吉林东部汪清新生代玄武岩中地幔包体的矿物化学：对该地区岩石圈地幔形成过程的启示   总被引：1，自引：0，他引：1  

宋樾  王建  刘金霖  谢志鹏  Keiko H.HATTORI 《地学前缘》2013,20(5):75-86

在对吉林汪清新生代玄武岩中橄榄岩包体进行全岩主、微量元素分析的基础上,重点分析了矿物的主、微量元素含量,讨论了华北克拉通东北缘与兴蒙造山带结合部位陆下岩石圈地幔所经历的部分熔融作用和地幔交代作用。橄榄石的Fo、单斜辉石以及尖晶石的Mg#和Cr#均表明该地区陆下岩石圈地幔相对饱满。对地幔橄榄岩透辉石微量元素模拟计算证实,汪清陆下岩石圈地幔经历了1%~3%的部分熔融作用,并遭受后期硅酸盐熔体交代作用。这些地幔特征与中国东部其他地区新生代主体岩石圈相似。研究结果证明,吉林汪清中、新生代以来岩石圈性质的转变是在汇聚板块构造体制下通过“拆沉作用”实现的。  相似文献   

Complex aromatic hydrocarbons in Stardust samples collected from comet 81P/Wild 2     

Simon J. CLEMETT  Scott A. SANDFORD  Keiko NAKAMURA‐MESSENGER  Friedrich H RZ  David S. McKAY 《Meteoritics & planetary science》2010,45(5):701-722

Abstract– The successful return of the Stardust spacecraft provides a unique opportunity to investigate the nature and distribution of organic matter in cometary dust particles collected from comet 81P/Wild 2. Analysis of individual cometary impact tracks in silica aerogel using the technique of two‐step laser mass spectrometry demonstrates the presence of complex aromatic organic matter. While concerns remain as to the organic purity of the aerogel collection medium and the thermal effects associated with hypervelocity capture, the majority of the observed organic species appear indigenous to the impacting particles and are hence of cometary origin. While the aromatic fraction of the total organic matter present is believed to be small, it is notable in that it appears to be N rich. Spectral analysis in combination with instrumental detection sensitivies suggest that N is incorporated predominantly in the form of aromatic nitriles (R–C≡N). While organic species in the Stardust samples do share some similarities with those present in the matrices of carbonaceous chondrites, the closest match is found with stratospherically collected interplanetary dust particles. These findings are consistent with the notion that a fraction of interplanetary dust is of cometary origin. The presence of complex organic N containing species in comets has astrobiological implications as comets are likely to have contributed to the prebiotic chemical inventory of both the Earth and Mars.  相似文献   

Mixing efficiency in decaying stably stratified turbulence     

Derek D. Stretch  James W. Rottman  S.Karan Venayagamoorthy  Keiko K. Nomura  Chris R. Rehmann 《Dynamics of Atmospheres and Oceans》2010

Mixing efficiency in stratified flows is a measure of the proportion of turbulent kinetic energy that goes into increasing the potential energy of the fluid by irreversible mixing. In this research direct numerical simulations (DNS) and rapid distortion theory (RDT) calculations of transient turbulent mixing events are carried out in order to study this aspect of mixing. In particular, DNS and RDT of decaying, homogeneous, stably-stratified turbulence are used to determine the mixing efficiency as a function of the initial turbulence Richardson number R_it0=(N_L0/_u0)²$R{i}_{t0}={(N{L}_0/u_0)}^2$, where N   is the buoyancy frequency and _L0$L_0$ and _u0$u_0$ are initial length and velocity scales of the turbulence. The results show that the mixing efficiency increases with increasing R_it0$R{i}_{t0}$ for small R_it0$R{i}_{t0}$, but for larger R_it0$R{i}_{t0}$ the mixing efficiency becomes approximately constant. These results are compared with data from towed grid experiments. There is qualitative agreement between the DNS results and the available experimental data, but significant quantitative discrepancies. The grid turbulence experiments suggest a maximum mixing efficiency (at large R_it0$R{i}_{t0}$) of about 6%, while the DNS and RDT results give about 30%. We consider two possible reasons for this discrepancy: Prandtl number effects and non-matching initial conditions. We conclude that the main source of the disagreement probably is due to inaccuracy in determining the initial turbulence energy input in the case of the grid turbulence experiments.  相似文献   

Low and high frequency Madden–Julian oscillations in austral summer: interannual variations     

Takeshi Izumo  Sébastien Masson  Jérome Vialard  Clément de Boyer Montegut  Swadhin K. Behera  Gurvan Madec  Keiko Takahashi  Toshio Yamagata 《Climate Dynamics》2010,35(4):669-683

