Die Kristallstruktur des Minerals Eclarit, (Cu,Fe) Pb9Bi12S28

Zusammenfassung Die Kristallstruktur des zuerst vonPaar, Chen undMeixner beschriebenen neuen Minerals wurde an der Originalprobe bestimmt. Für die prinzipielle Lösung der Struktur war eine Kombination von direkten und Pattersonmethoden erforderlich. Anhand von 2774 kristallographisch unabhängigen Röntgenreflexen (davon 1828 beobachtet) wurde die Struktur bis zu einem gewichtetenR-Wert von 10.7% isotrop verfeinert. Das Mineral ist orthorhombisch, RaumgruppePnma mit den Gitterkonstantena ₀=54.76Å,b ₀=4.030 Å,c ₀=22.74 Å undZ=4. Die Kristallstruktur ist durch galenitähnliche Bereiche, deren [110] Richtung parallel zurb ₀-Achse verläuft, gekennzeichnet. Die gegenseitige Anordnung dieser Bereiche ist teils kobellit-, teils cosalitähnlich. Die galenitähnlichen Bereiche sind vorwiegend wismuthhaltig (Koordination 3+2+1), während die Ph-Atome in einer trigonal-prismatischen Koordination mit 2 zusätzlichen Schwefelatomen vorwiegend als Bindeglieder dazwischen liegen.

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The crystal structure of eclarite, (Cu,Fe)Pb₉Bi₁₂S₂₈

Summary The crystal structure of the new mineral eclarite, first described byPaar, Chen andMeixner was determined using the original material. It was necessary to apply a combination of direct and Patterson methods. The structure was refined for 2774 independent reflections (1828 observed) with isotropic temperature factors to a weightedR-value of 10.7%. Eclarite crystallizes in the orthorhombic space groupPnma with lattice parametersa ₀=54.76 Å,b ₀=4.030 Å,c ₀=22.75 Å,Z=4. The structure is characterized by galena-like building units with [110] (galena) parallel to theb-axis. These units are linked to each other partly as in kobellite, partly as in cosalite structures. Bi prefers to occupy the metal positions in the galena-like units, coordinated by 3+2+1S, whereas Pb occupies preferably the positions coordinated trigonal prismatic with two additional S. The latter groups serve to connect the galena-like units.

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Herrn Professor Dr.Josef Zemann zum 60. Geburtstag gewidmet.     

Some electrical properties of fahlore Cu10(Zn,Fe)2(As,Sb)4S13

Natural Zn-tennantite Cu_10.10Ag_0.04(Zn_1.29-Fe_0.67)_1.96(As_3.04Sb_0.89)_3.93S_12.98 from Beresovskoe, Urals, behaves as an ordinary semiconductor in the temperature range 300–400 K and frequency range 10⁸–2.8·10¹⁰ Hz, and no ionic component conductivity is observed. This contrasts with the behaviour of synthetic tetrahedrites (both Cu-rich and Cu-poor) which are solid electrolytes. These results can be related to the number of vacancies per formula unit and the substitution scheme for the divalent metals in fahlore.     

Heyrovskýite, 6(Pb0.86Bi0.08(Ag,Cu)0.04)S . Bi2S3 from Hůrky,Czechoslovakia, a new mineral of genetic interest

Heyrovskýite has a composition range from 6(Pb_0.83Bi_0.10(Ag, Cu)_0.07) S . Bi₂S₃ to 6(Pb_0.92Bi_0.05(Ag, Cu)_0.03) S . Bi₂S₃. It is orthorhombic. Crystal forms {100}, {010}, {120}, {140}, {250}, and {321} (?) were observed; {010} and {140} are dominant. Elongated c, flattened (010). a:b:c _morph=0.432:1:0.128. Cell parameters a=13.705±0.013 Å, b=31.194±0.033, c=4.121±0.003, a:b:c _X-ray=0.439:1:0.132. The diffraction symbol is Bb, compatible with Bbmm, Bb2₁ m, Bbm2. Morphology corresponds to point groups mmm or mm2, reducing the possible space groups to Bbmm and Bbm2. Density at 20 °C is 7.17 g/cm³, calculated, 7.18; Z=4. Micro-indentation hardness (VHN) (50 g load) is 166 to 234 kp/mm². Strongly anisotropic; reflectance strongly variable, roughly the same as of galena. Etch tests: HNO₃ (1:1) and HCl (1:1) positive, FeCl₃ 20%, HgCl₂ 5%, KCN 20%, and KOH 40% all negative. Powder data are identical with those for phase II of Otto and Strunz (1968). Heyrovskýite is associated with galena and cosalite at H?rky, Czechoslovakia.     

