Mineralium Deposita最新文献

{"title":"Polyphase stratabound scheelite-ferberite mineralization at Mallnock, Eastern Alps, Austria","authors":"Florian Altenberger, Joachim Krause, Niki E. Wintzer, Christoph Iglseder, Jasper Berndt, Kai Bachmann, Johann G. Raith","doi":"10.1007/s00126-024-01250-x","DOIUrl":"https://doi.org/10.1007/s00126-024-01250-x","url":null,"abstract":"<p>A peculiar type of stratabound tungsten mineralization in metacarbonate rocks was discovered and explored at Mallnock (Austria) during the late 1980s. It is the only tungsten occurrence in the Eastern Alps in which scheelite is associated with wolframite (96 mol% ferberite). The tungsten prospect is located in the Austroalpine Drauzug-Gurktal Nappe System recording polyphase low-grade regional metamorphism. Raman spectroscopy of carbonaceous material yield maximum metamorphic temperatures of 296 ± 27 °C and 258 ± 27 °C, which are assigned to Variscan and Eoalpine metamorphism, respectively. Scheelite and ferberite occur as polyphase stockwork-like mineralization in Fe-rich magnesite in the northern ore zone (Mallnock North), whereas in the western ore zone (Mallnock West), scheelite-quartz veinlets are exclusively hosted in dolomitic marbles. LA-ICP-MS analyses of scheelite and ferberite yield low contents of Mo, Nb, Ta, and rare earth elements, but high contents of Na and Sr. Uranium is particularly high in scheelite (up to 200 µg/g) and makes this mineral a suitable target for U–Pb dating. In situ U–Pb dating of scheelite yielded an early Permian age (294 ± 8 Ma) for Mallnock West and a Middle Triassic age (239 ± 3 Ma) for Mallnock North. A monzodioritic dike close to Mallnock yielded a U–Pb apatite date of 282 ± 9 Ma and supports the polyphase formation of this mineralization. The U–Pb scheelite ages indicate that a model for tungsten metallogeny in the Eastern Alps must also consider remobilization of tungsten by metamorphic fluids. In the Alps, the Permian to Triassic period (ca. 290–225 Ma) is characterized by an overall extensional geodynamic setting related to the breakup of Pangea. Lithospheric thinning caused higher heat flow, low-P metamorphism, and anatexis in the lower crust, which led to enhanced crustal fluid flow in the upper crust. These processes were not only responsible for the formation of metasomatic hydrothermal magnesite and siderite deposits in the Eastern Alps but also for this unique magnesite-ferberite-scheelite mineralization at Mallnock.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"48 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140000995","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":"Osmium and zinc isotope constraints on the origin of chromitites from the Yarlung-Zangbo ophiolites, Tibet, China","authors":"Dongyang Lian, Fei Liu, Pengjie Cai, Weiwei Wu, Jie Li, Jarosław Majka, Zhiqin Xu, Jingsui Yang","doi":"10.1007/s00126-024-01252-9","DOIUrl":"https://doi.org/10.1007/s00126-024-01252-9","url":null,"abstract":"<p>Chromitites or chromite mineralization of varying degrees has been discovered in the various ophiolites along the east–west trending Yarlung-Zangbo Suture Zone (YZSZ) in Tibet, China. The high-Cr variety dominates the Yarlung-Zangbo chromitites, with rare high-Al chromitites reported in the Zedang, Dongbo, and Purang ophiolites. Using empirical equations, the calculated parental magmas that formed the high-Cr YZSZ chromitites are similar to boninitic melts. ¹⁸⁷Os/¹⁸⁸Os ratios of chromites from the YZSZ chromitites range from 0.12525 to 0.12933, lower than the proposed present-day ¹⁸⁷Os/¹⁸⁸Os values for the primitive upper mantle. The T_RD age variation of the YZSZ chromitites from late Neo-Proterozoic to early Triassic thus reflects that their parental magmas are derived from depleted mantle sources mixed with diachronous ancient mantle domains. The light Zn isotopic compositions of the YZSZ chromitites indicate that subducted materials (e.g., serpentinites and sediments) have contributed to the parental magma of the YZSZ chromitites. By compiling previously published data on mantle peridotites of the YZSZ ophiolites, we concluded that the YZSZ ophiolites may either have formed initially in an ultraslow-slow mid-ocean ridge environment and were then trapped in a supra-subduction zone environment, or have formed in an ultraslow-slow forearc spreading center in a supra-subduction zone environment. The Luobusa ophiolite hosting the largest chromite deposits is discriminated from the other ophiolites in the YZSZ by a thick dunitic transition zone. Previous theoretical modeling indicates that relative to olivine, only a small amount of cumulus chromites crystallize in cotectic volume ratios of around 100:1 to 100:2 of olivine to chromite, which means that large chromite bodies should always be accompanied by a significantly larger mass of dunites. Therefore, we concluded that a thick dunite transition zone or large masses of dunite of boninitic affinity is an indicator for chromitite prospecting in the future.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"232 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139915825","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":"Influence of magmatic and magmatic-hydrothermal processes on the lithium endowment of micas in the Cornubian Batholith (SW England)","authors":"F. Putzolu, R. Seltmann, A. Dolgopolova, R. N. Armstrong, R. K. Shail, J. Spratt, Y. Buret, C. Broderick, W. Brownscombe","doi":"10.1007/s00126-024-01248-5","DOIUrl":"https://doi.org/10.1007/s00126-024-01248-5","url":null,"abstract":"<p>The Cornubian Batholith (SW England) is an archetypal Variscan rare metal granite with potential for Li-mica mineralization. We present a petrographic, trace element and multivariate statistical study of micas from the Cornubian Batholith granite series and related hydrothermally altered units to assess the role of magmatic vs subsolidus processes and of fluxing elements (F and B) on the Li cycle during the evolution of the system. The mica types are as follows: (1) magmatic, which include Fe-biotite, protolithionite I and phengite-muscovite from the most primitive granites, and zinnwaldite I from more fractionated lithologies; (2) subsolidus, which encompass high-temperature autometasomatic Li-micas and low-temperature hydrothermal muscovite-phengite. Autometasomatic species include protolithionite II, zinnwaldite II and lepidolite, which were observed in the most fractionated and hydrothermally altered units, and occur as replacements of magmatic micas. Low-temperature hydrothermal Li-poor micas formed via alteration of magmatic and autometasomatic micas or as replacement of feldspars, and albeit occur in all studied lithologies they are best represented by the granite facies enriched in metasomatic tourmaline. The evolution of micas follows two major trends underlining a coupling and decoupling between the Li(F) and B fluxes. These include as follows: (1) a Li(F)-progressive trend explaining the formation of protolithionite I and zinnwaldite I, which fractionate Li along with Cs, Nb and Sn during the late-magmatic stages of crystallization, and of zinnwaldite II and lepidolite forming from the re-equilibration of primary micas with high-temperature Li-B-W-Tl-Cs-Mn-W-rich autometasomatic fluids; (2) a Li(F)-retrogressive trend explaining the low-temperature hydrothermal muscovitization, which represents the main Li depletion process. Trace element geochemistry and paragenesis of late muscovite-phengite support that muscovitization is a district-scale process that affected the upper parts of the granite cupolas through acidic and B(Fe-Sn)-saturated hydrothermal fluids associated with metasomatic tourmalinization, which were mixed with a low Eh meteoric component.