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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 x 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 <0.5 ppm. Because komatiites contain some of the world's highest metal tenor magmatic Ni-Cu sulfide deposits, the Cu variability in olivine as a function of the sulfide-saturation state highlights a potential application of olivine chemistry in the exploration for sulfide ore deposits. 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. [ABSTRACT FROM AUTHOR]

We present δ60Ni values for black shales, determined by double-spike MC-ICP-MS. The samples comprise Paleoproterozoic Talvivaara Ni–Zn–Co–Cu black shales from Finland, Neoproterozoic black shales from the Teplá-Barrandian Unit, Czech Republic, Early Cambrian Ni–Mo-rich black shales from the Yangtze Craton, and Devonian Ni–Zn–PGE black shales from Yukon, Canada. In addition, the sample set includes a black smoker sample from the Logatchev hydrothermal field, Mid-Atlantic Ridge. The δ60Ni values vary from − 0.84 ± 0.09 to + 0.62 ± 0.04‰ (2SD) with a median of − 0.10‰ (n = 28). Ni isotopic compositions were predominantly lighter than those of abiotic terrestrial and extraterrestrial samples (0.15 and 0.27‰), mantle (0.23‰, Gall et al. 2017), present-day seawater (1.44‰, Cameron and Vance 2014), dissolved Ni from riverine input (0.84‰, Cameron and Vance 2014), ferromanganese crusts (0.9–2.5‰, Gall et al. 2013), Devonian/Mississippian organic-rich marine sediments, lower Jurassic organic-rich marine sediments (0.2–2.5‰, average 0.92‰, n = 18, Porter et al. 2014), and euxinic sediments of the Black Sea (0.14–0.51‰, Vance et al. 2016). However, the range of δ60Ni values in our black shale samples was close to that of the weathering products of mafic/ultramafic rocks (ore and soil samples) ranging from − 0.60 to + 0.30‰ (Ratié et al. 2015; Spivak-Birndorf et al. 2018), Ni-sulfide ores hosted by Archean komatiites from Australia and Canada (− 0.10 to − 1.03‰, average − 0.70‰, n = 8, Gueguen et al. 2013), and Archean Ni-rich magmatic sulfides from Zimbabwe (− 0.28 to − 0.47‰, n = 6, Hoffman et al. 2014). Based on our observations and considering the extremely low contribution of direct biological uptake of Ni, and a dominant Ni residence in early Fe/Ni-sulfides, we suggest that our mostly light Ni isotopic compositions in metal-rich black shales result from sulfidization of organic matter and Ni removal into sulfides. [ABSTRACT FROM AUTHOR]

Deposits of Cu-Ni-platinum group elements (PGE)-rich sulfides occur along the North Range footwall of the Sudbury Igneous Complex, Ontario, Canada. The deposits have been modified chemically, mineralogically, and texturally by multiple syn- to postmagmatic hydrothermal events and are hosted mainly within Sudbury breccia, a contact metamorphosed and hydrothermally altered impact breccia. The composition of C1 to C6 unsaturated and saturated hydrocarbons in bulk fluid inclusion volatiles in the matrix of the Sudbury breccia was investigated using in-line rock-crushing gas chromatography (GC) in order to compare the hydrocarbon composition of this rock type in breccia zones containing economic footwall sulfide deposits at the Morrison deposit (Levack mine, North Range, Sudbury, Ontario) with barren breccia zones. Trace hydrocarbons, possibly abiogenic in origin, occur throughout the Sudbury Igneous Complex footwall and country rocks investigated. However, there are differences in the composition and abundance of bulk hydrocarbons released from mineralized and barren Sudbury breccia when fluid inclusions are opened. Volatiles released from samples of Sudbury breccia from sulfide-mineralized and sulfide-barren environments showed the following: (1) higher average abundances of light saturated hydrocarbons (C1-C4) and an approximately 2x higher total abundance of hydrocarbons (mol/g of rock basis) associated with samples from the mineralized study area, and (2) comparable average unsaturated hydrocarbon abundances in both settings, but a larger range in unsaturated hydrocarbon abundances in the mineralized study area. Differences in bulk hydrocarbon abundance and composition reflect differences in the abundance and hydrocarbon content of fluid inclusions trapped in the barren and mineralized Sudbury breccia zones. In addition, the compositional modification of circulating fluids by processes and conditions unique to the mineralized Sudbury breccia environment may have occurred prior to inclusion entrapment (e.g., modification by mineral catalysts, differences in temperature and oxygen fugacity). Preliminary spatial analysis of the hydrocarbon distribution within and surrounding the Morrison deposit shows that the total hydrocarbon abundance in the Sudbury breccia does not change with orebody proximity within a single host breccia zone. However, volatiles trapped in the Sudbury breccia matrix near the top of the footwall deposit, where it is physically connected to contact-style (Ni-Cu-PGE) ores, have elevated unsaturated hydrocarbon abundances (e.g., propene) compared to other parts of the same breccia zone distal to this zone of physical connection. Samples of the PGE-enriched Sudbury breccia and mineralized veins containing alteration assemblages characteristic of the footwall ore styles have higher unsaturated hydrocarbon abundances and unsaturated/saturated ratios compared to Sudbury breccia and vein samples that are PGE poor. Localized enrichments in unsaturated hydrocarbons in Sudbury breccia zones may be the result of specific ore minerals and metal complexes (involving the PGE and group VIII metals) that acted as catalytic agents, modifying the composition of initially light saturated hydrocarbon species prior to entrapment in fluid inclusions. To apply the analysis of hydrocarbon compositions in trapped fluid inclusions to discriminating mineralized from barren zones of Sudbury breccia, samples from targeted areas were compared to samples of barren Sudbury breccia ("background"). Although a large data set is presented here to establish these compositional fields, analysis of smaller sample subsets from each environment yields a statistically significant separation between the two environments. Total hydrocarbon abundance, C3/C1 ratios, and unsaturated/saturated hydrocarbon ratios are useful indicators of sulfide ore proximity and may help delineate regions enriched in PGE. [ABSTRACT FROM AUTHOR]

