Congressional Serial Set Volume 6002

Congressional Serial Set Volume 6002

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 edition. Excerpt: ... ore constituents. The nature of this effect affords one way of learning something of the character of these solutions, for it is as surely a record of their work as is the ore itself. In this branch of investigation, however, it is necessary, just'as in the study of the ores, to guard against crediting a certain result to a single process when in reality it may record the superposition of a later process, such as downward enrichment, upon another and earlier deposition. ALTERATION OF MONZONITE PORPHYRY OF THE WELLINGTON MINE. SELECTION OF MATERIAL. In the Wellington mine, near the east end of the Oro level, there was in 1909 a good opportunity of studying the alteration of the country rock near the east vein, which is reached from the hanging-wall side by a crosscut from the fresh diorite porphyry (Br. 217) described with a chemical analysis in Chapter III (p. 55). The part of the level whence the specimen came is about 350 feet below the surface. Although this is beyond the reach of oxidizing water, specimens from greater depth would have been preferable for this purpose could they have been obtained in the district. On the other hand, decidedly favorable features of this locality for comparisons of the kind to be undertaken are the very uniform character of the fine-grained porphyry and the opportunity of studying changes and collecting specimens along a single crosscut which passes directly from fresh rock into the vein, here about 5 feet wide, with fairly definite walls along which there is not much gouge. The vein of this place, moreover, contains only a small quantity of galena and does not appear to have been notably enriched by downward-moving solutions. The specimen (Br. 217) of which an analysis and description have been more

Product details

  • Paperback | 116 pages
  • 189 x 246 x 6mm | 222g
  • United States
  • English
  • black & white illustrations
  • 1236902246
  • 9781236902245