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91.
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93.
Mantle Xenoliths from the Southeastern Slave Craton: Evidence for Chemical Zonation in a Thick, Cold Lithosphere 总被引:7,自引:3,他引:7
We present the first data on the petrology of the mantle lithosphereof the Southeastern (SE) Slave craton, Canada. These are basedon petrographic, mineralogical and geochemical studies of mantlexenoliths in Pipe 5034 of the Cambrian Gahcho Kué kimberlitecluster. Major types of mantle xenoliths include altered eclogite,coarse garnet or spinel peridotite, and deformed garnet peridotite.The peridotites belong to the low-temperature suite and formedat T=6001300°C and P= 2580 kbar in a thick(at least 220250 km), cool lithosphere. The SE Slavemantle is cooler than the mantle of other Archaean cratons andthat below other terranes of the Slave craton. The thick lithosphereand the relatively cool thermal regime provide favourable conditionsfor formation and preservation of diamonds beneath the SE Slaveterrane. Similar to average Archaean mantle worldwide, the SESlave peridotite is depleted in magmaphile major elements andcontains olivine with forsterite content of 9193·5.With respect to olivine composition and mode, all terranes ofthe Slave mantle show broadly similar compositions and are relativelyorthopyroxene-poor compared with those of the Kaapvaal and Siberiancratons. The SE Slave spinel peridotite is poorer in Al, Caand Fe, and richer in Mg than deeper garnet peridotite. Thegreater chemical depletion of the shallow upper mantle is typicalof all terranes of the Slave craton and may be common for thesubcontinental lithospheric peridotitic mantle in general. Peridotiticxenoliths of the SE Slave craton were impregnated by kimberliticfluids that caused late-stage recrystallization of primary clinopyroxene,spinel, olivine and spinel-facies orthopyroxene, and formationof interstitial clinopyroxene. This kimberlite-related recrystallizationdepleted primary pyroxenes and spinel in Al. The kimberliticfluid was oxidizing, Ti-, Fe- and K-rich, and Na-poor, and introducedserpentine, chlorite, phlogopite and spinel into peridotitesat P < 35 kbar. KEY WORDS: kimberlite xenolith; lithosphere; mantle terrane; chemical zoning; thermobarometry; Slave craton 相似文献
94.
昆明市东川区泥石流信息系统的建立及其应用 总被引:4,自引:2,他引:4
根据东川区泥石流的成因、泥石流灾害信息源、各类数据的表达方式及泥石流信息系统的应用等,对东川区泥石流信息系统进行了系统分析,在此基础上利用3S技术,在ARCVIEW的AVENUE开发语言支持下,集成各类数据,建立东川区泥石流信息系统,最后讨论了该系统在泥石流危险度区划及灾害趋势分析中的应用。 相似文献
95.
The chemical forms, spatial distribution and sources of As, Hg, Cd, Pb and Zn in sediments of the Miyun reservoir were studied. The results of sequential extraction demonstrate that most of As, Pb and Zn were bound to the residual fraction, Hg was associated with the sulfide fraction while Cd was associated with the carbonate fraction and the residual fraction. On the vertical profiles the concentrations of the heavy metals in total and each fractions mostly decreased with increasing depths in sediments, suggesting that the heavy metals input from the upstream watershed increases yearly. Summation of the residual fraction, the sulfide fraction and the carbonate fraction accounts for 60.03%―85.60% of the total heavy metal contents in the sediments, which represent the geochemical background values of the elements and relate closely to soil erosion. Results of the main factor analysis show that most sediments of the reservoir come from the upstream soil erosion, the point source pollution and domestic waste. Moreover, the microbial activities taking place on the sediment-water interface are also one of the major factors to cause the increasing content of the organic matter fraction and the iron-manganese oxide fraction. Environmental change of the reservoir water could make the removability of the heavy metals increase, leading to the increase of their concentrations in pore water in sediments, and imperiling water quality of the reservoir. 相似文献
96.
