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Magmatic Ni-Cu-platinum group element (PGE) deposits are commonly located in tectonically active regions that typically undergo significant deformation and metamorphism and subsequent reworking of sulfide. The Munali Ni deposit is hosted by a dynamic intrusive mafic-ultramafic system situated within the Zambezi belt in southern Zambia. The deposit comprises Fe-Ni–dominant magmatic sulfides, present as a number of lenticular massive sulfide bodies that display a variety of magmatic and metamorphic sulfide textures. The sulfide lenses are uniformly deficient in iridium subgroup PGEs (IPGEs), Au, and Cu, with unusual but characteristically high bulk Ni/Cu ratios (~10) and a consistent precious metal mineral assemblage dominated by Pd and Pt tellurides. On a centimeter to meter scale, Cu tenors and Ni/Cu ratios are extremely variable (Ni/Cu between 0.1 and 71.5), while Ni and Pd tenors are consistent, indicative of the high mobility and variable concentrations of Cu sulfide within the deposit. Sulfur isotope signatures of the ore sulfides (δ34S ~6‰; Δ33S ~0‰) indicate a local crustal S contaminant from host marbles yet display S/Se ratios suggestive of a postmagmatic overprint. The consistent geochemical similarities of the bulk sulfide throughout the complex and the absence of primary silicate-sulfide textures suggest that the Munali ores were not sourced from a parental magma directly represented by units within the complex. Instead, it is suggested that the sulfide liquid was introduced from elsewhere in the magmatic system during the later stages of the emplacement of the complex. Fractional crystallization of the sulfide liquid during emplacement resulted in the primary segregation of a Cu-rich residual liquid that migrated away from the bulk of the Fe-Ni sulfide, accounting for the high bulk Ni/Cu ratio, with the potential for the accumulation of a separate and thus far undiscovered Cu orebody. In addition, intense deformation during the Pan-African orogeny and interaction with hydrothermal fluids have locally overprinted some of the primary magmatic textures, resulting in localized sulfide mobilization and the extreme variations of Ni/Cu ratio between sulfide samples. Munali therefore represents a complex dynamic deposit showcasing a variety of mechanisms for sulfide fractionation of an Ni-Cu-PGE orebody by both syn- and postmagmatic processes.

The volatile transfer in subduction zones and the role of sulfate as a vector for the mobilization of oxidized components from down-going slabs remain hotly debated issues. Orogenic spinel and garnet peridotite lenses from the Ulten Zone (Eastern Alps, Italy), exhumed as part of felsic metamorphic terranes in continental collision zones, bear witness to mass transfer processes in these pivotal environments. In this study, we carried out a multi-method investigation of mantle sulfides coexisting with four generations of carbonates, indicating coupled sulfur and carbon mobility throughout the peridotites’ metamorphic evolution as part of the Variscan subduction architecture. Detailed petrography, bulk rock measurements, in situ chemical and geochemical analyses of sulfides as well as Sr isotope analyses of associated clinopyroxene and amphibole are combined with the aim to constrain the origin, nature and effect of multiple C-O-H-S-bearing fluids and melts the peridotites interacted with. The first, pre-peak, metasomatic pulse (Stage 1) is represented by an H2S-CO2-bearing melt from the subduction-modified hot mantle wedge, which formed a pyroxenite layer hosting matrix pentlandite with δ34S of +2.77‰. Matrix carbonates occasionally occur in the coarse-grained peridotite under eclogite-facies conditions (Stage 2), with heavier δ34S (up to +3.43‰), radiogenic Sr (87Sr/86Srclinopyroxene > 0.7052) and elevated Pb abundances. These are ascribed to interaction with isotopically heavy melts carrying recycled crustal component, permissive of, but not requiring, involvement of oxidized S species. Conversely, isotopically lighter matrix pentlandite (δ34S = −1.62 to +0.67‰), and radiogenic Sr in amphibole (87Sr/86Sr = 0.7056) and associated dolomite (published data) from fine-grained garnet-amphibole peridotites may point to involvement of H2S-CO2-bearing crustal fluids, which variably equilibrated with the mantle before interacting with the peridotites. The post-peak Stage 3 marks the entrapment of peridotites into a tectonic melange. Here, kelyphitization of garnet is catalyzed by further ingress of a S-bearing fluid (δ34S = −0.38‰), while carbonate veining with occasional sulfides bear witness to channelized fluid flow. Sulfide and amphibole grains in retrogressed spinel peridotites reveal the highest contents of fluid-mobile elements (As, Sb) and 87Sr/86Sramphibole up to 0.7074, suggesting late interactions with isotopically heavy crustal fluids at high fluid-rock ratios. Textural observations indicate that, during Stage 4, serpentinization of peridotites at low ƒS2 played an active role not only in CO2 release by conversion of dolomite to calcite + brucite intergrowths, but also in local removal of 32S during the final exhumation stage. Late channelized sulfur remobilization is evidenced by the serpentine + magnetite (±millerite ± calcite) vein carrying > 300 ppm S. Overall, the relatively narrow range of sulfur isotope composition (δ34S = −1.62 to +3.76‰) is indicative of limited interaction with isotopically heavy crustal liquids, and points to a subordinate role of subduction-derived sulfate throughout the extended fluid(melt)/rock evolution of the Ulten Zone peridotites, first in the mantle wedge and then as part of a tectonic melange.

The Yilgarn Craton and its northern margin contain a variety of petrogenetically poorly defined small-volume alkaline ultramafic rocks of Proterozoic age. This study documents the petrography, mineral and bulk-rock geochemistry and Nd-Hf-Sr-Pb isotope compositions of a selected suite of these rocks. They comprise ~2.03–2.06 Ga ultramafic lamprophyres (UML) and carbonatites from the Eastern Goldfields Superterrane (EGS), ~0.86 Ga UML from Norseman, and orangeites from the Earaheedy Basin, including samples from Jewill (~1.3 Ga), Bulljah (~1.4 Ga) and Nabberu (~1.8–1.9 Ga). The Proterozoic UML and carbonatites from the EGS and Norseman display very consistent chondritic to superchondritic Nd-Hf isotope compositions and trace-element ratios similar to modern OIBs, which are indicative of a common mantle source across this wide alkaline province. These Nd-Hf isotope compositions overlap with the evolution trends of global kimberlites through time, thus suggesting that this mantle source could be deep and ancient as that proposed for kimberlites. Conversely, the orangeites located in the Earaheedy Basin along the northern margin of the Yilgarn Craton display trace element signatures similar to subduction-related calc-alkaline magmas. Taken together with their highly enriched Sr-Nd-Hf isotope compositions, these characteristics indicate an ancient lithospheric mantle source, which was probably metasomatised by subduction-related fluids. As the ages of the Bulljah and Jewill orangeites overlap with the breakup of the Columbia supercontinent, it is proposed that orangeite magmatism was triggered by changes in plate stress conditions associated with this event. This study provides a comprehensive picture of the genesis of Proterozoic alkaline magmatism in the Yilgarn Craton, highlighting the complex tectono-magmatic evolution of this lithospheric block after its assembly in the Archean.

The Proterozoic rock record displays secular change from ferruginous to an oxic hydrosphere over the course of 2 billion years; however, debate continues on the periodicity, rate of change and steps in following atmospheric oxygenation that ultimately led to an oxygenated ocean. This is partly due to poor preservation of the Paleoproterozoic marine sedimentary record in the few hundred million years after the Great Oxidation Event. Whereas the 2.0 Ga rock record preserves only rare chemical sediments, it contains significant mafic igneous provinces, which are known to locally host volcanogenic massive sulfide (VMS) deposits. These hydrothermal environments fossilize the ancient interaction at the seafloor interface between volcanic rocks and seawater. In this context, the 2.01 Ga Degrussa VMS deposit of the Paleoproterozoic Capricorn Orogen, Western Australia offers an opportunity to probe the ancient ocean composition. The Degrussa VMS deposit preserves massive sulfide mineralisation (pyrite – chalcopyrite – pyrrhotite ± sphalerite ± galena) hosted in turbiditic sedimentary rocks interlayered with basaltic flows and cut by numerous gabbroic sills. Exhalite layers are composed of hematite and jasper associated with magnetite. This study documents the multiple sulfur isotope composition of the Degrussa VMS deposit through an integrated analytical approach, which comprises bulk fluorination gas chromatography isotope ratio mass spectrometry and in situ secondary ion mass spectrometry. By comparing the ultra-high precision bulk measurements (n = 21) with in situ measurements of variably-textured grains of pyrite, chalcopyrite and pyrrhotite (n = 252), we determine that VMS mineralisation yields δ34S between +2‰ and +5‰ with a peak at ∼+2.9‰, and negative Δ33S signal ranging from −0.08 to 0.00‰. A two component δ34S-Δ33S mixing model indicates 11% of H2S derived from thermochemically reduced seawater sulfate mixed with magmatic H2S. The most negative Δ33S values must be explained by interaction with sulfate in the near-surface, undergoing complex dissolution-reprecipitation reactions, necessitating a minimum seawater sulfate reservoir of ∼2 mmol/L, or 7% modern seawater at 2.01 Ga.

