Mineralogy and Petrology最新文献

{"title":"Victor diamonds – replacement of carbon and nitrogen in the central Superior Craton mantle root associated with the Midcontinent Rift event","authors":"Luisa D. V. Carvalho,&nbsp;Anetta Banas,&nbsp;Pamela Wescott,&nbsp;Mitchell Galarneau,&nbsp;Kelsey Graversen,&nbsp;Richard Stern,&nbsp;Ingrid Chinn,&nbsp;Heidi E. Höfer,&nbsp;Karlis Muehlenbachs,&nbsp;Matthew Steele-MacInnis,&nbsp;David Fisher,&nbsp;Julie Kong,&nbsp;Thomas Stachel","doi":"10.1007/s00710-025-00895-4","DOIUrl":"10.1007/s00710-025-00895-4","url":null,"abstract":"<div><p>We studied the δ¹³C-δ¹⁵N-[N] (with [N] = N concentration) characteristics of 129 diamonds from the Victor Mine, Canada, to constrain the mode of their formation and the source of their C and N. In addition, we provide new inclusion chemistry data (<i>n</i> = 22) principally from sulfide-bearing diamonds (<i>n</i> = 19). High Ni (&gt; 18 wt%) and detectable Cr (&gt; 0.06 wt%) clearly distinguish peridotitic from eclogitic sulfides in Victor diamonds. Coexisting silicate inclusions confirm the lherzolitic affinity of peridotitic sulfide-bearing diamonds. The C isotope characteristics of Victor peridotitic diamonds mostly fall within the typical mantle range (–5.0 ± 2‰) and N isotopes, despite a large range, also have a mantle-like mode (–7.2‰). Eclogitic diamonds are more variable in their δ¹³C and δ¹⁵N values and account for the most extreme values (δ¹³C down to –23‰; δ¹⁵N up to + 3.2‰) of the distribution. Core-rim trends of decreasing N content associated with variations in δ¹³C and δ¹⁵N are observed in a number of plates cut from peridotitic diamonds. These covariations can be modelled as diamond precipitation in a fluid-limited system, associated with Rayleigh fractionation, from both reducing (CH₄-bearing) and oxidizing (CO₂ or CO₃²⁻-bearing) fluids. Variations in δ¹³C, however, are typically close to analytical precision and the modelled fractionation trends suggest the unexpected operation of two distinct diamond-fluid N isotope fractionation factors (positive and negative). While our models are permissive of fractionation processes, they cannot provide proof for their operation and alternative interpretations, involving fluid evolution for reasons unrelated to diamond formation, cannot be excluded.</p></div>","PeriodicalId":18547,"journal":{"name":"Mineralogy and Petrology","volume":"119 3","pages":"379 - 393"},"PeriodicalIF":1.1,"publicationDate":"2025-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145167772","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Age and mantle source characteristics of kimberlite-derived zircons from Brazil revealed by U–Pb, Hf and O isotopes","authors":"Izaac Cabral-Neto,&nbsp;D. Graham Pearson,&nbsp;Excelso Ruberti,&nbsp;Yan Luo,&nbsp;Richard A. Stern,&nbsp;Rogério G. Azzone,&nbsp;Matthew F. Hardman,&nbsp;Vidyã V. Almeida,&nbsp;Francisco V. Silveira","doi":"10.1007/s00710-025-00917-1","DOIUrl":"10.1007/s00710-025-00917-1","url":null,"abstract":"<div><p>We report new U–Pb, Hf and O isotope data for zircon megacrysts from three kimberlites and diamondiferous areas in Brazil: Juína and Paranatinga kimberlite fields (Amazonian craton) and the Alto Paranaíba Igneous Province (APIP, São Francisco craton). A total of 253 mantle-derived zircon grains from kimberlites, diamondiferous streams, and diamond mines were analysed. Our U–Pb age data indicates four main age peaks for zircon that suggest kimberlite magmatism: ca. 78 and 86 Ma in APIP, 92 Ma in Juína, and 122 Ma in Paranatinga. Zircon Hf isotope signatures vary systematically with location: Juína and Paranatinga εHf_i values are + 4.2 to + 9.3; APIP range from − 11.0 to 0.0. There is minimal variability in zircon oxygen isotopes, most falling within 2SD (standard deviation) of the range for typical mantle zircons (5.3 ± 0.6‰). Zircons from Juína and Paranatinga have lower δ¹⁸O values (+ 5.12 to + 5.07‰) than those from APIP (+ 5.38‰). The contrasting Hf and O isotope compositions between zircons from the Amazonian and São Francisco cratons indicate parental magma origins that have experienced variable interaction with lithosphere after separating from a convecting mantle source. The Hf isotopic data indicate that zircon megacrysts from the Juína and Paranatinga kimberlite fields have signatures consistent with mildly depleted global kimberlites, pointing to either a more depleted (higher time-integrated Lu/Hf) mantle source, or that the parental melt interacted with mantle lithosphere with highly positive εHf characteristics. In contrast, APIP zircons display “enriched” low εHf_i characteristics, perhaps suggesting a source more influenced by interaction with metasomatized mantle lithosphere.