scholarly journals ELECTRICAL PULSE DISAGGREGATION AND HYDROSEPARATION - OPTIMAL METHODOLOGY FOR DISCOVERING NEW PLATINUM GROUP MINERALS IN PRIMARY ROCKS

2021 ◽  
Author(s):  
N.S. Rudashevsky ◽  
◽  
V.N. Rudashevsky ◽  
O.V. Alikin ◽  
A.V. Chumakov ◽  
...  
Keyword(s):  
Single Layer ◽  
Electrical Pulse ◽  
High Tech ◽  
Thin Sections ◽  
Electrical Impulse ◽  
Platinum Group Minerals ◽  
Platinum Group

A new methodology - electrical impulse disintegration of ore + hydroseparation of material + high-tech mineralogical studies in single-layer polished thin sections of “heavy” concentrates - is considered in relation to the discoveries of new platinum group minerals (PGM) contained in bedrocks. Examples are considered - eight such new PGMs.

Differentiation Processes of the Ocellar Retina of the Honeybee (Apis Mellifera L.)

1990 ◽  
Vol 48 (3) ◽  
pp. 430-431
Author(s):  
Maria Anna Pabst
Keyword(s):  
Apis Mellifera ◽  
Distal Part ◽  
Cell Layer ◽  
Single Layer ◽  
Photoreceptor Cells ◽  
Distal Segment ◽  
Compound Eyes ◽  
Thin Sections ◽  
Ultrastructural Studies ◽  
Adult Worker

In addition to the compound eyes, honeybees have three dorsal ocelli on the vertex of the head. Each ocellus has about 800 elongated photoreceptor cells. They are paired and the distal segment of each pair bears densely packed microvilli forming together a platelike fused rhabdom. Beneath a common cuticular lens a single layer of corneagenous cells is present.Ultrastructural studies were made of the retina of praepupae, different pupal stages and adult worker bees by thin sections and freeze-etch preparations. In praepupae the ocellar anlage consists of a conical group of epidermal cells that differentiate to photoreceptor cells, glial cells and corneagenous cells. Some photoreceptor cells are already paired and show disarrayed microvilli with circularly ordered filaments inside. In ocelli of 2-day-old pupae, when a retinogenous and a lentinogenous cell layer can be clearly distinguished, cell membranes of the distal part of two photoreceptor cells begin to interdigitate with each other and so start to form the definitive microvilli. At the beginning the microvilli often occupy the whole width of the developing rhabdom (Fig. 1).

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.

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.

Platinum-group minerals from alluvial placers of the Kitoy river (south-east part of East Sayan, Russia)

2021 ◽  
Author(s):  
Olga Kiseleva ◽  
Yuriy Ochirov ◽  
Sergey Zhmodik ◽  
Brian Nharara
Keyword(s):  
Publishing House ◽  
Primary Source ◽  
Platinum Metal ◽  
Mineral Chemistry ◽  
Source Rocks ◽  
Tectonic Deformation ◽  
Platinum Group Minerals ◽  
Placer Deposits ◽  
Platinum Group ◽  
Eastern Sayan

