Geology topics

D. Counce

Publications and source records attributed to D. Counce.

4 recordsLinked to original sources

USGS2002

Results of weekly chemical and isotopic monitoring of selected springs in Norris Geyser Basin, Yellowstone National Park during June-September, 1995

Each year at Norris Geyser Basin, generally in August or September, a widespread hydrothermal 'disturbance' occurs that is characterized by simultaneous changes in the discharge characteristics of many springs, particularly in the Back Basin. During the summer season of 1995, water samples from eight widely distributed hot springs and geysers at Norris were collected each week and analyzed to determine whether chemical and isotopic changes also occurred in the thermal waters at the time of the disturbance. In addition, Beryl Spring in Gibbon Canyon, 5.8 km southwest of Norris Geyser Basin, was included in the monitoring program. Waters discharged by four of the monitored hot springs and geysers appear to issue from relatively deep reservoirs where temperatures are at least 270 C and possibly higher than 300 C. At the time of, and for several days after, the onset of the 1995 disturbance, the normally neutral-chloride waters discharged by these four features all picked up an acid-sulfate component and became isotopically heavier. The acid-sulfate component appears to be similar in composition to some waters discharged in 100 Spring Plain that issue from subsurface regions where temperatures are in the range 170-210 C. However, the two monitored springs that discharge acid-chloride-sulfate waters in the 100 Spring Plain region did not show any significant chemical or isotopic response to the annual disturbance. Beryl Spring, and two neutral-chloride hot springs at Norris that appear to draw their water from reservoirs where temperatures are 250 C or less, also did not show any significant chemical or isotopic response to the annual disturbance. After the start of the annual disturbance, chloride concentrations in water sampled from Double Bulger Geyser in the Back Basin increased from about 800 ppm to about 1500 ppm, nearly twice as high as any previously reported chloride concentration in a thermal water at Yellowstone. The isotopic composition of that water precludes an origin of the high chloride by evaporation at atmospheric pressure. One way to account for the unique chemical and isotopic composition of this highly concentrated wateris by recirculation of water that had gone through one cycle of adiabatic cooling during upflow (decompressional boiling) back down into the hydrothermal system, where it is reheated to greater than 220 C. This previously boiled water then undergoes additional cycles of decompressional boiling during subsequent upflow. Another way the unique chemical and isotopic composition of Double Bulger water might evolve is by excess boiling in the formation that results from a decrease in fluid pressure within the channels of upflow. The annual disturbance at Norris Geyser Basin generally appears to be triggered by a cyclic up and down movement of the boilingpoint curve within the hydrothermal system in response to changes in the potentiometric surface of the cold water that is adjacent to, and interconnected with, that hydrothermal system. Annual disturbance phenomena that are easily recognized at Norris Geyser Basin may not be easily recognized elsewhere in Yellowstone National Park because (1) the neutral-chloride waters at Norris ascend directly from higher-temperature and higherpressure reservoirs (270 to >300 C at Norris compared to 180-215C at Upper and Lower Geyser Basins) that are capable of producing massive amounts of high-pressure steam, and (2) the clay that makes hot spring and geyser waters become turbid at Norris, heralding the start of the disturbance, comes from acid altered rocks that are widely distributed at intermediate depths at Norris, and that are rare in other geyser basins.

Wyoming↗

USGS1999

Physical, chemical, and isotopic data for samples from the Anderson Springs area, Lake County, California, 1998-1999

