Second Russia-China International Meeting on the Central Asian Orogenic Belt (September 6–8th, 2017, Irkutsk, Russia) with post-conference excursion (September 9–12th, 2017, Baikal area, Siberia, Russia) continues tradition of the Russian-Chinese conferences begun in 2015.

The Eastern Tianshan belt, located in the southern CAOB, played an important role in the crustal evolution, particularly because it links the Southern Tianshan suture to the west with the Inner Mongolia Solonker suture to the east. However, some critical issues, such as the exact position and formation age of the final suture zone of the Paleo-Asian ocean are still obscure or in controversy. Thus, here we have performed detailed studies of the Kwabulake ophiolit zone, a key part of the southern suture of the CAOB. New LA- ICPMS zircon U–Pb ages, Hf isotopic values, and whole-rock geochemical data have been presented to: (1) constrain the age of the Kawabulake ophiolite, (2) understand the petrogenesis of the granodiorites and their tectonic setting, and (3) reveal their implications for geodynamics of the Eastern Tianshan belt.

The Eastern Sayan ophiolites (1020 Ma) of the Tuva-Mongolian microcontinent are believed to be the most ancient ophiolite of the Central Asian Orogenic Belt [Khain et al., 2002].

CAOB occupies a vast area that extends from the Urals to the Far East Asia and from the Siberian craton to the North China and Tarim cratons (Fig. 1, A). In order to better constrain Precambrian tectonic evolution of the CAOB, it is important to revisit Precambrian terranes of Mongolia as outlined in Badarch et al. [2002] that contain Archean to Proterozoic metamorphic basement and Neoproterozoic metasedimentary and volcanic rocks.

In the end of the 20th century folded structures of central Asia were regarded as formed by accretion and collision of the Paleo-Asian oceanic plate and Siberia continent.

Though Li isotope fractionation during mantle melting and differentiation of basaltic melts have been proved insignificant, Li isotopic systems during crustal processes remain unclear. To study this, we report combined petrological, Nd-Sr and Li isotopic data for the late Paleozoic coexisting I- and A-type granites in the East Junggar orogen of the Central Asian Orogenic Belt. The granites were formed responding to underplating of mafic magmas in the lower crust in a postcollisional, extensional regime, and intruded into the Paleozoic foldbelts that formed due to extensive oceanic subduction-accretion processes.

The late Neoproterozoic tholeiitic-boninitic lavas and minor magnesian andesites cropping out in the Kurai Ridge, southeast of the Gorny Altai terrane, represent magmatic products of the nascent Kuznetsk-Altai intra-oceanic island arc southwest off the Siberian continent. Samples of these rocks can provide key information about sub-arc mantle and slab-mantle interaction during the early phase of ocean-ocean subduction.

The southern Jiangxi province is located at east Nanling range, which is an important W-Sn metallogenic province of China. The Early Yanshanian Tianmenshan is composed of the main-phase porphyritic biotite granite and the highly differentiated fine-gained biotite granite, intruding in the Lower Cambrian Niujiaohe Formation. The main-phase granite and the late-stage highly differentiated granite emplaced at 152–158 Ma and 152–151 Ma, respectively. The later was in the center of the pluton as a ovalize shape, with a transitional contact with the main-phase granite.

At the latest geodynamic stage that is characterized by forces and processes of the last 90 Ma the lithosphere of Asia has been reactivated due to four main force factors: 1) mantle melting anomalies, 2) subduction-related interaction between the Pacific plates and the continental eastern margin, 3) convergent interaction between India and the continental southern margin, and 4) quasiperiodic orbital variations of the Earth. The starting point of the latest geodynamic stage [Rasskazov, Chuvashova, 2013] is consistent with the change of the Earth’s rotation due to the resonant interaction of its orbit with the orbit of the Mars in the time interval of 87–85 Ma [Ma et al., 2017].

The Baikal ledge rock formations in the Siberian craton structure are included in the Akitkan mobile belt which is considered as the Late Paleoproterozoic independent island arc system moved up to the ancient basement during the terrains amalgamation 1.91–2.00 Ga ago (Fig. 1) [Rosen, 2003; Gladkochub et al., 2009; Didenko et al., 2013].

Volcanic eruptions within the Baikal rift of predominantly basaltic composition belong to numerous small-volume eruptions, which took place in Cenozoic in Central Asia. The great majority of these eruptions occurred within the mobile belts in the southern framing of the Siberian craton. Only few of such eruptions have happened within the cratonic margin and these are of particular interest, because volcanic rock composition may provide insights on the composition of the cratonic lithosphere. Until recently, the Uda river area with the size of ~2000 km2 located within the Biryusa block of the Siberian craton (Fig. 1) was a white spot in terms of precise geochemical and isotopic data for basalts. Here we provide such data for the first time.