Eclarit, (Cu,Fe) Pb9Bi12S28, ein neues Sulfosalz von Bärenbad,Hollersbachtal, Salzburg, Österreich

Zusammenfassung Eclarit kommt in goldführenden Kupfererzen in Bärenbad westlich des Hollersbachtales in SH 1600 m ca. 1.5 km nördlich der Bleiglanz-Zinkblende-Flußspat-Lagerstätte der Achsel-Alm vor. Eclarit tritt in fächerförmigen Gruppierungen nadelförmiger Kristalle bis zu 1,5 cm Länge und in Aggregaten xenomorpher Körner rißausfüllend in kataklastischem Pyrit und Arsenkies in einer Quarzmatrix auf. Weitere Begleiterze sind: Kupferkies, Pyrrhotin, Sphalerit, Stannit s.str., ein joseitähnliches Mineral, ged. Wismut und ged. Gold. Mikrosonden-Analysen zeigen nur geringfügige Variation im Chemismus von Kom zu Kom. Die mittlere Zusammensetzung ist: Cu 0,9, Fe 0,6, Ag 0,3, Pb 34,5, Bi 45,8, Sb 1,5 und S 17,3 Gew.-% (Summe: 100,7). Die durchKupcik (1983) durchgeführte Strukturuntersuchung führte zu folgender Formel: (Cu,Fe)Pb₉(Bi,Sb)₁₂S₂₈, oder idealisiert: (Cu,Fe)Pb₉Bi₁₂S₂₈. Die empirische Formel auf der Basis S=28 lautet daher: (Cu_0,73 Fe_0,57 Ag_0,16) _1,46 Pb_8,61 (Bi_11,36 Sb_0,62) _11,98 S₂₈. Die daraus errechnete Dichte ist 6,88 g·cm^–3, somit in guter Übereinstimmung mit dem gemessenen Wert von 6,85 g·cm^–3. Eclarit kristallisiert orthorhombisch, RaumgruppePnma, und hat die Gitterkonstanten:a=54,76(4),b=4,030(3),c=22.75(3) Å,Z=4. Die stärksten Linien des Pulverdiagrammes sind: 3.63 (30) (905), 3.49 (40) (10.0.5, 606), 3.41 (100) (16.0.0, 811, 513, 712, 706), 3.01 (60) (0.15, 11.0.6, 115, 18.0.1), 2.89 (70) (11.1.3, 914), 2.74 (40) (216, 11.1.4, 116, 20.0.0), 2,14(50) (21.0.6, 119, 19.0.7, 019), 2,04(45) (16.1.7, 18.1.6, 22.1.3, 4.0.11), 2.01 (80) (020, 23.1.2, 5.0.11, 23.0.6), 1.73(35) (16.2.0, 10.2.5, 726). Eclarit ist weißgrau (Luft) bzw. bläulichgrau (Öl) gegen Bleiglanz, der Reflexionspleochroismus ist mittel bis deutlich, die Anisotropie deutlich (Luft) bzw. stark (Öl). Das Reflexionsvermögen in Luft gemessen bei den vier Standard-Wellenlängen ist: 480 nm: 51,2–45,2; 546 nm: 47,2–42,9; 589 um: 46,1–42,0; 644 nm: 45,0–40,2%. Die Mikrohärte (VHN₅₀) ist 87–191 kp·mm^–2, im Durchschnitt 163 kp·mm^–2.

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Eclarite, (Cu, Fe) Pb₉Bi₁₂S₂₈, a new sulfosalt from Bärenbad, Hollersbachtal, Salzburg Province, Austria

