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991.
Chemical brecciation processes in the Sue unconformity-type uranium deposits, Eastern Athabasca Basin (Canada) 总被引:1,自引:0,他引:1
G. Lorilleux M. Cuney M. Jbrak J. C. Rippert P. Portella 《Journal of Geochemical Exploration》2003,80(2-3):241-258
Chemical brecciation in sandstone is common in many unconformity-type uranium deposits of the Athabasca Basin, and is expressed in some of them as ball zone breccia. Ball zones are composed of rounded argillized sandstone fragments, varying in size from several centimeters to 1 m, wrapped in a clay matrix. The Sue C open pit provided a unique opportunity to map and to study such ball zones. Here, they were up to 5 m wide with a 20–30 m vertical extension. They were mainly observed along a reverse fault controlling the Sue A and B uranium deposits, and were well developed at intersections with dextral NE-trending structures. Their maturity, characterized by the matrix percentage, increased toward the unconformity and at fault intersections. They are characterized by massive quartz dissolution, hematite leaching, (Ca,Sr,LREE)Al-phosphates crystallization and replacement of dickite by illite. Illite composition indicates formation temperatures of 240–280 °C, close to peak diagenesis conditions in the basin. Mass balance calculations show that V, K, Rb, B, LREE, Mg, Cr, Sr, U and Y were added and Si and Fe leached out with up to 85% volume loss.Ball zones were initiated by tectonic fracturing in sandstone during reverse faulting. Consecutive permeability increase induced basement fluid circulation in the sandstone with quartz dissolution along fractures. With a silica saturation of the fluid of 90%, a minimum fluid/rock ratio of 38,000 is obtained. The rounded morphologies of the breccia fragments are attributed to a diffusion-limited regime of dissolution. The resulting increase of clay content led to self-sealing of the hydrothermal system. Seismic reactivation may have been periodically rejuvenated the permeability. These processes seem to be coeval with the formation of structurally controlled high-grade unconformity-type uranium mineralization. Formation of the ball zones required probably more than 1 million years. 相似文献
992.
993.
以大量的测试为基础,从煤层生气性、储气性、渗透性及围岩封盖性等方面对陕西韩城北部矿区煤层气的形成条件进行了研究与评价;划分了各煤层生、储、渗、盖类型,为本区今后煤层气勘探开发提供了科学依据。 相似文献
994.
To accurately measure the pH, Eh, EC and temperature of groundwater retrieved from boreholes, a deep groundwater sampling
apparatus was developed which provided sensory measurements both in situ and in a flow-through cell at ground level. Under
a pressure of 1×106 Pa the in situ accuracy of the apparatus sensor was within the following limits: pH ±0.2, temperature ±0.1°C, Eh ±10 mV,
and EC ±2.4%. The measuring and sampling of deep groundwater from a borehole of more than 1000 m in depth was performed continuously
for 30 days. Values of pH were the same for the in situ sensor, the flow-through cell sensor and the laboratory measurements
of the sampled water. At the beginning of the sampling period, Eh values of the in situ sensor indicated deep groundwater
conditions. The apparatus is particularly useful for Eh measurement. Chemical composition and stable isotope ratios indicated
that the groundwater sampled from more than 1000 m depth was a connate water with a chemical composition slightly different
from seawater of the present time, and the groundwater retrieved from 800 m depth was a meteoric water. Natural radioactive
elements are thought to be the origin of the tritium in the groundwater retrieved from the 1000 m depth.
Received: 6 August 1996 / Accepted: 22 October 1996 相似文献
995.
M. Ramonet J. C. Le Roulley P. Bousquet P. Monfray 《Journal of Atmospheric Chemistry》1996,23(2):107-136
The aim of the 222Rn measurements during the airborne campaign TROPOZ II, was first to help in the interpretation of the photochemical studies, and secondly to furnish a data set of 222Rn in the troposphere, for validation of atmospheric transport models. In this paper we present the 222Rn measurements, and their simulation with a 3-D atmospheric transport model based on observed winds. The 222Rn was measured using the active daughters deposit technique with isokinetic aerosol sampling. We have obtained 44 measurements distributed between 65° North and 55° South, from 1 to 11 km height. In 25% of cases, we found relatively high concentrations (> 300 mBq·scm) of 222Rn in the high troposphere (>8 km). The results of 3D simulations and the calculations of back-trajectories allow us to find the origins of the high 222Rn concentrations. The transport model reproduced most of the observed synoptic variations, but it overestimates the concentrations which implies a vertical transport of excessive velocity. 相似文献
996.