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"64 2 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139911359","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":"Fluid-rock sulfidation reactions control Au-Ag-Te-Bi precipitation in the Val-d’Or orogenic gold vein field (Abitibi subprovince, Canada)","authors":"","doi":"10.1007/s00126-024-01247-6","DOIUrl":"https://doi.org/10.1007/s00126-024-01247-6","url":null,"abstract":"<h3>Abstract</h3> <p>The Val-d’Or vein field (VVF), located in the southern Abitibi subprovince (Québec, Canada), is host to ~ 47 Moz gold and is therefore an example of a greenstone-hosted orogenic gold district. Gold is contained in quartz-tourmaline-carbonate veins that cut As-poor intermediate to mafic volcanic and intrusive rocks, including dioritic, granodioritic and gabbroic sills, dikes, stocks, and plutons. Five investigated orebodies (Goldex, Triangle, Plug #4, Pascalis Gold Trend, Beaufor) host gold in vein- and wallrock-hosted pyrite-rich sulfide aggregates (&gt; 95 vol%) that show a porous core domain (Py1), with abundant inclusions of carbonate, silicate, and Fe-oxides up to several tens of µm in size. A homogeneous pyrite rim domain (Py2) surrounds Py1 and contains most of the gold as native gold and polymetallic (Au-Ag-Te-Bi) inclusions, primarily calaverite and petzite. The two pyrites show different Au and As contents (Py1 = Au ≤ 30 ppm; As ≤ 67 ppm; Py2 = Au ≤ 1250 ppm; As ≤ 550 ppm). Pyrite shows a ubiquitous shift in δ³⁴S values of up to + 3.0‰ from Py1 (δ³⁴S = − 0.4‰ to 5.8‰, <em>n</em> = 32) to Py2 (δ³⁴S = 0.0‰ to 6.3‰, <em>n</em> = 59) and records a small, slightly negative Δ³³S signature between – 0.20‰ and 0.01‰. The δ³⁴S shift suggests that removal of reduced sulfur species from auriferous hydrothermal fluids causes the formation of inclusion-hosted gold in Py2 by a decrease in the fluid sulfur fugacity (<em>f</em>S₂) through wallrock sulfidation of Fe-oxides. The shift also correlates with locally enriched Co and Ni concentrations in Py1 (&lt; 1 wt%), compared to lower, oscillatory zoned concentrations (&lt; 0.1 wt%) in Py2, respectively, indicating an overall decrease in fluid oxygen fugacity (<em>f</em>O₂). Contemporaneously, a decrease in fluid tellurium fugacity (<em>f</em>Te₂) drives polymetallic inclusion-hosted gold formation in Py2, initially as calaverite followed by increasingly Ag-bearing petzite and hessite. The multiple sulfur isotopes and trace element compositions recorded in pyrite in the VVF indicate that a homogeneous fluid reservoir introduced gold-sulfide complexes. Even if considered a localized process at the ore-shoot scale, fluid-wallrock sulfidation reactions can lead to a coupled decrease in <em>f</em>S₂, <em>f</em>O₂, and <em>f</em>Te₂ of auriferous hydrothermal fluids in a greenstone-hosted As-poor gold district.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"22 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139715344","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":"Distribution of chalcophile elements during crystallisation and alteration of magmatic Ni-Cu-Co sulfide deposits in the anorthositic Espedalen Complex, Norway: pentlandite as an indicator for tracking metal tenors","authors":"Eduardo T. Mansur, Sarah A. S. Dare, Trond Slagstad, Jan Sverre Sandstad","doi":"10.1007/s00126-024-01246-7","DOIUrl":"https://doi.org/10.1007/s00126-024-01246-7","url":null,"abstract":"<p>This study presents an investigation of the distribution of trace elements within base metal sulfides from magmatic Ni-Cu-Co deposits from the Proterozoic anorthositic Espedalen Complex, Norway. The mineralisation occurs both as primary, undeformed sulfides and as deformed sulfides hosted within shear zones. Distinct deposits yield Ni tenors ranging from 3 to 10%, allowing the assessment of whether the metal tenor of a deposit is reflected in its sulfide composition. The results allow constraining geological processes spanning from the compositional traits of the parental melts to late-magmatic fluid interactions. Notably, the sulfides exhibit a relatively low concentration of chalcophile elements compared to other Ni-Cu-Co deposits worldwide, particularly platinum-group elements (PGE). This is because these deposits formed from PGE-depleted magmas. Elements compatible with monosulfide solid solution (MSS; Co, Rh, Ru, Ir, Os and Se) are predominantly hosted by sulfides, whereas a smaller proportion of incompatible elements (Pb, Cd, Ag, Bi, Zn, In, Tl, As, Sn and Mo) is also accommodated by sulfides. Our findings for sulfide composition support for the first time a positive correlation between Se concentrations in pentlandite and whole-rock Ni tenors for both Espedalen and magmatic Ni-Cu-Co sulfide deposits worldwide. This is because of the more efficient collection of both Ni and Se by an immiscible sulfide liquid under high R-factor regimes, combined with the fact that Se concentrations in pentlandite remain largely undisturbed during post-cumulus processes as opposed to other trace elements. Consequently, Se concentrations in pentlandite may serve as a proxy for metal enrichment in magmatic sulfide deposits.