The Kanowna Belle deposit is a world-class Archean orogenic gold system that witnessed multiple fluid episodes over a protracted deformation history. The hydrothermal fluid circulation episodes at the Kanowna Belle deposit initiated with the precipitation of early gold-bearing carbonate-famatinite-pyrite-telluride-electrum veins (V1a). These early veins were subsequently folded during a NE-SW shortening event (D1bKB) that led to the development of sericite-chlorite-pyrite stringers (V1b) and foliation (S1KB) dated at c. 2658 ± 9 Ma (U-Pb, xenotime). D1bKB structures are overprinted by quartz-carbonate-sericite-pyrite-gold veins (V2) controlled by the reverse faulting formed as a result of N-S shortening during D2KB. A subsequent deformation event (D3aKB) is related to sinistral shearing produced under ENE-WSW shortening and associated with the development of the Troy lodes and deposition of quartz-pyrite-sericite-gold veins (V3a) dated at c. 2628 ± 9 Ma (U-Pb, xenotime). The application of multiple sulfur isotope analyses of sulfides related to the different mineralization events resolves the hydrothermal fluid isotopic evolution through time. Despite the ore mineralogy differences of the V1, V2, and V3 vein sets, their associated sulfides yield small positive ∆33S (+ 0.1 to + 0.4‰; n = 231) values with two outliers (∆33S = + 0.5‰ and + 0.6‰) across all lithology types. The constant value of MIF-S through the three temporally different gold mineralization episodes implies that sulfur was derived from a single homogenized source of sulfur distal from the deposition site, irrespective of the Au endowment. The consistent small positive ∆33S sulfur isotope signature may support that the Archean orogenic gold system sourced sulfur and possibly hydrothermal fluids from a mantle/magmatic dominated source that homogenized with crustal sulfur at depth prior to gold deposition.

The anticoccidial activity of thymol, carvacrol, and saponins was assessed in an in vitro model of coccidiosis. Eimeria spp. sporozoites were collected from field samples, characterized and used for 2 different invasion assays on Madin-Darby Bovine Kidney cells (MDBK). The cells were challenged with 5 x 104 sporozoites without (control) or with various treatments: saponins (10 ppm), thymol and carvacrol (7 ppm each), or a combination of saponins, thymol, and carvacrol at 2 doses; MIX 1 (saponins 5 ppm, thymol 3.5 ppm and carvacrol 3.5 ppm) and MIX 2 (saponins 10 ppm, thymol 7 ppm and carvacrol 7 ppm). The treated cells were incubated at 37°C for 24 hours (invasion assay 1) and for 2, 24, and 48 hours (invasion assay 2). The efficiency of invasion was determined by counting the sporozoites left in the supernatant that were not able to invade the cells, while intracellular Eimeria DNA was detected by qPCR to confirm the data. Data were analyzed with ANOVA and differences were considered significant when p-value was ≤ 0.05. Data from invasion assay 1 showed that the thymol and carvacrol-containing blends significantly reduced invasion, especially in combination with saponins at the highest dose. Saponins alone did not have a strong inhibiting activity but acted synergistically with the other molecules. Interestingly, in invasion assay 2 it was found that the effect of the highest dose of the blend of saponins, thymol and carvacrol was already visible at 2 hours post infection, while the other treatments were significantly successful at 24 hours post infection. The invasion assay protocol was designed to screen molecules in vitro starting from field fecal samples and it can respresent a potential tool in Eimeria research. Moreover this study shows that invasion in MDBK cells by Eimeria sporozoites is inhibited in presence of thymol, carvacrol and saponins, thus highlighting the anticoccidial potential of these compounds.

The shallow marine and subaerial sedimentary and hydrothermal rocks of the ~3.48 billion-year-old Dresser Formation are host to some of Earth's oldest stromatolites and microbial remains. This study reports on texturally distinctive, spherulitic barite micro-mineralization that occur in association with primary, autochthonous organic matter within exceptionally preserved, strongly sulfidized stromatolite samples obtained from drill cores. Spherulitic barite micro-mineralization within the sulfidized stromatolites generally forms submicron-scale aggregates that show gradations from hollow to densely crystallized, irregular to partially radiating crystalline interiors. Several barite micro-spherulites show thin outer shells. Within stromatolites, barite micro-spherulites are intimately associated with petrographically earliest dolomite and nano-porous pyrite enriched in organic matter, the latter of which is a possible biosignature assemblage that hosts microbial remains. Barite spherulites are also observed within layered barite in proximity to stromatolite layers, where they are overgrown by compositionally distinct (Sr-rich), coarsely crystalline barite that may have been sourced from hydrothermal veins at depth. Micro-spherulitic barite, such as reported here, is not known from hydrothermal systems that exceed the upper temperature limit for life. Rather, barite with near-identical morphology and micro-texture is known from zones of high bio-productivity under low-temperature conditions in the modern oceans, where microbial activity and/or organic matter of degrading biomass controls the formation of spherulitic aggregates. Hence, the presence of micro-spherulitic barite in the organic matter-bearing Dresser Formation sulfidized stromatolites lend further support for a biogenic origin of these unusual, exceptionally well-preserved, and very ancient microbialites.

—The exposures, structure, mineralogy, and composition of unusual sulfide-bearing troctolites from the Yoko-Dovyren layered intrusion in the northern Baikal area (Russia) are described in detail for the first time. The troctolite succession (referred to as the Konnikov Zone) is characterized by the presence of pegmatoid poikilite sulfides and sulfide dissemination with diverse PGE mineralization. The former are dominated by pyrrhotite–troilite products of exsolution of monosulfide solid solution (mss), and the latter is composed mostly of cubanite–chalcopyrite assemblages produced from an intermediate Ni–Cu–Fe solid solution (iss). The positive covariations between the contents of sulfur and chalcogens (Se, Te) along with the sublinear dependence of the Pd, Pt, Au, and Cu contents on the Te contents indicate a sulfide control of the distribution of these elements in troctolite cumulates. According to the sulfide-normalized contents of these elements in rocks, the average “100% sulfides” in the samples are subdivided into two groups: (1) strongly depleted in PGE, Au, Cu, and Te and (2) with 10–50-fold enrichment in them. This division is consistent with the morphological and mineralogical differences between the groups. Of genetic significance is the fact that the mss assemblages are somewhat poorer in PGE and Te than the primitive sulfides from the Dovyren basal zone, whereas the assemblages with predominant copper sulfides are significantly richer in these elements. This fact is confirmed by LA-ICP-MS data on the trace-element composition of the sulfide phases. The established specific features indicate a limited scale of fractionation of immiscible sulfides during the solidification of the troctolite cumulates. The formation of PGE- and Te-rich assemblages can be related to the course of crystallization of a sulfide precursor similar to the most primitive sulfide liquid. This is consistent with the known laws of crystallization of sulfide systems and explains the abnormally high S/Te ratios in pegmatoid troctolites enriched in mss products. Thus, sulfide melts act as an agent that transports precious metals and chalcogens in the troctolite cumulate area. This conclusion requires specification of the physical mechanisms and parameters (rheology, permeability, wettability by sulfides of different phases, etc.) of the cumulus medium favoring the spatial separation of a monosulfide solution and Cu-containing PGE-rich fractions with their subsequent infiltration and deposition at the boundaries of critical low permeability.

