Section Six





	GRANTEE: UNIVERSITY OF ALASKA Geophysical Institute Fairbanks, Alaska 99775-7320 GRANT: DE-FG06-86ER13530 TITLE: A Study of Solar Prominences and Magnetospheric Substorms PERSONS IN CHARGE: L. C. Lee (907-474-7410; Fax 907-474-7290; E-mail lclee@geewiz.gi.alaska.edu) and S. I. Akasofu



	Objectives: The objectives are to examine and understand the (1) development of preconditions for solar flares, (2) role of magnetic reconnection in the solar eruptive processes, and (3) formation of a very thin current sheet during the substorm growth phase. Project Description: This project deals with the formation of a thin current sheet and magnetic reconnection in the solar corona and in the geomagnetotail. These problems have relevance to formation and eruption of solar prominences and magnetospheric substorms. The methodology of this study encompasses mathematical analysis and computer simulations. Specifically, the following topics are addressed: (1) formation of a current layer in a solar magnetic arcade under foot-point shearing, (2) magnetic reconnection and subsequent change of field line topology in a magnetic arcade system, (3) stretching of the near-earth tail due to nonuniform convection, and (4) thinning of the near-earth tail current sheet due to entropy anti-diffusion instability. Results: In the ideal MHD evolution of a magnetic arcade, no instability or nonequilibrium is found for any amount of shear, but a current layer is found to develop and become longer and thinner in the later stage. Thus, it is inferred that a fully open field is an asymptotic state for an infinite shear. When resistivity is applied to a sheared arcade, magnetic reconnection can take place only above a critical amount of shear.		The reconnection characteristics in magnetic arcades are found to depend on spatial resistivity patterns. A fast reconnection with small shock angles can be achieved only when the resistivity is confined to a small volume. In this case, high speed reconnection outflows can tear the magnetic island into a pair. The fast-moving island system creates a fast shock or a steepened fast mode structure that resembles an observed CME frontal loop. In a nonuniform magnetospheric convection, the electrostatic field in the ionosphere causes advection of the entropy function in the flux function space. The consequential stretching of the near-earth magnetotail induces a dusk-dawn electric field across the plasma sheet, which compensates for the dawn-dusk electrostatic field there. This can explain why no appreciable electric field is observed in the near-earth plasma sheet in the substorm growth phase. In the earth's magnetotail, the plasma pressure and the entropy per flux tube have opposite slopes in the flux function space. Thus, particle diffusion across the field line implies anti-diffusion of the entropy function. This results in an increase of the slope of both the pressure and the entropy, which leads to a self-accelerating process of current sheet thinning. This "entropy anti-diffusion instability" is proposed to explain the dipolarization of magnetic fields and the onset of magnetic reconnection in the near-earth tail.





		GRANTEE: AMERICAN GEOLOGICAL INSTITUTE 4220 King Street Alexandria, Virginia 22302-1502 GRANT: DE-FG05-94 ER 75979 TITLE: U.S.-Russian Geoscience Student Exchange Program PERSON IN CHARGE: Edward M. Davin (703-379-2480; Fax 703-379-7563)


		Objectives: The objective is to support administration and operation of the U.S.- Russian Geoscience Student Exchange Program. Results: On August 10, 1996, seven Russian students will complete their one-year training program and return to Moscow where they will enter careers in petroleum exploration and development with U.S. international oil companies or their Russian counterparts. This is the third class to complete the program, bringing the total to 22 students. On August 18th, seven new Russian students are scheduled to arrive in Houston to begin their one-year training program. This group of students was selected from applicants who had completed the five-year course in geoscience at Russian universities and who planned to make a career in petroleum exploration and development. Each student scored 500 or better on TOEFL (Test of English as a Foreign Language). Final selection was based on results of personal interviews with U.S. faculty advisors from the two participating uni		versities: Texas A&M University and the University of Texas-Austin. In Houston, the students will receive a technical orientation program in the offices of the oil company sponsors (i.e., one day each at Amoco, at Exxon, at Conoco, and at Texaco). Scheduling does not permit travel to the DOE/BDM facility in Bartlesville, OK. The program covers the range of knowledge and skills required to evaluate oil/gas prospects and consists of lectures and laboratory demonstrations. Each company emphasizes that geoscience skills are basic to building models of risk analysis. This orientation was requested by the faculty advisors to guide the students in their course selections. On August 23, the students will arrive at their assigned university for two semesters of academic training. The last phase of the program is a ten-week internship in the offices of the oil company sponsors, Houston, and at DOE/BDM, Bartlesville, where they have hands-on experience with teams of geoscientists working on oil prospects in Russia.





