The structures of two K-richterite crystals with the crystal chemical formulas (K0.44Na0.32 □ 0.24)Σ=1(Ca1.18Na0.82)Σ=2Mg5Si8O22OH2 and (K0.83Na0.02 □ 0.15)Σ=1(Ca1.11Na0.89)Σ=2Mg5Si8O22OH2 synthesized at a pressure of 3 GPa and a temperature of 1000°С in the MgSiO3 + CaMgSi2O6 + K2CO3 + Na2CO3 + CO2 + H2O system were studied by single-crystal X-ray analysis and Raman spectroscopy. The monoclinic cell parameters were obtained: a = 10.0256(5) and 9.9748(11) Å, b = 17.9874(7) and 17.9879(16) Å, c = 5.2687(3) and 5.2746(6) Å, Ve.c. = 916.17(18) and 918.52(8) Å3, β = 104.520(12)° and 104.821(5)°, sp. gr. С2/m (12), and Z = 2. The sites M(1), M(2), and M(3) are inhabited by Mg2+, while site M(4) is occupied simultaneously by Ca2+ and Na+. The Na+ cations not included in M(4) are located in position A, which also accommodates K+ cations. Raman spectroscopy made it possible to reveal vacancies in position A in both samples. The structure corresponds to the “ideal” structure of richterite group minerals. The unit cell volume of the measured crystals is directly proportional to the K content in position A. Based on the generalization of new and published data, an equation of the dependence of Vu.c. for amphiboles of the richterite Na(NaCa)Mg5Si8O22(OH)2–K-richterite K(NaCa)Mg5Si8O22(OH)2 series with a low tremolite component on the K content in position A is proposed.

The paper presents data on the formation of K–Na richterite in the enstatite + diopside association with K2CO3–Na2CO3–CO2–H2O fluid at 3 GPa and 1000°C as a model for the formation of this mineral in peridotites of the upper mantle. Richterite formation depends on the (H2O + CO2)/(K2CO3 + Na2CO3) and K2CO3/Na2CO3 ratios in the starting material. A high concentration of alkaline components in the fluid leads to the decomposition of clinopyroxene, the formation of olivine, and a change in the component composition of the pyroxene and amphibole. Fluids with a high potassium concentration are favorable for the formation of K-richterite similar in composition to that formed in metasomatized peridotites of the upper mantle. In some cases, such a fluid leads to the decomposition of amphibole and stabilization of alkaline melt. An increase in the activity of the sodium component results in richterite similar in composition to richterite from lamproites. The clarified relations can be used to assess the activities of fluid components and conditions for the formation of K-richterite. To update the data bank of the Raman spectra of minerals, the largest and most homogeneous amphibole crystals of different compositions were studied.

The paper summarizes authors' earlier and newly obtained experimental data on the formation of phlogopite and chromium-bearing potassium titanates of the crichtonite, magnetoplumbite, and hollandite groups, which are indicator minerals that characterize various stages of modal metasomatism in the upper mantle. Phlogopite-forming reactions were studied in the garnet–orthopyroxene system in the presence of H2O–KCl fluid at 3 and 5 GPa and 900–1000°C as simulating phlogopite formation in garnet peridotites and pyroxenites. Experiments have demonstrated regular variations in Ca and Cr contents in the garnet and Al in the pyroxenes, as well as the composition of the newly formed phlogopite, depending on the concentration of the potassium component (KCl or K2CO3) of the fluid. Experiments on the formation of potassium titanates (yimengite, mathiasite, and priderite) in the chromite–rutile/ilmenite–K2CO3–H2O–CO2 system at 3.5 and 5 GPa and 1200°C have proved that these minerals can be formed when chromite reacts with potassic aqueous–carbonic fluid, but these reactions require additional sources of titanium. These sources may be rutile and/or ilmenite, which are usually also produced by modal metasomatism of peridotites. The experiments thus confirm that the formation of titanates marks the most advanced stages of metasomatism in mantle peridotites. The experiments have shown that the formation of potassium titanates follows the formation of phlogopite, whereas assemblages of the titanates with phlogopite are produced at higher concentrations of the potassium component of the fluid than phlogopite alone. The relationships between the titanates are also a function of the activity of the potassium component in the fluid and, probably, pressure. The relationships and trends reproduced in the experiments clearly illustrate features of mineral assemblages and variations in compositions of minerals from metasomatized peridotites in the lithospheric mantle.

