Ore Geology Reviews最新文献

{"title":"New insights on the petrogenesis of the Koktokay No.3 pegmatitic dyke: Petrological and zirconological evidence from the Aral granitic complex (Xinjiang, China)","authors":"","doi":"10.1016/j.oregeorev.2024.106309","DOIUrl":"10.1016/j.oregeorev.2024.106309","url":null,"abstract":"<div><div>The Koktokay No.3 pegmatite dyke (KPD), containing numerous Li–Be–Nb–Ta–Cs mineral resources, is among the world’s most famous rare-metal deposits, and attracted much attention. Up to now, over thirty geochronological data have been reported ranging from 332 Ma to 120 Ma for the KPD, which causes uncertainty about the origin and petrogenesis of the pegmatite. In this contribution, whole-rock geochemistry and zircon geochronology have been conducted on the Aral biotite monzogranite (BMG), the Koktokay muscovite alkali-feldspar granite (MAG), and the KPD. Petrological and whole-rock geochemistry results reveal that the BMG is normal granite with medium SiO<sub>2</sub> (mean of 67.23 %), enriched in compatible trace elements such as Ba, Sr and Zr, and slight negative Eu anomalies, while the MAG belongs to highly-fractionated granite with high SiO<sub>2</sub> (mean of 73.92 %) and extensive negative Eu anomalies, and enriched in incompatible trace elements such as Rb, Ta, and U. Zircon morphology and LA–ICPMS analysis reveal that magmatic zircons from the BMG, hydrothermal zircons from the MAG and KPD yield lower intercept ages at 217.3 ± 2.4 Ma, 197.8 ± 4.7 Ma, and 195.4 ± 2.0 Ma, respectively. Combining with tectonic information and geochronological data of granitic activity and its mineralization in the Altay, this study explains the petrogenetic mechanism of the KPD after <span><span>Wang et al. (2021)</span></span>‘s metallogenic model: (1) In late stage of Middle Triassic, the collision between the Siberian plate and the Kazakhstan–Junggar plate caused a large number of thrust nappe faults and crust thickening in the Altay orogenic belt; At ∼217 Ma, the compression reached its peak, the crustal anatexis produced <em>syn</em>-collisional BMG (i.e., the Aral BMG); After the compressive peak, huge amount of granitic magma in deep-seated magma chamber underwent over 20 Myr of fractional crystallization, and the residual magma enriched in ore-forming materials (rare metal elements, volatile components, and aqueous fluids) occurred at the top of the magma chamber; (2) When the regional stress converted from compression to extension, the highly-fractionated residual magma ascended rapidly from the long-lived magma chamber along extensional faults at ∼195 Ma; The huge amount of melt-bearing fluids were exsolved from the residual magma in the course of its emplacement due to sharply decreasing pressure, and intruded into a large cavity generated by extensional fault; Along with slowly decreasing temperature, the melt-enriched fluids crystallized outside-in as (quasi-) concentric pegmatitic zones (i.e., KPD); (3) The residual magma which lost huge amount of fluid filled the lower space of the extensional system, and crystallized as post-collisional MAG (i.e., the Koktokay MAG). Based on the genetic relationship among tectonics, petrogenesis, and metallogeny, the proposed model shows material and energetic conversion processes from <em>syn</em>-","PeriodicalId":19644,"journal":{"name":"Ore Geology Reviews","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553562","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Anomalous tellurium enrichment associated with gold mineralization: A mineralogical and isotopic study of the Yongxin Te-Au deposit, northeast China","authors":"","doi":"10.1016/j.oregeorev.2024.106296","DOIUrl":"10.1016/j.oregeorev.2024.106296","url":null,"abstract":"<div><div>The Yongxin tellurium-gold (Te-Au) deposit, a large epithermal deposit in the Duobaoshan polymetallic metallogenic belt (DPMB) within eastern section of the Central Asian Orogenic Belt (CAOB), is