Light element data are required for robust and accurate lithogeochemical interpretations and are important components in the study of hydrothermal alteration and mineralization processes. In this contribution we review the latest available portable energy dispersive X-Ray Fluorescence (pXRF) technologies exclusively in the context of light element analysis, with focus on the acquisition of data for Na, Mg, Al and Si. We discuss pXRF hardware design limitations, quantify variables that attenuate X-ray energies through numerical modelling, including common pXRF configurations, and empirically investigate modern pXRF technologies used to mitigate X-ray attenuation and improve light element analysis. The void between the sample and detector is a key issue regarding the success of pXRF light element analysis. Dry-air (normal conditions), vacuum purge and helium flush systems are evaluated. Modelled data that use a nominal sample-detector void of 10 mm show that using helium in lieu of air improves X-ray transmission effectiveness from ≈2% to ≈99% for Na and ≈10% to ≈100% for Mg. Modelled detector window data show that using a graphene detector window in lieu of a traditional beryllium detector window improves X-ray transmission effectiveness for Na from ≈38% to ≈64% and ≈57% to ≈77% for Mg. Progressive X-ray transmission effectiveness equates to ≈63% Na and ≈76% Mg when using a helium-graphene pXRF configuration v. ≈1% for Na and ≈6% Mg when using a traditional in-air beryllium pXRF arrangement (i.e. without sample or X-ray entrance window media). Empirically determined improvements of the resolved signal are more modest than those of modelled X-ray transmission effectiveness data. Instrument noise, spectral overlaps and random counting errors are unavoidable and inherent with the limitations of modern detector technologies. However, the employment of helium with graphene detector window technology allows very precise data to be obtained at significantly shorter scan times (i.e. 20 s, instead of the traditional 60–180 s, i.e. 3–9 times faster): a scan time of 20 s can achieve a precision of ≈18% @ ≈0.4% Na and ≈8% @ ≈0.3% Mg for elemental interference-free samples. Precision will improve with increasing analyte concentration.

Magmatic arcs are terrestrial environments where lithospheric cycling and recycling of metals and volatiles is enhanced. However, the first-order mechanism permitting the episodic fluxing of these elements from the mantle through to the outer Earth’s spheres has been elusive. To address this knowledge gap, we focus on the textural and minero-chemical characteristics of metal-rich magmatic sulfides hosted in amphibole-olivine-pyroxene cumulates in the lowermost crust. We show that in cumulates that were subject to increasing temperature due to prolonged mafic magmatism, which only occurs episodically during the complex evolution of any magmatic arc, Cu-Au-rich sulfide can exist as liquid while Ni-Fe rich sulfide occurs as a solid phase. This scenario occurs within a ‘Goldilocks’ temperature zone at ~1100–1200 °C, typical of the base of the crust in arcs, which permits episodic fractionation and mobilisation of Cu-Au-rich sulfide liquid into permeable melt networks that may ascend through the lithosphere providing metals for porphyry and epithermal ore deposits., The presence and mobility of metal-rich sulfides in lower crustal magma chambers can act as a gateway for metals to be trapped, or released into ascending magmas that are then able to form upper crustal porphyry copper and gold deposits.

Cretaceous kimberlites in southern Africa have been suggested to host deeply subducted material in their mantle sources based on radiogenic isotope systematics. However, potential subducted material contributions to the volatile budget, including sulfur, of these kimberlites is unclear. Here we report new petrographic, geochemical, and isotopic data on sulfides and sulfates in sub-volcanic kimberlites from Kimberley, South Africa. The examined kimberlites were divided into four groups based on their sulfide mineralogy, sulfur contents, and isotopic compositions. None of these groups exhibit clear signs of mass-independent fractionation. Three samples contain sphalerite, have moderate bulk-sulfide S concentrations (203-329 mu g/g) and highly negative bulk-sulfide delta S-34 values (-10 to -13 parts per thousand). Four samples have moderate-to-high bulk-sulfide S contents (220-745 mu g/g), positive delta S-34(sulfide) values (+0.2 to +14 parts per thousand), and contain galena, pyrite or secondary Cu-sulfides as the dominant sulfides. These groups of S-rich kimberlites were probably contaminated by fluids sourced from local country rocks. The remaining eight samples contain negligible amounts of crustal sulfides (e.g., sphalerite, galena), have lower bulk-sulfide S concentrations (, Geochemistry, Geophysics, Geosystems, 22 (11), ISSN:1525-2027

We present a refined approach for acquiring sulfur (S) isotope compositions (33S/32S, 34S/32S) in apatite by secondary ion mass spectrometry (SIMS), including the characterisation of new reference materials. In order to test the method, we analyzed potential apatite reference samples for their S isotope ratios via three different bulk methods. The investigated apatite samples contain S concentrations between ~160 μg/g and 3100 μg/g and their 34S/32S (δ34S) ratios deviate by more than 25‰ from the Vienna-Canyon Diablo Troilite (VCDT) standard. We identified four candidates as new primary reference materials for routine SIMS S isotope measurements of apatite. Based on ICP-MS, EA-IRMS, and fluorination analyses, recommended S isotope values are +12.27± 0.22 (2σ) ‰ δ34S for SAP1, +14.02 ± 0.22 (2σ) ‰ δ34S for Big1, −1.06 ± 0.80 (2σ) ‰ δ34S for Durango-A, and −1.39 ± 0.48 (2σ) ‰ for Durango-B. By selecting one of those four primary standards for SIMS analysis, the S isotope values of the other reference materials and additional tested apatite specimens can be reproduced to within 1‰. Under optimized SIMS conditions, single spot uncertainty for δ34S that combines the within-spot precision and the repeatability of measurements of the primary apatite reference material during an analytical session is ±0.4‰ (95% CI). We also show that in apatite with S > 1000 μg/g, SIMS analysis permits the detection of mass-independent S isotope signatures (i.e., Δ33S) that are larger than ~1.0‰ if an average of multiple grains is used, and larger than ~1.5‰ for a single analytical point. Furthermore, our study shows that apatite can record S isotope signatures from extremely diverse environments, making this near-ubiquitous mineral a key candidate for tracing S source reservoirs and to track the pathway of magmatic-hydrothermal fluids in a wide range of geological settings.

We present the results of a comprehensive study on the concentrations of first-row transition elements (FRTE: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn), as well as Ga and Ge, in liquidus olivine from 2.7–3.5 Ga old Al-undepleted and Al-depleted komatiites from the Kaapvaal and Zimbabwe Cratons in southern Africa, the Yilgarn Craton in Australia, and the Superior Craton in Canada. The sample set includes komatiites that remained sulfur-undersaturated upon emplacement, as well as komatiites that reached sulfide saturation owing to assimilation of crustal sulfur.All olivine grains display concentrations of Mn, Zn, Ge, Co, Fe, Mg, and Ni similar to the Bulk Silicate Earth (BSE) values, with significant negative anomalies in Sc, Ti, V, Cr, Ga, and Cu. Olivine from the studied Al-depleted komatiites displays on average higher 100×Ga/Sc ratios (>5) than olivine from Al-undepleted komatiites (≤5). Because garnet preferentially incorporates Sc over Ga, the data suggest that elevated Ga/Sc ratios in komatiitic olivine are indicative of garnet retention in the source region of komatiites, highlighting the potential of olivine trace element chemistry as a proxy for the depth of komatiite melting and separation of the magma from the melting residue. Copper concentrations in the studied olivine grains are controlled by sulfur saturation of the host komatiite during olivine crystallization. Olivine from sulfur-undersaturated komatiite systems displays Cu concentrations mostly between 1 and 10 ppm, whereas olivine from sulfide-bearing komatiites has Cu contents of Olivine from the Paleo-Archean (3.5–3.3 Ga) komatiites displays overall higher V/Sc ratios (V/Sc = 2.1 ± 0.96; 2 S.D.) than olivine from their Neo-Archean (2.7 Ga) counterparts (V/Sc = 1.0 ± 0.81, 2 S.D.). Vanadium and Sc behave similarly during partial melting of the mantle and are similarly compatible in majorite garnet. However, V is redox-sensitive and its compatibility in olivine increases as the system becomes less oxidized, whereas Sc is redox-insensitive. We argue that olivine from the studied Paleo-Archean komatiites crystallized from more reduced magmas than their Neo-Archean counterparts. Elevated Fe/Mn ratios in olivine from Paleo-Archean komatiites mimic the V/Sc signatures and are interpreted to reflect that Fe2+ is more compatible in olivine than Fe3+. These results imply that V/Sc and Fe/Mn in komatiitic olivine may potentially provide insight into the evolution of the oxidation state of the Archean mantle. Additional studies that integrate the chemistry of komatiitic olivine with those of relict interstitial glass and melt/fluid inclusions are encouraged to fully understand and quantify the potential of FRTE in olivine as a proxy for the oxidation state of the mantle sources of komatiite magmas.

