The northwestern part of the Sevan–Shirak structural formation zone of the Lesser Caucasus contains ultra-high-K siliceous ignimbrites dating back to the Late Eocene–start of Early Oligocene (?), which associate with high-K volcanics of the calc-alkaline and shoshonite series. During Eocene–Oligocene time the Sevan–Shirak zone was an ensialic island arc with a Hercynian metamorphic basement. The formation of high-K and especially ultra-high-K rocks was due to the effects of mantle fluids on the continental crust.

The structure features of lavas and ignimbrites indicate a high role of volatiles in their formation and a rapid release of volatiles from cooling melt. This poses a high risk for the environment. For this reason it is important to study the structures of resulting volcanic rocks for predicting the degree of hazard in the event of a future resumption of volcanic activity.

Research subject. The orogenic marginal-continental and collisional volcanic-plutonic belts, and the zonality of magmatism and metallogeny within them, as well as the relationship of endogenous metallogeny with magmatic zonality and geodynamics of belt formation. Materials and methods include the long-term studies of the Devonian and Upper-Paleozoic belts of Kazakhstan and the Cretaceous-Paleogenic belt of Sikhote-Alin; an analysis of the alterations in the material parameters of magmatites; the identification of the front and rear parts of the belts and the arrangement features of metallogenic zones within their limits; and the data on other belts of the world. Results. For the marginal continental belts, an asymmetric change of the tholeiitic and low-potassium magmatites of the calcareous-alkaline petrochemical series of the frontal zone of the belt into the magmatites of the high-potassium branch of the calcareous-alkaline and shoshonite series of the rear zone (Devonian and Upper Paleozoic belts of Kazakhstan) has been established. In the same direction, the elemental, as well as the genetic type of deposits changes: pyrite copper-polymetallic frontal zones are replaced by molybdenum-copper-porphyry rear zones (near the border with the frontal zone) and then by rare metal ones. This is also characteristic of the Andean and Okhotsk-Chukchi belts. The collision belts are characterised by symmetrical zonality with a change from rare metal deposits in the centre to copper-polymetallic deposits at the edges (Mongolia). In some cases (Sikhote-Alin and Japan), the continuity of the marginal-continental belt is disrupted as a result of the mantle diapir (or plume), symmetrical magmatic and metallogenic zonality occurs with the change of polymetallic manifestations (near the ocean–continent boundary) to rare-metal ones in the distance. Conclusions. The change in the material parameters of the magmatites of the marginal-continental belts correlates with the removal of their ranges from the ocean–continent transition zone to the interior of the latter. In this case, copper-polymetallic pyrite ore formations are replaced by copperporphyry and then by rare metal ones in this direction. This is due to subduction processes. The collision situation is characterised by a symmetrical zonality of material magmatic parameters with respect to the crowding zone and a symmetrical arrangement of metallogenic zones with a change of rare metal deposits in the crowding zone to copper and polymetallic along the frame. These data are important for metallogenic prediction, as well as for palaeotectonic reconstructions.

Textural features of lava and ignimbrite formations indicate the high role of volatile components in their formation and the rapid release of volatile from the solidifying melt. This creates a high level of danger to the environment. Therefore, it is important to study the textures of the formed volcanites to predict the degree of danger in the event of a possible resumption of magmatic activity.

We compare the Late Cenozoic ignimbrites sampled in the Lesser Caucasus (Armenia) and in the Greater Caucasus (the Elbrus, Lower Chegem and Upper Chegem volcanic massifs in the Northern Caucasus). The Armenian ignimbrites contain 60–67 SiO2 wt %, while those sampled in the Northern Caucasus have 67–76 SiO2 wt %. The Armenian ignimbrites are moderately alkaline and alkaline rocks, while those from the Northern Caucasus are moderately alkaline and normal alkaline ones. The former contain more potassium, they belong to the high K branch of the calc-alkaline series, partly also to the shoshonite petrochemical series, while the northern Caucasian ignimbrites belong to the high K branch of the calc-alkaline petrochemical series, occurring near its boundary with the low K branch. These ignimbrites also differ in the concentrations of trace elements and REEs, and in isotope marks. The above differences between the ignimbrites sampled in Armenia and in the Northern Caucasus are also controlled by different styles of tectono-magmatic evolution in the respective regions, hence by different conditions of their lithospheres.