mainly hosted by syenogranite and mylonite. However, the Te-Au occurrence, precipitation mechanism and genesis in this deposit remain elusive. In this study, pyrite, the primary host of Te-Au mineralization, was studied utilizing multiparametric techniques such as scanning electron microscope (SEM), electron probe microanalysis (EPMA), in-situ laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) and femtosecond laser ablation coupled multi-collector inductively coupled plasma mass spectrometry (fs LA-MC-ICP-MS). The results show that there are three generations of pyrite termed here as Py1, Py2 and Py3. The coarse euhedral Py1 and fine vein Py2 contain negligible to low contents of Te and Au, whereas the anhedral aggregated Py3 with porosity and grain boundary (GB) shows the highest concentrations of Te and Au. Representative LA-ICP-MS profiles show that Te-Au occurs either as solid solution in the Py1 and Py2 or submicroscopic Au-Ag-Te-Bi inclusions, electrum and native gold in Py3. Thermodynamic data of telluride and sulfide show that the Te-Au was deposited under relatively oxidizing conditions with values of log <em>f</em> Te₂ ranging from −15.2 to −11.2 and log <em>f</em> S₂ from −16.7 to −12.1. at 200 °C. We infer that fluid mixing and fluid-rock interaction were the dominant mechanisms that triggered the precipitation of Te-Au in the Yongxin Te-Au deposit. Geochemical and geochronological data indicate that the likely source of Te is Te-rich oceanic sediments originating from the Western Pacific Plate. Pyrite and telluride from the gold deposits can be potential targets for Te exploration in the DPMB.</div></div>","PeriodicalId":19644,"journal":{"name":"Ore Geology Reviews","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142561416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Addressing imbalanced data for machine learning based mineral prospectivity mapping","authors":"","doi":"10.1016/j.oregeorev.2024.106270","DOIUrl":"10.1016/j.oregeorev.2024.106270","url":null,"abstract":"<div><div>Effective Mineral Prospectivity Mapping (MPM) relies on the ability of Machine Learning (ML) models to extract meaningful patterns from geophysical data. However, in mineral exploration, identifying the presence of mineral deposits is often a rare event compared with the overall geological landscape. This rarity leads to a highly imbalanced dataset, where positive instances (mineralized samples) are considerably less frequent than negative instances (non-mineralized samples). Imbalanced data can potentially bias ML models towards the majority class, leading to inaccurate predictions for the minority class (mineralized samples) which are of primary interest. To address this challenge, we proposed two-level methods in this study. At the data level, we employed imbalanced data handling techniques that operate on the training dataset and change the class distribution. At the algorithmic level, we adjusted the decision threshold of a model to balance the trade-off between false positives and false negatives. Experimental results are collected on a geophysical data from Lapland, Finland. The dataset exhibits a significant class imbalance, comprising 17 positive samples contrasted with <span><math><mrow><mn>1</mn><mo>.</mo><mn>84</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>6</mn></mrow></msup></mrow></math></span> negative samples. We investigate the effect of handling imbalanced data on the performance of four ML models including Multi-Layer Perceptron (MLP), Random Forest (RF), Decision Tree (DT), and Logistic Regression (LR). From the results, we found that the MLP model achieved the best overall performance, with total accuracy of 97.13% on balanced data using synthetic minority oversampling method. Random forest and DT also performed well, with accuracies of 88.34% and 89.35%, respectively. The implemented methodology of this work is integrated in QGIS as a new toolkit which is called EIS Toolkit <span><span>¹</span></span>for MPM.