Textural development in sulfide-matrix ore breccias in the Aguablanca Ni-Cu deposit, Spain, revealed by X-ray fluorescence microscopy

The intrusion-hosted Ni-Cu sulfide deposit at Aguablanca in south-western Spain contains a high proportion of ores in the form of sulfide-matrix ore breccias. These are polymict, comprising autoliths and xenoliths in sulfide-rich and/or sulfide-poor matrices. Inclusion lithologies include calc-silicate skarn rocks from the adjacent marbles, ultramafic and mafic cumulates, and remelted and recrystallized mafic rocks containing spinifex-like textures. Breccia textures have been investigated at mm to cm scale using desk-top and synchrotron-based microbeam XRF mapping which reveal a number of distinctive common features: disaggregation of inclusions into adjacent sulfide along original silicate grain boundaries; complex reverse and oscillatory zoning in Cr content of clinopyroxene grains within sulfide and inside inclusions; narrow reaction rims between country rock clasts and enclosing silicates; and preferential disposition of pyroxene crystals within pyrrhotite-pentlandite aggregates (original MSS) relative to inclusion-poor chalcopyrite. The observed range of textures is explained by a model of percolation of molten sulfide through a pre-existing silicate-matrix intrusion breccia, preferentially displacing a cotectic or eutectic plagioclase-pyroxene melt. The process is analogous to that believed to have formed interspinifex ore in komatiite-hosted deposits, and also to that responsible for superficially similar sulfide matrix ore breccias at Voisey’s Bay. The preserved range of textures is interpreted as being due to late stage gravity-driven percolation of sulfide liquid from above into a pre-existing partially molten intrusion breccia. This intrusion breccia itself may have been emplaced into the neck of the Aguablanca stock, in the waning stages of magma flow

New observations by X-ray fluorescence microscopy provide insights for the origin of Aguablanca sulfide-matrix breccias in SW Spain

Depto. de Mineralogía y PetrologíaFac. de Ciencias GeológicasTRUEMinisterio de Economía y Competitividadpu

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Geological – Geophysical 3D Modelling of the Mullikkoräme VMS deposit, Finland

The Mullikkoräme deposit, owned by Pyhäsalmi Mine Oy, is a satellite deposit located north east of the Pyhäsalmi mine in the eastern part of the Pyhäsalmi Volcanic Complex (PVC) in Central Finland. It is a VMS type deposit composed of five small vertical lenses of ore hosted by altered felsic and mafic volcanic rocks. Between 1990 and 1993, the Mullikkoräme deposit was mined out by Outokumpu Oy: since then, Pyhäsalmi Mine Oy kept exploring this area and many geophysical surveys were carried out, making available a large amount of information (geological, geophysical and geochemical information). This thesis aims at producing an integrated 3D geological model in order to identify new interesting prospective areas around the Mullikkoräme deposit. All the available geophysical, geological, geochemical data has been integrated into a unique comprehensive 3D gOcad© prospective geomodel. A draft 3D skeleton model is preliminary built from interpretative cross sections and surface geological maps. It is then improved and constrained using well data. After characterizing the main units geophysical response, 3D geological contacts, faults and geobodies are extended to deepest levels and interpolated using the available interpreted geophysical data (magnetic and gravity maps, conductivity, chargeability and seismic profiles, 3D gravity and conductivity block model). This model is then used to visualize the 3D structures, the lithologies and the geophysical anomalies in an integrated way in order to identify any new potential interesting targets. One of the main results of this project is a complete 3D geomodel of the area, integrating both geological information and geophysical information. It is used by the company to visualize all the data available in the area using a unique shared Earth model. A few really interesting targets have already been identified based on this 3D model, and drilling is being planned for November 2010.Validerat; 20101217 (root

The importance of volatiles in the formation of magmatic sulphide ore deposits: experimental constraints

Research studies provide growing evidence for the presence of fluids within magmatic mineral systems of mafic-ultramafic composition, although these ore-forming magmas are generally considered volatile-poor. Here we summarise the results of two experimental studies that clarify the role of volatiles in the formation of magmatic sulphide ore deposits in mafic-ultramafic magmas: (i) interaction experiments simulating magmatic assimilation of sulfate and/or organic compounds (Iacono-Marziano et al. 2017); (ii) a more recent experimental study shedding light on previously unnoticed physical processes ensuing from the association between sulphide melt and fluid phase (Iacono-Marziano et al. 2022). The silicate melt composition used for both studies is similar to the parental melt of Noril'sk-Talnakh ore bearing intrusions in Polar Siberia, and the starting materials of the experiments were samples in Noril'sk region. Moreover, the experiments were conducted at magmatic conditions relevant to emplacement pressures and temperatures of Noril'sk-Talnakh intrusions. Experimental findings are therefore directly applicable to these world-class ores, suggesting that volatiles may have played a crucial role in their formation. Several other magmatic sulphide ores present evidence of the occurrence of a fluid phase during ore formation; hence the mechanisms illustrated by the experiments are likely to be more common than currently considered

The importance of volatiles in the formation of magmatic sulphide ore deposits: experimental constraints

