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1.
T. A. Myskova R. I. Mil’kevich P. A. L’vov 《Stratigraphy and Geological Correlation》2012,20(2):166-178
During our study we obtained the first age datings of detrital zircons from metasandstones of the Ladoga Group (North Ladoga
Region, Russia) with the U-Pb isotopic method using the SHRIMP-II ion microprobe. The data obtained made it possible to clarify
the lower age limit of sedimentation and to obtain additional age data for evaluating the chemical composition and an age
of source areas. This work presents the results of isotopic-geochemical (Sm-Nd) and geochemical studies of metasediments.
High LREE concentrations, a high La/Sc ratio and a low Cr/h ratio, and the presence of a distinct Eu-minimum (Eu/Eu* = 0.54–0.72)
indicate a significant role of acidic terrigenous material in source areas. In addition, the data of the isotope analysis
of detrital zircons show that sediments of the Ladoga Group accumulated from the destruction of Proterozoic rocks (1.9–2.0
Ga; a proportion in sediments is 60–70%) and, to a lesser extent, Archean rocks (2.54–2.74 and 2.9–3.01 Ga; the proportion
in sediments is 30–40%). One of the Archean source areas could be granite-gneisses of the Pitkyaranta-Koirinoya dome structure
with the U-Pb zircon age of 2659 ± 15 Ma. We have established the lower age limit of sedimentation as 1.9 Ga within the measurement
error. The Sm-Nd model ages obtained (2.5–2.6 Ga for sediments of the Ladoga Group and over 3.4 Ga for granite-gneisses of
the dome structure) suggest a significant contribution of ancient crustal source area into source rocks. Our age data agree
well with those for svecofennides of Finland. 相似文献
2.
T. A. Myskova N. M. Ivanov M. A. Korsakova R. I. Mil’kevich N. G. Berezhnaya S. L. Presnyakov 《Stratigraphy and Geological Correlation》2013,21(4):337-358
The geological, geochemical, and isotopic-geochronological data obtained for Sumian moderate-basic metavolcanites of Shombozero and Lekhta structures of the Panayarvi-Vygozero belt shows that the Tunguda Formation is confined to the Paleoproterozoic structural and material complex. This formation is represented by the complex of weakly differentiated andesitobasalts and andesites of calc-alkaline series with higher contents of MgO and moderate contents of Al2O3 and rare earth elements. The rocks of the Tunguda Formation are different from the Late Archean basic rocks of the Hiziyarvi Formation represented mainly by tholeiitic basalts with low REE contents and undifferentiated spectrum of REE distribution. The age of volcanites of the Tunguda Formation was determined to be 2439 ± 21 Ma. The xenogenic zircons from metaandesites of the Tunguda Formation have Neoarchean age according to the 207Pb/206Pb ratio (from 2536 ± 4 to 2825 ± 7 Ma). The Neoarchean zircons, a negative value of ?Nd (?3.8), and indicative geochemical parameters are evidence that the crustal component took part in formation of the protolith of the studied rocks. 相似文献
3.
Rato M Gaspar MB Takahashi S Yano S Tanabe S Barroso C 《Marine pollution bulletin》2008,56(7):1323-1331
Imposex and organotin (OT) tissue contamination of the netted whelk Nassarius reticulatus (L.) were assessed in the continental shelves around the main estuaries of the central coast of Portugal (Lisbon: Tagus estuary; Setúbal: Sado estuary) and the main coastal lagoon in the Southern of Portugal (Faro: Ria Formosa). Pollution levels were higher in areas of more intense boat traffic and shipyard activities and imposex showed a clear decreasing gradient from the estuaries to the offshore, in relation to a similar gradient of tissue contamination by tributyltin. Remarkably, imposex was extensively spread over the adjacent continental shelves of Tagus and Sado estuaries. The current work shows that TBT pollution is undoubtedly a matter of concern not only for the above estuaries where harbours are implanted but also for the adjacent continental shelves, regardless the massive dilution of contaminants that may occur in these deeper areas. 相似文献
4.