A comparative study was established, considering the various characteristics of activity self-regulation, as well as their comparison with the levels of anxiety in musicians, depending on their specialization, as well as professional status. It was established that professional vocalists have clearer ideas about their capabilities, as well as a higher level of personal anxiety than avocational vocalists. Professional instrumentalists are less anxious and more collected at the time of execution than avocational instrumentalists or vocalists. Professional musicians, unlike avocational musicians, have a higher level of anxiety and less pronounced self-control of the self-regulation dynamics. The data obtained are of particular importance for students of musical educational institutions, as they emphasize the importance of maintaining control over the level of anxiety in order to increase their professional status. Establishing the degree, showing development of self-regulation skills and the level of anxiety, can be useful for a musician, as it will help to identify a number of possible problems that have a destructive or inhibitory effect on professional skills.

Phlogopite is accepted as a major mineral indicator of the modal metasomatism in the upper mantle within a very wide P-T range and fluid/melt compositions. It extensively forms in mantle peridotites transforming initial harzburgites and lherzolites to phlogopite wehrlites both in garnet and spinel-facies. A reaction 5En + Grt + [K2O + 2H2O in fluid] = Phl + Di (Grt – pyrope-grossular garnet CaMg2Al2Si3O12) is considered as the major mechanism for phlogopite formation in garnet-facies peridotites. This reaction is commonly accompanied by regular compositional changes of primary garnet and pyroxenes. In order to illustrate the regularities, we report result of experimental study of the phlogopite-forming reactions in the model systems pyrope-enstatite, grossular-pyrope-enstatite and knorringite-pyrope-enstatite systems in presence of a H2O-KCl fluid at pressure 3 and 5 GPa and temperatures of 900 and 1000°C. The experiments were aimed at the tracing of variations of grossular and knorringite contents in garnet, as well as Al content of pyroxenes, with variations of the KCl content in the fluid. The increase of XKCl in the fluid is accompanied by gradual decomposition of garnet and Al-bearing enstatite in all systems. The Al2O3 content in orthopyroxene decreases in the pyrope – enstatite system at 5 GPa and 900°C. In the system enstatite-pyrope-grossular at 5 GPa and 1000°C phlogopite forms at the KCl content 10 mol. % in the fluid. Further increase of the KCl content in the fluid results in gradual disappearance of garnet and orthopyroxene and stronger domination of phlogopite and clinopyroxene. Grossular content in garnet increases with the KCl concetration in the fluid up to 10 mol. %, but further increase of the KCl concentration to 20 mol. % results in decrease of the grossular content in garnet. In the system enstatite-pyrope-knorringite at the KCl content in the fluid 0 – 10 mol. %, garnet contains 8-9 mol. % of knorringite. Cr-bearing phlogopite (about 2 wt. % Cr2O3) appears in this system at 10 mol. % KCl in the fluid, and its formation results in a slight increase of the knorringite content in garnet. Because of relatively high SiO2 bulk content in comparison to the typical peridotite, Cr-bearing kyanite (not spinel) forms at 20 mol. % KCl in the fluid resulting in a decrease of the knorringite content in garnet down to 3-5 mol. %. The Cr2O3 content in the coexisting phlogopite concomitantly decreases by about 1 wt. %. The above experiments reproduced some characteristic regularities in variations of garnet and pyroxene compositions in the course of phlogopite formation in mantle peridotites. The applicability of the experimental results is illustrated by examples from peridotite xenoliths from kimberlites. These effects can be applied for the quantitative and qualitative estimates of variations in K activity during the modal mantle metasomatism.