</div></div>","PeriodicalId":19644,"journal":{"name":"Ore Geology Reviews","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Episodic fluid pulses in the Baiyun gold deposit, Liaodong Peninsula, Eastern China: Insights from in-situ trace elements, sulfur isotopes, and texture characteristics of pyrite","authors":"","doi":"10.1016/j.oregeorev.2024.106313","DOIUrl":"10.1016/j.oregeorev.2024.106313","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The driving mechanism behind the mineralization process remains ambiguous, whether it is propelled by a single fluid evolution or multiple fluid pulses. Minerals have the capacity to precisely document the fluid evolution. Hence, an accurate understanding of mineral formation is essential for a precise interpretation of fluid evolution. The Baiyun gold deposit is located in the Qingchengzi ore field in the Liaodong Peninsula of the North China Craton. The textural characteristics and geochemical composition of pyrite provide evidence for the formation process of the Baiyun gold deposit. Based on mineral assemblages, ore textures, and cross-cutting relationships, the Baiyun gold deposit can be divided into four stages: (I) disseminated/stockworked quartz-pyrite-K-feldspar, (II) quartz-pyrite-chalcopyrite-native gold vein, (III) quartz-pyrite-native gold ± galena ± sphalerite vein, and (IV) ore-barren calcite-quartz veinlets.&lt;/div&gt;&lt;div&gt;Native gold predominantly accumulates in stages II-III, each subdivided into two generations (Py2a, Py2b, Py3a, Py3b), with significant gold precipitation in the later Py2b and Py3b. Notably, Py2a displays high concentrations of As (avg. 412.66 ppm), Au (avg. 2.12 ppm), Ag (avg. 34.65 ppm), Co (avg. 471.88 ppm) and Te (avg. 39.79 ppm), contrasting with lower concentrations in Py2b for As (avg. 100.11 ppm), Au (avg. 0.99 ppm), Ag (avg. 8.33 ppm), Co (avg. 281.28 ppm) and Te (avg. 11.11 ppm). Stage III compares to stage II, with elements like Co (Py3a: avg. 2240.00 ppm; Py3b: avg. 170.15 ppm), Au (Py3a: avg. 0.74 ppm; Py3b: avg. 0.65 ppm), Ag (Py3a: avg. 5.33 ppm; Py3b: avg. 2.50 ppm), and As (Py3a: avg. 1132.91 ppm; Py3b: avg. 245.90 ppm) exhibiting similar trends of change. The δ&lt;sup&gt;34&lt;/sup&gt;S value trend (Py2a → Py2b: avg. 15.7 ‰ → avg. −8.0 ‰; Py3a → Py3b: avg. 11.5 ‰ → avg. −3.4 ‰) aligns with the trace element variations. Thermodynamic simulations, based on mineral compositions and sulfur isotopes, reveal difference fluid natures between Py2a (T = 300 °C; pH = 5.1–6.5; moderate &lt;em&gt;f&lt;/em&gt;O&lt;sub&gt;2&lt;/sub&gt; = −33.1 to −31.1) and Py3a (T = 250 °C; pH = 5.6–6.6; lower &lt;em&gt;f&lt;/em&gt;O&lt;sub&gt;2&lt;/sub&gt; = −39.2 to −36.1). Noteworthy differences exist not only in trace elements and sulfur isotopes between stages II-III but also in the micro-deformation of pyrite. Stage II is marked by plastic deformation (dominated by low-angle boundaries; 2–5°), resulting in a non-significant contribution to gold precipitation. In contrast, stage III exhibits brittle deformation (dominated by high-angle boundaries; &gt;5°), where gold primarily precipitates and enriches. The significant variations in trace elements, sulfur isotopes, fluid natures, and pyrite deformation indicate the occurrence of episodic fluid pulses. Furthermore, sulfur isotopes display both enrichment and depletion characteristics. This phenomenon may be related to sulfate reduction. The Paleoproterozoic strata serve as significant sulfur reservoirs within the region an","PeriodicalId":19644,"journal":{"name":"Ore Geology Reviews","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Unraveling the metallogenic mechanisms of uranium-rich ore bodies: Insights from Xinqiaoxi’s pitchblende geochronology and pyrite geochemistry","authors":"","doi":"10.1016/j.oregeorev.2024.106305","DOIUrl":"10.1016/j.oregeorev.2024.106305","url":null,"abstract":"<div><div>Granite-related