mineral paragenesis.</div><div>Fluid inclusion studies have shown that the early stages of the ore were formed by boiling at temperatures of 250–355 °C and approximately 1900 m depth of sea water, while the later stages developed at temperatures as low as 148 °C. The Te temperatures imply that NaCl-dominated solutions with partial mixing of CaCl₂ may be responsible for mineralization. The CO₂ phase present in the early stages of the ore may have been derived from the interaction of hydrothermal solutions with the underlying carbonate rocks. Salinity values of 0.2–7.62 wt% NaCl equ., compatible with the average salinity of Kuroko type VMS deposits, indicate that the Cerattepe deposit was formed in a marine environment.</div><div>The Co/Ni of pyrites (1–12, with an average of ∽2) and Zn/Cd of sphalerites (127–383) indicate an acidic source and magmatic source of acidic-andesitic for the ore-forming fluids, respectively. The δ³⁴S values −4.4 ‰ – +9.63 ‰ indicate a magmatic sulfur source, with partial sulfate-reduced sulfur. A magmatic-related source is also inferred from δ¹⁸O values (+8.5 and + 9.5 ‰.) for the Cerattepe deposit. The leaching, zone refinement, and replacement processes, followed by remobilization and precipitation of the metals, resulted in gold enrichment in the oxide zone. The new zircon U<img>Pb dating constrains the formation age of the Cerattepe deposit into a time span from 79 ± 1–76.8 ± 1 Ma, a younger age compared to other VMS deposits in the eastern Pontide region.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"84 4","pages":"Article 126167"},"PeriodicalIF":2.6,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141843480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mineral chemistry and geothermobarometry of metasedimentary rocks of Central Menderes Massif, Western Türkiye: Metamorphic evolution and source of metapelitic rocks","authors":"Fulya UZUN ,&nbsp;Namık AYSAL ,&nbsp;Marcel GUILLONG ,&nbsp;Julien M. ALLAZ","doi":"10.1016/j.chemer.2024.126199","DOIUrl":"10.1016/j.chemer.2024.126199","url":null,"abstract":"<div><div>The Menderes Massif (MM) is the largest metamorphic massif of Türkiye. This study was carried out to determine the origins, metamorphic conditions and age of garnet-mica schists covering large areas in the Central Menderes Massif (CMM). Detrital zircon dating of a garnet-mica schist derived from a quartzofeldspathic source measured the youngest zircon age to be 450 ± 61 Ma (102 % concordant, Th/U = 0.02) Ma and the oldest zircon age to be 1529 ± 18 Ma (97 % concordant, Th/U = 0.02) Ma. The ƐHf_(t) values of the selected zircon grains vary between −27.42 and −3.43, and the ¹⁷⁶Lu/¹⁷⁷Hf isotope values vary between 0.2820 and 0.2827, and these values are consistent with the values obtained from the orthogneisses and paragneisses of the massif. The presence of five Ordovician zircon grains in garnet-mica schists and the intrusive contact with Triassic granites indicate that the source rock of the schists may have been deposited in the Late Ordovician - Triassic interval. Mineral chemical analyses show that garnets are almandine, biotites are Fe-biotite and white micas are muscovite-phengite in composition, and they are affected by metamorphism (greenschist - lower amphibolite facies) under ∼5 kbar pressure and ∼600 °C temperature conditions. For the first time, rutile U<img>Pb dating shows that garnet-mica schists underwent metamorphism 43.1 ± 6.1 Ma ago. PT conditions and metamorphic ages obtained from garnet-mica schists show that the overlying units underwent metamorphism in the greenschist-lower amphibolite facies in the Lutetian (Eocene) period.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"84 4","pages":"Article 126199"},"PeriodicalIF":2.6,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"3D mineral prospectivity modeling using multi-scale 3D convolution neural network and spatial attention approaches","authors":"Xiaohui Li ,&nbsp;Yuheng Chen ,&nbsp;Feng Yuan ,&nbsp;Simon M. Jowitt ,&nbsp;Mingming Zhang ,&nbsp;Can Ge ,&nbsp;Zhiqiang Wang ,&nbsp;Yufeng Deng","doi":"10.1016/j.chemer.2024.126125","DOIUrl":"10.1016/j.chemer.2024.126125","url":null,"abstract":"<div><div><span><span>A significant proportion of recent mineral exploration has increasingly focused on the targeting of deep-seated orebodies. Mineral prospectivity modeling is one of the more important approaches that facilitates exploration targeting and the mitigation of risks associated with mineral exploration, particularly