Dunhang Block is located between the North China and the Tarim Cratons (Figure). It is bounded by the Beishan Orogenic Belt to the north and Altyn Tagh Orogenic Belt to the south, respectively; in the west the Qiemo-Xingxingxia fault separates the block from Tarim Craton, and in the east the Altyn Tagh Fault separates it from the Alxa block of western part of the North China Craton. Although Archean-Paleoproterozoic basement rocks, which are referred to as Milan Complex, exposed along the Northern Altyn Tagh Orogenic Belt, some researchers suggested that their rock associations, metamorphisms and evolutionary history present obviously different with those of the Dunhuang Complex in Dunhuang region, Gansu Provence, thus the Milan Complex should be excluded from the Dunhuang Block, and is considered as basement rocks of the southwestern Tarim Craton.

Early Cretaceous metamorphic core complexes (MCCs) are widespread in North-East Asia and indicate a large-scale crustal extension in this area [Wang et al., 2011, 2012]. Traditionally one of the formation mechanisms of MCCs is related to various magmatic activities including granitoid magmatism [Anderson et al., 1988, Hill et al., 1995; Lister, Baldwin, 1993]. Wang et al. [2012] have subdivided the intrusion associated with MCCs in NE Asia into pre-kinematic (~170–140 Ma), syn-kinematic (~150–125 Ma) and post-kinematic (~125–110 Ma). 40Ar/39Ar biotite and hornblende ages of 140–110 Ma are overlapping for all MCCs of NE Asia and represent the time of the final stage of the MCCs formation [Wang et al., 2012]. Here, we present overview of geochronological and geochemical data for Late Mesozoic granitoids of the Western Transbaikalia and our view on their role in formation of Transbaikalian MCCs.

There are several geodynamic models of the Central Asian Orogenic Belt (CAOB) development [Şengör et al., 1993, Zorin, 1999; Parfenov et al., 1999, 2003; Willem et al., 2012; and others]. The Mongol-Okhotsk Orogenic Belt (MOB) represents important part of CAOB. All geodymanic models of Late Riphean to Paleozoic structures of CAOB emphasize significance of subduction processes along Northern Asian craton margin at that time. Collage of CAOB terrains formed as a result of accretion of island arc, accretionary wedge, turbidite, and continental margin terrains to the Siberian paleocontinent.

The origin of the Central-Asian Orogenic Belt (CAOB), especially of its northern segment nearby the southern margin of the Siberian craton (SC) is directly related to development and closure of the Paleo-Asian Ocean (PAO). Signatures of early stages of the PAO evolution are recorded in the Late Precambrian sedimentary successions of the Sayan-Baikal-Patom Belt (SBPB) on the southern edge of SC. These successions are spread over 2000 km and can be traced along this edge from north-west (Sayan area) to south-east (Baikal area) and further to north-east (Patom area). Here we present the synthesis of all available and reliable LA-ICP-MS U-Pb geochronological studies of detrital zircons from these sedimentary successions.

The Main Mongolian Lineament (MML) separates northern “Caledonian” tectonic province from southern “Hercynian” in SW part of Mongolia of the Central Asian Orogenic Belt (CAOB). The position of Eastern part of MML is widely discussed at recent time, since, this is an important for reconstruction of geodynamic evolution of this region. Some researchers suggest that ophiolite from the Erdene Uul and Maykhan Tsakhir Uul mountain ranges are Eastern part of an ophiolitic nappe system thrust northwards over the Dzabkhan-Baydrag continent, namely the Khantaishir and the Dariv ophiolites [Štípská et al., 2010; Buriánek et al., 2017]. Others have a different view, they suggest that investigated ophiolites refers to Gobi-Altai ophiolite system (523±5 – 518±6 Ma), which likely formed in front of the Gobi Altai microcontinent by initiation of a new southdipping subduction zone following arc–microcontinent collision in Northwest Mongolia [Jian et al., 2014]. However, ophiolites of this critical region of Mongolian the CAOB have not been investigated in detail.

Numerous Early Cretaceous syn-thinning granitic domes are widespread in Mongolia and China-Mongolia border area. We observed relationships between deformation and magmatic activity that occurred in Baoder, Naran, Hanwula, Erdene, Altanshiree, Nartyn dome[Daoudene et al., 2012; Cheng et al., 2014; Guo et al., 2015], which developed in eastern Mongolia and China-Mongolia border area during Early Cretaceous crust-scale NW–SE extension.

Division of tectonic units in the eastern part of the Central Asian Orogenic Belt in northeast China has been a major concern and resulted in much fieldwork, but the division of these tectonic units in NE China is still controversial. Although detection of tectonic units in seismic sections is not straightforward, for this meeting, we shall try to relate tectonic units with the crustal and upper mantle structure and deformation derived from a ~2500 km long reflection seismic profile (Figure, red lines) in this area, recently acquired or reprocessed with support of China Geological Survey and the Chinese SinoProbe Project.

The origination and differentiation of rare metalbearing, alkaline granites has attracted extensive interests because of their economic significance.

