The paper presents the results of the petrographic and geochemical studies of igneous rocks of the Medvedev and Taezhniy massifs, including their first absolute dating. The massifs are located in central Nimnyr block of the n shield within the Leglier ore cluster of the Evotinskiy ore district (Southeast Russia, Aldan Shield). For the first time, the three-phase structure of the Medvedev massif has been defined, as observed in our expedition and petrographic studies. Rocks from the three phases of the Medvedev massif include quartz syenites, syenites, and monzonites, and rocks from the two phases of the Taezhniy massif include quartz monzonites and syenites. Geochemically, the rocks are close to volcanic island arcs, the formation of which was related by subducted oceanic crust of the Mongol–Okhotsk Ocean. The defined duality of the geochemical compositions of the igneous rocks of the massifs may be due to the presence of both mantle and crustal sources; however, it is most likely that these rocks resulted from the melting of a mixed mantle source or the latter was contaminated by the crust with further differentiation of melts in intermediate crust chambers. Additionally, geochemical characteristics suggest that the analyzed rocks are close to latite and shoshonite derivatives and can be considered as part of the monzonite–syenite formation type. The first identified periods of formation of igneous rocks in the Medvedev massif are 122.0–118.0 Ma and Taezhniy 117.5–114.5 Ma, which correspond to the Early Cretaceous (Aptian).

In the Verkhne-Timptonskiy gold ore district, located where the Stanovoy and Aldan blocks intersect (Aldan-Stanovoy shield), substantial placer gold deposits have been found in the Gonam, Timpton, and Iengra rivers. The exploration of certain deposits in this area began at the end of the 19th century. Despite exploration efforts conducted in the second half of the 20th century, only minor gold ore findings were made, with uncertain links to greenstones and igneous formations from various periods. After conducting a thorough analysis of both existing and new data on the geology and metallogeny of the Verkhne-Timptonskiy gold ore district, we have concluded that gold occurrences in diaphthorites of the Kholodnikan belt display characteristic features of orogenic-type gold deposits. These features include disseminated pyrite and veinlet mineralization containing iron (Fe), lead (Pb), zinc (Zn), copper (Cu) sulfides, and sulfosalts. The near-ore alterations are represented by silicification, sericitization, carbonatization, and beresitization, characteristic of mesothermal fluid systems. Moreover, we identified common features of the geological structure and metallogeny of the Verkhne-Timptonskiy gold ore district and the Jiaodong province of the North China Craton. Thus, gold mineralization in the Verkhne-Timptonskiy gold ore district and the Jiaodong province is spatially associated with suture zones. In the Verkhne-Timptonskiy gold ore district, the Amga zone of tectonic melange in the Paleoproterozoic era was one of the regions where cratonization of blocks of the Earth’s crust occurred. Later, it became a zone of permeability and concentration of tectonothermal and metallogenic events of various ages. The results obtained will help assess the metallogenic potential of the Verkhne-Timptonskiy district and the Aldan-Stanovoy shield as a whole. They make it possible to increase the efficiency of search operations and focus on localizing research objects.

The petrographic and geochemical characteristics of the Mesozoic igneous rocks of the Mikhailovsky massif, including the sills and dikes of the Evotinsky ore district located in the central part of the Nimnyr terrane of the Aldan-Stanovoy shield, were examined. This study revealed for the first time that the Mikhailovsky Massif is composed of quartz monzonites, while the sills and dikes are composed of quartz syenites. These rocks are geochemically close to the shoshonite-latite series of island arc rocks and are enriched in LREE and depleted in HREE, characterized by aweak negative Eu-anomaly. The sequence of magmatism development in the Mesozoic has been established: the formation of rocks of the Mikhailovsky massif and most small bodies occurred in the post-collision period, followed by the intrusion of quartzsyenite dike bodies in theanorogenicstages of territorial development.The study suggeststhat all the studied igneous rocks of the northeastern part of the Evotinsky region are characterized by a duality of geochemical composition,which indicates either intense mantle-crustal interactionor the existence of two sources of both mantle and crustal originat that time.

