The results of U-Pb SHRIMP-II dating of zircon from granitoids of Talitsky molybdenum-bearing massif (eastern slope of the Middle Urals)

Age position and geodynamic conditions of molybdenum metallization and productive granitoids of the Urals formation are very little studied now. This publication contains the results of isotopic dating of granites from Talitsa Cu-Mo-porphyry deposit which should help solve this problem. The timing of formation of the molybdenum-bearing granitoids of Talitsa deposit was determined by applying the U-Pb SHRIMP-II method through zircons (the Center for Isotopic Research of All Russian Geological Research Institute, St.Petersburg). The U-Pb-age has been calculated on 7 (from a total of 11 conduc­ted) measurements with probability of concordanсе 0.996 and MSWD = 0.105 and it is 297.4 ± 2.3 Ma. The results of U-Pb dating are similar to before published Re-Os ages of Talitsa molybdenite deposit: 299.9 ± ± 2.9 Ma and 298.3 ± 1.3 Ma. These data establishes the new unknown before age level of molybdenum metallization. Until recently there has been only data on the Yuzhno-Shameiskoe molybdenum deposit connected with the subalkaline granites of Malyshevo massif which is younger: 277.1 ± 1.1 Ma. According to the received data, the intrusion of investigated granitoids happened practically at the same time as the formation of the wide-spread in the western slope of the Middle Urals intrusive bodies which are accompanied by gold metallization (Verkhisetsky, Shartashsky and others). With such close (practically the same) time of formation the rocks of molybdenum-bearing and gold-bearing massifs significantly differ in petrochemical peculiarities, which probably determines their metallogenetic specialization. Granitoids forming gold-bearing quartz veins on chemical composition are rocks of calc-alkaline series (typical exemple - Shartashskyi massif with Beriozovsk gold deposite). The granitoids productive on of Cu-Mo-porphyry type metallization together with large number of normal alkalinity rocks includes subalkaline rocks such as monzodiorites and quartz monzodiorites

ВОЗРАСТНЫЕ РУБЕЖИ ПРОЯВЛЕНИЯ И ОСОБЕННОСТИ СОСТАВА РАННЕПАЛЕОЗОЙСКОГО МАГМАТИЗМА И СВЯЗАННЫХ С НИМ РЕДКОМЕТАЛЛЬНЫХ ПЕГМАТИТОВ В ЮГО-ВОСТОЧНОЙ ЧАСТИ САНГИЛЕНСКОГО БЛОКА ТУВИНО-МОНГОЛЬСКОГО МАССИВА

