Побузький гірничорудний район Українського щита. Структурно-петрофізична карта кристалічного фундаменту та деякі питання геології раннього докембрію

Structural and petrophysical map of a scale 1:100 000 of the Bug mining area (BMA), one of the most promising areas of ore minerals in the eastern part of the Ukrainian shield has been built. The area is located in the Middle Bug (sheets of topographic map M-35-XXXVI-eastern half and M-36-XXXI). Materials of geological survey of a scale 1:50 000, deep geological mapping of a scale 1:200 000, exploration, as well as: geophysical surveys of a scale 1:10 000—1:50 000, seismic and geoelectric deep sounding; special tectonic works on outcrops; published results of determining the isotopic age of Precambrian rocks have been put into the basis of the constructions.Authors tried to enclose only indisputable data such as material composition, structural and textural features, petrophysical characteristics of rocks, the contours and dimensions of bodies by geophysical data and drilling, tectonophysical parameters of discontinuous structures directly in the map content.Unclear and discussion debatable points on the map are not shown and discussed in the text. These problems include the tectonic position of BMA (the Bug Mining Area), which, according to the authors, belonged to the Bug megablock in the Archean and in the Proterozoic  it was divided by the  fault Talnov zone  and as a result of the process of shifting-pulling apart  its eastern part joined the Ingul megablock. The deep crust-mantle nature established in the territory of BMA of the large Golovanevsk and Bandurivka gravitation anomalies have been shown.The authors rejected the division of Early Precambrian rocks of granulite facies into suites as because the principle of a sequence of strata and correlation of sections in the area is not observed. The problem of the scope of the Dniester and Bug series from which rocks of Proterozoic kinzigite formations were excluded is being discussed here. Particular attention has been paid to the mechanisms of formation of subvertical layered banded structure of thickness of Early Precambrian granulite complexes of the area. It is shown that this structurally textured rock fabric formed in the early Proterozoic as a result of horizontal forces and horizontal movements of the substance and the folding has mainly near-fault shift character with subvertical hinges of folds, which is clearly seen in the horizontal sections and by the results of drilling.Построена структурно-петрофизическая карта масштаба 1:100 000 Побужского горнорудного района (ПГРР), одного из наиболее перспективных на рудные полезные ископаемые в западной части Украинского щита. Район расположен на Среднем Побужье (листы топографической карты М-35-XXXVI — восточная половина и М-36-XXXI). В основу построений положены материалы геологической съемки масштаба 1:50 000, глубинного геологического картирования масштаба 1:200 000, поисково-разведочных работ, а также геофизических съемок масштабов 1:10 000—1:50 000,сейсмического и геоэлектрического глубинного зондирования; специальных тектонофизических работ на обнажениях; опубликованных результатов определения изотопного возраста докембрийских горных пород. Непосредственно в содержание карты авторы постарались вложить только бесспорные данные, такие как вещественный состав, структурно-текстурные особенности, петрофизическая характеристика горных пород, контуры и размеры тел по геофизическим и буровым данным, тектонофизические параметры разрывных структур.Неясные и дискуссионные моменты на карте не показаны и обсуждены в тексте. К таким вопросам относится тектоническое положение ПГРР, который, по мнению авторов, в архее принадлежал Бугскому мегаблоку, а в протерозое был разделен Тальновской зоной разломов и в результате процесса сдвиго-раздвига его восточная часть отошла к Ингульскому мегаблоку. Показана глубинная коромантийная природа установленных на территории ПГРР крупных Голованевской и Бандуровской гравитационных аномалий.Авторы отказались от подразделения раннедокембрийских горных пород гранулитовой фации на свиты, так как принцип последовательности напластования и корреляции разрезов в районе не соблюдаются. Обсуждена проблема объема днестровско-бугской серии, из которой исключены породы кинцигитовой формации, имеющие протерозойский возраст. Особое внимание уделено механизмам формирования субвертикального слоисто-полосчатого строения толщи раннедокембрийских гранулитовых комплексов района. Показано, что эта структурно-текстурная ткань горных пород образовалась в раннем протерозое в результате действия горизонтальных сил и горизонтальных движений вещества, а складчатость имеет в основном приразломный сдвиговый характер с субвертикальными шарнирами складок, что хорошо видно в горизонтальных срезах и по результатам бурения.Побудовано структурно-петрофiзичну карту масштабу 1:100 000 Побузького гірничорудного району (ПГРР), одного з найперспективнiших на рудні корисні копалини в західній частині Українського щита. Район розмiщується на Середньому Побужжі (листи топографічної карти М-35-XXXVI — східна половина і М-36-XXXI). В основу побудов покладено матеріали геологічного знiмання масштабу 1:50 000, глибинного геологічного картування масштабу 1:200 000, пошуково-розвідувальних робіт, а також геофізичних знiмань масштабів 1:10 000—1:50 000, сейсмічного та геоелектричного глибинного зондування; спеціальних тектонофізичних робіт на відслоненнях; опублікованих результатів визначення ізотопного віку докембрійських гірських порід. Безпосередньо у зміст карти автори вклали тільки беззаперечні дані, такі як речовинний склад, структурно-текстурні особливості, петрофізична характеристика гірських порід, контури і розміри тіл за геофізичними та буровими даними, тектонофізичні параметри розривних структур. Неясні й дискусійні моменти на карті не показані, але обговорені у тексті. Одним з таких питань є тектонічне положення ПГРР, який, на думку авторів, в археї належав Бузькому мегаблоку, а в протерозої був розділений Тальнівською зоною розломів і в результаті процесів зсуву—розсуву його східна частина відійшла до Інгульського мегаблока. Показано глибинну коромантiйну природу встановлених на території ПГРР великих Голованівської і Бандурівської гравітаційних аномалій. Автори відмовилися від розділення ранньодокембрійських гірських порід гранулітової фації на світи, оскільки принцип послідовності нашарування і кореляції розрізів у районі не дотримується. Обговорено проблему обсягу дністровсько-бузької серії, з якої виключено породи кінцигітової формації, які мають протерозойський вік. Особливу увагу приділено механізмам формування субвертикальної шарувато-смугастої будови товщі ранньодокембрійського гранулітового комплексу району. Показано, що ця структурно-текстурна основа гірських порід утворилася в ранньому протерозої внаслідок дії горизонтальних сил і горизонтальних рухів речовини, а складчастість має переважно прирозломно-зсувний характер із субвертикальними шарнірами складок, що добре помітно в горизонтальних зрізах і за результатами буріння

