ISSN 00244902, Lithology and Mineral Resources, 2011, Vol. 46, No. 3, pp. 282–298. © Pleiades Publishing, Inc., 2011. Original Russian Text © A.D. Savko, L.T. Shevyrev, 2011, published in Litologiya i Poleznye Iskopaemye, 2011, No. 3, pp. 317–334.

Analysis of the Mineral Composition of Phanerozoic Sediments of the Voronezh Anteclise Cover: Implication for the Primary Diamond Potential A. D. Savko and L. T. Shevyrev Voronezh State University, Universitetakaya pl. 1, Voronezh, 394006 Russia email: [email protected] Received April 2, 2008

Abstract—Origin of diamond and its indicatorminerals found in the Cretaceous, Paleogene, and Quater nary sediments in the southern sector of the East European Platform has remained a debatable issue over the past period of approximately 40 years. It was assumed that the Cretaceous diamond in the Volch’e placer and Central deposit confined to the Voronezh anteclise was derived from the Uralian sources, whereas the Paleo gene diamond was derived from the South Ukrainian sources. Analysis of paleogeographic maps of new gen eration (scales 1: 200000–1: 500000) and new data on samples (50 samples 0.5–20 t each) examined by sci entists from the Geological Research Institute of Voronezh State University with the participation of authors of the present communication support the hypothesis of local origin of diamonds and localization of their provenance in the sedimentary cover of the Voronezh anteclise. This inference pertains to highpressure min erals detected in preQuaternary sediments. Diamond grains and indicatorminerals hosted in the Quater nary postglacial sediments of the Voronezh anteclise were likely derived from the Don glacial apron in the early Pleistocene (gQIds) from northern areas of the platform (southeastern Finland, Karelia, Kola Penin sula, and Zimnii Bereg area of the Arkhangel’sk region). Such grains are unsuitable for prospecting purposes. Lithofacies investigations made it possible to outline two areas in the Lipetsk and Voronezh regions that likely accommodate productive diatremes. DOI: 10.1134/S0024490211010068

In 1969, diamond grains were discovered in Aptian sediments of the northeastern Voronezh anteclise by I.F. Kashkarov and Yu.A. Polkanov (Institute of Min eral Resources, Simferopol) during the investigation of the Volch’e Zr–Ti placer in the Lipetsk district after successful prospecting at analogous sites in the Ukraine (Kashkarov and Polkanov, 1969). Application of the foam separation technology allowed these authors to extract 241 mineral grains (total weight about 10 mg) from the finegrained sand of the upper placer (83–86%, fraction 0.25–0.1 mm). Content of the commercial component in the placer (19% of pure diamond) was 0.0268 mg/m3, while dimension of grains was 90–340 µm. Sample taken in 1969 (900 kg) was characterized by a very high content of the heavy fraction (21.6%). In 1971, Yu.A. Polkanov recovered 21 diamond grains (100–250 µm in size) from Zr–Ti sands of the Novozybkov placer in the western Bryansk district (P3N1pl). Some placers (Aleksandria) con tained as much as 350 kg/t of heavy minerals in section intervals up to 2.5 m thick. In the Cenomanian silt of the Central deposit (Tambov district), 17 diamond micrograins were found later (Sekretarev, 1977). At the end of the 1990s, researchers of the Voronezh Univer sity started appraisal of the primary diamond potential under the supervision of N.N. Zinchuk, head of the

Yakutia Geological Research Association of TsNIGRI (AK ALROSA) at Mirnyi. Participation of scientists from Voronezh University was dictated by the lack of positive results in diamond prospecting in the south western subprovince of the East European Platform (Ukrainian Shield, Voronezh and Belorussian antec lises) and the objective demand for the development of novel methodical approaches. Unsuccessful experience of prospecting for pri mary diamond sources in the Ukraine since the 1960s suggests that problem of the detection of primary dia mond sources in the Ukraine and Voronezh can hardly be solved without a highquality scientific analysis of the geological setting. The Ukraine experienced sev eral bursts of interest in the diamond theme over the 40yearslong prospecting period. New finds of appar ently crucial diamond grains and kimberlite clasts in the Turonian chalk (Lake Beloe, Rovno district) pro moted the organization of detailed prospecting with the involvement of largescale drilling works that are highly expensive in boggy environment of the Ukrai nian forest area. Researchers returned to the scientific analysis of prospecting background after each failure and huger expenses. Largescale prospecting was never carried out in the Voronezh anteclise, although discussion about its diamond potential is going on for

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a long time. This region is characterized by the pres ence of finegrained psammites even in the basal hori zons of large sedimentary rhythms. Therefore, alloca tion of complicated processes of benefication and extraction of highpressure minerals is essential for this region. It was also necessary to search the source buried to an unknown depth. Conclusions made by researchers at Voronezh State University include the following important points. (1) Reference samples taken from sedimentary rocks for the examination of highpressure mineral associations in the Voronezh anteclise should be no less than 1 m3 in volume (the socalled lowvolume sampling successfully implemented in diamondiferous areas, such as Zimnii Bereg (northern Arkhangel’sk district) or Molodinsk and Malaya Botuoba (Yaku tia)), because the most informative coarseclastic sequences are rare even in the basal horizons of large sedimentary rhythms. Carryingout of this condition guarantees the gathering of highquality information even from finegrained clastites. Virtually each sample of the recommended volume contained background concentrations of diamond satellites. Their mineral and chemical compositions, as well as morphologies, were of great prospecting interest. Previously, standard 10l (usually barren) samples were taken here. (2) It is not expedient to carry out diamond sam pling in the most accessible Quaternary sequences, because the Voronezh anteclise represents a Quater nary glaciation region with diamondiferous areas located 1200 km away (Kola Peninsula, Finland, and northern Arkhangel’sk district). Therefore, diamonds and their satellites therein can be considered “alloch thonous” relative to the Voronezh anteclise. Prospect ing technologies applied successfully in Yakutia are ineffective here, because ice sheet is atypical for the Siberian Craton and its folded framing. (3) The obtained new data suggest that primary diamond sources existed in the study region in not only the Middle Paleozoic, but also younger produc tive epochs. The northeastern (Olym or Lipetsk) area likely accommodates diamondiferous magmatic rocks of the Mesozoic (Late Triassic–Jurassic) age, whereas the southeastern one includes the Laramian diamon diferous rocks. Indeed, all finds of diamond in the southeastern Voronezh anteclise and most pyrope grains with the knorringite component are confined to the bottom of the Paleogene deposits. In the adjacent Ukrainian area (Starobel’sk, Lugansk district), volca nic rocks (likely diatremes) with the K–Ar age of 71 Ma have been detected (Skarzhinskii et al., 1973). (4) It is expedient to carry out prospecting in areas with sedimentary cover of the anteclise developed above Archean cores of the basement, which did not get sufficient attention previously. Therefore, the first stage of our work was focused on the following issues: (1) creation of a complex of lithofacies maps and paleogeographic maps based thereupon for elucidation of the conduits of clastic LITHOLOGY AND MINERAL RESOURCES

