Eos, Vol. 73, No. 21, May 26, 1992

elevated temperature and pressure of granitic Rummel, F., Physical properties of the rock in the Schwarz, Lawrence Berkeley Laborartory, Berke­ rocks, Report LA-7224-T, Los Alamos Scientific granitic section of borehole GPK1, Soultz-sous- ley, Calif., 1981. Laboratory, Los Alamos, N. Mex., 1978. forets, Report EEC EN-3G-0092-D, Institut fur West, F. G., P. R. Kintzinger, and W. D. Purtymun, Pratt, H. R., H. S. Swolfs, W. F. Brace, A D. Black, Geophysik, Ruhr-Universitat Bochum, 1990. Hydrologic testing, geothermal test hole no. 2, and J. W. Handin, Elastic and transport proper­ Snow, D. T., Rock fracture spacings, openings, and Report LA-6017-MS, Los Alamos Scientific Labo­ ties of an in situ jointed granite, Int. J. Rock porosities, J. Soil Mech. Foundations Div., 94, 73, ratory, Los Alamos, N. Mex., 1975. Mech. Min. Sci. and Geomech. Abstr., 14, 35, 1968. Wilson, C. R., P. A. Witherspoon, J. C. S. Long, R. 1977. van Pollen, H. and D. B. Hoover, Waste disposal M. Galbraith, A. O. DuBois, and M. J. McPher- Prickett, G. R., Properties of the Rocky Mountain and earthquakes at the Rocky Mountain arsenal, son, Large scale hydraulic conductivity measure­ arsenal disposal reservoir and their relation to Derby, Colo., J. Petrol. Techno!, 22, 983, 1970. ments in fractured granite, Int. J. Rock Mech. Derby earthquakes, Quarterly of the Colo. School Voegele, M., R. McCain, M. Gronseth, and H. Pratt, Min. Sci. & Geomech. Abstr., 20(6), 269, 1983. of Mines, 63(1), 73, 1968. In situ permeability measurements for an under­ Zoback, M. D., & Hickman, S., In situ study of the Rummel, F., Gesteinsphysikalische Daten des Falk- ground compressed air storage project, in Proc. physical mechanisms controlling induced seis- enberger Granits, Annual Report BMFT ET-41501 3rd Internal. Well-Testing Symposium: Well Test­ micity at Monticello Reservoir, S. Carolina, J. CECE-8(D), Institut far Geophysik, Ruhr-Univer- ing in Low Permeability Environments, Report Geophys. Res., 87(B8), 6959, 1982. sitat Bochum, 1979. LBL-12076, edited by T. W. Doe and W. J.

laria-sericite deposits and either acid-sulfate Magmatic Contributions to or porphyry deposits. It is also clear that the pressure-temperature history of hydrothermal systems beneath volcanoes is greatly influ­ Hydrothermal Systems enced by processes such as caldera subsid­ PAGES 233-234 ence, sector collapse, and hydrothermal eruptions that can cause rapid pressure de­ Although there is agreement that many contents of the melt. Chemical modeling creases. hydrothermal systems in the upper crust de­ shows that there are three types of saline rive their thermal energy from magmas, de­ fluids, based on their conditions of forma­ Major Unanswered Questions bate continues over the extent to which mag­ tion: early, moderately saline fluids from The following questions were identified mas contribute water, metals, and sulfur to high-pressure melts of low water content; as needing further research: hydrothermal systems. A multidisciplinary late, extremely saline fluids from low-pres­ • What are the solubilities of volatiles in seminar was held November 10-16, 1991, in sure melts, and—most commonly—ex­ magmas? The solubility and behavior of sul­ Ebino and Kagoshima, Japan, to establish tremely saline fluids and a separate gas fur-bearing phases (vapors, crystals, and im­ current understanding about this topic and phase produced by immiscibility at pres­ miscible melts) in silicate melts need to be to explore the major unanswered questions sures less than a few hundred MPa. determined systematically. Much additional and the most promising research directions. It is also known that the partitioning of information on mixed volatile solubilities is The thirty-eight participants were from Japan metals between melt and aqueous fluid is needed for realistic modeling of melts. (eighteen), the U.S. (thirteen), Canada and more strongly affected by pressure than tem­ New Zealand (two each), and England, the • How do metals partition between melts perature, with low pressure favoring the con­ Philippines, and Russia (one each). Disci­ and the magmatic fluids? A comprehensive centration of metals in the aqueous phase. plines represented were volcanology, experimental program is needed emphasiz­ Furthermore, the greatest interaction be­ geochemistry (volcanic-gas, water, isotopes, ing the role of sulfur and its