Research subject. A meridional Tastau rift structure located in the Famenian sub-latitude rift system of Central Kazakhstan was investigated, including the specific features of its constituent sediments and volcanism, as well as the stages of its development.Materials and methods. The study was based on data collected during a long period of fieldwork, including a detailed study of the sequence of sedimentation processes, large-scale geocarting, sampling for various types of precision analyses.Results. The typomorphic features of the main rock types were determined. It was shown that basaltoid rocks occurred in the form of pillow structures with a hyaloclastite matrix between the pillows. Siliceous shales are saturated with thin ash silicic acid material. A geological scheme of the Tastau structure and its specific features was presented in a series of cross-sections. The developmental stages of this structure were established. The structure was referred to the rift type.Conclusion. The material and structural features of the investigated Tastau section are shown to be typical of the entire rift system of Central Kazakhstan. The pre-rift (Frasnian) stage is characterized by continental volcanism in the form of highpotassium and ultra-potassium rhyolite ignimbrites composing an encialic island-arc structure. These volcanites belong to the shoshonite and high-potassium lime-alkaline petrochemical series. The rift stage itself began in the Early Famenian age with the formation of a system of narrow deep troughs, into which the sea from the neighbouring Zhongaro-Balkhash sea region started to ingress. The conglomerates are characterized by thin flattened isometric pebbles, whose well-polished surface is similar to that of pebbles in modern sea beaches. The sandstones exhibit a high level of lamination and are characterized by poorly pelletized clastic material. The clastic material is represented by the underlying Frasnian rhyolitic ignimbrites carried in from the sides of the trough. The mature rift stage is characterized by the accumulation (under marine conditions) of pillow basalts and hyaloclastites and thin-layered silicite-clay-carbonate shales with abundant ash. The postrift stage is responsible for the formation of layered limestones of the Lower Tournaisian, developed also widely beyond the specified rift trough.