Determining the metallogenic specialization of igneous rocks in ore districts remains a pressing and often controversial challenge. Addressing this issue requires a comprehensive approach, that integrates petrographic and petrogeochemical data with geochronological studies of individual formations. Such integrated analysis, when contextualized within specific formation conditions and metallogenic assessments, provides a robust framework for interpretation. The Evotinsky massif, located within the eponymous Evotinsky placer ore region in the central Aldan-Stanovoy shield, represents one such critical formation. This study investigates its petrogenesis based on rock samples collected during fieldwork from 2018 to 2020, focusing on the massif’s main phases. Subsequent processing and major element analysis were performed using silicate and multielement techniques at the Department of Physicochemical Analysis Methods of the Diamond and Precious Metals Geology Institute SB RAS (Yakutsk). Trace element concentrations were determined by mass spectrometry at the САС Plasma LLC laboratory (Tomsk). Finally, geochronological U-Pb dating of zircons was conducted using SIMS (SHRIMP-II) at the Center for Isotope Research of the Karpinsky Russian Geological Research Institute (VSEGEI). The Evotinsky massif displays an antidromous structure and comprises two intrusive phases: an earlier phase of amphibole quartz syenites and a later phase of amphibole-pyroxene quartz monzonites. The rocks are classified within the high potassium calc-alkaline series, corresponding to derivatives of the shoshonite-latite series. Geochemical data indicate a mixed mantle and crustal source for the magmas. Petrochemical parameters and trace element ratios (Rb, Y, Yb, Ta) show compositions analogous to volcanic rocks from continental margins and island arcs. U-Pb zircon geochronology (SHRIMP II) constrains the emplacement of the amphibole quartz syenites to 119 ± 1 Ma and the amphibole-pyroxene quartz monzonites to 117 ± 1 Ma (Aptian, Early Cretaceous). In conclusion, the Evotinsky massif formed under back-arc extensional conditions during the final stages of the Mongol-Okhotsk Ocean closure. Furthermore, these findings demonstrate the massif’s significant potential for gold mineralization.

The article considers the features of the petrographic and geochemical compositions of the Mesozoic igneous rocks of the Polovinkinskaya depression from earth bores K1, K2, K3, located within the central part of the Aldan-Stanovoy shield, on the boundary of the Tynda and Nimnyr terranes within the Amginskaya zone of tectonic mélange. Based on the relationship of rocks, as well as on the features of the petrographic composition, the following sequence of introduction and formation is assumed: 1) gabbro; 2) hornblende-augite andesites. This is confirmed by the values and variations of the petrochemical composition. According to the petrochemical and geochemical characteristics, gabbros are close to the tholeiitic series. Andesites belong to the calc-alkaline petrochemical series, latites of the shoshonite type. The presence of such rocks as gabbro and andesites is typical for mature island arcs and active continental margins, which does not contradict the existing ideas of predecessors. Similar in geological structure objects are gold-producing gabbro-tonalite-granodiorite-granite (GTGG) massifs of the Urals, which are supra-subduction formations on the active continental margin of the Andean type. The presence of rocks of the GTGG formation within the Polovinkinskaya depression serves as a favorable factor for noble-metal ore-generating processes.

Researched magmatic rocks, which undergone the process of polymetamorphism in granulite, amphibolite and greenschist facies, earlier by some geologist was defined as paragneisses and (or) intrusive rocks. In this paper based on geological and geochemical data argue the magmatic nature of rocks and identity to the calc-alkaline series. The series consists of gabbros, diorites, quartz diorites, granodiorites, tonalites and trondhjemites. Contents of the rock-forming oxides and rare earth elements in these rocks are close to the widely known early Proterozoic gabbro-diorite-tonalite-trondhjemite series of the South-West Finland. These features indicate the probability of formation of the researched rocks with the participation of the subduction. As a results of studies established what in M complex possible inclusion of rocks and bodyes from other sites such as Ust-Timpton, Idzhek-Seym and Upper-Gonam pluton. The features of the MS include the linkage with the long-lived faults and associated dynamometamorphic changes of the bodies, polymetamorphism, superimposed chemical changes in the composition of primary rocks, as well as rarely preserved migmatite veinlets in the host rocks. Geochemical similarity of trondhjemite-, tonalites, granodiorites Mariin series and associated rocks with well-known early Proterozoic differentiated series of southwest Finland typical for the Proterozoic and Paleozoic continental margins suggests that the plutons of the Mariin series formed in an active continental margin setting.