共查询到20条相似文献,搜索用时 296 毫秒
1.
Guillaume Morard Denis Andrault Nicolas Guignot Julien Siebert Gaston Garbarino Daniele Antonangeli 《Physics and Chemistry of Minerals》2011,38(10):767-776
High pressure melting behavior of three Fe-alloys containing 5 wt% Ni and (1) 10 wt% Si, (2) 15 wt% Si or (3) 12 wt% S was
investigated up to megabar pressures by in situ X-ray diffraction and laser-heated diamond anvil cell techniques. We observe
a decrease in melting temperature with increasing Si content over the entire investigated pressure range. This trend is used
to discuss the melting curve of pure Fe. Moreover, our measurements of eutectic melting in the Fe–Fe3S system show a change in slope around 50 GPa concomitant with the fcc–hcp phase transition in pure solid iron. Extrapolations
of our melting curve up to the core–mantle boundary pressure yield values of 3,600–3,750 K for the freezing temperature of
plausible outer core compositions. 相似文献
2.
We performed comparative study of phase relations in Fe1−x
Ni
x
(0.10 ≤ x ≤ 0.22 atomic fraction) and Fe0.90Ni0.10−x
C
x
(0.1 ≤ x ≤ 0.5 atomic fraction) systems at pressures to 45 GPa and temperatures to 2,600 K using laser-heated diamond anvil cell and
large-volume press (LVP) techniques. We show that laser heating of Fe,Ni alloys in DAC even to relatively low temperatures
can lead to the contamination of the sample with the carbon coming from diamond anvils, which results in the decomposition
of the alloy into iron- and nickel-rich phases. Based on the results of LVP experiments with Fe–Ni–C system (at pressures
up to 20 GPa and temperatures to 2,300 K) we demonstrate decrease of carbon solubility in Fe,Ni alloy with pressure. 相似文献
3.
To study the behavior of macrocomponents and admixtures during the fractional crystallization of sulfide melts and the influence of As on noble metals in this process, we performed a quasi-equilibrium directional crystallization of melt of composition (at.%): Fe—35.5, Ni—4.9, Cu—10.4, and S—48.3, with admixtures of Pt, Pd, Rh, Ru, Ir, Au, Ag, As, and Co (each 0.1 at.%), which imitates the average (by Cu contents) compositions of massive ores at the Noril'sk Cu-Ni deposits. The following sequence of phase formation from melt has been established: mss (zone I) / mss + iss (zone II) / iss (zone III) (mss is (FezNi1–z)S1+δ, iss is (FexCuyNi1–x–y)zS1–z); it corresponds to the distribution of main elements along the sample (primary zoning). Distribution curves for macrocomponents in zones I and II of the sample were constructed, as well as the dependencies of their partition coefficients (k) between solid solutions and sulfide melt on the fraction of crystallized melt. The secondary (mineral) zoning resulted from subsolidus phase transformations has been revealed. Five subzones have been recognized: mss + cp (Ia) / mss + cp + pn (Ib) / mss + pc + pn (IIa) / mss + pc + pn + bn (IIb) / pc + bn + pn + unidentified microphases (III). Admixture species in the sample were studied: (1) admixtures dissolved in primary solid solutions and in main minerals resulted from solid-phase transformations and (2) admixtures forming their own mineral phases. The partition coefficients of Co, Rh, and Ru (mss/L), Ru, Ir, and Rh (mss/cp), and Co, Rh, and Pd (mss/pn) were determined. Minerals of noble metals have been recognized: Pt3Fe, PtFe, Au, (Ag,Pd), (Au,Pt), Ag, Ag3Cu, Au3(Cu,Ag,Pd,Pt), etc., and the regularities of their distribution in the sample have been established. It is shown that some noble-metal admixtures are prone to interact with As. Mineral arsenides and sulfoarsenides of noble metals produced during fractional crystallization have been recognized: PtAs2, Pd3As, (RhAsS), (IrAsS), and (Ir,Rh)AsS. The discovered drop-like inclusions of noble-metal arsenides suggest the separation of the initial sulfide-arsenide melt into two immiscible liquids. By indirect features, the micromineral inclusions are divided into primary, crystallized from melt, and secondary, produced in solid-phase reactions. The results of study are compared with literature experimental data obtained by the isothermal-annealing method and with the behavior of noble metals and As during the formation of zonal massive orebodies at the Noril'sk- and Sudbury-type deposits. 相似文献
4.
5.