Lithospheric structure along wide-angle seismic profile GEORIFT 2013 in Pripyat–Dnieper–Donets Basin (Belarus and Ukraine)

The GEORIFT 2013 (GR'13) WARR (wide-angle reflection and refraction) experiment was carried out in 2013 in the territory of Belarus and Ukraine with broad international co-operation. The aim of the work is to study basin architecture and deep structure of the Pripyat-Dnieper-Donets Basin (PDDB), which is the deepest and best studied Palaeozoic rift basin in Europe. The PDDB is located in the southern part of the East European Craton (EEC) and crosses Sarmatia-one of the three segments of the EEC. The PDDB was formed by Late Devonian rifting associated with domal basement uplift and magmatism. The GR'13 extends in NW SE direction along the PDDB strike and crosses the Pripyat Trough (PT) and Dnieper Graben (DG) separated by the Bragin Uplift (BU) of the basement. The field acquisition along the GR'13 (of 670 km total length) involved 14 shots and recorders deployed every similar to 2.2 km for several shot points. The good quality of the data, with first arrivals visible up to 670 km for several shot points, allowed for construction of a velocity model extending to 80 km depth using ray-tracing modelling. The thickness of the sediments (Vp <6.0 km s(-1)) varies from 1-4 km in the PT, to 5 km in the NW part of the DG, to 10-13 km in the SE part of the profile. Below the DG, at similar to 330-530 km distance, we observed an upwarping of the lower crust (with Vp of similar to 7.1 km s(-1)) to 25 km depth that represents a rift pillow or mantle underplate. The Moho shallows southeastwards from similar to 47 km in the PT to 40-38 km in the DG with mantle velocities of 8.35 and similar to 8.25 km s(-1) in the PT and DG, respectively. A near-horizontal mantle discontinuity was found beneath BU (a transition zone from the PT to the DG) at the depth of 50-47 km. It dips to the depth of similar to 60 km at distances of 360-405 km, similar to the intersecting EUROBRIDGE'97 profile. The crust and upper mantle structure on the GR'13 may reflect varying intensity of rifting in the PDDB from a passive stage in the PT to active rifting in the DG. The absence of Moho uplift and relatively thick crystalline crust under the PT is explained by its tectonic position as a closing unit of the PDDB, with a gradual attenuation of rifting from the southeast to the northwest. The most active stage of rifting is evidenced in the DG by a shallower Moho and by a presence of a rift pillow caused by mafic and ultramafic intrusions during the active phase. The junction of the PT and the DG (the BU) locates just at its intersection with the NS regional tectonic zone Odessa-Gomel. Most likely, the 'blocking' effect of this zone did not allow for further propagation of active rifting to the NW.Peer reviewe

The nature of inclined seismic boundary in the Earth crust of the Scythian plate along the DOBRE-5 Profile

