Открытый доступ Открытый доступ  Доступ закрыт Доступ предоставлен  Доступ закрыт Только для подписчиков

Том 27, № 5 (2019)

Article

pages 439-441 views

Experimental Study of Amphibole Crystallization from the Highly Magnesian Melt of Shiveluch Volcano, Kamchatka

Simakin A., Devyatova V., Salova T., Shaposhnikova O.

Аннотация

The paper reports results of an experimental study of amphibole crystallization from the highly magnesian andesite melt of Shiveluch volcano, Kamchatka. The experiments were carried out in IHPV at 300 MPa and 940–980°С in iron-saturated platinum capsules, using rapid quenching and temperature oscillations (in some experiments). The redox state of iron in the system was measured before and after the experiments using Mössbauer spectroscopy. The maximum size of the experimental amphibole crystals (up to 200 μm) was close to those of natural amphibole phenocrysts in the volcanic rocks of Shiveluch volcano. The experimental data show that the content of octahedrally coordinated Al (Al6) in the amphibole considerably varies with small variations in the intensive parameters (P, T, and \(f{{{\text{O}}}_{2}}\)) and composition of the melt, and the maximum Al6 concentration can be evaluated only by using a reasonably large dataset of amphibole analyses. A modified 13eCNK method is suggested to calculate the values of Al6 and Fe3+/Fe2+ with regard for the Ti concentration and the probable partial transfer of Mg into site B in high-Mg amphibole. Calculations with this modified technique yield lower Fe3+/Fe2+ and higher Al6 values. Our experimental data show that the temperature of amphibole liquidus crystallization decreases from about 990°C to 960°C when the oxygen fugacity drops from NNO + 1.5 to NNO + 0.4. In view of this, the transition from amphibole-bearing to anhydrous mineral assemblage in the magmas of Shiveluch volcano might have been caused by variations of the oxygen fugacity but not water. The application of our geobarometer to amphiboles from Shiveluch volcano (extrusions Krasnaya and Karan) yields the highest pressure estimate of above 1 GPa, corresponding to the PT conditions of the melting of garnet-bearing amphibolite in the lower crust.

Petrology. 2019;27(5):442-459
pages 442-459 views

The Relationship of the Relative Abundance of Masses of Granites and Rhyolites in the Earth’s Crust with the Patterns of the Rheology of the Granitic Magmas

Persikov E.

Аннотация

Many years ago, V. S. Sobolev suggested that the reason for the relative prevalence of intrusive and effusive rock masses in the earth’s crust lies in the patterns of viscosity of water-bearing magmas in a variable field of temperatures and pressures. Alas, in those years it was not possible to solve this problem on a quantitative physical-chemical basis, since experimental and theoretical studies of the viscosity of such melts at high pressures were just beginning. In the present work, new patterns of the viscosity of near-liquid water-bearing acidic magmas in a wide range of thermodynamic parameters and depths of the Earth’s crust (1–30 km) are established using the structural-chemical model of reliable and correct predictions and calculations of the viscosity of magmas of virtually any composition. It determined that these patterns really are a quantitative physical-chemical basis explaining the reason for the relative distribution of masses of intrusive and effusive rocks of acidic composition in the earth’s crust.

Petrology. 2019;27(5):460-466
pages 460-466 views

Subduction Sediment–Lherzolite Interaction at 2.9 GPa: Effects of Metasomatism and Partial Melting

Perchuk A., Serdyuk A., Zinovieva N.

