scholarly journals Micrometric Inclusions in Platinum-Group Minerals from Gornaya Shoria, Southern Siberia, Russia: Problems and Genetic Significance

Minerals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 327 ◽  
Author(s):  
Gleb V. Nesterenko ◽  
Sergey M. Zhmodik ◽  
Dmitriy K. Belyanin ◽  
Evgeniya V. Airiyants ◽  
Nikolay S. Karmanov
Keyword(s):  
Energy Dispersive Spectrometry ◽  
Present Contribution ◽  
Southern Siberia ◽  
Good Convergence ◽  
Wavelength Dispersive Spectrometry ◽  
Platinum Group Minerals ◽  
Genetic Significance ◽  
Sulfide Melt ◽  
The Subject ◽  
Platinum Group

Micrometric inclusions in platinum-group minerals (PGMs) from alluvial placers carry considerable information about types of primary rocks and ores, as well as conditions of their formation and alteration. In the present contribution, we attempt to show, with concrete examples, the significance of the data on the composition and morphology of micrometric inclusions to genetic interpretations. The PGM grains from alluvial placers of the Gornaya Shoria region (Siberia, Russia) were used as the subject of our investigation. In order to determine the chemical composition of such ultrafine inclusions, high-resolution analytical methods are needed. We compare the results acquired by wavelength-dispersive spectrometry (WDS; electron microprobe) and energy-dispersive spectrometry (EDS) and scanning electron microscopy (SEM) methods. The results obtained have good convergence. The EDS method is multi-elemental and more effective for mineral diagnostics in comparison with WDS, which is its certain advantage. The possible conditions for the formation of inclusions and layers of gold, sulfoarsenides and arsenides in Pt3Fe grains, which have an original sub-graphic and layered texture pattern, are discussed. They are the result of solid solution and eutectic decompositions and are associated with the magmatic stages of grain transformation, including the result of the interaction of Pt3Fe with a sulfide melt enriched with Te and As.

The evolution of the ore-forming system in the low sulfide horizon of the Noril'sk 1 intrusion, Russia

2019 ◽  
Vol 83 (5) ◽  
pp. 673-694 ◽  
Author(s):  
Nadezhda D. Tolstykh ◽  
Liudmila M. Zhitova ◽  
Maria O. Shapovalova ◽  
Ivan F. Chayka
Keyword(s):  
Mafic Magma ◽  
Chromian Spinel ◽  
Reducing Conditions ◽  
Platinum Group Minerals ◽  
Sulfide Melt ◽  
Formation And Evolution ◽  
Fe Alloys ◽  
Platinum Group ◽  
Monoclinic Pyrrhotite ◽  
Increased Activity

AbstractWe present here new data on the low-sulfide mineralisation in the upper endocontact of the Noril'sk 1 intrusion. Twenty four mineral species of platinum-group elements and their solid solutions, as well as numerous unnamed phases, including an Sb analogue of vincentite, As and Sn analogues of mertieite-I and a Sn analogue of mertieite-II have been found. It is shown that the features of the mineral association: (1) the atypical trend of TiO2 and Fe2+ in chromian spinel; (2) the composition of the Pt–Fe alloys with a Fe/Fe + Pt range of 0.26–0.37 (logfO2 ≈ – (9–10); and (3) crystallisation of high-temperature sperrylite from silicate melt (at >800°C and logfS2 < –10.5), which is possible under fO2 of FMQ to FMQ-2 in mafic magma, are due to the reducing conditions of their formation and evolution. Droplet-like inclusions of silicate-oxide minerals in сhromian spinels and sulfides in platinum-group minerals are interpreted to be trapped droplets of co-existing sulfide melt. The captured sulfide melt has evolved in the direction of increasing the fugacity of sulfur: troilite + pentlandite (Fe>Ni) – in sperrylite (paragenesis I) to monoclinic pyrrhotite + pentlandite (Ni≈Fe) + chalcopyrite – in Pt–Fe alloys (paragenesis II). Paragenesis from the sulfide aggregates in the silicate matrix are more fractionated: pyrrhotite + pyrrhotite (Ni>Fe) + chalcopyrite (III) and pyrite + pentlandite (Ni>>Fe) + millerite (IV). Pd arsenides and antimonides crystallised later than sperrylite and isoferroplatinum, as a result of the evolution of a sulfide melt with an increased activity of the element ligands (Te, Sn, Sb and As).

