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Igneous rocks of Nusab El Balgum are formed as an elongated complex mass covering an area of about 4 km × 12.5 km (50 km2), in the NNE-SSW direction of the Tarfawi-Qena-South Sinai trend, which is a branch of the Trans-African shear zone at the intersection with the Kalabsha fault, which is a branch from Guinean-Nubian lineaments. The continuous reactivation of these two major weakness zones from the late Triassic to recent times has created many generations of the magma batches. The exposed granitic rocks of these batches at Nusab El Balgum were represented by the fresh peralkaline granite (youngest) and hydrothermally altered granites (oldest). The fresh peralkaline granite takes the form of a small stock composed essentially of perthites, quartz, sodic pyroxenes, amphiboles (secondary), and rare albite according to the proportion of presence, respectively. The accessory minerals are zircon, bastnaesite-(Ce), columbite-(Fe), magnetite, barite, and sphalerite. The geochemical study indicated that this granite is peralkaline, ferroan, A-type (specifically belongs to the A1-subgroup), anorogeny, emplaced in a within-plate, and crystallized at relatively shallow depth from the alkali basaltic magma similar to the OIBs. Furthermore, it is enriched in the HFSE (e.g., Th, U, Nb, REE, and Zr). The hydrothermally altered granites are formed as an incomplete ring shape and a small stock. They were formed during the late Cretaceous age and were altered due to the hydrothermal solutions from the continuous reactivation affected weakness zones and the new magmatic batches. The hydrothermally altered granites are extremely rich in HFSE found in the accessory minerals such as zircon (different in shape, size, and contains inclusions of bastnaesite and columbite), columbite-(Fe&Mn), rare gittinsite, pyrochlore minerals (ceriopyrochlore and plumbopyrochlore) carlosbarbosaite, changbaiite, bastnaesite-(Ce), monazite-(Ce), stetindite, cerianite-(Ce), thorite, and uranothorite. These rocks were subjected to many highly superimposed hydrothermal alteration types, including propylitic, sericitic, potassic, silicification, argillic, and Fe-Mn oxy-hydroxides. The hydrothermal solutions with low temperatures and containing F1− and CO32−, PO43− and H2O caused redistribution; transportation and redeposition of the HFSE in these rocks, in addition to the clay minerals and K-metasomatism, were formed. The relations between the silicification index (SI = SiO2/(SiO2 + Al2O3) and Zr, Nb, Th, U, LREE, and HREE are positive but they become negative with the K-metasomatism. [ABSTRACT FROM AUTHOR]

Abstract Titanium (Ti) is typically hosted in detrital minerals in marine sediments and has long been considered to be immobile during diagenesis. In this study, the authigenic titania minerals, brookite and anatase, are observed in early Cambrian carbonaceous shales from the Meishucun and Zhajin sections of South China, respectively. Black shales in the Meishucun section have total organic carbon (TOC) contents from 1.6 to 3.9 wt% and HI (hydrogen index) values from 3.8 to 20 mg HC/g TOC, whereas black shales in the Zhajin section have much higher TOC (7.1–15.6 wt%) but lower HI (<2.0 mg HC/g TOC) and contain abundant bitumen (~3 vol%). Brookite in black shales from the Meishucun section crystallized invariably along cleavages of detrital biotite. This intimate association suggests that the Ti required to form titania minerals was derived from detrital biotite and that Ti was mobilized only on a nano- to micro-meter scale. In contrast, anatase aggregates in black shales from the Zhajin section are intergrown with bitumen. It is proposed that Ti in these shales was mobilized in low pH organic-rich fluids and, subsequently, preferentially precipitated as anatase with increasing pH. The mobilization of inert Ti in black shales is indicative of a possible diagenetic or post-diagenetic elemental redistribution in carbonaceous rocks. Our study further demonstrates that proxies based on geochemical component of black shales can be employed to estimate redox state of ancient oceans, but must be applied with caution. [ABSTRACT FROM AUTHOR]

Although it is well known that A-type granites are enriched in the rare earth elements (REE) and other high field strength elements (HFSE), the magmatic processes that concentrate these elements are still poorly understood. The 1.24 Ga Strange Lake pluton in northern Québec-Labrador provides an extraordinary example of hyper-enrichment in the REE, Zr, and Nb in a peralkaline A-type granite. The pluton consists of two hypersolvus granite units (southern and northern) and a transsolvus granite, all of which contain perthitic alkali feldspar as the earliest major mineral; the transsolvus granite also contains separate albite and microcline crystals. Arfvedsonite, a sodic amphibole, occurs exclusively as phenocrysts in the transsolvus granite, whereas in the hypersolvus granite it is present as a late, interstitial phase. The primary HFSE minerals are zircon, monazite-(Ce), gagarinite-(Ce) and the pyrochlore group minerals. Magma evolution was monitored by the alumina content in the bulk rock, which decreases from the southern to the northern hypersolvus granite and is lowest in the transsolvus granite. Alkalinity indices and bulk Si, Fe, Rb, REE, Zr, Nb concentrations show the opposite trend. Alkali feldspar compositions mirror the trend shown by the bulk rock, i.e., decreasing Al contents are accompanied by increasing Si, Fe 3+ , REE, Zr and Nb contents. The major driving forces for the evolution of the hypersolvus magma prior to emplacement were the early separation of a fluoride melt from the silicate melt and the crystallization of alkali feldspar and HFSE-rich phases (zircon, monazite-(Ce), pyrochlore group). An alkali feldspar-rich crystal-mush containing LREE-fluoride melt droplets was emplaced as the least evolved southern hypersolvus granite. Massive fractionation of alkali feldspar led to a sharp increase in ƒH 2 O and F − activity in the magma chamber that triggered the crystallization of arfvedsonite and was followed by emplacement of the northern hypersolvus granite, which contained a higher proportion of LREE-fluoride melt droplets. Further evolution in the magma chamber led to a transition from a miaskitic to an agpaitic composition. The transsolvus granite was intruded in the form of a low viscosity crystal mush of alkali feldspar, quartz, arfvedsonite (after appreciable crystallization of arfvedsonite) and LREE-fluoride melt droplets. Upon emplacement, arfvedsonite (and gagarinite-(Ce)) crystals segregated as cumulates in response to a combination of flow differentiation and gravity settling. The immiscible fluoride melt accumulated in a volatile-rich residual silicate magma, which migrated to the top of the pluton where it formed the F-REE-rich cores of highly mineralized pegmatites. [ABSTRACT FROM AUTHOR]