The Siberian craton consists of Archean blocks, which were welded up into the same large unit by ca 1.9 Ga [Gladkochub et al., 2006; Rojas-Agramonte et al., 2011]. The history of the constituent Archean blocks is mosaic because of limited number of outcrops, insufficient sampling coverage because of their location in remote regions and deep forest and difficulties with analytical studies of ancient rocks, which commonly underwent metamorphic modifications and secondary alterations. In this short note, we report data on discovery of unusual for Archean mafic rocks of ultimate fresh appearance. These rocks were discovered within southwestern Siberian craton in a region near a boundary between Kitoy granulites of the Sharyzhalgai highgrade metamorphic complex and Onot green-schist belt (Fig. 1). Here we present preliminary data on geochronology of these rocks and provide their geochemical characterization.

Tectonic-magmatic reworking of accretionary wedges is a key process responsible for differentiation and stabilization of continental crustal in accretionary orogens. This generic problem can be exemplified by magmatic evolution of the Chinese Altai which represents a high-grade core of the world's largest accretionary system, namely the Central Asian Orogenic Belt (CAOB). In the Chinese Altai, voluminous SilurianDevonian granitoids intruding a greywacke-dominated Ordovician flysch sequence. These intrusions are classically interpreted to originate from predominant (70‒90 %) juvenile (depleted mantle-derived) magma. However, their close temporal and spatial relationship with the regional anatexis of flysch rocks, allows us to examine the possibility that they were mainly derived from flysch rocks.

Evidence of melt-rock reaction between suprasubduction zone (SSZ) peridotites and island arc boninititc and tholeiitic melts are identified. This process is the cause of replacive dunites and pyroxenite veins forming, which are represent the ways of island-arc melts migration. The peridotite-melt interaction is confirmed by compositional features of rocks and minerals. Influence of boninitic melt in peridotites of South Sandwich island arc leads to increasing of TiO2 and Cr-number (Cr#) in spinels [Pearce et al., 2000] e.g. REE patterns of clinopyroxene from Voykar are equilibrium to boninitic melts [Belousov et al., 2009]. We show that pyroxenites are formed sequential, orthopyroxenites are originated firstly, websterites – after, and the main forming process is interaction of SSZ peridotites with percolating boninite-like melts.

Altai collision system of Hercynides was formed in Late Paleozoic as a result of oblique collision of Siberian continent and Kazakhstan composed terrane [Vladimirov et al., 2003; 2008; Xiao et al., 2010]. At the late stages of its evolution (time interval from 310–300 to 280–270 Ma) the huge different mafic and felsic magmatism occurred at the territory (Fig. 1) [Vladimirov et al., 2008; Khromykh et al., 2011, 2013, 2014, 2016; Kotler et al., 2015; Sokolova et al., 2016]. It is evident about increased thermal gradient in lithosphere and about significant role of mantle and active manifestation of mantle-crust interactions. Some magmatic complexes may be considered as indicators of mantle-crust interaction processes.

Previous geochronological and Sm-Nd isotopegeochemical studies have identified the main stages of the Precambrian continental crust formation in the central and eastern parts of the Aldan Shield [Kotov et al., 2006], while its western part (Chara-Olekma Geoblock) has not been adequately investigated yet in this respect.

The Dzabkhan microcontinent was defined by [Mossakovsky et al., 1994] as a cratonic terrane with an early Precambrian basement that combines highgrade metamorphic complexes of the Songino, Dzabkhan, Otgon, Baidarik, Ider and Jargalant Blocks. However, early Precambrian ages have so far only been recognized in the Baidarik and Ider blocks [Kozakov et al., 2007, 2011; Kröner et al., 2015].

We provide new field observations and isotopic data for key areas of the Central Asian Orogenic Belt (CAOB), reiterating that no excessive crustal growth occurred during its ca. 800 Ma long orogenic evolution. Many Precambrian blocks (microcontinents) identified in the belt are exotic and are most likely derived from the northern margin of Gondwana, including the Tarim craton.

Curved mountain belts, commonly referred as to oroclines that result from bending of quasi-linear orogenic belts, have fascinated generations of geologists. Such structures are widely recognized in modern and ancient orogens, and are fundamentally important for understanding geodynamics of convergent plate boundaries. However, how and why orogenic belts become bent has been in debate. Here we investigate the Kazakhstan Orocline in the Central Asian Orogenic Belt with an aim at understanding the geodynamics of oroclinal bending in accretionary orogens.

The key to defining the termination of accretion in an accretionary orogen is to recognize the initial magmatic processes that are generated at the time of ocean closure. We present new age, geochemical and isotopic data for magmatic rocks related to terminal collision along the Solonker-Xar Moron suture zone in the southern Central Asian Orogenic Belt (CAOB) that record such processes following closure of the PaleoAsian Ocean (Figure).

The occurrence of high-pressure and ultrahigh-pressure eclogites in the northern border of Qaidam basin in central China indicates the existence of a 350 km orogenic belt. These eclogites provide constraints for reconstructing the tectonic evolution history in this region. In this study, we analyzed nine eclogites sampled from the Xitieshan area, for their major and trace element abundances as well as 143Nd/144Nd isotopic ratios to investigate the factors controlling geochemical compositions of these eclogites and to infer the tectonic evolution in this region.