Summary Eclarite has been observed in gold-bearing copper ores at Bärenbad W of Hollersbachtal (ev. 1600 m), about 1.5 km north of the galena-sphalerite-fluorite deposit Achsel-Alm, Salzburg Province, Austria. It occurs as fan shaped aggregates of needle-like crystals up to 1.5 cm length, or as granular fracture-fillings of pyrite and arsenopyrite. Other associated minerals are chalcopyrite, pyrrhotite, sphalerite, stannite s.str., a joseite-type mineral, native bismuth and native gold, in a matrix of quartz. Microprobe analyses showed the mineral to be homogeneous, with only very limited variation in chemistry from grain to grain. The composition is (mean value of 16 analyses); Cu 0.9, Fe 0.6, Ag 0.3, Pb 34.3, Bi 45.8, Sb 1.5 and S 17.3 wt.-% (total 100.7). The structure analysis (Kupcik, 1983) showed the structural cell formula to be (Cu,Fe)Pb₉(Bi,Sb)₁₂S₂₈ or ideally (Cu,Fe)Pb₉Bi₁₂S₂₈. The empirical formula calculated on the basis of S=28 is: (Cu_0,73 Fe_0,57 Ag_0,16) _1,46 Pb_8,61 (Bi_11,36 Sb_0,62) _11,98 S₂₈. This gives a calculated density of 6.88, which is in good agreement with the measured value of 6.85 g·cm^–3. Eclarite is orthorhombic,Pnma,a=54.76(4),b=4.030(3),c=22.75(3) Å,Z=4. The strongest lines in the powder diffraction pattern are: 3.63(30) (905), 3.49(40) (10.0.5, 606), 3.41 (100) (16.0.0, 811, 513, 712, 706), 3.01 (60) (015, 11.0.6, 115, 18.0.1), 2.89 (70) (11.1.3, 914), 2.74 (40) (216, 11.1.4, 116, 20.0.0), 2.14 (50) (21.0.6, 119, 19.0.7, 019), 2.04 (45) (16.1.7, 18.1.6, 22.1.3, 4.0.11), 2.01 (80) (020, 23.1.2, 5.0.11, 23.0.6), 1.73 (35) (16.2.0, 10.2.5, 726). Eclarite is whitish-grey (air) and bluish-grey (oil) against galena, respectively; bireflectance is moderate to distinct, anisotropism distinct (air) and strong (oil), respectively. Reflectances in air are (wavelength,R _max ,R _min ): 480 nm: 51.2–45.2; 546 nm: 47.2–42.9; 589 nm: 46.1–42.0; 644 nm: 45.0–40.2%. Micro indentation hardness VHN₅₀ is 87–191 (av. 163) kp·mm^–2.

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Herrn Professor Dr.Josef Zemann zum 60. Geburtstag gewidmet.     

The crystal structure of arsentsumebite, Pb2Cu[(As, S)O4]2(OH)

Summary The crystal structure of arsentsumebite, ideally, Pb₂Cu[(As, S)O₄]₂(OH), monoclinic, space group P2₁/m, a = 7.804(8), b = 5.890(6), c = 8.964(8) ?, β = 112.29(6)°, V = 381.2 ?³, Z = 2, d_calc. = 6.481 has been refined to R = 0.053 for 898 unique reflections with I> 2σ(I). Arsentsumebite belongs to the brackebuschite group of lead minerals with the general formula Pb₂ Me(XO₄)₂(Z) where Me = Cu²⁺, Mn²⁺, Zn²⁺, Fe²⁺, Fe³⁺; X = S, Cr, V, As, P; Z = OH, H₂O. Members of this group include tsumebite, Pb₂Cu(SO₄)(PO₄)(OH), vauquelinite, Pb₂Cu(CrO₄)(PO₄)(OH), brackebuschite, Pb₂ (Mn, Fe)(VO₄)₂(OH), arsenbracke buschite, Pb₂(Fe, Zn)(AsO₄)₂(OH, H₂O), fornacite, Pb₂Cu(AsO₄)(CrO₄)(OH), and feinglosite, Pb₂(Zn, Fe)[(As, S)O₄]₂(H₂O). Arsentsumebite and all other group members contain M = M–T chains where M = M means edge-sharing between MO₆ octahedra and M–T represents corner sharing between octahedra and XO₄ tetrahedra. A structural relationship exists to tsumcorite, Pb(Zn, Fe)₂(AsO₄)₂ (OH, H₂O)₂ and tsumcorite-group minerals Me(1)Me(2)₂(XO₄)₂(OH, H₂O)₂. Received June 24, 2000; revised version accepted February 8, 2001     

First-principles study of the electronic properties of A2B3 minerals, with A=Bi,Sb and B=S,Se

We determine the valence electron density and the electron band structure of stibnite, bismutinite, guanajuatite and antimonelite using the density functional theory. All the compounds present similar electronic properties and exhibit a quasi-1D character. We perform a detailed analysis of the charge topology, the atomic static charges and volumes.     

Gersdorffit (in zwei Strukturvarietäten) und Sb-hältiger Parkerit,Ni3 (Bi,Sb)2 S2, von der Zinkwand,Schladminger Tauern, Österreich

Zusammenfassung Erzpetrographische Untersuchungen von Ni-reichen Erzproben der Ni–Co–Bi–(Ag)-Lagerstätte Zinkwand (Schladminger Tauern, Steiermark) führten zum Nachweis einer Paragenese von Gersdorffit, Nickelin, Pararammelsbergit, ged. Wismut, Wismutglanz und Parkerit. Gersdorffit tritt in zwei deutlich voneinander verschiedenen (Reflexionsvermögen, Mikrohärte) Komponenten M und I auf. Mikrosondenanalysen zeigen einheitlichen Chemismus der Komponente M, hingegen unterschiedlichen der Komponente I, hervorgerufen durch starken Zonarbau. Gersdorffit I repräsentiert vermutlich Gersdorffit mit ungeordneter Struktur und RaumgruppePa3, Gersdorffit M hingegen vertritt Gersdorffit mit RaumgruppeP2₁3. Gersdorffit, Nickelin und Parkerit weisen Gehalte von±2Gew.% Sb auf. Antimon-hältiger Parkerit ist von den bis heute nachgewiesenen vier Fundpunkten des Minerals nicht bekannt. Vorsichtige Abschätzung der Bildungstemperatur ergibt für die Gersdorffit-Nickelin-Pararammelsbergit-Assoziation sicher <450°C, für jene von Parkerit-ged. Wismut-Wismutglanz<273°C.

