In this contribution, we show that in miarolitic pegmatites during the crystallization of water-rich melts, samples of these mineral-forming melts were trapped in the form of water-rich melt inclusions, preserved primarily in quartz. The bulk concentration of water and the temperature are the system-determining parameters since from their analysis it follows that these melt inclusions depict pseudo-binary solvus curves in the coordinates of temperature and water concentration. Furthermore, using reduced coordinates (H2O/H2Ocrit vs. T/Tcrit) most melt inclusions of the studied pegmatites plot very well in a standardized and reduced solvus curve. The existence and formation of such uniform solvus curves is an expression of crystallization processes under nearly equilibrium conditions. However, many trace and some principal elements of the melt inclusions trapped near the solvus crest [H2O/H2Ocrit from 0.5 to 1.5 and T/Tcrit > 0.95] show unusual distributions, with very well-defined Gaussian and/or Lorentzian curves, characterized by defined area, width, offset, and height. This has been shown in many natural examples obtained from pegmatites. Only the offset values represent near-equilibrium conditions and corresponding element concentrations, which are equivalent to the regional Clarke number (Clarke number or Clark is the relative abundance of a chemical element, typically in the Earth's crust). We interpret these distributions as explanation for some extraordinary-chemical properties in this critical region: principally extremely high diffusion rates, low dynamic viscosity and extremely low surface tension. Near the critical point, we have both space and time-related non-equilibrium and equilibrium processes close together. Furthermore, we can show that the Gaussian and Lorentzian distribution are first approximations of the specific element distribution because at the critical point the enrichment of some elements reaches such an extent that the Gaussian and/or Lorentzian curves degenerate into a vertical line (are asymptotic to the concentration axis), which is determined by the maximum solubility of a species in the supercritical melt-water system. The highest concentration of Be, as an example, was observed in Ehrenfriedersdorf melt inclusions: 71490 ppm Be.
Камерні пегматити Волині у коростенських гранітах приурочені до зони, по якій до камер вільного росту кристалів тривалий час надходили продукти дегазації магми кислого й основного складу. Топаз -найпопулярніший мінерал во линських пегматитів. Характерна морфологічна особливість топазів із пегматитів Волині -сплощеність кристалів уздовж нормалі до граней призми {110}, внаслідок чого їхня зовнішня симетрія понижена (диссиметризація). На при кладі диссиметризованих кристалів топазу чітко окреслюється така колізія: поняття кристал у випадку його дис симетризації втрачає значення мінерального індивіду, набуває гетерогенної будови, яка кореспондується з втратою найголовніших властивостей кристала -однорідності та анізотропії. Для таких диссиметризованих кристалів за пропоновано термін "аномальний монокристал" -візуально однорідний кристал, окремі піраміди росту якого на мікро рівні належать до різних точкових груп симетрії. Всебічно висвітлена крізь призму симетріїдиссиметрії тема "Флю їдні потоки та морфологія слюд і топазів" у камерних пегматитах Волині. Зроблено висновок: стовбчасті кристали LiFe слюд (інколи без пінакоїда {001}) є наслідком активної взаємодії двох симетрій (принцип Кюрі) -флюїдного по току та кристала, а диссиметризація кристалів топазу відбувалась в умовах однобічного надходження глибинних флюїдних потоків із симетрією "стріли".
впервые проведено локальное (ионный микрозонд) исследование состава первичных расплавных включений в цирконе из азовского Zr-REE месторождения. среди них встречаются раскристаллизованные, доминирующие по количеству, и взорванные (растресканные) включения, образовавшиеся при воздействии на породу потоков со 2-флюида, характеризующегося высокими РТ-параметрами. относительно времени захвата кристаллом расплавные включения в цирконе можно разделить на две группы, отличающиеся по содержанию главных, редких и редкоземельных элементов: ранние включения кислого состава и поздние включения основного состава. ранние включения кислого состава, по сравнению с поздними, содержат значительно меньше fe, ca, REE, y, Zr, P, Th. минимальное содержание редких элементов установлено для ранних взорванных включений, потерявших герметичность под воздействием потоков высокотемпературных со 2-флюидов. состав этих включений соответствует калиевому полевому шпату с небольшой примесью альбита и фемического минерала. Поздние расплавные включения обогащены фтором, пересыщены REE, Zr, y и отражают процессы ликвации, приведшей к разделению сиенитового расплава на две несмешивающиеся жидкости-на богатую железом, несовместимыми элементами и фтором, и богатую кремнеземом. для обеих групп расплавных включений определены коэффициенты распределения Kd циркон/расплав для REE. Значения Kd для циркона из азовского месторождения значительно (в десятки и сотни раз) ниже, чем опубликованные данные для циркона из магматических кислых пород. выявлено, что на последних стадиях становления азовского месторождения, когда сиенитовый расплав пересыщается несовместимыми элементами (REE, Zr, y), циркон наследует состав REE расплава: формы спектров REE циркона и сингенетичного к нему стекла первичного включения идентичны, отличаясь лишь их содержанием.
