Basaltic rocks have been reacted with synthetic groundwater in closed-system, Dickson-type rocking autoclaves for periods of up to 5,000 hours. The experiments were carried out isothermally at 100°, 200°, and 300° C, 300 bars, and an initial water/rock mass ratio of 10. These conditions were intended to simulate those present in active geothermal systems. Fluid compositions changed rapidly during the early stages of the experiments. In the long-term, however, most species approached steady-­state values. At that stage, temperature appears to be the most important factor controlling fluid composition; the effect of rock type and starting fluid composition were far less significant. Comparison of long-term, stabilized fluid compositions with those produced in other dilute-water/whole-rock experiments (basaltic and non-basaltic) shows that experiments conducted at the same temperature attain similar overall fluid chemistries. Such behavior may reflect an approach to equilibrium of these fluids with thermochemically-similar alteration mineral assemblages. Stable fluid chemistries produced in these and other dilute­-water/whole-rock experiments (80 °-300 ° C) were then compared with reservoir data from several geothermal fields. The comparisons show that experiments of this type can reproduce many properties of geothermal reservoir fluids. Like geothermal fluids, compositional parameters (pH, cation/proton ratios, cation/cation ratios, and neutral species concentrations) for species in experimentally derived fluids are temperature dependent but are relatively independent of rock, water, and water/rock mass ratio. At lower temperatures (less than or equal to 250° C), many of these experimental parameter-temperature trends agree with geothermal trends. However, at higher temperatures ( greater than or equal to 250° C), the geothermal fluids have calculated high-temperature pH values 1 to 2 pH units lower than do the experimentally-derived fluids. This produces a consistent offset between values of experimental and natural cation/proton activity ratios. Possible causes for the offsets include: pervasive metastable mineral formation in experiments; and absence, in experiments, of the equivalent of a magmatic or metamorphic gas input. Results from modified water/rock experiments indicate that, while metastability may be a partial cause for the offsets, geothermal fluid parameters can be duplicated by addition of CO2. Furthermore, maintenance of high /CO2, low pH conditions required a CO2 flux. Magmatic gas flux is not always considered in chemical models of geothermal systems and its requirement in the experiments may indicate that E CO2 should be taken as an independent variable. Finally, comparable offsets could also be caused by the addition of exotic co2 or other acid gases during upflow or sampling of wet steam discharges. Field influences such as these would give rise to lower than actual reservoir pH's. Thus the offsets could indicate that some geothermal fluid pH's are more basic than commonly calculated and closer to those attained in water/rock experiments. Water/rock experiments are capable of simulating many of the chemical features of geothermal reservoir fluids but interpretation of experimental data is not straightforward. The closed-system and relatively short-term nature of the experiments must be considered when making comparisons with natural phenomena. Of equal importance is a clear understanding of the natural phenomena being modeled. / Earth and Environmental Science / Accompanied by two .pdf files: 1) Kacandes-Supplemental1-1989.pdf 2) Kacandes-Supplemental2-1989.pdf

The North Branch of the Neshaminy Creek Watershed is located near Doylestown in Bucks County, Pennsylvania. As has happened in many other suburbs of Philadelphia, the development of the North Branch Watershed has increased the demand on its water resources. This hydrogeologic study evaluates the Lockatong Formation's geologic control upon the hydrology of this watershed. Hydrogeologic information for this study was collected from March 1986 to May 1987. Investigations conducted during this study include geologic field observations of bedrock, a fracture trace analysis, a morphometric analysis of the North Branch stream network, establishment of a stream gauging network, establishment of a monitoring well network, measurement of Lake stage, establishment of a rating curve for a weir measuring the surface water outflow from the watershed, a pump test, monitoring the well recoveries of newly drilled wells, logging well drilling, an analysis of surface and groundwater quality and the formulation of a water budget. Ninety (90) percent of the North Branch watershed is underlain by the Lockatong Formation. The Lockatong Formation produces the primary geologic control of North Branch hydrology. This study proposes that the Lockatong Formation in the North Branch watershed has produced leaky confined groundwater conditions. Within this leaky confined groundwater system it has been suggested that the tilted Lockatong shale beds act as semi-confined aquifers transmitting groundwater coplanar to the Lockatong Formation bedding. Vertical groundwater leakage within this semi-confined system is allowed by sets of vertical fractures observed to exist within the Lockatong. Within this model of groundwater flow vertical fractures and shales not only provide means of transmitting groundwater, but also provide conduits for accepting groundwater recharge and discharging baseflow into streams. / Earth and Environmental Science

