Polymetallic Mineralization at the Shin-Ohtoyo Deposit, Harukayama District, Hokkaido, Japan

Abstract: The Shin-Ohtoyo Cu–Au deposit is located in the Harukayama district, 20 km west of Sapporo, Hokkaido, Japan. Both acid-type disseminated and adularia–quartz–type vein Au mineralizations have been recognized within a small distance of less than 500 m in the district. Mineralogical characteristics of sulfide ores from the Shin-Ohtoyo deposit have been proved to be polymetallic. Ore minerals containing Sn, V, Bi and Te are recognized. Nine ore types are recognized in terms of characteristic mineral assemblage; (1) chalcedonic quartz veinlets in silicified zone around the deposit, (2) bismuthinite, emplectite, friedrichite and tetrahedrite, (3) an unnamed Cu–Sn–Fe–Zn sulfide, colusite-series minerals, stannoidite, emplectite and tetrahedrite, (4) bournonite, Se-bearing galena and tetrahedrite, (5) luzonite/famatinite and Ag-bearing tetrahedrite, (6) colusite-series minerals, emplectite, aikinite and tetrahedrite/goldfieldite, (7) luzonite/famatinite, colusite-series minerals, mawsonite and tetra–hedrite/goldfieldite, (8) enargite, luzonite/famatinite and tetrahedrite, and (9) colusite-series minerals and tetrahedrite. The first occurrence of friedrichite and stibiocolusite from Japan are reported. The chemical formula of the unnamed phase corresponds to Cu₆(Cu, Fe, Zn)Sn₃S₁₀. Sulfur isotopic ratios (δ³⁴S) of sulfides from the stockpile range from –0. 5% to +1. 9%, and those from drill cores recovered by Metal Mining Agency of Japan (MMAJ) vary from –2. 7% to +0. 8%. Sulfur isotopic ratio of barite in a cavity in the silicified tuff breccia collected from the stock pile yields +27. 1%, while that of barite collected from MMAJ core is +21. 7%. Sulfur isotopic thermometry applied for a pair of barite (+21. 7%) and associated pyrite (+1. 8%) indicates about 300°C. High–Te tetrahedrite composition from both the chalcedonic quartz vein in the silicified zone around the Shin-Ohtoyo deposit and the polymetallic sulfide ores from the adit of the deposit, suggests that the Au mineralization in the former is attributed to a hydrothermal system marginal to the polymetallic mineralization.     

Theoretical studies of the electronic structure of copper in tetrahedral and triangular coordination with sulfur

Molecular orbital calculations are presented for the copper-sulfur polyhedral clusters CuS ₄ ^7? , CuS ₄ ^6? , CuS ₃ ^5? and CuS ₃ ^4? , which occur in many minerals. Calculated and experimental optical and X-ray energies are found to be in good agreement. The crystal field orbitals of Cu⁺ in tetrahedrally coordinated sulfides are found to be less tightly bound than the S3p nonbonding orbitals by about 2–3 eV whereas the e and t ₂ crystal field orbitals are split by about 1 eV. The crystal field splitting of Cu²⁺ in tetrahedral coordination is about 0.7–0.8 eV while the separation of the S3p nonbonding orbitals and the partially filled t ₂ crystal field orbital is about 2 eV. In triangular coordination both the Cu⁺ and Cu²⁺ crystal field orbitals are more stable than in tetrahedral coordination, more widely split and more strongly mixed with the S3p orbitals. CuS is shown to be unstable as the mixed oxidation state compound Cu^2+III (Cu^+IV)₂S^2?(S ₂ ^2? ); rather each Cu is predicted to have a fractional oxidation state and partially-empty crystal field orbitals.     

