scholarly journals Zircon as a Mineral Indicating the Stage of Granitoid Magmatism at Northern Chukotka, Russia

Geosciences ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 194
Author(s):  
Viktor I. Alekseev ◽  
Ivan V. Alekseev
Keyword(s):  
Morphological Evolution ◽  
Rare Metal ◽  
Geochemical Evolution ◽  
Gradual Change ◽  
Granitoid Magmatism ◽  
Mineral Inclusions ◽  
Rare Elements ◽  
Multi Stage ◽  
Magmatic Stage ◽  
Cretaceous Magmatism

A comparative study of the zircon composition and texture in granites of a three-stage Late Cretaceous magmatism in the Chaun area, Chukotka, Russia, was conducted in biotite granites (BG), quartz monzonites-monzogranites (MG), and zinnwaldite granites (ZG). The significance of the study entails determining the mineralogical indicators of similar granitoids in areas of multi-stage petrogenesis. It is shown that in the rock series of Northern Chukotka, BG → MG → ZG, a morphological evolution of zircon takes place: a reduction in size, elongation, a growing complexity of the crystallography, and an individual texture. In later generations of zircon, as a result of the recrystallization and metasomatism, rare-metal overgrowths, defects in the crystal structure, pores and fissures, and mineral inclusions appear, whereas the crystal-face indices and patterns become more complicated. We can observe the geochemical evolution of zircon: a gradual change in the concentration of trace elements (Hf, U, Y, Th, Nb, and Ti), rare earth elements (Yb, Er, and Dy, as well as Ce and Nd), and uncommon elements (Ca and Al). Rare elements (REE, Y, Hf, Nb, U, and Th) at the post-magmatic stage of the regional history acquired economic abundances. Zircon is therefore indicative of productive ore-magmatic systems.

scholarly journals Pre-Pegmatite Stage in Peralkaline Magmatic Process: Insights from Poikilitic Syenites from the Lovozero Massif, Kola Peninsula, Russia

Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 974
Author(s):  
Julia A. Mikhailova ◽  
Yakov A. Pakhomovsky ◽  
Olga F. Goychuk ◽  
Andrey O. Kalashnikov ◽  
Ayya V. Bazai ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Kola Peninsula ◽  
Hydrothermal Solution ◽  
Rare Metal ◽  
Lovozero Massif ◽  
Accessory Minerals ◽  
Rare Elements ◽  
Hydrothermal Stage ◽  
Magmatic Stage ◽  
Residual Solution

The Lovozero peralkaline massif (Kola Peninsula, Russia) is widely known for its unique mineral diversity, and most of the rare metal minerals are found in pegmatites, which are spatially associated with poikilitic rocks (approximately 5% of the massif volume). In order to determine the reasons for this relationship, we have investigated petrography and the chemical composition of poikilitic rocks as well as the chemical composition of the rock-forming and accessory minerals in these rocks. The differentiation of magmatic melt during the formation of the rocks of the Lovozero massif followed the path: lujavrite → foyaite → urtite (magmatic stage) → pegmatite (hydrothermal stage). Yet, for peralkaline systems, the transition between magmatic melt and hydrothermal solution is gradual. In the case of the initially high content of volatiles in the melt, the differentiation path was probably as follows: lujavrite → foyaite (magmatic stage) → urtitization of foyaite → pegmatite (hydrothermal stage). Poikilitic rocks were formed at the stage of urtitization, and we called them pre-pegmatites. Indeed, the poikilitic rocks have a metasomatic texture and, in terms of chemical composition, correspond to magmatic urtite. The reason for the abundance of rare metal minerals in pegmatites associated with poikilitic rocks is that almost only one nepheline is deposited during urtitization, whereas during the magmatic crystallization of urtite, rare elements form accessory minerals in the rock and are less concentrated in the residual solution.

The geochemical evolution of Nb–Ta–Sn oxides from pegmatites of the Cape Cross–Uis pegmatite belt, Namibia

2018 ◽  
Vol 83 (02) ◽  
pp. 161-179 ◽  
Author(s):  
Warrick C. Fuchsloch ◽  
Paul A. M. Nex ◽  
Judith A. Kinnaird
Keyword(s):  
Country Rock ◽  
Minor Element ◽  
Aqueous Fluid ◽  
Geochemical Evolution ◽  
Rare Element ◽  
Fractionation Process ◽  
North Central ◽  
Mineral Inclusions ◽  
Late Stages ◽  
Zonation Patterns