Alluvial platinum-group minerals as indicators of primary PGE mineralization (placers of southern Siberia)

2016 ◽  
Vol 57 (10) ◽  
pp. 1437-1464 ◽  
Author(s):  
S.M. Zhmodik ◽  
G.V. Nesterenko ◽  
E.V. Airiyants ◽  
D.K. Belyanin ◽  
V.V. Kolpakov ◽  
...  
Keyword(s):  
Southern Siberia ◽  
Platinum Group Minerals ◽  
Pge Mineralization ◽  
Platinum Group

Commands in Wolaitta

2017 ◽  
Author(s):  
Azeb Amha
Keyword(s):  
Sentence Type ◽  
Positive Polarity ◽  
Present Contribution ◽  
Grammatical Categories ◽  
The Subject ◽  
Leave Taking ◽  
And Gender ◽  
Syntactic Properties

This chapter examines expressions of commands (imperatives) in Wolaitta and the ways in which the imperative is distinguished from statements and questions. Although each sentence type is formally distinct, imperatives and questions share a number of morpho-syntactic properties. Similar to declarative and interrogative sentences, imperatives in Wolaitta involve verbal grammatical categories such as the distinction of person, number, and gender of the subject as well as negative and positive polarity. In contrast to previous studies, the present contribution establishes the function of a set of morphemes based on -árk and -érk to be the expression of plea or appeal to an addressee rather than politeness when issuing a command. Instead, politeness in commands is expressed by using plural (pro)nominal and verbal elements. The imperative in Wolaitta is a robust construction which is also used in formulaic speeches such as leave-taking as well as in blessing, curses, and advice.

scholarly journals Tamuraite, Ir5Fe10S16, a New Species of Platinum-Group Mineral from the Sisim Placer Zone, Eastern Sayans, Russia

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 545
Author(s):  
Andrei Y. Barkov ◽  
Nadezhda D. Tolstykh ◽  
Robert F. Martin ◽  
Andrew M. McDonald
Keyword(s):  
National Laboratory ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
Cell Parameters ◽  
Reflected Light ◽  
Platinum Group Minerals ◽  
Platinum Group ◽  
Probable Space ◽  
Layered Complex ◽  
Residual Melt

Tamuraite, ideally Ir5Fe10S16, occurs as discrete phases (≤20 μm) in composite inclusions hosted by grains of osmium (≤0.5 mm across) rich in Ir, in association with other platinum-group minerals in the River Ko deposit of the Sisim Placer Zone, southern Krasnoyarskiy Kray, Russia. In droplet-like inclusions, tamuraite is typically intergrown with Rh-rich pentlandite and Ir-bearing members of the laurite–erlichmanite series (up to ~20 mol.% “IrS2”). Tamuraite is gray to brownish gray in reflected light. It is opaque, with a metallic luster. Its bireflectance is very weak to absent. It is nonpleochroic to slightly pleochroic (grayish to light brown tints). It appears to be very weakly anisotropic. The calculated density is 6.30 g·cm−3. The results of six WDS analyses are Ir 29.30 (27.75–30.68), Rh 9.57 (8.46–10.71), Pt 1.85 (1.43–2.10), Ru 0.05 (0.02–0.07), Os 0.06 (0.03–0.13), Fe 13.09 (12.38–13.74), Ni 12.18 (11.78–13.12), Cu 6.30 (6.06–6.56), Co 0.06 (0.04–0.07), S 27.23 (26.14–27.89), for a total of 99.69 wt %. This composition corresponds to (Ir2.87Rh1.75Pt0.18Ru0.01Os0.01)Σ4.82(Fe4.41Ni3.90Cu1.87Co0.02)Σ10.20S15.98, calculated based on a total of 31 atoms per formula unit. The general formula is (Ir,Rh)5(Fe,Ni,Cu)10S16. Results of synchrotron micro-Laue diffraction studies indicate that tamuraite is trigonal. Its probable space group is R–3m (#166), and the unit-cell parameters are a = 7.073(1) Å, c = 34.277(8) Å, V = 1485(1) Å3, and Z = 3. The c:a ratio is 4.8462. The strongest eight peaks in the X-ray diffraction pattern [d in Å(hkl)(I)] are: 3.0106(26)(100), 1.7699(40)(71), 1.7583(2016)(65), 2.7994(205)(56), 2.9963(1010)(50), 5.7740(10)(45), 3.0534(20)(43) and 2.4948(208)(38). The crystal structure is derivative of pentlandite and related to that of oberthürite and torryweiserite. Tamuraite crystallized from a residual melt enriched in S, Fe, Ni, Cu, and Rh; these elements were incompatible in the Os–Ir alloy that nucleated in lode zones of chromitites in the Lysanskiy layered complex, Eastern Sayans, Russia. The name honors Nobumichi Tamura, senior scientist at the Advanced Light Source of the Lawrence Berkeley National Laboratory, Berkeley, California.

