Composición y edad de fragmentos de monacita de sedimentos terrígenos jurásicos superiores en la base de formación de bazhenov (área multan, siberia occidental)

La Formación Bazhenov es considerada como el principal estrato petrolero que es madre de casi todos los campos de la megacuenca petrolera de Siberia occidental. Por ahora es una de las formaciones más estudiadas de Siberia y, quizás, de Eurasia. Aúnque hay una cantidad enorme de estudios dedicados a la formación Bazhenov, no hay estudios mineralógicos detallados en el nivel moderno de hardware. Tampoco se han estudiado la edad y los fuentes de los materiales terrígenos de la formación. Hemos explorado la monacita detrítica de los sedimentos terrígenos jurásicos superiores del Área Multana en la base de la formación Bazhenov en el centro de Siberia Occidental, Distrito de Surgut. Todo el fosfato detrítico de la tierra rara pertenece al tipo cerio y se refiere como monacita-(Ce). El mineral es bastante disimilar en cuanto a sus propiedades químicas, especialmente a su contenido de torio. Unos fragmentos han estado sometidos a cambios superpuestos secundarios. Se redondea la monacita detrítica a grados diferentes lo cual es un indicador de varias distancias de la inundación del yacimiento de fosfato de la tierra rara. Según los datos químicos, la mayoría de la monacita ha sido lavado de las rocas mediana y básicas (probablemente, alcalinas y subalcalinas) así como de las rocas siálicas (granitoidas y capas asociadas). Según datación química, la mayoría de los pedazos monazíticos han sido lavado de las formaciones Proterozóicas muy viejas y rocas Proterozóicas tempranas. Los materiales terrígenos se derivan probablemente de los conjuntos rocosos de los márgenes sudoriental y oriental de la megacuenca de Siberia Occidental, tales como la Cresta Proterozóica de Yenisei o los conjuntos de rocas Proterozóicas Tempranas de la Falla de Altay y Sayan

Composición y edad de fragmentos de monacita de sedimentos terrígenos jurásicos superiores en la base de formación de bazhenov (área multan, siberia occidental)

Bazhenov Formation is regarded as the main oil-bearing stratum mothering nearly all the fields of the Western Siberia Oil-Gas-bearing Megabasin. Presently, it is one of the most studied formations of Siberia and, probably, Eurasia as a whole. While there is an enormous amount of studies devoted to the Bazhenov Formation, there are no detailed mineralogical studies at the modern hardware level. The age and sources of the terrigenous materials of the formation have not been studied as well. We have explored the detrital monazite from the upper-Jurassic terrigenous sediments of the Multan Area at the foundation of the Bazhenov Formation in the central part of Western Siberia, Surgut District. All the detrital rare earth phosphate is of the cerium kind being a monazite-(Се). The mineral is rather dissimilar in respect of its chemical properties, especially, the content of thorium. Some fragments have been subjected to superposed secondary changes. The detrital monazite is rounded to various degrees which is indicative of the various distances from the rare earth phosphate orebody washout. As per the chemical data, most of the monazite has been washed out from the medium and basic rocks (probably subalkaline or alkaline) as well as the sialic rocks (granitoids and associated veins). According to the chemical dating, most of the monazite fragments have been washed out of the very ancient Proterozoic formations and lower-Proterozoic rocks. Terrigenous materials derives probably from the rock assemblages of the eastern and south-eastern fringes of the Western Siberian megabasin such as the Proterozoic Yenisei Ridge or Lower-Proterozoic blocks of the Altay and Sayan Faulting.La Formación Bazhenov es considerada como el principal estrato petrolero que es madre de casi todos los campos de la megacuenca petrolera de Siberia occidental. Por ahora es una de las formaciones más estudiadas de Siberia y, quizás, de Eurasia. Aúnque hay una cantidad enorme de estudios dedicados a la formación Bazhenov, no hay estudios mineralógicos detallados en el nivel moderno de hardware. Tampoco se han estudiado la edad y los fuentes de los materiales terrígenos de la formación. Hemos explorado la monacita detrítica de los sedimentos terrígenos jurásicos superiores del Área Multana en la base de la formación Bazhenov en el centro de Siberia Occidental, Distrito de Surgut. Todo el fosfato detrítico de la tierra rara pertenece al tipo cerio y se refiere como monacita-(Ce). El mineral es bastante disimilar en cuanto a sus propiedades químicas, especialmente a su contenido de torio. Unos fragmentos han estado sometidos a cambios superpuestos secundarios. Se redondea la monacita detrítica a grados diferentes lo cual es un indicador de varias distancias de la inundación del yacimiento de fosfato de la tierra rara. Según los datos químicos, la mayoría de la monacita ha sido lavado de las rocas mediana y básicas (probablemente, alcalinas y subalcalinas) así como de las rocas siálicas (granitoidas y capas asociadas). Según datación química, la mayoría de los pedazos monazíticos han sido lavado de las formaciones Proterozóicas muy viejas y rocas  Proterozóicas tempranas. Los materiales terrígenos se derivan probablemente de los conjuntos rocosos de los márgenes sudoriental y oriental de la megacuenca de Siberia Occidental, tales como la Cresta Proterozóica de Yenisei o los conjuntos de rocas Proterozóicas Tempranas de la Falla de Altay y Sayan