Anderson Springs is located about 90 miles (145 kilometers) north of San Francisco, California, in the southwestern part of Lake County. The area was first developed in the late 1800s as a health resort, which was active until the 1930s. In the rugged hills to the south of the resort were four small mercury mines of the eastern Mayacmas quicksilver district. About 1,260 flasks of mercury were produced from these mines between 1909 and 1943. In the 1970s, the high-elevation areas surrounding Anderson Springs became part of The Geysers geothermal field. Today, several electric powerplants are located on the ridges above Anderson Springs, utilizing steam produced from a 240°C vapor-dominated reservoir. The primary purpose of this report is to provide physical, chemical, and isotopic data on samples collected in the Anderson Springs area during 1998 and 1999, in response to a Freedom of Information Act request. In July 1998, drainage from the Schwartz adit of the abandoned Anderson mercury mine increased substantially over a 2-day period, transporting a slurry of water and precipitates down a tributary and into Anderson Creek. In August 1998, J.J. Rytuba and coworkers sampled the Schwartz adit drainage and water from the Anderson Springs Hot Spring for base metal and methylmercury analysis. They measured a maximum temperature (Tm) of 85°C in the Hot Spring. Published records show that the temperature of the Anderson Springs Hot Spring (main spring) was 63°C in 1889, 42–52°C from 1974 through 1991, and 77°C in March 1995. To investigate possible changes in thermal spring activity and to collect additional samples for geochemical analysis, C.J. Janik and coworkers returned to the area in September and December 1998. They determined that a cluster of springs adjacent to the main spring had Tm=98°C, and they observed that a new area of boiling vents and small fumaroles (Tm=99.3°C) had formed in an adjacent gully about 20 meters to the north of the main spring. During August–October 1999, several field trips were conducted in the vicinity of Anderson Springs to continue monitoring and sampling the thermal manifestations. The new fumarolic area had increased in temperature and in discharge intensity since 1998, and a zone of dead trees had developed on the steep bank directly west of the fumaroles. Ground temperatures and diffuse flow of CO2 flow through soils were measured in the area surrounding the main spring and new fumaroles and in the zone of tree-kill.

California↗

USGS1998

Geochemical surveillance of magmatic volatiles at Popocatepetl volcano, Mexico

Surveillance of Popocatépetl volcanic plume geochemistry and SO 2 flux began in early 1994 after fumarolic and seismic activity increased significantly during 1993. Volatile traps placed around the summit were collected at near-monthly intervals until the volcano erupted on December 21, 1994. Additional trap samples were obtained in early 1996 before the volcano erupted again, emplacing a small dacite dome in the summit crater. Abundances of volatile constituents (ppm/day of Cl, S total , F, CO 2 , Hg, and As) varied, but most constituents were relatively high in early and late 1994. However, ratios of these constituents to Cl were highest in mid-1994. δ 34 S-S total in trap solutions ranged from 1.5‰ to 6.4‰; lowest values generally occurred during late 1994. δ 13 C-CO 2 of trap solutions were greatly contaminated with atmospheric CO 2 and affected by absorption kinetics. When trap data are combined with SO 2 flux measurements made through November 1996, Popocatépetl released about 3.9 Mt SO 2 , 16 Mt CO 2 , 0.75 Mt HCl, 0.075 Mt HF, 260 t As, 2.6 t Hg, and roughly 200 Mt H 2 O. Near-vent gas concentrations in the volcanic plume measured by correlation spectrometer (COSPEC) and Fourier transform infrared (FTIR) commonly exceed human recommended exposure limits and may constitute a potential health hazard. Volatile geochemistry combined with petrologic observations and melt-inclusion studies show that mafic magma injection into a preexisting silicic chamber has accompanied renewed volcanism at Popocatépetl. Minor assimilation of Cretaceous wall rocks probably occurred in mid-1994.

Mexico↗

USGS1991

A geochemical model of the Platanares geothermal system, Honduras

Results of exploration drilling combined with results of geologic, geophysical, and hydrogeochemical investigations have been used to construct a geochemical model of the Platanares geothermal system, Honduras. Three coreholes were drilled, two of which produced fluids from fractured Miocene andesite and altered Cretaceous to Eocene conglomerate at 450 to 680 m depth. Large volume artesian flows of 160-165??C, predominantly bicarbonate water are chemically similar to, but slightly less saline than widespread boiling hot-spring waters. The chemistry of the produced fluid is dominated by equilibrium reactions in sedimentary rocks at greater depths and higher temperatures than those measured in the wells. Chemical, isotope, and gas geothermometers indicate a deep fluid temperature of 200-245??C and reflect a relatively short residence time in the fractures feeding the wells. Chloride-enthalpy relations as well as isotopic and chemical compositions of well discharges, thermal springs, and local cold waters support a conceptual model of ascending high-temperature (minimum 225??C) parent fluid that has cooled conductively to form the 160-165??C shallow (to 680 m) fluid encountered by the wells. The hot-spring waters are formed by boiling and steam loss from more or less conductively cooled parent fluid. The more dilute boiling spring waters (Cl = ???32 mg/kg) have cooled from > 225??C to about 160??C by conduction and from 160??C to 98??C by boiling. The most concentrated boiling spring waters (Cl = 37 mg/kg) have cooled from > 225??C to about 200??C by conduction and from 200??C to 98??C by boiling. Intermediate concentrations reflect mixed cooling paths. ?? 1991.

Journal of Volcanology and Geothermal Research↗