	GRANTEE: AMERICAN MUSEUM OF NATURAL HISTORY Department of Earth and Planetary Sciences New York, New York 10024 GRANT: DE-FG02-92ER14265 TITLE: The Effect of Carbon on the Mechanical and Electrical Properties of Rocks PERSONS IN CHARGE: E. A. Mathez (212-769-5379; Fax 212-769-5339; E-mail mathez@amnh.org), A. G. Duba (Lawrence Livermore National Laboratory), and T. J. Shankland (Los Alamos National Laboratory)


	Objectives: Objectives are to understand how carbon films form on crack surfaces in rocks, determine how these films influence electrical conductivity, and explore the effect of growth of carbon in rocks on fracture propagation. Project Description: Experiments will be conducted to test two hypotheses. (1) As fractures open in the time leading up to failure along a fault, carbon is deposited as a continuous film on the new mineral surfaces and electrical conductivity increases. Subsequent changes in electrical conductivity occur as the connectivity of the initial fracture network is altered by continued deformation. (2) The rate of crack growth may be enhanced by the catalytic growth of carbons. Two sets of experiments will be conducted. In the first set we shall determine if carbon is deposited on new crack surfaces during rock deformation and its effect on electrical conductivity. The latter will be monitored as a rock approaches failure in the presence of a CO-CO₂-CH₄ gas mixture. In the second set of experiments acoustic emission will be monitored as the rocks are loaded to failure in an inert carbon-free atmosphere of N₂, and then identical experiments will be conducted in CO-CO₂-CH₄ gas mixtures. Results: The experimental technique to fracture rocks in a controlled C-O-H atmosphere at P = 100 MPa and T = 400°C and to simultaneously monitor resistance has been developed. The first experiments have been conducted on a carbon-free sandstone containing small quantities of Fe-oxide in the cement in an atmo		sphere of 5% CO--95%CO₂. Resistance exhibits a progressive increase with time and increased load. Sudden decreases in resistance are associated with micro-fracture events, as monitored by small changes in the load, and at failure large decreases in resistance are observed. Samples from several of the first experiments have been examined by X-ray photoelectron spectroscopy, which provides information on carbon concentration within several monolayers of the analytical surface. It has been found that samples run in CO-bearing atmospheres contain more carbon on the surfaces exposed by fracture than control samples run in Ar. At face value, the experiments support the first hypothesis listed above. The relations among electrical conductivity and graphite content, metamorphic grade, and fluid:rock interaction have been investigated for a suite of regionally metamorphosed graphitic carbonate rocks from the Waits River formation, Vermont. Graphitization was complete by the lowest grade of metamorphism (450°C, 450 MPa). Low- and medium-grade rocks contain 4400 and 2800 ppm of reduced carbon, respectively, but graphite does not form interconnected networks. High-grade rocks are almost completely devoid of graphite. The ¹³C and ¹⁸O values for carbonate and graphite are 4‰ lower in the high-grade compared to lower-grade rocks. The shift in isotope composition and graphite depletion of the high-grade rocks was caused by influxes of large quantities of magmatic water. Laboratory measurements of electrical conductivity of fluid-



	saturated rocks containing >7000 ppm carbon are almost an order of magnitude higher than expected from their fluid content alone. Graphite does not form an		interconnected network in these rocks, yet it combines with the saline fluids to significantly increase electrical conductivities.





