全文获取类型
收费全文 | 70篇 |
免费 | 1篇 |
国内免费 | 4篇 |
专业分类
大气科学 | 1篇 |
地球物理 | 6篇 |
地质学 | 52篇 |
海洋学 | 2篇 |
天文学 | 14篇 |
出版年
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 4篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2008年 | 3篇 |
2007年 | 9篇 |
2006年 | 2篇 |
2005年 | 2篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1992年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有75条查询结果,搜索用时 20 毫秒
1.
Pinarelli Laura Gioncada Anna Capaccioni Bruno Vaselli Orlando Downes Hilary 《Mineralogy and Petrology》2019,113(1):39-60
Mineralogy and Petrology - Vulcano is part of the Aeolian volcanic arc in the southern Tyrrhenian Sea. Its products were emplaced through multiple episodes of edifice building and collapse since... 相似文献
2.
3.
Alakit and Daldyn kimberlite fields,Siberia,Russia:Two types of mantle sub-terranes beneath central Yakutia? 总被引:1,自引:1,他引:0
I.V. Ashchepkov A.M. Logvinova T. Ntaflos N.V. Vladykin S.I. Kostrovitsky Z. Spetsius S.I. Mityukhin S.A. Prokopyev N.S. Medvedev H. Downes 《地学前缘(英文版)》2017,8(4):671-692
Mineral data from Yakutian kimberlites allow reconstruction of the history of lithospheric mantle.Differences occur in compositions of mantle pyropes and clinopyroxenes from large kimberlite pipes in the Alakit and Daldyn fields.In the Alakit field.Cr-diopsides are alkaline,and Stykanskaya and some other pipes contain more sub-calcic pyropes and dunitic-type diamond inclusions,while in the Daldyn field harzburgitic pyropes are frequent.The eclogitic diamond inclusions in the Alakit field are sharply divided in types and conditions,while in the Daldyn field they show varying compositions and often continuous Pressure-Temperature(P-T) ranges with increasing Fe~# with decreasing pressures.In Alakit,Crpargasites to richterites were found in all pipes,while in Daldyn,pargasites are rare Dalnyaya and Zarnitsa pipes.Cr-diopsides from the Alakit region show higher levels of light Rare Earth Elements(LREE)and stronger REE-slopes,and enrichment in light Rare Earth Elements(LREE),sometimes Th-U,and small troughs in Nb-Ta-Zr.In the Daldyn field,the High Field Strength Elements HFSE troughs are more common in clinopyroxenes with low REE abundances,while those from sheared and refertilized peridotites have smooth patterns.Garnets from Alakit show HREE minima,but those from Daldyn often have a trough at Yand high U and Pb.PTX/O2 diagrams from both regions show similarities,suggesting similar layering and structures.The degree of metasomatism is often higher for pipes which show dispersion in P-Fe~# trends for garnets.In the mantle beneath Udachnaya and Aykhal,pipes show 6-7 linear arrays of P-Fe~# in the lower part of the mantle section at 7.5-3.0 GPa,probably reflecting primary subduction horizons.Beneath the Sytykanskaya pipe,there are several horizons with opposite inclinations which reflect metasomatic processes.The high dispersion of the P—Fe~# trend indicating widespread metasomatism is associated with decreased diamond grades.Possible explanation of the differences in mineralogy and geochemistry of the mantle sections may relate to their tectonic positions during growth of the lithospheric keel.Enrichment in volatiles and alkalis possibly corresponds to interaction with subduction-related fluids and melts in the craton margins.Incorporation of island arc peridotites from an eroded arc is a possible scenario. 相似文献
4.