Вещественный состав метеорита Северный Колчим

New data on the material composition of the Severny Kolchim meteorite, found in the Perm region territory in 1965, is presented. It is established that the cosmic substance is composed of forsterite, enstatite, diopside, plagioclase (oligoclase, bitovnite), glass, chromite, magnetite, ilmenite, rutile, iron and nickel metals (kamasite, taenite and tetrataenite), sulphides (troilite, pentlandite), chlorapatite and merrillite. Some minerals, namely the diopside, tetrataenite, chlorapatite and merrillite, were determined in the Severny Kolchim meteorite first time. The data on the chemical composition of minerals and the trace element composition are given. It was verified that this meteorite is a nonequilibrium stone chondrite and belongs to the petrological type H3.Приведены современные данные о вещественном составе метеорита Северный Колчим, найденного на территории Пермского края в 1965 г. Установлено, что космическое вещество сложено форстеритом, энстатитом, диопсидом, плагиоклазами (олигоклазом, битовнитом), стеклом, хромитом, магнетитом, ильменитом, рутилом, металлами железа и никеля (камаситом, тэнитом и тетратэнитом), сульфидами (троилитом, пентландитом), хлорапатитом и мерриллитом. При этом диопсид, тетратэнит, хлорапатит и мерриллит определены в метеорите Северный Колчим впервые. Приведены данные о химическом составе минералов и микроэлементном составе породы. Сам метеорит является неравновесным каменным хондритом и относится к петрологическому типу H3

Mineralogy of the inclusions and age of zircon from granite basement of Verkhnerechensk area (Yamal peninsula)

The study of minerals-prisoners in accessory zircons is gradually evolving into an important geological-petrological task. Such a study can show not only the earliest mineral rock association, but also evaluate the “sealed” mineral paragenesis of zircon, which in turn indicates whether the accessory zircon is native to the host rock or redeposited (alien). In the present work, the mineralogy of zircon from granitoids of the crystalline basement of the Verkhnerechensk oil-exploration area (the southern part of the Yamal Peninsula, Western Siberia) has been studied. Granitoids are represented by homogeneous light gray fine-grained variety of biotite-quartz-feldspar composition and refer to monzoleucogranite, which formed over the sedimentary substrate, most likely under conditions of late orogenic surrounding. The time of magmatic intrusion and crystallization of granites according to the data of U-Pb dating of zircon (measurements carried out on the ion microprobe SHRIMP-II) is estimated as Late Permian (254.0 ± 3.0 (MSWD = 1.6) Ma). It is established that inclusions in zircon are represented by various minerals - fluorapatite, titanite, monazite-(Ce), albite, quartz, chamosite and calcite. The last two minerals, apparently, were not formed together with zircon, but are later secondary minerals formed as a result of the propylization of the rock. The time of secondary changes in the granitoid supposedly occurred in the Late Triassic, as one of the zircons gave a U-Pb dating of 204.7 ± 2.6 Ma. In general, accessory zircons and mineral inclusions contained in them belong to the “granite” association, and, apparently, are native to the enclosing monzoleucogranite