The article presents new data on ages (U-Pb zircon dating, SIMS SHRIMP-II) and chemical compositions of rocks from gabbro-granitic and granite-leucogranitic magmatic associations. These rocks preceded the formation of Li-enriched spodumene pegmatites of the Tserigiyngol-Burchin ore cluster (Russian: ЦБРУ), one of the main clusters in the South Sangilen pegmatite belt (SSB) located in the Tuva-Mongolian massif being a part of the Central Asian Fold Belt. We investigated the rocks from the Upper Tserigiyngol, Uchuglyk and Temenchulu plutons, and pegmatites from two neighbouring fields. We distinguish three impulses of granitic magmatism (517±7, 508±7, and 488±6 Ma), which are attributed to different stages of the Early Paleozoic collision orogeny (520-480 Ma). The period when the Li-enriched pegmatites were formed (494±7 Ma) is close to the magmatism impulse at 488±6 Ma. Differences are discovered in compositional and isotopic (Sm-Nd) features of granites dominating at the following stages of collisional orogeny: (1) early collision (517±7 Ma) – I-type granites, eNd(T)=0–1.5, TNd (DM-2st)=1.2–1.1 b.y., and (2) late collision (488±6 Ma) – A-2-type granites, eNd(T)=–3.0…–1.6, TNd (DM-2st)=1.5–1.4 b.y., which are due to different sources. Our study shows that facies transitions are absent between the late-collision granites (488±6 Ma) and the spodumene pegmatites from the Tserigiyngol-Burchin ore cluster (494±7 Ma), although these rocks are close in age. In terms of geochemical features, the spodumene pegmatites from the cluster are strongly different from both the late-collision granites and spodumene pegmatites from other SSB fields, including the large Tastyg lithium deposit. We have analysed the role of interactions between the crustal and mantle materials in the formation of granitoid sources in the Tserigiyngol-Burchin ore cluster, and described their evolution in time and the influence on the pegmatite rare-element specialization.Представлены новые данные о возрасте (U-Pb по циркону, SIMS SHRIMP-II) и вещественном составе пород из габбро-гранитоидной и гранит-лейкогранитовой магматических ассоциаций, предшествовавших образованию богатых литием сподуменовых пегматитов Церигийнгольско-Бурчинского рудно-магматического узла (ЦБРУ) – одного из ключевых в Южно-Сангиленском поясе (ЮСП) проявлений редкометалльных пегматитов Тувино-Монгольского микроконтинента, входящего в состав Центрально-Азиатского складчатого пояса. В ЦБРУ проведены исследования пород из трех массивов – Верхнецеригийнгольского, Учуглыкского и Теменчулу, а также пегматитов двух полей, расположенных рядом с ними. Результаты исследований позволили выделить в этом регионе три импульса гранитообразования (517±7, 508±7 и 488±6 млн лет), с последним из которых субсинхронно время формирования редкометалльных пегматитов (494±7 млн лет), и обосновать соответствие их возраста различным стадиям раннепалеозойского коллизионного орогенеза (520–480 млн лет). Установлено, что отличия состава и изотопных характеристик гранитоидов, доминировавших на разных стадиях орогенеза: (1) раннеколлизионной (517±7 млн лет) – гранитоиды I-типа, eNd(T)=0–1.5, TNd (DM-2st)=1.2–1.1 млрд лет и (2) позднеколлизионной (488±6 млн лет ) – граниты А-2-типа, eNd(T)=–3.0…–1.6, TNd (DM-2st)=1.5–1.4 млрд лет, обусловлены различием их источников. Несмотря на близкий возраст сподуменовых пегматитов ЦБРУ и гранитов позднеколлизионного импульса, между ними не выявлено фациальных переходов, а геохимические особенности пегматитов резко контрастируют не только с этими гранитами, но и со сподуменовыми пегматитами других полей ЮСП, включающих крупное месторождение лития Тастыг. На основании полученных результатов рассмотрена роль процессов корово-мантийного взаимодействия в формировании источников гранитоидов ЦБРУ, их эволюция во времени и степень влияния на особенности редкометалльной специализации пегматитов

ПРИНЦИПЫ СОСТАВЛЕНИЯ ТЕКТОНИЧЕСКИХ КАРТ АЗИИ И АРКТИКИ МАСШТАБОВ 1:2 500 000–1:5 000 000

An overview of the history of tectonic mapping in Russia is presented, and the principles of tectonic mapping are briefly described. Here, out attention is focused on the Tectonic Map of North, Central and East Asia (scale 1:2500000, 2014) and the Tectonic Map of the Arctic (scale 1:5000000, 2019) prepared by international projects of Karpinsky Russian Geological Research Institute (VSEGEI). The projects included participants from geological service agencies, universities and the academies of sciences of 13 countries. We describe the mapping approaches, structural features, legends, graphical design, and information at the map margins. The experience gained with the projects of these two tectonic maps will be used to compile the International Tectonic Map of Asia, scale 1:5000000 (ITMA-5000) and the Tectonic Map of Russia, scale 1:2500000.Приведена история развития отечественного тектонического картографирования с краткой характеристикой принципов составления тектонических карт разных лет. Главное внимание уделено Тектонической карте Северной, Центральной и Восточной Азии масштаба 1:2500000 (2014 г.) и Тектонической карте Арктики масштаба 1:5000000 (2019 г.), подготовленным в рамках международных проектов с участием геологических служб, университетов и академий наук 13 стран мира во Всероссийском научно-исследовательском институте им. А.П. Карпинского (ВСЕГЕИ). Охарактеризованы подходы к составлению этих карт, структуры и содержания легенд. Даны описания изобразительных средств и зарамочного оформления. Опыт, полученный при составлении тектонических карт Азии и Арктики, планируется применить при составлении Международной тектонической карты Азии масштаба 1:5000000 (ITMA-5000) и Тектонической карты России масштаба 1:2500000

