CONDITIONS OF FORMATION OF GABBRO-PERIDOTITES SILLS OF THE DOVYRENSKY INTRUSIVE COMPLEX (NORTHERN BAIKAL REGION)

Mineralogical and geochemical study of the gabbro-peridotite sills located in the near-bottom part of the Yoko-Dovyren stratified massif among the host terrigenous-carbonate rocks showed that the thickest (200–250 m) of them are differentiated from plagiolherzolites to olivine gabbronorites. Their formation is well described by fractional crystallization of the picrobasalt melt. When it entered the crystallization chamber, it had already contained some intratelluric crystals of high-magnesian olivine (up to 93 % Fo). The rock crystallization occurred in the temperature range 1234–985 °C at pressure 1.3–1.6 kb, corresponding to depth ~5–6 km. The calculated depth of separation of the initial melt from the mantle source was ~88 km, which corresponds to the lithostatic pressure ~28 kbar. In terms of geochemical parameters, the composition of the initial melt is characterized by dual nature: they are close to both the basalts of suprasubduction magmatism and the basalts of collisional volcanic-plutonic areas. We assume that formation of the Synnyr rift with the Dovyren intrusive complex is due to the destructive development of scattered spreading zones at the collisional-accretionary stage of the Baikal-Muya belt within 720–800 Ma

УСЛОВИЯ ФОРМИРОВАНИЯ СИЛЛОВ ГАББРО-ПЕРИДОТИТОВ ДОВЫРЕНСКОГО ИНТРУЗИВНОГО КОМПЛЕКСА (СЕВЕРНОЕ ПРИБАЙКАЛЬЕ)

Mineralogical and geochemical study of the gabbro-peridotite sills located in the near-bottom part of the Yoko-Dovyren stratified massif among the host terrigenous-carbonate rocks showed that the thickest (200–250 m) of them are differentiated from plagiolherzolites to olivine gabbronorites. Their formation is well described by fractional crystallization of the picrobasalt melt. When it entered the crystallization chamber, it had already contained some intratelluric crystals of high-magnesian olivine (up to 93 % Fo). The rock crystallization occurred in the temperature range 1234–985 °C at pressure 1.3–1.6 kb, corresponding to depth ~5–6 km. The calculated depth of separation of the initial melt from the mantle source was ~88 km, which corresponds to the lithostatic pressure ~28 kbar. In terms of geochemical parameters, the composition of the initial melt is characterized by dual nature: they are close to both the basalts of suprasubduction magmatism and the basalts of collisional volcanic-plutonic areas. We assume that formation of the Synnyr rift with the Dovyren intrusive complex is due to the destructive development of scattered spreading zones at the collisional-accretionary stage of the Baikal-Muya belt within 720–800 Ma.Минералого-геохимическое изучение габбро-перидотитовых силлов, расположенных в приподошвенной части Йоко-Довыренского расслоенного массива среди вмещающих терригенно-карбонатных пород, показало, что наиболее мощные (200–250 м) из них дифференцированы от плагиолерцолитов до оливиновых габбро-норитов и их формирование хорошо описывается фракционной кристаллизацией пикробазальтового расплава. При поступлении в камеру кристаллизации он уже содержал некоторое количество интрателлурических кристаллов высокомагнезиального оливина (до 93 % Fo). Кристаллизация пород происходила в интервале температур 1234–985 °С при давлении 1.3–1.6 кбар, отвечающем глубине ~5–6 км. Рассчитанная глубина отделения исходного расплава от мантийного источника составила ~88 км, что отвечает литостатическому давлению ~28 кбар. По геохимическим параметрам состав исходного расплава характеризуется двойственной природой: он близок как базальтам надсубдукционного магматизма, так и базальтам коллизионных вулканоплутонических ареалов. Можно предположить, что формирование Сыннырского рифта с довыренским интрузивным комплексом связано с деструктивными процессами развития рассеянных спрединговых зон на коллизионно-аккреционном этапе развития Байкало-Муйского пояса на рубеже 720–800 млн лет

Unidirectional motion of magnetic domain walls: The experiment and numerical simulation

The results of study of unidirectional motion of topologically different domain structures under the influence of periodic bipolar and unipolar magnetic field pulses applied perpendicular to the sample plane of (111) iron garnet single crystal plate are presented. The response of the domain structure to the field pulses was studied by direct observations utilizing the stroboscopic technique. Experimentally obtained dependences of the speed of unidirectional motion of stripe domains on the parameters of external bipolar pulsed magnetic field are compared with the results of numerical simulations. © Published under licence by IOP Publishing Ltd.Ministry of Science and Higher Education of the Russian Federation: 3.6121.2017The work was performed within the framework of the basic part of the state assignment of the Ministry of Science and Higher Education of the Russian Federation (project 3.6121.2017)

