Contributions to Mineralogy and Petrology最新文献

{"title":"Partitioning of highly siderophile elements between monosulfide solid solution and sulfide melt at high pressures","authors":"Raúl O. C. Fonseca,&nbsp;Christopher Beyer,&nbsp;Thilo Bissbort,&nbsp;Rebecca Hartmann,&nbsp;Stephan Schuth","doi":"10.1007/s00410-023-02092-y","DOIUrl":"10.1007/s00410-023-02092-y","url":null,"abstract":"<div><p>Base metal sulfides (Fe–Ni–Cu–S) are ubiquitous phases in mantle and subduction-related lithologies. Sulfides in the mantle often melt incongruently, which leads to the production of a Cu–Ni-rich sulfide melt and a solid residue called monosulfide solid solution (mss). Even though peridotite-hosted sulfides, which tend to be more Ni-rich, are likely completely molten at mantle potential temperatures, the same is not true for eclogite-hosted Ni-poor, Fe-rich sulfides. Because of this, solid crystalline mss may persist at higher pressures and equilibrate with co-existing sulfide melt along colder geotherms, like those associated with subduction zones. Because highly siderophile elements (HSE—Pt, Pd, Rh, Ru, Os, Ir, and Re) are known to fractionate as a result of mss/sulfide-melt equilibrium, the persistence of an mss/sulfide-melt assemblage to higher pressures may lead to the fractionation of these elements during the subduction process. In this contribution, we carried out an experimental investigation of the partitioning behavior of the HSE, as well as Cu and Ni, between mss and sulfide melt over a pressure and temperature range relevant to equilibration between Earth’s surface and transition zone depths (0.1 MPa to 14 GPa; 930–1530 <span>(^{circ })</span>C), and variable Ni contents in sulfide. Results show that at higher pressures, the HSE are considerably less fractionated as a result of mss and sulfide melt equilibrium compared to lower pressure conditions. This is exemplified by a lowering of the <span>(D_{i}^mathrm{mss/melt})</span> for the more compatible HSE (Ru, Os, Ir, Rh and Re) from around 10 at 0.1 MPa to just above or below unity at 14 GPa. Moreover, the higher the Ni content of the bulk sulfide assemblage, the larger the degree of change in the magnitude of HSE fractionation seen over the pressure range studied. The exchange coefficient (<span>(K_D^{textrm{Ru}-textrm{Pt}})</span>) between highly compatible HSE (Ru) and less compatible Pt illustrates a notable contrast. In the Ni-poor composition (E1), <span>(K_D^{textrm{Ru}-textrm{Pt}})</span> changes from 27 at 0.1 MPa to 6 at 14 GPa. In contrast, the Ni-rich composition exhibits a broader range, with <span>(K_D^{textrm{Ru}-textrm{Pt}})</span> ranging from 150 to 17 across the same pressure interval. Our results highlight key differences between experimental data obtained at lower and higher pressure, and how composition, namely the Ni content of sulfide, affects HSE partitioning behavior.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 2","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-023-02092-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139667402","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":"Rapid accumulation and ascent precedes caldera forming eruption of low viscosity magma","authors":"Corin Jorgenson,&nbsp;Luca Caricchi,&nbsp;Massimo Chiaradia,&nbsp;Mónica Ágreda-López,&nbsp;Guido Giordano","doi":"10.1007/s00410-023-02091-z","DOIUrl":"10.1007/s00410-023-02091-z","url":null,"abstract":"<div><p>Mafic magma is commonly associated with effusive eruptions, however several mafic volcanoes throughout the globe have produced explosive eruptions. Here we present one such volcano – Colli Albani. Colli Albani is 20 km SE of Rome and produced seven large volume ignimbrites. Field observations, mineral chemistry, and Sr and Nd isotopes in clinopyroxene show that the high potassic, silica undersaturated and CO<span>(_{2})</span>-rich magma typical of Colli Albani is produced by partial melting of a metasomatized mantle. Clinopyroxene based thermobarometry combined with thermal modelling, indicates rapid accumulation of magma into the shallow crust preceding the last caldera forming event (355 ka). The crystallization of high Mg# and high Cr<span>(_{2})</span>O<span>(_{3})</span> clinopyroxenes at low pressures and high temperatures indicates rapid magma ascent from the mantle. We suggest that a final rapid input of this deeply sourced magma destabilised the shallow and fast assembled magma reservoir and lead to the caldera forming event. Our findings have significant implications for the evaluation of the timescales of reactivation of Colli Albani and other similar long-quiescent calderas erupting low viscosity magmas, as rapid migration of magma to shallow reservoirs may result in short unrest periods prior to a large eruption.