ГЛУБИННОЕ СТРОЕНИЕ ЗЕМНОЙ КОРЫ СЕВЕРО-ВОСТОЧНОЙ ЕВРАЗИИ И ЕЕ КОНТИНЕНТАЛЬНЫХ ОКРАИН

The paper reports on the deep geophysical studies performed by the Geological Survey of Russia (VSEGEI) under the international project – Deep Processes and Metallogeny of Northern, Central and Eastern Asia. A model of the deep crustal structure is represented by a set of crustal thickness maps and a 5400-km long geotransect across the major tectonic areas of Northeastern Eurasia. An area of 50000000 km2 is digitally mapped in the uniform projection. The maps show the Moho depths, thicknesses of the main crustal units (i.e. the sedimentary cover and the consolidated crust), anomalous gravity and magnetic fields (in a schematic zoning map of the study area), and types of the crust. The geotransect gives the vertical section of the crust and upper mantle at the passive margin of the Eurasian continent (including submarine uplifts and shelf areas of the Arctic Ocean) and the active eastern continental margin, as well as an area of the Pacific plate.В работе представлены результаты обобщения и интерпретации глубинных геофизических исследований, выполненных Геологической службой России (ВСЕГЕИ) в рамках международного проекта «Глубинные процессы и металлогения Северной, Центральной и Восточной Азии». Модель глубинного строения земной коры представлена комплектом карт, отражающих мощностные параметры земной коры, и геотрансектом протяженностью 5400 км, пересекающим основные тектонические области Северо-Восточной Евразии. Комплект цифровых карт, охватывающих область в 50 млн км2, создан в единой проекции и включает карты глубины залегания поверхности Мохоровичича, мощности основных подразделений земной коры (осадочный чехол и консолидированная земная кора), аномального поля силы тяжести и аномального магнитного поля, использованных для районирования территории, а также карту типов земной коры. Геотрансект пересекает северо-восточную часть Евразии и характеризует вертикальный срез земной коры и верхней мантии пассивной окраины Евразийского континента (включая глубоководные поднятия Северного Ледовитого океана и его шельфовую часть), активную восточную континентальную окраину и выходит в область Тихоокеанской плиты

AGE AND COMPOSITION OF THE EARLY PALEOZOIC MAGMATIC ASSOCIATIONS AND RELATED RARE-ELEMENT PEGMATITES IN THE SOUTH-EASTERN PART OF THE SANGILEN BLOCK, TUVA-MONGOLIAN MASSIF

The article presents new data on ages (U-Pb zircon dating, SIMS SHRIMP-II) and chemical compositions of rocks from gabbro-granitic and granite-leucogranitic magmatic associations. These rocks preceded the formation of Li-enriched spodumene pegmatites of the Tserigiyngol-Burchin ore cluster (Russian: ЦБРУ), one of the main clusters in the South Sangilen pegmatite belt (SSB) located in the Tuva-Mongolian massif being a part of the Central Asian Fold Belt. We investigated the rocks from the Upper Tserigiyngol, Uchuglyk and Temenchulu plutons, and pegmatites from two neighbouring fields. We distinguish three impulses of granitic magmatism (517±7, 508±7, and 488±6 Ma), which are attributed to different stages of the Early Paleozoic collision orogeny (520-480 Ma). The period when the Li-enriched pegmatites were formed (494±7 Ma) is close to the magmatism impulse at 488±6 Ma. Differences are discovered in compositional and isotopic (Sm-Nd) features of granites dominating at the following stages of collisional orogeny: (1) early collision (517±7 Ma) – I-type granites, eNd(T)=0–1.5, TNd (DM-2st)=1.2–1.1 b.y., and (2) late collision (488±6 Ma) – A-2-type granites, eNd(T)=–3.0…–1.6, TNd (DM-2st)=1.5–1.4 b.y., which are due to different sources. Our study shows that facies transitions are absent between the late-collision granites (488±6 Ma) and the spodumene pegmatites from the Tserigiyngol-Burchin ore cluster (494±7 Ma), although these rocks are close in age. In terms of geochemical features, the spodumene pegmatites from the cluster are strongly different from both the late-collision granites and spodumene pegmatites from other SSB fields, including the large Tastyg lithium deposit. We have analysed the role of interactions between the crustal and mantle materials in the formation of granitoid sources in the Tserigiyngol-Burchin ore cluster, and described their evolution in time and the influence on the pegmatite rare-element specialization

PRINCIPLES OF TECTONIC MAPPING OF ASIA AND THE ARCTIC, SCALES 1:2500000 – 1:5000000

An overview of the history of tectonic mapping in Russia is presented, and the principles of tectonic mapping are briefly described. Here, out attention is focused on the Tectonic Map of North, Central and East Asia (scale 1:2500000, 2014) and the Tectonic Map of the Arctic (scale 1:5000000, 2019) prepared by international projects of Karpinsky Russian Geological Research Institute (VSEGEI). The projects included participants from geological service agencies, universities and the academies of sciences of 13 countries. We describe the mapping approaches, structural features, legends, graphical design, and information at the map margins. The experience gained with the projects of these two tectonic maps will be used to compile the International Tectonic Map of Asia, scale 1:5000000 (ITMA-5000) and the Tectonic Map of Russia, scale 1:2500000

