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Geochemical, geochronological (U–Pb on zircons, ID TIMS), and isotope–geochemical (Sm–Nd) studies of Kopri-type granitoids of the Tukuringra Complex have been carried out. The granitoids are located exclusively in the zone of the Dzheltulak suture, which separates the Dzhugdzhur–Stanovoi and Western Stanovoi superterranes of the Central Asian fold belt. It has been established that they can be classified as postcollisional adakite-like granitoids of elevated alkalinity and adakite-type basicity, formed in the age range between 127 ± 1 and 126 ± 1 Ma, which are part of the Late Mesozoic postcollisional Stanovoi volcano-plutonic belt that extends more than 1000 km in the sublatitudinal direction from the Sea of Okhotsk into the continent subparallel to the Mongolia–Okhotsk suture zone and stitches the Dzhugdzhur–Stanovoi and the Western Stanovoi superterranes. The structural position of the Kopri-type granitoid massifs registers the upper age limit of the Dzheltulak suture. Formation of the parent melts of these granitoids is associated with an essentially lithospheric source formed as a result of mixing of the Early Precambrian and a younger, apparently Phanerozoic component. In contrast to other granitoids of the Stanovoi belt that are close in composition and age, the granitoids under consideration are characterized by a certain increase in the role of the asthenospheric component in their source, which is probably due to their localization in the zone of elevated lithospheric permeability and at the junction of faults of different orientations, generally sublatitudinal, guided by the Mongolia–Okhotsk lineament, and northwestward, associated with the development of the Dzheltulak suture. [ABSTRACT FROM AUTHOR]

The biological significance of regional cladoceran morphotypes in the montane regions of the central Palearctic remains poorly understood. In the Holarctic Daphnia longispina complex (Cladocera: Daphniidae), several variants, lineages and species have been proposed as endemic for Southern Siberia. Daphnia turbinata Sars, for example, named after its unusual head shape, is known only from Southern Siberia. Here we sequence DNA of Daphnia from three mitochondrial genes (12S rRNA, 16S rRNA, and NADH dehydrogenase subunit 2, ND2) from 57 localities in Russia and Mongolia (the majority being from Southern Siberia) and place them in evolutionary context with existing data. Our aim was to examine regional endemism of the Daphnia longispina complex in Southern Siberian; to improve the phylogenetic understanding with improved taxonomic and regional sampling, and to better understand the influence of Pleistocene glaciation on the biogeography of these lineages. At least three lineages showed genetic evidence for endemism in Southern Siberia. There was strong support for D. turbinata as a sister lineage to to D. longispina/D. dentifera. Another endemic, Siberian D. cf. longispina, is a sister group to the longispina group in general. Within D. longispina s. str. there was an endemic Siberian clade with a western range boundary near the Yenisei River Basin. Gene flow estimates among populations (based on FST values) were very low for clades of D. longispina on a regional (the original 12S dataset), and on a pan-Eurasian (the extended 12S dataset) scale. Negative values of Fu’s FS and Tajima’s D tests prevailed for the species examined with significant values found for two D. longispina clades, D. dentifera, D. galeata and D. cristata. Our results support the notion that Southern Siberia is an important biogeographic region for cladocerans as it contained unexpected diversity of endemics (such as D. turbinata, D. cf. longispina and lineages of D. umbra and D. longsipina s.str.) and from being the geographic meeting place of expanding postglacial lineages from eastern and western refugia. [ABSTRACT FROM AUTHOR]

The results of Sm-Nd studies of metasedimentary rocks from the Tukuringra terrane, one of the largest units in the structure of the eastern part of the Mongolian-Okhotsk mobile belt, are reported. Metasedimentary rocks of the Algainskaya, Garmakanskaya, and Teploklyuchevskaya formations are characterized by similar model ages t = 1.5-1.1 Ga. This shows that the major protoliths of metasedimentary rocks of the terrane are characterized by Mesoproterozoic estimates of the Nd model ages. The results obtained allow us to assume that introduction of terrigenous material into the sedimentary basin mostly occurred from the continental massifs united into the Amur superterrane, since their magmatic and sedimentary complexes are characterized by identical values of the Nd model ages. [ABSTRACT FROM AUTHOR]

The paper presents the results of U-Pb geochronological and geochemical studies of the rocks of the monzodiorite-granodiorite association in the northeastern flank of the South Mongolia-Khingan orogenic belt, which composes a tectonic block among the provisionally Lower Paleozoic volcanosedimentary complexes of the Nora-Sukhotinsky Terrane. It is shown that the studied rocks have similar petrographic features (with the presence of transitional varieties) and form common trends in the petrographic diagrams. This suggests that they are members of a single magmatic association. The geochemical features of the monzodiorites, quartz monzodiorites, and granodiorites, in particular their enrichment in large ion lithophile elements (LILE) and depletion in some HFSE, indicate their similarity with island-arc magmatic rocks. The presence of monzonites and quartz monzonites in the studied monzodiorite-granodiorite association along with high K, Rb, Th, and Pb concentrations gives reasons to believe that it formed in active continental margin or ensialic island-arc environments. The granodiorites of the monzodiorite-granodiorite associations of the Nora-Sukhotinsky Terrane are dated at 440 ± 10 Ma and may be considered as a fragment of the early Silurian active continental margin or ensialic mature island arc in the structure of the South Mongolia-Khingan orogenic belt. [ABSTRACT FROM AUTHOR]

The structural data and available geochronological constraints suggest that the Gonzha tectonic block located in the northeastern part of the Argun-Idermeg superterranes, Central Asian orogenic belt, is considered as an analogue of Cordilleran metamorphic core complexes of western Transbaikalia. These metamorphic core complexes, as well as the Gonzha block, may have resulted from collapse of a Late Mesozoic orogen after closure of the Mongolia-Okhotsk paleo-ocean basin. [ABSTRACT FROM AUTHOR]

Fossil Mesozoic anomopods (Crustacea: Cladocera) have only been found twice previously, although this group apparently differentiated in the Palaeozoic. This paper describes the finding of anomopod ephippia of three different types in the locality Khutel-Khara, Mongolia (Lower Cretaceous, 129±9 Mya). This discovery demonstrates once more that the idea of rarity of cladocerans in Mesozoic fossils was motivated by insufficient attention of carcinologists to such fossils. [ABSTRACT FROM AUTHOR]

Pre-Pleistocene representatives of the crustacean order Ctenopoda Sars, 1865 are unknown. Here we describe Mesozoic fossil specimens of ctenopods from two localities in Mongolia: Khotont (Jurassic/Cretaceous boundary, about 145 Mya) and Khutel Khara (Lower Cretaceous, about 129 Mya). All specimens apparently belonged to the tribe Latonini Korovchinsky, 1986 of the subfamily Sidinae Baird, 1850. At the Khotont site, ctenopods were the most numerous microscopic animal fossils. We assigned these cladocerans to a new genus and species Archelatona zherikhini gen. nov., sp. nov. Our findings support a pre-Cretaceous origin for cladocerans. © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society, 2006, 146, 269–274. [ABSTRACT FROM AUTHOR]