The bottom of Lake Chebarkul’ was investigated by ground penetrating radar at the fall site of a large fragment of the Chelyabinsk meteorite. Linear profiles and 3D reconstructions revealed an ...anomalous depression of the lake floor relief and the disturbance of the structure of the ice cover, which indicate the possible place of meteorite fragment occurrence.
Questions on the use of the radionuclide .sup.68Ga in the medical institutions of the Russian Federation for diagnosis of malignant tumors were examined. The task of precise measurement of .sup.68Ga ...activity in order to decrease dose loads for patients and enhance the effectiveness of the diagnosis is very important. Calibration of the mobile RIS-3A reference dose calculator to .sup.68Ga activity was studied. Various methods of calibration, ensuring traceability to the National Primary Standard of the units of radionuclide activity, the specific activity of radionuclides, and the stream of alpha and beta particles and photons of radionuclide sources in GET 6-2016 are: the method of direct comparison with a UÉA-7 installation from GET 6-2016, using a sample of .sup.68Ga solution; and the use of a gamma spectrometer and sources based on other radionuclides with traceability of the unit of radionuclides to GÉT 6-2016. The expanded uncertainty budgets of the calibration coefficient are presented for both calibration procedures, using the UÉA-7 installation from GET 6-2016, and a gamma spectrometer with .sup.18F. The convergence of the measurement results of .sup.68Ga activity on the reference dose calibrator, with calibration coefficients obtained by different methods, was evaluated. The results obtained confirm the applicability of the various calibration methods. The results of the study may find application in ensuring the traceability to GET 6-2016 of the units of activity of other promising radionuclides introduced into medical practice.
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Ar, Sm-Nd, U-Pb, and Lu-Hf isotope data are reported on the gabbro of the Volkovsky Massif, the only massif of the Uralian Platinum Belt wherein economic copper-iron-vanadium and high-grade ...gold-palladium mineralization is present. The massif is made up of gabbro blocks with concentrically zoned structure and diorite intrusions in its core. In the northeast and southwest, the gabbro is cut by syenite of the Kushva Massif. Gabbro blocks mainly consist of the olivine-anorthite gabbro, while labradorite two- pyroxene gabbro intersects both olivine-anorthite gabbro and Ti-magnetite and copper-PGE mineralization developed in them. The study of both gabbro types by Sm-Nd isochron and U-Pb (SHRIMP II) zircon methods with subsequent REE and Lu-Hf isotope analysis of zircon made it possible to date reliably (428 ± 7 Ma (SHRIMP) and 436 ± 21 Ma (Sm-Nd)) postore labradorite gabbro and, correspondingly, the upper age limit of the mineralization of the Volkovsky Massif. Ore-bearing olivine-anorthite gabbro contain four different-age zircon populations: 2682 ± 37–972 ± 18 Ma, 655 ± 15 to 565 ± 9 Ma; 450 ± 12 Ma, and 343 ± 8 Ma. Hf-Nd isotope systematics showed that zircon with an age of 450 ± 12 Ma presumably marks the formation age of the rocks, the older zircon was trapped, while zircon with an age of 343 ± 8 Ma was formed during low-temperature transformation of the rock and sometimes contains excess radiogenic Hf. Proterozoic xenogenic zircon was inherited from diverse rocks of ancient crust, while the oldest grain with an age of 2065 Ma was possibly formed in a deep mantle source. Vendian zircon was presumably also entrapped, and its morphology and geochemistry point to the crystallization from a basaltic melt. The abundance of pre-Paleozoic zircon in the olivine-anorthite gabbro suggests significant contribution of ancient material in their petrogenesis. This material could serve as source of ore components (metals and sulfur) for unique copper-sulfide gold-PGE mineralization of the Volkovsky Massif.
The hydrogeochemical characteristics and zonation of the permafrost zone in the central part of the Yakutian diamond-bearing province formed mainly under the influence of cryogenic processes that ...occurred in the late Cenozoic. On the basis of field and experimental studies, conclusions were formulated that the perennial cryogenesis of the sedimentary cover in this region resulted in increasing the concentration of carbonate and sulfate compounds in groundwaters as well as increasing the concentration of easily soluble compounds (sodium, magnesium, and calcium chlorides).PUBLICATION ABSTRACT
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