We provide new insights into the prograde evolution of HP/LT metasedimentary rocks on the basis of detailed petrologic examination, element-partitioning analysis, and thermodynamic modelling of well-preserved Fe–Mg–carpholite- and Fe–Mg–chloritoid-bearing rocks from the Afyon Zone (Anatolia). We document continuous and discontinuous compositional (ferromagnesian substitution) zoning of carpholite (overall X Mg = 0.27–0.73) and chloritoid (overall X Mg = 0.07–0.30), as well as clear equilibrium and disequilibrium (i.e., reaction-related) textures involving carpholite and chloritoid, which consistently account for the consistent enrichment in Mg of both minerals through time, and the progressive replacement of carpholite by chloritoid. Mg/Fe distribution coefficients calculated between carpholite and chloritoid vary widely within samples (2.2–20.0). Among this range, only values of 7–11 correlate with equilibrium textures, in agreement with data from the literature. Equilibrium phase diagrams for metapelitic compositions are calculated using a newly modified thermodynamic dataset, including most recent data for carpholite, chloritoid, chlorite, and white mica, as well as further refinements for Fe–carpholite, and both chloritoid end-members, as required to reproduce accurately petrologic observations (phase relations, experimental constraints, Mg/Fe partitioning). Modelling reveals that Mg/Fe partitioning between carpholite and chloritoid is greatly sensitive to temperature and calls for a future evaluation of possible use as a thermometer. In addition, calculations show significant effective bulk composition changes during prograde metamorphism due to the fractionation of chloritoid formed at the expense of carpholite. We retrieve P–T conditions for several carpholite and chloritoid growth stages (1) during prograde stages using unfractionated, bulk-rock XRF analyses, and (2) at peak conditions using compositions fractionated for chloritoid. The P–T paths reconstructed for the Kütahya and Afyon areas shed light on contrasting temperature conditions for these areas during prograde and peak stages. 相似文献
6.
Victor Kress Lori E. Greene Matthew D. Ortiz Luke Mioduszewski 《Contributions to Mineralogy and Petrology》2008,156(6):785-797
We present the results of a series of density experiments in the system O–S–Fe–Ni–Cu. These experiments were designed to extend
our understanding of the physical properties of sulfide liquids, and to extend one-bar thermochemical models for sulfide liquids
to apply to low to moderate pressures. Density measurements indicate both positive and negative deviations from linear mixing
of partial molar volumes across this five-dimensional composition space. In terms of the homogeneous speciation model of Kress
(in Contrib Mineral Petrol 154:191–204, 2007), the best fit to experimental data can be achieved by starting with a model
where the volume of formation reaction for associated species initially is set to zero. Further refinement of this first-order
fit yields a volume mixing model which reproduces experimental data to within nearly the estimated experimental uncertainty.
Experimental ultrasonic and X-ray absorption data from the literature, along with the bulk modulus–volume relation of Anderson
and Nafe (J Geophys Res 16:3951–3963, 1965), allow the estimation of the pressure dependence of partial molar volumes for
sulfide liquid species. The resulting combined thermochemical model should be valid to about 2,000 K and 3 GPa. Application
of this thermochemical model in a simple adiabatic magma ascent scenario confirms earlier work suggesting that the pressure
dependence of sulfur solubility in sulfide-saturated magma will decrease with increasing pressure along geologically reasonable
paths in P–T–– space. 相似文献
7.