S K- and L-edge XANES and electronic structure of some copper sulfide minerals

The S K and L-edge x-ray absorption near-edge structures (XANES) of low bornite, cubanite, chalcocite, covellite, enargite and tetrahedrite have been measured with synchrotron radiation. The near-edge features are interpreted based on comparison with the S K- and L-edge spectra of chalcopyrite and a MO/energy band structure model. The XANES spectra of these sulfides reflect the DOS of unoccupied S s-, p- and d-like states near and above the Fermi level. In tetrahedral Cu-Fe sulfides, the Fe³⁺ 3d crystal field band has much more significant DOS of unoccupied S 3p-and 3s-like states than the Cu⁺ 3d crystal field band. For Cu sulfides, the Cu⁺ 3d crystal field band has the higher DOS of S 3p- and 3 s-like states in tetrahedral structure than in structures with the triangular CuS₃ cluster. The shifts in both S K- and L-edges correlate approximately linearly with the energy gap.     

Metal cation exchange reactions of ore minerals in Fe–Mn crusts of the Marcus Wake Rise (Pacific Ocean) in aqueous–salt solutions

It is shown that the reaction ability of metal cations of ore minerals in Fe–Mn crusts of the Marcus Wake Rise increases in the following manner: (Co²⁺ < Cu²⁺ < Ni²⁺) < (Mg²⁺ < Mn²⁺ < K⁺ ≈ Ca²⁺ ≈ Na⁺). The composition of the exchange complex of the ore minerals is constant and includes these metal cations. Ca²⁺ and Na⁺ are major contributors to the exchange capacity of the ore minerals. The capacity of the ore minerals by cations of alkali and base metals is 0.43–0.60 and 2.08–2.70 mg-equiv/g, respectively. The exchange capacity of the ore minerals by cations of base metals increases linearly with the increase in the MnO₂ content of the crust and does not depend on the geographical locations of the Marcus Wake guyots.     

Geomaterials related to photovoltaics: a nanostructured Fe-bearing kuramite,Cu<Subscript>3</Subscript>SnS<Subscript>4</Subscript>

The successful synthesis of nanoparticles of Fe-bearing kuramite, (Cu,Fe)₃SnS₄, is reported in this study. Nanocrystalline powders were obtained through a mild, environmentally friendly and scalable solvothermal approach, in a single run. The sample was the object of a multidisciplinary investigation, including X-ray diffraction and absorption, scanning electron microscopy and microanalysis, electron paramagnetic resonance, diffuse reflectance and Mössbauer spectroscopy as well as SQUID magnetometry. The nanoparticles consist of pure Fe-bearing kuramite, exhibiting tetragonal structure. The valence state of the metal cations was assessed to be Cu⁺, Sn⁴⁺ and Fe³⁺. The material presents a band gap value of 1.6 eV, which is fully compatible with solar cell applications. The uptake of Fe by nanokuramite opens a compositional field where the physical properties can be tuned. We thus foster the application of Fe-bearing nanokuramite for photovoltaics and energy storage purposes.     

Electronic environments in carrollite, CuCo2S4, determined by soft X-ray photoelectron and absorption spectroscopy

Fracture surfaces of a natural carrollite specimen have been characterised by synchrotron and conventional X-ray photoelectron spectroscopy and near-edge X-ray absorption spectroscopy. For the synchrotron X-ray measurements, the mineral surfaces were prepared under clean ultra high vacuum and were unoxidised. The characterisation was undertaken primarily to establish unequivocally the oxidation state of the Cu in the mineral, but also to obtain information on the electronic environments of the Co and S, and on the surface species. Experimental and simulated Cu L_2,3-edge absorption spectra confirmed an oxidation state of Cu^I, while Co 2p photoelectron and Co L_2,3 absorption spectra were largely consistent with the Co^III established previously by nuclear magnetic resonance spectroscopy. S 2p photoelectron spectra provided no evidence for S to be present in the bulk in more than one state, and were consistent with an oxidation state slightly less negative than S^-II. Therefore it was concluded that carrollite can be best represented by Cu^ICo^III₂(S₄)^-VII. The Cu^I oxidation state is in agreement with that expected for Cu tetrahedrally coordinated by S, but is in disagreement with the Cu^II deduced previously from some magnetic, magnetic resonance and Cu L-edge X-ray absorption spectroscopic measurements. A significant concentration of S species with core electron binding energies both lower and higher than the bulk value were formed at fracture surfaces, and these entities were assigned to monomeric and oligomeric surface S species. The density of Cu d states calculated for carrollite differed from that previously reported but was consistent with the observed Cu L₃ X-ray absorption spectrum. The initial oxidation of carrollite in air under ambient conditions was confirmed to be congruent, unlike the incongruent reaction undergone by a number of non-thiospinel sulfide minerals.     

