Background. Changes in the composition of clastic material reflect changes in both the paleogeographic environment and clast transport paths. In turn, this indicates changes in the conditions of regional development. The research relevance is determined by multidirectionality of Earth sciences, such as paleogeography, neotectonics, stratigraphy, hydrology, relief formation, etc.Aim. To establish the genesis of river valleys and bench complexes in the northern areas of the Irkutsk Oblast.Materials and methods. The clastic material of the Upper Paleozoic-Mesozoic sedimentary deposits in the northern areas of the Irkutsk Oblast was studied. The work is aimed at reconstructing the contours of sedimentary paleobasins of the Carboniferous, Permian, and Jurassic ages and the conditions of sedimentary strata formation. The results of site investigation and drilling works carried out in the 1960s and 1970s were interpreted from the standpoint of modern information.Results. The nature of river network formation and clast transport processes was determined. The direction and sources of clast transport were identified, along with the conditions of re-deposition of clastic material at different stages of the geological development of the area under study.Conclusions. The modern river network in the northern areas of the Irkutsk Oblast is based on the valleys formed under the action of catastrophic glacial water discharge flows.

The name of Anatoly Mikhailovich Sagalevich – Hero of the Russian Federation (2008), Doctor of Technical Sciences (1985), Professor, Chief pilot of the Deep-sea Manned Submersibles “Pisces” and “MIR” – is forever inscribed in the annals of the history of world and domestic oceanology. The State Darwin Museum also wants to express its gratitude to A. M. Sagalevich. With this article we want to thank A. M. Sagalevich for his cooperation and kind attitude towards the Museum, and also congratulate Anatoly Mikhailovich on his Anniversary!

To provide new insights into evolution of the primary ultramafic alkaline melts, we present an investigation of the primary and secondary melt inclusions within olivine macrocrysts and groundmass minerals from the Victoria monticellite-nepheline damtjernite, Anabar diamondiferous province, Siberia craton. The primary melt inclusions within olivine macrocrysts shown that initial damtjernite melts were K–Na bearing carbonate-silicate melts by composition whereas the K and Na associated within only silicate phases like that phlogopite, nepheline, kalsilite. That distinguishes these inclusions from similar inclusions in olivines from aillikites and kimberlites and emphasizes a more alkaline character of the damtjernitic parental melts. Based on the composition of melt inclusions within spinel and monticellite from magmaclastic groundmass, under the further evolution of the damtjernitic melts, K and Na are not only included in silicate daughter phases, but they can also form alkaline phosphates, carbonates, sulfates, and halides. That led to form the alkaline carbonate and saline sulfate-phosphate-chloride-carbonate liquids. This composition of the evolved ultramafic alkaline melt is common for melt inclusions within different minerals from aillikite, kimberlite and some carbonatites highlighted uniform mechanism of evolution of alkaline-ultramafic melts. Further accumulation of the fluid phase led to its reaction interaction with olivine with the formation of monticellite and degassing processes.

The paper presents new isotopic U–Pb zircon data (LA–ICP–MS method) on the intrusive rocks from the Chinorsai massif, which is spatially and probably genetically related to the large Jilau tungsten-gold deposit. This deposit, together with the other large Au deposits (Muruntau, Zarmitan, Kumtor, etc.) is part of the largest Au (Au–W) metallogenic belt of Tien Shan. The deposit is represented by small zones of scheelite-bearing skarn and later (overprinting) large stockwork of veins and veinlets with scheelite-gold mineralization that occurs within and near the intrusion. The concordant isotopic zircon U-Pb data (301.0 ± 2.6 Ma; MSWD = 2.6) are older than the isotopic zircon U–Pb data previously reported (about 288 Ma). This indicates a substantial extent of the magma emplacement and crystallization process that probably corresponded to several intrusive events or phases, which is a prerequisite for the formation of associated intrusive-related Au deposits. Also, the isotopic age determined highlights the earlier formation of gold-polymetallic-tungsten deposits as compared to Mo–W and Sn-W deposits in the region, which are related to the later Early Permian intrusions. In addition, zircon xenocrysts with much older age (from ca. 970 Ma to ca. 2200 Ma) have been identified; they probably represent the age of the orogenic basement including that of the basement terranes of the Tarim and Karakum cratons.

