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我国上古生界铝土矿为高铝,高硅、低铁的中一低铝硅比矿石。在近地表风化条件下形成的土状,半土状、多状孔、蜂窝状矿石,常形成高品级的富矿体。深部矿体SiO_2和S含量偏高,矿石质量较差。夹沟矿区的勘探资料说明,越往深部铝硅比越低,逐渐变为铝土岩和粘土岩。矿石体重特别有趣;当Al/Si<15时体重随铝硅比增大而增大,当Al/Si>15时体重随铝硅比增大而减小,许多矿区资料都说明中等品位矿石体重最大,富矿体重小。当矿体在浅部遭受风化时,易溶物质流失,结构疏松,体重变小,铝硅比值升高。水是表生富集最重要的因素,大部分富矿体位于氧化淋滤带中。矿层与地势往同一方向缓倾斜的构造一地貌单元,有利于表生富集,是寻找铝土矿富矿体的有利地区。在华北,表生富集带深度在120—150米,可作为勘探的下限。
China’s Upper Paleozoic bauxite is a medium-low aluminum-silicon ore of high-aluminum, high-silicon and low-iron. In the near surface weathering conditions formed earthy, semi-earth, porous, honeycomb ore, often form high-grade rich ore body. The contents of SiO_2 and S in deep ore bodies are high and the ore quality is poor. The exploration data in Jiagou Mining Area shows that the lower the ratio of Al to Si in deeper areas, the more it becomes bauxite and clay rock. The body weight of ore is particularly interesting. When Al / Si <15, the body weight increases with increasing Al / Si ratio. When Al / Si> 15, the body weight decreases with increasing Al / Si ratio. The largest, rich ore body weight is small. When the ore body weathering in the shallow, the soluble material loss, loose structure, weight becomes smaller, aluminum-silicon ratio increased. Water is the most important factor in superficial enrichment. Most of the ore bodies are located in the oxidation leaching zone. The tectonic-geomorphic units, which are gently inclined from the topography to the same direction, are favorable for supergene enrichment and are favorable areas for finding bauxite-rich ore bodies. In North China, surface enrichment with a depth of 120-150 meters, can be used as the exploration limit.