xt7z348gft8z https://exploreuk.uky.edu/dips/xt7z348gft8z/data/mets.xml Shaler, Nathaniel Southgate, 1841-1906. 1877 books b96-12-34887969 English Stereotyped for the Survey by Major, Johnston & Barrett, Yeoman Press, : [Frankfort, Ky. : Contact the Special Collections Research Center for information regarding rights and use of this collection. Lead Kentucky. On the origin of the galena deposits of the Upper Cambrian rocks of Kentucky / by N.S. Shaler. text On the origin of the galena deposits of the Upper Cambrian rocks of Kentucky / by N.S. Shaler. 1877 2002 true xt7z348gft8z section xt7z348gft8z GEOLOGICAL SURVEY OF KENTUCKY. N. S. SHALER, DIRECTOR. ON THE ORIGIN o0 THE GALENA DEPOSITS oF nR UPPER CAMBRIAN ROCKS OF KENTUCKY, BY N. S. SHALER. PART VIII. VOL. II. SECOND SERIES. 277 & 278 This page in the original text is blank. ON THE ORIGIN OF THE GALENA DEPOSITS OF THE UPPER CAMBRIAN ROCKS OF KENTUCKY. The deposits of galena in the Cambrian district of the State differ in some important regards from those which have been observed in the sub-carboniferous limestone, although there is in both cases a general agreement in the circumstances of occurrence. In both cases these deposits are limited to true fissure veins of a peculiar type. In both regions they occur in limestones only, and are not observed in the overlying sili- cious and argillaceous rocks. The associated minerals in both cases are substantially the same, though differing in their pro- portions and general appearance. We are driven by the facts to the conclusion that all these veins have been formed by infiltration of water charged with the substances that form the vein matter, the cavity of the vein having been first devel- oped by a movement of the rcsks in which it is found. There are, however, differences of character between the galena veins of the Livingston district and those of Central Ken- tucky that compel us to make a strong line between them. As is shown by the report of Mr. Norwood (see reports Ken- tucky Geological Survey, first volume, new series), the veins in the Livingston district very often give indications of abrupt faulting, and, in some cases at least, of several successive ver- tical disturbances acting in the same spot. There seems to have been a good deal of irregularly acting dislocating force in this region, which did not result in the formation of distinct mountain curves, but expended itself in the numerous sharp breaks that have disturbed all this district. I am inclined to attribute many of these veins of the Liv- ingston district to this faulting action, combined with the 279 4 ON THE ORIGIN OF THE GALENA DEPOSITS OF shrinking of the whole rock system from the loss of heat and other changes. The result was the formation of fissures of possibly great depth, the walls of which gaped apart, re- maining perhaps closed near the surface, where there was perhaps only a small contraction, or, possibly, none at all. The next stage of the process seems to have been the in- filtration of waters charged with carbonate of lead in solution, and its deposit by crystallizing action within these cavities. Subsequent changes brought about still further movements of the same character as those that formed the cavity at first, and through them the original deposits were often curi- ously broke up and mingled with other materials. In the Cambrian district, particularly in Henry county, the tendency to faulting seems to have been much less than in the western field. All the crevices I have seen do not show any distinct vertical movement of the wall rocks, but seem to have been formed by lateral dislocation alone. It is not easy to determine the causes of this shrinkage in the mass of rock throughout this region, but the evidence of its occurrence is tolerably clear at all points. It is manifested in every line of the section by the breakage of the mass of rock into vertical crevices, which have become to a greater or less extent filled with clay and other substances. At some points these crevices indicate a reduction of at least one fifteenth of the horizontal dimensions of the rock mass. Generally these shrinkage I am inclined to think that the general absence of mineral deposits in all the well-defined faults which I have seen in Kentucky is strong presumption against the occurrence of exten- sive mineral deposits in such breaks within this Commonwealth. The Pine Mountain fault, one of the most extensive and readily observable in the whole Appalachian district, has not yet given a trace of metallic deposits. The same is the case with the Kentucky River faults. In the case of the lode near Smithland, Livingston county, that on which the Royall mines are situated, there seems good evidence of a fault. With this evidence from other fissures I should feel it necessary to examine with care for evidence as to the time of formation of the fault itself as distinguished from the vein stuff. These deep-reaching contraction fissures naturally form lines of weakness, along which faults would propagate themselves in case the rocks were submitted to a breaking strain tending to form such disruptions In the case of the Royal1 mines and other openings on the fissure just referred to, this question would have little practi- cal value, inasmuch as the vein stone at that point may be reasonably expected to extend quits through the Waverly rock, as well as the sub-carboniferous limestone, on account of the cal- careous character of the former rock in its western extension. Without taking up the history of these dislocations of Kentucky in detail-a matter which will be reserved for use of the special memoirs on the geology of the State-it may be worth while to say that all the facts as yet collected point to the conclusion that al the faults, in Eastern Kentucky at least, are of a comparative recent origin, probably dating from a time long after the action of the forces concerned in making the deposits in the galena veins. 