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material in sedimentary basins; (2) subsequent devel opment of a network of bulk reference samples embracing the planned prospecting areas of the antec lise; (3) elucidation of horizons with highpressure mineral associations at different stratigraphic levels of the MesoCenozoic sedimentary cover; (4) discrimi nation of the region based on the highpressure min eral associations; (5) scrutinization of the detected diamond, pyrope, Crspinel, and picroilmenite grains to reconstruct the probable types and ages of primary sources. The works carried out in the study region made it possible to discover concentrations of the valuable min eral in intermediate collector rocks of the Early Creta ceous (northeastern) and Early Paleogene (southeast ern) ages. These works proved that some pyropes and Crspinels belong to the socalled diamond association. They also unraveled mineralogical evidence of Meso zoic (?) explosions in the sedimentary cover (Savko et al., 2007). These investigations would have been impossible without the friendly help of workers of the Nedra Scientific Association, Simferopol (A.I. Chashka, supervisor), where Yu.A. Polkanov, one of the discoverers of diamond in Voronezh, is working to this day. We are also grateful to Polkanov who gave his historical collection of diamond grains discovered in Volch’e in 1969 for description to Voronezh State Uni versity. We believe that investigations of diamond poten tial of the northeastern anteclise carried out with the participation of workers of the Aerogeologiya State Enterprise (A.Yu. Egorov, DSc, in particular) played an important role. We are also grateful to workers of the Geological Research Institute of Voronezh University (D.A. Dmitriev, O.N. Evdokimov, A.E. Zvonarev, A.A. Zhabin, V.V. Loskutov, and A.V. Shishov) who transported several tens of tons of sand samples from the basal horizons of the region. In this work, paleogeographic reconstructions based on lithofacies maps were always considered an essential element. Without the consideration of such maps, it would have been difficult to understand geo logical history of the region in the Phanerozoic marked by multiple variations of alimentation and sedimentation zones. The paper demonstrates lithofa cies schemes based on ample drilling data accumu lated in archives of geological organizations. GENERAL INFORMATION ABOUT THE GEOLOGICAL SETTING OF THE VORONEZH ANTECLISE The Voronezh anteclise (about 220000 km2 in area), a large tectonic structure of the East European Platform, is separated by natural boundaries (deep faults) from the adjacent aulacogens—Pachelma, Orshan (apophyse of the Volyn–Poles’e depression), Don–Medveditsa, and aulacogen system of the Greater Donbas (Valeev, 1978). Similar thicknesses of correlated sediments indicate that the anteclise under No. 3

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48° 42° Fig. 1. Geostructural scheme of the Voronezh crystalline massif (VCM). Modified after (Chernyshev et al., 1997; Valeev, 1978; Afanas’ev, 1983; Nozhkin and Krestin, 1984). (1–4) Early Precambrian lithostructural complexes: (1) Lower Archean (gneisses of the Oboyan Group AR1ob) and Upper Archean (greenstones of the Mikhailovsk Group AR2mh), (2) Lower Proterozoic (shales, metasandstones, and effusives of the Vorontsov Group PR1vc, Voronezh Formation PR1vr, and Panino sequence PR1pn in the eastern VCM—“Vorontsov basin”), (3) metasandstones and jaspilites (Kursk and Oskol groups), (4) Losev suture zone (primary sedimentary rocks of the Vorontsov Group PR1vc and Voronezh Formation PR1vr granitized in the Early Proterozoic); (5, 6) boundaries: (5) Voronezh crystalline massif with the Riphean aulacogen framing, (6) megablocks of VCM. (I–III) Megablocks: (I) Bryansk, (II) Kursk magnetic anomaly (KMA), (III) Khopersk or Voronezh.

went subsidence approximately similar to that in neg ative structures during the Neogea sedimentation. However, uplift and erosion here were much more sig nificant during hiatuses (Shevyrev, 1989). The fre quent active “floating” of anteclise crest was provoked by specific features of its deep structure. In the Voron ezh crystalline massif (VCM), which matches the ante clise in terms of area, the “granite” layer is marked by the greatest thickness (30–32 km) in the East European Platform. For example, its thickness is only 20–25 km in the Ukrainian Shield, 18 to 19 km in the Belorus sian anteclise, and 10–15 km or less in the Volga–Ural anteclise (Afanas’ev, 1983 and others). The anteclise basement is traditionally divided into the Bryansk, Kursk magnetic anomaly (KMA), and Khoper megablocks (Fig. 1). The Bryansk and KMA megablocks are composed of rocks of the Archean acrotheme coupled with rocks of its lower (gneisses of the Oboyan Group) and upper (greenstones of the Mikhailovsk Group) eonothemes. The KMA megablock

is characterized by rifttype structures (troughs) filled with Lower Proterozoic sequences, including jaspilites, shales, and sandstones of the Kursk Group and shists and effusives of the Oskol Group. The East Khoper (Voronezh) megablock comprises Lower Proterozoic sandstones, shales, and effusives of the Vorontsov pale obasin 70000 km2 in area (Savko and Gerasimov, 2002). The VCM basement is divided for a long time into hypothetical Archean massifs (rigid ancient struc tures). Large areas around Rossosh were identified as “the Archean Alekseev massif” in (Polishchuk, 1972, pp. 72, 73). This structure was identified as “large Ros sosh granitegneiss dome” in (Nozhkin and Krestin, 1984, p. 9). M.D. Berdnikov (1981) identified the hypothetic Olym massif in the western Lipetsk district. Nature of these large objects (thousands of kilometers) was unraveled by N.M. Afanas’ev who investigated materials from 13 DSS profiles across the anteclise (Savko et al., 2003b). The new version of the deep seis mic density model compiled by N.S. Afanas’ev and

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I.I. Krivtsov suggested an intricate “intermediate layer” between the core and mantle in the massifs mentioned above. This transitional layer is responsible for thickening of the crust to 60–70 km (Fig. 2). Ter ranes of such crust composed of the oldest rocks of the Oboyan Group (А1оb) are marked by a weak manifes tation of tectonomagmatic activation with a trend of highstand during sedimentation stages. All these facts make it possible to construct prognostic models based on the dominant concepts about the confinement of diamondiferous magmatites to terranes of the thickest LITHOLOGY AND MINERAL RESOURCES

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Archean (older than 2.5 Ga) crust. Precisely such areas likely accommodate primary sources of the Vor onezh diamond. PALEOGEOGRAPHIC SETTINGS AND ASSOCIATIONS OF PALEOZOIC HIGHPRESSURE MINERALS (HPM) Exposures of Upper Devonian terrigenous rocks are rare in the Voronezh anteclise. However, we attach a great significance to these rocks as collectors. Many No. 3

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Fig. 3. Lithofacies scheme of the Voronezh anteclise for the Middle Devonian Petino time. (1–5) Facies setting: (1) shallow marine with normal salinity and weak hydrodynamic activity, (2) the same with medium and weak (predominant) activity, (3) the same with medium activity; (4) coastalmarine with normal salinity and weak hydrodynamic activity, (5) the same with variable activity; (6–10) rocks: (6) mudstonetype varigrained (from fine to coarsegrained), (7) clays, including the mudstonetype, (8) carbonate clays, (9) dolomitized limestones, (10) marls; (11) plant remains; (12, 13) fauna remaius: (12) brachiopods, (13) fishes; (14) facies countours; (15) areas with finds of HPMs; (16) areas with finds of diamond.