</p></div>","PeriodicalId":18547,"journal":{"name":"Mineralogy and Petrology","volume":"119 3","pages":"607 - 625"},"PeriodicalIF":1.1,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145164151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Monazite, lanthanide-rich glasses, and other trace elements in copper smelter slags: constraints on critical metal behaviour in Si-Fe-rich melts","authors":"Hassan Gezzaz,&nbsp;Cristiana L. Ciobanu,&nbsp;Nigel J. Cook,&nbsp;Kathy Ehrig,&nbsp;Ashley Slattery,&nbsp;Benjamin Wade,&nbsp;Sarah Gilbert,&nbsp;Yuri T. Campo Rodriguez","doi":"10.1007/s00710-025-00897-2","DOIUrl":"10.1007/s00710-025-00897-2","url":null,"abstract":"<div><p>Furnace slags are potential new sources of critical metals. We undertook a micron- to nanoscale study that addresses speciation, distribution and associations of phases in air-cooled flash furnace (FF, oxidised) and electric furnace (EF, reduced) slags from the Olympic Dam mining-smelting-refinery operation. Results enable understanding of the behaviour and partitioning of critical metals between melt and cooling crystalline phases in a controlled smelter environment that mimics Fe-Si-rich systems in Nature. Melts at ~ 1300 °C result in slags that differ in the relative proportions of component phases. Both FF and EF slags comprise major magnetite and two, compositionally distinct Si-Fe-rich glasses (glass-1 and -2); fayalite is a main component of EF slag. Glass-1 is rich in REE + Y (4.5–5.4 wt%, Ce₂O₃ + La₂O₃) and contains dendritic monazite-(Ce). Glass-2 (~ 70 wt% SiO₂) contains &lt; 1 wt% Ce₂O₃ + La₂O₃. The EF slag reaction sequence is: magnetite <span>(rightarrow)</span> fayalite + glass-1 <span>(rightarrow)</span> monazite <span>(rightarrow)</span> glass-2. Immiscibility of REE-rich liquid from Si-Fe-rich melt is inferred from amorphous ‘monazite-like’ droplets. Chondrite-normalised fractionation patterns are defined by downwards-sloping LREE segments in both glasses. Partition coefficients are calculated for magnetite and fayalite relative to glasses. D_REY for HREE exceeds those for LREE in all phases and fayalite has an order of magnetite higher D_HREE than co-existing EF magnetite. Applying lattice strain models to experimental values show excellent fits for D_HREE-model trends, even if lattice strain is not the sole factor controlling partitioning. Melt polymerisation, variable/unpredictable oxidation states, and constraints from specific crystallographic sites, also impact on observed trends. This study provides clues to element behaviour in metallurgical plants that can assist potential utilization of copper smelter slags to meet the demand for REE and other contained critical metals.</p></div>","PeriodicalId":18547,"journal":{"name":"Mineralogy and Petrology","volume":"119 2","pages":"197 - 221"},"PeriodicalIF":1.1,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00710-025-00897-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145142316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Improved trace element discrimination of kimberlitic and carbonatitic zircon: implications for zircon origin in kimberlite and the search for superdeep diamonds","authors":"Matthew F. Hardman,&nbsp;D. Graham Pearson,&nbsp;S. Andy DuFrane,&nbsp;Izaac Cabral-Neto,&nbsp;Rogério G. Azzone,&nbsp;Qiao Shu,&nbsp;Jason Hinde,&nbsp;Alexei S. Rukhlov","doi":"10.1007/s00710-025-00916-2","DOIUrl":"10.1007/s00710-025-00916-2","url":null,"abstract":"<div><p>Zircon is a powerful pathfinder mineral for identifying igneous source rocks, including kimberlite and carbonatite. However, discrimination of zircons from these two lithologies is challenging due to their surprisingly limited published