AbstractThe Cape Cross–Uis pegmatite belt, Damara Orogen, north-central Namibia hosts multiple Ta–Nb- and Sn-oxide-bearing pegmatites. Columbite-group minerals, tapiolite, cassiterite and minor ixiolite and wodginite occur in abundance within pegmatites and display various compositional and internal structural mineralogical variations. Ta–Nb oxides display various zonation patterns indicative of multiple crystallisation phases, whereas cassiterite is dominantly homogeneous with minor euhedral columbite-group mineral inclusions. Ta–Nb oxides are mostly rich in Fe, with fractionation patterns in the columbite quadrilateral being sub parallel to the Ta/(Ta + Nb) axis; increasing Ta/(Ta + Nb) with little change in Mn/(Mn + Fe), which is consistent with classical trends in beryl-to-spodumene rare-element pegmatites. In addition, these trends suggest that co-crystallising minerals compete with Ta–Nb oxides for elements such as Mn, preventing Ta–Nb oxides from attaining Mn-rich compositions during the fractionation process. Cassiterite shows similar fractionation patterns with Fe > Mn and notable increases in the Ta content. Minor-element substitution in Ta–Nb oxides shows sharp decreases with increasing fractionation supporting the hypothesis that newly stabilised co-occurring minerals compete with columbite-group minerals for certain elements. Tapiolite shows the same minor-element trend, however, only for Sn and Ti suggesting cassiterite was a dominant competing mineral. Although crystallisation of Ta–Nb oxides from an aqueous fluid at the late-stages of pegmatite genesis is highly debated, significantly elevated Ta contents in metasomatised country rock, compared to unaltered country rock, may give new insight, suggesting that Ta may indeed partition into, and be transported by, an exsolved aqueous fluid. However, further studies of the country rock metasomatic contacts are required as currently the dataset is limited. The degree of fractionation as depicted by Ta–Nb and Sn oxides within pegmatites, indicate that a zonation from primitive to evolved pegmatites surrounding granites is not present and that pegmatites are probably not related to granites in the typical parent–daughter relationship.

scholarly journals IMPROVEMENT OF OFFICIAL CHARACTERISTICS OF THE SURFACE LAYER DETAILS BY APPLICATION OF SURFACE PLASTIC DEFORMATION AND GASODYNAMYNAMYNAMINE

2020 ◽  
pp. 90-100
Author(s):  
Viktor Matviychuk ◽  
Oleg Haidamak ◽  
Mykola Kolesnik
Keyword(s):  
Plastic Deformation ◽  
Surface Plastic Deformation ◽  
Cold Gas Dynamic Spraying ◽  
Thin Plates ◽  
Geometrical Parameters ◽  
Surface Plastic ◽  
Gradual Change ◽  
Gas Dynamic ◽  
Multi Stage ◽  
Cold Gas

The article investigates changes in the characteristics of the surface layers of parts processed by methods of surface plastic deformation (SPD). It is shown that at SPD the strength and hardness characteristics of the material increase and residual compression stresses are formed. On the basis of the study of the stress-strain state of the material at the SPD, its non-monotonicity is established, which is manifested in the gradual change of sign of the components of deformations and stresses. In this regard, a tensor-nonlinear damage accumulation model was used to evaluate the deformability of the material, which takes into account the directional nature of the damage and the anisotropy of the plasticity of the deformed metal. Based on this model, an expression was obtained to determine the plasticity resource used in the case of multi-stage SPD. According to the results of the calculations, it is established that the maximum plasticity resource used in the SPD is at a depth of approximately 0.1 of the diameter of the plastic footprint of the tool, and destruction at full exhaustion of the plasticity resource occurs in the form of peeling of thin plates of appropriate thickness. Recommendations for displacement of the most reinforced layers to the surface of the workpiece are developed, as well as recommendations for limiting deformation by the amount of plasticity resource used. The conducted research allows to assign the optimal modes of SPD at the stage of technological process design. A device for cold gas-dynamic spraying was developed and the possibility of creating antifriction sections using it was investigated. Graphs of dependence of geometrical parameters of the deposited layer on the sputtering distance are constructed and methods and schemes of preparation for deposition of the surface of the workpiece using SPD methods are developed. Experimental cold gas-dynamic spraying was carried out and optimal parameters of the process of spraying of antifriction layers of bronze and metal polymers (pressure, and the temperature of the compressed air and the temperature of the workpiece) on the formed roller surface were determined. A new concept of increasing the contact strength and durability of friction pairs is proposed.

scholarly journals Y-REE mineralization in biotite-arfvedsonite granites of the Katugin rare-metal deposit, Transbaikalia, Russia

2019 ◽  
Vol 487 (1) ◽  
pp. 88-92 ◽  
Author(s):  
A. E. Starikova ◽  
E. V. Sklyarov ◽  
V. V. Sharygin
Keyword(s):  
Rare Metal ◽  
Chemical Data ◽  
Host Granite ◽  
Ree Mineralization ◽  
Granite Formation ◽  
Metal Deposit ◽  
Mineral Phases ◽  
Magmatic Stage ◽  
Rare Metal Deposit ◽  
Melt Segregation

We provide the results of study of the extremely enriched in Y-REE carbonate-fluorine isolations from biotite-arfvedsonite granite of the Katugin rare metal deposit. New chemical data of isolations mineral phases - gagarinite-(Y), tveitite-(Y), fluocerite-(Ce), basnaesite, fluornatropyroclore, are delivered. Carbonate-fluoride globule in quartz of hosting granite gives possibility to estimate crystallization order. This finding might be the evidence of silicate-fluorine immiscibility suggested before for Y-REE segregations in the Katugin granites. Fluorine melt segregation took likely place at the magmatic stage of biotite-arfvedsonite granite formation. It causes host granite depletion with fluorine and redistribution of REE and Y in fluorine salt melt.