A remarkable invariance in the ratio of 1,3-dimethylcarbazole (DMC) to 1,6-DMC was discovered in crude oils from the Pearl River Mouth Basin, South China Sea. The remarkably invariant ratio is kept at a constant of about unity regardless of their concentrations, sources or maturities for the sampies. In combination with the molecular structures of 1,3- and 1,6-DMCs, the invariance might indicate that the nitrogen compounds share a common precursor with a skeleton of 1-methylcarbazole and are formed through methylation at C3 and C6 with an essentially identical rate. 相似文献
97.
Paul J. Sylvester 《Geostandards and Geoanalytical Research》2005,29(1):41-52
This annual review of laser-ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) covers the year 2003. Significant advances were made in understanding laser-sample interactions. In particular, research defined the distribution of particle sizes produced by the interplay of laser wavelength, laser pulse width and the gas environment of ablation. A link between particle sizes and elemental and isotopic fractionation at both the ablation site and in the ICP was established. Experimental 15 7 nm and femtosecond laser systems were tested with promising results. The number of applications of LA-ICP-MS in geology and environmental Earth science continued to grow with particular interest in element concentration and isotope ratio profiling of materials, linking composition to time scales. In situ isotopic ratio measurements were increasingly made using multicollector magnetic sector ICP-MS instruments. Other applications of wide interest included bulk sampling of rocks and ores prepared as lithium borate glasses; low level analysis of platinum-group elements, rhenium and gold in sulfides, metal and silicates; in situ uranium-lead zircon geochronology; and melt and fluid inclusion analysis. 相似文献
98.
99.
松花江上游地区汞污染的化学生态效应 总被引:5,自引:0,他引:5
采样分析了吉林省东部松花江上游金矿开采区及其附近水、土壤、动植物及河流沉积物样品中汞的含量,发现河流沉积物中汞的污染相当严重;受其影响当地的植物和两栖类动物——中国林蛙体内总汞和甲基汞含量也明显高于对照组。实验表明,林蛙内脏对汞的富集能力大于肌肉;秋季对汞的富集大于春季;河流沉积物中甲基汞的含量与林蛙体内甲基汞的含量有较好的正相关。汞污染的来源与区域内个体金矿的滥采滥排有直接关系,表明人类活动所产生的有毒重金属在地表过程中出现了化学生态效应。 相似文献
100.
Fan Zhang Xiong Xiao Lijie Wang Chen Zeng Zhengliang Yu Guanxing Wang Xiaonan Shi 《水文研究》2021,35(8):e14330
Climate factors play critical roles in controlling chemical weathering, while chemically weathered surface material can regulate climate change. To estimate global chemical weathering fluxes and CO2 balance, it is important to identify the characteristics and driving factors of chemical weathering and CO2 consumption on the Tibetan Plateau, especially in glaciated catchments. The analysis of the hydro-geochemical data indicated that silicate weathering in this area was inhibited by low temperatures, while carbonate weathering was promoted by the abundant clastic rocks with fresh surfaces produced by glacial action. Carbonate weathering dominated the riverine solute generation (with a contribution of 58%, 51%, and 43% at the QiangYong Glacier (QYG), the WengGuo Hydrological Station (WGHS), and the lake estuary (LE), respectively). The oxidation of pyrite contributed to 35%, 42%, and 30% of the riverine solutes, while silicate weathering contributed to 5%, 6%, and 26% of the riverine solutes at the QYG, WGHS, and LE, respectively. The alluvial deposit of easily weathering fine silicate minerals, the higher air temperature, plant density, and soil thickness at the downstream LE in comparison to upstream and midstream may lead to longer contact time between pore water and mineral materials, thus enhancing the silicate weathering. Because of the involvement of sulfuric acid produced by the oxidation of pyrite, carbonate weathering in the upstream and midstream did not consume atmospheric CO2, resulting in the high rate of carbonate weathering (73.9 and 75.6 t km−2 yr−1, respectively, in maximum) and potential net release of CO2 (with an upper constraint of 35.6 and 35.2 t km−2 yr−1, respectively) at the QYG and WGHS. The above results indicate the potential of the glaciated area of the Tibetan Plateau with pyrite deposits being a substantial natural carbon source, which deserves further investigation. 相似文献