Kuprienko, P.

Legostaeva, O.

Makarenko, I.

Savchenko, A.

Starostenko, V.

Geofizicheskiy Zhurnal

Наукова електронна бібліотека періодичних видань НАН України (Vernadsky National Library of Ukraine)

		3*  !"#$%&'()&**Variations in the crustal types of the Dnieper-Donets Basinand surrounding areas from 3D gravity modelling? V. Starostenko, P. Kuprienko, I. Makarenko, O. Legostaeva, A. Savchenko, 2010Institute of Geophysics, National Academy of Sciences of Ukraine, Kiev, Ukraineirinam@igph.kiev.uaThere are two reasons for constructing a newthree-dimensional density model of the Dnieper-Donets Basin (DDB) and surrounding areas. 1) Alack of reliable data on the structure of the deephorizons in the sedimentary cover and crystallinecrust. 2) Recently fresh geological and geophysicaldata have been obtained for the upper sedimentarylayers (up to depths of 5—6 km) from seismic data(DSS and MCSP) along the DOBRE1 and DO-BRE2 profiles [Grad et al., 2003, Maystrenko etal., 2003].In this study modern software has been applied[Starostenko et al., 1997; 2004]. It has a principaladvantage over standard approaches because den-sity maps of individual layers are automatically in-put into a PC, enabling geological environments tobe approximated very accurately. A technique of con-structing a 3D model and converting it into a sche-matic map of layers types are described in detailelsewhere [Kuprienko et al., 2007].3D modelling has resulted in a new pattern ofthe density for the whole crust of the DDB and sur-rounding areas. It has been used to compile sche-matic maps for a thickness of the "granitic, "diorit-ic" and "basaltic" layers (the upper, middle and lo-wer crust). Earlier based on the generalization ofrelationships of velocity vs. depth and density vs.velocity for different types of the crust, it has beenput forward a conditional subdivision of the wholecrust into three stages without sharp boundaries be-tween them. They have been defined as the upper,middle and lower crust. Due to traditions they havebeen named as "granitic, "dioritic" and "basaltic" lay-ers. Their parameters are as follows: 1) ?<2.75 gcm?3,VP<6.30 kms?1; 2) ?=2.75?2.90 gcm?3, VP=6,30??6,80 kms?1; 3) ?>2.90 gcm?3, VP>6.80 kms?1 re-spectively. Petrologically the first range of the pa-rameters is a mixture of acid and intermediate rocks.The second series is composed of a mixture of in-termediate and basic rocks (granodiorites, diorites,charnokites, many gneisses, shists, metabasicrocks, and gabbroids). The third row consists of in-trusive rocks of basic and ultrabasic compositionand metamorphic rocks (granulites, amphibolites)[Lithospheric …, 1993].A relationship of a thickness of each layer to atotal thickness of the crust demonstrates the con-tribution of each layer into a total thickness of thecrust. The name of the crustal type corresponds toprevailing portion of any layer.The portion of "granitic" layer (Fig. 1, a) withinthe DDB iz characterized by a ratio of 0—0.4. Thehighest values correspond to the southern flank ofPoltavskii megabloc (0.4), the northern side and thesouthern preflank zone of the Lokhvitskii and Pol-tavskii megablocs, as well as most of the northernflank, where the percent ratio is 0,3. The smallestproportion of the layer belongs to the central zoneof megablocs (0.0—0.1). On the rest of the areaslayer portion is 0.0—0.2.The portion of "dioritic" layer (Fig. 1, b) is thelargest in the south of the DDB, in south-east of thenorthern flank, in the central zone and southern pre-flank zone of the Chernigovskii, and Poltavskii andLokhvitskii megablocs (0.4—0.5). A small portion ofthis layer occurres in the southeastern part of thecentral zone of the Iziumskii megabloc and in thenorth-western Donbass (0.0—0.1). The rest of thearea is characterized by the values of 0.2—0.3.The maximum portion of the "basalt" layer (Fig. 1,c) is associated with the north-western Chernigovskiimegablock and the north-western part of the centralzone in the Lokhvitskii megabloc, the south-easternIziumskii megablock and the whole Donbass (0.5— !"#$%&'()&** 3+,	-.,/0.1,	0.00,	Fig. 1. Contribution of the "granitic" (a), "dioritic" (b) and "basaltic" (c) layers to a whole thicness of the crust in the Dnieper-Donets Basin and Donbass: 1 — the boundary of the DDB; 2 — the boundary of the northern flank of the DDB; 3 — thelongitudinal division of the DDB (after Arsiriy et al., 1984) zones: A — northern flank, B — sothern flank, C — Central; 4 — thetransversal division of the DDB (after Dolenko and Varich, 1989) megablocks: Ch — Chernigovskii, L — Lokhitskii, P —Poltavskii, Iz — Iziumskii, D — Donbass.0.7). The smallest ratio of the layer (0.2) is related tothe southern preflank zone of the Poltavskii megablocand the northern edge of the Iziumskii megablock. Inthe rest of area the ratio is 0.3—0.4.		