T. Müller R. Dohmen H. W. Becker Jan H. ter Heege S. Chakraborty 《Contributions to Mineralogy and Petrology》2013,166(6):1563-1576
Chemical interdiffusion of Fe–Mg along the c-axis [001] in natural diopside crystals (X Di = 0.93) was experimentally studied at ambient pressure, at temperatures ranging from 800 to 1,200 °C and oxygen fugacities from 10?11 to 10?17 bar. Diffusion couples were prepared by ablating an olivine (X Fo = 0.3) target to deposit a thin film (20–100 nm) onto a polished surface of a natural, oriented diopside crystal using the pulsed laser deposition technique. After diffusion anneals, compositional depth profiles at the near surface region (~400 nm) were measured using Rutherford backscattering spectroscopy. In the experimental temperature and compositional range, no strong dependence of D Fe–Mg on composition of clinopyroxene (Fe/Mg ratio between Di93–Di65) or oxygen fugacity could be detected within the resolution of the study. The lack of fO2-dependence may be related to the relatively high Al content of the crystals used in this study. Diffusion coefficients, D Fe–Mg, can be described by a single Arrhenius relation with $$D^{{{\text{Fe}} - {\text{Mg}}}} = 2. 7 7\pm 4. 2 7\times 10^{ - 7} {\text{exp(}}-3 20. 7\pm 1 6.0{\text{ kJ}}/{\text{mol}}/{\text{RT)m}}^{ 2} /{\text{s}}.$$ D Fe–Mg in clinopyroxene appears to be faster than diffusion involving Ca-species (e.g., D Ca–Mg) while it is slower than D Fe–Mg in other common mafic minerals (spinel, olivine, garnet, and orthopyroxene). As a consequence, diffusion in clinopyroxene may be the rate-limiting process for the freezing of many geothermometers, and compositional zoning in clinopyroxene may preserve records of a higher (compared to that preserved in other coexisting mafic minerals) temperature segment of the thermal history of a rock. In the absence of pervasive recrystallization, clinopyroxene grains will retain compositions from peak temperatures at their cores in most geological and planetary settings where peak temperatures did not exceed ~1,100 °C (e.g., resetting may be expected in slowly cooled mantle rocks, many plutonic mafic rocks, or ultra-high temperature metamorphic rocks). 相似文献
8.
Ghylaine Quitté Christopher Latkoczy Maria Schönbächler Alex N. Halliday Detlef Günther 《Geochimica et cosmochimica acta》2011,75(23):7698-7706
Eucrites are basaltic meteorites that cooled rapidly but are in many instances thermally metamorphosed and impact brecciated. The exact timing of these events remains unclear. In this study, Ni isotopic compositions and Fe/Ni elemental ratios are presented for two non-cumulate eucrites, Bouvante and Juvinas, including mineral separates from the latter. The samples are characterized by variable, well-resolved 60Ni-excesses consistent with the former presence of live 60Fe (t1/2 = 2.62 Ma) at the time of eucrite crystallization. A significant fraction of Ni with a terrestrial-like composition appears to be surface correlated. This Ni may be the product of terrestrial contamination or was introduced by a chondritic impactor during brecciation. Altogether, the data provide evidence for a complex and probably multi-stage history of Fe and/or Ni redistribution, which impedes the interpretation of the chronological data. 相似文献
9.
The paper reports data on the linear growth rates of synthetic diamond single crystals grown at high P–T parameters by the temperature-gradient technique in the Fe–Ni–C system. Techniques of stepwise temperature changes and generation of growth microzoning were applied to evaluate the growth rates of various octahedral and cubic growth sectors and variations in these rates with growth time. The maximum linear growth rates of the order of 100–300 µm/h were detected at the initial activation of crystal growth, after which the growth rates nonlinearly decreased throughout the whole growth time to 5–20 µm/h. The fact that the linear growth rates can broadly vary indicates that the inner structure and growth dynamics of single diamond crystals grown by the temperature-gradient technique should be taken into account when applied in mineral–geochemical studies (capture of inclusions, accommodation of admixture components, changes of the defective structure, etc.). 相似文献
10.
Suguru Takahashi Eiji Ohtani Hidenori Terasaki Yoshinori Ito Yuki Shibazaki Miho Ishii Ken-ichi Funakoshi Yuji Higo 《Physics and Chemistry of Minerals》2013,40(8):647-657
The phase and melting relations of the C-saturated C–Mg–Fe–Si–O system were investigated at high pressure and temperature to understand the role of carbon in the structure of the Earth, terrestrial planets, and carbon-enriched extraterrestrial planets. The phase relations were studied using two types of experiments at 4 GPa: analyses of recovered samples and in situ X-ray diffractions. Our experiments revealed that the composition of metallic iron melts changes from a C-rich composition with up to about 5 wt.% C under oxidizing conditions (ΔIW = ?1.7 to ?1.2, where ΔIW is the deviation of the oxygen fugacity (fO2) from an iron-wüstite (IW) buffer) to a C-depleted composition with 21 wt.% Si under reducing conditions (ΔIW < ?3.3) at 4 GPa and 1,873 K. SiC grains also coexisted with the Fe–Si melt under the most reducing conditions. The solubility of C in liquid Fe increased with increasing fO2, whereas the solubility of Si decreased with increasing fO2. The carbon-bearing phases were graphite, Fe3C, SiC, and Fe alloy melt (Fe–C or Fe–Si–C melts) under the redox conditions applied at 4 GPa, but carbonate was not observed under our experimental conditions. The phase relations observed in this study can be applicable to the Earth and other planets. In hypothetical reducing carbon planets (ΔIW < ?6.2), graphite/diamond and/or SiC exist in the mantle, whereas the core would be an Fe–Si alloy containing very small amount of C even in the carbon-enriched planets. The mutually exclusive nature of C and Si may be important also for considering the light elements of the Earth’s core. 相似文献
11.
