June/July 2011

Economic Geology

The foundations of modern economic geology (Part 4)

By R. J. (Bob) Cathro

Mineral deposit models have become increasingly important in exploration for deeper targets. Better models depend on an improved understanding of the processes involved in the origin (genesis) of the mineralizing fluids. It is hard to imagine that the leading geologists in the world were still arguing about the fundamentals of genesis as recently as 1890. It is impossible to discuss the pioneer geologists who led the discussions on ore genesis without starting with Franz Pošepny΄. It is sad that his name is almost forgotten today.

Pošepny was born in 1836 at Jilemnice, Czech Republic (formerly Starkenbach, Bohemia), which is located near the borders of Poland and Germany, about 100 kilometres northeast of Prague. Bohemia was part of the Hapsburg Empire until 1867, when it became part of the Austrian half of the Austro-Hungarian Empire, which existed until 1918. He was educated at the Polytechnical Institute in Prague and at the Mining Academy in Pˇríbram until 1859. After graduation, he entered the State service. Pošepny was one of the last influential economic geologists who spent most of his career in central Europe and was largely unknown in North America. It is interesting to compare his brief education with the leisurely international one enjoyed by Rothwell, Raymond and Emmons.

Early in his career as a government geologist, Pošepny worked in relative obscurity under incredibly difficult conditions. He was first assigned, without pay, to a government bureau in Romania. A year later he was transferred, at a salary of less than 50 cents US per day, to an interesting geological district where he was restricted to auditing the accounts of abandoned mines. His superior discouraged underground studies, telling him that he had much more important things to attend to than going down into old mines where he would only see rubbish and dirt. He was obliged, therefore, to pursue underground mapping in his spare time when no one was watching. His special aptitude for economic geology was eventually recognized and he was transferred to Rodna, now situated in northern Romania near the Ukraine border, to examine lead-zinc ore deposits and abandoned mines – at an increased salary of 75 cents a day.

After 11 years of service, while still only an “expectant” without a title and with only a meagre salary, he was offered the position of economic geologist for Hungary. That included six years of work (1873-1879) in the Tyrol and Salzburg districts in Austria, and an extended tour of the United States. It was followed by his appointment in 1879 as a professor at the Imperial and Royal School of Mining at Leoben, southwest of Vienna. There, he began to compile his field notes into lectures, integrate them with current European research, and develop a new genetic classification scheme.

However, he was soon transferred back to Pˇríbram to teach at the Mining Academy and to supervise a special investigation at the Adelbart shaft, the deepest in the world at about 1,100 metres (Cathro, 2006). The silver-lead-zinc vein mineralization was strongly oxidized to a depth of 135 metres, although some sulphide minerals were still present in the oxide zone. The reason that the mine was chosen for special study was that it was completely dry below 800 metres, making it an ideal place to prove that the deep mineralization must have been deposited from ascending hydrothermal solutions.

Kemp (1920) summarized the opposing views on mineral deposit genesis at the end of the 19th century as follows: “In the late 1870s, the investigation of Professor Fridolin Sandberger of the University of Wurzburg upon the relations of wall-rocks to the minerals of their veins, and his development of strongly emphasized support for the old-time theory of ‘lateral secretion’ had aroused much interest in the general topic of the origin of ores. The geologists at the Freiberg Mining Academy, represented in this instance by Professor Alfred Stelzner, were naturally opposed to these views and supported the theory of uprising solutions. Face to face every day with deep fissure-veins in several successive series, each connected with an outbreak of igneous rocks, they had favoured these views even as early as Agricola. The quaint and curious thesis of Werner in the closing years of the 17th century, that the fissures had been filed by precipitation from an overlying ocean, was but a temporary departure from the well-nigh inevitable interpretation. Hence, between Sandberger, the ‘lateral secretionist’ on the one side, and Stelzer, the ‘infiltration ascensionist’ on the other, a vigorous controversy raged.”

Pošepny recognized that mineral deposits formed above the water table were probably as a result of descending waters from the surface and could be described as lateral secretion. Then, he considered the processes of solution and deposition through subterranean water circulation in deeper zones. This was a refinement, based on a thorough review of the literature, of a theory advanced by the French geologist A. Daubree in 1887 and took into account numerous observations of underground springs in mines of the Erzgebirge and elsewhere by H. Muller.

Because deposits containing metals could be observed forming from mineral springs, it was obvious to Pošepny that circulating solutions were the key. Common sense told him that symmetrical crusts of argentiferous galena found at a depth of 1,100 metres (564 metres below sea level) in the Adelbert shaft, which had been mined continuously from surface, could only have been deposited from ascending mineral solutions. He concluded that all mineral deposits found in deeper zones must have been precipitated from ascending solutions. “The miners themselves have always held this opinion; in other words, they have all been ascensionists,” he wrote.

After his retirement to Vienna, Pošepny travelled widely throughout western and southern Europe and to the United States, and continued to publish steadily. No complete list of his publications has been found but it is believed to be between 100 and 200 papers.

The Chicago Exposition of August 1893 was the occasion of a special AIME meeting as part of the International Engineering Congress. By a fortunate coincidence, Franz Pošepny submitted his manuscript, in German, for presentation at the Chicago meeting and publication in the Transactions of the Institute. It summarized his life’s work and conclusions about the origin of mineralizing fluids. Fortunately, the secretary, Rossiter Raymond, recognized its importance and translated it into a masterpiece of lucid English. It was soon recognized as a landmark paper. Because Pošepny had suffered an accidental fall that prevented him from writing the text, he dictated it to his wife Clotilde, who had been his constant helpmate. Early in their marriage, they had decided to jointly specialize in European languages, she becoming fluent in those of western Europe while he learned those from the east. Neither was fluent in English.