Detection of beryllium in oxides and silicates by electron-probe microanalysis

The author developed the technique of electron-probe microanalysis for quantitative determination of beryllium content, providing the example of studying natural minerals (aluminosilicates and oxides). This technique allowed to obtain a quantitative content of beryllium (in combination with other elements) in the emeralds of the Mariinsky beryllium deposit and in zonal mariinskite-chrysoberyl from the chromitites of the Bazhenov ophiolite complex. All analyzes of minerals were performed on a CAMECA SX 100 electron probe microanalyzer with five wave spectrometers (IGG UB RAS). The pressure in the sample chamber was 2 × 10–4 Pa, in the electron gun region – 4 × 10–6 Pa, in wave spectrometers – 7 Pa. Accelerating voltage was 10 kV, the current of absorbed electrons on the Faraday cylinder (beam current) was 100–150 nA. Diameter of the electron beam focused on the sample was 2 μm, the angle of x-ray extraction was 40°. The spectra were obtained on wave spectrometers with TAP crystal analyzers (2d = 25.745 Å), LPET (2d = 8.75 Å), LiF (2d = 4.0226 Å), and PC3 (2d = 211.4 Å, a specialized crystal for determining the content of beryllium and boron); the author carried out all the elements measurements along the Kα-lines. To determine position of the analytical peak and the background from two sides with the minimum possible spectral overlap, the author preliminarily recorded spectra on wave spectrometers. The obtained microprobe analyzes of minerals with quantitative determination of beryllium converge well with the available theoretical compositions of beryl and chrysoberyl, which indicates the high efficiency of the developed technique. By using this technique, we can relatively quickly and reliably determine the quantitative content of beryllium in natural silicates and oxides, which is an acute need for geological researchers studying the mineralogy of beryllium deposits

THE CHEMICAL COMPOSITION AND DATING OF ACCESSORY ZIRCON FROM GRANITIC PEGMATITES IN THE NORTH-EASTERN PART OF THE ADUISKY MASSIF

This work is made relevant by the necessity to improve chemical dating methods, when applied to high atomic and thorium zircons, for which isotopic methods cannot be used. The purpose of the work is to study the chemical composition of the accessory zircon (cyrtolite) from granitic pegmatites in the north-eastern part of the Aduisky massif (in the Middle Urals) and determine how best to date it. Methodology. The study comprised quantitative analysis of the chemical composition of the zircon by using a CAMECA SX 100 X-ray electron probe micro-analyser (with an electron beam diameter from 1 μm, BSE, SE, Cat, and determination of elements from beryllium to uranium). To measure the intensity of elements, we have selected the following analytical lines: Y Lα, Si Kα, Zr Lα, Hf Mα (analysing crystal TAP), U Mβ, Pb Mα, Ca Kα, Th Mα (analysing crystal PET), Yb Lα, Er Lα, Lu Lα (analysing crystal LiF). Calculation of the age of the zircon was carried out acя/cording to well-known, existing methods in addition to those developed by the authors. Results. According to the microprobe analysis, the impurity content of ThO2, UO2 and PbO in the zircon varied significantly, within the ranges 0.13 to 2.69, 1.59 to 15.42 and 0.05 to 0.57 wt.%, respectively. The dating calculation was carried out for each mineral (in which the analysis took place). Their age was found to be between 280 and 219 Ma. At the same time, the weighted mean was 254 ± 6 Ma (with the Mean Square of Weighted Deviates being 0.17) and the isochron showed 255 ± 7 Ma. The values of the ages found for the zircon from the pegmatites “Mys-2” agree with the isotopic data. The period of formation of the Aduisky granite massive has been estimated to be between 291 ± 8.0 Ma and 256 ± 0.6 Ma (according to zircon and monazite dating, respectively) or within the range 255 to 241 Ma (according to mica dating). Conclusion. We have studied the accessory zircon (cyrtolite) from granite pegmatites from the “Mys-2” vein, in the north-eastern part of the Aduisky massif. We have obtained the chemical composition and calculated the age to be 255 ± 7 Ma. Dating calculations show that veined pegmatites and host granites were formed almost simultaneously (at least, in this part of the Aduisky massif). This situation justifies microprobe dating of the U-Th zircon content because the minerals are usually in a metamict state and not suitable for accurate age determination