Doklady Earth Sciences - New data on the minerals of the Fe–Ni–Co–Cu–S system in the differentiated intrusions of the Southern Urals are presented. Based on a detailed study... 相似文献
12.
We carried out experiments on crystallization of Fe-containing melts FeS2Ag0.1–0.1xAu0.1x (x = 0.05, 0.2, 0.4, and 0.8) with Ag/Au weight ratios from 10 to 0.1. Mixtures prepared from elements in corresponding proportions were heated in evacuated quartz ampoules to 1050 ºC and kept at this temperature for 12 h; then they were cooled to 150 ºC, annealed for 30 days, and cooled to room temperature. The solid-phase products were studied by optical and electron microscopy and X-ray spectroscopy. The crystallization products were mainly from iron sulfides: monoclinic pyrrhotite (Fe0.47S0.53 or Fe7S8) and pyrite (Fe0.99S2.01). Gold–silver sulfides (low-temperature modifications) are present in all synthesized samples. Depending on Ag/Au, the following sulfides are produced: acanthite (Ag/Au = 10), solid solutions Ag2–xAuxS (Ag/Au = 10, 2), uytenbogaardtite (Ag/Au = 2, 0.75), and petrovskaite (Ag/Au = 0.75, 0.12). They contain iron impurities (up to 3.3 wt.%). Xenomorphic micro- (<1–5 μm) and macrograins (5–50 μm) of Au–Ag sulfides are localized in pyrite or between the grains of pyrite and pyrrhotite. High-fineness gold was detected in the samples with initial ratio Ag/Au ≤ 2. It is present as fine and large rounded microinclusions or as intergrowths with Au–Ag sulfides in pyrite or, more seldom, at the boundary of pyrite and pyrrhotite grains. This gold contains up to 5.7 wt.% Fe. Based on the sample textures and phase relations, a sequence of their crystallization was determined. At ~1050 ºC, there are probably iron sulfide melt L1 (Fe,S ? Ag,Au), gold–silver sulfide melt L2 (Au,Ag,S ? Fe), and liquid sulfur LS. On cooling, melt L1 produces pyrrhotite; further cooling leads to the crystallization of high-fineness gold (macrograins from L1 and micrograins from L2) and Au–Ag sulfides (micrograins from L1 and macrograins from L2). Pyrite crystallizes after gold–silver sulfides by the peritectic reaction FeS + LS = FeS2 at ~743 ºC. Elemental sulfur is the last to crystallize. Gold–silver sulfides are stable and dominate over native gold and silver, especially in pyrite-containing ores with high Ag/Au ratios. 相似文献
13.
We have investigated melting relations in the Fe–O–S ternary system in the pressure range of 15–27 GPa and 1873 K. Subsolidus
phase relations are Fe, Fe3S2, and FeO up to 17 GPa and Fe, Fe3S, and FeO above this pressure. The eutectic temperature slightly decreases from ambient pressure to 17 GPa, whereas increases
above this pressure. The eutectic temperature in this study is 100 K lower than that in the Fe–S binary system. The oxygen
content in the Fe–O–S eutectic liquid drops when the coexisting solid phases changes from FeS to Fe3S2. The cotectic lines in the ternary phase diagram lie close to the Fe–FeS binary axis. The isothermal sections indicate that
oxygen solubility in the Fe–O–S liquid increases with increasing temperature, and with increasing sulfur content. The solubility
of sulfur in the solid Fe has a maximum value at the eutectic temperature, and decreases with increasing temperature. Our
results could have important implications for formation and composition of the Martian core. 相似文献
14.
正1 Introduction In the present paper,MgCl2·6H2O,FeCl3·6H2O,and CeCl3·6H2O were used as raw materials in the precipitationhydrothermal method to synthesize MgF eC e hydrotalcite.The effects of the Fe:Ce molar ratio on the composition,crystal structure,and thermal stability of hydrotalcite are examined.Energy-dispersive X-ray spectroscopy(EDS),X- 相似文献
15.