The unique charoite mineralization, established on the Murun alkaline massif in the northwestern part of the Aldan shield on the border of the Irkutsk region and Yakutia, is still of great interest to some of researchers (geologists, crystallographers, geochemists, etc.). The outcrops of charoite-bearing rocks at the “Sirenevyi Kamen” deposit are noted both in the indigenous outcrops and in eluvial clatters [Bondarenko, 2009].

The magmatic sulfide deposits in the Central Asian orogenic belt are hosted in a series of mafic–ultramafic intrusions in the Maksut zone (E Kazakhstan), the Kalatongke and the Huangshan zones in Xinjiang (NW China) and the Hongqiling zone in NE China. In the Maksut zone there are several intrusions, the best studied from which is the South Maksut intrusion with Cu–Ni–PGE mineralization.

Mongolia lies in the central part of the Central Asian Orogenic Belt [Mossakovsky et al., 1994; Zorin, 1999; Jahn, 2004; Khain et al., 2003; Badarch et al., 2002; Windley et al., 2007; Zhang et al, 2008], or Altaids [Şengör et al., 1993; Şengör, Natal’in, 1996; Wilhem et al., 2012], which is fringed by the Siberian craton in the north and by the Tarim and Sino-Korean Cratons in the south. According to the recent tectonic subdivision, the territory of Mongolia is subdivided into Northern and Southern domains which are separated by the so called Mid Mongolian Tectonic Line [Tomurtogoo, 2012]. The Herlen Massif is one of the important tectonic units of the South Mongolian domain in the Argun-Idermeg super terrane extending through the territories of Russia and China [Parfenov et al., 2009; Tomurtogoo, 2014b]. The Herlen massif, also known as Herlen superterrane [Tomurtogoo, 2012] or Idermeg terrane [Tomurtogoo, 2014a] is composed of Ereendavaa, Undur-Khaan, Idermeg and Gobian Altay-Baruun Urt terranes converged at the end of the Cambrianbeginning of the Ordovician [Badarch et al., 2002; Tomurtogoo, 2014b].

Bureya continental massif is one of the largest continental massifs in the eastern part of the Central Asian orogenic belt (CAOB) (Fig. 1), and knowledge of its geological structure is of fundamental importance in understanding the history of its formation.

At present, geochemical data are widely used for reconstructing geodynamic settings, especially, volcanic rocks of mafic composition, i.e., basalts, because they are widespread in many orogenic belts and are indicative of different geodynamic environments. In general, we propose the reconstruction of the tectonic settings of basalts according to their relationships with associated ocean plate stratigraphy (OPS) sediments, their petrogenesis and their geochemical features.

There are two episodes of magmatism along the northern margin of the North China block during the Late Carboniferous to Late Triassic, one at 310–250 Ma (Late Carboniferous to Permian) and the other at 235–210 Ma (Late Triassic). The former group comprises plutonic rocks (gabbro-diorite-monzodioritemonzogranite-granite), mafic to intermediate dykes (diorite to dolerite) and a few felsic volcanics (andesite to dacite).

Ultramafic and mafic lithologies, attributed to the orogenic terranes and formed under ultrahigh-pressure (UHP) and high-pressure (HP) conditions, have been intensively studied for the last decades. It is mainly related to a particular significance of these rocks for geodynamics, since they contain an important information on the fluid-rock interactions and element redistribution in the subduction-collision zones and could shed the light on the tectonic evolution of the studied region.

The Ku’erchu granitic pluton (283±4 Ma) was exposed in the eastern part of the South Tianshan Orogenic Belt. The granites from the intrusion are mainly composed of orthoclase (~45 vol. %), plagioclase (~15 vol. %), quartz (~20 vol. %), muscovite (~10 vol. %) and biotite (~5 vol. %), with accessory minerals including garnet, zircon and Fe-Ti oxide.

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The Amuria block occupies the eastern part of the Central Asian Orogenic Belt between the Siberia craton and the North China block (NCB) and bears important information to understand the evolution of the MongolOkhotsk suture and the amalgamation of East Asia.

Intra-oceanic arcs (IOAs) form at Pacific-type convergent margins, in the upper “stable” plate, when the subducting plate submerges to the depths of melting, i.e., to ca. 50–100 km. A typical IOA system, such as Mariana-Bonin and the Philippines Sea, consists of subduction zone, fore-arc region with accretionary prism, frontal or active arc, marginal basin with spreading center, and, in some cases, one or more remnant arcs and inactive marginal basin. The IOAs are very important elements of Pacific-type convergent margins as they represent major sites of juvenile continental crust formation (e.g. [Clift et al., 2003; Stern, 2010; Maruyama et al., 2011]), but are also the most important sites of crust removal by sediment subduction and tectonic/ subduction erosion [Stern, Scholl, 2010].

Continental crust is formed above subduction zones by well-known process of “juvenile crust growth”. This new crust is in modern Earth assembled into continents by two ways: (i) short-lived collisions of continental blocks with the Laurussian or later Eurasian continent along the “Alpine Himalayan collisional/interior orogens” in the heart of the Pangean continental plates realm; and (ii) long lived lateral accretion of ocean-floor fragments along “circum-Pacific accretionary/peripheral orogens” at the border of the PaleoPacific and modern Pacific oceanic plate.