specialists, including S.I. Mityukhin (1997) and M.V. Mikhailov (2000), believe that kimberlites, if any exist, produced only in the Middle Paleozoic produc tive epoch, which accommodates diatremes of the Arkhangel’sk and Vilyuisk subprovinces, Azov region, Azov massif, Luga area of the Leningrad district, and Zhlobin area of Belarus. Therefore, paleogeographic, mineralogical, and grain size characteristics of Devonian rocks in the southeastern part of the study region, the sole rocks accessible for study without the application of labori ous mining works, naturally attract the attention. The sequences sampled in Semiluki pertain to the middle Frasnian Petino Horizon (Fig. 3). In the stratotype section near the Petino Settlement, the horizon is composed of coastalmarine medium to varigrained sandstones and sands that include interbeds with abundant darkcolored minerals (natural panned samples). Paleogeographic data evidently suggest the input of material from a southern uplift in the Archean Rossosh massif. The basal horizon (0.15 m) of the Petino sand, which is coarser than the main portion of the terrigenous sequence, is enriched in chert gravel with grain size up to 3–5 mm. Sample 6006 (0.5 t) yielded the heavy fraction (20.3 g) with ilmenite (63.5%), magnetite (13.8%), and iron oxide aggre gates (17.2%). The sample virtually lacks garnets (rare

grains were observed only in the smallest fraction). Therefore, mineral composition of this sample is sim ilar to that of the coeval (D3fr2fm) continental sequences in the Osetrovka section of the Verkhnema mon area. The Xray spectral analysis of the heavy fraction showed the presence of picroilmenite, Cr spinel, and Crdiopside. The Crdiopside grains and its crystal fragments are very large (1.2 × 1.0 × 0.8, 1.1 × 0.8 × 0.6, and 0.5 × 0.4 × 0.4 mm). This statement is also valid for Crspinel (more than 33 points were detected). This group includes octahedral crystals (0.5 × 0.4 × 0.3, 0.6 × 0.4 × 0.4, 0.4 × 0.4 × 0.4 mm). We found three Crdiopside grains, including a rounded grain (0.3 × 0.2 × 0.2 mm) and a clast (0.2 × 0.15 × 0.15 mm). Highpressure minerals also occur in the continental Mamon (sand–kaolin) sequence of the Osetrovka sec tion in the southeastern part of the anteclise (D3 fr2fm, sample 6001). Examination of the heavy mineral frac tion (232.2 g) from the bulk rock sample (1.3 t) yielded an angular Crdiopside grain (0.27 mm). Psammites of the Petino Formation in Semiluki represent marine sediments accumulated in a hydro dynamically active realm at the initial stage of the large Petino–Livny tectonosedimentary cycle. In terms of accumulation period, they are closest to the most

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probable timing of the potentially diamondiferous diatremes that were likely formed in the Middle–Late Devonian (Mityukhin, 1997). Despite expectations, the highpressure mineral association extracted from the coastalmarine sand of the Petino Formation in Semiluki turned out to be different from the associa tion detected in the pyroperich Albian sand in the Verkhneturovo section, which is spatially close to Semiluki. Pyrope and diamond grains were not observed in the Upper Devonian continental Osetro vka sequence and coastalmarine sequences of the Frasnian basement (D3js) scrutinized in (Kantserov and Bykov, 1998). PETROGRAPHIC SETTINGS AND ASSOCIATIONS OF HPM IN THE MESOZOIC Sediments of the Dogger–Malm and Lower Creta ceous base (Neocomian–Aptian) in the Voronezh anteclise are traditionally described together since the wellknown work of V.N. Preobrazhenskaya (1966). Jurassic sediments fill up the NWextending valleys in the 30kmwide zone in the central part of the antec lise that separates the domains of Devonian and Car boniferous sediments on different slopes. In the KMA area, Jurassic rocks often occur on the Precambrian basement and consequently serve as primary collectors for the highpressure mineral associations. They are considered the most important intermediate collec tors in the Lipetsk district, where Jurassic and Neoco mian–Aptian sequences overlie the Famennian lime stones. The problem, however, lies in the fact that exposures of rocks accessible for study are rare in the anteclise. They are also not always suitable in terms of the grain size composition. The northeastern wall of the Mikhailovsk quarry near Zheleznogorsk (Kursk district) shows the base of the Bajocian–lower Bathonian (J2bjb1) coastal marine fine sand with rare chert pebbles. Thickness of the basal psammite layer is as much as 0.3 m in depres sions at the top of ferruginous quartzites. The psammite sample yielded a violet pyrope grain (0.5 × 0.2 × 0.1 mm) and rare picroilmenite (?) grains. Jurassic sediments in borehole 4209 drilled in the eastern part of the ore field yielded five angular diamond fragments with size ranging from 0.01 × 0.05 mm (four grains) to 0.05 × 0.07 mm (one grain). In 2002, they were examined by A.Yu. Egorov (Aerogeologiya State Enterprise) who assumed that diamonds can be affined to eclogites and hardly related to kimberlites (personal communica tion). They could be transported to marine basin from an ancient land that occupied the entire central part of the anteclise in the Bajocian–early Bathonian. The Cretaceous terrigenous sequences are accessi ble for sampling mainly in the northeastern sector of the Voronezh anteclise. Therefore, most “Cretaceous” reference samples characterize the Lipetsk and Tam bov sections in the easternmost area of the Kursk dis LITHOLOGY AND MINERAL RESOURCES

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trict and the northern half of the Voronezh district. Exposures accessible for sampling are rare in the southern and southwestern parts of the anteclise. One exposure was found in the southern Voronezh district (Cenomanian section in Osetrovka), while another exposure was detected in the western Belgorod district (Albian section in the Lebedino quarry). Workers of Voronezh State University studied highpressure min eral associations in the Neocomian, Aptian, Albian, and Cenomanian sediments. They chose two refer ence Neocomian sections—the Lipetsk district near the Renevka Settlement (Stanovlyansk area in the northwestern part of the district) and the Nizhnyaya Kolybelka area (Khlevnevo area in the south). Both sections turned out to be very interesting. In the first section, the shallowmarine greenish gray fine to mediumgrained sand (K1hb) yielded grains of sev eral highpressure minerals: nine pyrope grains (up to 0.4–0.6 mm across), including seven violet varieties, one redorange variety, and one reddish pink variety; 30 Crspinel grains (class 0.65 + 0.1 mm); one Cr diopside grain (0.25 × 0.15 × 0.15 mm); and picroil menite (?). Sands (K1hb) of Nizhnyaya Kolybelka are also coastalmarine sediments. However, they were accu mulated appreciably nearer to the southern washout zone in the sampling area (Fig. 4, site 5). This is reflected in the HPM composition. Sample 9 (volume 1 m3, 2100 kg) contained a record high amount of the heavy fraction (4.95%), which is two times higher than the amount in the sampled upper deposit of the Aptian Volch’e zirconium–titanium placer. The sample yielded three diamond grains–first finds of diamond in so ancient sequences of the anteclise. One grain (0.196 × 0.182 mm) represents a complicated combi nation of morphologies; the second grain, irregular angular fragment with gray tint (0.28 × 0.18 mm); and the third grain, irregularangular colorless crystal frag ment (0.236 × 0.308 mm). The sample also contained picroilmenite (?) and Crdiopside (one grain each). Previously, diamond was detected only at one site—shallowmarine titanium–zirconium placer near the Volch’e Settlement in the Dobrinsk area (Fig. 4, site 1). Repeated finds of diamond allowed sci entists of Voronezh State University to compile the Volch’e collection of 79 crystals and their fragments. Some diamond grains from this collection are presented in Fig. 5. It is noteworthy that some diamond grains are larger than the dominant grain size of host sand (98% in class –0.25 + 0.1 and 1.57% in class –0.1 mm). Dia mond satellites were not detected at that time like dur ing the first investigation of diamond potential of the section by I.F. Kashkarov and Yu.A. Polkanov in 1969. All diamond finds in the placer near the Volch’e Set tlement are scrutinized in (Savko et al., 2007). Let us only note here the presence of red diamond, an espe cially valuable variety, known from lamproites of the Australian Argyle Pipe, where the share of this variety No. 3