Theoretical studies on metal thioarsenites and thioantimonides: synergistic interactions between transition metals and heavy metalloids

Recently we established that the ternary complex, CuAsS(SH)(OH) has an unusually high stability and makes a large contribution to the total concentrations of both Cu and As in sulfidic solutions equilibrated with Cu and As sulfide minerals. This ternary complex has an unusual structure, containing a bond which is formally Cu(I)–As(III), along with a broken As–S bond. We have now found that complexes with similar structures exist for Au⁺ and Tl⁺ coordinated to AsS(SH)(OH)^-. However, such a direct metal–metalloid bond is not a requirement for stability. In fact, TlAsS(SH)(OH) is unstable while AuAsS(SH)(OH) is highly stable (compared to the aquo ion). Zn²⁺, Cd²⁺, Hg²⁺ and Pb²⁺ also form bonds to the As of AsS(SH)(OH), but without breaking any As–S bonds, and HgAsS(SH)(OH)⁺ and PbAsS(SH)(OH)⁺ are particularly stable complexes. Calculated structures are shown for these complexes, gas-phase energies are calculated, and formation constants in aqueous solution are estimated. The SbS(SH)(OH)^- ion forms analogous complexes, with similar stabilities. However, the Au⁺ complex of SbS(SH)(OH)^- is slightly less stable than the Cu⁺ complex, opposite to the order found for the AsS(SH)(OH)^- ligand. The Au⁺ and AuSH complexes of AsSSHOH^- or AsS(SH)₂ ^- may be implicated in "invisible gold" in arsenian pyrites. Vibrational frequencies are given for the AuAsS(SH)₃ ^- complex and the XANES energies of this complex and Au(SH)₂ ^- are compared. The existence of such strong complexes may explain the many correlations observed between the concentrations of coinage metals and metalloids.     

Nature of Co-bearing ferromanganese crusts of the Magellan Seamounts (Pacific Ocean): Communication 2. Ion exchange properties of ore minerals

The results of experimental studies of ion exchange properties of Co-bearing ferromanganese crusts in the Magellan Seamounts (Pacific Ocean) are discussed. Maximum reactivity in reactions with the participation of manganese minerals (Fe-vernadite, vernadite) is typical of Na⁺, K⁺, and Ca²⁺ cations, whereas minimum activity is recorded for cations Pb²⁺ and Co²⁺. The exchange complex of ore minerals in crusts is composed of Na⁺, K⁺, Ca²⁺, Mg²⁺, and Mn²⁺ cations. The exchange capacity of manganese minerals increases from the alkali metal cations to rare and heavy metal cations. Peculiarities of the affiliation of Co²⁺, Mn²⁺, and Mg²⁺ cations in manganese minerals of crusts are discussed. In manganese minerals, Co occurs as Co²⁺ and Co³⁺ cations. Metal cations in manganese minerals occur in different chemical forms: sorbed (Na⁺, K⁺, Ca²⁺, Mn²⁺, Co²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Pb²⁺); sorbed and chemically bound (Mg²⁺, Ni²⁺, Y³⁺, La³⁺, and Mo⁶⁺); and only chemically bound (Co³⁺). It is shown that the age of crust, its preservation time in the air-dry state, and type of host substrate do not affect the ion exchange indicators of manganese minerals. It has been established that alkali metal cations are characterized by completely reversible equivalent sorption, whereas heavy metal cations are sorbed by a complex mechanism: equivalent ion exchange for all metal cations; superequivalent, partly reversible sorption for Ba²⁺, Pb²⁺, Co²⁺, and Cu²⁺ cations, relative to exchange cations of manganese minerals. The obtained results refine the role of ion exchange processes during the hydrogenic formation of Co-bearing ferromanganese crusts.     

