The article describes the results of studies of crude oils microelements composition in Chekan, Tumutuk and Tumutuk-Chekan satellite deposits of Romashkinskoye oil field. It was found that mentioned deposits belong to the group enriched in microelements. Median content of trace element in different producing horizons differ markedly. Investigated crude oils are characterized by very high V/Cu and V/Pb, which may indicate a slight manifestation of catagenetic changes. However such conclusion contraries to the rather low values of V/Fe which imply a significant elaborateness of naphthides. Median values of Ni/Cu (from 146 to ~330) suggest the absence of significant migration of naphthides as well as a sufficiently low level of their catagenetic transformations. It was established that on the diagram Gd N /Yb N -Eu/Eu* majority of data points of crude oil are localized in the field typical of fine-grained clastic formations, in which a significant or dominant role belongs to the products of erosion of primitive Archean substrates. The median value of Pt/Pd in the whole oils of Romashkinskoye field is ~60. Crude oils of Chekan, Tumutuk and Tumutuk-Chekan deposits according to the ratio of platinum group elements belong to the ruthenium-rhodium type.
This publication provides an overview of the rare earth elements systematics in Pre-Ordovician phosphorites from various regions of the world. Based on the analysis of significant data bank it shows that currently there are no universal parameters, guided by which, could be more or less clearly to judge sedimentary and diagenetic environments of formation of phosphate rock in the first place - redox environments. Any reconstruction of this plan require a careful analysis of how the geological facts, and extensive and diverse geochemical information.
The Lower Сarboniferous volcanogenic-terrigenous strata on the eastern slope of the Middle and Northern Urals have been studied. It is shown that these formations are confined to the zones of regional strikeslips and were formed in the conditions of transtension. The geochemical parameters of volcanites show similarities with igneous rocks of both suprasubduction and intraplate environments, which does not contradict the ideas about their formation in the rear of the active continental margin.
The article analyzes the adequacy of compliance on paleogeodynamic nature of Upper Precambrian sedimentary associations - Bashkir meganticlinorium, Kama-Belaya aulacogene and Uchur-Maya region, received by geological methods and by using discriminant diagrams ?. Meynard et al., B.R. Roser and R. Korsch, and S.P. Verma and ?.S. Armstrong-Altrin. It is shown that among them there are notable differences.
Рассмотрены результаты анализа геохимических особенностей (модули Страхова и Бострёма, нормированные на хондрит и NASC спектры распределения редкоземельных элементов (РЗЭ), ЛРЗЭ/ТРЗЭNASC, Eu/Eu*NASC, Ce/Ce*NASC, Zr/Hf, Ce/La и др.) глинистых сланцев серебрянской и сылвицкой серий венда Кваркушско-Каменногорского антиклинория. Установлено, что глинистые сланцы и аргиллиты танинской, гаревской, койвинской и бутонской свит серебрянской серии, а также старопечнинской, перевалокской и усть-сылвицкой свит сылвицкой серии не содержат в своем составе эксгалятивного материала и принадлежат к «обычным» терригенным образованиям. В разрезах керносской свиты представлены глинистые сланцы трех разновидностей: 1) обычные терригенные образования; 2) породы с примесью эксгаляционного материал (в нормированных на NASC спектрах распределения РЗЭ в них преобладают тяжелые лантаноиды и наблюдается отрицательная Ce/Ce*NASC аномалия); 3) породы с существенной долей продуктов размыва основных магматических образований (индикатор - положительная Eu/Eu*NASC аномалия). Присутствие последних только в составе керносской свиты указывает на то, что в раннем венде на рассматриваемой нами территории существовал только один крупный эпизод основного магматизма, оказавший заметное влияние на процессы накопления субсинхронных ему осадочных образований. Аргиллиты чернокаменской свиты, исходя из типичных для них значний титанового и алюминиевого модулей, также в подавляющем большинстве не содержат прмеси гидротермального материала. Tолько в двух образцах данного уровня отчетливо выражна отрицательная Ce/Ce*NASC аномалия, а тяжелые РЗЭ преобладают над легкими, что позвояет предполагать присутствие в них эксгалятивных компонентов. В то же время значения отншений Ce/La и Zr/Hf и в этих образцах сопоставимы с типичными для обычных терригенных отложений. Высказано предположение, что накопление осадочных последовательностей раннего венда Кваркушско-Каменногорского антиклинория происходило в морских обстановках, сходных по ряду параметров с обстановками эмбриональных стадий раскрытия океанических бассейнов. Общий объем поступавших в бассейн гидротермальных компонентов был, по всей видимости, весьма незначительным и, кроме того, подвергался интенсивному разубоживанию терригенным материалом.
Lower Triassic sandstones in the southern part of Belsky depression (Pre-Uralian foredeep) contain detrital zircons with concordant U-Pb isotopic ages ranging from Neoarchean to the boundary of the Carboniferous and Permian. The distribution of rare and trace elements in zircons suggests that the majority of them fall into the Triassic sandstones due to erosion of basic rocks (or, taking into account the possibility of multiple recycling, most of them are crystallized in the rocks of basic composition). These data indicate a much wider age range of rocks in provenances in the Early Triassic, than it follows from petrographic observations. The micropetrografic data testify that the magmatic complexes which are distributed at present in Sakmara area were the sources of zircons with the Early and Middle Paleozoic datings. Detrital zircons with the Proterozoic and Neoarchean ages are likely redeposited from Riphean-Vendian Ural-Tau zone, where they were brought due to erosion of East European platform base. A small proportion of crystals with Late Paleozoic ages taking into account the geochemical and petrographic data, permits suggest that granite massifs of the Main Granitic axis of the Urals, during the formation of Pre-Uralian molasses has not been involved into erosion. Perhaps they have not yet been withdrawn to the surface, or were placed to the East line of the watershed. At the same time, a significant number of zircons with Precambrian age indicates that the Ural-Tau metamorphic formations were in the erosion zone. Consequently, the orogen watershed at that time was to the east of the zone. This is also evidenced by the presence in the Lower Triassic sandstones few crystals of zircon with Carboniferous age, the source of which could be to the west of modern Magnitogorsk megazone. On the basis of these data we suggest that the forming of coarse clastic formations of the final stage of orogeny in the southern Urals occurred mainly due to erosion of sedimentary, igneous and metamorphic complexes from modern western slope of the axial zone of the Urals.
Main lithogeochemical characteristics of Upper Precambrian sandstones from Kamsk-Belsk aulacogen and Shkapovo-Shikhan Depression are discussed. It is established that among these sandstones arkoses, subarkoses, litharenites and sublitharenites are predominated. Majority of these sandstones are first-cycle rocks and were formed due to direct erosion of crystalline basement of East European Platform. Lithogeochemical peculiarities of Riphean and Vendian sandstones indicate that these rocks were formed in passive and active continental margin conditions.