Scheelite is the main ore mineral in skarn-type tungsten deposits, and a common accessory mineral in a variety of rock-types. The Baoshan deposit in South China is one of the most important polymetallic scheelite skarn deposits in China, hosting 40,000 t of WO 3 with economic concentrations of Zn, Cu, and Ag. It is hosted by a calcic skarn that is zoned outwards mineralogically from garnet-clinopyroxene, through clinopyroxene-garnet, to wollastonite, and overprinted by retrograde minerals. Scheelite occurs in both the prograde and retrograde skarns, and is complexly zoned. On the basis of its textures, the scheelite was classified into three types. Scheelite I and II belong to the early and late prograde stages, respectively, and Scheelite III precipitated during the retrograde stage. The molybdenum (Mo) content of these scheelite types ranges from 54 ppm to 24 wt%, and the total rare earth element content ranges from 12 to 321 ppm. Rare earth element (REE) concentrations and chondrite-normalized REE profiles vary with the distribution of major elements. The profiles indicate variable degrees of REE enrichment, which correlates negatively with the Mo content. Molybdenum-rich scheelite displays a negative Eu anomaly, and Mo-poor scheelite a positive Eu anomaly. Crystal structure provided the first-order control on the minor and trace element composition of the scheelite. Incorporation of REE 3 + into scheelite was controlled partly by a coupled substitution involving Mo. The lattice strain model was used to estimate scheelite-fluid partition coefficients for the REE from the contents of these elements in the scheelite and to predict the relative distributions of the REE in the ore-forming fluids. It is proposed that conditions were initially oxidizing, leading to strong incorporation of Mo in Scheelite I, that they became more reducing with the crystallization of Scheelite II containing lesser Mo, and that during retrograde skarn formation there was a return to oxidizing conditions due to an influx of meteoric waters, which altered Scheelite II giving rise to the formation of Scheelite III. The study shows that the composition of scheelite recorded the history of the Baoshan hydrothermal system, and that the behaviour of the REE could be used to quantitatively reconstruct the changing physicochemical conditions during ore formation. [ABSTRACT FROM AUTHOR]

High-resolution scanning- and transmission-electron microscopy of pyrobitumen-hosted uraninite reveal that uraninite grains are highly porous aggregates of uniformly sized nanocrystals, and that many of their pores are filled by native gold. These texturally late gold grains, in turn, contain small pores occupied by former oil droplets that were converted to pyrobitumen during burial and metamorphism. The pyrobitumen in the pores of the gold grains contains in situ-formed uraninite nanocrystals. Galena also occupies the pores of the uraninite aggregates. In addition, this study reveals the first occurrence of rare lanarkite that engulfs the galena in the pores of the uraninite. On the basis of the nature of the uraninite and the filling of some of its pores with native gold, we propose a mineralization model for the deposition of the uranium and gold in the Carbon Leader Reef that calls upon the interaction of oil and aqueous (hydrothermal) fluids to form micro-emulsions. According to this model, uraninite nanocrystals precipitated from uranium-bearing hydrocarbon liquids and flocculated to form porous, uraninite aggregates. These liquids interacted with auriferous hydrothermal fluids in the Carbon Leader Reef, leading to the formation of a micro-emulsion at the interface between the two fluids. Gold precipitated as native metal around droplets of the oil owing to a reduction in oxygen fugacity, which destabilized the bisulfide species responsible for gold dissolution. Commonly, this process went hand in hand with the flocculation of the uraninite nanocrystals, causing entrapment of the native gold in the pores of the uraninite aggregates. The hydrocarbon liquid, which occurs as droplets in the gold and is the host to the uraninite aggregates, was transformed to pyrobitumen. As a result of this process, a thin pyrobitumen seam containing uraninite nanocrystals formed along the inner walls of the pores in the native gold. Lead introduced by the hydrocarbon liquid precipitated as galena. Interaction of the uraninite with hydrothermal fluids or radiolysis of the pore water facilitated the development of local zones of oxidation between galena and uraninite, which led to the crystallization of rare lanarkite. [ABSTRACT FROM AUTHOR]

Uranium (U) and iron (Fe) are generally considered to have contrasting aqueous geochemical behavior, with U dissolution being favored in oxidizing fluids as oxidized U (U6+) and Fe in reducing fluids as reduced Fe (Fe2+) species. However, high concentrations of both U and Fe have been reported for the ore fluids of uranium deposits, suggesting that the two elements can be co-transported in the same fluid. In this study, geochemical modeling, based on recent thermodynamic and experimental data for U and Fe species and fluid inclusion compositions from two types of hydrothermal U deposits (volcanic-related and unconformity-related), was conducted to investigate the nature and conditions of U Fe co-transportation. The results of the modeling indicate that high concentrations of U (>10, up to >100 ppm) and Fe (>1000 ppm) can be dissolved in acidic aqueous fluids (pH < ∼3.3) of moderate to high chlorinity (∼ 55 to 250 g/L Cl), for a wide range of log f O 2 above and below the magnetite-hematite (MH) buffer (from ∼ MH-5 to MH + 30), at temperatures from 150 to 250 °C. There are four different combinations of dominant dissolved U and Fe species depending on the pH and redox conditions: U6+ and Fe3+ species (UO 2 Cl 2 0 and FeCl 3 0) at relatively high f O 2 , U4+ and Fe2+ species (UCl 4 0 and FeCl 4 2−) at relatively low f O 2 , and U6+ and Fe2+ species (UO 2 Cl 2 0 and FeCl 4 2−) or U4+ and Fe3+ species (UCl 4 0 and FeCl 3 0) at intermediate f O 2 conditions. Because the most important U mineral in hydrothermal uranium deposits is uraninite (UO 2), in which U is present as U4+, a necessary condition for U mineralization is that U is either transported as U4+ species or, if transported as U6+ species, precipitation of uraninite is induced by a reducing agent. The recognition that U6+ and Fe2+ species can be co-transported in the same fluid indicates that uraninite can be precipitated without the need to invoke a reducing agent external to the ore fluid. The driver of uranium mineralization in this case is an increase in pH due to fluid-rock interaction that leads to the alteration of the rocks by clay minerals and associated coupled sorption-reduction. These findings provide for a more extensive range of conditions for U transport and deposition than previously imagined and require that interpretation of the conditions of uranium mineralization consider both oxygen fugacity and pH. This study underscores the potential for uranium deposits to occur in geological settings where reducing agents are either absent or insufficiently abundant to account for the observed mineralization, and the possibility for the transport of U in environments that might otherwise be considered unfavorable. [ABSTRACT FROM AUTHOR]

