M. Dennis Krohn

Relations of ammonium minerals at several hydrothermal systems in the western U.S.

Abstract Ammonium bound to silicate and sulfate minerals has recently been located at several major hydrothermal systems in the western U.S. utilizing newly-discovered near-infrared spectral properties. Knowledge of the origin and mineralogic relations of ammonium minerals at known hydrothermal systems is critical for the proper interpretation of remote sensing data and for testing of possible links to mineralization. Submicroscopic analysis of ammonium minerals from two mercury- and gold-bearing hot-springs deposits at Ivanhoe, Nevada and McLaughlin, California shows that the ammonium feldspar, buddingtonite, occurs as fine-grained euhedral crystals coating larger sulfide and quartz crystals. Ammonium feldspar seems to precipitate relatively late in the crystallization sequence and shows evidence for replacement of NH4+ by K+ or other monovalent cations. Some buddingtonite is observed in close association with mercury, but not with gold. Ammonioalunite is found in a variety of isolated crystal forms at both deposits. Nitrogen isotopic values for ammonium-bearing minerals show a 14‰ range in composition, precluding assignment of a specific provenance to the nitrogen. The correlations of nitrogen isotopic values with depth and ammonium content suggest some loss of nitrogen in the oxidizing supergene environment, possibly as a metastable mineral. The high ammonium content in these hydrothermal systems, the close association to mercury, and the small crystal size of the ammonium-bearing minerals all suggest that ammonium may be transported in a late-stage vapor phase or as an organic volatile. Such a process could lead to the formation of a non-carbonaceous organic aureole above a buried geothermal source. The discovery of a 10-km outcrop of ammonium minerals confirms that significant substitution of ammonium in minerals is possible over an extensive area and that remote sensing is a feasible means to detect such aureoles.

Near‐infrared detection of ammonium minerals

Diagnostic near‐infrared spectral features have been identified for minerals with ammonium (NH4+) bound in the crystal structure. Spectral bands near 2.12, 2.02, and 1.56 μm are characteristic of synthetic and natural NH4‐bearing minerals. Laboratory spectra of NH4‐bearing minerals are distinct from spectra of OH‐bearing minerals and have diagnostic shifts in band position among different mineral types. NH4‐bearing minerals were detected at several mineralized hot‐spring deposits in the western U.S. by means of hand‐held and airborne instruments. Near‐infrared detection of NH4‐bearing minerals may provide useful information for prospecting for certain ore deposits and may provide a better understanding of the nitrogen cycle within geologic environments.

CACOXENITE IN MIOCENE SEDIMENTS OF THE MARYLAND COASTAL PLAIN

Cacoxenite having the composition (Al4.0Fe22.5O7.1(OH)14.3(PO4)17(H2O)23.7)·50.3H2O was identified in a bed of mature quartz sand in the Miocene Calvert Formation near Popes Creek, Maryland. This is the first reported occurrence of this mineral in Atlantic Coastal Plain sediments north of Florida. The cacoxenite occurs as silt-size to sand-size grains, both as irregularly shaped aggregates and as radiating arrays of delicate acicular crystals. The presence of discrete cores and overgrowths in some grains indicates at least two generations of crystal growth. Electron microprobe analyses reveal excess Si and Al (relative to the ideal composition), which is believed to reflect ultra-fine clay particles within the cacoxenite grains. Admixed clays probably served as a substrate for the formation of ferric oxyhydroxides, which were subsequently converted to cacoxenite through the addition of dissolved phosphorus.