3  !"#$%&'()&**Fig. 2. Schemetic map of prognostic composition of the Earth’s crust in the DDB and Donbass from 3D gravity modelling.See Fig. 1 for conventions.Based on this information, six types of the crustare determined for the DDB and Donbass (Fig. 2).The granitic-dioritic crustal type has the smal-lest distribution which mainly occurs on the sou-thern flank of VCM (the Svatovo-Troitskii, Rossos-hanskyii blocks). Its small massif occurs on thenorthern flank of the Ush (the southern flank of thePoltavskii megablock).The dioritic type of the crust is distributed in thenorthwest and central parts of the southern slope ofVCM, in the southeast of the northern flank zone ofthe Chernigovskii and Poltavaskii megablocs, in thenorthern flank zone of the Lokhvitskii block, in al-most whole southern flank zone, on the southernedge, as well as in northern and southern Donbass.Leykobazaltic type of the crust is characteristicof the north-western Chernigovskii and Lokhvitskiimegablocs, north-western parts of the northern flankzone in the Chernigovskii, Poltavskii, Iziumskiimegablocs, as well as the north-western portion ofthe southern flank zone of the Iziumskii megabloc.Dioritic-basaltic type dominates in the centralregion of Poltavskii and the south-east of the cen-tral zone of the Lokhvitskii megablocs.Basaltic type of the crust is spread in the south-east of the northern and southern flank zones of theIziumskii megabloc, the most part of Donbass, inthe central zone and in the north-western part of thesouthern preflank in the Chernigovskii megabloc. Anisometric area is present in the southern part of thecentral zone in the Iziumskii megabloc.Basaltic-dioritic type of the crust occurs only inthe central zone of the Iziumskiy megabloc. Its pa-rameters are intermediate between basaltic type,which is distributed in the central part of the Don-bass, and diorititic — basaltic, typical for the cen-tral zone of DDB. A question arises whether thebelt of the basalt-diorite type of the crust is thetransitional zone between the DDB and Donbass?We should like to give a positive answer to this ques-tion.In conclusion, the granitic-dioritic type of the crustdominates in the flank zones while the basaltic andbasaltic-dioritic types are spread in the central beltof the DDB and Donbass. It demonstrates the in-crease in basicity of the rocks from the flanks tothe centre of the depression that proves an axialcompaction.Grad Y., Gryn’ D., Guterch A., Janik T., Veller R.,Lang R., Lyngsie S. B., Omelchenko V. D., Staros-tenko V. I., Stephenson R. A., Stovba S. N., Thy-bo H., Tolkunov A. DPBRE-fraction’99—velocitymodel of the crust and upper mantle beneath theDonbas Foldbelt (East Ukraine) // Tectonophysics.— 2003. — 371, 51—4. — P. 81—110.ReferencesMaystrenko Y., Stovba S., Stephenson R., Bayer U.,Menyoli E., Gajewski D., Huebscher C., Rabbel W.,Saintot A., Starostenko V., Thybo H., Tolkunov A.Crustal-scale pop-up structure in cratonic litho-sphere: DOBRE deep seismic reflection study ofthe Donbas fold belt, Ukraine // Geology. — 2003.— 31,  8. — P. 733—736. !"#$%&'()&** 3)+,	-.,/0.1,	0.00,	Starostenko V. I., Legostaeva O. V., Makarenko I. B.,Pavlyuk E. V., Sharypanov V. M. On automated com-putering geologic-geophysical maps images withthe first type ruptures and interactive regime visu-alization of three-dimensional geophysical modelsand their fields // Geophys. J. — 2004. — 26, 51.— P. 3—13 (in Russian).Starostenko V. I., Matsello V. V., Aksak I. N., Ku-lesh V. A., Legostaeva O. V., Yegorova T. P. Automa-tion of the computer input of images of geophysi-cal maps and their digital modeling // Geophys. J.— 1997. — 19, 51. — P. 3—13 (in Russian).Kuprienko P. Ya., Makarenko I. B., Starostenko V. I.,Legostaeva O. V. 3-D density model of the Earth’scrust and upper mantle of the Ukrainian Shield //Geophys. J. — 2007. — 29, 55. — P. 3—27 (inRussian).Lithospheric of the Central and East Europe . Generali-zation of the researches results / Ed. A. V. Chekunov.— Kiev: Nauk. dumka, 1993. — 258 p(in Russian).

Variations in the crustal types of the Dnieper-Donets Basin and surrounding areas from 3D gravity modelling

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Variations in the crustal types of the Dnieper-Donets Basin and surrounding areas from 3D gravity modelling

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