Gryaznov I. A. Zhimulev E. I. Sonin V. M. Lindenblot E. S. Chepurov A. A. Sobolev N. V. 《Doklady Earth Sciences》2019,489(2):1449-1452
Doklady Earth Sciences - The primary results are presented on the dissolution of plane-faced diamond crystals of octahedral habit in a Fe–Ni–S melt under 3.5 GPa and 1400°C. It was... 相似文献
16.
The behavior of nickel in the Earth’s mantle is controlled by sulfide melt–olivine reaction. Prior to this study, experiments were carried out at low pressures with narrow range of Ni/Fe in sulfide melt. As the mantle becomes more reduced with depth, experiments at comparable conditions provide an assessment of the effect of pressure at low-oxygen fugacity conditions. In this study, we constrain the Fe–Ni composition of molten sulfide in the Earth’s upper mantle via sulfide melt–olivine reaction experiments at 2 GPa, 1200 and 1400 °C, with sulfide melt \(X_{{{\text{Ni}}}}^{{{\text{Sulfide}}}}=\frac{{{\text{Ni}}}}{{{\text{Ni}}+{\text{Fe}}}}\) (atomic ratio) ranging from 0 to 0.94. To verify the approach to equilibrium and to explore the effect of \({f_{{{\text{O}}_{\text{2}}}}}\) on Fe–Ni exchange between phases, four different suites of experiments were conducted, varying in their experimental geometry and initial composition. Effects of Ni secondary fluorescence on olivine analyses were corrected using the PENELOPE algorithm (Baró et al., Nucl Instrum Methods Phys Res B 100:31–46, 1995), “zero time” experiments, and measurements before and after dissolution of surrounding sulfides. Oxygen fugacities in the experiments, estimated from the measured O contents of sulfide melts and from the compositions of coexisting olivines, were 3.0?±?1.0 log units more reduced than the fayalite–magnetite-quartz (FMQ) buffer (suite 1, 2 and 3), and FMQ ??1 or more oxidized (suite 4). For the reduced (suites 1–3) experiments, Fe–Ni distribution coefficients \(K_{{\text{D}}}^{{}}=\frac{{(X_{{{\text{Ni}}}}^{{{\text{sulfide}}}}/X_{{{\text{Fe}}}}^{{{\text{sulfide}}}})}}{{(X_{{{\text{Ni}}}}^{{{\text{olivine}}}}/X_{{{\text{Fe}}}}^{{{\text{olivine}}}})}}\) are small, averaging 10.0?±?5.7, with little variation as a function of total Ni content. More oxidized experiments (suite 4) give larger values of KD (21.1–25.2). Compared to previous determinations at 100 kPa, values of KD from this study are chiefly lower, in large part owing to the more reduced conditions of the experiments. The observed difference does not seem attributable to differences in temperature and pressure between experimental studies. It may be related in part to the effects of metal/sulfur ratio in sulfide melt. Application of these results to the composition of molten sulfide in peridotite indicates that compositions are intermediate in composition (\(X_{{{\text{Ni}}}}^{{{\text{sulfide}}}}\)?~?0.4–0.6) in the shallow mantle at 50 km, becomes more Ni rich with depth as the O content of the melt diminishes, reaching a maximum (0.6–0.7) at depths near 80–120 km, and then becomes more Fe rich in the deeper mantle where conditions are more reduced, approaching (\(X_{{{\text{Ni}}}}^{{{\text{sulfide}}}}\)?~?0.28)?>?140 km depth. Because Ni-rich sulfide in the shallow upper mantle melts at lower temperature than more Fe-rich compositions, mantle sulfide is likely molten in much of the deep continental lithosphere, including regions of diamond formation. 相似文献
17.
Takeshi Sakai Eiji Ohtani Hidenori Terasaki Masaaki Miyahara Masahiko Nishijima Naohisa Hirao Yasuo Ohishi Nagayoshi Sata 《Physics and Chemistry of Minerals》2010,37(7):487-496
Fe–Mg partitioning between post-perovskite and ferropericlase has been studied using a laser-heated diamond anvil cell at
pressures up to 154 GPa and 2,010 K which corresponds to the conditions in the lowermost mantle. The composition of the phases
in the recovered samples was determined using analytical transmission electron microscopy. Our results reveal that the Fe–Mg
partition coefficient between post-perovskite and ferropericlase (K
DPPv/Fp) increases with decreasing bulk iron content. The compositional dependence of K
DPPv/Fp on the bulk iron content explains the inconsistency in previous studies, and the effect of the bulk iron content is the most
dominant factor compared to other factors, such as temperature and aluminum content. Iron prefers ferropericlase compared
to post-perovskite over a wide compositional range, whereas the iron content of post-perovskite (X
FePPv, the mole fraction) does not exceed a value of 0.10. The iron-rich ferropericlase phase may have significant influence on
the physical properties, such as the seismic velocity and electrical conductivity at the core–mantle boundary region. 相似文献
18.
