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21.
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A. I. Grabezhev Yu. L. Ronkin V. N. Puchkov G. Yu. Shardakova O. B. Azovskova A. Gerdes 《Doklady Earth Sciences》2016,466(1):92-95
The Zelenodol porphyry Cu-(Au, Mo) deposit located about 65 km SSW of the city of Chelyabinsk is confined to the western part of the West Uralian Volcanogenic Megazone. The concordant U-Pb age of zircons from ore-bearing island-arc diorite porphyryis 418.3 Â ± 2.9 Ma. 相似文献
23.
A. V. Maslov Yu. V. Erokhin A. Gerdes Yu. L. Ronkin K. S. Ivanov 《Doklady Earth Sciences》2018,482(2):1275-1277
Detrital zircons (DZs) from arkose sandstones of the Upper Riphean Zilmerdak Formation (Southern Urals) yielded ages in the range of 3039–964 Ma. Grains with Late Karelian and Early and Middle Riphean ages compose 35, 34, and 26% of the total number of the analyzed zircons, respectively. This is similar to the age spectra of the Vendian sandstones (Asha Group), but it differs significantly from the age distribution typical of the Riphean stratotype sandstones. 相似文献
24.
Cambrian igneous formations in the Northern Urals were identified and described for the first time. It was established that the Timanide orogeny terminated in the Early Cambrian and was followed by continental rifting above a mantle plume in the Late Cambrian. 相似文献
25.
Mahdi Ghobadi Axel Gerdes Lia Kogarko Heidi Hoefer Gerhard Brey 《Geochemistry International》2018,56(8):766-783
In this study we present a fresh isotopic data, as well as U–Pb ages from different REE-minerals in carbonatites and phoscorites of Guli massif using in situ LA-ICPMS technique. The analyses were conducted on apatites and perovskites from calcio-carbonatite and phoscorite units, as well as on pyrochlores and baddeleyites from the carbonatites. The 87Sr/86Sr ratios obtained from apatites and perovskites from the phoscorites are 0.70308–0.70314 and 0.70306–0.70313, respectively; and 0.70310–0.70325 and 0.70314–0.70327, for the pyrochlores and apatites from the carbonatites, respectively.Furthermore, the in situ laser ablation analyses of apatites and perovskites from the phoscorite yield εNd from 3.6 (±1) to 5.1 (±0.5) and from 3.8 (±0.5) to 4.9 (±0.5), respectively; εNd of apatites, perovskites and pyrochlores from carbonatite ranges from 3.2 (±0.7) to 4.9 (±0.9), 3.9 (±0.6) to 4.5 (±0.8) and 3.2 (±0.4) to 4.4 (±0.8), respectively. Laser ablation analyses of baddeleyites yielded an eHf(t)d of +8.5 (± 0.18); prior to this study Hf isotopic characteristic of Guli massif was not known. Our new in situ εNd, 87Sr/86Sr and eHf data on minerals in the Guli carbonatites imply a depleted source with a long time integrated high Lu/Hf, Sm/Nd, Sr/Rb ratios.In situ U–Pb age determination was performed on perovskites from the carbonatites and phoscorites and also on pyrochlores and baddeleyites from carbonatites. The co-existing pyrochlores, perovskites and baddeleyites in carbonatites yielded ages of 252.3 ± 1.9, 252.5 ± 1.5 and 250.8 ± 1.4 Ma, respectively. The perovskites from the phoscorites yielded an age of 253.8 ± 1.9 Ma. The obtained age for Guli carbonatites and phoscorites lies within the range of ages previously reported for the Siberian Flood Basalts and suggest essentially synchronous emplacement with the Permian-Triassic boundary. 相似文献
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S.A. Barboza R. Alway T. Akpulat W.L. Esch P.J. Hicks Jr. M.L. Gerdes 《Marine and Petroleum Geology》2009
Hydrocarbon top seal analyses are particularly difficult in fluvial and marginal marine settings. Although these settings often contain beds comprised of a low-permeability, clay-rich lithology associated with high quality seals, their presence does not guarantee an effective seal because individual beds within the stratal unit may be laterally discontinuous. Lateral facies changes, truncation of fine-grained beds, or the presence of crevasse splays may provide cross-stratal migration pathways, reducing the effective sealing capacity to a magnitude less than the closure height. 相似文献
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29.
Hans J. Lippolt Rolf S. Wernicke Werner Boschmann 《Physics and Chemistry of Minerals》1993,20(6):415-418
In order to test the chronometer qualities of speculante for the (U + Th)/He dating method, 4He release experiments by stepwise heating of two specularites from the Rimbach mineralization locality in the southern Vosgues (France) have been carried out. The diffusion coefficients define linear Arrhenius plots within a temperature interval of 250 to 830 °C, which is suggestive of volume diffusion. Extrapolation of the diffusion behavior to 20° C yields diffusion coefficients (D20 values) smaller than 10?26 [cm2 s?1] for both hematites with activation energies at 116 [kJ/mole]. The results of our study suggest that specularite is a very helium retentive hematite variety which is capable of quantitatively retaining radiogenic helium over geologic periods of time. 相似文献
30.
Rolf Schruder 《地球表面变化过程与地形》1991,16(8):731-736
The local reach gradient of small gravel bed rivers (drainage area 0-8-110 km2) in the Eifel, West Germany, is adjusted to transport the river bed sediments. Transport of gravel becomes possible under high flow conditions (Shields entrainment factor ≈-03). Mean bed material size for riffle sections increases with distance downstream. For small drainage areas channel slope is a negative exponential function of drainage area, while for the larger region the additional influence of bedload size has to be considered. Good agreement with Hack's data (1957) for Virginia and Maryland, U.S.A., is achieved (S = 0.0066 (D50/A)- 40., r = 0.67). 相似文献