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Gersdorffite (in two structure varieties) and antimonian-parkerite, Ni₃ (Bi, Sb)₂S₂ of the Zinkwand, Cchladminger Tauern, Austria

Summary Ore petrologic investigations of a Ni-rich assemblage from the Ni–Co–Bi–(Ag)-deposit Zinkwand (Schladminger Tauern, Styria, Austria) resulted in the identification of gersdorffite, nickeline, pararammelsbergite, native bismuth, bismuthinite and the rate ore mineral parkerite, so far not recorded from that locality. Gersdorffite occurs as two distinctly different varieties M and I (reflectance, microhardness). Microprobe analyses show uniform composition of phase M, but compositional variations of phase I caused by strong zonal texture. Gersdorffite I probably represents gersdorffite with disordered structure with space groupPa3; gersdorffite M corresponds to the gersdorffite with space groupP2₁3. Gersdorffite, nickeline and parkerite contain about 2 wt.% Sb. Sb-containing parkerite has not been reported from the four known occurrences of that mineral. Temperature of formation for the Ni-minerals has been estimated to be (considerably?) below 450°C, for the Bi-bearing minerals below 273°C.

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Herrn Univ. Prof. Dr.H. Meixner zum 70. Geburtstag gewidmet.     

Anthropogenic components of heavy metal (Cd,Zn, Cu,Pb) budgets in the Lot-Garonne fluvial system (France)

Heavy metal (Zn, Cd, Cu and Pb) mass balances in the Lot-Garonne fluvial system have been established for 1999 and 2000. The mean annual discharges of these years are close to the mean discharge of the previous decade. The estimated annual dissolved and particulate fluxes in this model watershed integrate daily input from diffuse and point sources, diffusive fluxes at the water/sediment interface, changes in the dissolved-particulate partition and changes in sediment stock. Cadmium, Zn, Cu and Pb entering the Gironde estuary via the Garonne River (11–14 t a⁻¹ of Cd; 1330–1450 t a⁻¹ of Zn; 126–214 t a⁻¹ of Cu and 127–155 t a⁻¹ of Pb) are mainly transported in the particulate phase and the major part (i.e. ∼74 to 96% for Cd, ∼60% for Zn, ∼50 to 60% for Cu and ∼80% for Pb) is transported by the Lot River. The main anthropogenic heavy metal point source is located in a small upstream watershed (Riou-Mort River) accounting for at least 47% (Cd), ∼20% (Zn), ∼4% (Cu) and ∼7 to 9% (Pb) of the total heavy metal inputs into the Garonne River, although it contributes only 1% of the discharge. Mass balances for 1999 suggest that under mean annual hydrologic conditions on the basin scale, the heavy metal budget of the Lot-Garonne fluvial system is balanced and that the stocks of Cd [200 t; Environ. Tech. 16 (1995) 1145] and Zn in the Lot River sediment are constant under mean discharge conditions. Heavy metal input by molecular diffusion at the sediment surface represents an important component of dissolved metal inputs into the system (e.g. 30% for Cu). Except for Cu, these dissolved inputs are totally removed from solution by SPM. Based on the generally constant Zn/Cd (∼50) concentration ratio in sediment cores from the polluted Lot River reaches and the sediment stock of Cd [200 t; Environ. Tech. 16 (1995) 1145], the present day Zn stock in the Lot River sediments has been estimated at about 10,000 t. In addition to the mobilization of river-bed sediment and associated heavy metals by intense floods, local human activities, including river-bed dredging, may strongly modify the heavy metal budget of the river system. In 2000, the dredging-related remobilization of polluted Lot River sediment released 2–6 t Cd. This additional Cd point source was estimated to account for 15–43% of the gross inputs into the Gironde Estuary.     