The Mineralogy, Petrography and Minerals Department of the Irkutsk State Technical University (now the Irkutsk National Research Technical University) has been studying the structural, mineralogical and geochemical features of ore fields for over 30 years. We investigated more than 25 deposits of gold, uranium, rare, non-ferrous and ferrous metals, and published the prognostic metallogenic maps of the ore regions located in Eastern Siberia, Mongolia and Yakutia. Our experience shows that knowing only the genetic characteristics of ore objects is not sufficient for proper metallogenic studies. A complete set of deposit characteristics should include the data on structure, composition, localization conditions and other properties of ore objects and fields. We propose to introduce the “ore system” (OS) concept considering a combination of genetically (paragenetically) related and interrelated petrological, tectonic, metamorphic, mineralogical, geochemical and lithological elements formed during the pre-ore (preparatory) and ore-formation stages [Seminsky, 1990]. In contrast to the proposed OS concept, common terms, such as “ore-magmatic”, “oremetasomatic”, “ore-generating”, “ore-localizing” systems, usually consider only one aspect of the ore process or object [Russian Metallogenic Dictionary, 2003]. In our opinion, descriptions and typification of ore objects viewed as OS should refer to two groups of characteristics.

On the basis of isotopic-geochemical studies and analysis of geological evidences heterogeneity of Hamsara terrane has been determined. Formation of stationed metamorphosed layers underlying the Hamsara formation occurred not earlier than 630 Ma, probably in the oceanic island arc system. Acidic effusive rocks of Hamsara formation were formed in intraplate condition in the range of 462–464 Ma. Sediments of Hamsara formation couldn’t be the part of island arc system and belong to completely other period of geological region development. This is the time of completion of accretion-collision events in the northern part of Altai-Sayan fragment of CAFB adjacent to the Siberian platform.

Marbles are common constituents of high-temperature (HT) metamorphic terranes and shields. They have been traditionally considered as indicators of sedimentary or volcanic origin of related rocks involved into metamorphism which erases the primary features of the protoliths. This approach is correct in most cases, but carbonate and silicate-carbonate rocks, which often make linear bodies, may be allochthonous in some structurally and compositionally complex metamorphic terranes, as in the case of the Olkhon terrane.

The Neoproterozoic to Cenozoic collage of the Central Asian Orogenic Belt is well-known to include Precambrian continental blocks and microcontinents traditionally attributed to rifting of Siberia or Gondwana prior to CAOB assembly that significantly contributed into the geochemical and isotopic composition of younger subduction- and accretion-related crustal lithologies via processes of crust-mantle interaction and crustal recycling.

Comparative analysis of the crustal evolution of the Early Precambrian Belomorian and Trans-North China orogens (Fig. 1) has shown [Slabunov et al., 2015] that: Both belts were formed by the superposition of two Precambrian orogenies. The earth crust of the Belomorian belt was produced during the Mesoarchaean to Neoarchaean Belomorian collisional orogeny [Slabunov, 2008; Slabunov et al., 2006] and then was reworked during the Palaeoproterozoic Lapland-Kola collisional orogeny [Daly at al., 2006; Balagansky et al., 2014]. The earth crust of the Trans-North China orogen was formed during a Neoarchean accretionary orogeny and then was reworked during a Paleoproterozoic collisional orogeny [Zhao et al., 2012; Guo et al., 2012, 2005]. The Lapland granulite belt is the core of the Lapland-Kola Palaeoproterozoic collisional orogen in the Fennoscandian shield and the Khondolite belt occupies the same tectonic position in a Palaeoproterozoic collisional orogen in the North China craton.

Accretionary orogens are major sites of generation of continental crust but the spatial and temporal distribution of crust generation within individual orogens remains poorly constrained. Paleozoic (~540–270 Ma) granitic rocks from the Alati, Junggar and Chinese Tianshan segments of the Central Asian Orogenic Belt (CAOB) have markedly bimodal age frequency distributions with peaks of ages at ~400 Ma and 280 Ma for the Altai segment, and ~430 Ma and 300 Ma for the Junggar and Chinese Tianshan segments. Most of the magma was generated in short time intervals (~20–40 Ma), and variations in magma volumes and in Nd–Hf isotope ratios are taken to reflect variable rates of new crust generation within a long-lived convergent plate setting.

There has been much discussion about the evolution of the Southeastern CAOB in the past two decades [Tang, 1990; Hong et al., 1994; Xiao et al., 2003; Li, 2006; Chen et al., 2009; Jian et al., 2010]. Most people believed that the Palaeozoic Asia ocean was closed along the Solonker suture at Permian with two-direction subduction models [Xiao et al., 2003; Jian et al., 2010]. Three EW subparallel Permian granitic belts took place both side of the Solonker suture, including Erlian-Uliastai belt on north side of the Erlian-Hegengshan ophiolite, south Mongolia-Xilinhot belt the Erlian-Hegengshan ophiolite on the north and the Solonker suture on the south, and the Baotou-Chifeng belt along the north margin of North China Carton on the south of the Solonker suture. Most Permian granitoids in the ErlianUliastai belt and Mongolia-Xilinhot belt were intruded in Early-Middle Permian.