speciation. experimental, and modeling), igneous petrol­ tween magmatic and meteoric fluids around Promising studies of metals in natural melt ogy, geothermal geology, economic geology, an intrusion appears to occur in a narrow inclusions need to be augmented. fluid-inclusion study, geophysics, and physi­ zone separating regions of hydrostatic pres­ • What are the thermodynamic properties cal modeling. sure (with brittle failure) from regions of of saline solutions over a wide spectrum of lithostatic pressure (with plastic failure) at temperatures, pressures, and C0 concentra­ The seminar was organized around five 2 350-400°C. major topics: the composition of fluids in tions? Data are restricted primarily to the 18 NaCl-H 0 system and are incomplete, espe­ equilibrium with magma, the processes of High-temperature steam of 8 0 = 2 fluid separation from magma and the nature +7±2%o and 8D = -25±10%o from active cially at high temperatures and low pres­ of hydrothermal systems enveloping mag­ island-arc fumaroles is most likely of direct sures. To interpret fluid-inclusion observa­ mas, the geometry and dynamics of fluid magmatic origin. This characteristic 8D tions, PVTX data are needed at 200-900°C, flow in magma/hydrothermal systems, the range is distinct from the commonly ac­ 10-200 MPa, and a range of fluid composi­ tions (including effects of KC1, CaCl , FeCl , signatures and importance of magmatic flu­ cepted "magmatic water box" (8D = -40 to 2 x NaCl, C0 , H S, S0 , CH , and N ). ids in active hydrothermal and volcanic sys­ -80%o). 2 2 2 4 2 tems, and the signatures and importance of Magmatic contributions to extinct sys­ • What are the compositions of mag­ magmatic fluids in extinct hydrothermal sys­ tems are more difficult to recognize. 8180 matic fluids in crustal environments? Empha­ tems. and 8D of alunite and phyllosilicates in acid- sis should be placed on micro-sampling methods for stable-isotope and gas composi­ What Do We Know? sulfate deposits converge on the composi­ tion of high-temperature fumarole steam. A tions in individual fluid inclusions. By definition, magmatic fluids are aque­ • What is the nature and origin of perme­ magmatic source of S02 and H2S can be de­ ous fluids in chemical, isotopic, and thermal duced from coexisting alunite and pyrite in ability in the marginal zones of magmas and equilibrium with igneous melt, regardless of some epithermal deposits. Magmatic fluids immediately adjacent to magmas? Rheologi- the ultimate origin of the components. At are indicated by 8180 and 8D compositions cal properties that govern flow and fracture depths up to a few km, H 0 is usually the 2 and cogenetic highly saline fluid inclusions of magma and rocks at 200-900°C and 50- major constituent, although the fluids can in early alteration minerals of porphyry-cop­ 300 MPa need to be determined. Expanded contain significant C0 , S0 , H S, NaCl, KC1, 2 2 2 per deposits. In some cases these fluids ap­ field studies are needed to determine the FeCl , CaCl , HC1, HF, and metals. Experi­ x 2 pear to have deposited Cu, but phyllic alter­ nature and origin of porosity and permeabil­ mental data suggest that the NaCl/HCl ratio ation associated with Cu mineralization in ity in marginal zones. of magmatic fluids decreases with decreas­ several well-studied North American deposits • What is the physical and chemical tran­ ing pressure, such as during ascent in a vol­ indicates a significant contribution from me­ sition from the high-temperature near-mag- cano. teoric waters. matic environment to the lower-temperature The salinity of fluids separating from a Porphyry-copper deposits may pass up­ hydrothermal systems? Relatively shallow magma is controlled by pressure, the degree ward into acid-sulfate deposits, but there drilling in.a confined volcano-hydrothermal of crystallization, and the initial water and CI appears to be little gradation between adu- system such as White Island in New Zealand

This page may be freely copied. Eos, Vol. 73, No. 21, May 26, 1992

