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基于L2范数的常规全波形反演目标函数是一个强非线性泛函,在反演过程中容易陷入局部极小值.本文提出归一化能量谱目标函数来缓解全波形反演过程中的强非线性问题,同时能够有效地缓解噪声和震源子波不准等因素的影响.能量谱目标函数是通过匹配观测数据与模拟数据随频率分布的能量信息来实现最小二乘反演的,其忽略了地震数据波形与相位变化的细节特征,这在反演的过程中能够有效缓解波形匹配错位等问题.数值测试结果表明,基于归一化能量谱目标函数在构建初始速度模型、抗噪性和缓解震源子波依赖等方面都优于归一化全波形反演目标函数.金属矿模型测试结果表明,即使地震数据缺失低频分量,基于归一化能量谱目标函数的全波形反演方法在像金属矿这样的强散射介质反演问题上同样具有一定的优势. 相似文献
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F. Ruiz M. L. González-Regalado J. Borrego J. A. Morales J. G. Pendón J. M. Muñoz 《Environmental Geology》1998,34(4):270-278
The Holocene filling of the Tinto-Odiel Estuary comprises seven lithofacies over a Mio-Pliocene substrate. The sequence includes
three system tracts: lowstand system (10 000 to 8700 years BP), transgressive system (8700 to 7000 years BP), and regressive
system (7000 to Recent). Twenty sediment samples from the 50-m borehole were analyzed for their major components and minor
element concentrations. Two multivariate analysis methods, principal component analysis and cluster analysis, were performed
in the analytical data set to help visualize the sample clusters and the element associations. Samples corresponding to unpolluted,
pre-mining sediments are clearly separated by cluster analysis, mainly as a result of the low content in sulphide-associated
heavy metals such as Cu, Zn, As, Ag, and Pb. So, these sediments may be utilized as a background for geochemical analysis
(bulk sample) in other adjacent estuaries, both in sandy and silty-clayey sediments. As a consequence of large-scale mining
and smelting operations occurred since prehistoric times on the river banks, a rapid rise in the metal pollution was found
in the upper 2.5 m of the natural filling, with values exceeding up to ten times the natural background levels. In addition,
since the mid-1960s, large amounts of waste and pollutant effluents have been discharged from industries located around the
estuary, increasing the heavy metal content in the last 0.3 m of the natural sedimentation.
Received: 18 August 1997 · Accepted: 19 January 1998 相似文献
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How to utilize sulfur isotope for many domestic and foreign researchers to trace the sulfur source of metallic sulfide deposit has been explored for many years. Fruitful results have been gained now. Based on summing up the characteristics of sulfur isotopic composition of hydrothermal mineral from metallic sulfide deposits, this paper illuminated the total sulfur isotopic composition of ore-forming fluids is the key factor in estimating the sulfur source. This paper also summarized three approaches about how to obtain the total sulfur isotopic composition (δ34S∑S) of ore-forming fluids. They are physical-chemical equilibrium analysis, mineral paragenetic association analysis and Pinckey-Rafter, respectively. We gave some applied examples and made a brief comment of them as well. There are three points worth noting. Firstly, choosing appropriate approach is a critical factor to acquire the δ34S∑S successfully according to the characteristics of different types of metallic sulfide deposit. Secondly, currently, these above mentioned approaches and applications are effective after the establishment of equilibrium state of sulfur isotope. As to the sulfur isotopic disequilibrium condition in metallic sulfide deposits probably resulted from lower temperature or rapid emplacement, there are quite some problems in theory and technique. Therefore, an in-depth study should also be continued. Thirdly, it is a new development trend to study isotope composition of different forms of sulfur and to discuss their source, forming environment and process respectively, which is probably more effective and significant for tracing sulfur sources of metallic sulfide deposits. 相似文献
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Geochemistry of Triassic Carbonates: Exploration Guide to Pb–Zn Mineralization in North Tunisia
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Nejib Jemmali Fouad Souissi Emmanuel John M. Carranza Mohsen Henchiri 《Resource Geology》2016,66(4):335-350