trace element data. Zircon megacrysts from kimberlite can have a wide range of U–Pb ages, from Archean to Eocene in some locations, raising questions about their origin. Here, we determined the trace-element compositions of 170 new zircon megacrysts from kimberlites, four from carbonate-rich olivine lamproites, five from ultramafic lamprophyres, one from a lamprophyre, and two from a mica-amphibole-rutile-ilmenite-diopside (MARID) xenolith. We also determined the trace-element compositions of 220 new zircons from global carbonatites and related rocks. The kimberlitic zircons in the present study are all megacrysts with a relatively narrow range of trace-element compositions whereas the new carbonatite zircons are compositionally diverse and likely reflect formation under varied geological conditions from a variety of heterogeneous sources, as well as complex equilibrium mineral assemblages. We apply random forest (RF) and discriminant projection analysis (DPA) to distinguish zircons from kimberlite and carbonatite from those in many crustal lithologies. DPA-based graphical methods employ these elements to allow rapid evaluation of zircon provenance using elemental data with an intuitive and interpretable interface. We further apply our compiled database to attempt to search for a compositional fingerprint, using machine learning, that might be capable of distinguishing megacryst zircons from kimberlites containing superdeep diamonds from those that do not. We provide a Microsoft Excel workbook for the rapid classification of zircons using DPA, and an R-based software package for the classification of zircons using RF.</p></div>","PeriodicalId":18547,"journal":{"name":"Mineralogy and Petrology","volume":"119 3","pages":"583 - 605"},"PeriodicalIF":1.1,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145162706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrothermal quartz veins with Bi-bearing sulfidic mineralization and Bi-tellurides at the Gemerská Poloma talc deposit, Spišsko-gemerské rudohorie Mts., Slovakia","authors":"Julián Kondela,&nbsp;Sebastián Hreus,&nbsp;Slavomír Tóth,&nbsp;Roman Farkašovský","doi":"10.1007/s00710-025-00898-1","DOIUrl":"10.1007/s00710-025-00898-1","url":null,"abstract":"<div><p>Epigenetic hydrothermal quartz veins with mineral associations of Bi-bearing sulfides and sulfosalts with Bi-tellurides penetrate the rock environment of the Gemerská Poloma talc-magnesite deposit in the Central Western Carpathians in Slovakia. The main exploited mineral is talc. The newly discovered occurence of quartz-sulfidic veins within the talc-magnesite deposit was studied in detail. The association of sulfosalts and sulfides is represented by the dominant minerals of the tetrahedrite group, bournonite, pyrite, cobaltite, and arsenopyrite together with less common to rare galena, minerals of the aikinite-bismutinite group (Naik 0.3 – 38.6—bismuthinite-pekoite-gladite), native bismuth, nuffieldite, cosalite and jonassonite. Later fluid contributions led to the formation of tellurides, which are represented by rare hedleyite and tetradymite associated with ikunolite. Mineral associations indicate that the deposit was invaded by multiple phases of mineralization. An open system between the granite and the talc carbonate body is indicated by the formation of zavaritskite, which occurred as a result of low-temperature F-rich fluids. Bismuth and fluorine are most probably from the underlying granite, but source of Au, Co, Ni and Te is not clear. Chemical and heat exchanges between the granite and the overlying carbonate body along the shear zone resulted in sulfide mineralization that was dominantly controlled by hydrothermal activity.