The once predominately rural and agricultural Pine Run drainage basin, located near Doylestown in Central Bucks County, Pennsylvania, is experiencing urbanization at an accelerating rate. In this study geologic, hydrologic, and water quality data were collected, between March 1987 and May 1988, and used to examine the hydrogeology of the Pine Run Basin. Approximately 93% of the basin is underlain by the Stockton Formation which consists of a generally fining-­upward sequence of arkosic sandstone and conglomerate, siltstone, and shale. The few outcrops display lensing and interbedding between lithologies. The Lockatong Formation which is composed of a red-brown or blue-gray siltstone, shale, and argillite underlies approximately 7% of the basin. The general strike of the bedding is S55°W and the average dip is 12° toward the northwest. A diabase dike which has a general northeast-southwest trend cuts the upper shale member of the Stockton Formation and the Lockatong Formation. The arkose and well-cemented siltstone contain near vertical joint sets which contribute to the porosity and permeability of the rock. Pumping tests conducted at a well field on the north shore of the Pine Run Reservoir indicate the presence of a recharge boundary and suggest that induced recharge had occurred. Transmissivity values were calculated to be between 1872 gpd/ft. and 5955 gpd/ft. Storativity values were found to be between 3.5e-04 and 6.4e-05. The range of transmissivity and storativity values is due to the lithologic heterogeneity of the Stockton Formation. Arkose was the predominant water producer, but some siltstone units also produced an appreciable amount. Stream discharge was measured at four gaging stations and the groundwater storage changes were measured at ten wells over the study period. A hydrologic budget was constructed, using hydrologic and climatic data, in order to calculate recharge rates. The annual basin recharge rate was approximately 216,000 gpd/sq. mile which is low and reflects the below normal precipitation and the timing of the precipitation. The basin experienced its highest recharge rate in February (1.6e06 gpd/sq. mile) and its greatest storage loss in August (-1.7e06 gpd/sq. mile). During the growing season the upper subbasin had the highest baseflow/sq. mile while during the dormant season the subbasin containing the reservoir had the highest baseflow/sq. mile. This reservoir appears to act as an artificial recharge basin during the dormant season. The mean stream water temperature was found to be 14.34°C, ranging from 0° to 27.2°C. The mean pH of the stream water was 7.1 and the mean alkalinity was 26.81 ppm of bicarbonate. The specific conductance of the stream water was highest during the dormant season, with a mean specific conductance of 114.85 micromhos/cm, and lowest during the growing season, with a mean specific conductance of 104.05 micromhos/cm. These results are opposite to what was expected. The specific conductance ranged from 158.5 to 79 micromhos/cm. An anthropogenic cause is suspected for this behavior but a geologic origin cannot be dismissed. The functional relationship between stream discharge and specific conductance is best described by a log-log model. The mean groundwater temperature was found to be 11.96°C and ranged from 14.2° to 9.7°C. The specific conductance measured at two wells, 125 feet apart, had mean values 130.7 and 138.05 micromhos/cm. One well experienced a maximum of 183 micromhos/cm in November while the other reached a maximum of 180 micromhos/cm in July. Minimum values of 97.5 and 102 micromhos/cm were attained in March and January, respectively, for the same two wells. These variations illustrate the heterogeneity in the geochemistry of the Stockton Formation. The hydrogeology data suggests that the geology of the Pine Run Basin is conducive to artificial recharge either by focusing storm runoff into recharge basins or by pumping groundwater in order to induce recharge. Additionally both hydrogeologic and water quality data indicate the heterogenous nature of the aquifer within the Pine Run drainage basin. / Earth and Environmental Science

