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本文提出了西北大、中型内陆盆地内的生铀层双层结构模式,即生铀层=铀源层(长石砂岩红层)+积铀层(能使铀沉淀的灰色层)。其形成机理是:在形成长石砂岩红层的成岩后生作用中,长石被水云母化,长石、石英被自生的赤铁矿、针铁矿及水针铁矿所交代而变红。在这种氧化作用中,长石、石英等硅酸盐类矿物碎屑中的微量铀部分被活化释放出来。由于该层为氧化环境,释放出来的铀不能沉淀,只能和原来储存在孔隙间的含铀“囚水”一起,在成岩脱水过程中扩散到与其紧相邻的Eh值低的灰色还原层位中沉淀,形成铀的工业富集。由此可见,假若没有具备一定渗透性的富含还原剂的灰色层,尽管长石砂岩红层能提供足够的铀源,却形成不了铀矿床,只能分散掉。因此,只有当二者同时出现时,才能够形成铀矿床的生铀层位。该模式在找矿中的意义主要有三点;1.扩大了砂岩找矿中的铀源范围,我们除了应注意基底的铀源及盆地边缘外,现在还应注意大、中型内陆盆地中的上覆红层,特别是长石砂岩红层的铀源;2.在盆地成矿远景评价及其远景区段的选择上,这个模式是一个重要的找矿判据;3.若能较好地运用生铀层的主要标志长石砂岩红层,还有助于攻深找盲,预测深部的盲矿体。
This paper presents a dual-layer structure model of uranium in the large and medium-sized inland basins in Northwest China. That is, the uranium layer = uranium source layer (feldspathic sandstone red layer) + uranium layer (the gray layer that enables uranium precipitation). The formation mechanism is: During the diagenesis of forming the feldspathic sandstone red beds, feldspar is redistened by methematism, feldspar and quartz by the spontaneous hematite, goethite and water goethite. In this oxidation, trace amounts of uranium in silicate mineral feldspars such as feldspar and quartz are activated and released. Because this layer is an oxidizing environment, the uranium released can not be precipitated and can only diffuse into the uranium “trapped water” originally stored in the pores during the diagenesis and dehydration to the gray reduction layer immediately adjacent to it with low Eh Bit precipitation, the formation of uranium industrial enrichment. It can be seen from this that if there is no certain permeability of the gray layer containing reducing agent, although the feldspar sandstone red layer can provide enough uranium source, it can not form a uranium deposit and can only be dispersed. Therefore, uranium deposit uranium can only be formed when the two occur simultaneously. The significance of this model in prospecting mainly includes three points: 1. Expanding the range of uranium source in sandstone prospecting, besides paying attention to the uranium source and the edge of the basin, we should also pay attention now to the large and medium-sized inland basins Overlying the red beds, especially the red beds of feldspathic sandstones; 2. This model is an important prospecting criterion for the evaluation of the mineralization prospects of the basin and its long-term prospects; 3. If it is better Uses of red sandstone, the major indicator of a uranium layer, also helps to find out blindness and predict deep blind ore bodies.