The Genesis of Ore Deposits (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: Discussion at the Chicago Meeting, August, 1893, Including Communications Subsequently Received. "W. P. Blake, Shullsburg, Wis.: I desire to express my admiration of Prof. Posepny's memoir, and particularly of the charming manner and spirit of the introduction. With respect to his mention of the ore-deposits of Missouri and Wisconsin, reference may be made to my paper presented at this meeting (Trans., xxii., 621), showing the existence of dislocations and breaks in the bedding, and their apparent close relation with the localization of the ore-deposits as claimed by Dr. James G. Percival, and also so claimed by Dr. Jenney in his paper before us (Trans., xxii., 171). I have in my paper given reasons for believing that the zinc- and lead-ores in the strata above the compact Trenton limestones were formed by lateral secretion and concentration from above downwards, substantially as shown by Prof. J. D. Whitney, and not by the ascent of solutions through the fissures, as Prof. Posepny (p. 118) seems inclined to believe. In regard to the contemporaneity of the ore and the rocks, and in favor of a later introduction of ore through fault-fissures, Prof. Posepny (p. 124) cites the influence of these fissures. In my paper, already referred to, I have endeavored to show how faults may have influenced the deposition of ore without being themselves channels for the flow of mineral solutions, and how they may have caused the contemporaneous formation of metallic sulphides from sea-water in the body of a forming rock; the faulting fissure being formed at an early period in the foundation-rocks, and probably continuing to be a plane of break and movement in the deposits of later formation. Arthur Winslow, Jefferson City, Mo.: The results of extensive and long-continued studies, such...