Holocrystelline Conway granite, and 95X glass Bannock Rhyolite Tuff were reacted with 3.4x10·3M NaCl solution in Dickson rocking autoclave experiments conducted at 300°C. Granite and tuff experiment data were compared against similar basalt data to determine the effects of rock type (granite, glassy tuff, and 10·40X glass Basalt) and crystallinity in containing high-level nuclear waste. These data were evaluated to determine the degree to which short-term autoclave data correspond with the long-term chemistry of geothermal solutions. Redox comparisons of 300°C autoclave solutions indicate that the stable log fO2 produced by reactions with rhyolitic glass are 3-5 units more oxidizing than those with granite or basalts. More oxidized redox potential may result in higher waste container corrosion rates and solubility of UO2 for spent fuel rods, at a tuff repository site (i.e., Yucca Mountain, Nevada). The redox buffering capacity (based on FeO content) is also lowest for the glassy tuff, followed by granite and basalts, respectively. The exhaustion of highly soluble rhyolitic glass by oxidizing repository solutions may result in the more rapid acceleration of container corrosion· and U-complex release rates at a tuff repository (compared to granite and basalt). In these tuff and granite experiments Fe-Mg poor, Al-rich dioctahedral beidellitic smectites were formed. In comparison Fe·Mg rich, Al-poor trioctahedral smectite (saponite) was formed in 300°c basalt autoclave solutions. The precipitation of beidellitic smectites in the tuff and granite solutions resulted in comparatively acidic solutions (compared to basalt). For tuff and granite, lower repository solution pH may result in comparatively higher container corrosion rates, and greater solubility for UO2 in spent fuel rods. The illite/smectite mass ratio is higher for the secondary clay minerals removed from the tuff and granite experiments (compared to basalt). The formation of comparatively larger amounts of sorptive smectites in a basalt repository should result in comparatively lower radionuclide mobility (compared to tuff end granite). Lesser amounts of secondary minerals were formed in the granite experiments. The formation of less secondary minerals in granite repository solutions would result in comparatively higher radionuclide mobility at such a site (compared to basalt and tuff). High concentrations of Fin glass-influenced tuff repository solutions may result in higher solubility of uo2 for spent fuel rods. These geochemical criteria suggest that basalt may be the most suitable of the three repository host rock types compared (followed by granite and tuff, respectively). Experimental solution geothermometer, cation/proton mass ratio, and secondary mineral data from our high SiO2-rock:water experiments (holocrystalline granite and 95X-glass tuff), Temple basalt (10-40X glass) experiments and geothermal fields, when compared indicate that the granite autoclave solution came closest to emulating long-­term geothermal fluid chemistry, followed by the basalt and tuff solutions, respectively. These data indicate that the time interval necessary for short-term autoclave experiments to predict long-term geothermal fluid chemistry is a function of glass content. Natural geothermal field data is considered to be useful in predicting the long-term chemistry of high-level nuclear waste repository solutions. Our results indicate that rock crystallinity should be considered when selecting geothermal analog data for such purposes. / Earth and Environmental Science