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 2","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-023-02091-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139667523","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":"Oceanic mantle beneath ultraslow spreading ridges metasomatized by variably evolved melts","authors":"Wei-Qi Zhang,&nbsp;Chuan-Zhou Liu,&nbsp;Henry J. B. Dick,&nbsp;Ross N. Mitchell,&nbsp;Bo-Da Liu","doi":"10.1007/s00410-023-02093-x","DOIUrl":"10.1007/s00410-023-02093-x","url":null,"abstract":"<div><p>As the melting residue of the asthenosphere at ocean ridges, the oceanic mantle lithosphere is initially depleted, which might be re-enriched by various types of melts. However, the metasomatic enrichments in the sub-ridge mantle lithosphere are generally assumed to be limited, because these melts have low abundances of incompatible elements. In this study, we report a case of extreme metasomatic enrichment in abyssal peridotites from the Atlantis Bank oceanic core complex on the Southwest Indian Ridge. We identify two types of metasomatized peridotites (Type 1 and 2) and a clinopyroxenite, which show different degrees of interaction with evolved melts. Type 1 peridotite exhibits strong incompatible element zonation and negative Eu anomalies in clinopyroxene, indicating a short-term percolation of a modestly evolved mid-ocean ridge basalt (MORB). Type 2 peridotite shows textural and trace element features consistent with the impregnation of a highly evolved, oxide-saturated MORB magma. The clinopyroxenite shows remarkable enrichments in iron and incompatible trace elements and negative Eu anomalies in clinopyroxene and contains abundant zircon and apatite, which imply reaction with an extremely evolved Fe–Zr–P-rich melt. We attribute such extreme mantle metasomatic enrichments to the lateral infiltration of variably evolved melts from a local magmatic center, which is now exposed as the Atlantis Bank gabbroic massif. As slow- and ultraslow-spreading ridges exhibit similarly discontinuous lower crust, the intervening shallow mantle between local magmatic centers may have been pervasively metasomatized by the evolved melts, leading the way for substantial mantle enrichment.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 2","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139589437","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 texture and geochemistry as a recorder of nature and timing of metallogenesis: an example from the Zhaishang Au–Sb–W deposit, western Qinling, central China","authors":"Guoming Weng,&nbsp;Jiajun Liu,&nbsp;Emmanuel John M. Carranza,&nbsp;Degao Zhai,&nbsp;Jianping Wang,&nbsp;Huan Wang,&nbsp;Bin Zhang,&nbsp;Fangfang Zhang,&nbsp;Yinhong Wang,&nbsp;Dongxiang Jiang,&nbsp;Biao Sun","doi":"10.1007/s00410-023-02090-0","DOIUrl":"10.1007/s00410-023-02090-0","url":null,"abstract":"<div><p>Scheelite, one kind of common REE-rich and U-bearing hydrothermal mineral, is extensively developed in various types of gold deposits, which can be used to record nature and timing of metallogenesis. The Zhaishang Carlin-like gold deposit in the Qinling Orogen is a giant Au deposit, hosting 127t of Au @ 2.67 g/t with economic concentrations of tungsten and antimony. The study reports two types of scheelite based on the characteristics of petrography and geochemistry. Sch A shows significant oscillatory zoning with dark gray cathodoluminescence (CL) response, whereas Sch B displays patchy textures with brighter CL response. Systematic LA-ICP-MS U–Pb dating of Sch A and Sch B yields ages of 227.1 ± 3.2 Ma and 226.2 ± 6.9 Ma, respectively. The new dates, constraining the Zhaishang Au–W mineralization to ~ 227Ma, coincide well with the western Qinling magmatism, metallogenic and tectonic events. There are significant variations in concentration, the Sch A has low REE content (mean = 41.3 ppm), negative Eu-anomaly with slightly positive Ce-anomaly, whereas Sch B, with small negative or positive Eu-anomaly, has higher REE content (mean = 247 ppm) and higher positive Ce-anomaly. The positive correlation of Eu_N and Eu_N^* records oxidizing condition during the whole W mineralization event. Additionally, Sch B intergrown with selenides with an increase in the Ce-anomaly supports that the latter has higher oxygen fugacity environment. The Sr isotope signature for scheelite supports that ore-forming metals mostly inherited the host rock component, while the proportion of magma-derived Sr increased in the Sch B. Fluid–rock interactions co-precipitated Au and W caused by the release of Fe and Ca cations and the increase of pH. The study highlights that scheelite as a recorder can help in deciphering the nature and timing of metallogenesis of the studied Au–Sb–W deposit, and thus other similar Au–W deposits.