280 THE UPPER CAMBRIAN ROCKS OF KENTUCKY. cracks extend only through a fbot or two of the beds in a continuous way, the different beds yielding at different points, so that nothing like a continuous crevice is found. On the other hand, from point to point, we have these continuous deep-reaching fractures with separation of the walls, which to my mind are certain indications of a contraction that has extended through a great thickness of beds, and differs only in the magnitude of its action from the small crevices so abundantly found throughout the rocks. The deep-reaching crevices of considerable width seem most abundant where the small open joints are rare. In Campbell and the adjoining counties, where the limestone abounds in these open joints, I have never found an ore-bearing crevice; while in the counties within the Cambrian district, along the Kentucky river, where the rock is peculiarly free from small joints, these wide ore-bearing fissures are frequently found. We may, therefore, reasonably conclude that both these forms of fissuring are due to the same contraction of mass, and that some local conditions, possibly the difference in the massive- ness of the beds, determine which shall be the type formed in any particular region. The cleanness of these fractures, and the absence of all evidence of violence, is to my mind sufficient evidence that these fractures have not been attended by any wide-reaching movements. The fossil shells on the rock are often cut in two with perfect neatness, their broken edges being not in the least shattered or rubbed as they would have been had there been any such collision of the sides as is sure to occur where there has been true faulting. This is not the place for an exhaustive inquiry into the nature of the forces that have brought about this change in mass; but some idea of the nature of the forces involved is necessary to the compre- hension of the condition under which the vein-stones that fill them have been formed. There can be no doubt that this region was once buriedt under several thousand feet of strata, which have been worn away during the time since the emergence of the region from 281 5 6 ON THE ORIGIN OF THE GALENA DEPOSITS OF the sea. During the time these beds lay deep buried there was an accession of heat which may well have amounted to several hundred degrees of Farenheit. This expansion must have done much to pack the rocks together, and to bring about chemical changes attended by a loss of volume. When, therefore, the continued loss of heat, caused by the wearing away of the old rock covering, had greatly lowered the tem- perature, the tendency of the rock to contraction would be con- siderable. As against pressure rocks are tolerably elastic, but to tension they are much less so, and rend apart easily under its action; so that any considerable loss of heat would not be required in order to account for these deep-reaching rifts. A change of not over one hundred degrees Farenheit would be sufficient to cause the formation of a considerable number of rifts, probably as many as occur in this region. The possibilities are that these rifts began to form with the first considerable decrease of temperature, and increased in width as time went on and cooling advanced. As will be seen from the figures in Mr. Norwood's report, there is a very gen- eral tendency of these veins to be grouped in the shape of two or three gashes placed near to each other. The immedi- ate partitions are often thin walls, yet undisturbed by any violent movements. This affords another evidence of the tranquil nature of the movements involved in their production. It will also be seen that there is no evidence whatever of a vertical movement of the rocks on either side of the fissure. The beds lie at equal heights in both walls, and every feature of fault veins is quite wanting. We are therefore compelled to hold to the opinion that these veins are the product of shrinkage of the rocks. Having now briefly discussed the formation of the fissures in which these deposits occur, it remains for us to examine the methods of accumulation of the deposits contained within them. This inquiry, though touching on the domain of ab- stract theory concerning the genesis of such veins, is neces- sary to any proper understanding of their character, and of the prospects of their downward extension. 