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N. V. Sobolev F. V. Kaminsky W. L. Griffin E. S. Yefimova T. T. Win C. G. Ryan A. I. Botkunov 《Lithos》1997,39(3-4):135-157
The Sputnik kimberlite pipe is a small “satellite” of the larger Mir pipe in central Yakutia (Sakha), Russia. Study of 38 large diamonds (0.7-4.9 carats) showed that nine contain inclusions of the eclogitic paragenesis, while the remainder contain inclusions of the peridotitic paragenesis, or of uncertain paragenesis. The peridotitic inclusion suite comprises olivine, enstatite, Cr-diopside, chromite, Cr-pyrope garnet (both lherzolitic and harzburgitic), ilmenite, Ni-rich sulfide and a Ti-Cr-Fe-Mg-Sr-K phase of the lindsleyite-mathiasite (LIMA) series. The eclogitic inclusion suite comprises omphacite, garnet, Ni-poor sulfide, phlogopite and rutile. Peridotitic ilmenite inclusions have high Mg, Cr and Ni contents and high Nb/Zr ratios; they may be related to metasomatic ilmenites known from peridotite xenoliths in kimberlite. Eclogitic phlogopite is intergrown with omphacite, coexists with garnet, and has an unusually high TiO2 content. Comparison with inclusions in diamonds from Mir shows general similarities, but differences in details of trace-element patterns. Large compositional variations among inclusions of one phase (olivine, garnet, chromite) within single diamonds indicate that the chemical environment of diamond crystallisation changed rapidly relative to diamond growth rates in many cases. P-T conditions of formation were calculated from multiphase inclusions and from trace element geothermobarometry of single inclusions. The geotherm at the time of diamond formation was near a 35 mW/m2 conductive model; that is indistinguishable from the Paleozoic geotherm derived by studies of xenoliths and concentrate minerals from Mir. A range of Ni temperatures between garnet inclusions in single diamonds from both Mir and Sputnik suggests that many of the diamonds grew during thermal events affecting a relatively narrow depth range of the lithosphere, within the diamond stability field. The minor differences between inclusions in Mir and Sputnik may reflect lateral heterogeneity in the upper mantle. 相似文献
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大同盆地砷中毒病区沉积物中砷的吸附行为和影响因素分析 总被引:3,自引:0,他引:3
沉积物对砷的吸附-解吸作用是控制砷在地下水中的迁移和转化的决定性因素。对砷中毒重病区大同盆地山胡县沉积物中砷的吸附行为和影响因素研究结果表明,沉积物对砷的吸附符合Freundlich吸附等温模式,吸附量主要与沉积物颗粒大小、黏土矿物质量分数和类型、铁铝氧化物质量分数以及沉积物中As的质量分数有关,有机质质量分数对砷的吸附量影响需进一步深入研究。铝硅酸盐、铁铝氧化物质量分数较高且颗粒较细的黏土和亚黏土类沉积物对砷的吸附性较强;而铝硅酸盐、铁铝氧化物质量分数较低且颗粒较粗的细砂和粉砂类沉积物对砷的吸附性较差,其所处的含水层也是形成高砷地下水的主要含水层。pH值为5.5~8.0时,砷的吸附量最大。大同盆地高砷地下水pH条件非常不利于沉积物中砷的吸附,易形成高砷地下水。该区地下水10℃左右的温度条件非常有利于沉积物对砷的吸附,但由于影响因素较多,且地下水的温度在不同季节会发生一定的变化,其产生的影响还有待进一步研究。 相似文献
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Among the large rivers rising on the Tibetan Plateau and adjacent high mountains, the discharge and suspended sediment load of the Ayeyarwady (Irrawaddy) River are the least well known. Data collected between 1969 and 1996 at Pyay (Prome) are analysed to provide the best available modern estimate of discharge (379 ± 47 × 109 m3/year) and suspended sediment load (325 ± 57 × 106 t/year) for the river upstream of the delta head. A statistical comparison with data collected in the nineteenth century (1871 to 1879) shows discharge has significantly decreased in the last ~100 years. Regression and correlation analyses between discharge in the modern period and indices of El Niño–Southern Oscillation (ENSO) show a relationship. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Spatially filtered ridge regression (SFRR): A regression framework to understanding impacts of land cover patterns on urban climate
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Understanding the impacts of land cover pattern on the heat island effect is essential for sustainable urban development. Conventional model fitting methods have restricted ability to produce accurate estimates of the land cover‐temperature association due to the lack of procedures to address two important issues: spatial dependence in proximal spatial units and high correlations among predictor variables. In this study, we seek to develop an effective framework called spatially filtered ridge regression (SFRR) to estimate the variations in the quantity and distribution of land surface temperature (LST) in response to various land cover patterns. The SFRR effectively integrates spatial autoregressive models and ridge regression, and it achieves reliable parameter estimates with substantially reduced mean square errors. We show this by comparing the performance of the SFRR to other widely adopted models using Monte Carlo simulation followed by an empirical study over central Phoenix. Results highlight the great potential of the SFRR in producing accurate statistical estimates, providing a positive step toward informed and unbiased decision‐making across a wide variety of disciplines. (Code and data to reproduce the results in the case study are available at: https://github.com/cfan13/SFRRTGIS.git .) 相似文献
7.
