Economic Geology Volume 11 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1916 Excerpt: ...who describes these deposits, believes that these two types of ores are closely related in origin. He dissents from the views of Lindgren and decides in favor of the formation of both the Tularosa and Sierra Oscura copper ores by hot, ascending solutions. The geological evidence, while perhaps favoring the meteoric origin, is not conclusive. It is, moreover, probable that L: ndgren's views are partly based upon the supposed reducing action of the organic matter on copper solutions to form chalcocite. But we know that in the case of the Sierra Oscura and Nacimiento deposits chalcocite was not precipitated by organic matter, and it is not at all certain that such was the case in the Red Gulch deposit. As the copper ores occur in the nodules as well as in the plant replacements at Sierra Oscura, the role of carbon as a reducing agent is very improbable. As Lindgren himself has said, "The importance of precipitation by carbonaceous material has been overestimated....1,18 In this connection it is interesting to note that Clark19 failed to precipitate copper sulphide on: oal from a solution of copper and ferrous sulphates even at the?nd of 122 days. Lindgren's remark "It is necessary to explain vhy chalcocite is characteristic of these deposits and chalcopyite of the fissure veins "20 loses its force after the results of the nicroscopic examination are obtained. All students of ore-deposits must admit that at least some types i ore-deposits, though perhaps greatly in the minority, are ormed from meteoric waters, though, as Lindgren21 says, "The prevailing influence of igneous intrusions on ore deposition is, owever, so strong that it is difficult to establish the proofs of the less nspicuous deposition by purely meteoric water." 18 P...