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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].

The quadripartite/ orthogonal and domal Central European Watershed (CEW) at the NW edge of the Bohemian Massif has been studied by a terrain analysis (fluvial, colluvial, cryogenic, aeolian landforms) combined with geochronological dating (hydraulic correlation) of landforms and the resultant hydrographic correlation of relief generations. It resulted in a morphostratigraphic review (subdivided into a protostage- creating the terrestrial platform, prestages - controlling the physical and chemical regime of the landform series, and stages- fine-tuning of the modern landscape) of the Late Cretaceous to Quaternary relief generations that lead to the creation of the "3 + 1" model of the CEW. The term "3 + 1" refers to a triple junction supplemented with a fourth branch. The characteristic land-form type of the CEW is called the "intermediate sediment trap", a wetland caused by structural or impact-related damming processes. The evolution of the CEW is discussed by a set of four different drivers: The endogenous 1st order drivers are activities along lineamentary fault zones which demarcate the watershed systems. The 2nd order endogenous driver is the alkaline volcanic activity from the Late Cretaceous to the Holocene which contributed to dome-and starlike geomorphological expression. The 3rd order impact-related driver of the Ries Meteorite impact provoked a deflection and damming of channels thereby leading to one of the intermediate sediment traps. The 4th exogenous driver is the climate change. It is accountable for the transition from fluvial incision during the Late Cretaceous and Paleogene (humid-tropical climate zone) to a planation during the Neogene (tropical wet and dry paleoclimate zone). The Quaternary humid mid-latitude, dry continental, and (peri)glacial climate zones put the final touch on the CEW's geomorphological outward appearance. The influence of mining, metallurgy, and mineral processing on the landscape debated in the final stage 8 heralds the onset of the Anthropocene in the CEW. This review of the evolution of the CEW also lends support to the idea that an advanced terrain analysis can be an efficient tool for mineral exploration. a) Weathering and hydrological zones of the CEW at the western edge of the Bohemian Massif (Germany) the platform for the chronological constraining of landforms. The physica-chemical regime is based upon thermo-dynamical calculations. White: Uranium mineral zonation, brown: Manganese mineral zonation. b) The geodynamic structural and geodynamic magmatic controls on the quadripartite watershed system (3 + 1 model) and the geodynamic-geomorphological maturity concept accountable for the clockwise evolution of the quadripartite CEW. [Display omitted] • Terrain analysis - geochronological dating of landforms - correlation of relief generations • Morphostratigraphy (Late Cretaceous to Quaternary) in an orthogonal, quadripartite watershed system • Geotectonic, magmatic, extraterrestrial and climatic drivers during evolution • All landscape-forming processes involved: fluvial, mass wasting, cryogenic, aeolian, lacustrine. • Intermediate sediment traps are the characteristic feature of these watershed systems. [ABSTRACT FROM AUTHOR]

In this study, six basic Quaternary landform series (LFS) and their sedimentary deposits (LFS1 aeolian, LFS 2.1 to 2.2 mass wasting, LFS 3 cryogenic-glacial, LFS 4.1 to 4.6 fluvial, LFS 5.1 to 5.2 coastal-marine, LFS 6.1 to 6.3 lacustrine) are subdivided into subtypes and examined with regard to their sedimentological parameters and their mineralogical and chemical compositions. Emphasis is placed on the textural (related to transport and deposition), compositional (sediment load/weight, Eh and pH) and geodynamic maturity of the sedimentary deposits which are influenced by the parent lithology and bedrock tectonic and by the climate during the last 2 Ma. To constrain the development of the LFS and their sediments, composite trend-line diagrams are designed combining sedimentological (x-axis) and chemical/mineralogical dataset (y-axis): (1) sorting vs. heavy mineral content; (2) sphericity of grains vs. silica/carbonate contents; and (3) median vs. Ti/Fe ratios. In addition, the x-y plots showing the log SiO2/Al2O3 vs. log Na2O/K2O are amended by a dataset of the three most common clay minerals, i.e., kaolinite-, mica-, and smectite-group clay minerals. Such joint sedimentological-chemical-mineralogical investigations focused on the depositional environment of unconsolidated clastic sediments of Quaternary age can be used to describe the economic geology and environmental geology of mineral deposits in the pre-Quaternary sedimentary series according to the phrase: "The Present is the key to the Past". Both trend diagrams and compositional x-y plots can contribute to constraining the development of the full transect of landform series from the fluvial incision and slope retreat to reef islands fringing the coastal zone towards the open sea as far as they are built up of clastic sedimentary deposits enriched in siliceous and/or carbonate minerals. Climate zonation and crustal maturity are the exogenous and endogenous "drivers", as can be deduced from the compositional (mineralogy and chemistry) and physical (transport and deposition) variations observed in the Quaternary sediments. The current study bridges the gap between a review only based on literature and a hybrid manual generated by practical field studies devoted to applied geosciences in economic and environmental geology ("E & E issue"). [ABSTRACT FROM AUTHOR]

High volatile bituminous coal C and B is currently exploited at Spitsbergen-Svalbard, Norway. Several coal seams formed during the Palaeocene, of which some were reworked by mass wasting (MW), (glacial)-fluvial (GF) and coastal-marine wave-dominated (WM) processes under periglacial conditions during the Quaternary. This supergene alteration resulted in different landforms and deposit bearing four different types of depositional environments in Svalbard: (1) Invisible floral and faunal remains, (2) visible floral remains, (3) drift wood, (4) coal placers s. The subaerial slow- and fast-moving MW was accompanied by chemical weathering giving rise to jarosite coatings indicative of acidic meteoric solutions, whereas the remaining subaquatic processes operated under neutral to slightly alkaline conditions. Fast-moving MW and WM are productive processes, whereas GF ones are destructive with regard to coal accumulation. The most efficient tools to study the origin of the OM-bearing coarse-grained deposits are the morphology and orientation of bioclasts while the LER/HER (= low exothermic / high exothermic reaction) ratio is used for finer-grained OM-bearing sediments. The maceral analysis revealed that the landforms accounted for by GF and WM were emplaced as a result of geogenic and anthropogenic processes and aged younger than 1900 CE, while MW is Quaternary and true geogenic. Driftwood is cast in the role of a marker for coal-bearing (fluvial-) marine environments different in age and rank of coalification. With this in mind it is an excellent tool to drawn the boundary in paralic settings between the marine and fluvial impact. In conclusion, coal fragments are markers for short-term, periodical and fast landform-building processes, whereas siliciclasts from the host and bedrock are markers for long-term and episodical geomorphological and sedimentological supergene alteration. Unlabelled Image • Interaction of mass wasting, glacial-fluvial and coastal marine processes in a periglacial setting. • Presentation of the LER/HER (low-exothermic/high-exothermic reaction) method. • Organic and coalified matter types: From invisible organic matter to marine coal placers. • Geogenic and anthropogenic processes forming coal-bearing landforms and deposits since 1906. • Hydrodynamics of allochthonous coal and driftwood in a "natural coal laboratory". [ABSTRACT FROM AUTHOR]

In the periglacial South Atlantic Ocean five coastal landform series (CLFS): CLFS1 (Falkland Islands/Islas Malvinas), CLFS2 (Tierra del Fuego), CLFS3 (South Georgia + Scotia Ridge), CLFS 4 (South Shetland Archipelago) and CLFS 5 (Antarctic Peninsula) have been established and studied with regard to their geomorphology and sedimentary petrography. Although being several hundreds of kilometers apart from each other the majority of sites belong to the same climate zone, the polar tundra climate excluding the CLFS 1 which is more humid and the CLFS 5 on the opposite side that passes into the polar frost zone. The hydrographic regime is in the majority of cases microtidal, excluding some coastal regions in CLFS 1 and CLFS 5 where micro-mesotidal conditions exist around the volcanic edifices. The climate variation has an impact on the weathering of the landforms, which abruptly changes from chemical to physical between CLFS 3 and 4, and gradually from CLFS 1 to CLFS 3 (oxidic ⇒ reducing regime, pH ⇒ more acidic meteoric fluids). The mineral assemblages representative of the supergene mineralization reflect an incipient stage of on "icehouse-hothouse" transition. The CLFS 1 to 3 evolved in a geodynamically stable setting attested to by a high landscape maturity, whereas CLFS 4 and 5 are situated in a geodynamically mobile regime leading to structural landforms instead of sculptural ones of lower maturity. The CLFS1 to CLFS 3 are characterized by landscape types of plains, channels, fjords and bays which incise or truncate highly to partially