	GRANTEE: ARIZONA STATE UNIVERSITY Center for Solid State Science Box 871704 Tempe, Arizona 85287-1704 GRANT: DE-FG03-94ER14414 TITLE: A Microanalytical (SIMS) Study of the Trace Element and Isotopic Geochemistry of Diagenetic Silicates PERSONS IN CHARGE: Richard L. Hervig (602-965-3107; Fax 602-965-9004; E-mail richard.hervig@asu.edu) and Lynda Williams (602-965-5081; Fax 602-965-8102; E-mail lynda.williams@asu.edu)



	Objectives: Microanalyses of oxygen and boron isotopes in authigenic silicates are being obtained to determine their variation in hydrocarbon-producing sedimentary basins. These analyses can be used to constrain mass transport processes occurring during diagenesis and hydrocarbon migration. Project Description: The primary goals of the investigation are to determine whether quartz overgrowths or other authigenic minerals are zoned with respect to their O isotopes and discover the relation between the isotopic composition of sandstone minerals and provenance and burial diagenesis. The O-isotope microanalyses obtained guide the interpretation of the timing (during burial) of reservoir cementation and help shape models to explain the volumes and chemistry of paleofluids that influenced the reservoirs' burial history. Understanding the sources of mineral components and mass transfer processes will aid the understanding of fluid flow and hydrocarbon migration in sedimentary basins. This technique, combined with B-isotope and conventional SIMS trace element microanalyses, has been applied to diagenetic minerals in oil-producing wells from the Western Canadian Sedimentary Basin (WCSB), the Texas Gulf of Mexico Sedimentary Basin (GMSB), and the North Sea Sedimentary Basin (NSSB).		Results: The oxygen isotope microanalyses of hundreds of quartz grains from these three reservoirs (and new boron isotope analyses of clays) are summarized below: Provenance. In the WCSB and GMSB, detrital quartz varied only slightly from one value. The NSSB samples showed a bimodal variation suggesting metamorphic (¹⁸O ~ 16 per mil) and igneous (¹⁸O ~ 12 per mil) sources. Variability of authigenic quartz. Authigenic quartz is not mono-isotopic. The range of values was similar in all basins (~15‰), but they show different absolute values in ¹⁸O; WCSB: 20-34‰ per mil, GCSB: 22-35‰ per mil, NSSB: 13-28‰ per mil. This suggests that all basins experience quartz precipitation over a similar temperature range while the evolution of pore fluid ¹⁸O varies. Temperatures of precipitation. In all basins, high values of ¹⁸O were observed on texturally-defined "early" quartz, indicating initial precipitation temperatures &;40°C. In these basins, the sediments reside at such temperatures for more than 100 million years, so it may not be surprising to observe precipitation occurring at low temperature. Boron isotopes. Study of natural and synthetic clay minerals suggests that B-isotopes change by <2 per mil during the conversion of smectite to illite. Thus, authigenic clays record fluid conditions similar to those at the time of their initial formation.





	GRANTEE: ARIZONA STATE UNIVERSITY Departments of Geology and Chemistry/Biochemistry Box 871404 Tempe, Arizona 85287-1404 GRANT: DE-FG03-95ER14533 TITLE: Reaction Mechanisms of Clay Minerals and Organic Diagenesis: An HRTEM/AEM Study PERSONS IN CHARGE: Peter R. Buseck (602-965-3945; Fax 602-965-8102; E-mail pbuseck@asu.edu) and Huifang Xu


	Objectives: Objectives are to gain an improved understanding of the microstructures and reaction mechanisms in the following reaction processes during diagenesis: (1) berthierine-to-chamosite reaction and polytype transformation in chamosite, (2) smectite illitization and mechanism for the formation of periodically interstratified illite/smectite (I/S), and (3) textural and structural evolution of the organic matter vitrinite. Project Description: We will study clay and detrital minerals as well as organic matter in sequences of Upper Cretaceous and Lower Tertiary clastic rocks from the southern Rocky Mountains using a range of analytical and structural techniques. We are especially interested in (1) the berthierine-to-chamosite reaction, (2) smectite illitization, and (3) organic diagenesis. This research will lead to an improved understanding of the states of I/S, C/B, organic matter, and detrital minerals in diagenetic environments. The results will provide important information for determinations of reaction mechanisms and establishment of kinetic models that permit one to predict the extent to which the formation of certain clay minerals occurs at certain depths, temperatures, and times. Such fundamental data will help with evaluations of basinal diagenetic patterns in hydrocarbon exploration.		Results: The mechanisms for the formation of interstratified I/S and the smectite-to-illite reaction have been controversial, and many results are ambiguous because standard XRD and chemical analyses of clay fractions only provide average characteristics. We recently developed a method for characterizing illite and smectite layers in ambient air at room temperature by using scanning force microscopy (SFM). Our preliminary results show this method can be used to distinguish illite and smectite layers based on steps that show their 10- and 15-Å basal thicknesses. Since the SFM images provide three-dimensional information, they also show I/S morphology and hexagonal pits (similar to etch pits) on some surfaces. Also, the orientation relationship between the layers with hexagonal pits can be identified. TEM results of the I/S minerals show the same morphology as is revealed by SFM. We believe SFM is a potentially powerful method for studying interstratified I/S crystals since it can give three-dimensional information. The method avoids artifacts from dehydration of smectite layers in I/S samples. We also investigated clay-like minerals in intergranular pores and oölitic grains in sandstones. TEM images show they are coherently intergrown along (001) and consist of dominant chamosite (14 Å) and lesser berthierine (7 Å). Based on their chemical and textural features, we hypothesize that they are precipitation products of pore fluids.