This study investigates the prospectivity for porphyry Cu mineralisation of the early Paleozoic Loch Lilly-Kars Belt, which follows the southern margin of the Paleoproterozoic Broken Hill (...

The Black Swan Succession consists of an Archean bimodal dacite-komatiite association largely dominated by ultramafic cumulates hosting a number of massive and disseminated magmatic sulfide orebodies. Although it was affected by multiple alteration events, the low degree of penetrative deformation allowed the preservation of magmatic textures and stratigraphic relationships. In this context, we apply a combined multiple sulfur isotope and microchemical approach to unravel the potential of sulfides to simultaneously retain information about their magmatic and hydrothermal history. Negative Δ33S signatures in both massive (− 0.56‰) and disseminated (− 0.66‰) sulfide orebodies reflect the assimilation of photochemically derived sulfur into the komatiite magma, which attained sulfide liquid supersaturation through the assimilation of crustal material analogous to the intercalated breccia dacite hosting colloform sulfides (Δ33S = − 0.91‰). The slightly different Δ33S signatures between disseminated and massive orebodies reflect the assimilation of different proportions of crustally derived sulfur, and imply that the respective sulfide liquids segregated from distinct komatiite magma pulses. Subsequent alteration episodes imparted to the Black Swan Succession a concentric zonation consisting of a serpentinite core and talc-carbonate margins. The Black Swan disseminated orebody extends through both alteration styles without major variations in the dominant millerite-pyrite sulfide assemblage. Pyrite in both serpentinite and talc-carbonate samples exhibits a consistent trace element signature suggesting a relative immobile behavior of Ni and Co during the percolation of the talc-carbonate fluids. Conversely, variable δ34S signatures between the two alteration styles reflect mobilization of sulfur during talc-carbonate alteration. Whereas the 2‰ range of δ34S values in serpentinites can be attributed to moderate equilibrium fractionation processes, the 10‰ range of δ34S values in talc-carbonate rocks suggests that highly oxidizing fluids promoted the mobilization of sulfur as SO42−, which decreased the δ34S of the disseminated sulfides. Furthermore, sulfur isotope and microchemical signatures of euhedral pyrite from intercalated dacitic breccia indicate that this pyrite generation was deposited from a late hydrothermal event, which is characterized by variable and least negative Δ33S signatures (between − 0.20‰ and − 0.48‰) relative to all sulfide orebodies. These features suggest that the late fluids developed in a heterogeneous hydrothermal system with a minor component of sulfur recycled from the sulfide orebodies.

Dimensionality reduction provides a simple, two-dimensional representation of multi-element geochemical assays, which facilitates visualisation of complex data and enhances their interpretation. A recently proposed dimensionality reduction algorithm, namely t-distributed stochastic neighbour embedding (t-SNE), generates effective two-dimensional representations of a wide range of datasets based on pairwise statistical distances of the input. However, direct application to multi-element geochemical assays has been shown to produce representations which can fail to separate specimens by a desired geological property, such as state of hydration. Since t-SNE is a statistical distance-based method, these sub-optimal representations may be due to the presence of dimensions (i.e., elements) irrelevant to the desired property—an issue often termed the ‘curse of dimensionality’. To address this shortcoming, t-SNE was applied to (i) 31 elements in a geochemical assay database covering 16 000 drill core intervals intersecting the Kevitsa mafic-ultramafic intrusion (Lapland, Finland); and (ii) a subset of 11 elements capable of discriminating between unaltered and altered host rock specimens, as determined by a Random Forest classifier within a recursive feature elimination framework. The resulting representation more effectively separates altered and unaltered specimens, and we demonstrate that it produces more favourable representations than alternative well-known methods (namely, a self-organising map and principal components analysis) applied to the same dataset. We also demonstrate that the proposed t-SNE representation is applicable for re-logging of the specimens' alteration state as logged by geologists, and in particular provides visual insight into the labels suggested by a black box statistical re-logging algorithm.

Dyke intrusion is a highly dynamic process with seismicity preceding and accompanying magma emplacement on timescales of hours to days. Recent surveys of microseismicity indicate shear failure along fault planes parallel to the orientation of intruding dykes. However, the precision of earthquake hypocentre locations is typically limited to tens or hundreds of meters and cannot resolve whether the hypocentres relate to strain of wall rock fragments within the dykes, fault damage around the intrusions or peripherally in the country rock. Here we present high-resolution three-dimensional (3D) reconstructions of outstanding coastal exposures of a swarm of 19 dolerite dykes, near Albany, Western Australia using an unmanned aerial vehicle and Structure-from-Motion photogrammetry. It is observed that the number of faults and joints increases towards the dyke swarm, which, alongside mutually overprinting relationships, indicate that dyke emplacement and faulting were coeval. The faults contain cataclasites and are parallel to the dykes. In contrast, Mohr–Coulomb theory predicts shear failure on strike-parallel faults inclined ∼30° to the dyke plane. The faults and joints form a damage zone associated with the dyke swarm, even though the dykes themselves occupy Mode I extension fractures. These results confirm the recent geophysical evidence for dyke-parallel shear failure that can occur in the host rocks around intruding dykes. We suggest that coeval dyke-parallel seismicity both reactivated existing fracture networks and nucleated new fractures. Based on the premise that host-rock fracturing induces changes in elastic properties, remote stresses can reorientate locally leading to shear failure. This model provides for the first time an explanation for the origin of double-couple failure that is parallel in 3D (strike and dip) to dykes during their emplacement.

We present a data set of >1500 in situ O-Hf-U-Pb zircon isotope analyses that document the existence of a concealed Rodinian lithospheric keel beneath continental Zealandia. The new data reveal the presence of a distinct isotopic domain of Paleozoic–Mesozoic plutonic rocks that contain zircon characterized by anomalously low δ18O values (median = +4.1‰) and radiogenic εHf(t) (median = +6.1). The scale (>10,000 km2) and time span (>>250 m.y.) over which plutonic rocks with this anomalously low-δ18O signature were emplaced appear unique in a global context, especially for magmas generated and emplaced along a continental margin. Calculated crustal-residence ages (depleted mantle model, TDM) for this low-δ18O isotope domain range from 1300 to 500 Ma and are interpreted to represent melting of a Precambrian lithospheric keel that was formed and subsequently hydrothermally altered during Rodinian assembly and rifting. Recognition of a concealed Precambrian lithosphere beneath Zealandia and the uniqueness of the pervasive low-δ18O isotope domain link Zealandia to South China, providing a novel test of specific hypotheses of continental block arrangements within Rodinia.

