Читать книгу The Economic Aspect of Geology - C. K. Leith - Страница 15

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This is one of the newer special phases of geology which for a long time was regarded as the plaything of the petrographer or student of rocks. With the systematic development of the subject, however, it was found that the extremely numerous and complex alterations of rocks and minerals may be definitely grouped, and that they are controlled by broad principles. It became apparent also that these principles apply both to the economic and non-economic minerals and rocks—in other words, that the segregation of economic minerals is a mere incident in pervasive cycles of the alterations which affect all rocks. Metamorphic geology, therefore, for some geologists becomes a convenient approach to the subject of economic geology. It has the great advantage that it tends to keep all minerals and all processes of ore deposition in proper perspective with relation to rocks and rock processes in general. It is not argued that this is the only approach or that it is the best for all purposes. A brief account of this phase of geology is given in Chapter II.