M.?Yu.?KoreshkovaEmail author H.?Downes V.?A.?Glebovitsky N.?V.?Rodionov A.?V.?Antonov S.?A.?Sergeev 《Contributions to Mineralogy and Petrology》2014,167(2):973
Garnet granulite and pyroxenite xenoliths from the Grib kimberlite pipe (Arkhangelsk, NW Russia) represent the lower crust beneath Russian platform in close vicinity to the cratonic region of the north-eastern Baltic (Fennoscandian) Shield. Many of the xenoliths have experienced strong interaction with the kimberlite host, but in others some primary granulite-facies minerals are preserved. Calculated bulk compositions for the granulites suggest that their protoliths were basic to intermediate igneous rocks; pyroxenites were ultrabasic to basic cumulates. A few samples are probably metasedimentary in origin. Zircons are abundant in the xenoliths; they exhibit complex zoning in cathodoluminescence with relic cores and various metamorphic rims. Cores include oscillatory zircon crystallized in magmatic protoliths, and metamorphic and magmatic sector-zoned zircons. Recrystallization of older zircons led to the formation of bright homogeneous rims. In some samples, homogeneous shells are surrounded by darker convoluted overgrowths that were formed by subsolidus growth when a change in mineral association occurred. The source of Zr was a phase consumed during a reaction, which produced garnet. Late-generation zircons in all xenoliths show concordant U–Pb ages of 1.81–1.84 Ga (1,826 ± 11 Ma), interpreted as the age of last granulite-facies metamorphism. This event completely resets most zircon cores. An earlier metamorphic event at 1.96–1.94 Ga is recorded by some rare cores, and a few magmatic oscillatory zircons have retained a Neoarchaean age of 2,719 ± 14 Ma. The assemblage of metaigneous and metasedimentary rocks was probably formed before the event at 1.96 Ga. Inherited magmatic zircons indicate the existence of continental crust by the time of intrusion of magmatic protoliths in the Late Archaean. The U–Pb zircon ages correspond to major events recorded in upper crustal rocks of the region: collisional metamorphism and magmatism 2.7 Ga ago and reworking of Archaean rocks at around 1.95–1.75 Ga. However, formation of the granulitic paragenesis in lower crustal rocks occurred significantly later than the last granulite-facies event seen in the upper crust and correlates instead with retrograde metamorphism and small-volume magmatism in the upper crust. 相似文献
5.
6.
An analysis of Apollo lunar soil samples 12070,889, 12030,187, and 12070,891: Basaltic diversity at the Apollo 12 landing site and implications for classification of small‐sized lunar samples 下载免费PDF全文
Louise Alexander Joshua F. Snape Katherine H. Joy Hilary Downes Ian A. Crawford 《Meteoritics & planetary science》2016,51(9):1654-1677
Lunar mare basalts provide insights into the compositional diversity of the Moon's interior. Basalt fragments from the lunar regolith can potentially sample lava flows from regions of the Moon not previously visited, thus, increasing our understanding of lunar geological evolution. As part of a study of basaltic diversity at the Apollo 12 landing site, detailed petrological and geochemical data are provided here for 13 basaltic chips. In addition to bulk chemistry, we have analyzed the major, minor, and trace element chemistry of mineral phases which highlight differences between basalt groups. Where samples contain olivine, the equilibrium parent melt magnesium number (Mg#; atomic Mg/[Mg + Fe]) can be calculated to estimate parent melt composition. Ilmenite and plagioclase chemistry can also determine differences between basalt groups. We conclude that samples of approximately 1–2 mm in size can be categorized provided that appropriate mineral phases (olivine, plagioclase, and ilmenite) are present. Where samples are fine‐grained (grain size <0.3 mm), a “paired samples t‐test” can provide a statistical comparison between a particular sample and known lunar basalts. Of the fragments analyzed here, three are found to belong to each of the previously identified olivine and ilmenite basalt suites, four to the pigeonite basalt suite, one is an olivine cumulate, and two could not be categorized because of their coarse grain sizes and lack of appropriate mineral phases. Our approach introduces methods that can be used to investigate small sample sizes (i.e., fines) from future sample return missions to investigate lava flow diversity and petrological significance. 相似文献
7.
Mohsen Shadmehri Turlough P. Downes 《Monthly notices of the Royal Astronomical Society》2008,387(3):1318-1322
We investigate the linear theory of Kelvin–Helmholtz instability at the interface between a partially ionized dusty outflow and the ambient material analytically. We model the interaction as a multifluid system in a planar geometry. The unstable modes are independent from the charge polarity of the dust particles. Although our results show a stabilizing effect for charged dust particles, the growth time-scale of the growing modes gradually becomes independent of the mass or charge of the dust particles when the magnetic-field strength increases. We show that growth time-scale decreases with increasing the magnetic field. Also, as the mass of the dust particles increases, the growth time-scale of the unstable mode increases. 相似文献
8.