The study area is located at Snyder and Oliver Hills, Minerva, southeastern Adirondacks in New York State. The geologic setting of the study area is just south of the Anorthosite Suite of the Adirondack Massif. The rocks from the study area are granitic gneiss and amphibolite that were affected by high temperature metamorphism and deformation. The grade of metamorphism is interpreted from the mineral assemblage as relatively high P[H2O] granulite fades metamorphism. High temperature deformation is inferred since rock-forming minerals such as quartz, feldspar and calcite show microstructures related to plastic deformation. Strong and consistent rock fabrics are also found. Subhorizontal foliations are defined by compositional layering of mafic and felsic minerals. Subhorizontal east­west-trending lineations are defined by quartz ribbons and preferred orientation of mafic minerals. These conditions suggest subhorizontal ductile shear zone deformation in this area with the shear sense of hanging wall to the east or west. To determine the shear sense, c-axis orientation from the quartz ribbon and grain shape orientation were measured. The pattern of the structural elements from these analyses is close to being symmetric rather than asymmetric, although the hanging wall to the west sense is slightly dominant. However, at an outcrop near the lithologic contact between the granitic gneiss and the amphibolite, a dragging fold of amphibolite is found. The shear sense from this outcrop is clearly hanging wall to the west. The hanging wall to the west shear sense and the symmetric pattern from the structural elements may suggest a close-to-coaxial but non-coaxial deformation or very large strain accumulation in this area. Plastic deformation microstructures from the rock-forming minerals were carefully observed, since certain temperature conditions are required to form such textures. Microstructures found in this study include formation of quartz ribbons and quartz c-axis preferred orientation by basal <a> slip in quartz, feldspar subgrain boundaries by dislocation gliding, possibly cataclastic flow of feldspar grains, and deformation twins in calcite. The temperature conditions for these microstructures are plotted onto the regional cooling curve. These results may suggest that the deformation in this area lasted for a long period of time over a wide range of temperature conditions, although the nature of deformation, whether continuous or punctuated, is not exactly known. Regionally, this study area is very highly deformed and not much literature is yet available in the areas adjacent to the study area. Hence it is hoped that the results of this study will aid as data base to future southern Adirondack studies. / Earth and Environmental Science

A three-dimensional finite-difference groundwater flow model was used to evaluate hydrogeologic data for 9.9 square miles of Pine Run Basin, Bucks County, Pennsylvania. The steady-state model was calibrated using February 1988 field data including groundwater, stream, and reservoir elevations, groundwater recharge, baseflow measurements, stream seepage analyses, and aquifer tests. Pine Run Basin is underlain by Triassic continental rocks, chiefly arkosic sandstones, siltstones, and shales of the heterogeneous Stockton Formation. The Stockton Aquifer was modeled using three layers which parallel the basin's topography and represent a shallow unconfined aquifer and two underlying leaky-­confined aquifers. The hydraulic conductivity of the Stockton Aquifer is anisotropic with its primary axis parallel to the northeast striking beds. The model utilized a three-dimensional anisotropy ratio of 1.0: 0.5: 0.1 representing hydraulic conductivities parallel to strike, up and down dip, and perpendicular to bedding. The anisotropy ratios coincide well with the stratigraphic setting of a middle member comprised of braided stream channel deposits of arkosic sandstones paralleling the strike of the formation, and an upper member consisting of red shale overbank deposits fining upward into lake-bed deposits. Hydraulic conductivities of 10, 5, 1 and 0.8, 0.4, 0.08 ft/d were used for the middle and upper members, respectively. Model results indicate the unconfined aquifer contributes the majority of baseflow to Pine Run. Groundwater divides coincide with the surface water divides except for the dip slope boundary where underflow may occur. The model was most sensitive to changes in hydraulic conductivity and areal recharge. / Earth and Environmental Science

A hierarchic cyclic pattern consistent with the Milankovitch model of orbital forcing characterizes the Upper Silurian Tonoloway Formation. At three localities in Pennsylvania and Maryland, the Tonoloway Formation is divisible into three Third Order sequences (2 million years duration). The first of these Third Order sequences (44 to 53 meters thick) is an incomplete, shallowing-upward cycle divisible into four shallowing-­upward Fourth Order sequences (400 ky eccentricity), averaging 13.2 meters thick defined by the most open facies in the first Fifth Order cycle and the most restricted in the last. Each Fourth Order cycle is divisible into four shallowing-upward Fifth Order sequences (100 ky eccentricity), averaging 3.3 meters thick, defined by the most open facies in the second Sixth Order cycle and the most restricted in the last. Each Fifth Order sequence is divisible into three to five sharply bounded, shallowing-upward, Sixth Order cycles (20 ky precessional) containing a sharp, sea-level-fall surface separating its upper shallower facies from its lower deeper facies. These asymmetric cyclic patterns can be correlated between Mount Union, Pennsylvania and Pinto, Maryland, a distance of 150 kilometers. The similarity of symmetry and thickness of all cycles over this distance indicates that the principal cause of the stratigraphic fabric of the Tonoloway Formation was eustacy driven by multiple cycles of orbital perturbation. The greater overall thickness of the interval in Pennsylvania indicates greater rates of subsidence in this area. / Earth and Environmental Science