A re-appraisal of the chemical formula of nealite,Pb4Fe(AsO3)2Cl4 . 2H2O,on the basis of a crystal structure determination

Summary A crystal structure determination of the mineral nealite, Pb₄Fe(AsO₃)₂Cl₄ . 2H₂O, (a = 6.548(4), b = 10.243(8), c = 5.587(3) [Å]; = 96.2(1), = 89.6(1), = 97.7(1) [°]; Z = 1; space group ) was performed using single crystal X-ray data and a direct method strategy; the structural parameters were fitted by least squares techniques. The structure is characterized by isolated FeO₂Cl₂(H₂O)₂ octahedra (Fe-O: 2.08 Å, 2x, and 2.12 Å, 2x, Fe-Cl: 2.60 Å, 2x) and AsO₃ pyramids (As-O from 1.79 to 1.89 Å) which are connected by PbO₄Cl₄ and PbO₅Cl₄ polyhedra to a framework (with Pb-O distances from 2.22 to 3.34 Å, Pb-Cl distances from 3.10 to 3.54 Å). Oscillation photographs, exposed for 20 h, show very faint streaks indicating a doubling of c, probably caused by a partial ordering of a split lead atom position. Nealite is the first mineral found to contain a divalent iron atom coordinated to oxygen and chlorine atoms simultaneously.

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Änderung der chemischen Formel des Nealits, Pb₄Fe(AsO₃)₂Cl₄ . 2H₂O, basierend auf der Kristallstrukturbestimmung

Zusammenfassung Die Kristallstrukturbestimmung des Minerals Nealit, Pb₄Fe(AsO₃)₂Cl₄ . 2H₂O, a = 6.548(4), b = 10.243(8), c = 5.587(3) [Å]; = 96.2(1), = 89.6(1), = 97.7(1) [°]; Z = 1; Raumgruppe ) wurde anhand von röntgenographischen Einkristalldaten mit direkten Methoden durchgeführt und die Strukturparameter nach der Methode der kleinsten Quadrate verfeinert. Die Kristallstruktur ist charakterisiert durch isolierte FeO₂Cl₂(H₂O)₂-Oktaeder (Fe-O: 2.08 Å, 2x, und 2.12 Å, 2x, Fe-Cl: 2.60 Å, 2x) und AsO₃-Pyramiden (As-O von 1.79 Å bis 1.89 Å), welche durch PbO₄Cl₄ und PbO₅Cl₄-Polyeder zu einem Gerüst verknüpft sind (Pb-O von 2.22 bis 3.34 Å und Pb-Cl von 3.10 bis 3.54 Å). Schwenkaufnahmen, etwa 20 h belichtet, zeigen sehr feine Schwärzungsstreifen, die auf eine Verdopplung von c hinweisen, möglicherweise durch eine teilweise Ordnung einer aufgespaltenen Position eines Bleiatoms hervorgerufen. Nealit ist das erste Mineral, in dem ein zweiwertiges Eisenatom gleichzeitig an Sauerstoff- und Chloratome gebunden ist.

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Dedicated to Prof. Dr. Josef Zemann (Vienna) on the occasion of his 70^th birthday

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With 1 Figure     

The crystal structure of sonoraite,Fe3+Te4+O3(OH)·H2O

Summary Sonoraite, FeTeO₃(OH)·H₂O, is monoclinic,P 2₁/c, witha=10.984(2),b=10.268(2),c=7.917(2) Å, =108.49(2)°. For 8 formula units per cell the calculated density is 4.179(2) g/cm³; the observed value is 3.95(1) g/cm³. The Supper-Pace automated diffractometer was used to collect 1884 independent reflections which were corrected for absorption. The structure was determined by an automated symbolic addition procedure. It was refined to a residualR of 6.2% using anisotropic temperature factors for the cations and isotropic temperature factors for the oxygen atoms. Chains of octahedra about Fe extend along [101]; edge-sharing pairs of these octahedra are joined by corner sharing. The Fe–Fe distances across the shared edges are 3.05 and 3.20 Å, short enough to suggest magnetic interactions. All but one H₂O are involved in the chains. The Te⁴⁺ ions have a pseudotetrahedral coordination, with three oxygen ions forming one face of the tetrahedron and the lone electron pair of Te occupying the fourth corner. The O–Te–O average bond angle is 95°. The Fe chains are tied together by Te–O bonds in all three dimensions.

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Die Kristallstruktur von Sonorait, Fe³⁺Te⁴⁺O₃(OH).H₂O