Structural and hydrogeological zonation of the Baikal region is based on allocation of hydrogeological structures within the large tectonic complexes differing in development history. It is a southeast part of the Siberian platform, the Sayan-Baikalian folded belt and the western part of the Transbaikal folded region. The Cenozoic activation of the region which has led to emergence of the Baikal rift and movements on a series of large fault zones in Transbaikalia has substantially influenced on formation of collecting properties of rocks.

The South Tianshan is located to the north of the Tarim block and defines the southern margin of the Paleozoic Central Asian Orogenic Belt (CAOB). This study presents new structural data, geochronological and geochemical results for the Wuwamen ophiolite mélange in the Chinese segment of the South Tianshan. In the south, the Wuwamen ophiolite mélange shows typical block-in-matrix fabrics and occurs in the footwall of a south-dipping thrust fault, hanging wall of which is composed of weakly metamorphosed and deformed Lower Paleozoic marine to deep marine sequences from the South Tianshan. In the north, a southdipping thrust fault juxtaposes the Wuwamen ophiolite mélange in its hanging wall against the high-grade and strongly deformed metasedimentary rocks from the Central Tianshan in its footwall.

N.L. Dobretsov et al. [1985] first described the rock complexes in Eastern Sayan as ophiolites. Ophiolites formed in Dunzhugur island arc and were obducted onto Gargan block, a Neoarchean crystalline basement of the Tuva-Mongolian Massif (TMM), as a single nappe [Khain et al., 2002; Kuzmichev, 2004]. Zircons from plagiogranite were dated at 1021±5 Ma by multigrain TIMS and 1020±1 Ma by Pb-Pb single-grains evaporation method [Khain et al., 2002]. Later [Kuzmichev, Larionov, 2013] analysed 12 grains of detrital zircons from gravelstone of the Dunzhugur formation and obtained 206Pb/238U ages from 844±8 to 1048±12 Ma. Careful examination of these data shows that 206Pb/238U ages for concordant zircons only vary from 962±11 to 1048±12 Ma.

The Central Asian Orogenic Belt (CAOB), bounded by the Siberian craton to the north and the TarimNorth China cratons to the south, is a complex collage of microcontinental blocks, island arcs, oceanic crustal remnants and continental marginal facies rocks. It is one of the largest and most complex accretionary orogenic belts and the most important site of Phanerozoic continental growth on the Earth [Jahn et al., 2000, 2004; Kovalenko et al., 2004] The widespread occurrence of large volumes of granitoids, mostly with juvenile sources, is a typical characteristic of the CAOB. These granitoids have been intensely studied (e.g. [Jahn et al., 2000, 2004; Kovalenko et al., 2004; Sorokin et al., 2004; Vladimirov et al., 2001; Han et al., 2010; Wang et al., 2006, 2015; Wu et al., 2011; Li et al., 2013; Yarmolyuk et al., 2002]). However, these studies mainly focused on some certain countries or regions.

It is generally considered that there are different continental compositions between a subductional– collisional and an accretionary orogen, however, what are the differences and how to identify them has not been well understood. This study attempts to discuss this problem by comparing Nd isotopic compositions of granitoids in the Qinling-Dabie orogen, a typical subductional-collisional orogen, with those in southwestern segment of the Central Asian Orogenic Belt (CAOB), the world's largest phanerozoic accretionary orogenic belt.

Cenozoic ridge subduction and the resultant slab windows have been well documented worldwide [Sisson et al., 2003], especially along the western margins of North and South America [Thorkelson, Taylor, 1989]. The principal characteristics of ridge subduction, which can be used to recognise the process in ancient orogens, include: intrusion of ridge-generated magmas into a forearc in a near-trench position [Marshak, Karig, 1977]; this can be regarded as the hallmark of ridge subduction.

The exhumation and tectonic emplacement of eclogites and blueschists take place in forearc accretionary complexes by either forearc- or backarc-directed extrusion, but few examples have been well analysed in detail. Here we present an example of oblique wedge extrusion of UHP/HP rocks in the Atbashi accretionary complex of the Kyrgyz South Tianshan.

Mesozoic volcanic rocks are widespread throughout the Great Xing’an range, NE China. Their ages formed from about 180 Ma to 120 Ma, with a strong peak about 125 Ma, and several weak peaks at ∼116 Ma, ∼140 Ma and ∼156 Ma respectively in age histogram. These complicated age spectrum points out that the volcanism may be related not only with the subduction of the Pacific plate, but also with closure of the Okhotsk ocean.

We report a paleomagnetic investigation on Permian volcanic rocks in the middle-east Inner Mongolia, NE China, aiming to puzzle out the timing and position of the final closure of the eastern Paleo-Asian ocean (PAO) and further to better understand tectonic evolution of the Central Asian Orogenic Belt (CAOB). Two pre-folding characteristic components are isolated from the Sanmianjing and Elitu formations (~283–266 Ma) in the northern margin of the North China block (NMNCB) and the Dashizhai Formation (~280 Ma) in the Songliao-Xilinhot block (SXB), respectively.