2&s THE UPPER CAMBRIAN ROCKS OF KENTUCKY. The old view that attributed the formation of mineral veins to the ejection from a reservoir of molten matter of mineral substances, which penetrated along the passages leading to- wards the surface, has been quite abandoned as a usual ex- planation to be assigned to such phenomena. In its place has grown up the conviction that most veins are formed in essentially the same fashion as is the stalactitic material that accumulates in caverns, viz: by the deposition of matter dis- solved by water in one part of its course through the crust of the earth and laid down at another. The belief of metallurgists and others who have most studied the history of metals is, that the original condition of those substances was that of extensive dissemination, and that this local accumulation has been the result of actions that have come about in the changes of temperature, &c., taking place since the deposition of the beds containing the deposit. Until within a few years this opinion, very general in its outlines, has been the accepted view as to the origin of me- tallic deposits. It will be seen that it is imperfect, in that it does not sufficiently explain the curious limitation of certain species of metals to certain geological formations. In i862 a decided advance towards a clearer theory was made in the report of J. D. Whitney oil the lead district of Wisconsin, in which the ground was distinctly taken that the process of formation of mineral veins went oni in something like the following manner, viz: First, the dissolving out from the rocks of the earth of the mineral substances which were originally widely distributed therein, and their transportation to the waters of the sea. Second, the precipitation of these materials by the action of the decaying organic life on the sea floor, which, as we know, is capable of effecting such work. Third, the concentration of these materials through the action of the various processes that build up the veins. The follow- ing extract from the work of Prof. Whitney will serve to show the fashion in which this was suggested by him. On account of the close general resemblance of the geological condition 283 7 8 ON THE ORIGIN OF THE GALENA DEPOSITS OF of the upper Mississippi lead region to the Kentucky lead district, I have, by permission of the author, made extensive extracts from his report. These important suggestions remained practically unconsid- ered and without addition until many years after their publica- tion. In a course of unpublished lectures given by Professor Raphael Pumpelly at Harvard University in I869-'70, the idea of the cooperation of the secretive power of organic life in the series of actions leading to the formation of mineral veins was suggested and extensively discussed, though from a somewhat different point of view. For the first time the capacity of organic species to separate metals from the sea water and build them into their structure was publicly sug- gested as a means whereby the fixing of metals in strata could be brought about. In this process of concentration Professor Pumpelly gave great weight to the action of marine currents in accumulating masses of sea weeds and other organic substances on particular parts of the sea floor, and so leading to deposits in great part made up of the remains of animals which might contain some one metal in considerable quantities. By permission of Professor Pumpelly this lecture is published in the second appendix to this report. In i870 Dr. T. Sterry Hunt brought the matter to the notice of geologists in an extended discussion of the action of organic life in the localization of mineral substances. We seem to have here, as in many other cases in the process of scientific progress, the coincident and independent discovery of a series of facts by two observers, each working in ignorance of the other's researches. The first public announcement of this discovery was made by Professor Pumpelly; but priority, as determined by actual publication, is clearly to be awarded to Dr. Hunt. The researches that have been made into the composition of sea water and of sea weeds has gone far to support this hypothesis as to the function of marine organic life in the See Appendix No. I, taken from a "Report of a Geological Survey of the Upper Missis- sippi Lead Region, by J. D. Whitney, Albany, N. Y., 1862." 24 THE UPPER CAMBRIAN ROCKS OF KENTUCKY. making of mineral deposits. There can be no reasonable doubt that all the substances which have been detected by chemists have their place in the universal solution of the sea. The presence of silver, gold, copper, and other metals in the sea water is evident on a concentration of its contents. Some of these substances exist in considerable quantities. The assertion even been made that the silver of the sea will amal- gamate with the copper employed in sheathing ships, so that old copper long exposed to the moving sea may be worked for its silver won from the water. The idea prevails that this sep- aration of silver by the copper takes place more rapidly on the west shore of South America than in any other region. The researches of Forchhamer and others on the composition of marine invertebrate animals and plants long ago showed that there is a considerable amount of metallic substances laid up in the structure of marine forms, which, on their death and decay, would be laid down with the accumulating sediments of the sea floor. It is my impression, as above remarked, that