Palaeoproterozoic to Eoarchaean crustal growth in southern Siberia: a Nd-isotope synthesis

Nd-isotope analyses from 114 rock samples are reported from the southern part of the Siberian craton to establish a first-order crustal formation scheme for the region. The Nd-isotopedata show considerable variability within and among different cratonic units. In many cases this variability reflects differing degrees of mixing between juvenile and older (up to Eoarchaean) crustal components. The fragments of Palaeoproterozoic juvenile crust within the studied segment of the Siberian craton margin have Nd-model ages of 2.0-2.3 Ga. Voluminous Palaeoproterozoicgranites ( 1.85 Ga) were intruded into cratonic fragments and suture zones. These granites mark the stabilization of the southern Siberian craton. The complexity in the Nd data indicatea long history of crustal development, extending from the Eoarchaean to the Palaeoproterozoiceras, which is interpreted to reflect the amalgamation of distinct Archaean crustal fragments, with differing histories, during Palaeoproterozoic accretion at 1.9-2.0 Ga and subsequent cratonic stabilization at 1.85 Ga. Such a model temporally coincides with important orogenic events on nearly every continent and suggests that the Siberian craton participated in the formation of a Palaeoproterozoic supercontinent at around 1.9 Ga

ДЕСЯТОЕ ЮБИЛЕЙНОЕ ВСЕРОССИЙСКОЕ НАУЧНОЕ СОВЕЩАНИЕ «ГЕОДИНАМИЧЕСКАЯ ЭВОЛЮЦИЯ ЛИТОСФЕРЫ ЦЕНТРАЛЬНО-АЗИАТСКОГО ПОДВИЖНОГО ПОЯСА: ОТ ОКЕАНА К КОНТИНЕНТУ» (ИЗК СО РАН, 17–20 ОКТЯБРЯ 2012 Г.)

The article provides review about the 10th anniversary of All-Russia scientific conference «Geodynamic evolution of the lithosphere of the Central Asian Orogenic Belt: from ocean to continent», which was held on 17–20 October, 2012 at the Institute of the Earth’s Crust SB RAS in Irkutsk, Russia.В статье приводится информация о десятом юбилейном Всероссийском научном совещании «Геодинамическая эволюция литосферы Центрально-Азиатского подвижного пояса: от океана к континенту», которое проходило в Институте земной коры Сибирского отделения Российской академии наук (г. Иркутск) с 17 по 20 октября 2012 года

ВАЛЕНТИН СЕРГЕЕВИЧ ФЕДОРОВСКИЙ – КОРИФЕЙ CИБИРСКОЙ ГЕОЛОГИИ

The publication is devoted to the 80 anniversary of Valentin S. Fedorovsky, the coryphaeus of Siberian geology.Cтатья посвящена 80-летнему юбилею Валентина Сергеевича Федоровского, корифея Сибирской геологии

