Morphological studies of PGM grains in alluvial-fluvial placer deposits from the Bayerischer Wald, SE Germany: hollingworthite and ferroan platinum

Dill, Harald G.; Weber, B.; Steyer, Gustav

doi:10.1127/0077-7757/2010/0155

Cited by 9 publications

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“…7a). The Os-Ir-Ru alloys from the Rhine (Oberthür et al, 2016) and the Danube (Dill et al, 2009(Dill et al, , 2010 are generally similar to those described here from the Elbe.…”

Section: Mineral Compositions Of Os-ir-ru Alloyssupporting

confidence: 76%

“…Particles of PGMs in German rivers were identified in the Rhine (Dijkstra et al, 2016;Oberthür et al, 2016) and the Danube and their source regions (Dill et al, 2007(Dill et al, , 2009(Dill et al, , 2010Lehrberger, 1997). The Os-Ir-Ru alloys in the Danube, which share similarities to the alloys analyzed here, are thought to be derived from the Teplá-Barrandian unit of the Bohemian Massif, part of which extends into the Bavarian Forest along the Czech-German border (Dill et al, 2009(Dill et al, , 2010. However, gold particles are more common than PGMs within stream sediments of the Rhine, Danube and Elbe rivers (Albiez, 1951;Elsner, 2009;Goldenberg, 1988;Hofmann, 1965;Kirchheimer, 1969;Oberthür et al, 2016;Ramdohr, 1965).…”

Section: Introductionmentioning

confidence: 99%

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Mineralogy and mineral chemistry of detrital platinum-group minerals and gold particles from the Elbe, Germany

2023

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Abstract. In heavy mineral concentrates of the Elbe, gold and platinum-group minerals (PGMs) are observed. Two fractions (> 63 and < 63 µm) of the concentrate are analyzed by reflected-light microscopy, scanning electron microscopy with automated mineralogy software and electron microprobe analysis (EPMA). Other heavy minerals are cassiterite, ferberite, monazite, uraninite, columbite–tantalite, magnetite, zircon and cinnabar. Scanning electron microscopy determined the modal abundance of PGMs, gold and the other heavy minerals. The PGMs are mainly Os–Ir–Ru–(Pt) alloys, Pt–Fe alloys, sperrylite and rustenburgite. Compositional variation of PGMs and gold was analyzed by EPMA. This showed that Pt–Fe alloys are (1) native platinum (> 80 atom %), (2) ferroan Pt (20 atom % to 50 atom % Fe), (3) isoferroplatinum (2.64 to 3.04 apfu of sum PGE, platinum-group element), (4) tetraferroplatinum group with Ni + Cu + Fe ≈ 50 atom %, and (5) γ(Pt,Fe) with sum PGE > 3.04 apfu. The Os–Ir–Ru–(Pt) alloys show large compositional variations. Platinum and Fe enrichment is typically observed for Ir-rich Os–Ir–Ru alloys. Gold particles often show compositional zoning of Ag-rich cores and Ag-poor rims due to selective leaching of Ag. Similarly, Hg-rich rims of gold particles are analyzed. These are interpreted as the results of in situ amalgamation due to mobilization of Hg from the associated cinnabar particles. The size and shape of the gold particles generally argue for short transportation distances. Similarly, almost euhedral sperrylite and Pt–Fe alloys suggest a source region close to the sampling site. However, roundish Os–Ir–Ru–(Pt) alloys presumably have experienced longer transportation in the river. Gabbroic dikes of the Lusatia block contain sperrylite and gold particles, which can be the source for these particles found in the concentrate. The composition of the Os–Ir–Ru–(Pt) alloys is similar to previous studies on the Vestřev placer in Czech Republic. Both locations are within the drainage area of the Elbe and can therefore be the source of the PGM and gold particles in the concentrate.

