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111.
The importance of ocean temperature to global biogeochemistry 总被引:1,自引:0,他引:1
David Archer Author Vitae Pamela Martin Author Vitae Author Vitae Victor Brovkin Author Vitae Author Vitae Andrey Ganopolski Author Vitae 《Earth and Planetary Science Letters》2004,222(2):333-348
Variations in the mean temperature of the ocean, on time scales from millennial to millions of years, in the past and projected for the future, are large enough to impact the geochemistry of the carbon, oxygen, and methane geochemical systems. In each system, the time scale of the temperature perturbation is key. On time frames of 1-100 ky, atmospheric CO2 is controlled by the ocean. CO2 temperature-dependent solubility and greenhouse forcing combine to create an amplifying feedback with ocean temperature; the CaCO3 cycle increases this effect somewhat on time scales longer than ∼5-10 ky. The CO2/T feedback can be seen in the climate record from Vostok, and a model including the temperature feedback predicts that 10% of the fossil fuel CO2 will reside in the atmosphere for longer than 100 ky. Timing is important for oxygen, as well; the atmosphere controls the ocean on short time scales, but ocean anoxia controls atmospheric pO2 on million-year time scales and longer. Warming the ocean to Cretaceous temperatures might eventually increase pO2 by approximately 25%, in the absence of other perturbations. The response of methane clathrate to climate change in the coming century will probably be small, but on longer time scales of 1-10 ky, there may be a positive feedback with ocean temperature, amplifying the long-term climate impact of anthropogenic CO2 release. 相似文献
112.
挡土墙(桩)前堆载反压或预留土体分析与计算 总被引:1,自引:0,他引:1
提出了在挡土墙(桩)前堆载反压或预留土体时挡土墙(桩)的受力分析方法及计算公式,并用工程实例验证了该分析方法的实用性和计算公式的合理性。 相似文献
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东铺金矿成矿物质来源于海底火山喷流作用及壳源含金热流的再循环。边缘深大断裂控盆和产生的多期表部脆性变形,除使区域上古生界地层和早期形成的(火山喷发不整合)结构面卷入构造变形,形成不同规模、不同形状、不同性质的剪切透镜体、断层三角块和变形面理外,同时由于深部与浅表部构造的互通,使区内形成含金高热流场,导致不同层次的含金热流沿性质已发生改变的华力西不整合面(带)成矿与控矿。中低温热液交代充填,叠加冷水含金矿液次生淋漓作用,构成了区内独具特色的二元矿床类型。 相似文献
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东坪铅锌矿构控特征及矿床成因 总被引:1,自引:0,他引:1
东坪铅锌矿是巧家~小牛栏铅锌成矿亚带上一个有代表性的铅锌矿床,与处在同一成矿带上的其它铅锌矿床(点)有许多相似之处。不同的是该矿床由层间剥离空间或顺层挤压破碎带控制的矿床规模较大,并随上震旦统灯影组第二段赋矿层位延伸较远,显示较典型的层控加构控、与岩浆成因无关的沉积叠加中低温热液矿床类型。经对该区进一步物探与地质勘查证实:矿区SE边缘的巧家~小牛栏断层与派生的次一级NW向断层交汇部位,存在厚大的铅锌矿体,其深部也存在一定范围和宽度的“低阻高激化异常体”,应是该区今后找矿重点。 相似文献
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本文对西藏丁青玻安岩类深成岩的辉石和新喀里多尼亚玻安岩的斜顽辉石进行了矿物学工作及高分辨电镜观察。丁青斜方辉石堆晶岩辉石的超微结构包括:单斜辉石的(100)双晶、斜方辉石a/4平移畴结构及斜方辉石—单斜辉石相转变。玻安岩斜顽辉石典型超微结构是(100)双晶。由矿物的碎裂、错动以及斜方辉石—单斜辉石相变中只出现偶数倍单斜辉石等表明:矿物结晶及成岩过程中曾受应力作用、后者可能与岩石所处的构造位置有关。由辉石成分计算的地质温度表明,丁青堆晶斜方辉石岩的辉石是在高温下晶出、岩石固结温度是1013~1111℃,当它们在~1000℃下稳定时,斜方辉石出溶了单斜辉石片晶。将玻安岩斜顽辉石加热至1100℃后淬冷及按120℃/h速度冷却均未得到纯的斜顽辉石,可能斜顽辉石是原顽火辉石在应力环境中高温淬冷所成。 相似文献
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Philomène A. Verlaan Author Vitae David S. Cronan Author Vitae Charles L. Morgan Author Vitae 《Progress in Oceanography》2004,63(3):125-158
Regional variation of Mn, Fe, Co, Ni and Cu in ferromanganese oxides (nodules and crusts) in the central south Pacific is related to primary productivity, oxygen minimum layer, and calcium carbonate compensation depth. The largely latitudinal influence of these environmental parameters on nodule and crust composition reflects their predominantly latitudinal variation. Primary productivity is the principal regional environmental control, influencing diagenetic enrichment of these elements in nodules through its effect, mediated by the CCD, on supply and concentration of labile organic matter vs. carbonate remains to the sediments. It influences hydrogenetic enrichment of these elements in nodules and crusts through its effect, mediated by the oxygen minimum layer (mainly in the case of crusts), on their export from surface waters.The elements’ varying susceptibility to being scavenged or organically bound influences the contrasting composition of diagenetic vs. hydrogenetic ferromanganese oxides, which is further influenced by depth. Hydrogenesis is the fundamental process governing nodule and crust formation, superimposed on which is diagenesis under specific circumstances; both are subject to intermittent interruption, diminution and augmentation by changes in environmental parameters. Application of regionally operative environmental controls locally explains local compositional variations and helps refine exploration criteria for economically viable nodules and crusts. 相似文献
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2000年9月12日在青海省海南州兴海县西南发生了6.6级地震。震后发现,青海省6个专业台站的地震波速比在震前出现了下降-低值-发震的过程。波速比空间分布在兴海地震前形成了一个椭圆形的异常分布区,异常波速比的地震占总地震的73%。另外,在武台的尾波持续时间在兴海地震前显示出了较为完整的异常过程。 相似文献
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在对广东几个地区高岭土、高岭石研究的基础上,从结构的观点出发,详细分析讨论了风化过程中长石→高岭石转变的动力学机制,建立了高岭石形成的长石结构动态转化模型,并以此解释了高岭土矿床以及高岭石的某些特征和现象。 相似文献