<p>The studied area is in the southeastern region of Eastern Sayan. Several tectonically dissected ophiolite complexes were exposed along the margin of the Gargan block and tectonically thrust over this block. Placer nuggets of PGE alloys from the Kitoy river were examined using a scanning electron microscope. Platinum-group minerals (PGM's) in placer deposits provide vital information about the types of their primary source rocks and ores as well as the conditions of formation and alteration. The primary PGM's are Os-Ir-Ru alloys, (Os, Ru)S<sub>2</sub>, and (Os, Ir, Ru)AsS. (Os, Ru)S<sub>2</sub> form overgrowth around the Os-Ir-Ru alloys. The secondary, remobilized PGM's are native osmium, (Ir-Ru) alloys, garutite (Ir, Ni, Fe), zaccarinite (RhNiAs), selenides, tellurides (Os, Ir, Ru), and non-stoichiometric (Pd, Pt, Fe, Te, Bi) phases (Fig.1). Secondary PGM's (garutite and RhNiAs) form rims around Os-Ir-Ru alloys, intergrowth with them, or form polyphase aggregates. Such PGM's (identical in composition and microstructure) are also found in chromitites from Neoproterozoic ophiolite massifs of Eastern Sayan (Kiseleva et al., 2014; 2020). Platinum-metal minerals, exotic for ophiolites, are found among secondary PGM's such as selenides and tellurides (Os, Ir, Ru), (Pt, Pd)<sub>3</sub>Fe, Pd<sub>3</sub>(Te, Bi), (Au, Ag), and non-stoichiometric (Pd, Pt, Fe, Te, Bi) phases. They occur as inclusions in the Os-Ir-Ru alloys or fill cracks in crushed grains of primary PGM's. PGM's in placer deposits of the Kitoy river are similar to the mineral composition of PGE in chromitites of the Ospa-Kitoy ophiolitic massif, which contain Pt-Pd minerals and Pt impurities in Os-Ir-Ru alloys (Kiseleva et al., 2014). Selenides (Os-Ir-Ru) are rare within PGM's from ophiolite chromitites (Barkov et al., 2017; Airiyants et al., 2020) and also occur in chromitites of the Dunzhugur ophiolite massif (Kiseleva et al., 2016). Features of selenides and tellurides (Os, Ir, Ru) indicate their late formation as a result of the influence of magmatic and metamorphic fluids on primary PGE alloys. The filling of cracks in crushed (Os-Ir-Ru) alloys indicates that selenides and tellurides formed during tectonic deformation processes. The source of platinum-group minerals from the Kitoy river placer is the Ospa-Kitoy ophiolite massif, and primarily chromitites.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.eb9553e3c70065361211161/sdaolpUECMynit/12UGE&app=m&a=0&c=f3ccc1c7cf7d06094d2afaa34fe9d9a1&ct=x&pn=gepj.elif&d=1" alt=""></p><p>Figure 1. BSE microphotographs of PGM from from alluvial placers of the Kitoy river</p><p>Mineral chemistry was determined at the Analytical Centre for multi-elemental and isotope research SB RAS. This work supported by RFBR grants: No. 16-05-00737a,  19-05-00764а, 19-05-00464a and the Russian Ministry of Education and Science</p><p>References</p><p>Airiyants E.V., Belyanin D.K., Zhmodik S.M., Agafonov L.V., Romashkin P.A.  // Ore Geology Reviews. 2020. V. 120. P.  103453</p><p>Barkov A.Y., Nikiforov A.A., Tolstykh N.D., Shvedov G.I., Korolyuk V.N. // European J. Mineralogy. 2017. V.29(9). P.613-621.</p><p>Kiseleva O.N., Zhmodik S.M., Damdinov B.B., Agafonov L.V., Belyanin D.K. // Russian Geology and Geophysics. <strong>2014</strong>. V. 55. P. 259-272.</p><p>Kiseleva O.N., Airiyants E.V., Belyanin D.K., Zhmodik S.M., Ashchepkov I.V., Kovalev S.A. // Minerals. 2020. V. 10. N 141. P. 1-30.</p><p>Kiseleva O.N., Airiyants E.V., Zhmodik S.M., Belyanin D.K / Russian and international conference proceedings “The problems of geology and exploitation of platinum metal deposits” – St.Petersburg: Publishing house of St.Petersburg State University. 2016. 184 P.</p>

Laboratory-Based Bacterial Weathering of the Merensky Reef and Its Impact on Platinum Group Mineral Migration

2021 ◽  
Author(s):  
Ling Tan ◽  
Thomas Jones ◽  
Jianping Xie ◽  
Xinxing Liu ◽  
Gordon Southam
Keyword(s):  
Base Metal ◽  
Mineral Dissolution ◽  
Metal Sulfides ◽  
Acidithiobacillus Thiooxidans ◽  
Thin Sections ◽  
Secondary Minerals ◽  
Merensky Reef ◽  
Fe Oxides ◽  
Base Metal Sulfides ◽  
Platinum Group

Abstract Weathering of the Merensky reef was enhanced under laboratory conditions by Fe- and S-oxidizing bacteria: Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, and Leptospirillum ferrooxidans. These bacteria preferentially colonized pyrrhotite and pyrite, versus pentlandite and chalcopyrite (all of which were common within the rock substrate), promoting weathering. Weathering of base metal sulfides resulted in the precipitation of Fe oxides, Fe phosphate, and elemental sulfur as secondary minerals. Fe pyroxene weathered readily under acidic conditions and resulted in mineral dissolution, while other silicates (orthopyroxene and plagio-clase) precipitated Fe phosphate spherules or coatings on their surface. The deterioration of the platinum group metal (PGM) matrix (base metal sulfides and silicates) and the occurrence of a platinum grain associated with platinum nanoparticles observed in the biotic thin sections demonstrate that biogeochemical acid weathering is an important step in the active release of intact PGM grains. A platinum grain embedded in secondary Fe oxides/phosphate that had settled by gravity within the weathering solution demonstrates that secondary minerals that formed during weathering of PGM-hosting minerals also represent targets in PGM exploration by trapping and potentially slowing PGM migration. Dispersion halos surrounding or occurring downstream from PGM occurrences will likely produce two physical target classes—i.e., grains and colloids—under surficial weathering conditions.

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