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“…7a). The Os-Ir-Ru alloys from the Rhine (Oberthür et al, 2016) and the Danube (Dill et al, 2009(Dill et al, , 2010 are generally similar to those described here from the Elbe.…”

Section: Mineral Compositions Of Os-ir-ru Alloyssupporting

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Mineralogy and mineral chemistry of detrital platinum-group minerals and gold particles from the Elbe, Germany

2023

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“…The tie line between this sedimentological triplet and sedimentary petrography passes through morphometry [87]. In the current case, it is studied and discussed under separate cover, because it would only dilute the weight put behind the sedimentological triplet, because sediment petrography also encompasses the sand-and clay-sized particles which have no meaning for situmetry handled in the current way; they are relevant for granulometry and they are of high significance for morphometry covering the entire spectrum from crystal morphology of heavy and light minerals [22,24,[131][132][133][134][135][136][137][138][139][140]. The third component in the triangle sedimentology (GMS) and sediment petrography is geomorphology which in its numerical type, called terrain analysis, paves the way into geomorphometry, where terrain-related datasets are created but sedimentological and sediment-petrographic datasets are not (yet) considered (Figure 20).…”

Section: Synopsis and Outlookmentioning

confidence: 99%

A Natural GMS Laboratory (Granulometry-Morphometry-Situmetry): Geomorphological-Sedimentological-Mineralogical Terrain Analysis Linked to Coarse-Grained Siliciclastic Sediments at the Basement-Foreland Boundary (SE Germany)

et al. 2022

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The “natural GMS laboratory” (granulometry-morphometry-situmetry) is located within the Variscan Basement in SE Germany (Fichtelgebirge Mts.), which is uplifted relative to its Permo-Mesozoic foreland along a deep-seated lineamentary fault zone. This transitional study area is crossed by straight to low drainage systems in the basement, turning meandering channel systems into high sinuosity when entering the foreland. Due to its good geological coverage, the entire region is subjected to an advanced-level terrain analysis and completed with a sedimentological study focusing on the GMS tool. Unlike many applications in the past, the three components of the GMS tool that are of almost equal value ought to be used in combination and not as stand-alone procedures so as to be integrated into other near-surface geoscientific methods, e.g., sediment petrography. The strong points of granulometry of coarse-grained/gravel-sized sediments are its extension into the smaller sand and clay grain size intervals using the sorting, mean and/or median values for an environmental analysis. Morphometry can be linked to the compositional geosciences, e.g., mineralogy and geochemistry. The grain shape is intimately connected with the lithology, providing options from triaxial measuring of the lithoclast to the digital image analysis. It is a favorable tool to supplement the provenance of lithoclasts. Situmetry is the key element of hydrodynamic research and directly builds upon its sister methods. Its applications and numerical approaches are useful for the identification and quantification of physical land-forming processes. It is the fan sharpness and the orientation of lithoclasts relative to the direction of the talweg and in relation cross-sectional valley features that integrate the GMS tool into geological and geomorphological mapping, both of which result in a digital terrain model. Horizontal rose diagrams are useful for the upper reaches of drainage systems, be they of alluvial or non-alluvial types, and vertical ones for alluvial channels in the distal and proximal foreland where stacked patterns of depositional terraces are of widespread occurrence. In general, the GMS tool can be applied to sedimentological, geomorphological, petrographic and tectonic objects in basements and foreland basins; in applied geosciences, it is suitable for the identification of mineral resources and of areas vulnerable to geohazards, and in genetic geosciences for the discrimination of supergene chemical and physical depositional and land-forming processes.

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“…The alluvial-fluvial placer deposits intertongue with the aforementioned colluvial deposits with stream flow accumulation at their most distal position or overlap with each other during a stepwise uplift of the hinterland when the system becomes wetter (Figure 1, Figure 3a, and Figure 4). The alluvial-fluvial systems play a major part in the formation of sedimentary concentrations of the top-score among the precious metals and gemstones, gold, PGE (Platinum Group Elements), and diamonds, respectively [25][26][27]. A scarcely to non-vegetated system of alluvial fans debouching into a periodically flooded more or less straight drainage system is displayed in Figure 4a.…”