Fe-Zn exchange reaction between tetrahedrite and sphalerite in natural environments

Microprobe and fluid inclusion analyses of hydrothermal ore deposits containing the subassemblage sphalerite+ tetrahedrite-tennantite [(Cu, Ag)₁₀(Fe, Zn)₂(As,Sb)₄S₁₃] reveal that the Gibbs energies of the reciprocal reaction Cu₁₀Zn₂Sb₄S₁₃ + Cu₁₀Fe₂As₄S₁₃ = Cu₁₀Fe₂Sb₄S₁₃ + Cu₁₀Zn₂As₄S₁₃ and the Fe-Zn exchange reaction 1/2Cu₁₀Fe₂Sb₄S₁₃ + ZnS = 1/2Cu₁₀Zn₂Sb₄S₁₃ + FeS are within the uncertainties of the values established by Sack and Loucks (1985) and Raabe and Sack (1984), 2.59±0.14 and 2.07±0.07 kcal/gfw. However, this study suggests that the Fe-Zn exchange reaction between sphalerite and Sb and Ag-rich tetrahedrites does not obey the simple systematics suggested by Sack and Loucks (1985) wherein tetrahedrite is assumed to behave as an ideal reciprocal solution. Instead these studies show that the configurational Gibbs energy of this exchange reaction,RTln[(X _Fe/X _Zn)^TET(X _ZnS/X _FeS)^SPH], corrected for sphalerite nonideality exhibits both a local maximum and minimum as a function of Ag/(Cu+Ag) ratio at a givenX _FeS ^SPH and temperature. The local maximum forX _FeS ^SPH 0.10 corresponds to the position of the cell edge maximum established for natural tetrahedrites by Riley (1974), Ag/(Ag+Cu)0.4. These studies and the results of structural refinements of Ag-bearing tetrahedrites suggest that in low silver tetrahedrites Ag is preferentially incorporated in trigonal-planar sites but that in tetrahedrites with intermediate and greater Ag/(Ag+Cu) ratio, Ag is preferentially incorporated in tetrahedral sites. A nonconvergent site ordering model for tetrahedrite is developed to quantify and extrapolate these predictions.     

Use of L-edge X-ray absorption spectroscopy to characterize multiple valence states of 3d transition metals; a new probe for mineralogical and geochemical research

2p (L _2,3) X-ray absorption spectra are presented for a range of minerals to demonstrate the usefulness of L-edge spectroscopy as a symmetry- and valenceselective probe. 2p XAS provides a sensitive fingerprint of the electronic states of 3 d transition metals and can be applied to phases containing mixtures of such elements. Calculated spectra for 3d ⁿ → 2p ⁵ 3d ⁿ⁺¹ transitions provide a basis for the interpretation of the measured spectra. Thus, in principle, multiple valence states of a particular 3 d metal can be precisely characterized from a single L-edge spectrum. Examples of vanadium L-edge spectra are presented for a range of minerals; these complex spectra hold information concerning the presence of vanadium in multiple valence states. The Cu L-edge spectrum of sulvanite (Cu₃ VS₄) indicates the presence of both Cu⁺ and Cu²⁺; the V L-edge spectrum of the same sample shows that both V²⁺ and V⁵⁺ are present. Spectral simulations representing mixtures of Fe d ⁵ and Fe d ⁶ states are used to quantify Fe³⁺/∑Fe in a spinel, a glass, and an amphibole, all of which contain Fe as a major component. To illustrate the sensitivity of 2p XAS in a dilute system, the Fe L-edge spectrum of amethyst (α-SiO₂: Fe) has been recorded; this spectrum shows that ～68% of the Fe in amethyst is Fe²⁺, and ～32% is Fe³⁺. Although previous studies on amethyst using other spectroscopic methods cite evidence for Fe⁴⁺, there is no indication in the L-edge spectrum for Fe⁴⁺ in amethyst. Comparison of theoretical and experimental spectra not only allows the valence states of 3 d ions to be recognised, but also provides site-symmetry information and crystal field parameters for each ion site.     