Geological and tectonic interpretation of high-speed seismic model along the profile DOBRE-5 elaborated in 2011 by DSS method (wide-angle refraction and reflection (WARR)) with the main aim of clarifying the structure of the lithosphere and geodynamic features of the southwestern edge of the East-European platform (Scythian plate) has been conducted. Amplifying volumetric seismic tectonic model of the Scythian plate has been plotted; structural-high-speed element — sloping seismic boundary along the DOBRE-5 profile has been revealed, its location has been defined more precisely and possible mechanisms of formation have been proposed: it corresponds to the northern border of the Early Permian active over-thrust or thrust edge of southern dip and of formation of front-rank molassa sag, the so-called Euxinian orogenic belt or the North Crimean suture formed by the closure of the Paleo-Tethys Ocean in the late Paleozoic—Triassic, subduction of the East-European platform (EEP) under the Scythian plate (SP) southward and their collision. On the surface Pre-Cretaceuos basement of the North Crimean suture can be traced as Golitsyn and Azov fault zones usually considered as the border between EEP and SP. Dipping seismic border is a listric surface that falls to the south-southeast, with angles in the longitudinal intersection, α = 17°, and in sections perpendicular to the EEP and SP, α = 22°to 38°. This inclination of the DSB is close to the dip of the South-Crimean suture zone that was previously assumed by Yudin V.V

Features of the potential seismogenic zone of the Ingul and Srednepridneprovsky megablocks of the Ukrainian Shield

Special features of seismogenic zone of the Ingul and MiddleDnieper megablocks of the Ukrainian Shield have been analyzed. Several seismogenic zones with small areas have been subdivided within its limits, which differ by degree of contrast of geologicalgeophysical characteristics of the Earth's crust (velocity of propagation of seismic waves, special features of M discontinuity occurrence, heat flow, electroconductivity anomalies)

Seismic model of the crust and upper mantle in the Scythian Platform: the DOBRE-5 profile across the north western Black Sea and the Crimean Peninsula

International audienceThe Scythian Platform (ScP) with a heterogeneous basement of Baikalian–Variscan–Cimmerian age is located between the East European Craton (EEC) on the north and the Crimean–Caucasus orogenic belt and the Black Sea (BS) Basin on the south. In order to get new constrains on the basin architecture and crustal structure of the ScP and a better understanding of the tectonic processes and evolution of the southern margin of the EEC during Mesozoic and Cenozoic time, a 630-km-long seismic wide-angle refraction and reflection (WARR) profile DOBRE-5 was acquired in 2011 October. It crosses in a W–E direction the Fore-Dobrudja Trough, the Odessa Shelf of the BS and the Crimean Plain. The field acquisition included eight chemical shot points located every 50 km and recorded by 215 stations placed every ∼2.0 km on the land. In addition, the offshore data from existing profile 26, placed in the Odessa Shelf, were used. The obtained seismic model shows clear lateral segmentation of the crust within the study region on four domains: the Fore-Dobrudja Domain (km 20–160), an offshore domain of the Karkinit Trough at the Odessa Shelf of the BS (km 160–360), an onshore domain of the Central Crimean Uplift (Crimean Plain, km 360–520) and the Indolo-Kuban Trough at the Kerch Peninsula (km 520–620) that is the easternmost part of the Crimea. Two contrasting domains of the ScP within the central part of the DOBRE-5 profile, the Karkinit Trough and the Central Crimean Uplift, may represent different stages of the ScP formation. A deep Karkinit Trough with an underlying high-velocity (>7.16 km s−1) lower crust body suggests its rifting-related origin during Early Cretaceous time. The Central Crimean Uplift represents a thick (up to 47 km) crustal domain consisting of three layers with velocities 5.8–6.4, 6.5–6.6 and 6.7–7.0 km s−1, which could be evidence of this part of the ScP originating on the crust of Precambrian craton (EEC). The thick heterogeneous basement of the Central Crimean Uplift shows inclusions of granitic bodies associated with magmatic activity related with Variscan orogeny within the ScP. General bending and crustal scale buckling of the Central Crimean Uplift with a wavelength of 230 km could be an effect of the Alpine compressional tectonics in the adjacent Crimean Mountains. The extended/rifted continental margin of the ScP (EEC) at the Odessa Shelf and buckling/uplifted domain of the Central Crimean Uplift affected by compressional tectonics, are separated by the N–S oriented Western Crimean Fault. The crust of the southern margin of the EEC is separated from the ScP, which originated on the EEC crust tectonised and reworked during the Palaeozoic–Mesozoic, by the crustal fault of ∼W–E orientation, which corresponds with the Golitsyn Fault observed at the surface between the EEC and the ScP. The Fore-Dobrudja Domain with a thick (>10 km) heterogeneous basement and two subhorizontal layers in the crystalline crust (with velocities 6.2–6.3 and 6.4–6.65 km s−1) differs from the ScP crust and its origin could be very similar to that of the Trans-European Suture Zone and Palaeozoic West European Platform