this important function of organic life in the production of mineral deposits was first suggested by Professor Pumpelly in his lectures above referred to, of which no printed report was ever made. It is important to notice, however, that, as long ago as 1858, Dr. T. Sterry Hunt began a series of inves- tigations as to the action of organic life in the deposition of various substances, such as carbonate and phosphate of lime, &c., which had been built into their structures, that led natu- rally to the inquiry into the important action of marine life in the deposition of metallic substances. A discussion of this important hypothesis will be found in the assembled papers of Dr. Hunt. It does not come within the province of this report to at- tempt an exhaustive inquiry into this question of the origin of these lead deposits of the upper Cambrian. From the sug- gestions already given, it will be seen that this balance of opinion among the best informed chemists and metallurgists inclines to the conclusion that organic life is closely concerned 'See Appendix No. III at the end of this report. 28S 9 1o ON THE ORIGIN OF THE GALENA DEPOSITS OF in the localization of the metallic deposits, at least in the little changed rocks, such as compose all our Kentucky formations, and that in this work the action takes place in two ways: Firstly, by the taking into the organic structure of the metal- lic substances which pass into the sea bottom on its decay. Secondly, by the effect of the gases, particularly the sulphur- etted hydrogen, released by decay, in precipitating the me- tallic substances dissolved in the sea. The practical opera- tion of these processes is somewhat as follows: The fixed, and to a certain extent the swimming, animals of the sea, taking this or that substance in their growth, deliver it up at their death to certain tracts of the ocean bottom, and in their decay take continually more of these substances into imprison- ment in the accumulating sediment. As this power of separating metallic substances varies in different species, it therefore differs in different sections of the ocean floor and in different periods in the earth's history. If this theory be true, then, other things being equal, we should expect to find that those formations which indicate the ex- istence of abundant organic life on the sea floor where they are being deposited would be the most likely to furnish con- siderable quantities of metals. Such, in fact, we find to be the case wherever these deposits have been worked under similar conditions to those existing in the region we are now considering. The evidence cannot be safely regarded as affording a basis for definite and final assertion; but there can be no reasonable doubt that, in going downwards into rocks containing little evidence of organic life, we have reason to fear that we shall pass out of the richest part of a galena vein and into leaner territory. Some of the metal derived from the rock where it was deposited will, doubtless, often work downwards into the fissure when it runs in sandstones or other rocks where life has never been abundant. But this must be, in a good degree, accidental, as the deposit gener- ally takes place at the point where the metal-charged waters oozed through the walls of the fissure. There is little reason to suppose that there could be more of the metallic substance 286 THB UPPER CAMBRIAN ROCKS OF KENTUCKY. in the sandstone or shale beds than in the limestone beds. Another reason to fear the unprofitable nature of galena veins in sandstone beds would be from the contraction of the fissure, owing to the change of rock. We have seen that the most of the veins found in Kentucky are the product of con- traction or shrinkage taking place in the stratified rocks. This form of vein is always characterized by very variable width, and is likely to widen in the limestones and to contract in sandstones and shales. The general character of the deposits of ore in the mineral veins of Kentucky may be the better understood when we consider some of the facts of distribution of these veins. The blue or Cambrian limestone abounds in these veins, especially in its upper part, where the organic life has left abundant fos- sil record of its existence. The equivalents of the Niagara series, rather carboniferous, have little trace of lead. The black or Ohio shale is almost without mineral beds of any importance; the. same may be said of the Waverly series in Eastern Kentucky, where we find sandstones and argillaceous limestones rarely penetrated with lead-bearing rocks. When, however, we come up to the sub-carboniferous limestone, then, again, we find the lead-bearing veins in great abundance. Now when, as in Central Kentucky, we follow the line over which the carboniferous limestone has retreated, we are struck with the fact that, where it has been worn away from the lower lying beds, the Waverly and black or Ohio shale, these beds from which the carboniferous limestone has been stripped away, are characterized by the want of mineral veins, as above set forth. We have no reason to doubt that the limestone that once overlaid these beds was as well marked by its mineral veins as are the areas which still exist. We are, therefore, led to believe that these veins