Aerial gamma ray surveys are an important tool for national security, scientific, and industrial interests in determining locations of both anthropogenic and natural sources of radioactivity. There is a relationship between radioactivity and geology and in the past this relationship has been used to predict geology from an aerial survey. The purpose of this project is to develop a method to predict the radiologic exposure rate of the geologic materials by creating a high resolution background model. The intention is for this method to be used in an emergency response scenario where the background radiation environment is unknown. Two study areas in Southern Nevada have been modeled using geologic data, images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), geochemical data, and pre-existing low resolution aerial surveys from the National Uranium Resource Evaluation (NURE) Survey. Using these data, geospatial areas that are homogenous in terms of K, U, and Th, referred to as background radiation units, are defined and the gamma ray exposure rate is predicted. The prediction is compared to data collected via detailed aerial survey by the Department of Energy's Remote Sensing Lab - Nellis, allowing for the refinement of the technique. By using geologic units to define radiation background units of exposed bedrock and ASTER visualizations to subdivide and define radiation background units within alluvium, successful models have been produced for Government Wash, north of Lake Mead, and for the western shore of Lake Mohave, east of Searchlight, NV.
Other| April 01, 1996 Synthesis of high-pressure hydrous magnesium silicates; observations and analysis Pamela C. Burnley; Pamela C. Burnley Princeton University, Center for High Pressure Research and Department of Geological and Geophysical Sciences, Princeton, NJ, United States Search for other works by this author on: GSW Google Scholar Alexandra Navrotsky Alexandra Navrotsky Search for other works by this author on: GSW Google Scholar American Mineralogist (1996) 81 (3-4): 317–326. https://doi.org/10.2138/am-1996-3-405 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Tools Icon Tools Get Permissions Search Site Citation Pamela C. Burnley, Alexandra Navrotsky; Synthesis of high-pressure hydrous magnesium silicates; observations and analysis. American Mineralogist 1996;; 81 (3-4): 317–326. doi: https://doi.org/10.2138/am-1996-3-405 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract Specimens of dense high-pressure hydrous magnesium silicates, notably phase A, phase B, and superhydrous phase B, have been synthesized for use in calorimetric and spectroscopic experiments. X-ray diffraction and electron microprobe analysis were used to study both major and minor phases occurring in the experimental products. We observed the formation of phase A at 16 GPa, 1172 °C; phase B at 15 GPa, 1158 °C; chondrodite at 12 GPa, 1158 °C; and clinohumite at 12 GPa, 1170 °C. These pressures and temperatures are higher than those reported in previous studies. We also observed the formation of phases E and superhydrous B at conditions at which they have been previously observed. However, we propose that there is a high-low transition in superhydrous B. We have not identified phase C in the pressure-temperature-bulk compositional space where it has been observed in previous studies. We conclude that this phase may be identical with superhydrous B, as previously suggested, or that in some studies a humite may have been misidentified as phase C. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.
High-temperature oxide melt solution calorimetry with molten 2PbO{center_dot} B{sub 2}O{sub 3} as a solvent can be used for determining enthalpies of formation of carbonates and hydrous silicates. Under conditions of gas flow at 1-2 cm{sup 3}/s, all H{sub 2}O and CO{sub 2} is expelled from the solvent, leading to a reproducible final thermodynamic state. Both analytical data and a number of thermodynamic cycles show that, under these conditions, the volatiles neither dissolve in nor interact energetically with the melt. 27 refs., 4 figs., 4 tabs.
This study compares high resolution forward models of natural gamma-ray background with that measured by high resolution aerial gamma-ray surveys. The ability to predict variations in natural background radiation levels should prove useful for those engaged in measuring anthropogenic contributions to background radiation for the purpose of emergency response and homeland security operations. The forward models are based on geologic maps and remote sensing multi-spectral imagery combined with two different sources of data: 1) bedrock geochemical data (uranium, potassium and thorium concentrations) collected from national databases, the scientific literature and private companies, and 2) the low spatial resolution NURE (National Uranium Resource Evaluation) aerial gamma-ray survey. The study area near Cameron, Arizona, is located in an arid region with minimal vegetation and, due to the presence of abandoned uranium mines, was the subject of a previous high resolution gamma-ray survey. We found that, in general, geologic map units form a good basis for predicting the geographic distribution of the gamma-ray background. Predictions of background gamma-radiation levels based on bedrock geochemical analyses were not as successful as those based on the NURE aerial survey data sorted by geologic unit. The less successful result of the bedrock geochemical model is most likely due to a number of factors including the need to take into account the evolution of soil geochemistry during chemical weathering and the influence of aeolian addition. Refinements to the forward models were made using ASTER visualizations to create subunits of similar exposure rate within the Chinle Formation, which contains multiple lithologies and by grouping alluvial units by drainage basin rather than age.
We are studying changes in knowledge of science and attitudes regarding science among participants in a summer Research Experiences for Undergraduates program run by the Atlanta Consortium for Research in the Earth Sciences. Existing survey instruments do not detect changes in our participants' attitudes over the course of our program and also fail to detect differences between our geoscience faculty and a group of college students with limited exposure to college level science. Therefore, we are developing a new survey instrument based on clusters of statements representing a variety of philosophical positions, from which respondents must pick one statement. We compare the distribution of the choices made by a group of respondents with the distribution of choices made by geoscience faculty. The first version of the instrument was able to differentiate between three different groups of students with different science backgrounds. Some of the statement clusters detected changes in our RUE program participants' attitudes over the course of the program. We believe that with further modification, an instrument can be developed that will detect changes induced by participation in a research experience. We have also studied the use of open-ended questions regarding the nature of science. Statistical analysis of responses to open-ended questions can also differentiate between college students with different science backgrounds and detect some changes over the course of our program.