Sulfur K- and L-edge X-ray absorption spectroscopy of sphalerite,chalcopyrite and stannite

Sulfur K-edge x-ray absorption spectra (XANES and EXAFS) and L-edge XANES of sphalerite (ZnS), chalcopyrite (CuFeS₂) and stannite (Cu₂FeSnS₄) have been recorded using synchrotron radiation. The K- and L-edge XANES features are interpreted using a qualitative MO/energy band structure model. The densities of unoccupied states at the conduction bands of sphalerite, chalcopyrite and stannite are determined using S K- and L-edge XANES features (up to 15 eV above the edge), combined with published metal K-edge XANES. The SK- and L-edge XANES also indicate that, for sphalerite, the Fe²⁺ 3d band at the fundamental gap has little or no bonding hybridization with S 3p and S 3s orbitals; for chalcopyrite, the Cu⁺ 3d and Fe³⁺ 3d bands have strong mixing with S 3p and S 3s states, while for stannite the Cu⁺ 3d band strongly hybridizes with S 3p and S 3s orbitals, but the Fe²⁺ 3d band does not. The post-edge XANES features (15–50 eV above the edge) of sphalerite, chalcopyrite and stannite are similar. These features are related to the tetrahedral coordination of sulfur in all these structures, and interpreted by a multiple scattering model. The resonance energies from both the K-edge and L-edge XANES for these minerals are well correlated with reciprocal interatomic distances and lattice spaces. Sulfur K-edge EXAFS analyses using Fourier transform and curve fitting procedures are presented. Comparison of the structural parameters from EXAFS with x-ray structure data shows that the first shell bond distances (BD) from EXAFS are usually accurate to ±0.02 Å, and that coordination numbers (CN) are generally accurate to ±20 percent. For sphalerite, EXAFS analysis yields the structure parameters for the first three neighbour shells around a sulfur atom; the BD and CN even for the third shell are in close agreement with the x-ray structure, and the Debye-Waller term decreases from the first shell to the third shell. It is shown that sphalerite (ZnS) is a good model compound for EXAFS analysis of sulfur in chalcogenide glasses and metalloproteins.     

Ion exchange properties of manganese and iron minerals in oceanic micronodules

The results of experimental studies of ion exchange properties of manganese and iron minerals in micronodules (MN) from diverse bioproductive zones of the World Ocean are considered. It was found that the sorption behavior of these minerals is similar to that of ore minerals from ferromanganese nodules (FMN) and low-temperature hydrothermal crusts. The exchange complex of minerals in the MN includes the major (Na⁺, K⁺, Ca²⁺, Mg²⁺, and Mn²⁺) and the subordinate (Ni²⁺, Cu²⁺, Co²⁺, Pb²⁺, and others) cations. Reactivity of theses cations increases from Pb²⁺ and Co²⁺ to Na⁺ and Ca²⁺. Exchange capacity of MN minerals increases from the alkali to heavy metal cations. Capacity of iron and manganese minerals in the oceanic MN increases in the following series: goethite < goethite + birnessite < todorokite + asbolane-buserite + birnessite < asbolane-buserite + birnessite < birnessite + asbolane-buserite < birnessite + vernadite Fe-vernadite + Mn-feroxyhyte. The data obtained supplement the available information on the ion exchange properties of oceanic ferromanganese sediments and refine the role of sorption processes in the redistribution of metal cations at the bottom (ooze) water-sediment interface during the MN formation and growth.     