The Madden–Julian oscillation (MJO) is the main component of intraseasonal variability of the tropical convection, with clear climatic impacts at an almost-global scale. Based on satellite observations, it is shown that there are two types of austral-summer MJO events (broadly defined as 30–120 days convective variability with eastward propagation of about 5 m/s). Equatorial MJO events have a period of 30–50 days and tend to be symmetric about the equator, whereas MJO events centered near 8°S tend to have a longer period of 55–100 days. The lower-frequency variability is associated with a strong upper-ocean response, having a clear signature in both sea surface temperature and its diurnal cycle. These two MJO types have different interannual variations, and are modulated by the Indian Ocean Dipole (IOD). Following a negative IOD event, the lower-frequency southern MJO variability increases, while the higher-frequency equatorial MJO strongly diminishes. We propose two possible explanations for this change in properties of the MJO. One possibility is that changes in the background atmospheric circulation after an IOD favour the development of the low-frequency MJO. The other possibility is that the shallower thermocline ridge and mixed layer depth, by enhancing SST intraseasonal variability and thus ocean–atmosphere coupling in the southwest Indian Ocean (the breeding ground of southern MJO onset), favour the lower-frequency southern MJO variability.  相似文献   

An index for tropical temperate troughs over southern Africa     

Satyaban B. Ratna  Swadhin Behera  J. Venkata Ratnam  Keiko Takahashi  Toshio Yamagata 《Climate Dynamics》2013,41(2):421-441

Strong cases of the tropical temperate troughs (TTT) that are responsible for the most of the summer rainfall over subtropical southern Africa are analyzed. An index for identifying the TTT is introduced for the first time using anomalies of outgoing longwave radiation (OLR) and the wind. The TTT is associated with a ridge-trough-ridge wave-like structure in the lower troposphere over southern Africa and the adjoining Indian Ocean. Therefore, the index considers physical processes that occur over southern Africa, adjoining the Atlantic and Indian Oceans to depict the variability of the TTT events. Unusually strong TTT events are identified when the standard deviations of the TTT indices defined by the OLR and wind anomalies in the selected regions are above 1.5 and 0.5 respectively. After applying this criterion and filtering out consecutive events, 55 TTT events are identified during the study period of December–January–February seasons from 1980–1981 to 2009–2010. From the composite analyses of those 55 events, it is found that the TTTs evolve with suppressed (enhanced) convection over the southwest Indian Ocean adjacent to Madagascar (southern Africa). The suppressed convection is, in turn, found to be associated with the enhanced convection around Sumatra in the southeast tropical Indian Ocean. This may explain why more TTT events occur in La Niña years as compared to El Niño years. Time evolution of the canonical TTT event shows that it starts 3 days prior to the mature phase of the event, suggesting possible predictability. After reaching a matured state, the system moves east toward the Indian Ocean and decays within the subsequent couple of days. In addition, the intertropical convergence zone (ITCZ) structure changes over Southern Africa/Madagascar during the TTT event and remains similar to climatology over other regions. The results indicate that the continental part of the ITCZ intensifies prior to the TTT event and then spreads southward following the mid-latitude influence during and after the event.  相似文献   

Deep and intermediate-depth non-double couple earthquakes: interpretation of moment tensor inversions using various passbands of very broadband seismic data     

Keiko Kuge  Hitoshi Kawakatsu 《Geophysical Journal International》1992,111(3):589-606

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The proximal facies of the Tosu pyroclastic-flow deposit erupted from Aso caldera,Japan     

Keiko Suzuki-Kamata  Hiroki Kamata 《Bulletin of Volcanology》1990,52(5):325-333

The Tosu pyroclastic flow deposit, a low-aspect-ratio ignimbrite (LARI), has widely distributed breccia facies around Aso caldera, Japan. The proximal facies, 9–34 km away from the source, consists of 3 different lithofacies, from bottom to top: a lithic-enriched and fines-depleted (FD) facies, a lithic-enriched (LI) facies with an ash matrix, and a fines- and pumice-enriched (NI) facies. Modes of emplacement of FD, LI, and NI are interpreted as ground layer, 2b-lithic-concentration zone, and normal ignimbrite, respectively. These stratigraphic components in the Tosu originated from the flow head (FD) and the flow body (LI and NI), and were generated by a single column collapse event. Remarkably thick FD and LI, in contrast to thin NI, suggest that due to high mobility most ash and punice fragments in the Tosu were carried and deposited as NI in the distal area. Heavier components were selectively deposited as FD and LI in the proximal area. The rate of falloff of lithic-clast size in the Tosu shows an inflection at 20 km from the source. In a survey of well-documented pyroclastic flows, the inflection distance of a LARI is generally greater than that of a high-aspect-ratio ignimbrite, so that the eruption of the former is probably more intense than the latter.  相似文献   