Pumping of 3.01 x 108 gallons per square mile (gal/mi2) of groundwater from a carbonate aquifer near New Hope, Pa. changed the hydrogeologic system of a small watershed by inducing groundwater inflow and accelerating ground subsidence. A deficit in the annual water budget indicated that 1. 7 x 108 gal/mi2 of groundwater flowed into the Primrose Creek Watershed as inflow from adjacent drainage basins to supply the demand of the pumps in the New Hope Crushed Stone Company's (NHCS) quarry operation. Pumping accelerated sinkhole collapse by the following mechanisms: the loss of buoyant support as a result of a lowering of the water table, increased groundwater velocities caused by the steepening of hydraulic gradients, induced recharge in areas which previously rejected recharge. / Earth and Environmental Science

The sinistral Crum Creek shear zone is a zone of ductile strain located in Delaware County, Pennsylvania, and is internal to the Philadelphia structural block. The sinistral Crum Creek shear zone is an antithetic conjugate structure to the dextral Rosemont shear zone. Geometry, opposing shear sense, angular relationships and post-Taconian timing support a conjugate model for these structures. The Crum Creek shear zone is 1.5 to 3.0 kilometers wide, strikes approximately north-south, dips steeply to the east, and affects the schists and amphibolites of the Wissahickon Formation and the western margin of the Springfield granodioritic gneiss. The trace of earlier structures into the Crum Creek zone as well as the shape of the western margin of the Springfield gneiss indicate sinistral offset across the shear zone. This sinistral displacement is supported by the presence of Type I S-C mylonite developed along the western margin of the Springfield gneiss. Taconian isograds in the Wissahickon Formation were displaced approximately 4 kilometers across the Crum Creek shear zone in a manner consistent with sinistral offset Transposition of the Taconian isograds along the margins of the shear zone indicates that deformation along the Oum Creek shear zone occured atl.east after the peak of Taconian metamorphism. Opposing shear sense, identical geometries and an angular difference of 35° to 400 between the Crum Creek and Rosemont shear zones support a model of conjugate ductile structures. The implications are that the principal compressive stress array was oriented relative to present day coordinates such that a1 plunged shallowly west-northwest, a2 plunged steeply to the northeast and <J3 plunged shallowly south-southwest. This stress array indicates that the maximum compression direction was oriented at a high angle to the Crum Creek shear zone (>65°), and that structural escape occurred subhorizontal. These conclusions are consistent with the geometry of a map-scale conjugate box fold that developed between the conjugate shear zones. / Earth and Environmental Science

This study is an investigation of the effects of Martic shear zone deformation in the Honey Brook Upland, a region north of the Chester Valley, southeastern Pennsylvania. The Chester Valley and rocks adjacent to its southern boundary lie within the Martic shear zone, a zone of high ductile strain in southeastern Pennsylvania. This study found planar fabric in rocks in the southern and central regions of the Honey Brook Upland which resemble that of the Martic shear zone. Along the southern boundary of the Upland, a mylonitic fabric dips steeply to vertically, and its strike while varying, averages approximately N75E, similar in attitude to the Martic zone. Slightly north of the southern shear band, in the central Upland section, grain size is slightly coarser, although strike and dip resemble the southern shear zone and structures vary. Metamorphic facies assemblages in the southern and central regions consist of an upper amphibolite facies mineral assemblage overprinted by greenschist facies. The strong planar fabric composed of relict high temperature mineral assemblages on which a greenschist facies assemblage has been superimposed, is common in the Martic shear zone. This investigation found that the strong planar fabric, while enhanced by greenschist facies metamorphism, is primarily due to the amphibolite facies metamorphism and accompanying deformation. / Earth and Environmental Science