Morphology of seamounts at the Mendeleev Rise, Arctic Ocean

Geological and geophysical studies undertaken during the Russian Arktika-2012 Expedition of 2012 produced evidence of basement outcrops on the steep slopes of the Mendeleev Rise seamounts. Observations of the outcrops from research submarines showed that part of the steep slopes interpreted as basement outcrops based on seismic data were overlain by a light sediment cover. The actual areas of the basement outcrops are therefore much less than indicated by the seismic data alone. The outcrops found are of 5–10 to 100–200 m and are often stretched along some hypsometric level or arranged obliquely, crossing a slope at an angle to the horizon. The rocks are massive and layered, often strongly weathered, cavernous, with visible fissures and extended by dislocations

Morphology of seamounts at the Mendeleev Rise, Arctic Ocean

Geological and geophysical studies undertaken during the Russian Arktika-2012 Expedition of 2012 produced evidence of basement outcrops on the steep slopes of the Mendeleev Rise seamounts. Observations of the outcrops from research submarines showed that part of the steep slopes interpreted as basement outcrops based on seismic data were overlain by a light sediment cover. The actual areas of the basement outcrops are therefore much less than indicated by the seismic data alone. The outcrops found are of 5–10 to 100–200 m and are often stretched along some hypsometric level or arranged obliquely, crossing a slope at an angle to the horizon. The rocks are massive and layered, often strongly weathered, cavernous, with visible fissures and extended by dislocations

Zircon geochronology of bottom rocks in the central Arctic Ocean: analytical results and some geological implications

In the past few years sampling of deepwater seabed gained an increasingly important role in studying geological structure of the Arctic Ocean. A common concept of virtually uninterrupted pelagic drape in the Amerasia Basin and exclusively ice-rafted nature of all clastic components that occur in bottom sediments was challenged by recent discoveries of bedrock exposures in the sea floor, while correlation of results of analytical study of bottom samples collected by the Russian expeditions in 2000, 2005 and 2007 with bathymetric environments at respective sites suggested that certain dredged and cored coarse rock fragments appeared meaningful for bedrock characterization if even the source sub-pelagic outcrop was not positively documented. The first results of age determinations of detrital zircons that were extracted from coarse fragments of lithic sedimentary rocks resting on the seabed and in the immediate sub-bottom, as well as of zircons from fragments of magmatic/metamorphic rocks and of zircon grains separated directly from sub-pelagic unlithified sediments are in agreement with published interpretations of the Lomonosov Ridge bedrock as composed of Mesozoic terrigenous sequences; the presence of an older Neoproterozoic(?) – Early-Middle Paleozoic basement is also possible. The Mendeleev Rise bedrock, too, is believed to mainly consist of Paleozoic-Early(?) Mesozoic sedimentary superstructure that may locally rest on the Earliest Paleozoic or even older units. Basaltic rocks likely to originate from the High Arctic Large Igneous Province (HALIP) has not so far been found among the collected fragments but limited loose zircon grains probably derived from broadly contemporaneous magmatic products were recorded in sub-pelagic sediment along with dropstones of variably metamorphosed Precambrian mafic and granitoid rocks. INTRODUCTION Great progress in acquisition of new bathymet-ric and geophysical data relevant to understanding the geological structure and history of the Arctic Ocean, including the tectonic nature of enigmatic Central-Arctic bathymetric highs, was achieved in recent years by the Arctic countries through their programs for delineation of respective extended continental shelves. However, only limited direct geological information was obtained on the compo-sition of sub-bottom bedrock concealed by almost continuous drape of young sediments. Only at a few sites can the lithic fragments recovered by bottom sampling be interpreted with sufficient confidence as representing in situ submarine bedrock, while in most cases they are regarded ice rafted debris (IRD) of questionable derivation. In search of provenance of lithic and mineral clastic components in bottom sediments we conducted age determinations on zircon crystals of two categories: (1) extracted from the rock fragments and (2) separated directly from hemipelagic sediments. In this paper we present the results of more than 700 zircon U-Pb age measurements completed before 2012. The samples labeled AF00, AF05, AF07 were collected during MS " Akademik Fedorov " cruises Arctic-2000, 2005, 2007, those marked ALR07 were acquired in 2007 on board NIB (nuclear icebreaker) " Rossiya " , and two specimens designated BC were selected for the analysis from clastic material sampled by RV " Polarstern " in the course of ARK-XXIII/3-2008 cruise