The formation of leucosyenites in the Velyka Vyska syenite massif was provoked by the liquation layering of magmatic melt. This assumption is based on the presence of two primary melt inclusions of different chemical composition in zircon crystals from Velyka Vyska leucosyenites. They correspond to two types of silicate melts. Type I is a leucosyenite type that contains high SiO2 concentrations (these inclusions dominate quantitatively); type II is a melanosyenite type that contains elevated Fe and smaller SiO2 concentrations. The liquation layering of magmatic melt was slow because the liquates are similar in density; leucosyenite melt, which is more abundant than melt of melanosyenite composition, displays greater dynamic viscosity; the initial sizes of embryos of melanosyenite composition are microscopic. Sulphide melt, similar in composition to pyrrhotite, was also involved in the formation of the massif. Zircon was crystallized at temperatures over 1300°С, as indicated by the homogenization temperatures of primary melt inclusions. The REE distribution spectra of the main parts (or zones,) of zircon crystals from the Velyka Vyska massif are identical to those of zircon from the Azov and Yastrubets syenite massifs with which high-grade Zr and REE (Azov and Yastrubets) ore deposits are associated. They are characteristic of magmatically generated zircon. Some of the grains analyzed contain rims that are contrasting against the matrix of a crystal, look dark-grey in the BSE image and display flattened REE distribution spectra. Such spectra are also typical of baddeleyite, which formed by the partial replacement of zircon crystals. The formation of a dark-grey rim in zircon and baddeleyite is attributed to the strong effect of high-pressure СО2-fluid on the rock. The formation patterns of the Velyka Vyska and Azov massifs exhibit some common features: (а) silicate melt liquation; (b) high ZrO2 concentrations in glasses from hardened primary melt inclusions; (c) the supply of high-pressure СО2-fluid flows into Velyka Vyska and Azov hard rocks. Similar conditions of formation suggest the occurrence of high-grade Zr and REE ores in the Velyka Vyska syenite massif.
Various aspects of the genesis of primary fluid inclusions (0.01-1.0 sometimes up to 2 mm) with a large number of mineral inclusions in topaz crystals from chamber pegmatites of Volyn were analyzed. The data could be interpreted in two fundamentally different ways. The first argues for crystals grown in a magmatic melt; the second for an aqueous solution, with a density close to critical. The essence of the discrepancy is the reliability of the identification of the nature of mineral phases in the primary inclusions, if they are crystals captured during growth (xenogenic) or daughter crystals from the fluid. The xenogenic origin of the phases is indicated by the following observations: 1) The location of the mineral inclusions on the growing faces of the topaz crystals depends on the orientation of the crystal’s axis [001] relative to the horizontal plane. It determines the faces on which small mineral phases could be deposited from an aqueous suspension during the growth of topaz crystals. The studied crystals are dominated by individuals in which the mineral inclusions are located on the growing faces {011}, {021}, (001) (and others) of the crystal head. During growth, they were approximately in an upright position. 2) The filling of primary fluid inclusions is not constant. The volume of mineral phases in the inclusions varies from 40 to 95%, often 70-75%, the rest of the volume is gas and aqueous solution. Liquid-gas (liquids ˂ 40%) inclusions without or with < 5% solid phases are very rare. In addition, the ratio between the volumes of different mineral phases in the inclusions is not constant. 3) Light rims (Becke lines) around the inclusions record a change in the refractive indices (caused by a different chemical composition) of topaz when inclusions are acquiring the equilibrium form of the negative crystal. 4) The xenogenic nature of the mineral phases of the primary fluid inclusions in topaz is indirectly confirmed by the value of the fluid pressure (260-300 MPa)of the magmatic melt (determined by the method of homogenization of these inclusions), as it denies the possibility of chamber pegmatite formation at depths of 9-11 km. Thus, the peculiar mineral inclusions were deposited on the face of growing topaz crystals of small mineral phases from a turbid aqueous suspension, which boiled violently. We conclude that topaz crystals in chamber pegmatites of Volyn grew in aqueous solution at a temperature of 380-415ºС and a pressure of 30-40 MPa.
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