The process of slab tearing profoundly affects interchanges of material and energy between the lithosphere and asthenosphere and has been invoked as a trigger of magmatism in modern and ancient subduction‐collision systems. Horizontal slab tears may occur after continental collision and subsequent slab break‐off, whereas vertical slab tears may occur in response to along‐strike variations in rollback velocity, thereby ripping the subducting lithosphere. Previous studies have documented tearing of subducting slabs in modern convergent settings using geophysical methods, but in ancient collisional belts, where these methods cannot be applied, detection of slab tearing is more difficult, particularly if the oceanic plate was fully subducted and the geological evidence for subduction is limited. Here, we employ multiproxy element‐isotope imaging, as well as zircon petrochronology and whole‐rock geochemistry, to assess evidence of vertical tearing of the Mianlue slab in the Triassic Qinling Orogen in central China. Our results show evidence of anomalous, inferred tear‐related magmatism east of 107°E, at 225–210 Ma. Vertical tearing of the northward subducting Mianlue slab is recorded by geochemically anomalous igneous rocks, and the recognition of N–S to NE–SW trending boundaries defined by Sr‐Nd‐Hf isotopes, elemental ratios (Nb/Ta, and Ca/Al), Mg#, and reduced crustal thickness between 107° and 108°E. The inferred vertical tear may have been driven by slab rollback of the Mianlue slab at 225–210 Ma. The results show that multiproxy element‐isotope imaging (e.g., of εNd(t), εHf(t), (87Sr/86Sr)i, Nb/Ta, Mg#, and Ca/Al) can be used to reconstruct the evolution of fossil subduction systems. Plain Language Summary: Subduction zones are natural factories for the circulation of material in the Earth as they allow tectonic plates to descend into the mantle. Pieces of subducting plates, normally referred to as slabs, can be torn and segmented, but reconstructing the geometry of such tears in ancient convergent plate boundary settings is difficult. Based on the observation that slab tearing can trigger anomalous magmatism in convergent plate margins, we present a multiproxy geochemical and isotopic imaging method that enables us to understand the process of slab tearing in the Qinling Orogen (China) during the Triassic. We found that igneous rocks from the Qinling Orogen, east of 107°E, are geochemically anomalous (relative to typical arc rocks). These rocks are dated 225–210 Ma. By imaging various geochemical characteristics, our results demonstrate that the subducting Mianlue slab was likely torn at longitude 107°–108°E, thereby producing geochemically and isotopically anomalous mafic and felsic magmatism. Key Points: The geometry of slab tearing in an ancient orogen is constrained by a multiproxy geochemical approachAnomalous arc magmatism dated at 225–210 Ma is identified in the Qinling Orogen east of 107°EThe Mianlue slab underwent southward vertical slab tearing at 107°−108°E in the Late Triassic [ABSTRACT FROM AUTHOR]

Porphyry and epithermal ore deposits, which are the products of magmatic hydrothermal fluids, are intimately associated with volcanoes in continental and island arcs above subduction zones, but the exact nature of this relationship has remained enigmatic. Although metal deposition is usually thought to occur during the waning stages of volcanism, numerous ore deposits have been demonstrated to be synvolcanic. Here we show how the formation of these deposits is tied to volcanic cycles. We relate the chemical variations in vapors from Merapi volcano, Indonesia, to different stages of its eruptive cycle. The chemical compositions of volcanic vapors from subduction zone volcanoes are then compared globally to those of fluid inclusions from porphyry-epithermal deposits. These data show that adiabatic decompression is the principal control on mineralization. The data also suggest that volcanic and subvolcanic magmatic-hydrothermal systems are under lithostatic pressure during quiescence but decompress rapidly during injections of mafic magma and explosive eruptions. During quiescence, the magma evolves through fractional crystallization and devolatilization, gradually becoming oxidized and enriched in gold and other incompatible metals. Upon the injection of sulfur-rich mafic magmas, subvolcanic intrusions brecciate the overlying rocks, the systems are depressurized, the volcanoes erupt explosively, supercritical fluids unmix into vapor and brine, and base metal sulfides precipitate. [ABSTRACT FROM AUTHOR]

The polymetallic Mykonos vein system in the Cyclades, Greece, consists of 15 tension-gashes filled with barite, quartz, pyrite, sphalerite, chalcopyrite and galena in ca. 13.5 Ma, I-type, Mykonos monzogranite. Zones of silica and chlorite–muscovite alteration are associated with the veins and overprint pervasive silicification, phyllic and argillic alteration that affected large parts of the monzogranite. The mineralization cements breccias and consists of an early barite–silica–pyrite–sphalerite–chalcopyrite assemblage followed by later argentiferous galena. A combination of fluid inclusion and stable isotope data suggests that the barite and associated mineralization were deposited from fluids containing 2 to 17 wt.% NaCl equivalent, at temperatures of ~ 225° to 370 °C, under a hydrostatic pressure of ≤ 100 bars. The mineralizing fluids boiled and were saturated in H 2 S and SO 2 . Calculated δ 18 O H2O and δD H2O , initial 87 Sr/ 86 Sr isotope compositions and the trace and REEs elements contents are consistent with a model in which the mineralizing fluids were derived during alteration of the Mykonos intrusion and subsequently mixed with Miocene seawater. Heterogeneities in the calculated δ 34 S SO4 − 2 and δ 34 S H2S compositions of the ore fluids indicate two distinct sources for sulfur, namely of magmatic and seawater origin, and precipitation due to reduction of the SO 4 − 2 during fluid mixing. The physicochemical conditions of the fluids were pH = 5.0 to 6.2, log f S2 = − 13.8 to − 12.5, log f O2 = − 31.9 to − 30.9, log f H2S(g) = − 1.9 to − 1.7, log f Te2 = − 7.9 and logα(SO 4 − 2 (aq) /H 2 S (aq) ) = + 2.6 to + 5.5. We propose that retrograde mesothermal hydrothermal alteration of the Mykonos monzogranite released barium and silica from the alkali feldspars. Barite was precipitated due to mixing of SO 4 − 2 -rich Miocene seawater with the ascending Ba-rich magmatic fluid venting upwards in the pluton. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the behavior of Cu, Zn, and Pb in magmatic–hydrothermal systems is essential in developing models for the genesis of hydrothermal ore deposits in subduction environments. A commonly held view is that the metals originate in magmas of intermediate to felsic composition from which they partition directly into exsolving aqueous fluids. In this paper, we build on the results of an earlier study in which we showed that Fe, Cu, Co and Ni at Merapi volcano, Indonesia, were transferred from a mafic melt to an immiscible sulfide melt, and then to a magmatic volatile phase which carried them to the surface. Here we examine the pathways taken by the volatile phase and the behavior of Cu, Zn and Pb in the upper part of the magmatic system beneath Merapi volcano. Based on the composition of a suite of silicate melt inclusions and thermodynamic modeling, we show that the mafic melt did not hybridize with the resident felsic melt but instead transferred metals to the latter by exsolving a magmatic volatile phase which dissolved the Cu-rich sulfide melt and then percolated upwards through the felsic melt, enriching it in Cu and Pb. It is this fluid which transported the metals to the surface and potentially also to subsurface environments of ore formation. [Copyright &y& Elsevier]

