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美国主要铀源是产于陆相、扁豆状砂岩层中的铀矿床。这种类型的岩层可能是寻找新的有工业价值矿床——实际上是新的铀矿区和矿带——的最好场所,这些矿床对于满足未来铀的需求是很必要的。一个包含大的铀矿产区和矿带的模式可提供对于选择岩层和地区有用的地质关系,这些岩层和地区可能含有工业价值的矿床。对于大型铀矿床有利的主岩是与泥岩成互层的砂岩扁豆体;这些泥岩层或一些上覆岩层通常含有火山灰。在几乎全部主岩层中均保存有煤化木化石,这表明沉积作用是在一个具有高潜水面的地势低的岩系上发生的,该处形成了水饱和岩层的非氧化条件。在成矿过程中,由于河流原始坡降或轻微的构造翘起,主岩层倾伏平缓。成矿溶液是由重力作用而向下流动的地下水。在距主岩沉积或侵蚀作用边缘数哩或数十哩的带中(深度由浅处到中等),在有适宜还原条件的许多地方,矿石在稳定条件下缓慢地形成。还原剂不清楚,也许是各种各样的。卷型矿床看来是稍晚于主岩堆积之后形成的,而板状矿床可能是在沉积作用之后不久形成的。在美国有许多广泛分布的砂岩层,这些岩层具有某些或者全部有利于铀矿床形成的岩性特征,它们产于各种地质构造和不同年代的地区中。如果寻找新的矿区,就需要应用地质标志来选择勘查砂岩层和地区,这些岩层和地区很可能含有有工业价值的矿床。本文选择了若干地区和一个假定实例来说明,应用地质关系作为初步评价可能勘查目标的标志。广泛的室内和野外研究可揭露其他可能的勘查岩层和地区。
The main uranium source in the United States is uranium deposits produced in continental and lenticular sandstone formations. This type of rock formation may be the best place to look for new industrial-value deposits - indeed, new uranium deposits and ore belts - that are necessary to meet future uranium needs. A model containing large uranium deposits and ore belts provides useful geological relationships with selected strata and areas that may contain industrial value deposits. The main rocks that are favorable for large uranium deposits are sandstone lentils interbedded with mudstones; these mudstones or some overburden usually contain volcanic ash. Coal-bearing wood fossils are preserved in almost all of the main rock layers, indicating that the sedimentation took place on a low-lying rock mass with a high-submerged surface where non-oxidizing conditions of water-saturated rock formations were formed. During the mineralization process, the main strata dip gently due to the original slope of the river or slight tenting. Mineralization solutions are groundwater flowing downward by gravity. In zones with miles or tens of miles from the main rock deposition or erosion (depths from shallow to medium), ore slowly forms under steady conditions in many places with suitable reduction conditions. The reductant is unclear and may be varied. The volcanic deposits appear to be formed slightly later than the host rock, and plate-like deposits may have formed shortly after sedimentation. There are many widely distributed sandstone layers in the United States that have some or all of the lithologic features that contribute to the formation of uranium deposits that are found in various geological formations and areas of different ages. Finding new mines requires the use of geological markers for the exploration of sandstone formations and areas that are likely to contain valuable deposits of industrial value. This paper selected a number of areas and a hypothetical example to illustrate the application of geologic relationships as a hallmark of a preliminary assessment of probable targets. Extensive in-house and field studies expose other possible exploration strata and areas.