Ebino Plateau area of Kirishima andesite volcano, southern Kyushu, /991). Shinmoedake crater and fumarole, further to the southeast, Japan, site of the Japan-u.s. Seminar on Magmatic Contributions to were the site of a 1959 phreatic eruption. Seismic tremor beneath Hydrothermal Systems. The Iwoyama fumaroles (middle) discharge this crater began during the seminar, followed by increased fu­ J75°C vapors with a small magmatic component (HCI and other marolic activity, and culminated 2 weeks later in mild ash eruption gases) diluted by a meteoric hydrothermal system (J. W. Hedenquist for several days. Demagnetization is now continuing. (Photo by Shu­ and M. Aoki, "Meteoric interaction with magmatic discharges in Ja­ kosha Printing Co., Ltd) [Original color image appears in the pan and the significance for mineralization," Geology, 19, 1041, back of this volume. J

shows particular promise for exploring this with adjacent systems of different types? phyry environment? These environments question. Most studies of hydrothermal systems, partic­ have been encountered at -3 km in four • What similarities or differences are ularly those of ore deposits, focus on the geothermal areas throughout the world, but there in the composition and volatile evolu­ central, strongly affected parts of the sys­ no quantitative information is available other tion of ore-forming and barren magmas? tems, neglecting the edges that may provide than approximate temperatures (>400°C) Comprehensive comparative studies of the important genetic constraints. and pressures (>24 MPa in excess of hydro­ magmatic and hydrothermal evolution of ore­ • What is the duration of the mineraliz­ static). A program is needed to determine bearing and barren porphyry intrusions are ing process? With the advent of precise iso­ the temperatures, fluid compositions, and needed, emphasizing fluid and glass inclu­ topic age-measurements on individual fluid the nature of the rock in the pressure-transi­ sions and paragenesis of primary and hydro­ inclusions, it is becoming possible to distin­ tion zone. thermal phases. • guish events that differ little in age, thus ad­ How does the interaction of magma • What are the mechanics, dynamics, with hydrothermal systems influence or trig­ dressing the question of the active life of and rates of formation of porphyry intru­ ger volcanic eruptions? Studies are needed hydrothermal systems. sions? Geologically constrained numerical to evaluate and amplify the suggestion that • What are the geologic factors that pro­ modeling is required, involving the possibly the anhydrite and high S02 in the products duce "telescoping" of ore deposits? Inte­ non-linear interactions of magma composi­ of Nevado del Ruiz and Pinatubo volcanoes grated studies should address the effects that tion and properties, pressure, stress, strain are related to the vaporization of a hydro­ abrupt events in shallow volcanic and geo­ release, and hydraulic fracturing. thermal system by magmatic intrusions. • Does the focusing of magmatic fluids thermal environments have on deep pres­ [om batholiths influence the size and style sures, with resultant changes in the exsolu­ Conclusions of ore and geothermal systems at higher lev­ tion of volatiles from magma and the els? Regional geological and geophysical distribution of metals between the melt and Investigations to date have produced a studies are needed of the igneous and tec­ the aqueous phase. general framework for the interaction of Ionic environments of large porphyry depos­ • Do the high-temperature and high-pres­ magma and hydrothermal systems. Some ns. sure environments that exist at depth in important advances can be made simply by • What do the edges of hydrothermal some active geothermal systems represent a broadening the communication and cooper­ systems look like and how do they merge transition to a potentially mineralized por- ation among disciplines and viewing this

This page rnav be freelv copied. Eos, Vol. 73, No. 21, May 26, 1992 complex topic from many perspectives. Fun­ spacecraft such as the Cosmic Background first hearing on May 6, Johnston probed dis­ damentally, however, understanding mag­ Explorer and the Infrared Astronomical Satel­ agreements among experts in the field of matic contributions to hydrothermal systems lite. A number of other Explorer missions are global climate change. While opinions var­ will require expanded experimental investi­ under development. The report describes ied among the four witnesses over the effect gations, numerical modeling, field studies, two new initiatives. The first is "Discovery," of human actions, all agreed with the assess and drilling. a series of inner solar system programs. An ment of the Intergovernmental Panel on Cli­ Principal sponsors of the meeting were