ABOUT FINDING NATIVE GOLD, SILVER, COPPER, LEAD, BISMUTH AND TUNGSTEN IN LIPOVKA PEGMATITES (MIDDLE URAL)

The relevance of the work is conditioned by the need for a more complete study of the mineralogy of rare-metal granite pegmatites of the Lipovskoye vein field. The purpose of the study is to describe the findings of native metals (gold, silver, copper, lead, bismuth and tungsten) in granite pegmatites of the Lipovskoye vein field. Research methodology. Detailed study of chemical composition, morphology and relationships of native metals with associated minerals. For this study we have chosen samples from the three types of granitic pegmatites – classical quartz-feldspar (mostly intragranitic), desilicated (apogranite plagioclasite) and contaminated lithium-bearing. Results. The paper describes native metals (gold, silver, copper, lead, bismuth and tungsten), which we have found in rare-metal pegmatites of the Lipovskoye vein field. The discovery of the native metals is the first on this facility. The microprobe analysis of such native metals as gold and silver showed the variability of their chemical composition from the type of pegmatite in which they are present. The formation of native lead should be logically linked to the destruction and recrystallization of high uranium thin rims of zircons. The formation of bismuth and tungsten may have occurred during recrystallization of accessory tantalumniobates. Summary. The finding of the native metals in granitic pegmatites is quite explainable. This is because these core rocks are formed in the post-magmatic stage of the silicate crystallization intrusions and they can contain typomorphic rocks for these metals. The absence of mineral concentrators (sulfides) in pegmatites clearly explains the small size and high dispersion of metals

The inclusion of grothite in the zircon from granitoids of the crystalline basement of the Southern Yamal Peninsula

Grothite – rare F-Al-rich type of titanite – has been found in accessory zircon from the granitoids of the pre-Jurassic basement of the Verkhnerechensky oil-gas area (in the southern part of the Yamal Peninsula) as a result of the study. Titanite forms rare inclusions (so-called minerals-prisoners) in the central parts of zircon crystals; in our sample of 35 individuals only two grains of titanite have been discovered. The measurement of the chemical composition of the mineral has been carried out on an electron-probe microanalyzer CAMECA SX 100, equipped with five wave spectrometers (IGG UrB RAS, Ekaterinburg). According to the microprobe analysis, the mineral has an unusual chemical composition, it shows the presence of significant concentrations of alumina (Al2O3 to 8.5 wt.%), rare earths elements (REE to 4.3 wt.%), and fluorine (F to 2 wt.%). This grothite is dramatically different in chemical composition from the accessory titanite of the matrix granitoid (monzoleicogranite), which is characterized by values close to the reference sphene. Overall, grothite is an intermediate connection between the two extreme members CaTiSiO4O (titanite) – CaAlSiO4F (synthesized Al-F-titanite), and the Verkhnerechensky mineral content of a hypothetical Al-F-titanite achieves a high level of 24–26 %. Unfortunately, grothite is crystallized in a wide range of temperatures and pressures which does not allow its use in thermodynamic reconstructions. The existence of grothite (or Al-F-titanite) is apparently determined not so much on the PT-conditions of rocks' formation, but most likely on the chemistry of the environment. So it is obvious that the Verkhnerechensky titanite was formed in the melt with an increased concentration of fluorine. It is the first record of grothite in the form of inclusions in accessory zircon

Xenoliths in the alkali basalts of Makhtesh Ramon of Desert Negev (Israel) as indicators of mantle metasomatosis and magma generation