The results of experimental studies are presented for reactions in the orthopyroxene–garnet–phlogopite system in the presence of H2O–KCl fluid at 3–5 GPa and 900–1000°C, which model the processes of phlogopite formation in garnet peridotites and pyroxenites during alkaline metasomatism of the upper mantle. The experiments demonstrated regular variations in the composition of garnet, pyroxenes, and phlogopite depending on the KCl content of the fluid. With increasing KCl content of the fluid, enstatite and garnet become unstable, the Al2O3 content of enstatite decreases, and the amount of grossular and knorringite components in garnet are maximum at a KCl content of ~10 mol %. Our results illustrate well the regular variations in the compositions of the coexisting minerals and their zoning in phlogopite-bearing peridotites of the lithospheric mantle.

The conditions of genesis of diamondiferous ultrabasic and basic rocks from xenoliths in kimberlite were studied by combining the data from analytical investigations of their mineral phases and experimental results of the study of melting relations in the diamond-forming mineral systems of the upper mantle. The compositions of minerals in some samples of metasomatized diamondiferous eclogite associated with diamond-free eclogite from kimberlite of the Udachnaya pipe (Yakutia) were studied for the first time. The new results obtained in addition to the literature data were applied for generalization of estimates of genetically important characteristics of the chemical compositions of garnets, Ca-clinopyroxenes, and omphacites from diamond-bearing peridotite, pyroxenite, and eclogite. As a result, it was found that quite “fresh” minerals of diamondiferous rocks have typomorphic differences from the same minerals of diamond-free upper-mantle rocks. At the same time, it is significant that the compositions of minerals from diamondiferous rocks and paragenetic inclusions in diamonds are identical. These peculiarities of mineralogy of diamondiferous rocks are genetically significant; based on the mantle–carbonatite theory of the origin of diamond and associated mineral phases, this provides support for the same physicochemical origin of diamonds, minerals of diamondiferous rocks, and paragenetic inclusions in diamonds. Finally, the following genetic conclusions are made. (1) Completely miscible silicate (±oxide)–carbonate melts with dissolved carbon are the parental medium in petrogenesis of diamondiferous ultrabasic and basic rocks. (2) The physicochemically consistent formation of diamondiferous rocks and paragenetic inclusions of peridotitic and eclogitic minerals in diamonds occurred in the common diamond-forming chambers/reservoirs of parental melts; diamond-free peridotite, pyroxenite, and eclogite were the host mantle rocks for such chambers. (3) The origin of continuous series of diamondiferous peridotite–pyroxenite–eclogite rocks is controlled by the fractional ultrabasic–basic evolution of parental melts with exhaustion of olivine and orthorhombic pyroxene via the peritectic reactions. (4) Ascending flows of kimberlite magmas destroyed the parental chambers and captured diamonds with inclusions, individual minerals, their intergrowths, diamondiferous ultrabasic and basic rocks; at the entrance and exit from the chambers, they captured differentiated diamond-free host rocks of the mantle as well. (5) With further ascent from the mantle to the Earth’s crust, the material of diamond-forming chambers and diamond-free mantle was mixed in convecting kimberlite magma and was transported from the mantle to cumulative crustal chambers. (6) Kimberlite magmas were gradually solidified in stationary cumulative chambers with the release of highly compressed fluids; with an increase of pressure up to the critical values, they intruded into the rocks of the roof and ejected kimberlite with xenoliths of diamondiferous and mantle rocks to the surface with the formation of explosion pipes.

Образование флогопита в системе ортопироксен-гранат в присутствии флюида H 2 O

The salt components of aqueous and aqueous-carbonic fluids are very important agents of metasomatism and partial melting of crustal and mantle rocks. The paper presents examples and synthesized data on mineral associations in granulite- and amphibolite-facies rocks of various composition in the middle and lower crust and in upper-mantle eclogites and peridotites that provide evidence of reactions involving salt components of fluids. These data are analyzed together with results of model experiments that reproduce some of these associations and make it possible to more accurately determine their crystallization parameters.

In order to model phlogopite formation in the upper-mantle garnet peridotites, it was performed an experimental study of the reaction En + 1/3Prp + [2/3KCl + 1/3H2O] = 1/3Phl + 1/3Cl-Phl in the presence of a H2O–KCl fluid with XKCl = 0.05–0.4 at pressure of 5 GPa and temperatures of 900–1250 °C. Experiments showed that the decrease of the Al content in orthopyroxene and the increase of the Cl content in phlogopite are good indicators of the KCl activity in the fluid. These relationships can be used to quantify the KCl activity during the metasomatic processes in the upper mantle.

