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目前,北美已开采或正开采的深部密西西比河谷型矿藏,最初都是由钻探发现的。当这类盲矿存在于稳定地台的碳酸盐岩和页岩层序中时,传统的地球化学方法就无力检测出它们。“酶”浸析是一种选择性分析技术,为的是确定土壤中非晶质氧化锰吸收的微量元素。在世界上许多地区,酶浸折法检测土壤中与地下盲矿有关的低级别地球化学异常都很有效。在田纳西州Elmwood矿田所采的土壤样,酶浸析法分析结果表明,在370m深的地下矿体上方存在高衬度异常。在土壤化学平衡区,Zn矿体上方出现了“综合”异常。其特征表现为,矿体上方出现不对称的卤素异常晕,晕的中心为低值带;成矿金属元素(Zn和Pb)和矿体伴生微量元素(Cl、Ba和Mn)在卤素异常环内形成顶端异常,处于矿体的正上方。大多数情况下,农业活动不会影响酶浸析法的测量结果。但在田纳西州中部的某些地区,农业活动似乎改变了土壤中非晶质氧化锰的比铡。土壤中MnO_2平衡一旦被破坏,酶浸析法获得的资料就没有规律。在这种情况下,通过资料处理,取各微量元素测值与Mn测值之比值,这样获得的异常可圈划出地下盲矿体。
Currently, deep Mississippi valley deposits that have been mined or are being mined in North America were initially discovered by drilling. When such blind deposits exist in carbonate and shale sequences of stable platforms, they can not be detected by conventional geochemical methods. Enzyme leaching is a selective analysis technique that is used to determine the amount of trace elements absorbed by amorphous manganese oxide in the soil. In many parts of the world, enzymatic dipping is very effective in detecting low-grade geochemical anomalies associated with underground blind mines in soils. Soil samples collected from the Elmwood field in Tennessee showed that there was a high-contrast anomaly over the 370 m deep underground orebodies. In the chemical equilibrium region of soil, there appeared a “general” anomaly above the Zn ore body. It is characterized by an asymmetric halogen halo above the ore body and a low halo zone at the center of the halogens. Metallogenic elements (Zn and Pb) and associated trace elements (Cl, Ba and Mn) Within the formation of the top of the anomaly, just above the ore body. In most cases, agricultural activity does not affect the measurement of enzyme leaching. In some parts of central Tennessee, however, agricultural activity seems to have changed the odds ratio for amorphous manganese oxide in the soil. Once the balance of MnO 2 in the soil is destroyed, the data obtained by the enzyme leaching method are not regular. In this case, through the data processing, taking the ratio of the measured value of each trace element to the measured value of Mn, the anomaly thus obtained can circle the underground blind orebody.