</p></div>","PeriodicalId":18547,"journal":{"name":"Mineralogy and Petrology","volume":"119 2","pages":"175 - 196"},"PeriodicalIF":1.1,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00710-025-00898-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145142388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Clinotobermorite-related Cs2Ca4Si6O17 – the first cesium calcium silicate","authors":"Volker Kahlenberg","doi":"10.1007/s00710-025-00918-0","DOIUrl":"10.1007/s00710-025-00918-0","url":null,"abstract":"<div><p>In the course of a systematic investigation of the ternary system Cs₂O-CaO-SiO₂, a phase with the chemical composition Cs₂Ca₄Si₆O₁₇ was discovered. Synthesis experiments were performed using a starting mixture with an oxide ratio of Cs₂O:CaO:SiO₂ = 2:1:3 contained in a lid-covered platinum crucible. The educts were heated to 1000 °C at 2 °C/min, annealed at maximum temperature for two hours, and then cooled to 700 °C at 0.3 °C/min before final quenching in air to ambient conditions. The crystal structure was determined from a single-crystal diffraction data set collected at 15 °C using direct methods. The previously unknown compound crystallizes in space group <i>P</i> 2₁/<i>n</i> and has the following basic crystallographic data: <i>a</i> = 11.1053(7) Å, <i>b</i> = 7.3138(4) Å, <i>c</i> = 22.2609(15) Å, β = 98.289(6)°, <i>V</i> = 1789.2(2) ų and Z = 4. The final refinement calculations converged to R1 = 0.045 and wR2 = 0.106, for 2967 observed reflections with I &gt; 2σ(I). The silicate anions correspond to unbranched <i>dreier</i> double chains running along [010]. Charge compensation is achieved by the incorporation of cesium and calcium cations distributed over a total of six independent sites within the asymmetric unit. The calcium atoms are surrounded by six or seven oxygen atoms in the form of uncapped and monocapped trigonal prisms, respectively. The CaO₆- and CaO₇-polyhedra share common edges forming 7.5 Å wide sheets parallel (001), the presence of which is reflected in the pronounced platy morphology of the crystals. The cesium cations in turn have more irregular coordination environments involving seven and eight oxygen ligands. The crystal structure of Cs₂Ca₄Si₆O₁₇ shows a closer structural relationship with the MDO₁-polytype of clinotobermorite, which is discussed in detail. The structural investigations were complemented by the determination of the thermal expansion tensor for the temperature interval between - 80 °C and 15 °C.</p></div>","PeriodicalId":18547,"journal":{"name":"Mineralogy and Petrology","volume":"119 2","pages":"161 - 173"},"PeriodicalIF":1.1,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00710-025-00918-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145145697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Multistage diamond formation, mantle uplift and changing geothermal regimes recorded by inclusions in Kimberley diamonds","authors":"Paolo Nimis,&nbsp;Herman S. Grütter,&nbsp;Fabrizio Nestola","doi":"10.1007/s00710-025-00908-2","DOIUrl":"10.1007/s00710-025-00908-2","url":null,"abstract":"<div><p>Thermobarometry of composite peridotitic mineral inclusions in De Beers Pool diamonds (Kimberley, South Africa) has yielded puzzling results. Most non-touching inclusions record higher temperatures than touching inclusions, but both types record conditions colder than the Kimberley xenolith geotherm. Scenarios previously proposed to explain this discrepancy (lithosphere cooling after diamond formation, cooling of discrete diamond-growth pathways by slab-derived fluids, and diamond formation under various thermal regimes) fail to fully account for the observed thermobarometric outcomes. We propose an alternative scenario based on elastic theory of inclusion–host systems, which reconciles the contrasting pressure–temperature (<i>P–T</i>) estimates. Forward model calculations show that <i>P–T</i> conditions similar to those estimated for the touching inclusions can result from the development of overpressures on the inclusions. Our model requires initial diamond formation under conditions colder than a 35-mW/m² geotherm, followed by mantle uplift (~ 60 km, possibly multi-stage) and reequilibration on the Late Cretaceous xenolith geotherm (~ 40 mW/m²). The initial cold conditions could be promoted by foundering of shallow lithospheric materials. Consequent development of exsolution textures could favor entrapment of composite orthopyroxene–garnet inclusions in these early forming diamonds. The subsequent large uplift may be the result of Archean and possibly, in part, later tectonic events. The diamonds with the ‘warmer’ non-touching inclusions belong to one or more generations of uncertain age, which formed on a relaxed geotherm that was distinctly colder (~ 37 mW/m²) than the xenolith geotherm. Our proposed scenario may offer a generic explanation for sporadic cases of ‘cold’ touching inclusions reported at other localities.