eroded mountain blocks which were uplifted near the coast and thereby overprint relic landforms such as peneplains and pediments. The three geomorphological processes shaping the area between land and sea are (1) coastal marine – landforms given in brackets (beach, cliffs - beach scarps, dunes plus aeolian sand sheets, fjord remodeled into channels, bays (drowned cirque glaciers), wave-cut platforms, tidal flats (rocky), tombolo), (2) glacial (boulder trains, cirque-tarn-lip, cryopediments (?), glacial-fluvial channels, moraines, outburst valleys and spillways, pattern grounds (plus stone runs), roches moutonnées through-to U-shaped valleys, and (3) mass wasting (rock fall transitional into –slide, talus plus soil creep). While mass wasting is a rather conservative process, the glacial land-forming processes increase in quality and intensity from CLFS 1 to CLFS 3. The coastal marine processes are rather conservative, excluding those processes which interdigitate with glacial marine processes, e.g., evolution of fjords and when strongly controlled by the magmatic and metamorphic lithology. The CLFS 4 and CLFS 5 are magmatic-arc, rift-, and fold belt-related. Both reference sites mark a volcanic landscape arising from the sea, the first one under subaerial, the second one under subglacial conditions. In these modern geodynamic settings structural volcanic landforms (cones, maars, craters, pyroclastic fans of flow and surge deposits, flat-topped volcanic plateaus, tuya) predominate. The coastal marine, glacial and mass wasting induced landform types resemble those of the CLFS 1 to CLFS 3. Among the mass wasting slide and flow deposits are more common near the beach. Among the glacial deposits moraines, arêtes and nunataks are more common in the coastal hinterland. The wave-dominated coastal marine landforms (beach, cliffs-beach scarps, wave cut platforms) become more variegated when the tidal range increases (tidal channel ⇒ ephemeral stream, tidal flats). There are also mixed types between alluvial-fluvial and glacial marine named embryonic glacial-marine fan deltas. Based upon the current study an approximation of the relief generations or palaeo-landscapes can be achieved for the coastal region (hinderland + beach) in the S Atlantic Ocean: Peneplanation (relic form) – Oligo-Miocene ⇒ pedimentation (relic form) – Neogene ⇒ Glaciation and deglaciation conducive to depositional and erosive sculptural landforms = Volcanic activity conducive to structural landforms –Pleistocene-Holocene ⇒ Coastal marine and mass wasting processes conducive to depositional and erosive sculptural landforms - Pleistocene-Holocene. By analogy with similar geodynamic landscape types elsewhere the two principal landscapes are denominated as "Meso-Afro-American "(CLFS 1 to 3) and "Neo-American" (CLFS 4 and 5). These two technical terms are self-explanatory as to the geodynamic parent material and eligible for a maturity-based correlation of landscapes. The combination of the clast orientation, granulometry, grain morphology and shape in combination with sorting and clast mineralogy (visual lithological inspection ⇒ X-ray diffraction ⇒ scanning electron microscope supplemented with WDX/EDX ⇒ electron microprobe ⇒ micro-Raman spectrometry) has proved to be a valuable tool to lend support to the genetic interpretation of the existing landform types mentioned above and to bridge the gap between actuogeological processes and ancient equivalent sites as being subjected to an environment or paleogeographic analyses. The poor chemical supergene alteration in the periglacial-coastal study area renders it favorable for the application of these sedimentological and mineralogical methods. In conclusion, this methodological approach is promising for all those climate zones with limited chemical weathering for which the diagrams and tables are designed as reference types such cold as hot dry cold climate zones and mountainous regions. Environments typical of depositional and transport processes driven by the (1) hydraulic and entrainment equivalence, (2) attrition and (3) winnowing are the prime targets for the use of these methods. Even polycyclic reworking processes in coastal landscapes where marine, glacial and gravity driven processes interfere with each other around structural geomorphological landforms or have originated from relic ones may be differentiated from each other. Image 1 • 2 geodynamic landscape types and correlation with the northern hemisphere. • 5 landform types studied as to the coastal, glacial, mass wasting processes. • Geomorphology, sedimentology of sculptural, structural, relic landforms. • Gravel analysis –situmetry, granulometry, morphometry and mineralogy. • Actuogeological replica of ancient coastal zones under periglacial regimes. [ABSTRACT FROM AUTHOR]