The Valley of Ten Thousand Smokes I. Thc Fumerolic Incrustations and Their Bearing on Ore Deposition. II. The Acid Gases Contributed to the Sea During Volcanic Activity. by E. G. Zeis Chemist, Geophysical Laboratory, Carnegie Institution of Washington; Member of the 1919 National Geographic Expedition to the Valley of Ten Thousand Smokes TABLE OF CONTENTS INTRODUCTION........ 1 I. THE INCRUSTATIONS AND THEIR BEARING ON 5 ORE DEPOSITION. A. Incrustations formed through vapor-phase activity ......... 5 Reactions producing magnetite ..........7 Othcr mincrals depositcd from the vapor .... 11 Differcntial conccntration................. 15 Change in mineral specics with fall in temp- crature ..................... . 18 Decomposition of magnetite ............... 18 Development of galena and sphalerite 18 B. Incrustations resulting from attack on the pumice by the steam and acid gases 21 Sulfate and fluoride areas 22 Molybdenum blue area 28 Bismuth and thallium areas 30 Fumaroles showing waning activity. Discussion of differential concentration 31 ____ C. Volitile products othcr than steam, HCl and HF ..........37 The halides.............................. 37 Sulfur, selenium and tellurium ....... 39 Occurrence of Boron oxide in incrustat;ons. 41 Role of hydrogen sulfide........... 45 D. The metallic constituents in lavas ............ 47 Prcvious work.... Combined chemical and spectrographic method. 48 Necessity for the cooperation of geologist and chemist....55 Analyses of the new Valley lavas............ 55 General analysis.......................... 55 Combined chemical and spectrographic analysis.............56 Discussion of rcsults.............. 57 II. THE ACID GASES CONTRIBUTED TO THE SEA DURING VOLCAN[C ACTiVITY..................... 61 Hydrochloric acid............ 61 Hydrofluoric acid ....................... 65 Conclusion and dscussion of heat losses. . 73 Summary .................... 76____
SUMMARY Part I. In this section, incrustations found in the volcanic area known as the Valley of Ten Thousand Smokes are described, the determination of the metallic constituents in the new lavas is detailed, and the bearing of the incrustations and acid emana tions on ore deposition is discussed. The Valley contains approximately a cubic mile of rhyolitic pumice that was deposited after having been blown through the old floor of the Valley. Many fumaroles are located in the pumiceous area. The persistence of relatively high temperatures (97 degrees—650 degrees) and great volumes of steam since the eruption of I9I2 indicate that the emanations derive their heat from a fairly deep-seated igneous body. The emanations contain over 99 per cent of steam together with approximately 0. I 2 per cent HCl, 0.03 per cent HF and 0.03 per cent H2S. The acid gases and steam have altered the pumice and have brought about a great concentration of the sulfates, chlorides and fluorides of the bases in the pumice. The acid emana tions have also transported metallic constituents in the vapor phase from the igneous intrusion to the surface. Especial attention has been directed to those areas in which magnetite, molybdenum blue, fluorides, and sulfur were deposited. Analytical data are presented which reveal the fact that nearly all of the incrustations contain appreciable amounts of the following metallic constituents: Lead, zinc, molybdenum, copper, arsenic, antimony, tin, and silver. In addition, nickel and cobalt were found in the magnetite; thallium and bismuth in the molyl~denum blue areas; selenium and tellurium in the sulfur areas. All of these constituents have the following property in common— their halides, sulfides or oxides have appreciable vapor pressures at the elevated temperatures found in the Valley in 19I9. The amount of material that can be transported in the vapor-phase will depend on the partial pressure of the acid gases, on the vapor pressure of the halide, sulfide or oxide, on the ease with which hydrolysis can take place and finally on the velocity with which the steam is moving. Evidence is presented to show that the magnetite and the metallic constituents contained therein were derived through a vapor phase activity. Important changes in mineral species are likely to take place with fall in temperature of the gaseous emanations. Thus, the magnetite deposited in the fumaroles was decomposed when the temperature had dropped to a point where active condensation of the acid steam took place. Hydrogen sulfide the characteristic ,gas of low temperatures, combined with the lead and zinc in the magnetite to form galena and sphalerite. ____