Abstract: Knowledge of the thermodynamic properties of aqueous nickel chloride complexes is important for understanding and quantitatively evaluating nickel transport in hydrothermal systems. In this paper, UV–Visible spectroscopic measurements are reported for dissolved nickel in perchlorate, triflic acid and sodium chloride solutions at temperatures up to 250°C and 100bar. The observed molar absorbance of Ni2+ in both perchlorate and triflic acid solutions is similar, and the absorbance peak migrates toward lower energy (red-shift) with increasing temperature. The spectra of nickel chloride solutions show a systematic red-shift with increasing temperature and/or chloride concentration. This allowed identification of the nickel chloride species as NiCl+, NiCl2(aq) and NiCl3 -, and determination of their formation constants. Based on the experimental data reported in this paper and those of previous experimental studies, formation constants for these nickel chloride complexes have been calculated for temperatures up to 700°C and pressures up to 2000bar. The solubility of millerite (NiS) and pentlandite (Ni4.5Fe4.5S8) calculated using these constants shows that nickel dissolves in significantly higher concentrations in hydrothermal solutions than previously estimated. However, the solubility is considerably lower than for corresponding cobalt sulphide minerals. This may explain why hydrothermal nickel deposits are encountered so much less frequently than hydrothermal deposits of cobalt. [Copyright &y& Elsevier]

Abstract: The volumetric properties of H2O–H2S fluid mixtures have been determined experimentally at temperatures of 150 to 400°C and pressures up to 240bar. Using these data and existing equations of state, we have developed a thermodynamic model for H2O–H2S fluid mixtures. This model is based on an asymmetric description of phases, which includes an activity model and a P–T-dependent Henry’s law constant for the liquid, and equations of state with mixing rules for the vapour. The fugacity of the vapour was calculated using the cubic equations of state of with density-dependent and composition-dependent mixing rules. Sets of binary interaction parameters for these equations were fitted to the experimental data obtained in this study supplemented by high-temperature PVTx data for H2O–H2S fluid mixtures reported in the literature. The Peng–Robinson equation used in conjunction with density-dependent mixing rules was found to be the most accurate of the available equations in representing the properties of the vapour phase. The errors in the pressure of the homogeneous vapour mixtures estimated using the above equations of state (relative deviation from the experimentally determined pressure) were comparatively low, ∼5% to 8%. However, the errors were significantly higher for the estimated pressure of vapour saturated with liquid, i.e., along the vapour–liquid phase boundary (11–15%), due to the polar nature of H2O and H2S and the resulting highly non-ideal behaviour of the fluid mixtures. The results of this study make it possible to reliably estimate the volumetric properties of aqueous fluids containing H2S at temperatures and pressures up to 400°C and 240bar, i.e., for conditions commonly encountered in natural hydrothermal systems. [Copyright &y& Elsevier]

Abstract: This experimental study sheds light on the complexation of gold in reduced sulphur-bearing vapour, specifically, in H2O–H2S gas mixtures. The solubility of gold was determined in experiments at temperatures of 300, 350 and 365°C and reached 2.2, 6.6 and 6.3μg/kg, respectively. The density of the vapour varied from 0.02 to 0.22g/cm3, the mole fraction of H2S varied from 0.03 to 0.96, and the pressure in the cell reached 263bar. Statistically significant correlations of the amount of gold dissolved in the fluid with the fugacity of H2O and H2S permit the experimental data to be fitted to a solvation/hydration model. According to this model, the solubility of gold in H2O–H2S gas mixtures is controlled by the formation of sulphide or bisulphide species solvated by H2S or H2O molecules. Formation of gold sulphide species is favoured statistically over gold bisulphide species and thus the gold is interpreted to dissolve according to reactions of the form: Equilibrium constants for Reaction (A1) and the corresponding solvation numbers (KA 1 and n) were evaluated from the study of . The equilibrium constants as well as the hydration numbers for Reaction (A2) (KA 2 and m) were adjusted simultaneously by a custom-designed optimization algorithm and were tested statistically. The resulting values of log KA 2 and m are −15.3 and 2.3 at 300 and 350°C and −15.1 and 2.2 at 365°C, respectively. Using the calculated stoichiometry and stability of Reactions (A1) and (A2), it is now possible to quantitatively evaluate the contribution of reduced sulphur species to the transport of gold in aqueous vapour at temperatures up to 365°C. This information will find application in modelling gold ore-forming processes in vapour-bearing magmatic hydrothermal systems, notably those of epithermal environments. [Copyright &y& Elsevier]

Earth is the "blue planet," with more than 70% of its surface covered in water and the equivalent of up to four oceans of water in its interior. This abundance of water has a profound impact on the processes that shape our planet as well as the development of the organisms that inhabit it. To understand this impact, it is necessary to know the properties and compositions of this fluid. At present, this information is largely unavailable, because direct samples of fluid are rare, especially for early Earth and Earth's interior, and other estimators are semiquantitative, at best. Here we propose a different approach in which the composition of the fluid is reconstructed from that of minerals, based on the characteristic trace element partitioning between minerals and aqueous fluids. We show experimentally that this partitioning is systematic and obeys lattice-strain theory. It depends strongly on element complexation in the fluid, but this dependence is predictable and can be accommodated. Unlike fluids, minerals with preserved compositions are readily available in the geological record, and this approach therefore provides a powerful and widely applicable tool to reconstruct a quantitative record of fluid composition for the full range of Earth environments and for its earliest history. [ABSTRACT FROM AUTHOR]