Transmetallation of Gd-DTPA by Cu,Y and lanthanides and its impact on the hydrosphere

The concurrent exchange of REE³⁺ and Y³⁺ (combined to M³⁺) and Cu²⁺ for Gd³⁺ in Gd-DTPA (Gd-diethylenetriaminepentaacetic acid or gadopentetic acid) in the presence of clay is a very slow process if the concentrations of M³⁺, Cu²⁺ and Gd-DTPA in solution are in the range of 0.01–22 nmol/L. The kinetics of transmetallation was followed for 1033 h without reaching equilibrium, although the release of metal ions from the clay pool is a fast process. The sum of all newly formed mono-nuclear M-DTPA species is less than the difference [Gd-DTPA_o] − [Gd-DTPA] even after 1033 h but the sum of all derived M-DTPA + Cu-DTPA chelates exceeds this difference indicating that within this time span poly-nuclear chelates of Cu also formed. Formation of CuGd-DTPA chelates is the fastest process followed by formation of less stable MGd-DTPA chelates. With progress of formation of CuGd-DTPA the concentration of Gd-DTPA is lowered and consequently MGd-DTPA decomposes. Furthermore Cu²⁺ reacts with MGd-DTPA to form CuM-DTPA. The observed rate constants vary from species to species, whereas the pseudo-first-order-rate constants k_M are nearly the same for all lanthanides. The observed rate constant for k_Cu exceeds those of k_M because Cu concentrations are higher than M. The changes in M speciation under the influence of DTPA are estimated for a typical composition of surface water. Input of Gd-DTPA leaves only La and, to a lesser degree, Ce unaffected by transmetallation. The total concentrations of both Cu and intermediate to heavy REE increase, whereas total Gd decreases because released Gd³⁺ is adsorbed by clay minerals. Depending on Cu²⁺ and GdL²⁻ concentrations in natural surface and groundwaters, Gd-DTPA decreases by about 10% within a year. Equilibrium is theoretically reached only after more than 70 a.     

An X-ray photoelectron and absorption spectroscopic investigation of the electronic structure of cubanite, CuFe2S3

X-ray photoelectron and absorption spectra have been obtained for natural specimens of cubanite and compared with the corresponding spectra for chalcopyrite. Synchrotron X-ray photoelectron spectra of surfaces prepared by fracture under ultra-high vacuum revealed some clear differences for the two minerals, most notably those reflecting their different structures. In particular, the concentration of the low binding energy S species formed at cubanite fracture surfaces was approximately double that produced at chalcopyrite surfaces. However, the core electron binding energies for the two S environments in cubanite were not significantly different, and were similar to the corresponding values for the single environment in chalcopyrite. High binding energy features in the S 2p and Cu 2p spectra were not related to surface species produced either by the fracture or by oxidation, and most probably arose from energy loss due to inter-band excitation. Differences relating to the Fe electronic environments were detectable, but were smaller than expected from some of the observed physical properties and Mössbauer spectroscopic parameters for the two minerals. X-ray absorption and photoelectron spectra together with the calculated densities of states for cubanite confirmed an oxidation state of Cu^I in the mineral. It was concluded that the best formal oxidation state representation for cubanite is Cu^I(Fe₂)^VS ₃ ^?II .     

The crystal structure of ilinskite, NaCu5O2(SeO3)2Cl3, and review of mixed-ligand CuOmCln coordination geometries in minerals and inorganic compounds

The crystal structure of ilinskite, NaCu₅O₂(SeO₃)₂Cl₃, a rare copper selenite chloride from volcanic fumaroles of the Great fissure Tolbachik eruption (Kamchatka peninsula, Russia), has been solved by direct methods and refined to R ₁?=?0.044 on the basis of 2720 unique observed reflections. The mineral is orthorhombic, Pnma, a?=?17.769(7), b?=?6.448(3), c?=?10.522(4) Å, V?=?1205.6(8) ų, Z?=?4. The The CuO_mCl_n coordination polyhedra share edges to form tetramers that have 'additional' O1 and O2 atoms as centers. The O1Cu₄ and O2Cu₄ tetrahedra share common Cu atoms to form [O₂Cu₅]⁶⁺ sheets. The SeO₃ groups and Cl atoms are adjacent to the [O₂Cu₅]⁶⁺ sheets to form complex layers parallel to (100). The Na⁺ cations are located in between the layers. A review of mixed-ligand CuO_mCl_n coordination polyhedra in minerals and inorganic compounds is given. There are in total 26 stereochemically different mixed-ligand Cu-O-Cl coordinations.     