A. D. Beard H. Downes E. Hegner S. M. Sablukov V. R. Vetrin K. Balogh 《Contributions to Mineralogy and Petrology》1998,130(3-4):288-303
Minor magmatic intrusions of kimberlite, melilitite and cpx-melilitite occur in the southern part of the Kola Peninsula,
Russia, on the Terskii Coast and near the town of Kandalaksha. They yield K-Ar ages of 382 ± 14 Ma and 365 ± 16 Ma, similar
to the magmatic rocks from the Kola Alkaline Province. The Terskii Coast kimberlites have mineralogical and geochemical affinities
with group 1 kimberlites, whereas the Kandalaksha monticellite kimberlite more closely resembles calcite kimberlites. The
lower Al2O3 content in the Kola kimberlites indicates a strongly depleted harzburgitic source, while higher Al2O3 in the melilitites suggests a lherzolitic source. The Terskii Coast kimberlites are anomalously potassic and significantly
enriched in P and Ba compared to other group 1 kimberlites. In contrast, the melilitites are sodic and are anomalously depleted
in P compared to worldwide melilitites. Trace element patterns of the Kola kimberlites and melilitites indicate the presence
of K- and P-rich phases in the mantle source. To account for the K-troughs shown by both magma types, a K-rich phase such
as phlogopite is thought to be residual in their sources; however, the anomalous K-enrichment in the Terskii Coast kimberlites
may indicate that an additional metasomatic K-rich phase (e.g. K-richterite and/or a complex K-Ba-phosphate) existed in the
kimberlite source. The P-depletion in the melilitites may suggest that a phosphate phase such as apatite remained residual
in the melilititic source. However, anomalous P-enrichment in the kimberlites cannot be explained by complete melting of the
same phase because the kimberlites are a smaller degree melt; thus, it is most likely that another metasomatic phosphate mineral
existed in the source of the kimberlites. The Kola kimberlites and melilitites are all strongly LREE-enriched but the kimberlites
have a steeper REE pattern and are significantly more depleted in HREE, indicating a higher proportion of garnet in their
source. Higher Nb/Y ratios and lower SiO2 values in the kimberlites indicate that they were a smaller degree partial melt than the melilitites. The presence of diamonds
in the Terskii Coast kimberlites indicates a relatively deep origin, while the melilitites originated from shallower depth.
The non-diamondiferous Kandalaksha monticellite kimberlite has lower abundances of all incompatible trace elements, suggesting
a higher degree of partial melting and/or a less enriched and shallower source than the Terskii Coast kimberlites. The 87Sr/86Sri, 143Nd/144Ndi and Pb isotope compositions confirm that the Terskii Coast kimberlites have close affinities with group 1 kimberlites and
were derived from an asthenospheric mantle source, while the Kandalaksha monticellite kimberlite and Terskii Coast melilitites
were derived from lithospheric mantle. Impact of a Devonian asthenospheric mantle plume on the base of the Archaean-Proterozoic
lithosphere of the Kola Peninsula caused widespread emplacement of kimberlites, melilitites, ultramafic lamprophyres and other
more fractionated alkaline magmas. The nature of the mantle affected by metasomatism associated with the plume and, in particular,
the depth of melting and the stability of the metasomatic phases, gave rise to the observed differences between kimberlites
and the related melilitites and other magmas.
Received: 3 March 1997 / Accepted: 7 October 1997 相似文献
9.
Vertical measurements of , and N2O concentrations, and uptake, and oxidation rates were measured at 5 sites in western Cook Strait, New Zealand, between 31 March and 3 April 1983. Nitrate increased with depth at all stations reaching a maximum of 10.5 μg-atom at the most strongly stratified station whereas was relatively constant with depth at all stations (~0.1 μg-atom ). The highest rates of oxidation generally occurred in the near surface waters and decreased with depth. N2O levels were near saturation with respect to the air above the sea surface and showed no obvious changes during 24 h incubation. oxidation by nitrifying bacteria may account for about 30% of the total utilization (i.e. bacterial+agal) and, assuming oxidation through to , may supply about 40% of the algal requirements of in the study area. These results suggest that bacterial nitrification is of potential importance to the nitrogen dynamics of the western Cook Strait, particularly with respect to the nitrogen demands of the phytoplankton. 相似文献
10.
Katherine H. Joy Ian A. Crawford Hilary Downes Sara S. Russell Anton T. Kearsley 《Meteoritics & planetary science》2006,41(7):1003-1025
Abstract— LaPaz Icefield (LAP) 02205, 02226, and 02224 are paired stones of a crystalline basaltic lunar meteorite with a low‐Ti (3.21–3.43% TiO2) low‐Al (9.93–10.45% Al2O3), and low‐K (0.11–0.12% K2O) composition. They consist mainly of zoned pyroxene and plagioclase grains, with minor ilmenite, spinel, and mesostasis regions. Large, possibly xenocrystic, forsteritic olivine grains (<3% by mode) contain small trapped multiphase melt inclusions. Accessory mineral and mesostasis composition shows that the samples have experienced residual melt crystallization with silica oversaturation and late‐stage liquid immiscibility. Our section of LAP 02224 has a vesicular fusion crust, implying that it was at one time located sufficiently close to the lunar surface environment to have accumulated solar‐wind‐implanted gases. The stones have a comparable major element composition and petrography to low‐Ti, low‐Al basalts collected at the Apollos 12 and 15 landing sites. However, the LAP stones also have an enriched REE bulk composition and are more ferroan (Mg numbers in the range of 31 to 35) than similar Apollo samples, suggesting that they represent members of a previously unsampled fractionated mare basalt suite that crystallized from a relatively evolved lunar melt. 相似文献