Abstract: The solubility of gold in H2S gas has been investigated at temperatures of 300, 350 and 400°C and pressures up to 230bars. Experimentally determined values of the solubility of Au are 0.4–1.4ppb at 300°C, 1–8ppb at 350°C and 8.6–95ppb at 400°C. Owing to a positive dependence of the logarithm of the fugacity of gold on the logarithm of the fugacity of H2S, it is proposed that the solubility of Au can be attributed to formation of a solvated gaseous sulfide or bisulfide complex through reactions of the type:orwhich are -dependent; n is a statistical solvation number. If the redox potential is buffered by S/H2S (the case in our study), the corresponding reactions are:or Values of n for these latter reactions were calculated to be 1.8 and 1.2 at 300°C, 1.7 and 1.0 at 350°C, 2.2 and 1.7 at 400°C, respectively. The equilibrium constants for reactions 3 and D increase with temperature and have values of log K =−11.1±0.2 at 300°C (both reactions), −10.7±0.3 and −10.5±0.3 at 350°C, and −10.6±0.2 and −10.4±0.2 at 400°C, respectively. At the conditions of this study, the solubility of gold in H2S gas is relatively high, and the results obtained provide strong evidence that H2S can play an important role in the vapor transport of gold and the formation of hydrothermal gold deposits. [Copyright &y& Elsevier]

Two world-first examples of mangan oxide skarns were investigated in this study, namely the Panorama skarn of Drama and the Thapsana skarn of Paros Island, in the Rhodope and Attico-Cycladic Massifs, respectively. Transitional calcic-to-mangan exoskarn at Panorama is exposed in the garnet-epidote zone (Grt-Ep), proximal to the Panorama (micro-)granite. In Paros Island, mangan skarn is related to rhodonite (Rdn ± Ves), johannsenite-spessartine (Jhn-Sps) and spessartine-cummingtonite (Sps-Cum) zones, adjacent to marbles and/or gneisses and the Thapsana leucogranite. A two-stage manganese-oxide assemblage is present in the Thapsana skarn and comprises jacobsite, hausmannite, braunite with minor magnetite (stage I) followed by hollandite, cryptomelane and pyrite (stage II) with gangue rhodochrosite, calcite, and ankerite. Multiple isotopic evidence (i.e., δ18O, δD, δ44Ca, δ26Mg, 87Sr/86Sr, U/Pb) support the granitic source of the Mn-rich metasomatic fluids in both case studies. The Thapsana mangan skarn formed at a pressure of ∼110 MPa and a temperature range of ∼305° to 565 °C, from initially acidic (pH = 3.5), saline (up to ∼48.0 wt% NaCl equivalent), Mn chloride-bearing, skarn-forming fluids with elevated log[α Mn 2+/(α H +)2] and log[α Mn 3+/(α H +)3]. Fluid inclusions results obtained from the Jhn-Sps zone suggest phase separation of the metasomatic fluids at ∼480 °C and ∼120 MPa and ∼400 °C and ∼100 MPa. Thermodynamic modeling suggests that the manganoan skarn assemblages formed due to simple cooling and fluid-rock interaction, increase in pH and changes in the redox state of the metasomatic fluids in concert with successive deposition of Mn2+ and Mn3+ assemblages. This led to a paragenesis that comprises early anhydrous manganoan silicates, followed by more complex assemblages dominated by hydrous manganoan silicates and Mn3+ oxides. In this study we propose a metallogenic model in which mangan skarns are formed proximally to their parental leucogranites, primarily from anatectic reworking of crustal Mn-rich sources (e.g., gneisses and marbles) that delivered peraluminous melts with increased primary endowments in manganese. Exsolution of chloride magmatic fluids atypically enriched in incompatible manganese, deposited manganoan silicates and oxides with declining temperature in the skarn environment. However, in situ reworking of manganese upon fluid-rock interaction during skarnification cannot be discounted as an additional contributing source for manganese. The results of this study encourage us to propose the establishment of a new mangan-oxide mineralized skarn class as a distinct candidate for skarn mineralization. [Display omitted] • A new type of Mn-oxide skarn mineralization is proposed. • Mangan skarns are genetically linked to peraluminous granitoids. • Mn-skarns are mainly formed from anatectic reworking of crustal Mn-rich sources. • Skarn formation occurred at temperatures between 550 °C and 380 °C at low pressures. • Mn-skarns formed mainly by phase separation, cooling, and Mn redox state. [ABSTRACT FROM AUTHOR]

The heat capacity of natural xenotime-(Y) and synthetic DyPO 4 and ErPO 4 crystals was determined by differential scanning calorimetry (DSC) at temperatures of 298.15 K to 868.15 K and a pressure of 0.1 MPa. The aim of the study was to develop a method to accurately measure the isobaric heat capacity ( C P ) of rare earth element (REE) phosphates, compare the results to data from adiabatic calorimetric experiments, and evaluate the deviation from ideality of the C P of the natural xenotime-(Y) solid solution. The measured C P data (in J mol −1 K −1 ) can be described by the relationships: 185.5 − 751.9T −0.5 − 3.261e + 06 T −2 for DyPO 4 ; 207.2 − 1661T −0.5 − 5.289e + 05 T −2 for ErPO 4 ; and 208 − 1241T −0.5 − 2.493e + 06 T −2 for xenotime-(Y); where T is the temperature in K. The heat capacity data for natural xenotime-(Y) were used to determine the excess function for the solid solution, which yields an excess heat capacity ranging between 7.9 and 10.7%, well within the range of the DSC method used in this study. The experiments indicate that xenotime-(Y) forms a non-ideal solid solution. Future DSC studies will provide important data for developing a solid solution model for the incorporation of REE in xenotime-(Y). [ABSTRACT FROM AUTHOR]