The paper presents the first data of the isotopic zircon U–Pb study (LA–ICP–MS method) on the granodiorite-granite from the Sardara (Sarykty) pluton in the district of the giant Muruntau Au deposit in the Western Tien Shan (Uzbekistan). In a single sample, three age groups of zircon crystals identified, with their concordant U–Pb age being 322.0 ± 3.7 Ma (MSWD = 3.1, 4 zircon grains), 301.6 ± 2.1 Ma (MSWD = 0.17, 11 zircon grains), and 289.1 ± 4.9 Ma (MSWD = 0.98, 2 zircon grains), respectively. The scatter of the isotope age data obtained can be interpreted using the model of subsequent crystallization of various zircon generations in variably-deep magmatic batches, followed by zircon capturing during the magma differentiation and crystallization. Notable is a quite close coincidence of the two (the younger) age intervals to the concordant U–Pb zircon ages, which were published before for the granitoid rocks found directly at the Muruntau deposit. The latter thus can represent the dike “splits” occurred at the respective stages of the magma evolution (progressing differentiation) in the deeper batches of the granitoid magma, with its larger intrusions represented by the Sardara (Sarykty) and other plutons outcropping at some distance from the deposit. Overall, the older isotopic U–Pb zircon data of the Sardara (Sarykty) pluton (in the order of 322 Ма and 302 Ма, respectively) correspond closer to the subduction event, whereas the younger U–Pb zircon data (in the order of 289.5 Ma) are quite relevant to the post-collisional stage occurred in the region. Therefore, the initiation and initial development of the magma batches in the Muruntau deposit district could occur in the subduction environment but the final granitoid magma differentiation and crystallization were completed already at the post-collisional stage.

The results of studying primary and secondary melt inclusions within olivine macrocrysts and groundmass minerals from monticellite–nepheline damtjernites of the Victoria pipe (Anabar diamondiferous province, Siberia craton) are presented. They were used to reconstruct the evolution of the ultramafic alkaline melt during the formation of the pipe. It is shown that the primary damtjernite melts were K–Na bearing carbonate–silicate in composition. Here, K and Na in the primary melt inclusions within olivine macrocrysts enter the composition of essentially silicate daughter phases. According to this, they are different in composition from similar inclusions in olivine from aillikites and kimberlites and emphasize the more alkaline character of the damtjernitic parental melts. At the subsequent stages of melt evolution during pipe formation, Na and K in the studied inclusions not only enter silicate daughter phases but can also form alkaline phosphates, carbonates, sulfates, and halides. This leads to the formation of alkaline carbonate and saline sulfate–phosphate–chloride–carbonate solutions. According to this, the evolution of the damtjernitic melt is similar to that of aillikite and carbonatite melts and can serve as a uniform mechanism of evolution of alkaline–ultramafic melts. The further reactionary interaction of the fluid phase with olivine led to the formation of monticellite and processes of degassing.

The LA–ICP–MS U–Pb age was determined for the first time for zircon from granodiorites–granites of the Sardara (Sarykty) intrusive in area of the giant Muruntau gold deposit in Western Tien Shan (Uzbekistan). Three crystal groups were identified in a combined sample: their concordant U–Pb age is 322.0 ± 3.7 (four grains), 301.6 ± 2.1 (11 grains), and 289.5 ± 4.9 Ma (two grains) (MSWD = 3.1, 0.17, and 0.98, respectively). The dispersion of the isotopic age can be explained using a model of a successive crystallization of different zircon generations in magmatic chambers at various depths and their further entrapment upon differentiation/crystallization of new magma portions. The similarity of two (youngest) age intervals with concordant U–Pb ages previously published for zircons of granitoid rocks directly at the Muruntau deposit is noteworthy. The latter ages could thus represent dike branching at the corresponding stages of evolution (progressive differentiation) of deeper sources of granitoid magma, the larger intrusions of which include Sardara (Sarykty) and other plutons exposed at some distance from the deposit. The older U–Pb isotopic ages of zircons from granitoids of the Sardara (Sarykty) pluton (~322 and 302 Ma) generally correspond to the subduction stage, whereas the youngest zircons (~289.5 Ma) correspond to the postcollision stage of the region. The origination and initial evolution of the magmatic sources in area of the Muruntau deposit could thus occur under subduction conditions; however, the final differentiation and crystallization of granitoid magma has finished at the postcollision stage.

The paper shows the genetic diversity of the structure and mineral composition of the ores of the Gorevsky Pb-Zn deposit, reveals the main signs of synchronous deposition of ore matter from near-bottom ore-bearing solutions associated with sedimentation processes in the sedimentary basin, considers textural and structural features and mineral associations of ores accompanying various metamorphism processes and postmagmatic processes. A model of the initially primary sedimentary-diagenetic origin of the ores of the Gorevsky Pb-Zn deposit under the conditions of catagenesis and the important role of the processes of redistribution and redeposition of the ore substance by interstitial solutions of the primary ore material is detailed. The study is based on the method of detailed study of the textural and structural features of ores in polished and polished samples. microstructural and mineral features and composition of ore and non-metallic minerals using modern methods of studying the substance. The bulk of the ores of the Gorevsky deposit demonstrate the textural and structural features of synsedimentary deposits, which are simultaneous with the host carbonaceous-micaceous-siliceous-carbonate rocks and retain these main structural features both at the macro and micro levels. The results obtained are compared and analyzed in comparison with other polymetallic deposits in Russia and in other regions of the world