Stability relations of Mn–Fe–Al piemontite

Abstract Comparison of the stability relations of Fe-piemontite, Pm₁₇Ps₁₇Cz₆₆ (Ca₂Al₂Mn_0.5 Fe_0.5Si₃O₁₂(OH)), with similar experimentally determined results on Pm₃₃Cz₆₇ suggests that, at moderate f_o2, addition of Fe to piemontite raises its thermal stability and slightly decreases its sensitivity to oxygen fugacity. Reversal study of the reaction: Fe-piemontite + quartz = garnet (Gr₃₃Sp₂₇And₄₀) + anorthite + fluid at P_fluid= 2 kbar in cold-seal apparatus using solid oxygen buffers was completed. The data indicated breakdown of Pm₁₇Ps₁₇Cz₆₆ at 645°± 10° C along the Cu₂O–CuO buffer, 477°± 10° C along the Cu–Cu₂O buffer, and 365°± 10° C for the hematite-magnetite buffer. Mn-free clinozoisite and epidote have been shown to be stable to much higher temperatures than piemontite at moderate f_o2 (< Cu–Cu₂O). At very high f_o2, however, the presence of Mn⁺³ in a distorted octahedral site may permit persistence of piemontite to higher temperatures than Mn-poor epidote minerals. The compositional range of natural Fe–Mn–Al piemontites supports these results. Cation partitioning from piemontite-bearing parageneses also indicates crystallization at high f_o2, but application of the cited results should be made with caution. Synthetic phases were too fine-grained for optical or microprobe analysis, and reaction was often incomplete. The assumption that all Fe + Mn was contained in piemontite and garnet, respectively, in the low- and high-temperature assemblages is supported by the cell dimensions for these synthetic minerals, which are close to predicted values. The reaction is pseudo-univariant, as solid solution in garnet and piemontite would be f_o2-dependent in a more complex chemical system. Although bulk rock and fluid compositions may also have a marked effect on the stability of natural epidote–piemontite, f_o2 is the major control on Fe : Mn : Al in epidote minerals.     

Sorption of heavy metal cations by low-temperature deposits of Pacific hydrothermal fields

Cation exchange reactions with participation of heavy metals Mn, Co, Ni, Cu, Zn, Cd, Ba, and Pb were studed in oceanic low-temperature hydrothermal deposits of various mineral compositions and in hydrogenic Fe-Mn crusts. Individual minerals and their assemblages differ significantly in absorptive capacity, which increases in the following order: hematite ? Si-protoferrihydrite < protoferrihydrite < geothite < nontronite ? Fe-vernadite + Mn-feroxyhyte < Fe-free vernadite < bernessite + Fe-free vernadite < bernessite; i.e., it successively increases from the mineral with a coordination type of lattice to minerals with a layer-type structure. The exchange complex of all minerals includes Na⁺, K⁺, Ca²⁺, and Mg²⁺, i.e., the main cations of seawater. In Mn minerals, Mn²⁺ is the main exchange component. The contribution of all the mentioned cations to the exchange capacity of minerals is as high as 90–98%. The highest absorptive capacity among the examined low-temperature oceanic deposits is characteristic of hydrothermal Mn minerals. Their capacity exceeds substantially that of hydrothermal oxides, hydroxides, Fe-aluminosilicates, and hydrogenic Fe-Mn minerals. The absorptive capacity of all examined Mn minerals relative to heavy metals increases in the same order: Ni < Zn < Cd < Mn < Co < Pb < Cu.     