Экспериментально и теоретически обоснованы перитектические механизмы, определяющие ультрабазит-базитовую эволюцию магматизма в режиме фракционной кристаллизации и генезис перидотит-пироксенит-эклогитовых серий пород гранат-перидотитовой фации верхней мантии. Исследованы ликвидусные фазовые отношения дифференцированного мантийного вещества в многокомпонентной системе оливин−клинопироксен/омфацит−корунд–коэсит методом политермических сечений, в граничных фазах которых воспроизведены составы минералов перидотитов и эклогитов. На ликвидусе ультрабазитовой системы оливин−ортопироксен−клинопироксен−гранат происходит перитектическая реакция ортопироксена и расплава с образованием клинопироксена как механизм «клинопироксенизации ортопироксена» с выходом к регрессивной моновариантной котектике оливин + клинопироксен + гранат + расплав. Дальнейшая эволюция магматизма экспериментально исследована при 6 ГПа в ультрабазит-базитовой системе оливин−диопсид−жадеит−гранат с изменчивыми составами диопсид-жадеитовых твердых растворов (клинопироксен ↔ омфацит). На ликвидусе тройной системы оливин−диопсид−жадеит установлена перитектическая реакция оливина и расплава с образованием граната как механизм «гранатизации оливина» и выхода к котектике омфацит + гранат + расплав с формированием биминеральных эклогитов. Определено строение ликвидуса системы оливин–диопсид–жадеит–гранат и раскрыта его критическая роль как «физико-химического мостика» между ультрабазитовыми оливинсодержащими перидотит-пироксенитовыми и базитовыми кремнеземнасыщенными эклогитовыми составами вещества гранат-перидотитовой фации. Полученными экспериментальными физико-химическими результатами раскрыты генетические связи ультрабазитовых и базитовых пород и механизмы непрерывной фракционной магматической эволюции и петрогенезиса от оливинсодержащих перидотит-пироксенитовых пород до кремнеземнасыщенных эклогит-гроспидитовых. Это объясняет непрерывные петрохимические тренды для породообразующих компонентов в клинопироксенах и гранатах дифференцированных пород гранат-перидотитовой фации.

The peritectic mechanisms controlling the ultramafic–mafic evolution of magmatism during fractional crystallization and the genesis of peridotite–pyroxenite–eclogite rock series of the garnet–peridotite facies of the upper mantle were substantiated experimentally. The melting phase relations of differentiated mantle material in the olivine–clinopyroxene/omphacite–corundum–coesite multicomponent system were studied by the polythermal sections method; their boundary phases reproduced the compositions of peridotitic and eclogitic minerals. The peritectic reaction between orthopyroxene and melt with the formation of clinopyroxene proceeds at the liquidus of the olivine–orthopyroxene–clinopyroxene–garnet system as the mechanism for “clinopyroxenization of orthopyroxene,” which yields the regressive olivine + clinopyroxene + garnet + melt monovariant cotectic reaction. The further evolution of magmatism was studied experimentally at 6 GPa in the ultramafic–mafic olivine–diopside–jadeite–garnet system with a variable composition of the diopside–jadeite solid solutions (clinopyroxene ↔ omphacite). The peritectic reaction between olivine and melt with the formation of garnet was detected on the liquidus of the triple system olivine–diopside–jadeite as the of olivine garnetization mechanism yielding the omphacite + garnet + melt cotectic reaction with the formation of bimineral eclogite. The structure of the liquidus of the olivine–diopside–jadeite–garnet system was defined, as well as its critical role as the “physicochemical bridge” between the ultramafic olivine-bearing peridotite–pyroxenite composition and mafic silica-saturated eclogitic composition of matter within the garnet–peridotite facies. The experimental physicochemical results illustrate the genetic links between ultramafic and mafic rocks and the mechanisms of continuous fractional magmatic evolution and petrogenesis from olivine-bearing peridotite–pyroxenite rocks to silica-saturated eclogite–grospydite rocks. This explains the complete petrochemical trends for the rock-forming components in clinopyroxenes and garnets from differentiated rocks of the garnet–peridotite facies.