uranium deposits are essential for the global uranium supply, with the uranium-rich ore bodies within these deposits being crucial to their value. However, the sources of uranium, fluid characteristics, and metallogenic mechanisms within these uranium-rich ore bodies remain unclear. In this study, we analyzed pitchblende and pyrite from the Xinqiaoxi uranium deposit to determine uranium age and clarify the mineralization of uranium-rich ore bodies. The pitchblende samples provided a U-Pb age of 58.5 ± 3 Ma (MSWD = 3.4), closely aligns with the mineralization ages in other uranium deposits within the Xiazhuang uranium ore-field. This consistency suggests a significant uranium mineralization event in South China during this period. The vein-like and concentric structure of the pitchblende, coupled with its enrichment in U, Sr, As, W, and Mo but depletion in Th, Pb, and REEs, indicates a strong association with hydrothermal activity. Moreover, its REE pattern closely resembles that of the host rock (Xiazhuang and Maofeng granites), suggesting the latter as a crucial uranium source. Pyrite and pitchblende are coeval, yet pyrite was formed slightly earlier than pitchblende. Pyrite exhibits depletion in Co and Ni but enrichment in As, along with high Co/Ni ratios ranging from 1.68 to 12.2, indicative of a medium- to low temperature hydrothermal genesis. Furthermore, the positive cerium (Ce) anomaly observed in pyrite may indicate elevated oxygen fugacity in the fluids during precipitation. The δ³⁴S values of pyrite (−10.42 ‰ to −15.26 ‰, averaging −13.44 ‰) are consistent with those of the host rock (Xiazhuang and Maofeng granites), indicating a primary sulfur source from the host rock. Additionally, pyrite may serve as a reductant, facilitating the formation of uranium ore. Our proposed genetic model suggests that CO₂-rich oxidizing fluids facilitate uranium leaching from host rocks, resulting in the formation of a uranium-enriched fluid that migrates along faults, where U⁶⁺ undergoes reduction to U⁴⁺ within secondary fracture zones, facilitated by reductants such as pyrite.</div></div>","PeriodicalId":19644,"journal":{"name":"Ore Geology Reviews","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Geology and mineralization of the Yangla polymetallic orefield in northwestern Yunnan, SW China: Age, petrogenesis and rare-metal metallogenic implications of aplite dykes","authors":"","doi":"10.1016/j.oregeorev.2024.106315","DOIUrl":"10.1016/j.oregeorev.2024.106315","url":null,"abstract":"<div><div>Aplite dykes commonly represent more evolved magma and are closely associated with rare metal mineralization. However, the multiphase magmatism and rare metal mineralization of aplite dykes in the Yangla orefield have not been well-constrained. Here, we present new data on the Linong aplite dykes and the associated Jiangbian granodiorite in the Yangla orefield, including data of zircon U-Pb age and Hf isotopes, and lithogeochemistry and Pb-Sr-Nd isotopes, in order to elucidate their emplacement age, petrogenesis, and rare metal mineralization potential. The three aplite dykes studied were emplaced at 214.3 ± 5.1 Ma, 209.2 ± 5.2 Ma, and 205.5 ± 3.4 Ma. These Late Triassic aplite dykes have high SiO₂ (75.81–76.94 wt%) and K₂O (avg. 5.60 wt%) and are peralkaline–metaluminous (A/CNK = 0.86–0.93). They have high whole-rock (⁸⁷Sr/⁸⁶Sr)_i (0.6947–0.7094), ε_Nd(t) (−6.26 to − 5.77), (²⁰⁶Pb/²⁰⁴Pb)_t = 18.365–18.804, (²⁰⁷Pb/²⁰⁴Pb)_t = 15.688–15.715, (²⁰⁸Pb/²⁰⁴Pb)_t = 38.436–38.681, and zircon ε_Hf(t) =  − 8.10 to + 1.62. The Triassic (208–228 Ma) Jiangbian granodiorite is high-K calc-alkaline, metaluminous/weakly peraluminous (A/CNK = 0.52–1.19) with high Al₂O₃ (12.49–16.74 wt%). They have high (⁸⁷Sr/⁸⁶Sr)_i (0.7075–0.7102), whole-rock ε_Nd(t) (−6.12 to − 5.88), (²⁰⁶Pb/²⁰⁴Pb)_t = 18.155–18.384, (²⁰⁷Pb/²⁰⁴Pb)_t = 15.665–15.698, (²⁰⁸Pb/²⁰⁴Pb)_t = 38.579–38.719, and zircon ε_Hf(t) =  − 4.20 to + 2.40. These geochemical features