Harzburgite to lherzolite and back again: metasomatic processes in ultramafic xenoliths from the Wesselton kimberlite, Kimberley, South Africa 总被引:17,自引:1,他引:16
W. L. Griffin S. R. Shee C. G. Ryan T. T. Win B. A. Wyatt 《Contributions to Mineralogy and Petrology》1999,134(2-3):232-250
Garnets from phlogopite harzburgite xenoliths from the Wesselton kimberlite show zoning from low-Ca harzburgitic cores to
rims with lherzolitic Ca-Cr relations. Garnet cores are depleted in Y and HREE, but have sinuous REE patterns enriched in
the MREE. Rimwards increase in Ca and decrease in Cr and Mg is accompanied by increases in Zr, Y, Ti and HREE. Secondary replacement
rims on some garnets consist of garnet with low Ca and Cr, but high Mg, Ti and HREE. The zoning, and the secondary replacement
rims, are attributed to different stages of a metasomatic process that has converted harzburgite to lherzolite, at temperatures
near 1000 °C. Modelling of zoning profiles suggests that the process can be divided into three parts: (a) Inwards diffusion
of Ca, Zr and Y over periods of 10,000–30,000 years, from a fluid depleted in Ti, Ga and Y; (b) formation of overgrowths high
in Ca, Zr, Y and Ti, followed by annealing over periods of several thousand years; (c) formation of secondary reaction rims
of low-Ca garnet, on very short timescales prior to eruption. The sinuous REE patterns of the garnet cores are regarded as
“primary” features reflecting an ancient metasomatic event superimposed on a depleted protolith. The high Zr/Y, Zr/Ti and
Zr/Ca of the fluids corresponding to stage (a) are ascribed to the presence of phlogopite and garnet in the matrix near the
fluid source (presumed to be a melt, possibly a kimberlite precursor), leading to the development of concentration fronts
in the percolating fluid. The overgrowths of stage (b) appear to coincide with the precipitation of phlogopite in the rock.
The low Ca of the fluid responsible for the secondary replacement rims of stage (c) may reflect the late precipitation of
clinopyroxene or Ca-carbonate as part of the metasomatic assemblage. These processes have significantly modified the modal,
major- and trace-element composition of the mantle volume sampled by the Wesselton kimberlite, within <1 Ma of eruption. Recognition
of such effects and their distribution in time and space is essential to understanding of the evolution of the subcontinental
lithospheric mantle.
Received: 11 February 1998 / Accepted: 24 June 1998 相似文献
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Acta Geotechnica - Most studies investigating the effect of cyclic loading on soil properties have been conducted for saturated soils. Embankments such as fill dams, roads and railways are usually... 相似文献
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Myint Win Bo Victor Choa Kai Sin Wong Arul Arulrajah 《Geotechnical and Geological Engineering》2011,29(1):65-74
Ultra-soft soil with high moisture content will experience large strain deformation under one-dimensional compression with
little or no gain in effective stress. Such deformation behaviour does not comply with Terzaghi’s effective stress gain theory.
The e-log sv¢ \sigma_{v}^{\prime } relationship of ultra-soft soil is non-linear with large compression index in the first order of log cycle. This paper proposes
three compression indices (Cc1* C_{c1}^{*} , Cc2* C_{c2}^{*} and Cc3* C_{c3}^{*} ) for stresses covering three log cycles. Good prediction of settlement magnitude is possible with these newly proposed compression
parameters for ultra-soft soil. In addition, implicit finite difference model applying the large strain theory is also proposed
and validated with results from laboratory measurements. The time factor curves for ultra-soft soil with large strain compression
are also proposed and validated. 相似文献
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Myint Win Bo Arul Arulrajah Patimapon Sukmak Melvyn Leong 《Marine Georesources & Geotechnology》2016,34(8):782-791
An engineering geological study was undertaken to determine the engineering properties, and mineralogy of ultrasoft soils (USS) obtained from a nearshore mine tailings sedimentation pond. The USS is a high plasticity clay of high water content and low shear strength. Marine bathymetric and seismic reflection surveys were undertaken in the sedimentation pond located in the foreshore of the Eastern part of the Republic of Singapore. Specimens collected from the bore holes were tested to determine the engineering and mineralogy properties of the USS. Field vane shear tests were undertaken just adjacent to the sampling bore holes to determine the shear strength properties of the USS. The mineralogical properties of the USS were determined using X-ray diffraction and scanning electron microscope techniques. The USS is under consolidated soil where higher density and lower water content were found at deeper depth. The USS had three different compression indices under three log cycles of effective stress between 1–10, 10–100, and 100–1,000 kPa. This is the main characteristic of USS, which diverts from reconstituted soil. The outcome of this research is fundamental for understanding the compression behavior and subsequently the development of a constitutive model for USS, typical found in sedimentary pond. 相似文献