we find in the sub- carboniferous limestone do not extend into the subjacent sand- stones and shales. It should, however, be distinctly noticed that this difference depends not upon the geological position of the rock, but on its mineralogical character; and that where, as in Western Kentucky, the Waverly series takes on a7 I I 12 ON THE ORIGIN OF THE GALENA DEPOSITS OF the nature of a limestone, it may happen that it will protract the lead-yielding fissures downward to great depths. I am inclined to believe that the lead-yielding veins in that district may in some cases be followed about a thousand feet down before they pass into rock of a sandy constitution. The question will, perhaps, be asked why, inasmuch as we find some of the ancient rocks, as gneiss, mica schist, and other similar materials, containing lead veins, there should be a basis for the idea that organic life is necessary for the con- centration of such metals. This question opens one of the broad fields of geology, and it cannot be discussed in detail in this report. The answer can, however, be indicated in a general way. It is now the belief of most geologists that all the rocks now visible on the surface of the earth have been laid down on the sea floors by the action of water; that they were once limestones, sandstones, and shales, essentially like our familiar rocks, that still carry in their fossils and their structure most evident marks of their origin. These rocks, having been deep buried beneath subsequent accumulations of like materials, subjected to great and long continued pres- sure heat, and the manifold changes that go in their train, have gradually had their particles so re-arranged that their original character is often quite lost or only traceable by slen- der threads of evidence. In the vast periods of time, and amid the ever changing circumstances of these metamorphic rocks, the metals may have been carried from point to point, and from level to level, in the series of rocks, being again and again dissolved by heated and gas-containing waters, which took them up at one place to lay them down at another. The veins in the highly altered rocks, the mica schists, for instance, may have been originally laid down in some much higher rocks of another character, and only brought to their present level by the long-continued circulation of heated waters, be- ing, perhaps, several times deposited and redissolved in the course of their downward journey. In our Kentucky rocks. however, we get but the first stage only of this migration of the particles of metal after their deposition in the organic 288 THE UPPER CAMBRIAN ROCKS OF KENTUCKY. 13 remains. The metals have been concentrated into fissures in the immediate neighborhood of their deposition, but have been subjected to no further change. The following figure will show, in a diagrammatic way, the apparent condition of the Kentucky series of rocks. It should be understood that this figure is intended as an illustration of an opinion rather than as a graphic representation of the facts I 10 .-S, t; 0 VoL l.-K9 289 14 ON THE ORIGIN OF THE GALENA DEPOSITS OF It will be noticed that this diagram indicates generally ver- tical fissures with tolerably regular walls, all clearly the work of a contraction of the mass. On examining Professor Whit- ney's work, "1 The Lead Region of the Upper Missouri," it will be seen that there have been extensive deposits of the lead and associated substances in ordinary caverns in that region- a large part of the workable deposits coming from beds that have been formed in caverns rather than as fissures. Possibly some of the lead deposits of Western Kentucky, occurring in the carboniferous limestones, may also be regarded as occupy- ing caverns rather than fissures; but at this time I am quite convinced that the evidence is rather against this view and in favor of the theory that this class of deposits has never, in this region, been found in caverns excavated by water. I have carefully observed many such underground channels, both in the Cambrian and Sub-carboniferous limestones, with a view to ascertaining whether any such deposit is now going on, with the definite result that not a trace of such action is observable at the present time. I am satisfied that the upper- most caves .in Kentucky date back at least a million of years, and that they were probably in existence during the middle Tertiary period; yet in none of them is there the least trace of the deposition of lead. It seems to me that this fact clearly proves that the formation of these veins is most explicable by the supposition that they were segregated while the rocks were subjected to conditions of heat that do not now exist in them. At the same time it must be said that their mechanical condition forbids the supposition that they have ever been subjected to any very high temperature. To sum up in brief the general condition of our Kentucky vein metals, we may make the following propositions, viz: ist. That the fissures or veins in which they occur have generally been formed by the shrinkage of the rocks in which they are found, and not by the deeper-seated causes which form fault veins. See Antiquity of the Caverns and Cavern Life of the Ohio Valley, Memoirs KentuCkY Geological Survey, volume I, part I, 1876. 