全球N-MORB和E-MORB分类方案对比   总被引：3，自引：2，他引：1  

第鹏飞  陈万峰  张旗  王金荣  汤庆艳  焦守涛 《岩石学报》2018,34(2):264-274

N-MORB与E-MORB是大洋中脊玄武岩常用的分类,二者地球动力学意义不同,备受学术界关注。对于N-MORB与E-MORB的分类识别标志,不同作者有不同的见解。MORB中可以根据Rb/Nd≤0.15、K/Ti≤0.11、(La/Sm)_N≤0.8、K_2O/TiO_20.09、ΔNb=1.74+lg(Nb/Y)-1.92lg(Zr/Y)0、(La/Sm)_N1、100K_2O/TiO_2≤13等7种指标来识别N-MORB,否则为E-MORB。究竟何种标志区分效果较好、比较适合大多数MORB的情况?学术界对此还较少有人讨论。为此,本文尝试利用大数据方法,采用全球全体扩张中心数据,对上述7种标志进行对比,发现(La/Sm)_N1的标志比较适合大多数MORB的情况。为此,我们将(La/Sm)_N1和(La/Sm)_N≥1的所有数据,选取La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu、Ba、Cs、Hf、K、Nb、Pb、Rb、Sc、Sr、Ta、Th、Ti、Tl、U、V、Y、Zr等31个元素,利用两两元素对数比值进行投图,并计算85%置信度的置信椭圆交叠率,共得出36856个元素对组合,根据最小交叠率的原则,得出使用稀土元素La、Ce、Pr、Sm和其他高场强元素Nb、Zr、Hf、Y之间的比值关系判别效果较好。我们又利用以上得出的8种元素进行投图判定,发现以La为分子或以La/Hf、La/Zr元素比值做为区分标志可以得出更好的结果。因此建议考虑应用以上元素之间的相关关系共同判定N-MORB与E-MORB。  相似文献   

Haitaite-(La), LaU4+Fe3+2(Ti13Fe2+4Fe3+)Σ18O38, a New Member of the Crichtonite Group     

WANG Fenggang  FAN Guang  LI Ting  GE Xiangkun  WU Yu  WANG Tao  YAO Jian 《《地质学报》英文版》2022,96(6):2007-2014

Haitaite-(La), (La, Ce)(U4+, U6+, Fe2+)(Fe3+, Al)2(Ti, Fe2+, Fe3+)18O38, is a new member of the crichtonite group. It is named after the Haita Village in the Miyi County of Sichuan Province, China, where the mineral was discovered. The mineral occurs as black opaque centimeter-sized aggregates in the external contact zone between the Neoproterozoic (~800 Ma) alkali feldspar granite and the Mesoproterozoic (~1700 Ma) micaschist. In the studied sample, haitaite-(La) is associated with other minerals, including ilmenite, magnetite, rutile, zircon, brannerite and uraninite. The new mineral is a black, metallic phase and has a Mohs hardness of 6, with a density of 4.99 g/cm3 (calculated) and 5.03 g/cm3 (measured). Haitaite-(La) is opaque in transmitted light and grayish-white under reflected light, with a reflectivity between 22.5% and 16.42% in the 400–700 nm band (SiC, in the air). The compositions of the mineral were measured by EPMA, the U4+/U6+ ratio was determined by X-ray photoelectron spectroscopy and the Fe2+/Fe3+ ratio was determined by M?ssbauer spectroscopy. Haitaite-(La) is trigonal, belongs to R3ˉ and has unit-cell parameters a = 10.3678(5) ?, c = 20.8390(11) ?, V = 1939.9(2) ?3, Z = 3. The crystalline structure is composed of octahedra with 9 layers of close-packed octahedra (M1, M3, M4, M5), tetrahedra (M2) and contains large 12-coordinated M0 sites.  相似文献   