Гранитоиды КМВ представлены сиенитграносиенитщелочногранитной ассоциацией. Давший их расплав сформировался в две стадии. Изначально он был насыщен летучими компонентами преимуще ственно углекислого состава и хлором. Это способствовало его быстрому подъему к поверхности земли и расслоению с образованием полосчатости. Первичные отношения изотопов Sr и Nd, обильные и разнообраз ные ксенолиты, цирконы с более древними ядрами, нарушения изотопных равновесий Ar и Sr свидетельству ют, что расплав явился результатом преобразования разнородного исходного материала, главным образом корового происхождения. В то же время близость изотопных отношений Sr у разных типов гранитоидов, близость состава разноокрашенных полосок, идентичность содержания и характера распределения в них РЗЭ говорят о высокой степени гомогенезированности расплава. Кристаллизация его начиналась с выделения короткопризматических цирконов, апатита, сфена, затем пироксенов при температурах 1 280 0 С 10 0 С и давлении более 5 кбар. Позднее образовывались длиннопризматические цирконы, плагиоклаз, амфибол, био тит при температуре 1010 950 0 С и давлении 5 3 кбар. Взаимодействие расплава с породами эвапаритовой толщи юры миоцена при движении к поверхности земли привело к его обогащению F, B, S, Sr, Ba. Дальнейший подъем магмы к поверхности земли сопровождался интенсивным катаклазом вкрапленников, неравномерным распределением в расплаве флюида, который обогащал отдельные полосы и струи. В менее обогащенных флюидом (темноокрашеных) полосках деформация вкрапленников более интенсивная, чем в обогащенных (светлоокрашенных) полосках. Температура гомогенизации РВ в лейстах плагиоклаза темноокрашенных по лосок колеблется от 900 0 С до 850 0 С, а светлоокрашенных полосок в пределах 880 820 0 С. Основная масса полосок состоит из одних и тех же минералов (полевые шпаты, пироксен, амфибол, биотит, кварц, магне тит), но в обогащенных флюидом (светлоокрашенных) полосках больше плагиоклаза и кварца, с чем и связана их более светлая окраска. В матриксе обедненных флюидом (темноокрашенных) полосок больше темноцвет ных минералов, что придает им более темную окраску. CMWgranitoids are represented by syenite granosyenite alkaline granitic association. There are two stages in the formation of the melt that created them. Initially it was saturated with volatile, predominantly carbonic, and chlorine. This contributed to its rapid rise to the surface of the earth and delamination with the formation of banality. Primary ratios of Sr and Nd isotopes, abundant and diverse xenoliths, zircons containing more ancient nuclei, violations of the Ar and Sr isotopic equilibria indicate that the melt was the result of a deep transformation of a heterogeneous starting material, mainly of crustal origin. At the same time, the proximity of the Sr isotopic ratios in different types of granitoids, the proximity of the composition of differently colored stripes, the identity of the content and distribution pattern of REEs indicate a high degree of homogenesis of the melt. Its crystallization began with the separation of shortprismatic zircons, apatite, sphene, then pyroxenes at temperatures of 1280 C 10 C and pressures of more than 5 kbar. The residual melt was saturated with volatile and REE. Later, longprismatic zircons, plagioclase, amphibole, biotite were formed at a temperature of 1010 950 0 C and a pressure of 5 3 kbar. The interaction of the melt with the rocks of the Jurassic Miocene evaparite strata when moving to the surface of the earth led to its enrichment by xenoliths of varying degrees of processing and borrowing from the host rocks F, B, S, Sr, Ba. The further rise of magma to the earths surface was accompanied by an intense cataclase of released phenocrysts, an uneven distribution of uid in the melt, which enriched individual bands or streams. In the less enriched (darkcolored) strips of uid, the phenocrysts are more intense than in the enriched (lightcolored) strips.The temperature of homogenization of RV in the sheets of plagioclase of darkcolored strips varies from 900 0 С to 850 0 С, and lightcolored strips within 880 820 0 С. The main mass of strips of different colors consists of the same minerals (feldspars, pyroxene, amphibole, biotite, quartz, magnetite), but in the (lightcolored) strips enriched with uid, more plagioclase and quartz are found, with which they are lighter in color. In the uiddepleted (dark colored) strip, there are more darkcolored minerals, which gives it a darker color.

Рассмотрены и обобщены геологические материалы, полученные к настоящему времени по территории Казахстана и Тянь-Шаня. На этой основе показаны главные особенности строения выделяемых там разнотипных и разновозрастных палеоструктур – континентальных массивов, бассейнов с океанической корой, островных дуг, краевых вулкано-плутонических поясов, а также зон трансформных разломов. Выяснены характер и возможные причины их эволюции и преобразований, отразившихся на формировании и развитии мозаичного структурного ансамбля на окраине существовавшего с неопротерозоя Палеоазиатского океана. Выделены и проанализированы основные этапы геодинамических изменений в истории палеозоид Казахстана и Тянь-Шаня и предложена модель вероятного хода тектонических событий в регионе. Модель проиллюстрирована с использованием опубликованных палеомагнитных данных, серией палеотектонических реконструкций, построенных для интервалов времени 950–900, 850–800, 750–700, 650–630, 570–550, 530–515, 500–470, 460–440 и 390–380 млн лет.

Geological information on Kazakhstan and the Tien Shan obtained up to the present time has been considered and integrated in order to demonstrate the main features of continental massifs, basins with oceanic crust, island arcs, marginal volcanic-plutonic belts, and transform fault zones differing in type and age. We ascertained the character and probable causes of their evolution and transformations resulting in the origination and development of mosaic structural assembly at margin of the Paleoasian ocean that existed from Neoproterozoic. The main stages of the geodynamic history of Paleozoides in Kazakhstan and Tien Shan are characterized, and a model of the probable course of regional tectonic events has been proposed. This model is illustrated by published paleomagnetic data and a series of paleotectonic reconstructions for time intervals 950–900, 850–800, 750–700, 650–630, 570–550, 530–515, 500–470, 460–440, and 390–380 Ma.