Interactions in a Fe–C–O–H–N system that controls the mobility of siderophile nitrogen and carbon in the Fe0-saturated upper mantle are investigated in experiments at 6.3–7.8 GPa and 1200–1400 °C. The results show that the γ-Fe and metal melt phases equilibrated with the fluid in a system unsaturated with carbon and nitrogen are stable at 1300 °C. The interactions of Fe3C with an N-rich fluid in a graphite-saturated system produce the ε-Fe3N phase (space group P63/mmc or P6322) at subsolidus conditions of 1200–1300 °C, while N-rich melts form at 1400 °C. At IW- and MMO-buffered hydrogen fugacity (fH2), fluids vary from NH3- to H2O-rich compositions (NH3/N2?>?1 in all cases) with relatively high contents of alkanes. The fluid derived from N-poor samples contains less H2O and more carbon which mainly reside in oxygenated hydrocarbons, i.e., alcohols and esters at MMO-buffered fH2 and carboxylic acids at unbuffered fH2 conditions. In unbuffered conditions, N2 is the principal nitrogen host (NH3/N2?≤?0.1) in the fluid equilibrated with the metal phase. Relatively C- and N-rich fluids in equilibrium with the metal phase (γ-Fe, melt, or Fe3N) are stable at the upper mantle pressures and temperatures. According to our estimates, the metal/fluid partition coefficient of nitrogen is higher than that of carbon. Thus, nitrogen has a greater affinity for iron than carbon. The general inference is that reduced fluids can successfully transport volatiles from the metal-saturated mantle to metal-free shallow mantle domains. However, nitrogen has a higher affinity for iron and selectively accumulates in the metal phase, while highly mobile carbon resides in the fluid phase. This may be a controlling mechanism of the deep carbon and nitrogen cycles. 相似文献
19.
A. V. Mokhov T. A. Gornostaeva P. M. Kartashov A. P. Rybchuk O. A. Bogatikov 《Doklady Earth Sciences》2018,481(1):898-901
The close intergrowth of two native alloys of the compositions Ni0.59Cu0.24Al0.15Fe0.01Mn0.01 and Pd0.55Pt0.36Rh0.09 with a size of 10 μm has been discovered in the regolith from the Mare Crisium. A conclusion on its exhalative origin is made. 相似文献
20.
Magmatic PGE and Ni–Cu deposits form in contrasting geologic environments and periods. PGE deposits predominantly occur in
large layered intrusions emplaced during the late Archean and early Proterozoic into stabilized, relatively S-poor cratonic
lithosphere that provides enhanced preservation potential. The magmas ascend through intracratonic sutures where extension
and rifting is limited. Crystallization under conditions of low regional stress, with limited magma-induced sagging due to
underlying thick buoyant sub-continental mantle lithosphere, is consistent with their laterally continuous layering. Most
of the global resources occur in three large intrusions: Bushveld, Great Dyke and Stillwater. Due to the large size (tens
of kilometres) and limited complexity of the deposits, they are relatively easy to locate and delineate. As a result, the
search space is relatively mature and few new discoveries have been made in the last few decades. The parental magmas to the
intrusions are predominantly derived from the convecting mantle but, in addition, the involvement of the sub-continental lithospheric
mantle is suggested by the relative Pt enrichment of most of the major deposits. In contrast to the PGE deposits, Ni–Cu deposits
form throughout geologic time, but with the largest deposits being younger than ca. 2 Ga. The sulfide ores are concentrated
under highly dynamic conditions within lava channels and magma conduits. The deposits are preferentially located near craton
margins towards which mantle plumes have been channelled and where mantle magmas can readily ascend through abundant trans-lithospheric
structures. Magma flow is focused and locally enhanced by shifting compressive–extensional tectonic regimes, and abundant
S-rich crustal rocks provide an external S source that is required for the majority of deposits. The igneous bodies hosting
the deposits tend to be irregular and small, tens to hundreds of metres in width and height, and are difficult to locate.
As a result, the search space remains relatively immature. Understanding their tectonic setting helps reduce the prospective
search space for world-class examples. 相似文献