under cover. Recent advances in 3D mineral prospectivity modeling enable the effective extraction of predictive information from three-dimensional geological models, enabling more accurate exploration targeting of deep-seated orebodies. These advancements have synergized with deep learning approaches to improve the efficiency of mineral exploration based on nonlinear and multi-layer sensing attributes, effectively enabling the identification and extraction of key relationships between 3D predictive maps and </span>mineralization<span>. The main deep learning method used for 3D mineral prospectivity modeling is convolutional neural network (CNN) modeling. However, this research typically does not consider the multiscale features of geological structures<span>, meaning further improvements can be made to this modeling approach. This paper introduces a multi-scale 3D convolutional neural network model (3D CNN) incorporating a spatial attention mechanism and an Inception module (MSAM-CNN) for 3D mineral prospectivity modeling. By integrating Inception modules and spatial attention mechanisms, the network's capability to identify multi-scale geological features and delineate key predictive areas is significantly enhanced compared to typical CNN approaches. This new approach provides further improvement in the accuracy and generalization capability of 3D mineral prospectivity modeling. To evaluate the effectiveness of this model, we undertook 3D mineral prospectivity modeling within the area of the Baixiangshan iron deposit, in the Ningwu Basin of the Middle-Lower Yangtze River Metallogenic Belt, China. The results show that the multi-scale 3D convolutional neural network model is remarkably robust and has good generalization capabilities. The approach can also can effectively delineate targets within the deep and peripheral areas of the deposit, providing targets for future exploration. The addition, performance indicators, ROC curve, and Capture-Efficiency curve generated during this modeling consistently demonstrate that the MSAM-CNN model outperforms Inception-enhanced CNN (M-CNN), CNN, Random Forest (RF), and </span></span></span>Support Vector Machine (SVM) models. All of this indicates that MSAM-CNN approaches can effectively extract 3D spatial features within 3D predictive maps during 3D mineral prospectivity modeling better than other approaches that are commonly used, indicating that thius approach represents a promising tool for the accurate and precise identification of targets during future exploration for deep-seated mineralization.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"84 4","pages":"Article 126125"},"PeriodicalIF":2.6,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140927553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identifying fluid pathways in hydrothermal deposits using hidden Markov models: Representation of fluid flow as exploration criteria","authors":"Juexuan Huang,&nbsp;Zhankun Liu,&nbsp;Hao Deng","doi":"10.1016/j.chemer.2024.126180","DOIUrl":"10.1016/j.chemer.2024.126180","url":null,"abstract":"<div><div>Hydrothermal mineral systems are formed by the transport of metals from large source areas through convective fluid flow, subsequent leading to deposition of these metals at specific sites. The fluid pathways are crucial for connecting mineral sources with favorable zones of mineral deposition. However, due to the complexity of fluid flow and limitations in sampling cost, assay cost, and expert experience, inferring fluid pathways poses a significant challenge. In this paper, we leverage the continuous and extensive characteristics of exploration data to identify fluid pathways in hydrothermal deposits, uncovering the hidden patterns from their mineralization footprints and favorable structural features within the data. By modeling the fluid flow as a Markov process, we tailor a hidden Markov model (HMM) to identify fluid pathways using observations of mineralization and structural features. Specifically, we identify the latent geometry of fluid pathways by maximizing their posterior probability as represented by the HMM. We then represent the identified fluid pathways as two quantitative and mappable exploration criteria—trajectory length and pathway flux—which serve as predictor variables in 3D mineral prospectivity mapping. Our method is applied to the Xiadian orogenic gold deposit in the Jiaodong Peninsula, China. The results suggest that the formation of Xiadian deposit is attributed to a series of fluid trajectories originating from two injection points. By using the exploration criteria derived from the identified fluid pathways, we significantly enhance the accuracy and efficacy of mineral prospectivity mapping, demonstrating the proposed HMM as an effective artificial intelligence tool for mineral exploration targeting.