Mineralium Deposita最新文献

{"title":"Uranium-rich pyrochlore, thorite and associated minerals in the Muluozhai rare-earth deposit (Sichuan, SW China): implications for the geochemistry of high-field-strength elements in carbonatites and mineral exploration","authors":"Anton R. Chakhmouradian, Yan Liu, Ekaterina P. Reguir","doi":"10.1007/s00126-025-01357-9","DOIUrl":"https://doi.org/10.1007/s00126-025-01357-9","url":null,"abstract":"<p>The Muluozhai rare-earth deposit in the Mianning-Dechan metallotect (China) is hosted by carbonatites genetically linked to subduction and plate collision in the eastern Tibet. The Muluozhai carbonatites comprise variable proportions of bastnäsite-(Ce), fluorite, barite and calcite, along with abundant xenoliths of nordmarkite and metabasalt wall-rocks. Muluozhai is unusual among similar deposits in plate-collision zones owing to its locally high levels of Nb, Th and U arising from the presence of U-rich pyrochlore (+ minor betafite, 19.4–29.4 wt% UO₂) and thorite (5.5–15.4 wt% UO₂) associated with zircon (up to 3.0 wt% ThO₂ and 2.0 wt% UO₂), rutile (up to 16.3 wt% Nb₂O₅ and 1.7 wt% V₂O₃) and molybdenite. The chemical variation of pyrochlore at Muluozhai records contemporaneous crystallization of zircon, thorite, fluorite and other F-rich minerals, followed by rutile, and culminates with anion-deficient Sr-rich compositions indicative of hydrothermal alteration. Pyrochlore-group phases are rare in carbonatites from plate-collision zones, and the few known examples can be distinguished from those in anorogenic occurrences, including previously and currently active Nb mines, using a combination of discrimination criteria (e.g., their U, Ti and Ta contents, Th/U, Ta/Ti and Ti/Nb ratios). Using a global database of carbonatite compositions, we suggest that these differences reflect, to some extent, the unusual geochemistry of plate-collision carbonatites and their mantle sources with respect to high-field-strength elements. However, some geochemical characteristics of these rocks (e.g., variations in Th/U and Nb/Ta ratios) may stem from “nugget effects” caused by early pyrochlore or thorite fractionation. Implications of these data for niobium exploration are discussed.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"97 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143695314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A significant gem corundum deposit in rhyolitic ignimbrite: the enigmatic Rock Creek sapphire deposit, Montana, USA","authors":"Philippe M. Belley, Jake Broders","doi":"10.1007/s00126-025-01358-8","DOIUrl":"https://doi.org/10.1007/s00126-025-01358-8","url":null,"abstract":"<p>Detrital sapphire (gem corundum) in the Rock Creek deposit (Montana, USA) is identified as having originated from Eocene peraluminous rhyolitic ignimbrite, which occurs as clasts in sapphire-producing colluvium. Fine-grained corundum and other heavy minerals (allanite, various garnets, rare chromite, and others) occur in this rhyolite tuff in similar concentrations to the sapphire ore gravels, indicating derivation of the ore gravels by weathering of the tuff. Fine ash and biotite in tuff clasts show signs of subaerial alteration. The corundum-bearing tuff is predominantly composed of vitric ash particles with subordinate lithic fragments (Belt Supergroup quartzite), crystals (plagioclase, biotite, quartz), carbonised wood, and trace concentrations of various heavy minerals. A gem quality sapphire crystal (recovered by mining) hosts a secondary assemblage of plagioclase, Ti–rich/Al-poor biotite (identical to biotite phenocrysts in tuff), and vesicular rhyolitic glass filling a thin fracture through the grain, which indicates that sapphire was present in the rhyolitic magma before extrusion. The peraluminous composition of Rock Creek rhyolite, together with the presence of corundum, garnet of variable composition (some comparable to garnet in amphibolite xenoliths), and chromite suggest the assimilation of varied crustal rocks. The high alumina saturation index and rapid quenching of the rhyolite magma may promote corundum survival. Sapphire distribution at Rock Creek is expected to be controlled by Eocene paleotopography, the structure of the eruptive volcanic center(s), and the Quaternary weathering, erosion, and deposition of unconsolidated sapphire-bearing gravels.