2017-2018年冬季黑龙江省气温异常成因分析     

班晋  李永生  赵佳莹  孙镆涵 《黑龙江气象》2019,36(1):14-17,23

2017-2018年冬季全省平均气温为-19.7℃,较历年同期偏低2.2℃,为1981年以来的第3位,仅次于2000年和2012年。本文利用NCEP再分析资料,对2017-2018年黑龙江省冬季气温异常成因进行分析,结果表明大气环流的异常是造成黑龙江省冬季气温异常偏低的直接原因。东亚季风环流系统表现为:东亚冬季风强度偏强,西伯利亚高压偏强,500hPa东亚大槽异常偏深。分析下垫面外强迫因素,2017-2018年赤道中东太平洋出现拉尼娜事件,分析显示拉尼娜事件发生可能导致冬季风偏强,从而也是造成全省气温偏低的主要原因之一。  相似文献   

Processes Leading to Second-Year Cooling of the 2010-12 La Ni(n)a Event,Diagnosed Using GODAS     

FENG Licheng  ZHANG Rong-Hua  WANG Zhanggui  CHEN Xingrong 《大气科学进展》2015,32(3)

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IMPACT OF LATENT HEAT FLUX ON INDIAN SUMMER MONSOON DURING EL NI(N)O/LA NI(N)A YEARS     

M. V. Subrahmanyam  WANG Dong-xiao 《热带气象学报(英文版)》2011,17(4)

El Ni(n)o or La Ni(n)a manifest in December over the Pacific and will serve as an index for the forecasting of subsequent Indian summer monsoon,which occurs from June to mid-September.In the present article,an attempt is made to study the variation of latent heat flux (LHF) over the north Indian Ocean during strong El Ni(n)o and strong La Ni(n)a and relate it with Indian monsoon rainfall.During strong El Ni(n)o the LHF intensity is higher and associated with higher wind speed and lower cloud amount.During E1 Ni(n)o all India rainfall is having an inverse relation with LHF.Seasonal rainfall is higher in YY+1 (subsequent year) than YY (year of occurrence).However there is a lag in rainfall during El Ni(n)o YY+1 from June to July when compared with the monthly rainfall.  相似文献   

2011年4月江西降水异常偏少的初步诊断分析   总被引：1，自引：0，他引：1  

马锋敏  张超美  张传江  廖敏 《气象与减灾研究》2011,(4):16-22

利用1959-2011年北半球500 hPa高度格点资料、74项环流特征量资料和1974-2011年NOAA OLR月平均资料,结合江西83个气象观测站的1959-2011年4月降水资料,对2011年4月江西降水异常偏少成因进行了初步诊断分析.结果表明:江西省4月降水有一定的周期性,2011年4月降水处于少雨期;La ...  相似文献   

The impact of ecosystem functional type changes on the La Plata Basin climate     

Seung-Jae LEE  E. Hugo BERBERY  Domingo ALCARAZ-SEGURA 《大气科学进展》2013,30(5):1387-1405

In this paper, the effects of land cover changes on the climate of the La Plata Basin in southern South America are investigated using the Weather and Research Forecasting (WRF) Model configured on a 30/10km two-way interactive nested grid. To assess the regional climate changes resulting from land surface changes, the standard land cover types are replaced by time-varying Ecosystem Functional Types (EFTs), which is a newly devised land-cover classification that characterizes the spatial and interannual variability of surface vegetation dynamics. These variations indicate that natural and anthropogenic activities have caused changes in the surface physical parameters of the basin, such as albedo and roughness length, that contributed to regional climate changes. EFTs are obtained from functional attributes of vegetation computed from properties of the Normalized Difference Vegetation Index (NDVI) to represent patches of the land surface with homogeneous energy and gas exchanges with the atmosphere. Four simulations are conducted, each experimental period ranging from September to November in two contrasting years, 1988 and 1998. The influence of an identical EFT change on the surface heat fluxes, 2-m temperature and humidity, 10-m winds, convective instabilities and large-scale moisture fluxes and precipitation are explored for 1988 (a dry year) and 1998 (a wet year). Results show that the surface and atmospheric climate has a larger response to the same EFT changes in a dry year for 2-m temperature and 10-m wind; the response is larger in a wet year for 2-m water vapor mixing ratio, convective available potential energy, vertically integrated moisture fluxes and surface precipitation. For EFTs with high productivity and a weak seasonal cycle, the nearsurface temperature during the spring of 1988 and 1998 increased by as much as 1℃ in the central and western portions of La Plata Basin. Additionally, for higher productivity EFTs, precipitation differences were generally positive in both dry and wet years, although the patterns are not uniform and exhibit certain patchiness with drier conditions.  相似文献   