The deep crustal continental components and architecture of the Central Asian Orogenic Belt have long been a matter of debate [Wang et al., 2009; Kröner et al., 2014; Xiao et al., 2015; Yang et al., 2017]. We present an integrated study of geochronological and Hf-inzircon isotopic data for xenocrystic zircons from the Paleozoic granitoid rocks and associated felsic volcanic rocks of the Chinese Altai, East Junggar and nearby regions. The aim is to trace the age spatial distribution of deep old crustal components in these key parts of the western Central Asian Orogenic Belt.

Xing’an-Inner Mongolia Orogenic Belt (XIMOB) exposed in the eastern section of the Central Asian Orogenic Belt (CAOB) is generally thought to have resulted from closure of the Paleo-Asian ocean [Şengör et al., 1993]. However, the current hot debate is focused on whether the orogen formed through continuous subduction and accretion over a prolonged period of time until the closure of the Paleo-Asian ocean at the Early Triassic [Xiao et al., 2003], or through the subduction of the Paleo-Asian ocean and related collision in the Early-Mid Devonian [Xu et al., 2013], and the tectonic setting in the Late Paleozoic to Mesozoic has been a pivotal issue.

The Alxa block is situated to the south of the CAOB, situated to the east of the Tarim block and west of the NCC. Voluminous intrusive and extrusive rocks outcrop in the northern Alxa block and adjacent southern CAOB. Most of them are thought to be related to the closure of the Paleo-Asia Ocean and subsequent collision [Wu, 1993; Wu et al., 1998; Zhang et al., 2013; Dan et al., 2016].

Accretionary orogens form along convergent plate margins due to the ongoing subduction of oceanic lithosphere, and comprise accretionary prisms, magmatic arcs, back-arc domains, ophiolitic mélanges and possibly oceanic plateaus and continental fragments [Condie, 2007; Cawood et al., 2009]. Based on the dips and velocities of subducting slabs, accretionary orogens can be divided into retreating and advancing type, as exemplified by modern SW Pacific and Andes, respectively [Royden, 1993; Cawood et al., 2009].

Цель статьи – представить главные особенности Гренвилл-Свеконорвежского орогена (ГСНО) и предложить модель тектонической и геодинамической эволюции этого орогена, опираясь на результаты исследований докембрийских тектонических структур аналогичного типа в пределах Восточно-Европейского кратона. Исследование условий и обстановок возникновения и эволюции ГСНО представляет специальный интерес в связи с тем, что он территориально и в определенном смысле «идейно» размещен в центре Родинии – предполагаемого неопротерозойского суперконтинента. ГСНО был сформирован в мезонеопротерозое во внутренней области континента Лавроскандия. В настоящее время синформная тектоническая структура ГСНО разделена на два сектора: Гренвиллский вдоль юго-восточной окраины Канадского щита и Свеконорвежский на юго-западе Скандинавии. Единство Лавроскандии в мезонеопротерозое дважды нарушалось в результате формирования океанических структур, подобных Атлантическому океану. Целостность континента через некоторое время восстанавливалась при участии процессов субдукции океанической литосферы, аккреции и обдукции островодужных и океанических террейнов. В истории формирования ГСНО выделяются два периода: первый («подготовительный») в интервале от ~1.90 до ~1.16 млрд лет и второй (собственно формирование ГСНО) – в интервале от ~1.19 до ~0.90 млрд лет. Проявления гранулитового метаморфизма неоднократно зафиксированы до Гренвиллского орогенеза: 1.67–1.66, 1.47–1.45, 1.37–1.35 и 1.20–1.18 млрд лет назад. Оттавский этап собственно Гренвиллского метаморфизма датирован 1.16 и 1.05–1.03 млрд лет. Метаморфизм в основании Аллохтонного пояса соответствует гранулитовой фации повышенных давлений и в ряде мест – высокотемпературной эклогитовой фации (800–900 °С при давлении в интервале между 14 и 20 кбар). Возраст метаморфизма в породах Параавтохтонного пояса равен 1.05–0.95 млрд лет, уровень метаморфизма возрастает от зеленосланцевой фации близ Гренвиллского фронта до амфиболитовой фации повышенных давлений близ Пограничного надвига аллохтона, демонстрируя инвертированную метаморфическую зональность. Для Свеконорвежского сектора характерен гранулитовый метаморфизм повышенных дав- лений и локально, в основании аллохтонных и в пределах параавтохтонного комплексов, отмечены высокотемпературные эклогиты. Отличительной особенностью ГСНО является широкое проявление специфического интрузивного магматизма. Массивы анортозит-мангерит-чарнокит-гранитоидного (АМЧГ) и анортозит-рапакиви-гранитного (АРГ) комплексов, сформированные 1.8–1.5 млрд лет назад, широкой дугой обрамляют ороген. Во внутренней области ГСНО массивы этих комплексов были последовательно сформированы 1.16– 1.13 и 1.09–1.05, 0.99–0.96 и 0.93–0.92 млрд лет назад; вслед за внедрением массивы неравномерно подверглись гранулитовому метаморфизму. Высокотемпературный характер магматизма и метаморфизма, многократное повторение термальных импульсов и грандиозный объем коры, подвергшейся высокотемпературным преобразованиям, указывают на мантийный плюм в качестве наиболее адекватного источника тепловой энергии. Модель внутриконтинентального развития ГСНО противоречит популярным представлениям о возникновении этого орогена в результате столкновения и объединения ранее удаленных континентов (Лаврентии, Балтики и Амазонии), которые, как предполагается, завершили сборку суперконтинента Родиния. Сделан вывод о необходимости пересмотра представлений о тектонической позиции и геодинамической эволюции ГСНО, который не является аналогом Тибет-Гималайского орогена.