Аннотация

We present the results of analogue experiments carried out in a piston–cylinder apparatus at 750–900°C and 2.9 GPa aimed to simulate metasomatic transformation of the fertile mantle caused by fluids and melts released from the subducting sediment. A synthetic H2O- and CO2-bearing mixture that corresponds to the average subducting sediment (GLOSS, Plank and Langmuir (1998)) and mineral fractions of natural lherzolite (analogue of a mantle wedge) were used as starting materials. Experiments demonstrate that the mineral growth in capsules is controlled by ascending fluid and hydrous melt (from 850°C) flows. Migration of the liquids and dissolved components develops three horizontal zones in the sedimentary layer with different mineral parageneses that slightly changed from run to run. In the general case, however, the contents of omphacite and garnet increase towards the upper boundary of the layer. Magnesite and omphacite (±garnet ± melt ± kyanite ± phengite) are widespread in the central zone of the sedimentary layer, whereas SiO2 polymorph (± kyanite ± phengite ± biotite ± omphacite ± melt) occurs in the lower zone. Clinopyroxene disappears at the base of lherzolite layer and the initial olivine is partially replaced by orthopyroxene (± magnesite) in all experiments. In addition, talc is formed in this zone at 750°C, whereas melt appears at 850°C. In the remaining volume of the lherzolite layer, metasomatic transformations affect only grain boundaries where orthopyroxene (± melt ± carbonate) is developed. The described transformations are mainly related to a pervasive flow of liquids. Mineral growth in the narrow wall sides of the capsules is probably caused by a focused flow: omphacite grows up in the sedimentary layer, and talc or omphacite with the melt grow up in the lherzolite layer. Experiments show that metasomatism of peridotite related to a subducting sediment, unlike the metasomatism related to metabasites, does not lead to the formation of garnet-bearing paragenesis. In addition, uprising liquid flows (fluid, melt) do not remove significant amounts of carbon from the metasedimentary layer to the peridotite layer. It is assumed that either more powerful fluxes of aqueous fluid or migration of carbonate-bearing rocks in subduction melanges are necessary for more efficient transfer of crustal carbon from metasediments to a mantle in subduction zones.

Petrology. 2019;27(5):467-488
pages 467-488 views

Mineral Indicators of Reactions Involving Fluid Salt Components in the Deep Lithosphere

Safonov O., Butvina V., Limanov E., Kosova S.

Аннотация

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.

Petrology. 2019;27(5):489-515
pages 489-515 views

Granitization and High-Temperature Metasomatism in Mafic Rocks: Comparison between Experimental Data and Natural Observations

Khodorevskaya L.

Аннотация

The paper reports newly obtained data that append older results of experimental modeling of granitization processes. The experiments were aimed at modeling high-temperature metasomatism of mafic rocks, a process that involves the transfer of major components at 750°C and 500 MPa at a pressure gradient. The source of the transported Si, Ca, and Mg in the experiments was garnet. The solution was pure H2O and 25 wt % NaCl aqueous solution. In the experiments, garnet was decomposed into pyroxenes, amphiboles, plagioclase, and minor amounts of melt, ilmenite, and iron oxides. The associated partial dissolution led to the transfer and redeposition of the dissolved components on the surface of a gabbroanorthosite underlay and to the development of mineral rims, which were analogous to those produced at garnet decomposition. The compositions of the newly formed minerals in the rims were identical to those produced at metamorphism of gabbroanorthosite at Т ≥ 750°C, P > 700 MPa. When the mineral rim was formed, some elements are removed, and this process was controlled by the composition of the fluid phase. The pure H2O fluid removed Fe, Ca, and Mg. The aqueous fluid containing NaCl (XNaCl ≈ 0.1) did not extract Ca from minerals. This indicates that no high NaCl concentrations are typical of fluid in processes that form basificates at granitization. The experiments have shown that H2O and H2O–NaCl fluids remove more Fe that other elements. Preferable Fe extraction from naturally occurring associations is evident from the elevated Fe mole fractions of the mafic minerals and from the fact that the basificates typically contain magnetite and hematite.

Petrology. 2019;27(5):516-533
pages 516-533 views

Liquid Immiscibility and Problems of Ore Genesis: Experimental Data

Shapovalov Y., Kotelnikov A., Suk N., Korzhinskaya V., Kotelnikova Z.