The solubility of Yttrium (III) fluoride as a function of fluoride activity was investigated experimentally at 100, 150, 200 and 250°C and vapor-saturated water pressure. Data obtained from the experiments were used to determine the solubility product of YF3(s), the fluoride speciation of Y and the stability constants of the corresponding complexes. The dominant Y-fluoride species at the temperatures investigated is the di-fluoride complex ( ). Consequently, fluoride speciation of Y differs substantially from that of the lanthanides (Ln), which dominantly form mono-fluoride complexes (LnF2+) at these temperatures. The logarithm of the solubility product (log K sp) of YF3(s) is −20.8±0.50, −21.5±0.46, −22.4±0.56 and −24.3±0.12 at 100, 150, 200 and 250°C, respectively. The logarithm of the formation constant (log β) of is 8.3±0.77, 10.7±0.43, 12.1±0.31 and 13.3±0.16 at the same temperatures, respectively. Differences in the speciation of Y from that of the lanthanide, holmium (Ho), quantitatively explain the fractionation between these geochemical twin elements, which has been reported for many fluoride-rich hydrothermal systems. Our results emphasize the usefulness of the Y/Ho ratio as a geochemical indicator in hydrothermal systems. [ABSTRACT FROM AUTHOR]

Abstract: The hyperacidic brines of the Kawah Ijen crater lake and Banyu Pahit river, East Java, Indonesia, induce an intense alteration on their magmatic host rock. This alteration is a proxy for water–rock interaction in magmatic–hydrothermal systems and associated high-sulphidation mineralizing environments, as well as for how these systems translate changes in the magmatic system to surface emissions, which are used in volcanic hazard monitoring. Detailed bulk chemical study of altered and unaltered samples shows that alteration is characterised by near-complete leaching of all major and trace elements, except for Pb, Sn and Sb, which are progressively enriched (Pb up to 15-fold absolute enrichment). The resulting element release is complementary to the observed changes in composition of the Banyu Pahit water downstream, when corrected for dilution, indicating that alteration progressively increases the element load. The signature of the change in water chemistry is best explained by complete alteration of fresh rock, rather than mature alteration, which might be expected given the advanced altered state of the riverbed. Together with mass balance considerations, this indicates that the dominant element source is material falling into the river from the valley flanks. The chemical signature of the crater lake is inconsistent with the observed alteration in samples from the hydrothermal system, and likewise is best explained by surface input of cations from rocks falling in from the crater walls. This indicates that the lake water cation chemistry is not a direct reflection of the underlying magmatic–hydrothermal system and that its cation content is therefore not an appropriate monitor of changes in volcanic activity. [Copyright &y& Elsevier]

Fluid-saturated experiments were conducted to investigate the partitioning of boron among haplogranitic melt, aqueous vapor and brine at 800 °C and 100 MPa. Experiments were carried out in cold-seal pressure vessels for 1 to 21 days, and utilized powdered synthetic subaluminous haplogranite glass doped with 1000 ppm B (crystalline H3BO3) and variable amounts of NaCl and H2O at a fluid/haplogranite mass ratio=1:1. Run-product glasses were analyzed for boron concentration by secondary ion mass spectrometry (SIMS) and for major elements and chlorine by electron microprobe. The composition of the coexisting fluid was calculated by mass balance. Boron partition coefficients between aqueous vapor and hydrous granitic melt range from 3.1 to 6.3, and demonstrate a clear preference of boron for the vapor over the hydrous melt. Partition coefficients between brine and hydrous granitic melt vary from 0.45 to 1.1, suggesting that boron has no preference for the brine or the melt. The bulk fluid–melt partition coefficients for low-salinity and high-salinity experiments are DB(vapor/melt)=4.6±1.3 and DB(brine/melt)=0.91±0.49, respectively. The corresponding vapor–brine partition coefficient is 5.0±3.1, demonstrating that boron partitions preferentially into the vapor over the brine at the conditions of this study. The preferential incorporation of boron in the aqueous vapor is controlled by borate speciation and solution mechanism. The dominant borate species in aqueous fluids, H3BO3o, is highly soluble in aqueous vapor (XB2O3=0.187); however, B2O3 is immiscible in NaCl liquid. Consequently, concentrations of boron in aqueous vapor are significantly higher than in the coexisting brine. Furthermore, Na–B complexing in the melt at high chlorine fluid contents stabilizes boron in the melt thereby contributing to the non-preferential partitioning of boron between brine and melt. The commonly observed association of tourmalinization (boron metasomatism), brecciation and ore deposition in nature is consistent with the preferential partitioning of boron into aqueous vapor of magmatic-hydrothermal systems predicted by this study. [Copyright &y& Elsevier]

Permian granitoids have been identified in the Zhalageamu district, Inner Mongolia, NE China, which provide an excellent opportunity to constrain the tectonic evolution of the Central Asian Orogenic Belt (CAOB). In this study, we determined the zircon U Pb ages of the quartz diorite, granodiorite porphyry, diorite porphyry and granite porphyry at Zhalageamu. These ages are 269.5 ± 1.8, 261.4 ± 1.9, 256.4 ± 2.0 and 255.2 ± 2.0 Ma, respectively. The granitoids have high contents of SiO 2 (61.95–75.41 wt%) and Al 2 O 3 (11.87–15.88 wt%), and their A/CNK ratios range from 0.91 to 1.44. Their Na 2 O + K 2 O contents range from 6.04 to 9.28 wt% and help classify them as having calc-alkaline to high-K calc-alkaline affinity. The low P 2 O 5 contents of the quartz diorite, diorite porphyry and granite porphyry and their decrease with increasing SiO 2 , in combination with low 10,000*Ga/Al ratios (1.51–2.58) and Zr + Nb + Ce + Y contents (128–264 ppm) identify them as I-type granitoids, whereas the strongly peraluminous character of the granodiorite porphyry classifies it as an S-type granite. These I-type granitoids are characterized by an enrichment in large ion lithophile elements (LILE; e.g., Rb, Ba and Th) and a depletion in high field strength elements (HFSE; e.g., Nb, Ta and Ti). This, and their weakly negative Eu anomalies on chondrite-normalized REE diagrams, are features of typical arc magmatic rocks. The ɛ Nd (t) values and initial 87Sr/86Sr ratios range from 2.9 to 4.2 and 0.7010 to 0.7039, respectively, and both sets of values point to a mantle source. Hafnium isotopic analysis of quartz diorite yielded positive ε Hf (t) values of 8.5–12.3 and young two-stage Hf model ages (T DM2) of 0.51–0.72 Ga, suggesting a juvenile crustal source. These features are similar to those of locally occurring coeval volcanic arc rocks, indicating that the Zhalageamu granitoids mostly formed by partial melting of juvenile mantle-derived crust. Our geochemical and Sr-Nd-Hf isotopic data show that the Zhalageamu granitoids were generated in a subduction setting related to the northward subduction of the Paleo-Asian Ocean. [Display omitted] • The granitoids from the Zhalageamu district occurred between 269 and 255 Ma. • The granitoids formed by partial melting of juvenile mantle-derived crust. • The Paleo-Asian Ocean closed after late Permian. [ABSTRACT FROM AUTHOR]