The Petrographic Code of Russia is a body of major rules and recommendations that establish a unified and standardized petrographic terminology and nomenclature for endogenic and impact rocks and the taxonomy of petrographic units. The single system of terms and concepts underlying the petrographic code shall be obligatory for all departments and organizations in conducting geological operations in the territory of Russia. This system shall be applied when state geological maps of various scales and series legends for them are prepared and when maps are created under international projects. The structure of the second and third editions of the Code was modified compared with that of the first edition, and this edition includes new appendices. With regard for new standards and requirement of geological practice, additional sections concerning sedimentary-volcanic, migmatite, and some other rocks were introduced into the Code. The sections devoted to metamorphic and metasomatic rocks were revised and amended, and arguments were proposed justifying the recognition (as an individual genetic type) of fluid-explosion rocks, which can be accompanied by ore mineralization of various types. Most definitions are revised, many entries are reworked and or abridged, and new entries are added. The revised wording of the Code involves recommendations from the International Commission on Systematics in Petrology of the International Unit of Geological Sciences.

Correct diagnostics of rocks requires the 3D study of the structure of their basis, since a splinter-like basis structure may occur only in a single observed section of a specimen of a rock that has a more complex structure of the plane-parallel or linear type. Ignimbrites differ from lavas with a similar silica content primarily in the presence of fiamme, a smooth outline of the phenocrysts, and their constant cataclasis; they differ from pyroclastic lavas by having broken-down phenocrysts enclosed in an undisturbed groundmass with smooth and undulating outlines of the volcanic particles and by the presence of fiamme showing a regular pattern of evolving composition. The study of the morphological and material features of all components of ignimbrites in their relationships with the silica content of the melt and the attitude of the ignimbrite geologic bodies they compose corroborates the hypothesis that ignimbrites are generated by the complex evolution of a gas-saturated melt of the emulsified type rather than by baking (welding) of ash-fall particles.

Ignimbrites in the Devonian and Late Paleozoic volcanic belts in central Kazakhstan were produced in various geotectonic environments and are diverse in composition. The bulk composition of the Devonian ignimbrites is rhyolitic. The Eifelian rocks of the Chingiz island-arc system belong to the calc-alkaline series and are enriched in Zr, Nb, Y, and REE (predominantly LREE). The Frasnian ignimbrites that were formed in unusual island arcs of the Mediterranean type are ultrapotassic. Compared to the Eifelian ignimbrites, they bear lower concentrations of Zr, Nb, Y, and REE but are richer in Rb and Ba. Both rock varieties show clearly pronounced Eu minima and Ce anomalies. The Carboniferous and Permian ignimbrites were generated within a volcanic belt in a continental margin. The Carboniferous ignimbrites are mostly of dacite-rhyolite and sometimes of dacitic andesite composition. Compared to the Devonian ignimbrites, they are depleted in Zr, Nb, and Y at higher concentrations of Ba and low REE sums, which are notably dominated by LREE; their Eu minima are small, and they have no Ce anomalies. The Permian ignimbrites are predominantly of rhyolite composition. The Early Permian rocks have REE sums close to those in the Carboniferous rocks, but the former have clearly pronounced Eu minima and Ce anomalies. The Late Permian ignimbrites have total REE concentrations close to those in the Devonian ignimbrites, but the former are strongly enriched in LREE and have prominent Eu minima and Ce anomalies. The major-and trace-element composition of fiamme in all ignimbrite varieties varies depending on the relative age of the fiamme. The REE patterns of the fiamme differ from massif to massif, but their systematic changes from older to younger fiamme are similar. Along with the identity of the isotopic characteristics of whole-rock ignimbrite samples and fiamme of different ages in them, this testifies that the ignimbrites were formed not via the mixing of various melts but by the systematic evolution of a parental melts, which were different for different massifs.

First U-Pb zircon isotopic dates were obtained for rocks from the Devonian volcanic belt in Kazakhstan. The granodiorites of the Zhabden Massif (Karamendinskii Complex) were dated at 391 ± 1 Ma. The Sm-Nd isotopic system of a whole-rock granodiorite sample (ɛNd = 2.5) suggests a high percentage of mantle material in the initial granite melt, which is in good agreement with known data on granitoids in neighboring territories in Kazakhstan. With regard for the isotopic dates obtained for the granodiorites, the material of their source was separated from the mantle at 946 Ma.