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"56 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143672808","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Linking two types of breccias to sediment-hosted stratiform copper (SSC) and iron oxide-copper-gold (IOCG) deposits in the Kangdian metallogenic belt, SW China","authors":"Xue-Qing Yin, Xin-Fu Zhao, Zhi-Kun Su, Hai-Tao Lin, Zhi-Min Zhu, Wen-Lei Song, Martin Yan Hei Li, Kui-Dong Zhao","doi":"10.1007/s00126-025-01354-y","DOIUrl":"https://doi.org/10.1007/s00126-025-01354-y","url":null,"abstract":"<p>Voluminous breccias, collectively known as the Yinmin Breccia, are widely distributed in the Kangdian metallogenic belt, Southwest China. Both sediment-hosted stratiform copper (SSC) and iron oxide-copper-gold (IOCG) deposits occur in the belt and exhibit close spatial association with these breccias. However, the origin of the Yinmin Breccia and its relationship to the two types of ore deposits remain enigmatic. Here, we integrate petrological studies with new age constraints and stable isotopic systematics to address these issues. Detailed field mapping and petrological observations allow for the classification of the conventional Yinmin Breccia into two types, namely the monomict and polymict breccias. The monomict breccia contains clasts predominantly of fragments of the Yinmin Formation and cements of quartz, carbonates, and locally sulfides, a mineral assemblage similar to the components of SSC mineralization. In contrast, the polymict breccia contains clasts of the monomict breccia, rocks of the host sequences, and dolerite intrusions, all of which are altered and cemented by IOCG-related hydrothermal mineral assemblages. Moreover, the IOCG-type alteration is observed to locally overprint and postdate the SSC mineralization and monomict breccias. A dolerite intrusion crosscutting the SSC orebody and monomict breccia yields a zircon U-Pb age of 1698 ± 29 Ma, providing a lower limit on the timing of the monomict brecciation and SSC mineralization. B-C-O-S isotopic data suggest that the monomict breccia resulted from dissolution and collapse of evaporites, whereas the polymict breccia formed due to over-pressurizing of magmatic-hydrothermal fluid during the IOCG mineralization process. We hence propose that the SSC and IOCG deposits in the Kangdian region are products of two discrete mineralization events which coincidentally occurred in the same location. This work highlights the critical linkage between hydrothermal breccias and regional mineralization.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"87 3 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143599123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The gradual shift from forearc basalt-like to boninite-like magmatism during intra-oceanic subduction-initiation recorded by ophiolitic chromite deposits from Cuba","authors":"D. Domínguez-Carretero, J. A. Proenza, N. Pujol-Solà, F. Gervilla, C. Villanova-de-Benavent, V. Colás, K. Núñez-Cambra, E. Piñero-Pérez, A. Garcia-Casco","doi":"10.1007/s00126-025-01355-x","DOIUrl":"https://doi.org/10.1007/s00126-025-01355-x","url":null,"abstract":"<p>Cuba contains the largest number of ophiolitic chromite deposits throughout the Americas. Most of these deposits are found within the mantle section of the Eastern Cuba and Camagüey ophiolitic massifs, which contain four different chromite mining districts (Camagüey, Mayarí, Sagua de Tánamo, and Moa-Baracoa). In addition to their potential as economic resources, chromite deposits are also excellent petrogenetic indicators to interpret the nature of ancient upper mantle, processes of melt formation in the mantle, and large-scale geodynamic processes. In this sense, major and trace elements of unaltered Cr-spinel cores together with chromitite whole-rock PGE composition reveal that high-Al Camagüey and Moa-Baracoa chromite districts were formed in equilibrium with forearc basalts (FAB)-like magmas during the incipient intra-oceanic subduction of the proto-Caribbean lithosphere underneath the Caribbean lithosphere, in a subduction-initiation process. Conversely, the high-Cr Mayarí chromite district was formed in equilibrium with more hydrated melts of boninitic affinity, typical of a more advanced stage of the subduction-initiation process. Nonetheless, the shift from FAB-like to boninite-like magmatism in an intra-oceanic subduction is gradual. This progressive change is well-recorded in the Sagua de Tánamo district that contains both high-Al and high-Cr chromitites. Thus, the studied ophiolitic chromitites allow tracing the complete magmatic evolution of an intra-oceanic subduction-initiation process. Furthermore, our data exhibits that accessory Cr-spinel composition of peridotites surrounding chromitites can be used as a prospecting indicator to anticipate the composition of ophiolitic chromitite bodies. Systematically, Cr-spinel from dunites associated with high-Al chromite deposits have lower Cr# values compared to the accessory Cr-spinel from the associated harzburgites. On the contrary, Cr-spinel from dunites of high-Cr chromite deposits show higher Cr# compared to the accessory Cr-spinel from the host harzburgites.