КОМПЛЕКСЫ МЕТАМОРФИЧЕСКИХ ЯДЕР ЗАБАЙКАЛЬЯ: ОБЗОР

Metamorphic core complexes (hereafter MCC) revealed in the Transbaikalia have similar features of their patterns. Three levels can be distinguished by structural­material indicators: core, zone of mylonites (dynamically metamorphosed rocks) and overlying formations. The cores are composed of the Paleozoic granites and granitogneisses. Zones of mylonites skirt the cores and are characterized by various tectonites which are formed at the expense of the core rocks. The overlying formations include volcanogenic­sedimentary series of the Mesozoic and the Upper Palaeozoic. The rocks are not metamorphosed, yet subject to brittle deformations. Structurally, they are detached and deposited above the zone of mylonites.In Transbaikalia, MCC are characterized by synmetamorphic structural paragenesises of one type: low­angle schistosity, micro­ and macro­structures (folds, mineral streaking, boudinage, pressure shadows, C–S structure, kick­bends). According to the kinematic analyses, they were formed by the simple shear mechanism along the zones of deeply penetrating regional dislocations which plunged in the south­eastward direction. Tectonic transportation of the materials developed in the same direction, i.e. the top parts of tectono­stratigraphic sections were displaced against the lower parts in the south­eastward direction. Extension deformations tended in the north­west – south­east direction. Such movements facilitated formation of synthetic listric normal faults and rift basins. The most intensive tectonic exposure period is determined as 112–123 mln years, while the period of metamorphism is assessed as 140–130 mln years. The rocks in depth of the deep dislocation were transformed in conditions of amphibole facies of metamorphism (Т=590–640 °С; Р=3.2–4.6 kbar).According to our structural-­geological, petrological and isotopic data, the age of the majority of the metamorphic formations of the Transbaikalia is determined as the Late Mesozoic. They were formed in the extension regime due collapse of the Late Mesozoic orogeny, that was caused by accretion­collision events during the Early Mesozoic. Thickening of the continental crust contributed to increase of heat flow and higher plasticity at the crustal bottom. The orogen was thus unstable and flowing and caused regional extension and dislocations at the middle­crust level. Thinning of the crust was accompanied by isostatic uplifting which facilitated emergence of the structural metamorphic complexes of the middle­crust levels on the surface and formation of the metamorphic core complexes.Установленные в Забайкалье комплексы метаморфических ядер (metamorphic core complexes – МСС) характеризуются близкими чертами строения. По структурно-вещественным признакам в них выделяются три структурных уровня: ядро, зона милонитов (динамометаморфизованных пород) и образования покрова. Ядра сложены палеозойскими гранитами и гранитогнейсами. Милониты окаймляют ядра и характеризуются разнообразными тектонитами, возникшими за счет пород ядра. К покровным образованиям относятся вулканогенно-осадочные серии мезозоя и верхнего палеозоя. Породы не метаморфизованы, но подвержены хрупким деформациям. Располагаются они структурно выше зоны милонитов, отделяясь от них детачментом.Для МСС Забайкалья характерны однотипные синметаморфические структурные парагенезисы: пологая сланцеватость, микро- и макроструктуры (складки, линейность, будинаж, тени давления, C–S-структуры, кинкбанды). Кинематический анализ указывает, что их становление происходило по механизму простого сдвига по зонам глубокопроникающих региональных срывов, погружавшихся в юго-восточном направлении. В этом же направлении осуществлялся тектонический транспорт вещества, т.е. верхние части тектоностратиграфических разрезов относительно нижних смещались на юго-восток. Деформация растяжения характеризовалась трендом северо-запад – юго-восток. Такие движения способствовали возникновению синтетических листрических сбросов и формированию  рифтовых впадин. Время наиболее интенсивного тектонического экспонирования определяется значениями 112 – 123 млн лет, а время проявления метаморфизма – 140–130 млн лет. Породы в зоне глубинного срыва были преобразованы в условиях амфиболитовой фации метаморфизма (Т=590–640 °С и Р=3.2–4.6 кбар).Структурно-геологические, петрологические и изотопные данные показывают, что значительная часть метаморфических образований Забайкалья имеет позднемезозойский возраст. Их формирование происходило в режиме растяжения и связано с коллапсом позднемезозойского орогена, который возник в процессе раннемезозойских аккреционно-коллизионных событий. Утолщение континентальной коры способствовало усилению теплового потока и повышению пластичности в низах коры. Это предопределило неустойчивость орогена и его растекание, что привело к возникновению регионального растяжения и срывов на среднекоровом уровне. Утонение коры сопровождалось изостатическим поднятием, что способствовало выводу на поверхность структурновещественных комплексов среднекоровых уровней и формированию комплексов метаморфических ядер

THE 10TH ANNIVERSARY ALLRUSSIA SCIENTIFIC CONFERENCE «GEODYNAMIC EVOLUTION OF THE LITHOSPHERE OF THE CENTRAL ASIAN OROGENIC BELT: FROM OCEAN TO CONTINENT» (IEC SB RAS, 17–20 OCTOBER, 2012)

The article provides review about the 10th anniversary of All-Russia scientific conference «Geodynamic evolution of the lithosphere of the Central Asian Orogenic Belt: from ocean to continent», which was held on 17–20 October, 2012 at the Institute of the Earth’s Crust SB RAS in Irkutsk, Russia