In several fumarole areas another type of differential concentration took place. Very little hydrogen sulfide issued from a number of vents, yet sulfates were abundant in the incrustations, evidently the gas oxidized about as rapidly as formed. Lead and zinc sulfates were found in the incrustations, but owing to its greater insolubility more of the former was present than the latter. Barium was found in nearly all of the incrustations, especially in those containing large amounts of chlorides, fluorides and sulfates, and was derived through decomposition of the pumice by acid emanations. It is probable that a portion of the various metallic constituents found in the molybdenum blue areas was also obtained from the pumice at or near the surface. No extensive ore body is likely to be formed in the Valley of Ten Thousand Smokes, due to the fact that the metallic constituents and acid waters can be readily carried into the drainage system of the area. The type of ore concentration described in this paper is much more likely to take place in the hearth or feeder channels of a quiescent volcano. If a difference in temperature and in pressure can be established, the volatile materials of the magma can escape; they will be acid even though the igneous body may be alkaline or neutral. These emanations can carry upwards large amounts of metallic constituents and can profoundly alter the rock materials which they penetrate. This type of concentration will at first be independent of the concentration caused by the separation of the sulfides from magmatic fluids; subsequently, however, the two types of concentration are likely to merge gradually into one another. The analyses of the unaltered pumice and rhyolitic glass found in the Valley revealed the fact that their composition is identical with that of similar material ejected by Mt. Katmai. It is inferred from these results that the igneous materials in the two areas have a common fairly deep-seated source. The pumice and glassy rhyolite were also examined for metallic constituents such as lead, copper and zinc. The combined chemical and spectrographic procedure used in the determination of the minute amounts of these substances is detailed. Especial attention is directed to the method used in making the necessary blank runs on the few reagents required for ana]ysis. The same metallic constituents that were found concentrated in the incrustations were also found in the igneous rnaterials and none were derived from the reagents. Special attention is drawn to the two factors involved in the role played by acid gases in the emanations. The intensity factor, or concentration of the acid gases in the steam controls in a large ____
measure the amount of halidcs or sulfides that can be transported. The capacity factor or total amount of acid constituents emitted per unit of time determines (I ) the amount of alteration which these acid gases produce in the rocks over which they are passing and (2) the amount of each acid gas which is directly contlibuted to the sea.
Part II. In this section the contributions of the acid constituents to the sea are considered. It is shown that approximately I.25 x I0^5 metric tons of HCI 0.2 x I0^6 metric tons of HFwere exhaled into the atmosphere in a year's time. At least three fourths of each amount of acid is directly added to the sea through atmospheric agencies. Additional evidence is brought forth to show that volcanic activity is not caused by infiltration of sea water and hence the acid gases given off during volcanic activity are real contributions to the sea. It has been observed repeatedly that river water emptying into the sea contains much less chlorine than is required to satisfv the sodium content; the opposite holds for the ocean waters. Suess and Becker suggested that the hydrochloric acid given off by vol canoes might account for the difference. Additional evidence is given in support of this theory. It is shown, for instance, that the one volcanic area of the Valley of Ten Thousand Smokes contributed I per cent of the total hydrochloric acid required to make up the deficit of chlorine in the river waters. The hydrofluoric acid contributed to the sea is next discussed. It is shown that a single area, such as the Valley, could have supplied all of the fluorine at present in the ocean, in a period of 8xI0^6 years. This is a period much shorter than the lowest estimate of the age of the ocean. Attention is, however, called (l) to the fact that great amounts of fluorine are removed from the sea through biochemical processes and ( 2 ) that even traces of fluorine can be removed from solutions through coprecipitation with calcium phosphate or calcium carbonate. In this connection, data are presented which give an idea of the huge amounts of fluorine that are locked up in the sedimentary phosphate deposits of the world. Analytical data are presented which give the concentration of boric acid in the fumaroles. An obvious concentration of boric acid In one of the fumarole areas of the valley is next discussed. A greater depth of igneous material may have been available here or preliminary concelltration may have taken place during some ear!icr period of volcanic or other igneous activity. It is also shown that the hydrogen sulfide contributed to the _____
atmosphere wil1 be eventua1ly oxidized to sulfuric acid which; in turn is precipitated into the sea through atmospheric agencies. Attention is also directed to the hydrogen sulfide wh;ch is liberated by an igneous body beneath the surface and is contributed to the ground water. Here again the total amount is effective in precipitating the insoluble sufides of metals that may be present. Finally, the steam and heat losses in the Valley are considered.
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Last revision June 21, 1995