The accurate characterization of mafic and ultramafic rocks is a challenging but necessary task given the spatial and genetic relationship of mineralization with specific lithologies (e.g. komatiite hosted nickel-sulfides preferentially associated with cumulate-rich ultramafic rocks). Rock classification is further complicated as most mafic and ultramafic rocks have undergone varying degrees of alteration. The accuracy and reproducibility of characterization can be significantly improved by using portable energy dispersive X-ray fluorescence (pXRF) chemical data with portable visible and near-infrared (pVis-NIR) mineralogical data. A new workflow using pXRF and pVis-NIR is presented and used to reliably characterize mafic and ultramafic rocks from the Yilgarn Craton, Western Australia. The workflow involves six steps: (1) Mitigate and identify compound processing and closure issues. For example, we used a pXRF with helium flush to reliably and rapidly measure light elements and mitigate closure, i.e. problems related to data failing to sum to 100%. (2) Identify and exclude geochemically heterogeneous samples. Heterogeneity may be unrelated to alteration and caused by veining or small-scale structure interleaving of different rock types. Geochemical heterogeneity was evaluated using skewness and kurtosis of SiO2 data. (3) Relate rocks from similar magmatic, weathering and alteration events. This was achieved by interpreting data grouping of Vis-NIR ferric and ferrous iron data via a 852 nm/982 nm reflectance v. 651 nm/982 nm reflectance plot and the ferrous abundance index. Unrepresentative data were omitted. (4) Correct XRF iron data, and characterize lithology and alteration. Values ascribed to regions in the TAS (total alkali silica) diagram were used to approximate FeO and Fe2O3. Subsequently, geochemical indices (e.g. Mg#) were used to characterize the alteration box plot. (5) Characterize fractionation in detail. Fractionation variation diagrams were used to interpret fractionation, e.g. MgO v. Al2O3, Ca/Al v. Al2O3, Ni/Cr v. Ni/Ti, and MgO v. Cr. (6) Identify and quantify talc alteration and serpentinization. This included the use of a new alteration plot (Mg# v. 1410 nmRAD/Albedo) to estimate serpentinization and identify relationships between serpentine, carbonate, chlorite and talc abundances. The results and observations contained in this contribution have important implications for progressive technologies such as core logging platforms that are equipped with pXRF and pVis-NIR instruments.

We recently described the genetic antimicrobial resistance and virulence profile of a collection of 279 commensal E. coli of food-producing animal (FPA), pet, wildlife and human origin. Phenotypic antimicrobial resistance (AMR) and the role of commensal E. coli as reservoir of extra-intestinal pathogenic Escherichia coli (ExPEC) virulence-associated genes (VAGs) or as potential ExPEC pathogens were evaluated. The most common phenotypic resistance was to tetracycline (76/279, 27.24%), sulfamethoxazole/trimethoprim (73/279, 26.16%), streptomycin and sulfisoxazole (71/279, 25.45% both) among the overall collection. Poultry and rabbit were the sources mostly associated to AMR, with a significant resistance rate (p &gt, 0.01) to quinolones, streptomycin, sulphonamides, tetracycline and, only for poultry, to ampicillin and chloramphenicol. Finally, rabbit was the source mostly associated to colistin resistance. Different pandemic (ST69/69*, ST95, ST131) and emerging (ST10/ST10*, ST23, ST58, ST117, ST405, ST648) ExPEC sequence types (STs) were identified among the collection, especially in poultry source. Both ST groups carried high number of ExPEC VAGs (pandemic ExPEC STs, mean = 8.92, emerging ExPEC STs, mean = 6.43) and showed phenotypic resistance to different antimicrobials (pandemic ExPEC STs, mean = 2.23, emerging ExPEC STs, mean = 2.43), suggesting their role as potential ExPEC pathogens. Variable phenotypic resistance and ExPEC VAG distribution was also observed in uncommon ExPEC lineages, suggesting commensal flora as a potential reservoir of virulence (mean = 3.80) and antimicrobial resistance (mean = 1.69) determinants.

The long-lived geodynamic evolution of the Permo-Triassic boundary between Laurasia and Gondwana may have created the ideal conditions for the genesis of a trans-continental Ni-Cu-PGE-(Au-Te) mineralised belt in Europe. This working hypothesis stems from the recent understanding that orogenic processes play a fundamental role in the onset of chemical and physical triggers for the transport of metals from the metasomatised mantle through to various crustal levels. An insight into our renewed framework for the polyphased genetic evolution of magmatic sulfide mineral systems is provided by a series of mineralised occurrences in the Ivrea Zone of NW Italy, which formed at multiple stages over a > 80 Ma time interval. Between 290-250 Ma, a series of hydrated and carbonated ultramafic alkaline pipes containing Ni-Cu-PGE-(Te-Au) mineralisation was emplaced in the lower continental crust. At ~200 Ma, a subsequent mineralising event occurred in association with the emplacement of the La Balma-Monte Capio (LBMC) intrusion. Modelling of the LBMC parental magma shows derivation from ~30% partial melting of an anhydrous juvenile mantle at moderate pressure (< 7 GPa). The inferred composition of the parental melt is consistent with magmatism associated with the Central Atlantic Magmatic Province (CAMP). However, its tellurium-enriched composition together with the S-C-O isotope signature of the associated magmatic sulfide mineralisation cannot be reconciled with the CAMP source. It is argued that the geochemical and isotopic signature of the LBMC intrusion reflects interaction and mixing of a primitive magma sourced from a juvenile source with localised domains enriched in carbonate and metal-rich sulfides located in the lower crust, consistent with the composition of the Permo-Triassic pipes. Evidence of this magmatic interaction informs on the first-order processes that control enhanced metallogenic fertility along the margins of lithospheric blocks. The scenario depicted here is consistent with reactivation and enrichment of a Gondwana margin Ni-Cu-PGE-(Te-Au) mineral system during the breakup of Pangea. The lessons learnt in the Ivrea Zone natural laboratory may inform on the genesis of other Permo-Triassic magmatic mineral systems in continental Europe, such as the deposits in north-west Czech Republic and southern Spain, which display significant analogies with their counterparts in the Ivrea Zone. We suggest that these systems may have a common DNA related to a metallogenic belt forming at different stages during the complex evolution and multi-phase activation of the margin between Laurasia and Gondwana. The nature and localisation of the magmatic sulfide mineral systems along this belt indicate that enhanced potential for ore formation at lithospheric margins may be due not only to favourable architecture, but also to localised enhanced metal and volatile fertility. Importantly, this hypothesis may explain why ore deposits along the margins of lithospheric blocks are not distributed homogeneously along their entire extension but generally form clusters. As mineral exploration is essentially a search space reduction exercise, this new understanding may prove to be important in predictive exploration targeting for new mineralised camps in Europe and elsewhere globally, as it provides a way to prioritise segments with enhanced fertility along extensive lithospheric block margins.

Background Enterocytes exert an absorptive and protective function in the intestine, and they encounter many different challenging factors such as feed, bacteria, and parasites. An intestinal epithelial in vitro model can help to understand how enterocytes are affected by these factors and contribute to the development of strategies against pathogens. Results The present study describes a novel method to culture and maintain primary chicken enterocytes and their characterization by immunofluorescence and biomolecular approaches. Starting from 19-day-old chicken embryos it was possible to isolate viable intestinal cell aggregates that can expand and produce a self-maintaining intestinal epithelial cell population that survives until 12 days in culture. These cells resulted positive in immunofluorescence to Cytokeratin 18, Zonula occludens 1, Villin, and Occludin that are common intestinal epithelial markers, and negative to Vimentin that is expressed by endothelial cells. Cells were cultured also on Transwell® permeable supports and trans-epithelial electrical resistance, was measured. This value gradually increased reaching 64 Ω*cm2 7 days after seeding and it remained stable until day 12. Conclusions Based on these results it was confirmed that it is possible to isolate and maintain chicken intestinal epithelial cells in culture and that they can be suitable as in vitro intestinal model for further studies.