The ground layer of Ata pyroclastic flow deposit,southwestern Japan — evidence for the capture of lithic fragments     

Keiko Suzuki-Kamata 《Bulletin of Volcanology》1988,50(2):119-129

Lithic fragments in the ground layer of the Ata pyroclastic flow deposit, southwestern Japan, were supplied from two different sources. One is the eruptive vent and the other is the basement rock exposed underneath the path of flow. Lithic fragments captured at the eruptive vent gradually decrease in size with distance from the source. Local increases of ML or Md are proportional to increased amounts of captured lithic fragments. The pyroclastic flow eroded basement formations on slopes dipping away from the source, and deposited the lithics within the ground layer on slopes dipping towards the source. The ground layer was found only in the western half of the Ata pyroclastic flow deposit. The absence of the ground layer in the eastern half of the pyroclastic flow deposit is interpreted to result from a selective loss of lithics when the flow traversed a bay or a lake located just east from the vent.  相似文献   

Ground motion characteristics and shaking damage of the 11th March 2011 M w9.0 Great East Japan earthquake     

Katsuichiro Goda  Antonios Pomonis  Siau Chen Chian  Mark Offord  Keiko Saito  Peter Sammonds  Stuart Fraser  Alison Raby  Joshua Macabuag 《Bulletin of Earthquake Engineering》2013,11(1):141-170

A catastrophic M _w9.0 earthquake and subsequent giant tsunami struck the Tōhoku and Kanto regions of Japan on 11th March 2011, causing tremendous casualties, massive damage to structures and infrastructure, and huge economic loss. This event has revealed weakness and vulnerability of urban cities and modern society in Japan, which were thought to be one of the most earthquake-prepared nations in the world. Nevertheless, recorded ground motion data from this event offer invaluable information and opportunity; their unique features include very strong short-period spectral content, long duration, and effects due to local asperities as well as direction of rupture/wave propagation. Aiming at gaining useful experience from this tragic event, Earthquake Engineering Field Investigation Team (EEFIT) organised and dispatched a team to the Tōhoku region of Japan. During the EEFIT mission, ground shaking damage surveys were conducted in Sendai, Shirakawa, and Sukagawa, where the Japan Meteorological Agency intensity of 6+ was observed and instrumentally recorded ground motion data were available. The damage survey results identify the key factors for severe shaking damage, such as insufficient lateral reinforcement and detailing in structural columns from structural capacity viewpoint and rich spectral content of ground shaking in the intermediate vibration period range from seismic demand viewpoint. Importantly, inclusion of several ground motion parameters, such as nonlinear structural response, in shaking damage surveys, can improve the correlation of observed ground motion with shaking damage and therefore enhance existing indicators of potential damage.  相似文献   

A primitive dark inclusion with radiation‐damaged silicates in the Ningqiang carbonaceous chondrite     

Michael ZOLENSKY  Keiko NAKAMURA  Michael K. WEISBERG  Martin PRINZ  Tomoki NAKAMURA  Kazumasa OHSUMI  Akihiro SAITOW  Masae MUKAI  Matthieu GOUNELLE 《Meteoritics & planetary science》2003,38(2):305-322

Abstract— A petrologic and TEM study of a remarkable dark inclusion (DI) in the Ningqiang CV3 chondrite reveals that it is a mixture of highly primitive solar nebula materials. The DI contains two lithologies. The first, lithology A, contains micron‐sized olivine and pyroxene grains rimmed by amorphous materials with compositions similar to the underlying crystalline grains. The second, lithology B, appears to preserve the mineralogy of lithology A before formation of the amorphous rims. Overall, the Ningqiang DI appears to record the following processes: 1) formation (condensation and Fe‐enrichment) of olivine crystals in the nebula with compositions of Fo_42–62; 2) irradiation, resulting in amorphitization of the olivine and pyroxene to varying degrees; 3) partial annealing, resulting in formation of fairly large, euhedral olivine and pyroxene grains with remnant amorphous sharply‐bounded rims; 4) in some cases, prolonged annealing, resulting in the formation of microcrystalline olivine or pyroxene rims. The latter annealing would have been a natural consequence of irradiation near the critical temperature for olivine; and 5) mixture of the above materials (lithology A) with nebular condensate high‐Ca pyroxene and olivine, which escaped nebular processing, to become lithology B. We suggest that the amorphous rims in lithology A formed in an energetic solar event such as a bi‐polar outflow or FU‐orionis flare.  相似文献