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"84 4","pages":"Article 126180"},"PeriodicalIF":2.6,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142187182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Age and composition of perovskite in ultramafic lamprophyres from the Zima alkaline-ultramafic carbonatite complex, the southern margin of the Siberian craton: Petrogenetic implications","authors":"Yazgul Nugumanova ,&nbsp;Anna Doroshkevich ,&nbsp;Anastasia Kalugina ,&nbsp;Dmitry Chebotarev ,&nbsp;Ivan Izbrodin ,&nbsp;Tong Hou","doi":"10.1016/j.chemer.2024.126159","DOIUrl":"10.1016/j.chemer.2024.126159","url":null,"abstract":"<div><div><span><span><span><span>This paper presents data on the age and trace element composition of perovskites from dykes of ultramafic </span>lamprophyres<span> (aillikites) of the Zima alkaline-ultramafic carbonatite complex (Bolshaya Tagna and Bushkanay) located within the Urik-Iya graben, Eastern Sayan region, southern margin of the Siberian </span></span>craton. The studied samples exhibit similar textural and structural features but differ slightly in the mineral composition of the groundmass. They have a porphyritic structure, a massive texture, and consist of olivine macrocrystals embedded in a fully crystallized groundmass composed of perovskite, </span>apatite, spinel, </span>phlogopite<span><span>, garnet, carbonates, </span>clinopyroxene and other minerals. The macrocrystals quantity varies between 40 and 50 vol%. With the exception of a single sample from the Bushkanay dyke, olivine is entirely replaced by serpentine and/or talc.</span></div><div><span>Perovskites from aillikites of the Bolshaya Tagna intrusion exhibit crystals with normal zoning showing a decrease in Na, REE<span>, and Nb contents with center-to-rim increasing Ca content. In contrast, minerals from the aillikites of the Bushkanay dyke demonstrate reverse zoning, with an increase in Na, REE, and Sr and decrease in Ca contents from the center to the rim. We suggest that during crystallization of perovskites, the magma parental to the aillikites of the Bolshaya Tagna intrusion and the Bushkanay dyke had nearly similar trace element composition, but after crystallization of the cores of perovskite crystals each melt portion evolved independently. The samples from the Bushkanay dyke show an increase in </span></span><em>f</em>O₂ and the residual magma enrichment in REE, Na, and Sr as evidenced by their elevated contents at the rims of perovskite grains. In the Bolshaya Tagna aillikites after crystallization of perovskite cores, the melt was depleted in REE, Na, and Nb.</div><div>Based on U-Pb dating of perovskites, the age of aillikites from the Bolshaya Tagna intrusion is 583–654 Ma. Perovskite from aillikites of the Bushkanay dyke is relatively young, with an age of 575 ± 39 Ma. The obtained ages are consistent with the age of formation of Neoproterozoic alkaline-ultramafic carbonatite complexes of the Siberian craton and other occurrences of aillikites in a response to extension of the Rodinia lithosphere.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"84 4","pages":"Article 126159"},"PeriodicalIF":2.6,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141530518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrogenetic implications, geochemistry and tectonic framework of albitite hosted magnetite in North Delhi Fold Belt: Application of geochemistry and apatite chemistry","authors":"Sigma Dwivedy","doi":"10.1016/j.chemer.2024.126176","DOIUrl":"10.1016/j.chemer.2024.126176","url":null,"abstract":"<div><div>The iron ore bodies in the form of lensoidal and pocket type deposits occur within the Meso to Neo-Proterozoic meta-sedimentary rocks and albitites of Ajabgarh Group of Delhi Supergroup in Khetri basin, Western India. These are exposed as detached and linear ore bodies at the southern (western flank) and south-eastern (eastern flank) part of the Khetri copper deposit which follows the regional trend of the host rocks. The detailed field and petrographic studies reveal that the magnetite and hematite are associated with major silicates like quartz, actinolite, muscovite, biotite, albite and, K-feldspar. Some minor occurrences of apatite, sphene, ilmenite and monazite are also found. This work is focused on understanding the evolution of albitite-hosted magnetite with respect to tectonic signatures, the source of mineralizing fluid, and its spatial relationship with the regional albitites and meta-sediments. To interpret the above, whole rock geochemistry of albitite rocks, magnetite ore and mineral chemistry of fluorapatite, were adopted.