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 2","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139589726","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":"First evaluation of stiff-in-soft host–inclusion systems: experimental synthesis of zircon inclusions in quartz crystals","authors":"Joseph P. Gonzalez,&nbsp;Jay B. Thomas,&nbsp;Mattia L. Mazzucchelli,&nbsp;Ross J. Angel,&nbsp;Matteo Alvaro","doi":"10.1007/s00410-023-02081-1","DOIUrl":"10.1007/s00410-023-02081-1","url":null,"abstract":"<div><p>Quartz crystals with zircon inclusions were synthesized using a piston-cylinder apparatus to experimentally evaluate the use of inclusions in “soft” host minerals for elastic thermobarometry. Synthesized zircon inclusion strains and, therefore, pressures (<i>P</i>_inc) were measured using Raman spectroscopy and then compared with the expected inclusion strains and pressures calculated from elastic models. Measured inclusion strains and inclusion pressures are systematically more tensile than the expected values and, thus, re-calculated entrapment pressures are overestimated. These discrepancies are not caused by analytical biases or assumptions in the elastic models and strain calculations. Analysis shows that inclusion strain discrepancies progressively decrease with decreasing experimental temperature in the α-quartz field. This behavior is consistent with inelastic deformation of the host–inclusion pairs induced by the development of large differential stresses during experimental cooling. Therefore, inclusion strains are more reliable for inclusions trapped at lower temperature conditions in the α-quartz field where there is less inelastic deformation of the host–inclusion systems. On the other hand, entrapment isomekes of zircon inclusions entrapped in the β-quartz stability field plot along the α–β quartz phase boundary, suggesting that the inclusion strains were mechanically reset at the phase boundary during experimental cooling and decompression. Therefore, inclusions contained in soft host minerals can be used for elastic thermobarometry and inclusions contained in β-quartz may provide constraints on the <i>P</i>–<i>T</i> at which the host–inclusion system crossed the phase boundary during exhumation.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 2","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-023-02081-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139589524","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":"Constraining magma storage conditions of the Toba magmatic system: a plagioclase and amphibole perspective","authors":"Jordan Lubbers,&nbsp;Adam J. R. Kent,&nbsp;Shanaka de Silva","doi":"10.1007/s00410-023-02089-7","DOIUrl":"10.1007/s00410-023-02089-7","url":null,"abstract":"<div><p>Silicic magma reservoirs are responsible for producing the largest explosive eruptions in the geologic record. Petrologic and geochronological data provide evidence for these systems spending substantial periods of time (10⁴–10⁵ yrs) within the upper crust prior to eruption; however, the long-term thermochemical evolution of these systems is not fully understood, as existing petrologic data make it challenging to quantify the time interval a magmatic system has spent at certain temperatures, or its “thermal history”. Here, we investigate the 74 ka Youngest Toba Tuff (YTT), one of the largest explosive eruptions in the geologic record, to better constrain the long-term thermal evolution of its magmatic system. We combine forward models of Sr diffusion in plagioclase and hornblende, mineral thermometry, and pre-existing trace-element evolution models to quantify the thermochemical evolution of the YTT magmatic system. We find that plagioclase crystals record decades to centuries of storage at temperatures <span>(&gt;sim)</span>750 <span>(^circ)</span>C, while hornblende records up to 6200 years at the same temperatures. Hornblende crystallizes at temperatures around 820 <span>(^circ)</span>C and adjusting our diffusion modeling to this temperature results in no more than 900 years at initial crystallization conditions. Combined with previous trace-element modeling work, these results indicate that although there was chemical diversity for long durations in the YTT magma system sufficient to produce unique composition eruptive products, the entire system was experiencing a relatively similar thermal history that did not allow for large bodies of eruptible magma to be present for long periods (<span>(&gt;&gt;)</span> 10²–10³ years). Rather, we suggest that magmas within the YTT magmatic system were stored for long durations at thermal conditions where they were uneruptible and only remobilized within a few centuries prior to eruption.