</p></div>","PeriodicalId":18547,"journal":{"name":"Mineralogy and Petrology","volume":"119 3","pages":"413 - 432"},"PeriodicalIF":1.1,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00710-025-00908-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145168707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Tales from diamond surface features – A tribute to Derek Robinson","authors":"David Phillips","doi":"10.1007/s00710-025-00911-7","DOIUrl":"10.1007/s00710-025-00911-7","url":null,"abstract":"<div><p>Diamonds entrained by kimberlites and olivine lamproites formed predominantly in peridotite and eclogite substrates within the lithospheric mantle. The main growth forms of monocrystalline diamonds are octahedral and cubic. However, many diamonds also exhibit a range of surface features derived during mantle residence and/or entrainment to surface. In pioneering research, Derek Robinson developed an interpretative catalogue of diamond morphologies and surface features, improving understanding of diamond growth, plastic deformation, oxidative etching and resorption processes, and the impacts of sedimentary transport and diamond recovery practices. He also established the sequence of events reflected in diamond physical characteristics. The etching and resorption surface features developed on diamonds provide important constraints on their exposure to oxidizing fluids (mainly CO₂, H₂O) in the mantle and/or kimberlite melt. There is broad consensus that common resorption features such as tetrahexahedroid (THH) forms result from interaction with H₂O-bearing kimberlite fluids. However, other surface features on trigonal octahedral faces (e.g., deep hexagonal pits, triangular plates) have been attributed to either pre-kimberlite mantle metasomatism or variations in kimberlite melt/fluid conditions. Evidence supporting mantle resorption includes cathodoluminescence (CL) imaging of internal diamond growth layers and rounded diamonds in some mantle xenoliths. As most diamonds in mantle xenoliths are typically sharp-edged with few etch features, the formation of specific surface etch features by pre- (or syn-) kimberlite mantle metasomatism is equivocal. Alternative explanations include limited ingress of kimberlitic fluids into host xenoliths during entrainment, ascent and/or emplacement, sampling of multiple diamond resorption groups from different pulses of kimberlite magma with distinct volatile compositions eruption/degassing histories.</p></div>","PeriodicalId":18547,"journal":{"name":"Mineralogy and Petrology","volume":"119 3","pages":"327 - 342"},"PeriodicalIF":1.1,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00710-025-00911-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145168128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Large irregular Type IIa and Type IIb diamonds: valuable sublithospheric gems that elude conventional indicators","authors":"Evan M. Smith,&nbsp;Ingrid Chinn,&nbsp;Suzette Timmerman","doi":"10.1007/s00710-025-00901-9","DOIUrl":"10.1007/s00710-025-00901-9","url":null,"abstract":"<div><p>Two diamond varieties are described in this review paper whose geological origin has only recently been illuminated. The first is large irregular Type IIa (nitrogen-poor) diamonds, which includes many famous, high-quality gems such as the Cullinan and the Koh-i-Noor. This variety has been named CLIPPIR (Cullinan-like, large, inclusion poor, pure, irregular, resorbed) diamonds based on their distinguishing overall characteristics. Metallic Fe-Ni-C-S melt inclusions, which are thought to represent the growth medium, are the most common material trapped within them, followed by Ca-silicates and low-Cr majoritic garnet. Heavy iron isotope signatures show the metallic melt evolves from a subducted protolith phase such as magnetite or metal alloys formed by serpentinization. The second diamond variety is Type IIb (nitrogen-poor and boron-bearing) diamonds, which are often blue in color, such as the Hope diamond. They