Xenoliths in the Early Cretaceous alkali basalts of Makhtesh Ramon basin (southern Israel) are represented by essentially olivine rocks: dunite (usually including clinopyroxen) - 5% of the total amount, lherzolite - 21%, wehrlite - 28%, clinopyroxenite - 34%, gabbro - 12 %. According #Mg = Mg/(Mg + Fe), xenolith rocks form several discrete groups corresponding to the following values #Mg: >0.85 (dunite, lherzolite, some wehrlites), 0.85-0.75 (wehrlite, olivine clinopyroxenite), 0.75-0.65 (olivine clinopyroxenite, clinopyroxenite), 0.60-0.45 (gabbro). Primary mantle rocks are represented by lherzolite, other xenoliths are the products of metasomatism, which preceded and accompanied magma generation. The main minerals of ultramafic xenoliths- olivine slightly enriched by CaO, clinopyroxene with varying content of TiO2 (1-4%), Al2O3 (2-12%), Na2O (0.5-2%) and #Mg = 0.92-0.59, spinelids: chromite (Cr2O3 = 20-38%), Al spinel and titanomagnetite (TiO2 = 10-21%, Cr2O3 = 0.3-8%, Al2O3 = = 1.5-13%, MgO = 2-7%). Rich inTiO2, Al2O3 and Na2O clinopyroxene together with plagioclase, anorthoclase, kaersutite, rhenite, ilmenite, “orthopyroxene” and “feldspar” glass веlong to late ultramafic paragenesic associated with the process of partial melting. Orthopyroxene in ultramafic rocks is unstable and usually is replaced by minerals of the late paragenesis. Gabbroic xenoliths consist of low-titanium and low-aluminiferous clinopyroxene (#Mg = 0.66-0.56), orthopyroxene (#Mg ≈ 0.5), plagioklase An45-55, often with rims of anorthoclase, titanomagnetite of the same composition as in the ultramafic rocks, ilmenite. Xenoliths have the signs of partial melting and metasomatic transformation preсеding to melting. As a result the orthopyroxene from lherzolite is replaced by clinopyroxene. This leads to the width development of wehrlites and olivine clinopyroxenites. During metasomatosis the content of Mg, Cr and Ni falls while Ti, Fe, Al, Ca grows, as well as the content of large ion lithophile an high-strength elements providing increase of fertility of basalt magmatic source. Composition of the produced melt is close to basanite. The glass, cementing crystallization products, preserved in xenoliths, has a composition close to the orthopyroxene-feldspar mixtures. The mineral phases in such glass presented by clinopyroxene, kaersutite, rhenite, plagioclase, anorthoclase, nepheline, titanomagnetite and ilmenite

Bismuth-nickel mineralization in chromitites of Mariinskii deposit (Urals emerald mines)

The unusual Bi-Ni mineralization, represented by parkerite, millerite, bismutohauchecornite, bismuthinite, nickeline and, possibly nickel analogue of smythite (?), found in the metasomatically altered chromite rocks of the Mariinsky emerald-beryllium deposit is described. Chromitites with Bi-Ni mineralization are found in the mica complexes in direct connection with serpentinite bodies., Polished sections from the selected chromite samples were examined with the CAMECA SX 100 electron probe microanalyzer (IGG UrB RAS). In the study of sulfide and arsenide mineralization, the accelerating voltage was 15 kV, the electron beam current - 30 nA, the duration of intensity measured at a peak was 10 sec, at the background was 5 seconds, the diameter of the analysis point was 2 μ. For microprobe analyzes, the following standard samples were used: pure metals (Bi, Ni, Co), alloys (GaSb) and sulphides with arsenides (pyrrhotite, sphalerite, InAs). The formation of the studied unusual Bi-Ni mineralization in metasomatically altered micaceous chromite ores of the Ural Emerald Mines is directly related to the formation of rare-metal pegmatites of the nearby Aduiskiy granite massif. The acidic fluid flow associated with the introduction of pegmatite veins transformed not only the chromite bodies, but also the serpentinites, which containing them, with the formation of talc-carbonate and talc-anthophyllite rocks, mica rocks and other high-temperature apohyperbasite metasomatites. This fluid, enriched in Be and F, which superimposed on the chromite matrix, that formed such unusual metasomatic mineral paragenesis as chromite, muscovite-aluminoseladonite, fluorophlogopite, tourmaline (fluorodravit-dravite), mariniskite-chrysoberyl, fluorapatite, eskolaite, zircon, sulphide, chromferide and native metals. The source of bismuth certainly was acidic fluids, nickel is contained in the hyperbasites themselves, sulfur and arsenic could be from hyperbasitic intrusions (they often contain impregnations of millerite, hizlewoodite and mauherite) and from granitoid ones. Such mineralization is typical for sulfide copper-nickel ores and hydrothermal veins of a five-element formation, in ophiolite bodies and associated chromite rocks such mineral association was not observed. The discovery of bismutohauchecornite is the first, and parkerite - the third in the Urals. Formation of Bi-Ni-mineralization took place in the temperature range from 300oC to 200oC