The metasomatised continental mantle may play a key role in the generation of some ore deposits, in particular mineral systems enriched in platinum-group elements (PGE) and Au. The cratonic lithosphere is the longest-lived potential source for these elements, but the processes that facilitate their pre-concentration in the mantle and their later remobilisation to the crust are not yet well-established. Here, we report new results on the petrography, major-element, and siderophile- and chalcophile-element composition of native Ni, base metal sulphides (BMS), and spinels in a suite of well-characterised, highly metasomatised and weakly serpentinised peridotite xenoliths from the Bultfontein kimberlite in the Kaapvaal Craton, and integrate these data with published analyses. Pentlandite in polymict breccias (failed kimberlite intrusions at mantle depth) has lower trace-element contents (e.g., median total PGE 0.72 ppm) than pentlandite in phlogopite peridotites and Mica-Amphibole-Rutile-Ilmenite-Diopside (MARID) rocks (median 1.6 ppm). Spinel is an insignificant host for all elements except Zn, and BMS and native Ni account for typically 26 ppm in BMS in other peridotite xenoliths from the Kaapvaal craton. This represents a strong dilution of the original PGE abundances at the mineral scale, perhaps starting from precursor PGE alloy and small volumes of residual BMS. The latter may have been the precursor to native Ni, which occurs in an unusual Ni-enriched zone in a harzburgite and displays strongly variable, but overall high PGE abundances (up to 81 ppm). In strongly metasomatised peridotites, Au is enriched relative to Pd, and was probably added along with S. A combination of net introduction of S, Au +/− PGE from the asthenosphere and intra-lithospheric redistribution, in part sourced from subducted materials, during metasomatic events may have led to sulphide precipitation at ~80–120 km beneath Bultfontein. This process locally enhanced the metallogenic fertility of this lithospheric reservoir. Further mobilisation of the metal budget stored in these S-rich domains and upwards transport into the crust may require interaction with sulphide-undersaturated melts that can dissolve sulphides along with the metals they store., Lithos, 380-381, ISSN:0024-4937

Over the last 40 years the gray wolf (Canis lupus) re-colonized its historical range in Italy increasing human-predator interactions. However, temporal and spatial trends in wolf mortality, including direct and indirect persecution, were never summarized. This study aims to fill this gap by focusing on the situation of Tuscany and Emilia-Romagna regions, hosting a significant proportion of the Italian wolf population, by: (i) identifying the prevalent causes of wolf mortality, (ii) summarizing their temporal and spatial patterns and (iii) applying spatially-explicit Generalized Linear Models to predict wolf persecution. Between October 2005 and February 2021, 212 wolf carcasses were collected and subjected to necropsy, being involved in collisions with vehicles (n = 104), poisoned (n = 45), wounded with gunshot (n = 24) or blunt objects (n = 4) and being hanged (n = 2). The proportion of illegally killed wolves did not increase through time. Most persecution events occurred between October and February. None of our candidate models outperformed a null model and covariates such as the density of sheep farms, number of predations on livestock, or human density were never associated to the probability of having illegally killed wolves, at the municipal scale. Our findings show that conventional correlates of wolf persecution, combined with a supposedly high proportion of non-retrieved carcasses, fail to predict illegal wolf killings in areas where the species have become ubiquitous. The widespread spatial distribution of illegal killings indicates that persecution probably arises from multiple kinds of conflicts with humans, beyond those with husbandry. Wolf conservation in Italy should thus address cryptic wolf killings with multi-disciplinary approaches, such as shared national protocols, socio-ecological studies, the support of experts’ experience and effective sampling schemes for the detection of carcasses.

The Andean margin of the South American continent has been magmatically and tectonically active for over 330 million years. It is the type location where “Cordilleran-type” magmatism and orogenesis are manifest. In Argentina and Chile, between the latitudes of 28° and 40° S, magmatism related to the Gondwanan “Cordilleran-type” orogeny is reflected in a series of Carboniferous to Triassic intrusions. A comprehensive model exists for the petrogenesis of such magmas in Chile, however there is relatively little understanding of the nature and timing of Permo-Triassic magmatism in the Frontal Cordillera and Precordillera in Argentina. To address this, we present a new dataset of in situ zircon U–Pb, O and Hf isotopes from 15 felsic intrusions from Argentina. Zircon geochronology shows that magmatism in this region commenced at ca. 285 Ma and continued until ca. 250 Ma. Zircon O and Hf isotopes suggest that the oldest Permian magmas were derived from young supracrustal sources, with elevated δ18O (~ 8.5 to 7.5‰) and negative eHf values (~ − 1 to − 3 eHf). The emplacement of these magmas was coeval with the formation of mantle-derived magmas characterised by mantle-like δ18O (~ 6.0 to 5.5‰) and moderately positive eHf values (~ 4 to 1 eHf). As magmatism continued, transitional isotope signatures became predominant as melts of these disparate sources interacted and hybridised. It is proposed that under a compressional regime, mantle-derived magmas were halted in the lower continental crust, where they exchanged heat and volatiles with an older fertile lithosphere to generate melts from supracrustal sources. A shift in the stress regime at ca. 285 Ma permitted both crustally derived and juvenile mantle-derived magmas to exploit newly formed conduits to rise into the upper crust. A regional compilation of zircon O and Hf isotopes from felsic igneous rocks reveals a coherent secular trend over ~ 100 million years, where the oldest magmatism exhibits a dominant supracrustal component and younger magmas progressively (over 50 Ma) transition towards juvenile mantle-like isotopic compositions. This new dataset from Argentina fills a significant gap in the previous regional models between 285 and 250 Ma and documents the isotopic response of magmas produced in back-arc regions to a transition between compression and extensional/neutral stress regimes. These results give insight into the generation of new, or recycling of, continental crust in a back-arc setting and how the transition from compression to extension is imperative for ore-forming magmas to reach the upper crust.

Formaggio di Fossa di Sogliano is a traditional Italian Protected Designation of Origin (PDO) cheese ripened for a minimum of 5 months, with the feature of a ripening of at least 80 to at most 100 days in pits, digged into tuffaceous rocks according to medieval tradition of Italy. In this study, a challenge test using Listeria innocua as a surrogate of Listeria monocytogenes was performed, with the aim of increasing knowledge concerning the impact of the Fossa cheese process, and especially of the traditional ripening process of this PDO, on the behaviour of L. monocytogenes. Pasteurized milk was experimentally inoculated with 4.5 log CFU/mL cocktail by three L. innocua strains, and L. innocua and Mesophilic Lactic Acid Bacteria (LAB) counts as well as the evolution of temperatures, pH and aw values were monitored throughout the manufacturing and ripening processes. Throughout the ripening in maturation room a constant temperature of 8°C was observed reaching a temperature between 10 and 15.5°C during ripening into pit. In the final products data for LAB concentration, pH and aw values were roughly in accordance with literature, even if some differences were, probably due to variability of artisanal cheese productions. The numbers of L. innocua showed a slight decrease but remained stable until the end of ripening in maturation room, whereas a significant reduction of the microorganism was observed in the final product, at the end of the ripening into the pit. The findings give scientific evidence that the process of this PDO prevented the L. innocua growth, allowing us to speculate a similar behaviour of L. monocytogenes. Based on this study, the recommendation to extend as much as possible the ripening into pit (from 80 to 100 days) was provided to food business operators as a risk mitigation strategy to be implemented.

Orogenic peridotites associated with high-grade felsic rocks record mass exchange between crust and mantle reservoirs at convergent plate margins. In this geodynamic framework, fluids released by submerging slabs can mobilize redox-sensitive elements such as carbon (C) and sulfur (S) and percolate the mantle wedge, eventually forming hydrate minerals associated with carbonate and sulfide phases at appropriate T, P and f O2 conditions. The introduction of sulfur into the sub-continental lithospheric mantle (SCLM) wedge and its mobilization at grain-scale can be investigated by means of in situ δ34S analyses of mantle wedge sulfides, which may have inherited the composition of the fluid sources. To date, the impact of the S transfer through the SCLM wedge is poorly known and limited in situ S isotope values of sulfides from mantle wedge peridotite are available in literature. Our study focuses on the Ulten Zone (UZ) orogenic-garnet peridotites, which provide an ideal case to investigate the S mobilization through the SCLM wedge and the effects of crustal fluids on the sulfide δ34S signature, especially during the exhumation stage. We therefore integrate a well-constrained paragenesis with mineral chemistry and in situ S isotope signature of sulfides. The UZ peridotites were involved in a collisional setting during the Variscan orogenesis, recording HP-eclogite-facies conditions and exhumation after their incorporation in a mélange with the associated garnet-kyanite gneisses. A suite of coarse to fine-grained peridotites was investigated in order to cover all the metasomatic stages preserved in these rocks, considering the grade of serpentinization and the occurrence of carbonates. Microstructural observations and major element compositions indicate that pentlandite (± chalcopyrite ± chalcocite ± sphalerite) is the ubiquitous primary sulfide, which is commonly replaced by secondary heazlewoodite and millerite in medium to highly serpentinized peridotite. Pentlandite occurs in different textural positions related to several metasomatic stages: (i) polycrystalline aggregates (pentlandite + Cl-apatite + phlogopite + ilmenite + calcite-brucite intergrowths) included in spinel (in garnet); (ii) interstitial in matrix; (iii) in carbonate and serpentine veins. Overall, the S isotope signature of pentlandite exhibits a relatively narrow range between -1.62 and +3.76 ‰. The relatively low S isotope values require a mantle-like source for the metasomatizing fluids enriched in sulfur, with possible contamination with fluids of other different sources. These new results show that sulfur was introduced into the lithospheric mantle and mobilized by influxes of late metasomatic fluids, in part related to the serpentinization, and provide additional constraints on the S isotope composition of the SCLM wedge.