Experimental and Theoretical Study of Stripe Magnetic Domain Structure Drift in Iron Garnet Crystals

The results of experimental and theoretical study of magnetic domain structure drift in low frequency oscillating magnetic field oriented perpendicular to the sample plate are presented. Experimental study was performed on uniaxial iron garnet (TbErGd)₃(FeAl)₅O₁₂ (111) plate with rhombic anisotropy for the case when orientation of domain walls of stripe domains is preserved. Dynamic domain structure was revealed by means of magnetooptic Faraday effect and registered by high speed digital camera at the speed equal to 1200 fps. Theoretical model based on the motion equations for coupled harmonic oscillators that takes into account attenuation and field inhomogeneity along the plate is proposed

LIFETIME OF SPIRAL DYNAMIC DOMAINS IN IRON GARNET FILMS

In this paper investigation of lifetime of spiral dynamic domains in iron garnet film in magnetic field with a constant gradient field was performed. It is shown that dependence of spiral domains lifetime on amplitude of magnetic field has a peak in the middle of the amplitude range of spiral domains existence.Работа выполнена в рамках базовой части Госзадания Минобрнауки РФ (проект №3.6121.2017)

THE STRUCTURE OF DOMAIN WALLS IN SINGLE-CRYSTAL PLATES WITH COMBINED MAGNETIC ANISOTROPY

The structure of magnetic domain walls in single-crystal plates with combined magnetic anisotropy was investigated using micromagnetic simulation. The asymmetric changes in do-main wall structure in constant magnetic field were revealed.Работа выполнена в рамках базовой части госзадания Министерства науки и высшего образования РФ (проект No 3.6121.2017)

Faraday instability on viscous ferrofluids in a horizontal magnetic field: Oblique rolls of arbitrary orientation

A linear stability analysis of the free surface of a horizontally unbounded ferrofluid layer of arbitrary depth subjected to vertical vibrations and a horizontal magnetic field is performed. A nonmonotonic dependence of the stability threshold on the magnetic field is found at high frequencies of the vibrations. The reasons of the decrease of the critical acceleration amplitude caused by a horizontal magnetic field are discussed. It is revealed that the magnetic field can be used to select the first unstable pattern of Faraday waves. In particular, a rhombic pattern as a superposition of two different oblique rolls can occur. A scaling law is presented which maps all data into one graph for the tested range of viscosities, frequencies, magnetic fields and layer thicknesses.Comment: 8 pages, 6 figures, RevTex

(Table) Argon isotope ratios and argon ages of rocks obtained from the Chernorud zone, western Baikal area

Structural-petrologic and isotopic-geochronologic data on magmatic, metamorphic, and metasomatic rocks from the Chernorud zone were used to reproduce the multistage history of their exhumation to upper crustal levels. The process is subdivided into four discrete stages, which corresponded to metamorphism to the granulite facies (500-490 Ma), metamorphism to the amphibolite facies (470-460 Ma), metamorphism to at least the epidote-amphibolite facies (440-430 Ma), and postmetamorphic events (410-400 Ma). The earliest two stages likely corresponded to the tectonic stacking of the backarc basin in response to the collision of the Siberian continent with the Eravninskaya island arc or the Barguzin microcontinent, a process that ended with the extensive generation of synmetamorphic granites. During the third and fourth stages, the granulites of the Chernorud nappe were successively exposed during intense tectonic motions along large deformation zones (Primorskii fault, collision lineament, and Orso Complex). The comparison of the histories of active thermal events for Early Caledonian folded structures in the Central Asian Foldbelt indicates that active thermal events of equal duration are reconstructed for the following five widely spiced accretion-collision structures: the Chernorud granulite zone in the Ol'khon territory, the Slyudyanka crystalline complex in the southwestern Baikal area, the western Sangilen territory in southeastern Tuva, Derbinskii terrane in the Eastern Sayan, and the Bayankhongor ophiolite zone in central Mongolia. The dates obtained by various isotopic techniques are generally consistent with the four discrete stages identified in the Chernorud nappe, whereas the dates corresponding to the island-arc evolutionary stage were obtained only for the western Sangilen and Bayankhongor ophiolite zone