imply that both the aplite dykes and granodiorite have their primary magma derived from partial melting of the Proterozoic basement, with minor mantle input. The aplite samples have an average estimated crystallization temperature of 712 ℃, and relatively low magmatic oxygen fugacity ([log(fo₂)] = − 21.98 to – 5.48, avg. = –17.05), which are slightly higher than that of most Triassic granitoids in the Yangla orefield. The result shows that the crystallization temperature and oxygen fugacity gradually increase, while the ¹⁷⁶Hf/¹⁷⁷Hf and ε_Hf(t) gradually decrease. Our new and published geochemical data from the Yangla granitoids reveal that the aplite dykes and granodiorite were formed in a post-collisional setting. Whole-rock Nb/Ta, Zr/Hf, Rb/Sr, Ba/Rb, and zircon REE features of the aplite dykes highly mimic those of typical Sn-W related granites, suggesting certain Sn-W rare metals mineralization potential in the Yangla orefield.</div></div>","PeriodicalId":19644,"journal":{"name":"Ore Geology Reviews","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142586388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"In situ U–Pb dating of dolomite: Reliable ages for sandstone-hosted uranium deposits in the southern Songliao Basin, NE China","authors":"","doi":"10.1016/j.oregeorev.2024.106331","DOIUrl":"10.1016/j.oregeorev.2024.106331","url":null,"abstract":"<div><div>Previously, the ages of U mineralization in sandstone-hosted uranium deposits have not been adequately constrained due to the absence of suitable minerals for precise radiometric dating. To ascertain the mineralogenetic epoch and origin of the ore-forming fluids in the sandstone-hosted uranium deposits within the southern Songliao Basin of northeastern China, we conducted U–Pb dating, major and trace element analyses, and Sr isotope analyses on carbonate minerals taken from the sandstone. In this study, we present a novel U–Pb age of 92.5 ± 6.9 Ma (MSWD = 0.56) for calcite nodules, which is interpreted as the depositional age of the target formation hosting the ore. The age of the main mineralization stage is constrained by two types of high uranium carbonate minerals: the dolomite coexists with siderite and recrystallized framboidal pyrite, whereascoarse-grained ankerite occurs with dawsonite enveloping dolomite. The dolomite vein yields an age of ∼60 Ma (62.8 ± 0.5 Ma, MSWD = 2.7; 60.0 ± 0.4 Ma, MSWD = 6.4), the coarse-grained ankerite may be contemporaneous with the widely distributed diabase with an age of ∼40 Ma, which is interpreted two U mineralization ages. The ∼92 Ma calcite nodules are characterized by low U and U/Th ratios and relatively flat REE distribution patterns, and the high ⁸⁷Sr/⁸⁶Sr ratios (0.7109–0.7327) and the dispersed trace element composition can be attributed to fluid–rock interactions. In contrast, dolomite veins with an age of approximately 60 Ma exhibit elevated MnO and Y/Ho ratios, as well as patterns enriched in heavy rare earth elements (HREEs); the ⁸⁷Sr/⁸⁶Sr ratios range from 0.7066 to 0.7092, indicating their association with hydrocarbon seep-related carbonates of microbial origin. The coarse-grained ankerite, which has high REE + Y values and hump-shaped, MREE-enriched patterns with low Y/Ho ratios and negligible to positive Eu anomalies, combined with the spatial relationship between the ankerite-bearing sandstone sample and diabase, indicates that the ankerite is the product of hydrothermal processes. This ∼60 Ma dolomite presents initial evidence indicating that the Hulihai deposit is contemporaneous with a significant regional tectonic inversion event and preceded or coincided with hydrocarbon fluid activity in the southern Songliao Basin. Based on the spatial and temporal correlations, it is plausible that both the Palaeocene (∼60 Ma) tectonic reversal event and the Eocene hydrothermal event (∼40 Ma) were causally linked to sandstone-hosted uranium deposits in the southern Songliao Basin. The present study demonstrates the robustness of in situ carbonate mineral U–Pb dating as a valuable tool for geochronological investigations pertaining to sandstone-hosted uranium deposits.