The Triassic carbonate rocks in Northern Tunisia (Nappes, Domes, Jurassic Mountains zones), consist of massive carbonates, clays and gypsum with authigenic minerals. These are associated with several Pb–Zn deposits and occurrences. At Jebel Ichkeul, Bechateur and Oum Edeboua, these Triassic carbonates exhibit enrichment in Pb (0.32 to 228 ppm), Zn (17 to 261 ppm), Cd (5 to 6 ppm) and Co (0.3 to 89.5 ppm), with respect to their average contents in crustal carbonates. The enrichment is more pronounced at Oum Edeboua (near the ore zone). Permeability is one of the most effective factors of dispersion of metallic trace elements, causing the development of geochemical halos. The genetic relationship of the Triassic carbonate rocks with the ore deposits was controlled by diapirism and tectonic movements, which favored mineralization along the Triassic‐cover contact as well as the remobilization of metals from the mineralized rocks. Analysis of metallic trace elements in Triassic rocks provides clues to the presence of possible mineral deposits. These could be effectively used for both geochemical interpretation and mineral exploration. Carbon and O‐isotope data (– 9.3‰ < δ13C < +3‰; +21.9 < δ18O < +31‰) suggest that the Triassic carbonates of all study areas have marine carbonates as their origin; some of them show significantly lower δ18O values indicating some exchange with hydrothermal fluids. Calcites associated with mineralization at Oum Edeboua have δ13C of –6.2‰ to –8.22‰ and δ18O of +24.88‰ to +25‰. The C‐isotope compositions of these calcites are 13C depleted, indicating an organic origin. 相似文献
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Dominance of point source in heavy metal distributions in sediments of a major Sydney estuary (Australia) 总被引:1,自引:0,他引:1
Size-normalized (<63 μm) distributions of Cu, Zn, and Pb in the surficial sediments of one of Sydneys' four major estuaries
– the Georges River/Botany Bay estuary – are not facies or depositionally controlled, but rather their distribution is dominated
by source. Point sources (waste dumps, sewage overflows, and discharge from a polluted river) are responsible for elevating
sediment heavy-metal concentrations up to 50 times above background. Nonpoint sources contribute in raising baseline levels
to four times background and comprise mainly stormwater and also marinas, moorings, and wharfs/jetties. Heavy metals disgorged
from a point source (Cooks River) strongly impact the sediments in the lower estuary, which has implications for the construction
of a new runway for Sydney airport.
Received: 3 October 1994 · Accepted: 21 September 1995 相似文献
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The influence of parent rock and soil material on the corrosion rate of metallic fragments that remained in soil after World
War I in the Soča front area (Slovenia), as well as the corrosion products of these fragments, were studied. The results of
corrosion tests did not indicate appreciable differences in corrosion rates between various corrosion media. Consequently,
the corrosion rates are influenced mostly by soil aeration, soil humidity and also by microstructures of alloys. Soil type
seems to have the most influence on corrosion products. For the pH and Eh ranges that prevail in the studied soils, goethite
is the only stable iron mineral. Lead minerals are not stable, and lead, in a Pb2+ cation form, is probably adsorbed onto some minerals – especially goethite – or is bound with organic matter. In distric
brown soil, lead stays in the cation form as Pb2+ because of high soil acidity. Cuprite is stable in rendzina and brown soil on limestone, whereas in distric brown soil copper
stays in solution as Cu2+.
Received: 7 October 1999 · Accepted: 8 March 2000 相似文献
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采用自适应模糊神经网络的方法,以金属离子外层主量子数(n)、电荷(Z)、半径(r)、适配价轨道数因子(w)及价电子结构因子(S)等为参数,关联金属—EDTA配合物稳定常数。利用减法聚类算法确定模糊神经网络的结构,并结合模糊推理系统进行该网络参数的调整,网络仿真的结果是满意的。在此基础上,预测了13种金属—EDTA配合物稳定常数。 相似文献