We derive a novel method for determining the oxidation state of a magma as zircon crystallized, with a standard error of ±0·6 log unit ƒO2, using ratios of Ce, U, and Ti in zircon, without explicit determination of the ionic charge of any of them, and without independent determination of crystallization temperature or pressure or parental melt composition. It yields results in good agreement with oxybarometry on Fe–Ti oxide phenocrysts and hornblende phenocrysts quenched in eruptive I- and A-type dacites and rhyolites, but our zircon oxybarometer is also applicable to slowly cooled plutonic rocks and applicable to detrital and xenocrystic zircons. Zircon/melt partition coefficients of Ce and U vary oppositely with ƒO2 variation in the silicate melt. The Ce/U ratio in zircon also varies with the Ce/U element ratio in the silicate melt. During mafic-to-felsic magmatic differentiation, Ce and U are incorporated mainly in calcium-dominated lattice sites of clinopyroxene, hornblende, apatite, and occasionally titanite and/or allanite, all of which have a similar degree of preference for Ce over U. We employ the U/Ti ratio in zircon and in silicate melt as a magmatic differentiation index. Convergent- and divergent-plate-margin differentiation series consistently follow the relation log (Ce/U) ≈ –0·5 log (U/Ti) + C' in silicate melts of basaltic to rhyolitic composition. That correlation permits thermodynamic derivation of the oxybarometry relation among those elements in zircon: log fO2(sample)−log fO2(FMQ)≈42n+1log[Ce/(Ui×Ti)z]+C, wherein Ui denotes age-corrected initial U content, FMQ represents the reference buffer fayalite + magnetite + quartz, superscript z denotes zircon, and n varies with the average valence of uranium in the zircon’s parental silicate melt. We empirically calibrate this relation, using 1042 analysed zircons in 85 natural populations having independently constrained log ƒO2 in the range FMQ – 4·9 to FMQ + 2·9, to obtain the equation log fO2(sample)−log fO2(FMQ)=3·998(±0·124) log[Ce/(Ui×Ti)z]+2·284(±0·101) with a correlation coefficient R = 0·963 and standard error of 0·6 log unit ƒO2 in calc-alkalic, tholeiitic, adakitic, and shoshonitic, metaluminous to mildly peraluminous and mildly peralkaline melts in the composition range from kimberlite to rhyolite. Thermodynamic assessment and empirical tests indicate that our formulation is insensitive to varying crystallization temperature and pressure at lithospheric conditions. We present a revised equation for Ti-in-zircon thermometry that accounts appropriately for pressure as well as reduced activity of TiO2 and SiO2 in rutile- and quartz-undersaturated melts. It can be used to retrieve absolute values of ƒO2 from values of ΔFMQ obtained from a zircon analysis.

Salmonella spp. represent a public health concern for humans and animals due to the increase of antibiotic resistances. In this scenario, the use of essential oils (EOs) could be a valid tool against Salmonella contamination of meat. This work compares the in vitro effectiveness of an Italian mixture of feed additives based on EOs (GR-OLI) with EO of Origanum vulgare L., recently admitted by European Food Safety Authority (EFSA) for animal use. Twenty-nine Salmonella serotypes isolated from poultry and pig farms were used to assess GR-OLI and O. vulgare EO antimicrobial propeties. O. vulgare EO was active on the disaggregation of mature biofilm, while GR-OLI was capable of inhibiting biofilm formation and disaggregating preformed biofilm. Furthermore, GR-OLI inhibited bacterial adhesion to Caco-2 cells in a dose-dependent manner. Both products showed inhibition of bacterial growth at all time points tested. Finally, the synergistic action of GR-OLI with commonly used antibiotics against resistant strains was investigated. In conclusion, the mixture could be used both to reduce the meat contamination of Salmonella spp. before slaughter, and in synergy with low doses of ciprofloxacin against resistant strains. Although EOs as feed additives are already used in animal husbandry, no scientific study has ever highlighted their real antimicrobial potential.

Large-scale mantle convective processes are commonly reflected in the emplacement of Large Igneous Provinces (LIPs). These are high-volume, short-duration magmatic events consisting mainly of extensive flood basalts and their associated plumbing systems. One of the most voluminous LIPs in the geological record is the ~ 2.06 billion-year-old Bushveld Igneous Complex of South Africa (BIC), one of the most mineralised magmatic complexes on Earth. Surprisingly, the known geographic envelope of magmatism related to the BIC is limited to a series of satellite intrusions in southern Africa and has not been traced further afield. This appears inconsistent with the inferred large size of the BIC event. Here, we present new radiometric ages for alkaline magmatism in the Archean Yilgarn Craton (Western Australia), which overlap the emplacement age of the BIC and indicate a much more extensive geographic footprint of the BIC magmatic event. To assess plume involvement at this distance, we present numerical simulations of mantle plume impingement at the base of the lithosphere, and constrain a relationship between the radial extent of volcanism versus time, excess temperature and plume size. These simulations suggest that the thermal influence of large plume events could extend for thousands of km within a few million years, and produce widespread alkaline magmatism, crustal extension potentially leading to continental break-up, and large ore deposits in distal sectors. Our results imply that superplumes may produce very extensive and diverse magmatic and metallogenic provinces, which may now be preserved in widely-dispersed continental blocks. © 2020, The Author(s)., Scientific Reports, 10 (1), ISSN:2045-2322

Marek's disease (MD) is a lymphoproliferative disease caused by Gallid alphaherpesvirus 2 (GaHV-2), which primarily affects chickens. However, the virus is also able to induce tumours in turkeys, albeit less frequently than in chickens. This study reports the molecular characterization of a GaHV-2 strain detected in a flock of Italian meat-type turkeys exhibiting visceral lymphomas. Sequencing and phylogenetic analysis of the meq gene revealed that the turkey GaHV-2 has molecular features of high virulence and genetic similarity with GaHV-2 strains recently detected in Italian commercial and backyard chickens. GaHV-2 is ubiquitous among chickens despite vaccination, and chicken-to-turkey transmission is hypothesized due to the presence of broilers in neighbouring pens.RESEARCH HIGHLIGHTS A GaHV-2 strain from Italian turkeys was molecularly characterized.The turkey strain presented molecular characteristics of high virulence in its meq gene.The turkey strain was closely related to previously detected chicken strains.

Magmatic systems play a crucial role in enriching the crust with volatiles and elements that reside primarily within the Earth’s mantle, including economically important metals like nickel, copper and platinum-group elements. However, transport of these metals within silicate magmas primarily occurs within dense sulfide liquids, which tend to coalesce, settle and not be efficiently transported in ascending magmas. Here we show textural observations, backed up with carbon and oxygen isotope data, which indicate an intimate association between mantle-derived carbonates and sulfides in some mafic-ultramafic magmatic systems emplaced at the base of the continental crust. We propose that carbon, as a buoyant supercritical CO2 fluid, might be a covert agent aiding and promoting the physical transport of sulfides across the mantle-crust transition. This may be a common but cryptic mechanism that facilitates cycling of volatiles and metals from the mantle to the lower-to-mid continental crust, which leaves little footprint behind by the time magmas reach the Earth’s surface., NERC Minerals Security of Supply (SOS) NE/M010848/1, Australian Research Council CE11E0070, Consolidated Nickel Mines, University of Leicester