</div></div>","PeriodicalId":19644,"journal":{"name":"Ore Geology Reviews","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142586461","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Hydrothermal niobium (Nb) mineralization and mobilization in the world-class Madeira Sn-Nb-Ta granitic deposit (Amazonas, Brazil)","authors":"","doi":"10.1016/j.oregeorev.2024.106321","DOIUrl":"10.1016/j.oregeorev.2024.106321","url":null,"abstract":"<div><div>The Madeira deposit is a world-class tin (Sn) deposit characterized by a unique mineralogical assemblage composed of a massive cryolite (NaAlF₃) deposit associated with economically important metals like Nb (0.20 wt% Nb₂O₅). Although hydrothermal alteration has long been recognized in the cryolite formation, its effects on the mineralization and mobility of Nb remain obscure. This study presents new data on the Nb mineralization of the Pitinga core and border albite-enriched granites provided by nanoscale and site-selective approaches, using transmission electron microscopy and synchrotron-radiation analyses. Pyrochlore is the main Nb ore mineral with three distinct compositional types (U-Pb, Pb-U and Y-bearing varieties). Hydrothermal processes lead to the extensive alteration of pyrochlore into columbite (later designated as columbitization) by a coupled dissolution-reprecipitation mechanism, which evidences the alterability of pyrochlore in a hydrothermal context. Nanoscale analyses of veins and reaction interfaces reveal the presence of additional Nb hosts including fergusonite-(Y), Nb-bearing uraninite and Nb-bearing coffinite which formed from the alteration of pyrochlore. The nature of the altered phases mainly depends on the composition of the parent pyrochlore. Their formation, occurring in absence of direct proximity with remaining pyrochlore, shows that Nb mobilization at macroscopic scale is possible in F-rich reducing fluids. Niobium L₃-edge XANES spectroscopy on bulk samples representative of the different facies show that hydrothermal processes change the Nb mineralization by converting primary U-Pb-bearing pyrochlore into columbite and Pb-U/Y-bearing pyrochlores. The columbitization process of pyrochlore led to the increase of the Nb ore grade. Nonetheless, hydrothermal alteration modified Nb mineral liberation, thereby limiting the recovery of the full range of Nb host phases.</div></div>","PeriodicalId":19644,"journal":{"name":"Ore Geology Reviews","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142586144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Crystallographic insights and crystal fractionation simulations of alkali- and water-bearing beryl: Implications for magmatic–hydrothermal evolution and Be enrichment mechanisms","authors":"","doi":"10.1016/j.oregeorev.2024.106278","DOIUrl":"10.1016/j.oregeorev.2024.106278","url":null,"abstract":"<div><div>Beryl, an economically significant mineral containing high concentrations of the critical metal Be, has been the subject of considerable characterization regarding its crystal structure and chemical composition. Despite this, discerning between alkali- and H₂O-bearing beryls solely based on the alkali and water contents within the structural channels of beryl has remained a challenge. Additionally, the mechanisms that cause granitic melts to become enriched in Be remain ambiguous. Through comprehensive chemical and structural analyses of representative alkali-water-bearing beryl samples from Igla of East Egypt and Baishawo of South China, this contribution improves the beryl classification model and provides new perspectives on Be enrichment mechanisms. This analysis has demonstrated that a linear correlation exists between the water content and alkali content of hydrous beryls, and identified