290 THE UPPER CAMBRIAN ROCKS OF KENTUCKY. 15 2d. That these fissures, dependent for their origin on the peculiarities of constitution of particular beds, cannot safely be expected to continue indefinitely downwards below the level of the beds in which they are seen. 3d. That the absence of metallic veins in the sandstones that were originally overlaid by limestones, which limestones are vein-bearing, is a corroboration of the view that these veins are limited to the limestone rocks. 4th. That the general presence of metalliferous veins in the limestones of the State, and their general if not universal absence in the sandstones, is a strong proof of the truth of the theory that assigns to organic life the function of separat- ing these metals from the sea and laying them down in the stratified rocks. 5th. That the cycle of change of metals, as, indeed, of all substances, is as follows: Dissolved from the earth by the water, which is aided in its work by its contained gases and heat, they find their way to the sea; then the organisms living in the waters or on the bottom, select the substances accord- ing to their peculiar organic laws; built into the growing deposits of the sea bottom, they become part of the earth's crust, and come again within the action of those forces that work them into their concentrated state, or, mayhap, wash them again into the sea, and so repeat the eternal circle. In the appendix to this report I have, by permission of the authors, reprinted extracts from the writings of Professors J. 1). Whitney and Raphael Pumpelly and Dr. T. Sterry Hunt, thus bringing together all the important contributions known to me that bear on this question. The reader is requested to bear in mind that the views above suggested, though they seem to satisfy the facts better than is usually the case in geological theories, must not be taken as matters of final demonstration. There can be no d(oubt that the balance of probabilities is greatly in their favor, and that they may fairly be made the basis of a judgment by those who seek even the least light where else would be only darkness. 291 t6 ON THE ORIGIN OF THE GALENA DEPOSITS OF With reference to the economic bearing of these conclu- sions above set forth, little needs be said. The economic side of the problem is not greatly affected thereby, save in the conclusion that few of our lead deposits, if any, may reason- ably be expected to be continuous to great depths or to im- prove in descending. The reports of Dr. Peter make it plain that all our lead ores are singularly poor in silver; in no case has enough been found to warrant extraction. With careful mining some of the lodes will possibly pay for working; but there can be no doubt that at least half a dozen other sources of mineral wealth within the State promise a better return for capital and enterprise. Already there has been a large amount of money expended in the opening of lead ores in the State; probably not less than half a million dollars has bee" spent in such workings. Very little lead has been mar- keted. I doubt whether four hundred tons have ever been obtained from all the workings put together, and but two or three openings can now be said to be promising in their ap- pearance. I feel, therefore, compelled to say, that however single ventures may turn out, the prospect of the industry to the Commonwealth is by no means good. 292 THE UPPER CAMBRIAN ROCKS OF KENTUCKY. APPENDIX 1. oItem a Raptm -th Uppe Wiiippi LEd Reo by Proem J. D. Whitinm, eapelned bY P-1-h of the Author.] "In view of all these facts, we consider it as a matter settled beyond all possibility of doubt, that the lead deposits of the Northwest must have been introduced into the fissures from above, and by precipitation from a solution. In reference to this last clause, we have not thought it necessary to adduce any evidence to disprove the theory of the igneous origin of the ore, or of its having been brought up from below, either by sublimation, or by actual injection. Since, how- ever, both of these ideas have been maintained by different persons writing on the region, although every fact seems to be entirely opposed to any hypothesis of igneous action, it may be proper to sum up as concisely as possible the evidence in favor of aqueous deposition. '1ist. The generally recognized aqueous origin of the sul- phurets: deposits of sulphurets of iron and other metals are frequently produced accidentally or intentionally in the chem- ist's laboratory, by the decomposition of solutions containing the metals by sulphuretted hydrogen. H 2d. The occurrence of the sulphurets of lead and iron in the lead region, in forms which they could not have assumed, except as deposited from a solution-as in the form of casts of fossils, and in connection with stalactites and stalagmitic masses of calcite. An instance of this kind is to be seen in the Wheatley collection at Union College, and is shown in the annexed wood-cut, which represents a large stalag- m ,, mite, with a small mass of galena on the end of it, in a position which it would be difficult to imagine it to have reached, except in solution, dropping from above, eStalagmie Gk, exactly as the rest of the stalagmite was formed. Instances have been mentioned