Highly atypical mineralization involving Pd-Pt, Au-Ag, REE, Y, Zr, U, Th, and Cl-F-enriched minerals is found in zones with base metal sulfides (BMS; ~5 vol.% to 20 vol.%) in the eastern portion of the Oktyabrsky deposit in the Norilsk complex (Russia). The overall variations in Mg# index, 100 Mg/(Mg + Fe2+ + Mn), in host-rock minerals are 79.8 → 74.1 in olivine, 77.7 → 65.3 in orthopyroxene, 79.9 → 9.2 in clinopyroxene, and An79.0 → An3.7. The span of clinopyroxene and plagioclase compositions reflects their protracted crystallization from early magmatic to late interstitial associations. The magnesian chromite (Mg# 43.9) trends towards Cr-bearing magnetite with progressive buildups in oxygen fugacity; ilmenite varies from early Mg-rich to late Mn-rich variants. The main BMS are chalcopyrite, pyrrhotite, troilite, and Co-bearing pentlandite, with less abundant cubanite (or isocubanite), rare bornite, Co-bearing pyrite, Cd-bearing sphalerite (or wurtzite), altaite, members of the galena-clausthalite series and nickeline. A full series of Au-Ag alloy compositions is found with minor hessite, acanthite and argentopentlandite. The uncommon assemblage includes monazite-(Ce), thorite-coffinite, thorianite, uraninite, zirconolite, baddeleyite, zircon, bastnäsite-(La), and an unnamed metamict Y-dominant zirconolite-related mineral. About 20 species of PGM (platinum group minerals) were analyzed, including Pd-Pt tellurides, bismuthotellurides, bismuthides and stannides, Pd antimonides and plumbides, a Pd-Ag telluride, a Pt arsenide, a Pd-Ni arsenide, and unnamed Pd stannide-arsenide, Pd germanide-arsenide and Pt-Cu arseno-oxysulfide. The atypical assemblages are associated with Cl-rich annite with up to 7.54 wt.% Cl, Cl-rich hastingsite with up 4.06 wt.% Cl, ferro-hornblende (2.53 wt.% Cl), chlorapatite (>6 wt.% Cl) and extensive solid solutions of chlorapatite, fluorapatite and hydroxylapatite, Cl-bearing members of the chlorite group (chamosite; up to 0.96 wt.% Cl), and a Cl-bearing serpentine (up to 0.79 wt.% Cl). A decoupling of Cl and F in the geochemically evolved system is evident. The complex assemblages formed late from Cl-enriched fluids under subsolidus conditions of crystallization following extensive magmatic differentiation in the ore-bearing sequences.
A shell-like polycrystalline grain (ca. 1 mm) of W-(Mo)-bearing Os-Ir alloy (11.4.18.6 wt% W; up to 1.5% Mo) is present in a very old collection (probably the 1890s) of tiny nuggets from Trinity Co., California. An extensive compositional series [(Os0.43-0.80Ir0.28-0.05) W0.12-0.18], and inverse Ir-Os correlation, are observed; the mean composition [Os0.676W0.153Ir0.124Fe0.021Mo0.015Ru0.011; Σatoms = 1], based on results of 50 electron-microprobe analyses, displays a ratio (Os + Ir):W of 5:1. The observed variations and element correlations suggest that (W + Mo) contents are controlled by Ir, and incorporated via the following substitution scheme: [(W + Mo) + Ir] ↔ Os. The X-ray diffraction data indicate that the W-rich alloy has a hexagonal close-packed structure, related to that of osmium and allargentum, with a = 2.7297(4) Å, c = 4.3377(6) Å, and V = 27.99(1) Å3; the c:a ratio is 1.59. The probable space-group is P63/mmc, and Z = 2; the calculated density is 21.86(1) g/cm3. The W-rich alloy is associated with an Os-Ru-Ir alloy rich in Fe (7.0.9.7 wt%), which exhibits atomic Fe ↔ [Os + Ru] and Ir ↔ [Os + Ru] mechanisms of substitution. We suggest that these W-(Mo)- and Fe-rich alloys formed by metasomatic alteration of a primary Os-Ir-Ru alloy, associated with mineralized ultramafic-mafic rocks of ophiolite afinity. A fluid phase may well have remobilized and transported W, Mo, and Fe. The W-rich alloy likely crystallized from a reducing fluid under conditions of low fugacities of O2 and S2, thus promoting the observed siderophile behavior of W and Mo. These unusual W-(Mo)- and Fe-rich alloy grains were likely derived, as a placer material, from the Trinity ophiolite complex of northern California.