依据全频域的Biot理论,推导了在Biot的流体饱和孔隙介质中,平面P波垂直井轴入时与井孔相互作用所产生的井内声压场的解析表达式.通过数值计算,对井内声压场出现的共振响应进行了分析.重点研究在不同频率段渗透率对井内声压的影响及偏离井轴记录时声压的变化.结果表明,在井内测量地震波声压,全频域都有明显影响;测量大于500HZ的地震信号,检波器偏离井轴放置以及方位不同的影响不能忽略;渗透率变化对井内声压的影响程度最大不超过弹性固体情况(零渗透率)下相应声压的1/5. 相似文献
997.
报道了自行设计的收集、吸附、吸收多级串联采样装置,成功地用于一次采集焦炉烟气中以三种形态存在的有机污染物。经GC/MS检测出293神有机污染物,其中71种为重点污染物。此项技术能够全面真实地反映焦炉烟气中全量多环芳烃和其它复杂有机污染物的状况。 相似文献
998.
“面型”岩石测量方法可成倍地减少样品采集量和分析工作量,大幅度降低了工作成本。增强了样品的代表性,并且能够消除“测网效应”,快速有效地查明区域或矿区地球化学特征以及矿化富集部位。 相似文献
999.
上海深部硬土渗透特性试验研究 总被引:1,自引:1,他引:0
上海深部硬土层的沉降显著滞后于水位变化, 本文通过一系列渗透试验进行了相关问题的研究, 包括初始水力坡度, 结核对渗透性的影响, 压力对渗透性的作用, 以及孔隙比与渗透系数之间规律的研究。结果表明硬土的渗透速率与水力坡度之间符合良好的线性关系, 满足达西定律; 大量的致密结核对渗透性影响微弱; 应力增加导致渗透性降低, 渗透系数与孔隙比呈指数规律变化。基于试验成果评价了1989~2007年天然硬土的渗透性变化, 此期间硬土层边界水位下降了近30m, 硬土层的沉降造成了该层渗透性的降低, 但土层的平均渗透系数改变不大。 相似文献
1000.
Identifying the Representative Elementary Volume for Permeability in Heterolithic Deposits Using Numerical Rock Models 总被引:1,自引:0,他引:1
Using a range of realistic 3D numerical lithofacies (dm-scale) models of ripple laminated sandstone intercalated with mudstone
we evaluate how single-phase permeability varies as a function of sample support. The models represent a range of mudstone
content which is typical for tidal deposits. Furthermore, the spatial distribution of flow barriers (i.e. mudstone) is not
random, but governed by sedimentological rules giving a variable anisotropy ratio as a function of mudstone content. Both
vertical and horizontal permeability are found to vary at small sample volumes, but these fluctuations reduce as the sample
volume increases. The vertical permeability increases while the horizontal permeability is nearly constant as a function of
sample support for small mudstone contents. For higher mudstone content, the horizontal permeability decreases while the vertical
permeability is nearly constant as a function of sample support. We propose a criterion, based on a normalised standard deviation,
to determine the Representative Elementary Volume (REV). The size of the REV is dependent on both the property measured (vertical
and horizontal permeability) and the correlation lengths of the lithological elements (i.e. lithofacies). Based on this we
identify three flow upscaling regimes that each require a different method for upscaling: (1) layered systems where the arithmetic
and harmonic averages are appropriate, (2) systems close to the percolation threshold where a percolation model should be
used, and (3) discontinuous systems where an effective medium method provides the best estimate of permeability. The work
gives, by using numerical experiments on a range of heterogeneous systems, a new insight in determination of the REV for permeability
at the lithofacies scale and its relation to sedimentological parameters. 相似文献