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281.
Jianlin Zhu Guangming Zeng 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,21(2):143-149
Detrended fluctuation analysis (DFA) and power spectrum density are applied to verify the presence of temporal scaling behavior and long-range persistence (LRP) of weekly hydrogen ion deposition (WHD), NO3- and SO42- deposition series in National Atmospheric Deposition Program, USA, for the period 1978–2001. The results show a common scaling behavior for all sites analyzed. Two distinct scaling regions are identified by DFA1, one corresponding to 1 month to 1 year and the other to 1 year to 5 years. The WHD series obey power-law in two temporal regimes respectively with mean DFA1 scaling exponents α
1≈0.68 and α
2≈0.45, implying the presence of LRP in the acid deposition series and there is a tendency for a large deposition event to be followed by another large event, and vice versa. For DFA2–DFA4, however, the annual crossover, which divides the temporal scale into two regimes, disappears gradually with the order q of DFAq increasing, and the two scaling regimes turn to share the same scaling exponent close to α
1. The result indicates that the scaling behavior exits in the two regimes with the same scaling exponent α
1, and LRP prevails during the examined 1-month to 5-years scale. NO3- and SO42- deposition evolve the same way as WHD does, implying the pollutants involving in acid deposition may share some prominent mechanism controlling their evolutions. We ascribe the long-range power-law scaling of acid deposition evolutions to the self-organized critical behavior of atmosphere under pollution stress and it should be considered in the trend prediction of acid deposition as an important factor. 相似文献
282.
283.
南海1∶100万永暑礁幅海洋区域地质调查成果 总被引:1,自引:0,他引:1
1∶100万永暑礁幅海洋区域地质调查成果揭示了该区地壳的浅、中、深层地质特征。浅层主要研究海底地形、地貌、表层沉积物、矿产资源、潜在地质灾害等;中层主要研究新生代地层、断裂体系、岩浆岩、含油气盆地远景等;深层则研究磁性基底、深层断裂、莫霍面分布特征等。本成果在以下几方面有重要突破:①通过对比新生代以来的地层,确定各沉积盆地地层特征和相互关系,在此基础上预测油气资源前景;②分析表层沉积物类型,预测本区未来可能具有开发价值的固体矿产资源;③利用磁性基底和莫霍面数据分析本区地壳结构特征。 相似文献
284.
利用1971~2000年逐月SODA (Simple Ocean Data Assimilation) 同化资料(Carton等,2004)、1980~2000年逐月NCEP/NCAR再分析资料(Kalnay等,1996)探讨中部型(暖海水首先出现在120°W以西)和东部型(暖海水首先出现在120°W以东)El Ni?o事件赤道纬向风应力及洋流的异常变化与暖海水信号的传播特征。研究指出:(1)中部型和东部型El Ni?o事件发生时,太平洋上赤道海表最大西风应力距平在西太平洋地区都有显著的东传现象,但中部型El Ni?o事件西风应力距平强度强,造成西太平洋赤道表层的东向流可达东太平洋地区,这类El Ni?o事件强度偏强。(2)中部型El Ni?o事件,赤道表层洋流辐合区及其下沉运动由西太平洋向东太平洋传播,辐合下沉运动抑制了深层冷海水上翻,西太平洋暖水能够传到东太平洋与西太平洋赤道表层洋流辐合区及其下沉运动的东移有关。(3)东部型El Ni?o事件西太平洋赤道表层洋流辐合区及其下沉运动没能直接传到东太平洋地区,东太平洋暖水形成与局地(120°W以东)辐合下沉运动抑制深层冷海水上翻有关;东部型El Ni?o事件暖池次表层的暖水,不是沿着西太平洋赤道次表层向东传播到东太平洋地区,而是由南太平洋西边界流将暖池海水带到40°S左右的西风漂流区, 再由西风漂流平流到东太平洋。 相似文献
285.
Well Zheng-1 is located in the combined area of the central uplift and the north Tianshan piedmont depression in the Junggar Basin. Two oil-bearing beds are recognized at 4788–4797 m of the Lower Cretaceous Tugulu Formation (K1tg) and 4808.5–4812.5 m of the Lower Jurassic Sangonghe Formation (J1s). The geochemical characteristics of family composition, carbon isotopic composition, saturated hydrocarbons, sterane and terpane biomarkers and carotane of two crude oils are described in this paper. The results show that the geochemical characteristics of the two crude oils are basically similar to each other, indicating they were all derived mainly from the high mature, brine, algae-rich lake facies sediments. Oil-source correlation revealed that crude oils of the two beds were derived mainly from the source rocks of Permian and mixed by the oil derived from the source rocks of Jurassic and Triassic. This is consistent with the geological background with several sets of source rocks in the area studied. 相似文献
286.