Section: Alluvial-fluvial Placersmentioning

confidence: 99%

Gems and Placers—A Genetic Relationship Par Excellence

Dill¹

2018

Minerals

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Gemstones form in metamorphic, magmatic, and sedimentary rocks. In sedimentary units, these minerals were emplaced by organic and inorganic chemical processes and also found in clastic deposits as a result of weathering, erosion, transport, and deposition leading to what is called the formation of placer deposits. Of the approximately 150 gemstones, roughly 40 can be recovered from placer deposits for a profit after having passed through the “natural processing plant” encompassing the aforementioned stages in an aquatic and aeolian regime. It is mainly the group of heavy minerals that plays the major part among the placer-type gemstones (almandine, apatite, (chrome) diopside, (chrome) tourmaline, chrysoberyl, demantoid, diamond, enstatite, hessonite, hiddenite, kornerupine, kunzite, kyanite, peridote, pyrope, rhodolite, spessartine, (chrome) titanite, spinel, ruby, sapphire, padparaja, tanzanite, zoisite, topaz, tsavorite, and zircon). Silica and beryl, both light minerals by definition (minerals with a density less than 2.8–2.9 g/cm3, minerals with a density greater than this are called heavy minerals, also sometimes abbreviated to “heavies”. This technical term has no connotation as to the presence or absence of heavy metals), can also appear in some placers and won for a profit (agate, amethyst, citrine, emerald, quartz, rose quartz, smoky quartz, morganite, and aquamarine, beryl). This is also true for the fossilized tree resin, which has a density similar to the light minerals. Going downhill from the source area to the basin means in effect separating the wheat from the chaff, showcase from the jeweler quality, because only the flawless and strongest contenders among the gemstones survive it all. On the other way round, gem minerals can also be used as pathfinder minerals for primary or secondary gemstone deposits of their own together with a series of other non-gemmy material that is genetically linked to these gemstones in magmatic and metamorphic gem deposits. All placer types known to be relevant for the accumulation of non-gemmy material are also found as trap-site of gemstones (residual, eluvial, colluvial, alluvial, deltaic, aeolian, and marine shelf deposits). Running water and wind can separate minerals according to their physical-chemical features, whereas glaciers can only transport minerals and rocks but do not sort and separate placer-type minerals. Nevertheless till (unconsolidated mineral matter transported by the ice without re-deposition of fluvio-glacial processes) exploration is a technique successfully used to delineate ore bodies of, for example, diamonds. The general parameters that matter during accumulation of gemstones in placers are their intrinsic value controlled by the size and hardness and the extrinsic factors controlling the evolution of the landscape through time such as weathering, erosion, and vertical movements and fertility of the hinterland as to the minerals targeted upon. Morphoclimatic processes take particular effect in the humid tropical and mid humid mid-latitude zones (chemical weathering) and in the periglacial/glacial and the high-altitude/mountain zones, where mechanical weathering and the paleogradients are high. Some tectono-geographic elements such as unconformities, hiatuses, and sequence boundaries (often with incised valley fills and karstic landforms) are also known as planar architectural elements in sequence stratigraphy and applied to marine and correlative continental environments where they play a significant role in forward modeling of gemstone accumulation. The present study on gems and gemstone placers is a reference example of fine-tuning the “Chessboard classification scheme of mineral deposits” [1] and a sedimentary supplement to the digital maps that form the core of the overview “Gemstones and geosciences in space and time” [2].

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Morphological studies of PGM grains in alluvial-fluvial placer deposits from the Bayerischer Wald, SE Germany: hollingworthite and ferroan platinum

Cited by 9 publications

References 0 publications

Mineralogy and mineral chemistry of detrital platinum-group minerals and gold particles from the Elbe, Germany

Mineralogy and mineral chemistry of detrital platinum-group minerals and gold particles from the Elbe, Germany

A Natural GMS Laboratory (Granulometry-Morphometry-Situmetry): Geomorphological-Sedimentological-Mineralogical Terrain Analysis Linked to Coarse-Grained Siliciclastic Sediments at the Basement-Foreland Boundary (SE Germany)

Gems and Placers—A Genetic Relationship Par Excellence

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