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"182 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139660180","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":"Scheelite U–Pb dating constraints on the timing of the formation of the Zhazixi Sb-W deposit in South China","authors":"","doi":"10.1007/s00126-024-01249-4","DOIUrl":"https://doi.org/10.1007/s00126-024-01249-4","url":null,"abstract":"<h3>Abstract</h3> <p>The Zhazixi deposit hosted in sedimentary rocks is a major Sb-W deposit in South China. The mineral scheelite, which can be dated by the U-Pb method, commonly occurs in both tungsten (W)-dominated and antimony (Sb)-dominated ore veins of the deposit. Cathodoluminescence (CL) images reveal the presence of three distinct stages of scheelite (Sch-I, Sch-II and Sch-III) within the deposit. These three scheelites were dated using in-situ laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), yielding U-Pb ages of 158.1±5.4 Ma and 157.6 ± 4.9 Ma for Sch-I, 155 ± 11 Ma for Sch-II, and 151.3±6.1 Ma for Sch-III. These data suggest that the Zhazixi Sb-W deposit formed during the Late Jurassic (160–150 Ma) rather than the Late Triassic as previously suggested. Considering the temporal similarity with low-temperature hydrothermal Sb deposits in the Xiangzhong metallogenic province (XZMP), the formation of the Sb-W deposit may have followed a similar genetic model, where meteoric groundwater circulated to depth and extracted metals from fertile basement rocks through fluid-rock interaction, resulting in the generation of ore fluids. This study highlights that Late Jurassic low-temperature hydrothermal Sb-polymetallic mineralization in the XZMP is likely more extensive than previously perceived.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"87 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139644119","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 magmatic origin of propylitic alteration of the Zhengguang epithermal Au-Zn deposit, Heilongjiang, China: evidence from mineral compositions and H–O-Sr isotopes","authors":"Le Wang, Ming-Jian Cao, Shen Gao, Massimo Chiaradia, Pete Hollings, Ke-Zhang Qin, Xin-Yu Zou, Guo-Xue Song, Xu-Yong Pang, Guang-Ming Li","doi":"10.1007/s00126-023-01243-2","DOIUrl":"https://doi.org/10.1007/s00126-023-01243-2","url":null,"abstract":"<p>The origin of propylitic fluids in intermediate sulfidation mineralization has not been investigated in detail. Here, we present an extensive petrographic, geochemical, and isotopic (O-H-Sr) study of propylitic epidote, chlorite, and calcite from the Zhengguang intermediate sulfidation epithermal Au-Zn deposit, NE China. Propylitic minerals can be divided into three main types based on their different textural occurrences, namely interstitial cement of clasts of hydrothermal breccia, replacement of primary plagioclase or hornblende, and vein infill of cracks, with late, minor calcite as amygdules in vesicles of andesite representing a fourth textural occurrence. The H-O isotope compositions and mass balance calculations suggest that most propylitic epidote records a dominant (&gt; 50%) contribution of magmatic fluids. The decrease of the average δ¹⁸<span>({mathrm O}_{{mathrm H}_2mathrm O};)</span>values equilibrated with different types of epidote (cement 6.8 ± 0.7‰, replacement 5.1 ± 1.1‰, vein 4.5 ± 1.4‰, 1 SD), and the decreasing content of high-temperature elements (e.g., Cu-Mo) from cement, through replacement to vein epidote and chlorite, collectively