tend to occur in deposits containing abundant CLIPPIR diamonds. Inclusions in Type IIb diamonds range from meta-basaltic to meta-peridotitic assemblages, similar to what has been documented previously in sublithospheric diamonds, including Ca-silicates, ferropericlase, retrogressed bridgmanite, stishovite, CF phase (a Na-rich aluminosilicate), low-Cr majoritic garnet, as well as metal alloys, sulfides, and oxides. Boron isotopes support a model whereby the hydrous phases in cold slab meta-serpentinites break down as the slab warms, releasing boron and hydrous fluids that contribute to diamond growth. CLIPPIR and Type IIb diamonds are both established as sublithospheric (superdeep) and their formation involves the subduction of cold, seawater-altered oceanic lithosphere to the mantle transition zone and uppermost lower mantle. These diamonds can contribute significantly to mine revenue but are difficult to detect and predict because they do not correlate with conventional indicator minerals or with other diamonds, including micro-diamonds. Geochronology suggests that sublithospheric diamonds ascend in buoyant packages of rock and reside at the base of the continents before being sampled by kimberlites. CLIPPIR and Type IIb diamonds at surface might be accompanied by distinct sublithospheric indicator xenocrysts or signatures, though these may evolve and re-equilibrate during upper mantle storage. Exploration for sublithospheric diamond potential should focus on indicator minerals from the base of the lithosphere and the possibility of an accreted layer.</p></div>","PeriodicalId":18547,"journal":{"name":"Mineralogy and Petrology","volume":"119 3","pages":"305 - 325"},"PeriodicalIF":1.1,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145163010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 Sequoia kimberlite complex, central Slave Craton – A new superdeep diamond location","authors":"Luísa D.V. Carvalho,&nbsp;Buddy Doyle,&nbsp;Thomas Stachel,&nbsp;Richard Stern,&nbsp;Matthew Steele-MacInnis,&nbsp;Fabrizio Nestola,&nbsp;D. Graham Pearson","doi":"10.1007/s00710-025-00899-0","DOIUrl":"10.1007/s00710-025-00899-0","url":null,"abstract":"<div><p>We present the first study of 73 micro- and macro-diamonds and their inclusions from the Sequoia kimberlites, Central Lac de Gras kimberlite field, NWT. Nitrogen aggregation systematics show the presence of a diamond population that resided in the mantle at high temperatures (&gt; 1250 ºC; 17% of all Type I diamonds), plus a high proportion of Type II diamonds (26%). Raman analysis of mineral inclusions in 24 diamonds reveals that the Sequoia kimberlites sampled both lithospheric (19 diamonds) and sublithospheric (5 diamonds) mantle sources. Olivine crystals coexisting with minerals characteristic of retrogressed sublithospheric assemblages display an extreme shift in Raman peak positions, indicating high pressure of entrapment. In one diamond, we observed the typical X-ray diffraction reflections of preserved ringwoodite, indicating the coexisting olivine identified by Raman is retrogressed. The preserved ringwoodite was stable in the transition zone. Lithospheric diamonds are of peridotitic affinity and the presence of clinopyroxene inclusions indicates sampling of possibly younger, less depleted portions of the mantle beneath Lac de Gras. Eight percent of the studied diamonds are fibrous and trap mineral micro-inclusions derived from peridotitic substrates. The diamond C and N isotope compositions are generally within typical mantle values, but the δ¹³C variability significantly exceeds the mantle range to both lower and higher values. Diamond internal variations in δ¹³C-δ¹⁵N exceeding the mantle range document the influence of subducted fluids in diamond formation. This first look at Sequoia diamonds underlines the need for exploration approaches that assess the presence of lherzolitic and sublithospheric-derived diamonds during indicator mineral assessment.</p></div>","PeriodicalId":18547,"journal":{"name":"Mineralogy and Petrology","volume":"119 3","pages":"395 - 409"},"PeriodicalIF":1.1,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145161546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}