A multi‐proxy study of Holocene environmental change recorded in alluvial deposits along the southern coast of the Pampa region,Argentina 
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ADEL Mil PALANISAMY Satheesh Kumar SHAFIEI Shafigh FAZLI Hasan ZORRIEHZAHRA Mohammad Jalil 《海洋学报(英文版)》2016,35(8):39-43
Sturgeons are the most important principal market species in the Caspian Sea. In the present study, measurement of blood parameters was carried out with the aim of evaluating the normal value of hematological and serum biochemical parameters of brood stocks Acipenser persicus during spawning season. Blood samples were collected from 36 brood stocks of A. persicus (18 males and 18 females) during the spawning season. Higher value of red blood cells, white blood cells, haemoglobin, haematocrit was observed in male breeders with significant differences between female breeders (p>0.05). Haemoglobin and haematocrit value in this study was within the range of 8.70 to 9.2 g/dL and 29.73% to 30.26%, respectively. The statistically significant differences between mean corpuscular volumes, mean corpuscular haemoglobin, lymphocyte and neutrophil percentages, aspartate aminotransferase, alkaline phosphatase and creatine kinase were observed in the male and female brood stocks. It is concluded from this study, some of the hematological and serum biochemical parameters of male and female A. persicus breeders were significantly varied from each other. In comparative investigation with earlier reports, the values of red blood cells, haemoglobin and haematocrit are highly varied due to age variations of fish. However, further studies are necessary to understand the impact of sexual, age, size, length, and season and habitat variation. Serum biochemical parameters can be used for confirming the maturity of A. persicus and monitoring any changes in the water quality parameters and soil. 相似文献
6.
N. F. Mazurin M. K. Matskevich V. T. Mil’chenko M. A. Novitskii 《Russian Meteorology and Hydrology》2010,35(6):386-393
The turbulence characteristics measured in the surface layer over a real underlying surface are presented. The measurements
are carried out at the 3- and 16-m levels using acoustic anemometers; at the lower level, the measurements are doubled. The
diurnal cycle is obtained of the temperature flux and friction velocity. To obtain the temperature flux, so-called “acoustic”
temperature is used as calculated from the sound speed data with corrections for air humidity and pressure. The normalized
characteristics of turbulence are presented as dependent on dimensionless height z/L. The values of temperature flux and friction velocity increase with height: their day-integral values at 16-m level exceed
those at 3-m level for about 20 and 35%, respectively. 相似文献
7.
8.
J. P. Milési P. Ledru P. Ankrah V. Johan E. Marcoux Ch. Vinchon 《Mineralium Deposita》1991,26(3):228-238
The traditional concept of the Early Proterozoic gold deposits in Ghana — i.e. gold-bearing shear zones overlain by Tarkwaian paleoplacers containing reworked gold derived from the shear-zones — needs to be reconsidered in the light of recent research in Ghana, the Ivory Coast and French Guiana. This research has revealed a consistent pattern of geostructural and metallogenic evolution in which both the Birimian and the Tarkwaian rocks were deformed by a major Eburnean compression (D2). It has shown that the NE-SW faults controlling the Gold Coast Range shear-zone mineralization (Ashanti-Prestea) were formed during the Eburnean D2 episode of thrusting that was followed by hydrothermal activity with the emplacement of auriferous arsenopyrite and then by the development of quartz veinlets and native gold; thus the shear-zone mineralization could only have appeared during the D2 late-orogenic stage. It has also shown evidence of post-depositional D2 deformation in the gold sites examined in the Tarkwa gold-bearing conglomerate, although the effects are limited and primary lithological controls have been preserved that reveal these deposits to be modified paleo-placers. Thus, the Tarkwaian gold could not be derived from the gold-bearing shear-zones. 相似文献
9.
The stratabound polymorph Loulo gold deposits and occurrences were discovered in sedimentary rocks of the Early Proterozoic
Birimian Formation, in the Kéniéba region of SW Mali. Early work showed reserves in the Loulo-0 and Loulo-3 deposits of 28
t of gold in ore averaging 4.43 g/t Au, to depths of 140 m; recent drilling has found mineralization to at least 300 m depth.
Early tourmalinization of the sedimentary host rock is indicated by reworked tourmalinite pebbles in non-tourmalinized hanging-wall
rocks. Mineralization, restricted to highly tourmalinized zones, occurs as: (a) pre-D1 (deformation) disseminated pyrite with
micron-size inclusions of gold particles; (b) syn-/late-D2 stockworks with minor disseminated sulphides and native gold. Gold
in the sulphides is small (10–40 gm), and occurs at pyrite-crystal edges, filling cracks and/or as inclusions. Post-D2 stockwork
mineralization derived from the pre-D1 one that was emplaced with tourmaline, as is indicated by the small differences between
pre-D1 and post-D2 sulphur isotopes, as well as by the type of quartz vein that indicates an almost closed system. In West
Africa, the pre-D1 mineralization of Early Birimian age represents the first major introduction of gold into the Proterozoic.
It attributes a major metallogenic role to the tourmalinized sandstone that indicates crustal accretion in West Africa during
the Early Proterozoic.
Editorial handling: D.D. Klemm 相似文献
10.