	GRANTEE: BOSTON UNIVERSITY Center for Computational Science and Department of Physics Cambridge, Massachusetts GRANT: DE-FG02-95ER14498 TITLE: Interpretation of Geodetic Crustal Strains Using Massively Parallel Supercomputer Simulations of Nonlinear Dynamical Models PERSONS IN CHARGE: William Klein (617-353-2188; Fax 617-353-9393; E-mail klein@buphyc.bu.edu) and J. B. Rundle (CIRES and Department of Geosciences, University of Colorado)



	Objectives: The underlying objective of this basic research is to understand the fundamental physical processes giving rise to the hazards and risks a variety of critical energy facilities face from several kinds of tectonic instabilities, notably earthquakes, volcanic eruptions, and landslides, in concert with the International Decade of Natural Disaster Reduction. Project Description: A variety of nonlinear dynamical processes operate within the complex earth system and are observed to display the signatures of many of the same phenomena as, for example, neural networks, driven foams, and magnetic depinning in high temperature superconductors. In particular, scaling (fractal distributions), nonlinear thresholds, and spatial interactions are all features possessed by these systems. Signatures of these processes include the appearance of scaling (geometric and dynamical fractal distributions), global and local self-organization, intermittency (transitions from "laminar" to "turbulent" behavior), chaos, and the emergence of coherent space-time structures. The geodynamical effects observed in earthquake systems, particularly crustal straining, dynamical segmentation, and intermittent seismicity, are being modeled in massively parallel simulations in an effort to clarify the origins of these phenomena. Simulations and theoretical investigations are particularly aimed at quantifying the limits of predictability for disasters that occur within the earth system. We are currently developing both the simulation methods for earthquake models and the statistical mechanical analy		sis techniques needed to understand and interpret the results. From these simulations, we will then predict geodetic and other deformations associated with impending earthquakes to be tested against global positioning system, synthetic aperature radar, and other field data. Results: During this second year of the project, we have been led by physical considerations to examine mean field models for the dynamics of driven systems with thresholds. Such systems have been used to successfully model earthquakes, neural networks, driven foams, and magnetic depinning transitions in superconductors. In a variety of results, we found that (1) these systems have Boltzmann energy fluctuations, (2) a spatial-temporal coarse graining procedure can be defined that leads to a well-defined Ito-Langevin equation for the mean field dynamics, and (3) a new class of models called "Traveling Density Wave" models can be constructed that have a Lyapunov functional and are governed by the same kind of Ito-Langevin equations. The significance of this work is that these scientifically and technologically important classes of systems can be understood using statistical field theoretic tools developed over the past few decades for analyzing equilibrium systems. Thus we have shown that meanfield threshold systems can be mapped into systems that have appealing and elegantly simple symmetries, scaling properties, and dynamical patterns. These systems are also subject to both first and second order "phase" transitions in the dynamical variables.