Zusammenfassung Sonorait, FeTeO₃(OH)·H₂O, ist monoklin, P 2₁/c, mit den folgenden Zelldimensionen:a=10,984(2),b=10,268(2),c=7,917(2) Å, =108,49(2)°. Mit 8 Formel-Einheiten errechnet man eine Dichte von 4,179(2) g/cm³; die gemessene Dichte beträgt 3,95(1) g/cm³. Das Supper-Pace automatische Diffraktometer wurde zur Sammlung von 1884 unabhängigen Reflexen benutzt, welche für Absorption korrigiert wurden. Die Struktur wurde mit Hilfe eines vollständig automatischen Programms für symbolische Addition bestimmt. Mit anisotropen Temperaturfaktoren für die Kationen und mit isotropen Temperaturfaktoren für die Sauerstoff-Atome wurde ein Residuum von 6,2% erreicht. Ketten von Eisen-Oktaedern erstrecken sich entlang [101]; Oktaeder-Paare mit gemeinsamen Kanten sind über Eckenverknüpfung verbunden. Die Fe–Fe-Abstände über die gemeinsamen Kanten betragen 3,05 und 3,20 Å, kurz genug, um zu magnetischer Wechselwirkung führen zu können. Nur ein H₂O-Molekül ist nicht Teil einer Kette. Die Te⁴⁺-Ionen befinden sich in pseudotetraedrischer Koordination; drei Sauerstoff-Ionen bilden eine Fläche des Tetraeders, die vierte Ecke wird durch das einsame Elektronenpaar von Te besetzt. Der Mittelwert des O–Te–O-Bindungswinkels beträgt 95° Die Fe-Ketten werden durch Te–O-Bindungen dreidimensional verbunden.

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Synthesis and some properties of iron- and vanadium-bearing kyanites, (Al,Fe3+)2SiO5and (Al,V3+)2SiO5

Iron- and vanadium-bearing kyanites have been synthesized at 900 and 1100° C/20 kb in a piston-cylinder apparatus using Mn₂O₃/Mn₃O₄- and MnO/Mn-mixtures, respectively, as oxygen buffers. Solid solubility on the pseudobinary section Al₂SiO₅-Fe₂SiO₅(-V₂SiO₅) of the system Al₂O₃-Fe₂O₃(V₂O₃)-SiO₂ extends up to 6.5 mole% (14mole %) of the theoretical end member FeSiO₅(V₂SiO₅) at 900°C/20 kb. For bulk compositions with higher Fe₂SiO₅ (V₂SiO₅) contents the corundum type phases M₂O₃(M = Fe³⁺, V³⁺) are found to coexist with the Fe³⁺(V³⁺)-saturated kyanite solid solution plus quartz. The extent of solid solubility on the join Al₂SiO₅-Fe₂SiO₅ at 1 100°C was not found to be significantly higher than at 900° C. Microprobe analyses of iron bearing kyanites gave no significant indication of ternary solid solubility in these mixed crystals. Lattice constants a ₀, b ₀, c ₀, and V₀ of the kyanite solid solutions increase with increasing Fe₂SiO₅- and V₂SiO₅-contents proportionally to the ionic radii of Fe³⁺ and V³⁺, respectively, the triclinic angles ,, remain constant. Iron kyanites are light yellowish-green, vanadium kyanites are light green. Iron kyanites, (Al_1.87 Fe _0.13 ³⁺ )SiO₅, were obtained as crystals up to 700 m in length.     

Single crystal growth of the modified spinel (β) and spinel (γ) phases of (Mg,Fe)2SiO4 and some geophysical implications

Single crystals of ferromagnesian orthosilicates with modified spinel (β) and spinel (γ) structure as large as 500 μm have been grown by solid state crystallization at high temperature and high pressure using an MA8-type apparatus driven in a 2,000-ton uniaxial press. This system is capable of generating pressures of 24.0 (±0.3) GPa at 2,400 (±50)°C for one hour in a sample assembly volume of 0.14 cm³. Crystals larger than 100 μm were observed to grow only at pressures within 5 percent of the phase boundary between the stability fields of the β and γ phases. Experimental determination of the phase boundaries between β or β+γ and γ phases for (Mg,Fe)₂SiO₄ has been extended to 22 GPa and 2,400°C. The effect of configurational entropy due to disordering is evaluated to be minimal on the basis of the cationic distribution in the synthesized samples; thus, we conclude that the phase boundary between β or β+γ and γ phases remains essentially linear to 2,400°C. In (Mg,Fe)₂SiO₄ solid solutions, the stability field of the γ phase shifts towards the lower pressures with increasing iron content at a rate of a 1 GPa for each 10 mole percent Fe. Assignment of the β→β+γ→γ transition to the seismic 550 km discontinuity is rejected by the present phase diagram results for (Mg_0.9Fe_0.1)₂SiO₄ and measurement of acoustic velocities for β and γ Mg₂SiO₄, but the discontinuity may be caused by a phase transition of pyroxene to a garnet-like structure.     