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Fig. 4. Lithofacies scheme of the Aptian age. (1–13) Facies setting: (1) shallowmarine with normal salinity and medium and weak hydrodynamic activity, (2) the same with medium (predominant) and high activity; (3) coastalmarine with normal salinity and weak and medium (predominant) hydrodynamic activity; (4) the same with medium (predominant) and weak hydrodynamic activity; (5) the same with medium activity; (6) the same with medium (predominant) and high activity; (7) the same with high activity; (8) lagoonal and liman, shallowwater and freshened, (9) large waterlogged lakes and shallowwater freshened lagoons; (10) lacus trineboggy; (11) alluvial (undivided); (12) alluvial channel; (13) alluvial floodplain and oxbow; (14–19) rocks: (14) gravel, (15) fine and mediumgrained sand, (16) finegrained sand, (17) silt, (18) dolomite, (19) tripolitype clay; (20–23) inclusions: (20) pebble, (21) micas, (22) phosphorites, (23) glauconite; (24) fine plant detritus; (25) direction of clast material transport. See Fig. 3 for other explanations. Numerals designate sites of HPM location in the Lower Cretaceous sediments: Volch’e (1), Kudiyarovka2 (2), Sentsovo (3), Lev Tolsctoi (4), Nizhnyaya Kolybelka (K1hb), (5) Zakharovka (6), Gnilusha (7), Droskovo (8), Soroch’i Kusty (9), Barkovo (10), Gnezdilovo (11), Soldatskoe (K1–2 als), (12) Khokhol’skii (13), StelitsaBlizhnyaya (14), Medvedevo, Renevka (15), Chelkino (16).

makes up one millionth of all other diamond varieties (Khar’kiv et al., 1997). In the Aptian age, variability of hydrodynamic con ditions in the shallowmarine zone on the northern slope of the anteclise and vigorous nearbottom cur rents promoted an active erosion of sediments accu mulated therein and high concentrations of the heavy fraction, which is most favorable for sampling. Here, study of even intraformation parts of sections with signs of natural panning turned out to be efficient. The authors sampled an interlayer with dark minerals in the ballast quarry near the town of Lev Tolstoy (Fig. 4, site 4). The heavy fraction yielded seven diamond grains, which are similar in terms of morphology and dimension to those in placers near the Volch’e Settle ment. This site also yielded the largest diamond grain (0.42 × 0.2 mm) among diamonds found so far in the

Voronezh anteclise—an irregular wedgeshaped col orless and transparent fragment with smooth to irreg ular surface. Appreciable decrease in the amount of diamonds and their satellites from the Volch’e deposit toward north and the consequent diversion from primary sources provoked the southward and southeastward shift of sampling areas. Sands of the shallowmarine zone were replaced by the coastalmarine varieties along this direction. The latter samples yielded the first finds of diamond grains (Fig. 4, sites 2, 5, 6) attended by the following minerals: one pyrope grain, 15 picroilmenite grains, and two Crdiopside grains. Based on the Xray spectral data, garnet from Kudi yarovka2 is unrelated to kimberlite: the Cr2O3 con tent therein is only 0.011–0.016%.

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(a)

0.1 mm

(b)

0.1 mm

(c)

0.1 mm

(d)

0.1 mm

(f)

0.1 mm

(e)

0.1 mm

Fig. 5. Photographs of diamonds from the Volch’e placer (K1a): (a) octahedron; (b) octahedron intergrowths; (c) equant octahe dron with smooth edges; (d) octahedron elongated along axis of the fourth order; (e) coarselayered octahedron; (f) octahedron.

Pyrope of the diamond subfacies was detected in the Medvedino section of the Aptian coastalmarine psam mites (Fig. 4, site 15). Sample 7012 (2 t) contained 0.01% of the heavy fraction (class –0.5 + 0.1 mm), i.e., approximately 200 g. This sample yielded, in LITHOLOGY AND MINERAL RESOURCES

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addition to picroilmenite, three pyrope grains—vio let (0.3 × 0.2 mm), violetpink (0.25 × 0.2 mm), and reddish orange (0.7 × 0.3 mm). The violet and violet pink varieties are subangular grains with smooth edges and corners. The violet grain has a cubic form with No. 3

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fineshagreen surface. The violetpink variety is char acterized by pitted surface on one side and grooved surface on the other side. The reddish orange grain is marked by elongated subangular shape and fine shagreen surface. The first variety is marked by the refraction index typical of pyrope (1.753) and high Cr2O3 content (13.25%). South of Nizhnyaya Kolybelka, Aptian sequences are represented by continental facies of the alluvial plain. The section includes intervals of the coarse grained channel sand with gravel admixture (sections of the Latno refractory clay deposit, Belgorod district). The Khokhol’skii Settlement (Fig. 4, site 13) hosts a plant of the Voronezhrudoupravlenie Open Joint Stock Company that obtains gravelfiller for concrete production by the wet dispersion method. Separation tailings are enriched in the heavy fraction. The dark colored concentrate is accumulated in depressions along the dumped water. The concentrate contains zircon, titanium minerals, and gold flakes. The HPM group is only represented by single picroilmenite (?) grains. This feature is also typical of the base of Aptian continental sediments from quarries in Strelitsa (Fig. 4, site 14). Depletion of the HPM association could be related to limited provenance area, which is typical of alluvial sequences, and specificity of the mineral composition of primary source. It is known that the accessory mineral assemblage in the red dia mondcontaining lamproites of West Australia differs from the assemblage in the Yakutian or South African varieties. In rocks of the Argyle diatreme, pyrope grains are very rare and diamond satellites are repre sented by sphene, anatase, rutile, priderite and other Tibearing minerals, manganoilmenite, and sulfides of Ni, Cu, and Fe; magnesiochromite, almandine, Cr diopside, and orthopyroxene are considered xeno genic minerals; and picroilmenite is lacking (Lam proity, 1991). Thanks to finds in Medvedino, HPM associations in the Aptian sediments of the Lipetsk district allow us to approximately describe the primary source of diamond in the northeastern Voronezh ante clise. The diamondiferous body is likely composed of “kimberlite—lamproites,” according to A.D. Khar’kiv et al. (1998), rather than pure lamproites. These researchers used this term for the description of pro ductive rocks in Zimnii Bereg and the Punna field (Madhya Pradesh, northern India) that are markedly depleted in the conventional diamond satellites. In the southeastern part of the anteclise, associa tions of mineralindicators in sedimentary sequences of the Voronezh and eastern Belgorod areas differ from the Lipetsk varieties. In the Lebedinsk quarry (Fig. 6, site 1), we sampled the basal horizon of Albian psam mites and the underlying weathering crust (0.1 m) developed after Aptian sands. The heavy fraction is dominated by the following two mineral associations: ilmenite–garnet–tourmaline–staurolite association with iron hydroxides and zircon (class –2 + 0.5 mm) and the zircon–garnet–ilmenite–staurolite associa

