Uniquely high-grade iodide mineralization in the oxidation zone of the Rubtsovskoe base-metal deposit,Northwest Altai,Russia

Unusual, high-grade iodide mineralization comprising marshite, miersite, and iodargyrite has been discovered in the oxidation zone of the Rubtsovskoe VHMS base-metal deposit, Northwest Altai, Russia. The distribution of iodides reveals distinct zoning. Iodargyrite is widespread in the upper part of the oxidized orebody at the hypsometric level of +156 to 163 masl. The iodargyrite zone extends for more than 150 m. The content of iodargyrite in gossan occasionally reaches 1–5 vol %. Marshite is localized at the lower level (+146 to +151 masl); the zone enriched in marshite is about 50 m in extent. The marshite content in the high-grade oxidized ore with native copper and in the zone of wall-rock argillic alteration is typically close to 1 vol %, occasionally reaching 7–10 vol %. Miersite occurs sporadically in association with both iodargyrite and low-Ag marshite, which are antagonistic mineral species. Iodargyrite is stoichiometric AgI (2H polytype with a = 4.574 and c = 7.519 Å). Isostructural cubic marshite CuI and miersite (Ag,Cu)I make up an isomorphic series within compositional limits Mar₁₀₀Mie₀-Mar₉Mie₉₁ and a break between Mar_82.5Mie_17.5 and Mar₅₇-Mie₄₃; the a parameter of their unit cells varies from 6.050 to 6.424 Å. The crystal morphology, properties, and mode of iodide occurrence are described in the paper. According to the suggested genetic model, the source of iodine was related to exhalations of seafloor fumaroles accompanying volcanic-hydrothermal-sedimentary ore formation. Iodine is absorbed by clay in the wide zone of wall-rock argillic alteration. During the early stages of sulfide ore oxidation, sulfuric acid oxidized iodine to (I⁵⁺O₃)^?, and it was subsequently reduced and fixed in poorly soluble Ag⁺ and Cu⁺ iodides.     

Gamma-ray emission expected from Kepler’s SNR

Nonlinear kinetic theory of cosmic ray (CR) acceleration in supernova remnants (SNRs) is used to investigate the properties of Kepler’s SNR and, in particular, to predict the γ-eay spectrum expected from this SNR. Observations of the nonthermal radio and X-ray emission spectra as well as theoretical constraints for the total supernova (SN) explosion energy E _sn are used to constrain the astronomical and particle acceleration parameters of the system. Under the assumption that Kepler’s SN is a type Ia SN we determine for any given explosion energy E _sn and source distance d the mass density of the ambient interstellar medium (ISM) from a fit to the observed SNR size and expansion speed. This makes it possible to make predictions for the expected γ-eay flux. Exploring the expected distance range we find that for a typical explosion energy E _sn=10⁵¹ erg the expected energy flux of TeV γ-rays varies from 2×10⁻¹¹ to 10⁻¹³ erg/(cm² s) when the distance changes from d=3.4 kpc to 7 kpc. In all cases the γ-eay emission is dominated by π ⁰-decay γ-rays due to nuclear CRs. Therefore Kepler’s SNR represents a very promising target for instruments like H.E.S.S., CANGAROO and GLAST. A non-detection of γ-rays would mean that the actual source distance is larger than 7 kpc.     

Calorimetric Study of Natural Basic Copper Phosphate—Pseudomalachite

The thermochemical study of a natural basic copper phosphate, pseudomalachite Cu₅(PO₄)₂(OH)₄ (Virneberg deposit, Germany), was carried out using high-temperature melt solution calorimetry method with a Tian–Calvet microcalorimeter. The enthalpy of formation of the mineral from elements was obtained to be Δ _f H_el(298.15 K) =–3214 ± 13 kJ/mol. The value of the Gibbs energy of pseudomalachite formation calculated using literature data on its standard entropy is Δ _f H_el^°(298.15 K) =–2812 ± 13 kJ/mol.     

Natisite,Na2TiSiO5, an Indicator Mineral of Hyperagpaitic Hydrothermal Assemblages in the Lovozero and Khibiny Alkaline Plutons,Kola Peninsula: Occurrence,Crystal Chemistry,and Genetic Features

Geology of Ore Deposits - Natisite, a natural tetragonal (P4/nmm) modification of Na2TiSiO5 = Na2TiO(SiO4) is an abundant indicator mineral of relatively low-temperature (no higher than...     

New Data on Mineralogy and Crystal Chemistry of the Lovozerite Group: Unusual Varieties of Kazakovite and Litvinskite

Geology of Ore Deposits - Unusual chemical and structural varieties of two lovozerite-group minerals from the Lovozero alkaline complex (Kola Peninsula) were studied by means of electron microprobe...     

Thermodynamic Properties of Natural Cuspidine

The paper reports pioneering data on the calorimetrically determined enthalpy of formation from elements of cuspidine, Ca fluordiorthosilicate Ca₄Si₂O₇F₂, from the Tyrny-Auz Mo–W deposit in Kabardino- Balkaria, Russia. The data were obtained by high-temperature melt solution calorimetry. The determined value is ΔfH_el° (298.15 K) =–5190 ± 13 kJ/mol. The paper reports estimated S°(298.15 K) and Δ_fG_el° (298.15 K) of cuspidine.     

Crystal structure and refined formula of garyansellite Mg<Subscript>2</Subscript>Fe<Superscript>3+</Superscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>(OH) · 2H<Subscript>2</Subscript>O

Single-crystal study of the structure (R = 0.0268) was performed for garyansellite from Rapid Creek, Yukon, Canada. The mineral is orthorhombic, Pbna, a = 9.44738(18), b = 9.85976(19), c = 8.14154(18) Å, V = 758.38(3) ų, Z = 4. An idealized formula of garyansellite is Mg₂Fe³⁺(PO₄)₂(OH) · 2H₂O. Structurally the mineral is close to other members of the phosphoferrite–reddingite group. The structure contains layers of chains of M(2)O₄(OH)(H₂O) octahedra which share edges to form dimers and connected by common edges with isolated from each other M(1)O₄(H₂O)₂ octahedra. The neighboring chains are connected to the layer through the common vertices of M(2) octahedra and octaahedral layers are linked through PO₄ tetrahedra.     

Crystal structure of nitrate cancrinite synthesized under low-temperature hydrothermal conditions

Doklady Earth Sciences -     

Calorimetric Study of Natural Anapaite

The thermochemical study of natural hydrous calcium and iron phosphate, anapaite Ca₂Fe(PO₄)₂ · 4H₂O (Kerch iron ore deposit, Crimea, Russia), was carried out using high-temperature melt solution calorimetry with a Tian-Kalvet microcalorimeter. The enthalpy of formation of the mineral from elements was obtained to be Δ _f H_el°(298.15 K) =–4812 ± 16 kJ/mol. The values of the standard entropy and the Gibbs energy of anapaite formation are S°(298.15 K) = 404.2 J/K mol and Δ _f G_el°(298.15 K) =–4352 ± 16 kJ/mol, respectively.