Deep geodynamics and uranium giants of southeastern Russia

The southeast of Russia with hydrothermal and hydrogenic U deposits is one of the largest provinces in the world with the unique U-bearing El’kon (South Yakutia) and Urulyungui (Transbaikalia) regions with similar geological, magmatic, petrological-geochemical characteristics and resources and commonly accepted formation from mantle derivatives. The seismotomographic data of the region indicate the presence of an oceanic slab that stagnated in its transit zone (410–670 km). The Pt-bearing alkaline-ultramafic massifs of the Inagli-Konder-Feklistovskii belt and the superlarge U-bearing regions are located along the east-northeastern flank and western frontal zone of the slab, respectively. The formation of the U-bearing regions, as well as the Pt-bearing massifs with dunitic core, is caused by involvement of derivatives of the lower mantle into the upper mantle plumes that was accompanied by the melting of the lithosphere. The acceptance of the influence of the deep geodynamics of the southeast of Russia on formation of the U-bearing regions allows us to outline the areas of further detailed studies along the frontal zone of the slab.     

Metallogenic analysis of the type gold-bearing districts in the southern and eastern framing of the North Asian Craton: Geotectonic position,geological structure,and specifics of formation

Large ore-placer districts in the southern and eastern framing of the North Asian Craton (Bodaibo, Upper Selemdzha, South Verkhoyansk, and Ten’ka) are characterized by some common features such as the confinement to the areas of the decreased crustal thickness and gravity gradient zones traced by deep-seated faults; the fold-thrust structure of the terrigenous-black-shale sequences; the phyllitic, greenschist, and sometimes epidote-amphibolite metamorphism of the ore-bearing rocks; and the complex and long history of the Au accumulation, which involved the subsequent stepwise change from the ore-preparatory to the ore-generating stages. The latter stage is spatially and temporally related with manifestations of orogenic (volcanoplutonic) magmatism, which produced mineralization of the gold-quartz, gold-sulfidequartz, gold-black shale, gold-rare metal, and gold-silver formations. The peculiarities of their spatial relations (juxtaposition-superposition or lateral zoning) determine the scales of the noble metal concentration, the economic significance of the deposits, and the metallogenic potential of the regions. The revealed similarity in the evolution and structure of the compared districts should be taken into account in choosing new promising areas and estimating the potential gold-bearing territories in the framing of the North-Asian and other cratons.     

New U-Pb isotopic data on the age of metamorphic and igneous rocks of the western margin of the Selenga-Stanovoi orogenic belt

New data on the isotopic age of zircons from metamorphic and igneous rocks are given for the Berezitovoe and Kirovskoe deposits located in the eastern margin of the Selenga-Stanovoi orogenic belt. The zircons were studied with the LA-ICP-MS method in the State Key Laboratory of Continental Dynamics, Northwestern University, Sian, Shansi province, People’s Republic of China. The results allowed us to reveal three age epochs in formation of the eastern part of the Selenga-Stanovoi orogenic belt (1.87 Ga; 380–330 Ma; 138–125 Ma), which have significant importance for understanding of the geological structure of the south-eastern framework of the North Asian craton.     

Reconstruction of the ore-forming system in the Mnogovershinnoe gold-silver deposit (Lower Amur River Region) based on the structure of ore-bearing zones and isotopic studies

The hydrothermal ore-forming paleosystem of the Mnogovershinnoe deposit is reconstructed by defining lithothectonic elements constituting ore-bearing zones with account for their formation mechanisms and positions in the conditional geochronological scale of the hydrothermal activity and isotopic data. The use of lithotectonic elements for deciphering ore genesis events made it possible to take into account both synchronously and successively formed parts of ore bodies, which substantially improved the quality of the reference data for developing a dynamic model of the deposit. The approach proposed for reconstructing the hydrothermal paleosystem of the Mnogovershinnoe deposit may be used for developing models of other ore objects.     

The deep geodynamics of Southeast Russia and the setting of platinum-bearing basite-hyperbasite massifs

The southeastern part of the North Asia craton was found to contain several circular basite-hyperbasite plutons with associated commercial platinoid placers. An analysis of geodynamic models for the formation of the region and materials of seismic tomography showed that the subduction processes that were active in the Asia-Pacific convergence zone during Mesozoic time generated a stagnant oceanic slab in the transitional mantle zone. The NE and SW boundaries of the slab appear to be coincident with transform faults. The projection of the transform fault that bounds the slab on the north-northeast coincides with the Konder-Feklistov metallogenic belt that was identified previously and its Aldan (Inagli) segment. The high platinoid potential of the circular massifs in the belt is explained by the effects of lower-mantle derivates on ascending upper-mantle plumes.     

Deep-seated structure and gold content of Russia and China contiguous territories

On the contiguous territories of southeastern Russia and northeastern China,many gold-bearing areas are conjugate in space with the gradient zones of the gravity field.Large gold-ore districts,defining in many respects the metallogenic signature of the region,are located on the joints of differently oriented gradient zones.In the best-studied districts,the Precambrian protrusions,staged distribution of magmatic chambers (by vertical) above the Mohorovicic discontinuity and restriction to the peripheral parts of intrusive massifs have been recognized.Different-type gold deposits in the studied ore-placer districts and nodes are often located on the areas of joint of the granitoid massifs and subvolcanic bodies with depressions.Availability of areals of metasomatic alterations of rocks,placers,and ore occurrences of precious metals on such but poorly studied areas can serve as the basis for the revision and detailed forecasting-prospecting works to develop the mineral-raw material base of the region for precious metals.     

Spatial and temporal variations in infrared emissions of the upper atmosphere. 1. Atomic oxygen (λ 63 μm) emission

Rocket and balloon measurement data on atomic-oxygen (λ 63 µm) emission in the upper atmosphere are presented. The data from the longest (1989–2003) period of measurements of the atomic-oxygen (λ 63 µm) emission intensity obtained by spectral instruments on sounding balloons at an altitude of 38 km at midlatitudes have been systematized and analyzed. Regularities in diurnal and seasonal variations in the intensity of this emission, as well as in its relation with solar activity, have been revealed.