Lead isotope studies of strata-bound,vein-type,and unconformity-related Pb,Sb, and Bi ore mineralizations from the western edge of the Bohemian Massif (F.R. Germany)

Specimens from strata-bound/stratiform Kieslager, lineament-bound, and unconformity-related Pb occurrences from the NE Bavarian Saxothuringian and Moldanubian belts and samples from stibnite and polymetallic Sb-Au quartz veins were analyzed for their lead isotope composition.The strata-bound Pb at Bodenmais yielded an Upper Proterozoic ²⁰⁷Pb/²⁰⁶Pb model age which correlates with the assumed stratigraphic age of the host rock. Late Precambrian rift activity may have triggered the formation of this ore mineralization. This type of Pb was also found in the Kieslager at Waldsassen hosted by Early Paleozoic country rocks and in the fluorite veins at Kittenrain.The vein-type lineament-bound, and unconformity-related Pb occurrences show a similar isotopic pattern which suggests that this type of Pb originated from the same source. The ²⁰⁷Pb/²⁰⁶Pb model ages which are too old compared to the assumed age of formation and the accelerated ²⁰⁸Pb evolution indicate that the detritus of the source rock underwent a high-grade metamorphism in the Precambrian.The formation of the unconformity-related Pb concentrated in galena of fluorite-barite veins is correlated with late Variscan magmatic intrusions. The older model ages of about 100–150 Ma from the lineament-bound lead, located along deep-seated lineamentary fault zones, suggest an earlier separation of this type of Pb possibly triggered by the Caledonian A-subduction-related metamorphism.     

汞银黝铜矿Ag6 (Cu4Hg2) Sb4S13——黝铜矿族新矿物

作为黝铜矿族矿物的新成员,汞银黝铜矿(Argentotetrahedrite-(Hg),IMA 2020-079),Ag6(Cu4 Hg2) Sb4S13,发现于湘黔汞矿带北段之保靖东坪Hg-Ag矿床中,是该矿床的主要矿石矿物和回收对象.汞银黝铜矿单晶晶体尺寸约为5～20 μm,呈粒径20～300 μm的粒状、片状集合...     

P-T-X conditions,origin, and evolution of Cu-bearing fluids of the shear zone-hosted Huogeqi Cu–(Pb–Zn–Fe) deposit,northern China

Huogeqi is a shear zone-hosted epigenetic deposit within the greenschist-amphibolite facies of the Mesoproterozoic Langshan Group in the Langshan district on the northern margin of the North China Craton (NCC). Copper mineralization in the Huogeqi deposit was formed in two stages: a main-stage controlled by the shear zone and characterized by brittle-ductile ore-forming structures and a lower greenschist facies mineral assemblage, and a late stage characterized by open space-filling textures and low-temperature minerals. Based on microthermometric and Raman microprobe analysis, the main-stage Cu-bearing fluid was mesothermal, low-salinity and H₂O–CH₄-dominant, and was generated by an interaction between a deep-crustal metamorphic fluid and graphite-bearing host rocks. This interaction resulted in a more CH₄-rich fluid, which was more amenable to be immiscible. We showed that immiscibility of the H₂O–CH₄ fluid occurred due to temperature decrease, prior to the main-stage Cu mineralization; Cu was finally precipitated from the resultant H₂O-rich aqueous fluid. Main-stage Cu mineralization temperature was obtained using various methods: 310–370 °C by intersection of isochors of coexistent CH₄ and aqueous inclusions; 364 ± 41 °C on average by pressure correction of the homogenization temperatures of aqueous inclusions; and 362 ± 26 °C using the chlorite geothermometer. Pressure during Cu-deposition fluctuated between lithostatic and hydrostatic at depths of ca. 10–12 km, but it seemingly had no effect on the mineralization process. The late-stage Cu-bearing fluid was a low temperature, low salinity, H₂O of meteoric origin.     

The transport and fate of Fe,Mn, Cu,Zn, Cd,Pb and SO4 in a groundwater plume and in downstream surface waters in the Coeur d'Alene Mining District,Idaho, U.S.A.

The controls on metal concentrations in a plume of acidic (pH 3.29–5.55) groundwater in the Moon Creek watershed in Idaho, U.S.A., were investigated with the use of property-property plots. A plot of Ca vs S demonstrated that a plume of contaminated groundwater was being diluted by infiltration of rain and creek water at shallow depths and by ambient groundwater near bedrock. The small amount of dissolved Fe (2.1 mg/l) was removed while dissolved Pb was added, reaching a maximum concentration of 0.37 mg/l. The other metals (Zn ≤ 16, Al ≤ 6.2, Cu ≤ 2.1 and Cd ≤ 0.077 mg/l) in the shallow groundwater were essentially conserved until they emerged as a seep along the creek bank. Upon mixing with the creek water, groundwater was diluted by factors between 11 and 50, and the pH of the mixture became neutral. Metals originating from the contaminated groundwater were removed in the creek in the following order: Fe > Al > Pb ≫ Cu > Mn > Zn = Cd.Pb and Cu continued to be removed from solution even as the creek passed adjacent to a tailings pile. In contrast, Zn concentrations in the creek increased adjacent to the tailings area, presumably as a result of the reemergence of the upgradient plume as the creek lost elevation.Below the tailings dam, contaminated creek water (400–800 μg Zn/l) was diluted by both smaller side streams and a creek of equal flow. The presence of 3 distinctive water masses required the use of two tracers (dissolved Si and S) to distinguish between mixing and geochemical reactions. The removal of metals was greater during low flow conditions. Pb was removed to the greatest extent, falling below detection limits (0.5 μ/l) at the first sampling location. Copper and Mn were removed to a lesser extent during low flow conditions and approached conservative behavior during high flow conditions. During a 5-km journey through two hydrological regimes, less than 10% of the dissolved Zn and Cd was lost.     