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 2","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139763173","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":"Porosity generation via spatially uncoupled dissolution precipitation during plagioclase replacement in quartz undersaturated fluids","authors":"Astin Nurdiana,&nbsp;Atsushi Okamoto,&nbsp;Masaoki Uno,&nbsp;Noriyoshi Tsuchiya","doi":"10.1007/s00410-023-02088-8","DOIUrl":"10.1007/s00410-023-02088-8","url":null,"abstract":"<div><p>The replacement of feldspars is commonly characterized by pseudomorphism and reaction-induced pore generation. However, the effects of compositions of feldspars and fluids on porosity generation during alteration are still poorly understood. In this study, we conducted a series of hydrothermal experiments on plagioclase replacement by 2 M KCl or NaCl aqueous solutions at 600 °C and 150 MPa for 1–8 days, using plagioclase with different compositions (anorthite, An₉₆Ab₄; labradorite, An₆₆Ab₃₃Or₁; albite, An₁Ab₉₉) with or without quartz. Albite replacement by K-feldspar was not affected by the presence of quartz, whereas anorthite was unaltered in the quartz-absent fluid. The replacement of labradorite by KCl(aq) showed different results: in the presence of quartz, labradorite was altered by K-feldspar, whereas in the absence of quartz, alteration proceeded significantly with the generation of large pores hosted by secondary anorthite coupled with euhedral K-feldspar overgrowth. Such textural relationship and oxygen isotope-labeled experiments reveal that silica-deficient fluid enhances the uncoupled dissolution reprecipitation process. The Si and Al ions in the reacted aqueous solution diffused outside the labradorite grains and encountered K⁺-rich solutions to grow K-feldspar. The experiments with polycrystalline rocks composed of amphibole + labradorite using 2 M KCl aqueous solution indicated the replacement of labradorite grains by anorthite and K-feldspar overgrowth, as found in single-crystal experiments. Our results indicate that the silica concentration in the fluids has different influences on the saturation indices of albite, anorthite, and K-feldspars in saline fluids, which significantly affect the replacement textures and porosity generation in crustal rocks.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00410-023-02088-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139437557","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":"Hawaiian postshield volcanism over the past 55 million years","authors":"Lauren N. Harrison,&nbsp;James S. Scoates,&nbsp;Dominique Weis","doi":"10.1007/s00410-023-02078-w","DOIUrl":"10.1007/s00410-023-02078-w","url":null,"abstract":"<div><p>The Hawaiian-Emperor chain, the surface expression of the Hawaiian mantle plume which has been active for at least 81 Ma, is divided into the Emperor Seamounts (81–47 Ma), Northwest Hawaiian Ridge (NWHR, 47–6 Ma), and Hawaiian Islands (&lt; 6 Ma). Hawaiian volcanism evolves through four volcanic stages: alkalic preshield, tholeiitic shield (80–90% volcano volume), alkalic postshield (∼1%), and silica undersaturated rejuvenated (&lt; 0.1%). Here, the elemental and isotopic compositions (Pb–Hf–Nd–Sr) of postshield basalts from 13 NWHR and one young Emperor Seamount volcanoes (~ 8.5 to 55 Ma) are investigated. NWHR postshield basalts tend to have more depleted isotopic signatures than shield basalts at the same volcano and exhibit Loa and Kea geochemical affinity identified in the shield stage. The seamounts Unnamed (33 Ma), Academician Berg (32 Ma), and Townsend Cromwell (~ 34 Ma) have the lowest ¹⁴³Nd/¹⁴⁴Nd and ¹⁷⁶Hf/¹⁷⁷Hf of the NWHR. This indicates a larger proportion of an enriched component in the source of these NWHR volcanoes compared to the younger volcanoes, likely tied to lower degrees of partial melting. The Loa-trend Daikakuji seamount (47.5 Ma) is distinctive and exhibits the most radiogenic Pb and Sr isotopic compositions observed in NWHR postshield basalts. The least radiogenic ⁸⁷Sr/⁸⁶Sr is from Jingū, a young (~ 55 Ma) Emperor Seamount volcano, and plots between the fields defined by Hawaiian Island postshield basalts and those erupted at the oldest Emperor Seamount (Detroit, ~ 76 Ma). These multi-isotopic trends highlight the different mantle source compositions required between the oldest Emperor Seamounts and the younger Hawaiiian basalts and support a direct compositional link between Hawaiian postshield lavas and their respective shield stages regardless of significant changes in magma flux, mantle potential temperature, absolute plate motion, and volcanic propagation rate over time.