FEDOROVSKY, VALENTIN S. – THE CORYPHAEUS OF SIBERIAN GEOLOGY

The publication is devoted to the 80 anniversary of Valentin S. Fedorovsky, the coryphaeus of Siberian geology

METAMORPHIC CORE COMPLEXES OF THE TRANSBAIKALIA: REVIEW

Metamorphic core complexes (hereafter MCC) revealed in the Transbaikalia have similar features of their patterns. Three levels can be distinguished by structural­material indicators: core, zone of mylonites (dynamically metamorphosed rocks) and overlying formations. The cores are composed of the Paleozoic granites and granitogneisses. Zones of mylonites skirt the cores and are characterized by various tectonites which are formed at the expense of the core rocks. The overlying formations include volcanogenic­sedimentary series of the Mesozoic and the Upper Palaeozoic. The rocks are not metamorphosed, yet subject to brittle deformations. Structurally, they are detached and deposited above the zone of mylonites.In Transbaikalia, MCC are characterized by synmetamorphic structural paragenesises of one type: low­angle schistosity, micro­ and macro­structures (folds, mineral streaking, boudinage, pressure shadows, C–S structure, kick­bends). According to the kinematic analyses, they were formed by the simple shear mechanism along the zones of deeply penetrating regional dislocations which plunged in the south­eastward direction. Tectonic transportation of the materials developed in the same direction, i.e. the top parts of tectono­stratigraphic sections were displaced against the lower parts in the south­eastward direction. Extension deformations tended in the north­west – south­east direction. Such movements facilitated formation of synthetic listric normal faults and rift basins. The most intensive tectonic exposure period is determined as 112–123 mln years, while the period of metamorphism is assessed as 140–130 mln years. The rocks in depth of the deep dislocation were transformed in conditions of amphibole facies of metamorphism (Т=590–640 °С; Р=3.2–4.6 kbar).According to our structural-­geological, petrological and isotopic data, the age of the majority of the metamorphic formations of the Transbaikalia is determined as the Late Mesozoic. They were formed in the extension regime due collapse of the Late Mesozoic orogeny, that was caused by accretion­collision events during the Early Mesozoic. Thickening of the continental crust contributed to increase of heat flow and higher plasticity at the crustal bottom. The orogen was thus unstable and flowing and caused regional extension and dislocations at the middle­crust level. Thinning of the crust was accompanied by isostatic uplifting which facilitated emergence of the structural metamorphic complexes of the middle­crust levels on the surface and formation of the metamorphic core complexes

Effects of Various Ripening Media on the Mesoporous Structure and Morphology of Hydroxyapatite Powders

Mesoporous hydroxyapatite (HA) materials demonstrate advantages as catalysts and as support systems for catalysis, as adsorbent materials for removing contamination from soil and water, and as nanocarriers of functional agents for bone-related therapies. The present research demonstrates the possibility of the enlargement of the Brunauer–Emmett–Teller specific surface area (SSA), pore volume, and average pore diameter via changing the synthesis medium and ripening the material in the mother solution after the precipitation processes have been completed. HA powders were investigated via chemical analysis, X-ray diffraction analysis, Fourier-transform IR spectroscopy, transmission electron microscopy (TEM), and scanning (SEM) electron microscopy. Their SSA, pore volume, and pore-size distributions were determined via low-temperature nitrogen adsorption measurements, the zeta potential was established, and electron paramagnetic resonance (EPR) spectroscopy was performed. When the materials were synthesized in water–ethanol and water–acetone media, the SSA and total pore volume were 52.1 m2g−1 and 116.4 m2g−1, and 0.231 and 0.286 cm3g−1, respectively. After ripening for 21 days, the particle morphology changed, the length/width aspect ratio decreased, and looser and smaller powder agglomerates were obtained. These changes in their characteristics led to an increase in SSA for the water and water–ethanol samples, while pore volume demonstrated a multiplied increase for all samples, reaching 0.593 cm3g−1 for the water–acetone sample