排序方式: 共有35条查询结果,搜索用时 15 毫秒
21.
Nikolenko E. I. Logvinova A. M. Izokh A. E. Afanasiev V. P. Oleynikov O. B. Biller A. Ya. 《Doklady Earth Sciences》2018,480(1):656-660
Doklady Earth Sciences - A comparative study of the chemical compositions of chromium spinel and polyphase inclusions has been carried out. Chromium spinels were separated from the concentrate of... 相似文献
22.
Yu. V. Seryotkin V. L. Skvortsova A. M. Logvinova N. V. Sobolev 《Doklady Earth Sciences》2017,476(2):1155-1158
The crystallographic orientation of three diamonds and 19 olivine inclusions from Udachnaya kimberlite pipe was studied using monocrystal X-ray diffractometry. No epitaxial olivine inclusions were found. 相似文献
23.
A. M. Logvinova R. Wirth D. A. Zedgenizov L. A. Taylor 《Geochemistry International》2018,56(4):283-291
An aragonite inclusion in natural diamond was identified using techniques of transmission electron microscopy, electron microdiffraction, and microprobe analysis. The inclusion is hosted in a colorless octahedral diamond crystal from the Komslomolskaya pipe in Yakutia. The diamond crystal shows a zoned distribution of its admixtures and defects. The structure parameters of the inclusion (∠[001]/[201] = 66° and certain lattice spacings) correspond to the calculated parameters of the orthorhombic unit cell of a Ca carbonate polymorph. The aragonite inclusion contains admixtures of MgO (0.81), MnO (0.58), and FeO (0.13 wt %). The find of a syngenetic aragonite inclusion in diamond is unique and proves that diamond can be formed in carbonatized mantle peridotite at depths of at least 300 km. The inclusion hosts identifiable microphases of Ni-rich sulfides (37–41 wt % Ni), titanite, hydrous silicate, magnetite, and fluid. This association indicates that the diamond and aragonite crystallized from a carbonate–silicate–sulfide melt or highdensity fluid. 相似文献
24.
I.V. Ashchepkov T. Ntaflos A.M. Logvinova Z.V. Spetsius H. Downes N.V. Vladykin 《地学前缘(英文版)》2017,8(4):775-795
New versions of the universal Jd-Di exchange clinopyroxene barometer for peridotites,pyroxenites and eclogites,and also garnet barometer for eclogites and peridotites were developed.They were checked using large experimental data sets for eciogitic(~530) and peridotitic systems(650).The precision of the universal Cpx barometer for peridotites based on Jd-Di exchange is close to Cr-Tschermalite method produced by Nimis and Taylor(2000).Cpx barometer was transformed by the substitution of major multiplier for K_D by the equations dependent from Al-Na-Fe.Obtained equation in combination with the thermometer of Nimis and Taylor(2000) allow to reconstruct position of the magma feeder systems of the alkali basaltic magma within the mantle diapirs in modern platforms like in Vitim plateau and other Southern Siberia localities and several localities worldwide showing good agreement of pressure ranges for black and green suites.These equations allow construct PTX diagrams for the kimberlite localities in Siberia and worldwide calculating simultaneously the PT parameters for different groups of mantle rocks.They give very good results for the concentrates from kimberlite lamproites and placers with mantle minerals.They are useful for PT estimates for diamond inclusions.The positions of eclogite groups in mantle sections are similar to those determined with new Gar—Cpx barometer produced by C.Beyer et al.(2015).The Fe rich eclogites commonly trace the boundary between the lower upper parts of subcontinental lithospheric mantle(SCLM) at 3-4 CPa marking pyroxenite eclogites layer.Ca-rich eclogites and especially grospydires in SCLM beneath Precambrian kimberlites occurs near pyroxenite layer but in younger mantle sections they became common in the lower parts.The diamondiferous Mg Cr-less group eclogites referring to the ancient island arc complexes are also common in the middle part of mantle sections and near 5-6 GPa.Commonly eclogites in lower apart of mantle sections are remelted and trace the high temperature convective branch.The Mg-and Fe-rich pyroxenites also show the extending in pressure trends which suggest the anatexic melting under the influence of volatiles or under the interaction with plums. 相似文献
25.