H-O-S-Cu-Pb Isotopic Constraints on the Origin of the Nage Cu-Pb Deposit, Southeast Guizhou Province, SW China

The Nage Cu-Pb deposit,a new found ore deposit in the southeast Guizhou province,southwest China,is located on the southwestern margin of the Jiangnan Orogenic Belt.Ore bodies are hosted in slate and phyllite of Neoproterozoic Jialu and Wuye Formations,and are structurally controlled by EW-trending fault.It contains Cu and Pb metals about 0.12 million tonnes with grades of 0.2 wt% to 3.4 wt% Cu and 1.1 wt% to 9.27 wt% Pb.Massive and disseminated Cu-Pb ores from the Nage deposit occur as either veinlets or disseminations in silicified rocks.The ore minerals include chalcopyrite,galena and pyrite,and gangue minerals are quartz,sericite and chlorite.The H-O isotopic compositions of quartz,S-Cu-Pb isotopic compositions of sulfide minerals,Pb isotopic compositions of whole rocks and ores have been analyzed to trace the sources of ore-forming fluids and metals for the Nage Cu-Pb deposit.The δ65CuNBS values of chalcopyrite range from-0.09% to +0.33‰,similar to basic igneous rocks and chalcopyrite from magmatic deposits.δ65CuNBS values of chalcopyrite from the early,middle and final mineralization stages show an increasing trend due to63Cu prior migrated in gas phase when fluids exsolution from magma.δ34SCDT values of sulfide minerals range from 2.7‰ to +2.8‰,similar to mantle-derived sulfur(0±3‰).The positive correlation between δ65CuNBS and δ34SCDT values of chalcopyrite indicates that a common source of copper metal and sulfur from magma.δDH2OSMOW and δ18OH2O-SMOW values of water in fluid inclusions of quartz range from 60.7‰ to 44.4‰ and +7.9‰ to +9.0‰(T=260°C),respectively and fall in the field for magmatic and metamorphic waters,implicating that mixed sources for H2O in hydrothermal fluids.Ores and sulfide minerals have a small range of Pb isotopic compositions(208Pb/204Pb=38.152 to 38.384,207Pb/204Pb=15.656 to 17.708 and 206Pb/204Pb=17.991 to 18.049) that are close to orogenic belt and upper crust Pb evolution curve,and similar to Neoproterozoic host rocks(208Pb/204Pb=38.201 to 38.6373,207Pb/204Pb=15.648 to 15.673 and 206Pb/204Pb=17.820 to 18.258),but higher than diabase(208Pb/204Pb=37.830 to 38.012,207Pb/204Pb=15.620 to 15.635 and206Pb/204Pb=17.808 to 17.902).These results imply that the Pb metal originated mainly from host rocks.The H-O-S-Cu-Pb isotopes tegather with geology,indicating that the ore genesis of the Nage Cu-Pb deposit is post-magmatic hydrothermal type.     

Experimental Study on Surface Reactions of Heavy Metal Ions With Quartz—Aqueous Ion Concentration Dependence

Adsorption of divalent metal ions, including Cu²⁺, Pb²⁺, Zn²⁺, Cd²⁺ and Ni²⁺, on quartz surface was measured as a function of metal ion concentration at 30°C under conditions of solution pH= 6. 5 and ion strength I = 0. 1mol/L. Results of the experimental measurements can be described very well by adsorption isotherm equations of Freudlich. The correlation coefficients (r) of adsorption isotherm lines are > 0. 96. Moreover, the experimental data were interpreted on the basis of surface complexation model. The experimental results showed that the monodentate-coordinated metal ion surface complex species (SOM⁺) are predominant over the bidentate-coordinated metal ion surface complex species [(SO)₂M] formed only by the ions Cu²⁺, Zn²⁺ and Ni²⁺. And the relevant apparent surface complexation constants are lgK_M = 2.2–3.3 in order of K_Cd≥K_Pb > K_Zn > K_Ni≥K_Cu, and lgβ_M = 5.9-6.8 in order of β_Ni > β_Zn > β_Cu. Therefore, the reactive ability of the ions onto mineral surface of quartz follows the order of Cd > Pb > Zn > Ni> Cu under the above-mentioned solution conditions. The apparent surface complexation constants, influenced by the surface potential, surface species and hydrolysis of metal ions, depend mainly on the Born solvation coefficient of the metal ions. This project was financially supported by the National Natural Science Foundation of China (No. 49572091).