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"30 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143569498","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Syn-tectonic emplacement of Li-bearing pegmatites related to detachment faulting in the Dahongliutan pegmatite belt, Western Kunlun, NW China","authors":"Tao Hong, Matthieu Harlaux, Ming-Guo Zhai, Yue-Jun Wang, Xing-Wang Xu, Xiao-Ping Xia, Jun Gao, Jun-Lin Tang, Ming-Xi Hu, Huan-Xiang Gao","doi":"10.1007/s00126-025-01352-0","DOIUrl":"https://doi.org/10.1007/s00126-025-01352-0","url":null,"abstract":"<p>The Late Triassic to Early Jurassic (ca. 220 to 190 Ma) Dahongliutan pegmatite belt, located in the Western Kunlun orogenic belt, NW China, is a newly discovered, large Li-Be ore district comprising &gt; 320 individual rare-metal pegmatites. The pegmatite belt was emplaced in a post-orogenic setting in relation with a ductile shear zone related to the Dahongliutan detachment fault, which is spatially and temporally related to post-orogenic exhumation. Deformed spodumene pegmatites, mostly striking NW with dip angle of 50 ~ 80°, occur within or adjacent to the NW-striking detachment fault. We present new field observations, mineralogical, geochemical and geochronological results from the Dahongliutan pegmatite belt, which lead to the following conclusions: 1) High-medium temperature/middle-to-low pressure metamorphic rocks and granitoids were intruded by ductile-deformed spodumene-bearing pegmatites during development of the gneissic domes; 2) Spodumene pegmatites from the Aktas, Kalaka, Bailongshan and Longmenshan deposits record two age groups, a first one during the Upper Triassic at ca. 212–205 Ma, and a second one during the Lower Jurassic at ca. 195–193 Ma, as revealed by in-situ Rb–Sr dating of micas and U–Pb dating of columbite-group minerals; 3) Textural observations and geochemical analyses of coexisting quartz and spodumene further indicate that ductile deformation provided favorable conditions for enrichment of Li and Be in pegmatites. The Western Kunlun-Songpan Ganzi rare-metal pegmatite belt shows a close spatial and genetic relationship with ductile shear zones induced by detachment faulting, making it a potential proxy for exploration targeting of Li-Be-mineralized occurrences at the regional scale as well as in other metallogenic provinces worldwide.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"29 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143532635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Orogenic arc-related Ni-Cu-(PGE) mineralization of the Ransko massif, Czech Republic, and implications for the metallogeny of the European Variscan belt","authors":"Lukáš Ackerman, Vojtěch Wertich, Jan Pašava, Martin Kubeš, Petr Rambousek, Jitka Míková, Jiří Sláma, Václav Santolík, Andreas Pack, Robert A. Creaser, Karel Malý, Tomáš Magna","doi":"10.1007/s00126-025-01353-z","DOIUrl":"https://doi.org/10.1007/s00126-025-01353-z","url":null,"abstract":"<p>The Ransko (ultra)mafic massif, Bohemian Massif, Czech Republic, hosts several Ni–Cu–(PGE) deposits and peculiar Zn–Cu–Ba ores. Geochronology integrated with petrography, bulk-rock, and mineral compositions together with Sr–Nd–Pb–Hf–Os–O isotopic systematics of barren and variably mineralized (ultra)mafic lithologies as well as massive ores reveal a complex evolution of the Ransko massif and its mineralizations. The Sm–Nd and U–Pb ages obtained for gabbros and cross-cutting granite porphyry, respectively, overlap with Re–Os ages of Ni–Cu–(PGE) and Zn–Cu ores and limit the formation age of (ultra)mafic rocks and metal accumulations to ~ 370–345 Ma. Compositional variations indicate derivation of parental melts of the Ransko massif from metasomatized, Variscan sub-arc mantle and underscore the importance of assimilation–fractional crystallization and crystal accumulation processes. The Ni–Cu ores were emplaced through the gravity-driven percolation of dense sulfide liquids along previously weakened structures associated with the downward crystal fractionation. The orogenic and arc-related nature of the Ransko Ni–Cu–(PGE) mineralization shares some remarkable similarities with some other Ni–Cu deposits in the European Variscan Belt highlighting the significance of these deposits emplaced in arc-related crustal domains. Yet, the variable nature of these mineralizations indicates complex processes that happen during the emplacement and evolution of the parental magmas driving their favourable metal contents.