Potential Influence of a Developing La Niña on the Sea-Ice Reduction in the Barents–Kara Seas     

Rui Luo  Peng Zhang  Juan Dou 《大气与海洋》2013,51(3):182-194

Abstract

The potential influence of a developing La Niña on Arctic sea-ice annual variability is investigated using both observational data and an atmospheric general circulation model. It is found that during the developing phase of an eastern Pacific (EP) La Niña event in June, July, and August (JJA) and September, October, and November (SON), the sea-ice concentration (SIC) over the Barents–Kara Seas declines more than 15%. The local atmospheric circulation pattern associated with the EP La Niña is characterized as a weak decrease in geopotential height over the Barents–Kara Seas, combined with an anticyclone in the North Atlantic. The corresponding southerly winds push warm waters northward into the key sea-ice reduction region and directly accelerate sea-ice melt. Meanwhile, the abundant moisture contained in the lower troposphere is transported into the Arctic region by winds resulting from the local barotropic structure. The humid atmosphere contributes to both net shortwave and longwave radiation and thus indirectly accelerates the decline in sea ice. Simulations by the European Centre Hamburg Model, version 5.4, are forced by observed sea surface temperature anomalies associated with EP La Niña events. The results of the simulations capture the North Atlantic anticyclone and reproduce the moisture transport, which supports the premise that an EP La Niña plays a crucial role in sea-ice reduction over the Barents–Kara sector from the perspective of atmospheric circulation and net surface heat flux.  相似文献   

Localised coherent response of the La Molina basin (Lima,Peru) to earthquakes,and future approaches suggested by Parkway basin (New Zealand) experience     

W.R. Bill Stephenson  R.A. Benites  P.N. Davenport 《Soil Dynamics and Earthquake Engineering》2009

Earthquake records from a 1984 temporary seismograph array set up in La Molina, Lima, Peru, are re-analysed. The array comprised eight three-component geophones; seven soil based and one rock based. Values of horizontal-to-vertical spectral ratio (HVSR) for two small earthquakes peaked at around 1.3 Hz. In one distant earthquake, four of the seven soil-based stations showed a peak at 1.25 Hz in soil-to-rock spectral ratio (SSR), the same dominant frequency observed during an aftershock of a damaging earthquake. Because this frequency is not compatible with the shear wave velocity profile attributed to La Molina, and because the spectral peak is confined to a small ground area, it is concluded that the peak is caused by a localised deposit of soft soil. Because the area associated with the spectral peak includes the area of great damage in 1974, it is concluded that coherent monochromatic behaviour is responsible for the damage.  相似文献   

2011年全球重大天气气候事件及其成因   总被引：2，自引：0，他引：2  

司东  李修仓  任福民  徐良炎  袁媛  龚志强 《气象》2012,38(4):480-489

2011年,全球气温偏高,为有观测记录以来的第十个暖年,是近60年来出现拉尼娜事件的年份中全球气温最高的一年。2011年,全球热带气旋活动较常年偏少。4月,一次拉尼娜事件结束,9月又一次拉尼娜事件生成。年初,低温、寒流席卷亚洲大部,暴风雪频繁袭击北美地区。西欧和中国东部出现严重春旱。夏季,非洲东部经历了20世纪80年代以来最严重的干旱,而东南亚、巴基斯坦和中南美洲洪涝灾害严重。全球极端偏暖事件主要出现在欧洲西部和西北部、南亚南部、东亚中西部、北美东南部等地;极端偏冷事件主要出现在东亚、澳大利亚、非洲南部和美国东北部和西部等地。而南美中东部、东南亚及中国东南部、日本、澳大利亚北部、非洲西部等地出现了极端强降水事件。研究发现,2010／2011年拉尼娜事件和台风活动是导致东南亚洪涝出现的重要原因,而巴基斯坦洪涝主要与印度洋正位相偶极型海温分布有关。  相似文献