Аннотация

The paper reports the results of an experimental study of phase relations and distribution of elements in silicate melt–salt melt systems (carbonate, phosphate, fluoride, chloride), silicate melt I – silicate melt II, and fluid–magmatic systems in the presence of alkali metal fluorides. Extraction of a number of ore elements (Y, REE, Sr, Ba, Ti, Nb, Zr, Ta, W, Mo, Pb) by salt components was studied in liquid immiscibility processes within a wide temperature range of 800–1250°С and pressure of 1–5.5 kbar. It is shown that partition coefficients are sufficient for concentration of ore elements in amounts necessary for the genesis of ore deposits. In a fluid-saturated trachyrhyolite melt, the separation into two silicate liquids has been determined. The partition coefficients of a number of elements (Sr, La, Nb, Fe, Cr, Mo, K, Rb, Cs) between phases L1 and L2 have been obtained. The interaction processes of a heterophase fluid in the granite (quartz)–ore mineral–heterophase fluid (Li, Na, K-fluoride) system were studied at 650–850°C and P = 1 kbar. The formation of the phase of a highly alkaline fluid-saturated silicate melt concentrating Ta and Nb is shown as a result of the interaction of the fluid with rock and ore minerals.

Petrology. 2019;27(5):534-551
pages 534-551 views

Согласие на обработку персональных данных с помощью сервиса «Яндекс.Метрика»

1. Я (далее – «Пользователь» или «Субъект персональных данных»), осуществляя использование сайта https://journals.rcsi.science/ (далее – «Сайт»), подтверждая свою полную дееспособность даю согласие на обработку персональных данных с использованием средств автоматизации Оператору - федеральному государственному бюджетному учреждению «Российский центр научной информации» (РЦНИ), далее – «Оператор», расположенному по адресу: 119991, г. Москва, Ленинский просп., д.32А, со следующими условиями.

2. Категории обрабатываемых данных: файлы «cookies» (куки-файлы). Файлы «cookie» – это небольшой текстовый файл, который веб-сервер может хранить в браузере Пользователя. Данные файлы веб-сервер загружает на устройство Пользователя при посещении им Сайта. При каждом следующем посещении Пользователем Сайта «cookie» файлы отправляются на Сайт Оператора. Данные файлы позволяют Сайту распознавать устройство Пользователя. Содержимое такого файла может как относиться, так и не относиться к персональным данным, в зависимости от того, содержит ли такой файл персональные данные или содержит обезличенные технические данные.

3. Цель обработки персональных данных: анализ пользовательской активности с помощью сервиса «Яндекс.Метрика».

4. Категории субъектов персональных данных: все Пользователи Сайта, которые дали согласие на обработку файлов «cookie».

5. Способы обработки: сбор, запись, систематизация, накопление, хранение, уточнение (обновление, изменение), извлечение, использование, передача (доступ, предоставление), блокирование, удаление, уничтожение персональных данных.

6. Срок обработки и хранения: до получения от Субъекта персональных данных требования о прекращении обработки/отзыва согласия.

7. Способ отзыва: заявление об отзыве в письменном виде путём его направления на адрес электронной почты Оператора: info@rcsi.science или путем письменного обращения по юридическому адресу: 119991, г. Москва, Ленинский просп., д.32А

8. Субъект персональных данных вправе запретить своему оборудованию прием этих данных или ограничить прием этих данных. При отказе от получения таких данных или при ограничении приема данных некоторые функции Сайта могут работать некорректно. Субъект персональных данных обязуется сам настроить свое оборудование таким способом, чтобы оно обеспечивало адекватный его желаниям режим работы и уровень защиты данных файлов «cookie», Оператор не предоставляет технологических и правовых консультаций на темы подобного характера.

9. Порядок уничтожения персональных данных при достижении цели их обработки или при наступлении иных законных оснований определяется Оператором в соответствии с законодательством Российской Федерации.

10. Я согласен/согласна квалифицировать в качестве своей простой электронной подписи под настоящим Согласием и под Политикой обработки персональных данных выполнение мною следующего действия на сайте: https://journals.rcsi.science/ нажатие мною на интерфейсе с текстом: «Сайт использует сервис «Яндекс.Метрика» (который использует файлы «cookie») на элемент с текстом «Принять и продолжить».