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"557 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143518790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deformation, alteration and implicit 3D geomodelling of deposit-scale controls of vein-hosted copper mineralization of the Frontier Mine, Democratic Republic of Congo","authors":"Heike Fourie, Alexander Kisters, Ian James Basson","doi":"10.1007/s00126-025-01351-1","DOIUrl":"https://doi.org/10.1007/s00126-025-01351-1","url":null,"abstract":"<p>The structurally controlled, vein-hosted copper deposit of the Frontier Mine is distinct from the vast majority of sediment-hosted, stratiform Cu(-Co) deposits of the Zambian Copperbelt. Successively emplaced vein sets document the close interplay between the progressive structural evolution of the deposit, recording northeast-southwest shortening, and associated hydrothermal fluid flow and alteration (albitization). The deposit is hosted by greenschist-facies metasedimentary rocks of the Mwashya Subgroup in the first-order hinge zone of a regional-scale, refolded, recumbent fold (F₁/F₂). Early bedding/S₁-parallel veins (Vein Set 1) formed during layer-parallel shearing and the onset of recumbent folding (F₁). This early vein generation is relatively poorly mineralized, but was associated with a near-pervasive, bedding-parallel albitization and replacement of the mainly metapelitic wall rocks. The reaction hardening process promoted brittle deformation during the subsequent upright refolding (F₂) of the rocks and the formation of a second generation of highly mineralized, saddle-reef type veins (Vein Set 2) in the hinges of particularly upright F₂ folds (F₁/F₂). The controls of Vein Set 2 by fold hinges defines the overall shoot-like geometry of the orebody, parallel to the SE-plunging folds. The subhorizontal orientation and brecciated textures of a subsequent Vein Set 3 underline the formation of veins through continued northeast-southwest shortening of the brittle wall rocks during the lock up of the refolded first-order fold. The overprinting and structural relationships between vein sets, alteration and the regional fold structures signify a syn-tectonic, long-lived, multi-phase mineralization history during the Lufilian Orogeny. </p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"24 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143495330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Apatite as a pathfinder to tin mineralisation: prospects and caveats","authors":"Martin F. Mangler, Nicholas J. Gardiner, Dominic Skeat, Nick M. W. Roberts, Simon Tapster","doi":"10.1007/s00126-025-01350-2","DOIUrl":"https://doi.org/10.1007/s00126-025-01350-2","url":null,"abstract":"<p>Granite-related mineral deposits are major primary sources of the critical metals tin (Sn) and lithium (Li). The utility of accessory minerals such as zircon and apatite as pathfinders to these ore deposits has been a subject of great interest in recent years, with a number of geochemical discriminants having been developed to distinguish barren from metal-fertile and mineralised intrusions. Here, we study the potential of apatite as an indicator mineral for tin and lithium mineralisation using a compilation of published apatite trace element data as well as new data for the mineralised Cornubian batholith and barren Bhutanese leucogranites. Critical examination of common geochemical discriminants tracing magma fractionation and redox conditions (Mn, Eu/Eu*, La/Yb_N and Sr/Y) reveals large and overlapping data scatter for both barren and Sn-fertile intrusions. This calls into question the utility of these petrogenetic indicators to pinpoint tin metallogeny. Instead, <i>prima facie</i> metal concentrations directly related to tin mineralisation (i.e., Sn and Li) are consistently elevated in apatite from fertile and mineralised intrusions. Based on our data compilation, Li and Sn concentrations in apatite are the most robust indicators for Sn (and Li) mineralisation, and we encourage the community to include Li and Sn in their analytical routines to further test these observations and explore their implications for tin metallogeny.