indicates a decreasing role of magmatic fluids. Replacement epidote and chlorite are enriched in Sr-Mn-Y-Sb, whereas replacement epidote and calcite record similar (⁸⁷Sr/⁸⁶Sr)_i values to the andesitic host rock, suggesting that replacement minerals inherit certain elements from plagioclase and hornblende, and the Sr isotope signature of the wall rocks. We highlight that propylitic alteration in epithermal deposits can involve significant proportions of magmatic fluids and texturally different alteration mineral types should be considered when using mineral isotopic or chemical compositions to track fluid sources or to vector towards the location of intrusive centers.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"2 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139489427","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":"Mechanism of germanium enrichment in the world-class Huize MVT Pb–Zn deposit, southwestern China","authors":"Pan-Pan Niu, Manuel Muñoz, Olivier Mathon, Suo-Fei Xiong, Shao-Yong Jiang","doi":"10.1007/s00126-023-01242-3","DOIUrl":"https://doi.org/10.1007/s00126-023-01242-3","url":null,"abstract":"<p>The world-class Huize deposit hosts significant germanium (Ge) resources in the Sichuan–Yunan–Guizhou (SYG) Mississippi Valley-type (MVT) Pb–Zn province of China. The distribution and enrichment mechanism of Ge is still poorly understood. In the main ore-forming stage of Huize, we identified six sphalerite colors from C1 (black) to C6 (white) in transmitted light. Two color sequences are confirmed, including C1 → C2 → C3 → C6 and C1 → C2 → C4 → C5 → C6. We used multiple analytical methods to reveal the Ge distribution and incorporation mechanism into sphalerite and the possible enrichment factors. Our results show that Ge occurs as argutite (GeO₂), and in the sphalerite crystal lattice, C1 and C3 sphalerite has up to 593 ppm Ge. Two substitution mechanisms, i.e., Ge⁴⁺ + □_(vacancy) → 2Zn²⁺ (e.g., C1 and C2) and Ge⁴⁺ + 2Cu⁺ → 3Zn²⁺ (e.g., C2, C3, C4, and C5), are inferred from the Huize sphalerite. They show different spatial structures of sphalerite and a weak shift of the white line observed by high-resolution X-ray absorption near-edge structure (XANES) spectroscopy. The trace-element composition of sphalerite suggests that reduced sulfur content of the ore-forming fluid contributes to Ge enrichment, followed by high temperature (&gt; 300 °C).</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"116 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139436814","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":"Geochemistry and Sm─Nd─Fe─Si isotope compositions as insights into the deposition of the late Neoarchean Qidashan banded iron formation, North China Craton","authors":"Changle Wang, Zidong Peng, Xiaoxue Tong, Liang Gao, Lianchang Zhang","doi":"10.1007/s00126-024-01245-8","DOIUrl":"https://doi.org/10.1007/s00126-024-01245-8","url":null,"abstract":"<p>Banded iron formations (BIFs) are chemical sediments that reflect the composition of the seawater from which they were deposited. Therefore, they provide a key part of the evidence for the modern scientific understanding of paleoenvironmental conditions in Archean and Paleoproterozoic times. Although BIFs have been extensively studied, many aspects (e.g., specific mechanisms controlling iron (Fe) and silicon (Si) precipitations) of their origin still remain enigmatic because of the lack of modern analogues. In China, abundant BIFs occur throughout within the late Neoarchean volcanic and sedimentary succession and therefore are the principal source of Fe for the Chinese steel industry. Here, we examine the ~ 2.53 Ga Qidashan BIF, one of the most extensive BIFs in China, by conducting a detailed petrographic and multi-proxy investigation to well constrain its formation mechanism. The BIF consists mainly of magnetite and quartz with lesser amounts of calcite and various types of silicate minerals, of which the content of Al-rich minerals (i.e., chlorite) is rare, coupled with a low abundance of detrital geochemical indicators (e.g., Al and Ti), suggesting that