tion with leucoxene, kyanite–sillimanite, tourmaline, and rutile (–0.5 + 0.1 mm). This site yielded pyropes and picroilmenites (ilmenite with MgO > 1%). The samples contained 23 angular pyrope fragments: four violetpink fragments, one pale violetpink fragment, and 18 fragments ranging from pale to dark violet vari eties (the dark violet “inky” variety is represented by one grain). The grain size varies from 0.4 to 0.9 mm (predominant size 0.5–0.7 mm). The dark violet “inky” pyrope is marked by a very high Cr2O3 content (10.78%), which is record high for so old rocks. Based on this and other parameters (6.43% CaO, 19.42% MgO), this variety is assigned to the diamondiferous dunite–harzburgite association. In terms of facies affiliation, Albian psammites of the Lebedinsk quarry are classified as sediments of the shallowmarine zone related to the medium and active hydrodynamic environments. At a distance of 60 km southeastward, the psammites grade into gravel–pebble sands of the coastalmarine zone. A large Albian land begins further 40 km southeastward. It is important that the land projection, which is closest to the pyropebear ing section, matches the buried Archean Rossosh mas sif in the crystalline basement of the anteclise. A similar but depleted HPM association character izes the contact between Aptian and Albian psammites exposed by ditch near the Verkhneturovo Settlement in the northwestern Voronezh district (Fig. 6, site 2). This area yielded three pyrope grains, two Crdiopside grains (octahedra), and picroilmenite. One violet irregular pyrope grain (1.0 × 0.6 × 0.5 mm) includes a tuberous sector; the second grain (0.3 × 0.25 × 0.2 mm) represents a rectangular pale violet fragment; and the third grain (0.15 × 0.15 × 0.1 mm) is a flattened angular pale violet fragment with a conchoidal fracture. The first grain is enriched in Cr2O3 (7.012%). The Cenomanian sediments in the study region are united with the Albian sediments into the Bryansk Group. In the southeastern sections, the Cenomanian portion is stratigraphically individualized, because it overlies the Paleozoic sequence (Shkurlat, Osetrovka). Comparison of Figs. 6 and 7 shows that washout zones of the Albian and Cenomanian sediments interchange places in the eastern part of the anteclise. This situa tion was responsible for the compositional discrep ancy between mineralsatellite associations in the northern and southern sectors of the anteclise—min erals were delivered from different separate primary sources. Figure 7 shows the position of the Tsentral’noe (Central) zirconium–titanium placer, where the Volch’etype diamond grains are known long ago. Here, small diamond grains occur together with tita nium and zirconium minerals accumulated on the shallowwater shelf during a relatively low hydrody namic activity. Diamond grains were mainly trans ported to the placer from the intermediate Aptian col lector: the content and size of mineral grains here are lower relative to the Aptian sediments of the Volch’e

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Voronezh IIBIIА

IIBA

G G

1 Gubkin Liski

F

Novokhopersk

IIAB F

F

IIIВ

F G

G Pavlovsk G

IIIBC F

IVD 1 Veidelevka 2

G 0

25

50

75

100 km

Fig. 6. Lithofacies scheme of the southern part of the Voronezh anteclise for the Albian age. (1) Denudation zone; (2) direction of Vrrich pyrope transport. See Figs. 3 and 4 for other explanations.

deposit. Both placers are marked by the lack of indica tor minerals, probably, because they are related to the single Lipetsk provenance. A different HPM aureole (lowCr pyrope, Crspinel, and picroilmenite rather than diamond) is typical of the Cenomanian shallowmarine psammites in the southwestern field of the anteclise. Most impor tant HPMs were detected in Boldyrevka, Nizhnede vitsk, and, particularly, Svoboda Settlement area north of Kursk (Fig. 7, sites 2–4). In the latter area, 15 pyrope grains were extracted from sample 7007. Five grains were observed as pinkviolet rounded and subangular varieties (0.6 × 0.5 × 0.5; 0.6 × 0.4 × 0.25; 0.4 × 0.4 × 0.35; chips 0.2 × 0.2 × 0.15; 0.25 × 0.15 × 0.1 mm); ten grains, as pinkorange and orangepink elongateoval grains and chips (from 0.7 × 0.5 × 0.25 to 0.2 × 0.1 mm). Based on the Xray spectral analysis, one grain contains a small amount of Cr2O3 (3.06%). Crspinel was detected as octahedral crystal fragments (0.75 × 0.75, 0.6 × 0.4, and 0.5 × 0.45 × 0.4 mm) with lus trous or slightly dull faces and scratches parallel to one of the edges. Well edged or oval grains (0.1–0.15 mm) are more widespread. Diversity of HPMs of the southern association is attributed to their own (not Lipetsk) kimberlite source. Relative to the Albian section in the Lebedinsk quarry and basal Paleogene collector (Zhilino, Kantemirov area), the indicatormineral content in Cenomanian sediments is lower in the southwestern part of the anteclise and absent at all near the Osetro vka Settlement, probably, due to low activity of hydro dynamic processes and lack of strong bottom currents. LITHOLOGY AND MINERAL RESOURCES

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PALEOGEOGRAPHIC SETTINGS AND ASSOCIATIONS OF THE CENOZOIC HPM Paleogene basal sediments of the Voronezh antec lise are assigned to the Upper Paleocene Sumsk Suprahorizon on the left bank of the Don River and to the Eocene Kanev, Buchak, and Kiev horizons on the right bank. They postdated the prolonged (10–15 Ma) hiatus that left huge masses of friable eluvium known as “Khoper Horizon.” The impetuous Late Paleocene transgression marked a large tectonosedimentary stage that embraced the southern and southeastern areas of the Voronezh anteclise. The depth and irregularity of reworking of the older sedimentary piles are suggested by variability of petrographic composition of the Paleogene collector. At the 0.8kmlong contact between the Santonian siliceous rocks and sediments of the Suma Suprahorizon near the Nizhnii Byk Set tlement (Fig. 8, site 2), the basal glauconite clays replace the dense pebblecontaining sandstones that grade into gravelstones along the strike. Precisely the reworking depth of older sediments suggested that Paleogene rocks in southern areas of the anteclise can accommodate diamond comparable (in terms of value and diversity) with Aptian sediments in the northeastern part of the anteclise. Even higher similarity of Paleogene sections (Buchak Horizon, Fig. 9) with the Aptian Lipetsk sections is indicated by the presence of intraformation erosion surfaces with heavy mineral concentrations. However, the similarity ends here. The Aptian sequences contain diamond grains almost devoid of satelliteminerals. In the Paleogene sand, in contrast, the indicatormineral assemblage is diverse, while the diamond grains are No. 3

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SAVKO, SHEVYREV IIBC Bryansk F FF

F

5F IIBA F

G

Tambov

IIB

6

IIB IIBA F

G

F

G

IIBC F F

F

Sevsk IIBA F F F IIBC F

IIC G F

4

F

F G

F

F F F F IIBC F F F IIB G F

F

F

G F

Ertil F

IIBC

G

IIBC Voronezh

3

F F

G

F F FF F

F

IIB

FF

Borisoglebsk

2 Bobrov IIBC

G

F F

F Belgorod G F F IIBC

25

0

25

50

IIB G F F IIIBC G F F F F IIBC F 1 IIIBC Pavlovsk F F F F G Kalach F IIIАC F F F F F F G F F F F F F F G IIIBC F F F F F F 75 km IIIBA F IIIBC Boguchar IIIBA G F F

Ostrogozhsk Ф IIAB

Fig. 7. Lithofacies scheme of the Voronezh anteclise for the Cenomanian age. Numerals in Figs. 7–9 designate HPM locations. Kotovka (1), Boldyrevka (2), Nizhnedevitsk (3), Svoboda (4), Polpino (5), Tsentral’noe deposit (6). See Figs. 3, 4, and 6 for other explanations.