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"78 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143401616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The mineralogical distribution of Ni in mantle rocks controls the fertility of magmatic Ni-sulfide systems","authors":"Daryl E. Blanks, David A. Holwell, Isra S. Ezad, Andrea Giuliani, Marco L. Fiorentini, Stephen F. Foley","doi":"10.1007/s00126-025-01349-9","DOIUrl":"https://doi.org/10.1007/s00126-025-01349-9","url":null,"abstract":"<p>Mantle-derived mafic-ultramafic melts are the primary host for magmatic Ni-Cu-Co-PGE deposits. One common assumption about this mineral system is that Ni-fertility is a product of high-degree melting of anhydrous mantle peridotites, including a substantial contribution from olivine. However, in metasomatised mantle rocks, which partially melt at lower temperatures than anhydrous peridotites, Ni is hosted by a range of minerals, including hydrous phases such as phlogopite and amphibole in addition to olivine and orthopyroxene. The lower melting point of these hydrous phases makes Ni in phlogopite a potentially significant contributor to the Ni enrichment of mantle melts from metasomatised assemblages. We analyse a suite of phlogopite-bearing mantle rocks which display variably metasomatised assemblages using SEM mapping to quantify mineral assemblages, and laser ablation ICP-MS to determine the Ni deportment in these rocks. Phlogopite in hydrous peridotites contains 859–1126 ppm Ni equating to ~ 12% of the bulk Ni content in an assemblage containing 25% phlogopite. Mica-Amphibole-Rutile-Ilmenite-Diopside rocks contain phlogopite with 428–715 ppm Ni, which can contribute up to 50% of the bulk Ni in an assemblage of 30% phlogopite. At temperatures below the dry peridotite solidus (&lt; 1300 °C), phlogopite can become a significant contributor of Ni to mantle melts. Thus, partial melting of metasomatised hydrous assemblages can produce Ni-fertile mafic-ultramafic magmas without substantial temperature perturbations such as those associated with mantle plumes. This opens up a range of geodynamic settings for Ni sulfide fertility, away from large igneous provinces and their plumbing systems, into settings such as orogenic belts, arcs and intraplate rifts.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"37 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143055090","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unravelling the mechanisms underlying marine redox shifts during sedimentary manganese metallogenesis: insights from the Carboniferous Muhu deposit, China","authors":"Zhi-Guo Dong, Bang-Lu Zhang, Lian-Chang Zhang, Fei-Yu Dong, Jie Li, Zi-Dong Peng, Bo Wan, Chang-Le Wang","doi":"10.1007/s00126-024-01343-7","DOIUrl":"https://doi.org/10.1007/s00126-024-01343-7","url":null,"abstract":"<p>Sedimentary manganese (Mn) mineralization requires a switch between anoxic and oxic water column conditions, which is commonly explained by the “bathtub ring” model and more recently interpreted by the emerging “episodic ventilation” model. To date, however, it remains unclear regarding how to distinguish between these two mechanisms, profoundly influencing Mn ore prospecting. Here, we conducted a comprehensive investigation on the Muhu Mn deposit in northwestern China. The upward lithological variations from breccia-dominated to fine-grained siliciclastic units (e.g., black shales) are typical of sequence characteristics of rifted basins. Black shales were deposited in deep waters due to continued tectonic subsidence that resulted in hydrographic restriction and bottom water euxinia, as indicated by their high ratios of Fe_HR/Fe_T and Fe_Py/Fe_HR, as well as relatively low Mo/TOC ratios. The Mn ore beds are interbedded with black shales and consist of divalent Mn minerals (e.g., rhodochrosite). They display shale-normalized positive cerium anomalies and negative inorganic carbon isotopes and Mo isotopes, suggesting that these Mn carbonate minerals originated from the diagenetic conversion of primary buried Mn oxides deposited under oxic benthic conditions. Taken together, the intimate spatial association between Mn ore beds and black shales records a dynamic temporal redox change. Such a redox shift is consistent with the “episodic ventilation” scenario, where incursions of oxygenated seawater triggered the deposition of initial Mn oxides. In contrast with the “bathtub ring” model, the ventilation scenario represents distinct spatial-temporal configurations of redox-hydrological conditions. Therefore, deciphering the detailed redox variations of Mn-hosting sedimentary successions, in conjunction with paleogeographic reconstruction, is the key to distinguishing between these two mechanisms.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"32 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143020306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}