		GRANTEE: BROWN UNIVERSITY Department of Geological Sciences Providence, Rhode Island 02912 GRANT: DE-FG02-90ER14144 TITLE: Diffusional Transport and Fluid Connectivity in Mineral Aggregates PERSONS IN CHARGE: R. A. Yund and J. R. Farver (401-863-1931; Fax 401-863-2058; E-mail ray@gech031.geo.brown.edu)



		Objectives: The objective of this study is to experimentally determine bulk diffusional transport rates of oxygen (as molecular water) and selected geologically and environmentally important ion species in natural and hot-pressed single and polyphase aggregates of common mineralogies over a range of temperatures, pressures, and coexisting fluid compositions. In addition, the connectivity of coexisting fluids in these aggregates is evaluated from the bulk diffusivity measurements. The results provide much needed data on the nature of grain boundaries in rocks and the rates of transport of chemical components through rocks. Applications of these data include evaluating the retentiveness of different geological media for the isolation and confinement of nuclear and chemical waste, modeling the migration of hydrocarbons through different rock types to refine exploration and development strategies for more efficient oil and natural gas recovery, and determining patterns of circulation of hydrothermal meteoric water and associated ore-body deposition and geothermal energy systems. Project Description: Bulk diffusional transport rates are determined in natural and hot-pressed aggregates of common mineralogies either "as is" or after textural equilibration with fluids common to natural environments (H₂O±CO₂±NaCl fluids). The transport rates are determined from profiles of chemical or isotopic tracers measured using an ion microprobe (SIMS). The bulk diffusivities are correlated with the physical nature of the grain boundaries and sample textures that are characterized using transmission and scanning electron microscopy (TEM) and (SEM).		Results: Previous workers have suggested that diffusional transport rates are significantly greater in rocks containing micas or other sheet silicates. To test this idea, a series of experiments has been initiated to determine diffusional transport rates of oxygen and several important cations (K, Sr, and Ba) in a natural ultramylonite sample. The sample is fine-grained (<10 mm) and is composed of ~15% biotite, ~25% quartz, ~60% feldspars, plus minor oxides. The mica grains define a strong foliation. The experimental charges were prepared using sawn and polished pieces of ultramylonite oriented relative to the foliation. Samples were weld-sealed in a thick-walled Au tube along with a weld-sealed thin-walled Pt tube containing ¹⁸O-enriched water ±⁴¹K and ¹³⁴Ba. Diffusion experiments were run at 350°-550°C and 100 MPa pressure under hydrothermal conditions. The samples were pre-annealed at the temperature and pressure of the diffusion anneals for at least one week in order to allow any microcracks that may have formed during run-up to heal and to equilibrate the grain boundaries. The tracer(s) was then introduced by slowly decreasing the pressure, at constant temperature, until the Pt tube ruptured (typically to ~60 MPa). TEM examination of samples before and after the diffusion experiments shows no apparent change in the microstructures. The complex mineralogy of the ultramylonite sample greatly complicates the determination of diffusion rates for the cations; however, the bulk diffusion rates obtained for oxygen are similar to those obtained in monomineralic quartz aggregates pre-annealed in 6M NaCl to produce an interconnected fluid distribution.



	The rates are 4-6 orders of magnitude greater than oxygen grain boundary diffusion in quartz and feldspar aggregates with unconnected fluid distributions, and the activation energy obtained is similar to water self-diffusion in water (25-30 kJ/mol) and significantly lower than activation energies for oxygen grain boundary diffusion in quartz and feldspar aggregates (80-110 kJ/mol). The rapid oxygen bulk diffusional transport rates measured in the ultramylonite indicate the presence of an interconnected fluid. The TEM observations show no evidence for interconnected grain-edge channels (as were seen in the monomineralic quartz aggregates pre-annealed in 6M NaCl), suggesting that the fluid is distributed along mica-mica and/or mica-second phase boundaries. If aqueous fluids wet mica		boundaries, bulk diffusional transport rates would be greatly increased in mica-bearing lithologies. In addition, oxygen grain boundary diffusion rates have been determined in natural (Solnhofen limestone) and hot-pressed calcite aggregates. The experiments were done at 350°-500°C and 100 MPa pressure under hydrothermal conditions. There is no difference in the measured oxygen grain boundary diffusion rates between the natural sample and the hot-pressed aggregates. The D' values are similar to oxygen grain boundary diffusion rates measured in feldspar aggregates with unconnected fluid distributions and yield a similar activation energy of ~110 kJ/mol. Consistent with the measured D' values, TEM observations show no evidence for an interconnected fluid distribution in these calcite samples.