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139111916","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":"Trace element systematics of magnetite from alkaline mafic–ultramafic intrusions of the Permian Emeishan large igneous province, SW China","authors":"Zhen-Chao Wang,&nbsp;Xiao-Wen Huang,&nbsp;Ping-Ping Liu,&nbsp;Mei-Fu Zhou","doi":"10.1007/s00410-023-02087-9","DOIUrl":"10.1007/s00410-023-02087-9","url":null,"abstract":"<div><p>Trace element compositions of magnetite of alkaline mafic–ultramafic rocks were not previously studied but are potentially useful to constrain their petrogenesis and related metallogenesis. In the Permian Emeishan large igneous province, subalkaline mafic–ultramafic intrusions are widely distributed, but sparse alkaline counterparts are recognized, including the Mouding intrusion. The alkaline intrusions are mainly composed of clinopyroxenite, melteigite, jacupirangite, gabbro, syenogabbro, monzogabbro and monzonite. All these lithologies contain magnetite with composite, sandwich and trellis types of ilmenite intergrowths due to heterogeneous oxy-exsolution. Chromium contents of magnetite grains in the magnetite clinopyroxenite unit of the Mouding intrusion decrease from 1257 to 41 ppm within an 80 m interval, which can best be explained by the diffusion-controlled in situ crystallization in a crystal-liquid framework. Notably, magnetite grains from these alkaline intrusions are rich in Nb, Ta, Zr and Hf relative to those from subalkaline intrusions and iron oxide–apatite (IOA), iron oxide copper gold (IOCG) and porphyry deposits. This enrichment demonstrates that the high field strength elements (HFSE) are rich in the parental magmas of alkaline intrusions and have high partition coefficients between magnetite and alkaline magma. Our study demonstrates that magnetite grains in alkaline mafic–ultramafic intrusions have distinctively different trace element compositions from those in subalkaline intrusions, being useful tools in discriminating magma series and understanding the crystallization processes.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139096250","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":"Implications for metallogenic evolution of the giant Zhenyuan gold deposit (Yunnan, SW China) from textures and geochemical compositions of pyrite","authors":"Huichao Zhang,&nbsp;Nigel J. Cook,&nbsp;Hongrui Zhang,&nbsp;Zengqian Hou,&nbsp;Peng Chai,&nbsp;Wei Li,&nbsp;Sarah Gilbert","doi":"10.1007/s00410-023-02086-w","DOIUrl":"10.1007/s00410-023-02086-w","url":null,"abstract":"<div><p>Pyrite, the most common sulfide mineral, is a ubiquitous component of many hydrothermal gold deposits. Geochemical patterns within the refractory pyrite structure represent a valuable repository of information that can help constrain the sources of ore-forming materials, and the evolution of ore-forming processes over time. However, there are still a lot of debates on the mechanisms of physico-chemical processes in ore-forming fluid controlling trace element and sulfur isotope distributions in pyrite during growth. In our manuscript, we use cutting-edge complementary microanalytical methods to understand the origin and evolution of zoned gold-bearing pyrite in samples from the largest gold deposit in the Ailaoshan gold belt, SW China, Zhenyuan (exceeding 100t Au, average grade: 5.3 g/t). Pyrite, arsenopyrite, chalcopyrite, and stibnite are the most abundant sulfide minerals in most orebodies. Of these, pyrite is dominant and is also the most important host for gold. Two types of pyrite can be clearly distinguished: framboidal pyrite and hydrothermal pyrite. Gold is most commonly hosted by hydrothermal pyrite. Framboidal pyrite, mainly hosted by carbonaceous slate, hosts negligible Au, and features low δ³⁴S values ranging from − 35.0 (± 0.9) to − 25.6 (± 1.0)‰. Hydrothermal pyrite is characterized by complex intra-grain zoned textures with alternating As-rich and As-poor bands readily recognizable on backscattered electron images. Scanning electron microscopy and trace-element analyses show that both visible and invisible gold occur only in the As-rich bands. Compared to the As-poor bands (72.1% of Au concentration data &lt; 1.96 ppm, <i>n</i> = 43), the As-rich bands are characterized by far higher concentrations of Au (up to 1420 ppm), Cu, Ag, Sb, and Tl, but lower concentrations of Co and Ni. <i>In-situ</i> sulfur isotope analysis indicates that the δ³⁴S values of As-rich zones range from − 7.3 (± 0.6) to 2.9 (± 0.6)‰ and are similar to those of As-poor zones (from − 6.9 (± 0.7) to 2.8 (± 0.6)‰), but distinct from the framboidal pyrite. Combined with published fluid inclusion data and a probable age for the magmatic event associated with mineralization, these data suggest that magmatic–hydrothermal fluids contributed most ore-forming materials and that periodic boiling led to formation of the rhythmic As-rich and As-poor bands in pyrite. Our data for pyrite constrain the evolution of ore-forming processes and provide new insights into the formation of zoned pyrite, with the conclusions having broad implications for analogous hydrothermal gold deposits worldwide.</p></div>","PeriodicalId":526,"journal":{"name":"Contributions to Mineralogy and Petrology","volume":"179 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139079456","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}