</div><div>The whole rock geochemistry of albitite suggests that the parent rocks are of calc-alkaline magma series that are originated from the subduction-related rift zone of volcanic arc environment. The apatite chemistry signifies that these are evolved from the highly fractionated granitic rocks (granitoid) at moderate to high oxidizing conditions. Some deformed apatite grains are also encountered having small distorted monazite inclusions. Thus, it has an indication of high-temperature metasomatic/hydrothermal fluids that may be responsible for the removal of REEs from apatite and re-nucleate as monazite inclusions within it. Therefore, the overall evidence and associations of albitite with apatite-magnetite is demonstrating that the source rock of the study area could have evolved from the arc system of active continental margin which was abundant with Fe, U, REEs, etc. Hence, the sources rocks were suitably metasomatized by hydrothermal fluids channelized through the regional shear zone and simultaneous precipitation of the magnetite in the study area. The dominance of magnetite, associated REEs, apatite, and non-association of sulfide minerals with the magnetite in the area of study has close similarities with the IOA type deposits.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"84 4","pages":"Article 126176"},"PeriodicalIF":2.6,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142255627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Manifold learning-based UMAP method for geochemical anomaly identification","authors":"Qingteng Zhang,&nbsp;Yue Liu,&nbsp;Hao Fang","doi":"10.1016/j.chemer.2024.126157","DOIUrl":"10.1016/j.chemer.2024.126157","url":null,"abstract":"<div><div>Geochemical data are usually high-dimensional data that could contain dozens of elements. Geochemical distribution patterns and anomalies related to mineralization and lithological features are always hidden in these high-dimensional data, which cannot be directly observed from the data. To solve this problem, a manifold learning-based uniform manifold approximation and projection (UMAP) method, was introduced to recognize mineralization-related geochemical anomalies from high-dimensional geochemical data in this study. The UMAP method is a nonlinear dimensionality reduction method, which is suitable for dimensionality reduction and visualization of high-dimensional data. A case study was conducted to demonstrate the advantages of the UMAP method for identifying ion-adsorbed rare-earth-element (REE) mineralization-related anomalies from high-dimensional data in the Nanling region, China. Factor analysis was used to determine ion-adsorbed REE mineralization-related element combination that consists of 10 elements. High-dimensional geochemical data were reduced to two dimensions based on the UMAP method. The results indicated that the UMAP method can effectively characterize the spatial distributions of ion-adsorbed REE mineralization-related anomalies by dimensionality reduction analysis and visualization analysis of high-dimensional geochemical data in the study area. To illustrate the superiority of the UMAP method, a comparative study was conducted between the UMAP and other three manifold learning methods, namely locally linear embedding (LLE), isometric feature mapping (Isomap) and t-distributed stochastic neighbor embedding (t-SNE). The performance of the four manifold learning methods was evaluated by receiver operating characteristic (ROC) curve and prediction-area (P-A) plot, showing that the performance of the UMAP method is superior to that of the LLE, Isomap and t-SNE methods in terms of recognizing ion-adsorbed REE mineralization-related anomalies and the spatial distributions of the REE-bearing geological bodies in the Nanling belt.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"84 4","pages":"Article 126157"},"PeriodicalIF":2.6,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141399663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}