• Hg anomalies of the end-CS 2 sediments were caused by eruptions of the ca. 510 Ma LIP. • Volcanic eruptions led to a high terrestrial SO 4 2 − input into the end-CS 2 ocean. • Upwelling of euxinic waters was the direct cause for the ca. 506 MA trilobite crisis. The first major mass extinction of trilobites occurred at the transition from Cambrian Series 2 (CS 2) to Miaolingian (M) and coincided with a large marine transgression and volcanic eruptions of a large igneous province (LIP). Understanding the causal links between these events is important in deciphering environmental changes and life evolution at that time. This paper presents S-Hg-C isotopic and Fe speciation data for calcareous shales from the CS 2 -M Yangliugang Formation in the Dongjin section, South China. In the lower part of this section (Interval I), calcareous shales have limited S isotopic differences between carbonate-associated sulfates (δ 34 S CAS) and pyrites (δ 34 S Py) with Δ 34 S values from –4.2‰ to +8.3‰; they also have high Fe HR /Fe T ratios from 0.5 to 0.66, that are indicative of a low SO 4 2 − content in anoxic seawater. Calcareous shales from Interval I display at least two Hg/TOC peaks (up to 207 ppb/wt%), coincident with volcanic eruptions associated with the ca. 510 Ma Kalkarindji LIP in Australia. In the middle part of the Dongjin section (Interval II), calcareous shales display negative excursions of Δ 199 Hg values, δ 34 S Py values and Fe HR /Fe T ratios, which were likely led by a large terrestrial input into a marginal basin from where Interval II deposited. Calcareous shales in the upper part of the section (Interval III) contain pyrite framboids with a mean diameter of <4 μm and high ratios of Fe HR /Fe T (>0.82) and Fe Py /Fe HR (>0.78), indicating an euxinic depositional environment. They also record negative excursions in δ 13 C and δ 202 Hg (with low values down to –3.05‰ and –1.68‰, respectively), providing evidence for ocean upwelling. The negative shift of δ 13 C values in the Dongjin section was temporally comparable to the C isotope excursions that coincided with the Redlichiid-Olenellid Extinction Carbon Isotope Excursion (ROECE). We conclude that volcanic eruptions of the ca. 510 Ma Kalkarindji LIP enhanced the continental erosion rate, leading to a high terrestrial SO 4 2 − input and an accumulation of H 2 S in deep marginal basins at the end of CS 2. The subsequent ocean upwelling (>506 Ma) brought anoxic/euxinic seawaters into the continental shelf, contributing to the mass extinction of Redlichiid and Olenellid. [ABSTRACT FROM AUTHOR]

The high mobility of boron during fluid-rock interaction makes it an effective tracer for the sources of magmatic and metamorphic fluids, as recorded in minerals such as tourmaline and muscovite. Although advances have been made in quantifying the fractionation of boron isotopes among different phases, boron isotope fractionation in complex silicate melts remains poorly understood. Here, we propose appropriate models for the BO 3 and BO 4 units in silicate melts covering a wide range of chemical compositions and boron coordination structures in silicate magmas, and report the results of a theoretical investigation of boron isotope fractionation among silicate melt, minerals and fluids using a first principles theoretical approach. A comparison of measured and calculated α factors in mineral-melt and fluid-melt systems shows good agreement, suggesting the applicability of a simplified treatment of boron coordination structures in silicate melt. The results of this study show that the proportion of trigonal/tetrahedral coordinated boron and the B/Si ordering in silicate tetrahedral layers control the boron isotope fractionation among different phases, and that the effect of chemical composition is minor (less than 2‰ at 600 K). The temperature-dependent boron isotope fractionations are described as 1000lnα mica-basic fluid = 0.8–2.4 × (1000/T) - 0.8 × (1000/T)2, 1000lnα mica-acidic fluid = 7.0–14.0 × (1000/T) - 1.2 × (1000/T)2 and 1000lnα mica-tur = 1.9–5.4 × (1000/T) -3.4 × (1000/T)2 (T is temperature in Kelvins). At magmatic temperatures, ∆11B values between mineral/fluid and melt also vary with the proportion of the BO 4 unit in the melt. This study underpins the applicability of the white mica-tourmaline geothermometers and boron isotopes for fluid source identification, and also offers an explanation of boron isotope fractionation in systems that contain complex silicate melts. Unlabelled Image [ABSTRACT FROM AUTHOR]

The garnet-epidote zone in the Xanthi Fe-skarn at the Rhodope Metallogenetic Massif, northern Greece, includes noteworthy cerium mineralization manifested by the presence of epidote-(Ce) containing up to ~130,000 ppm ΣREE and ~ 87,000 ppm Ce. The REE skarn represents a late evolutionary phase of the Xanthi's Fe-skarn in a collisional setting.- The epidote-(Ce) was deposited under pressures of ~1000 bars, at temperatures of ~345° to ~400 °C, from an almost pH neutral, saline, Ce-bearing, heterogeneous trapped, skarn-forming fluids with elevated log[ α REE 3+/(α H +)3] values. Thermodynamic two-stage modeling suggests that Ca metasomatism (e.g., decrease of the log α Ca2+ (aq) values) coupled with Ce fractionation (e.g., increase of the log α Ce(CO 3)+ (aq) values) of the skarn-forming fluids led to the formation of epidote-(Ce). The major mechanism for the Ce-enrichment in the metasomatic fluids was the remobilization of the REE from the I-type granodiorite of Xanthi, in a back-arc setting due to subduction retreat. Unlabelled Image • The Garnet-Epidote zone in the Xanthi Fe-skarn at the Rhodope Metallogenetic Massif, comprises epidote-(Ce) containing up to 87000 ppm Ce. • The Ce enrichment in the skarn-forming fluid was due to remobilization of the REE from the I-type granodiorite of Xanthi. • Xanthi pluton displays a composite petrotectonic evolution of emplacement as a metaluminous, I-type intrusion with VAG+Syn-COLG geochemical character for its easternmost mafic lithotypes, while the felsic lithotypes of main pluton body are peraluminous of S-type affinity and display WPG characteristics, marking probably the back-arc extension and upper plate delamination in Rhodope massif. [ABSTRACT FROM AUTHOR]