Chemistry, Raman and infrared spectroscopic characterization of the phosphate mineral reddingite: (MnFe)3(PO4)2(H2O,OH)3, a mineral found in lithium-bearing pegmatite

Detailed investigation of an intermediate member of the reddingite–phosphoferrite series, using infrared and Raman spectroscopy, scanning electron microcopy and electron microprobe analysis, has been carried out on a homogeneous sample from a lithium-bearing pegmatite named Cigana mine, near Conselheiro Pena, Minas Gerais, Brazil. The determined formula is $ ({\text{Mn}}_{1.60} {\text{Fe}}_{1.21} {\text{Ca}}_{0.01} {\text{Mg}}_{0.01} )_{\sum 2.83} ({\text{PO}}_{4} )_{2.12} \cdot ({\text{H}}_{2} {\text{O}}_{2.85} {\text{F}}_{0.01} )_{\sum 2.86} $ , indicating predominance in the reddingite member. Raman spectroscopy coupled with infrared spectroscopy supports the concept of phosphate, hydrogen phosphate and dihydrogen phosphate units in the structure of reddingite-phosphoferrite. Infrared and Raman bands attributed to water and hydroxyl stretching modes are identified. Vibrational spectroscopy adds useful information to the molecular structure of reddingite–phosphoferrite.     

Stable isotopic composition of soil calcite (O,C) and gypsum (S) overlying Cu deposits in the Atacama Desert,Chile: Implications for mineral exploration,salt sources,and paleoenvironmental reconstruction

Soils overlying two porphyry Cu deposits (Spence, Gaby Sur) and the Pampa del Tamarugal, Atacama Desert, Northern Chile were collected in order to investigate the extent to which saline groundwaters influence “soil” chemistry in regions with thick Miocene and younger sediment cover. Soil carbonate (calcite) was analyzed for C and O isotopes and pedogenic gypsum for S isotopes. Soil calcite is present in all soils at the Spence deposit, but increases volumetrically above two fracture zones that cut the Miocene gravels, including gravels that overlie the deposit. The C isotope composition of carbonate from the soils overlying fracture zones is indistinguishable from pedogenic carbonate elsewhere at the Spence deposit; all δ¹³C_VPDB values fall within a narrow range (1.40–4.23‰), consistent with the carbonate having formed in equilibrium with atmospheric CO₂. However, δ¹⁸O_VPDB for carbonate over both fracture zones is statistically different from carbonate elsewhere (average δ¹⁸O_VPDB = 0.82‰ vs. −2.23‰, respectively), suggesting involvement of groundwater in their formation. The composition of soils at the Tamarugal anomaly has been most strongly affected by earthquake-related surface flooding and evaporation of groundwater; δ¹³C_VPDB values (−4.28‰ to −2.04‰) are interpreted to be a mixture of dissolved inorganic C (DIC) from groundwater and atmospheric CO₂. At the Spence deposit, soils only rarely contain sufficient SO₄ for S isotope analysis; the SO₄-bearing soils occur only above the fracture zones in the gravel. Results are uniform (3.7–4.9‰ δ³⁴S_CDT), which is near the middle of the range for SO₄ in groundwater (0.9–7.3‰). Sulfur in soils at the Gaby Sur deposit (3.8–6.1‰ δ³⁴S_CDT) is dominated by gypsum, which primarily occurs on the flanks and tops of hills, suggesting deposition from SO₄-rich fogs. Sulfate in Gaby Sur deposit gypsum is possibly derived by condensation of airborne SO₄ from volcanic SO₂ from the nearby Andes. At the Gaby Sur deposit and Tamarugal anomaly, pedogenic stable isotopes cannot distinguish between S from porphyry or redeposited SO₄ from interior salars.The three sites studied have had different histories of salt accumulation and display variable influence of groundwater, which is interpreted to have been forced to the surface during earthquakes. The clear accumulation of salts associated with fractures at the Spence deposit, and shifts in the isotopic composition of carbonate and sulfate in the fractures despite clear evidence of relatively recent removal of salts indicates that transfer from groundwater is an ongoing process. The interpretation that groundwaters can influence the isotopic composition of pedogenic calcrete and gypsum has important implications for previous studies that have not considered this mechanism.