the BIF is relatively pure with insignificant terrigenous contamination. A wide range of Nd isotope compositions and shale-normalized patterns and specific anomalies of rare earth elements, especially highly positive Eu anomalies, indicate that the BIF precipitated from seawater imprinted by high-temperature hydrothermal fluids. Furthermore, there is a significantly negative correlation between Nd isotope values and total Fe contents of the BIF. This suggests that such enhanced hydrothermal activity provided vast volumes of dissolved Fe(II) necessary for the formation of the BIF via alteration of ancient continental crust. In addition, the Qidashan BIF was deposited under pervasively anoxic conditions, as revealed by the absence of shale-normalized Ce anomalies and the presence of consistently positive Fe isotope values. Hence, anoxygenic photosynthesis is the most plausible mechanism responsible for Fe(II) oxidation. Given that Fe─Si bonding has a strong impact on Si isotope fractionation, the formation of primary Fe(III) oxyhydroxides should have exerted a first-order control on the negative Si isotope signatures observed in the studied BIF samples. It is also noted that the BIF possesses a variation of negative Si isotope values, further implying that diagenetic dissolution and reprecipitation of silica took place after primary Si precipitation associated with Fe.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"122 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139400502","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 Boring Billion: A key to resolving controversy on ore-fluid source models for orogenic gold deposits?","authors":"David I. Groves, M. Santosh, Qingfei Wang, Liang Zhang, Hesen Zhao","doi":"10.1007/s00126-023-01244-1","DOIUrl":"https://doi.org/10.1007/s00126-023-01244-1","url":null,"abstract":"<p>Orogenic gold systems are arguably the most variable mineral system globally in terms of an extreme range of depositional depths, corresponding P–T conditions and wallrock alteration assemblages, structural controls and styles, and element associations. This diversity has ignited controversy on genetic models for the two decades since orogenic gold became a widely accepted term. From the diverse genetic models proposed, the two groups of fluid-source models that meet most genetic constraints are the following: (1) deposition from crustal fluids via metamorphic devolatilization at the amphibolite-greenschist transition, or potentially even deeper under specific tectonic conditions, and (2) deposition from sub-crustal fluids either by direct devolatilization of subducted oceanic crust and overlying sediment wedge or of previously metasomatized and fertilized mantle lithosphere. Both models normally postulate gold deposition within a geodynamic system that evolves from extension through compression into syn-gold transpression. Crustal metamorphic models normally invoke subduction-driven geodynamic systems that involve advection of crustal metamorphic fluids up crustal-scale faults. In contrast, sub-crustal devolatilization models involve subduction-related processes as both geodynamic drivers and gold sources with fault-controlled fluid conduits extending to below the Moho. The overall lack of orogenic gold and other subduction-related mineral systems during the unique Boring Billion (1.8–0.8 Ga) period provides an important constraint on this genetic debate. Boring Billion orogens had varying geodynamic drivers, asthenosphere upwelling, and low-P metamorphic terranes with crustal-scale faults, all parameters consistent with formation of orogenic gold systems, during subduction-independent accordion-type tectonics. The absence of orogenic gold during the Boring Billion provides critical evidence against the crustal metamorphic model and furthers the sub-crustal model which requires subduction as both the geodynamic driver and auriferous fluid source.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":"47 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139112018","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}