Silver deposits have long been considered to form due to the direct precipitation of silver minerals from aqueous fluids, in which the metal is transported as chloride and/or bisulfide complexes. Ultra-high-grade silver ores have silver contents up to tens of weight-percent in the form of silver sulfides and native silver. Ore-forming fluids of most silver deposits, however, typically contain low silver contents of parts per million silver. The challenge is to explain how fluids with such low concentrations of silver can form ultra-high-grade silver ores. Here, we present direct mineralogical evidence from natural samples showing that the high-grade silver ores form from the aggregation of silver sulfide nanoparticles through intermediate microparticles and dendrites to acanthite crystals. Native silver grows from silver sulfides via solid-state silver ion aggregation. This study traces the formation of silver sulfides from their nanoparticulate precursors, thereby providing insights into the genesis of ultra-high-grade silver ores in a variety of metallogenic settings., Competing Interests: Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Phanerozoic orogenic gold mineralization at craton margins is related to the metasomatism of the lithospheric mantle by crustal material. Slab subduction transfers Au from the crust to the metasomatized mantle and oxidizes the latter to facilitate the mobilization of Au into mantle melts. The role of volatiles in the mobilization of Au in the mantle is unclear because of the absence of direct geochemical evidence relating the mantle source of Au to Au mineralization in the overlying crust. This study uses lithium isotopes from a large suite of lamprophyres to characterize the mantle beneath the eastern North China Craton, which hosts giant Mesozoic gold deposits. Our results indicate a strong genetic link between carbonate metasomatism in the mantle and Au mineralization in the overlying crust. Although pre-enrichment of Au in the mantle is critical for forming giant Au provinces, the oxidation of the lithospheric mantle controls the mobilization of Au.

Pyrite is the most common sulfide mineral in hydrothermal ore-forming systems. The ubiquity and abundance of pyrite, combined with its ability to record and preserve a history of fluid evolution in crustal environments, make it an ideal mineral for studying the genesis of hydrothermal ore deposits, including those that host critical metals. However, with the exception of boiling, few studies have been able to directly link changes in pyrite chemistry to the processes responsible for bonanza-style gold mineralization. Here, we report the results of high-resolution secondary-ion mass spectrometry and electron microprobe analyses conducted on pyrite from the Brucejack epithermal gold deposit, British Columbia. Our δ 34 S and trace element results reveal that the Brucejack hydrothermal system experienced abrupt fluctuations in fluid chemistry, which preceded and ultimately coincided with the onset of ultra-high-grade mineralization. We argue that these fluctuations, which include the occurrence of extraordinarily negative δ 34 S values (e.g., -36.1‰) in zones of auriferous, arsenian pyrite, followed by sharp increases of δ 34 S values in syn-electrum zones of nonarsenian pyrite, were caused by vigorous, fault valve-induced episodic boiling (flashing) and subsequent inundation of the hydrothermal system by seawater. We conclude that the influx of seawater was the essential step to forming bonanza-grade electrum mineralization by triggering, through the addition of cationic flocculants and cooling, the aggregation of colloidal gold suspensions. Moreover, our study demonstrates the efficacy of employing high-resolution, in situ analytical techniques to map out individual ore-forming events in a hydrothermal system., Competing Interests: Competing interests statement:D.F.M. holds a postdoctoral research fellowship at McGill University which is fully funded by Newmont Corporation.

Aqueous complexation has long been considered the only viable means of transporting gold to depositional sites in hydrothermal ore-forming systems. A major weakness of this hypothesis is that it cannot readily explain the formation of ultrahigh-grade gold veins. This is a consequence of the relatively low gold concentrations typical of ore fluids (tens of parts per billion [ppb]) and the fact that these "bonanza" veins can contain weight-percent levels of gold in some epithermal and orogenic deposits. Here, we present direct evidence for a hypothesis that could explain these veins, namely, the transport of the gold as colloidal particles and their flocculation in nanoscale calcite veinlets. These gold-bearing nanoveinlets bear a remarkable resemblance to centimeter-scale ore veins in many hydrothermal gold deposits and give unique insight into the scale invariability of colloidal flocculation in forming hyperenriched gold deposits. Using this evidence, we propose a model for the development of bonanza gold veins in high-grade deposits. We argue that gold transport in these systems is largely mechanical and is the result of exceptionally high degrees of supersaturation that preclude precipitation of gold crystals and instead lead to the formation of colloidal particles, which flocculate and form much larger masses. These flocculated masses aggregate locally, where they are seismically pumped into fractures to locally form veins composed largely of gold. This model explains how bonanza veins may form from fluids containing ppb concentrations of gold and does not require prior encapsulation of colloidal gold particles in silica gel, as proposed by previous studies., Competing Interests: The authors declare no competing interest., (Copyright © 2021 the Author(s). Published by PNAS.)

Steel production is currently the largest industrial source of atmospheric CO2. As annual steel production continues to grow, the need for effective methods of reducing its carbon footprint increases correspondingly. The carbonation of the calcium-bearing phases in steel slag generated during basic oxygen furnace (BOF) steel production, in particular its major constituent, larnite {Ca2SiO4}, which is a structural analogue of olivine {(MgFe)2SiO4}, the main mineral subjected to natural carbonation in peridotites, offers the potential to offset some of these emissions. However, the controls on the nature and efficiency of steel slag carbonation are yet to be completely understood. Experiments were conducted exposing steel slag grains to a CO2-H2O mixture in both batch and flow-through reactors to investigate the impact of temperature, fluid flux, and reaction gradient on the dissolution and carbonation of steel slag. The results of these experiments show that dissolution and carbonation of BOF steel slag are more efficient in a flow-through reactor than in the batch reactors used in most previous studies. Moreover, they show that fluid flux needs to be optimized in addition to grain size, pressure, and temperature, in order to maximize the efficiency of carbonation. Based on these results, a two-stage reactor consisting of a high and a low fluid-flux chamber is proposed for CO2 sequestration by steel slag carbonation, allowing dissolution of the slag and precipitation of calcium carbonate to occur within a single flow-through system., (Copyright © 2014. Published by Elsevier B.V.)