The Pošepny paper was published in the Transactions in 1893 and was so popular that it was included in a separate volume titled “The Genesis of Ore-Deposits,” which was issued by AIME in 1895 as a teaching aid for instructors and students. It contained the original paper, the criticisms that it elicited, and Pošepny΄’s reply. Unfortunately, he died on March 27 of that year and never saw the volume, which sold out quickly.

His 1893 paper continued to arouse so much interest that it became the catalyst for a long overdue debate by eminent economic geologists, most of whom worked for the U.S. Geological Survey mapping the new mining districts in the western United States. Most of their results were published by AIME and led to an additional series of extremely important papers on ore genesis at a meeting held in February 1900. They were collected and edited under Dr. Raymond’s guiding hand and published in 1902 as an 805-page second edition (known as the “Pošepny Volume”) titled Genesis of Ore Deposits. This important book included papers by C. R. Van Hise, S. F. Emmons, Walter Harvey Weed, Waldemar Lindgren, J. H. L. Vogt, J. F. Kemp, William P. Blake, and T. A. Rickard.

As Raymond put it, “From the bare outline of his life that I have given, it is evident that (Pošepny΄) trod no easy path to eminence and fame. For many years he was utilized without being adequately appreciated; ordered from place to place; scantily paid and arbitrarily overruled; his far-reaching plans thwarted by short-sighted officialism intent upon more immediate practical results. For this, government bureaus are not necessarily to be blamed. Pošepny΄ was, heart and soul, not a government official, but the lover and slave of science. And governments do not exist for the promotion of science. The utmost which they can legitimately do in that direction is to assist the progress of science on grounds of political economy.”

Dr. Raymond also praised Pošepny΄’s “free dedication to the Institute (of his treatise) … In estimating the generosity of the author, it must be borne in mind that the copyright of such a work, the fruit of years of study and of practice as an instructor, is of no little value to a European professor, and constitutes one of the legitimate rewards of his (otherwise not highly-paid) labor.”

In the words of Kemp (1920), “[the decade following the publication of the Pošepny Volume was] extremely fruitful in new ideas. The part played by igneous phenomena, whether in the way of direct magmatic crystallizations or of after-effects; the contact-zones and their elucidation; the actual processes of replacement and the changes in wall-rocks; the phenomena of secondary enrichment; the restriction in depth of the meteoric ground-water – one fundamental question after another crowded to the front. Dr. Raymond … was fully alive to the interest and importance of it all, and conceived the idea that (another) volume under the immediate oversight of Samuel Franklin Emmons would adequately summarize the rapid evolution of ideas. … (Emmons) undertook the task, selected the papers, wrote the very valuable introductory review and, alas, passed away just before the manuscript went to press. It thus became the Emmons Memorial Volume (1913), and took its place on every mining geologist’s book-shelf beside the Pošepny Volume.”

It is quite ironic that Pošepny and Emmons ended up as neighbours on library shelves because their careers were so different. Emmons was born in 1841 into a wealthy family in Boston and was named after an ancestor who was related to Benjamin Franklin. After earning a BA degree from Harvard, he studied for two years at the Imperial School of Mines in Paris, another year at Freiberg, and then travelled in Europe for another year. Beaumont, Daubree and von Cotta were among his professors. On his return home in 1867, he joined the Geological Exploration of the Fortieth Parallel under Clarence King, the first geological survey funded by the U.S. government. When the U.S. Geological Survey was created in 1879, Emmons was one of the first scientists hired. The next year, he began a landmark study of the Leadville district and became one of the most prolific and eminent of the early USGS geologists (Becker, 1911).

Acknowledgments

Back in early 2003, when I was still bemoaning the lack of published information on this topic, I mentioned to Brian Skinner of Yale University that he was the obvious person to write about the history of economic geology (he was the editor of the journal Economic Geology from 1969 to 1996). He replied that he had so many things he was working on that he doubted he would ever get around to it and he encouraged me by providing a short list of the references I should read. One of the first authors was Franz Pošepny and I have been grateful to Dr. Skinner ever since for bringing him to my attention and filling a big hole in my education.

 


References

Becker, G. F. (1911). Biographical notice of Samuel Franklin Emmons. In (S. F. Emmons, ed.), Ore deposits. New York: The American Institute of Mining Engineers,  xxix-xlvii.
Cathro, R. J. (2006). The central European silver deposits. CIM Magazine, 1(2),  65-67.
Emmons, S. F. (1913). Ore deposits. New York, The American Institute of Mining Engineers, 954p.
Kemp, J. F. (1920). Reminiscences. In (T. A. Rickard, ed.), Rossiter Worthington Raymond: a memorial. New York: The American Institute of Mining Engineers,  43-52.
Pošepny΄, F. (1893). The genesis of ore-deposits. Transactions of the American Institute of Mining Engineers, 23, 197-369. This paper was reprinted in 1902 as part of a special volume titled The genesis of ore-deposits, second edition, R. W. Raymond (ed). New York, The American Institute of Mining Engineers, 806p.

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