Ultra mensuram tendere. Zur Maßlosigkeit mönchischer Askese (David von Augsburg, García Jiménez de Cisneros, Bernardino de Laredo)

2018 ◽  
Vol 23 (1) ◽  
pp. 29-47
Author(s):  
Christina Johanna Bischoff
Keyword(s):  
Early Modern ◽  
General Problem ◽  
Present Contribution ◽  
The Subject

AbstractThe present contribution deals with excess in medieval and early modern monastic asceticism. It claims that excess, in this context, is not an individual option, but a general problem inherent to Christian asceticism. By giving priority to self-denial, this type of asceticism promotes a self-regulated, autonomous subjectivity which is clearly an unintentional by-product of the asceticism. Therefore individual asceticism oscillates between prohibited self-fashioning and, as a response, intensified self-denial. The problem is outlined in an introductory chapter about ‘De exterioris et interioris hominis compositione’ by David of Augsburg. Following this, two early modern Spanish books are used to illustrate how spiritual texts deal with the ambivalences of asceticism. The ‘Exercitatorio de la vida spiritual’ by García Jiménez de Cisneros regulates asceticism in detail, while the ‘Subida del monte Sión’ by Bernardino de Laredo allows the subject more room for interpretation; this however comes at the price of a fictionalisation of asceticism.

DETRITAL PLATINUM-GROUP MINERALS IN RIVERS DRAINING THE EASTERN BUSHVELD COMPLEX, SOUTH AFRICA

2004 ◽  
Vol 42 (2) ◽  
pp. 563-582 ◽  
Author(s):  
T. Oberthur ◽  
F. Melcher ◽  
L. Gast ◽  
C. Wohrl ◽  
J. Lodziak
Keyword(s):  
South Africa ◽  
Bushveld Complex ◽  
Platinum Group Minerals ◽  
Platinum Group

Sulfide mineral chemistry and platinum-group minerals of the UG-2 chromitite in the northern limb of the Bushveld Igneous Complex, South Africa

2021 ◽  
Vol 59 (6) ◽  
pp. 1339-1362
Author(s):  
Malose M. Langa ◽  
Pedro J. Jugo ◽  
Matthew I. Leybourne ◽  
Danie F. Grobler
Keyword(s):  
Platinum Group Element ◽  
Mineral Chemistry ◽  
Sulfide Mineral ◽  
Sulfide Minerals ◽  
Group Element ◽  
Igneous Complex ◽  
Northern Limb ◽  
Platinum Group Minerals ◽  
Platinum Group ◽  
Bushveld Igneous Complex

ABSTRACT The UG-2 chromitite layer, with its elevated platinum-group element content, is a key marker horizon in the eastern and western limbs of the Bushveld Igneous Complex and the largest platinum-group element chromite-hosted resource of its kind in the world. In contrast, much less is known about its stratigraphic equivalent in the northern limb, the “UG-2 equivalent” (UG-2E) chromitite. Recent studies on chromite mineral chemistry show similarities between the UG-2 and sections of the UG-2E, but also that the UG-2E was partially contaminated by assimilation of local metasedimentary rocks. Here, we provide a detailed characterization of sulfide minerals and platinum-group minerals in a suite of samples from the UG-2E and compare the results with data obtained from a reference suite of samples from the UG-2. Results from petrographic observations, electron probe microanalysis, laser ablation-inductively coupled plasma-mass spectrometry, quantitative evaluation of materials by scanning electron microscopy, and δ34S isotopes show that: (1) sulfide minerals in the UG-2E and UG-2 consist mainly of pentlandite-chalcopyrite-pyrrhotite, but pyrrhotite is significantly more abundant in the UG-2E and almost absent in the UG-2; (2) iron contents in pentlandite from the UG-2E are significantly higher than in the UG-2; (3) platinum-group element contents within sulfide minerals are different between the two chromitites; (4) UG-2E platinum-group minerals are dominated by arsenides and bismuthotellurides, and by alloys and platinum-group element-sulfide minerals in the UG-2; (5) sulfide mineral chemistry and δ34S values indicate some crustal contamination of the UG-2E; and (6) sulfide mineral and secondary silicate mineral textures in both the UG-2E and UG-2 are indicative of minor, millimeter- to centimeter-scale, hydrothermal alteration. From our observations and results, we consider the UG-2E chromitite in the northern limb to be the equivalent to the UG-2 in the eastern and western limbs that has been contaminated by assimilation of Transvaal Supergroup footwall rocks during emplacement. The contamination resulted in UG-2E sulfide mineral elemental contents and platinum-group mineral types and abundances that are distinct from those of the UG-2 in the rest of the Bushveld.

Sign in / Sign up

Export Citation Format

Share Document