We describe occurrences of platinum-group minerals (PGM) and an uncommon mineral enriched in Cl, and provide a brief review of Cl-bearing minerals associated with basic–ultrabasic complexes. An unusual phosphohedyphane-like phase (~30 µm), close to CaPb4(PO4)3Cl, occurs in one of the PGM-bearing veins of massive sulfides in the Monchepluton layered complex, Kola Peninsula, Russia. These veins consist of varying amounts of pyrrhotite, pentlandite, chalcopyrite, pyrite and accessory grains of galena; they are fairly abundant in the heavy-mineral concentrate, as are small (<0.1 mm) grains of PGM: michenerite, sperrylite, Bi-enriched members of the merenskyite–moncheite series and kotulskite, also rich in Bi. The PGE mineralization is attributed to a low-temperature deposition at the hydrothermal stage. The pyromorphite–phosphohedyphane solid solution likely formed as a secondary phase under conditions of a progressive build-up of oxygen fugacity via oxidation reactions of a precursor grain of galena and involving Ca, as an incompatible component of the sulfides, in a medium of residual fluid enriched in Cl.
ABSTRACT Background: The 13 C‐urea breath test detects the presence of Helicobacter pylori from an enrichment of breath 13 CO 2 , which, in turn, is critically dependent on the amount of dilution by endogenous CO 2 production. The production of CO 2 differs according to age (adults > children), sex (male > female) weight, and height. The cutoff value of 2.4 Δ‰ (delta over baseline, DOB) for the 13 C‐urea breath test, defined in adults, does not take into account actual CO 2 production. Therefore, this cutoff value (2.4 Δ‰) may or may not be appropriate for children. The purpose of this study was to determine a cutoff value that would provide accurate results in pediatric patients, independent of their differences in anthropometric parameters. Methods: Estimates of CO 2 production were combined with DOB values to calculate the host‐dependent urea hydrolysis rate. Results: Calculated as urea hydrolysis rate, the cutoff range for adults was 10.4 to 10.9 µg/min. Individual ranges were concentric (men, 9.6‐10.9 µg/min; women, 8.5‐12.2 µg/min). Results in studies of 312 children show that a urea hydrolysis rate of more than 10 µg/min may also be appropriate to predict H. pylori infection. Conclusion: Calculating 13 C‐urea breath test values as urea hydrolysis rate removes the effect of individual anthropometric differences on test outcome and provides a single cutoff value for pediatric patients of all ages.
An unusual phase rich in Cl (78.4 wt.% Pb, 19.2% Cl) and close in composition to penfieldite [Pb 2 Cl 3 (OH)] was found as a ~5 m inclusion in chalcopyrite, in a spatial association with platinum-group minerals, in a sulfide-poor (≤5 vol.% of base-metal sulfides) enstatite orthocumulate of the Merensky Reef, Bushveld layered complex, South Africa.This seems to be the first reported occurrence of a Pb-Cl-(OH) compound in mafic-ultramafic rocks.The associated platinum-group minerals are members of the braggite series, cooperite (which forms large intergrowths with braggite: up to 0.5 mm in the longest dimension), members of the rustenburgite-atokite and merenskyite-moncheite series, zoned laurite, and an unknown stannosulfide of Pt, the likely chemical formula of which is PtSnS.The stannosulfide probably formed at a hydrothermal stage from microvolumes of a latestage fluid or liquid.The Cl-rich phase precipitated from a late-stage solution rich in Cl, or formed as a result of replacement of a precursor mineral (probably galena) by an aqueous hydrochloric solution at a very low temperature, at the final stage of hydrothermal alteration.