We applied seismic modeling for a detailed 3D geologic model of the Ftin Flon mining camp (Canada) to address some imaging and interpretation issues related to a 17 km2 3D survey acquired in the camp and described in a complementary paper (part 1). A 3D geologic volumetric model of the camp was created based on a compilation of geologic data constraints from drillholes, surface geologic mapping, interpretation of 2D seismic profiles, and 3D surface and grid geostatistical modeling techniques. The 3D modeling methodology was based on a hierarchical approach to account for the heterogeneous spatial distribution of geologic constraints. Elastic parameters were assigned within the model based on core sample measurements and correlation with the different lithologies. The phase-screen algorithm used for seismic modeling was validated against analytic and finite-difference solutions to ensure that it provided accurate amplitude-variation-with-offset behavior for dipping strata. Synthetic data were generated to form zero-offset (stack) volume and also a complete prestack data set using the geometry of the real 3D survey. We found that the ability to detect a clear signature of the volcanogenic massive sulfide with ore deposits is dependent on the mineralization type (pyrite versus pyrrhotite rich ore), especially when ore-host rock interaction is considered. In the presence of an increasing fraction of the host rhyolite rock within the model volume, the response from the lower impedance pyrrhotite ore is masked by that of the rhyolite. Migration tests showed that poststack migration effectively enhances noisy 3D DMO data and provides comparable results to more computationally expensive prestack time migration. Amplitude anomalies identified in the original 3D data, which were not predicted by our modeling, could represent potential exploration targets in an undeveloped part of the camp, assuming that our a priori earth model is sufficiently accurate. [ABSTRACT FROM AUTHOR]

• A novel silicon quantum dots based nano-fluid was developed. • With a high salinity and thermal resistance, the developed nano-fluid reduced IFT and improved water wettability. • Both imbibition and core flooding experiments were carried out in tight Bakken cores with the nano-fluid. • The nano-fluid will be a potential oil displacing agent for tight formation EOR. A novel silicon quantum dots (SiQDs) based nano-fluid was first developed for effectively recovering Bakken Oil. The Bakken Formation is one of the largest contiguous deposits of unconventional oil in the USA and Canada. However, the oil recovery rate is only 5%−10% due to the existence of abundant tiny pores and ultra-low permeability. In this work, a novel nano-fluid was developed using ultra-small sized silicon quantum dots (SiQDs) coated with a zwitterionic surfactant. The nano-fluid exhibited good stability in synthetic high salinity brine containing divalent cations at high temperature and excellent capabilities in reducing interfacial tension and altering wettability, making it a good enhanced oil recovery (EOR) agent for tight Bakken Formation. Experimental results showed that the developed nano-fluid recovered 25.72 %OOIP (original oil-in-place) from Bakken core samples by spontaneous imbibition, which was 7.49 %OOIP higher than using surfactant alone. Similar results were obtained in the core flooding tests, where 41.98 %OOIP was finally recovered by the nano-fluid, compared to 30.28% in surfactant case. Herein, the mechanisms of disjoining pressure and synergistic effects between surfactant and nanoparticles have also been put forward. In short, the developed quantum dots based nano-fluid has played an instructive and a reference role in the application of oil field and would be a potential oil displacing agent for EOR. [ABSTRACT FROM AUTHOR]

The integrated analysis of seismic rock properties, lithogeochemical data, and mineral compositional data, estimated via scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), provides insight into the effects of hydrothermal alteration on seismic reflectivity in the footwall of the Lalor volcanogenic massive sulfide (VMS) deposit, Manitoba, Canada. The effects of hydrothermal alteration on variations in acoustic impedance are secondary in magnitude and superimposed on the dominant acoustic impedance contrast between felsic and mafic volcanic protoliths. This secondary effect is due to an increase in P-wave velocity with increasing intensity of hydrothermal alteration, as measured by the Ishikawa and Carbonate-Chlorite-Pyrite alteration indices. Mixture modeling of the seismic rock properties and mineral percentages suggests that the increase in seismic velocity is due to an increase in abundance of cordierite, which is one of the diagnostic aluminum silicates for hydrothermally-altered volcanic rocks metamorphosed in the upper almandine amphibolite facies. The synthetic seismic data of a simple VMS model consisting of mafic-felsic host rock contacts, a sulfide ore lens, and a discordant hydrothermal conduit, consisting of the amphibolite-facies mineral assemblage (600 °C, 6 kbar) encountered at Lalor, show enhanced seismic reflections at conduit-host rock contacts, in comparison to its greenschist facies equivalent (350 °C, 2.5 kbar). This zone of enhanced seismic reflectivity in the footwall of the massive sulfide ore zone is also recognized on the Lalor seismic data suggesting that high-grade terrains hosting VMS deposits possess enhanced potential for the seismic detection of their footwall hydrothermal alteration zones. [ABSTRACT FROM AUTHOR]