Установлена роль динамометаморфизма как основного фактора при формировании рудоносных залежей золота в Абчадской зоне разлома на примере рудного поля Мукодек. Рудный объект отнесен к рудно‐формационному золотосеребряному типу зон милонитизации и рассланцевания. Исходные вмещающие породы, обладающие повышенным геохимическим фоном Au, являются источником рудного вещества. При процессах динамометаморфизма увеличивается количество золотых частиц. Большая их часть подвергается укрупнению. От первичных пород динамометаморфитами наследуется положительная корреляция между количеством частиц и концентрациями золота. Формирование динамометаморфического комплекса рудного поля происходило как минимум в две стадии. На ранней стадии (321±1.9 млн лет) в результате механохимического (деформационного) преобразования вмещающих пород образовались золотоносные минерализованные динамометаморфиты серицит‐хлорит‐анкерит‐альбит‐кварцевого состава. Во вторую (280±15 млн лет) – сформировались рудные жилы альбит‐доломит‐кварцевого состава с промышленными содержаниями золота.

На основе данных о механизмах очагов землетрясений выполнен расчет сейсмотектонических деформаций для района землетрясения Мауле, Мw=8.8, 2010 г. Детально исследованы особенности деформаций на разных глубинах. В районе основной сейсмодислокации землетрясения Мауле и севернее характер поля деформаций до глубин 70 км является обычным для зон субдукции: наблюдается укорочение в направлении погружения океанической плиты. Ниже глубины 70 км характер деформирования резко меняется на горизонтальное удлинение. После главного события, так же как и до него, в очаговой области преобладает близширотное укорочение, но область основных сейсмодислокаций окружена отдельными участками с противоположным типом деформаций – близширотным удлинением. Детальный анализ сейсмотектонических деформаций в области океанического поднятия к западу от глубоководного желоба позволил выявить локальные участки близширотного удлинения вблизи южной и северной границы будущей области деструкции землетрясения Мауле. Обнаружение таких участков может иметь важное прогностическое значение для заблаговременного выделения областей подготовки сильных субдукционных землетрясений.

Рассмотрены особенности практического применения нового подхода к структурно‐парагенетическому анализу приразломных трещин [Seminsky, 2014, 2015], полученные в процессе опробования методики для изучения трещиноватости в Западном Прибайкалье и Центральной Монголии. В этой связи даны рекомендации по сбору и первоначальной обработке фактического материала. Приведено краткое описание метода и его отличительные детали. Новый подход заключается в сравнении природных сетей трещин с эталонными трещинными сетями. Он позволяет определить характеристики разломной зоны (строение, морфогенетический тип и др.) на основе массовых замеров ориентировок трещиноватости. Сравнительный анализ базируется на выявлении основного разрывного парагенезиса вблизи разломов – это тройка взаимно перпендикулярных систем трещин. В методике используется качественный подход к ранговой иерархии разрывов и полей напряжений, основанный на генетической соподчиненности. Фактическим материалом служит трещиноватость тектонического происхождения, для идентификации которой приведен ряд признаков – основными являются геометрическая структура трещинной сети (системная или хаотическая) и сколовый тип трещин. Другие генетические типы трещин (первичные, гипергенные) можно анализировать новым методом при условии существенного участия в их формировании тектонических напряжений, что определяется наличием соответствующих признаков. Приемы проведения геолого‐структурных наблюдений едины для всех пунктов, увеличение числа которых повышает эффективность метода. Приведены конкретные параметры для построения круговых диаграмм трещиноватости. К анализу привлекаются все максимумы на диаграмме для сравнения с эталонными трафаретами. Специальные критерии оценки диаграмм минимизируют ошибки случайного совпадения и обеспечивают надежность полученных решений. Рассмотрены различные вопросы интерпретации природных трещинных сетей, касающиеся угловых величин между сопряженными системами трещин, наличия нетипичных трещинных парагенезисов и разломных зон смешанного типа, структурно‐вещественных неоднородностей. Представленные в статье рекомендации по применению нового структурно‐парагенетического метода на основании полученного опыта в отношении подбора исходных полевых данных и их обработки служат практическим дополнением к методике проведения анализа в процессе спецкартирования разломных зон и выявления полей напряжений [Seminsky, 2014, 2015]. Предложенные сведения будут полезны для успешного освоения нового подхода по исследованию разломной структуры верхней части земной коры при решении прикладных и фундаментальных задач, связанных с изучением разломов.