UM Scharler MJ Ayers AM de Lecea M Pretorius ST Fennessy JA Huggett 《African Journal of Marine Science》2016,38(1):S193-S203
Riverine influences on nearshore oceanic habitats often have detrimental consequences leading to algal blooms and hypoxia. In oligo- to mesotrophic systems, however, nutrient delivery via rivers may stimulate production and even be a vital source of nutrients, as may nutrient supplements from upwelling. We investigated the nutrient content (C, N, P) and stoichiometry of sediment, and several pelagic, benthopelagic and benthic species in the KwaZulu-Natal (KZN) Bight, a narrow shelf area on the south-east coast of South Africa, bordering the Agulhas Current. Three suggested nutrient sources to the bight are the Thukela River in the central region of the bight, upwelling in the northern part and a semi-permanent eddy (Durban Eddy) in the southern part. Elemental content of the various groups studied showed significantly higher values for most groups at the site near the Thukela River. C:P and N:P were highest in the southern part of the bight, and lowest near the Thukela Mouth or at Richards Bay in the north, indicating the latter were the P-richer sites. Sediment organic matter showed lowest elemental content, as expected, and zooplankton stoichiometry was highest compared to all other biotic groups. Environmental heterogeneity played a greater role in organismal C, N and P content and stoichiometry compared to phylogeny, with the exception of the differences in C:P and N:P of zooplankton. From this bight-wide study, the higher elemental content and lower ratios at the Thukela Mouth site supported previous findings of the importance of coastal nutrient sources to the bight ecosystem. Reductions in river flow for water use in the catchment areas may therefore have negative consequences for the productivity of the entire ecosystem. 相似文献
26.
Tomilenko A. A. Bul’bak T. A. Logvinova A. M. Sonin V. M. Sobolev N. V. 《Doklady Earth Sciences》2018,481(1):953-957
The primary data are presented on gas chromatography–mass spectrometry of volatile material in diamonds from the placers in the northeast of the Siberian Platform. The new data obtained testify to the crucial role of hydrocarbons and their derivates in the processes of diamond formation within the Earth’s mantle. It was shown that the registered variations in the composition of volatile components in the treated diamonds were caused by a combination of processes including the transformation of redox conditions of the crystallization of diamonds.
相似文献27.
Temporal variability of wetland invertebrates was examined at two scales—inter-annual and seasonal—to determine whether it could confound results of spatially extensive wetland surveys. The inter-annual study collected samples from the Bullock Creek wetland (BCW) each summer for 4 years; the seasonal study collected samples quarterly for 14 months from two wetlands (Mahinapua and Shearer). Water pH, temperature and conductivity were also measured concurrently. Three site groupings were identified in BCW, reflecting differences in physical–chemical parameters, which varied temporally but never converged. Few annual differences were found in invertebrate relative abundances in BCW, and ordination produced three sample groups, each of which contained distinct invertebrate communities. Water pH differed consistently between Mahinapua and Shearer. Relative abundances of nine taxa varied seasonally; however, ordination showed that both wetlands always supported discrete invertebrate communities. These results suggest that temporal fluctuations of invertebrates do not affect our ability to discriminate between wetlands. 相似文献
28.
29.
A. Ya. Biller A. M. Logvinova S. A. Babushkina O. B. Oleynikov N. V. Sobolev 《Doklady Earth Sciences》2018,478(1):15-19
Pyrope–almandine garnets (Mg# = 28.3–44.9, Ca# = 15.5–21.3) from a heavy mineral concentrate of diamondiferous kimberlites of the largest diamond deposit, the Yubileinaya pipe, along with kimberlite- like rocks and diamondiferous volcano–sediments of the Laptev Sea coast, have been found to contain polymineral, predominantly acicular inclusions, composed of aggregates of shrilankite (Ti2ZrO6), rutile, ilmenite, clinopyroxene, and apatite. The presence of shrilankite as an inclusion in garnets from assumed garnet–pyroxene rocks of the lower crust, lifted up by diamond-bearing kimberlite, allows it to be considered as an indicator mineral of kimberlite, which expands the possibilities when searching for kimberlite in the Arctic. 相似文献
30.