Ore-bearing discrimination of granite rock mass in Nanling area based on data-driven
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摘要: 【目的】花岗岩作为成矿作用的重要参与者,对它的研究有利于了解钨锡成矿作用的地球化学过程和区分岩体的含矿性。【方法】本文收集了南岭地区含钨花岗岩、含钨锡花岗岩和不含矿花岗岩的主量元素和稀土元素数据,共42个岩体466组数据。总结对比了三类岩体的地球化学特征,从数据驱动和机器学习的角度区分了三类岩体的含矿性和岩石地球化学特征之间的关联,运用受限玻尔兹曼机来训练自编码神经网络以消除主量元素和稀土元素之间量级的差别,并且提取中间特征,再将中间特征输入随机森林和多层BP神经网络,建立AE-RF和AE-BP岩体含矿性分类模型。通过随机森岭输出了分类特征重要性。【结果】结果表明,含钨花岗岩的演化程度最高,含钨锡花岗岩次之,不含矿花岗岩最低。两种模型在测试集上都有很高的正确率(>90%),并且在盲测试集上AE-BP模型的实际运用效果更好。随机选择了6组岩体作为盲测试集,二十一个岩体中有13个岩体正确率大于80%,有两个岩体正确率大于70%小于80%,有两个岩体正确率大于50%小于70%。还有四个岩体正确率小于50%。铁锰磷钙镁等主量元素和轻重稀土元素是区分三类岩体的重要特征。【结论】机器学习能够很好地反映出三类花岗岩的含矿性,地球化学特征的相似性会导致模型错误分类,陂头岩体有一定的成矿潜力。铁锰磷钙镁等主量元素决定了岩体能否含矿,而轻稀土是区分含钨岩体和含钨锡岩体的重要指标,认为岩浆的分异演化程度决定了岩体能否含矿,而幔源物质的加入是区别岩体含钨还是含钨锡的特征。Abstract: As an important participant in mineralization, the study of granite is helpful to understand the geochemical process of tungsten-tin mineralization and distinguish the ore-bearing property of rock mass. In this paper, the data of major elements and rare earth elements of tungsten-bearing granite, tungsten-tin-bearing granite and non-ore-bearing granite in Nanling area are collected, a total of 466 sets of data of 42 rock masses. The geochemical characteristics of the three types of rock masses are summarized and compared.The relationship between ore-bearing properties and geochemical characteristics of rock mass is explored from the perspective of data-driven and machine learning. The restricted Boltzmann machine is used to train the auto-encoder neural network to eliminate the dimensional difference between major elements and rare earth elements, and the intermediate features are extracted. Then the intermediate features are input into random forest and multi-layer BP neural network to establish AE-RF and AE-BP rock mass ore-bearing classification models. The importance of classification characteristics is output by random forest. The results show that the evolution degree of tungsten-bearing granite is slightly higher, followed by tungsten-tin-bearing granite, and the ore-free granite is the lowest.Both models have high accuracy ( > 90 % ) on the test set, and the practical application effect of the AE-BP model on the blind test set is better. Six groups of rock masses were randomly selected as the blind test set. Among the 21 rock masses, the correct rate of 13 rock masses was greater than 80 %, the correct rate of two rock masses was greater than 70 % less than 80 %, and the correct rate of two rock masses was greater than 50 % less than 70 %. There are four rock mass accuracy is less than 50 %. Major elements such as iron, manganese, phosphorus, calcium and magnesium and light and heavy rare earth elements are important features to distinguish the three types of rock masses. The similarity of geochemical characteristics and the difference of tungsten-tin deposit types will lead to the wrong classification of the model, and it is pointed out that the Beitou rock mass has certain metallogenic potential. The main elements such as iron, manganese, phosphorus, calcium and magnesium determine whether the rock mass can contain ore, while light rare earth is an important index to distinguish tungsten-bearing rock mass and tungsten-tin-bearing rock mass. It is believed that the degree of differentiation and evolution of magma determines whether the rock mass can contain ore, and the addition of mantle-derived materials is to distinguish whether the rock mass contains tungsten or tungsten-tin.
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