早中生代的扬子大陆向华北大陆的深俯冲碰撞作用以及中、新生代的华北东部岩石圈减薄作用是国际大陆动力学问题研究的两个热点。然而,把它们有机联系起来,探讨深部岩石圈演化动力学过程的研究还很少。报道了中国大陆科学钻探先导孔(CCSD-PP1)橄榄岩的矿物岩石化学分析结果。这些橄榄岩亏损玄武质组分(如低w(CaO+Al2O3)、高Mg^#等),并经历了中元古代来自软流圈的碳酸岩熔体的交代作用和早中生代的超高压再平衡过程。结合已发表的华北捕虏体橄榄岩资料,对这一橄榄岩的原始地幔属性进行了分析。发现CCSD-PP1橄榄岩与华北古老岩石圈地幔组成相似,是早中生代来自华北岩石圈的构造侵入体。早中生代华北岩石圈的伸展减薄与苏鲁超高压变质岩石的折返提供了早期软流圈物质上涌的构造体制。 相似文献
287.
利用为期一年的卫星遥感温度(SABER/TIMED)资料重建了120°E子午圈内中间层和低热层大气潮汐各主要频率分量(周日、半日和8小时潮汐).这些主要频率分量随高度振幅增大,在97 km高度达到显著的振幅;其中迁移性周日潮汐在97 km高度出现极大振幅,然后随高度衰减.本文从考察迁移性成分和非迁移性成分各自在总潮汐中贡献角度出发,着重讨论了那些对形成该子午圈中97 km高度上整体潮汐扰动起控制作用的潮汐成分.结果显示,对周日和半日频率这两种潮汐而言,迁移性成分控制了它们的总体时空分布.在春分季节,迁移性周日潮的控制作用最显著,决定了赤道和两半球热带的活动中心;其中北半球副热带地区的季节变化形势与以往利用武汉(30°N,114°E)流星雷达风测量资料开展分析得到的结果是一致的;其他季节受非迁移性成分明显影响,例如,在本文关注的2005年中,夏至季节受(1,0)模、(1,-3)模和(1,-2)模的共同影响形成了从赤道向南延伸的活动中心,极值中心位于赤道附近,振幅达到了20 K以上,是全年的最大值.受迁移性成分控制,半日潮活动主要出现在两半球热带地区,北半球活动中心位于秋分季节(振幅达到13 K),南半球活动中心位于春分和夏至之间.其他季节受非迁移成分的影响,形成若干分布在两半球的活动中心.在本文关注的40°S~40°N范围内,与周日潮和半日潮相比,8小时潮汐具有显著较低的振幅;另外,虽然迁移性成分在一年中的大部分时间系统地分布在两半球热带地区,但是非迁移成分具有与迁移性成分相当或更大的振幅,在整体上控制了这种潮汐的时空分布. 相似文献
288.
Precambrian banded iron formations (BIFs) in the Quadrilátero Ferrífero host a special kind of Au–Pd mineralization known as Jacutinga. The main orebodies are hosted within the Cauê Syncline, a SW-verging fold that involves Paleoproterozoic metasedimentary rocks in the Itabira District, a regional synclinorium with BIFs in the core of synclinal folds in the northeastern part of Quadrilatéro Ferrífero, Minas Gerais. Structural analysis reveals two important features of the district: the polydeformed character of the rocks and the importance of brittle structures in the control of the orebodies. Two deformational events are recognized in this area. The first event developed the main foliation, S1, that is the enveloping surface of the Cauê Syncline. The second event is better defined in the northern boundary of the structure where it is represented by a right-lateral wrench fault zone that has developed a foliation, S2, that truncates S1. This wrench fault was also responsible for the development of a system of fractures (Frm) that host the Au–Pd mineralization. The auriferous bodies of Cauê Syncline (Y, X, Área Central, Aba Norte, Noroeste and Aba Leste/Aba Leste Inferior) were generated during this second event. Shear fractures (R, R′ and P) and tension fractures (T) developed in response to the wrench fault system under brittle conditions. The best-developed, and most commonly mineralized fractures are R and T in all auriferous bodies. Elsewhere, the best mineralization occurs in the contacts of hematite bodies (soft/hard) and intrusive rocks with fractured itabirites. Other mineralization (Aba Norte, Área Central and X) is hosted on the contacts of other units.A system of fractures, as well as their intersections, thus represents the structural control on Jacutinga bodies and is responsible for the geometry of the orebodies. Of importance, there is no control by mineral/stretching lineations, fold axes and other ductile structure on the geometry and plunge of the orebodies. 相似文献
289.
L.M. Lobato J.O.S. Santos N.J. McNaughton I.R. Fletcher C.M. Noce 《Ore Geology Reviews》2007,32(3-4):674
U–Pb SHRIMP results of 2672 ± 14 Ma obtained on hydrothermal monazite crystals, from ore samples of the giant Morro Velho and Cuiabá Archean orogenic deposits, represent the first reliable and precise age of gold mineralization associated with the Rio das Velhas greenstone belt evolution, in the Quadrilátero Ferrífero, Brazil. In the basal Nova Lima Group, of the Rio das Velhas greenstone belt, felsic volcanic and volcaniclastic rocks have been dated between 2792 ± 11 and 2751 ± 9 Ma, coeval with the intrusion of syn-tectonic tonalite and granodiorite plutons, and also with the metamorphic overprint of older tonalite–trondhjemite–granodiorite crust. Since cratonization and stable-shelf sedimentation followed intrusion of Neoarchean granites at 2612 + 3/− 2 Ma, it is clear that like other granite–greenstone terranes in the world, gold mineralization is constrained to the latest stages of greenstone evolution. 相似文献