scanty. In 2001, diamond was detected in the coastal marine conglomerate of the Sumsk Formation near the Mikhailovka Settlement along the Tatarka River (near the town of Novokhopersk, Voronezh district) in sample 5171 with a volume of 0.2 m3 (Nedra Scientific Production Enterprise, Simferopol, sample taken by A.I. Chashka). The sample turned out to be a repeat edly reworked fragment of octahedral crystal (0.25 × 0.20 × 0.20 mm) associated with pyrope and chromite. Three diamond grains were found in sample 7001, which characterizes the coastalmarine Buchak sand section in Nizhnii Byk (Fig. 9, site 5). One grain likely represents a octahedron fragment with relict edge marked by platysteplike overgrowth and elongate tet rahedral apex. Primary and chip surfaces (0.33 × 0.25 × 0.23 mm) are smooth and lustrous. The second crystal has cubic habitus with an edge 0.15–0.17 mm long. Its two apices are broken. The crystal is characterized by pittedtuberous edges and steplike edges with some edges marked by rhombododecahedral surfaces. The color is yellow. One of the axes of fourth order is dis

torted—the face has a rhombic profile with the long and short diagonals equal to 0.21 and 0.19 mm, respectively. One of the edges shows an equant hole— a trace of another mineral removed during the thermo chemical decomposition. The third diamond grain (0.18 × 0.18 × 0.1 mm in size) is a fragment of uncer tain habitus with slightly dull surface. These three dia mond grains were found together with pyrope (14 grains), Crspinel, and Crdiopside (table). Pyrope is abundant in the coastalmarine basal sand of the Buchak Horizon in the ZhilinoPoddubnyi section in the southern Rossosh massif (Fig. 9, site 3). Sample 7003 (2.3 t) yielded only violet 79 grains with onefourth part belonging to grain class 0.5–0.9 mm, i.e., coarsegrained sand dimension. The Xray spec tral analysis suggests that some of these grains are kim berlitic (Сr2O3 up to 13.25%). The CaO–Cr2O3 dia gram (Fig. 10) shows that the pyrope grains found here mainly correspond to this mineral from lherzolites that dominate in the Yakutian kimberlites. In terms of the composition of major components, pyrope almandine is similar to garnets of the diamondiferous

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IIIA, IIIBC

4 IIIBC

3

2

Pavlovsk Kalach

IIBC IIIABC

10

0

1

10

20

30 km

Fig. 8. Lithofacies scheme of the Voronezh anteclise for the Late Paleocene Sumian time (Savko et al., 2001a). Novobogor oditskoe (1), Nizhnii Byk (2), Erzhovka or Novomikhailovka (3), Pykhovka (4). See Figs. 3 and 4 for other explanations.

eclogite associations but differ by lesser contents of secondary components (Ti and Na). However, it is rather difficult to assess the significance of the latter parameters for genetic interpretations. The pyrope grains found in our work cannot be assigned to the eclogite type, for example, because they are enriched in Cr2O3 typical of garnet from ultrabasic rocks. Since the chemical properties of all local mineral satellites cannot be scrutinized, let us refer the readers to mono graph (Savko et al., 2007) and cite here only some analyses of new finds. Diamond grains detected several times in Quater nary sequences (Mikhailov et al., 2000) were attrib uted to local sources. We assume, however, that appli cation of Quaternary rocks for diamond prospecting is very limited and possible only if we clearly understand the genetic and stratigraphic position of sampled intervals. In the early Pleistocene, i.e., 427–374 ka BP according to (Kholmovoi, 1999), the study region was occupied by the Don glacial apron fed by the diamon diferous northern part of the East European Platform. Participants of the prospecting team of Voronezh State University found that the moraine section near the Verkhnii Ikorets Settlement includes a dilapidated boulder of dark gray ultrabasic breccia. The rock con tained Crspinels and other highpressure minerals. LITHOLOGY AND MINERAL RESOURCES

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We can reasonably assume a distal provenance for not only boulders in the Shoksha quartzites and rapakivi, but also diamonds and their satellites. It is assumed that the Don and postDon Quater nary sequences of the Voronezh anteclise (the recent ravine alluvium included) were formed with a certain participation of the allochthonous moraine material. In order to check this assumption, we scrutinized the Osetrovka exposure group along the Don River, where one can see sediments of the Mamon sequence (D3 fr2fm), Cenomanian coastalmarine and Qua ternary (fQ1ds) fluvioglacial sediments. This section is unique, because the Devonian, Cenomanian, and Quaternary sequences are composed of similar gravel–pebble material with varigrained sand and clay. The Devonian and Cenomanian sequences related to a single provenance (Voronezh anteclise crest) are marked by a continuity of mineral composition of the heavy fraction. In contrast, the lower Pleistocene flu vioglacial sequences of the Don apron are enriched in the alien material, such as garnets (they are absent in D3 fr2fm and К2s sequences), unrounded large idio morphic ilmenite and picroilmenite crystals, lilac zir con, chert clasts with the typical Carboniferous brigo zoan, and others. No. 3

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Fig. 9. Lithofacies scheme of the Voronezh anteclise for the Eocene Buchak time (Savko et al., 2001a) and locations of HPMs (box) and diamond (triangle). Occurrences: Krivonosovo (1), Ekaterinovka (2), Zhilino–Poddubnyi (3), Novobelaya (4), Nizh nii Byk (5). See Figs. 3 and 4 for other explanations.

DISCUSSION The very interesting problem of detection of pri mary diamond sources scattered in sedimentary sequence of the Voronezh anteclise cannot be solved with understanding the intricate temporal succession of positions of differentage washout and accumula tion zones. All materials related to this aspect are gen eralized in Fig. 11. When describing examples of the facies affiliation of finds of diamond and satellites in Phanerozoic sediments, we often mentioned the Ros sosh and Olym massifs in the Early Precambrian base ment as the potential suppliers of material in water basins. They are shown in Fig. 11 by two separate areas

of the most significant finds of the association of all diamond satellite minerals (pyrope + Crspinel + picroilmenite + Crdiopside). Paleogene sequences are most promising for prog nostic models of the hypothetic HPMs in the Archean Rossosh massif. These sediments abandoned by a sea transgressing from the Dnieper–Donets depression in the northeastern direction are retained in a 600kim long zone extending from the Veshenskaya Settlement (northern Rostov) to Novozybkov (Bryansk district). Owing to high hydrodynamic activity during the initial transgression, the older sedimentary material was also mixed with the irregularly heavy minerals (highpres sure species included). The basal Paleogene horizon

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CaO, % 10 9 8 7

I

39 75

6 65

46 49 42 47 47

135

75 54 24 76 53 50 31 6 23 4857 8 28 45 56 41 40 58 59 30 44 55 79

37

5 4 3

52

C1 34

II

138

IV

77

III

2 1 0 2

3

4

5

6

7

8

9 Сr2O3, %

Fig. 10. Distribution of data points of CaO and Cr2O3 in pyrope grains in sample 7003 taken from the basal sand of the middle Eocene Buchak Formation. Zhilino–Poddubnyi section, Kantemirov area, Voronezh district. Based on (Savko et al., 2007). Zones: (I) wehrlite, (II) lherzolite, (III) harzburgite–dunite, (IV) inclusions in diamond.