example of a Discovery program is the Mars mate Change that global temperatures have the Japan Society for the Promotion of Sci­ Environmental Survey Pathfinder (MESUR). increased 0.3°-0.6°C over the past century. ence and the U.S. National Science Founda­ This mission would establish sixteen small Robert Watson, Chief of Atmospheric Chem­ tion, under the Japan-U.S. Cooperative Sci­ stations on Mars to study its meteorology, istry at NASA, added that concentrations of ence Program. Associate sponsors included internal seismic activity, and local surface greenhouse gases are increasing due to hu­ the Geological Survey of Japan, Kagoshima properties. Another Discovery program man activity, and current circulation models and Miyazaki Prefectures, the Kagoshima would be a Near-Earth Asteroid Rendezvous predict that this will result in more warming. University Research Center for the South Pa­ (NEAR) mission. The report envisions a total The scientists concurred that significant cific, the Metal Mining Agency of Japan, the mission cost of up to $150 million. uncertainties made policy decisions difficult. Tsukuba Expo 85 Fund, and the U.S. Geolog­ On May 8, NASA awarded initial mission Steven Schneider of the National Center for ical Survey. studies of MESUR to the Jet Propulsion Labo­ Atmospheric Research got no argument Extended abstracts by all attendees and ratory and NEAR to the Applied Physics Lab­ when he advocated a "prudent response." an expanded version of this report, which is oratory of Johns Hopkins University. The two He recommended first taking actions that are based on summaries of group discussions at missions are scheduled for launch in 1996 beneficial in any case, such as improving the seminar, will be published in mid-1992 and 1998, respectively. energy efficiency, and taking stronger action as Report 279 of the Geological Survey of The second category of initiatives is enti­ if further data warrants it. This "no-regrets" Japan, available outside North America for tled "Toward Other Planetary Systems," fo­ strategy is favored by the Bush Administra­ the cost of postage from Jeffrey Hedenquist, cusing on whether or not our solar system is tion. Michael MacCracken of Lawrence Liver- G.S.J., Higashi 1-1-3, Tsukuba 305, Japan, unique. Important in this effort, which would more National Laboratory added that "there's Fax 81-298-54-3533. Within North America, largely consist of ground-based observato­ no such thing as a free lunch; the public has obtain copies from Patrick Muffler, USGS, MS ries, is the construction of a second IO­ to realize" they can't have "a certain lifestyle 910, Menlo Park, CA 94205; fax 415-329-5203; meter telescope at the Keck Observatory in with no risk." e-mail pmuffler@mojave. wr.usgs.gov.—LJ. Hawaii. The cost of this program through The policy of the administration has been Patrick Muffler, US. Geological Survey; Jeffrey 1999 would be less than $100 million. to resist setting rigid emission reduction W. Hedenquist, Geological Survey of Japan; NASA has been working on the Small goals. None of the scientists felt that such Stephen E. Kesler, Department of Geological Planetary Projects Plan for more than a year, arbitrary goals would be particularly useful. Sciences, University of Michigan, Ann Arbor; and is requesting $10 million for fiscal year Pete Domenici (R-N.Mex.) recapitulated their and Eiji Izawa, Faculty of Engineering, Ky­ 1993 for this activity. The report states that advice: "I don't hear any of you saying we ushu University, Hakozaki 6-10-1, Higash- "NASA will continue to seek new candidate should fix targets and goals." iku, Fukuoka, 812, Japan small projects. Emphasis will be on develop­ On May 12, Johnston's committee heard ing additional Discovery missions and on the from various members of the administration study of scientifically focused, small mis­ involved in negotiating the Earth Summit sions to the outer planets. Outer planet con­ convention. The convention, as advocated by NASA's Small Planetary cepts will have to have strictly limited scien­ the Bush Administration, focuses on all Mission Plan Released tific objectives to meet small mission cost greenhouse gases, not just carbon dioxide. It criteria. These studies will involve academia does not, however, dictate specific reduction PAGE 234 and independent research institutions so that goals. Instead, according to Robert Rein- their interest and capabilities can continue stein, a Deputy Assistant Secretary at the De­ A ten-page report just submitted to Con­ to be appraised."