The Journal of Geology, Vol. 21: A Semi-Quarterly Magazine of Geology and Related Sciences; January-December, 1913 (Classic Reprint) - Softcover

Inhaltsangabe

Excerpt from The Journal of Geology, Vol. 21: A Semi-Quarterly Magazine of Geology and Related Sciences; January-December, 1913

The past half-century has been a period of rapid development of mines and mining, both in America and in other countries, and as a consequence,' the basal facts regarding the occurrence Of ores are now comparatively well understood. The geologic causes for the location Of ore-bodies in certain zones or horizons are in many cases known, and many former theories are generally accepted as facts. The transportation of ores by aqueous solutions, the origin of some of these solutions in cooling igneous magmas, and the secondary enrichment of many ore-bodies through the agency of meteoric waters; such are some of the ideas which have withstood prolonged criticism and have become established tenets Of geologic faith. But beyond basal facts, adduced almost solely from field evidence, our knowledge of the mechanism of ore depositions is somewhat vague and unsatisfactory. Only prolonged investigation along chemical and physico-chemical lines will render possible a reasonably accurate understanding of the complex com position oi ore-bearing solutions, of the reactions of these solutions with the wall rocks, of the causes for the deposition of minerals from them, and of many other problems connected with the depo sition of ores.

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