The Nimbus Ag-Zn-(Au) volcanic-hosted massive sulfide (VHMS) deposit represents an exceptional orebody in the Yilgarn Craton of Western Australia. It is located in a zone of juvenile crust running N-S through the Eastern Goldfields Superterrane. However, unlike most other VHMS occurrences associated with the 2690–2680 Ma rift sequence (Teutonic Bore, Jaguar, Bentley, Erayinia), it is hosted by the ca. 2705 Ma plume-related stratigraphy, which is more typically associated with komatiite-hosted nickel-sulfide mineralization. The Nimbus deposit displays hybrid VHMS-epithermal characteristics resulting from low temperature and shallow water conditions, which developed a quartz-carbonate-sericite dominated alteration assemblage in the dacite host rocks. Sulfide mineralization comprises pyrite, sphalerite, galena, arsenopyrite, Ag-Sb-Pb-Bi sulfosalts, and rare chalcopyrite. In this study, we applied a combination of in-situ analytical techniques to monitor the evolving sulfur isotope signature of the mineralizing fluids, and propose that the Nimbus VHMS deposit developed as a result of a bimodal fluid history. In the first stage, the hydrothermal system – powered by plume-related magmatism – deposited a series of barren pyrite lenses with colloform textures. Their variable but consistently negative mass-independent sulfur isotope fractionation signature (Δ33S = −0.81%) reflects the interaction between mantle-derived magmatic fluids and Archean seawater. The ubiquitous presence of carbon-rich porous textures and the remnants of carbonaceous “nests” in colloform pyrite also indicate a significant contribution of microbial sulfate reducers during the incipient stages of sulfide precipitation. The gradual formation of colloform lenses eventually sealed the hydrothermal system establishing a physical barrier that limited the interaction with seawater. This process promoted the onset of higher temperature and pressure conditions required to form the high-grade Zn-Ag mineralization, sourcing sulfur and fluids largely from a magmatic reservoir (Δ33S = +0.09%). Whereas the identification of a predominantly magmatic sulfur source is supported by sulfur isotope signatures, the recognition of a magmatic origin of the fluid may only be inferred indirectly. It is consistent with the observed quartz-sericite alteration style and the proposed mechanism of sulfide deposition via decompression, which does not require any interaction with seawater. The trace element distribution of the ore-related sulfides also supports a closed hydrothermal system developed through multiple fluid pulses. Indeed, this ore-forming scenario is commonly favored by high confining pressures, which at Nimbus were established following the deposition of the colloform pyrite lenses that progressively sealed the hydrothermal system creating the favorable conditions for mineralization.

The Golden Mile and Mount Charlotte deposits in the Kalgoorlie Terrane, Western Australia, display three main mineralization styles: Fimiston, comprised of interconnected shear zones associated with ankerite-pyrite ± hematite- ± magnetite-gold-telluride alteration; Oroya, made up of breccia bodies with V-muscovite-ankerite-pyrite ± pyrrhotite-gold-telluride alteration; and Mount Charlotte, which consists of vein arrays with symmetrical ankerite-sericite-albite-pyrite ± pyrrhotite ± gold alteration. Pyrite is in equilibrium with gold in all three mineralization styles and has been selected as a proxy to record the sulfur source of the mineralizing fluids as well as the nature of the hydrothermal processes. The δ34S, Δ33S, and Δ36S analyses on pyrite grains from the different mineralization styles, including oxidized and reduced sulfide-oxide assemblages, reveal (1) a large variation in δ34S (from − 12.6 to + 23.5‰), and (2) a previously unrecognized occurrence of anomalous Δ33S and Δ36S signatures (from − 1.0 to + 1.1‰ and from − 2.3 to + 0.9‰, respectively). It is argued that the mineralizing fluids that formed the Golden Mile and Mount Charlotte deposits record mixing among three components: mantle sulfur, oxidized seawater sulfur (e.g., SO4), and reduced elemental sulfur (e.g., S8). Petrographic evidence in conjunction with Δ33S and Δ36S data suggest that MIF-S was acquired during the deposition of shales and basalts present in the Kalgoorlie Terrane and later mixed with mantle-derived sulfur during the mineralization events. The negative δ34S values that predominate in Fimiston style mineralization are consistent with a prevalence of oxidized fluids during the ore-forming process, as reflected by the presence of hematite-pyrite-magnetite-gold assemblages. Conversely, the positive δ34S values that dominate in the Mt Charlotte and Oroya mineralization styles reflect a reducing environment, as reflected by the presence of pyrite-pyrrhotite-gold assemblages.

The Paleoproterozoic Ammassalik Intrusive Complex of south-east Greenland is located at the margin between the Rae Craton to the north and the North Atlantic Craton to the south. The complex is part of the Nagssugtoqidian Mobile Belt emplaced at mid- to lower-crustal level and represents an eastward continuation of the Nagssugtoqidian Orogen of western Greenland. We present new whole-rock geochemical and isotopic data (whole-rock Rb-Sr, Sm-Nd, U-Pb, Lu-Hf and zircon U-Pb, Lu-Hf, O) acquired from the Ammassalik Intrusive Complex, with the aim of reassessing its petrogenesis and evolution. The intrusive rocks and surrounding host-rocks show typical calc-alkaline signatures as well as negative Ta, Nb and Ti anomalies. The new U-Pb age data indicate a protracted magmatic history over ca. 40 Ma, involving at least three successive magmatic pulses between ca. 1910 and 1870 Ma emplaced into a granulite facies biotite-garnet paragneiss with ca. ≤ 1990 Ma protolith ages. Whole-rock trace element and isotope geochemistry indicate that the magmas that formed the Ammassalik Intrusive Complex were derived from a mildly enriched (eNd0 = −0.8 to –3.8; eSr0 = +24 to +42) and deep, garnet-bearing (MREE/HREE fractionated patterns) mantle source, possibly the sub-continental lithospheric mantle. However, the observed decreasing zircon eHf values with time (eHf0 = +2.8 to −12.5) indicate increasing degrees of crustal contamination involving variably 18O-enriched crustal material (δ18O = 7–9‰) into the mafic magmas of the complex. This interpretation suggests that the mantle-derived magma do not have a deep, garnet-bearing source, but that the continental arc signature in the Ammassalik Intrusive Complex igneous rocks may have been inherited from the assimilation of partial melts of the garnet-bearing host-rocks. In addition, based on the new crystallisation ages broadly coeval with the Columbia supercontinent build up, marked by the formation of world-class Ni-Cu deposits globally, it is proposed that the Ammassalik Intrusive Complex and the south-east Greenland region were in direct continuity of the mineralised Kotalahti belt (Svecofennian Province, Finland). Together with the recent discovery of Ni-Cu mineralisation in the Ammassalik Intrusive Complex, our study further supports the high prospectivity of south-east Greenland for orthomagmatic Ni-Cu deposits.

The true solubilities of highly siderophile elements in silicate and oxide minerals may be difficult to measure because of their low abundances and the tendency of these elements to occur as minute inclusions or “micronuggets”. In order to mitigate this latter problem, we present a new approach that makes use of the solid-state diffusion of such elements into pre-existing crystals. The diffusion of Rh, Ru and Ir was measured in San Carlos olivine, and synthetic monocrystalline forsterite and MgAl2O4-spinel, at atmospheric pressure, 1300 to 1400 °C and oxygen fugacities from air to that of the quartz-fayalite-magnetite (FMQ) oxygen buffer. The activities of all main components were controlled in each experiment by solid-state buffer assemblages: SiOR2R and MgO in olivine experiments were controlled by forsterite (olivine) + periclase (magnesiowustite) (fo + per or sco + mw), or forsterite (olivine) + protoenstatite (fo + en or sco + opx). Activities of AlR2ROR3R and MgO in the spinel experiments were buffered by spinel + periclase (sp + per) or spinel + corundum (sp + cor) mineral assemblages. The diffusion profiles were measured by LA-ICP-MS in both traverse and drilling modes, and by NanoSIMS. Good agreement was obtained between the methods with spatial resolution significantly higher in LA-ICP-MS drilling mode and NanoSIMS at 0.2 μm and 0.1 μm, respectively, compared to 5 μm by LA-ICP-MS in the traverse mode. Diffusion coefficients were more than five times slower, and solubilities five times lower, in the low MgO activity experiments compared with those carried out at high MgO activity at the same temperature and fO2. Our results show that at 1400PoPC and FMQ + 1.5 the maximum solubility of Rh in olivine in equilibrium with metal is 0.7 ppm in high SiOR2R activity mineral associations (those with orthopyroxene) and