two distinct types of H₂O molecules — Type I and II. Major elements are uniformly distributed throughout beryl grains, whereas trace elements exhibit core–rim zonation. Crystal–chemical characteristics of alkali- and water-bearing beryls provide valuable insights into pegmatite evolution, with implications for understanding mineralizing processes and formation conditions. The distributions of alkali metals, Mg, Mn and Fe in alkali-rich and H₂O-rich (ARHR) beryl suggest that the pegmatite in the beryl-bearing zones is the product of magmatic metls. Low Fe/Mg ratios of alkali-poor and H₂O-rich (APHR) beryl are associated with hydrothermal alkali-metasomatism. Using the Baishawo Be–Li–Nb–Ta pegmatite deposit as a case study, we utilize crystal fractionation simulations to demonstrate the alkali- and water-bearing beryls crystallized after high degrees of magma evolution. The study contributes to the classification of beryl varieties based on chemistry and structure, and provides new insights into Be enrichment mechanism in granitic melts and hydrothermal fluids.</div></div>","PeriodicalId":19644,"journal":{"name":"Ore Geology Reviews","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Textures and chemistry of columbite-group minerals record magmatic–hydrothermal processes in the Baishitouquan pluton in the Eastern Tianshan, NW China","authors":"","doi":"10.1016/j.oregeorev.2024.106319","DOIUrl":"10.1016/j.oregeorev.2024.106319","url":null,"abstract":"<div><div>Rare-metal granites result from a combination of magmatic and hydrothermal processes. The mineralogical, textural, and chemical characteristics of columbite-group minerals (CGMs), which are ubiquitous in rare-metal granites and pegmatites, can serve as records of the magmatic–hydrothermal processes responsible for the evolution of these granitic systems. The highly evolved Baishitouquan (BST) granite pluton, located in the Eastern Tianshan of NW China, hosts the large-scale Zhangbaoshan (ZBS) Rb deposit (Rb₂O reserve of 67080 t), making it of economic significance. The BST pluton comprises a series of gradual lithological zones, which, from bottom to top, are leucogranite (Zone-a), amazonite-bearing granite (Zone-b), amazonite granite (Zone-c), topaz-bearing amazonite granite (Zone-d), topaz albite granite (Zone-e), and amazonite pegmatite veins. Based on textural and chemical characteristics, five types of CGMs were identified — CGMs with no zoning, and oscillatory zoned, normally zoned, hydrothermally overprinted, and patchy CGMs. The CGMs that exhibit no zoning, oscillatory zoning, and normal zoning mainly occur in Zones-a to -c, suggesting that the lithological and geochemical variations in these zones formed as a result of the magmatic evolution of the BST magma. Hydrothermally overprinted CGMs and those with a patchy texture mainly occur in Zones-d and -e, and the pegmatite veins, suggesting that the evolution of these zones involved hydrothermal processes. From Zone-a to Zone-c, the Ta# and Mn# of CGMs increase gradually, suggesting a gradual evolution of the BST magma. The CGMs are characterized by REE tetrad effect (TE_1,3) that is consistently greater than 1.1 and increases from Zone-a to the pegmatite veins, indicative of increased melt–fluid interaction during evolution of the BST magma. It is, therefore, suggested that the BST magma evolved not only via high degrees of fractional crystallization, but also by the interaction of the melt with hydrothermal fluids, the latter of which likely originated by exsolution from the evolving melt. Based on the mineralogical, textural, and chemical characteristics of CGMs in the BST pluton, a petrogenetic model is proposed to explain the magmatic–hydrothermal evolution of the BST granitic magma.</div></div>","PeriodicalId":19644,"journal":{"name":"Ore Geology Reviews","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142586145","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}