served as depository of the most reliable information about the distribution of diamond and its satellites (primarily kimberlitic varieties) in the sedimentary cover. Along the Veshenskaya–Novozybkov profile, sediments with the maximal concentration of the most representative HPMs (Crrich pyrope, Crspinels of the coesite subfacies with Cr2O3 > 65%, and highMg picroilmenites) are confined to the southern part of the Archean Rossosh massif, while the depleted dis persion aureole is located in the adjacent area overly ing the Early Proterozoic basement (Lebedinsk iron ore quarry of KMA; Mamon sector of the Voronezh geologiya IndustrialGeological Association, Verkh nemamon area, Voronezh district). Problem of the primary diamond potential of the study region is far from solution. In particular, we still do not understand reason for the virtually complete absence of indicatorminerals in the Devonian, Car boniferous, and Jurassic sedimentary sequences of the Voronezh anteclise that are closest (in terms of accu mulation timing) to the predicted Middle Paleozoic diatremes. Two models can be assumed based on the lithofacies analysis. According to the first model, concentration of HPMs in sediments of the heavy fraction and its com LITHOLOGY AND MINERAL RESOURCES

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ponents is related to the coastal and nearbottom (cur rent) hydrodynamic activity rather than the transgres sion scale. Slow (although largescale) Devonian and Carboniferous transgressions had an insignificant impact upon the substrate except for the onset of the large Petino–Livny stage that promoted the formation of small zirconium–titanium placers. The presence of pebblestones in sections of the Lebedinsk and Mikhailovsk iron ore quarries suggests that the Bajo cian–early Bathonian transgression was more active, but it did not extend to the probably diamondiferous zone of Archean massifs in the Rossosh–Kastornaya– Olym basement. Consequently, the transgression was not involved in reworking of the assumed diamondif erous material. The hydrodynamic environment was more active in the Early Cretaceous and Paleogene, resulting in the coastal and submarine erosion of sedi ments and the appearance of high HPM concentra tions in some places. Another model presumes a younger (Mesozoic and even Laramian, i.e., Cretaceous–Paleogene bound ary) age for the primary diamond sources. In Creta ceous and Neocomian sediments from the northern areas of the Lipetsk district, we detected a specific association of unusual (in shape) minerals, such as No. 3

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0

7004

Bryansk

7

50

5198 14

13

12

100

7005

8

150 km

Belgorod

7007 Kursk

Orel

7008

5152

11

Liski

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RM

7011

5155

Lipetsk 5150

6006 Voronezh 5154

5, 6

3

1 5151

4

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6004 7003 6003 7003, 5156

5153

9

OM

7010

6005

7006

10

2

7014

7013

7012

5148

6000, 6001, 6002 5158

5149

5175

7001, 5174

7001 5171

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OM

5195

10

7 8 7 9

6

4

2

5

3

1

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Fig. 11. Distribution of HPMs in the sedimentary cover of the Voronezh anteclise. (1–4) Mineral association: (1) diamond– pyrope–Crspinel–picroilmenite, (2) diamond (diamond grains are not accompanied by other HPMs), (3) pyrope–Crspinel– picroilmenite with minerals of the kimberlitic diamond subfacies, (4) pyrope–Crspinel–picroilmenite; (5) separate finds of Cr spinels, picroilmenite, and Crdiopside; (6) sectors lacking HPMs in reference samples; (7) Mamon sector, where pyrope grain of the diamond subfacies was found in Paleogene sediments; (8) reference samples and numbers; (9) outlines pf prospective areas of the Rossosh (RM) and Olym (OM) massifs; (10) probable location of the central part of the prospective Rossosh kimberlite field.

CONCLUSIONS

pyrite, cryoconite, primary iron, and other primary alloysintermetallides (Savko et al., 2001). They are characterized by the spherical, dropshaped, and con torted forms, as well as thickening along the frontal (relative to motion vector) direction. All these facts suggest a rapid crystallization of minerals from the finely dispersed and rapidly moving particles of a mol ten or glowing material. Such mechanism is typical for the formation of minerals during volcanic explosions and dispersion of the meteoric material. However, forms analogous to particles of the volcanic ash glass (related to the explosive impact of a relatively refrac tory and brittle material) suggest the explosive origin of minerals.

The data presented above suggest that the Voronezh anteclise accommodates diamondiferous fields of not only Middle Paleozoic, but also MesoCenozoic age. The field predicted in the Archean Olym massif in the western Lipetsk district, where the discovery of dia mond in the sedimentary cover is most significant, likely comprises one or two industrially productive kimberlite–lamproite pipes and some pipeshaped bodies of other rocks. Thus, this field can be similar to the Verkhotina (Kepa) field in the Arkhangel’sk dia mondiferous province, which accommodates one highly productive Vladimir Grib pipe (570 × 480 m or

Color of pyrope grains in samples 7001 (Paleogene, Nizhnii Byk) and 7003 (Paleogene, Zhilino–Poddubnyi) depending on their chemical composition. Camebax50 SX. N.I. Kononova (MGU), analyst Grain no. 59 58 55 78 48 57 53 80 54 56 50 79 76 75 52 136 77 135 51 49 47 134 81

Sample Cr2O3 7003 7003 7003 7003 7003 7003 7003 7003 7003 7003 7003 7003 7003 7003 7003 7001 7003 7001 7003 7003 7003 7001 7003

1.71 1.8 1.9 2.35 2.62 2.72 2.97 3.03 3.16 3.35 3.4 3.41 3.47 3.7 3.84 4.2 5.31 5.34 6.12 6.87 7.04 9.34 13.25

Al2O3

FeO

MgO

CaO

TiO2

MnO

SiO2

21.95 22.39 23.05 22.34 21.89 22.11 21.56 21.56 21.55 19.81 21.33 21.66 21.34 21.13 21.27 21.14 20.33 20.33 18.96 17.86 17.93 16.74 13.61

10.12 10.02 9.18 7.39 7.76 9.14 8.41 7.2 9.09 6.71 7.68 8.22 7.65 7.38 7.45 8.88 7.86 8.61 7.22 7.15 7.28 7.35 7.4

18.67 18.41 20.55 19.24 19.39 18.39 19.31 19.79 18.2 20.28 19.06 19.49 19.06 18.95 20.04 19.85 21.04 18.36 18.79 19.21 19.29 18.59 18.87

3.98 4.07 3.51 5.35 5.41 5.35 5.67 5.29 5.72 4.62 5.63 4.81 5.65 6.22 5.04 4.5 3 5.91 5.39 5.86 5.63 5.22 5.61

0.08 0.06 0.08 0.03 0.1 0.08 0.03 0.01 0.09 0.98 0.12 0.07 0.01 0 0.24 0.1 0.04 0.12 0 0.59 0.14 0.15 0.07

0.46 0.46 0.4 0.57 0.43 0.47 0.44 0.33 0.51 0.23 0.42 0.57 0.49 0.38 0.45 0.53 0.45 0.49 0.47 0.37 0.38 0.51 0.47

40.85 40.96 41.2 41.67 41.49 41.4 41.53 41.75 41.09 41.38 41.4 41.71 40.94 40.97 41.15 40.44 41.4 40.38 40.99 40.72 41.01 40.74 39.69

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Color Lilac weak Lilac weak Lilac weak Lilac weak Lilac weak Lilac weak Lilac weak Lilac moderate Lilac moderate Lilac moderate Lilac moderate Lilac moderate Lilac moderate Lilac moderate Lilac moderate Lilac moderate Lilac intense Lilac intense Lilac intense Lilac intense Lilac intense Lilac intense Lilac intense