Geochemical Evolution and Ore-Bearing Metasomatites of the Bag-Gazryn Multiphase Array of Rare-Metal Li-F-Granites (Mongolia)

2018 ◽  
Vol 483 (3) ◽  
pp. 310-315 ◽  
Author(s):  
V. Antipin ◽  
◽  
M. Kuzmin ◽  
D. Odgerel ◽  
L. Kushch ◽  
...  
Keyword(s):  
Rare Metal ◽  
Geochemical Evolution

Spatial, temporal and geochemical evolution of Oligo–Miocene granitoid magmatism in western Anatolia, Turkey

2012 ◽  
Vol 21 (4) ◽  
pp. 961-986 ◽  
Author(s):  
Şafak Altunkaynak ◽  
Yıldırım Dilek ◽  
Can Ş. Genç ◽  
Gürsel Sunal ◽  
Ralf Gertisser ◽  
...  
Keyword(s):  
Geochemical Evolution ◽  
Western Anatolia ◽  
Granitoid Magmatism

Fossil horses from “Eohippus” (Hyracotherium) to Equus: scaling, Cope's Law, and the evolution of body size

Paleobiology ◽  
1986 ◽  
Vol 12 (4) ◽  
pp. 355-369 ◽  
Author(s):  
Bruce J. MacFadden
Keyword(s):  
Body Size ◽  
Body Mass ◽  
Morphological Evolution ◽  
Natural Populations ◽  
Evolutionary Rates ◽  
Middle Pleistocene ◽  
Gradual Change ◽  
Regression Equations ◽  
Extant Species ◽  
Body Sizes

The evolution of body size in fossil horses is frequently depicted as a gradual, progressive trend toward increased body size (Cope's Law). Body size (actually body mass) was estimated for 40 species of fossil horses using dental and skeletal characters and regression equations derived from the same characters in extant species of Equus with known body mass. After body sizes were estimated, rates of morphological evolution, in darwins (d), were calculated between known ancestral and descendant fossil horse species. For the first half of horse evolution (from ca. 57 to 25 ma) body mass remained relatively static between about 25 and 50 kg with very slow evolutionary rates of 0.003–0.04 d. During the early–middle Miocene (from ca. 25 to 10 ma) there was a major diversification of body mass to about 75–400 kg and consistently higher evolutionary rates between 0.04 and 0.24 d. Since the late Miocene, body mass has generally increased with a maximum seen (in natural populations) in Equus scotti (ca. 500 kg) during the middle Pleistocene. Therefore, for horses, the traditional interpretation of gradual increase in body size through time is oversimplified because: (1) although the exception to the rule, 5 of 24 species lineages studied are characterized by dwarfism; and (2) the general trend seems to have been a long period (32 ma) of relative stasis followed by 25 ma of diversification and progressive (although not necessarily gradual) change in body size.

scholarly journals PALEOZOIC GRANITOID MAGMATISM OF THE URALS: THE REFLECTION OF THE STAGES OF THE GEODYNAMIC AND GEOCHEMICAL EVOLUTION OF A COLLISIONAL OROGEN

2021 ◽  
Vol 12 (2) ◽  
pp. 225-245
Author(s):  
V. V. Kholodnov ◽  
G. Yu. Shardakova ◽  
V. N. Puchkov ◽  
G. A. Petrov ◽  
E. S. Shagalov ◽  
...  
Keyword(s):  
Large Datasets ◽  
Geological Mapping ◽  
Igneous Rocks ◽  
Geochemical Evolution ◽  
Mobile Belt ◽  
The Urals ◽  
Isotope Geochronology ◽  
Subsequent Formation ◽  
Granitoid Magmatism ◽  
Collisional Orogen

The Ural mobile belt is an intracontinental epioceanic orogen that has already gone through all stages of the geodynamic development. Igneous rocks formed during each stage are important indicators for understanding the evolution of this belt and determining potential ore contents of its segments. We consolidated large datasets on petrogeochemistry and isotope geochronology of the Paleozoic (490–250 Ma) granitoids associated with the opening and evolution of the Ural paleoocean and the subsequent formation of the collisional orogen. Using these data, we have revised the ages of several tectono-magmatic events, clarified the paleogeodynamic settings for the generation of granitoids of different compositions, and described the roles of mantle-crust interactions and the plume factor in the formation of the mature continental crust in the study area. The results can be useful for geological mapping and improving the assessment of the potential ore contents in granitoid complexes that differ in origin and composition.

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