—Richard M. Jones, Ameri­ partment of State, the agreement calls on gress outlines a new strategy for NASA plan­ can Institute of Physics industrialized countries to "take the lead in etary programs emphasizing small missions. limiting greenhouse gases" and providing If implemented, this plan would represent a information on the actions taken and their shift away from large "flagship" missions Earth Summit Science, results. It also provides for partnerships be­ that have characterized many programs of tween industrialized and developing nations NASA's Solar System Exploration Division. Policy Discussed for technology transfer and cooperation in research and monitoring. There are a number of reasons for this PAGES 234-235 shift in strategy. The current NASA appropria­ Department of Energy Acting Deputy Sec­ tions bill requires "a plan to stimulate and The United Nations Conference on Envi­ retary Linda Stuntz called the convention "an develop small planetary or other space sci­ ronment and Development, the "Earth Sum­ action-oriented package" that rejects arbi­ ence projects, emphasizing those which mit," convenes in Rio de Janeiro on June 3. trary, rigid time tables and "allows each na­ could be accomplished by the academic or President Bush has pledged to attend part of tion to pursue [reductions] without harm to research communities." Budgetary realities the 2-week conference. The highlight of the their economy." She stated that "no nation make it more difficult to fly large missions. summit will be the signing of an interna­ has set forth a plan to reduce emissions in There is also concern about a "significant tional framework convention to reduce emis­ the level of detail the U.S. has done" in its gap" in data from planetary missions be­ sions of greenhouse gases. The final ele­ National Energy Strategy. Stuntz testified that tween 1998 and 2004. ments of the agreement were negotiated in the NES was expected to hold greenhouse Under this plan, small planetary projects New York last week by representative of 143 gas emissions "near" 1990 levels through would have focused scientific objectives and countries. In anticipation of the Rio confer­ 2000, but not stabilize them exactly. Richard utilize a limited number of mature instru­ ence, the Senate Committee on Energy and Morganstern, Assistant Administrator for Pol­ ments, with little or no development of new Natural Resources held two standing-room- icy Planning and Evaluation at the Environ­ technology. University/industry partnerships only hearings, reviewing the scientific basis mental Protection Agency, added that a would be responsible for mission implemen­ for global warming due to greenhouse gases 7-11% reduction was expected from other­ tation over a period of less than 3 years, and discussing the details of the proposed wise projected emission levels. All the ad­ working within firm cost ceilings. The mis­ convention. ministration witnesses supported Johnston's sions would be riskier, although less would The committee's chairman is J. Bennett energy bill as an important step in the right be at stake. Johnston (D-La.), author of S2166, the Na­ direction, although Stuntz noted that the ad­ NASA has experience with projects of this tional Energy Security Act of 1992, which ministration also plans to take additional size, having launched sixty-six Explorer was recently passed by the Senate. At the actions.

This page may be freely copied. Vol. 73, No. 21, May 26, 1992

Ebino Plateau GreG of Kirishima andesite volcano, southern Kyushu, /991). Shinmoedake crater and fumarole, further 10 the southeast, Japan, site of the Japan·u.s. Seminar on Magmatic Contributions to were the site of a 1959 phreatic eruption. Seismic tremor beneath Hydrothermal Systems. The lwoyama fumaroles (middle) discharge this crater began during the seminar, followed by increased tu­ 175°C vapors with a small magmatic component (Hel and other marolic activity, and culminated 2 weeks later in mild ash eruption gases) diluted by a meteoric hydrothermal system (1. W. Hedenquist for several days. Demagnetization is now continuing. (Photo by Shu­ and M. Aoki, "Meteoric interaction with magmatic discharges in Ja­ kosha Printing Co., Ltd) pan and the significance for mineralization," Geology, 19, 1041,