International audienceResearch studies provide growing evidence for the presence of fluids within magmatic mineral systems of mafic-ultramafic composition, although these ore-forming magmas are generally considered volatile-poor. Here we summarise the results of two experimental studies that clarify the role of volatiles in the formation of magmatic sulphide ore deposits in mafic-ultramafic magmas: (i) interaction experiments simulating magmatic assimilation of sulfate and/or organic compounds (Iacono-Marziano et al. 2017); (ii) a more recent experimental study shedding light on previously unnoticed physical processes ensuing from the association between sulphide melt and fluid phase (Iacono-Marziano et al. 2022). The silicate melt composition used for both studies is similar to the parental melt of Noril'sk-Talnakh ore bearing intrusions in Polar Siberia, and the starting materials of the experiments were samples in Noril'sk region. Moreover, the experiments were conducted at magmatic conditions relevant to emplacement pressures and temperatures of Noril'sk-Talnakh intrusions. Experimental findings are therefore directly applicable to these world-class ores, suggesting that volatiles may have played a crucial role in their formation. Several other magmatic sulphide ores present evidence of the occurrence of a fluid phase during ore formation; hence the mechanisms illustrated by the experiments are likely to be more common than currently considered

The role of magma degassing in sulphide melt mobility and metal enrichment

International audienceA strong association between sulfide droplets and gas bubbles has been observed in both experimental and natural samples (e.g. the picrogabbrodolerites of the Norilsk-Talnakh ore-bearing intrusions), suggesting that the fluid phase may have a major control on the segregation and mobility of the sulfide melt. Here we show how the association between sulfide melt and gas bubbles during magma degassing can have consequences for the accumulation of the sulfide liquid but also for its metal enrichment. Two types of experiments are presented involving magma degassing in sulfide-bearing mafic magmas at 1200°C and variable pressure: experiments simulating the interaction of the magma with coal, and experiments simulating magma decompression. Despite a marked difference in the composition of the fluid phase of the two types of experiments, the sulfide melt and the fluid phase are always associated, with each gas bubble being generally connected to one or several sulfide droplets. By facilitating the coalesce of the sulfide droplets attached to the same gas bubble, the fluid phase therefore seems to play a crucial role on the accumulation of the sulfide liquid. Large sulfide blebs are produced by this process in experimental samples, suggesting that magma degassing can be a potentially critical mechanism for sulfide mobility and accumulation in magmas. Moreover, magma degassing can also play a role on metal content of the sulfide melt: metal enrichment of the sulfide droplets is observed in the degassed samples, due to the consumption of the sulfide melt consequent upon magma degassing. In experimental samples, limited degassing produces metal-enriched sulfide melts, while extensive degassing generates PGMs. The possible implication of this process in the formation of ore-deposits and particularly in those of Norilsk-Talnakh is discussed, with a particular attention to the disseminated sulfides in the picrogabbrodolerites and the S-poor, PGE-rich ores

Magmatic sulfide ore deposits

Magmatic sulfide ore deposits are products of natural smelting: concentration of elements from silicate magmas (slags) by immiscible sulfide liquid (matte). Deposits occupy a spectrum from accumulated pools of matte within small igneous intrusions or lava flows, forming orebodies mined primarily for Ni and Cu, to stratiform layers of weakly disseminated sulfides, mined for platinum group elements, within large mafic-ultramafic intrusions. One of the world’s most valuable deposits, the Platreef in the Bushveld Complex in South Africa, has aspects of both of these end members. Natural matte compositions vary widely between and within deposits, controlled largely by the relative volumes of matte and slag that interact with one another

The critical role of magma degassing in sulphide melt mobility and metal enrichment

International audienceAbstract Much of the world’s supply of battery metals and platinum group elements (PGE) comes from sulphide ore bodies formed in ancient sub-volcanic magma plumbing systems. Research on magmatic sulphide ore genesis mainly focuses on sulphide melt-silicate melt equilibria. However, over the past few years, increasing evidence of the role of volatiles in magmatic sulphide ore systems has come to light. High temperature-high pressure experiments presented here reveal how the association between sulphide melt and a fluid phase may facilitate the coalescence of sulphide droplets and upgrade the metal content of the sulphide melt. We propose that the occurrence of a fluid phase in the magma can favour both accumulation and metal enrichment of a sulphide melt segregated from this magma, independent of the process producing the fluid phase. Here we show how sulphide-fluid associations preserved in the world-class Noril’sk-Talnakh ore deposits, in Polar Siberia, record the processes demonstrated experimentally

Platinum-group element and gold contents of arsenide and sulfarsenide minerals associated with Ni and Au deposits in Archean greenstone belts

Post-magmatic alteration of certain magmatic Ni sulfide ores in Western Australia, the Miitel deposit and the Sarah's Find prospect, produced Ni–As–PGE haloes around massive sulfides. A study of the composition of arsenide grains from these hydrothermal haloes, along with arsenides from various magmatic and hydrothermal mineralized environments in other localities, was conducted in order to compare their composition, and assess their potential use as indicator minerals for exploration vectoring, as well as to gain knowledge on their crystallization history. Concentrations in trace elements such as platinum-group elements (PGEs), Au and other metals was obtained by laser ablation inductively coupled plasma mass spectroscopy analyses. Results show that variations in PGEs and Au compositions can be related to the magmatic vs. hydrothermal origin of the grains; and to their provenance from deposits enriched in either Ni, Au or both. Magmatic NiCoFe sulfarsenides have strongly correlated, high IPGE (Os, Ir, Ru, Rh) contents up to 100 ppm Ir, compared with maximum values in hydrothermal sulfarsenides of ~1 ppm. Gold in hydrothermal sulfarsenides from Au-mineralized ultramafic rocks extends up to 500 ppm, with typical values of 3–30 ppm; similar values are also found in nickeline (also called niccolite). These results suggest that nickel arsenides could potentially be used as indicator minerals for nickel and gold exploration. Trace-element contents of arsenide grains in shear zones could be used to deduce the presence of Ni or Au mineralization upstream in the fluid pathway