Numerical computation of hurricane effects on historic coastal hydrology in Southern Florida

IntroductionNumerical models are critical for assessing the effects of sea level rise (SLR), hurricanes, and storm surge on vegetation change in the Everglades National Park. The model must be capable of representing short-timescale hydrodynamics, salinity transport, and groundwater interaction. However, there is also a strong need to adapt these numerical models to hindcast past conditions in order to examine long-term effects on the distribution of vegetation that cannot be determined using only the modern record.MethodsBased on parameters developed for a numerical model developed for the recent 1996 to 2004 period, a hindcast model was developed to represent sea level and water management for the period of 1926 to 1932, constrained by the limited hydrology and meteorology data available from the historic past. Realistic hurricane-wind and storm surge representations, required for the hindcast model, are based on information synthesized from modern storm data. A series of simulation scenarios with various hurricane representations inserted into both hindcast and recent numerical models were used to assess the utility of the storm representation in the model and compare the two simulations.ResultsThe comparison of the hindcast and recent models showed differences in the hydrology patterns that are consistent with known differences in water delivery systems and sea level rise. A 30× lower-resolution spatially variable wind grid for the hindcast produced similar results to the original high-resolution full wind grid representation of the recent simulation. Storm effects on hydrologic patterns demonstrated with the simulations show hydrologic processes that could have a long-term effect on vegetation change.ConclusionsThe hindcast simulation estimated hydrologic processes for the 1926 to 1932 period. It shows promise as a simulator in long-term ecological studies to test hypotheses based on theoretical or empirical-based studies at larger landscape scales.

Post-Hurricane Irene coastal oblique aerial photographs collected from Ocracoke Inlet, North Carolina, to Virginia Beach, Virginia, August 30-31, 2011

The U.S. Geological Survey (USGS) conducts baseline and storm-response photography missions to document and understand the changes in vulnerability of the Nations coasts to extreme storms. On August 30-31, 2011, the USGS conducted an oblique aerial photographic survey (during Field Activity Number [FAN] 11CCH04) from Ocracoke Inlet, North Carolina, to Virginia Beach, Virginia, aboard a Piper Navajo Chieftain aircraft at an altitude of 500 feet (ft) and approximately 1,200 ft offshore (Figure 2, http://pubs.usgs.gov/ds/0979/html/ds979_fig2.html). This mission was flown to collect data for assessing incremental changes since the last survey, which was flown in May 2008 (http://compass.er.usgs.gov/activity_popup.php?id=114), and can be used for assessing future coastal change. The photographs provided here are Joint Photographic Experts Group (JPEG) images. The photograph locations are an estimate of the position of the aircraft and do not indicate the location of the feature in the images. (See the Navigation Data page, for additional details: http://pubs.usgs.gov/ds/0979/html/ds979_nav.html). These photographs document the configuration of the barrier islands and other coastal features at the time of the survey. ExifTool (http://www.sno.phy.queensu.ca/~phil/exiftool/) was used to add the following to the header of each photo: time of collection, Global Positioning System (GPS) latitude, GPS longitude, keywords, credit, artist (photographer), caption, copyright, and contact information. Photographs can be opened directly with any JPEG-compatible image viewer by clicking on a thumbnail on the contact sheet. All image times are recorded in Coordinated Universal Time (UTC). Table 1 (http://pubs.usgs.gov/ds/0979/html/ds979_table.html) provides detailed information about the assigned location, name, date, and time the photograph was taken along with a link to the photograph. In addition to the photographs, a Google Earth Keyhole Markup Language (KML) file is provided and can be used to view the images by clicking on the marker and then clicking on either the thumbnail or the link above the thumbnail. The KML files were created using the photographic navigation files. Note: A KML number was assigned to each photograph to aid navigation of the Google Earth file. These numbers correspond to the site labels in Google Earth.

Research on the impacts of past and future hurricanes on the endangered Florida manatee: Chapter 6J in Science and the storms-the USGS response to the hurricanes of 2005

U.S. Geological Survey (USGS) research on Florida manatees (Trichechus manatus latirostris) from 1982 through 1998 identified lower apparent survival rates for adult manatees during years when Hurricane Elena (1985), the March “Storm of the Century”(1993), and Hurricane Opal (1995) hit the northern coast of the Gulf of Mexico. Although our analysis showed that a significant number of our monitored individual manatees failed to return to their winter homes after these storms, their actual fate remains unknown. With the aid of new satellite technology to track manatees during storms and new statistical techniques to determine survival and emigration rates, researchers are working to understand how hurricanes impact the endangered species by studying manatees caught in the path of the destructive hurricanes of 2004 and 2005.