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1.2 ha) with a diamond reserve of 5 · 106 US $ (proven in the State Reserve Commission), one diamondfree diatreme, and several pipes with rocks of other com positions (Verichev, 2002). Based on examination of the Lipetsk diamond collection in Voronezh State University, V.I. Koptil, an eminent expert in mineral ogy from the ALROSA JointStock Company, noted that the northeastern part of the anteclise can host pri mary diamond sources with a content of 0.8 car/t or one magnitude higher. Based on largescale finds, as well as dimension and appearance, of indicatormin erals, the southeastern part of the Voronezh district (Rossosh massif) has a high potential for the discovery of the second field with the Yakutiantype diatremes. However, one issue remains open: how much prospec tive are the predicted bodies, since diamond crystal are too scarce in the samples. Figure 11 shows areas of the Archean Olym and Rossosh massifs, where diatremes of the predicted synonymous kimberlite fields are assumed. REFERENCES Afanas’ev, N.S., Petrophysics of Precambrian Rocks and Geological Setting of the Voronezh Crystalline Massif, Extended Abstract of PhD (Geol.–Min.) Dissertation, Lenin grad: Leningr. Gos. Univ., 1983. Berdnikov, M.D., Rapakivi Granites of the Voronezh Crystal line Massif, Izv. Akad. Nauk SSSR, 1981, no. 2, pp. 67–76. Chernyshov, N.M., Nenakhov, V.M., Lebedev, I.P., and Strik, Yu.N., Model of the Geodynamic Development of the Voronezh Massif in the Early Precambrian, Geotekton ika, 1997, no. 3, pp. 21–30 [Geotectonics (Engl. Transl.), 1997, no. 3, pp. 18–27]. Kantserov, V.A. and Bykov, I.N., MineralSatellites of Dia mond in Phanerozoic Rocks in the Southeastern Voronezh Anteclise, in Sovremennye problemy geologii. Materialy yubileinoi nauchnoi sessii geolfaka (Modern Problems in Geology: Materials of the Jubilee Session of the Faculty of Geology), Voronezh: Voronezh. Gos. Univ., 1998, pp. 71–73. Kashkarov, I.F. and Polkanov, Yu.A., Finds of Diamond in Titanium–Zirconium Sands, Dokl. Akad. Nauk SSSR, 1964, vol. 157, no. 5, pp. 1129–1130. Khar’kiv, A.D., Zinchuk, N.N., and Kryuchkov, A.I., Korennye mestorozhdeniya almazov Mira (primary Dia mond Deposits in the World), Moscow: Nedra, 1998. Khar’kiv, A.D., Zinchuk, N.N., and Zuev, V.M., Istoriya almaza (History of Diamond), Moscow: Nedra, 1997. Kholmovoi, G.V., Stratigraphic Position and Structure of the Don Cryichron, Vest. VGU, Ser. Geol., 1999, no. 7, pp. 86–91. Lamproity (Lamproites), Bogatikov, S.A., Ed., Moscow: Nauka, 1991. Mikhailov, M.V., Belyaev, G.A., Kuz’mina, T.S., et al., Per spectives of the Detection of New Middle Paleozoic Diamond Deposits in the Russian Platform, Region. Geol. Metallog., 2000, no. 12, pp. 158–177. Mityukhin, S.I., Geological–Genetic and Empirical Prin ciples of the Identification of the Taxon of the Subprovince

of Kimberlites and Related Convergent Rocks, Otechest. Geol., 1997, no. 1, pp. 23–28. Nozhkin, A.D. and Krestin, E.S., Radioaktivnye elementy v porodakh rannego dokembriya (na primere KMA) (Radioac tive Elements in Early Precambrian Rocks with KMA as Example), Moscow: Nauka, 1984. Polishchuk, V.D., Tectonics, in Geologiya, Gidrogeologiya i Zheleznye Rudy Basseina Kurskoi Magnitnoi Anomalii, Mos cow: Nedra, 1970, vol. 1, part 1 (Precambrian). Preobrazhenskaya, V.N., Yura i nizy nizhnego mela territorii Tsentral’noChernozemnykh oblastei (Jurassic and Lower Part of the Lower Cretaceous in the Central Chernozem Zones), Voronezh: Voronezh. Gos. Univ., 1966. Savko, K.A. and Gerasimov, V.Yu., Petrology and Geospeed ometry of Metamorphic Rocks in the Eastern Voronezh Crys talline Massif, in Tr. NII Geologii VGU , Voronezh: Voronezh. Gos. Univ., 2002, issue 8. Savko, A.D., Manukovskii, S.V., Mizin, A.I., et al., Lithology and Facies of PreNeogene Sediments in the Voronezh Anteclise, in Tr. NII Geologii VGU, Voronezh: Voronezh. Gos. Univ., 2001a, issue 3. Savko, A.D., Shevyrev, L.T., and Il’yash, V.V., Associations of Indicator Minerals of Diamond Potential in Sedimen tary Cover of the Voronezh Anteclise, in Problemy almaznoi geologii i nekotorye puti ikh resheniya (Problems of Dia mond Geology and Some Pathways of Their Resolution), Voronezh: Voronezh. Gos. Univ., 2001b, pp. 423–433. Savko, A.D., Shevyrev, L.T., and Egorov, A.Yu., New Finds of Diamond in the Lower Cretaceous (Aptian) Collector Rocks in the Northeastern Voronezh Anteclise, in Problemy prognozirovaniya, poiskov i izucheniya mestorozhdenii poleznykh iskopaemykh na poroge XXI veka (Problems of the Prognosis, Prospecting, and Study of Mineral Deposits at the Turn of XXI Century), Voronezh: Voronezh. Gos. Univ., 2003a, pp. 249–253. Savko, A.D., Zinchuk, N.N., Shevyrev, L.T., et al., Dia mond Potential of the Voronezh Anteclise, in Tr. NII Geol. VGU, Voronezh: Voronezh. Gos. Univ., 2003b, issue 17. Savko, A.D., Shevyrev, L.T., and Il’yash, V.V., Diamonds and Their Satellites in Sedimentary Cover of the Voronezh Anteclise, in Tr. NII Geol. VGU, Voronezh: Voronezh. Gos. Univ., 2007, issue 47. Sekretarev, I.E., Cretaceous Titanium–Zirconium Placers in the Northeastern Voronezh Anteclise, in Protsessy obra zovaniya rossypei v beregovykh zonakh drevnikh i sovremen nykh morei i okeanov (Processes of Placer Formation in Coastal Zones of Ancient and Modern Seas and Oceans), Riga: AN Latv. SSR, 1977, pp. 149–151. Shevyrev, L.T., Geological Development of the Voronezh Anteclise, Extended Abstract of DSc. (Geol.–Min.) Disserta tion, Moscow: MGRI, 1989. Skarzhinskii, V.I., Belokon, V.G., Kuznetsova, S.V., et al., Manifestation of Alpian Volcanism on the Southern Slope of the Voronezh Massif, Dokl. Akad. Nauk Ukr. SSR, Ser. B., 1973, pp. 46–48. Valeev, R.N., Avlakogeny VostochnoEvropeiskoi platformy (Aulacogens of the East European Platform), Moscow: Nedra, 1978. Verichev, E.M., Geological Conditions of the Formation and Exploration of the V. Grib Deposit, Extended Abstract of PhD (Geol.–Min.) Dissertation, Moscow: Mosk. Gos. Univ., 2002.

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